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A Study of Real-Time Treatment Quality Assurance

X Pan

X Pan*, W Bradley, C Boyd, K Kennedy, L Robertson, D Jones, M Wauqua, L Smith, T Ochran, The University of Texas Health Science center at Tyler, Tyler, Texas

SU-E-T-224 Sunday 3:00PM - 6:00PM Room: Exhibit Hall

Purpose: The purpose of this work is to investigate real-time radiation treatment quality assurance (QA) in radiation therapy.

Methods: An ArcCheck phantom was selected as a patient named patient_AC for this study. CT simulation was performed for patient_AC and 2 treatment plans, i.e., a sliding window (S_IMRT_Plan) and a step-and-shoot (SS_IMRT_Plan) IMRT plan, were designed using Eclipse treatment planning system (TPS). Pre-treatment QA was done prior to treating patient_AC using an ArcCheck phantom (Sun Nuclear Corporation) and electronic portal imaging device (EPID) (portal dosimetry, Varian Medical System). Integrated image was taken for each beam during the treatment by EPID at the source-detector distance of 150cm. Absolute intensity of the image was measured in an area of 1cmx1cm centered at the crosshair position. The cumulative intensity in the treatment was used to verify the dose delivered along the treatment course. The variation of the intensity was measured by taking the first treatment data as a reference. Exit dose of the patient_AC was calculated in the Eclipse TPS and was compared to the measured intensity by EPID relatively.

Results: 12 and 11 treatments were finished using the SS_IMRT_Plan and the S_IMRT_Plan, respectively. The cumulative intensity of the first treatment is 21.36CU for the ss_IMRT_Plan, and 24.55CU for the s_IMRT_Plan, respectively. The variation of the absolute intensity during the treatments for both plans is within 0.5 CU [range -0.10 to 0.29 CU, average 0.05CU for SS_IMRT_Plan; range -0.20 to 0.05 CU, average -0.09CU for S_IMRT_Plan], and the relative difference is within 2% [range -0.45% to 1.38%, average 0.23% for SS_IMRT_Plan; range -0.81% to 0.21%, average -0.36% for S_IMRT_Plan]. Exit dose calculated in the Eclipse TPS for both plans agreed well relatively with the intensity measured by EPID.

Conclusions:The proposed method can provide a way to real-time monitor the dose delivered to the patient.

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