Cone-beam computed tomography and its applications in dental and maxillofacial radiology

Clinical Super-Resolution Computed Tomography of Bone Microstructure: Application in Musculoskeletal and Dental Imaging

PURPOSE

Clinical cone-beam computed tomography (CBCT) devices are limited to imaging features of half a millimeter in size and cannot quantify the tissue microstructure. We demonstrate a robust deep-learning method for enhancing clinical CT images, only requiring a limited set of easy-to-acquire training data.

METHODS

Knee tissue from five cadavers and six total knee replacement patients, and 14 teeth from eight patients were scanned using laboratory CT as training data for the developed super-resolution (SR) technique. The method was benchmarked against ex vivo test set, 52 osteochondral samples are imaged with clinical and laboratory CT. A quality assurance phantom was imaged with clinical CT to quantify the technical image quality. To visually assess the clinical image quality, musculoskeletal and maxillofacial CBCT studies were enhanced with SR and contrasted to interpolated images. A dental radiologist and surgeon reviewed the maxillofacial images.

RESULTS

The SR models predicted the bone morphological parameters on the ex vivo test set more accurately than conventional image processing. The phantom analysis confirmed higher spatial resolution on the SR images than interpolation, but image grayscales were modified. Musculoskeletal and maxillofacial CBCT images showed more details on SR than interpolation; however, artifacts were observed near the crown of the teeth. The readers assessed mediocre overall scores for both SR and interpolation. The source code and pretrained networks are publicly available.

CONCLUSION

Model training with laboratory modalities could push the resolution limit beyond state-of-the-art clinical musculoskeletal and dental CBCT. A larger maxillofacial training dataset is recommended for dental applications.

Optimizing radiation safety in dentistry: Clinical recommendations and regulatory considerations

BACKGROUND

The value of dental radiographs to oral health care decision making must be balanced with radiation safety to minimize patient exposure and occupational risk of oral health care providers. This review summarizes recommendations and regulatory guidance regarding dental radiography and cone-beam computed tomography. An expert panel presents recommendations on radiation safety, appropriate imaging practices, and reducing radiation exposure.

TYPES OF STUDIES REVIEWED

A systematic search run in Ovid MEDLINE, Embase, and Cochrane Database of Systematic Reviews identified relevant topical systematic reviews, organizational guidelines, and regulatory reviews published in the peer-reviewed literature since 2010. A supplemental search of the gray literature (eg, technical reports, standards, and regulations) identified topical nonindexed publications. Inclusion criteria required relevance to primary oral health care (ie, general or pediatric dentistry).

RESULTS

A total of 95 articles, guidance documents, and regulations met the inclusion criteria. Resources were characterized as applicable to all modalities, operator and occupational protection, dose reduction and optimization, and quality assurance and control.

PRACTICAL IMPLICATIONS

Understanding factors affecting imaging safety and applying fundamental principles of radiation protection consistent with federal, state, and local requirements are essential for limiting patient ionizing radiation exposure, in conjunction with implementing optimal imaging procedures to support prudent use of dental radiographs and cone-beam computed tomographic imaging. The regulatory guidance and best practice recommendations summarized in this article should be followed by dentists and other oral health care providers.

Diagnostic performance of stitched and non-stitched cross-sectional cone-beam computed tomography images of a non-displaced fracture of ovine mandibular bone

Purpose

This study assessed the diagnostic performance of stitched and non-stitched cross-sectional cone-beam computed tomography (CBCT) images of non-displaced ovine mandibular fractures.

Materials and Methods

In this ex vivo study, non-displaced fractures were artificially created in 10 ovine mandibles (20 hemi-mandibles) using a hammer. The control group comprised 8 hemi-mandibles. The non-displaced fracture lines were oblique or vertical, <0.5 mm wide, 10-20 mm long, and only in the buccal or lingual cortex. Fracture lines in the ramus and posterior mandible were created to be at the interface or borders of the 2 stitched images. CBCT images were obtained from the specimens with an 80 mm × 80 mm field of view before and after fracture induction. OnDemand software (Cybermed, Seoul, Korea) was used for stitching the CBCT images. Four observers evaluated 56 (28 stitched and 28 non-stitched) images to detect fracture lines. The diagnostic performance of stitched and non-stitched images was assessed by calculating the area under the receiver operating characteristic curve (AUC). Sensitivity and specificity values were also calculated (alpha=0.05).

