S-PI-RADS and PI-RRADS for Biparametric MRI in the Detection of Prostate Cancer and Post-treatment Local Recurrence.

The application of biparametric magnetic resonance imaging (bpMRI) [T2-weighted (T2W) and diffusion weighted imaging (DWI)/apparent diffusion coefficient (ADC)] using dedicated structured methods, such as Simplified Prostate Imaging Reporting and Data System (S-PI-RADS) for the detection, categorization, and management of prostate cancer (PCa) is reported. Also, Prostate Imaging Reporting for Local Recurrence and Data System (PI-RRADS) for the detection and assessment of the probability of local recurrence after radiotherapy (RT) or radical prostatectomy (RP) in patients with biochemical recurrence (BCR) is proposed. Both S-PI-RADS and PI-RRADS assign to DWI/ADC a main role for the above purpose. S-PI-RADS identifies four categories and, on the basis of the qualitative and quantitative analysis of the restricted diffusion on ADC map and lesion volume, distinguishes two categories of lesions: category 3 (moderately homogeneous hypointense on ADC map) and category 4 (markedly homogeneous or inhomogeneous hypointense on ADC map). Ιn category 3, two subcategories (3a: volume <0.5 cm3 and 3b: volume ≥0.5 cm3) suggesting clinical management. PI-RRADS distinguishes four assessment categories and suggests the stratification of the probability (ranging from very low for category 1 to very high for category 4) of local disease recurrence. In clinical practice, S-PI-RADS and PI-RRADS, based on bpMRI represent a potential valid approach that may facilitates the detection and management of PCa and for detecting local recurrence after treatment improving communication with other professionals.

Reproducibility of manual segmentation in muscle imaging.

PURPOSE: To assess the reproducibility of a manual muscle MRI segmentation method that follows a specific set of recommendations developed in our center. MATERIALS AND METHODS: Nine healthy volunteers underwent a muscle MRI examination that included a TSE T2 sequence of the thighs. Muscle segmentation was performed by three operators: an expert operator (OP1) with 3 years of experience and two radiology residents (OP2 and 3) who were both given basic segmentation instructions, whereas only OP2 underwent additional supervised training from OP1. Intra- and inter-operator Dice similarity coefficient (DSC) was calculated. RESULTS: OP1 showed the highest average intra-operator DSC values (0.885), whereas OP2 had higher average DSC (0.856) compared to OP3 (0.818). The highest inter-operator agreement was observed between Operators 1 and 2 (0.814) and the lowest between OP2 and OP3 (0.702). Confidence interval (CI) analysis showed that the most experienced operator also had the least variability in drawing the ROIs, whereas OP2 showed both higher intra-operator reproducibility compared to OP3 and higher inter-operator agreement with OP1. The muscles that showed the least reproducibility were the semimembranosus and the short head of the biceps femoris. DISCUSSION: Following specific recommendations such as these ones derived from our single-center experience leads to an overall high reproducibility of manual muscle segmentation and is helpful in improving both intra-operator and inter-operator reproducibility in less experienced operators.

Variable echo time imaging for detecting the short T2* components of the sciatic nerve: a validation study.

OBJECTIVE: The aim of this study was to develop and validate an MRI protocol based on a variable echo time (vTE) sensitive to the short T2* components of the sciatic nerve. MATERIALS AND METHODS: 15 healthy subjects (M/F: 9/6; age: 21-62) were scanned at 3T targeting the sciatic nerve at the thigh bilaterally, using a dual echo variable echo time (vTE) sequence (based on a spoiled gradient echo acquisition) with echo times of 0.98/5.37 ms. Apparent T2* (aT2*) values of the sciatic nerves were calculated with a mono-exponential fit and used for data comparison. RESULTS: There were no significant differences in aT2* related to side, sex, age, and BMI, even though small differences for side were reported. Good-to-excellent repeatability and reproducibility were found for geometry of ROIs (Dice indices: intra-rater 0.68-0.7; inter-rater 0.70-0.72) and the related aT2* measures (intra-inter reader ICC 0.95-0.97; 0.66-0.85) from two different operators. Side-related signal-to-noise-ratio non-significant differences were reported, while contrast-to-noise-ratio measures were excellent both for side and echo. DISCUSSION: Our study introduces a novel MR sequence sensitive to the short T2* components of the sciatic nerve and may be used for the study of peripheral nerve disorders.