Three-dimensional reconstruction of individual cervical vertebrae from cone-beam computed-tomography images

INTRODUCTION

The visualization of cervical vertebral morphology has potential in skeletal age assessment; however, thus far, it has only been described in planar images. The objective of this article is to present a novel segmentation algorithm for automatic 3-dimensional (3D) reconstruction of individual cervical vertebrae from cone-beam computed-tomography (CBCT) volumetric data sets.

METHODS

CBCT data sets of 3 subjects representing different skeletal age groups with no potential health influences on cervical anatomy were identified from a larger subject sample. A visualization toolkit was used to demonstrate the surface topologic shape of cervical vertebrae C1 through C3. The cervical vertebrae were segmented by using a custom algorithm based on individual voxel intensity distribution analysis and propagation from a densitometric start point to generate the whole vertebra. The segmentation algorithm was combined with toolkit visualization to render and save the cervical vertebra in 3D space.

RESULTS

The developed segmentation algorithm separated individual cervical vertebrae successfully. It was robust and efficient. Observed 3D cervical vertebral morphologic features from the 3 examples matched the known 2-dimensional sagittal shape changes of the cervical vertebra with respect to subject age and skeletal maturation.

CONCLUSIONS

Segmentation of individual vertebrae proved possible from CBCT volumetric data sets. This provides a 3D approach to the biologic aging of orthodontic patients by using images of the cervical spine. It also has potential in studying disease processes such as spinal fractures consequent to osteoporosis.

Effects of imaging system and exposure on accurate detection of the second mesio-buccal canal in maxillary molar teeth

OBJECTIVES

The objectives of this study were to determine observer ability to detect the second mesio-buccal canal (MB2) in maxillary molars using analog film, CMOS, and photostimulable phosphor x-ray detectors across a wide range of radiation exposures and to determine the optimal exposures for these modalities accurately detecting presence of the MB2.

RESEARCH DESIGN

Using 6 experimental models with 2 maxillary molars in each, images were generated with the 3 detector modalities at nominal x-ray beam angulations of 0 degrees and 10 degrees across a range of radiation exposures. Observers independently assessed presence of the MB2 in images presented in random order. Horizontal root sections were then evaluated to determine true MB2 presence.

RESULTS

For single images at optimal exposures, the correct number of mesiobuccal canals could be identified 55% of the time for CMOS (RVG 6000), 44% of the time for analog x-ray film (InSight), and 39% of the time for photostimulable phosphor (DenOptix). Statistically significant differences were observed between the imaging modalities (chi2 = 23.4, crucial value = 5.99, P < or = .05). RVG 6000 CMOS outperformed both DenOptix photostimulable phosphor (z score = -5.5) and InSight analog direct exposure x-ray film (z score = 4). Exposure affected the rate of accuracy for MB2 detection across the exposure range tested for RVG 6000 and for film, but not to any appreciable degree for DenOptix.

CONCLUSIONS

The CMOS detector (RVG-6000) performed best for evaluating presence of the MB2. This was the only modality to exceed 50% reliability with optimal exposure when single images were considered.

Time and motion study: a comparison of two photostimulable phosphor imaging systems used in dentistry

OBJECTIVES

To compare two photostimulable phosphor (PSP) dental radiographic systems in terms of time efficiency in making full mouth intraoral X-ray surveys (FMS).

METHODS

PSP systems compared were (1) DenOptix) (Kavo/Gendex, Des Plaines, IL) and (2) ScanX) (Air Techniques, Hicksville, NY). Twenty one FMS of a DXTRR) Manikin (Dentsply, Des Plaines, IL) were made with each of the systems. Time for each procedural step was determined using a stopwatch. Steps studied were: (1) plate erasure; (2) packaging; (3) positioning/exposure; (4) unpacking, loading processor, scanning; and (5) image transfer to virtual FMS mount. The first six test runs for each system were excluded to eliminate the learning curve period influencing results. An independent groups t-test was employed for statistical analysis. The a priori was set at P< or =0.05.

