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The article discusses the use of positron emission tomography (PET) and computed tomography (CT) in detecting cancer in the head, neck, and skull base. It explains how the radiopharmaceutical F-18 flourodeoxyglucose (FDG) is taken up by tumor cells due to their increased glucose utilization, leading to the detection of malignancies. The text also highlights how other factors like foreign body material, infection, and inflammation can mimic the appearance of neoplasms in the skull base, providing examples and insights into PET-CT imaging. [Extracted from the article]

Background: A recently released digital solid-state positron emission tomography/x-ray CT (PET/CT) scanner with bismuth germanate (BGO) scintillators provides an artificial intelligence (AI) based system for automatic patient positioning. The efficacy of this digital-BGO system in patient placement at the isocenter and its impact on image quality and radiation exposure was evaluated. Method: The digital-BGO PET/CT with AI-based auto-positioning was compared (χ2, Mann–Whitney tests) to a solid-state lutetium-yttrium oxyorthosilicate (digital-LYSO) PET/CT with manual patient positioning (n = 432 and 343 studies each, respectively), with results split into groups before and after the date of a recalibration of the digital-BGO auto-positioning camera. To measure the transverse displacement of the patient center from the scanner isocenter (off-centering), CT slices were retrospectively selected and automatically analyzed using in-house software. Noise was measured as the coefficient of variation within the liver of absolute Hounsfield units referenced to air. Radiation exposure was recorded as dose-length product (DLP). Off-centering measurements were validated by a phantom study. Results: The phantom validation study gave < 1.6 mm error in 15 off-centering measurements. Patient off-centering was biased 1.92 ± 1.79 cm (mean ± standard deviation) in the posterior direction which was significantly different from the 0.22 ± 1.21 cm bias in the left lateral direction (p < 0.0001, Wilcoxon). After recalibration, 27% (38/140) of the studies had off-centering results > 2.5cm for the digital-BGO, which was significantly better than the 49% (143/292, p < 0.001) before recalibration and better than for the digital-LYSO: 54% (119/222, p < 0.001) before and 55% (66/121, p < 0.001) after. On average, CT image quality was superior for non-obese patients who were most closely aligned with the isocenter: noise increased by 3.2 ± 0.1% for every 1 cm increase in off-centering. DLP increased by 144 ± 22 Gy cm for every 1 cm increase in anterior off-centering. Conclusion: AI-based automatic patient positioning in a digital-BGO PET/CT scanner significantly reduces patient off-centering, thereby improving image quality and ensuring proper radiation exposure. [ABSTRACT FROM AUTHOR]

The overexpression of the epidermal growth factor receptor (EGFR) in certain types of prostate cancers and glioblastoma makes it a promising target for targeted radioligand therapy. In this context, pairing an EGFR-targeting peptide with the emerging theranostic pair comprising the Auger electron emitter cobalt-58m (58mCo) and the Positron Emission Tomography-isotope cobalt-55 (55Co) would be of great interest for creating novel radiopharmaceuticals for prostate cancer and glioblastoma theranostics. In this study, GE11 (YHWYGYTPQNVI) was investigated for its EGFR-targeting potential when conjugated using click chemistry to N1-((triazol-4-yl)methyl)-N1,N2,N2-tris(pyridin-2-ylmethyl)ethane-1,2-diamine (TZTPEN). This chelator is suitable for binding Co2+ and Co3+. With cobalt-57 (57Co) serving as a surrogate radionuclide for 55/58mCo, the novel GE11-TZTPEN construct was successfully radiolabeled with a high radiochemical yield (99%) and purity (>99%). [57Co]Co-TZTPEN-GE11 showed high stability in PBS (pH 5) and specific uptake in EGFR-positive cell lines. Disappointingly, no tumor uptake was observed in EGFR-positive tumor-bearing mice, with most activity being accumulated predominantly in the liver, gall bladder, kidneys, and spleen. Some bone uptake was also observed, suggesting in vivo dissociation of 57Co from the complex. In conclusion, [57Co]Co-TZTPEN-GE11 shows poor pharmacokinetics in a mouse model and is, therefore, not deemed suitable as a targeting radiopharmaceutical for EGFR. [ABSTRACT FROM AUTHOR]

ABSTRACT: Currently, the second most commonly diagnosed cancer in the world is lung cancer, and 85% of cases are non-small cell lung cancer (NSCLC). With growing knowledge of oncogene drivers and cancer immunology, several novel therapeutics have emerged to improve the prognostic outcomes of NSCLC. However, treatment outcomes remain diverse, and an accurate tool to achieve precision medicine is an unmet need. Radiomics, a method of extracting medical imaging features, is promising for precision medicine. Among all radiomic tools, 18F-fluorodeoxyglucose positron emission tomography (18F-FDG PET)-based radiomics provides distinct information on glycolytic activity and heterogeneity. In this review, we collected relevant literature from PubMed and summarized the various applications of 18F-FDG PET-derived radiomics in improving the detection of metastasis, subtyping histopathologies, characterizing driver mutations, assessing treatment response, and evaluating survival outcomes of NSCLC. Furthermore, we reviewed the values of 18F-FDG PET-based deep learning. Finally, several challenges and caveats exist in the implementation of 18F-FDG PET-based radiomics for NSCLC. Implementing 18F-FDG PET-based radiomics in clinical practice is necessary to ensure reproducibility. Moreover, basic studies elucidating the underlying biological significance of 18F-FDG PET-based radiomics are lacking. Current inadequacies hamper immediate clinical adoption; however, radiomic studies are progressively addressing these issues. 18F-FDG PET-based radiomics remains an invaluable and indispensable aspect of precision medicine for NSCLC. [ABSTRACT FROM AUTHOR]

Light-chain multiple myeloma (LCMM) is a rare subtype of plasma cell neoplasm, usually linked to kidney involvement and lytic bone lesions. However, case presents as osseus tumors are very uncommon. A 63-year-old male patient complained of persistent rib pain. Computed tomographic imaging showed an isolated bone tumor in the eighth rib. Further positron emission tomography–computed tomographic scan revealed multiple lytic bone lesions in other areas. Biopsy of the rib lesion confirmed the presence of plasma cells producing kappa light chains. The patient received 4 cycles of daratumumab, bortezomib, lenalidomide, and dexamethasone treatments, resulting in significant improvement. Reviewing literatures, osseus tumor with osteosclerotic lesions has been rarely described in LCMM, underlining the challenge in diagnosis and stressing the importance of considering LCMM in the differential diagnosis of bone tumors. [ABSTRACT FROM AUTHOR]

Background/Objectives: The purpose of this study was to develop the gemcitabine-loaded drug-eluting beads (G-DEBs) for transarterial chemoembolization (TACE) in rabbit renal tumors and to evaluate their antitumor effect using 2-deoxy-2-[(18)F]fluoro-D-glucose positron emission tomography/X-ray computed tomography (18F-FDG PET/CT). Methods: DEBs were prepared by polyvinyl alcohol-based macromer crosslinked with N-acryl tyrosine and N,N′-methylenebis(acrylamide). Gemcitabine was loaded through ion change to obtain G-DEBs. Their particle size and drug release profile were characterized. VX2 tumors were implanted in the right kidney of rabbits to establish the renal tumor model. The tumor-bearing rabbits received pre-scan by 18F-FDG PET/CT, followed by targeted transarterial injection of G-DEBs under digital subtraction angiography (DSA) guidance. The rabbits received another 18F-FDG PET/CT scan 10 or 14 days after the treatment. The therapeutic effect was further validated by histopathological analysis of the dissected tumors. Results: The average particle size of the microspheres was 58.06 ± 0.50 µm, and the polydisperse index was 0.26 ± 0.002. The maximum loading rate of G-DEBs was 18.09 ± 0.35%, with almost 100% encapsulation efficiency. Within 24 h, GEM was eluted from G-DEBs rapidly and completely, and more than 20% was released in different media. DSA illustrated that G-DEBs were delivered to rabbit renal tumors. Compared with the untreated control group with increased tumor volume and intense 18F -FDG uptake, the G-DEBs group showed significant reductions in tumor volume and maximum standard uptake value (SUVmax) 10 or 14 days after the treatment. Histopathological analysis confirmed that the proliferating area of tumor cells was significantly reduced in the G-DEBs group. Conclusions: Our results demonstrated that G-DEBs are effective in TACE treatment of rabbit VX2 renal tumors, and 18F-FDG PET/CT provides a non-invasive imaging modality to monitor the antitumor effects of TACE in renal tumors. [ABSTRACT FROM AUTHOR]

Background: Ovarian cancer is a challenging disease. Accurate staging and restaging are critical for improving treatment outcomes and determining the prognosis. Imaging is an indispensable component of ovarian cancer management. Hybrid imaging modalities, including positron emission tomography/computed tomography (PET/CT), are emerging as potential noninvasive imaging tools for improved management of ovarian cancer. Methods: This study involved 24 female patients exhibiting increasing CA-125 levels throughout clinical follow-up. All patients underwent comprehensive history-taking and clinical evaluation. Then all patients were evaluated using PET-CT scans, the histopathology results served as the gold standard against which the PET-CT results were compared. Results: The CT specificity was 100% and its sensitivity was 75%. PET-CT had 92.9% sensitivity and a 100% specificity rate. When ROC curve analysis is performed on SUV max of the lesion to separate benign from malignant masses, it reveals a sensitivity of 89.29%, specificity of 100%, and AUC of 0.911 at the cut-off point of 4.2. When comparing differentiated from poorly differentiated malignant masses, using ROC curve analysis on SUV max to the lesion, the results show that the sensitivity is 70.83 percent, the specificity is 100%, and the AUC is 0.708 at a cutoff point of 6.7. Conclusion: FDG PET/CT can greatly impact the evaluation of primary and recurrent ovarian cancer, leading to considerable changes in patient care. [ABSTRACT FROM AUTHOR]

