Robustness of apparent diffusion coefficient-based lymph node classification for diagnosis of prostate cancer metastasis.

OBJECTIVES: The aim of this proof-of-principle study combining data analysis and computer simulation was to evaluate the robustness of apparent diffusion coefficient (ADC) values for lymph node classification in prostate cancer under conditions comparable to clinical practice. MATERIALS AND METHODS: To assess differences in ADC and inter-rater variability, ADC values of 359 lymph nodes in 101 patients undergoing simultaneous prostate-specific membrane antigen (PSMA)-PET/MRI were retrospectively measured by two blinded readers and compared in a node-by-node analysis with respect to lymph node status. In addition, a phantom and 13 patients with 86 lymph nodes were prospectively measured on two different MRI scanners to analyze inter-scanner agreement. To estimate the diagnostic quality of the ADC in real-world application, a computer simulation was used to emulate the blurring caused by scanner and reader variability. To account for intra-individual correlation, the statistical analyses and simulations were based on linear mixed models. RESULTS: The mean ADC of lymph nodes showing PSMA signals in PET was markedly lower (0.77 × 10-3 mm2/s) compared to inconspicuous nodes (1.46 × 10-3 mm2/s, p < 0.001). High inter-reader agreement was observed for ADC measurements (ICC 0.93, 95%CI [0.92, 0.95]). Good inter-scanner agreement was observed in the phantom study and confirmed in vivo (ICC 0.89, 95%CI [0.84, 0.93]). With a median AUC of 0.95 (95%CI [0.92, 0.97]), the simulation study confirmed the diagnostic potential of ADC for lymph node classification in prostate cancer. CONCLUSION: Our model-based simulation approach implicates a high potential of ADC for lymph node classification in prostate cancer, even when inter-rater and inter-scanner variability are considered. CLINICAL RELEVANCE STATEMENT: The ADC value shows a high diagnostic potential for lymph node classification in prostate cancer. The robustness to scanner and reader variability implicates that this easy to measure and widely available method could be readily integrated into clinical routine. KEY POINTS: • The diagnostic value of the apparent diffusion coefficient (ADC) for lymph node classification in prostate cancer is unclear in the light of inter-rater and inter-scanner variability. • Metastatic and inconspicuous lymph nodes differ significantly in ADC, resulting in a high diagnostic potential that is robust to inter-scanner and inter-rater variability. • ADC has a high potential for lymph node classification in prostate cancer that is maintained under conditions comparable to clinical practice.

Prognostic implication of myocardial perfusion and contractile reserve in end-stage renal disease: A direct comparison of myocardial perfusion scintigraphy and dobutamine stress echocardiography.

BACKGROUND: We aimed to compare the prognostic value of myocardial perfusion scintigraphy (MPS) and dobutamine stress echocardiography (DSE) in patients with end-stage renal disease (ESRD) without known coronary artery disease. METHODS: Two-hundred twenty-nine ESRD patients who applied for kidney transplantation at our centre were prospectively evaluated by MPS and DSE. The primary endpoint was a composite of myocardial infarction (MI) or all-cause mortality. The secondary endpoint included MI or coronary revascularization (CR) not triggered by MPS or DSE at baseline. RESULTS: MPS detected reversible ischemia in 31 patients (13.5%) and fixed perfusion defects in 13 (5.7%) patients. DSE discovered stress-induced wall motion abnormalities (WMAs) in 28 (12.2%) and at rest in 18 (7.9%) patients. MPS and DSE results agreed in 85.6% regarding reversible defects (κ = 0.358; P < .001) and in 90.8% regarding fixed defects (κ = 0.275; P < .001). Coronary angiography detected relevant stenosis > 50% in only 15 of 38 patients (39.5%) with pathological findings in MPS and/or DSE. At a median follow-up of 8 years and 10 months, the primary endpoint occurred in 70 patients (30.6%) and the secondary endpoint in 24 patients (10.5%). The adjusted Cox hazard ratios (HRs) for the primary endpoint were 1.77 (95% CI 1.02-3.08; P = .043) for perfusion defects in MPS and 1.36 (95% CI 0.78-2.37; P = ns) for WMA in DSE. The secondary endpoint was significantly correlated with the findings of both modalities, MPS (HR 3.21; 95% CI 1.35-7.61; P = .008) and DSE (HR 2.67; 95% CI 1.15-6.20; P = .022). CONCLUSION: Perfusion defects in MPS are a stronger determinant of all-cause mortality, MI and the need for future CR compared with WMAs in DSE. Given the complementary functional information provided by MPS vs DSE, results are sometimes contradictory, which may indicate differences in the underlying pathophysiology.

