Temperature mapping with MR imaging of molecular diffusion: application to hyperthermia

Area of Science:

• Biomedical Engineering
• Medical Imaging
• Oncology

Background:

• Accurate temperature monitoring is essential for effective and safe hyperthermia (HT) cancer therapy.
• Current noninvasive thermometry methods, such as magnetic resonance (MR) imaging based on T1 relaxation time, lack the required temperature accuracy (1°C/cm).

Purpose of the Study:

• To propose and evaluate a novel noninvasive thermometry method using molecular diffusion MR imaging for hyperthermia applications.
• To assess the accuracy and potential clinical utility of diffusion-based temperature mapping in HT.

Main Methods:

• Utilized the temperature dependence of molecular diffusion, which is more sensitive than T1 relaxation.
• Acquired diffusion and derived temperature images with a 2x2 mm pixel size using a clinical 0.5-T MR imaging system and a modified HT device.
• Validated temperature measurements against thermocouple readings in a polyacrylamide gel phantom.

Main Results:

• Achieved high accuracy in temperature determination, with deviations within 0.5°C of thermocouple measurements in regions of interest (0.8 cm²).
• Demonstrated the feasibility of obtaining precise temperature images using molecular diffusion MR imaging.
• The method showed potential for monitoring blood perfusion in addition to temperature.

Conclusions:

• Molecular diffusion MR imaging offers a highly accurate and sensitive noninvasive method for temperature monitoring in hyperthermia.
• This technique surpasses the accuracy limitations of T1-based MR thermometry for HT applications.
• The proposed method holds promise for enhancing the safety and efficacy of clinical hyperthermia and potentially monitoring perfusion.