Good practices in radiography

Frequently asked questions by the health professionals

» Is it a good practice to select "high speed" type intensifying screens that require relatively low exposure and use them for all radiographic procedures in my facility? 
» How does performing a reject analysis in radiography reduce unnecessary exposure to patients? 
» Does the quality of the chemical processing of radiographic film have any effect on the radiation exposure of a patient? 
» Is the radiation exposure to a patient affected by the size of the image (area covered by the X-ray beam)? 

» Is it a good practice to select "high speed" type intensifying screens that require relatively low exposure and use them for all radiographic procedures in my facility?

No.

While high-speed intensifying screens are appropriate for many examinations, especially where patient exposure is a concern, they do not produce the necessary visibility of detail that is required for some types of radiography, such as of the chest and the skeletal system. The appropriate intensifying screens and film for each type of clinical examination should be specified in the procedure manual for the facility.

It is desirable to have a selection of intensifying screens available so that an appropriate one can be selected for a given procedure. Radiographers should have a good knowledge of the characteristics of the intensifying screens available in their facilities. The intensifying screens that provide optimal imaging for each examination with regard to image information and patient exposure should be identified and made known to the staff.

» How does performing a reject analysis in radiography reduce unnecessary exposure to patients?

A reject analysis is performed by saving all ‘rejected’ films and then evaluating them periodically to determine the cause of the rejects and repeated exposures. The objective is to reduce the number of repeated examinations by correcting technical problems and improving the skills of the staff. A reject analysis is an important function in a quality assurance programme in radiology.

When using digital radiography, procedures should be established for identifying and analyzing all images that were repeated because of problems with quality, positioning, etc. This information should be used for training and guidance to reduce the need for repeated exposures. 

» Does the quality of the chemical processing of radiographic film have any effect on the radiation exposure of a patient?

Yes, maintaining high-quality film processing reduces unnecessary patient exposure in several ways. First, if films are underdeveloped and appear underexposed, the usual reaction is to increase the exposure of the patient and the film in an attempt to compensate. This results in unnecessary patient exposure. Second, if the processing is not properly controlled and fluctuates with time, some films might be incorrectly exposed and require repeating. This results in unnecessary exposure to patient. The appropriate action is to have a good film processor quality control programme that ensures both adequate and consistent processing.

» Is the radiation exposure to a patient affected by the size of the image (area covered by the X-ray beam)?

Yes. 

The advantage is that by reducing the size of the beam some tissues and organs are kept outside the direct beam. Significant dose reduction, especially to sensitive tissues and organs, can be achieved with beam collimation and use of shielding devices placed on the patient’s body.