Interventional MRI of the breast: lesion localisation and biopsy.

With the growing use of breast MRI an increasing need exists for reliable MR-guided preoperative localisation or even MR-guided needle biopsy. In this article an overview is given of the different approaches and the present state of the art. With closed magnets the following approaches have been made: freehand localisation (similar to CT-guided freehand localisation), and freehand localisation combined with a frameless stereotaxic system operating with support by ultrasound. One localisation device for supine localisation and a thermoplastic mesh for breast stabilisation have been reported. Most investigators have used compression devices to immobilize the breast and prevent shift during needle insertion. Thus far, one immobilisation and aiming device has been designed for open magnets. A small number of experiences exist with interventions on open MR units using a navigation system. Wire localisations are presently a well-established procedure. Magnetic-resonance-guided needle biopsy has been accomplished in closed systems as well as by the use of breast immobilisation devices. However, problems still exist due to severe needle artefacts, tissue shift during the intervention and fast equalization of contrast enhancement in lesions with surrounding tissue. Therefore, needle biopsy is not recommended for lesions < 10 mm. Magnetic-resonance-guided vacuum biopsy is somewhat more invasive but promises to solve most of these problems.