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Early identification of patients with diffuse large B-cell lymphoma (DLBCL) who are likely to experience disease recurrence or refractory disease after rituximab plus cyclophosphamide, doxorubicin, vincristine, and prednisone (R-CHOP) would be useful for improving risk-adapted treatment strategies. We aimed to assess the prognostic value of

Variations in HER2 expression between the primary tumor and metastases may contribute to drug resistance in HER2-positive metastatic esophagogastric cancer (mEGC).

Reliable biomarkers for neuroendocrine tumor (NET) management during peptide receptor radionuclide therapy (PRRT) are lacking. We validated the role of two circulating biomarkers, the PRRT-predictive-quotient (PPQ) as a predictive marker for response and NETest as a monitoring biomarker. Furthermore, we evaluated whether tissue-based genetic alterations were effective in predicting progression-free survival (PFS).

From the Newsline Editor: The Highlights Lecture, presented at the closing session of each SNMMI Annual Meeting, was originated and presented for more than 30 years by Henry N. Wagner, Jr., MD. Beginning in 2010, the duties of summarizing selected significant presentations at the meeting were divided annually among 4 distinguished nuclear and molecular medicine subject matter experts. Each year Newsline publishes these lectures and selected images. The 2021 Highlights Lectures were delivered on June 15 as part of the SNMMI Virtual Annual Meeting. In this issue we feature the second part of the lecture by Heiko Schöder, MD, MBA, chief of the Molecular Imaging and Therapy Service at Memorial Sloan Kettering Cancer Center (New York, NY) and a professor of radiology at the Weill Medical College of Cornell University (New York, NY), who spoke on oncology and therapy highlights from the meeting. The first part of the lecture appeared in the October issue of Newsline. Note that in the following presentation summary, numerals in brackets represent abstract numbers as published in The Journal of Nuclear Medicine (2021;62[suppl 1]).

Consensus about a standard segmentation method to derive metabolic tumor volume (MTV) in classical Hodgkin lymphoma (cHL) is lacking, and it is unknown how different segmentation methods influence quantitative PET features. Therefore, we aimed to evaluate the delineation and completeness of lesion selection and the need for manual adaptation with different segmentation methods, and to assess the influence of segmentation methods on the prognostic value of MTV, intensity, and dissemination radiomics features in cHL patients. Methods: We analyzed a total of 105 (18)F-FDG PET/CT scans from patients with newly diagnosed (n = 35) and relapsed/refractory (n = 70) cHL with 6 segmentation methods: 2 fixed thresholds on SUV4.0 and SUV2.5, 2 relative methods of 41% of SUV(max) (41max) and a contrast-corrected 50% of SUV(peak) (A50P), and 2 combination majority vote (MV) methods (MV2, MV3). Segmentation quality was assessed by 2 reviewers on the basis of predefined quality criteria: completeness of selection, the need for manual adaptation, and delineation of lesion borders. Correlations and prognostic performance of resulting radiomics features were compared among the methods. Results: SUV4.0 required the least manual adaptation but tended to underestimate MTV and often missed small lesions with low (18)F-FDG uptake. SUV2.5 most frequently included all lesions but required minor manual adaptations and generally overestimated MTV. In contrast, few lesions were missed when using 41max, A50P, MV2, and MV3, but these segmentation methods required extensive manual adaptation and overestimated MTV in most cases. MTV and dissemination features significantly differed among the methods. However, correlations among methods were high for MTV and most intensity and dissemination features. There were no significant differences in prognostic performance for all features among the methods. Conclusion: A high correlation existed between MTV, intensity, and most dissemination features derived with the different segmentation methods, and the prognostic performance is similar. Despite frequently missing small lesions with low (18)F-FDG avidity, segmentation with a fixed threshold of SUV4.0 required the least manual adaptation, which is critical for future research and implementation in clinical practice. However, the importance of small, low (18)F-FDG–avidity lesions should be addressed in a larger cohort of cHL patients.