Pain in survivors of Ewing sarcoma: Prevalence, associated factors and prediction of recurrence.

BACKGROUND: While the prognosis of patients with Ewing sarcoma (EwS) is improving, little is known about the frequency of pain and its risk factors in survivors of EwS. This study aims to analyse the prevalence and risk factors of pain and its predictive value for recurrence. PATIENTS AND METHODS: In patients with remission after treatment of EwS, frequency and characteristics of pain within the first 5 years of follow up were assessed retrospectively. RESULTS: Of 80 patients, 37 (46%) presented with at least one episode of pain. Chronic pain (>3 months) was observed in 10 patients (13%). Experience of at least one episode of pain was associated with prior combined local treatment (surgery and radiation compared to surgery alone; odds ratio [OR] 5.83, 95% confidence interval [CI] 1.43-34.9, P = .007). A total of 59 episodes of pain were observed, including 47 acute and 12 chronic episodes. Lower limb pain accounted for 46% (27/59) of all episodes of pain, and was associated with primary tumour of the pelvis or lower extremity (OR 4.29, 95% CI 1.18-18.21, P = .025), which represented 64% (51/80) of all EwS. The positive predictive value of pain for recurrence was only 12%. CONCLUSION: Pain is a common problem in survivors of EwS, which mostly affects the lower extremity, and should be regularly assessed. Interventions to reduce pain may be particularly important in patients with combined local treatment with surgery and radiation, who seem to be at considerably increased risk for pain. Patients presenting with pain should be examined for recurrence.

Efficacy of 90Y-Radioembolization in Metastatic Colorectal Cancer Depending on the Primary Tumor Side.

BACKGROUND: Metastatic colorectal cancer (mCRC) is associated with different molecular biology, clinical characteristics, and outcome depending on the primary tumor localization. We aimed to evaluate the effectiveness of 90Y-radioembolization (RE) for therapy of colorectal liver metastases depending on the primary tumor side. METHODS: We performed a retrospective analysis of n = 73 patients with mCRC and RE in our university liver center between 2009 and 2018. Patients were stratified according to the primary tumor side (left vs. right hemicolon), treatment response was assessed by the Response Evaluation Criteria in Solid Tumors (RECIST) at follow-up after 3 months. Kaplan-Meier analysis was performed to analyze survival followed by Cox regression to determine independent prognostic factors for survival. RESULTS: Prior to RE, all patients had received systemic therapy, with either stable or progressive disease, but no partial or complete response. In n = 22/73 (30.1%) patients, the primary tumor side was in the right colon; in n = 51/73 (69.9%) patients, in the left colon. Hepatic tumor burden was ≤25% in n = 36/73 (49.3%) patients and >25% in n = 37/73 (50.7%) patients. At 3 months, n = 21 (33.8%) patients showed treatment response (n = 2 [3.2%]; complete response, n = 19 [30.6%]; partial response), n = 13 (21.0%) stable disease, and n = 28 (45.2%) progressive disease after RE. The median survival in case of primary tumor side in the left colon was significantly higher than for primary tumors in the right colon (8.7 vs. 6.0 months, p = 0.033). The median survival for a hepatic tumor burden ≤25% was significantly higher than that of >25% (13.9 vs. 4.3 months, p < 0.001). The median overall survival was 6.1 months. CONCLUSION: The median survival after RE in hepatic-mCRC depends on the primary tumor side and the preprocedural hepatic tumor burden.

