Farahani K, Saxton R E, Yoon H C, De Salles A A, Black K L, Lufkin R B
Department of Radiological Sciences, UCLA School of Medicine, Los Angeles, CA 90024-1721, USA.
Magn Reson Imaging. 1999 Dec;17(10):1489-94. doi: 10.1016/s0730-725x(99)00094-6.
Focal regions of T1-shortening have been observed in magnetic resonance imaging (MRI)-monitored thermal ablations of perfused tissues. The aims of this study were two-fold: to find evidence for heat-induced conversion of hemoglobin (Hb) to methemoglobin (mHb), and to investigate the effects of heat treatment of in-vitro blood components upon their MR relaxation times. Spectrophotometric studies were performed to confirm the heat-induced formation of methemoglobin. Preparations of whole and fractionated blood, previously submitted to elevated temperatures of 40 degrees C to 80 degrees C, were imaged and the relaxation times were calculated. Optical absorption spectra of samples containing free Hb, heated to 60 degrees C, showed increased light absorption at 630 nm, evident of mHb presence. Short T1 values in whole blood (1.13 s) and packed red blood cell (0.65 s) compartments, heated at 60 degrees C, compared to their baseline values (1.62 s and 0.83 s, respectively), were attributed to mHb formation. In relation to MRI-guided thermal interventions, these results suggest a possible explanation for observation of hyperintense regions on T1-weighted images.
在磁共振成像（MRI）监测的灌注组织热消融过程中，已观察到T1缩短的局灶性区域。本研究的目的有两个：寻找血红蛋白（Hb）热诱导转化为高铁血红蛋白（mHb）的证据，并研究体外血液成分热处理对其磁共振弛豫时间的影响。进行了分光光度研究以证实热诱导高铁血红蛋白的形成。对预先加热到40℃至80℃的全血和分级血液制剂进行成像，并计算弛豫时间。加热到60℃的含有游离Hb的样品的光吸收光谱显示在630nm处光吸收增加，这证明了mHb的存在。与基线值（分别为1.62s和0.83s）相比，在60℃加热的全血（1.13s）和红细胞压积（0.65s）隔室中的短T1值归因于mHb的形成。关于MRI引导的热干预，这些结果为T1加权图像上高强度区域的观察提供了一种可能的解释。
