TITLE:
Dosimetric Study of the Effect of Calypso-Compatible Couch Top for Spine Stereotactic Body Radiation Therapy
AUTHORS:
Ahmad Amoush, Long Huang
KEYWORDS:
SBRT, Couch, TPS
JOURNAL NAME:
International Journal of Medical Physics, Clinical Engineering and Radiation Oncology,
Vol.12 No.1,
February
22,
2023
ABSTRACT: Purpose: To study the effect of the Qfix kVue Calypso-compatible couch top on the
dosimetry of Spine Stereotactic Body Radiation Therapy (SBRT). Methods and
Materials: The computed tomography (CT) data set for Qfix kVue
Calypso-compatible couch top with rails were imported into the treatment
planning system (TPS). Nine patients who underwent spine SBRT were selected for
this study. The inclusion criteria included patients who were treated on a
stereotactic linear accelerator with 5 fractions or less from 2016 to 2017
without the couch model. Seven patients were treated with static
intensity-modulated radiation therapy (IMRT) fields and two patients were
treated using volumetric modulated arc therapy (VMAT) technique. The dose was
recalculated for 1) couch top and rails setup (CR) 2) couch-top no rails setup
(CNR), and then compared to 3) no couch no-rails setup (NCNR). Dose to 100% of the target volume (D100%), Dose to cover 99% of
the target volume (D99%), Dose to cover 95% of the target volume (D95%),
Dose to cover 90% of the target volume
(D90%), volume receiving 100% of the prescription dose (V100%),
conformity index (CI), dose gradient index (DGI), and spinal cord threshold and
maximum dose were compared to the plan with NCNR. Results: The average
D100% was 77.89% ± 11.78%, 74.51% ± 12.24%, and 75.83 ± 12.67% for NCNR, CR,
CNR (р = 0.84), respectively. The average D99% was 91.64% ± 9.57%, 89.93% ± 9.48%,
and 91.15% ± 9.55% for NCNR, CR, CNR (р = 0.98), respectively. The average D95%
was 99.14% ± 9.96%, 95.23% ± 9.76, and 96.78% ± 9.84% for NCNR, CR, CNR (р = 0.047),
respectively. The average D90% was 101.3% ± 0.65%, 97.11% ± 2.48%, and 98.75%
± 2.12% for NCNR, CR, CNR (р = 0.0004), respectively. The maximum dose to the
spinal cord was 1750.79 ± 41.84, 1672.90 ± 40.90, and 1709.91 ± 41.35 (cGy) for
NCNR, CR, CNR (р = 0.97), respectively. In all cases, the spinal cord threshold
dose was far below the tolerances and the differences were insignificant.
Average CI was 1.18 ± 0.16, 0.53 ± 0.39, and 0.86 ± 0.24 for NCNR, CR, CNR (р = 0.0002), respectively. Conclusions: The
study investigated the dosimetric impact of Qfix kVue Calypso-compatible
couch top on the quality of the spinal SBRT
treatment using static IMRT or VMAT techniques. IMRT plans showed more
sensitivity to the couch being in the plan than the VMAT plans.