Multiple Magnetic Resonance Imaging Techniques In Differentiating Glioma Recurrence From Cerebral Radiation Necrosis

Objective Malignant glioma is the most common malignant tumor in adult brain.Due to some unfavorable factors,such as aggressive growth,the tumor can not be completely removed.Due to the presence of chemotherapeutic resistance in cancer patients.Although a standard regimen of oral Temozolomide Combined with radiotherapy can significantly improve the survival of patients with malignant glioma,the prognosis is still poor.Most of the patients who received standardized treatment still had high risk of recurrence.The purpose of radiotherapy is to treat residual tumors and inhibit tumor recurrence,but radiation therapy may also cause radiation damage to brain tissue.Radiation-induced brain damage and recurrence of gliomas are hardly distinguishable on conventional morphological imaging techniques,such as CT or MRI images.We choose different treatments for the two lesions,and the prognosis of the two is different.So the key to the treatment is the early diagnosis.We used the method of extracranial irradiation to establish a rat model of radiation necrosis in brain tissue,and then established a rat intracranial C6 glioma model by means of tumor inoculation.In these two clock models,different imaging parameters are obtained through various magnetic resonance imaging techniques.Statistical analysis of each group of data,in the identification of two different lesions,to obtain a diagnostic true positive rate and true negative rate of 100% of the diagnostic mix.Materials and Methods The 10 ul glioma cell suspension with a concentration of 1* 108/ml of C6 was injected into the right caudate nucleus of the rat by a microinjection pump and a stereotactic injection.The tumor growth was observed by magnetic resonance imaging(MRI).The Varian linear accelerator irradiated rats left 1x 1cm2 brain tissue,a total dose of 40 Gy.The development of radionecrosis of brain tissue was observed by magnetic resonance imaging(MRI).The radionecrosis model of rat brain tissue and the image of intracranial C6 glioma model in rats were collected through the 7T small animal magnetic resonance imaging equipment of Bruker company in Germany.The magnetic resonance(MRI)CE-T1 WI,T2WI,MRS,DWI and PWI images of two kinds of lesions were collected.The image data of two kinds of lesion models corresponding to MRS,DWI and PWI are obtained through the analysis software of the matching images.The methods of statistical analysis were used to obtain the different parameters in the imaging of two kinds of lesions.According to these parameters,the optimal magnetic resonance imaging method was selected to identify two different lesions.The diagnostic combination of the sensitivity and specificity of recurrent and radionecrosis of glioma was obtained by statistical analysis.Results 10 Wistar rats were inoculated with C6 glioma,and the head magnetic resonance imaging(MRI)was used to observe the intracranial progress of the tumor.The best time of image acquisition was between second weeks after inoculation-3weeks.A total of 10 Wistar rats were irradiated with radiation.After irradiation for 48 weeks,abnormal hyperintensity of T2 appeared on the left side of the 8 rats,of which2 of the high signal were flake,and the boundary was not clear with the surrounding normal brain tissue.Using 7T small animal magnetic resonance device,we selected 8brain necrosis models and C6 glioma models in each group,including CE-T1 WI,T2WI,MRS,DWI and PWI.The corresponding data of the DWI,MRS and PWI images of two kinds of lesion sites obtained by using the matching image analysis software.CE-T1 WI showed the lesion enhancement signal;brain tumor group and radiation necrosis group NAA/Cr values 0.43 + 0.13,0.54 + 0.15(P=0.128);Cho/NAA = 4.07 + 1.29,1.99 + 0.67(P=0.001);Cho/Cr = 2.63 + 0.59,1.48 + 0.58(P=0.002)r ADC respectively;1.82 + 0.74,3.16 + 0.64(P=0.002);r CBV = 3.29 +0.27,1.34 + 0.19(P=0.00);r CBF = 2.25 + 0.18,1.28 + 0.06(P=0.00).The diagnostic formula to identify the two kinds of lesions.First consider the Cho/NAA and Cho/Cr,when Cho/NAA = 4.07 and Cho/Cr = 2.63;lesions of glioma recurrence;when Cho/NAA<4.07 and Cho/Cr<2.63,lesions of radioactive brain tissue necrosis;when Cho/NAA and Cho/Cr do not meet the above conditions,according to the r ADC further judgment,when r ADC = 1.82 when the lesion for glioma recurrence,when r ADC = 3.16,lesions of radioactive brain tissue necrosis.When r ADC = 1.82 ~ 3.16,which do not distinguish between two kinds of diseases,according to the r CBV value and r CBF value and determine the nature of the lesions.We set the threshold value for diagnosis was 4.09,when r CBV+r CBF = 4.09,we believe that the lesions of tumor tissue;when r CBV+r CBF < 4.09,we believe that the lesions of radiation necrosis.The diagnostic accuracy of this method in the identification of glioma and brain tissue radionecrosis in this animal experiment is 100%Conclusions The advantages of the modeling method include the stability of the model,the simple operation and the high success rate.In this practice,C6 glioma cell suspension(1 * 108/ml)was injected into the right cerebral caudate nucleus region by stereotactic injection,and the rat brain glioma model was successfully established.The intracranial glioma model of rats was collected by magnetic resonance imaging(MRI).The best time for image acquisition was second weeks to third weeks after the tumor was inoculated with the tumor.The above method was used to irradiate the left brain of the rat with the total dose of 40 Gy.Finally,the radio necrosis model of rat brain tissue was successfully established.After 24 weeks of irradiation in rats,the magnetic resonance T2 WI changed at the irradiation site.After 36 weeks of irradiation,we found the abnormal high signal in T2.In our study,we have obtained the best imaging diagnostic formula for identifying two kinds of lesions.