IN VIVO EVALUATION OF CR LABELED RBCS FOR USE IN MRI

造影剂已被证明可以增加临床 磁共振成像（MRI）的应用。 然而，质子 保留在血管内空间中的MRI造影剂是 目前不可用。 这样的试剂可以提供 非侵入性高分辨率方法来定位急性 出血和识别组织梗塞。 铬（Cr） 标记的红细胞已经显示出降低体外的T1 灌注组织，使其成为潜在的血管内造影剂 剂 将使用急性胃肠道出血的动物模型 以评估该试剂在鉴定 血液从血管内溢出。 十 将用Cr标记狗血液体积的百分比， 之后血液将被泵入 胃肠道（GI）以固定的速率。 灵敏度 将评价MRI检测GI出血部位的能力 对于消化道的不同位置和各种 模拟出血率。 T1和T2的变化 输注Cr标记RBC的正常犬组织将 研究以评估识别梗死的可行性 和这个探员 T1和T2测量肺，肝， 将制备收缩前和收缩后脾和肾组织 in vivo. 显示出最大变化的组织 将选择T1进行实验鉴定 造成了梗塞 T1和T2测量值是否正常 对比增强后的犬组织显示 这些参数变化不足以识别梗死， Cr标记的红细胞将被热损伤，以靶向 网状内皮系统的选择性增强。 变化 在正常犬肝脏和脾脏的T1和T2中， 输注热损伤的Cr标记的红细胞，然后将 评估。 如果足够，将研究切除的脾脏 使用热处理的细胞会出现对比度增强 在正常组织中。 最后，Cr处理的RBC的存活将 追究 少量的51Cr将被包括在 用于标记红细胞的非放射性Cr。 定期 标记后对犬的血液进行采样， 以这种方式处理的细胞的存活曲线。 这 调查将提供重要信息， Cr标记的红细胞是否有潜力成为 临床上重要的MRI造影剂。

Contrast agents have been shown to increase the clinical utility of magnetic resonance imaging (MRI). However, a proton MRI contrast agent which remains in the intravascular space is currently not available. Such an agent may provide a noninvasive high resolution method to locate an acute hemorrhage and identify tissue infarction. Chromium (Cr) labeled RBCs have been shown to decrease the T1 of in vitro perfused tissue, making it a potential intravascular contrast agent. An animal model of acute GI hemorrhage will be utilized to evaluate the utility of this agent in identification of extravasation of blood from the intravascular space. Ten percent of the blood volume of a dog will be labeled with Cr, following which the blood will be pumped into the gastrointestinal (GI) tract at a fixed rate. The sensitivity of MRI to detect the site of GI hemorrhage will be evaluated for different locations of the alimentary tract and various rates of simulated hemorrhage. Changes in the T1 and T2 of normal canine tissue with infusion of Cr labeled RBCs will be studied to evaluate the feasibility of identifying infarction with this agent. T1 and T2 measurements of lung, liver, splenic and renal tissue, pre-and post-contract, will be made in vivo. The tissue which demonstrates the greatest change in T1 will be selected for identification of experimentally created infarction. Should T1 and T2 measurements of normal canine tissue following contrast enhancement indicate insufficient change of these parameters to identify infarction, Cr labeled red cells will be heat damaged to target the reticuloendothelial system for selected enhancement. Changes in T1 and T2 of normal canine liver and spleen, following infusion of heat damaged Cr labeled red cells, will then be evaluated. Infarcted spleens will be studied if sufficient contrast enhancement occurs with the use of heat treated cells in normal tissue. Lastly, the survival of Cr treated RBCs will be investigated. A small quantity of 51Cr will be included in the nonradioactive Cr utilized to label red cells. Periodic sampling of the dog's blood following labeling will yield a survival curve for cells treated in this manner. This investigation will provide important information concerning whether Cr labeled RBCs have the potential to become a clinically important MRI contrast agent.