The evolution and application of dental maxillofacial imaging modalities

Deep learning in the diagnosis for cystic lesions of the jaws: a review of recent progress

Cystic lesions of the gnathic bones present challenges in differential diagnosis. In recent years, artificial intelligence (AI) represented by deep learning (DL) has rapidly developed and emerged in the field of dental and maxillofacial radiology (DMFR). Dental radiography provides a rich resource for the study of diagnostic analysis methods for cystic lesions of the jaws and has attracted many researchers. The aim of the current study was to investigate the diagnostic performance of DL for cystic lesions of the jaws. Online searches were done on Google Scholar, PubMed, and IEEE Xplore databases, up to September 2023, with subsequent manual screening for confirmation. The initial search yielded 1862 titles, and 44 studies were ultimately included. All studies used DL methods or tools for the identification of a variable number of maxillofacial cysts. The performance of algorithms with different models varies. Although most of the reviewed studies demonstrated that DL methods have better discriminative performance than clinicians, further development is still needed before routine clinical implementation due to several challenges and limitations such as lack of model interpretability, multicentre data validation, etc. Considering the current limitations and challenges, future studies for the differential diagnosis of cystic lesions of the jaws should follow actual clinical diagnostic scenarios to coordinate study design and enhance the impact of AI in the diagnosis of oral and maxillofacial diseases.

Magnetic resonance imaging for jawbone assessment: a systematic review

PURPOSE

To evaluate the accuracy of magnetic resonance imaging (MRI) for jawbone assessment compared to reference-standard measurements in the literature.

MATERIALS AND METHODS

An electronic database search was conducted in PubMed, EMBASE, Scopus, Web of Science, and the Cochrane Library in June 2022, and updated in August 2023. Studies evaluating the accuracy of MRI for jawbone assessment compared with reference-standard measurements (histology, physical measurements, or computed tomography) were included. The outcome measures included bone histomorphometry and linear measurements. The risk of bias was assessed by the Quality Assessment Tool for Diagnostic Accuracy Studies (QUADAS-2). The review was registered in the PROSPERO database (CRD42022342697).

RESULTS

From 63 studies selected for full-text analysis, nine manuscripts were considered eligible for this review. The studies included assessments of 54 participants, 35 cadavers, and one phantom. A linear measurement error ranging from 0.03 to 3.11 mm was shown. The accuracy of bone histomorphometry varies among studies. Limitations of the evidence included heterogeneity of MRI protocols and the methodology of the included studies.

CONCLUSION

Few studies have suggested the feasibility of MRI for jawbone assessment, as MRI provides comparable results to those of standard reference tests. However, further advancements and optimizations are needed to increase the applicability, validate the efficacy, and establish clinical utility of these methods.

Incidental findings in cone beam computed tomography (CBCT) scans for implant treatment planning: a retrospective study of 404 CBCT scans

OBJECTIVES

To investigate the prevalence of incidental findings and need for further dental treatment and analyse the influence of size of field-of-view (FOV) and age in cone beam computed tomography (CBCT) for pre-implant planning.

METHODS

404 CBCT scans were examined retrospectively for incidental findings and need for further dental treatment. Incidental finding-frequencies and need for further treatment were assessed for different age (< 40 years, 40-60 years, > 60 years) and FOV groups (small, medium, large). Intraexaminer and interexaminer agreements were evaluated.

RESULTS

In 82% of the scans at least one incidental finding was found, with a total of 766 overall. More incidental findings were found in scans with large FOV (98% vs. 72%, OR = 22.39 large vs. small FOV, p < 0.0001) and in scans of patients > 60 years (OR = 5.37 patient's age > 60 years vs. < 40 years, p = 0.0003). Further dental treatment due to incidental findings was needed in 31%. Scans with large FOV were more likely to entail further treatment (OR = 3.55 large vs. small FOV, p < 0.0001). Partial edentulism and large FOV were identified as risk factors for further treatment (p = 0.0003 and p < 0.0001). Further referral of the patient based on incidental findings was judged as indicated in 5%. Intra- and inter-examiner agreements were excellent (kappa = 0.944/0.805).

