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节180度脉冲，因此无法使用自旋回波序列成像19F-MR。我们选择了梯度回波序列法之一的FISP进行成像。测量条件如下：TR=50ms， TE=7.5ms，翻转角度10hz。成像的最低浓度限制约为20mM，并观察到表面线圈的灵敏度分级。结果与1H-MR图像一致。(2)评价19F- mrs对肿瘤的治疗作用：可以从肝脏和膀胱中获得19F的光谱，但由于其浓度受仪器限制，无法成像。我们采用植入式肿瘤动物模型进行了研究。5-氟尿嘧啶（5-FU）在肿瘤组织中的峰值较高，但其下降速度较正常组织慢。肿瘤中未见荧光核苷酸峰。在肝脏肿瘤模型中，5-FU的降低和FBAL的升高较正常肝脏慢。我们认为5-FU在肿瘤中的保留成为治疗效果的一个指标，因为高浓度的5-FU可以抑制肿瘤生长，并且有报道称5-FU的剂量依赖性效果。

(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.