Marcel Noujeim

Evaluation of high-resolution cone beam computed tomography in the detection of simulated interradicular bone lesions

OBJECTIVES The purpose of this study is to assess the accuracy of limited-volume high-resolution cone beam CT (CBCT) in the detection of periodontal bone loss. METHODS 163 simulated periodontal lesions of different depths were created in dried human hemimandibles. Specimens were imaged using the intraoral paralleling technique and limited-volume CBCT (3DX Accuitomo; Morita Co. Ltd, Kyoto, Japan). Ten viewers examined the images. Data were analysed with receiver operating characteristics (ROC) analysis. ROC curves were generated and the areas under the maximum-likelihood curves (A(z)) were compared. Other statistical analyses were used to detect the normality of the distribution of the results. RESULTS The results are reported as the individual viewer ROC curve areas for each of the two imaging modalities. In all experiments the A(z) area for CBCT (0.770-0.864) was larger than the A(z) area for periapical film (0.678-0.783); statistical tests showed a statistically significant difference between the two modalities. CONCLUSIONS Results indicate that the CBCT technique has better accuracy and diagnostic value than periapical films in the detection of interradicular periodontal bone defects.

Metal artefact reduction with cone beam CT: an in vitro study

BACKGROUND Metal in a patients mouth has been shown to cause artefacts that can interfere with the diagnostic quality of cone beam CT. Recently, a manufacturer has made an algorithm and software available which reduces metal streak artefact (Picasso Master 3D® machine; Vatech, Hwaseong, Republic of Korea). OBJECTIVES The purpose of this investigation was to determine whether or not the metal artefact reduction algorithm was effective and enhanced the contrast-to-noise ratio. METHODS A phantom was constructed incorporating three metallic beads and three epoxy resin-based bone substitutes to simulate bone next to metal. The phantom was placed in the centre of the field of view and at the periphery. 10 data sets were acquired at 50-90 kVp. The images obtained were analysed using a public domain software ImageJ (NIH Image, Bethesda, MD). Profile lines were used to evaluate grey level changes and area histograms were used to evaluate contrast. The contrast-to-noise ratio was calculated. RESULTS The metal artefact reduction option reduced grey value variation and increased the contrast-to-noise ratio. The grey value varied least when the phantom was in the middle of the volume and the metal artefact reduction was activated. The image quality improved as the peak kilovoltage increased. CONCLUSION Better images of a phantom were obtained when the metal artefact reduction algorithm was used.

Cone beam CT scans with and without artefact reduction in root fracture detection of endodontically treated teeth

OBJECTIVES Cone beam CT (CBCT) is used widely to depict root fracture (RF) in endodontically treated teeth. Beam hardening and other artefacts due to gutta-percha may increase the time of the diagnosis and result in an incorrect diagnosis. Two CBCT machines, ProMax(®) (Planmeca, Helsinki, Finland) and Master 3D(®) (Vatech, Hwaseong, Republic of Korea), have the option of applying an artefact reduction (AR) algorithm. The aim of this study was to determine whether using an AR algorithm in two CBCT machines enhances the accuracy of detecting RFs in endodontically treated teeth. METHODS 66 roots were collected and decoronated. All roots were treated endodontically using the same technique with gutta-percha and zinc oxide cement. One-half of the roots were randomly selected and fractured using a nail that was tapped gently with a hammer until complete fracture resulted in two root fragments; the two root fragments were glued together with one layer of methyl methacrylate. The roots were placed randomly in eight prepared beef rib fragments. RESULTS The highest accuracy was obtained when the ProMax was used without AR. The lowest accuracy was obtained with the Master 3D when used with AR. For both machines, accuracy was significantly higher without AR than with AR. Both with and without AR, the ProMax machine was significantly more accurate than the Master 3D machine. The same rank ordering was obtained for both sensitivity and specificity. CONCLUSIONS For both machines, AR decreased the accuracy of RF detection in endodontically treated teeth. The highest accuracy was obtained when using the ProMax without AR.

