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Colorectal cancer is the third most common malignancy worldwide, and rectal cancer (RC) accounts for 29% of all cases. Local staging of RC is crucial for the purposes of addressing patients appropriately to surgery alone or to preoperative chemoradiotherapy (pCRT) followed by total mesorectal excision (TME). Combined pCRT and TME may negatively affect rectal function, so rectum-sparing approaches such as transanal local excision have been proposed as an alternative to TME for patients showing a major or complete clinical response on restaging after pCRT. Magnetic resonance imaging (MRI) has a fundamental role in the local staging and restaging of RC, with or without positron emission tomography (PET). PET/MRI enables a multiplanar high-resolution morphological study of the pelvis, providing important information on cell density and metabolic activity with diffusion-weighted imaging (DWI) and 18 F fluorodeoxyglucose uptake respectively. This article offers a pictorial review of the MRI anatomy of the ano-rectal region and an update on local RC staging with a hybrid 18 F-FDG PET/MRI scan. [ABSTRACT FROM AUTHOR]

Objective: To compare the diagnostic value of striatal (123) I-2β-carbomethoxy-3β-(4-iodophenyl)-N-(3-fluoropropyl) nortropane ((123) I-FP-CIT) single photon emission computed tomography (SPECT) and (123) I-metaiodobenzylguanidine ((123) I-MIBG) myocardial scintigraphy in differentiating dementia with Lewy bodies (DLB) from other dementia types.Methods: This prospective longitudinal study included 30 patients with a clinical diagnosis of DLB and 29 patients with non-DLB dementia (Alzheimer disease, n = 16; behavioral variant frontotemporal dementia, n = 13). All patients underwent (123) I-FP-CIT SPECT and (123) I-MIBG myocardial scintigraphy within a few weeks of clinical diagnosis. All diagnoses at each center were agreed upon by the local clinician and an independent expert, both unaware of imaging data, and re-evaluated after 12 months. Each image was visually classified as either normal or abnormal by 3 independent nuclear physicians blinded to patients' clinical data.Results: Overall, sensitivity and specificity to DLB were respectively 93% and 100% for (123) I-MIBG myocardial scintigraphy, and 90% and 76% for (123) I-FP-CIT SPECT. Lower specificity of striatal compared to myocardial imaging was due to decreased (123) I-FP-CIT uptake in 7 non-DLB subjects (3 with concomitant parkinsonism) who had normal (123) I-MIBG myocardial uptake. Notably, in our non-DLB group, myocardial imaging gave no false-positive readings even in those subjects (n = 7) with concurrent medical illnesses (diabetes and/or heart disease) supposed to potentially interfere with (123) I-MIBG uptake.Interpretation: (123) I-FP-CIT SPECT and (123) I-MIBG myocardial scintigraphy have similar sensitivity for detecting DLB, but the latter appears to be more specific for excluding non-DLB dementias, especially when parkinsonism is the only "core feature" exhibited by the patient. Our data also indicate that the potential confounding effects of diabetes and heart disease on (123) I-MIBG myocardial scintigraphy results might have been overestimated. Ann Neurol 2016;80:368-378. [ABSTRACT FROM AUTHOR]