Development and implementation of an automatic air delineation technique for MRI-guided adaptive radiation therapy. Phys Med Biol 2022 Jul 12;67(14)
Date
06/23/2022Pubmed ID
35732168Pubmed Central ID
PMC9639194DOI
10.1088/1361-6560/ac7b65Scopus ID
2-s2.0-85134474387 (requires institutional sign-in at Scopus site) 4 CitationsAbstract
Objective.Auto-delineation of air regions on daily MRI for MR-guided online adaptive radiotherapy (MRgOART) of abdominal tumors is challenging since the air packets occur randomly and their MR intensities can be similar to some other tissue types. This work reports a new method to auto-delineate air regions on MRI.Approach.The proposed method (named DIFF method) consists of (1) generating a combined volumeVcomb, which is a union of the air-containing organs on a reference MR image offline, (2) transferringVcombfrom the reference MR to a daily MR via DIR, (3) combining the transferredVcombwith a region of high DIR inaccuracy, and (4) applying a threshold to the obtained final combined volume to generate the air volumes. The high DIR inaccuracy region was calculated from the absolute difference between the deformed daily and the reference images. This method was tested on 36 abdominal daily MRI sets acquired from 7 patients on a 1.5 T MR-Linac. The performance of DIFF was compared with alternative auto-air generation methods that (1) does not account for DIR inaccuracies, and (2) uses rigid registration instead of DIR.Main results.The results show that the proposed DIFF method can be fully automated and can be executed within 25 s. The Dice similarity coefficient of manual and DIFF auto-generated air contours was >92% for all cases, while it was 90% for the alternative auto-delineation methods. Dosimetrically, the auto-generated air regions using DIFF resulted in practically identical DVHs as those generated by using manual air contours.Significance.The DIFF method is robust and accurate and can be implemented to automatically consider the inter- and intra- fractional air volume variations during MRgOART for abdominal tumors. The use of DIFF method improves dosimetric accuracy as compared to other methods, especially beneficial for the patients with large daily abdominal air volume variations.
Author List
Ahunbay E, Parchur AK, Paulson E, Chen X, Omari E, Li XAAuthors
Ergun Ahunbay PhD Professor in the Radiation Oncology department at Medical College of WisconsinEenas Omari PhD Assistant Professor in the Radiation Oncology department at Medical College of Wisconsin
Abdul Kareem Parchur Medical Physicist Assistant in the Radiation Oncology department at Medical College of Wisconsin
Eric Paulson PhD Chief, Professor in the Radiation Oncology department at Medical College of Wisconsin
MESH terms used to index this publication - Major topics in bold
Abdominal NeoplasmsHumans
Image Processing, Computer-Assisted
Magnetic Resonance Imaging
Radiotherapy Dosage
Radiotherapy Planning, Computer-Assisted
