Why should a practice like mine switch to Digital Radiography?
Time is the only thing there is no more of, and it is what we trade for money. When it comes to time, DR wins.
5-Year costs of ownership. All digital imaging equipment is expensive to purchase. Some is more expensive to own than others. Be sure you understand costs of maintenance, service contracts, and software support. Also, calculate the costs associated with not transitioning to DR. You'll be surprised to see how much film radiography costs in terms of time and materials.
Talk to your financial advisor. Currently there are many financing incentives being offered by lenders and leasing companies. There are also very significant tax considerations currently available depending on your tax bracket.
What determines the quality of a digital image?
The quality of a digital image is primarily determined by three components:
Contrast - as expressed in shades of gray. Also referred to as Bit Depth or Dynamic Range.
Resolution - as expressed as Pixel Pitch (the distance in microns between the center of one pixel and its neighbors). The equivalent of Line Pairs in analog film
Image Algorithms - these are software based recipes of brightness, edge enhancement, etc. which the computer adds to the image prior to its being displayed.
Why do I want so many shades of gray?
The human eye can only detect 32 shades of gray (x-ray film has 64 shades). The software image algorithms effectively take the gray scale (4000 - 64,000 or 12-16 Bit in digital systems) of the raw image and map it into a format that can be detected by the human eye. Shades of gray are of the utmost importance in a diagnostic event as these shades are a critical aspect in discriminating one structure from another. The more shades of gray you have - the more diagnostic capability you own.
What is Pixel Pitch and why is it important?
Resolution is determined by Pixel Pitch. The medical Standard for Pixel Pitch is 100-150 microns. When the pixel pitch exceeds 150 the image appears grainy, at 100 or less the individual pixels become too close for the eye to resolve (the human eye can resolve increments of 25 microns *a human hair is about 40 microns) and the image gets a blurry or "glossy" look.
What are Image Algorithms?
Raw image content revealed to the eye is a function of software based processes known as Image Algorithms. It is through these software tools that image contrast and clarity are achieved. It is important to know that algorithms come in two forms: lossy and lossless. Lossy algorithms sacrifice data in creating edge enhancement process' for more distinct transition from adjacent tissues. Lossy algorithms make for "nicer" images in some cases and do have some utility. The problem with a system that utilizes ONLY lossy algorithms is that these algorithms, when applied, can mask diagnostic information or create artifacts that can be confused for disease conditions. A classic example of this situation involves orthopedic implants. The black halo that surrounds the implant, as a result of the lossy algorithm being applied, can be erroneously be diagnosed as an infection (osteomyelitis) at worst. At best, the image can be diagnosed as "inconclusive" based on the edge enhancement being applied.
Lossless algorithms, on the other hand, contain no edge enhancement features which sacrifice data and produce erroneous images. The grayscale shows a smooth transition from tissue to tissue.
What constitutes a "Legal Read"?
The ACR recommends the following standards in the monitor from which diagnostic interpretation of images are made: Resolution at 2 Megapixel (MP), Brightness of 400 Candelas (also referred to as Nitts), and a Contrast Ratio of 1000:1. These are the minimum specifications in a monitor that assure all of the image diagnostic content is available to the eye.
