The Application Study Of MR Amide Proton Transfer Imaging On Identification Of Intracranial Tumor

BackgroundPrimary intracranial lymphoma, brain metastases, glioma is common malignant tumor in intracranial. Because of the pathology of them are different, the treatment is also different. Therefore, it is very important for treatment and prognosis to make correct preoperative diagnosis.MRI is widely used in hospitals for medical diagnosis with its no radiation, good image of soft tissues. Conventional MRI for differential diagnosis of those tumor mainly rely on the location, size, number, configuration, signal strength and the form of contrast. Accurate differential diagnosis could be made according to the characteristics and the clinical history. But it does not always work. Some specialized application such as the diffusion-weighted imaging, diffusion-tensor imaging, perfusion-weighted imaging, MR spectroscopy used in clinic, but the sensitivity and specificity of the differential are different in different researches. Amide proton transfer (APT) imaging is a new molecular imaging method base on chemical exchange-dependent saturation transfer (CEST), which can detect the amide protons of endogenous proteins and peptides. The APT imaging was used in analyze stoke, differential diagnosis different grades of glioma and differentiation of recurrent glioblastoma multiforme from radiation necrosis. But the differentiation between different intracranial malignant tumor or different metastases use this technology have not been deeply investigation. The APT imaging was used in this study to analyze the image feature of different intracranial malignant tumor and metastases base on different pathology. To evaluate the value of this new medical image technique, in the differentiation of intracranial tumor.Purpose1. To evaluate the differential diagnosis value of APT in high grade glioma with metastasis and lymphoma2. To evaluate the differential diagnosis value of APT in cerebral metastases from lung cancer of different pathological subtype.Materials and Methods1. Patients114 untreated intracranial tumor patients underwent MRI scan, including conventional, enhanced and APT sequences. Pathologic types of all cases were confirmed by surgical excision or stereotactic biopsy except for patients with metastases. All the patients were divided into 3 groups, primary intracranial lymphoma (22 cases), metastases (39 cases), and high-grade glioma (49cases).2. MRI examining methodsAll patients were examined using body coil for radiofrequency (RF) transmission and 16-channel sensitivity-encoding coil for reception on a Philips Aiehiva 3.0T MR scanner. The routine scaning sequences performed included T1-weighted (repetition time=400msec; echo time=20msec), T2-weighted (repetition time=2800msec; echo time= 105msec), FLAIR (repetition time=8000msec; echo time = 125msec); the field of view was 230×230 mm2, the matrix was 256 x256, and the slice thickness was 5 mm. In order to avoid interference effect the APT scanning was performed on the maximal slice of the tumor after T1-weighted, T2-weighted, FLAIR. Second-order shimming was used before APT scanning, the off-resonance RF pulse was used to presaturation. Then 0.2ml/kg weight of Gd-DTPA (Magnevist; Bayer Schering, Guangzhou, China) was injected through the median cubital vein, and Gd-enhanced T1-weighted images were acquired.3. APT rate measurementUse Sun UltraSparc Station software (Sun Microsystems, Mountain View, CA) to analyze the raw data of APT, measure the APT rate and build pcolor using programs written in interactive data language IDL (Research Systems, Inc., Boulder, CO, USA). The quantitative image analysis was performed by two radiologists who had 15 years of experience in brain tumor imaging, respectively. The APT rates of three ROIs(regions of interest) including the tumor core, edema near tumor margin on T1-contrast so called peritumoral area,the contralateral normal-appearing white matter, CNAWM were measured, each area repeat 5 times and average the results.4. Statistical AnalysisThe average APT rates and corresponding 95% confidence intervals were calculated using SPSS 13.0. Paired-Sample T Test was used to determine whether the differences in APT rates for the tumor core and CNAWM, the peritumoral area and CNAWM were significant, The analysis of variance (ANOVA) post-hoc tests were used to determine whether the differences in APT rates for tumor core, area near tumor margin on T1-constrast of three types of tumor were significant., Independent-Samples T Test was used to compare the different of APT rates in the tumor core between metastases of SCLC and of NSCLC, The level of significance was set at P<0.05.5. ResultsIn primary intracranial lymphoma group, the pathological types of 22 cases were diffuse large B cell lymphoma; 39 cases Metastases group include:28 cases of brain metastases from lung tumor,4 cases of brain metastases from breast tumor,2cases of brain metastasis from liver tumor,2 cases from kidney tumor,2 cases from colorectal cancer, gastric tumor and 1 case of brain metastasis; There are 49 cases in high grade glioma group, including 8 cases of anaplastic astrocytoma,10 cases of anaplastic oligodendrocytes tumor, anaplastic astrocytoma in 1 case, less anaplastic ependymoma in 1 case.23 cases of glioblastoma, including 4 cases of gliosarcoma,2 cases of postoperative recurrence of glioblastoma. On the color images, the signal of the core of lymphoma showed higher than metastase and high grade glioma. The signal of the core of metastases showed equally to the high grade gliomas in intratumoral but showed great differents in peritumoral. the means of APTR of lymphoma,metastases and high-grade gliomas were (3.43±0.67)%、(2.52±0.43)%、and (2.72±0.59)%in intratumoral part, the difference was statistically significant(P=0.000) in intratumoral part, the difference of the APTR of lymphoma with metastases and high-grade gliomas was statistically significant(P=0.000); the difference of the APTR of metastases and high-grade gliomas was not statistically significant(P=0.092); the APTR between the two were (1.47%±0.23%) and (1.81%±0.31%) in peritumoral region, the difference was statistically significant(P=0.038).The signal of tumor core of metastases of SCLC showed nearly equal to NSCLC, but the APTR of SCLC(2.37±0.39)% is higher than NSCLC(2.11±0.23)%,the difference was statistically significant. (P=0.037)Conclusion1. APT value of lymphoma, metastasis and high grade glioma were significantly higher than peritumoral region and contralateral normal-appearing white matter (CNAWM), and tumor core of lymphoma higher than high grade glioma, peritumoral region of high grade glioma higher than metastases. APT is an effective and complementary method for conventional MRI, it has a positive contribution to distinguish lymphoma, metastasis and high grade glioma. APT combined with convential MRI, is helpful to distinguish lymphoma, metastasis and high grade glioma.2. APT ratio of tumor core of small cell lung cancer with cerebral metastasis were significantly higher than non-small cell lung cancer with cerebral metastasis, which demonstrate APT signal is related to the pathological pattern of the primary tumor. It’s suitable for patient who were difficult for biopsy or surgery. It can also be used to guide treatment by speculating original pathological pattern backwardly.