PET/CT Imaging and Physiology of Mice on High Protein Diet.

BACKGROUND: High protein (HP) diets have been proposed to reduce body weight in humans. The diets are known to alter energy metabolism, which can affect the quality of [18F]FDG PET heart images. In this preclinical study, we therefore explore the impact of a prolonged HP diet on myocardial [18F]FDG uptake. METHODS: C57BL/6J (Black six (Bl6)) and apolipoprotein E-deficient (apoE-/-) mice were fed chow, a HP diet, or a low protein (LP) diet for 12 weeks. At baseline and after treatment, the animals were injected with 33.0 MBq of [18F]FDG and a 30 min PET/CT scan was made. Myocardial volume and [18F]FDG uptake were quantified using PET and the % of body fat was calculated from CT. RESULTS: Myocardial [18F]FDG uptake was similar for all diets at the follow-up scan but an increase between baseline and follow-up scans was noticed in the LP groups. Myocardial volume was significantly smaller in the C57BL HP group compared to the other Bl6 groups. Body weight increased less in the two HP groups compared to the chow and LP groups. Body fat percentage was significantly higher in the LP groups. This effect was stronger in C57BL mice (28.7%) compared to apoE-/- mice (15.1%). CONCLUSIONS: Myocardial uptake of [18F]FDG in mice is not affected by increased protein intake but [18F]FDG uptake increases when the amount of protein is lowered. A lower body weight and percentage of body fat were noticed when applying a HP diet.

18F-PSMA-1007 PET/CT at 60 and 120 minutes in patients with prostate cancer: biodistribution, tumour detection and activity kinetics.

PURPOSE: PSMA-targeted PET in patients with prostate cancer (PCa) has a significant impact on treatment decisions. By far the most frequently used PSMA ligand is 68Ga-labelled PSMA-11. However, due to the availability of larger amounts of activity, 18F-labelled PSMA ligands are of major interest. The aim of the present study was to evaluate the biodistribution and performance of the novel 18F-labelled ligand PSMA-1007 at two different time points. METHODS: This retrospective analysis included 40 consecutive patients (mean age 68.7 ± 8.1 years) referred for PSMA PET/CT. 18F-PSMA-1007 PET/CT was performed for localization of biochemical relapse, primary staging or therapy follow-up. Circular regions of interest were placed on representative slices of the liver, spleen, kidney, abdominal aortic blood pool, bone marrow (fourth lumbar vertebral body), urinary bladder and gluteus muscle at 60 and 120 min after injection. In malignant lesions the maximum standardized uptake (SUVmax) was measured within volumes of interest at both time points. All SUVs at 60 min were compared with those at 120 min after injection. RESULTS: The activity in the blood pool, urinary bladder and gluteus muscle was very low and decreased significantly over time (P < 0.001). Uptake in the liver, spleen and kidney showed a significant increase over time and uptake in the bone marrow remained stable. Overall, 135 PCa lesions were detected at 60 min and 136 lesions at 120 min after injection. The median SUVmax increased significantly (P < 0.001) from 10.98 to 15.51 between 60 and 120 min. CONCLUSION: PCa lesions show a significant increase in 18F-PSMA-1007 uptake at 120 min compared with 60 min after injection. In addition, accumulation of the tracer in the urinary bladder was very low leading to improved contrast of adjacent PCa lesions. Increasing accumulation in the liver may limit the sensitivity of the tracer in detecting liver metastases.

Targeting PSMA by radioligands in non-prostate disease-current status and future perspectives.

BACKGROUND: Prostate-specific membrane antigen (PSMA) is the up-and-coming target for molecular imaging of prostate cancer. Despite its name, non-prostate-related PSMA expression in physiologic tissue as well as in benign and malignant disease has been reported in various publications. Unlike in prostate cancer, PSMA expression is only rarely observed in non-prostate tumor cells. Instead, expression occurs in endothelial cells of tumor-associated neovasculature, although no endothelial expression is observed under physiologic conditions. The resulting potential for tumor staging in non-prostate malignant tumors has been demonstrated in first patient studies. This review summarizes the first clinical studies and deduces future perspectives in staging, molecular characterization, and PSMA-targeted radionuclide therapy based on histopathologic examinations of PSMA expression. CONCLUSIONS: The non-exclusivity of PSMA in prostate cancer opens a window to utilize the spectrum of available radioactive PSMA ligands for imaging and molecular characterization and maybe even therapy of non-prostate disease.

