Is positron emission tomography/magnetic resonance imaging a reliable tool for detecting vascular activity in treated childhood-onset Takayasu's arteritis? A multicentre study.

OBJECTIVES: Toassess whether 18F-fluordeoxiglucose (18F-FDG) PET/MRI) with angiographic sequences can contribute to detecting vessel wall inflammation in patients with childhood-onset Takayasu's arteritis (c-TA) under immunosuppressive therapy. METHODS: A three-centre cross-sectional study was conducted. 18F-FDG PET/MRI scans were performed in c-TA patients and in oncologic patients, who served as the control group. Clinical and laboratory characteristics were also analysed. RESULTS: Seventeen c-TA patients (65% females) between the ages of 6 and 21 years with a mean disease duration of 9.4 years were recruited. Only one patient presented clinical disease activity and six (35.6%) had increased ESR and/or CRP levels. The most frequent magnetic resonance angiography (MRA) findings were stenosis and thickening, observed in 82.4 and 70.6% of c-TA patients, respectively. 18F-FDG PET revealed 18F-FDG uptake greater than the liver in at least one arterial segment in 15 (88.2%) patients in a qualitative analysis and a median maximum standardized uptake value (SUVmax) of 3.22 (interquartile range 2.76-3.69) in a semi-quantitative analysis. c-TA patients presented significantly higher SUVmax values than oncologic patients (P < 0.001). A positive correlation between SUVmax and CRP levels (ρ = 0.528, P = 0.029) was seen. CONCLUSION: A state-of-the-art imaging modality was used in c-TA patients and revealed a strong arterial FDG uptake even in patients in apparent remission. We suppose that this finding may represent silent activity in the vessel wall; however, we cannot exclude the possibility of arterial remodelling. Importantly, a negative imaging scan may help in immunosuppression withdrawal in daily clinical practice.

Role of MRI in Staging of Penile Cancer.

Penile cancer is one of the male-specific cancers. Accurate pretreatment staging is crucial due to a plethora of treatment options currently available. The 8th edition American Joint Committee on Cancer-Tumor Node and Metastasis (AJCC-TNM) revised the staging for penile cancers, with invasion of corpora cavernosa upstaged from T2 to T3 and invasion of urethra downstaged from T3 to being not separately relevant. With this revision, MRI is more relevant in local staging because MRI is accurate in identifying invasion of corpora cavernosa, while the accuracy is lower for detection of urethral involvement. The recent European Urology Association (EAU) guidelines recommend MRI to exclude invasion of the corpora cavernosa, especially if penis preservation is planned. Identification of satellite lesions and measurement of residual-penile-length help in surgical planning. When nonsurgical treatment modalities of the primary tumor are being considered, accurate local staging helps in decision-making regarding upfront inguinal lymph node dissection as against surveillance. MRI helps in detection and extent of inguinal and pelvic lymphadenopathy and is superior to clinical palpation, which continues to be the current approach recommended by National Comprehensive Cancer Network (NCCN) treatment guidelines. MRI helps the detection of "bulky" lymph nodes that warrant neoadjuvant chemotherapy and potentially identify extranodal extension. However, tumor involvement in small lymph nodes and differentiation of reactive vs. malignant lymphadenopathy in large lymph nodes continue to be challenging and the utilization of alternative contrast agents (superparamagnetic iron oxide), positron emission tomography (PET)-MRI along with texture analysis is promising. In locally recurrent tumors, MRI is invaluable in identification of deep invasion, which forms the basis of treatment. Multiparametric MRI, especially diffusion-weighted-imaging, may allow for quantitative noninvasive assessment of tumor grade and histologic subtyping to avoid biopsy undersampling. Further research is required for incorporation of MRI with deep learning and artificial intelligence algorithms for effective staging in penile cancer. Level of Evidence: 5 Technical Efficacy: Stage 3 J. Magn. Reson. Imaging 2020;51:1612-1629.