CONCLUSIONS

A considerable number of incidental findings with need for further dental treatment was found in partially edentulous patients and in patients > 60 years. In pre-implant planning of elderly patients, the selection of large FOV CBCT scans, including dentoalveolar regions not X-rayed recently, help to detect therapeutically relevant incidental findings.

Pre-eruptive intracoronal resorption in orthodontic patients: A retrospective analysis of 3,143 patients

OBJECTIVES

The aim of this retrospective study was to analyze the occurrence and characteristics of pre-eruptive intracoronal resorptions in a clinical orthodontic patient population.

MATERIALS AND METHODS

Patients treated in an orthodontic department (University of Pécs, Pécs, Hungary) were included. Unerupted teeth on panoramic radiographs were analyzed for intracoronal radiolucent lesions. For each patient, the demographic data, jaw localization, number of unerupted teeth with pre-eruptive intracoronal resorption lesions, number of lesions per tooth, size and localization of pre-eruptive intracoronal resorption defects, affected tooth's surface, pulp involvement and ectopic position of the tooth with defects were recorded.

RESULTS

In the 3,143 patients investigated, 55 teeth in 49 patients showed pre-eruptive intracoronal resorption lesions (subject incidence: 1.56%). The incidence on unerupted teeth was 0.25%. Pre-eruptive intracoronal resorption was significantly more common in mandibles (43 mandibular vs. 12 maxillary lesions) with an odds ratio of 12.84 (95% Confidence Interval: 5.19-31.74) and no gender differences were found (p = 0.746). The occurrence of pre-eruptive intracoronal resorption was highest in the youngest (7-10 years) mixed dentition status group (p < 0.001). Most of the lesions (44 of 55, or 80.0%) were localized in the dentin, occupying two-third or less of the dentin thickness. Only 12.73% (7/55) of the lesions were not localized on the occlusal surface. Of the lesions, 89.1% (49/55) showed no obvious size increase over an average follow-up of 36.4 ± 8.1 months.

CONCLUSIONS

Pre-eruptive intracoronal resorption may occur mainly in the mixed dentition stage in orthodontic patients. Careful and attentive radiographic evaluations may facilitate early detection and follow-up of the lesions' possible dimensional changes, especially when resorption influences orthodontic extraction therapy.

Cone-Beam Computed Tomography as a Prediction Tool for Osteoporosis in Postmenopausal Women: A Systematic Literature Review

This literature review was conducted to analyze the capability of cone-beam computed tomography (CBCT) to accurately identify low bone mass density in women. A systematic search of MEDLINE, Embase, Scopus, Google Scholar, the Cochrane Library, and Science Direct was performed to identify relevant articles, and the Cochrane risk of bias criterion was used to determine the methodological quality of the included studies. All ten included studies assessed primary research on the capacity of CBCT to accurately diagnose insufficient bone mineral density. All relevant data were extracted, and the results were summarized narratively. The results indicated that the CBCT has good sensitivity and specificity and high accuracy in predicting osteoporosis. Four of the included studies measured qualitative values, while the others concentrated on quantitative values and found lower values in osteoporosis patients compared to those of osteopenic and healthy patients. All the studies compared CBCT grayscale values with dual energy X-ray absorptiometry scores, which strengthened our confidence in the accuracy of CBCT’s diagnostic capability. CBCT is considered a feasible predictive tool for detecting patients who are at risk of osteoporosis, although further research is needed to confirm the evidence and enhance its common use among health care professionals.

Prevalence of dental implant positioning errors: A cross-sectional study

Purpose

This study evaluated the prevalence of dental implant positioning errors and the most frequently affected oral regions.

Materials and Methods

A sample was obtained of CBCT images of 590 dental implants from 230 individuals who underwent diagnosis at a radiology center using cone-beam computed tomography from 2017 to 2020. The following variables were considered: thread exposure, violation of the minimum distance between 2 adjacent implants and between the implant and tooth, and implant contact with anatomical structures. Descriptive data analysis and the Pearson chi-square test (P<0.05) were performed to compare findings according to mouth regions.

