ABSTRACT
The study aimed to evaluate the planning characteristics of spinal stereotactic body
radiotherapy (SBRT) using mono- and dual-isocentric volumetrically modulated arc therapy
(VMAT) techniques. The dosimetric indices were compared between different beam arrangement
techniques for spinal SBRT planning, including spinal cord avoidance, planning target
volume (PTV) dose coverage, conformity, homogeneity, and gradient index. A total of
8 PTVs were contoured on RANDO phantom computed tomography (CT) images, with 4 PTVs
per section of the spine (thoracic and lumbar). VMAT plans for each PTV were generated
using 4 different beam arrangement techniques with a 6-MV FFF photon beam, two of
which were mono-isocentric (MI) and 2 of which were dual-isocentric (DI). Dose calculations
for all plans were performed using the Acuros XB algorithm. The study found that when
non-contiguous spinal lesions are widely spaced, it may be more effective to use 4-Arcs
DI to generate a better homogeneity index and gradient index, whereas 2-Arcs MI was
beneficial for closely spaced lesions. Furthermore, the use of more arcs with a dual
isocenter reduced the volume of partial cord receiving 10 Gy (V10Gy), maximum dose to 0.03 cc of partial cord (D0.03cc), and monitor units (MUs). The results showed that DI has a higher plan quality than
MI for treating non-contiguous spine SBRT, with better homogeneity and a lower dose
to the spinal cord, as well as comparable tumor coverage, delivery accuracy, and adequate
tumour coverage. 4-Arcs DI had the sharpest dose falloff and achieved the lowest overall
spinal cord doses at the expense of twice the treatment time as 2Arcs-MI. These results
could help figure out which VMAT beam arrangements are best for treating non-contiguous
spinal tumors.
Keywords
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Article info
Publication history
Published online: February 24, 2023
Accepted:
January 22,
2023
Received in revised form:
January 16,
2023
Received:
September 9,
2022
Publication stage
In Press Corrected ProofIdentification
Copyright
© 2023 American Association of Medical Dosimetrists. Published by Elsevier Inc. All rights reserved.
