Korean J Radiol.  2018 Aug;19(4):809-817. 10.3348/kjr.2018.19.4.809.

Comparison of Filtered Back Projection, Hybrid Iterative Reconstruction, Model-Based Iterative Reconstruction, and Virtual Monoenergetic Reconstruction Images at Both Low- and Standard-Dose Settings in Measurement of Emphysema Volume and Airway Wall Thickness: A CT Phantom Study

Affiliations
  • 1Department of Radiology, Korea University Ansan Hospital, Korea University College of Medicine, Ansan 15355, Korea. kiylee@korea.ac.kr
  • 2Department of Pulmonology, Korea University Ansan Hospital, Korea University College of Medicine, Ansan 15355, Korea.
  • 3Department of Radiology, Korea University Guro Hospital, Korea University College of Medicine, Seoul 08308, Korea.
  • 4Department of Radiology, Korea University Anam Hospital, Korea University College of Medicine, Seoul 02841, Korea.
  • 5Medical Science Research Center, Korea University Ansan Hospital, Korea University College of Medicine, Ansan 15355, Korea.

Abstract


OBJECTIVE
To evaluate the accuracy of emphysema volume (EV) and airway measurements (AMs) produced by various iterative reconstruction (IR) algorithms and virtual monoenergetic images (VME) at both low- and standard-dose settings.
MATERIALS AND METHODS
Computed tomography (CT) images were obtained on phantom at both low- (30 mAs at 120 kVp) and standard-doses (100 mAs at 120 kVp). Each CT scan was reconstructed using filtered back projection, hybrid IR (iDose4; Philips Healthcare), model-based IR (IMR-R1, IMR-ST1, IMR-SP1; Philips Healthcare), and VME at 70 keV (VME70). The EV of each air column and wall area percentage (WA%) of each airway tube were measured in all algorithms. Absolute percentage measurement errors of EV (APEvol) and AM (APEWA%) were then calculated.
RESULTS
Emphysema volume was most accurately measured in IMR-R1 (APEvol in low-dose, 0.053 ± 0.002; APEvol in standard-dose, 0.047 ± 0.003; all p < 0.001) and AM was the most accurate in IMR-SP1 on both low- and standard-doses CT (APEWA% in low-dose, 0.067 ± 0.002; APEWA% in standard-dose, 0.06 ± 0.003; all p < 0.001). There were no significant differences in the APEvol of IMR-R1 between low- and standard-doses (all p > 0.05). VME70 showed a significantly higher APEvol than iDose4, IMR-R1, and IMR-ST1 (all p < 0.004). VME70 also showed a significantly higher APEWA% compared with the other algorithms (all p < 0.001).
CONCLUSION
IMR was the most accurate technique for measurement of both EV and airway wall thickness. However, VME70 did not show a significantly better accuracy compared with other algorithms.

Keyword

Computed tomography; Model-based iterative reconstruction; Virtual monoenergetic image; Emphysema volume; Airway wall thickness

MeSH Terms

Emphysema*
Tomography, X-Ray Computed
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