A CBCT study of the gravity-induced movement in rotating rabbits.

A CBCT study of the gravity-induced movement in rotating rabbits. Phys Med Biol. 2018 Apr 18;: Authors: Barber J, Shieh CC, Counter W, Sykes JR, Bennett P, Ahern V, Corde S, Heng SM, White P, Jackson M, Liu P, Keall PJ, Feain I Abstract Fixed-beam radiotherapy systems with subjects rotating about a longitudinal (horizontal) axis are subject to gravity-induced motion. Limited reports on the degree of this motion, and any deformation, has been reported previously. The purpose of this study is to quantify the degree of anatomical motion caused by rotating a subject around a longitudinal axis, using cone-beam CT (CBCT). 
 
 In the current study, a purpose-made longitudinal rotating was aligned to a Varian TrueBeam kV imaging system. CBCT images of three live rabbits were acquired at fixed rotational offsets of the cradle. Rigid and deformable image registrations back to the original position were used to quantify the motion experienced by the subjects under rotation. 
 
 In the rotation offset CBCTs, the mean magnitude of rigid translations was 5.7 ± 2.7 mm across all rabbits and all rotations. The translation motion was reproducible between multiple rotations within 2.1 mm, 1.1 mm, and 2.8 mm difference for rabbit 1, 2, and 3, respectively. The magnitude of the mean and absolute maximum deformation vectors were 0.2 ± 0.1 mm and 5.4 ± 2.0 mm respectively, indicating small residual deformations after rig...
Source: Physics in Medicine and Biology - Category: Physics Authors: Tags: Phys Med Biol Source Type: research