Med Phys. 2012 Jun;39(6):3825. doi: 10.1118/1.4735610.

SU-E-T-521: Dosimetric Effect on Variation of Patient Size in Prostate Volumetric Modulated Arc Therapy.

Medical physics

J Chow, R Jiang

PMID: 28518480 DOI: 10.1118/1.4735610

Abstract

PURPOSE: To evaluate dosimetric variations of planning target volume (PTV) on critical organs such as rectal wall, bladder and femoral head, when the patient size changes due to weight loss in prostate volumetric modulated arc therapy (VMAT).

METHODS: Three patients with small (32.0 cm

RESULTS: D99% of the PTV and CTV were found to have increased 2.65 ± 0.03% per cm and 2.75 ± 0.15% per cm of reduced depth in the range of 0.5 and 2 cm. D30% of the rectal wall and bladder increased 2.29 ± 0.12% per cm and 2.31 ± 0.83% per cm, respectively. D5% of the femoral head increased by 3.30 ± 0.11% per cm of reduced depth. Moreover, there was more than 5% increase of minimum, maximum and means doses for the PTV, CTV and critical organs when the reduced depth reached 2 cm.

CONCLUSIONS: This study provided estimated results of dosimetric changes due to variation of patient size in prostate VMAT. The dosimetric information should help radiation oncology staff to justify changes of dose distribution, when patient weight loss occurs during prostate VMAT. Dose variations of more than 5% were found when the patient's reduced depth was equal to 2 cm. Actual or potential conflicts of interest do not exist.

© 2012 American Association of Physicists in Medicine.

Keywords: Anatomy; Cancer; Dosimetry; Photons; Tissues

Publication Types

• Journal Article