A Dosimetric Parameter Reference Look-Up Table for GRID Collimator-Based Spatially Fractionated Radiation Therapy - PubMed (original) (raw)
A Dosimetric Parameter Reference Look-Up Table for GRID Collimator-Based Spatially Fractionated Radiation Therapy
Hualin Zhang et al. Cancers (Basel). 2022.
Abstract
Computations of heterogeneity dose parameters in GRID therapy remain challenging in many treatment planning systems (TPS). To address this difficulty, we developed reference dose tables for a standard GRID collimator and validate their accuracy. The .decimal Inc. GRID collimator was implemented within the Eclipse TPS. The accuracy of the dose calculation was confirmed in the commissioning process. Representative sets of simulated ellipsoidal tumours ranging from 6-20 cm in diameter at a 3-cm depth; 16-cm ellipsoidal tumours at 3, 6, and 10 cm in depth were studied. All were treated with 6MV photons to a 20 Gy prescription dose at the tumour center. From these, the GRID therapy dosimetric parameters (previously recommended by the Radiosurgery Society white paper) were derived. Differences in D5 through D95 and EUD between different tumour sizes at the same depth were within 5% of the prescription dose. PVDR from profile measurements at the tumour center differed from D10/D90, but D10/D90 variations for the same tumour depths were within 11%. Three approximation equations were developed for calculating _EUD_s of different prescription doses for three radiosensitivity levels for 3-cm deep tumours. Dosimetric parameters were consistent and predictable across tumour sizes and depths. Our study results support the use of the developed tables as a reference tool for GRID therapy.
Keywords: GRID therapy; equivalent uniform dose; peak valley dose ratio; reference table; spatially fractionated radiation therapy.
Conflict of interest statement
The authors declare no conflict of interest.
Figures
Figure 1
(a) Commercially available GRID collimator by High Dose Radiation Grid, Radiation Products Design, Albertville, MN, USA. The image is provided by the vendor. (b) Commercially available GRID collimator by .decimal Inc.TM, Sanford, FL, USA. The image is provided by the vendor.
Figure 2
(a) Percent depth-dose curves of a 10 × 10 cm2 open field and a 10 × 10 cm2 GRID collimated field. (b) Radial and transverse dose profiles of GRID therapy measured in a water tank at 1, 1.5, 2, 3, 5 and 10 cm depths for a 6 MV beam for the brass .decimal Inc.TM GRID collimator.
Figure 3
Peak/valley dose ratios were determined from measured dose profiles at different depths using a 10 × 10 cm2 field size for the .decimal Inc.TM GRID collimator. The data for a Cerrobend GRID collimator made by Radiation Protection DesignsTM (RPD), measured by Meigooni et al. [17] were plotted for comparison. The peak and valley doses are from or near the central axis. The off-axis values are the same (within 2%), because the apertures were designed to be divergent and to deliver the same dose from different holes.
Figure 4
Dose profile comparison between TPS (red line) and radiochromic film measurement (blue line) for a 10 × 10 cm2 field made at 5 cm depth in solid water for a 6 MV beam. Radiochromic film measurements can be made for additional checks of TPS calculations and MU verification. The 3% error bars were added to the film data. In this figure, a transverse profile comparison was used as an example. In this dose validation process, a gamma analysis was performed resulting in a 99% passing rate with a 3% (global)/3 mm criterion using a 10% (global) minimum dose threshold.
Figure 5
Schematic diagram of tumor geometry and depths used in the test plans. (a) shows ellipsoidal tumours with the same height of 6 cm but different sizes in the transverse dimension located at the depth of 3 cm. (b) shows tumours with a height of 6 cm and transverse dimension of 16 cm located at the depths of 3, 6 and 10 cm, respectively.
Figure 6
Schematic diagram of GRID collimator (a) and dose projection (b) in an ellipsoid shaped tumor shown in a TPS.
Figure 7
(a) Percent depth dose curves of a 10 × 10 cm2 GRID field. The Eclipse-calculated PDD (blue) was compared with the water tank-scanned data (red). (b) A comparison of radial (top) and transverse (bottom) dose profiles of GRID therapy at 3 cm depth calculated by Eclipse TPS (red) and measured by a water tank scanning system (blue).
Figure 8
Differential (a) and cumulative (b) dose–volume histograms of tumors with different sizes centered at the depth of 3 cm (A), and the same size of tumor (16 cm) centered at 3, 6, and 10 depths (B). All tumors are ellipsoidal. The tumor height (along the beam direction) is 6 cm, in the plane perpendicular to the beam direction, the tumor shape is circular with the various diameters ranging from 6 to 20 cm.
References
- Neuner G., Mohiuddin M.M., Vander Walde N., Goloubeva O., Ha J., Cedric X.Y., Regine W.F. High-dose spatially fractionated GRID radiation therapy (SFGRT): A comparison of treatment outcomes with Cerrobend vs. MLC SFGRT. Int. J. Radiat. Oncol. Biol. Phys. 2012;82:1642–1649. doi: 10.1016/j.ijrobp.2011.01.065. -DOI -PubMed
- Penagaricano J., Phase I. Clinical Trial of GRID Therapy in Pediatric Osteosarcoma of the Extremity. [(accessed on 16 February 2022)];2017 Available online: https://clinicaltrials.gov/ct2/show/NCT03139318.
- Penagaricano J.A., Moros E.G., Ratanatharathorn V., Yan Y., Corry P. Evaluation of spatially fractionated radiotherapy (GRID) and definitive chemoradiotherapy with curative intent for locally advanced squamous cell carcinoma of the head and neck: Initial response rates and toxicity. Int. J. Radiat. Oncol. Biol. Phys. 2010;76:1369–1375. doi: 10.1016/j.ijrobp.2009.03.030. -DOI -PubMed
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