Results

Most (74.4%) of the 590 implants were poorly positioned, with the posterior region of the maxilla being the region most frequently affected by errors. Among the variables analyzed, the most prevalent was thread exposure (54.7%), followed by implant contact with anatomical structures, violation of the recommended distance between 2 implants and violation of the recommended distance between the implant and teeth. Thread exposure was significantly associated with the anterior region of the mandible (P<0.05). The anterior region of the maxilla was associated with violation of the recommended tooth-implant distance (P<0.05) and the recommended distance between 2 adjacent implants (P<0.05). Implant contact with anatomical structures was significantly more likely to occur in the posterior region of the maxilla (P<0.05).

Conclusion

Many implants were poorly positioned in the posterior region of the maxilla. Thread exposure was particularly frequent and was significantly associated with the anterior region of the mandible.

Pre-eruptive intracoronal radiolucencies in permanent dentition of children in Tamil Nadu-A cross-sectional study

BACKGROUND

Pre-eruptive intracoronal radiolucency (PEIR) poses a challenge to paediatric dentists as it cannot be clinically detected.

AIM

To estimate the prevalence and coexisting factors of PEIR in permanent teeth of children and adolescents in western Tamil Nadu, India.

DESIGN

This cross-sectional study assessed 5012 digital panoramic radiographs of children and adolescents below 14 years of age obtained from private digital imaging centers, dental clinics, and dental colleges located in five districts of western Tamil Nadu. The prevalence and PEIR and its coexisting factors were assessed by two independent calibrated investigators. Data were analyzed using the chi-square test.

RESULTS

The subject prevalence and tooth prevalence of PEIR were estimated to be 3.2% and 0.4%, respectively. Maxillary canines and mandibular premolars were commonly involved. Majority of the lesions were limited to less than one-third of dentin thickness (74%) and distal aspect of the crown (45.1%). Ectopic positioning (9.3%) and dental caries in the preceding primary tooth (9.9%) were the most common coexisting factors.

CONCLUSION

Pre-Eruptive Intracoronal Radiolucency defects were commonly seen in maxillary canines, mandibular premolars, and distal aspect of the crown involving less than one-third dentin thickness. Ectopic positioning and caries in primary teeth were commonly seen along with the PEIR defects.

Computer tomographic differential diagnosis of ameloblastoma and odontogenic keratocyst: classification using a convolutional neural network

OBJECTIVE

To analyse the automatic classification performance of a convolutional neural network (CNN), Google Inception v3, using tomographic images of odontogenic keratocysts (OKCs) and ameloblastomas (AMs).

METHODS

For construction of the database, we selected axial multidetector CT images from patients with confirmed AM (n = 22) and OKC (n = 18) based on a conclusive histopathological report. The images (n = 350) were segmented manually and data augmentation algorithms were applied, totalling 2500 images. The k-fold × five cross-validation method (k = 2) was used to estimate the accuracy of the CNN model.

RESULTS

The accuracy and standard deviation (%) of cross-validation for the five iterations performed were 90.16 ± 0.95, 91.37 ± 0.57, 91.62 ± 0.19, 92.48 ± 0.16 and 91.21 ± 0.87, respectively. A higher error rate was observed for the classification of AM images.

CONCLUSION

This study demonstrated a high classification accuracy of Google Inception v3 for tomographic images of OKCs and AMs. However, AMs images presented the higher error rate.

Surgical guides for esthetic crown lengthening procedures: Periodontal and prosthetic aspects

BACKGROUND

In patients with gingival exposure on smiling due to altered passive eruption, esthetic crown lengthening is often indicated. Meticulous planning and surgical precision are key for successful outcomes. Surgical guides are helpful tools that are seldomly reported on in the literature related to esthetic crown lengthening procedures.

TYPES OF STUDIES REVIEWED

The authors searched the literature for articles that described the planning, tools, and execution related to esthetic crown lengthening procedures.

RESULTS

Several techniques have been reported to guide the esthetic crown lengthening procedure, ranging from direct bone level measurement to 3-dimensional printed surgical guides.

PRACTICAL IMPLICATIONS

This review serves the clinician as an aid in the decision-making process for esthetic crown lengthening procedures and available surgical guide options, including computer-based guides.

