Impact on liver position under breath-hold by computed tomography contrast agents in stereotactic body radiotherapy of liver cancer

Hideharu Miura; Shuichi Ozawa; Minoru Nakao; Yoshiko Doi; Katsumaro Kubo; Masahiro Kenjo; Yasushi Nagata

doi:10.5603/RPOR.a2021.0131

Impact on liver position under breath-hold by computed tomography contrast agents in stereotactic body radiotherapy of liver cancer

Rep Pract Oncol Radiother. 2021 Dec 30;26(6):1035-1044. doi: 10.5603/RPOR.a2021.0131. eCollection 2021.

Authors

Hideharu Miura^{1

2}, Shuichi Ozawa^{1

2}, Minoru Nakao^{1

2}, Yoshiko Doi^{1

2}, Katsumaro Kubo¹, Masahiro Kenjo^{1

2}, Yasushi Nagata^{1

2}

Affiliations

¹ Hiroshima High-Precision Radiotherapy Cancer Center, Hiroshima, Japan.
² Department of Radiation Oncology, Institute of Biomedical and Health Sciences, Hiroshima University, Hiroshima, Japan.

Abstract

Background: We investigated variations in liver position relative to the vertebral bone for liver cancer treated with stereotactic body radiation therapy under expiratory phase breath-hold (BH) for treatment with contrast-enhanced-computed tomography (CECT), non-CECT, and cone-beam computed tomography (CBCT).

Materials and methods: Seventeen consecutive patients using a contrast enhancement (CE) agent for the CT simulation session for this retrospective study were selected. The first computed tomography (CT) scan without the use of CE agent in the expiratory phase was used for treatment planning (pCT). The remaining three CT scans without a CE agent under expiratory phase BH were acquired successively without repositioning to evaluate the intra-fraction variation in liver position. Furthermore, a three-phase CT scan (arterial, portal, and late phases) accompanied by a CE agent under expiratory phase BH was acquired for target delineation. CBCT scans without the use of a CE agent under expiratory phase BH were acquired for treatment. Inter-fractional variations (non-CECT or CECT) in liver position were measured using the difference between CBCT and pCT or each 3 phase CECT images, respectively.

Results: The average ± standard deviations for intrafractional, non-CECT interfractional variations, and CECT interfractional variations were 1.0 ± 1.3, 2.5 ± 2.6, and 6.4 ± 6.4 mm, respectively, in the craniocaudal (CC) direction. Intra- and inter-fractional variations in liver position were relatively small for non-CECT. However, significant inter-fractional liver position variations in CECT were observed in the expiratory phase BH. The position of the liver should be carefully considered when applying CECT images for image-guided radiotherapy.

Keywords: contrast enhancement agent; image-guided radiotherapy; inter-fraction liver position; intra-fraction liver position; liver cancer radiotherapy; stereotactic body radiotherapy.