Background: Although the integration of positron emission tomography into radiation therapy treatment planning has become part of clinical routine, the best method for tumor delineation is still a matter of debate. In this study, therefore, we analyzed a novel, radiomics-feature-based algorithm in combination with histopathological workup for patients with non-small-cell lung cancer. Methods: A total of 20 patients with biopsy-proven lung cancer who underwent [18F]fluorodeoxyglucose positron emission/computed tomography (FDG-PET/CT) examination before tumor resection were included. Tumors were segmented in positron emission tomography (PET) data using previously reported algorithms based on three different radiomics features, as well as a threshold-based algorithm. To obtain gold-standard results, lesions were measured after resection. Pathological volumes and maximal diameters were then compared with the results of the segmentation algorithms. Results: A total of 20 lesions were analyzed. For all algorithms, segmented volumes correlated well with pathological volumes. In general, the threshold-based volumes exhibited a tendency to be smaller than the radiomics-based volumes. For all lesions, conventional threshold-based segmentation produced coefficients of variation which corresponded best with pathologically based volumes; however, for lesions larger than 3 ccm, the algorithm based on Local Entropy performed best, with a significantly better coefficient of variation (p = 0.0002) than the threshold-based algorithm. Conclusions: We found that, for small lesions, results obtained using conventional threshold-based segmentation compared well with pathological volumes. For lesions larger than 3 ccm, the novel algorithm based on Local Entropy performed best. These findings confirm the results of our previous phantom studies. This algorithm is therefore worthy of inclusion in future studies for further confirmation and application. [ABSTRACT FROM AUTHOR]

PURPOSE: To evaluate natural language processing (NLP) methods to infer metastatic sites from radiology reports. METHODS: A set of 4,522 computed tomography (CT) reports of 550 patients with 14 types of cancer was used to fine-tune four clinical large language models (LLMs) for multilabel classification of metastatic sites. We also developed an NLP information extraction (IE) system (on the basis of named entity recognition, assertion status detection, and relation extraction) for comparison. Model performances were measured by F1 scores on test and three external validation sets. The best model was used to facilitate analysis of metastatic frequencies in a cohort study of 6,555 patients with 53,838 CT reports. RESULTS: The RadBERT, BioBERT, GatorTron-base, and GatorTron-medium LLMs achieved F1 scores of 0.84, 0.87, 0.89, and 0.91, respectively, on the test set. The IE system performed best, achieving an F1 score of 0.93. F1 scores of the IE system by individual cancer type ranged from 0.89 to 0.96. The IE system attained F1 scores of 0.89, 0.83, and 0.81, respectively, on external validation sets including additional cancer types, positron emission tomography-CT ,and magnetic resonance imaging scans, respectively. In our cohort study, we found that for colorectal cancer, liver-only metastases were higher in de novo stage IV versus recurrent patients (29.7% v 12.2%; P <.001). Conversely, lung-only metastases were more frequent in recurrent versus de novo stage IV patients (17.2% v 7.3%; P <.001). CONCLUSION: We developed an IE system that accurately infers metastatic sites in multiple primary cancers from radiology reports. It has explainable methods and performs better than some clinical LLMs. The inferred metastatic phenotypes could enhance cancer research databases and clinical trial matching, and identify potential patients for oligometastatic interventions. [ABSTRACT FROM AUTHOR]

Objective Methods Results Conclusions To define the natural history, patterns of recurrence and treatment modalities for local prostate cancer (PCa) recurrence following radical prostatectomy (RP) and radiation therapy (RT), and to investigate factors that could predict metastasis‐free survival (MFS) in this unique patient population.We queried a prospectively maintained PCa registry to identify men developing in‐field recurrence (IFR) following RP and RT from 2008 to 2021 at a single institution. IFR was defined as biopsy‐proven recurrent PCa or the presence of persistent positron emission tomography‐avid lesions in the prior radiation field without evidence of metastasis. Cox regression was conducted to determine predictors of MFS. Kaplan–Meier methods were used to calculate MFS, cancer‐specific survival (CSS) and overall survival (OS) for patients in three primary therapy categories: cryoablation, androgen deprivation therapy (ADT) alone, and surveillance.Of 4575 patients from our registry, 108 (2.3%) with IFR were identified. The median (interquartile range [IQR]) time to IFR from salvage treatment was 78 (50–126) months. A total of 29 patients (26%) were managed with cryoablation, 23 (21%) with ADT, and 28 (25%) with surveillance. The median (IQR) follow‐up was 76 (48–100) months. There were no statistically significant differences in MFS (P = 0.67) or OS (P = 0.07) among the three primary treatment cohorts. Patients treated with ADT or cryoablation had longer CSS compared to patients managed with surveillance (P = 0.047).We found that IFR may present years after completion of primary treatment for PCa. While curative management strategies may be attempted, local and distant metastatic recurrence is common and often requires systemic therapy. [ABSTRACT FROM AUTHOR]

We present a challenging case of Epstein-Barr virus–related isolated small bowel post-transplant lymphoproliferative disorder (PTLD) in a pediatric heart transplant recipient presenting as recurrent gastrointestinal (GI) bleeding and subsequently a GI fistulous tract with associated intra-abdominal abscess. Diagnosis was not confirmed until exploratory laparoscopy was performed, with excision of the fistulous tract revealing evidence of PTLD on pathology. Early diagnosis of GI-PTLD remains a challenge, especially if isolated in the small intestine. Diagnosis may rely on positron emission tomography/ computed tomography scan (PET/CT) or invasive intervention to obtain appropriate tissue samples for pathology diagnosis. [ABSTRACT FROM AUTHOR]

Photothermal anticancer therapy based on plasmonic nanoparticles is proposed to enhance treatment efficacy while mitigating unintended side effects. However, most studies blindly rely on the accumulation of nanoparticles at the tumor site, which may result in inefficient treatment. In this study, the aim is to evaluate relevant parameters to improve plasmonic photothermal therapy. Gold nanorods (AuNRs) with an optimized aspect ratio and either amino or carboxylic acid surface functionalization are selected as photothermal agents. AuNR biocompatibility and photothermal activity in 2D and 3D human MDA‐MB‐231 triple‐negative breast cancer cell models, evaluating localized hyperthermal cell death upon irradiation with resonant near‐infrared (NIR) light, are analyzed first. To ensure reliable tracking of biodistribution in vivo, AuNRs are labeled with the positron emitter copper‐64 (64Cu), and their distribution in a murine MDA‐MB‐231 tumor model is studied via positron emission tomography (PET) imaging. PET images reveal enhanced tumor accumulation of carboxylic acid‐functionalized AuNRs compared to amino‐functionalized AuNRs post‐intravenous administration. Relatively low NIR laser power densities (0.5 W cm−2) are used for controlled heating – keeping local temperature below 50 °C – upon irradiation of intravenously and intratumorally administered AuNRs. As a result, tumor growth is significantly decelerated, even 9 days after application of photothermal therapy. [ABSTRACT FROM AUTHOR]

Background/Aim: This study aimed to evaluate the diagnostic accuracy of prostate-specific membrane antigen (PSMA)-directed positron emission tomography/ computed tomography (PET/CT) in pelvic nodal staging, using postoperative histopathology data as the reference standard. Patients and Methods: From January 2020 to June 2024, 78 patients with clinically significant prostate cancer (PCa) (ISUP Grade Group 2) underwent radical prostatectomy plus extended pelvic lymph node dissection (ePLND): 60 (77%) vs. 18 (23%) men had an intermediate vs. high risk PCa. All the patients underwent PSMA PET/TC before surgery for clinical staging and nodes focal uptake (standardized uptake value "SUVmax) was evaluated to rule out the presence of metastases. Results: PSMA PET/CT was suspicious for nodes metastases in 16/78 (20.5%) men (median SUVmax 26.2), conversely, histology demonstrated nodes metastases in 18/78 (23.1%). PSMA PET/CT was negative for nodal involvement in all Grade Group 2 (GG2) PCa, positive in 4/4 (100%) GG3 PCa, and in 10/14 (71.4%) GG5 PCa. In detail, PSMA PET/CT was false negative in 2/4 PCa, characterized by GG5 plus ductal adenocarcinoma. Overall, PSMA PET/CT sensitivity, specificity, positive and negative predictive value, and diagnostic accuracy in diagnosing nodal metastases were equal to 87.5, 96.8, 87.5 96.7, and 92.3%, respectively. Conclusion: PSMA PET/CT demonstrated an overall diagnostic accuracy of 92.3% in nodal staging (100% in GG2 PCa), which decreased to 63.6% in GG5 PCa. In high-risk patients or in case of ductal adenocarcinoma, a negative PSMA PET/CT does not rule out the need for ePLND. [ABSTRACT FROM AUTHOR]

