A comparison of jaw dimensional and quality assessments of bone characteristics with cone-beam CT, spiral tomography, and multi-slice spiral CT.

PURPOSE: For proper preoperative planning of oral implants, the need has increased for tomographic imaging for precise determination of anatomic dimensions. However, concern for radiation exposure, which is substantial with computerized tomography (CT), has also grown. In the present study, the validity of jawbone width assessment and delineation by means of cone-beam CT (CBCT) and spiral tomography on dry mandibles was compared. Secondly, the subjective image quality of CBCT images with those obtained by multi-slice spiral CT (MSCT) of a fixed ex vivo cadaver with its soft tissues was compared. MATERIALS AND METHODS: The study included 25 dry human mandibles for the dimensional study and 1 formalized maxilla for image quality assessment. Measurements of the mandibles by means of a digital sliding caliper acted as the gold standard. Radiographic examination of the premolar and canine regions was performed with both CBCT and spiral tomography. Observational measurements were carried out by postgraduates in oral imaging. Subjective image quality was assessed on the fixed maxilla, including soft tissues, by comparing CBCT and MSCT. Inter- and intraobserver variability were determined. RESULTS: Direct mandibular measurements were on average 0.23 mm (SD 0.49) and 0.34 mm (SD 0.90) larger than the CBCT and spiral tomography measurements, respectively. Subjective image quality of the CBCT was significantly better than for the MSCT with regard to visualization and delineation of the lamina dura and periodontal ligament space. Subjective image quality of the MSCT was significantly better for the MSCT than the CBCT for the gingiva and cortical bone. CONCLUSIONS: These results indicate that on dry mandibles, jawbone width measurements by means of CBCT and spiral tomography are reliable, even if on average they slightly underestimate the bone width. For the subjective image quality, the CBCT offered better visualization of details of the small bony structures. Spiral tomography offered better visualization of the cortical bone and the gingiva.

Semi-automated ultrasound facial soft tissue depth registration: method and validation.

A mobile and fast, semi-automatic ultrasound (US) system was developed for facial soft tissue depth registration. The system consists of an A-Scan ultrasound device connected to a portable PC with interfacing and controlling software. For 52 cephalometric landmarks, the system was tested for repeatability and accuracy by evaluating intra-observer agreement and comparing ultrasound and CT-scan results on 12 subjects planned for craniofacial surgery, respectively. A paired t-test evaluating repeatability of the ultrasound measurements showed 5.7% (n = 3) of the landmarks being significantly different (p < 0.01). US and CT-scan results showed significant differences (p < 0.01) using a Wilcoxon signed rank test analysis for 11.5% (n = 6) of the landmarks. This is attributed to a difference in the volunteer's head position between lying (CT) and sitting (US). Based on these tests, we conclude that the proposed registration system and measurement protocol allows relatively fast (52 landmarks/20 min), non-invasive, repeatable and accurate acquisition of facial soft tissue depth measurements.

State-of-the-art on cone beam CT imaging for preoperative planning of implant placement.

Orofacial diagnostic imaging has grown dramatically in recent years. As the use of endosseous implants has revolutionized oral rehabilitation, a specialized technique has become available for the preoperative planning of oral implant placement: cone beam computed tomography (CT). This imaging technology provides 3D and cross-sectional views of the jaws. It is obvious that this hardware is not in the same class as CT machines in cost, size, weight, complexity, and radiation dose. It is thus considered to be the examination of choice when making a risk-benefit assessment. The present review deals with imaging modalities available for preoperative planning purposes with a specific focus on the use of the cone beam CT and software for planning of oral implant surgery. It is apparent that cone beam CT is the medium of the future, thus, many changes will be performed to improve these. Any adaptation of the future systems should go hand in hand with a further dose optimalization.

Assessment of bone segmentation quality of cone-beam CT versus multislice spiral CT: a pilot study.

OBJECTIVES: The objective of this study was to quantitatively assess the quality of jawbone models generated from cone beam computed tomography (CBCT) by comparison with similar models obtained from multislice spiral computed tomography (MSCT). MATERIAL AND METHODS: Three case studies were performed involving images of anthropomorphic head phantoms and real patients acquired with 3 CBCT (NewTom 9000 DVT, Accuitomo 3D, and i-CAT) and 2 MSCT scanners (Somatom VolumeZoom and Lightspeed). Bone was segmented from the CBCT and MSCT images using global thresholding. CBCT vs MSCT segmentation differences were assessed by comparing bone thickness measurements at anatomically corresponding sites, identified automatically by CBCT to MSCT image registration. RESULTS: There was a statistically significant difference between the MSCT and CBCT segmented bone thicknesses, varying from 0.05 +/- 0.47 mm (i-CAT) up to 1.2 +/- 1.00 mm (3D Accuitomo, posterior maxilla). CONCLUSIONS: An automated, reproducible, and observer-independent method has been developed to assess the quality of CBCT bone models using MSCT as a clinically established method of reference. Our validation method is generally applicable in cases where no geometric ground-truth is available.