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Objectives: The roles of magnetic resonance imaging (MRI) -based radiomics approach and deep learning approach in cervical adenocarcinoma (AC) have not been explored. Herein, we aim to develop prognosis-predictive models based on MRI-radiomics and clinical features for AC patients., Methods: Clinical and pathological information from one hundred and ninety-seven patients with cervical AC was collected and analyzed. For each patient, 107 radiomics features were extracted from T2-weighted MRI images. Feature selection was performed using Spearman correlation and random forest (RF) algorithms, and predictive models were built using support vector machine (SVM) technique. Deep learning models were also trained with T2-weighted MRI images and clinicopathological features through Convolutional Neural Network (CNN). Kaplan-Meier curve was analyzed using significant features. In addition, information from another group of 56 AC patients was used for the independent validation., Results: A total of 107 radiomics features and 6 clinicopathological features (age, FIGO stage, differentiation, invasion depth, lymphovascular space invasion (LVSI), and lymph node metastasis (LNM) were included in the analysis. When predicting the 3-year, 4-year, and 5-year DFS, the model trained solely on radiomics features achieved AUC values of 0.659 (95%CI: 0.620-0.716), 0.791 (95%CI: 0.603-0.922), and 0.853 (95%CI: 0.745-0.912), respectively. However, the combined model, incorporating both radiomics and clinicopathological features, outperformed the radiomics model with AUC values of 0.934 (95%CI: 0.885-0.981), 0.937 (95%CI: 0.867-0.995), and 0.916 (95%CI: 0.857-0.970), respectively. For deep learning models, the MRI-based models achieved an AUC of 0.857, 0.777 and 0.828 for 3-year DFS, 4-year DFS and 5-year DFS prediction, respectively. And the combined deep learning models got a improved performance, the AUCs were 0.903. 0.862 and 0.969. In the independent test set, the combined model achieved an AUC of 0.873, 0.858 and 0.914 for 3-year DFS, 4-year DFS and 5-year DFS prediction, respectively., Conclusions: We demonstrated the prognostic value of integrating MRI-based radiomics and clinicopathological features in cervical adenocarcinoma. Both radiomics and deep learning models showed improved predictive performance when combined with clinical data, emphasizing the importance of a multimodal approach in patient management., (© 2024. The Author(s).)

Purpose: The potential limitations of hepatic [ 18 F]FDG-PET imaging for individuals with obesity and excessive liver fat (NAFLD) are being investigated. In this study, we aim to determine the reliability of standardized uptake values (SUVs) focusing on adjustment for liver fat content (LFC) derived from DIXON images and the effects of whole-body normalizations., Methods: Lean and with obesity volunteers who underwent [ 18 F]FDG-PET/MRI were reviewed retrospectively. DIXON fat images were used to determine LFC and for adjustment of SUV mean . The hepatic SUVs (mean, fat adjusted mean and max) were normalized to body weight, lean body mass and body surface area. Blood samples were analysed for glucose, serological liver enzymes and lipoproteins for further correlation of [ 18 F]FDG uptake., Results: Out of 11 volunteers with obesity (M:8, F:3, BMI:30-39 kg/m 2 ), 9 confirmed the presence of NAFLD (>5.6 % fat). 22 age-matched lean volunteers (M:10, F:11, BMI:19-26 kg/m 2 ) were used as control group. Both SUV mean , before and after adjustment to LFC, did not provide any difference between lean and with obesity groups under BW, LBM and BSA. SUV max BW showed a difference between groups (p = 0.05). SUVs were independent of levels of GPT, GOT, gGT, insulin, HOMA-IR, triglycerides, cholesterol and LDL. Volunteers with low HDL were clustered with an increased hepatic [ 18 F]FDG uptake., Conclusion: Our method for adjustment of hepatic [ 18 F]FDG-PET with DIXON fat images allows to achieve accurate results for individuals with NAFLD and obesity. For homogenic results, raw SUV mean should be combined with adjustment for liver fat, appropriate normalization and consideration of HDL levels., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier B.V. All rights reserved.)

Purpose: The human brain is characterized by interacting large-scale functional networks fueled by glucose metabolism. Since former studies could not sufficiently clarify how these functional connections shape glucose metabolism, we aimed to provide a neurophysiologically-based approach., Methods: 51 healthy volunteers underwent simultaneous PET/MRI to obtain BOLD functional connectivity and [ 18 F]FDG glucose metabolism. These multimodal imaging proxies of fMRI and PET were combined in a whole-brain extension of metabolic connectivity mapping. Specifically, functional connectivity of all brain regions were used as input to explain glucose metabolism of a given target region. This enabled the modeling of postsynaptic energy demands by incoming signals from distinct brain regions., Results: Functional connectivity input explained a substantial part of metabolic demands but with pronounced regional variations (34 - 76%). During cognitive task performance this multimodal association revealed a shift to higher network integration compared to resting state. In healthy aging, a dedifferentiation (decreased segregated/modular structure of the brain) of brain networks during rest was observed. Furthermore, by including data from mRNA maps, [ 11 C]UCB-J synaptic density and aerobic glycolysis (oxygen-to-glucose index from PET data), we show that whole-brain functional input reflects non-oxidative, on-demand metabolism of synaptic signaling. The metabolically-derived directionality of functional inputs further marked them as top-down predictions. In addition, the approach uncovered formerly hidden networks with superior efficiency through metabolically informed network partitioning., Conclusions: Applying multimodal imaging, we decipher a crucial part of the metabolic and neurophysiological basis of functional connections in the brain as interregional on-demand synaptic signaling fueled by anaerobic metabolism. The observed task- and age-related effects indicate promising future applications to characterize human brain function and clinical alterations., Competing Interests: Declaration of competing interest R. Lanzenberger received investigator-initiated research funding from Siemens Healthcare regarding clinical research using PET/MR. He is a shareholder of the start-up company BM Health GmbH since 2019. M. Hacker received consulting fees and/or honoraria from Bayer Healthcare BMS, Eli Lilly, EZAG, GE Healthcare, Ipsen, ITM, Janssen, Roche, and Siemens Healthineers. All other authors report no conflict of interest in relation to this study., (Copyright © 2024 The Author(s). Published by Elsevier Inc. All rights reserved.)

The neurobiological basis of learning is reflected in adaptations of brain structure, network organization and energy metabolism. However, it is still unknown how different neuroplastic mechanisms act together and if cognitive advancements relate to general or task-specific changes. Therefore, we tested how hierarchical network interactions contribute to improvements in the performance of a visuo-spatial processing task by employing simultaneous PET/MR neuroimaging before and after a 4-week learning period. We combined functional PET and metabolic connectivity mapping (MCM) to infer directional interactions across brain regions. Learning altered the top-down regulation of the salience network onto the occipital cortex, with increases in MCM at resting-state and decreases during task execution. Accordingly, a higher divergence between resting-state and task-specific effects was associated with better cognitive performance, indicating that these adaptations are complementary and both required for successful visuo-spatial skill learning. Simulations further showed that changes at resting-state were dependent on glucose metabolism, whereas those during task performance were driven by functional connectivity between salience and visual networks. Referring to previous work, we suggest that learning establishes a metabolically expensive skill engram at rest, whose retrieval serves for efficient task execution by minimizing prediction errors between neuronal representations of brain regions on different hierarchical levels., (© 2022. The Author(s).)