Recurrence of Ewing sarcoma: Is detection by imaging follow-up protocol associated with survival advantage?

BACKGROUND: The Cooperative Ewing Sarcoma Study and the Late Effects Surveillance System of the Society for Paediatric Oncology and Haematology recommend a structured follow-up imaging protocol (FUIP) for patients with Ewing sarcoma (EwS) with decreasing frequency of imaging over the first 5 years. The present study aims to assess the effectiveness of the FUIP for EwS patients regarding survival after relapse. PATIENTS AND METHODS: A retrospective multicenter analysis on 160 eligible patients with EwS recurrence was performed. Potential survival differences following recurrence diagnosis between patients with protocol-detected and symptomatic relapse were investigated using the Kaplan-Meier method. Additional subgroup analyses were performed on the relapse type. Overall survival (OS) was calculated from diagnosis of relapse to last follow-up or death. RESULTS: In the multicenter analysis, recurrence was detected by FUIP in 77 of 160 patients (48%) and due to symptoms in 83 patients (52%). Regarding the entire study population, OS was significantly superior in patients with protocol-detected relapse compared to patients with symptomatic relapse (median, 2.4 vs. 1.2 years; P < 0.001). In the subgroup analyses, patients whose lung recurrences were detected by the FUIP experienced longer survival after recurrence than those whose recurrences were detected symptomatically (P = 0.023). In the 83 symptomatic patients, pain was the most prevalent symptom of relapse (72%). CONCLUSION: FUIP may benefit survival in EwS relapse, especially in lung recurrence. Pain was the leading symptom of relapse.

[(18)F]FDG PET/CT outperforms [(18)F]FDG PET/MRI in differentiated thyroid cancer.

PURPOSE: To evaluate the diagnostic potential of PET/MRI with [(18)F]FDG in comparison to PET/CT in patients with differentiated thyroid cancer suspected or known to have dedifferentiated. METHODS: The study included 31 thyroidectomized and remnant-ablated patients who underwent a scheduled [(18)F]FDG PET/CT scan and were then enrolled for a PET/MRI scan of the neck and thorax. The datasets (PET/CT, PET/MRI) were rated regarding lesion count, conspicuity, diameter and characterization. Standardized uptake values were determined for all [(18)F]FDG-positive lesions. Histology, cytology, and examinations before and after treatment served as the standards of reference. RESULTS: Of 26 patients with a dedifferentiated tumour burden, 25 were correctly identified by both [(18)F]FDG PET/CT and PET/MRI. Detection rates by PET/CT and PET/MRI were 97 % (113 of 116 lesions) and 85 % (99 of 113 lesions) for malignant lesions, and 100 % (48 of 48 lesions) and 77 % (37 of 48 lesions) for benign lesions, respectively. Lesion conspicuity was higher on PET/CT for both malignant and benign pulmonary lesions and in the overall rating for malignant lesions (p < 0.001). There was a difference between PET/CT and PET/MRI in overall evaluation of malignant lesions (p < 0.01) and detection of pulmonary metastases (p < 0.001). Surgical evaluation revealed three malignant lesions missed by both modalities. PET/MRI additionally failed to detect 14 pulmonary metastases and 11 benign lesions. CONCLUSION: In patients with thyroid cancer and suspected or known dedifferentiation, [(18)F]FDG PET/MRI was inferior to low-dose [(18)F]FDG PET/CT for the assessment of pulmonary status. However, for the assessment of cervical status, [(18)F]FDG PET/MRI was equal to contrast-enhanced neck [(18)F]FDG PET/CT. Therefore, [(18)F]FDG PET/MRI combined with a low-dose CT scan of the thorax may provide an imaging solution when high-quality imaging is needed and high-energy CT is undesirable or the use of a contrast agent is contraindicated.

