TY - JOUR
T1 - Vector analysis of prostate patient setup with image-guided radiation therapy via kv cone beam computed tomography
AU - Perks, Julian
AU - Turnbull, Helen
AU - Liu, Tianxiao
AU - Purdy, James
AU - Valicenti, Richard
PY - 2011/3/1
Y1 - 2011/3/1
N2 - Purpose: To analyze the daily setup variations in a cohort of intensity-modulated radiation therapy (IMRT) prostate cancer patients who had received daily image-guided RT without the use of fiducial markers to determine if daily image guidance is necessary. Methods and Materials: 2134 Kilovoltage (kV) cone beam computed tomography (CBCT) images were analyzed, with three shifts recorded for each image. The number of times that the vector of the combined shifts would have exceeded the planning tumor volume (PTV) margin was tallied. Then, the average scalar shift of the first five images was removed from all subsequent images for a given patient, and the number of days for which the shift vector was greater than the three-dimensional clinical tumor volume-PTV (3D CTV-PTV) margin (8 mm, created with rolling ball technique) was recorded. Additionally, the scalar shifts from every other fraction were studied to determine if the individual patients shift vector would be adequately sampled if CBCT was not performed daily, thus reducing patient imaging dose without compromising treatment quality. Results: There were 297 cases where the vector shift was initially greater than the PTV margin. By correcting each patients data set by the average shift of their first five images the total was 248 cases. By considering only every other image of each patient data set (after correction for the first 5 days), only 137 days in which the CTV was outside the PTV would have been seen. Conclusions: Daily imaging is recommended for prostate cancer IMRT patients in order to know the 3D (vector) position of the CTV and to ensure that it is always within the PTV margin. Correcting the data set by the average shift from the first 5 days reduces the overall number of outlier days but does not eliminate them completely.
AB - Purpose: To analyze the daily setup variations in a cohort of intensity-modulated radiation therapy (IMRT) prostate cancer patients who had received daily image-guided RT without the use of fiducial markers to determine if daily image guidance is necessary. Methods and Materials: 2134 Kilovoltage (kV) cone beam computed tomography (CBCT) images were analyzed, with three shifts recorded for each image. The number of times that the vector of the combined shifts would have exceeded the planning tumor volume (PTV) margin was tallied. Then, the average scalar shift of the first five images was removed from all subsequent images for a given patient, and the number of days for which the shift vector was greater than the three-dimensional clinical tumor volume-PTV (3D CTV-PTV) margin (8 mm, created with rolling ball technique) was recorded. Additionally, the scalar shifts from every other fraction were studied to determine if the individual patients shift vector would be adequately sampled if CBCT was not performed daily, thus reducing patient imaging dose without compromising treatment quality. Results: There were 297 cases where the vector shift was initially greater than the PTV margin. By correcting each patients data set by the average shift of their first five images the total was 248 cases. By considering only every other image of each patient data set (after correction for the first 5 days), only 137 days in which the CTV was outside the PTV would have been seen. Conclusions: Daily imaging is recommended for prostate cancer IMRT patients in order to know the 3D (vector) position of the CTV and to ensure that it is always within the PTV margin. Correcting the data set by the average shift from the first 5 days reduces the overall number of outlier days but does not eliminate them completely.
KW - Cone beam CT
KW - Fiducial markers
KW - Prostate
KW - Shift analysis
KW - kV imaging
UR - http://www.scopus.com/inward/record.url?scp=79551488576&partnerID=8YFLogxK
U2 - 10.1016/j.ijrobp.2010.04.008
DO - 10.1016/j.ijrobp.2010.04.008
M3 - Article
C2 - 20643510
AN - SCOPUS:79551488576
SN - 0360-3016
VL - 79
SP - 915
EP - 919
JO - International Journal of Radiation Oncology Biology Physics
JF - International Journal of Radiation Oncology Biology Physics
IS - 3
ER -