Using MRI to measure position and anatomy changes and assess their impact on the accuracy of hyperthermia treatment planning for cervical cancer

Abstract

Purpose

We studied the differences between planning and treatment position, their impact on the accuracy of hyperthermia treatment planning (HTP) predictions, and the relevance of including true treatment anatomy and position in HTP based on magnetic resonance (MR) images.

Materials and methods

All volunteers were scanned with an MR-compatible hyperthermia device, including a filled waterbolus, to replicate the treatment setup. In the planning setup, the volunteers were scanned without the device to reproduce the imaging in the current HTP. First, we used rigid registration to investigate the patient position displacements between the planning and treatment setup. Second, we performed HTP for the planning anatomy at both positions and the treatment mimicking anatomy to study the effects of positioning and anatomy on the quality of the simulated hyperthermia treatment. Treatment quality was evaluated using SAR-based parameters.

Results

We found an average displacement of 2 cm between planning and treatment positions. These displacements caused average absolute differences of ∼12% for TC25 and 10.4%–15.9% in THQ. Furthermore, we found that including the accurate treatment position and anatomy in treatment planning led to an improvement of 2% in TC25 and 4.6%–10.6% in THQ.

Conclusions

This study showed that precise patient position and anatomy are relevant since these affect the accuracy of HTP predictions. The major part of improved accuracy is related to implementing the correct position of the patient in the applicator. Hence, our study shows a clear incentive to accurately match the patient position in HTP with the actual treatment.

Keywords:

• MR imaging
• hyperthermia treatment planning
• hyperthermia treatment
• accuracy
• changes in anatomy and position
• SAR distribution

Acknowledgments

The authors thank Theresa Feddersen, Ioannis Androulakis and Gennaro Bellizzi for their assistance during the volunteer experiments. Furthermore, the authors thank Pelle ter Haar for his help in the process of tissue delineation, Piotr A. Wielopolski for his support in the development of the MR protocol, and Erik van Werkhoven for his advice in the statistical analysis.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This research has been made possible by the Dutch Cancer Society and the Netherlands Organization for Scientific Research (NWO) as a part of their joint Partnership Programme: ‘Technology for Oncology’ grant number: 15195 and the Dutch Cancer Society grant KWF-DDHK 2013-6072. Additionally, our research was supported by COST Action MyWave CA17115 ‘European network for advancing Electromagnetic hyperthermic medical technologies’.