Dental cone beam CT: An updated review

Cone beam computed tomography (CBCT) is a diverse 3D x-ray imaging technique that has gained significant popularity in dental radiology in the last two decades. CBCT overcomes the limitations of traditional two-dimensional dental imaging and enables accurate depiction of multiplanar details of maxillofacial bony structures and surrounding soft tissues. In this review article, we provide an updated status on dental CBCT imaging and summarise the technical features of currently used CBCT scanner models, extending to recent developments in scanner technology, clinical aspects, and regulatory perspectives on dose optimisation, dosimetry, and diagnostic reference levels. We also consider the outlook of potential techniques along with issues that should be resolved in providing clinically more effective CBCT examinations that are optimised for the benefit of the patient.

Predictability and image quality of low-dose cone-beam computed tomography in computer-guided implantology: An experimental study

OBJECTIVES

To investigate the predictability and image quality of low-dose cone-beam computed tomography (LD-CBCT) in computer-guided implantology.

METHODS

Pig cadaver mandibles were imaged using high-definition CBCT (HD-CBCT) and LD-CBCT (HD-CBCT: 85 kV, 6 mA, 14.2 s, 767 frames, 1184 mGycm², voxel size 80 µm, effective dose 231 µSv; LD-CBCT: 85 kV, 10 mA, 2.1 s, 384 frames, 84 mGycm², voxel size 160 µm, effective dose 16 µSv; Orthophos SL, Dentsply Sirona, Bensheim, Germany). Digital impressions were taken using intraoral scanning (IOS; Omnicam, Dentsply Sirona). Data of CBCT modalities and IOS were aligned. Forty-eight implants were planned virtually (24 implants per modality; Bone Level 4.1 × 10 mm; Straumann AG, Basel, Switzerland). Implants were inserted using templates by initial pilot drilling ("partially-guided implantation"). Implant positions were recorded using IOS. Geometric deviations between planned and definitive positions were assessed regarding implant apex, entry-point and angle. CBCT image quality was evaluated by raters twice on a four point scale. The results were exploratively compared (linear models, Mann-Whitney-U tests).

RESULTS

Regarding implant apex, deviations were greater for LD-CBCT (mean 3.0±1.2 mm), as compared to HD-CBCT (mean 2.3±1.1 mm). For entry-point, no distinct difference was detected with a mean deviation of 1.4±0.9 mm in LD-CBCT, and 1.7±0.6 mm in HD-CBCT. Regarding angle, deviations were greater for LD-CBCT (mean 13.2±6.3°), as compared to HD-CBCT (mean 9.2±5.3°). The image quality of HD-CBCT provided to be better (mean 2.7±0.6) than that of LD-CBCT (mean 2.5±0.6).

CONCLUSIONS

Within the partially-guided approach, the results underline the potential of LD-CBCT alternatively to HD-CBCT for computer-guided implantology. Advantages of HD-CBCT need to be balanced against the higher radiation dose.

Age-related changes in the effect of rapid maxillary expansion on the position of labially impacted maxillary canines: A case-control study

INTRODUCTION

The early diagnosis and interception of potential maxillary canine impaction is the most desirable approach for correcting their path of eruption. However, there is still a lack of evidence regarding the effect of rapid maxillary expansion (RME) on labially impacted canines. This study aimed to investigate the age-related effect of RME on labially impacted maxillary canines in order to reduce the risk of their impaction in the mixed dentition and to examine the proper timing of interceptive treatment.

METHODS

All patients aged 7-10 years were treated with an RME appliance using the same protocol. The distance to the occlusal plane, axis to the midline, and distribution in different sectors-depending on the patients' age-were evaluated for maxillary canines before and after treatment on panoramic radiographs in order to detect changes in the position of the impacted canines. These geometric measurements in the impacted canines were also validated by observing the nontreated canines at each age.

RESULTS

Significant differences existed between the impacted canines and the erupted canines in all 3 categories in all age groups. RME treatment modulated the position of the impacted canines in all age groups. Interestingly, a statistically significant difference before and after RME in all categories was detected in patients aged <8 years. A discriminant analysis also showed a positive association of RME treatment with the risk of labially impacted canines. The standardized regression coefficients showed that the angulation of the maxillary canine was the most important predictor for impaction.

CONCLUSIONS

Our findings indicate that RME treatment in the early mixed dentition was effective for managing labially impacted maxillary canines. An age of 7-8 years with early mixed dentition might be the most appropriate timing for therapeutic intervention on the basis of RME treatment for buccal canine impaction.