Results

The AUC was calculated to be 0.862 and 0.825 for the stitched and non-stitched images, respectively (P=0.747). The sensitivity and specificity were 90% and 75% for the non-stitched images and 85% and 87% for the stitched images, respectively. The inter-observer reliability was shown by a Fleiss kappa coefficient of 0.79, indicating good agreement.

Conclusion

No significant difference was found in the diagnostic performance of stitched and non-stitched cross-sectional CBCT images of non-displaced fractures of the ovine mandible.

Importance of 3-dimensional imaging in the early diagnosis of chondroblastic osteosarcoma

The aim of this report is to present a case of chondroblastic osteosarcoma located in the right maxillary premolar region of a 17-year-old female patient. The initial clinical presentation and 2-dimensional (2D) radiographic methods proved inadequate for a definitive diagnosis. However, a cone-beam computed tomography scan revealed a hyperdense, heterogeneous lesion in the right maxillary premolar region, exhibiting a characteristic "sun-ray" appearance. To assess soft tissue involvement, a medical computed tomography scan was subsequently conducted. A positron emission tomography scan detected no metastasis or indications of secondary tumors. T1- and T2-weighted magnetic resonance imaging showed signal heterogeneity within the lesion, including areas of low signal intensity at the periphery. A histological examination conducted after an incisional biopsy confirmed the diagnosis of high-grade chondroblastic osteosarcoma. The patient was then referred to an oncology department for chemotherapy before surgery. In conclusion, these findings suggest that early diagnosis using 3-dimensional imaging can detect chondroblastic osteosarcoma in its early stages, such as before metastasis occurs, thereby improving the patient's prognosis.

Odontogenic Sinusitis: From Diagnosis to Treatment Possibilities-A Narrative Review of Recent Data

The maxillary sinus is a structure at the border of specialties: otorhinolaryngology and maxillofacial surgery. Due to this fact, regarding etiology, it can be affected by both the rhinogenic and odontogenic path and can impose diagnostic difficulties. The etiopathogenic mechanisms that can affect the Schneiderian membrane are mainly inflammatory, iatrogenic, traumatic, and tumorous in nature. From a microbiological point of view, the bacteriology is polymorphic, including both aerobic and anaerobic species in acute OS, the predominating species in acute OS being aerobic, and in chronic anaerobic germs. The role of fungi in the determination of this pathology and in the production of the biofilm that leads to resistance to antibiotic treatment is also discussed. The present paper aims to present the etiopathogenesis, bacteriology, clinical manifestations, as well as treatment of odontogenic sinusitis (OS) from an updated perspective through reviewing the literature. If unilateral maxillary sinusitis is usually due to odontogenic causes, this does not clinically exclude the possibility of strictly rhinogenic causes in the occurrence of sinusitis. This underlines the important role of complex oral and rhinological clinical examination as well as the role of preclinical examinations in specifying the certainty diagnosis. Simple radiography, orthopantomography, CT, and CBCT are compared in terms of diagnostic accuracy. The treatment of OS is complex, involving medication, dental, and surgical measures. The value of endoscopic surgery is emphasized, comparing its advantages over the classic Caldwell-Luc technique.

A Narrative Review on Current Diagnostic Imaging Tools for Dentomaxillofacial Abnormalities in Children

The current review narrates the findings and discusses the available diagnostic tools for detecting structural abnormalities. The review discusses several diagnostic tools, such as magnetic resonance imaging, cone beam computed tomography, multi detector row CT and positron emission tomography. The vital findings and comparative analysis of different diagnostic tools are presented in this review. The present review also discusses the advent of newer technologies, such as the HyperionX9 scanner with less field of view and 18F-FDG PET/CT (positron emission tomography with 2-deoxy-2-[fluorine-18] fluoro-D-glucose, integrated with computed tomography), which can give more efficient imaging of dentomaxillofacial structures. The discussion of effective comparative points enables this review to reveal the available diagnostic tools that can be used in the detection of dentomaxillofacial abnormalities in the pediatric population. The advantages and disadvantages of each tool are discussed, and the findings of past publications are also presented. Overall, this review discusses the technical details and provides a comparative analysis of updated diagnostic techniques for dentomaxillofacial diagnosis.

High-speed flat-detector computed tomography for temporal bone imaging and postoperative control of cochlear implants

PURPOSE

Flat-detector computed tomography (FD-CT) is the standard for cochlear implant (CI) imaging. FD-CT systems differ in technical characteristics. Our aim was an evaluation of two different FD-CT generations with different protocols and hardware regarding image quality, radiation dose, and scan time.