In 2013, the journal Science named cancer immunotherapy as the “breakthrough of the year” based on targeted approaches using chimeric antigen receptor (CAR) T-cells. CD19-specific CAR T-cell therapy has revolutionized the treatment landscape for patients with relapsed B-cell acute lymphocytic

> See the associated article on page [480][1]. The report for an oncologic PET/CT scan is the primary method by which the physician interpreting the scan communicates with the referring physician and health-care team. The content of this report provides information on disease extent, biologic

Trastuzumab with chemotherapy improves clinical outcomes in patients with human epidermal growth factor receptor 2 (HER2)–positive esophagogastric adenocarcinoma (EGA). Despite the therapeutic benefit, responses are rarely complete, and most patients develop progression. To our knowledge, this is the first report evaluating 89Zr-trastuzumab in HER2-positive EGA; here, we evaluate the safety, pharmacokinetics, biodistribution, and dosimetry 89Zr-trastuzumab. Methods: Trastuzumab was conjugated with deferoxamine and radiolabeled with 89Zr. A mean activity of 184 MBq was administered to 10 patients with metastatic HER2-positive EGA. PET imaging, whole-body probe counts, and blood draws were performed to assess pharmacokinetics, biodistribution, and dosimetry. Results: No clinically significant toxicities were observed. At the end of infusion, the estimated 89Zr-trastuzumab in plasma volume was a median 102% (range, 78%–113%) of the injected dose. The median biologic half-life T1/2β was 111 h (range, 78–193 h). The median biologic whole-body retention half-life was 370 h (range, 257–578 h). PET images showed optimal tumor visualization at 5–8 d after injection. The maximum tumor SUV ranged from no to minimal uptake in 3 patients to a median of 6.8 (range, 2.9–22.7) for 20 lesions in 7 patients. Dosimetry estimates from OLINDA showed that the organs receiving the highest absorbed doses were the liver and heart wall, with median values of 1.37 and 1.12 mGy/MBq, respectively. Conclusion: 89Zr-trastuzumab imaging tracer is safe and provides high-quality images in patients with HER2-positive EGA, with an optimal imaging time of 5–8 d after injection.

Hypoxic tumors exhibit increased resistance to radiation, chemical, and immune therapies. 18F-fluoromisonidazole (18F-FMISO) PET is a noninvasive, quantitative imaging technique used to evaluate the magnitude and spatial distribution of tumor hypoxia. In this study, pharmacokinetic analysis (PKA) of 18F-FMISO dynamic PET extended to 3 h after injection is reported for the first time, to our knowledge, in stage III–IV non–small cell lung cancer (NSCLC) patients. Methods: Sixteen patients diagnosed with NSCLC underwent 2 PET/CT scans (1–3 d apart) before radiation therapy: a 3-min static 18F-FDG and a dynamic 18F-FMISO scan lasting 168 ± 15 min. The latter data were acquired in 3 serial PET/CT dynamic imaging sessions, registered with each other and analyzed using pharmacokinetic modeling software. PKA was performed using a 2-tissue, 3-compartment irreversible model, and kinetic parameters were estimated for the volumes of interest determined using coregistered 18F-FDG images for both the volume of interest–averaged and the voxelwise time–activity curves for each patient’s lesions, normal lung, and muscle. Results: We derived average values of 18F-FMISO kinetic parameters for NSCLC lesions as well as for normal lung and muscle. We also investigated the correlation between the trapping rate (k3) and delivery rate (K1), influx rate (Ki) constants, and tissue-to-blood activity concentration ratios (TBRs) for all tissues. Lesions had trapping rates 1.6 times larger, on average, than those of normal lung and 4.4 times larger than those in muscle. Additionally, for almost all cases, k3 and Ki had a significant strong correlation for all tissue types. The TBR–k3 correlation was less straightforward, showing a moderate to strong correlation for only 41% of lesions. Finally, K1–k3 voxelwise correlations for tumors were varied, but negative for 76% of lesions, globally exhibiting a weak inverse relationship (average R = −0.23 ± 0.39). However, both normal tissue types exhibited significant positive correlations for more than 60% of patients, with 41% having moderate to strong correlations (R > 0.5). Conclusion: All lesions showed distinct 18F-FMISO uptake. Variable 18F-FMISO delivery was observed across lesions, as indicated by the variable values of the kinetic rate constant K1. Except for 3 cases, some degree of hypoxia was apparent in all lesions based on their nonzero k3 values.