Purpose of the Report: F-FDG PET is limited for assessment of central nervous system lymphoma (CNSL) due to physiologic tracer accumulation in the brain. We prospectively evaluated the novel PET tracer Ga-pentixafor, which targets the C-X-C chemokine receptor 4 (CXCR4), for lesion visualization and response assessment of CNSL., Materials and Methods: Seven CNSL patients underwent Ga-pentixafor PET/MRI with contrast enhancement (CE-MRI) and diffusion-weighted sequences. The accuracy of Ga-pentixafor PET for CNSL lesion detection relative to the CE-MRI reference standard was determined. Standardized uptake values (SUVmean and SUVmax), PET-based (PTV) and MRI-based (VOLMRI) tumor volumes, and apparent diffusion coefficients (ADCs) were assessed, and correlation coefficients were calculated. Three SUVmax thresholds (41%, 50%, and 70%) were evaluated for PTV definitions (PTV41%, PTV50%, and PTV70%) and tested against VOLMRI using paired sample t tests., Results: Twelve Ga-pentixafor PET/MRI examinations (including 5 follow-up scans) of 7 patients were evaluated. Ga-pentixafor PET demonstrated 18 lesions, all of which were confirmed by CE-MRI; there were no false-positive lesions on PET (accuracy, 100%). PTV41% showed the highest concordance with lesion morphology, with no significant difference compared with VOLMRI (mean difference, -0.24 cm; P = 0.45). The correlation between ADCmean and SUVmean41% (r = 0.68) was moderate. Changes in PTV41% on follow-up PET/MRI showed the same trend as VOLMRI changes, including progression of 1 lesion each in patient 1 (+456.0% PTV41% and +350.8% VOLMRI) and patient 3 (+110.4% PTV41% and +85.1% VOLMRI)., Conclusions: Ga-pentixafor PET may be feasible for assessment and follow-up of CNSL. Future studies need to focus on testing its clinical value to distinguish between glioma and CNSL, and between radiation-induced inflammation and viable residual tumor.

Background: Respiratory patient motion causes blurring of the PET images that may impact accurate quantification of perfusion and infarction extents in PET myocardial viability studies. In this study, we investigate the feasibility of correcting for respiratory motion directly in the PET-listmode data prior to image reconstruction using a data-driven, projection-based, respiratory motion compensation (DPR-MoCo) technique., Methods: The DPR-MoCo method was validated using simulations of a XCAT phantom (Biograph mMR PET/MR) as well as experimental phantom acquisitions (Biograph mCT PET/CT). Seven patient studies following a dual-tracer ( 18 F-FDG/ 13 N-NH 3 ) imaging-protocol using a PET/MR-system were also evaluated. The performance of the DPR-MoCo method was compared against reconstructions of the acquired data (No-MoCo), a reference gate method (gated) and an image-based MoCo method using the standard reconstruction-transform-average (RTA-MoCo) approach. The target-to-background ratio (TBR LV ) in the myocardium and the noise in the liver (CoV liver ) were evaluated for all acquisitions. For all patients, the clinical effect of the DPR-MoCo was assessed based on the end-systolic (ESV), the end-diastolic volumes (EDV) and the left ventricular ejection fraction (EF) which were compared to functional values obtained from the cardiac MR., Results: The DPR-MoCo and the No-MoCo images presented with similar noise-properties (CoV) (P = .12), while the RTA-MoCo and reference-gate images showed increased noise levels (P = .05). TBR LV values increased for the motion limited reconstructions when compared to the No-MoCo reconstructions (P > .05). DPR-MoCo results showed higher correlation with the functional values obtained from the cardiac MR than the No-MoCo results, though non-significant (P > .05)., Conclusion: The projection-based DPR-MoCo method helps to improve PET image quality of the myocardium without the need for external devices for motion tracking.

Patients after solid organ kidney transplantation (KTX) often suffer from acute kidney injury (AKI). Parameters as serum creatinine indicate a loss of kidney function, although no distinction of the cause and prognosis can be made. Imaging tools measuring kidney function have not been widely in clinical use. In this observational study we evaluated 2-deoxy-2[18F] fluoro-D-glucose (FDG) PET/MRI in thirteen patients after KTX with AKI as a functional assessment of the graft. Twenty-four healthy volunteers served as control. General kidney performance (GKP), initial flow (IF) and renal response function (RF) were calculated by standardized uptake values (SUV) and time activity curves (TAC). The GKP measured for the total kidney and medulla was significantly higher in healthy patients compared to patients after KTX (p = 0.0002 and p = 0.0004, respectively), but no difference was found for the GKP of the cortex (p = 0.59). The IF in KTX patients correlated with renal recovery, defined as change in serum creatinine 10 days after PET/MRI (r = 0.80, p = 0.001). With regard to the RF, a negative correlation for tubular damage was found (r = -0.74, p = 0.004). In conclusion, parameters obtained from FDG PET/MRI showed a possible predictive feature for renal recovery in KTX patients undergoing AKI.

Background: Sympathetic reinnervation after heart transplantation (HTX) is a known phenomenon, which has an impact on patient heart rate variability and exercise capacity. The impact of reinnervation on myocardial structure has not been evaluated yet., Propose: To evaluate the feasibility of simultaneous imaging of cardiac reinnervation and cardiac structure using a hybrid PET/MRI system., Study Type: Prospective / pilot study., Subjects: Ten patients, 4-21 years after cardiac transplantation., Field Strength/sequence: 3 T hybrid PET/MRI system. Cine SSFP, T 1 mapping (modified Look-Locker inversion recovery sequence) pre/postcontrast as well as dynamic [ 11 C]meta-hydroxyephedrine ([ 11 C]mHED) PET., Assessment: All MRI and PET parameters were evaluated by experienced readers using dedicated postprocessing software packages for cardiac MRI and PET. For all parameters a 16-segment model for the left ventricle was applied., Statistical Tests: Mann-Whitney U-test; Spearman correlations., Results: Thirty-six of 160 myocardial segments showed evidence of reinnervation by PET. On a segment-based analysis, mean native T 1 relaxation times were nonsignificantly altered in segments with evidence of reinnervation (1305 ± 151 msec vs. 1270 ± 112 msec; P = 0.1), whereas mean extracellular volume (ECV) was significantly higher in segments with evidence of reinnervation (35.8 ± 11% vs. 30.9 ± 7%; P = 0.019). There were no significant differences in wall motion (WM) and wall thickening (WT) between segments with or without reinnervation (mean WM: 7.6 ± 4 mm vs. group B: 9.3 ± 7 mm [P = 0.13]; WT: 79 ± 63% vs. 94 ± 74% [P = 0.27]) under resting conditions., Data Conclusion: The assessment of cardiac reinnervation using a hybrid PET/MRI system is feasible. Segments with evidence of reinnervation by PET showed nonsignificantly higher T 1 relaxation times and a significantly higher ECV, suggesting a higher percentage of diffuse fibrosis in these segments, without impairment of rest WM and WT., Level of Evidence: 3 Technical Efficacy: Stage 3 J. Magn. Reson. Imaging 2019;50:1326-1335., (© 2019 The Authors. Journal of Magnetic Resonance Imaging published by Wiley Periodicals, Inc. on behalf of International Society for Magnetic Resonance in Medicine.)

