Studies on clinical significance of metabolic or functional tumor imaging by clinical MR machine

为了完成影像诊断，除了定位肿瘤本身外，还需要特定的特征，如肿瘤分级和治疗干预后的生存能力。PET似乎适合这种情况，并具有代谢成像的能力，但它并没有得到广泛的应用。目前，我们已尝试用临床MR机替代正电子发射计算机断层扫描(PET)作为脑肿瘤放射治疗的代谢或功能成像，并对其临床意义进行了评价。目前的研究包括两部分：(1)体内~1H磁共振波谱(MRS)代谢成像，(2)动态增强磁共振功能成像(Disk MRI)，(1)体内~1H磁共振波谱代谢成像。为确定~1H MRS对预测脑肿瘤放疗疗效的价值，对8例原发或转移性脑肿瘤患者在放疗前和放疗中进行了~1H MRS检查。在各种光谱代谢物峰中，以无氧糖酵解为代表的乳酸峰在放射敏感病例中早在20Gy时就显著降低，而在抗辐射病例中乳酸峰即使在治疗结束时也没有减少。结论：磁共振乳酸峰的评估有助于早期预测脑肿瘤的放射治疗效果。(2)动态磁化率增强磁共振功能成像。本文对11例脑肿瘤患者在放疗前后进行了盘状MRI检查，以确定该方法在监测脑肿瘤放射治疗效果方面的临床价值。计算的积分图像，代表局部脑血容量(RCBV)，也被用来评估肿瘤血管床。放射治疗时肿瘤血管床、血管生成的变化与1H-MRS一样，似乎也是一个很好的疗效指标。

In addition to orient a tumor itself, specific characterization such as tumor grading and its viability on therapeutic intervention should be necessary to complete imaging diagnosis. PET is appeared to suit for this and with its ability of metabolic imaging, but it is not widely available. At present, we have attempted to use clinical MR machine as an alternative for PET as metabolic or functional imaging of brain tumor on radiation therapy and its clinical significance has been evaluated. Present studies consist of two parts : (1) metabolic imaging by in vivo ^1H MR spectroscopy (MRS), and (2) functional imaging by dynamic suceptiblity contrast MR imaging (DISC MRI).(1) Metabolic imaging by in vivo ^1H MR spectroscopy. To determine whether assessment of ^1H MRS is useful for predicting the outcome of radiotherapy on brain tumor, ^1H MRS studies were performed in eight patients with primary or metastatic brain tumor before and during radiotherapy. Among various spectroscopic metabolite peaks, lactate peak, that is represented by anaerobic glycolysis, substantially decreased in the radio sensitive cases as early as 20Gy, whereas the lactate peak did not decrease even at the end of therapy in radioresistant cases. It is concluded that assessment of the lactate peak on MRS adjunctivecly contribute to the early prediction of radiotherapeutic effect on brain tumors.(2) Functional imaging by dynamic susceptibility contrast MR imaging (DISC MRI). DISC MRI was performed on eleven patients with brain tumors before and after radiotherapy to determine whether this method is clinically useful for monitoring radiotherapeutic effect on brain tumors. The calculated integrating images, that represent regional cerebral blood volume (rCBV), were also produced for evaluation of the tumor vascular beds. Changes of the tumor vascular bed, angiogenesis, on radiotherapy were also appeared to be a good indicator of therapeutic effect as well as ^1H-MRS.