Open AccessDiffusion‐weighted MRI of the lung at 3T evaluated using echo‐planar‐based and single‐shot turbo spin‐echo‐based acquisition techniques for radiotherapy applications
Author(s) -
Tyagi Neelam,
Cloutier Michelle,
Zakian Kristen,
Deasy Joseph O.,
Hunt Margie,
Rimner Andreas
Publication year - 2019
Publication title -
journal of applied clinical medical physics
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.83
H-Index - 48
ISSN - 1526-9914
DOI - 10.1002/acm2.12493
Subject(s) - nuclear medicine , diffusion mri , single shot , kurtosis , imaging phantom , effective diffusion coefficient , medicine , standard deviation , radiology , magnetic resonance imaging , physics , mathematics , optics , statistics
Abstract Purpose To compare single‐shot echo‐planar ( SS ‐ EPI )‐based and turbo spin‐echo ( SS ‐ TSE )‐based diffusion‐weighted imaging ( DWI ) in Non‐Small Cell Lung Cancer ( NSCLC ) patients and to characterize the distributions of apparent diffusion coefficient ( ADC ) values generated by the two techniques. Methods Ten NSCLC patients were enrolled in a prospective IRB ‐approved study to compare and optimize DWI using EPI and TSE ‐based techniques for radiotherapy planning. The imaging protocol included axial T2w, EPI ‐based DWI and TSE ‐based DWI on a 3 T Philips scanner. Both EPI ‐based and TSE ‐based DWI sequences used three b values (0, 400, and 800 s/mm 2 ). The acquisition times for EPI ‐based and TSE ‐based DWI were 5 and 8 min, respectively. DW ‐ MR images were manually coregistered with axial T2w images, and tumor volume contoured on T2w images were mapped onto the DWI scans. A pixel‐by‐pixel fit of tumor ADC was calculated based on monoexponential signal behavior. Tumor ADC mean, standard deviation, kurtosis, and skewness were calculated and compared between EPI and TSE ‐based DWI . Image distortion and ADC values between the two techniques were also quantified using fieldmap analysis and a NIST traceable ice‐water diffusion phantom, respectively. Results The mean ADC for EPI and TSE ‐based DWI were 1.282 ± 0.42 × 10 −3 and 1.211 ± 0.31 × 10 −3 mm 2 /s. The average skewness and kurtosis were 0.14 ± 0.4 and 2.43 ± 0.40 for DWI ‐ EPI and −0.06 ± 0.69 and 2.89 ± 0.62 for DWI ‐ TSE . Fieldmap analysis showed a mean distortion of 13.72 ± 8.12 mm for GTV for DWI ‐ EPI and 0.61 ± 0.4 mm for DWI ‐ TSE . ADC values obtained using the diffusion phantom for the two techniques were within 0.03 × 10 −3 mm 2 /s with respect to each other as well as the established values. Conclusions Diffusion‐weighted turbo spin‐echo shows better geometrical accuracy compared to DWI ‐ EPI . Mean ADC values were similar with both acquisitions but the shape of the histograms was different based on the skewness and kurtosis values. The impact of differences in respiratory technique on ADC values requires further investigation.