Background: It is difficult to distinguish between the brain metastasis progression (BMP) and brain radionecrosis (BRN) on the basis of 18F-3,4-dihydroxyphenylalanine positron emission tomography/computed-tomography (18F-FDOPA PET/CT) data. The advent of silicon photomultiplier (SiPM) PET technology makes it possible to study dynamic volumes and potentially improve diagnostic accuracy. We developed a method for processing 18F-FDOPA PET/CT in the differential diagnosis between BMP and BRN. The method involves a short (3-second) sampling time during a 4-minute acquisition on a SiPM-PET/CT machine. We prospectively included 15 patients and 19 metastases. All acquisitions were performed in list mode acquisition for 25 min on a four-ring SiPM PET/CT system. We calculated the ratios between the maximum activity in the lesion's voxel and the mean activity in the contralateral region (VOImax/CLmean) or the mean activity in the white matter (VOImax/WMmean). Results: Seven lesions were classified as BMP and twelve were classified as BRN. Statistically significant intergroup differences in the VOImax/CLmean and VOImax/WMmean activity ratios were observed for both the clinical volume and the early acquisition. The best performing quantitative variable was the VOImax/CLmean ratio on early acquisition, with a diagnostic accuracy of 94.7%, a sensitivity of 100%, and a specificity of 91.7%. Conclusion: The 18F-FDOPA PET/CT data acquired a few minutes after the bolus injection confirms its value in differentiating between BMP and BRN, compared to the much longer classic clinical protocol. [ABSTRACT FROM AUTHOR]

Objective: To assess the diagnostic performance of 18F‐fluoro‐2‐deoxy‐d‐glucose (18F‐FDG) positron emission tomograpy (PET)/computed tomography (CT) in nodal staging before radical cystectomy (RC) and pelvic lymph node dissection (PLND) for bladder cancer (BCa). Materials and Methods: This analysis was based on a cohort of 199 BCa patients undergoing RC and bilateral PLND between 2015 and 2022. Neoadjuvant chemotherapy (NAC) or immunotherapy (NAI) was administered after oncological evaluation. All patients received preoperative 18F‐FDG PET/CT to assess extravesical disease. Point estimates for true negative, false negative, false positive, true positive, sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), and accuracy of conventional imaging and PET/CT were calculated. Subgroup analysis in patients receiving neoadjuvant treatment was performed. Results: At preoperative evaluation, 30 patients (15.1%) had 48 suspicious nodal spots on 18F‐FDG PET/CT. At RC and bilateral PLND, a total of 4871 lymph nodes (LNs) were removed with 237 node metastases corresponding to 126 different regions. Pathological node metastases were found in 17/30 (57%) vs 39/169 patients (23%) with suspicious vs negative preoperative 18F‐FDG PET/CT, respectively (sensitivity = 0.30, specificity = 0.91, PPV = 0.57, NPV = 0.77, accuracy = 0.74). On per‐region analysis including 1367 nodal regions, LN involvement was found in 19/48 (39%) vs 105/1319 (8%) suspicious vs negative regions at PET/CT, respectively (sensitivity = 0.15, specificity = 0.98, PPV = 0.40, NPV = 0.92, ACC = 0.90). Similar results were observed for patients receiving NAC (n = 44, 32.1%) and NAI (n = 93, 67.9% [per‐patient: sensitivity = 0.36, specificity = 0.91, PPV = 0.59, NPV = 0.80, accuracy = 0.77; per‐region: sensitivity = 0.12, specificity = 0.98, PPV = 0.32, NPV = 0.93, ACC = 0.91]). Study limitations include its retrospective design and limited patient numbers. Conclusions: In eight out of 10 patients with negative preoperative 18F‐FDG PET/CT, pN0 disease was confirmed at final pathology. No differences were found based on NAC vs NAI treatment. These findings suggest that 18F‐FDG PET/CT could play a role in the preoperative evaluation of nodal metastases in BCa patients, although its cost‐effectiveness is uncertain. [ABSTRACT FROM AUTHOR]

INTRODUCTION: Olfactory dysfunction can be an early sign of Alzheimer's disease (AD). We used tau positron emission tomography‐magnetic resonance (PET‐MR) to analyze a key region of the olfactory circuit, the piriform cortex, in comparison to the adjacent medial temporal lobe. METHODS: Using co‐registered magnetic resonance imaging (MRI) and 18F‐PI‐2620 tau PET‐MR scans in 94 older adults, we computed tau uptake in the piriform‐periamygdaloid cortex, amygdala, entorhinal‐perirhinal cortices, and hippocampus. RESULTS: We found an ordinal cross‐sectional increase in piriform cortex tau uptake with increasing disease severity (amyloid‐negative controls, amyloid‐positive controls, mild cognitive impairment [MCI] and AD), comparable to entorhinal‐perirhinal cortex. Amyloid‐positive controls showed significantly greater tau uptake than amyloid‐negative controls. Negative correlations were present between memory performance and piriform uptake. Piriform uptake was not elevated in cognitively unimpaired Parkinson's disease. DISCUSSION: Cross‐sectionally, there is an early increase in tau uptake in the piriform cortex in AD but not in Parkinson's disease. Highlights: Positron emission tomography–magnetic resonance (PET‐MR) analysis of the piriform cortex sheds light on its role as a potential early region affected by neurodegenerative disorders underlying olfactory dysfunction.Uptake of tau tracer was elevated in the piriform cortex in Alzheimer's disease (AD) and mild cognitive impairment (MCI) but not in Parkinson's disease (PD).Memory performance was worse with greater piriform uptake. [ABSTRACT FROM AUTHOR]

This review focuses on the pivotal role of radiotracers in breast cancer imaging, emphasizing their importance in accurate detection, staging, and treatment monitoring. Radiotracers, labeled with radioactive isotopes, are integral to various nuclear imaging techniques, including positron emission tomography (PET) and positron emission mammography (PEM). The most widely used radiotracer in breast cancer imaging is 18F-fluorodeoxyglucose (18F-FDG), which highlights areas of increased glucose metabolism, a hallmark of many cancer cells. This allows for the identification of primary tumors and metastatic sites and the assessment of tumor response to therapy. In addition to 18F-FDG, this review will explore newer radiotracers targeting specific receptors, such as estrogen receptors or HER2, which offer more personalized imaging options. These tracers provide valuable insights into the molecular characteristics of tumors, aiding in tailored treatment strategies. By integrating radiotracers into breast cancer management, clinicians can enhance early disease detection, monitor therapeutic efficacy, and guide interventions, ultimately improving patient outcomes. Ongoing research aimed at developing more specific and sensitive tracers will also be highlighted, underscoring their potential to advance precision medicine in breast cancer care. [ABSTRACT FROM AUTHOR]

Background: The distance traveled by the positron before annihilation with an electron, the so‐called positron range, negatively effects the positron emission tomography (PET) image quality for radionuclides emitting high‐energy positrons such as Gallium‐68 (68Ga). Purpose: In this study, the effect of a tissue‐independent positron range correction for Gallium‐68 (68Ga‐PRC) was investigated based on phantom measurements. The effect of the 68Ga‐PRC was also explored in four patients. Methods: The positron range distribution profile of 68Ga in water was generated via Monte Carlo simulation. That profile was mapped to a spatially invariant 3D convolution kernel which was incorporated in the OSEM and Q.Clear reconstruction algorithms to perform the 68Ga‐PRC. In addition, each reconstruction method included point spread function (PSF) modeling and time‐of‐flight information. For both Fluorine‐18 (18F) and 68Ga, the NEMA IQ phantom was filled with a sphere‐to‐background ratio of 10:1 and scanned with the GE Discovery MI 5R PET/CT system. Standard non‐positron range correction (PRC) reconstructions were performed for both radionuclides, while also PRC reconstructions were performed for 68Ga. Reconstructions parameters (OSEM: number of updates, Q.Clear: beta value) were adapted to achieve similar noise levels between the corresponding reconstructions. The effect of 68Ga‐PRC was assessed for both OSEM and Q.Clear reconstructions and compared to non‐PRC reconstructions for 68Ga and 18F in terms of image contrast, noise, recovery coefficient (RC), and spatial resolution. For the clinical validation, 68Ga‐labeled prostate‐specific membrane antigen (68Ga‐PSMA) and 68Ga‐DOTATOC PET scans were included of two patients each. For each PET scan, patients were injected with 1.5 MBq/kg of 68Ga‐PSMA or 68Ga‐DOTATOC and the contrast‐to‐noise ratio (CNR) was calculated and compared to the non‐PRC reconstructions. Results: For OSEM reconstructions, including the 68Ga‐PRC improved the RC by 9.4% (3.7%–19.3%) and spatial resolution by 21.7% (4.6 mm vs. 3.6 mm) for similar noise levels. For Q.Clear reconstructions, 68Ga‐PRC modeling improved the RC by 6.7% (2.8%–10.5%) and spatial resolution by 15.3% (5.9 mm vs. 5.0 mm) while obtaining similar noise levels. In the patient data, the use of 68Ga‐PRC enhanced the CNR by 13.2%. Conclusions: Including 68Ga‐PRC in the PET reconstruction enhanced the image quality of 68Ga PET data compared to the standard non‐PRC reconstructions for similar noise levels. Limited patient results also supported this improvement. [ABSTRACT FROM AUTHOR]

Background: The study aimed to overview radiopharmaceuticals used for the nuclear medicine (NM) imaging of prostate cancer (Pca) since the first mentions in the literature up to recent reports, with the special focus on positron emission tomography- computed tomography (PET-CT) radiotracers. Materials and methods: We found over 3500 articles discussing the role of PET-CT in Pca patients' management published within 1990-2023. We summarized the past and present interests of the Authors when the Pca diagnostic imaging and the use of radiotracers in Pca diagnosis are considered. Eventually, we have compared the radiotracers' introduction in the literature with the United States (U.S.) Food and Drug Administration (FDA) approval timeline. Results: The most mentions by the Authors were made of the following PET-CT study compounds: 2-[18F]fluoroethyl- choline ([18F]FECh), gallium-68-labelled prostate-specific membrane antigen using peptide-11, ([68Ga]Ga-PSMA-11), carbon- 11-labelled acetic acid ([11C]acetate), and the anti-1-amino-3--[18F]-fluorocyclobutane-1-carboxylic acid (anti-3-[18F]FACBC, Axumin®), as well as the non-tumour-specific 2-deoxy-2-[18F]fluoro-D-glucose ([18F]FDG). The most recent studies analysis showed an increasing interest of the Authors not only in a relatively new Pca-specific [68Ga]Ga-PSMA-11, but also in a widely used non-specific [18F]FDG. Conclusions: The literature analysis results lead to the conclusion that Pca remains a constant focus of the NM drug development with particularly high interest in PET-CT-dedicated radiotracers. [ABSTRACT FROM AUTHOR]

