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Purpose: To analyze changes in MRI diagnostic accuracy in main rectal tumor (T) evaluation resulting from the use of diffusion-weighted imaging (DWI), according to the degree of experience of the radiologist., Methods: This is a cross-sectional study of a database including one hundred 1.5 T MRI records (2011-2016) from patients with biopsy-proven rectal cancer, including primary staging and post-chemoradiotherapy follow-up. All cases were individually blindedly reviewed by ten radiologists: three experienced in rectal cancer, three specialized in other areas, and four residents. Each case was assessed twice to detect perirectal infiltration: first, evaluating just high-resolution T2-weighted sequences (HRT2w); second, evaluation of DWI plus HRT2w sequences. Results were pooled by experience, calculating accuracy (area under ROC curve), sensitivity and specificity, predictive values, likelihood ratios, and overstaging/understaging. Histology of surgical specimens provided the reference standard., Results: DWI significantly improved specificity by experienced radiologists in primary staging (63.2% to 75.9%) and, to a lesser extent, positive likelihood ratio (2.06 to 2.87); minimal changes were observed post-chemoradiotherapy, with a slight decrease of accuracy (0.657 to 0.626). Inexperienced radiologists showed a similar pattern, but with slight enhancement post-chemoradiotherapy (accuracy 0.604 to 0.621). Residents experienced small changes, with increased sensitivity/decreased specificity in both primary (69% to 72%/67.2% to 64.7%) and post-chemoradiotherapy (68.1% to 73.6%/47.3% to 44.6%) staging., Conclusions: Adding DWI to HRT2w significantly improved specificity for the detection of perirectal infiltration at primary staging by experienced radiologists and also by inexperienced ones, although to a lesser extent. In the post-neoadjuvant treatment subgroup, only minimal changes were observed.

Objectives: To estimate, on the basis of anthropometric and demographic variables, the depth (Dp) and diameter (Dm) of femoral and jugular vessels, which have been located and measured by ultrasound, in pediatric patients., Method: 750 measurements of Dp and Dm of the femoral vein (FV), femoral artery (FA) and internal jugular vein (IJV) were made in 125 pediatric patients. The values were correlated with patients' sex, weight, age, size and body surface area (BSA)., Results: Mean Dp values were 0.72 (0.34) cm for FA, 0.79 (0.35) cm for FV and 0.77 (0.24) cm for IJV. Mean antero-posterior Dm values were 0.37 (0.17) cm for FA, 0.42 (0.22) cm for FV and 0.59 (0.23) cm for IJV. In the studied pediatric patients, femoral and jugular vessels depth correlated with age, size, weight and BSA ( R  = 0.46-0.60); vascular depth could be estimated from patients' weight and size (FA-Dp: R  = 0.71; FV-Dp: R  = 0.72; IJV-Dp: R  = 0.53). Correlation with diameter was better for FA and FV ( R  = 0.81-0.89) than for IJV ( R  = 0.42-0.51); vascular diameter could be estimated from patient's size (FA-Dm: R  = 0.89; FV-Dm: R  = 0.86; IJV-Dm: R  = 0.52)., Conclusions: FV, FA and IJV depth and diameter correlated with weight, size, age and body surface area in the studied pediatric patients. Correlation was better for femoral than for jugular vessels. Depth could be estimated from patients' weight and size, while diameter could be estimated from the size. Such estimations may facilitate the choice of vessels to be cannulated, length and diameter of cannulation needles and the diameter of catheters to be used in pediatric patients.