Boulos Bechara

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.

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.

Contrast-to-noise ratio with different large volumes in a cone-beam computerized tomography machine: An in vitro study

OBJECTIVES The objectives were to determine whether the images obtained from different cone-beam computerized tomography (CBCT) field of view (FOV) sizes with varying scan time and kilovolt peak using the Picasso Master 3D machine (Vatech, Hwasung, South Korea) differ in contrast-to-noise ratio (CNR). STUDY DESIGN A phantom was used. Scans were acquired using the same voxel size, 2 scan times (15 and 24 seconds) for 3 different FOV sizes and 5 different kilovolt peaks. The contrast and CNR were calculated for each FOV. RESULTS The CNRs were similar for the 2 scan times for all 3 FOV sizes. The CNR was lower in the 20 × 19 cm FOV compared with the other 2 FOVs for both scan times. CONCLUSIONS The CNR does not vary significantly with increasing scan times for all FOV sizes. Smaller FOVs result in enhanced CNR and contrast.

Evaluation and Reduction of Artifacts Generated by 4 Different Root-end Filling Materials by Using Multiple Cone-beam Computed Tomography Imaging Settings.

INTRODUCTION After endodontic surgery, radiographic assessment is the method of choice to monitor bone defect healing. Cone-beam computed tomography scans are useful to check and identify the reasons of failure of surgical intervention or confirm healing; however, the artifact generated by some root-end filling material might compromise this task. The objective of the study was to compare the amount of artifacts generated by 4 root-end filling materials and to test multiple exposure settings used with these materials, when the effective dose generated by each protocol was taken into consideration. METHODS Twenty central incisors were endodontically treated with retrograde obturation by using amalgam, Biodentine, MTA, and Super-EBA (5 of each). They were placed in a skull with soft tissue simulation and scanned by using the Planmeca Promax Max with different kilovolt peaks (kVp): 66, 76, 84, and 96 with and without the use of metal artifact reduction (MAR) algorithm and with low, normal, and high resolution and high definition. The Dose Area Product was registered, and the effective dose was calculated. RESULTS Amalgam generated the highest amount of artifacts, whereas MAR and low resolution created fewer artifacts than other settings. The artifacts were also reduced with 96 kVp. The effective dose calculated with low resolution was remarkably lower than other resolutions. CONCLUSIONS When used as root-end filling material, Biodentine, MTA, and Super-EBA generated fewer artifacts than amalgam. The use of 96 kVp with MAR and low resolution also reduced artifacts on the image and at the same time generated the lowest effective dose.

Contrast-to-noise ratio with different settings in a CBCT machine in presence of different root-end filling materials: an in vitro study

OBJECTIVES To compare the contrast-to-noise ratio (CNR) of multiple acquisition settings for four types of retrograde filling materials in CBCT images taken for endodontic surgery follow-up. METHODS 20 maxillary central incisors were endodontically treated and obturated with 4 different root-end filling materials: amalgam, mineral trioxide aggregate, SuperEBA(™) (Harry J Bosworth Company, Skokie, IL) and Biodentine™ (Septodont, Saint-Maur-des-Faussés, France). Teeth were placed in a skull and scanned, one by one, with the Planmeca ProMax(®) 3D Max (Planmeca, Helsinki, Finland); at different voltages: 66, 76, 84 and 96 kVp; with low, normal and high resolution and high definition (HD); with and without metal artefact reduction (MAR). Images were analyzed using ImageJ software (National Institutes of Health, Bethesda, MD) to calculate the CNR. The dose-area product was registered, and the effective dose calculated. RESULTS No statistically significant difference was noted between the four materials. 84 and 96 kVp with low resolution and the use of MAR-generated images that have statistically better CNR than 66 and 76 kVp with HD, normal and high resolutions and without MAR. The use of low resolution also generated the smallest value of effective dose. CONCLUSIONS The best setting for radiographic follow-up in an endodontic surgery with retrograde filling on the Planmeca ProMax is 96 kVp with low resolution and high MAR; this setting produced one of the lowest effective doses.

Effect of JPEG compression on the diagnostic accuracy of periapical images in the detection of root fracture

The ability of a periapical radiograph to exhibit the fracture depends on many factors including, but not limited to, the resolution of the image. The quality can be reduced by the image compression. The purpose of this study is to evaluate the effect of Joint Photographic Experts Group (JPEG) compressions on the diagnostic capability of periapical images in the detection of root fractures. Ten dry human mandibles containing 151 teeth were used in this study. Mandibles were radiographed with direct digital imaging sensor using the paralleling technique. Four observers detected root fracture on the images saved in one uncompressed and two compressed formats. Receiver operating characteristic (ROC) and anova analyses were performed to compare the performance of the three different systems and evaluate the effect of the compression on the accuracy of root fracture detection. Results did not show any statistically significant difference between the original, large images presented in tagged image file format (TIFF) and the two compressed images (JPEG medium file and JPEG small file images) in the detection of root fractures. The intra-rater comparison showed a significant consistency in the detection of the fracture. The compression reduced the file size considerably (from 1.77 MB to 453 and 95 Kb), but it did not affect the accuracy of root fracture detection. The file size reduction, on the other hand, is very beneficial for image electronic storage and mainly in teleradiology.

Location of Posterosuperior Alveolar Artery and Correlation with Maxillary Sinus Anatomy.

The blood supply to both the lateral wall of the maxillary sinus and the overlying membrane originates from the posterosuperior alveolar artery (PSAA) and the infraorbital artery. The purpose of the present study was to evaluate the anatomic characteristics of the PSAA in a large number of subjects of the Lebanese population. Images of 696 sinuses were analyzed using cone beam computed tomography (CT). Coronal, axial, and sagittal CT images were evaluated for the presence of an osseous canal in the lateral wall of the sinus, and the prevalence, position, and location of the canal were studied and presented.