Background and objective: Patients suspected to have lung cancer, undergo endobronchial ultrasound bronchoscopy (EBUS) for the purpose of diagnosis and staging. For presumptive curable patients, the EBUS bronchoscopy is planned based on images and data from computed tomography (CT) images and positron emission tomography (PET). Our study aimed to evaluate the feasibility of a multimodal electromagnetic navigation platform for EBUS bronchoscopy, integrating ultrasound and segmented CT, and PET scan imaging data. Methods: The proof-of-concept study included patients with suspected lung cancer and pathological mediastinal/hilar lymph nodes identified on both CT and PET scans. Images obtained from these two modalities were segmented to delineate target lymph nodes and then incorporated into the CustusX navigation platform. The EBUS bronchoscope was equipped with a sensor, calibrated, and affixed to a 3D printed click-on device positioned at the bronchoscope's tip. Navigation accuracy was measured postoperatively using ultrasound recordings. Results: The study enrolled three patients, all presenting with suspected mediastinal lymph node metastasis (N1-3). All PET-positive lymph nodes were displayed in the navigation platform during the EBUS procedures. In total, five distinct lymph nodes were sampled, yielding malignant cells from three nodes and lymphocytes from the remaining two. The median accuracy of the navigation system was 7.7 mm. Conclusion: Our study introduces a feasible multimodal electromagnetic navigation platform that combines intraoperative ultrasound with preoperative segmented CT and PET imaging data for EBUS lymph node staging examinations. This innovative approach holds promise for enhancing the accuracy and effectiveness of EBUS procedures. [ABSTRACT FROM AUTHOR]

Introduction: Insulinoma is a rare disease, however the most common cause of hypoglycemia due to excess insulin secretion. Diagnosis and localization can be challenging. This study evaluated the clinical features, diagnostic workup, management, and outcomes of patients with insulinoma. Methods: The records of 13 patients with insulinoma who were followed up at İstanbul University, İstanbul Faculty of Medicine were retrospectively reviewed. Results: The mean age of the 13 patients (female/male: 11/2) was 43.9±12.5 years at diagnosis. The mean tumor diameter was 14.3±6.7 mm and localized at the head in 30.8%, at the tail and/or body in 61.6%, and at both the head and body in 7.6% of patients. The tumor was correctly localized by magnetic resonance imaging in 10/13 patients, 68Ga DOTATATE positron emission tomography/ computed tomography in 4/8, endoscopic ultrasound in 3/7, and selective arterial calcium stimulation in 4/4 patients. Eleven patients were operated. Distal pancreatectomy was performed in 4 patients, distal pancreatectomy plus splenectomy in 3, and enucleation in 4 of the patients. The median follow-up duration was 4 years. In 8 patients, cure was achieved with surgery alone. Somatostatin receptor analog (SSRA) treatment was initiated in 2 cases and one of whom developed lymph node metastasis 2.5 years after surgery under SSRA treatment and she was reoperated. These patients had stable disease at the last visit. Conclusion: Insulinomas are usually small tumors, but they can cause severe symptoms. A multidisciplinary approach is required for diagnosis and treatment. In some patients, different imaging modalities may be necessary for tumor localization. [ABSTRACT FROM AUTHOR]

A combined positron emission particle tracking (PEPT) and X-ray computed tomography (CT) technique is presented, and its utility is demonstrated through investigation of flow in a pipe with twisted tape swirl insert with varying flow conditions (diameter-based Reynolds numbers 16,300–63,300). A description of this technique is given, as well as data handling practices used to relate geometric information captured by CT to fluid flow data gathered via PEPT. It is found that the CT component is readily capable of capturing the stainless steel insert geometry in this present system, but the use of combined plastic and metal materials leads to artifacts in imaging of the plastic surface. Nonetheless, CT data are related to PEPT flow measurements, and average velocity fields are calculated via a pseudo-framing and interpolation scheme and used to visualize and interrogate key flow phenomena within the system. Radial velocity profiles of the mean flow characteristics are seen to collapse to a nearly common form across all flow conditions considered. Helical vortices are seen propagating through the flow field, generated by bypass flow around the gap between the insert and pipe wall, with additional coherent secondary flow structures seen in the higher Reynolds number cases. These findings enhance the understanding of the mixing mechanisms in these swirl flows and encourage the continued development of PEPT-CT methodologies for 3D flow measurements in optically inaccessible systems. [ABSTRACT FROM AUTHOR]

Objective(s): This study aimed to examine the influence of changes in CT values on PET images, specifically focusing on errors in CT-based attenuation correction and scatter coincidence correction (CTAC/SC) caused by gastrointestinal gas. Furthermore, it aimed to demonstrate the effectiveness of time-of-flight (TOF) PET in reducing CTAC/SC errors. Methods: PET images were reconstructed using multiple CT images with varying CT values. The study then compared the fluctuations in pixel values of the PET images corresponding to the different CT values utilized for CTAC/SC between non-TOF and TOF acquisitions. Results: PET pixel values fluctuated with changes in CT values. In the phantom study, TOF showed a significantly smaller change in PET pixel value of 1.00±0.27 kBq/mL compared to 3.72±1.33 kBq/mL in the non-TOF at sites with a CT change of +1000 HU. In the patient study, a linear regression analysis was performed to determine the effect of changes in CT values due to gastrointestinal gas migration on standard uptake value (SUV).The results showed that the TOF group had a lower ratio of change in SUV to change in CT values compared to the non-TOF group. These findings revealed that PET pixel values exhibited fluctuations in response to changes in CT values, and TOF-PET effectively mitigated CTAC/SC errors arising from gastrointestinal gas. Conclusions: TOF-PET has the potential to reduce the occurrence of suspicious accumulation. [ABSTRACT FROM AUTHOR]

Movement disorders are chronic neurological syndromes with both treatable and non-treatable causes. The top causes of movement disorders are Parkinson's disease and related disorders. Functional imaging investigations with Single Photon Emission Computed Tomography (SPECT) and Positron Emission Tomography (PET) images play vital roles in diagnosis and differential diagnosis to guide disease management. Since there have been new advanced imaging technologies and radiopharmaceuticals development, there is a need for up-to-date consensus guidelines. Thus, the Nuclear Medicine Society of Thailand, the Neurological Society of Thailand, and the Thai Medical Physicist Society collaborated to establish the guideline for Nuclear Medicine investigations in movement disorder for practical use in patient care. We have extensively reviewed the current practice guidelines from other related societies and good quality papers as well as our own experience in Nuclear Medicine practice in movement disorders. We also adjust for the most suitability for application in Thailand and other developing countries. [ABSTRACT FROM AUTHOR]

Introduction. Inflammation is known to be related to the development, spread, prognosis, and treatment response in cancer patients. Our study aimed to evaluate the correlation between inflammation indices and positron emission tomography-computed tomography (PET/CT) parameters and investigate their relationship with progression-free survival (PFS) and overall survival (OS) in patients diagnosed with stage-IV non-small cell lung cancer (NSCLC). Material and methods. Demographic, clinicopathological, laboratory, and PET/CT data of 179 patients diagnosed with stage-IV NSCLC who presented to the Oncology Department of Dicle University, Faculty of Medicine between 2010-2020 were retrieved from patient files and the hospital database system. Results. The median age at diagnosis was 64 (27-87) years. All patients included in the study had NSCLC: 72.6% had adenocarcinoma, 21.2% had squamous cell carcinoma, and 6.1% had other histological types. Of the 78 patients who were subjected to molecular analysis, 26 (33.3%) were EGFR-mutation positive. During the 10-month median follow-up, median first-line PFS was 6 months (95% CI 5.00-6.99), and median OS was 10 months (95% CI 7.8-12.1). The multivariate analysis performed for first-line PFS determined hemoglobin (HR = 1.01; 95% CI 1.003-1.02; p = 0.005) and PET total lesion glycolysis (TLG) (HR = 1.002; 95% CI 1.001-1.003; p = 0.003) values as independent prognostic factors. The multivariate analysis for OS determined positive EGFR mutation status (HR = 0.385; 95% CI 0.213-0.696; p = 0,014) and performance status (HR = 1.88; 95% CI 1.092-3.238; p = 0,008) as independent prognostic factors. Conclusions. Our study determined the hemoglobin level and PET TLG from PET/CT parameters to be independent prognostic factors for PFS, and performance status and EGFR mutation positivity to be independent prognostic factors for OS. [ABSTRACT FROM AUTHOR]

