# Dosimetric comparison of MRI-guided and CT-guided intracavitary and interstitial brachytherapy for locally advanced cervical cancer

## TL;DR

This study compares MRI and CT guidance in brachytherapy for cervical cancer, finding MRI improves dosimetry and protects the rectum better.

## Contribution

The study provides a novel dosimetric comparison between MRI and CT guidance in brachytherapy for cervical cancer.

## Key findings

- MRI guidance results in larger HR-CTV and IR-CTV volumes compared to CT guidance.
- MRI guidance provides better rectum protection with statistically significant differences in D2cc.
- Bladder and small intestine D2cc values show no significant difference between MRI and CT guidance.

## Abstract

To compare the differences in dosimetry and toxicities between Magnetic Resonance Imaging (MRI) and Computed Tomography (CT)-guided intracavitary and interstitial implantation for locally advanced cervical cancer, respectively.

We analyzed 40 cases of locally advanced cervical cancer admitted to our hospital from January 2023 to September 2024. Patients underwent CT-guided intracavitary and interstitial implantation followed by MRI scanning. We compared the volume of HR-CTV and IR-CTV, the dosimetric differences of HR-CTV D90 and IR-CTV D90, and the dosimetric differences of D2cc for the bladder, rectum, and small intestine under the two localization methods.

The mean HR-CTV and IR-CTV volumes were larger using CT guidance compared with MRI guidance (P<0.05), the differences were statistically significant. The HR-CTV D90 and IR-CTV D90 were smaller using CT than MRI guidance. The difference was statistically significant (P<0.05). There was a statistically significant difference in the rectum D2cc between CT and MRI guidance (P<0.05), while there was no statistically significant difference for the D2cc of the bladder and small intestine between the two methods (P>0.05).

Intracavitary and interstitial implantation under MRI guidance can significantly improve HR-CTV and IR-CTV D90 with reduced target volume and good protection of the rectum, and there is no significant difference for the bladder and small intestine.