MRI of frozen tissue demonstrates a phase shift

Area of Science:

• Medical Physics
• Biomedical Engineering
• Oncology

Background:

• Accurate temperature monitoring is crucial for effective prostate cancer cryosurgery.
• Current methods for temperature mapping during cryoablation are limited.
• A novel approach is needed to guide and optimize cryoablation treatments.

Purpose of the Study:

• To investigate a novel phase shift phenomenon for temperature mapping in cryosurgery.
• To evaluate the potential of this phase shift as a temperature sensing method during cryoablation.
• To compare the observed phase shift with conventional proton resonant frequency shift methods.

Main Methods:

• In vivo canine experiments were conducted to observe temperature-induced phase shifts.
• Ex vivo tissue samples were used to validate the findings.
• Phase shift measurements were performed at varying temperatures and echo times (e.g., 0.1 ms at 0.5 T).

Main Results:

• A significant temperature-dependent phase shift was observed within frozen tissue.
• The magnitude of the phase shift (~0.7 °/°C) was substantially larger than conventional proton resonant frequency shift (~0.008 °/°C).
• The phase shift demonstrated minimal dependence on echo times, indicating it is not a frequency change artifact.

Conclusions:

• The observed phase shift offers a promising novel method for temperature mapping in cryoablation.
• This technique may enable precise real-time temperature monitoring during prostate cancer cryosurgery.
• Further research can optimize this method for clinical application in cryoablation therapies.