Core biopsies obtained using PET/CT guidance contain bound radiotracer and therefore provide information about tracer uptake in situ. Our goal was to develop a method for quantitative autoradiography of biopsy specimens (QABS), to use this method to correlate 18F-FDG tracer uptake in situ with histopathology findings, and to briefly discuss its potential application. Methods: Twenty-seven patients referred for a PET/CT-guided biopsy of 18F-FDG–avid primary or metastatic lesions in different locations consented to participate in this institutional review board–approved study, which complied with the Health Insurance Portability and Accountability Act. Autoradiography of biopsy specimens obtained using 5 types of needles was performed immediately after extraction. The response of autoradiography imaging plates was calibrated using dummy specimens with known activity obtained using 2 core-biopsy needle sizes. The calibration curves were used to quantify the activity along biopsy specimens obtained with these 2 needles and to calculate the standardized uptake value, SUVARG. Autoradiography images were correlated with histopathologic findings and fused with PET/CT images demonstrating the position of the biopsy needle within the lesion. Logistic regression analysis was performed to search for an SUVARG threshold distinguishing benign from malignant tissue in liver biopsy specimens. Pearson correlation between SUVARG of the whole biopsy specimen and average SUVPET over the voxels intersected by the needle in the fused PET/CT image was calculated. Results: Activity concentrations were obtained using autoradiography for 20 specimens extracted with 18- and 20-gauge needles. The probability of finding malignancy in a specimen is greater than 50% (95% confidence) if SUVARG is greater than 7.3. For core specimens with preserved shape and orientation and in the absence of motion, one can achieve autoradiography, CT, and PET image registration with spatial accuracy better than 2 mm. The correlation coefficient between the mean specimen SUVARG and SUVPET was 0.66. Conclusion: Performing QABS on core-biopsy specimens obtained using PET/CT guidance enables in situ correlation of 18F-FDG tracer uptake and histopathology on a millimeter scale. QABS promises to provide useful information for guiding interventional radiology procedures and localized therapies and for in situ high-spatial-resolution validation of radiopharmaceutical uptake.

The written report (or its electronic counterpart) is the primary mode of communication between the physician interpreting an imaging study and the referring physician. The content of this report not only influences patient management and clinical outcomes but also serves as legal documentation of services provided and can be used to justify medical necessity, billing accuracy, and regulatory compliance. Generating a high-quality PET/CT report is perhaps more challenging than generating a report for other imaging studies because of the complexity of this hybrid imaging modality. This article discusses the essential elements of a concise and complete oncologic (18)F-FDG PET/CT report and illustrates these elements through examples taken from routine clinical practice.

Treatment of oropharyngeal squamous cell carcinoma with chemoradiotherapy can now accomplish excellent locoregional disease control, but patient overall survival (OS) remains limited by development of distant metastases (DM). We investigated the prognostic value of staging (18)F-FDG PET/CT, beyond clinical risk factors, for predicting DM and OS in 176 patients after definitive chemoradiotherapy.The PET parameters maximum standardized uptake value (SUVmax), metabolic tumor volume (MTV), and total lesion glycolysis (TLG) were recorded. Univariate Cox regression was used to examine the prognostic value of these variables and clinical prognosticators for local treatment failure (LTF), OS, and DM. Multivariate analysis examined the effect of SUVmax, TLG, and MTV in the presence of other covariates. Kaplan-Meier curves were used to evaluate prognostic values of PET/CT parameters.Primary tumors were distributed across all stages. Most patients underwent chemoradiotherapy only, and 11 also underwent tonsillectomy. On univariate analysis, primary tumor MTV was predictive of LTF (P = 0.005, hazard ratio [HR] = 2.4 for a doubling of MTV), DM and OS (P0.001 for both, HR = 1.9 and 1.8, respectively). The primary tumor TLG was associated with DM and OS (P0.001, HR = 1.6 and 1.7, respectively, for a doubling of TLG). The primary tumor SUVmax was associated with death (P = 0.029, HR = 1.1 for a 1-unit increase in standardized uptake value) but had no relationship with LTF or DM. In multivariate analysis, TLG and MTV remained associated with death after correcting for T stage (P = 0.0125 and 0.0324, respectively) whereas no relationship was seen between standardized uptake value and death after adjusting for T stage (P = 0.158).Parameters capturing the volume of (18)F-FDG-positive disease (MTV or TLG) provide important prognostic information in oropharyngeal squamous cell carcinoma treated with chemoradiotherapy and should be considered for risk stratification in this disease.