Evaluation of a cone beam CT artefact reduction algorithm

OBJECTIVES An algorithm and software to reduce metal artefact has been developed recently and is available in the Picasso Master 3D® (VATECH, Hwaseong, Republic of Korea), which under visual assessment produces better quality images than were obtainable previously. The objective of this in vitro study was to investigate whether the metal artefact reduction (MAR) algorithm of the Picasso Master 3D machine reduced the incidence of metal artefacts and increased the contrast-to-noise ratio (CNR) while maintaining the same gray value when there was no metallic body present within the scanned volume. METHODS 20 scans with a range of 50-90 kVp were acquired, of which 10 had a metallic bead inserted within a phantom. The images obtained were analysed using public domain software (ImageJ; NIH Image, Bethesda, MD). Area histograms were used to evaluate the mean gray level variation of the epoxy resin-based substitute (ERBS) block and a control area. The CNR was calculated. RESULTS The MAR algorithm increased the CNR when the metallic bead was present; it enhanced the ERBS gray level independently of the presence of the metallic bead. The image quality also improved as peak tube potential was increased. CONCLUSION Improved quality of images and regaining of the control gray values of a phantom were achieved when the MAR algorithm was used in the presence of a metallic bead.

Applications of cone-beam computed tomography in fractures of the maxillofacial complex

Imaging plays an essential role in the evaluation of maxillofacial fractures both pre- and postoperatively. Several studies support the use of conventional two-dimensional imaging for traumas involving mainly the mandible, but for more complex situations advanced imaging modalities such as computed tomography (CT) and magnetic resonance imaging have higher indication. Nowadays, besides CT, cone-beam computed tomography (CBCT) has appeared as a reasonable and reliable alternative considering radiation dosage, image quality and comfort for the patient. The purpose of this study was to review the fracture patterns involving the maxillofacial complex, provide a technical and practical comparison between CT and CBCT, and finally present the potential applications of CBCT illustrated with clinical examples.

Accuracy of Cone Beam Computed Tomography in Determining the Location of the Genial Tubercle

OBJECTIVE: To determine the accuracy of cone beam computed tomography (CT) to predict the location of the genial tubercle. STUDY DESIGN AND SETTING: Cadaver study for anatomic analysis of 17 adult human cadaver heads. Each skull/cadaver head underwent radiographic imaging with cone beam CT and cadaver dissection. Measurements, including mandibular height (MH), genial tubercle width (GTW), genial tubercle height (GTH), distance from inferior border of mandible to genial tubercle (IBM/GT), and mandibular thickness (MT) were recorded. RESULTS: Statistical analysis with paired t test showed no significant difference between cadaver dissections versus cone beam measurements. Ninety-five percent confidence intervals (CI) were as follows: GTW (−0.2 to 1.0), GTH (−0.1 to 0.9), distance IBM/GT (−0.8 to 5.0), MH (−1.3 to −2.6), and MT (−0.1 to 0.3). CONCLUSION: These results show the accuracy of the 3D cone beam CT in the anatomic location of the genial tubercle. SIGNIFICANCE: This radiographic technique may prove useful in pre-operative planning for the mandibular osteotomy in genioglossus advancement procedures.

Development of a new dental panoramic radiographic system based on a tomosynthesis method.

The objective of this study was to develop a new practical method to reconstruct a high-quality panoramic image in which radiographers would be free from the onerous task of correctly locating the patients jaws within the image layer of the panoramic unit. In addition, dentists would be able to freely select any panoramic plane to be reconstructed after the acquisition of the raw scan data. A high-speed data acquisition device was used with a CdTe (cadmium telluride) semiconductor detector and a sophisticated digital signal-processing technique based on tomosynthesis was developed. The system processes many vertical strip images acquired with the detector and generates a high-resolution and high-contrast image. To apply the tomosynthesis technique to the acquired strip images correctly, the actual movement of the panoramic unit was measured, including the X-ray tube and detector, in a scan using a calibration phantom and the authors generated a shift amount table needed for the shift-and-add tomosynthesis operation. The results of the experiments with a PanoACT-1000 panoramic unit, which was a PC-1000 panoramic unit fitted with a high frame rate semiconductor detector SCAN-300FPC, demonstrated the capability of a tomosynthesis technique which, when applied to the strip images of a dry skull phantom, could change the location and inclination of an imaging plane. This system allowed the extraction of an optimum-quality panoramic image regardless of irregularities in patient positioning. Moreover, the authors could freely reconstruct a fine image of an arbitrary plane with different parameters from those used in the original data acquisition to study fine anatomical details in specific locations.