METHODS

Two temporal bone specimens (- / + CI = TB₀/TB₁) were scanned using three different scanners: two FD-CT systems with different scanning protocols (standard FD-CT: 20 s 70 kV, 20 s 109 kV; high-speed FD-CT [HS-FD-CT]: 7 s 109 kV, 9 s 109 kV, 14 s 72 kV) and MS-CT (5 s 120 kV). Acquired datasets were evaluated in consensus reading regarding qualitative and quantitative parameters: addressing CI- and cochlea-specific parameters, cochlea delineation, lamina spiralis ossea visibility, distinction of single CI electrodes, determination of intracochlear implant position, stapes delineation, and mastoidal septation were assessed. Addressing protocol-specific parameters, radiation dose (dose-length-product/DLP), and scan time were assessed.

RESULTS

Two HS-FD-CT protocols (14 s/9 s) provide higher or equivalent diagnostic information regarding CI- and cochlea-specific parameters compared to both standard FD-CT protocols. The fastest HS-FD-CT protocol (7 s)-providing inferior diagnostic information compared to all other FD-CT protocols-still exceeds MS-CT. The highest DLP was recorded for the 14 s HS-FD-CT protocol (TB₁ = 956 mGycm); the lowest DLPs were recorded for the 7 s HS-FD-CT protocol (TB₀ = 188 mGycm) and for MS-CT (TB₀ = 138 mGycm), respectively. HS-FD-CT allows a significant reduction of scan time compared to standard FD-CT.

CONCLUSION

High-speed FD-CT improves visualization of temporal bone anatomy and postoperative assessment of CIs by combining excellent image quality, fast scan time, and reasonable radiation exposure.

Patterns of Cone-Beam Computed Tomography (CBCT) Utilization by Various Dental Specialties: A 4-Year Retrospective Analysis from a Dental and Maxillofacial Specialty Center

The study aimed to analyze the uses of cone-beam computed tomography (CBCT) in the diagnosis and treatment in various dental specialties. This 4-year cross-sectional study analyzed the records of 1409 individuals who underwent a CBCT at the Oral and Maxillofacial Center at Sheba Medical Center, Israel. The average age of the patients was 27.9 ± 11.5 (range: 9-86 years). Patients were referred for CBCT by the following departments: Oral and Maxillofacial Surgery (1063; 75.5%), Endodontics (182; 12.9%), Periodontology (122; 8.6%) and Orthodontics (42; 3.0%). Most CBCT radiographs evaluated the maxilla (774; 55.0%), followed by the mandible (481; 34.1%) and both (154; 10.9%). The target anatomical structures included: bone (694; 49.3%), teeth (307; 21.7%), and both jaws (408; 29.0%). The main indications for CBCT use were: assessment of anatomical structures and implant sites (787; 55.9%), determine root canals morphology (182; 12.9%), visualization of impacted teeth, tooth alignment, and localization (177; 12.6%), suspected cysts or tumors (148; 10.5%), evaluation of Temporomandibular joint disorders (106; 7.5%) and other reasons (9; 0.6%). In 279 (19.8%) of cases, the diagnosis changed following CBCT, mainly in Orthodontics tooth analysis (28 (66.7%); p < 0.001). Practitioners and health authorities should be aware of this baseline information regarding CBCT use in the diagnosis and assessment of various oral and maxillofacial pathologies, anomalies and tooth position relative to anatomic structures. Continuing research and publications of CBCT utilization and guidelines are recommended.

A meta-review of effective doses in dental and maxillofacial cone beam CT using the ROBIS tool

OBJECTIVES

To apply the ROBIS tool for assessment of risk of bias (RoB) in systematic reviews (SRs) in a meta-review on effective doses (EDs) in dental and maxillofacial cone beam CT.

METHODS

Three electronic databases and reference lists of included SRs were searched. Eligible SRs were classified as having low, high or unclear RoB. Findings of SRs were synthesised and data from primary studies combined to relate ED to field of view (FOV) and operating potential (kV).

RESULTS

Seven SRs were included: three displayed low RoB, three high and one had unclear RoB. Only one SR related ED to image quality. Deficiencies in reporting of eligibility criteria, study selection and synthesis of results in SRs were identified. FOV height had a significant relationship with ED, explaining 27.2% of its variability. Median ED for three FOV categories differed significantly. Operating potential had a weak relationship with ED, with no significant difference in median ED between three operating potential groups.

