The Role of Multidirectional Diffusion Weighted Imaging in the diagnosis of breast carcinoma in Magnetic Resonance Imaging

Magnetic resonance imaging (MRI) is increasingly used in breast imaging. Diffusion imaging (DWI) is used in conjunction with contrast enhanced series. There is a signal difference between the stationary and moving water molecules in DWI, due to the fact that all molecules receive a first gradient pulse and then another pulse at the 180 degree-reverse direction of the first one. The stationary molecules have zero signal after the two of the pulses and show restriction (low signal). However, the moving molecule is not at the same location and escape from the 180 degree pulse with an energy in the end of the gradients. Multidirectional Diffusion-Weighted Imaging (MDDWI) gives information signifying water’s capacity to move freely in a direction according to its physiological and pathological boundaries, which is referred to as fractional anisotropy (FA). This study aimed to determine the usefulness of FA maps in differentiating benign and malignant breast lesions.

The patients who had breast MRI including MDDWI series and went through pathological evaluation (79 patients with 86 lesions) were included in the study. The FA values were measured in addition to the conventional Diffusion-ADC values. Also, diffusion restriction and pathology results were noted. The lesion FA and ADC values, diffusion assessment, and pathology results were compared using the Student t-test.

The patients were between 23 and 76 years and the mean age for benign lesions was 43.9, whereas it was 50.4 for the malignant lesions. Forty-five patients had benign and 41 had malignant lesions. The mean ADC values were significant between benign and malignant lesions (correspondingly; 1256.5x10–3 mm²/s. and 978.7x10–3 mm²/s.) The FASD value of each lesion was found to be significant for malignant lesions (100x10–3 ), especially those with restricted diffusion. In addition, for lesions with restricted diffusion, the maximum FA (75x10–3 ) and mean FA (200x10–3 ) values were found to be significant for malignancy. A cut-off point of 500×10–3 of FA max was found to be a value that could be used to increase the specificity of suspicious lesions with restricted diffusion

Restricted diffusion is used as a supporting finding for biopsy indication, but due to its lower specificity DWI cannot be very helpful in increasing the specificity of conventional breast MRI. In the search of finding a tool to increase the specificity of breast MRI, FA values seem to have the potential in differentiating benign lesions.