Dosimetric analysis on computed tomography myelography based treatment planning in stereotactic body radiotherapy for spinal metastases

Hidetoshi Shimizu; Yutaro Koide; Koji Sasaki; Yui Watanabe; Shoichi Haimoto; Takahiro Aoyama; Hiroyuki Tachibana; Tohru Iwata; Tomoki Kitagawa; Takeshi Kodaira

doi:10.1016/j.meddos.2023.03.008

Dosimetric analysis on computed tomography myelography based treatment planning in stereotactic body radiotherapy for spinal metastases

Med Dosim. 2023;48(3):187-192. doi: 10.1016/j.meddos.2023.03.008. Epub 2023 Apr 15.

Authors

Affiliations

¹ Department of Radiation Oncology, Aichi Cancer Center Hospital, Nagoya, Aichi, 464-8681, Japan. Electronic address: hishimizu@aichi-cc.jp.
² Department of Radiation Oncology, Aichi Cancer Center Hospital, Nagoya, Aichi, 464-8681, Japan.
³ Graduate School of Radiological Technology, Gunma Prefectural College of Health Sciences, Maebashi, Gunma, 371-0052, Japan.
⁴ Radiation Therapy Center, Yachiyo Hospital, Anjyo, Aichi, 446-8510, Japan.
⁵ Department of Neurosurgery, Aichi Cancer Center Hospital, Nagoya, Aichi, 464-8681, Japan.
⁶ Department of Radiation Oncology, Aichi Cancer Center Hospital, Nagoya, Aichi, 464-8681, Japan; Graduate School of Medicine, Aichi Medical University, Nagakute, Aichi, 480-1195, Japan.

PMID: 37068981
DOI: 10.1016/j.meddos.2023.03.008

Abstract

This study aimed to quantitatively evaluate the influence of enhanced contrast on the CT myelography image of the spinal cord and/or cauda equina in addition to the target volume in spine SBRT treatment planning. In total, 19 patients who had previously undergone spine SBRT were randomly selected. The rigid image registration accuracy of CT myelography that aligned with the treatment planning CT was evaluated by calculating the normalized mutual information (NMI) and Pearson's correlation coefficient for the vertebral landmarks. At postregistration, the contrast-enhanced region of the CT myelography image was replaced with water-mass density, and the original treatment plan was recalculated on this image. For comparison, the dose was also recalculated on the contrast-enhanced CT myelography images. The NMI and Pearson's correlation coefficients for landmarks were 0.39 ± 0.12 and 0.97 ± 0.04, respectively. The mean D_0.035cc of the spinal cord and/or cauda equina on the CT myelography image with the contrast-enhanced region replaced by water-mass density showed -0.37% ± 0.64% changes compared with that of the treatment planning CT. Conversely, the mean D_0.035cc in contrast-enhanced CT myelography changed by -1.39% ± 0.51%. The percentage change in D_98% for the planning target volume was confirmed to be small by replacing the contrast-enhanced region with water-mass density (p < 0.01). The dose calculation of the target volume, spinal cord, and/or cauda equina using the CT myelography image that replaced the contrast-enhanced region with water-mass density could be a more appropriate procedure with less dose calculation uncertainty.

Keywords: CT myelography; Enhanced contrast; Radiotherapy; Spinal cord; Spine SBRT.

Publication types

Letter