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Table 2 Summary of target volume coverage, heterogeneity index, and dose to organs at risk for proton plans calculated with pencil beam algorithm (PBA), recalculation of PBA plan using Monte Carlo (MC), re-optimized plan using MC and fixed RBE, and re-optimized plan using MC with variable RBE among 8 mediastinal lymphoma patients with free-breathing CT simulation scans (left 4 columns). Comparison plans on deep inspiration breath hold (DIBH) scans with optimized PBS plan using MC versus photon techniques. Median volume or dose with interquartile range (IQR) in parentheses. Pair-wise dose differences were compared using a Wilcoxon signed-rank test. Significant p-values (< 0.05) are bolded for emphasis

From: Comparative photon and proton dosimetry for patients with mediastinal lymphoma in the era of Monte Carlo treatment planning and variable relative biological effectiveness

Median (IQR) FB PBPB cRBE FB PBMC cRBE FB MCMC cRBE FB MCMC vRBE DIBH MCMC cRBE DIBH IMRT
ITV or CTV target coverage
 V99* 100% (100–100%) 80.6% (66.2–91.4%) 99.9% (99.6–100%) 98.7% (69.8–99.4%) 99.7% (99.6–99.9%) 99.3% (99–99.8%)
 V95 100% (100–100%) 98.4% (96.7–99.3%) 100% (100–100%) 100% (99.8–100%) 100% (99.9–100%) 99.9% (99.8–100.0%)
 Global dose max 107.6% (106.1–108.1) 108.1% (105.5–109.1) 109.2% (107.9–109.5) 112.5% (110.5–114.4) 109.7% (109.4–109.9) 112.3% (111.2–112.7%)
 Homogeneity index (D95/D5) 0.97 (0.95–0.97) 0.94 (0.93–0.96) 0.97 (0.97–0.97) 0.95 (0.95–0.96) 0.96 (0.96–0.97) 0.96 (0.95–0.96)
Dose to normal structures
 Mean lung (Gy) 6.6 (4.4–9.2) 6.6 (4.6–9.2) 7.1 (5.0–8.9) 7.5 (5.7–9.0) 5.9 (4.8–7.8) 8.9 (8.1–11.7)
 Lung V20 16.3% (9.7–21.4) 16.1% (9.6–21.3) 16.8% (10.7–20.1) 17.1% (13.8–20.5) 12.3% (9.8–16.5%) 17.6% (10.6–24.8)
 Lung V5 30.5% (22.3–45.4) 31.4% (23.3–47.2) 33.4% (25.4–43.9) 34.9% (26.4–44.5) 31.0% (24.2–38.4%) 53.3% (45.1–61.6)
 Mean heart (Gy) 9.3 (7.6–12.2) 9.1 (7.4–11.8) 9.9 (7.7–12.0) 10.2 (8.7–12.0) 8.6 (6.5–10.9) 10.4 (9.0–15.1)
 Mean left breast (Gy) 2.0 (0.5–4.2) 2.1 (0.6–4.3) 2.2 (0.6–4.8) 2.0 (0.6–4.5) 2.1 (0.6–4.0) 4.1 (1.2–7.5)
 Mean right breast (Gy) 1.2 (0.3–2.6) 1.3 (0.4–2.7) 1.4 (0.6–2.9) 1.7 (0.6–2.9) 1.4 (0.9–3.3) 2.9 (1.9–5.6)
 Max spinal cord (Gy) 13.8 (13.0–17.2) 16.5 (14.4–20.0) 17.9 (15.4–20.9) 19.0 (16.6–21.5) 19.7 (15.0–21.0) 30.4 (27.0–31.7)
 Max esophagus (Gy) 31.5 (31.3–32.3) 31.0 (30.7–31.3) 32.1 (31.1–32.5) 31.9 (31.3–32.8) 32.0 (31.7–32.3) 31.7 (31.6–32.5)
P-value FB PBPB cRBE vs FB PBMC cRBE FB PBMC cRBE vs FB MCMC cRBE FB PBPB cRBE vs FB MCMC cRBE FB MCMC cRBE vs DIBH photon DIBH MCMC cRBE vs DIBH photon
ITV or CTV target coverage
 V99* 0.012 0.018 0.093 0.12 0.16
 V95 0.012 0.012 0.20 0.075 0.36
 Global dose max 0.48 0.16 0.06 0.012 0.012
 Homogeneity index (D95/D5) 0.018 0.012 0.28 0.25 0.20
Dose to normal structures
 Average lung (Gy) 0.08 0.21 0.16 0.012 0.012
 Lung V20 0.29 0.33 0.33 0.26 0.16
 Lung V5 0.012 0.33 0.05 0.012 0.012
 Average heart (Gy) 0.012 0.093 1.00 0.16 0.025
 Average left breast (Gy) 0.35 0.12 0.046 0.028 0.028
 Average right breast (Gy) 0.028 0.043 0.028 0.028 0.046
 Max spinal cord (Gy) 0.05 0.33 0.017 0.012 0.017
 Max esophagus (Gy) 0.012 0.011 0.58 0.78 1.00
  1. *Volume of ITV or CTV covered by 99% isodose line
  2. Abbreviations: FB Free breathing; DIBH, deep inspiration breath hold; cRBE, constant RBE; MCMC, plan optimized and calculated with Monte Carlo algorithm; PBMC, plan optimized with pencil-beam algorithm and re-calculated with Monte Carlo algorithm; PBPB, plan optimized and calculated with pencil-beam algorithm; vRBE, variable RBE