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<p>This study evaluates the dosimetric impact of arc simulation angular resolution in VMAT-based Single Isocentre Multiple Target (SIMT) SRS, focusing on their dependence on target size, isocentre distance, number of arcs, and arc type. A phantom study analysed angular resolution (0.5°, 1°, 2°) effects on dosimetric accuracy for PTVs of 0.5&#xa0;cm, 1&#xa0;cm, and 2&#xa0;cm at distances of 2.5&#xa0;cm, 5&#xa0;cm, and 7.5&#xa0;cm from the isocentre using conformal arc and VMAT plans. Clinical validation involved 32 patients with 2–8 brain metastases, comparing plans recalculated at 1° and 2° resolutions. Dosimetric parameters included: <i>D</i><sub>near-Min</sub>, <i>D</i><sub>near-Max</sub>, <i>D</i><sub>mean</sub>, <i>D</i><sub>median</sub>, TV<sub>PIV</sub>, CI<sub>Paddick</sub>, GI, and Brain-GTV 12&#xa0;Gy. For the 0.5&#xa0;cm diameter target located at 7.5&#xa0;cm distance from isocentre, phantom results showed TV<sub>PIV</sub>, <i>D</i><sub>mean</sub>, and GI deviations of 7.91%, 1.8%, and 0.85 for single-conformal arcs, which decreased to 4.84%, 1.3%, and 0.77 with 4-conformal arcs, and 3.4%, 0.96%, and 0.5 for 4-arc VMAT. Deviations varied based on target size, isocentre distance, number of arcs, and arc type. Clinical results mirrored the phantom study, with maximum TV<sub>PIV</sub> and GI deviations of 2.76% and 0.65 for the smallest target (0.6&#xa0;cm) located at 7.5&#xa0;cm distance for four-arc VMAT. Other dosimetric parameters showed minimal variations (&lt; 1%). Correlation analysis revealed strong associations between dosimetric differences, target size, and distance (<i>r</i> = 0.6–0.78 for small targets). MANOVA identified TV<sub>PIV</sub> as the only significant parameter (<i>p</i> = 0.01). A 1° angular resolution significantly improves dosimetric accuracy for small, distally located targets in SIMT SRS.</p>

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Dosimetric impact of arc simulation angular resolution in single-isocentre multi-target stereotactic radiosurgery

  • 期刊论文

  • 发表日期：

    2025年1月15日

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  • Perumal Murugan,
  • Ravikumar Manickam,
  • Tamilarasan Rajamanickam,
  • Sivakumar Muthu,
  • C. Dinesan,
  • Karthik Appunu,
  • Abishake Murali

摘要

This study evaluates the dosimetric impact of arc simulation angular resolution in VMAT-based Single Isocentre Multiple Target (SIMT) SRS, focusing on their dependence on target size, isocentre distance, number of arcs, and arc type. A phantom study analysed angular resolution (0.5°, 1°, 2°) effects on dosimetric accuracy for PTVs of 0.5 cm, 1 cm, and 2 cm at distances of 2.5 cm, 5 cm, and 7.5 cm from the isocentre using conformal arc and VMAT plans. Clinical validation involved 32 patients with 2–8 brain metastases, comparing plans recalculated at 1° and 2° resolutions. Dosimetric parameters included: Dnear-Min, Dnear-Max, Dmean, Dmedian, TVPIV, CIPaddick, GI, and Brain-GTV 12 Gy. For the 0.5 cm diameter target located at 7.5 cm distance from isocentre, phantom results showed TVPIV, Dmean, and GI deviations of 7.91%, 1.8%, and 0.85 for single-conformal arcs, which decreased to 4.84%, 1.3%, and 0.77 with 4-conformal arcs, and 3.4%, 0.96%, and 0.5 for 4-arc VMAT. Deviations varied based on target size, isocentre distance, number of arcs, and arc type. Clinical results mirrored the phantom study, with maximum TVPIV and GI deviations of 2.76% and 0.65 for the smallest target (0.6 cm) located at 7.5 cm distance for four-arc VMAT. Other dosimetric parameters showed minimal variations (< 1%). Correlation analysis revealed strong associations between dosimetric differences, target size, and distance (r = 0.6–0.78 for small targets). MANOVA identified TVPIV as the only significant parameter (p = 0.01). A 1° angular resolution significantly improves dosimetric accuracy for small, distally located targets in SIMT SRS.