Comparison Between Diffusion-Weighted MRI and

Background High‐risk neuroblastoma (HR‐NB) has a variable response to preoperative chemotherapy. It is not possible to differentiate viable vs. nonviable residual tumor before surgery. Purpose To explore the association between apparent diffusion coefficient (ADC) values from diffusion‐weighted magnetic resonance imaging (DW‐MRI), 123I‐meta‐iodobenzyl‐guanidine (123I‐mIBG) uptake, and histology before and after chemotherapy. Study Type Retrospective. Subjects Forty patients with HR‐NB. Field Strength/Sequence 1.5T axial DW‐MRI (b = 0,1000 s/mm2) and T2‐weighted sequences. 123I‐mIBG scintigraphy planar imaging (all patients), with additional 123I‐mIBG single‐photon emission computed tomography / computerized tomography (SPECT/CT) imaging (15 patients). Assessment ADC maps and 123I‐mIBG SPECT/CT images were coregistered to the T2‐weighted images. 123I‐mIBG uptake was normalized with a tumor‐to‐liver count ratio (TLCR). Regions of interest (ROIs) for primary tumor volume and different intratumor subregions were drawn. The lower quartile ADC value (ADC25prc) was used over the entire tumor volume and the overall level of 123I‐mIBG uptake was graded into avidity groups. Statistical Tests Analysis of variance (ANOVA) and linear regression were used to compare ADC and MIBG values before and after treatment. Threshold values to classify tumors as viable/necrotic were obtained using ROC analysis of ADC and TLCR values. Results No significant difference in whole‐tumor ADC25prc values were found between different 123I‐mIBG avidity groups pre‐ (P = 0.31) or postchemotherapy (P = 0.35). In the “intratumor” analysis, 5/15 patients (prechemotherapy) and 0/14 patients (postchemotherapy) showed a significant correlation between ADC and TLCR values (P 10% viable tumor (P 50% viable tumor than those with 10–50% viable tumor (P