Hybrid PET/MR offers new opportunities in radiation oncology for tissue/tumour characterisation and response assessment. Attenuation correction (AC) is an important issue especially in the presence of immobilization devices and flat table tops (FTT). The goal of this study was to compare two methods of AC using CT- and 68 Ge/ 68 Ga transmission scan-based attenuation maps (μ-maps) for a custom-designed FTT. Measurements were performed in the mMR PET/MR and TrueV PET/CT Biograph Siemens scanners with three different phantoms, namely the Siemens MR-QA, a cubic canister and the NEMA IEC body phantom. The study revealed that the MR image quality is not hampered by the presence of the FTT. For cubic canister applying the scanner's inherent AC alone resulted in inaccuracies in PET images, with up to -4.0% underestimation of the activity. The mean NEMA sphere activity measurements without FTT, agreed within 3.5% with the respective inserted activity. Placing the FTT in the PET/MR scanner resulted in a difference to the injected activity of 4.5% when the table was not corrected for. By introducing the μ-maps the discrepancy between the used activity and the measurements decreased down to 2.6%. To improve the AC of the FTT the creation of a dedicated μ-map was necessary while the CT-based μ-map performed equally good as the source transmission scan-based one., (Copyright © 2019 Associazione Italiana di Fisica Medica. Published by Elsevier Ltd. All rights reserved.)

Aim: To assess if tumour grading based on dynamic [18F]FET positron emission tomography/magnetic resonance imaging (PET/MRI) studies is affected by different MRI-based attenuation correction (AC) methods., Methods: Twenty-four patients with suspected brain tumours underwent dynamic [18F]FET-PET/MRI examinations and subsequent low-dose computed tomography (CT) scans of the head. The dynamic PET data was reconstructed using the following AC methods: standard Dixon-based AC and ultra-short echo time MRI-based AC (MR-AC) and a model-based AC approach. All data were reconstructed also using CT-based AC (reference). For all lesions and reconstructions, time-activity curves (TACs) and time to peak (TTP) were extracted using different region-of-interest (ROI) and volume-of-interest (VOI) definitions. According to the most common evaluation approaches, TACs were categorised into two or three distinct curve patterns. Changes in TTP and TAC patterns compared to PET using CT-based AC were reported., Results: In the majority of cases, TAC patterns did not change. However, TAC pattern changes as well as changes in TTP were observed in up to 8% and 17% of the cases when using different MR-AC methods and ROI/VOI definitions, respectively. However, these changes in TTP and TAC pattern were attributed to different delineations of the ROIs/VOIs in PET corrected with different AC methods., Conclusion: PET/MRI using different MR-AC methods can be used for the assessment of TAC patterns in dynamic [18F]FET studies, as long as a meaningful delineation of the area of interest within the tumour is ensured., Key Points: • PET/MRI using different MR-AC methods can be used for dynamic [18F]FET studies. • A meaningful segmentation of the area of interest needs to be ensured, mandating a visual validation of the delineation by an experienced reader.

Objective: To evaluate the frequency of artifacts in MR-based attenuation correction (AC) maps and their impact on the quantitative accuracy of PET-based flow and metabolism measurements in a cohort of consecutive heart failure patients undergoing combined PET/MR imaging., Methods: Myocardial viability studies were performed in 20 patients following a dual-tracer protocol involving the assessment of myocardial perfusion ( 13 N-NH 3 : 813 ± 86 MBq) and metabolism ( 18 F-FDG: 335 ± 38 MBq). All acquisitions were performed using a fully-integrated PET/MR system, with standard DIXON-attenuation correction (DIXON-AC) mapping for each PET scan. All AC maps were examined for spatial misalignment with the emission data, total lung volume, susceptibility artifacts, and tissue inversion (TI). Misalignment and susceptibility artifacts were corrected using rigid co-registration and retrospective filling of the susceptibility-induced gaps, respectively. The effects of the AC artifacts were evaluated by relative difference measures and perceived changes in clinical interpretations., Results: Average respiratory misalignment of (7 ± 4) mm of the PET-emission data and the AC maps was observed in 18 (90%) patients. Substantial changes in the lung volumes of the AC maps were observed in the test-retest analysis (ratio: 1.0 ± 0.2, range: 0.8-1.4). Susceptibility artifacts were observed in 10 (50%) patients, while six (30%) patients had TI artifacts. Average differences of 14 ± 10% were observed for PET images reconstructed with the artifactual AC maps. The combined artifact effects caused false-positive findings in three (15%) patients., Conclusion: Standard DIXON-AC maps must be examined carefully for artifacts and misalignment effects prior to AC correction of cardiac PET/MRI studies in order to avoid misinterpretation of biased perfusion and metabolism readings from the PET data.

Purpose: Type 4 chemokine receptor (CXCR4) plays an important role in immune cell migration during the atherosclerosis progression. We aimed to evaluate [ 68 Ga]Pentixafor positron emission tomography (PET) in combination magnetic resonance imaging (MRI) for in vivo quantification of CXCR4 expression in carotid plaques., Methods: Seventy-two patients with lymphoma were prospectively scheduled for whole body [ 68 Ga]Pentixafor PET/MRI with an additional T2-weighted carotid sequence. Volumes of interest (VOIs) were drawn along the carotid bifurcation regions, and the maximum tissue-to-blood ratios (TBR) of [ 68 Ga]Pentixafor uptake were calculated. Lesions were categorized into non-eccentric (n = 27), mild eccentric (n = 67), moderately (n = 41) and severely (n = 19) eccentric carotid atherosclerosis. A different cohort of symptomatic patients (n = 10) with carotid stenosis scheduled for thrombendarterectomy (TEA) was separately imaged with 3T MRI with dedicated plaque sequences (time of flight, T1-, and T2-weighted). MRI findings were correlated with histochemical assessment of intact carotid plaques., Results: At hybrid PET/MRI, we observed significantly increased [ 68 Ga]Pentixafor uptake in mildly (mean TBR max  = 1.57 ± 0.27, mean SUV max  = 2.51 ± 0.39), moderately (mean TBR max  = 1.64 ± 0.37, mean SUV max  = 2.61 ± 0.55) and severely eccentric carotids (mean TBR max  = 1.55 ± 0.26, mean SUV max  = 2.40 ± 0.44) as compared to non-eccentric carotids (mean TBR max  = 1.29 ± 0.21, mean SUV max  = 1.77 ± 0.42) (p ≤ 0.05). Histological findings from TEA confirmed that prominent CXCR4 expression was localized within inflamed atheromas and preatheromas. Co-localization of cellular CXCR4 and CD68 expression in the plaque was observed by immunofluorescence staining., Conclusions: In vivo evaluation of CXCR4 expression in carotid atherosclerotic lesions is feasible using [ 68 Ga]Pentixafor PET/MRI. In atherosclerotic plaque tissue, CXCR4 expression might be used as a surrogate marker for inflammatory atherosclerosis.