[(68)Ga]DOTATATE PET/MRI and [(18)F]FDG PET/CT are complementary and superior to diffusion-weighted MR imaging for radioactive-iodine-refractory differentiated thyroid cancer.

PURPOSE: The purpose of this study was to determine whether [(68)Ga]DOTATATE PET/MRI with diffusion-weighted imaging (DWI) can replace or complement [(18)F]FDG PET/CT in patients with radioactive-iodine (RAI)-refractory differentiated thyroid cancer (DTC). METHODS: The study population comprised 12 patients with elevated thyroglobulin and a negative RAI scan after thyroidectomy and RAI remnant ablation who underwent both [(18)F]FDG PET/CT and [(68)Ga]DOTATATE PET/MRI within 8 weeks of each other. The presence of recurrent cancer was evaluated on a per-patient, per-organ and per-lesion basis. Histology, and prior and follow-up examinations served as the standard of reference. RESULTS: Recurrent or metastatic tumour was confirmed in 11 of the 12 patients. [(68)Ga]DOTATATE PET(/MRI) correctly identified the tumour burden in all 11 patients, whereas in one patient local relapse was missed by [(18)F]FDG PET/CT. In the lesion-based analysis, overall lesion detection rates were 79/85 (93 %), 69/85 (81 %) and 27/82 (33 %) for [(18)F]FDG PET/CT, [(68)Ga]DOTATATE PET/MRI and DWI, respectively. [(18)F]FDG PET(/CT) was superior to [(68)Ga]DOTATATE PET(/MRI) in the overall evaluation and in the detection of pulmonary metastases. In the detection of extrapulmonary metastases, [(68)Ga]DOTATATE PET(/MRI) showed a higher sensitivity than [(18)F]FDG PET(/CT), at the cost of lower specificity. DWI achieved only poor sensitivity and was significantly inferior to [(18)F]FDG PET in the lesion-based evaluation in the detection of both extrapulmonary and pulmonary metastases. CONCLUSION: [(18)F]FDG PET/CT was more sensitive than [(68)Ga]DOTATATE PET/MRI in the evaluation of RAI-refractory DTC, mostly because of its excellent ability to detect lung metastases. In the evaluation of extrapulmonary lesions, [(68)Ga]DOTATATE PET(/MRI) was more sensitive and [(18)F]FDG PET(/CT) more specific. Furthermore, DWI did not provide additional information and cannot replace [(18)F]FDG PET for postoperative monitoring of patients with suspected RAI-refractory DTC.

Radiomics-Based Prediction Model for Outcome of Radioembolization in Metastatic Colorectal Cancer.

PURPOSE: To evaluate the benefit of a contrast-enhanced computed tomography (CT) radiomics-based model for predicting response and survival in patients with colorectal liver metastases treated with transarterial Yttrium-90 radioembolization (TARE). MATERIALS AND METHODS: Fifty-one patients who underwent TARE were included in this single-center retrospective study. Response to treatment was assessed using the Response Evaluation Criteria in Solid Tumors (RECIST 1.1) at 3-month follow-up. Patients were stratified as responders (complete/partial response and stable disease, n = 24) or non-responders (progressive disease, n = 27). Radiomic features (RF) were extracted from pre-TARE CT after segmentation of the liver tumor volume. A model was built based on a radiomic signature consisting of reliable RFs that allowed classification of response using multivariate logistic regression. Patients were assigned to high- or low-risk groups for disease progression after TARE according to a cutoff defined in the model. Kaplan-Meier analysis was performed to analyze survival between high- and low-risk groups. RESULTS: Two independent RF [Energy, Maximal Correlation Coefficient (MCC)], reflecting tumor heterogeneity, discriminated well between responders and non-responders. In particular, patients with higher magnitude of voxel values in an image (Energy), and texture complexity (MCC), were more likely to fail TARE. For predicting treatment response, the area under the receiver operating characteristic curve of the radiomics-based model was 0.75 (95% CI 0.48-1). The high-risk group had a shorter overall survival than the low-risk group (3.4 vs. 6.4 months, p < 0.001). CONCLUSION: Our CT radiomics model may predict the response and survival outcome by quantifying tumor heterogeneity in patients treated with TARE for colorectal liver metastases.

