Imaging Sci Dent.  2017 Jun;47(2):75-86. 10.5624/isd.2017.47.2.75.

Application of a newly developed software program for image quality assessment in cone-beam computed tomography

• de Oliveira MVL
• Santos AC
• Paulo G
• Campos PS
• Santos J

• KMID: 2389887
• DOI: http://doi.org/10.5624/isd.2017.47.2.75

Abstract

PURPOSE
The purpose of this study was to apply a newly developed free software program, at low cost and with minimal time, to evaluate the quality of dental and maxillofacial cone-beam computed tomography (CBCT) images.
MATERIALS AND METHODS
A polymethyl methacrylate (PMMA) phantom, CQP-IFBA, was scanned in 3 CBCT units with 7 protocols. A macro program was developed, using the free software ImageJ, to automatically evaluate the image quality parameters. The image quality evaluation was based on 8 parameters: uniformity, the signal-to-noise ratio (SNR), noise, the contrast-to-noise ratio (CNR), spatial resolution, the artifact index, geometric accuracy, and low-contrast resolution.
RESULTS
The image uniformity and noise depended on the protocol that was applied. Regarding the CNR, high-density structures were more sensitive to the effect of scanning parameters. There were no significant differences between SNR and CNR in centered and peripheral objects. The geometric accuracy assessment showed that all the distance measurements were lower than the real values. Low-contrast resolution was influenced by the scanning parameters, and the 1-mm rod present in the phantom was not depicted in any of the 3 CBCT units. Smaller voxel sizes presented higher spatial resolution. There were no significant differences among the protocols regarding artifact presence.
CONCLUSION
This software package provided a fast, low-cost, and feasible method for the evaluation of image quality parameters in CBCT.

Keyword

Image Quality; Cone-Beam Computed Tomography; Quality Control; Quality Assurance

MeSH Terms

Artifacts
Cone-Beam Computed Tomography*
Methods
Noise
Polymethyl Methacrylate
Quality Control
Signal-To-Noise Ratio
Polymethyl Methacrylate

Figure

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  Fig. 1 Structure of study

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  Fig. 2 Design of the phantom CQP-IFBA. A. Seven discs and location landmarks, B. docking slot inside the regular discs

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  Fig. 3 Rectangular ROIs (vertical and horizontal) are drawn to identify highest standard deviation on disc 3.

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  Fig. 4 Images obtained in CBCT scanners. A. Disc 1 for geometric accuracy, B. Disc 2 with ROI's positioned to evaluate the image uniformity, C. Disc 2 with a circular ROI (Ø 30 mm) in the center, D. Disc 3 with central hole containing air, E. Disc 4 used to evaluate the SNR and CNR in centered and periphery elements, F. Disc 05 with pattern bars, G. Disc 06 to evaluate the low contrast, and H. Disc 7 with three metallic rods and subtracted PMMA background

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  Fig. 5 Low contrast evaluation according to the protocol and contrast-to-noise ratio (CNR) in seven rods with diverse diameters

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  Fig. 6 Spatial resolution of CBCT units: A. Cranex 3Dx_ C1, B. Cranex 3Dx_ C2, C. Scanora 3D_ S1, D. Scanora 3D_ S2, E. NewTom 5G_ N1, F. NewTom 5G_ N2, and G. NewTom 5G_ N3

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  Fig. 7 Data storage system.

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