Background: [ 18 F]-2-fluoro-2-deoxy-D-glucose (18F-FDG) positron emission tomography/computed tomography (FDG-PET/CT) imaging provides important information about the size and metabolic activity of lesions caused by Echinococcus multilocularis and is therefore recommended for the initial assessment and follow-up of human alveolar echinococcosis (AE). The introduction of positron emission tomography/magnetic resonance imaging (PET/MRI) into clinical practice in affluent health care systems provides an alternative dual imaging modality, which has not yet been evaluated for AE., Objective: Here, we describe the initial clinical experience with comparative PET/CT and PET/MR imaging in four human AE patients at an Austrian reference centre., Results: PET/MR imaging showed comparable diagnostic capacity for liver lesions attributable to E. multilocularis infection, with a discrepancy only in the assessment of calcifications in one patient. Effective doses of radiation were 30.4-31 mSV for PET/CT, which were reduced in PET/MRI to the exposure of 18 F-FDG only (4.9-5.5 mSv)., Conclusions: PET/MRI provides comparable diagnostic information for AE management. The reduction in radiation exposure compared to PET/CT may be of particular importance for children and young patients not amenable for curative surgery requiring repeated long-term follow-up with dual imaging modalities. Further studies are warranted to prospectively evaluate the potential of PET/MRI in the management of AE., (© 2019 John Wiley & Sons Ltd.)

Pharmacological imaging of the effects of selective serotonin reuptake inhibitors (SSRI) may aid the clarification of their mechanism of action and influence treatment of highly prevalent neuropsychiatric conditions if the detected effects could be related to patient outcomes. In a randomized double-blind design, 38 healthy participants received a constant infusion of 8 mg citalopram or saline during either their first or second of two PET/MR scans. Resting-state functional MRI (fMRI) was acquired simultaneously with PET data on the binding of serotonin transporters (5-HTT) using [ 11 C]DASB. Three different approaches for modeling of pharmacological fMRI response were tested separately. These relied on the use of regressors corresponding to (1) the drug infusion paradigm, (2) time courses of citalopram plasma concentrations and (3) changes in 5-HTT binding measured in each individual, respectively. Furthermore, the replication of results of a widely used model-free analysis method was attempted which assesses the deviation of signal in discrete time bins of fMRI data acquired after start of drug infusion. Following drug challenge, average 5-HTT occupancy was 69±7% and peak citalopram plasma levels were 111.8 ± 21.1 ng/ml. None of the applied methods could detect significant differences in the pharmacological response between SSRI and placebo scans. The failed replication of SSRI effects reported in the literature despite a threefold larger sample size highlights the importance of appropriate correction for family-wise error in order to avoid spurious results in pharmacological imaging. This calls for the development of analysis methods which take regional specialization and the dynamics of brain activity into account., (Copyright © 2019 Elsevier B.V. and ECNP. All rights reserved.)

The aim of this study was to assess whether sequential multiparametric 18 [F]fluoro-desoxy-glucose ( 18 [F]FDG)/[ 18 F]fluoromisonidazole ([ 18 F]FMISO) PET-MRI in breast cancer patients is possible, facilitates information on tumor heterogeneity, and correlates with prognostic indicators. In this pilot study, IRB-approved, prospective study, nine patients with ten suspicious breast lesions (BIRADS 5) and subsequent breast cancer diagnosis underwent sequential combined [ 18 F]FDG/[18F]FMISO PET-MRI. [ 18 F]FDG was used to assess increased glycolysis, while [ 18 F]FMISO was used to detect tumor hypoxia. MRI protocol included dynamic breast contrast-enhanced MRI (DCE-MRI) and diffusion-weighted imaging (DWI). Qualitative and quantitative multiparametric imaging findings were compared with pathological features (grading, proliferation, and receptor status) and clinical endpoints (recurrence/metastases and disease-specific death) using multiple correlation analysis. Histopathology was the standard of reference. There were several intermediate to strong correlations identified between quantitative bioimaging markers, histopathologic tumor characteristics, and clinical endpoints. Based on correlation analysis, multiparametric criteria provided independent information. The prognostic indicators proliferation rate, death, and presence/development of recurrence/metastasis correlated positively, whereas the prognostic indicator estrogen receptor status correlated negatively with PET parameters. The strongest correlations were found between disease-specific death and [ 18 F]FDG mean ( R =0.83, p < 0.01) and between the presence/development of metastasis and [ 18 F]FDG max ( R =0.79, p < 0.01), respectively. This pilot study indicates that multiparametric [ 18 F]FDG/[ 18 F]FMISO PET-MRI might provide complementary quantitative prognostic information on breast tumors including clinical endpoints and thus might be used to tailor treatment for precision medicine in breast cancer.

Purpose: Primary staging of prostate cancer relies on modalities, which are limited. We evaluate simultaneous [ 68 Ga]Ga-PSMA-11 PET (PSMA-PET)/MRI as a new diagnostic method for primary tumor-node-metastasis staging compared with histology and its impact on therapeutic decisions., Experimental Design: We investigated 122 patients with PSMA-PET/MRI prior to planned radical prostatectomy (RP). Primary endpoint was the accuracy of PSMA-PET/MRI in tumor staging as compared with staging-relevant histology. In addition, a multidisciplinary team reassessed the initial therapeutic approach to evaluate its impact on the therapeutic management., Results: PSMA-PET/MRI correctly identified prostate cancer in 119 of 122 patients (97.5%). Eighty-one patients were treated with RP and pelvic lymphadenectomy. The accuracy for T staging was 82.5% [95% confidence interval (CI), 73-90; P < 0.001], for T2 stage was 85% (95% CI, 71-94; P < 0.001), for T3a stage was 79% (95% CI, 43-85; P < 0.001), for T3b stage was 94% (95% CI, 73-100; P < 0.001), and for N1 stage was 93% (95% CI, 84-98; P < 0.001). PSMA-PET/MRI changed the therapeutic strategy in 28.7% of the patients with either the onset of systemic therapy/radiotherapy ( n = 16) or active surveillance ( n = 19)., Conclusions: PSMA-PET/MRI can provide an accurate staging of newly diagnosed prostate cancer. In addition, treatment strategies were changed in almost a third of the patients due to the information of this hybrid imaging technique., (©2018 American Association for Cancer Research.)