Myocardial perfusion imaging and coronary calcium scoring with a two-slice SPECT/CT system: can the attenuation map be calculated from the calcium scoring CT scan?

PURPOSE: Coronary artery calcium scoring can complement myocardial perfusion imaging (MPI). The purpose of this study was to evaluate the feasibility and accuracy of using the CalciumScore-CT derived from a combined SPECT/CT device also for SPECT attenuation correction (AC). METHODS: The study group comprised 99 patients who underwent both post-stress and rest MPI using a two-slice SPECT/CT system. For AC, one of the two scans was accompanied by a CalciumScore-CT scan (CalciumScore-CTAC) and the other by a conventional spiral CT (AttenCorr-CT) scan (AttenCorr-CTAC). In 48 patients the CalciumScore-CT scan was acquired with the post-stress scan and the AttenCorr-CT scan with the rest scan, and in 51 patients the order was reversed. The accuracy of the images based on AC was determined qualitatively by consensus reading with respect to the clinical diagnoses as well as quantitatively by comparing the perfusion summed stress scores (SSS) and the summed rest scores (SRS) between attenuation-corrected and uncorrected images. RESULTS: In comparison to the uncorrected images CalciumScore-CTAC led to regional inaccuracies in 14 of 51 of studies (27.5%) versus 12 of 48 studies (25%) with AttenCorr-CTAC for the stress studies and in 5 of 48 (10%) versus 1 of 51 (2%) for the rest studies, respectively. This led to intermediate and definite changes in the final diagnosis (ischaemia and/or scarring) in 12% of the studies (12 of 99) and in 7% of the studies (7 of 99) with CalciumScore-CTAC and in 9% of the studies (9 of 99) and 4% of the studies (4 of 99) with AttenCorr-CTAC. Differences in SSS and SRS with respect to the uncorrected images were greater for the CalciumScore-CTAC images than for the AttenCorr-CTAC images (ΔSSS 4.5 ± 5.6 and 2.1 ± 4.4, p = 0.023; ΔSRS 4.2 ± 4.9 and 1.6 ± 3.2, p = 0.004, respectively). CONCLUSION: Using the same CT scan for calcium scoring and SPECT AC is feasible. Image interpretation must, however, include uncorrected images since CT-based AC relatively often introduces artefacts into the myocardial perfusion images. This effect is somewhat more pronounced with CalciumScore-CTAC than with AttenCorr-CTAC.

177 Lu-DOTATATE (Lutathera) Therapy in 68 Ga-DOTATATE PET/CT-Negative Liver Metastases of a Neuroendocrine Tumor.

ABSTRACT: A 73-year-old man with metastatic pancreatic neuroendocrine tumor was evaluated with 68 Ga-DOTATATE PET/CT for peptide receptor radionuclide therapy. Both PET-positive and negative lesions were seen in the liver, along with extrahepatic metastases. Histopathology was obtained from one of the PET-negative liver lesions to exclude secondary malignancy. Histology confirmed a well-differentiated (G2) metastasis of pNET with high somatostatin receptor expression. We initiated peptide receptor radionuclide therapy with close monitoring of the PET-negative liver metastases. We present a rare case, where posttherapeutic scintigraphy revealed vigorous uptake of 177 Lu-DOTATATE even in the 68 Ga-DOTATATE PET-negative liver metastases. Follow-up PET/CT showed a partial response to therapy.

First clinical experience with fractionated intracavitary radioimmunotherapy using [177Lu]Lu-6A10-Fab fragments in patients with glioblastoma: a pilot study.