Study Between Panoramic Radiography and Cone Beam-Computed Tomography in the Diagnosis of Ameloblastoma, Odontogenic Keratocyst, and Dentigerous Cyst

OBJECTIVE

To determine how the diagnosis may or may not be influenced by cone-beam computed tomography (CBCT), comparing the diagnostic hypotheses obtained using images of panoramic radiographs and CBCT in cases of ameloblastoma, odontogenic keratocyst, and dentigerous cyst.

STUDY DESIGN

Five cases were selected for each lesion. Panoramic radiographs and CBCT scans were analyzed by 15 dentists for the formulation of the diagnostic hypotheses. Two observers performed the analyses and measurement of qualitative and quantitative features of the lesions evaluated in the CBCT.

RESULTS

There was no statistically significant difference in correct diagnostic average between panoramic radiography and CBCT, but there was a significant difference in correct diagnostic average in the diagnosis of ameloblastoma using CBCT compared to panoramic radiography. Master's and PhD-level observers had greater correct diagnostic average in the diagnosis of odontogenic keratocyst using panoramic radiograph compared to specialists, with a significant difference.

CONCLUSION

Cone-beam computed tomography images revealed that the ameloblastomas were greater in size and expansion compared to the odontogenic keratocyst and the dentigerous cysts. Ameloblastomas showed a higher incidence of multiloculated aspects compared to odontogenic keratocyst and dentigerous cysts. There were no differences between quantitative and qualitative features of odontogenic keratocyst and dentigerous cysts.

Cone beamed computed tomography in pediatric dentistry: Concepts revisited

Oral diagnosis and treatment planning is of utmost importance in pediatric dentistry. Although intraoral and conventional radiographic procedures have been used extensively since decades, there two-dimensional representation has raised many questions. Cone beamed computed tomography with 3-D technology is a replacement for conventional 2-D imaging and has a wide application among child patients in pediatric dentistry. This article therefore deals with current facts and myths about clinical situations where CBCT is indicated in pediatric patients.

Knowledge and Attitude of Iranian Dentists towards Cone-Beam Computed Tomography

Objectives

We aimed to evaluate the knowledge and attitude of Iranian dentists towards cone-beam computed tomography (CBCT).

Materials and Methods

A 20-item questionnaire was distributed among 410 Iranian dentistry graduates attending the 56th Congress of Iranian Dental Association held in Tehran, Iran. The questionnaire included items on demographic characteristics, namely full name, age, gender, work experience, type of current activity (individual or group), and the highest educational level. In addition, the questionnaire contained items on the knowledge and attitude of dentists. The obtained data were analyzed using statistical tests.

Results

In this study, 49.3% and 22.4% of the subjects were male and female, respectively, 47.1% of whom used CBCT, while 49.8% did not. In detail, 72.2% of the dentists used the technique to evaluate the location of implants, whereas 19.7%, 3.2%, and 2.7% of the subjects applied it to localize the inferior alveolar nerve (IAN), evaluate the location of implants and localize the IAN, and perform cephalometric analysis, respectively. The main causes of lack of prescription of CBCT entailed high cost (80%), high rate of patient absorbed dose (27.6%), insufficient number of CBCT centers (46.3%), and the long duration of the process (15.6%).

Conclusion

CBCT is an advantageous imaging technique in dentistry. Considering the increased application of CBCT in dentistry, attending workshops could help train dentists to use the technique.

New evolution of cone-beam computed tomography in dentistry: Combining digital technologies

Panoramic radiographs and computed tomography (CT) play a paramount role in the accurate diagnosis, treatment planning, and prognostic evaluation of various complex dental pathologies. The advent of cone-beam computed tomography (CBCT) has revolutionized the practice of dentistry, and this technique is now considered the gold standard for imaging the oral and maxillofacial area due to its numerous advantages, including reductions in exposure time, radiation dose, and cost in comparison to other imaging modalities. This review highlights the broad use of CBCT in the dentomaxillofacial region, and also focuses on future software advancements that can further optimize CBCT imaging.