Abstract Background PET/CT is currently the gold standard for lung cancer staging, and it is also used to identify distant and nodal metastases. High-resolution MRI can also be used to diagnose and provide morphological details about lung cancer. Standardized uptake value ‘SUV’ calculated from PET/CT gives information about tumor behavior where the SUV reflects metabolic tumor activity. Apparent diffusion coefficient ‘ADC’ calculated from DW-MRI is a quantitative imaging marker aiming to assess tumor cellularity which reflects tumor behavior. The study aimed to correlate ADC assessed by DW-MRI and metabolic activity determined by SUV max in PET/CT in local and nodal staging of newly diagnosed NSCLC. Results Our study involved twenty-one patients who were pathologically proven to be NSCLC, 19 males (90.5%) and 2 females (9.5%), with a median age of 61 years (ranging from 37 to 84 years). Among all NSCLC primary mass lesions, we observed a statistically significant inverse correlation between SUV max achieved from PET/CT and ADC max, ADC mean, and ADC min calculated from DW-MR (r = − 0.509 and p = 0.019, r = − 0.472 and p = 0.031 and r = − 0.434 and p = 0.049 for correlation between SUV max of PET/CT and ADC max, ADC mean and ADC min of DW-MR, respectively). Additionally, we observed another statistically significant inverse correlation between SUV max achieved from PET/CT and ADC max, ADC mean, and ADC min calculated from DW-MR in NSCLC mediastinal lymph nodes (r = − 0.699 and p = 0.011, r = − 0.58 and p = 0.048 and r = − 0.629 and p = 0.028 for correlation between SUV max of PET/CT and ADC max, ADC mean and ADC min of DW-MR, respectively). Conclusions ADC values calculated from DW-MRI might act as a new prognostic tool owing to its significant inverse correlation with SUV max achieved from PET/CT in NSCLC primary mass lesions as well as mediastinal lymph nodes.

The background energy spectrum of lutetium oxyorthosilicate/lutetium yttrium oxyorthosilicate scintillation crystals used in positron emission imaging systems is a research topic of great interest owing to the possibility of using its structure to perform detector calibration and quality control without the need of using external radiation sources. In this paper, the background energy spectra for crystals of different sizes and geometries, including cuboids, frusta, cylinders, tetrahedra, and spheres, have been computed. This was done using a previously developed analytical model that requires the photon absorption probabilities for each shape, obtained through simulations using the PENELOPE Monte Carlo code. It has been found that crystals of different geometries, but with the same volume-to-surface area ratio, give rise to very similar background energy spectra, simplifying its computation. In addition, simple ray tracing simulations were performed, and a robust geometrical model was devised to investigate the geometrical grounds of this practical and compelling result. [ABSTRACT FROM AUTHOR]

Background: PET/CT is currently the gold standard for lung cancer staging, and it is also used to identify distant and nodal metastases. High-resolution MRI can also be used to diagnose and provide morphological details about lung cancer. Standardized uptake value 'SUV' calculated from PET/CT gives information about tumor behavior where the SUV reflects metabolic tumor activity. Apparent diffusion coefficient 'ADC' calculated from DW-MRI is a quantitative imaging marker aiming to assess tumor cellularity which reflects tumor behavior. The study aimed to correlate ADC assessed by DW-MRI and metabolic activity determined by SUV max in PET/CT in local and nodal staging of newly diagnosed NSCLC. Results: Our study involved twenty-one patients who were pathologically proven to be NSCLC, 19 males (90.5%) and 2 females (9.5%), with a median age of 61 years (ranging from 37 to 84 years). Among all NSCLC primary mass lesions, we observed a statistically significant inverse correlation between SUV max achieved from PET/CT and ADC max, ADC mean, and ADC min calculated from DW-MR (r = − 0.509 and p = 0.019, r = − 0.472 and p = 0.031 and r = − 0.434 and p = 0.049 for correlation between SUV max of PET/CT and ADC max, ADC mean and ADC min of DW-MR, respectively). Additionally, we observed another statistically significant inverse correlation between SUV max achieved from PET/CT and ADC max, ADC mean, and ADC min calculated from DW-MR in NSCLC mediastinal lymph nodes (r = − 0.699 and p = 0.011, r = − 0.58 and p = 0.048 and r = − 0.629 and p = 0.028 for correlation between SUV max of PET/CT and ADC max, ADC mean and ADC min of DW-MR, respectively). Conclusions: ADC values calculated from DW-MRI might act as a new prognostic tool owing to its significant inverse correlation with SUV max achieved from PET/CT in NSCLC primary mass lesions as well as mediastinal lymph nodes. [ABSTRACT FROM AUTHOR]

Use of prostate-specific membrane antigen positron emission tomography to determine disease extent provides a novel method for risk stratification for patients with nonmetastatic castration-resistant prostate cancer and may contribute to future risk-adapted treatment algorithms. Previously, we demonstrated that prostate-specific membrane antigen positron emission tomography (PSMA-PET) revealed distant metastases in 109/200 patients (39% distant nodes, 24% bone, and 6% visceral organ) with nonmetastatic castration-resistant prostate cancer (nmCRPC) and high-risk features (International Society of Urological Pathology score ≥4 and/or prostate-specific antigen doubling time ≤10 mo) without metastases by conventional imaging. However, the impact of disease extent determined by PSMA-PET on patient outcomes is unknown. We followed these 200 patients for a median of 43 mo after PSMA-PET and retrospectively assessed the association between patient characteristics, PSMA-PET findings, treatment management, and outcomes using a Kaplan-Meier model and Cox multivariable regressions. Among assessed disease characteristics, polymetastatic disease (five or more distant lesions on PET) was independently associated with shorter overall survival (OS; median 61 mo vs not reached; hazard ratio [95% confidence interval], 1.81 [1.00–3.27]; p = 0.050) and time to new metastases (median 38 vs 60 mo; 1.80 [1.10–2.96]; p = 0.019), and initial pN1 status with shorter OS (55 mo vs not reached; 1.94 [1.12–3.37]; p = 0.019). Following PSMA-PET, locoregional salvage therapies were used most commonly in no/local disease (58%), and androgen receptor signaling inhibitors were used in distant metastatic disease (51%). PSMA-PET provides additional risk stratification for patients with nmCRPC. Polymetastatic disease (five or more distant lesions) is associated with worse outcomes. A novel sensitive imaging technology, called prostate-specific membrane antigen positron emission tomography (PSMA-PET), allows doctors to detect the spread of prostate cancer, known as distant metastases, earlier and more accurately than in the past. In our study, PSMA-PET detected none to many metastases in patients who were considered free of distant metastasis by conventional imaging. These findings predicted outcomes and were used to select appropriate treatment. [ABSTRACT FROM AUTHOR]

11C methionine (11C-MET) is increasingly being used in addition to contrast-enhanced MRI to plan for radiotherapy of patients with glioblastomas. This study aimed to assess the recurrence pattern quantitatively. Glioblastoma patients undergoing 11C-MET PET examination before primary radiotherapy from 2018 to 2023 were included in the analysis. A clinical target volume was manually created and fused with MRI-based gross tumor volumes and MET PET-based biological target volume. The recurrence was noted as an area of contrast enhancement on the first MRI scan, which showed progression. The recurrent tumor was identified on the radiological MR images in terms of recurrent tumor volume, and recurrences were classified as central, in-field, marginal, or ex-field tumors. We then compared the MET-PET-defined biological target volume with the MRI-defined recurrent tumor volume regarding spatial overlap (the Dice coefficient) and the Hausdorff distance. Most recurrences occurred locally within the primary tumor area (64.8%). The mean Hausdorff distance was 39.4 mm (SD 32.25), and the mean Dice coefficient was 0.30 (SD 0.22). In patients with glioblastoma, the analysis of the recurrence pattern has been mainly based on FET-PET. Our study confirms that the recurrence pattern after gross tumor volume-based treatment contoured by MET-PET is consistent with the FET-PET-based treatment described in the literature. [ABSTRACT FROM AUTHOR]

Background: This study addresses the technical gap between clinical radiation therapy (RT) and preclinical small‐animal RT, hindering the comprehensive validation of innovative clinical RT approaches in small‐animal models of cancer and the translation of preclinical RT studies into clinical practices. Purpose: The main aim was to explore the feasibility of biologically guided RT implemented within a small‐animal radiation therapy (SART) platform, with integrated quad‐modal on‐board positron emission tomography (PET), single‐photon emission computed tomography, photon‐counting spectral CT, and cone‐beam CT (CBCT) imaging, in a Monte Carlo model as a proof‐of‐concept. Methods: We developed a SART workflow employing quad‐modal imaging guidance, integrating multimodal image‐guided RT and emission‐guided RT (EGRT). The EGRT algorithm was outlined using positron signals from a PET radiotracer, enabling near real‐time adjustments to radiation treatment beams for precise targeting in the presence of a 2‐mm setup error. Molecular image‐guided RT, incorporating a dose escalation/de‐escalation scheme, was demonstrated using a simulated phantom with a dose painting plan. The plan involved delivering a low dose to the CBCT‐delineated planning target volume (PTV) and a high dose boosted to the highly active biological target volume (hBTV) identified by the 18F‐PET image. Additionally, the Bayesian eigentissue decomposition method illustrated the quantitative decomposition of radiotherapy‐related parameters, specifically iodine uptake fraction and virtual noncontrast (VNC) electron density, using a simulated phantom with Kidney1 and Liver2 inserts mixed with an iodine contrast agent at electron fractions of 0.01–0.02. Results: EGRT simulations generated over 4,000 beamlet responses in dose slice deliveries and illustrated superior dose coverage and distribution with significantly lower doses delivered to normal tissues, even with a 2‐mm setup error introduced, demonstrating the robustness of the novel EGRT scheme compared to conventional image‐guided RT. In the dose‐painting plan, doubling the dose to the hBTV while maintaining a low dose for the PTV resulted in an organ‐at‐risk (OAR) dose comparable to the low‐dose treatment for the PTV alone. Furthermore, the decomposition of radiotherapy‐related parameters in Kidney1 and Liver2 inserts, including iodine uptake fractions and VNC electron densities, exhibited average relative errors of less than 1.0% and 2.5%, respectively. Conclusions: The results demonstrated the successful implementation of biologically guided RT within the proposed quad‐model image‐guided SART platform, with potential applications in preclinical RT and adaptive RT studies. [ABSTRACT FROM AUTHOR]