The objective of this study was to determine whether posttherapy (131)I SPECT/CT changed the need for additional cross-sectional imaging or modified the American Thyroid Association risk of recurrence classification. We performed planar imaging and SPECT/CT in a consecutive series of patients after (131)I therapy.Planar imaging and SPECT/CT were performed on 148 consecutive patients with thyroid carcinoma (125 papillary, 2 follicular, 8 Hürthle cell, and 13 poorly differentiated) approximately 5 d after the therapeutic administration of 1,739-8,066 MBq (47-218 mCi) of (131)I. The indication for treatment was postsurgical ablation (n = 109) or recurrent or metastatic disease with rising thyroglobulin levels (n = 39). SPECT/CT scans were obtained for all subjects for 1 bed position (38 cm), which included the neck and upper chest. Additional SPECT/CT scans of the abdomen or pelvis were acquired if suggestive findings were noted on planar images. All patients were treated in real time, according to the standard of care in our practice. At that time, clinical decisions regarding thyroid tumor classification were made by our multidisciplinary group based on all data, including operative findings, pathology, imaging, and thyroglobulin levels. In a retrospective analysis, planar and SPECT/CT images were interpreted independently, and sites of uptake were categorized as likely benign, malignant, or equivocal. An experienced thyroid endocrinologist used a combination of surgical histopathology and scan findings to determine whether additional cross-sectional imaging was required and determined if the imaging findings changed the patient's risk category.In 29 patients, 61 additional cross-sectional imaging studies were avoided using SPECT/CT, compared with medical decision making based on the planar images alone. In 7 of 109 postsurgical patients, SPECT/CT findings changed the initial American Thyroid Association risk of recurrence classification. The sensitivity of planar imaging and SPECT/CT for identification of focal (131)I uptake in the thyroid bed was similar in the postsurgical and recurrence cohorts. For metastatic disease in the neck, characterization of (131)I uptake by SPECT/CT in the postsurgical group was significantly better than that by planar scanning (P0.01). Among the 109 postsurgical patients, the characterization of iodine uptake in the lung, liver, and bone was also more accurate using SPECT/CT than planar scanning (P0.01). The CT portion of SPECT/CT demonstrated non-iodine-avid lesions in 32 of 148 patients.SPECT/CT data provided information that reduced the need for additional cross-sectional imaging in 29 patients (20%) and significantly altered the initial risk of recurrence estimates in 7 of 109 patients (6.4%), thereby altering patient management recommendations with regard to frequency and intensity of follow-up studies.

In the Western world, more than 90% of head and neck cancers are head and neck squamous cell carcinomas (HNSCCs). The most appropriate treatment approach for HNSCC varies with the disease stage and disease site in the head and neck. Concurrent chemoradiotherapy has become a widely used means for the definitive treatment of locoregionally advanced HNSCC. Although this multimodality treatment provides higher response rates than radiotherapy alone, the detection of residual viable tumor after the end of therapy remains an important issue and is one of the major applications of (18)F-FDG PET. Studies have shown that negative (18)F-FDG PET or PET/CT results after concurrent chemoradiotherapy have a high negative predictive value (>95%), whereas the positive predictive value is only about 50%. However, when applied properly, FDG PET/CT can exclude residual disease in most patients, particularly patients with residual enlarged lymph nodes who would otherwise undergo neck dissection. In contrast to other malignancies, data are limited on the utility of (18)F-FDG PET for monitoring the response to induction chemotherapy in HNSCC or for assessing treatment response early during the course of definitive chemoradiotherapy. The proliferation marker (18)F-3'-deoxy-3'fluorothymidine is currently under study for this purpose. Beyond standard chemotherapy, newer treatment regimens in HNSCC take advantage of our improved understanding of tumor biology. Two molecules important in the progression of HNSCC are the epidermal growth factor receptor and the vascular endothelial growth factor (VEGF) and its receptor VEGF-R. Drugs attacking these molecules are now under study for HNSCC. PET probes have been developed for imaging the presence of these molecules in HNSCC and their inhibition by specific drug interaction; the relevance of these probes for response assessment in HNSCC will be discussed. Hypoxia is a common phenomenon in HNSCC and renders cancers resistant to chemo- and radiotherapy. Imaging and quantification of hypoxia with PET probes is under study and may become a prerequisite for overcoming chemo- and radioresistance using radiosensitizing drugs or hypoxia-directed irradiation techniques and for monitoring the response to these techniques in selected groups of patients. Although (18)F-FDG PET/CT will remain the major clinical tool for monitoring treatment in HNSCC, other PET probes may have a role in identifying patients who are likely to benefit from treatment strategies that include biologic agents such as epidermal growth factor receptor inhibitors or VEGF inhibitors.

