Magnetic resonance diffusion imaging detects structural damage in biological tissues upon hyperthermia.

Area of Science:

• Biophysics
• Medical Imaging
• Biomaterials

Background:

• Hyperthermia therapy uses heat to treat diseases, but understanding heat-induced tissue damage is crucial.
• Quantitative magnetic resonance (MR) imaging offers a non-invasive method to probe tissue properties.

Purpose of the Study:

• To investigate the extent and mechanism of hyperthermic damage in biological tissues using quantitative MR imaging.
• To assess the potential of MR diffusion imaging in evaluating heat-induced changes in tissues.

Main Methods:

• Utilized multiple delay-multiple echo and pulsed-gradient spin echo MR imaging sequences on rabbit tissues and duck embryos.
• Acquired MR images before and after heat treatment (45°C for 30 min) using a 1.5-Tesla scanner.
• Generated maps of proton spin density, relaxation times, and water self-diffusion parameters based on relaxation and diffusion models.

Main Results:

• Heat treatment significantly increased tissue water self-diffusion coefficients, diffusion barrier size, and fractal parameters, approaching free water values.
• Minimal changes were observed in spin density and relaxation times of tissue water post-heating.
• Quantitative MR imaging effectively detected alterations in tissue water diffusion.

Conclusions:

• Significant changes in water self-diffusion behavior are attributed to macromolecular denaturation (proteins, fibers) at elevated temperatures.
• MR diffusion imaging is a powerful tool for investigating heat damage mechanisms in biological tissues.
• This technique holds potential for clinical assessment of hyperthermia efficacy in cancer therapy.