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Patient Dependent Options for Image Guidance Procedures in Radiotherapy: Prostate Cancer


T Piotrowski

T Piotrowski1,2*, K Kaczmarek1, A Jodda1, A Ryczkowski1, T Bajon1, G. Rodrigues3,4, S Yartsev3,4, (1) Greater Poland Cancer Centre, Poznan, Poland, (2) University of Medical Sciences, Poznan, Poland, (3) London Health Sciences Centre, London, Ontario, Canada, (4) Western University, London, Ontario, Canada.

SU-E-J-42 Sunday 3:00PM - 6:00PM Room: Exhibit Hall

Purpose:
Retrospective analysis of image guidance data in radiation treatments of prostate cancer patients allows for simulation of imaging scenarios with less frequent or modified procedures. The correlation of patient specific features with inter-fraction prostate variations can be explained using patient cohorts with large amounts of daily image data.

Methods:
The 6,085 setup correction shifts performed during radiotherapy of 216 prostate cancer patients on helical tomotherapy units in two cancer centers were analyzed with respect to automatic and manual matching procedures in co-registration of planning kV and pre-treatment MVCT studies. Margins needed to account for inter-fraction target motion for a daily automatic corrections scheme and three schemes with limited imaging based on one, three and five first fractions as a reference were calculated. The body mass index (BMI) was calculated for all patients and the times required for different steps in the co-registration process were evaluated.

Results:
The margin calculated for the daily automatic shift scheme was significantly lower than any of the margins calculated for the limited imaging schemes. The average time needed for management of the daily automatic correction shift during the whole course of the treatment was equal to 5 minutes, and was 30 times shorter than time needed for the daily registration based on automatic and manual correction shifts. Larger setup correction shifts were observed for the patients with higher BMI values.

Conclusion:
The patients with normal BMI values (BMI<25) require a significantly smaller setup correction and may be treated with a limited number of imaging sessions followed by treatment without imaging using external marks that take into account average systematic shift and personalized margins obtained from the data of the first several fractions. The overweight (2530) patients may be treated with daily automatic co-registration and reduced personalized margins.

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