Imaging Sci Dent.  2018 Mar;48(1):31-39. 10.5624/isd.2018.48.1.31.

Effect of field-of-view size on gray values derived from cone-beam computed tomography compared with the Hounsfield unit values from multidetector computed tomography scans

• Shokri A
• Ramezani L
• Bidgoli M
• Akbarzadeh M
• Ghazikhanlu-Sani K
• Fallahi-Sichani H

• KMID: 2406980
• DOI: http://doi.org/10.5624/isd.2018.48.1.31

Abstract

PURPOSE
This study aimed to evaluate the effect of field-of-view (FOV) size on the gray values derived from conebeam computed tomography (CBCT) compared with the Hounsfield unit values from multidetector computed tomography (MDCT) scans as the gold standard.
MATERIALS AND METHODS
A radiographic phantom was designed with 4 acrylic cylinders. One cylinder was filled with distilled water, and the other 3 were filled with 3 types of bone substitute: namely, Nanobone, Cenobone, and Cerabone. The phantom was scanned with 2 CBCT systems using 2 different FOV sizes, and 1 MDCT system was used as the gold standard. The mean gray values (MGVs) of each cylinder were calculated in each imaging protocol.
RESULTS
In both CBCT systems, significant differences were noted in the MGVs of all materials between the 2 FOV sizes (P < .05) except for Cerabone in the Cranex3D system. Significant differences were found in the MGVs of each material compared with the others in both FOV sizes for each CBCT system. No significant difference was seen between the Cranex3D CBCT system and the MDCT system in the MGVs of bone substitutes on images obtained with a small FOV.
CONCLUSION
The size of the FOV significantly changed the MGVs of all bone substitutes, except for Cerabone in the Cranex3D system. Both CBCT systems had the ability to distinguish the 3 types of bone substitutes based on a comparison of their MGVs. The Cranex3D CBCT system used with a small FOV had a significant correlation with MDCT results.

Keyword

Cone-Beam Computed Tomography; Multidetector Computed Tomography; Bone Density

MeSH Terms

Bone Density
Bone Substitutes
Cone-Beam Computed Tomography*
Multidetector Computed Tomography*
Phantoms, Imaging
Water
Bone Substitutes
Water

Figure

• 

  Fig. 1 A. Schematic view shows the radiographic phantom constructed with 4 different materials. B. The radiographic phantom is positioned in a cone-beam computed tomography system.

• 

  Fig. 2 Samples of cone-beam computed tomographic images and selection of the region of interest for calculating the mean gray value (MGV), using the Cranex 3D system with a large field of view (axial cuts). A. Water. B. Nanobone. C. Cenobone. D. Cerabone.

• 

  Fig. 3 Multidetector computed tomography images. A. Water. B. Nanobone. C. Cenobone. D. Cerabone.

• 

  Fig. 4 Mean gray values of the 4 materials scanned with 2 conebeam computed tomography (CBCT) systems with 2 field-of-view (FOV) sizes and comparison with the results of multidetector computed tomography (MDCT) as the gold standard.

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