Incidence of anomalous canals in the base of the skull: a retrospective radio-anatomical study using cone-beam computed tomography

PURPOSE

Several skull-base foramina including foramen meningo-orbitale, craniopharyngeal canals, canaliculus innominatus, foramen vesalius, palatovaginal canals, and canalis basalis medianus are visible on cone-beam computed tomographs. A good understanding of the anatomical variants of these foramina is important to accurately diagnose fractures, understand the paths that infections may take, and identify associated anomalies. We used cone-beam computed tomography to measure the incidences of skull-base foramen variants in a normal population.

METHODS

A total of 350 subjects (200 females, 150 males, 6-30 years of age) were included. The prevalences of foramen meningo-orbitale, craniopharyngeal canals, canaliculus innominatus, foramina vesalius, palatovaginal canals, and canalis basalis medianus were evaluated by age and gender.

RESULTS

Subject age ranged from 6 to 30 years (mean age ± SD = 15.1 ± 4.08). Foramen meningo-orbitale, craniopharyngeal canals, canaliculus innominatus, foramen vesalius, palatovaginal canal, and canalis basalis medianus were observed in 51 (14.6%), 19 (5.4%), 60 (17.1%), 145 (41.1%), 34 (9.7%), and 15 (4.3%) patients, respectively.

CONCLUSIONS

Skull-base foramina are important clinically and radiologically. Imaging of such variants via cone-beam computed tomography is valuable for both physicians and patients. Few studies of skull-base foramina have used cone-beam computed tomography. Additional research is required for a fuller understanding of this phenomenon.

A systematic review on incidental findings in cone beam computed tomography (CBCT) scans

OBJECTIVES

Cone beam CT's use (CBCT) in dentistry is increasing. Incidental findings (IFs: discoveries unrelated to the original purpose of the scan), are frequently found as a result of a large field of view. The aim of the systematic review is to analyze present literature on IFs using CBCT.

METHODS AND MATERIALS

The authors searched online databases of studies and assessed the prevalence of IFs among patients undergoing head and neck CBCT scans. STROBE criteria was used to evaluate the quality of the studies.

RESULTS

The original search retrieved 509 abstracts of which only 10 articles met the inclusion criteria. The sample size varied between 90 and 1000 participants. The frequency of IFs of the selected articles were 24.6-94.3%. The most common non-threatening IFs were found in the airway, such as mucous retention cyst (55.1%) and sinusitis (41.7%). Other non-threatening IFs were soft tissue calcifications such as calcified stylohyloid ligament (26.7%), calcified pineal gland (19.2%), and tonsillolith (14.3%). Threatening IFs were rare findings (1.4%). Three articles reported incidental carotid artery calcifications with a prevalence of 5.7-11.6%. Pathological findings were not common between the articles, but still relevant (2.6%). The studies had a risk of bias varying from moderate to low.

CONCLUSIONS

There is a high frequency of IFs, yet not all of them require immediate medical attention. The low prevalence of threatening IFs emphasizes that CBCT should not be considered a substitution for conventional radiographs, but when used, the scans should be evaluated by a maxillofacial radiologist.

An ex vivo comparative study of occlusal and proximal caries using terahertz and X-ray imaging

OBJECTIVES:

To examine the effectiveness of terahertz (THz) pulsed imaging (TPI) in comparison to intraoral photostimulable phosphor late (PSP) and cone beam CT (CBCT) for the detection of dental caries ex vivo.

METHODS:

Newly extracted 32 human permanent teeth surfaces (16 with caries and 16 without caries) were serially sectioned mesiodistally and imaged by using four image sets as follows: (1) CBCT; (2) PSP; (3) THz movie video; and (4) THz static images. All images were evaluated twice separately by two calibrated observers for the presence/absence of caries using a 5-grade rating/confidence scale. Weighted κ coefficients were calculated. Different image sets were compared with the histological gold-standard using the receiver operating characteristic and area under curves for each image set were compared using χ² tests, with a significance level of α = 0.05.

RESULTS:

Intra- and interobserverκ-values for all image sets were almost excellent ranging between 0.777 and 0.988. Mean Az values of observers and readings were 0.898 for CBCT, 0.888 for PSP images, 0.853 for THz static images and 0.781 for THz video movie. No statistically significant differences (p > 0.05) were found between Az values for the different image sets. When observer scores were evaluated according to caries location again no statistically significant differences (p > 0.05) were found between Az values for the occlusal and proximal caries for the four image sets.

