# Magnetic resonance thermometry in the target volume versus intraluminal probe thermometry for hyperthermia treatment monitoring

## TL;DR

This study compares MR thermometry with probe measurements for monitoring hyperthermia treatment, showing promising results for retrospective temperature evaluation.

## Contribution

The study demonstrates the feasibility of MR thermometry for evaluating temperatures in the hyperthermia target volume.

## Key findings

- MR thermometry at probe sites had a median absolute error of ≤0.7°C.
- MR temperatures in the HTV deviated by a median absolute error of 0.5°C from probe temperatures.
- Correlations between MR and probe temperatures ranged from 0.74–0.79 overall and 0.64–0.96 per patient.

## Abstract

•Magnetic resonance thermometry at probe sites showed median absolute errors within 0.7 °C.•Magnetic resonance temperatures in the target volume were comparable to probe measurements.•Correlations between magnetic resonance and probe temperatures ranged from 0.74–0.79 overall and 0.64–0.96 per patient.•Magnetic resonance thermometry was feasible for retrospective target temperature evaluation.•Further improvements are needed for real-time treatment guidance.

Magnetic resonance thermometry at probe sites showed median absolute errors within 0.7 °C.

Magnetic resonance temperatures in the target volume were comparable to probe measurements.

Correlations between magnetic resonance and probe temperatures ranged from 0.74–0.79 overall and 0.64–0.96 per patient.

Magnetic resonance thermometry was feasible for retrospective target temperature evaluation.

Further improvements are needed for real-time treatment guidance.

Hyperthermia, the elevation of target temperature to 39–44 °C, is monitored using temperature probes. However, these provide limited spatial information, sampling only a few discrete locations. Magnetic resonance (MR) thermometry currently offers an option for three-dimensional (3D) temperature monitoring during hyperthermia. This study compares and correlates temperatures measured by intraluminal probes with MR-based temperatures in (1) the anatomical region containing the intraluminal probes and (2) the hyperthermia target volume (HTV), located at a distance from the probes and representing the primary region of clinical interest.

Thirteen locally advanced cervical cancer (LACC) patients treated with radiotherapy and hyperthermia were included. Hyperthermia was monitored using intraluminal probes and MR thermometry. MR-based temperatures were compared to intraluminal probe temperatures. Repeated measures correlation was applied to correlate probe and MR-based temperatures in the HTV across all data and on a patient-specific basis.

MR-based temperatures at probe locations showed good agreement with probe measurements (median absolute error ≤ 0.7 °C). In the HTV, MR-based temperatures deviated by a median absolute error of 0.5 °C from probe temperatures. Repeated measures correlations (rrm) between MR and probe-based HTV temperatures ranged from 0.74 to 0.79 across all data and 0.64–0.96 on a patient-specific basis.

MR thermometry demonstrated promising performance for retrospective evaluation of temperature distributions in the HTV. While its current reliability for real-time treatment guidance remains limited, our results support further development towards broader clinical implementation in hyperthermia.