Abstract
BackgroundThe demand for dose verification during treatment has risen with the increasing use of intensity-modulated radiation therapy (IMRT) and volumetric modulated arc therapy (VMAT) in modern radiation therapy. This study aims to validate the transmission factors of a new transmission detector, the Dolphin online monitoring system (IBA Dosimetry, Schwarzenbruck, Germany), for clinical use.MethodsThe transmission factors of the Dolphin detector were evaluated using 6 MV, 6 flattening filter free (FFF), 10 MV, and 10 FFF clinical beams from a TrueBeam STx linear accelerator system. Two-dimensional (2D) dose distributions were measured through portal dosimetry with and without Dolphin to derive the transmission factors. The measurements were performed using 10 IMRT and 10 VMAT treatment plans. The transmission factors were calculated using a non-negative least squares problem solver for the 2D dose matrix. Normalized plans were generated using the derived transmission factors. Patient-specific quality assurance with normalized plans was performed using portal dosimetry and an ArcCheck detector to verify the transmission factors. The gamma passing rates were calculated for the 2%/2 mm and 1%/1 mm criteria.ResultsThe transmission factors for the 6 MV, 6 FFF, 10 MV, and 10 FFF beams, were 0.878, 0.824, 0.913, and 0.883, respectively. The average dose difference between the original plan without Dolphin and the normalized plan with Dolphin was less than 1.8% for all measurements. The mean passing rates of the gamma evaluation were 98.1 ± 2.1 and 82.9 ± 12.6 for the 2%/2 mm and 1%/1 mm criteria, respectively, for portal dosimetry of the original plan. In the case of the portal dosimetry of the normalized plan, the mean passing rates of the gamma evaluation were 97.2 ± 2.8 and 79.1 ± 14.8 for the 2%/2 mm and 1%/1 mm criteria, respectively.ConclusionsThe Dolphin detector can be used for online dosimetry when valid transmission factors are applied to the clinical plan.
Highlights
The demand for dose verification during treatment has risen with the increasing use of intensitymodulated radiation therapy (IMRT) and volumetric modulated arc therapy (VMAT) in modern radiation therapy
The measured transmission factors decreased with the increasing field size
Our results showed a maximum difference of 0.8% for the four energies in each transmission factor
Summary
The demand for dose verification during treatment has risen with the increasing use of intensitymodulated radiation therapy (IMRT) and volumetric modulated arc therapy (VMAT) in modern radiation therapy. Intensity-modulated radiation therapy (IMRT), volumetric modulated arc therapy (VMAT), and stereotactic ablative radiotherapy (SABR) are used for precise radiation delivery [1, 2]. These techniques can generate a sophisticated dose distribution, delivering high doses to the target with lower doses to. Park et al Radiation Oncology (2018) 13:156 chamber, or film before first treatment Such pretreatment plan verifications have certain limitations [11, 12]. This approach does not ensure that the planned dose is delivered to the patient during all treatment fractions because the mechanical conditions of the treatment machine can vary
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