A study of ^<19>F-MRI as a new imaging modality for tumor and utility on tumor therapy

(1)由于表面线圈难以调整180度脉冲，19 F-MR自旋回波序列无法用于19 F-MR成像。采用梯度回波序列中的FISP方法进行成像。测量条件如下：TR= 50 ms，TE=7.5ms，翻转角10 °。成像的最低浓度限制为约20 mM，并且还观察到表面线圈的灵敏度分级。此结果与1H-MR图像相似。(2)~（19）F-MRS在肿瘤治疗中的应用~（19）F-MRS可以从肝脏和膀胱中获得~（19）F-MRS谱，但由于~（19）F-MRS浓度受仪器限制，不能成像。本实验采用种植性肿瘤动物模型进行研究。5-氟尿嘧啶（5-FU）在肿瘤中的峰值较高，其下降速度较正常组织慢。肿瘤内未见荧光素峰。在肝癌模型中，5-FU的降低和FBAL的升高比正常肝脏缓慢。由于高浓度的5-FU可抑制肿瘤生长，且有剂量依赖性的疗效，我们认为5-FU在肿瘤中的滞留可作为疗效的一个指标。

(1) Imaging of 19F-MRSpin echo sequence could not be used for imaging of 19F-MR,because of difficulty of adjustment of 180-degree pulse by surface coil. We chose FISP,which is one of method of gradient echo sequence, for imaging. The condition for measurement was as follows ; TR=50ms, TE=7.5ms, Flip angle 10ﾟ. The lowest limitation of concentration for imaging was about 20mM,and gradation of sensitivity by surface coil was also observed. This result was the seme as images of 1H-MR.(2) The evaluation of tumor therapy by 19F-MRSThe spectra of 19F were able to be obtained from the liver and urinarry bladder, but to make image was impossible because the concentration would be under limitation of the instrument. We conducted a study by the animal model of implanted tumor. The peak of 5-fluorouracil (5-FU) was high in the tumor and the decrease rate of 5-FU was slower than that in the normal tissue. The peak of fluoronucleotide was not observed in the tumor. In the liver tumor model, the decrease of 5-FU and increase of FBAL were slower than those in the normal liver. We considered that the retention of 5-FU in the tumor become an index of therapeutic effect, because high concentration of 5-FU causes inhibition of tumor growth and dose-dependent efficathy of 5-FU has been reported.