NAVIGATION

In the detection and assessment of breast cancer by MRI, a gadolinium contrast agent is used to highlight lesions and their extent. Subtraction and fat suppression techniques are used to minimise loss of visibility.

The screening of the general population by MRI is not practical because of its high cost and limited availability. Although MRI screening is at least 10 times more expensive than mammographic screening, studies suggest that the use of MRI might be the most cos-efficient screening modality, especially in cases with a high risk probability of breast cancer.

The MRI breast imaging is performed with the aid of specialty dedicated breast coils, usually a bilateral multichannel system. The MRI system can be a whole body scanner with a magnet of 1.0 T or more. Such MRI scanners feature a slice thickness of 2.5 mm or less and a plain resolution of 1.3 mm or less. A high end 1.5 T scanner can achieve a Voxel size of 2 mm or less. 

MRI sensitivity for breast lesions is high, however its specificity is not adequate. Therefore, MRI-guided biopsies are often performed for histological examinations. Two different MRI-guided intervention methods are used:

• 1. The free-hand technique, which allows wire localisation within 10-15 mm of the lesion
• 2. The stereotactic approach which features much better precision.

There are several biopsy devices on the market including: coaxial core needle system, stereotactic system, biopsy guidance device and vacuum-assisted core biopsy gun. Standard whole body scanners can be used to perform breast MRI imaging, if the appropriate breast coils are available. These types of systems benefit from greater versatility in the radiology department. Currently, dedicated machines are available. The advantage of such machines is that they are custom-designed for breast MRI, and patient comfort is therefore optimised. The staff working on these scanners will become specialised in the needs of this particular patient group.

Standard 1.5 T multi-purpose MRI scanners cost between 1.1 – 1.9 million dollars. Dedicated breast MRI scanners costs 1.4 – 1.8 million dollars. All MRI scanners require investment in terms of physical space, running costs, maintenance and staffing. A dedicated breast scanner will require almost the same costs.