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. 2020 Feb 5;15(2):e0228376.
doi: 10.1371/journal.pone.0228376. eCollection 2020.

Chest CT in patients after lung transplantation: A retrospective analysis to evaluate impact on image quality and radiation dose using spectral filtration tin-filtered imaging

Alexander Wressnegger  1 , Helmut Prosch  1 , Bernhard Moser  2 , Walter Klepetko  2 , Peter Jaksch  2 , Christopher Lambers  2 , Konrad Hoetzenecker  2 , Christian Schestak  1 , Albert De Bettignies  1 , Lucian Beer  1 , Georg Apfaltrer  3 , Helmut Ringl  1 , Paul Apfaltrer  1   4
Affiliations

Chest CT in patients after lung transplantation: A retrospective analysis to evaluate impact on image quality and radiation dose using spectral filtration tin-filtered imaging

Alexander Wressnegger et al. PLoS One. .

Abstract

Objectives: The purpose of this study was to investigate the impact of a 150kV spectral filtration chest imaging protocol (Sn150kVp) combined with advanced modeled iterative reconstruction (ADMIRE) on radiation dose and image quality in patients after lung-transplantation.

Methods: This study included 102 patients who had unenhanced chest-CT examinations available on both, a second-generation dual-source CT (DSCT) using standard protocol (100kVp, filtered-back-projection) and, on a third-generation DSCT using Sn150kVp protocol with ADMIRE. Signal-to-noise-ratio (SNR) was measured in 6 standardized regions. A 5-point Likert scale was used to evaluate subjective image quality. Radiation metrics were compared.

Results: The mean time interval between the two acquisitions was 1.1±0.7 years. Mean-volume-CT-dose-index, dose-length-product and effective dose were significantly lower for Sn150kVp protocol (2.1±0.5mGy;72.6±16.9mGy*cm;1.3±0.3mSv) compared to 100kVp protocol (6.2±1.8mGy;203.6±55.6mGy*cm;3.7±1.0mSv) (p<0.001), equaling a 65% dose reduction. All studies were considered of diagnostic quality. SNR measured in lung tissue, air inside trachea, vertebral body and air outside the body was significantly higher in 100kVp protocol compared to Sn150kVp protocol (12.5±2.7vs.9.6±1.5;17.4±3.6vs.11.8±1.8;0.7±0.3vs.0.4±0.2;25.2±6.9vs.14.9±3.3;p<0.001). SNR measured in muscle tissue was significantly higher in Sn150kVp protocol (3.2±0.9vs.2.6±1.0;p<0.001). For SNR measured in descending aorta there was a trend towards higher values for Sn150kVp protocol (2.8±0.6 vs. 2.7±0.9;p = 0.3). Overall SNR was significantly higher in 100kVp protocol (5.0±4.0vs.4.0±4.0;p<0.001). On subjective analysis both protocols achieved a median Likert rating of 1 (25th-75th-percentile:1-1;p = 0.122). Interobserver agreement was good (intraclass correlation coefficient = 0.73).

Conclusions: Combined use of 150kVp tin-filtered chest CT protocol with ADMIRE allows for significant dose reduction while maintaining highly diagnostic image quality in the follow up after lung transplantation when compared to a standard chest CT protocol using filtered back projection.

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Conflict of interest statement

The authors have declared that no competing interests exist.

Figures

Fig 1
Fig 1. Quantitative image quality assessment.
Example for the assessment of quantitative image quality of lung parenchyma by positioning a region of interest (ROI) and measuring Hounsfield units (HU) and image noise (standard deviation of the attenuation value). A) 3rd generation Sn150kVp protocol. B) 2nd generation 100kVp protocol.
Fig 2
Fig 2. Example images of the two protocols with corresponding DLP.
Images of both protocols with corresponding dose-length product (DLP). A) 3rd generation Sn150kVp protocol: DLP = 81.5 mGy*cm. B) 2nd generation 100kVp protocol: DLP = 208 mGy*cm.
See this image and copyright information in PMC

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