IMPROVING  THE  DETAIL  of  X-RAYS

Radiographic definition is the DETAIL quality of an x-ray.   Excellent radiographic definition requires careful adherence to a list of MULTIPLE factors.

FACTORS AFFECTING RADIOGRAPHIC DEFINITION (DETAIL)

 1.       Grid

            This is probably the most common reason for poor radiographic definition.

            a.         Grid ratio - 12:1 is recommended, unless you want to utilize full spine techniques, in which case you sometimes have to settle for 10:1.

            b.         Lines-per-inch - 80 lpi for a reciprocating bucky, or 103 lpi for a stationary grid.  If you are making a new purchase, purchase a stationary grid in a grid cabinet, rather than a reciprocating bucky.

            The higher the grid ratio and lpi, the better the clean-up of scatter.  12:1 103 lpi is optimal for upright radiography.  If you do not know what kind of grid you have, take the front laminate surface off (multiple screws or velcro), upon which you will be looking at the surface of your grid, which should have a sticker on it, giving its particulars. 

 2.        Film and screen speed

            With every increase in film and screen speed, there is a decrease in radiographic definition.  At this time, a 400-speed system is recommended.  This is fast enough to allow low patient radiation dose and lesser tube work load, while still providing good radiographic definition (assuming all other factors affecting definition are controlled). 

 3.        Patient motion

            Caused by exposure times that are too great, or failure to stabilize patient. 

 4.        Collimation

            Tighter collimation creates better definition by limiting the amount of body tissue exposed, which then reduces the amount of scatter radiation being generated from the tissues.  This is a very important and under-rated point in obtaining clearer films, particularly on large patients. 

 5.        Film/screen contact

            Tight contact is necessary.  Old cassettes may not close tightly. 

 6.        Film quality

            Cheap brands of film have insufficient silver content to produce a good image.   Also may have greater base fog.   Buy one box of the most expensive film that is compatible with your intensifying screens and just try it to see if you can see the difference.

 7.        OFD/SID

            If the object-to-film distance must be increased, the source-to-image distance must also be increased in order to avoid magnification and distortion.  This is why lateral cervicals (which remove the spine from the surface of the bucky due to the width of the shoulders) should be taken at 72" SID. 

 8.        Focal spot size

            The small focal spot allows better definition; however, it is to be used only for small parts such as cervical and extremity studies and children.  (The large focal spot must be used for the larger body parts, in order to distribute heat to a larger area of the anode target.) 

 9.        Fog