Abstract
As stated by the Fleischner Society, an additional computed tomography (CT) scan in expiration is beneficial in patients with chronic obstructive pulmonary disease (COPD). It was thus the aim of this study to evaluate the radiation risk of a state-of-the-art paired inspiratory-expiratory chest scan compared to inspiration-only examinations. Radiation doses to 28 organs were determined for 824 COPD patients undergoing routine chest examinations at three different CT systems–a conventional multi-slice CT (MSCT), a 2nd generation (2nd-DSCT), and 3rd generation dual-source CT (3rd-DSCT). Patients examined at the 3rd-DSCT received a paired inspiratory-expiratory scan. Organ doses, effective doses, and lifetime attributable cancer risks (LAR) were calculated. All organ and effective doses were significantly lower for the paired inspiratory-expiratory protocol (effective doses: 4.3 ± 1.5 mSv (MSCT), 3.0 ± 1.2 mSv (2nd-DSCT), and 2.0 ± 0.8 mSv (3rd-DSCT)). Accordingly, LAR was lowest for the paired protocol with an estimate of 0.025 % and 0.013% for female and male patients (50 years) respectively. Image quality was not compromised. Paired inspiratory-expiratory scans can be acquired on 3rd-DSCT systems at substantially lower dose and risk levels when compared to inspiration-only scans at conventional CT systems, offering promising prospects for improved COPD diagnosis.
Highlights
With an incidence of over 300 million persons and 3.17 million deaths per year worldwide, chronic obstructive pulmonary disease (COPD) is a frequent and severe inflammatory disorder of the lungs [1,2]
We retrospectively analyzed Computed tomography (CT) scans of COPD patients performed over a three-year period in regular health care at three different CT systems of the same manufacturer (Siemens Healthineers, Forchheim, Germany): a conventional multi-slice CT (MSCT) (Somatom Emotion 16), a 2nd-DSCT (Somatom Definition FLASH), and a 3rd-DSCT (Somatom FORCE) equipped with a tin filter for spectral shaping [13,14,16]
The average equivalent doses of 28 tissues and organs defined in International Commission on Radiological Protection (ICRP) publication 103 [16] were estimated for each individual CT scan from the respective dose-length product (DLP) by using scanner- and sex-specific dose conversion coefficients
Summary
With an incidence of over 300 million persons and 3.17 million deaths per year worldwide, chronic obstructive pulmonary disease (COPD) is a frequent and severe inflammatory disorder of the lungs [1,2]. Do expiratory CT scans show a stronger correlation with airway and lung function parameters, but they allow for the quantification of air trapping and residual volume [6,7]. Several hardware and software innovations—such as automated tube current modulation, low voltage imaging, spectral shaping, dynamic collimation, as well as iterative image reconstruction—have substantially decreased the radiation dose of CT scans [9,10,11,12,13,14,15] These hardware and software techniques are available in clinical routine by using high-end CT systems and may help to (over-)compensate the increased radiation exposure associated with the acquisition of paired inspiratory-expiratory scans of COPD patients. Based on the equivalent organ doses determined for these patients, effective doses as well as age- and sex-specific lifetime attributable cancer risks (LAR) were estimated
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