Volumetric-Modulated Arc Therapy: Effective and Efficient End-to-End Patient-Specific Quality Assurance

Journal Article · Sun Apr 01 04:00:00 EDT 2012 · International Journal of Radiation Oncology, Biology and Physics

DOI:https://doi.org/10.1016/J.IJROBP.2011.01.018· OSTI ID:22056199

O'Daniel, Jennifer ^[1]; Das, Shiva; Wu, Q Jackie; Fangfang, Yin ^[1]

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1. Department of Radiation Oncology, Duke University Medical Center, Durham, NC (United States)

Purpose: To explore an effective and efficient end-to-end patient-specific quality-assurance (QA) protocol for volumetric modulated arc radiotherapy (VMAT) and to evaluate the suitability of a stationary radiotherapy QA device (two-dimensional [2D] ion chamber array) for VMAT QA. Methods and Materials: Three methods were used to analyze 39 VMAT treatment plans for brain, spine, and prostate: ion chamber (one-dimensional absolute, n = 39), film (2D relative, coronal/sagittal, n = 8), and 2D ion chamber array (ICA, 2D absolute, coronal/sagittal, n = 39) measurements. All measurements were compared with the treatment planning system dose calculation either via gamma analysis (3%, 3- to 4-mm distance-to-agreement criteria) or absolute point dose comparison. The film and ion chamber results were similarly compared with the ICA measurements. Results: Absolute point dose measurements agreed well with treatment planning system computed doses (ion chamber: median deviation, 1.2%, range, -0.6% to 3.3%; ICA: median deviation, 0.6%, range, -1.8% to 2.9%). The relative 2D dose measurements also showed good agreement with computed doses (>93% of pixels in all films passing gamma, >90% of pixels in all ICA measurements passing gamma). The ICA relative dose results were highly similar to those of film (>90% of pixels passing gamma). The coronal and sagittal ICA measurements were statistically indistinguishable by the paired t test with a hypothesized mean difference of 0.1%. The ion chamber and ICA absolute dose measurements showed a similar trend but had disparities of 2-3% in 18% of plans. Conclusions: After validating the new VMAT implementation with ion chamber, film, and ICA, we were able to maintain an effective yet efficient patient-specific VMAT QA protocol by reducing from five (ion chamber, film, and ICA) to two measurements (ion chamber and single ICA) per plan. The ICA (Matrixx Registered-Sign , IBA Dosimetry) was validated for VMAT QA, but ion chamber measurements are recommended for absolute dose comparison until future developments correct the ICA angular dependence.

• OSTI ID: 22056199
• Journal Information: International Journal of Radiation Oncology, Biology and Physics, Journal Name: International Journal of Radiation Oncology, Biology and Physics Journal Issue: 5 Vol. 82; ISSN IOBPD3; ISSN 0360-3016
• Country of Publication: United States
• Language: English

Related Subjects

62 RADIOLOGY AND NUCLEAR MEDICINE
BRAIN
DOSIMETRY
FILMS
IONIZATION CHAMBERS
PATIENTS
PLANNING
PROSTATE
QUALITY ASSURANCE
RADIATION DOSES
RADIOTHERAPY
VERTEBRAE