Image quality evaluation of dual-layer spectral CT in comparison to single-layer CT in a reduced-dose setting

Thuy Duong Do; Stephan Rheinheimer; Hans-Ulrich Kauczor; Wolfram Stiller; Tim Weber; Stephan Skornitzke

doi:10.1007/s00330-020-06894-7

Image quality evaluation of dual-layer spectral CT in comparison to single-layer CT in a reduced-dose setting

Eur Radiol. 2020 Oct;30(10):5709-5719. doi: 10.1007/s00330-020-06894-7. Epub 2020 May 11.

Authors

Thuy Duong Do¹, Stephan Rheinheimer¹, Hans-Ulrich Kauczor^{1

2}, Wolfram Stiller^{1

2}, Tim Weber¹, Stephan Skornitzke³

Affiliations

¹ Clinic for Diagnostic and Interventional Radiology (DIR), Heidelberg University Hospital, Im Neuenheimer Feld 110, 69120, Heidelberg, Germany.
² Translational Lung Research Center (TLRC), Member of the German Center for Lung Research (DZL), Heidelberg, Germany.
³ Clinic for Diagnostic and Interventional Radiology (DIR), Heidelberg University Hospital, Im Neuenheimer Feld 110, 69120, Heidelberg, Germany. stephan.skornitzke@med.uni-heidelberg.de.

Abstract

Objectives: To quantitatively and qualitatively evaluate image quality in dual-layer CT (DLCT) compared to single-layer CT (SLCT) in the thorax, abdomen, and pelvis in a reduced-dose setting.

Methods: Intraindividual, retrospective comparisons were performed in 25 patients who received at least one acquisition of all three acquisition protocols SLCT_low (100 kVp), DLCT_high (120 kVp), and DLCT_low (120 kVp), all covering the venous-phase thorax, abdomen, and pelvis with matched CTDI_vol between SLCT_low and DLCT_low. Reconstruction parameters were identical between all scans. Image quality was assessed quantitatively at 10 measurement locations in the thorax, abdomen, and pelvis by two independent observers, and subjectively with an intraindividual forced choice test between the three acquisitions. Dose-length product (DLP) and CTDI_vol were extracted for dose comparison.

Results: Despite matched CTDI_vol in acquisition protocols, CTDI_vol and DLP were lower for SLCT_low compared to DLCT_low and DLCT_high (DLP 408.58, 444.68, 647.08 mGy·cm, respectively; p < 0.0004), as automated tube current modulation for DLCT_low reached the lower limit in the thorax (mean 66.1 mAs vs limit 65 mAs). Noise and CNR were comparable between SLCT_low and DLCT_low (p values, 0.29-0.51 and 0.05-0.20), but CT numbers were significantly higher for organs and vessels in the upper abdomen for SLCT_low compared to DLCT_low. DLCT_high had significantly better image quality (Noise and CNR). Subjective image quality was superior for DLCT_high, but no difference was found between SLCT_low and DLCT_low.

Conclusions: DLCT_low showed comparable image quality to SLCT_low, with the additional possibility of spectral post-processing. Further dose reduction seems possible by decreasing the lower limit of the tube current for the thorax.

Key points: • Clinical use of reduced-dose DLCT is feasible despite the required higher tube potential. • DLCT with reduced dose shows comparable objective and subjective image quality to reduced-dose SLCT. • Further dose reduction in the thorax might be possible by adjusting mAs thresholds.

Keywords: Abdomen; Radiation exposure; Thorax; Tomography, X-ray computed.

Publication types

Comparative Study

MeSH terms

Abdomen / diagnostic imaging
Algorithms
Female
Humans
Image Processing, Computer-Assisted / methods
Male
Middle Aged
Observer Variation
Pelvis / diagnostic imaging
Radiation Dosage*
Radiographic Image Interpretation, Computer-Assisted / methods*
Radiometry
Retrospective Studies
Thorax / diagnostic imaging
Tomography, X-Ray Computed / methods*