The role that inhaled particulate matter plays in the development of post-deployment lung disease among US service members deployed to Southwest Asia during the Global War on Terrorism has been difficult to define. There is a persistent gap in data addressing the relationship between relatively short-term (months to a few years) exposures to high levels of particulate matter during deployment and the subsequent development of adverse pulmonary outcomes. Surgical lung biopsies from deployed service members and veterans (DSMs) and non-deployed service members and veterans (NDSMs) who develop lung diseases can be analyzed to potentially identify residual deployment-specific particles and develop associations with pulmonary pathological diagnoses. We examined 52 surgical lung biopsies from 25 DSMs and 27 NDSMs using field emission scanning electron microscopy (FE-SEM) with energy dispersive x-ray spectroscopy (EDS) to identify any between-group differences in the number and composition of retained inorganic particles, then compared the particle analysis results with the original histopathologic diagnoses. We recorded a higher number of total particles in biopsies from DSMs than from NDSMs, and this difference was mainly accounted for by geologic clays (illite, kaolinite), feldspars, quartz/silica, and titanium-rich silicate mixtures. Biopsies from DSMs deployed to other Southwest Asia regions (SWA-Other) had higher particle counts than those from DSMs primarily deployed to Iraq or Afghanistan, due mainly to illite. Distinct deployment-specific particles were not identified. Particles did not qualitatively associate with country of deployment. The individual diagnoses of the DSMs and NDSMs were not associated with elevated levels of total particles, metals, cerium oxide, or titanium dioxide particles. These results support the examination of particle-related lung disease in DSMs in the context of comparison groups, such as NDSMs, to assist in determining the strength of associations between specific pulmonary pathology diagnoses and deployment-specific inorganic particulate matter exposure. [ABSTRACT FROM AUTHOR]

Introduction: A newly developed clinical organ-targeted Positron Emission Tomography (PET) system (also known as Radialis PET) is tested with a set of standardized and custom tests previously used to evaluate the performance of Positron Emission Mammography (PEM) systems. Methods: Imaging characteristics impacting standardized uptake value (SUV) and detectability of small lesions, namely spatial resolution, linearity, uniformity, and recovery coefficients, are evaluated. Results: In-plane spatial resolution was measured as 2.3 mm ± 0.1 mm, spatial accuracy was 0.1 mm, and uniformity measured with flood field and NEMA NU-4 phantom was 11.7% and 8.3% respectively. Selected clinical images are provided as reference to the imaging capabilities under different clinical conditions such as reduced activity of 2-[fluorine-18]-fluoro-2-deoxy-D-glucose (18F-FDG) and time-delayed acquisitions. SUV measurements were performed for selected clinical acquisitions to demonstrate a capability for quantitative image assessment of different types of cancer including for invasive lobular carcinoma with comparatively low metabolic activity. Quantitative imaging performance assessment with phantoms demonstrates improved contrast recovery and spill-over ratio for this PET technology when compared to other commercial organ-dedicated PET systems with similar spatial resolution. Recovery coefficients were measured to be 0.21 for the 1 mm hot rod and up to 0.89 for the 5 mm hot rod of NEMA NU-4 Image Quality phantom. Discussion: Demonstrated ability to accurately reconstruct activity in tumors as small as 5 mm suggests that the Radialis PET technology may be well suited for emerging clinical applications such as image guided assessment of response to neoadjuvant systemic treatment (NST) in lesions smaller than 2 cm. Also, our results suggest that, while spatial resolution greatly influences the partial volume effect which degrades contrast recovery, optimized count rate performance and image reconstruction workflow may improve recovery coefficients for systems with comparable spatial resolution. We emphasize that recovery coefficient should be considered as a primary performance metric when a PET system is used for accurate lesion size or radiotracer uptake assessments. [ABSTRACT FROM AUTHOR]

Time‐of‐flight (TOF) technique, traditionally used in high energy physics (HEP) and positron emission tomography (PET), is now being explored for lower energy applications like computed tomography (CT). Regardless of the application, pushing the current boundaries in time resolution calls for novel technologies and materials exhibiting ultra‐fast time response. Semiconductor nanocrystals like cesium lead halide perovskites (CsPbBr3), benefiting from quantum confinement effects, feature ultra‐fast decay and, when combined with a suitable bulk scintillator following a heterostructure concept, can also provide the necessary stopping power. In this work, thin films of CsPbBr3 on top of BGO, LYSO:Ce, and GAGG:Ce,Mg wafers are fabricated to test their impact on the single crystal scintillator time resolution under soft X‐rays excitation (about 10 keV). It is demonstrated that the CsPbBr3 layer significantly improves the overall time resolution in all cases, achieving up to a tenfold improvement with BGO and GAGG:Ce,Mg. Under 511 keV γ‐rays, a proof‐of‐concept of the heterostructure design for TOF‐PET using CsPbBr3 thin film deposited on GAGG:Ce,Mg bulk crystal is successfully tested. Shared events depositing energy in both materials are identified, resulting in more than twofold improved coincidence time resolution: 118 ± 4 ps full‐width‐at‐half‐maximum (FWHM) compared to the 272 ± 8 ps of solely GAGG:Ce,Mg. [ABSTRACT FROM AUTHOR]

The synaptic hypothesis is an influential theory of the pathoetiology of schizophrenia (SCZ), which is supported by the finding that there is lower uptake of the synaptic terminal density marker [11C]UCB-J in patients with chronic SCZ than in control participants. However, it is unclear whether these differences are present early in the illness. To address this, we investigated [11C]UCB-J volume of distribution (V T) in antipsychotic-naïve/free patients with SCZ who were recruited from first-episode services compared with healthy volunteers. Forty-two volunteers (SCZ n = 21, healthy volunteers n = 21) underwent [11C]UCB-J positron emission tomography to index [11C]UCB-J V T and distribution volume ratio in the anterior cingulate, frontal, and dorsolateral prefrontal cortices; the temporal, parietal and occipital lobes; and the hippocampus, thalamus, and amygdala. Symptom severity was assessed in the SCZ group using the Positive and Negative Syndrome Scale. We found no significant effects of group on [11C]UCB-J V T or distribution volume ratio in most regions of interest (effect sizes from d = 0.0–0.7, p >.05), with two exceptions: we found lower distribution volume ratio in the temporal lobe (d = 0.7, uncorrected p <.05) and lower V T / f p in the anterior cingulate cortex in patients (d = 0.7, uncorrected p <.05). The Positive and Negative Syndrome Scale total score was negatively associated with [11C]UCB-J V T in the hippocampus in the SCZ group (r = −0.48, p =.03). These findings indicate that large differences in synaptic terminal density are not present early in SCZ, although there may be more subtle effects. When taken together with previous evidence of lower [11C]UCB-J V T in patients with chronic illness, this may indicate synaptic density changes during the course of SCZ. [ABSTRACT FROM AUTHOR]

Positron emission tomography (PET)-guided radiation therapy is a novel tracked dose delivery modality that uses real-time PET to guide radiation therapy beamlets. The BIOGUIDE-X study was performed with sequential cohorts of participants to (1) identify the fluorodeoxyglucose (FDG) dose for PET-guided therapy and (2) confirm that the emulated dose distribution was consistent with a physician-approved radiation therapy plan. This prospective study included participants with at least 1 FDG-avid targetable primary or metastatic tumor (2-5 cm) in the lung or bone. For cohort I, a modified 3 + 3 design was used to determine the FDG dose that would result in adequate signal for PET-guided therapy. For cohort II, PET imaging data were collected on the X1 system before the first and last fractions among patients undergoing conventional stereotactic body radiation therapy. PET-guided therapy dose distributions were modeled on the patient's computed tomography anatomy using the collected PET data at each fraction as input to an "emulated delivery" and compared with the physician-approved plan. Cohort I demonstrated adequate FDG activity in 6 of 6 evaluable participants (100.0%) with the first injected dose level of 15 mCi FDG. In cohort II, 4 patients with lung tumors and 5 with bone tumors were enrolled, and evaluable emulated delivery data points were collected for 17 treatment fractions. Sixteen of the 17 emulated deliveries resulted in dose distributions that were accurate with respect to the approved PET-guided therapy plan. The 17th data point was just below the 95% threshold for accuracy (dose-volume histogram score = 94.6%). All emulated fluences were physically deliverable. No toxicities were attributed to multiple FDG administrations. PET-guided therapy is a novel radiation therapy modality in which a radiolabeled tumor can act as its own fiducial for radiation therapy targeting. Emulated therapy dose distributions calculated from continuously acquired real-time PET data were accurate and machine-deliverable in tumors that were 2 to 5 cm in size with adequate FDG signal characteristics. [ABSTRACT FROM AUTHOR]

The β+-emitting radionuclide 86gY (t1/2 = 14.7 h) forms a matched-pair with the β--emitting therapeutic radionuclide 90Y (t1/2 = 2.7 d) for theranostic application in medicine. This approach demands a precise knowledge of the positron emission probability of the PET nuclide which was until recently rather uncertain for 86gY. In this work, an 86gY source of high radionuclidic purity was prepared and a direct measurement of the positron emission intensity per 100 decay of the parent (hereafter "positron emission intensity") was performed using high-resolution HPGe detector γ-ray spectroscopy. The electron capture intensity was also determined as an additional check by measuring the Kα and Kβ X-rays of energies 14.1 and 15.8 keV, respectively, using a low energy HPGe detector. From those measurements, normalized values of 27.2 ± 2.0% for β+-emission and 72.8 ± 2.0% for EC were obtained. These results are in excellent agreement with values recently reported in the literature based on a detailed decay scheme study.

