TY - JOUR
T1 - Comparison of treatment planning approaches for spatially fractionated irradiation of deep tumors
AU - Sheikh, Khadija
AU - Hrinivich, William T.
AU - Bell, Leslie A.
AU - Moore, Joseph A.
AU - Laub, Wolfram
AU - Viswanathan, Akila N.
AU - Yan, Yulong
AU - McNutt, Todd R.
AU - Meyer, Jeffrey
N1 - Publisher Copyright:
© 2019 The Authors. Journal of Applied Clinical Medical Physics published by Wiley Periodicals, Inc. on behalf of American Association of Physicists in Medicine.
PY - 2019/6
Y1 - 2019/6
N2 - Purpose: The purpose of this work was to compare the dosimetry and delivery times of 3D-conformal (3DCRT)-, volumetric modulated arc therapy (VMAT)-, and tomotherapy-based approaches for spatially fractionated radiation therapy for deep tumor targets. Methods: Two virtual GRID phantoms were created consisting of 7 “target” cylinders (1-cm diameter) aligned longitudinally along the tumor in a honey-comb pattern, mimicking a conventional GRID block, with 2-cm center-to-center spacing (GRID2 cm) and 3-cm center-to-center spacing (GRID3 cm), all contained within a larger cylinder (8 and 10 cm in diameter for the GRID2 cm and GRID3 cm, respectively). In a single patient, a GRID3 cm structure was created within the gross tumor volume (GTV). Tomotherapy, VMAT (6 MV + 6 MV-flattening-filter-free) and multi-leaf collimator segment 3DCRT (6 MV) plans were created using commercially available software. Two tomotherapy plans were created with field widths (TOMO2.5 cm) 2.5 cm and (TOMO5 cm) 5 cm. Prescriptions for all plans were set to deliver a mean dose of 15 Gy to the GRID targets in one fraction. The mean dose to the GRID target and the heterogeneity of the dose distribution (peak-to-valley and peak-to-edge dose ratios) inside the GRID target were obtained. The volume of normal tissue receiving 7.5 Gy was determined. Results: The peak-to-valley ratios for GRID2 cm/GRID3 cm/Patient were 2.1/2.3/2.8, 1.7/1.5/2.8, 1.7/1.9/2.4, and 1.8/2.0/2.8 for the 3DCRT, VMAT, TOMO5 cm, and TOMO2.5 cm plans, respectively. The peak-to-edge ratios for GRID2 cm/GRID3 cm/Patient were 2.8/3.2/5.4, 2.1/1.8/5.4, 2.0/2.2/3.9, 2.1/2.7/5.2 and for the 3DCRT, VMAT, TOMO5 cm, and TOMO2.5 cm plans, respectively. The volume of normal tissue receiving 7.5 Gy was lowest in the TOMO2.5 cm plan (GRID2 cm/GRID3 cm/Patient = 54 cm3/19 cm3/10 cm3). The VMAT plans had the lowest delivery times (GRID2 cm/GRID3 cm/Patient = 17 min/8 min/9 min). Conclusion: Our results present, for the first time, preliminary evidence comparing IMRT-GRID approaches which result in high-dose “islands” within a target, mimicking what is achieved with a conventional GRID block but without high-dose “tail” regions outside of the target. These approaches differ modestly in their ability to achieve high peak-to-edge ratios and also differ in delivery times.
AB - Purpose: The purpose of this work was to compare the dosimetry and delivery times of 3D-conformal (3DCRT)-, volumetric modulated arc therapy (VMAT)-, and tomotherapy-based approaches for spatially fractionated radiation therapy for deep tumor targets. Methods: Two virtual GRID phantoms were created consisting of 7 “target” cylinders (1-cm diameter) aligned longitudinally along the tumor in a honey-comb pattern, mimicking a conventional GRID block, with 2-cm center-to-center spacing (GRID2 cm) and 3-cm center-to-center spacing (GRID3 cm), all contained within a larger cylinder (8 and 10 cm in diameter for the GRID2 cm and GRID3 cm, respectively). In a single patient, a GRID3 cm structure was created within the gross tumor volume (GTV). Tomotherapy, VMAT (6 MV + 6 MV-flattening-filter-free) and multi-leaf collimator segment 3DCRT (6 MV) plans were created using commercially available software. Two tomotherapy plans were created with field widths (TOMO2.5 cm) 2.5 cm and (TOMO5 cm) 5 cm. Prescriptions for all plans were set to deliver a mean dose of 15 Gy to the GRID targets in one fraction. The mean dose to the GRID target and the heterogeneity of the dose distribution (peak-to-valley and peak-to-edge dose ratios) inside the GRID target were obtained. The volume of normal tissue receiving 7.5 Gy was determined. Results: The peak-to-valley ratios for GRID2 cm/GRID3 cm/Patient were 2.1/2.3/2.8, 1.7/1.5/2.8, 1.7/1.9/2.4, and 1.8/2.0/2.8 for the 3DCRT, VMAT, TOMO5 cm, and TOMO2.5 cm plans, respectively. The peak-to-edge ratios for GRID2 cm/GRID3 cm/Patient were 2.8/3.2/5.4, 2.1/1.8/5.4, 2.0/2.2/3.9, 2.1/2.7/5.2 and for the 3DCRT, VMAT, TOMO5 cm, and TOMO2.5 cm plans, respectively. The volume of normal tissue receiving 7.5 Gy was lowest in the TOMO2.5 cm plan (GRID2 cm/GRID3 cm/Patient = 54 cm3/19 cm3/10 cm3). The VMAT plans had the lowest delivery times (GRID2 cm/GRID3 cm/Patient = 17 min/8 min/9 min). Conclusion: Our results present, for the first time, preliminary evidence comparing IMRT-GRID approaches which result in high-dose “islands” within a target, mimicking what is achieved with a conventional GRID block but without high-dose “tail” regions outside of the target. These approaches differ modestly in their ability to achieve high peak-to-edge ratios and also differ in delivery times.
KW - deep-seated tumors
KW - grid therapy
KW - spatially fractionated radiotherapy
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U2 - 10.1002/acm2.12617
DO - 10.1002/acm2.12617
M3 - Article
C2 - 31112629
AN - SCOPUS:85067229467
SN - 1526-9914
VL - 20
SP - 125
EP - 133
JO - Journal of applied clinical medical physics
JF - Journal of applied clinical medical physics
IS - 6
ER -