The task of science is to stake out the limits of the knowable, and to center consciousness within them .Rudolf VirchowThe Continuing Education article by Spagnoli et al. on pages [1800–1815][1] of this issue of The Journal of Nuclear Medicine ( [1][2] ) provides an excellent review of the

Screening for cancer remains a very emotional and hotly debated issue in contemporary medical practice. An analysis of published data reveals a multitude of opinions based on a limited amount of reliable data. Even for breast cancer screening, which is now widely practiced in the United States and many European countries, there is continuing controversy regarding the appropriate age limits for screening mammography and, in fact, concerning the value of mammography itself. Similarly, there is no agreement as to whether screening for lung or prostate cancer is meaningful as currently practiced. Recommendations and decisions regarding cancer screening should be based on reliable data, not good intention, assumptions, or speculation. Therefore, we first explain the underlying principles and premises of screening and then briefly discuss current controversies regarding screening for breast, prostate, and lung cancers. Recently, some authors advocated CT, PET, or PET/CT for whole-body screening without support from reliable data. We discuss the potential financial, legal, and radiation safety implications associated with whole-body CT or PET cancer screening. We conclude from the available data that neither CT nor PET/CT cancer screening is currently warranted. Far from providing a desirable binary answer (presence of absence of cancer), in nonselected populations the procedures frequently yield equivocal or indeterminate findings that require further evaluation, with associated costs and potential complications. The clinical and statistical relevance of occasionally detected cancers is likely too low to justify population-wide screening efforts with these 2 imaging modalities. Ultimately, the true utility, or lack thereof, of PET and PET/CT for cancer screening can be assessed only in a prospective randomized trial. Because of prohibitive costs and the required length of follow-up, it is unlikely that such a trial will ever be conducted. Rather than spending time and resources on screening studies, medical practitioners should continue using whole-body PET/CT for diagnosing, staging, and restaging cancer and for monitoring treatment effects. Researchers should also investigate the utility of whole-body PET/CT for the surveillance of selected groups of patients who have cancer, who have completed curative treatment, but who remain at high risk for recurrent disease.

The goal of this study was to describe our initial experience with the deep-inspiration breath-hold (DIBH) technique in combined PET/CT of the thorax. This article presents particular emphasis on the technical aspects required for clinical implementation.In the DIBH technique, the patient is verbally coached and brought to a reproducible deep inspiration breath-hold level. The first "Hold" period, which refers to the CT session, is considered as the reference. This is followed by 9- to 20-s independent breath-hold PET acquisitions. The goal is to correct for respiratory motion artifacts and, consequently, improve the tumor quantitation and localization on the PET/CT images and inflate the lungs for possible improvement in the detection of subcentimeter pulmonary nodules. A physicist monitors and records patient breathing during PET/CT acquisition using a motion tracker. Patient breathing traces obtained during acquisition are examined on the fly to assess the reproducibility of the technique.Data from 8 patients, encompassing 10 lesions, were analyzed. Visual inspection of fused PET/CT images showed improved spatial matching between the 2 modalities, reduced motion artifacts especially in the diaphragm, and increased the measured standardized uptake value (SUV) attributed to reduced motion blurring, as compared with the standard clinical PET/CT images.The practice of DIBH PET/CT is feasible in a clinical setting. With this technique, consistent lung inflation levels are achieved during PET/CT sessions, as judged by both motion tracker and verification of spatial matching between PET and CT images. Breathing-induced motion artifacts are significantly reduced using DIBH compared with free breathing, enabling better target localization and quantitation. The DIBH technique showed an increase in the median SUV by 32.46%, with a range from 4% to 83%, compared with SUVs measured on the clinical images. The median percentage reduction in the PET-to-CT lesions' centroids was 26.6% (range, 3%-50%).