Background: Tumour hypoxia is a recognised cause of radiotherapy treatment resistance in head and neck squamous cell carcinoma (HNSCC). Current positron emission tomography-based hypoxia imaging techniques are not routinely available in many centres. We investigated if an alternative technique called oxygen-enhanced magnetic resonance imaging (OE-MRI) could be performed in HNSCC. Methods: A volumetric OE-MRI protocol for dynamic T1 relaxation time mapping was implemented on 1.5-T clinical scanners. Participants were scanned breathing room air and during high-flow oxygen administration. Oxygen-induced changes in T1 times (ΔT1) and R2* rates (ΔR2*) were measured in malignant tissue and healthy organs. Unequal variance t-test was used. Patients were surveyed on their experience of the OE-MRI protocol. Results: Fifteen patients with HNSCC (median age 59 years, range 38 to 76) and 10 non-HNSCC subjects (median age 46.5 years, range 32 to 62) were scanned; the OE-MRI acquisition took less than 10 min and was well tolerated. Fifteen histologically confirmed primary tumours and 41 malignant nodal masses were identified. Median (range) of ΔT1 times and hypoxic fraction estimates for primary tumours were -3.5% (-7.0 to -0.3%) and 30.7% (6.5 to 78.6%) respectively. Radiotherapy-responsive and radiotherapy-resistant primary tumours had mean estimated hypoxic fractions of 36.8% (95% confidence interval [CI] 17.4 to 56.2%) and 59.0% (95% CI 44.6 to 73.3%), respectively (p = 0.111). Conclusions: We present a well-tolerated implementation of dynamic, volumetric OE-MRI of the head and neck region allowing discernment of differing oxygen responses within biopsy-confirmed HNSCC. Trial registration: ClinicalTrials.gov, NCT04724096. Registered on 26 January 2021. Relevance statement: MRI of tumour hypoxia in head and neck cancer using routine clinical equipment is feasible and well tolerated and allows estimates of tumour hypoxic fractions in less than ten minutes. Key points: • Oxygen-enhanced MRI (OE-MRI) can estimate tumour hypoxic fractions in ten-minute scanning. • OE-MRI may be incorporable into routine clinical tumour imaging. • OE-MRI has the potential to predict outcomes after radiotherapy treatment. [ABSTRACT FROM AUTHOR]

An experimental–theoretical methodology is developed to investigate the characteristics of turbulence in horizontal particle-liquid pipe flows. Using a discrete wavelet transform, the three-dimensional Lagrangian trajectories of the liquid phase experimentally determined by positron emission particle tracking are decomposed into their deterministic and stochastic sub-trajectories, which are then utilized to construct profiles of local fluctuating velocity components and turbulent kinetic energy. The results for a single-phase flow are independently validated using computational fluid dynamic simulation and the analysis parameters are fine-tuned using direct numerical simulation data from the literature. In a particle-liquid flow, the investigation explores the influence of various factors including particle size, density, and concentration on turbulence intensity. Remarkably, the results demonstrate significant effects of the particle size and density on liquid turbulence. The enhanced understanding gained regarding turbulence intensity helps to advance our fundamental interpretation of the dynamics of particle-liquid flows, thus potentially aiding the rational design of such complex flows and associated equipment. [ABSTRACT FROM AUTHOR]

Positron Emission Mammography (PEM) is a valuable molecular imaging technique for breast studies using pharmaceuticals labeled with positron emitters and dual-panel detectors. PEM scanners normally use large scintillation crystals coupled to sensitive photodetectors. Multiple interactions of the 511 keV annihilation photons in the crystals can result in event mispositioning leading to a negative impact in radiopharmaceutical uptake quantification. In this work, we report the study of crystal scatter effects of a large-area dual-panel PEM system designed with either monolithic or pixelated lutetium yttrium orthosilicate (LYSO) crystals using the Monte Carlo simulation platform GATE. The results show that only a relatively small fraction of coincidences (~20%) arise from events where both coincidence photons undergo single interactions (mostly through photoelectric absorption) in the crystals. Most of the coincidences are events where at least one of the annihilation photons undergoes a chain of Compton scatterings: approximately 79% end up in photoelectric absorption while the rest (<1%) escape the detector. Mean positioning errors, calculated as the distance between first hit and energy weighted (assigned) positions of interaction, were 1.70 mm and 1.92 mm for the monolithic and pixelated crystals, respectively. Reconstructed spatial resolution quantification with a miniDerenzo phantom and a list mode iterative reconstruction algorithm shows that, for both crystal types, 2 mm diameter hot rods were resolved, indicating a relatively small effect in spatial resolution. A drastic reduction in peak-to-valley ratios for the same hot-rod diameters was observed, up to a factor of 14 for the monolithic crystals and 7.5 for the pixelated ones. [ABSTRACT FROM AUTHOR]

Background: Positron Emission Tomography-Magnetic Resonance (PET-MR) scanners could improve ano-rectal radiotherapy planning through improved Gross Tumour Volume (GTV) delineation and enabling dose painting strategies using metabolic measurements. This requires accurate quantitative PET images acquired in the radiotherapy treatment position. Purpose: This study aimed to evaluate the impact on GTV delineation and metabolic parameter measurement of using novel Attenuation Correction (AC) maps that included the radiotherapy flat couch, coil bridge and anterior coil to see if they were necessary. Methods: Seventeen ano-rectal radiotherapy patients received a 18FFluoroDeoxyGlucose PET-MR scan in the radiotherapy position. PET images were reconstructed without (CTACstd) and with (CTACcba) the radiotherapy hardware included. Both AC maps used the same Computed Tomography image for patient AC. Semi-manual and threshold GTVs were delineated on both PET images, the volumes compared and the Dice coefficient calculated. Metabolic parameters:Standardized Uptake Values SUVmax,SUVmean and Total Lesion Glycolysis (TLG) were compared using paired t-tests with a Bonferroni corrected significance level of p = 0.05/8 = 0.006. Results: Differences in semi-manual GTV volumes between CTACcba and CTACstd were approaching statistical significance (difference -15.9%±1.6%, p = 0.007), with larger differences in low FDG-avid tumours (SUVmean < 8.5 gmL-1). The CTACcba and CTACstd GTVs were concordant with Dice coef- ficients 0.89 ± 0.01 (manual) and 0.98 ± 0.00 (threshold).Metabolic parameters were significantly different, with SUVmax, SUVmean and TLG differences of -11.5% ±0.3% (p < 0.001), -11.6%±0.3% (p < 0.001) and -13.7% ±0.6% (p = 0.003) respectively. The TLG difference resulted in 1/8 rectal cancer patients changing prognosis group,based on literature TLG cut-offs,when using CTACcba rather than CTACstd. Conclusions: This study suggests that using AC maps with the radiotherapy hardware included is feasible for patient imaging. The impact on tumour delineation was mixed and needs to be evaluated in larger cohorts. However using AC of the radiotherapy hardware is important for situations where accurate metabolic measurements are required, such as dose painting and treatment prognostication. [ABSTRACT FROM AUTHOR]

Prostate cancer typically follows a characteristic pattern of metastatic spread to the pelvic lymph nodes and bone. Atypical patterns of metastasis are rare but have been documented. In African men, this disease tends to follow a more aggressive course, with the possibility of an atypical site of metastatic spread. We present a case of a 58-year- old African male with metastatic castrate-resistant prostate cancer who presented with both typical and atypical patterns of metastatic disease detected by a fluorine 18 prostate-specific membrane antigen positron emission tomography/ computed tomography scan. This patient also had a good response to radioligand therapy. [ABSTRACT FROM AUTHOR]

The present work demonstrates the biosynthesis of silver nanoparticles (AgNPs) using Coffea arabica leaf extract. The AgNPs prepared by green route from C. arabica leaf were characterized through UV–visible, X-ray diffraction, transmission electron microscopy and energy-dispersive electron spectroscopy. Later, the prepared NPs were conjugated with cysteamine–folic acid and utilized as a contrast medium for in vitro targeted imaging of folic acid receptor-expressing malignant cells by computerized tomography (CT). At 80 kVp, the targeted cells exhibited CT values which were two times greater than that of the non-targeted cells. The results were compared with the folic acid-negative cell lines as well as the effective inhibition of folic acid receptor using free folic acid substrate. The outcome of the present study suggests that the fabricated cysteamine–folic acid-conjugated silver nanoparticles could be utilized as a potential contrast agent for molecular CT imaging. This information can be taken into consideration for applying AgNPs in enhancing radiation dose where nanoparticles containing greater X-ray attenuation were applied. [ABSTRACT FROM AUTHOR]

