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Evaluation of DVH Based Patient-Specific Quality-Assurance Using COMPASS

S Sharma*, V Subramani , S Chander , S Bhaskar , S Pathy , P Kumar , N Gopishankar , S Thulkar , M Singh , A Binjola , All India Institute of Medical Sciences New Delhi


(Sunday, 7/14/2019)  

Room: ePoster Forums

Purpose: Aim is to evaluate 3D DVH based pre-treatment plan verification results using COMPASS, in addition with conventional 2D-planar quality assurance.

Methods: Twenty (20) head and neck patients treated with VMAT were planned with 6MV X-rays using Elekta VersaHD linear-accelerator. Prescription dose was ranging from 1.8Gy to 3.0Gy per-fraction. Treatment planning was done using Elekta Monaco(5.11) treatment planning system. 2D-planar dose measurements were performed with IBA-I'matriXX evolution detector array using My-QA-Patients software. For 2D-Gamma index evaluation 3%/2mm, 10% threshold criteria was used. 3D-dose measurements were performed using IBA-COMPASS software in combination with I’matriXX evolution detector. Monaco calculated and COMPASS (measured and calculated) doses were compared using DVH, in terms of doses to planning target volume (PTV) and organ at risks (OAR). For PTV D95, D2 and D50 (dose received by 95%, 2% and 50% volume), similarly for OARs D2 and D50 was noted.

Results: 2D-Gamma pass rate for Monaco calculated and I’matriXX measured 2D fluence were 97.6±2.2% for 3%/2mm criteria. Monaco versus COMPASS computed variations (cGy) were as: PTVD95(-53.62±158.32cGy), PTVD2(58.24±81.68cGy),PTVD50(-32.17±82.87cGy) respectively. Rt.-EyeD2(-59.77±131.83),D50(6.08±92.43cGy); Lt.-EyeD2(-64.70±111.72cGy),D50(-9.47±94.21cGy); Rt.-Optic-nerveD2(-135.72±170.83cGy),D50(-56.63±114.39cGy); Lt.-Optic-nerveD2(-156.50±178.76cGy),D50(-50.60±123.95cGy); BrainstemD2(-73.67±122.45cGy),D50(-33.81±68.17cGy); Spinal-cordD2(9.97±55.56cGy), D50(4.37±38.94cGy).Monaco computed versus COMPASS measured variations (cGy) were as: PTVD95(238.44±125.35cGy),PTVD2(227.04±139.78cGy),PTVD50(236.17±99.87cGy) respectively. Rt.-EyeD2(127.78±247.37),D50(150.49±143.99cGy); Lt.-EyeD2(186.59±231.78cGy), D50(171.76±153.13cGy); Rt.-Optic-nerveD2(133.88±172.69cGy), D50(86.90±293.56cGy); Lt.-Optic-nerveD2(53.98±222.39cGy), D50(117.76±289.02cGy); BrainstemD2(38.88±112.91cGy), D50(7.73±110.68cGy); Spinal-cordD2(21.42±125.32cGy), D50(-3.05±121.99cGy).COMPASS computed versus COMPASS measured variations (cGy) were as: PTVD95(240.46±172.04cGy),PTVD2(235.20±148.43cGy),PTVD50(231.90±156.30cGy) respectively. Rt.-EyeD2(239.24±102.41), D50(162.16±180.85cGy); Lt.-EyeD2(212.51±182.04cGy), D50(189.45±220.45cGy); Rt.-Optic-nerveD2(207.13±120.48cGy), D50(143.52±113.64cGy); Lt.-Optic-nerveD2(212.72±224.67cGy), D50(168.36±139.59cGy); BrainstemD2(112.54±160.31cGy), D50(46.30±111.11cGy); Spinal-cordD2(11.43±153.92cGy), D50(-7.43±127.73cGy).

Conclusion: 2D-Gamma pass-rate was 97.6±2.2% for 3%/2mm criteria. COMPASS calculated and measured doses showed good agreement (<2.4Gy) with Monaco calculated dose, therefore can be used in clinic for pre-treatment quality-assurance.


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TH- External beam- photons: Quality Assurance - IMRT

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