TY - JOUR
T1 - Dosimetric Consequences of Intrafraction Prostate Motion
AU - Li, Haisen S.
AU - Chetty, Indrin J.
AU - Enke, Charles A.
AU - Foster, Ryan D.
AU - Willoughby, Twyla R.
AU - Kupellian, Patrick A.
AU - Solberg, Timothy D.
N1 - Funding Information:
We acknowledge the support of Philips Radiation Oncology Systems, Madison, WI, in providing access to the research version (8.1s) of their Pinnacle treatment-planning software.
PY - 2008/7/1
Y1 - 2008/7/1
N2 - Purpose: To analyze characteristics of intrafraction prostate motion, monitored using the Calypso system, and investigate dosimetric consequences of the motion for different clinical target volume (CTV) to planning target volume (PTV) margins. Methods and Materials: Motion characteristics were analyzed for 1,267 tracking sessions and 35 patients. Using prostate-PTV margins of 0, 1, 2, 3, and 5 mm, dose metrics for the prostate gland, bladder, and rectum were evaluated for scenarios including patient population, individual patients showing the greatest motion during the course of treatment, and the individual session with the largest overall movement. Composite dose distributions incorporating motion blurring were calculated by convolving static intensity-modulated radiotherapy plans with corresponding motion probability functions. Results: For prostate-PTV margins of 2 mm or greater, intrafraction motion did not compromise prostate dose coverage for either the patient population or individual patients. For the patient showing the largest overall movement, the prostate equivalent uniform dose was reduced by only 17.4 cGy (0.23%), and the minimum prostate dose remained greater than 95% of the nominal dose. For margins less than 2 mm, the prostate dose-volume histogram in the same patient was slightly compromised, and the equivalent uniform dose was reduced by 38.5 cGy (0.51%). Sparing of the bladder and rectum was improved substantially by reducing margins. Conclusions: Although significant motion can be observed during individual fractions, the dosimetric consequences are insignificant during a typical course of radiotherapy (30-40 fractions) with CTV-PTV margins of 2 mm or greater provided that the Calypso system is applied for pretreatment localization. Further reduction of the margin is possible if intrafraction realignment is performed.
AB - Purpose: To analyze characteristics of intrafraction prostate motion, monitored using the Calypso system, and investigate dosimetric consequences of the motion for different clinical target volume (CTV) to planning target volume (PTV) margins. Methods and Materials: Motion characteristics were analyzed for 1,267 tracking sessions and 35 patients. Using prostate-PTV margins of 0, 1, 2, 3, and 5 mm, dose metrics for the prostate gland, bladder, and rectum were evaluated for scenarios including patient population, individual patients showing the greatest motion during the course of treatment, and the individual session with the largest overall movement. Composite dose distributions incorporating motion blurring were calculated by convolving static intensity-modulated radiotherapy plans with corresponding motion probability functions. Results: For prostate-PTV margins of 2 mm or greater, intrafraction motion did not compromise prostate dose coverage for either the patient population or individual patients. For the patient showing the largest overall movement, the prostate equivalent uniform dose was reduced by only 17.4 cGy (0.23%), and the minimum prostate dose remained greater than 95% of the nominal dose. For margins less than 2 mm, the prostate dose-volume histogram in the same patient was slightly compromised, and the equivalent uniform dose was reduced by 38.5 cGy (0.51%). Sparing of the bladder and rectum was improved substantially by reducing margins. Conclusions: Although significant motion can be observed during individual fractions, the dosimetric consequences are insignificant during a typical course of radiotherapy (30-40 fractions) with CTV-PTV margins of 2 mm or greater provided that the Calypso system is applied for pretreatment localization. Further reduction of the margin is possible if intrafraction realignment is performed.
KW - Calypso system
KW - Dose blurring
KW - Intrafraction prostate motion
KW - Prostate-to-PTV margin
KW - Real-time tracking
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U2 - 10.1016/j.ijrobp.2007.10.049
DO - 10.1016/j.ijrobp.2007.10.049
M3 - Article
C2 - 18234439
AN - SCOPUS:42949150341
SN - 0360-3016
VL - 71
SP - 801
EP - 812
JO - International Journal of Radiation Oncology Biology Physics
JF - International Journal of Radiation Oncology Biology Physics
IS - 3
ER -