Image Sciences Institute, University Medical Center Utrecht, Utrecht, the Netherlands.
Imaging Division, University Medical Center Utrecht, Utrecht, the Netherlands.
Magn Reson Med. 2021 Nov;86(5):2647-2655. doi: 10.1002/mrm.28877. Epub 2021 Jun 1.
To demonstrate that interleaved MR thermometry can monitor temperature in water and fat with adequate temporal resolution. This is relevant for high intensity focused uUltrasounds (HIFU) treatment of bone lesions, which are often found near aqueous tissues, as muscle, or embedded in adipose tissues, as subcutaneous fat and bone marrow.
Proton resonance frequency shift (PRFS)-based thermometry scans and T -based 2D variable flip angle (2D-VFA) thermometry scans were acquired alternatingly over time. Temperature in water was monitored using PRFS thermometry, and in fat by 2D-VFA thermometry with slice profile effect correction. The feasibility of interleaved water/fat temperature monitoring was studied ex vivo in porcine bone during MR-HIFU sonication. Precision and stability of measurements in vivo were evaluated in a healthy volunteer under non-heating conditions.
The method allowed observing temperature change over time in muscle and fat, including bone marrow, during MR-HIFU sonication, with a temporal resolution of 6.1 s. In vivo, the apparent temperature change was stable on the time scale of the experiment: In 7 min the systematic drift was <0.042°C/min in muscle (PRFS after drift correction) and <0.096°C/min in bone marrow (2D-VFA). The SD of the temperature change averaged over time was 0.98°C (PRFS) and 2.7°C (2D-VFA).
Interleaved MR thermometry allows temperature measurements in water and fat with a temporal resolution high enough for monitoring HIFU ablation. Specifically, combined fat and water thermometry provides uninterrupted information on temperature changes in tissue close to the bone cortex.
证明交错式磁共振测温技术能够以足够的时间分辨率监测水和脂肪中的温度。这对于高强度聚焦超声（HIFU）治疗骨病变是相关的，因为骨病变通常位于靠近水组织的位置，如肌肉，或嵌入脂肪组织中，如皮下脂肪和骨髓。
交替地随时间获取基于质子共振频率偏移（PRFS）的测温扫描和基于 T 的二维可变翻转角（2D-VFA）测温扫描。使用 PRFS 测温技术监测水中的温度，使用具有切片轮廓效应校正的 2D-VFA 测温技术监测脂肪中的温度。在猪骨的离体研究中，研究了交错式水/脂肪温度监测的可行性。在非加热条件下，对健康志愿者进行了体内测量精度和稳定性的评估。
该方法允许在磁共振 HIFU 超声过程中观察肌肉和脂肪（包括骨髓）中的温度随时间的变化，时间分辨率为 6.1s。在体内，在实验时间尺度上，表观温度变化是稳定的：在 7 分钟内，肌肉中的系统漂移<0.042°C/min（PRFS 经漂移校正后）和骨髓中的漂移<0.096°C/min（2D-VFA）。平均随时间变化的温度变化的 SD 为 0.98°C（PRFS）和 2.7°C（2D-VFA）。
交错式磁共振测温技术允许以足够高的时间分辨率进行水和脂肪中的温度测量，足以监测 HIFU 消融。具体而言，脂肪和水的组合测温提供了关于靠近骨皮质的组织温度变化的不间断信息。
