Efforts should be made to remove patients from trauma backboards before CT when automatic tube current modulation (ATCM) is used, according to a recent study published by Clinical Radiology.

“Despite recent studies supporting rapid removal of patients from backboards, trauma patients are variably left on backboards during imaging, including during computed tomography (CT),” M.L. Gunn, University of Washington in Seattle, and colleagues wrote. “Time for discontinuation of backboards varies among institutions and sometimes varies within the same institution. Although not supported by clinical evidence, some facilities maintain patients on backboards following hospitalization until they have been fully cleared by imaging from serious injuries.”

Gunn et al. scanned an anthropomorphic phantom with and without a trauma backboard with two different CT systems, GE’s LightSpeed 16 Pro and Siemens’ Definition AS+. Their findings revealed a number of reasons why, whenever possible, hospital staff should remove patients from trauma backboards before CT.

1. Backboards attenuate photons

Comparing beam attenuation of a trauma backboard and a CT table alone, the researchers found that backboards lead to an increase in attenuation that ranged from 17 percent to more than 20 percent.

“These findings confirm that backboards are not radiolucent and do add an additional layer of attenuation to the CT X-ray beam,” the authors wrote.

2. Backboard use during CT scanning with ATCM results in increased tube current and radiation output

Both CT systems showed a significant increase in tube current when ATCM was used, though it was a much higher increase when using the GE system. The increase in tube current ranged from 39 to 98 mAs (18 to 31 percent) with the GE LightSpeed 16 Pro, and it ranged from 7 to 21 mAs (2 to 7 percent) with the Siemens’ Definition AS+.

Also, an increase in radiation dose was observed with both CT systems, with CTDI_vol increasing as much as 27 percent. The range of increase was 2 to 3 mGy·cm (22 to 27 percent) with the GE system and 0.3 to 0.4 mGy·cm (3 to 4 percent) with the Siemens System.

“The primary aim of ATCM is to maintain a constant reconstructed image noise in patients of varying size, shape, and attenuation, which typically will result in a decreased total radiation output compared to using a constant tube current; however, as the present study demonstrated, when additional attenuating structures, such as backboards, remain in the scan field, the total radiation output can increase during CT with ATCM,” the authors wrote.

3. Entrance skin dose increases when backboard is used during CT scanning

The authors explained that it was also important to measure entrance skin dose (ESD), because it “represents a more precise measurement of radiation dose actually reaching the phantom.”

The results showed a significant increase in ESD, specifically in the anterior and posterior pelvis, in both CT systems.

Focusing on the anterior pelvis, ESD increased up to 15 percent with the GE system and up to 25 percent with the Siemens system.

Looking ahead: Is reducing backboard use feasible?

Gunn and colleagues said they understand the convenience of using trauma backboards to transfer patients, especially in cases of severe injuries or elderly patients, but hospitals should still explore other potential solutions.

“There are alternatives to backboards for ease of patient transfer,” the authors wrote. “At Harborview Medical Center; Seattle, Washington a slide board is utilised to transfer patients safely and efficiently on and off of the CT table while maintaining the patient's spine in a neutral in-line position. The slide board transfer method has been described by other Level 1 trauma centres. Vacuum mattresses are another alternative to backboards, although their effect on radiation dose was not evaluated in the present study.”

The authors added that reducing backboards as soon as patients are transported to the emergency department (ED) is an achievable goal. At their own trauma center, backboard use dropped from a rate of 77 percent to 3 percent thanks to the implementation of a new policy.