Nonrigid Patient Setup Errors in the Head-and-Neck Region

Abstract

The simplification of the patient as a rigid body was shown to result in significant errors due to relative motion in the H&N region. Margins for compensation of relative motion exceeded margins for compensation of patient positioning errors.

A strategy for the use of image-guided radiotherapy (IGRT) on linear accelerators and its impact on treatment margins for prostate cancer patients

“…High resolution images at the time of treatment, automatic registration and calculation of required shifts with respect to a planning CT provide the tools for utmost precision in patient positioning [9,10,17]. However, the process is time consuming and in clinical reality, a compromise between complexity of treatment and extensive workload has to be elaborated [5,12,14,[18][19][20].…”

“Augmented Reality” in Conventional Simulation by Projection of 3-D Structures into 2-D Images

“…Tilts were not considered separately in this study, even though our software supports all rigid transformations of structure sets, including rotations [15]. These can be neglected as those rotations, which appear to be most significant in radiotherapy, refer to internal organ movements: the prostate is rotating up to 30° around the L-R axis through the apex caused by varying filling of the rectum and the bladder [5,7,8].…”

kV Cone-Beam CT-Based IGRT

“…In head and neck cancer, large set-up uncertainties were measured in anatomical subregions [50,58,77]. The region of interest for image registration should be limited to the anatomical subregions that require the highest accuracy of set-up.…”