RESULTS

The total time involved in producing a FMS was not proven to be statistically significant comparing DenOptix) and ScanX). The mean procedure time for DenOptix) was 31.2 min; for ScanX) it was 27.1 min. While the processing time with ScanX) (mean time: 3.9 min) was shorter than for DenOptix) (mean time =7.8 min), the opposite was true for the image transfer to FMS format with the time much shorter with DenOptix) using VixWin) software (mean time =2.0 min) compared with ScanX) using Vipersoft) (mean time =3.9 min). The differences between the systems for these two steps did prove to be statistically significant (P< or =0.05).

CONCLUSIONS

Although the mean time to make a FMS was slightly shorter on average with ScanX) than DenOptix), this difference was not proven to be statistically significant (P>0.05) in terms of time efficiency in producing a FMS.

Development of imaging selection criteria and procedures should precede cephalometric assessment with cone-beam computed tomography

Cone-beam computed tomography (CBCT) systems for craniofacial imaging are now available from several manufacturers. CBCT potentially provides opportunities for 3-dimensional cephalometrics in orthodontic assessment of bony landmarks and air-bounded surfaces such as the facial skin. Two-dimensional cephalogram simulation could facilitate the transfer of growth projections from existing data sets as a starting point for use of a new 3-dimensional paradigm. Three methods are described to simulate conventional 2-dimensional cephalograms from CBCT images and volumetric data sets. However, certain precautions are required to assure that selection criteria and imaging parameters guarantee a radiation dose that is as low as reasonably achievable.

Effects of scintillator on the modulation transfer function (MTF) of a digital imaging system

OBJECTIVE

To investigate the effects of 2 components (scintillator and x-ray generator) in the imaging chain on the modulation transfer function (MTF) of a charge-coupled device (CCD) digital intraoral radiographic system.

STUDY DESIGN

Three screens composed of 3 different scintillator materials, namely europium-doped lutetium oxide transparent optical ceramic (TOC), thallium-doped cesium iodide (CsI), and terbium-doped gadolinium oxysulfide (GOS), were compared. Each was used, in turn, in conjunction with a CCD detector having a pixel dimension of 19.5 mum. Two different x-ray generators were also used to evaluate this variable. MTF was investigated using the slanted slit method.

RESULTS

The TOC provided a good modulation response for low and middle frequencies, reducing to 0 only at a high cutoff frequency. With CsI and GOS, the system MTF dropped to 0 at a lower cutoff frequency than was the case with TOC. Hence, TOC provided higher spatial resolution than the other 2 scintillators tested under the experimental conditions applied. The differences in MTF attributed to the scintillator type were proportional and consistent.

CONCLUSIONS

Despite constant pixel dimensions, MTF was affected to a considerable degree by the scintillator applied and the x-ray generator used in conjunction with the same CCD imaging device. TOC shows potential as a possible replacement for CsI and GOS as a scintillator screen material for intraoral digital x-ray imaging using a solid-state detector, providing higher spatial resolution under the given experimental conditions.

Clinical applications of cone-beam computed tomography in dental practice

Cone-beam computed tomography (CBCT) systems have been designed for imaging hard tissues of the maxillofacial region. CBCT is capable of providing sub-millimetre resolution in images of high diagnostic quality, with short scanning times (10-70 seconds) and radiation dosages reportedly up to 15 times lower than those of conventional CT scans. Increasing availability of this technology provides the dental clinician with an imaging modality capable of providing a 3-dimensional representation of the maxillofacial skeleton with minimal distortion. This article provides an overview of currently available maxillofacial CBCT systems and reviews the specific application of various CBCT display modes to clinical dental practice.

A Cochrane Systematic Review Finds No Evidence to Support the Use of Antibiotics for Pain Relief in Irreversible Pulpitis

The Cochrane Systematic Review promotes evidence-based outcomes studies. The review summarized here was conducted in an attempt to achieve reliable evidence concerning the effectiveness, or otherwise, of prescribing antibiotics for patients having irreversible pulpitis. A competent search strategy was developed and used across several databases including MEDLINE to identify randomized controlled trials for inclusion. Assessment of methodological quality was based on criteria defined by The Cochrane Collaboration. Clinical outcome, expressed in terms of pain relief, was examined. There was a relative dearth of research providing a high level of evidence. Only one methodologically sound trial was found that compared pain relief with systemic antibiotic/analgesic treatment against a placebo/analgesic combination during the acute preoperative phase of irreversible pulpitis. Although the selected study used a relatively small, low-powered sample, it did provide some evidence that there is no significant difference in pain relief for patients with untreated irreversible pulpitis who received antibiotics versus those who did not. These findings increase the rationale to investigate the teaching of safe and effective antibiotic prescribing in endodontics and to advance the development of appropriate evidence-based clinical guidelines.

