Retrospective assessment of a single fiducial marker tracking regimen with robotic stereotactic body radiation therapy for liver tumours

Masao Nakayama; Kazuyuki Uehara; Hideki Nishimura; Shuhei Tamura; Yoshiki Munetomo; Shinji Tsudou; Hiroshi Mayahara; Naritoshi Mukumoto; Moshi Geso; Ryohei Sasaki

doi:10.1016/j.rpor.2019.06.001

Retrospective assessment of a single fiducial marker tracking regimen with robotic stereotactic body radiation therapy for liver tumours

Rep Pract Oncol Radiother. 2019 Jul-Aug;24(4):383-391. doi: 10.1016/j.rpor.2019.06.001. Epub 2019 Jun 21.

Authors

Affiliations

¹ Division of Radiation Oncology, Kobe University Graduate School of Medicine, 7-5-2 Kusunokicho, Chuou-ku, Kobe City, Hyogo 650-0017, Japan.
² Discipline of Medical Radiations, School of Biomedical & Health Sciences, RMIT University, Bundoora Campus, Victoria 3083, Australia.
³ Division of Radiation Oncology, Kobe Minimally Invasive Cancer Center, 8-5-1 Minatojima-nakamachi, Chuou-ku, Kobe City, Hyogo 650-0046, Japan.
⁴ Department of Radiation Oncology, Hyogo Cancer Center, 13-70 Kitaojicho, Akashi City, Hyogo 637-8558, Japan.

Abstract

Aim: To investigate tumour motion tracking uncertainties in the CyberKnife Synchrony system with single fiducial marker in liver tumours.

Background: In the fiducial-based CyberKnife real-time tumour motion tracking system, multiple fiducial markers are generally used to enable translation and rotation corrections during tracking. However, sometimes a single fiducial marker is employed when rotation corrections are not estimated during treatment.

Materials and methods: Data were analysed for 32 patients with liver tumours where one fiducial marker was implanted. Four-dimensional computed tomography (CT) scans were performed to determine the internal target volume (ITV). Before the first treatment fraction, the CT scans were repeated and the marker migration was determined. Log files generated by the Synchrony system were obtained after each treatment and the correlation model errors were calculated. Intra-fractional spine rotations were examined on the spine alignment images before and after each treatment.

Results: The mean (standard deviation) ITV margin was 4.1 (2.3) mm, which correlated weakly with the distance between the fiducial marker and the tumour. The mean migration distance of the marker was 1.5 (0.7) mm. The overall mean correlation model error was 1.03 (0.37) mm in the radial direction. The overall mean spine rotations were 0.27° (0.31), 0.25° (0.22), and 0.23° (0.26) for roll, pitch, and yaw, respectively. The treatment time was moderately associated with the correlation model errors and weakly related to spine rotation in the roll and yaw planes.

Conclusions: More caution and an additional safety margins are required when tracking a single fiducial marker.

Keywords: AP, anterior–posterior; CTV, clinical target volume; CyberKnife; Fiducial marker tracking; GTV, gross tumour volume; ITV, internal target volume; LED, light-emitting diode; LR, left–right; Liver tumour; PTV, planning target volume; SBRT, stereotactic body radiation therapy; SD, standard deviation; SI, superior–inferior; Synchrony system; XST, Xsight Spine Tracking.