Fiducial marker position affects target volume in stereotactic lung irradiation

Hiroaki Akasaka; Kazufusa Mizonobe; Yuya Oki; Kazuyuki Uehara; Masao Nakayama; Shuhei Tamura; Yoshiki Munetomo; Haruna Kawaguchi; Jun Ishida; Aya Harada; Takeaki Ishihara; Hikaru Kubota; Hiroki Kawaguchi; Ryohei Sasaki; Hiroshi Mayahara

doi:10.1002/acm2.13596

Fiducial marker position affects target volume in stereotactic lung irradiation

J Appl Clin Med Phys. 2022 Jun;23(6):e13596. doi: 10.1002/acm2.13596. Epub 2022 Apr 4.

Authors

Hiroaki Akasaka^{1

2}, Kazufusa Mizonobe¹, Yuya Oki¹, Kazuyuki Uehara¹, Masao Nakayama^{2

3}, Shuhei Tamura⁴, Yoshiki Munetomo⁴, Haruna Kawaguchi⁵, Jun Ishida⁵, Aya Harada¹, Takeaki Ishihara⁶, Hikaru Kubota⁶, Hiroki Kawaguchi⁶, Ryohei Sasaki⁶, Hiroshi Mayahara¹

Affiliations

¹ Division of Radiation Oncology, Kobe Minimally Invasive Cancer Center, Chuo-ku Kobe, Hyogo, Japan.
² Division of Radiation Oncology, Kobe University Graduate School of Medicine, Chuo-ku Kobe, Hyogo, Japan.
³ Division of Radiation Therapy, Kita-Harima Medical Center, Hyogo, Japan.
⁴ Division of Radiological Technology, Kobe Minimally Invasive Cancer Center, Chuo-ku Kobe, Hyogo, Japan.
⁵ Department of Radiology, Kobe Minimally Invasive Cancer Center, Chuo-ku Kobe, Hyogo, Japan.
⁶ Division of Radiation Oncology, Kobe University Hospital, Chuo-ku Kobe, Hyogo, Japan.

Abstract

Purpose: Real-time tracking systems of moving respiratory targets such as CyberKnife, Radixact, or Vero4DRT are an advanced robotic radiotherapy device used to deliver stereotactic body radiotherapy (SBRT). The internal target volume (ITV) of lung tumors is assessed through a fiducial marker fusion using four-dimensional computed tomography (CT). It is important to minimize the ITV to protect normal lung tissue from exposure to radiation and the associated side effects post SBRT. However, the ITV may alter if there is a change in the position of the fiducial marker with respect to the tumor. This study investigated the relationship between fiducial marker position and the ITV in order to prevent radiation exposure of normal lung tissue, and correct target coverage.

Materials and methods: This study retrospectively reviewed 230 lung cancer patients who received a fiducial marker for SBRT between April 2015 and September 2021. The distance of the fiducial marker to the gross tumor volume (GTV) in the expiratory (d_ex ) and inspiratory (d_in ) CT, and the ratio of the ITV/V(GTV_ex ), were investigated.

Results: Upon comparing each lobe, although there was no significant difference in the d_diff and the ITV/V(GTV_ex ) between all lobes for d_ex < 10 mm, there was significant difference in the d_diff and the ITV/V(GTV_ex ) between the lower and upper lobes for d_ex ≥ 10 mm (p < 0.05). Moreover, there was significant difference in the d_diff and the ITV/V(GTV_ex ) between d_ex ≥10 mm and d_ex < 10 mm in all lung regions (p < 0.05).

Conclusion: The ITV that had no margin from GTVs increased when d_ex was ≥10 mm for all lung regions (p < 0.05). Furthermore, the increase in ITV tended to be greater in the lower lung lobe. These findings can help decrease the possibility of adverse events post SBRT, and correct target coverage.

Keywords: CyberKnife; fiducial marker; internal target volume; lung cancer; radiotherapy; stereotactic body radiotherapy.

MeSH terms

Fiducial Markers
Four-Dimensional Computed Tomography / methods
Humans
Lung / diagnostic imaging
Lung / pathology
Lung Neoplasms* / diagnostic imaging
Lung Neoplasms* / radiotherapy
Lung Neoplasms* / surgery
Radiosurgery* / methods
Radiotherapy Planning, Computer-Assisted / methods
Retrospective Studies