CONCLUSIONS:

Terahertz pulsed imaging was found to be successful for the detection of dental caries ex vivo.

Application of portable digital radiography for dental investigations of ancient Egyptian mummies during archaeological excavations: Evaluation and discussion of the advantages and limitations of different approaches and projections

Purpose

In the age of X-ray computed tomography (CT) and digital volume tomography (DVT), with their outstanding post-processing capabilities, indications for planar radiography for the study of the dentition of ancient Egyptian mummies may easily be overlooked. In this article, the advantages and limitations of different approaches and projections are discussed for planar oral and maxillofacial radiography using portable digital X-ray equipment during archaeological excavations. Furthermore, recommendations are provided regarding projections and sample positioning in this context.

Materials and Methods

A total of 55 specimens, including 19 skeletonized mandibles, 14 skeletonized skulls, 18 separate mummified heads, and 4 partially preserved mummies were imaged using portable digital X-ray equipment in the course of archaeological excavations led by the University of Basel in the Valley of the Kings between 2009 and 2012. Images were evaluated by 2 authors with regard to the visibility of diagnostically relevant dental structures using a 4-point grading system (Likert scale).

Results

Overall, the visibility of diagnostically relevant dental structures was rated highest by both authors on X-ray images acquired using a dental detector. The tube-shift technique in the lateral projections of mandibular dentition achieved the second-best rating, and lateral projections achieved the third-best rating.

Conclusion

Conventional planar digital X-ray imaging, due to its ubiquity, remains an excellent method–and often the only practicable one–for examining the skulls and teeth of ancient Egyptian mummies under field conditions. Radiographic images of excellent diagnostic quality can be obtained, if an appropriate methodology regarding the selected projections and sample placement is followed.

The Risk Factors that Can Increase Possibility of Mandibular Canal Wall Damage in Adult: A Cone-Beam Computed Tomography (CBCT) Study in a Chinese Population

Background

The objective of this study was to analyze the factors that can increase the possibility of mandibular canal (MC) defect in Chinese people, to evaluate the risk of nerve impairment, and to choose the proper operative method to reduce the risk of mandibular alveolar nerve injury during the extraction of mandibular third molar (MTM).

Material/Methods

A total of 954 patients (1,304 MTMs) who underwent orthopantomography (OPG) and cone-beam computed tomography (CBCT) between July 2014 and December 2014 were included in this study. The age and gender of patients, impacted type (high impaction, moderate impaction, and low impaction), Winter classification of MTM, position of MTM relative to MC, vertical classification of MTM and MC, and the feature images of OPG were collected and compared to the imperfection of the MC wall in CBCT images.

Results

The wall situation of MC was significantly correlated with the age of the patient, the depth of the molar, the position of the roots, and six imaging appearances on OPG. There was no significant difference based on gender.

Conclusions

Most incomplete walls of MCs could be inferred by OPG. However, images based on CBCT could clarify the defect of the MC and also could clearly display the spatial relationship between the root and inferior alveolar canal.

Comparison of diagnostic methods for early interproximal caries detection with near-infrared light transillumination: an in vivo study

Background

Although numerous studies have used digital intraoral imaging, only a few studies have used photo-optical methods for the diagnosis of caries. Moreover, several limitations exist in terms of observers (experience and specialty) and the caries lesion itself. Hence, the aims of this study were to evaluate the diagnostic capability of near-infrared light transillumination (NILT) and PSP-Bitewing radiographs and to compare the interobserver and intraobserver differences in addition to observers’ experience level to detect early interproximal caries lesions in vivo.

Methods

A total of 52 untreated posterior teeth with and without varying degrees of early interproximal carious lesions were included. Bitewing radiographs using digital phosphor plates (PSP-Bitewing) and NILT were used to clarify the diagnosis. An oral and maxillofacial radiologist and a restorative dentistry consultant evaluated the images twice. A separate appointment for clinical validation and restoration was made. Kappa coefficients were calculated to assess both intraobserver and interobserver agreements for each evaluation method. Scores obtained from PSP-Bitewing and NILT were compared with the clinical validation via receiver operating characteristic (ROC) analysis.