Objective: 68Ga has a half-life of 68 minutes, with 89% of its decay is through positron emission. It is available from generator systems and possesses suitable property for labeling radioligands. These aspects make 68Ga a promising tracer for positron emission tomography (PET) imaging. This study aims to develop the purification process of the 68Ga eluates from 68Ge/68Ga generator after its recommended shelf-life and ensuring the quality through the radiolabeling process. Materials and Methods: In this study, we explored the development of a purification method for 68Ga eluted from a 68Ge/68Ga generator before radiolabeling was investigated. Cation and anion exchange chromatography techniques were combined to remove trace amounts of competing metal ion impurities. Post-purification, the eluate’s metal contents were analyzed using inductively coupled plasma atomic emission spectroscopy (ICP-AES). Breakthrough of 68Ge was measured using a multi-channel analyzer (MCA) spectrometer with high-purity germanium (HPGe) radiation detectors. Additionally, the radiochemical purity of 68Ga-NOTA-RGD was analyzed by high-performance liquid chromatography (HPLC). Results: Metal impurities including Fe(II), Zn(II) and Al(III) were reduced by 61%, 38% and 44% respectively. The 68Ge breakthrough was approximately ~10–3%. The labeling efficiency with NOTA-RGD, a tracer for angiogenesis imaging, resulted in an average yield of 68Ga-NOTA-RGD (not corrected for decay) of around 50%, with a radiochemical purity by HPLC of approximately 98%–99%. Conclusion: Cation exchange in combination with anion exchange chromatography was thus proven to be an efficient method for purification of the 68Ga eluate from a 68Ge/68Ga generator prior to labeling the 68Ga PET radiotracer. [ABSTRACT FROM AUTHOR]

Objective: The diagnosis of neurosarcoidosis (NS) remains challenging due to the difficulty to obtain central nervous system (CNS) biopsies. Various diagnostic parameters are considered for the definition of possible, probable and definite NS. Magnetic resonance imaging (MRI) is the imaging gold standard and considered in diagnostic criteria. Fluorodeoxyglucose positron emission (18F-FDG PET) is sometimes performed additionally to identify possible systemic biopsy targets. However, at present, its findings are not incorporated into the diagnostic criteria for neurosarcoidosis (NS). Methods: We conducted a single center retrospective search for the period 2020–2022, for patients with neurological symptoms in a diagnostic context of suspected NS who underwent MRI and additional 18F-FDG PET scans to identify potential hypermetabolism in the CNS and biopsy targets. Results: We identified three cases of NS, where Gadolinium-enhanced MRI scans did not show abnormalities while 18F-FDG PET revealed hypermetabolic lesions in areas of the CNS. Additional MRI scans were still inconclusive for structural changes. We diagnosed a "probable" NS in all cases with histopathological confirmation of systemic sarcoidosis which led to an intensified therapy regime. Discussion: 18F-FDG PET is an early indicator for metabolic changes. It appears to be a useful add-on to improve accuracy of diagnostic criteria in suspected NS without MRI findings. [ABSTRACT FROM AUTHOR]

Because of their many advantages, such as simplicity of handling, affordability, and environmental friendliness, green magnetic nanoparticles (GMNPs) are currently receiving more attention than prevailing magnetic nanoparticles (MNPs). The synthesis and application of GMNPs inspired by biological systems are encouraged by rising ecological consciousness and stringent environmental restrictions and also deal with in detail in this manuscript. The current report presents the biological and environmental uses of GMNPs in-depth. Numerous biomedical applications, including imaging and diagnosis, cancer therapy, immunoassay, genetic engineering, and supported enzymes (proteins and peptides), among others, successfully use GMNPs. The GMNPs would be coupled with tiny sensors, microsystems, and microfluidics modules to boost the signal sensitivity for the identification of environmental contaminants, diseases, poisons, drugs, and trace biomarkers from clinical, environmental, and dietary examples. The GMNPs were essential elements in gene delivery and gene therapy initiatives, among other genetic engineering endeavors. They have also been extensively used for environmental applications such as wastewater treatment, organic pollutants decontamination, electrochemical sensing, industrial and radioactive wastes treatment, pollutant adsorption and removal etc. The use of GMNPs, particularly biosynthesized MNPs, is also believed to be more cost-effective than the majority of regularly used traditional MNPs. In addition, Green magnetic nanoparticles applied as supported enzymes, proteins and peptides catalyst, positron emission tomography, computed tomography, magnetic resonance imaging, theranostics, thermo-chemotherapy, electrochemical immunoassay and efficient detection of coronavirus is a significant issue in modern analytical chemistry and other fields. The opportunities of using GMNPs in the place of traditional MNPs have also been proposed. [ABSTRACT FROM AUTHOR]

Introduction: Alzheimer's disease (AD), the most common form of dementia, is characterized by progressive cognitive decline. To address this, we conducted a randomized, double-blinded, sham-controlled study to investigate the therapeutic potential of transcranial direct current stimulation (tDCS) on patients with amyloid positron emission tomography (PET)- positive AD. Methods: Participants already undergoing pharmacological treatment and testing positive for amyloid PET were divided into Active-tDCS (n = 8) and Sham-tDCS (n = 8) groups. For 12 weeks, participants or their caregivers administered daily bi-frontal tDCS (YMS-201B+, Ybrain Inc., Seongnam, Korea) at home (2 mA, 30 min). Pre- and post-intervention assessments included neuropsychological tests and blood sample measurements for oligomerized beta-amyloid. Results: The Active-tDCS group demonstrated significant improvements in cognitive domains such as language abilities, verbal memory, and attention span and in frontal lobe functions compared to the Sham-tDCS group. Furthermore, the Active-tDCS group showed a marked reduction in postintervention plasma Aβ oligomerization tendency level, suggesting changes in pivotal AD-associated biomarkers. Discussion: Our results emphasize the potential therapeutic benefits of tDCS for mild AD patients with amyloid PET positivity and stress the urgency for broader research, considering the global challenges of dementia and the need to pursue innovative therapeutic strategies. [ABSTRACT FROM AUTHOR]

Objective(s): Breast carcinoma is the most common type of cancer in females. This study aims to compare fluorine-18-fluorodeoxyglucose (18F-FDG) uptake pattern and apparent diffusion coefficient (ADC) value for the detection of the primary tumour and axillary metastases of invasive ductal breast carcinoma. Methods: This study included 40 breast carcinoma lesions taken from 39 patients. After staging by positron emission tomography-computed tomography (PET/CT) and diffusion-weighted magnetic resonance imaging (MRI), breast surgery with axillary lymph node dissection or sentinel lymph node biopsy was performed. Results: Primary lesion detection rate for PET/CT and diffusion-weighted MRI was high with 39 of 40 lesions (97.5%). The sensitivity and specificity for the detection of metastatic lymph nodes in axilla were 40.9%, 88.9%, with 18F-FDG PET/CT scans and 40.9%, 83.3%, for dw-MRI, respectively. No significant correlation was detected between ADC and SUVmax or SUVmax ratios. Estrogen receptor (p=0.007) and progesterone receptor (p=0.036) positive patients had lower ADC values. Tumour SUVmax was lower in T1 than T2 tumour size (p=0.027) and progesterone receptor-positive patients (p=0.029). Tumour/background SUVmax was lower in progesterone receptor-positive patients (p=0.004). Tumour/liver SUVmax was higher in grade III patients (p=0.035) and progesterone receptor negative status (p=0.043). Conclusions: This study confirmed the high detection rate of breast carcinoma in both modalities. They have same sensitivity for the detection of axillary lymph node metastases, whereas the PET/CT scan had higher specificity. Furthermore, ADC, SUVmax and SUVmax ratios showed some statistical significance among the patient groups according to different pathological parameters. [ABSTRACT FROM AUTHOR]

In order to support or refute the clinical suspicion of cranial giant cell arteritis (GCA), a supplemental imaging modality is often required. High-resolution black blood Magnetic Resonance Imaging (BB MRI) techniques with contrast enhancement can visualize artery wall inflammation in GCA. We compared findings on BB MRI without contrast enhancement with findings on 2-deoxy-2-[18F]fluoro-D-glucose positron emission tomography/low-dose computed tomography (2-[18F]FDG PET/CT) in ten patients suspected of having GCA and in five control subjects who had a 2-[18F]FDG PET/CT performed as a routine control for malignant melanoma. BB MRI was consistent with 2-[18F]FDG PET/CT in 10 out of 10 cases in the group with suspected GCA. In four out of five cases in the control group, the BB MRI was consistent with 2-[18F]FDG PET/CT. In this small population, BB MRI without contrast enhancement shows promising performance in the diagnosis of GCA, and might be an applicable imaging modality in patients. [ABSTRACT FROM AUTHOR]

Positron Emission Particle Tracking (PEPT) is a radioactive tracer-based approach to studying dynamic physical processes and multiphase flows. Short-lived positron-emitting isotopes are loaded onto suitable substrates used as tracer particle flow followers in physical and engineering-relevant systems. Coincident photons from electron-positron annihilation are detected using large arrays of pixelated scintillators, with the reconstructed photon trajectories collectively used to determine tracer particle dynamics. We have developed indirect radiochemical, and direct physical activation, techniques for producing tracer particles for such studies, and we report on the current state of the art with focus on the direct approach with high-energy alpha-particle beams. The 16O(α,x)18F reactions have been explored as viable candidates in producing the pure positron emitter 18F from natural 16O-bearing targets. Silicon dioxide (SiO2) glass spheres of diameters of 5 to 10 mm were irradiated in a 100-MeV alpha-particle beam of around 800-nA current for approximately 2 h. Radioisotope activation yields were characterized by half-life measurements and gamma-ray spectroscopy, with the highest yield being 18F (<2.5 mCi). Contaminants from other reaction channels were observed and characterized, including the positron emitter 43Sc and negative beta emitter 24Na, produced from alpha and neutron activation of contaminant species in the target material, respectively. The activation technique is shown to be a reasonable candidate to complement and enhance existing tracer particle production techniques for PEPT and other radiotracer-based studies. [ABSTRACT FROM AUTHOR]