Computed tomography: improved COPD diagnostics – lower radiation exposure

Computed tomography examination Source: REB Images via Getty Images

COPD is a common and serious disease of the lungs and is associated with narrowing of the airways. Over 300 million people worldwide suffer from COPD, and about 3.17 million people die from it every year.

In order to diagnose the disease and determine the type and severity, CT examinations are increasingly used.

Double imaging offers greater informative value

The international Fleischner Society of renowned thoracic radiologists recommends that CT scans for COPD diagnosis be performed not only in the inhaled lung state (inspiration) but also in the exhaled state (expiration) in order to increase the informative value. However, this also means doubling the radiation exposure and radiation risk.

According to an extensive patient study in which the BfS was involved, technical innovations lead to a lower radiation exposure than with conventional technology with only one image – even with double imaging. The exposure in a combined inspiration-expiration study on the latest dual-source systems of the third generation was lower than in a pure inspiration study on only slightly older dual-source systems of the second generation.

As part of the study, the BfS calculated the radiation exposure associated with the medical examinations – depending on the CT device used – as well as the associated risk of a radiation-induced tumour.

Diagnostic benefit outweighs the risk

According to estimates of the BfS, such a combined CT examination for a woman aged 50 increases the risk of her developing cancer in her lifetime by 0.025%. For a 50-year-old man, this risk is increased by 0.013%. This means that, statistically speaking, cancer attributable to CT diagnostics occurs in only one in 4,000 women and only one in 7,700 men examined in this way. The difference between the sexes can be explained, among other things, by the fact that the breast tissue is exposed to CT radiation and is thus more susceptible to developing tumours.

However, the increase in risk is so low in both sexes that even with multiple examinations over a longer period of time, the risk is to be assessed as considerably lower than the diagnostic benefit.

Innovations in hardware and software reduce radiation exposure

The study impressively demonstrates the importance of technical innovations for the reduction of radiation exposure using the example of COPD patients.

Dual-source CT is an X-ray diagnostic cross-sectional imaging procedure. In this process, two offset X-ray tubes and opposing radiation detectors rotate in a spiral around the patient's body. With the help of a computer program, the signals detected are used to generate sectional images without superimposition. On these images, tissue structures of different density are displayed in high contrast (i.e. in easily distinguishable shades of grey). The dose reduction achieved was mainly due to innovative tin filtering of the X-ray spectrum.

The lead author of the study is Joshua Gawlitza from Saarland University Hospital in Homburg.