Damianou Christakis, Pavlou M, Velev O, Kyriakou K, Trimikliniotis M
Frederick Institute of Technology, Limassol, Cyprus.
Ultrasound Med Biol. 2004 Mar;30(3):397-404. doi: 10.1016/j.ultrasmedbio.2003.10.018.
The effectiveness of magnetic resonance imaging (MRI) to monitor therapeutic protocols of high-intensity focused ultrasound (HIFU), in freshly excised pig kidney cortex is investigated. For high quality imaging, the pulse sequence fast spin echo (FSE) T1- and T2-weighted, and proton density were evaluated. For fast imaging, the pulse sequence T1-weighted fast spoiled gradient (FSPGR) was used. The main goal was to evaluate the MRI detection of large lesions (bigger than 1 cm x 1 cm x 1 cm) that is achieved by moving the transducer in a predetermined pattern. The contrast between lesion and kidney tissue is excellent with either T1-weighted or T2-weighted FSE. With T1-weighted FSE, the best contrast is observed for recovery time (TR) between 200 ms and 400 ms. With T2-weighted FSE best contrast can be achieved for echo time (TE) between 16 and 32 ms. T2-weighted FSE was proven as the best pulse sequence to detect cavitational activity. This advantage is attributed to the significant difference in signal intensity between air spaces and necrotic tissue. Air spaces appear brighter than thermal lesions. Therefore, for therapeutic protocols created using cavitational mode, T2-weighted FSE may be the optimum pulse sequence to use. The proton density pulse sequence does not provide any advantage over the T1- and T2-weighted pulse sequences. Using T1-weighted FSPGR, acquisition time as low as 5 s could be achieved. Good contrast and signal-to-noise ratio (SNR) are achieved with TR = 100 ms and flip angle between 75 to 90 degrees. The above techniques were very successful in detecting large lesion volumes.
研究了磁共振成像（MRI）监测高强度聚焦超声（HIFU）对新鲜切除猪肾皮质治疗方案的有效性。为获得高质量成像，评估了快速自旋回波（FSE）序列的T1加权、T2加权及质子密度加权成像。为实现快速成像，采用了T1加权快速扰相梯度回波（FSPGR）序列。主要目的是评估通过按预定模式移动换能器实现对大于1 cm×1 cm×1 cm大病灶的MRI检测。T1加权或T2加权FSE序列下，病灶与肾组织之间的对比度极佳。在T1加权FSE序列中，恢复时间（TR）在200 ms至400 ms之间时观察到最佳对比度。在T2加权FSE序列中，回波时间（TE）在16至32 ms之间时可实现最佳对比度。T2加权FSE序列被证明是检测空化活动的最佳脉冲序列。这一优势归因于气腔与坏死组织之间信号强度的显著差异。气腔比热损伤显得更亮。因此，对于采用空化模式的治疗方案，T2加权FSE序列可能是最佳的脉冲序列。质子密度脉冲序列相比T1加权和T2加权脉冲序列没有任何优势。使用T1加权FSPGR序列，采集时间可低至5 s。当TR = 100 ms且翻转角在75至90度之间时，可获得良好的对比度和信噪比（SNR）。上述技术在检测大体积病灶方面非常成功。
