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，19F-MRSpin回波序列不能用于19F-MR的成像。我们选择了梯度回波序列方法中的一种FISP方法进行成像。测量条件为：tr=50ms，TE=7.5ms，翻转角10ﾟ。成像的最低浓度下限约为20 mM，并观察到表面线圈的灵敏度分级。(2)用~(19)F-MR评价肿瘤治疗效果可从肝脏和膀胱获得~(19)F的波谱，但由于仪器浓度的限制，不可能成像。通过移植瘤动物模型进行了实验研究。肿瘤组织中5-氟尿嘧啶(5-FU)的峰值较高，5-FU下降速率较正常组织慢。在肿瘤中未观察到氟核苷酸的峰。在肝肿瘤模型中，5-FU的下降和FBAL的上升均慢于正常肝脏。我们认为，5-FU在肿瘤中的滞留成为疗效的一个指标，因为高浓度的5-FU会抑制肿瘤的生长，而且已经有报道了5-FU的剂量依赖效应。

(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.