Using cone-beam computed tomography to evaluate the impact of XXXX status on target position in prostate radiotherapy.

@entity1 @entity263 @entity1494
PURPOSE: To assess @entity1494 status and its impact on target position during daily intensity-modulated radiation therapy (IMRT) using cone-beam computed tomography (CBCT) in @entity263 @entity1 . @entity1 AND METHODS: 23 @entity1 with @entity263 undergoing image-guided IMRT (78 Gy in 39 fractions) were included. On-board CBCT images were acquired daily and an endorectal balloon was placed daily. All @entity1 were instructed to have a full bladder. The interfraction changes in bladder dimensions in left-right (LR), anterior-posterior (AP), and superior-inferior (SI) directions were measured from CBCT images. Distances from the uppermost part of prostate to pubic bone (PP) and from the uppermost part of prostate to treatment isocenter (PI) were measured to determine changes in target position. Standard deviation (SD) in all fractions of each @entity1 was used to compare the variations between @entity1 . Bladder dimension change ratio and Z-score were used to normalize data between @entity1 . RESULTS: A total of 867 CBCT images were evaluated. The average LR, AP, and SI bladder dimensions were 7.8 +/- 1.5 cm, 6.7 +/- 1.4 cm, and 5.6 +/- 1.7 cm, respectively. The average LR, AP, and SI bladder dimension change ratios were 0.88 +/- 0.17, 0.90 +/- 0.15, and 0.86 +/- 0.32, respectively. The SD was significantly greater in SI dimension than in LR (p < 0.001) and AP (p < 0.001) dimensions. The interfraction changes in the three bladder dimensions were significantly larger than those of target position, and did not correlate with target position changes. CONCLUSION: Though they were not negligible, changes in @entity1494 status did not have a significant impact on target position.
