lwalogo2.jpg (2930 bytes)

Home Up

Techniques


X-ray Tech Advice Common Problems Shielding Tips Collimation Scatter Radiation Techniques

 

                             

 

DIGITAL TECHNIQUES

As with film, digital techniques vary depending on the brand and type of digital imaging receptor used.  We have pretty good technique guides for all of our digital systems and if you wish to email us with your brand of system, we would be happy to email you a guide that should work for you.  We also need to know if you are using a high frequency generator or single phase.  With Fuji's CR system, you are provided with an S number that is inversely proportional to dose.  Therefore each image provides the technologist with a reference number of whether sufficient radiation was used.  Too high an S number means insufficient dose and that usually means a "grainy" image as noise is too high a percentage of the total image.

DEVELOPING A TECHNIQUE "CHART" FROM A TECHNIQUE "GUIDE"

This is truly the "third rail" of radiology and most manufacturers and dealers run from the issue and rightfully so.  The problem of course is that we all want instant easy answers to complex issues.  There is a reason why Radiation Technologists complete a 2 year college program in order to become trained in this field.  They understand techniques and the physics relationships between kVp, mAs, screen film combinations and processing.  Throw in the variables of various processors with different immersion times, varying numbers of rollers, various brands of chemistry and processing temperature and one can quickly begin to see why no one can print a "One Size fits All" technique chart.  Here are some additional variables.  Screen film combinations present vastly different outcomes.  Various brands of x-ray tubes will emit different amounts of radiation as will generators.   Individual calibration, the type of table tops, different grid ratios and effective filtration all affect the MR output of a given installation.  Finally, consider when chemistry was last changed and the replenishment rates that your processor enjoys.  In a "slow" facility (meaning most clinics, chiropractors, & veterinarians) where only a couple of films per day may be processed, the chemistry will tend to oxidize or go flat since replenishment will not keep up with the oxidation process.  Running a few "dummy" films a day will help this problem, provided you have a processor that will turn on the pumps with an exposed film.  Going to digital will solve the retake dilemma.

Without going through the physics of radiation (please go to your library and review such books as "Fundamentals of Radiology by Eastman Kodak or other technical reference books on medical radiology) suffice it to say that the subject is complex and the education ongoing.  Most operators of x-ray apparatus should attend some formal classes in order to develop a basic understanding of radiology.

The first step should be to contact your State Radiation Dept and see what classes may be offered in order to increase your education.  In Washington State, Susan Vlasuk, DC, DACBR offers an excellent State approved class for learning basic and intermediate radiography.  Additional information is provided at her website http://www.drvxray.com

We offer simple guides to get you started, but each facility will have to develop their own specific chart and the chart should be posted in the control booth as often required by State law.

Sophisticated quality control systems have been developed over the years to solve the problems associated with processor and chemistry change.  These kits are not inexpensive and involve a phantom, that is exposed at a known exposure, processing the film and reading the density of the phantom with a densitometer.  The optical density is recorded and compared to the reference density that was obtained with optimum chemistry.  The technique can then be adjusted to keep the optical density in the expected and usable range.

Veterinary Use Only

Initial advice should be obtained from your referring radiologist.  They may be able to offer technique assistance or set you up with a guide for a reasonable fee.

If your films are too dark, reduce the mAs by 50% and do a retake.  If too light, increase the mAs by doubling and either way you will quickly get a readable film.  It is always best to begin with a properly calibrated x-ray machine and a processor with fresh chemistry. 

Of course going digital solves the technique dilemma.

Last Updated 3/03/2014

Copyright 1999