Sodium hypochlorite accident with evaluation by cone beam computed tomography

AIM To show the radiographic manifestation of sodium hypochlorite after accidental injection past the apical foramen and into the soft tissues. SUMMARY A female patient was seen for an emergency visit after suffering a sodium hypochlorite accident at her general dentists office. The patient was seen within 1 h of the accident and was in pain associated with facial swelling. Radiographs, including a Cone Beam Computed Tomography (CBCT), and photographs were taken. Endodontic emergency treatment was initiated. The patient was reassured and given pain medication and antibiotics. Follow-up visits were scheduled over 6 days when the swelling had resolved. KEY LEARNING POINTS • Importance of multiple radiographic images during preoperative endodontic evaluation when undertaking endodontic retreatment. • Knowledge of apical anatomy as related to surrounding structures. • Effect of sodium hypochlorite when injected in the soft tissues.

Number of basis images effect on detection of root fractures in endodontically treated teeth using a cone beam computed tomography machine: an in vitro study

OBJECTIVES The objective of this study was to compare the accuracy of root fracture detection in endodontically treated teeth using scans acquired with a 180° rotation motion compared with a 360° after which the patient exposure and number of basis images are doubled. METHODS Sixty-six roots were collected and decoronated. All were treated endodontically. One-half of the roots were fractured, resulting in 2 root fragments which were then glued together. The roots were placed randomly in 8 prepared beef rib fragments. Five reviewers independently reviewed the scans twice, at different times. RESULTS The specificity of the 360° scan was significantly higher than the 180° scan; doubling the basis images leads to a significant decrease in false-positive rates. Accuracy and sensitivity were not significantly different. CONCLUSIONS Only the specificity is improved by the increased rotation and doubling of images. The accuracy and sensitivity are not improved.

Comparison of cone beam CT scans with enhanced photostimulated phosphor plate images in the detection of root fracture of endodontically treated teeth

OBJECTIVES Two-dimensional intraoral radiography is the most common tool for diagnosing root fractures (RFs). Cone beam CT (CBCT) is widely used to depict RFs in endodontically treated teeth. Beam hardening and other artefacts caused by gutta percha may result in an incorrect diagnosis when using CBCT only. A comparison of two CBCT machines with photostimulated phosphor (PSP) plate images enhanced with the equalization tool was carried out to detect RFs in endodontically treated teeth. METHODS 66 roots were collected, decoronated and treated endodontically using the same technique with gutta percha. 33 of these roots were randomly selected and fractured; the 2 root fragments were glued together with 1 layer of methyl methacrylate and placed randomly in 8 prepared beef rib fragments. Large fields of view (FOVs) were acquired with one CBCT unit and small FOVs with the second CBCT unit. Periapical radiographs (using intraoral PSP plates) were also acquired. A contrast enhancement tool was used when evaluating the PSP plate images. RESULTS Small FOV images had significantly higher accuracy (area under the receiver operating characteristic curve) and sensitivity in detecting RFs than PSP plates and large FOV images. The specificity of the enhanced PSP images was higher than, although not significantly higher than, the small FOV images and was significantly higher than the large FOV images. CONCLUSIONS CBCT small FOVs should be acquired for depicting RFs of endodontically treated teeth. Images obtained using PSP plates had the lowest rate of false-positive results and their use can save the patient a radiation dose.