Abstract:

Abstract:Objective  To study the changes of blood-brain barrier permeability during radiotherapy of brain glioma with volumetric modulated arc therapy(VMAT),and to explore the feasibility to selectively open the blood brain barrier.Methods Eight patients with postoperative glioma (WHO Ⅱ - Ⅳ grade glioma)  received VMAT were selected,all the patients received PTV 60 Gy/30 f dose prescriptions.99mTc-DTPA brain SPECT was performed before and during radiotherapy 30 Gy,50 Gy and 2 weeks after the end of irradiation.A frame of transverse 99mTc-DTPA brain SPECT image that best displayed the gliomas was chosen,and the regions of radiation(P),normal brain tissue around the radiation area(N) and the background outside the soft tissues around the cranium(B)were collected.The radioactive counts of every area were measured and the ratios of the total counts(P/B and N/B
) before and during radiotherapy 30 Gy,50 Gy and 2 weeks after the end of irradiation were calculated.
Results The average ratios of P/B and N/B were 121.2±51.1 and 82.6±42.3 before radiotherapy,and  243.6±115.4 and 88.4±53.2 during radiotherapy 30 Gy,and 256.5±110.6 and 92.6±49.8 during radiotherapy 50 Gy,and 239.3±105.9 and 86.4±45.2 at 2 weeks after the end of radiotherapy,respectively.Compared with before radiotherapy,the P/B in radiotherapy 30 Gy,50 Gy and 2 weeks after the end of irradiation groups had statistically significant differences (P<0.05);compared with before radiotherapy,the N/B in radiotherapy 30 Gy,50 Gy and 2 weeks after the end of irradiation groups had no statistically significant differences (P> 0.05).Conclusion
When VMAT technology is used in the patients with glioma, the  protection of the normal brain tissue is better, and the change of blood-brain barrier permeability is not obvious. However, the permeability of the regions
 of radiation increases significantly, and the blood-brain barrier should be selectively opened, which can reduce normal brain tissue damage for interventions with chemotherapy.

Key words: volumetric modulated arc therapy;blood-brain barrier;glioma;99mTc-DTPA