Hürthle cell carcinoma is an uncommon and occasionally aggressive differentiated thyroid cancer associated with increased mortality compared with other differentiated thyroid malignancies. Because it generally has lower iodine avidity, 18F-FDG PET has been suggested as a more accurate imaging modality. However, there is limited information with regard to the true diagnostic accuracy and prognostic value of 18F-FDG PET in this disease.All patients with Hürthle cell thyroid cancer who underwent their first 18F-FDG PET scan between May 1996 and February 2003 were identified retrospectively. 18F-FDG PET scans were reviewed and compared with all available imaging studies, including CT, ultrasound, and radioiodine scintigraphy (RIS). Abnormal 18F-FDG uptake was assessed visually and by measuring the maximum standardized uptake value (SUVmax) of the most intense lesion. Clinical follow-up for at least 1 y or until death was required for inclusion.Forty-four patients met inclusion criteria. The median follow-up was 2.9 y. There were 24 positive and 20 negative 18F-FDG PET scans with 1 false-positive and 1 false-negative study, resulting in a diagnostic sensitivity of 95.8% and a specificity of 95%. In 5 of 11 patients who had both positive CT and 18F-FDG PET findings, 18F-FDG PET revealed additional sites of disease. Furthermore, 18F-FDG PET correctly classified as negative 3 patients with false-positive CT findings. In 3 of 6 patients with positive RIS, 18F-FDG PET revealed additional sites of metastatic disease. Ten patients with positive 18F-FDG PET had negative RIS. Only 1 patient with negative 18F-FDG PET had positive RIS. The SUVmax also provided prognostic information: In a stepwise fashion, each increase in intensity by SUVmax unit was associated with a 6% increase in mortality (P0.001). The 5-y overall survival in patients with SUVmax10 was 92%; it declined to 64% in those with SUVmax10 (P0.01).18F-FDG PET has excellent diagnostic accuracy in Hürthle cell thyroid cancer patients, improving on CT and RIS. Intense 18F-FDG uptake in lesions is an indicator of a poor prognosis. Our data suggest that all patients with Hürthle cell thyroid cancer should undergo 18F-FDG PET as part of their initial postoperative staging and periodically to screen for occult recurrence, particularly in patients with elevated serum thyroglobulin.

(18)F-FDG PET has a high accuracy in staging head and neck cancer, but its role in patients with clinically and radiographically negative necks (N0) is less clear. In particular, the value of combined PET/CT has not been determined in this group of patients.In a prospective study, 31 patients with oral cancer and no evidence of lymph node metastases by clinical examination or CT/MRI underwent (18)F-FDG PET/CT before elective neck dissection. PET/CT findings were recorded by neck side (left or right) and lymph node level. PET/CT findings were compared with histopathology of dissected nodes, which was the standard of reference.Elective neck dissections (26 unilateral, 5 bilateral; a total of 36 neck sides), involving 142 nodal levels, were performed. Only 13 of 765 dissected lymph nodes harbored metastases. Histopathology revealed nodal metastases in 9 of 36 neck sides and 9 of 142 nodal levels. PET was TP in 6 nodal levels (6 neck sides), false-negative in 3 levels (3 neck sides), true-negative in 127 levels (23 neck sides), and false-positive in 6 levels (4 neck sides). The 3 false-negative findings occurred in metastases smaller than 3 mm or because of inability to distinguish between primary tumor and adjacent metastasis. TP and false-positive nodes exhibited similar standardized uptakes (4.8 +/- 1.1 vs. 4.2 +/- 1.0; P = not significant). Sensitivity and specificity were 67% and 85% on the basis of neck sides and 67% and 95% on the basis of number of nodal levels, respectively. If a decision regarding the need for neck dissection had been based solely on PET/CT, 3 false-negative necks would have been undertreated, and 4 false-positive necks would have been overtreated.(18)F-FDG PET/CT can identify lymph node metastases in a segment of patients with oral cancer and N0 neck. A negative test can exclude metastatic deposits with high specificity. Despite reasonably high overall accuracy, however, the clinical application of PET/CT in the N0 neck may be limited by the combination of limited sensitivity for small metastatic deposits and a relatively high number of false-positive findings. The surgical management of the N0 neck should therefore not be based on PET/CT findings alone.