Introduction: The brain's energy budget can be non-invasively assessed with different imaging modalities such as functional MRI (fMRI) and PET (fPET), which are sensitive to oxygen and glucose demands, respectively. The introduction of hybrid PET/MRI systems further enables the simultaneous acquisition of these parameters. Although a recently developed method offers the quantification of task-specific changes in glucose metabolism (CMRGlu) in a single measurement, direct comparison of the two imaging modalities is still difficult because of the different temporal resolutions. Thus, we optimized the protocol and systematically assessed shortened task durations of fPET to approach that of fMRI., Methods: Twenty healthy subjects (9 male) underwent one measurement on a hybrid PET/MRI scanner. During the scan, tasks were completed in four blocks for fMRI (4 × 30 s blocks) and fPET: participants tapped the fingers of their right hand repeatedly to the thumb while watching videos of landscapes. For fPET, subjects were randomly assigned to groups of n = 5 with varying task durations of 10, 5, 2 and 1 min, where task durations were kept constant within a measurement. The radiolabeled glucose analogue [ 18 F]FDG was administered as 20% bolus plus constant infusion. The bolus increases the signal-to-noise ratio and leaves sufficient activity to detect task-related effects but poses additional challenges due to a discontinuity in the tracer uptake. First, three approaches to remove task effects from the baseline term were evaluated: (1) multimodal, based on the individual fMRI analysis, (2) atlas-based by removing presumably activated regions and (3) model-based by fitting the baseline with exponential functions. Second, we investigated the need to capture the arterial input function peak with automatic blood sampling for the quantification of CMRGlu. We finally compared the task-specific activation obtained from fPET and fMRI qualitatively and statistically., Results: CMRGlu quantified only with manual arterial samples showed a strong correlation to that obtained with automatic sampling (r = 0.9996). The multimodal baseline definition was superior to the other tested approaches in terms of residuals (p < 0.001). Significant task-specific changes in CMRGlu were found in the primary visual and motor cortices (t M1  = 18.7 and t V1  = 18.3). Significant changes of fMRI activation were found in the same areas (t M1  = 16.0 and t V1  = 17.6) but additionally in the supplementary motor area, ipsilateral motor cortex and secondary visual cortex. Post-hoc t-tests showed strongest effects for task durations of 5 and 2 min (all p < 0.05 FWE corrected), whereas 1 min exhibited pronounced unspecific activation. Percent signal change (PSC) was higher for CMRGlu (∼18%-27%) compared to fMRI (∼2%). No significant association between PSC of task-specific CMRGlu and fMRI was found (r = 0.26)., Conclusion: Using a bolus plus constant infusion protocol, the necessary task duration for reliable quantification of task-specific CMRGlu could be reduced to 5 and 2 min, therefore, approaching that of fMRI. Important for valid quantification is a correct baseline definition, which was ideal when task-relevant voxels were determined with fMRI. The absence of a correlation and the different activation pattern between fPET and fMRI suggest that glucose metabolism and oxygen demand capture complementary aspects of energy demands., (Copyright © 2018 Elsevier Inc. All rights reserved.)

Positron emission tomography (PET) and magnetic resonance imaging (MRI) have both been used for decades in cardiovascular imaging. Since 2010, hybrid PET/MRI using sequential and integrated scanner platforms has been available, with hybrid cardiac PET/MR imaging protocols increasingly incorporated into clinical workflows. Given the range of complementary information provided by each method, the use of hybrid PET/MRI may be justified and beneficial in particular clinical settings for the evaluation of different disease entities. In the present joint position statement, we critically review the role and value of integrated PET/MRI in cardiovascular imaging, provide a technical overview of cardiac PET/MRI and practical advice related to the cardiac PET/MRI workflow, identify cardiovascular applications that can potentially benefit from hybrid PET/MRI, and describe the needs for future development and research. In order to encourage its wide dissemination, this article is freely accessible on the European Radiology and European Journal of Hybrid Imaging web sites., Key Points: • Studies and case-reports indicate that PET/MRI is a feasible and robust technology. • Promising fields of application include a variety of cardiac conditions. • Larger studies are required to demonstrate its incremental and cost-effective value. • The translation of novel radiopharmaceuticals and MR-sequences will provide exciting new opportunities.

Purpose: The expression of chemokine receptor type 4 (CXCR4) was found co-localized with macrophages on the atherosclerotic vessel wall and participated in the initial emigration of leukocytes. Gallium-68 [ 68 Ga]Pentixafor has recently been introduced for the imaging of atherosclerosis by targeting CXCR4. We sought to evaluate human atherosclerotic lesions using [ 68 Ga]Pentixafor PET/MRI., Methods: Thirty-eight oncology patients underwent [ 68 Ga]Pentixafor PET/MR imaging at baseline. Maximum standardized uptake values (SUV max ) were derived from hot lesions in seven arterial segments and target-to-blood ratios (TBR) were calculated. ANOVA post-hoc and paired t test were performed for statistical comparison, Spearman's correlation coefficient between uptake ratios and cardiovascular risk factors were assessed. The reproducibility of [ 68 Ga]Pentixafor PET/MRI was assessed in seven patients with a follow-up exanimation by Pearson's regression and Bland-Altman plots analysis., Results: Thirty-four of 38 patients showed 611 focal [ 68 Ga]Pentixafor uptake that followed the contours of the large arteries. Both prevalence and mean TBR max were highest in the descending aorta. There were significantly higher TBR values found in men (1.9 ± 0.3) as compared to women (1.7 ± 0.2; p < 0.05). Patients with mean TBR max  > 1.7 showed a significantly higher incidence of diabetes, hypertension hypercholesterolemia and history of cardiovascular disease than patients with mean TBR max  ≤ 1.7. [ 68 Ga]Pentixafor uptake showed a good reproducibility (r = 0.6, p < 0.01), and there was no difference between the mean TBR max values of plaque lesions (TBR baseline 1.8 ± 0.3 vs TBR follow-up 1.8 ± 0.3) (p = 0.9)., Conclusion: Patients with high arterial uptake showed increased incidence of cardiovascular risk factors, suggesting a potential role of [ 68 Ga]Pentixafor in characterization of atherosclerosis.

Except for task-specific functional MRI, the vast majority of imaging studies assessed human brain function at resting conditions. However, tracking task-specific neuronal activity yields important insight how the brain responds to stimulation. We specifically investigated changes in glucose metabolism, functional connectivity and white matter microstructure during task performance using several recent methodological advancements. Opening the eyes and right finger tapping had elicited an increased glucose metabolism in primary visual and motor cortices, respectively. Furthermore, a decreased metabolism was observed in the regions of the default mode network, which allowed absolute quantification of commonly described deactivations during cognitive tasks. These brain regions showed widespread task-specific changes in functional connectivity, which stretched beyond their primary resting-state networks and presumably reflected the level of recruitment of certain brain regions for each task. Finally, the corresponding white matter fiber pathways exhibited changes in axial and radial diffusivity during the tasks, which were regionally distinctive for certain tract groups. These results highlight that even simple task performance leads to substantial changes of entire brain networks. Exploiting the complementary nature of the different imaging modalities may reveal novel insights how the brain processes external stimuli and which networks are involved in certain tasks.

