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Commissioning and Validation of the Dolphin Transmission Detector and Compass Software

T Knewtson1*, S Pokhrel1 , A Wiles1 ,A Baker3, M Ballo1,2 , E W Izaguirre1,2 , (1) university Tennessee Health Science Center, Methodist university Hospital, Memphis, TN., (2) West Cancer Center, Germantown, TN., (3) Methodist Healthcare, Memphis,TN.


(Monday, 7/30/2018) 9:30 AM - 10:00 AM

Room: Exhibit Hall | Forum 7

Purpose: To commission and validate the IBA Dolphin transmission detector for use during patient specific quality assurance and to compare the detector’s spatial and dosimetric accuracy with respect to other commercially available patient specific QA devices and film.

Methods: Patient specific IMRT and SBRT QA was performed using the Dolphin ion chamber array transmission detector (5mm central ion chamber spacing), Matrixx ion chamber array detector (7.6mm ion chamber spacing), ArcCheck diode array detector (10mm helical diode spacing), and radiochromic film on an Elekta Synergy linac equipped with 160 Agility MLC’s. A range of IMRT and VMAT patients were selected to test the versatility and dependability of the Dolphin detector to perform patient specific QA. The Dolphin and Matrixx data were reconstructed using the Compass software, and the results were compared using the Compass 2D and 3D dosimetry tools. The reconstructed data from the Dolphin and Matrixx were first compared to each other and then independently compared to treatment planning system and Compass predicted dose. The results found using the Compass analysis tools were then independently verified against the dosimetric data from the ArcCheck and film.

Results: Reconstructed 3D dose distributions based on the Dolphin measurements when compared to the 3D reconstructed Matrixx measurements show up to 2% overall dose differences to the target and critical structures. A 3D comparison between the Dolphin and the treatment planning system shows an overall dose difference up to 3%. Overall gamma passing rates agree with ArcCheck measurements within 3% and 2D analysis using film show agreement within 3%.

Conclusion: The results show that the Dolphin is an effective tool for performing patient specific QA for IMRT and VMAT treatment plans and its spatial and dosimetric accuracy is independent of the complexity of the delivered fields.


Radiation Therapy, Radiation Detectors, Photon Detectors


TH- External beam- photons: Quality Assurance - VMAT

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