Added Value of Contrast Medium in Whole-Body Hybrid Positron Emission Tomography/Magnetic Resonance Imaging: Comparison between Contrast-Enhanced and Non-Contrast-Enhanced Protocols.

OBJECTIVE: To compare the diagnostic ability and time efficiency of contrast-enhanced (CE) whole body fluorodeoxyglucose (FDG) positron emission tomography/magnetic resonance imaging (PET/MRI) protocol and non-CE (NCE) protocol. SUBJECTS AND METHODS: Ninety-three patients with known primary tumors underwent whole-body hybrid FDG PET/MRI during the follow-up of their malignancies with the use of NCE and CE protocols. The NCE PET/MRI protocol consisted of diffusion-weighted (b = 0 and 800 s/mm2) and T1-weighted Turbo Flash in the axial plane and T2-weighted HASTE sequence in the coronal planes (Σ = 25 min). The CE PET/MRI protocol was performed by acquiring axial serial CE 3D FS VIBE images in the upper abdomen, completing the whole body in the late phase in the axial plane (Σ = 30 min). RESULTS: There was a statistically significant difference between the total number of lesions detected by the CE protocol (median 2, interquartile range (IQR) 0-14) and that detected by the NCE protocol (median 1, IQR 0-5; p < 0.001). More malignancies were detected in the abdomen (p < 0.001) and brain (p < 0.001) with the CE PET/MRI protocol, whereas no significant difference was present when comparing the 2 protocols in the detection of malignancies in the head and neck (p = 0.356), thorax (p = 0.09), lymph nodes (p = 0.196), and bone (p = 0.414). CONCLUSION: The CE FDG PET/MRI protocol enables fast and accurate detection of malignancies compared to the NCE FDG PET/MRI protocol, particularly in the upper abdomen and brain. Diagnostic ability and time efficiency can be increased with the proposed short CE protocol in place of the whole body PET/MRI protocol including both NCE and CE imaging sequences.

Insufficiency fractures after pelvic radiotherapy in patients with prostate cancer.

PURPOSE: To assess the incidence, predisposing factors, and clinical characteristics of insufficiency fractures (IF) in patients with prostate cancer, who received pelvic radiotherapy as part of their definitive treatment. METHODS AND MATERIALS: The charts of 134 prostate cancer patients, who were treated with pelvic radiotherapy between 1998 and 2007 were retrospectively reviewed. IF was diagnosed by bone scan and/or CT and/or MRI. The cumulative incidence of symptomatic IF was estimated by actuarial methods. RESULTS: Eight patients were identified with symptomatic IF after a median follow-up period of 68 months (range, 12-116 months). The 5-year cumulative incidence of symptomatic IF was 6.8%. All patients presented with lower back pain. Insufficiency fracture developed at a median time of 20 months after the end of radiotherapy and was managed conservatively without any need for hospitalization. Three patients were thought to have metastatic disease because of increased uptake in their bone scans. However, subsequent CT and MR imaging revealed characteristic changes of IF, avoiding any further intervention. No predisposing factors for development of IF could be identified. CONCLUSIONS: Pelvic IF is a rare complication of pelvic radiotherapy in prostate cancer. Knowledge of pelvic IF is essential to rule out metastatic disease and prevent unnecessary treatment, especially in a patient cohort with high-risk features for distant spread.