With the introduction of digital radiography, new possibilities have opened up that have not existed before in the world of developer and fixer radiography. One of these new possibilities is the potential to extract two images from the one exposure. How valid is this technique when applied to patients who are referred for chest and thoracic spine radiography?

Patient History

This elderly patient presented to the Emergency Department with spontaneous onset of chest and thoracic spine pain. The patient has a history of COAD and osteoporosis.

Technique

The radiographer has performed an erect PA and lateral X-ray examination using the AEC. The lateral chest image is shown below.

When using digital radiography, it is tempting at this stage for the radiographer to: apply post-processing coning to this image; apply a lateral thoracic spine algorithm; and re-save the image as a lateral thoracic spine view.This approach will save the patient an additional radiation dose and will prevent the patient from being subject to the unnecessary rigors of undertaking an additional lateral thoracic spine view. These laudable objectives must be offset against the fact that the lateral thoracic spine and lateral chest exposure techniques are diametrically opposed. The lateral chest exposure technique uses a small exposure time to limit movement unsharpness of soft tissue structures. The lateral thoracic spine exposure technique uses a long exposure time technique to blur the soft tissues of the thorax. Do you think the radiographer has demonstrated the lateral thoracic spine anatomy adequately on this lateral chest image? The radiographer proceeded to undertake a lateral thoracic spine examination.

A breathing lateral thoracic spine exposure technique was employed to good effect. The lateral and upper lumbar vertebral bodies are clearly visualised. There is evidence of osteoporosis (pencilling of the vertebral bodies). There are several wedge fractures with severe wedging of L1. Compare this image with the thoracic vertebra demonstrated on the lateral chest image above

It is clear that the exposure technique had a significant beneficial effect on the quality of the lateral thoracic spine image. This is not to suggest that this approach should be applied universally. Indeed, there may be occasions where, on balance, "digital double dipping" is the correct choice. This is a judgement that can and should be made by the radiographer. You should have a low threshold for seeking assistance from senior radiography staff, radiologist and/or the referring doctor where the choice is not clear.

Good radiography is that which is the best yield/risk for that patient,
at that time, and for their likely conditions.