Room: AAPM ePoster Library
Purpose: establish the validity of Magnetic Resonance (MR) thermometry studies in vivo without the need of patient studies, a pilot study was done. This consisted of the agreement between MR reproducibility in volunteers and in patients before and during the hyperthermia treatment.
Methods: specific clinical MR protocol was developed and implemented in which always two proton resonant frequency shift (PRFS) scans were performed directly after each other, i.e. for the baseline scan and for the scans during treatment, that combined are the input to calculate the PRFS. The subtraction of the two repeated PRFS scans led to temperature error maps. Three anonymized patient data were included and the baseline procedure was performed twice in a similar fashion for 3 volunteers. Patients and volunteers were placed inside the MR compatible radiofrequency hyperthermia device that was placed into a 1.5T MR scanner. The clinically-standard dual-echo gradient-echo sequence was applied. Covariance thresholding was applied to mask the areas with a low signal-to-noise. The temperature error maps were evaluated for baseline and during treatment.
Results: analysis of all temperature maps indicates that the temperature error is by far the lowest in the dorsal region. This region presents stable position due to the lack of movement and due to its distance from moving organs. The temperature accuracy in both groups was 0.2°C. The minimum temperature precision found for baseline and treatment conditions was 2.7°C and 3.4°C, respectively.
Conclusion: this pilot study, we found an accuracy value below 1°C of the MR thermometry reproducibility in patients when using non-heating volunteer studies, which indicates that volunteer studies might be predictive for reproducibility in patients. The validity of using volunteers to estimate the limitations of MR thermometry and improve its accuracy was established. A verification study involving more patients and volunteers is ongoing.
Funding Support, Disclosures, and Conflict of Interest: This research has been made possible by the Dutch Cancer Society and the Netherlands Organisation for Scientific Research (NWO) as part of their joint Partnership Program: "Technology for Oncology".