Breast Screening With the Aid of MRI

In the detection and assessment of breast cancer by MRI, gadolinium contrast agent is used to highlight lesions and their extent. Subtraction and fat suppression techniques are used to minimize 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 cost 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 freehand technique which allows wire localization within 10?5 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 these machines is that they are custom-designed for breast MRI, and patient comfort is therefore optimized. The staff working on these scanners will become specialized 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.

New scanner expedites work - Otago Daily Times

 University of Otago dental radiography unit charge technologist Diane Campbell checks the 3D images created on the university's new cone beam neck and head CT scanner. Photo by Peter McIntosh. University of Otago dental school staff are welcoming the commissioning of equipment that puts Dunedin at the forefront of digital scanning technology.

While the patient sits comfortably in a chair, the German-made cone beam head and neck CT scanner can capture a complete 360-degree, 240-frame set of images in just 14 seconds.

It is understood to be only the third machine of its type in New Zealand.
The others are in Auckland and Christchurch.

The scanner produces 3-D images that technologists, dentists and doctors can use to examine teeth, jawbones, skulls, nasal passages and sinuses.

At the push of a button, viewers can order an image at whatever angle is required. The images can be rotated on screen and saved for inspection later.

The scanner was a ''fantastic resource'', dental school facilities and clinical services associate dean Dr Warwick Duncan said.

''We have been sending about one patient a month to Auckland but there was a backlog. Plus there was the inconvenience and expense of the travel.''

The university received the scanner as an unexpected extra, he said.

When it advertised for companies to supply 73 mannequins and associated digital and computerised equipment for the dental simulation laboratory, the company that won the bid said it would also supply a digital dental X-ray machine and the cone beam scanner for the money the university was prepared to spend.

The simulation laboratory, which cost almost $4 million to create and fit out in the old dental school library, opened at the start of last year.

However, Dr Duncan said because a new room had to be built for the cone beam scanner and three staff trained, the scanner was not commissioned until the end of September.

Fewer than 20 patients from Otago and Southland had been scanned so far, although he expected usage to increase substantially this year.

For dentists, the scanner was invaluable when planning the manufacture and insertion of dental implants.

In the past, it could take up to a year to plan the placement of implants, have them made and insert them, Dr Duncan said.

Now, a complete set of a patient's images could be emailed directly to the implant manufacturer overseas, usually in the United States or Sweden, and the implants made to fit.

The patient only had to be seen twice, he said, once to be scanned and once to have the implants fitted. The manufacture of the implants was also quicker.

Dr Duncan expected Dunedin's scanner would also be used by dental and medical researchers, and by medical specialists when correcting dental and facial deformities or carrying out reconstructive surgery after accident or illness.

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