Installation guide

37
USER QUALITY ASSURANCE & MAINTENANCE
PROGRAM FOR THE CR-PRO
I NTRODUCTION :
Understanding the basic fundamentals and automating the decisions involved in obtaining
good results of x-ray imaging is the foundation of the approach Radlink has taken in the
development of the CR Pro.
G ENERAL :
The x-ray tube is essentially a point source of a cone-shaped beam of x-rays. The “x-
rays” themselves are composed of streams of “light” particles called photons, the same
photons that make up visible light, as from a flash light or ordinary light bulb. The
difference is the wavelength of the photons; x-ray photons are a thousand times shorter
wavelength than visible light. It is this short wavelength that allows x-rays to penetrate
objects. The shorter the wavelength, the easier it is for x-rays to penetrate more and more
dense objects. For example, longer wavelength x-rays can only go through flesh and not
bone, but shorter wavelengths can go through bone easily and create the images
necessary to “see” skeletal bone structure, etc.
C ONSIDERATIONS THAT A FFECT CR I MAGES :
There are several factors that contribute to the latent image the x-rays leave on the CR
plate:
1. Distance from the x-ray source point to the imaging CR plate (SID).
2. Kilovolts applied to the x-ray tube determine maximum shortest wavelength for
penetration (kVp)
3. Product of the x-ray tube current and the time of exposure (mAs).
4. Filtration of the x-rays at the x-ray tube source, usually 1.5mm to 2.5mm of
aluminum, and sometimes copper on the order of 0.5mm thick. This filtration
removes a large part of the longest wavelengths.
5. Whether or not a “grid” is used to cut down scattered x-rays produced by thick
body parts that have the effect of “fogging” or reducing contrast in the image.
6. Thickness of the body part being x-rayed.
7. The sensitivity of the CR plate itself to the x-rays interacting with the phosphor
coating which stores the latent image.
These are the seven factors that the x-ray radiology technician (XRT) considers when
taking an x-ray of a patient. The table of these factors, developed by the XRT is known as
the “Techniques Chart.”
R ADLINK ’ S A PPROACH
Recognizing that no two XRTs will use the exact same Techniques Chart, and no two
sites will use the same techniques, Radlink has developed a proprietary techniques
algorithm that can store a generic Techniques Chart by body part. This Techniques
Chart takes into account the above factors. The XRT simply uses the generic Techniques