Journal
INTERNATIONAL JOURNAL OF HYPERTHERMIA
Volume 32, Issue 6, Pages 673-687Publisher
TAYLOR & FRANCIS LTD
DOI: 10.1080/02656736.2016.1179799
Keywords
Mild hyperthermia; MR-HIFU; PRF-shift MR thermometry; phase drift
Funding
- National Institutes of Health [1R01CA199037-01]
- Cancer Prevention and Research Initiative of Texas [R1308]
- UT Southwestern Medical Center
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There is growing interest in performing hyperthermia treatments with clinical magnetic resonance imaging-guided high-intensity focused ultrasound (MR-HIFU) therapy systems designed for tissue ablation. During hyperthermia treatment, however, due to the narrow therapeutic window (41-45 degrees C), careful evaluation of the accuracy of proton resonant frequency (PRF) shift MR thermometry for these types of exposures is required. Purpose: The purpose of this study was to evaluate the accuracy of MR thermometry using a clinical MR-HIFU system equipped with a hyperthermia treatment algorithm. Methods: Mild heating was performed in a tissue-mimicking phantom with implanted temperature sensors using the clinical MR-HIFU system. The influence of image-acquisition settings and post-acquisition correction algorithms on the accuracy of temperature measurements was investigated. The ability to achieve uniform heating for up to 40 min was evaluated in rabbit experiments. Results: Automatic centre-frequency adjustments prior to image-acquisition corrected the image-shifts in the order of 0.1 mm/min. Zero- and first-order phase variations were observed over time, supporting the use of a combined drift correction algorithm. The temperature accuracy achieved using both centre-frequency adjustment and the combined drift correction algorithm was 0.57 degrees +/- 0.58 degrees C in the heated region and 0.54 degrees +/- 0.42 degrees C in the unheated region. Conclusion: Accurate temperature monitoring of hyperthermia exposures using PRF shift MR thermometry is possible through careful implementation of image-acquisition settings and drift correction algorithms. For the evaluated clinical MR-HIFU system, centre-frequency adjustment eliminated image shifts, and a combined drift correction algorithm achieved temperature measurements with an acceptable accuracy for monitoring and controlling hyperthermia exposures.
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