A comparative evaluation of Cone Beam Computed Tomography (CBCT) and Multi-Slice CT (MSCT). Part II: On 3D model accuracy

https://doi.org/10.1016/j.ejrad.2009.04.016Get rights and content

Abstract

Aim

The study aim was to compare the geometric accuracy of three-dimensional (3D) surface model reconstructions between five Cone Beam Computed Tomography (CBCT) scanners and one Multi-Slice CT (MSCT) system.

Materials and methods

A dry human mandible was scanned with five CBCT systems (NewTom 3G, Accuitomo 3D, i-CAT, Galileos, Scanora 3D) and one MSCT scanner (Somatom Sensation 16). A 3D surface bone model was created from the six systems. The reference (gold standard) 3D model was obtained with a high resolution laser surface scanner. The 3D models from the five systems were compared with the gold standard using a point-based rigid registration algorithm.

Results

The mean deviation from the gold standard for MSCT was 0.137 mm and for CBCT were 0.282, 0.225, 0.165, 0.386 and 0.206 mm for the i-CAT, Accuitomo, NewTom, Scanora and Galileos, respectively.

Conclusion

The results show that the accuracy of CBCT 3D surface model reconstructions is somewhat lower but acceptable comparing to MSCT from the gold standard.

Introduction

Successful dental implant rehabilitation requires accurate pre-operative surgical planning. Crucial to its success is accurate positioning of the implant prosthesis in the jaw to avoid damaging vital nervous and vascular structures. To realize those objectives, contemporary planning techniques rely on three-dimensional (3D) surface model representations of the jaw bone obtained from computed tomography (CT) scans [1], [2]. The 3D surface models can be used to plan the implant procedure pre-operatively and also to create physical cast models of the jaws using stereolithography technology [3], [4]. Those models facilitate surgical Implant placement procedure in conjunction with appropriate pre-operative planning [5].

Cone Beam Computed Tomography (CBCT) technology has been used for pre-operative implant planning, evaluation of the jaws and preliminary assessment of the bone volume required for orthognathic surgery [6], [7], [8]. CBCT provides images of diagnostic quality with reasonably low radiation dose [9], [10]. CBCT is used to create different two-dimensional (2D) tomographic slices and projection images as well as 3D volume and surface reconstructions. The geometric accuracy of CBCT based on phantom and dry skulls with metallic markers samples is well established [11], [12], [13], [14]. Also, 2D tomographic slices and projection images reconstructions were found to be highly accurate in comparison with physical measurements [15], [16].

However, the accuracy of 3D surface models reconstructions from CBCT has not yet been thoroughly evaluated. The quality of those models is largely dependent on the scanner type, scanning parameters and reconstruction settings [17]. Recently, the accuracy of CBCT 3D surface and volume reconstructions based on linear cephalometric measurements has been estimated to be within 1–2 mm [18], [19]. However, the accuracy of the linear measurements in those studies is both observer and landmark dependent. A method that matches CBCT 3D model with a ‘reference’ 3D model using point-based registration algorithm was proposed and used to evaluate the total geometric accuracy of CBCT 3D surface models [6]. This method is completely automatic and observer-independent and it evaluates the entire bone surface. The objective of this study is to assess the accuracy of 3D surface model from five clinical CBCT scanners in comparison with 3D surface models obtained from multi-slice CT (MSCT). A high resolution laser surface scanner is used to create the reference ‘gold standard’ 3D model.

Section snippets

Materials and methods

One dry human mandible was obtained with approval from the Institute for Biomedical Research (BIOMED of University Hasselt, Belgium). The mandible was first scanned by a XC50 Cross Scanner® (Metris, Leuven, Belgium) with three laser planes, mounted on a Wenzel LH57 3D coordinate measurement machine (Fig. 1). The laser scanner allows obtaining surfaces in the form of a point cloud with an accuracy of 15 μm. The mandible was placed in a plastic container and embedded in water to provide some level

Results

Mean deviations of the CBCT and MSCT measurements from the gold standard are summarized in Table 2. All deviations were statistically significant at p = 0.05, however, most deviations were small that their relevance is limited. MSCT had the least mean deviation (0.137) while for CBCT it was between 0.165 and 0.386 mm. The matching fit level of each model was marked with a colour bar. The mandibular border, posterior margins and some teeth margins were the parts that did not fit well with the laser

Discussion

This study was conducted to assess and compare the geometric accuracy of 3D surface model reconstructions from five clinical dental CBCT scanners with that of a clinical MSCT system. The results demonstrate higher segmentation accuracy of MSCT compared to CBCT. This could be due to that MSCT has a higher inherent image contrast with a better contrast to noise ratio in comparison with CBCT systems currently available [21]. The superiority of MSCT is mainly due to higher X-ray throughput and

Conclusion

CBCT still has somewhat lower segmentation accuracy than MSCT. Yet, anatomical landmarks and models are produced in a reliably and clinically applicable way. The accuracy of the mandibular contours was lower than the body because of the halation defects. Considering these results with low radiation, short scanning time and good image quality, CBCT could be helpful for surgery including implant placement in the orofacial region.

References (29)

  • D.P. Sarment et al.

    Accuracy of implant placement with a stereolithographic surgical guide

    Int J Oral Maxillofac Implants

    (2003)
  • D. van Steenberghe et al.

    High precision planning for oral implants based on 3-D CT scanning. A new surgical technique for immediate and delayed loading

    Appl Osseointegration Res

    (2004)
  • D. van Steenberghe et al.

    Accuracy of drilling guides for transfer from three-dimensional CT-based planning to placement of zygoma implants in human cadavers

    Clin Oral Implants Res

    (2003)
  • N. Van Assche et al.

    Accuracy of implant placement based on pre-surgical planning of three-dimensional cone-beam images: a pilot study

    J Clin Periodontol

    (2007)
  • Cited by (0)

    View full text