Accuracy of linear temporomandibular joint measurements with cone beam computed tomography and digital cephalometric radiography

INTRODUCTION

Cone beam computed tomography (CBCT) is making headway into imaging for orthodontics. The purpose of this study was to define CBCT multi-planar reformatted projections for temporomandibular joint (TMJ) examination and compare the accuracy of linear measurements of the TMJ and related structures from these projections with similar measurements made with conventional cephalograms and with the anatomic truth.

METHODS

Linear dimensions between 11 anatomical sites were measured with a digital caliper to assess the anatomic truth for 25 dry human skulls. The skulls were imaged with iCAT (Xoran Technologies, Ann Arbor, Mich/Imaging Sciences International, Hatfield, Pa) CBCT, and cephalograms were made in all 3 orthogonal planes (lateral cephalometric [LC], posteroanterior [PA], and submentovertex [SMV]) acquired with photostimulable phosphor plates. Linear measurements were made on 7 custom CBCT reconstructions and the digital cephalograms. Modality means and the natural log of the standard deviations were compared post hoc against the actual dimensions by using analysis of variance with the Dunnett t test. Significance was set at P < .05.

RESULTS

All CBCT measurements were accurate; however, 3 of 5 LC measurements, 4 of 5 PA measurements, and 4 of 6 SMV measurements varied significantly from the truth. Intraobserver CBCT measurements were highly reliable compared with anatomic truth and significantly more reliable than measurements made from LC, PA, and SMV images.

CONCLUSIONS

Custom oblique multi-planar reformatted reconstructions with iCAT CBCT provide accurate and reliable linear measurements of mandibular and TMJ dimensions.

Effects of scintillator on the detective quantum efficiency (DQE) of a digital imaging system

OBJECTIVE

To compare the effects of scintillator on the detective quantum efficiency (DQE) of a charge-coupled device (CCD) digital intraoral radiographic system.

STUDY DESIGN

Three screens composed of 3 different scintillator materials, namely europium-doped lutetium oxide (Lu2(O3):Eu3+), transparent optical ceramic (TOC), thallium-doped cesium iodide (CsI:Tl; CsI), and terbium-doped gadolinium oxysulfide (Gd2(O2)S:Tb; GOS) were compared, in turn, in combination with a CCD detector having square pixels with height and width dimensions of 19.5 microm. DQE was investigated using the slanted-slit-derived MTF and surrogate signal-to-noise ratio (SNR) measurements derived from calculations of the mean and standard deviations from the mean pixel values of multiple random patches from various uniform exposures. An Irix x-ray generator operated at 70 kVp and 8 mA, with a nominal focal spot size of 0.7 mm and 2.5 mm Al equivalent filtration, was used in making all exposures.

RESULTS

Using TOC, the peak DQE was 62% at 5 cycles/mm. For CsI, the peak DQE was 22% at 2 cycles/mm. With GOS, the peak DQE was 10% at 1 cycle/mm.

CONCLUSION

Under identical experimental settings, TOC consistently resulted in higher DQE than CsI and commercially available GOS scintillators combined with the same high-resolution solid-state detector.

Applying DICOM to dentistry

There are more than 160,000 dentists licensed in the United States. For the dental patient, the dentist is both radiologist and treating clinician. The American Dental Association (ADA) has been a member of the Digital Imaging and Communication in Medicine (DICOM) Standard Committee since 1996. DICOM v.3 provides image object definitions for digital transmission radiography (Dx) with special categorization for intraoral projections (Io), and it also provides for color photography used in dentistry. Digital dental radiographs include transmission images of the head and jaws, pantomography, tomography and cone-beam computed tomography. In 2000, the ADA resolved to strive for interoperability of digital dental images, using the DICOM Standard as the backbone of the effort. ADA Working Group 12.1 was tasked with development of specifications and also with educating the dental profession concerning digital image interoperability. DICOM-related interoperability demonstrations are now a part of the ADA Annual Congress, in the form of seminar and as a noncommercial exhibit.