CONCLUSION

The ROBIS tool should have a role for meta-reviews of different aspects of radiology. The disappointing results for RoB might be remedied by developing standards to improve the quality of reporting of primary dosimetry studies and of SRs. Future dosimetry studies should always relate ED to image quality or diagnostic accuracy.

ADVANCES IN KNOWLEDGE

This meta-review is the first to implement ROBIS for SRs of ED and identified that trustworthiness of some SRs is questionable. The percentage change in average ED per cm increase in FOV height could be calculated, emphasizing the importance of FOV as a determinant of ED in CBCT.

Effective dose estimation in cone-beam computed tomography for dental use by Monte-Carlo simulation optimizing calculation numbers using a step-and-shoot method

OBJECTIVE

The objective of this study was to perform effective dose estimation in cone-beam CT for dental use (CBCT) using a Monte-Carlo simulation employing a step-and-shoot method as well as to determine the optimal number of steps.

METHODS

We simulated 3DX Accuitomo FPD8 as a CBCT model and estimated the effective doses of a large and a small field of view (FOV) examination against the virtual Rando phantom using a particle and heavy ion transport code system. We confirmed the results compared to those from a thermo-luminescence dosemeter (TLD) system in a real phantom and investigated how the reduced angle calculations could be accepted.

RESULTS

The effective doses of both FOVs estimated with each one degree were almost the same as those estimated from the TLD measurements. Considering the effective doses and the itemized organ doses, simulation with 5° and 10° is acceptable for the large and small FOV, respectively. We tried to compare an effective dose with a large FOV as well as with multiple small FOVs covering the corresponding area and found that the effective dose from six small FOVs was approximately 1.2 times higher than that of the large FOVs.

CONCLUSION

We successfully performed a Monte-Carlo simulation using a step-and-shoot method and estimated the effective dose in CBCT. Our findings indicate that simulation with 5° or 10° is acceptable based on the FOV size, while a small multiple FOV scan is recommended from a radiation protection viewpoint.

An electromagnetic tracking implantation navigation system in dentistry with virtual calibration

BACKGROUND

Dental implant placement navigation systems based on optical tracking have been widely used in clinics. However, electromagnetic (EM) navigation method that does not suffer from problems of hidden line-of-light has not yet been described.

METHODS

This work proposes an EM-guided navigation method named TianShu-ESNS with virtual calibration. Model (12 implants) and animal experiments (pig head: six implants) were conducted to evaluate its performance and stability.

RESULT

The mean virtual calibration error was 0.83 ± 0.20 mm. The mean deviations at the entry point, end point and angle in the phantom experiment of TianShu-ESNS were 1.23 ± 0.17 mm, 1.59 ± 0.20 mm and 1.83 ± 0.27°, respectively. In the animal experiment, the same deviations were 1.25 ± 0.07 mm, 1.57 ± 0.35 mm and 1.90 ± 0.60°, respectively.

CONCLUSIONS

The experimental results show that TianShu-ESNS with the virtual calibration method could serve as a promising tool to eliminate the line-of-light hidden problem and simplify operation procedure in dental implant placement.

Cross-Sectional Imaging of Third Molar-Related Abnormalities

Third molars may be associated with a wide range of pathologic conditions, including mechanical, inflammatory, infectious, cystic, neoplastic, and iatrogenic. Diagnosis of third molar-related conditions can be challenging for radiologists who lack experience in dental imaging. Appropriate imaging evaluation can help practicing radiologists arrive at correct diagnoses, thus improving patient care. This review discusses the imaging findings of various conditions related to third molars, highlighting relevant anatomy and cross-sectional imaging techniques. In addition, key imaging findings of complications of third molar extraction are presented.

The practice of oral and maxillofacial radiology during COVID-19 outbreak

The current coronavirus disease 2019 (COVID-19) outbreak has brought substantial challenges to the world health system, including the practice of dental and maxillofacial radiology (DMFR). DMFR will carry on an imperative role in healthcare during this crisis. This rapid communication has collected and evaluated all the best current evidence and published guidelines as well as professional recommendations to help maxillofacial radiologists and dental practitioners for safer radiological and imaging examinations on healthy, suspected, or confirmed COVID-19 patients during outbreak. Some strategies have been depicted including procedural indications, infection control, and correct employment of personal protection equipment along with evoking the proper practice environment during and after the COVID-19 outbreak.