It is possible to reduce the exposition to ionizing radiation for lung computed tomography scan analysis?

Introduction

The computed tomography (CT) scan can be used to measure the lung weight-volume and to determine the degree of inflation (not aerated, poorly aerated, well aerated, over aerated tissue). Nowadays to accurately study the lung, a whole thoracic CT scan must be performed, thus exposing the patient to a large dose of ionizing radiation. A possible solution could be to acquire only three CT lung sections instead of scanning the whole lung. We previously showed that in ALI/ARDS patients three lung sections are able to accurately estimate the lung inflation similar to the whole CT scan.

Objective

To evaluate whether three lung sections gives comparable data to the whole lung CT analysis in patients with unilateral pneumonia.

Materials and methods

Thirty-two patients with unilateral pneumonia were studied (mean age 64.2 ± 20.4 years, 18 males, BMI 25.4 ± 2.8 kg/m², PaO₂/FiO₂ 261.1 ± 102.8, SAPS-II 35.3 ± 16.8, 14 mechanically ventilated). Each patient underwent a whole lung spiral CT scan. The lung regions of interest were manually delineated on each CT slice, using dedicated software (MALUNA; University of Mannheim, Germany). The three CT lung sections were selected at the level of the aortic arch, carina and at the mid right atrium (representing the lung apex, hilum and base). Lung quantitative analysis was performed with specific software (SOFT-E-FILM; University of Milan). The agreement between the two methods was evaluated using Bland-Altman analysis considering each compartment of lung inflation (expressed as the percentage of the total weight).

Results

For the nonaerated tissue the mean of the difference ± 2SD was 0.015 ± 0.096, poorly aerated was 0.011 ± 0.056, well aerated – 0.025 ± 0.084 and over aerated – 0.001 ± 0.014.

Conclusion

Our data show that a lung CT scan of only three sections can provide comparable information on the distribution of lung inflation as a whole lung CT scan.

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