TY - JOUR
T1 - MRI-based treatment planning and dose delivery verification for intraocular melanoma brachytherapy
AU - Zoberi, Jacqueline Esthappan
AU - Garcia-Ramirez, Jose
AU - Hedrick, Samantha
AU - Rodriguez, Vivian
AU - Bertelsman, Carol G.
AU - Mackey, Stacie
AU - Hu, Yanle
AU - Gach, H. Michael
AU - Rao, P. Kumar
AU - Grigsby, Perry W.
N1 - Publisher Copyright:
© 2017 American Brachytherapy Society
PY - 2018/1
Y1 - 2018/1
N2 - Purpose Episcleral plaque brachytherapy (EPB) planning is conventionally based on approximations of the implant geometry with no volumetric imaging following plaque implantation. We have developed an MRI-based technique for EPB treatment planning and dose delivery verification based on the actual patient-specific geometry. Methods and Materials MR images of 6 patients, prescribed 85 Gy over 96 hours from Collaborative Ocular Melanoma Study–based EPB, were acquired before and after implantation. Preimplant and postimplant scans were used to generate “preplans” and “postplans” respectively. In the preplans, a digital plaque model was positioned relative to the tumor, sclera, and nerve. In the postplans, the same plaque model was positioned based on the imaged plaque. Plaque position, point doses, percentage of tumor volume receiving 85 Gy (V100), and dose to 100% of tumor volume (Dmin) were compared between preplans and postplans. All isodose plans were computed using TG-43 formalism with no heterogeneity corrections. Results Shifts and tilts of the plaque ranged from 1.4 to 8.6 mm and 1.0 to 3.8 mm, respectively. V100 was ≥97% for 4 patients. Dmin for preplans and postplans ranged from 83 to 118 Gy and 45 to 110 Gy, respectively. Point doses for tumor apex and base were all found to decrease from the preimplant to the postimplant plan, with mean differences of 16.7 ± 8.6% and 30.5 ± 11.3%, respectively. Conclusions By implementing MRI for EPB, we eliminate reliance on approximations of the eye and tumor shape and the assumption of idealized plaque placement. With MRI, one can perform preimplant as well as postimplant imaging, facilitating EPB treatment planning based on the actual patient-specific geometry and dose-delivery verification based on the imaged plaque position.
AB - Purpose Episcleral plaque brachytherapy (EPB) planning is conventionally based on approximations of the implant geometry with no volumetric imaging following plaque implantation. We have developed an MRI-based technique for EPB treatment planning and dose delivery verification based on the actual patient-specific geometry. Methods and Materials MR images of 6 patients, prescribed 85 Gy over 96 hours from Collaborative Ocular Melanoma Study–based EPB, were acquired before and after implantation. Preimplant and postimplant scans were used to generate “preplans” and “postplans” respectively. In the preplans, a digital plaque model was positioned relative to the tumor, sclera, and nerve. In the postplans, the same plaque model was positioned based on the imaged plaque. Plaque position, point doses, percentage of tumor volume receiving 85 Gy (V100), and dose to 100% of tumor volume (Dmin) were compared between preplans and postplans. All isodose plans were computed using TG-43 formalism with no heterogeneity corrections. Results Shifts and tilts of the plaque ranged from 1.4 to 8.6 mm and 1.0 to 3.8 mm, respectively. V100 was ≥97% for 4 patients. Dmin for preplans and postplans ranged from 83 to 118 Gy and 45 to 110 Gy, respectively. Point doses for tumor apex and base were all found to decrease from the preimplant to the postimplant plan, with mean differences of 16.7 ± 8.6% and 30.5 ± 11.3%, respectively. Conclusions By implementing MRI for EPB, we eliminate reliance on approximations of the eye and tumor shape and the assumption of idealized plaque placement. With MRI, one can perform preimplant as well as postimplant imaging, facilitating EPB treatment planning based on the actual patient-specific geometry and dose-delivery verification based on the imaged plaque position.
KW - Brachytherapy
KW - Dosimetry
KW - Magnetic resonance imaging
KW - Melanoma
KW - Ocular
UR - http://www.scopus.com/inward/record.url?scp=85041683467&partnerID=8YFLogxK
U2 - 10.1016/j.brachy.2017.07.011
DO - 10.1016/j.brachy.2017.07.011
M3 - Article
C2 - 28818442
AN - SCOPUS:85041683467
SN - 1538-4721
VL - 17
SP - 31
EP - 39
JO - Brachytherapy
JF - Brachytherapy
IS - 1
ER -