Total error shift patterns for daily CT on rails image-guided radiotherapy to the prostate bed

Abstract

BackgroundTo evaluate the daily total error shift patterns on post-prostatectomy patients undergoing image guided radiotherapy (IGRT) with a diagnostic quality computer tomography (CT) on rails system.MethodsA total of 17 consecutive post-prostatectomy patients receiving adjuvant or salvage IMRT using CT-on-rails IGRT were analyzed. The prostate bed's daily total error shifts were evaluated for a total of 661 CT scans.ResultsIn the right-left, cranial-caudal, and posterior-anterior directions, 11.5%, 9.2%, and 6.5% of the 661 scans required no position adjustments; 75.3%, 66.1%, and 56.8% required a shift of 1 - 5 mm; 11.5%, 20.9%, and 31.2% required a shift of 6 - 10 mm; and 1.7%, 3.8%, and 5.5% required a shift of more than 10 mm, respectively. There was evidence of correlation between the x and y, x and z, and y and z axes in 3, 3, and 3 of 17 patients, respectively. Univariate (ANOVA) analysis showed that the total error pattern was random in the x, y, and z axis for 10, 5, and 2 of 17 patients, respectively, and systematic for the rest. Multivariate (MANOVA) analysis showed that the (x,y), (x,z), (y,z), and (x, y, z) total error pattern was random in 5, 1, 1, and 1 of 17 patients, respectively, and systematic for the rest.ConclusionsThe overall daily total error shift pattern for these 17 patients simulated with an empty bladder, and treated with CT on rails IGRT was predominantly systematic. Despite this, the temporal vector trends showed complex behaviors and unpredictable changes in magnitude and direction. These findings highlight the importance of using daily IGRT in post-prostatectomy patients.

Prostate bed motion may cause geographic miss in post‐prostatectomy image‐guided intensity‐modulated radiotherapy

“…The mean movement calculated in this study is similar to that shown in previous studies . Table shows the mean magnitude and standard deviations of the prostate bed motion calculated by other groups who have also used CBCT imaging .…”

“…Variability was seen between the bony anatomy match and the surgical clip matches in all planes for both the superior and inferior clips, with the least difference in the L/R plane. Other groups have also found that movement is least in the lateral plane, and this was also seen to be the case in the definitive prostate setting . More movement was seen in all planes in the upper prostate bed than in the lower prostate bed.…”

Gold seed fiducials in analysis of linear and rotational displacement of the prostate bed

“…Prostate bed motion (PBM) has been examined thoroughly by ultrasound-based technologies [10,11], by CBCT in combination of rectal wall or surgical clips localization [6,[12][13][14], by electronic portal imaging device (EPID) and gold seed fiducials localization [4], and by orthogonal kV images together with radiofrequency beacons or surgical clips localization [5,15]. In this study we investigate the prostate bed localization difference between soft tissue registration and gold seed fiducial localization.…”

Definition and visualisation of regions of interest in post‐prostatectomy image‐guided intensity modulated radiotherapy

“…Previous authors have reported that the PB moves independently of bony anatomy, [15][16][17][18][19] and in a number of these studies CBCT scans were used to assess this movement. 10,20,21 This has implications for daily image guidance techniques applied during radiotherapy treatment in post-prostatectomy patients.…”