Purpose: Imaging biomarkers assessed with magnetic resonance imaging (MRI) and/or positron emission tomography (PET) enable non-invasive tumor characterization in cervix cancer patients. We investigated the spatio-temporal stability of hypoxia, perfusion, and the cell density of tumors over time by repetitive imaging prior to, during, and after radio-chemotherapy., Procedures: Thirteen patients were included in this prospective study. The imaging protocol included the following: [ 18 F]fluoromisonidazole ([ 18 F]FMISO)-PET/x-ray computed tomography (CT) and multiparametric (mp)-MRI at four time-points (TP): baseline (BL); and weeks 2 (TP1), 5 (TP2), and 19 after treatment start (follow-up FU). Complete datasets for six patients could be assessed for tumor volume, enhancement kinetics, diffusivity, and [ 18 F]FMISO-avidity (P1-P6). In addition, two patients completed all PET/CT examinations (P7-P8) but not all MR scans; however, one of them had no hypoxia (P8). Descriptive statistics, correlations, and voxel-by-voxel analysis were performed. For various, independent reasons, five patients could not complete the study according to the protocol with all imaging sequences., Results: Median tumor ADCs (in ×10 -3  mm 2 /s) were 0.99 ± 0.10 at BL, 1.20 ± 0.12 at TP1, 1.33 ± 0.14 at TP2, and 1.38 ± 0.21 at FU. The median TBR peak (tumor-to-background) was 2.7 ± 0.8 at BL, 1.6 ± 0.2 at TP1, 1.8 ± 0.3 at TP2, and 1.7 ± 0.3 at FU. The voxel-by-voxel analysis of the [ 18 F]FMISO uptake at BL and TP1 showed no correlation. Between TP2 and TP1 and FU and TP2, weak correlations were found for two patients., Conclusions: Longitudinal mp-MR and PET imaging enables the in vivo tumor characterization over time. While perfusion and cell density decreased, there was a non-uniform change of hypoxia observed during radiotherapy. To assess the potential impact with regard to more personalized treatment approaches, hypoxia imaging-based dose painting for cervix cancer requires further research.

Since 2010 the portfolio of positron emission tomography (PET)-based imaging has been expanded by industry with the introduction of combined whole-body PET/MRI systems with the intent of merging PET-based molecular imaging with the strengths of MRI. PET/MRI has created a lot of hype in the scientific community but comparatively little traction in the clinic. The first years of whole-body PET/MRI were used to address inherent technical challenges; however, it is now time to make use of the full potential of this integrated imaging modality. This opinion piece highlights the continuing challenges for the clinical adoption of PET/MRI and cautions against putting too much emphasis on comparisons with clinical PET/CT. In order for PET/MRI to enter clinical practice, cross-specialty co-operation must be pursued with rigour and use-case scenarios must be propagated, following long-awaited expansion of reimbursement strategies and protocol standardization.

Unlabelled: The aim of this study was to assess the reproducibility of standard, Dixon-based attenuation correction (MR-AC) in PET/MR imaging. A further aim was to estimate a patient-specific lean body mass (LBM) from these MR-AC data., Methods: Ten subjects were positioned in a fully integrated PET/MR system, and 3 consecutive multibed acquisitions of the standard MR-AC image data were acquired. For each subject and MR-AC map, the following compartmental volumes were calculated: total body, soft tissue (ST), fat, lung, and intermediate tissue (IT). Intrasubject differences in the total body and subcompartmental volumes (ST, fat, lung, and IT) were assessed by means of coefficients of variation (CVs) calculated across the 3 consecutive measurements and, again, across these measurements but excluding those affected by major artifacts. All subjects underwent a body composition measurement using air displacement plethysmography (ADP) that was used to calculate a reference LBMADP A second LBM estimate was derived from available MR-AC data using a formula incorporating the respective tissue volumes and densities as well as the subject-specific body weights. A third LBM estimate was obtained from a sex-specific formula (LBMFormula). Pearson correlation was calculated for LBMADP, LBMMR-AC, and LBMFormula Further, linear regression analysis was performed on LBMMR-AC and LBMADP., Results: The mean CV for all 30 scans was 2.1 ± 1.9% (TB). When missing tissue artifacts were excluded, the CV was reduced to 0.3 ± 0.2%. The mean CVs for the subcompartments before and after exclusion of artifacts were 0.9 ± 1.1% and 0.7 ± 0.7% for the ST, 2.9 ± 4.1% and 1.3 ± 1.0% for fat, and 3.6 ± 3.9% and 1.3 ± 0.7% for the IT, respectively. Correlation was highest for LBMMR-AC and LBMADP (r = 0.99). Linear regression of data excluding artifacts resulted in a scaling factor of 1.06 for LBMMR-AC CONCLUSION: LBMMR-AC is shown to correlate well with standard LBM measurements and thus offers routine LBM-based SUV quantification in PET/MR. However, MR-AC images must be controlled for systematic artifacts, including missing tissue and tissue swaps. Efforts to minimize these artifacts could help improve the reproducibility of MR-AC., (© 2016 by the Society of Nuclear Medicine and Molecular Imaging, Inc.)

Purpose: PET with (18)F-FDG has the potential to assess vascular macrophage metabolism. (18)F-FDG is most often used in combination with contrast-enhanced CT to localize increased metabolism to specific arterial lesions. Novel (18)F-FDG PET/MRI hybrid imaging shows high potential for the combined evaluation of atherosclerotic plaques, due to the superior morphological conspicuity of plaque lesions. The purpose of this study was to evaluate the reliability and accuracy of (18)F-FDG PET/MRI uptake quantification compared to PET/CT as a reference standard in patients with carotid atherosclerotic plaques., Methods: The study group comprised 34 consecutive oncological patients with carotid plaques who underwent both PET/CT and PET/MRI with (18)F-FDG on the same day. The presence of atherosclerotic plaques was confirmed by 3 T MRI scans. Maximum standardized uptake values (SUVmax) for carotid plaque lesions and the average SUV of the blood pool within the adjacent internal jugular vein were determined and target-to-blood ratios (TBRs, plaque to blood pool) were calculated., Results: Atherosclerotic lesions with maximum colocalized focal FDG uptake were assessed in each patient. SUVmax values of carotid plaque lesions were significantly lower on PET/MRI than on PET/CT (2.3 ± 0.6 vs. 3.1 ± 0.6; P < 0.01), but were significantly correlated between PET/CT and PET/MRI (Spearman's r = 0.67, P < 0.01). In contrast, TBRmax values of plaque lesions were similar on PET/MRI and on PET/CT (2.2 ± 0.3 vs. 2.2 ± 0.3; P = 0.4), and again were significantly correlated between PET/MRI and PET/CT (Spearman's r = 0.73, P < 0.01). Considering the increasing trend in SUVmax and TBRmax values from early to delayed imaging time-points on PET/CT and PET/MRI, respectively, with continuous clearance of radioactivity from the blood, a slight underestimation of TBRmax values may also be expected with PET/MRI compared with PET/CT., Conclusion: SUVmax and TBRmax values are widely accepted reference parameters for estimation of the radioactivity of atherosclerotic plaques on PET/CT. However, due to a systematic underestimation of SUVmax and TBRmax with PET/MRI, the optimal cut-off values indicating the presence of inflamed plaque tissue need to be newly defined for PET/MRI.

