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Statistical Analysis of Patient's Treatment Site Specific QA Using MapCHECK2 for Local Delivery Guideline

X Ding*, A Olszanski, University of Pennsylvania, Philadelphia, PA

SU-E-T-202 Sunday 3:00PM - 6:00PM Room: Exhibit Hall

Purpose:
We statistically evaluated the results of dosimetry quality assurance (DQA) measurements and derived local confidence limits for different treatment site to establish our institutional guideline for patient's treatment site specific QA procedure.

Methods:
104 patients were treated using IMRT and VMAT with head and neck (H&N) cancer (16 cases,15.4%), prostate or pelvis cancer (28 cases 26.9%), breast cancer (21 cases 20.2%), lung cancer (12 cases 11.5%) and brain tumor (27 cases, 26.0%) in which all H&N patients were treated using VMAT while others were treated with IMRT. All IMRT's composite-fields were measured with MapCHECK2 while 16 H&N VMAT plans were undertaken using MapCHECK2 with an isocentric setup holder. The Distance-to-Agreement (DTA) 3%3mm criteria were used to evaluate the QA plans. The mean DTA values and standard deviations were used to develop the local confidence for each treatment site. Local confidence limits (CL) were derived using concept confident limit of (100-mean)+1.96σ. T-test was used to compare DTA 3%/3mm between different treatment site.

Results:
The percentage of points passing the DTA 3%/3mm for different treatment site as follow: H&N cancer was 96.8±2.2%, Prostate or pelvis cancer was 98.0±2.6%, Lung cancer was 97.5±3.1%, Brain tumor was 98.4±2.4%, Breast cancer was 99.4±1.1%. The result shows breast IMRT DTA passing rate is significantly higher than lung IMRT(p=0.020), prostate or pelvis IMRT(p=0.028) and H&N VMAT (p=0.00005). Brain IMRT DTA passing rate is significantly higher than H&N VMRT(p= 0.045). Confident limit for H&N site is 7.6% (92.4% passing), prostate or pelvis cancer is 7.1% (92.9% passing), Breast site is 2.8%(97.1% passing), lung cancer is 8.6% (91.4% passing)and brain tumor is 6.2% (93.8% passing).

Conclusion:
This study indicates that different treatment site may have different degree of intensity modulation resulting different DTA passing rate. Different local confident limit may be needed for different treatment sites or techniques.

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