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Clinical experience using Delta 4 phantom for pretreatment patient-specific quality assurance in modern radiotherapy

Published online by Cambridge University Press:  15 November 2018

R. P. Srivastava  and
C. De Wagter
R. P. Srivastava*
Affiliation:
Department of Radiation Oncology, Ghent University Hospital, Gent, Belgium Radiotherapy Association Meuse Picardie, Centre Hospitalier Mouscron, Mouscron, Belgium
C. De Wagter
Affiliation:
Department of Radiation Oncology, Ghent University Hospital, Gent, Belgium Department of Radiation Oncology and Experimental Cancer Research, Ghent University Hospital, Gent, Belgium
*
Author for correspondence: R. P. Srivastava, Department of Radiation Oncology, Ghent University Hospital, C. Heymanslaan 10, Radiotherapiepark, 9000 Gent, Belgium. Tel: +3293323030. E-mail: rajupsrivastava@hotmail.com
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Abstract

Purpose

In advanced radiotherapy techniques such as intensity-modulated radiation therapy (IMRT), the quality assurance (QA) process is essential. The aim of the study was to assure the treatment planning dose delivered during delivery of complex treatment plans. The QA standard is to perform patient-specific comparisons between planned doses and doses measured in a phantom.

Materials and method

The Delta 4 phantom (Scandidos, Uppsala, Sweden) has been used in this study. This device consists of diode matrices in two orthogonal planes inserted in a cylindrical acrylic phantom. Each diode is sampled per beam pulse so that the dose distribution can be evaluated on segment-by-segment, beam-by-beam, or as a composite plan from a single set of measurements. Ninety-five simple and complex radiotherapy treatment plans for different pathologies, planned using a treatment planning system (TPS) were delivered to the QA device. The planned and measured dose distributions were then compared and analysed. The gamma index was determined for different pathologies.

Results

The evaluation was performed in terms of dose deviation, distance to agreement and gamma index passing rate. The measurements were in excellent agreement between with the calculated dose of the TPS and the QA device. Overall, good agreement was observed between measured and calculated doses in most cases with gamma values above 1 in >95% of measured points. Plan results for each test met the recommended dose goals.

Conclusion

The delivery of IMRT and volumetric-modulated arc therapy (VMAT) plans was verified to correspond well with calculated dose distributions for different pathologies. We found the Delta 4 device is accurate and reproducible. Although Delta4 appears to be a straightforward device for measuring dose and allows measure in real-time dosimetry QA, it is a complex device and careful quality control is required before its use.

Keywords

gamma indexintensity-modulated radiation therapymulti-leaf collimatorquality assurancevolumetric-modulated arc therapy
Type
Technical Note
Information
Journal of Radiotherapy in Practice , Volume 18 , Issue 2 , June 2019 , pp. 210 - 214
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Copyright
© Cambridge University Press 2018 

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Footnotes

Cite this article: Srivastava RP, De Wagter C (2019) Clinical experience using Delta 4 phantom for pretreatment patient-specific quality assurance in modern radiotherapy. Journal of Radiotherapy in Practice18: 210–214. doi: 10.1017/S1460396918000572

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