Fifty-seventh annual meeting of the American association of physicists in medicine
TU-EF-210-05: A Fast and Efficient Method for Determining Coagulation Temperatures of Tissue-Mimicking Thermal Therapy Gel Phantoms: Validated by Magnetic Resonance Thermometry
To develop a simple and efficient method for determining coagulation temperatures of transparent thermal therapy gel phantoms. Tissue-mimicking thermal therapy phantoms (TMTTPs) that coagulate at specific temperatures are valuable tools for developing and evaluating treatment strategies related to therapy using focused ultrasound, laser, microwave or radiofrequency ablation. The specific formula for a TMTTP will depend on the application and as such finding the coagulation temperature for a specific TMTTP is crucial.
We used a previously published TMTTP formula with 2% (w/v) of bovine serum albumin as the temperature sensitive protein. Using the programmable heating settings of a polymerase chain reaction (PCR) machine we heated 50 µl gel samples to various temperatures for 3 min and imaged them to determine the coagulation temperature by quantifying the resulting opacity. These measured coagulation temperatures were then validated using high-intensity focused ultrasound (HIFU) heating and magnetic resonance thermometry and T2 mapping using a clinical MR-HIFU system.
The PCR heating method produced consistent and reproducible coagulation of the gel samples, and the coagulation temperature was determined by a 7.5% increase in opacity compared to non-coagulated gel samples. The resulting coagulation temperatures for TMTTPs of increasing pH levels were found to be 43.6 ± 0.4 °C, 53.1 ± 0.8 °C and 60.1 ± 1.0 °C for a pH of 4.25, 4.50 and 4.75, respectively. The corresponding coagulation temperatures determined by MR thermometry were within the range of 50 to 55 °C for pH 4.50 and within 58 to 66 °C for pH 4.75.
The PCR heating method provides a fast and reproducible measurement of the coagulation temperature of transparent TMTTPs. The temperatures determined using this method were well within the range of coagulation temperatures determined using the MR-thermometry validation.
Dr. Ari Partanen is a paid employee of Philips Healthcare