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. 2024 Aug;25(8):e14410.
doi: 10.1002/acm2.14410. Epub 2024 May 29.

Dosimetric characterization for GRID collimator-based spatially fractionated radiation therapy: Dosimetric parameter acquisition and machine interchangeability investigation

Zhengzheng Xu  1   2 , Salim Balik  1   2 , Kaley Woods  1   2 , Zhilei Shen  1   2 , Chihyao Cheng  2 , Jing Cui  1   2 , Haihong Gallogly  1   2 , Eric Chang  1   2 , Lauren Lukas  1   2 , Andrew Lim  1   2 , Yutaka Natsuaki  1   2 , Jason Ye  1   2 , Lijun Ma  1   2 , Hualin Zhang  1   2
Affiliations

Dosimetric characterization for GRID collimator-based spatially fractionated radiation therapy: Dosimetric parameter acquisition and machine interchangeability investigation

Zhengzheng Xu et al. J Appl Clin Med Phys. 2024 Aug.

Abstract

Purpose: The purpose of this study is to characterize the dosimetric properties of a commercial brass GRID collimator for high energy photon beams including 15 and 10 MV. Then, the difference in dosimetric parameters of GRID beams among different energies and linacs was evaluated.

Method: A water tank scanning system was used to acquire the dosimetric parameters, including the percentage depth dose (PDD), beam profiles, peak to valley dose ratios (PVDRs), and output factors (OFs). The profiles at various depths were measured at 100 cm source to surface distance (SSD), and field sizes of 10 × 10 cm2 and 20 × 20 cm2 on three linacs. The PVDRs and OFs were measured and compared with the treatment planning system (TPS) calculations.

Results: Compared with the open beam data, there were noticeable changes in PDDs of GRID fields across all the energies. The GRID fields demonstrated a maximal of 3 mm shift in dmax (Truebeam STX, 15MV, 10 × 10 cm2). The PVDR decreased as beam energy increases. The difference in PVDRs between Trilogy and Truebeam STx using 6MV and 15MV was 1.5% ± 4.0% and 2.1% ± 4.3%, respectively. However, two Truebeam linacs demonstrated less than 2% difference in PVDRs. The OF of the GRID field was dependent on the energy and field size. The measured PDDs, PVDRs, and OFs agreed with the TPS calculations within 3% difference. The TPS calculations agreed with the measurements when using 1 mm calculation resolution.

Conclusion: The dosimetric characteristics of high-energy GRID fields, especially PVDR, significantly differ from those of low-energy GRID fields. Two Truebeam machines are interchangeable for GRID therapy, while a pronounced difference was observed between Truebeam and Trilogy. A series of empirical equations and reference look-up tables for GRID therapy can be generated to facilitate clinical applications.

Keywords: GRID collimator; GRID therapy; peak valley dose ratio; spatially fractionated radiation therapy.

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Conflict of interest statement

The authors declare no conflicts of interest.

Figures

FIGURE 1
FIGURE 1
GRID collimator used in this study (DotDecimal, Sanford, Florida).
FIGURE 2
FIGURE 2
Measured PDDs for open and GRID fields on STX with 6, 10, and 15 MV beams. Data from STX was presented as an example. The changes in dmax were marked with arrows.
FIGURE 3
FIGURE 3
Dose profiles of a 20 × 20 cm2 GRID field using 15 MV on STX at various depths. All profiles were normalized to the central peak value at dmax.
FIGURE 4
FIGURE 4
PVDRs versus depth, and corresponding polynomial fittings for GRID fields of different geometries on different linacs.
FIGURE 5
FIGURE 5
GRID beam profiles of TPS calculations (1 mm and 2 mm resolutions) and water tank measurement.
See this image and copyright information in PMC

References

    1. Kudrimoti M, Regine W, Meigooni A, Ahmed M, Mohiuddin M. High dose spatially fractionated radiation (GRID): a new paradigm in the management of advanced cancers. Int J Radiat Oncol Biol Phys. 2001;51(3):50‐51. - PubMed
    1. Gao M, Mohiuddin M, Hartsell W, Pankuch M. Spatially fractionated (GRID) radiation therapy using proton pencil beam scanning (PBS): feasibility study and clinical implementation. Med Phys. 2018;45(4):1645‐1653. - PubMed
    1. Schültke E, Balosso J, Breslin T, et al. Microbeam radiation therapy—grid therapy and beyond: a clinical perspective. Br J Radiol. 2017;90(1078):20170073. - PMC - PubMed
    1. Peñagarícano JA, Moros EG, 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(5):1369‐1375. - PubMed
    1. Zwicker RD, Meigooni A, Mohiuddin M. Therapeutic advantage of grid irradiation for large single fractions. Int J Radiat Oncol Biol Phys. 2004;58(4):1309‐1315. - PubMed