The standardized uptake value (SUV) is the most commonly used parameter to quantify the intensity of radiotracer uptake in tumors. Previous studies suggested that measurements of (18)F-FDG accumulation in tissue might be affected by the image reconstruction method, but the clinical relevance of these findings has not been assessed.Phantom studies were performed and clinical whole-body (18)F-FDG PET images of 85 cancer patients were analyzed. All images were reconstructed using either filtered backprojection (FBP) with measured attenuation correction (MAC) or iterative reconstruction (IR) with segmented attenuation correction (SAC). In a subset of 15 patients, images were reconstructed using all 4 combinations of IR+SAC, IR+MAC, FBP+SAC, and FBP+MAC. For phantom studies, a sphere containing (18)F-FDG was placed in a water-filled cylinder and the activity concentration of that sphere was measured in FBP and IR reconstructed images using all 4 combinations. Clinical studies were displayed simultaneously and identical regions of interest (ROIs, 50 pixels) were placed in liver, urinary bladder, and tumor tissue in both image sets. SUV max (maximal counts per pixel in ROI) and SUV avg (average counts per pixel) were measured.In phantom studies, measurements from FBP images underestimated the true activity concentration to a greater degree than those from IR images (20% vs. 5% underestimation). In patient studies, SUV derived from FBP images were consistently lower than those from IR images in both normal and tumor tissue: Tumor SUV max with IR+SAC was 9.6 +/- 4.5, with IR+MAC it was 7.7 +/- 3.5, with FBP+MAC it was 6.9 +/- 3.0, and with FBP+SAC it was 8.6 +/- 4.1 (all P0.01 vs. IR+SAC). Compared with IR+SAC, SUV from FBP+MAC images were 25%-30% lower. Similar discrepancies were noted for liver and bladder. Discrepancies between measurements became more apparent with increasing (18)F-FDG concentration in tissue.SUV measurements in whole-body PET studies are affected by the applied methods for both image reconstruction and attenuation correction. This should be considered when serial PET studies are done in cancer patients. Moreover, if SUV is used for tissue characterization, different cutoff values should be applied, depending on the chosen method for image reconstruction and attenuation correction.

PET/CT is a new imaging technology that has already found a number of clinical applications in oncologic imaging. Widespread introduction into clinical practice started approximately 2.5 years ago. Consequently, the available data are largely preliminary. Nevertheless, it can already be stated that the synthesis of structural and metabolic information improves the accuracy of primary staging and the detection of recurrent disease and has the realistic potential to change patient management in 10 to 20% of cases. PET/CT fusion images can directly guide biopsies or surgical interventions. This article summarizes preliminary data of PET/CT studies and highlights potential clinical applications for PET/CT, with particular emphasis on lymphoma, melanoma and gastrointestinal tumors.

The routine use of PET/CT fusion imaging in a large oncology practice has led to the realization that (18)F-FDG uptake into normal fat and muscle can be a common source of potentially misleading false-positive PET imaging in the neck, thorax, and abdomen. The goal of this study was to characterize this normal variant of (18)F-FDG uptake in terms of incidence and characteristic extent.All body scans done on our PET/CT scanners in July and August 2002 were retrospectively reviewed. All cases in which increased (18)F-FDG uptake in the neck was not localized to lymph nodes or other obvious anatomic sites on the CT scans were included in this study. Sites of any unexplained (18)F-FDG uptake in the rest of the body were also recorded.A total of 863 PET scans (476 males, 387 females; age, 2-88 y; mean age, 57 y) were reviewed. The following distinctive patterns of nonpathologic (18)F-FDG activity were observed: (a) neck fat, 20 patients (2.3%); (b) paravertebral uptake, 12 patients (1.4%); (c) perinephric fat, 7 patients (0.8%); (d) mediastinal fat, 8 patients (0.9%); (e) normal musculature, 12 patients (1.4%). Patients showing paravertebral uptake, perinephric fat, and mediastinal fat were all associated with the neck fat pattern, singly or in combination. On the other hand, patients showing the normal musculature pattern did not show any of the other uptake. In this analysis, the incidence of (18)F-FDG uptake in sites other than the neck is restricted to the patient population with neck fat uptake and may be an underestimation of the true incidence. Neck fat is found predominantly in females, whereas normal musculature is usually seen in males (P0.01, Fisher exact test). Neck fat is also seen significantly more in the pediatric population (4/26 = 15%) than in the adult population (16/837 = 1.9%) (P0.01, Fisher exact test).Increased (18)F-FDG uptake is sometimes seen in individual muscles and in adipose tissue in the neck and shoulder region, axillae, mediastinum, and perinephric regions. There is also associated (18)F-FDG uptake in the intercostal spaces in the paravertebral regions. (18)F-FDG uptake in neck fat is more commonly seen in female patients and the pediatric population. The pattern of uptake as well as the age and sex distribution suggest that the (18)F-FDG in fat is in the brown adipose tissue. It is important to recognize this uptake pattern to avoid false interpretation of this benign normal variant as a malignant finding on (18)F-FDG PET scans.