Cheng K H, Hernandez M
Biophysics Laboratory, Department of Physics, Texas Tech University, Lubbock 79409.
Cancer Res. 1992 Nov 1;52(21):6066-73.
The use of quantitative nuclear magnetic resonance (MR) imaging to investigate the extent and mechanism of hyperthermic damage in biological tissues has been studied. By using the multiple delay-multiple echo and pulsed-gradient spin echo MR imaging sequences, multiple frame MR images of freshly harvested rabbit tissues (brain, kidney, and muscle) and intact duck embryos in shells were obtained before and after heat treatment (45 degrees C for 30 min) using a clinical 1.5-Tesla whole-body superconducting MR scanner. Based on the relaxation and diffusion models, maps of the proton spin density, relaxation times, and various self-diffusion parameters of tissue water were generated from these multiple frame MR images. Our results indicated that the values of the diffusion barrier size and fractal parameter of the tissues and the self-diffusion coefficient of tissue water increased significantly, i.e., approached that of free water, after the heat treatment. In comparison, only slight changes in the spin density and relaxation times of the tissue water were found after the identical heat treatment. We concluded that the significant changes in the self-diffusive behavior of the tissue water are due to the denaturation of macromolecules (e.g., protein and fiber) within the tissues at elevated temperatures. We further suggested that MR diffusion imaging represents a powerful tool to investigate the extent and mechanism of heat damage of biological tissues in vivo and therefore bears important potential in the clinical assessment of the therapeutic efficacy of hyperthermia in cancer therapy.
已对使用定量核磁共振（MR）成像研究生物组织中热损伤的程度和机制进行了研究。通过使用多重延迟 - 多重回波和脉冲梯度自旋回波MR成像序列，在使用临床1.5特斯拉全身超导MR扫描仪对新鲜收获的兔组织（脑、肾和肌肉）以及完整带壳鸭胚胎进行热处理（45℃，30分钟）之前和之后，获得了多帧MR图像。基于弛豫和扩散模型，从这些多帧MR图像生成了组织水的质子自旋密度、弛豫时间和各种自扩散参数的图谱。我们的结果表明，热处理后，组织的扩散屏障尺寸和分形参数值以及组织水的自扩散系数显著增加，即接近自由水的值。相比之下，相同热处理后，仅发现组织水的自旋密度和弛豫时间有轻微变化。我们得出结论，组织水自扩散行为的显著变化是由于高温下组织内大分子（如蛋白质和纤维）的变性所致。我们进一步认为，MR扩散成像代表了一种强大的工具，可用于研究体内生物组织热损伤的程度和机制，因此在评估热疗在癌症治疗中的疗效的临床评估中具有重要潜力。
