Impact of magnetic resonance imaging-related geometric distortion of dose distribution in fractionated stereotactic radiotherapy in patients with brain metastases

Shingo Ohira; Yuta Suzuki; Hayate Washio; Yuki Yamamoto; Soichiro Tateishi; Shoki Inui; Naoyuki Kanayama; Minoru Kawamata; Masayoshi Miyazaki; Teiji Nishio; Masahiko Koizumi; Katsuyuki Nakanishi; Koji Konishi

doi:10.1007/s00066-023-02120-7

Impact of magnetic resonance imaging-related geometric distortion of dose distribution in fractionated stereotactic radiotherapy in patients with brain metastases

Strahlenther Onkol. 2024 Jan;200(1):39-48. doi: 10.1007/s00066-023-02120-7. Epub 2023 Aug 17.

Authors

Affiliations

¹ Department of Radiation Oncology, Osaka International Cancer Institute, Osaka, Japan. shingo.oohira@oici.jp.
² Department of Medical Physics and Engineering, Osaka University Graduate School of Medicine, Suita, Japan. shingo.oohira@oici.jp.
³ Department of Diagnostic and Interventional Radiology, Osaka International Cancer Institute, Osaka, Japan.
⁴ Department of Medical Physics and Engineering, Osaka University Graduate School of Medicine, Suita, Japan.
⁵ Department of Radiation Oncology, Osaka International Cancer Institute, Osaka, Japan.

PMID: 37591978
DOI: 10.1007/s00066-023-02120-7

Abstract

Purpose: The geometric distortion related to magnetic resonance (MR) imaging in a diagnostic radiology (MR_DR) and radiotherapy (MR_RT) setup is evaluated, and the dosimetric impact of MR distortion on fractionated stereotactic radiotherapy (FSRT) in patients with brain metastases is simulated.

Materials and methods: An anthropomorphic skull phantom was scanned using a 1.5‑T MR scanner, and the magnitude of MR distortion was calculated with (MR_DR-DC and MR_RT-DC) and without (MR_DR-nDC and MR_RT-nDC) distortion-correction algorithms. Automated noncoplanar volumetric modulated arc therapy (HyperArc, HA; Varian Medical Systems, Palo Alto, CA, USA) plans were generated for 53 patients with 186 brain metastases. The MR distortion at each gross tumor volume (GTV) was calculated using the distance between the center of the GTV and the MR image isocenter (MIC) and the quadratic regression curve derived from the phantom study (MR_RT-DC and MR_RT-nDC). Subsequently, the radiation isocenter of the HA plans was shifted according to the MR distortion at each GTV (HA_DC and HA_nDC).

Results: The median MR distortions were approximately 0.1 mm when the distance from the MIC was < 30 mm, whereas the median distortion varied widely when the distance was > 60 mm (0.23, 0.47, 0.37, and 0.57 mm in MR_DR-DC, MR_DR-nDC, MR_RT-DC, and MR_RT-nDC, respectively). The dose to the 98% of the GTV volume (D_98%) decreased as the distance from the MIC increased. In the HA_DC plans, the relative dose difference of D_98% was less than 5% when the GTV was located within 70 mm from the MIC, whereas the underdose of GTV exceeded 5% when it was 48 mm (-26.5% at maximum) away from the MIC in the HA_nDC plans.

Conclusion: Use of a distortion-correction algorithm in the studied MR diagnoses is essential, and the dosimetric impact of MR distortion is not negligible, particularly for tumors located far away from the MIC.

Keywords: Brain metastasis; Dose distribution; MR distortion; Stereotactic irradiation.

MeSH terms

Algorithms
Brain Neoplasms* / diagnostic imaging
Brain Neoplasms* / radiotherapy
Brain Neoplasms* / secondary
Humans
Magnetic Resonance Imaging / methods
Radiosurgery* / methods
Radiotherapy Dosage
Radiotherapy Planning, Computer-Assisted / methods

Grants and funding

21K07742/JSPS KAKENHI