Evaluation of correlations among apparent diffusion coefficient and permeability parameters from dynamic contrast-enhanced MR in brain tumour parenchyma and peritumoral area

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Brain tumors are a diverse group of neoplasms and the second leading cause of cancerrelated deaths in male ages 20-39 (years of age) [1].Each brain tumor has their own unique tumor microenvironment and it is different from tumor parenchyma (TP) to peritumoral (PT) area, and is characterized by varying degrees of hypercellularity, cytoplasmic and nuclear pleomorphism, mitoses, and endothelial proliferation.A number of MR imaging techniques have been developed to probe the tumor microenvironment.The frequently applied techniques are diffusion weighted imaging (DWI) and dynamic contrast-enhanced MRI (DCE-MR), they reflect the tumor microenvironment from different angles and both have been used as independent imaging biomarkers for brain tumor diagnosis.
Investigating correlations among the parameters of DWI and DCE-MR would provide a different perspective of not only the parameters themselves but also in defining the tumor microenvironment and thus could assist in tumor diagnosis and tumor treatment monitoring.Few study have been done here [2][3][4].Therefore, we attempted to evaluate the correlations of permeability parameters and ADC based on various brain tumor types and in different tumor regions (TP and PT).

Methods and materials
In accordance with ethical guidelines for human research, and in compliance with the Health Insurance Portability and Accountability Act (HIPAA).This study was approved by our institution.written informed consent was obtained from each adult patient or their legal guardian.
Our study prospectively included 45 patients (M 23 ,F: 22 ; mean age: 46 y) who were examined by conventional, diffusion weighted imaging (DWI) and dynamic contrastenhanced T1w MR perfusion (DCE-MR).For each tumor, ROI was placed after consensus of two experienced radiologists, 6-10 and 4-5 regions of interest (ROIs) were manually placed on (are defined as ) TP and PT (within a 1cm distance from the outer enhancing tumor margin) area, respectively.Fig. 1  ), extra-vascular extra-cellular volume fraction (Ve), reflux constant (Kep) and iAUC (initial Area Under Curve in 60 seconds)) were calculated by a commercial software tool (TISSUE 4D; Siemens Healthcare, Erlangen, Germany).Further, their correlations were assessed.
Statistical analysis was carried out using the software ( SPSS 16.0 chicago illinois USA).Correlations among permeability parameters and ADC was calculated by Spearman correlation analysis.P<0.05 was considered statistically significant.© Department of Radiology, Sun Yat-Sen University, The First Affiliated Hospital -Guangzhou/CN Among the permeability parameters, of TP and PT, irrespective of the brain tumor types or confined to one certain type of brain tumor, the Ktrans, Ve and iAUC were mutually positively correlated with each other (p#0.03)Fig. 2 on page 6 .Moreover, irrespective of brain tumor types, mean ADC, in TP and PT, were significantly inversely correlated with mean Ktrans, Ve, iAUC (p<0.000) and positively correlated with mean kep (p<0.000)Fig. 2 on page 6 .Further, specific to gliomas, similar correlations were found in TP and PT area (except mean Kep, in PT area, is without correlation with mean ADC); to metastases, only mean Ve in TP area was associated with ADC (p=0.04).Moreover, in TP, mean Kep in lymphoma and Ve in meningiomas were not significantly correlated with mean ADC Fig. 3 on page 6 ., Ve and iAUC, in TP and PT area, were changed coincidentally.Irrespective of the brain tumor types and ROI positions, there existed correlations among permeability parameters and ADC.These findings may help to better understanding of these parameters and to narrow the scope of selecting imaging biomarkers for accurate tumor diagnosis and treatment monitoring.

Fig. 1 :
Fig. 1: Fig.1 A example of ROIs placing.A 39 years old male with low grade gliomas (WHO#) in bilateral frontal lobe on T1-weighted contrast-enhanced MRI.ROI 3 and ROI 4 were placed in the tumor parenchyma and peritumoral area, respectively.
on page 4 .ADC values were mesured from ADC map, and permeability parameters (Volume transfer constant