Purpose: to determine the efficacy of magnetization transfer imaging (MTI) and diffusion-weighted imaging (DWI) in differential diagnosis of brain tumor, infection and infarct in children
Methods and Materials: 48 boys and 27 girls (age range: newborn to 17 years, average 8.54 years) underwent MRI using a 1.5T magnet. In addition to conventional MRI, axial 2D FLASH images were obtained (160/14/150/1 acquisition/14 slices, 177x256 matrix, 20cm FOV, 5mm thick/1mm gap, 1 min 26 s) with and without magnetization transfer pulse (1.5KHz frequency offset, 8000). Axial DWI was acquired using fat-saturated single-shot SE-EPI (220/139/900/4/19, EPI factor 128, b=0, 900 in 3 directions, 128x128, 50 s). ADC was determined by drawing ROI on lesions on the ADC map using T1W and T2W images as guide. Magnetization transfer ratio (MTR) was calculated using the equation: (SI0 - SIm )/SI0 x100 where SI0 and SIm are the signal intensities of the lesion on the FLASH images without and with magnetization transfer pulse respectively. The ADC and MTR of tumor, infection and infarct were compared using the two-tailed t-test for independent samples. Significance was defined at p<0.05.
Results: Of 113 lesions, there was no significant difference between ADCs and MTRs of 22 chronic infarct (2.24±0.76 x10 -3, 19.74±10.74) and 6 subacute infarct (2.26±1.05x10-3, 20.37±14.30), 22 low-grade astrocytomas (1.72±0.56 x10-3, 27.53±8.41) and 26 other benign tumors (1.49±0.41 x10-3, 32.18±9.51), 8 medulloblastomas (1.23±0.44 x10-3, 31.38±6.35) and benign tumors. There was significant difference between ADCs and MTRs of low-grade astrocytomas and medulloblastomas (0.027, 0.018), 6 acute infectious lesions (0.66±0.18 x10-3, 33.16±1.05) and infarct (0.001, 0). ADC (1.61±0.50 x10-3) and MTR (29.40±8.62) of benign tumors and low-grade astrocytomas were significantly higher (p=0.042, 0.001) than ADC and lower (p=0.040, 0) than MTR of medulloblatomas and acute infection. Medulloblastomas had significantly higher ADC and lower MTR than acute infection (0.030, 0.007). Subacute and chronic infarct had higher ADC (0, 0) and lower MTR (0, 0.002) than medulloblastomas, low-grade astrocytomas or benign tumors.
Conclusion: Both MTI and DWI are useful in differential diagnosis of brain tumor, acute infection, and infarct in children.