Journal of Isfahan Medical School

Journal of Isfahan Medical School

Analyzing the radiobiological effects of co-registered MRI and CT images in improving the accuracy of helical tomotherapy treatment of rectal cancer

Document Type : Original Article(s)

Authors
Baranoosh Rahmani
Iraj Abedi
Mohsen Saeb
Department of Medical Physics, School of Medicine, Isfahan University of Medical Sciences, Isfahan, Iran
10.48305/jims.v44.i862.0731
Abstract
Background: Owing to the limitations of computed tomography (CT) imaging, magnetic resonance imaging (MRI) is used as a complementary tool for radiotherapy treatment planning. This study aimed to investigate the effect of combining magnetic resonance imaging (MRI) and computed tomography (CT) on target volume determination, dose distribution, and radiobiological evaluation of treatment plans in helical Tomotherapy (HT) for rectal cancer.
Methods: MRI and CT images were collected from 10 patients with rectal cancer. The images were fused using a Deformable Image Registration algorithm, and tumor volumes, including GTV, CTV, and PTV, were delineated. Subsequently, the mean dose, tumor control probability (TCP), and normal tissue complication probability (NTCP) were calculated and compared between the two approaches.
Results: The mean GTV, CTV, and PTV volumes in the CT-based target delineation method were significantly larger than those in the MRI/CT-based method (p=0.034, p=0.034, and p=0.024, respectively). However, the significant reduction in the PTV did not result in a statistically significant increase in the TCP (p=0.085). With decreasing target volumes, the mean doses received by the bladder, small bowel, and femoral heads were significantly reduced (p=0.006, p=0.027, p=0.002, and p=0.045, respectively).
Conclusion: The integration of MRI with CT in helical Tomotherapy for rectal cancer enables more accurate target volume delineation and improves radiobiological parameters, including reduced dose to organs at risk, without compromising treatment efficacy. This approach can significantly enhance the safety and quality of the radiotherapy plans.

Highlights

Baranoosh Rahmani: Google Scholar

Iraj Abedi: Google Scholar ,PubMed

Mohsen Saeb: Google Scholar

Keywords
Magnetic Resonance Imaging
X-Ray Computed Tomography
Rectal Neoplasms
Tomotherapy
Radiotherapy
Subjects
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Journal of Isfahan Medical School
Volume 44, Issue 862
2nd Week, July
July and August 2026
Pages 731-738

  • Receive Date 17 August 2025
  • Accept Date 19 July 2026