Antibiotic use for irreversible pulpitis

BACKGROUND

Irreversible pulpitis, which is characterised by acute and intense pain, is one of the most frequent reasons that patients attend for emergency dental care. Apart from removal of the tooth the customary way of relieving the pain of irreversible pulpitis is by drilling into the tooth, removing the inflamed pulp (nerve) and cleaning the root canal. However, a significant minority of dentists continue to prescribe antibiotics to stop the pain of irreversible pulpitis.

OBJECTIVES

The objective of this review was to provide reliable evidence regarding the effectiveness of prescribing systemic antibiotics for irreversible pulpitis by comparing clinical outcomes expressed as pain relief.

SEARCH STRATEGY

We searched the following databases: Cochrane Oral Health Group Trials Register and Pain, Palliative Care and Supportive (PaPaS) Care Group Trials Register to 6th September 2004; the Cochrane Central Register of Controlled Trials (CENTRAL) The Cochrane Library Issue 3 2004; MEDLINE (1966 to 6th September 2004); EMBASE (1980 to week 36 2004).

SELECTION CRITERIA

This review includes one randomised controlled trial which compared pain relief with systemic antibiotics and analgesics, against placebo and analgesics in the acute preoperative phase of irreversible pulpitis.

DATA COLLECTION AND ANALYSIS

Only one trial is included in this review, therefore pooling of data from studies was not possible and a descriptive summary is presented.

MAIN RESULTS

One trial involving 40 participants was included in this review. There was a close parallel distribution of the pain ratings in both the intervention and placebo groups over the 7 day study period. The between-group differences in sum pain intensity differences (SPID) for the penicillin group were (6.0+/-10.5), and for placebo (6.0+/-9.5) P = 0.776. The sum pain percussion intensity differences (SPPID) for the penicillin group were (3.5+/-7.5) and placebo (2.0+/-7.0) P = 0.290, with differences as assessed by the Mann-Whitney-Wilcoxon test considered to be statistically significant at P < 0.05. There was no significant difference in the mean total number of ibuprofen tablets (P = 0.839) and Tylenol tablets (P = 0.325), in either group over the study period. The administration of penicillin over placebo did not appear to significantly reduce the quantity of analgesic medication taken (P > 0.05) for irreversible pulpitis.

AUTHORS' CONCLUSIONS

This review which was based on one methodologically sound but low powered small sample trial provided some evidence that there is no significant difference in pain relief for patients with untreated irreversible pulpitis who did or did not receive antibiotics in addition to analgesics.

A comparison of 18 different x-ray detectors currently used in dentistry

PURPOSE

There has been a proliferation of available dental x-ray detectors over the recent past. The purpose of this short technical report is to provide a basic comparison of spatial resolution, contrast perceptibility, and relative exposure latitudes of 18 current dental x-ray detectors, including solid-state systems (CCD and CMOS), photostimulable phosphors, and analog film.

METHODS

Spatial resolution was measured using a 0.025 mm Pb phantom test grid with a measurement range from 1.5 to 20 lp/mm. For contrast perceptibility, a 7-mm thick aluminum perceptibility test device with wells of 0.1-0.9 mm depth at 0.1 mm intervals and 1 defect of 1.5 mm was used. The relative exposure latitude was determined by expert consensus using clear discrimination of the enamel-dentin junction as the lower limit and pixel blooming or unacceptable levels of cervical burnout as the upper limit.

RESULTS

The highest spatial resolution was found with Kodak InSight film, RVG-ui (CCD), and RVG 6000 (CMOS) detectors, each of which achieved 20 lp/mm, followed by the Planmeca Dixi2 v3 at > or =16 lp/mm. Contrast resolution was at least to 0.2 mm through 7 mm aluminum for all 18 detectors, with the best results being found for the Visualix HDI, RVG-ui, RVG 5000, and RVG 6000 detectors and the Schick CDR wired and wireless systems. The greatest exposure ranges were found with photostimulable phosphors and the Kodak RVG 6000 and RVG 5000 detectors.

CONCLUSIONS

Most current x-ray detectors generally perform well in terms of spatial and contrast resolutions, and in terms of exposure latitude. These findings were independent of the modality applied.