Readout-segmented echo-planar diffusion-weighted imaging improves geometric performance for image-guided radiation therapy of pelvic tumors.

Diffusion-weighted imaging using echo-planar imaging (EPI) is prone to geometric inaccuracy, which may limit application to image-guided radiation therapy planning, as well as for voxel-based quantitative multi-parametric or multi-modal approaches.

This research investigates pelvic applications at 3T of a standard single-shot (ssEPI) and a prototype readout-segmented (rsEPI) technique.

Apparent diffusion coefficient (ADC) accuracy and geometric performance of rsEPI and ssEPI were compared using phantoms, and in vivo, involving 8 patients prior to MR-guided brachytherapy for locally advanced cervical cancer, and 19 patients with prostate cancer planned for tumor-targeted radiotherapy. Global and local deviations in geometric performance were tested using Dice Similarity Coefficients (DC) and Hausdorff Distances (HD).

In cervix patients, DC increased from 0. 76±0. 14 to 0. 91±0. 05 for the high risk clinical target volume, and 0. 62±0. 26 to 0. 85±0. 08 for the gross tumor target volume. Tumors in the peripheral zone of the prostate gland were partly projected erroneously outside of the posterior anatomic boundary of the gland by 3. 1±1. 6mm in 11 of 19 patients using ADC-ssEPI but not with ADC-rsEPI.

Both cervix and prostate ssEPI are prone to clinically relevant geometric distortions at 3T. rsEPI provides improved geometric performance without post-processing.

Radiotherapy and oncology : journal of the European Society for Therapeutic Radiology and Oncology. 2015 Aug 08 [Epub ahead of print]

Warren D Foltz, David A Porter, Anna Simeonov, Amanda Aleong, David Jaffray, Peter Chung, Kathy Han, Cynthia Ménard

Radiation Medicine Program, Princess Margaret Cancer Centre, University Health Network, Toronto, Canada.  Fraunhofer Mevis, Bremen, Germany. , Radiation Medicine Program, Princess Margaret Cancer Centre, University Health Network, Toronto, Canada. , Radiation Medicine Program, Princess Margaret Cancer Centre, University Health Network, Toronto, Canada. , Radiation Medicine Program, Princess Margaret Cancer Centre, University Health Network, Toronto, Canada. , Radiation Medicine Program, Princess Margaret Cancer Centre, University Health Network, Toronto, Canada. , Radiation Medicine Program, Princess Margaret Cancer Centre, University Health Network, Toronto, Canada. , Radiation Medicine Program, Princess Margaret Cancer Centre, University Health Network, Toronto, Canada.

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