MRI

Magnetic Resonance Imaging (MRI) is a technique that uses radio-waves and a powerful magnetic field to produce images of the breast. No x-rays are involved.

Ascot Radiology have now installed a new generation machine that uses a powerful 3 Tesla magnet to produce very detailed images. Dedicated breast coils are used to provide optimal images of the breast. These pictures are then processed by a computer and can be stored and analysed in various ways. Computer aided diagnosis (CAD) improves accuracy and versatility of this investigation.

The biggest problem with MRI in the past has been that we did not have a method for localising small MRI detected abnormalities for biopsy. The new machine has an MRI guided biopsy system that solves this problem. The system uses a computer to accurately calculate the coordinates of an abnormality within the breast and then guides a biopsy needle into the correct location through the skin and breast tissue. This biopsy is done using local anaesthetic.

MRI does not replace clinical examination, mammograms and ultrasound in routine diagnosis, but now plays an important part in providing more accurate assessment of certain situations.

Indications for MRI:

1.Pre-op planning for breast conserving surgery. In some situations MRI can provide a better estimate of the size and extension of a tumour than mammography or ultrasound. This applies particularly in younger women with dense breast tissue. MRI can also detect other areas of cancer in both breasts. Multifocal or bilateral cancer will require more extensive treatment.

2. Surveillance after breast cancer surgery. This can be difficult due to scar tissue and distortion of the breast. MRI can sometimes be useful in distinguishing recurrence of the cancer from post-operative scar tissue.

3. Screening high-risk younger women. Early studies suggest that MRI may be more accurate in finding cancers than mammography in high-risk women. This increased detection has not been shown as yet to translate into a lower mortality. MRI screening does produce more false-postitive results that may require further procedures including surgical biopsy.

4. Assessment for implant rupture.

False positives - One of the drawbacks of MRI is that it is very sensitive and consequently often finds abnormal areas that are not due to cancer. These false positives can create a lot of anxiety and result in additional investigations and biopsy.

False negatives - Like all imaging investigations MRI is not 100% accurate. It can miss some cancers and create a false sense of security. It remains important to review MRI imaging in conjunction with other tests and to ensure that concordance is achieved. Careful follow-up using other established imaging modalities such as ultrasound and mammography may still be appropriate.

MRI examination requires the patient to lie on her stomach with the breasts hanging freely through cushioned openings. The examination table is then moved into a hollow cylinder surrounded by the large magnet. Multiple images are taken over a period of 30 - 60 minutes. You will need to remain very still while images are taken. If you suffer from claustrophobia or severe anxiety a mild sedative can be administered for this procedure. Intravenous contrast may be used for some of these sequences.

Patients with some metallic devices may not be suitable for this procedure.

Advise the radiologist if you think you may be pregnant.

MRI scanning is a valuable tool in our armamentarium for the assessment and management of breast problems. We are fortunate to have access to the latest technology in this area.