Bazrafshan Babak, Hübner Frank, Farshid Parviz, Hammerstingl Renate, Paul Jijo, Vogel Vitali, Mäntele Werner, Vogl Thomas J
Institute for Diagnostic and Interventional Radiology, J.W. Goethe-University Hospital, Theodor-Stern-Kai 7, 60590, Frankfurt am Main, Germany,
Lasers Med Sci. 2014 Jan;29(1):173-83. doi: 10.1007/s10103-013-1306-5. Epub 2013 Mar 28.
The purpose of this study was to evaluate magnetic resonance (MR) temperature imaging of the laser-induced thermotherapy (LITT) comparing the proton resonance frequency (PRF) and T 1 thermometry methods. LITT was applied to a liver-mimicking acrylamide gel phantom. Temperature rise up to 70 °C was measured using a MR-compatible fiber-optic thermometer. MR imaging was performed by a 1.5-T scanner utilizing fast gradient echo sequences including a segmented echo planar imaging (seg-EPI) sequence for PRF and the following sequences for T 1 method: fast low-angle shot (FLASH), inversion recovery turbo flash (IRTF), saturation recovery turbo flash (SRTF), and true fast imaging (TRUFI). Temperature-induced change of the pixel values in circular regions of interest, selected on images under the temperature probe tip, was recorded. For each sequence, a calibration constant could be determined to be -0.0088 ± 0.0002 ppm °C(-1) (EPI), -1.15 ± 0.03 °C(-1) (FLASH), -1.49 ± 0.03 °C(-1) (IRTF), -1.21 ± 0.03 °C(-1) (SRTF), and -2.52 ± 0.12 °C(-1) (TRUFI). These constants were evaluated in further LITT experiments in phantom comparing the calculated temperatures with the fiber optic-measured ones; temperature precisions of 0.60 °C (EPI), 0.81 °C (FLASH), 1.85 °C (IRTF), 1.95 °C (SRTF), and 3.36 °C (TRUFI) were obtained. Furthermore, performing the Bland-Altman analysis, temperature accuracy was determined to be 0.23 °C (EPI), 0.31 °C (FLASH), 1.66 °C (IRTF), 1.19 °C (SRTF), and 3.20 °C (TRUFI). In conclusion, the seg-EPI sequence was found to be more convenient for MR temperature imaging of LITT due to its relatively high precision and accuracy. Among the T 1 method sequences, FLASH showed the highest accuracy and robustness.
本研究的目的是评估激光诱导热疗（LITT）的磁共振（MR）温度成像，比较质子共振频率（PRF）和T1测温方法。将LITT应用于模拟肝脏的丙烯酰胺凝胶体模。使用与MR兼容的光纤温度计测量高达70°C的温度升高。通过1.5-T扫描仪进行MR成像，利用快速梯度回波序列，包括用于PRF的分段回波平面成像（seg-EPI）序列以及用于T1方法的以下序列：快速小角度激发（FLASH）、反转恢复快速小角度激发（IRTF）、饱和恢复快速小角度激发（SRTF）和真快速成像（TRUFI）。记录在温度探头尖端下方图像上选择的圆形感兴趣区域中像素值的温度诱导变化。对于每个序列，可以确定校准常数为-0.0088±0.0002 ppm °C-1（EPI）、-1.15±0.03 °C-1（FLASH）、-1.49±0.03 °C-1（IRTF）、-1.21±0.03 °C-1（SRTF）和-2.52±0.12 °C-1（TRUFI）。在体模的进一步LITT实验中，将计算温度与光纤测量温度进行比较，评估了这些常数；获得的温度精度分别为0.60°C（EPI）、0.81°C（FLASH）、1.85°C（IRTF）、1.95°C（SRTF）和3.36°C（TRUFI）。此外，进行布兰德-奥特曼分析，确定温度准确性分别为0.23°C（EPI）、0.31°C（FLASH）、1.66°C（IRTF）、1.19°C（SRTF）和3.20°C（TRUFI）。总之，由于其相对较高的精度和准确性，发现seg-EPI序列对于LITT的MR温度成像更方便。在T1方法序列中，FLASH显示出最高的准确性和稳健性。