Purpose: The aim of this study was to investigate in 18 patients with ischaemic stroke classified as cryptogenic and presenting non-stenotic carotid atherosclerotic plaques the morphological and biological aspects of these plaques with magnetic resonance imaging (MRI) and (18)F-fluoro-deoxyglucose positron emission tomography ((18)F-FDG PET) imaging., Methods: Carotid arteries were imaged 150 min after injection of (18)F-FDG with a combined PET/MRI system. American Heart Association (AHA) lesion type and plaque composition were determined on consecutive MRI axial sections (n = 460) in both carotid arteries. (18)F-FDG uptake in carotid arteries was quantified using tissue to background ratio (TBR) on corresponding PET sections., Results: The prevalence of complicated atherosclerotic plaques (AHA lesion type VI) detected with high-resolution MRI was significantly higher in the carotid artery ipsilateral to the ischaemic stroke as compared to the contralateral side (39 vs 0 %; p = 0.001). For all other AHA lesion types, no significant differences were found between ipsilateral and contralateral sides. In addition, atherosclerotic plaques classified as high-risk lesions with MRI (AHA lesion type VI) were associated with higher (18)F-FDG uptake in comparison with other AHA lesions (TBR = 3.43 ± 1.13 vs 2.41 ± 0.84, respectively; p < 0.001). Furthermore, patients presenting at least one complicated lesion (AHA lesion type VI) with MRI showed significantly higher (18)F-FDG uptake in both carotid arteries (ipsilateral and contralateral to the stroke) in comparison with carotid arteries of patients showing no complicated lesion with MRI (mean TBR = 3.18 ± 1.26 and 2.80 ± 0.94 vs 2.19 ± 0.57, respectively; p < 0.05) in favour of a diffuse inflammatory process along both carotid arteries associated with complicated plaques., Conclusion: Morphological and biological features of high-risk plaques can be detected with (18)F-FDG PET/MRI in non-stenotic atherosclerotic plaques ipsilateral to the stroke, suggesting a causal role for these plaques in stroke. Combined (18)F-FDG PET/MRI systems might help in the evaluation of patients with ischaemic stroke classified as cryptogenic.

Purpose: The pretherapeutic assessment of prostate cancer is challenging and still holds the risk of over- or undertreatment. This prospective trial investigates positron emission tomography (PET) with [(18)F]fluoroethylcholine (FEC) combined with endorectal magnetic resonance imaging (MRI) for the assessment of primary prostate cancer., Experimental Design: Patients with prostate cancer based on needle biopsy findings, scheduled for radical prostatectomy, were assessed by FEC-PET and MRI in identical positioning. After prostatectomy, imaging results were compared with histologic whole-mount sections, and the PET/MRI lesion-based semiquantitative FEC uptake was compared with biopsy Gleason scores and postoperative histology., Results: PET/MRI showed a patient-based sensitivity of 95% (36/38; 95% confidence interval (CI), 82%-99%). The analysis of 128 prostate lesions demonstrated a sensitivity/specificity/positive predictive value/negative predictive value/accuracy of 67%/35%/59%/44%/54% (P = 0.8295) for MRI and 85%/45%/68%/69%/68% (P = 0.0021) for PET, which increased to 84%/80%/85%/78%/82% (P < 0.0001) by combined FEC-PET/MRI in lesions >5 mm (n = 98). For lesions in patients with Gleason >6 tumors (n = 43), MRI and PET achieved 73%/31%/71%/33%/60% (P = 1.0000) and 90%/62%/84%/73%/81% (P = 0.0010), which were improved to 87%/92%/96%/75%/88% (P < 0.0001) by combined PET/MRI. Applying semiquantitative PET analysis, carcinomas with Gleason scores >6 were distinguished from those with Gleason ≤ 6 with a specificity of 90% and a positive predictive value of 83% (P = 0.0011; needle biopsy 71%/60%, P = 0.1071)., Conclusions: In a prospective diagnostic trial setting, combined FEC-PET/MRI achieved very high sensitivity in the detection of the dominant malignant lesion of the prostate, and markedly improved upon PET or MRI alone. Noninvasive Gleason score assessment was more precise than needle biopsy in this patient cohort. Hence, FEC-PET/MRI merits further investigation in trials of randomized, multiarm design., (©2014 American Association for Cancer Research.)

Purpose: The purpose of this study is to evaluate left ventricular functional parameters in healthy mice and in different murine models of cardiomyopathy with the novel blood pool (BP) positron emission tomography (PET) tracer [68Ga]-albumin., Procedures: ECG-gated microPET examinations were obtained in healthy mice, and mice with dilative (DCM) and ischemic cardiomyopathy (ICM) using the novel BP tracer [68Ga]-albumin (AlbBP), as well as [18F]-FDG microPET. Cine-magnetic resonance imaging (MRI) examination performed on a clinical 1.5-T MRI provided the reference standard measurements., Results: When considering the combined group of healthy controls, DCM and ICM AlbBP-PET significantly overestimated the magnitudes of EDV (AlbBP, 181±86 μl; cine-MRI, 125±80 μl; P<0.001) and ESV (AlbBP, 136±92 μl; cine-MRI, 96±77 μl; P<0.001), whereas the EF (AlbBP, 31±16%; cine-MRI, 33±21%; P=0.910) matched closely to cine-MRI results, as did findings with [18F]-FDG. High correlations were found between the measured cardiac parameters (EDV: R=0.978, ESV: R=0.989, and LVEF: R=0.992)., Conclusions: Measuring left ventricular function in mice with [68Ga]-albumin BP PET is feasible and showed a high correlation compared to cine-MRI, which was used as a reference standard.

A combination of solid-state NMR spectroscopy and MRI was used to evaluate the formation of extracellular matrix in poly(D,L-lactide-co-glycolide) (PLGA) bone implants. Porous PLGA scaffolds were implanted into rat tibiae and analysed after 2, 4 or 8 weeks. MRI clearly delineated the implants within the cancellous bone. Differences in the trabecular structure of the implanted material and native bone were demonstrated. In addition, implants were analyzed by solid-state NMR spectroscopy under magic angle spinning. (13)C NMR spectra showed the unambiguous signature of collagen formed in the scaffolds, but also the characteristic signals of the PLGA matrix, indicating that resorption was not complete after 8 weeks. Furthermore, (31)P NMR spectroscopy detected the inorganic component of the matrix, which is composed of bioapatite. (31)P NMR spectra were quantified and this analysis revealed that the amount of inorganic extracellular matrix formed de novo was significantly lower than in native bone. This demonstrates that solid-state NMR spectroscopy, in particular in combination with MRI, can provide useful information on the composition and structure of the extracellular matrix, and serve as a tool to evaluate the quality of tissue engineering strategies., (Copyright © 2011 John Wiley & Sons, Ltd.)

