The Research Of The Clinical Application Of BOLD-fMRI Guiding The Protection Of The Motor Cortex During Postoperative Radiotherapy For Brain Astrocytoma

Objective To investigate the clinical value of blood oxygenation level dependentfunctional magnetic resonance imaging (BOLD-fMRI) in guiding the dose reduction andfunctional protection of the motor cortex during postoperative radiotherapy for brainastrocytoma. And use BOLD-fMRI technology to research the influence on the motor cortexfrom the astrocytomas and its surgical resection.Methods There have been27postoperative cases of brain astrocytoma whose tumorlesions were near the motor cortex.All of the patients were examined by routine MRI andBOLD-fMRI.Then, marking the location and scope of the motor cortex which would bedealed with as the Organs at Risk (OAR) on the position-CT images that were guided by theresults of BOLD-fMRI.In other words,as much as possible to reduce the received dosewithout therapeutic dose loss of the target area.Finally,the radiotherapy plans which wouldreduce the received dose of the motor cortex could be formulated and compared with theroutine plans that could not reduced the received dose.By analying the activation maps of themotor cortex from BOLD-fMRI, to understand the influence of astrocytoma and its surgicalresection.Result①18cases’ target areas were near the normal motor cortex,and15cases’lesions of them showed invasive growth and pushed the motor cortex,even partially damagedit.The postoperative motor cortex which marked by the "battlement-like" time-signal intensitycurve did not completely correspond with the normal anatomical location and the normal hemisphere that had not been affected by the tumor and its removal surgery.9cases’postoperative motor cortex on the affected hemisphere were damaged partially and narrowedsignificantly,and6cases’ postoperative motor cortex of them were in the unconventionalmotor area.②When patients undergo dose reduction for protection,the average received dosein the motor cortex decreased,on the affected hemisphere,which showed minimun0.76%,maximum59.20%,average30.78%,whereas,on the normal hemisphere,which showedminimun23.33%, maximum68.30%,average48.07%.The coefficient of variation were71.41%and36.71%on affected hemisphere and normal hemisphere respectivly.Tworadiotherapy plan,on the affected and normal hemisphere,show statisticallysignificant(P<0.05).On9patients’ affected hemisphere, the motor cortex adjacented to oroverlaped with the target areas,therefore,the average received dose reduction in the motorcortex was lower than the overall,which showed minimun0.76%,maximum18.61%,average12.21%.Conclusion BOLD-fMRI could help us to visually observe the influence ofastrocytoma and its surgical resection on the motor cortex before radiotherapy. And then,could help to reduce the received dose of the motor cortex while ensuring the therapetic doseto the target area when formulating the postoperative radiotherapy plan for brainastrocytoma,thus protecting the motor function and improving patients’ quality of life.