BACKGROUND: Following resection and standard adjuvant radio- and chemotherapy, approved maintenance therapies for glioblastoma are lacking. Intracavitary radioimmunotherapy (iRIT) with 177Lu-labeled 6A10-Fab fragments targeting tumor-associated carbonic anhydrase XII and injected into the resection cavity offers a novel and promising strategy for improved tumor control. METHODS: Three glioblastoma patients underwent tumor resection followed by standard radio- and chemotherapy. These patients with stable disease following completion of standard therapy underwent iRIT on compassionate grounds. After surgical implantation of a subcutaneous injection reservoir with a catheter into the resection cavity, a leakage test with [99mTc]Tc-DTPA was performed to rule out leakage into other cerebral compartments. IRIT comprised three consecutive applications over three months for each patient, with 25%, 50%, 25% of the total activity injected. A dosimetry protocol was included with blood sampling and SPECT/CT of the abdomen to calculate doses for the bone marrow and kidneys as potential organs at risk. RESULTS: All three patients presented without relevant leakage after application of [99mTc]Tc-DTPA. Two patients underwent three full cycles of iRIT (592 MBq and 1228 MBq total activity). One patient showed histologically proven tumor progression after the second cycle (526 MBq total activity). No relevant therapy-associated toxicities or adverse events were observed. Dosimetry did not reveal absorbed doses above upper dose limits for organs at risk. CONCLUSIONS: In first individual cases, iRIT with [177Lu]Lu-6A10-Fab appears to be feasible and safe, without therapy-related side effects. A confirmatory multicenter phase-I-trial was recently opened and is currently recruiting.

Optimized Whole-Body PET MRI Sequence Workflow in Pediatric Hodgkin Lymphoma Patients.

18F-FDG PET/MRI might be the diagnostic method of choice for Hodgkin lymphoma patients, as it combines significant metabolic information from PET with excellent soft-tissue contrast from MRI and avoids radiation exposure from CT. However, a major issue is longer examination times than for PET/CT, especially for younger children needing anesthesia. Thus, a targeted selection of suitable whole-body MRI sequences is important to optimize the PET/MRI workflow. Methods: The initial PET/MRI scans of 84 EuroNet-PHL-C2 study patients from 13 international PET centers were evaluated. In each available MRI sequence, 5 PET-positive lymph nodes were assessed. If extranodal involvement occurred, 2 splenic lesions, 2 skeletal lesions, and 2 lung lesions were also assessed. A detection rate was calculated dividing the number of visible, anatomically assignable, and measurable lesions in the respective MRI sequence by the total number of lesions. Results: Relaxation time-weighted (T2w) transverse sequences with fat saturation (fs) yielded the best result, with detection rates of 95% for nodal lesions, 62% for splenic lesions, 94% for skeletal lesions, and 83% for lung lesions, followed by T2w transverse sequences without fs (86%, 49%, 16%, and 59%, respectively) and longitudinal relaxation time-weighted contrast-enhanced transverse sequences with fs (74%, 35%, 57%, and 55%, respectively). Conclusion: T2w transverse sequences with fs yielded the highest detection rates and are well suited for accurate whole-body PET/MRI in lymphoma patients. There is no evidence to recommend the use of contrast agents.

Simultaneous PET/MR imaging of the brain: feasibility of cerebral blood flow measurements with FAIR-TrueFISP arterial spin labeling MRI.

