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Dosimetric study for spine stereotactic body radiation therapy: magnetic resonance guided linear accelerator versus volumetric modulated arc therapy

Poonam Yadav
Poonam Yadav
, 
Hima B. Musunuru
Hima B. Musunuru
, 
Jacob S. Witt
Jacob S. Witt
, 
Michael Bassetti
Michael Bassetti
, 
John Bayouth
John Bayouth
 et 
Andrew M. Baschnagel
Andrew M. Baschnagel
   | 24 sept. 2019
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Article Category: Research Article
Publié en ligne: 24 sept. 2019
Pages: 362 - 368
Reçu: 24 mars 2019
Accepté: 22 juil. 2019
DOI: https://doi.org/10.2478/raon-2019-0042
© 2019 Poonam Yadav, Hima B. Musunuru, Jacob S. Witt, Michael Bassetti, John Bayouth, Andrew M. Baschnagel, published by Sciendo
This work is licensed under the Creative Commons Attribution-NonCommercial-NoDerivatives 3.0 License.

Figure 1

Isodose distribution (right) for TrueBeamTM STx VMAT and MRIdian Linac Plans: 30 Gy to gross tumor volume (GTV) and 27 Gy to planning target volume (PTV) in 3 fractions. On left, solid and dashed lines represents dose volume histogram for TrueBeamTM STx VMAT and MRIdian Linac Plans for GTV, PTV, Spinal Cord and Spinal Cord+2mm.
Isodose distribution (right) for TrueBeamTM STx VMAT and MRIdian Linac Plans: 30 Gy to gross tumor volume (GTV) and 27 Gy to planning target volume (PTV) in 3 fractions. On left, solid and dashed lines represents dose volume histogram for TrueBeamTM STx VMAT and MRIdian Linac Plans for GTV, PTV, Spinal Cord and Spinal Cord+2mm.

Figure 2

A metastatic tumor in the vertebral body of lumbar spine and adjacent spinal cord scan acquired on 1.5T diagnostic magnetic resonance (MR) and 0.345T ViewRay MRIdian Linac system. MRIdian scan allows for accurate delineation of the tumor and the spinal cord without having to rely on the fused diagnostic MR scan.
A metastatic tumor in the vertebral body of lumbar spine and adjacent spinal cord scan acquired on 1.5T diagnostic magnetic resonance (MR) and 0.345T ViewRay MRIdian Linac system. MRIdian scan allows for accurate delineation of the tumor and the spinal cord without having to rely on the fused diagnostic MR scan.

Figure 3

Fractional 0.345T MRIdian Linac MR scan (Top) and Kilo Voltage Cone Beam (Bottom) used for daily setup verification before radiotherapy treatment. Visibility of spinal cord on 0.345T is demonstrated increasing the accuracy on treatment delivery.
Fractional 0.345T MRIdian Linac MR scan (Top) and Kilo Voltage Cone Beam (Bottom) used for daily setup verification before radiotherapy treatment. Visibility of spinal cord on 0.345T is demonstrated increasing the accuracy on treatment delivery.

Figure 4

Fractional 0.345T MRIdian Linac MR scan (Left) and TomoTherapy® Mega Voltage CT (Right) used for daily setup verification before radiotherapy treatment. Visibility of target (red) on 0.345T is demonstrated.
Fractional 0.345T MRIdian Linac MR scan (Left) and TomoTherapy® Mega Voltage CT (Right) used for daily setup verification before radiotherapy treatment. Visibility of target (red) on 0.345T is demonstrated.

Figure 5

0.345T MRIdian Linac cine acquired in sagittal plane. Any changes in reference setup results in shutting the radiation beam off as tracking structure (green) moves outside the boundary (red).
0.345T MRIdian Linac cine acquired in sagittal plane. Any changes in reference setup results in shutting the radiation beam off as tracking structure (green) moves outside the boundary (red).

