The Study Of Changes Of Blood-brain Barrier Permeability In The Procession Of Whole Brain Radiotherapy By SPECT

Objective: This paper is to evaluate the changes of blood-brain barrier(BBB) permeability in procession of the whole brain radiotherapy with brain SPECT and seek the optimal time of chemotherapy. At the same time it is to observe the potential value of SPECT in the diagnosis of brain tumours. Methods: 25 cases with brain tumours received whole brain radiotherapy by 60Co- r rays or 6Mv-x rays, total dose was 40Gy delivered in 4 weeks. All the patients received SCT scanning and SPECT examination before radiotherapy. The SPECT examination was re-examined at the dose of 20Gy and 40Gy in procession of radiotherapy respectively. All the data were saved into soft discs and calculated by PEGASYS software. We select an optimal planar imaging and set ROI in same size at the brain tumours(T), normal tissue(N) and basic regions(B,1-2 pixels from the soft tissues around skulls) and recorded their radioactive counts. We evaluated the degrees of BBB permeability by calculation the T/B and N/B of the cases before radiotherapy and within procession of radiotherapy at thedose of 20Gy and 40 Gy respectively. In addition, the numbers of tumors detected by SPECT with that of SCT were compared each other. If the results obtained from SCT and SPECT are different, the patients have to receive an MRI examination. The MRI is gold standard in our study. All the data were calculated with SPSS 10.0. The statistic methods of Tamhane and X2test were used. Results: 1. All the patients had improvements of BBB permeability in normal brain tissues after radiotherapy (p<0.05), while the difference between 20Gy and 40Gy were not significant statistically (P>0.05). 2. The results of T/B were increased in the postoperative glioma cases that were given whole brain radiotherapy. But there were no significant statistic difference (p>0.05) among the pre-radiation, intra-radiation and post-radiation groups. 3. The BBB permeability of the brain metastasis tumours was significantly improved (p<0.05) after radiotherapy compared with that of pre-radiotherapy, but there was no difference between groups of 20Gy and 40Gy(p>0.05). This result indicates that the BBB permeability will not increase further by giving more doses after 20Gy. 4.The sensitivity of SPECT diagnosis for brain tumors is 97.44%, while that of SCT is 92.31%, There was no significant difference between SCT and SPECT(P>0.05). Conclusions: 1. The BBB permeability of normal brain tissues will be increased following tumour invasion or radiation therapy. 2. Whole brain radiation will enhance the permeability of BBB. To those brain tumours cases withoutsurgical resection, the chemotherapy should be operated at the dose of 20Gy. Because the BBB have the highest permeability at the moment, the boost dose of radiation will not be following permeable improvements. 3. There was no significant changes of BBB permeability in the postoperative brain glioma cases between Pre-radiotherapy and post-radiotherapy, we suggest that the chemotherapy should be given as early as possible after operation. 4. The SPECT can detect the changes of BBB permeability sensitively in the process of radiation therapy and do well in the brain tumour detections. It is an important adjunctive method in the diagnosis of the brain tumours.