BACKGROUND: Hybrid positron emission tomography/magnetic resonance imaging (PET/MRI) with simultaneous data acquisition promises a comprehensive evaluation of cerebral pathophysiology on a molecular, anatomical, and functional level. Considering the necessary changes to the MR scanner design the feasibility of arterial spin labeling (ASL) is unclear. PURPOSE: To evaluate whether cerebral blood flow imaging with ASL is feasible using a prototype PET/MRI device. MATERIAL AND METHODS: ASL imaging of the brain with Flow-sensitive Alternating Inversion Recovery (FAIR) spin preparation and true fast imaging in steady precession (TrueFISP) data readout was performed in eight healthy volunteers sequentially on a prototype PET/MRI and a stand-alone MR scanner with 128 × 128 and 192 × 192 matrix sizes. Cerebral blood flow values for gray matter, signal-to-noise and contrast-to-noise ratios, and relative signal change were compared. Additionally, the feasibility of ASL as part of a clinical hybrid PET/MRI protocol was demonstrated in five patients with intracerebral tumors. RESULTS: Blood flow maps showed good delineation of gray and white matter with no discernible artifacts. The mean blood flow values of the eight volunteers on the PET/MR system were 51 ± 9 and 51 ± 7 mL/100 g/min for the 128 × 128 and 192 × 192 matrices (stand-alone MR, 57 ± 2 and 55 ± 5, not significant). The value for signal-to-noise (SNR) was significantly higher for the PET/MRI system using the 192 × 192 matrix size (P < 0.01), the relative signal change (δS) was significantly lower for the 192 × 192 matrix size (P = 0.02). ASL imaging as part of a clinical hybrid PET/MRI protocol could successfully be accomplished in all patients in diagnostic image quality. CONCLUSION: ASL brain imaging is feasible with a prototype hybrid PET/MRI scanner, thus adding to the value of this novel imaging technique.

Hybrid CMR- and FDG-PET-Imaging Gives New Insights Into the Relationship of Myocardial Metabolic Activity and Fibrosis in Patients With Becker Muscular Dystrophy.

BACKGROUND: Cardiac involvement in patients with Becker muscular dystrophy (BMD) is an important predictor of mortality. The cardiac phenotype of BMD patients is characterized by slowly progressive myocardial fibrosis that starts in the left ventricular (LV) free wall segments and extends into the septal wall during the disease course. PURPOSE: Since the reason for this characteristic cardiac phenotype is unknown and comprehensive approaches using e.g. hybrid imaging combining cardiovascular magnetic resonance (CMR) with 18F-fluorodeoxyglucose (FDG) positron emission tomography (PET) are limited, the present study addressed this issue by a comprehensive non-invasive imaging approach. METHODS: Hybrid CMR- and FDG-PET-imaging was performed in N = 14 patients with BMD on a whole-body Biograph mMR system (Siemens, Erlangen, Germany). The CMR protocol comprised cine- and late-gadolinium-enhancement (LGE)-imaging. Metabolism was assessed with FDG-PET after oral glucose loading to effect myocardial carbohydrate uptake. PET was acquired for 65 min starting with tracer injection. Uptake values from 60 to 65 min p.i. were divided by the area under the blood activity curve and reported as percentages relative to the segment with maximal myocardial FDG uptake. RESULTS: A characteristic pattern of LGE in the LV lateral wall was observed in 13/14 patients whereas an additional septal LGE pattern was documented in 6/14 patients only. There was one patient without any LGE. Segmental FDG uptake was 88 ± 6% in the LV lateral wall vs. 77 ± 10% in the septal wall (p < 0.001). There was an inverse relationship between segmental FDG activity compared to segmental LGE extent (r = -0.33, p = 0.089). There were N = 6 LGE-positive patients with a segmental difference in FDG uptake of >15% in the LV lateral wall compared to the septal wall = ΔFDG-high group (lateral FDG = 91±3% vs. septal FDG = 69±8%; p < 0.001) while the remaining N = 7 LGE-positive patients showed a segmental difference in FDG uptake of ≤ 15% = ΔFDG-low group (lateral FDG = 85±7% vs. septal FDG = 83 ± 5%; p = 0.37). Patients in the ΔFDG-high group showed only a minor difference in the LGE extent between the LV lateral wall vs. septal wall (p = 0.09) whereas large differences were observed in the ΔFDG-low group (p < 0.004). CONCLUSIONS: Segmental FDG uptake-reflecting myocardial metabolic activity-is higher in the LV free wall of BMD patients-possibly due to a higher segmental work load. However, segmental metabolic activity seems to be dependent on and limited by the respective segmental extent of myocardial fibrosis as depicted by LGE-imaging.

Radioembolization, Principles and indications.

Radioembolization is the selective application of radionuclide-loaded microspheres into liver arteries for the therapy of liver tumours and metastases. In this review, we focused on therapy planning and dosimetry, as well as the main indications of 90Y-glass and resin microspheres and 166Ho-microspheres.