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3 Considerations When Choosing a Digital Mammo System

Posted by Vikki Harmonay on Wed, Nov 6, 2013 @ 11:11 AM

Need a digital mammography system?  As in all medical imaging equipment, there are plenty of choices and considerations to keep in mind.  Because this equipment comes with a hefty price tag, it’s important to do your homework before you make a decision. 

mammo considerationsDigital mammography is also called full-field digital mammography (FFDM.)  Simply put, images from digital mammography are recorded directly onto a computer, which eliminates the need for physical storage.  The digital image is available to the technologist almost instantly.  The study is also available for viewing on any PACS workstation, so it can be saved and manipulated by the radiologist.  There’s also another important advantage: digital mammograms deliver about three-fourths of the radiation that film-screen mammograms do.  

There are, however, two primary disadvantages, as well:  digital mammography is more expensive.  It’s also not as widely available as film-screen mammography.

Now, let’s look at those three considerations.

#1 Choosing the Right Digital Detector Technology

There are two methods of image capture used in digital mammography.  Each represents a different generation of technology: Indirect Conversion and Direct Conversion.

Indirect Conversion detectors were used in early digital mammography equipment.  It involved a two-step process for X-ray detection. Indirect conversion detectors utilize a scintillating layer to absorb the X-ray and generate light photons, which are detected by a photodiode array. A common scintillator used is Cesium-iodide with thallium doping (Csl(TI).)  The process results in some light scatter during conversion and can reduce resolution.

Direct Conversion digital detectors represent a technological advance, eliminating problems associated with the light scatter that’s inherent in indirect conversion systems. Amorphous selenium (a-Se) is the most common photoconductor material used in direct conversion detectors. The detectors use a photoconductor to absorb the X-ray and directly generate the signal. The photoconductor thickly constructed in order to stop the majority of the incident X-rays.  This can be done without adversely affecting the spatial resolution, which is an important consideration in mammography with its dual needs of high resolution and low radiation exposure.

#2 Detector Size Matters

The MQSA (Mammography Quality Standards Act) requires mammography facilities to use at least two screen-film cassette sizes: 18 x 24 cm and 24 x 30 cm.  Both detector sizes have excellent image quality, but in this case, bigger is better.  A 18cm x 24cm digital detector size is inadequate to take images of approximately 20-30 percent of women in the U.S.  These women have large or dense breasts, and would require multiple compressions and repositioning if the smaller detector is used.  The process of mammography can be stressful enough, without further compounding the situation.

The benefits of using the larger 24cm x 30cm detector image includes the ability to crop the image to reduce data transfer, as well as the reduced need for display and storage space. In addition, there are no additional material costs. There is one downside to the larger detector size:  positioning small breasts can be more challenging.  However, by using small compression paddles in conjunction with the larger detector, the problem can be solved.

#3 Image Resolution is Essential

When reading a mammographic image, it’s essential that you are able to see extremely small objects. After all, micro-calcifications can be small as 100 to 200 microns. Digital detectors are comprised of pixels, and the smaller the pixel, the higher the resolution. As the pixel size of any digital imaging system is made smaller, the amount of data contained in the image rapidly increases, which increases system costs in terms of data storage, network bandwidth and display capabilities. In other words, the more detail you can see, the more your system will cost. 

Don’t be Afraid to Ask for Help

Choosing the right digital mammography system can be complicated.  The experts at Atlantis Worldwide can help you weigh your options and choose a solution that fits your needs and your budget.  We can help you understand the options available from the top brands (Hologic, General Electric and Seimens), as well as whether you should purchase a brand new system, or a refurbished one.  To find out more, contact us today! 212-366-9100 



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Meet the Author: Vikki Harmonay

Topics: Buying Imaging Equipment, Mammography, Medical Imaging Comparisons