Accuracy of surface registration compared to conventional volumetric registration in patient positioning for head‐and‐neck radiotherapy: A simulation study using patient data. Issue 12 (10th November 2014)

• Record Type: Journal Article
• Authors: Kim, Youngjun; Li, Ruijiang; Na, Yong Hum; Lee, Rena; Xing, Lei
• Is Part Of: Medical physics. Volume 41:Issue 12(2014)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2014-11-10
• Subjects: biomedical optical imaging -- computerised tomography -- data acquisition -- diagnostic radiography -- image registration -- iterative methods -- medical image processing -- patient monitoring -- phantoms -- radiation therapy -- skin; Therapeutic applications, including brachytherapy -- Radiography -- Visual imaging -- Computed tomography -- Registration -- Therapeutic applications; Computerised tomographs -- Radiation therapy -- Biological material, e.g. blood, urine; Haemocytometers -- Digital computing or data processing equipment or methods, specially adapted for specific applications -- Image data processing or generation, in general; surface registration -- optical surface imaging -- patient setup -- patient positioning -- radiotherapy; Surface treatments -- Cone beam computed tomography -- Medical imaging -- Surface morphology -- Inductively coupled plasma -- Radiosurgery -- Surface optics -- Stereoscopy; Medical physics -- Periodicals; Medical physics; Geneeskunde; Natuurkunde; Toepassingen; Biophysics; Periodicals; Periodicals; Electronic journals; 610.153
• DOI: 10.1118/1.4898103
• Languages: English
• ISSNs: 0094-2405

Abstract

Abstract : Purpose: 3D optical surface imaging has been applied to patient positioning in radiation therapy (RT). The optical patient positioning system is advantageous over conventional method using cone‐beam computed tomography (CBCT) in that it is radiation free, frameless, and is capable of real‐time monitoring. While the conventional radiographic method uses volumetric registration, the optical system uses surface matching for patient alignment. The relative accuracy of these two methods has not yet been sufficiently investigated. This study aims to investigate the theoretical accuracy of the surface registration based on a simulation study using patient data. Methods: This study compares the relative accuracy of surface and volumetric registration in head‐and‐neck RT. The authors examined 26 patient data sets, each consisting of planning CT data acquired before treatment and patient setup CBCT data acquired at the time of treatment. As input data of surface registration, patient's skin surfaces were created by contouring patient skin from planning CT and treatment CBCT. Surface registration was performed using the iterative closest points algorithm by point–plane closest, which minimizes the normal distance between source points and target surfaces. Six degrees of freedom (three translations and three rotations) were used in both surface and volumetric registrations and the results were compared. The accuracy of each method was estimated by digital phantom tests. Results: Based on the results of 26 patients, the authors found that the average and maximum root‐mean‐square translation deviation between the surface and volumetric registrations were 2.7 and 5.2 mm, respectively. The residual error of the surface registration was calculated to have an average of 0.9 mm and a maximum of 1.7 mm. Conclusions: Surface registration may lead to results different from those of the conventional volumetric registration. Only limited accuracy can be achieved for patient positioning with an approach based solely on surface information.