Cone Beam CT Imaging Analysis of Interfractional Variations in Bladder Volume and Position During Radiotherapy for Bladder Cancer
- Department of Radiation Oncology, Cross Cancer Institute, Edmonton, Alberta (Canada)
- Department of Medical Physics, Cross Cancer Institute, Edmonton, Alberta (Canada)
- Department of Experimental Oncology, Cross Cancer Institute, Edmonton, Alberta (Canada)
Purpose: To quantify daily bladder size and position variations during bladder cancer radiotherapy. Methods and Materials: Ten bladder cancer patients underwent daily cone beam CT (CBCT) imaging of the bladder during radiotherapy. Bladder and planning target volumes (bladder/PTV) from CBCT and planning CT scans were compared with respect to bladder center-of-mass shifts in the x (lateral), y (anterior-posterior), and z (superior-inferior) coordinates, bladder/PTV size, bladder/PTV margin positions, overlapping areas, and mutually exclusive regions. Results: A total of 262 CBCT images were obtained from 10 bladder cancer patients. Bladder center of mass shifted most in the y coordinate (mean, -0.32 cm). The anterior bladder wall shifted the most (mean, -0.58 cm). Mean ratios of CBCT-derived bladder and PTV volumes to planning CT-derived counterparts were 0.83 and 0.88. The mean CBCT-derived bladder volume (+- standard deviation [SD]) outside the planning CT counterpart was 29.24 cm{sup 3} (SD, 29.71 cm{sup 3}). The mean planning CT-derived bladder volume outside the CBCT counterpart was 47.74 cm{sup 3} (SD, 21.64 cm{sup 3}). The mean CBCT PTV outside the planning CT-derived PTV was 47.35 cm{sup 3} (SD, 36.51 cm{sup 3}). The mean planning CT-derived PTV outside the CBCT-derived PTV was 93.16 cm{sup 3} (SD, 50.21). The mean CBCT-derived bladder volume outside the planning PTV was 2.41 cm{sup 3} (SD, 3.97 cm{sup 3}). CBCT bladder/ PTV volumes significantly differed from planning CT counterparts (p = 0.047). Conclusions: Significant variations in bladder and PTV volume and position occurred in patients in this trial.
- OSTI ID:
- 21372158
- Journal Information:
- International Journal of Radiation Oncology, Biology and Physics, Vol. 76, Issue 4; Other Information: DOI: 10.1016/j.ijrobp.2009.03.022; PII: S0360-3016(09)00456-8; Copyright (c) 2010 Elsevier Science B.V., Amsterdam, The Netherlands, All rights reserved.; ISSN 0360-3016
- Country of Publication:
- United States
- Language:
- English
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