Dose volume parameters for PTV, GTV, Spinal Cord and Cauda Equina for MRIdian Linac IMRT plans Vs TrueBeamTM STx VMAT plans

Structures TrueBeamTM STx VMAT MRIdian Linac IMRT p-value
PTV Median(range) Median(range)
D98% (Gy) 25.7 (15.6–29.5) 26.5 (17.7–29.7) 0.20
D50% (Gy) 29.0 (27.9–39.1) 30.0 (26.4–33.2) 0.77
Conformity Index 0.97 (0.93–1.0) 0.97 (0.90–1.0) 0.13
Dose Homogeneity Index 0.22 (0.05–0.6) 0.19 (0.1–0.57) 0.49
R50 6.1 (2.9–16.7) 5.2 (2.8–11.9) 0.05
GTV
D50% (Gy) 31.6 (30.4–34.2) 31.7 (31.0–34.6) 0.36
D98% (Gy) 30.12 (25–33.63) 30.35 (29.17–32.89) 0.23
Conformity Index 0.99 (0.95–1.0) 0.99 (0.96–1.0) 0.58
Dose Homogeneity Index 0.09 (0.04–0.33) 0.08 (0.01–0.18) 0.30
R50 32 (6.08–69.0) 29 (5.8–66.0) 0.01
Spinal Cord
Max dose (Gy) 12.6 (9.1–15.6) 13.3 (10.35–17.3) 0.13
D0.03 (Gy) 12 (9.0–15.3) 12.8 (9.5–16.5) 0.25
Cauda Equina
Max dose (Gy) 16 (0.22–28.0) 18 (0.3–32) 0.38
D0.03 (Gy) 13 (0.2–20.0) 16 (0.25–31) 0.07

Detailed Dose volume histogram parameters for PTV, GTV, Spinal Cord and Cauda Equina for MRIdian Linac IMRT plans Vs TrueBeamTM STx VMAT plans

PTV GTV Spinal Cord Cauda Equina
Case # Volume Maximum Dose (Gy) D95 ( Gy) Volume Maximum Dose (Gy) D95 ( Gy) Maximum Dose (Gy) D0.03 cc (Gy) Maximum Dose (Gy) D0.03 cc (Gy)
(cc) MRIdian Linac IMRT True Beam VMAT MRIdian Linac IMRT True Beam VMAT (cc) MRIdian Linac IMRT True Beam VMAT MRIdian Linac IMRT True Beam VMAT MRIdian Linac IMRT True Beam VMAT MRIdian Linac IMRT True Beam VMAT MRIdian Linac IMRT True Beam VMAT MRIdian Linac IMRT True Beam VMAT
1 60.37 34.69 35.44 27.43 27.50 7.02 34.69 35.44 32.46 33.76 14.82 14.77 14.67 14.47 19.70 21.72 19.67 20.19
2 50.63 32.45 32.27 27.00 27.31 6.82 32.94 32.41 30.11 30.05 13.33 13.45 13.02 13.10 20.00 21.15 19.92 18.95
3 66.3 36.41 37.00 27.75 27.12 27.67 36.41 37.00 32.58 29.61 17.01 11.69 16.56 10.90 21.07 14.12 20.23 13.58
4 47.63 31.68 30.85 27.19 27.94 18.8 34.02 33.45 30.06 30.52 13.25 15.65 12.62 15.34 24.08 21.19 22.48 19.79
5 2.6 33.87 30.71 27.73 27.26 0.9 33.87 32.02 30.24 30.21 12.58 13.81 11.92 12.90 9.31 12.37 7.73 7.56
6 3.93 33.52 31.40 27.67 27.89 1.65 33.52 34.96 32.17 27.39 10.35 9.10 10.32 9.09 16.44 18.01 12.58 12.32
7 3.05 32.64 30.88 27.50 27.82 1.07 32.65 33.70 30.44 29.02 11.17 10.10 11.15 10.09 32.13 28.01 31.16 19.32
8 25.43 32.73 34.07 27.92 27.99 2.31 32.73 34.07 30.31 31.43 13.72 10.98 13.22 10.36 13.72 10.6 13.19 10.25
9 29.02 33.95 34.14 27.50 27.60 1.89 35.70 34.14 30.05 30.52 11.04 9.25 9.53 8.96 0.32 0.22 0.25 0.21
10 38.29 33.02 33.95 27.88 27.02 2.51 33.02 33.95 30.45 30.51 17.30 14.11 14.51 13.75 3.54 3.67 3.20 3.40
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