Background: Previously proposed classifications for carotid plaque and cerebral parenchymal hemorrhages are used to estimate the age of hematoma according to its signal intensities on T1w and T2w MR images. Using these classifications, we systematically investigated the value of cardiovascular magnetic resonance (CMR) in determining the age of vessel wall hematoma (VWH) in patients with spontaneous cervical artery dissection (sCAD)., Methods: 35 consecutive patients (mean age 43.6 ± 9.8 years) with sCAD received a cervical multi-sequence 3T CMR with fat-saturated black-blood T1w-, T2w- and TOF images. Age of sCAD was defined as time between onset of symptoms (stroke, TIA or Horner's syndrome) and the CMR scan. VWH were categorized into hyperacute, acute, early subacute, late subacute and chronic based on their signal intensities on T1w- and T2w images., Results: The mean age of sCAD was 2.0, 5.8, 15.7 and 58.7 days in patients with acute, early subacute, late subacute and chronic VWH as classified by CMR (p < 0.001 for trend). Agreement was moderate between VWH types in our study and the previously proposed time scheme of signal evolution for cerebral hemorrhage, Cohen's kappa 0.43 (p < 0.001). There was a strong agreement of CMR VWH classification compared to the time scheme which was proposed for carotid intraplaque hematomas with Cohen's kappa of 0.74 (p < 0.001)., Conclusions: Signal intensities of VWH in sCAD vary over time and multi-sequence CMR can help to determine the age of an arterial dissection. Furthermore, findings of this study suggest that the time course of carotid hematomas differs from that of cerebral hematomas.

Objectives: : To compare [F]- -fluoro-D-glucose (FDG) positron emission tomography (PET)/computed tomography (CT), used in clinical routine to detect inflamed arteries in patients with arteritis, with high resolution dynamic contrast-enhanced (DCE) magnetic resonance imaging (MRI) in its ability to measure inflammation in carotid and vertebral arteries., Materials and Methods: : This study was performed with written informed consent, Health Insurance Portability and Accountability Act (HIPAA) compliance, and institutional review board approval. DCE-MRI of the carotid and vertebral arteries of 17 patients with suspected arteritis was acquired at 3T (2D saturation-recovery spoiled gradient echo, in plane resolution 0.625 × 0.625 mm) using a dedicated 4-channel carotid coil. Patients underwent [F] FDG-PET/CT within 1 week of the MRI scan. The blood pool-corrected mean standardized uptake value (mean target-to-background ratio [TBRmean]) was measured on PET/CT images at the identical location as the region-of-interest in the magnetic resonance images. MRI signal intensity data was analyzed to generate estimates of the tissue extraction fraction and interstitial volume using a 2-compartment model., Results: : [F]-FDG PET/CT TBRmean was significantly higher in patients with than without arteritis (1.55 ± 0.34 vs. 1.06 ± 0.14, P = 0.001). Patients diagnosed with arteritis had significantly higher extraction fractions as measured by DCE-MRI than patients without arteritis (8.79% ± 2.19% vs. 5.82% ± 1.13%, P = 0.002). TBRmean correlated significantly with the extraction fraction (r = 0.73, P < 0.001). DCE-MRI and FDG-PET/CT yielded the same sensitivity (86%) and specificity (90%) for the detection of arteritis. Intra- and interreader reproducibility was good with Intraclass Correlation Coefficients of 0.82 and 0.78, respectively., Conclusions: : DCE-MRI is able to measure arterial inflammation reliably and noninvasively with good correlation to [F]-FDG PET/CT in patients suffering from arteritis of the supraaortic arteries.

Background and Purpose: Vessel wall inflammation (VWI) may be a pathogenetic factor in cervical artery dissection (CAD). We used contrast-enhanced high-resolution MRI (hrMRI) and positron emission tomography CT (PET-CT) to systematically investigate VWI in spontaneous CAD., Methods: In this monocentric, prospective, observational study, all consecutive patients with acute, MRI-confirmed, spontaneous CAD admitted to our center between August 2007 and August 2009 were included. VWI was defined as perivascular contrast enhancement in hrMRI and increased perivascular [18F]-fluorodesoxyglucose uptake in PET-CT. VWI was further differentiated between local (restricted to the site of dissection) and generalized (exceeding the site of dissection)., Results: A total of 37 patients were included. Multiple dissections were seen in 10 patients (27%). Twenty-five patients received both modalities as planned, 8 received only PET-CT, and 4 received only hrMRI. A subset of patients showed signs of a generalized VWI in hrMRI (4/29 patients, 14%) and PET-CT (8/33 patients, 24%). In patients who received both modalities, all with hrMRI signs of generalized VWI were PET-CT positive (3/3), whereas some PET-CT-positive patients were hrMRI-negative (4/7). If present, generalized VWI in hrMRI completely resolved within 6 months. The presence of >2 simultaneous dissections (seen in 2 patients) was significantly associated with generalized VWI in hrMRI (P=0.015) but marginally not in PET-CT (P=0.053)., Conclusions: A subset of patients with spontaneous CAD showed signs of a generalized transient inflammatory arteriopathy in contrast-enhanced hrMRI and PET-CT. This subset of patients may be more prone to multiple dissections.

Purpose: To assess whether a radiomics and machine learning (ML) model combining quantitative parameters and radiomics features extracted from simultaneous multiparametric 18F-FDG PET/MRI can discriminate between benign and malignant breast lesions. Methods: A population of 102 patients with 120 breast lesions (101 malignant and 19 benign) detected on ultrasound and/or mammography was prospectively enrolled. All patients underwent hybrid 18F-FDG PET/MRI for diagnostic purposes. Quantitative parameters were extracted from DCE (MTT, VD, PF), DW (mean ADC of breast lesions and contralateral breast parenchyma), PET (SUVmax, SUVmean, and SUVminimum of breast lesions, as well as SUVmean of the contralateral breast parenchyma), and T2-weighted images. Radiomics features were extracted from DCE, T2-weighted, ADC, and PET images. Different diagnostic models were developed using a fine Gaussian support vector machine algorithm which explored different combinations of quantitative parameters and radiomics features to obtain the highest accuracy in discriminating between benign and malignant breast lesions using fivefold cross-validation. The performance of the best radiomics and ML model was compared with that of expert reader review using McNemar's test. Results: Eight radiomics models were developed. The integrated model combining MTT and ADC with radiomics features extracted from PET and ADC images obtained the highest accuracy for breast cancer diagnosis (AUC 0.983), although its accuracy was not significantly higher than that of expert reader review (AUC 0.868) (p = 0.508). Conclusion: A radiomics and ML model combining quantitative parameters and radiomics features extracted from simultaneous multiparametric 18F-FDG PET/MRI images can accurately discriminate between benign and malignant breast lesions. [ABSTRACT FROM AUTHOR]