Purpose: to investigate the diagnostic opportunities of contrast magnetic resonance imaging with the effect of magnetization transfer effect in the diagnosis of focal metastatic lesions in the brain.Materials and methods.Images of contrast MRI of the brain of 16 patients (mean age 49 ± 18.5 years) were analysed. Diagnosis of the direction is focal brain lesion. All MRI studies were carried out using the Toshiba Titan Octave with magnetic field of 1.5 T. The contrast agent is “Magnevist” at concentration of 0.2 ml/kg was used. After contrasting process two T1-weighted studies were performed: without T1-SE magnetization transfer with parameters of pulse: TR = 540 ms, TE = 12 ms, DFOV = 24 sm, MX = 320 × 224 and with magnetization transfer – T1-SE-MTC with parameters of pulse: ΔF = −210 Hz, FA(МТС) = 600°, TR = 700 ms, TE = 10 ms, DFOV = 23.9 sm, MX = 320 x 224. For each detected metastatic lesion, a contrast-to-brain ratio (CBR) was calculated. Comparative analysis of CBR values was carried out using a non-parametric Wilcoxon test at a significance level p < 0.05. To evaluate the sensitivity and specificity of the techniques in the detection of metastatic foci (T1-SE and T1-SE-MTC), ROC analysis was used. The sample is divided into groups: 1 group is foci ≤5 mm in size, 2 group is foci from 6 to 10 mm, and 3 group is foci >10 mm. Results.Comparative analysis of CBR using non-parametric Wilcoxon test showed that the values of the CBR on T1-weighted images with magnetization transfer are significantly higher (p <0.001) that on T1-weighted images without magnetization transfer. According to the results of the ROC analysis, sensitivity in detecting metastases (n = 90) in the brain on T1-SE-MTC and T1-SE was 91.7% and 81.6%, specificity was 100% and 97.6%, respectively. The accuracy of the T1-SE-MTC is 10% higher in comparison with the technique without magnetization transfer. Significant differences (p < 0.01) between the size of the foci detected in post-contrast T1- weighted images with magnetization transfer and in post-contrast T1-weighted images without magnetization transfer, in particular for foci ≤5 mm in size, were found. Conclusions1. Comparative analysis of CBR showed significant (p < 0.001) increase of contrast between metastatic lesion and white matter on T1-SE-MTC in comparison with T1-SE.2. The sensitivity, specificity and accuracy of the magnetization transfer program (T1-SE-MTC) in detecting foci of metastatic lesions in the brain is significantly higher (p < 0.01), relative to T1-SE.3. The T1-SE-MTC program allows detecting more foci in comparison with T1-SE, in particular foci of ≤5 mm (96% and 86%, respectively, with p < 0.05).
Detecting tail behavior: mean excess plots with confidence bounds
