[P232] Deformable image registration for CT-images of the thorax region. (August 2018)

• Record Type: Journal Article
• Authors: Sarudis, Sebastian; Karlsson, Anna; Bibac, Dan; Nyman, Jan; Bäck, Anna
• Is Part Of: Physica medica. Volume 52(2018)Supplement 1
• Page Start: 166
• Page End: 167
• Publication Date: 2018-08
• Subjects: Medical physics -- Periodicals; Biophysics -- Periodicals; Biophysics -- Periodicals; Imagerie médicale -- Périodiques; Radiothérapie -- Périodiques; Rayons X -- Sécurité -- Mesures -- Périodiques; Physique -- Périodiques; Médecine -- Périodiques; 610.153
• DOI: 10.1016/j.ejmp.2018.06.518
• Languages: English
• ISSNs: 1120-1797

Abstract

Abstract : Purpose: Evaluate the performance of three commercial deformable image registration (DIR) algorithms for computed tomography (CT) images of the thorax. Methods: Deformable registrations were performed on CT-images of a thorax phantom with tumor inserts and on six 4-dimensional patient CT-series of the thorax. For each DIR the shape and position of the deformed structures and the corresponding structures in the target image that the DIRs were set to reproduce, were compared for shifts between 0–53 mm. Two quantitative measures were used, the center of mass shift (CMS) and the Dice Similarity Coefficient (DSC) as well as visual examination of the registered images. Dose calculations on the deformed patient images were compared to calculations on the un-deformed target images for the gross tumor volume (GTV) (mean dose and D98% ), lung (V20Gy, V12Gy ), heart and spinal cord (D2% ). Results: In phantoms, moving structures with constant volume and shifts ⩽30 mm were reproduced with DSC⩾0.91 and CMS⩽0.9 mm by all the algorithms. For shifts >30 mm two algorithms failed. Deformations including volume changes were less accurate with 3/12 and 9/12 DIRs considered visually unacceptable, corresponding to CMS>2.0 mm and DSC<0.87, for the best and the worst algorithm respectively. For patients, the organs at risk were reproduced with DSC⩾0.83. GTV shifts of 7 and 16 mm were reproduced with DSC⩾0.88 by all the algorithms. GTV shifts of 22 and 27 mm were reproduced with DSC⩾0.90 by two algorithms while one of the algorithms resulted in DSC⩽0.40. GTV shifts of 23 and 53 mm could not be reproduced by any of the algorithms. Including both phantom and patient cases, the best and worst algorithm succeeded in visually acceptable DIRs, corresponding to CMS<2.0 mm and DSC⩾0.87, for 18/25 and 12/25 cases respectively. Visually acceptable DIRs resulted in absorbed dose deviations in the evaluated dose parameters of ⩽3.6 percentage units. Conclusions: Visually acceptable DIRs were achievable for moving structures with constant volume and shifts ⩽30 mm in phantoms and shifts⩽16 mm in patients. Visually acceptable DIRs implied dose deviations ⩽3.6 percentage units on patient CT-images of the thorax region.