Results

No significant differences were found between PSP-Bitewing radiography and NILT for detecting early interproximal carious lesions with high average Az results. Both intraobserver and interobserver agreement values were relatively higher for NILT evaluation. The Az values increased at second evaluations for both caries detection methods.

Conclusions

NILT examination has an appropriate sensitivity and diagnostic accuracy for detecting early interproximal caries lesions and can be considered as a method of choice for detecting caries without the use of ionizing radiation.

Digital orthodontic radiographic set versus cone-beam computed tomography: an evaluation of the effective dose

Objective:

The aim of this study was to compare the equivalent and effective doses of different digital radiographic methods (panoramic, lateral cephalometric and periapical) with cone-beam computed tomography (CBCT).

Methods:

Precalibrated thermoluminescent dosimeters were placed at 24 locations in an anthropomorphic phantom (Alderson Rando Phantom, Alderson Research Laboratories, New York, NY, USA), representing a medium sized adult. The following devices were tested: Heliodent Plus (Sirona Dental Systems, Bernsheim, Germany), Orthophos XG 5 (Sirona Dental Systems, Bernsheim, Germany) and i-CAT (Imaging Sciences International, Hatfield, PA, USA). The equivalent doses and effective doses were calculated considering the recommendations of the International Commission of Radiological Protection (ICRP) issued in 1990 and 2007.

Results:

Although the effective dose of the radiographic set corresponded to 17.5% (ICRP 1990) and 47.2% (ICRP 2007) of the CBCT dose, the equivalent doses of skin, bone surface and muscle obtained by the radiographic set were higher when compared to CBCT. However, in some areas, the radiation produced by the orthodontic set was higher due to the complete periapical examination.

Conclusion:

Considering the optimization principle of radiation protection, i-CAT tomography should be used only in specific and justified circumstances. Additionally, following the ALARA principle, single periapical radiographies covering restricted areas are more suitable than the complete periapical examination.

The Effects of Imaging Enhancement Tools in the Detection of Horizontal Root Fractures

INTRODUCTION

Detection of root fracture is challenging both clinically and radiographically. Root fractures occur in different planes with unpredictable presentations.

AIM

The aim of the study was to evaluate the diagnostic accuracy of selected digital image enhancement tools in the detection of horizontal Root Fracture (RF).

MATERIALS AND METHODS

Fifty three roots, of single and multi-rooted teeth, in eight dentate human cadaver mandibles were selected for this study. Following minimally traumatic extraction of the teeth, horizontal fractures were induced in 23 roots and remounted in the empty sockets of their respective human dry mandibles. The remaining teeth with no fractures were used as the control group. Twenty two periapical radiographs were obtained by using the paralleling technique and using Complementary Metal Oxide Semiconductor (CMOS). Image J software was used to enhance the original images with the Inversion (IN), Histogram-Equalization (EQ) and Polynomial (Poly) tools. A total of 88 periapical images (original and three enhanced images) were reviewed independently by three Oral and Maxillofacial Radiologists and two Endodontists. Receiver Operating Characteristic (ROC) curve analysis was used to evaluate the accuracy of fracture detection and the kappa statistic was used to assess agreement among reviewers.

RESULTS

The diagnostic accuracy for one of the observers was significantly different in detection of RF with only EQ enhancement tool. Sensitivity and specificity were not significantly different. Interobserver agreement showed no significant difference between imaging methods. Intra-observer agreement was high to moderate.

CONCLUSION

There was no significant difference between the different imaging modalities. No statistical difference for the agreement was found among or between the endodontists and radiologists in this study.

The Reliability of Panoramic Radiography Versus Cone Beam Computed Tomography when Evaluating the Distance to the Alveolar Nerve in the Site of Lateral Teeth

BACKGROUND The aim of this study was to compare the reliability of panoramic radiography (PR) and cone beam computed tomography (CBCT) in the evaluation of the distance of the roots of lateral teeth to the inferior alveolar nerve canal (IANC). MATERIAL AND METHODS 100 PR and 100 CBCT images that met the selection criteria were selected from the database. In PR images, the distances were measured using an electronic caliper with 0.01 mm accuracy and white light x-ray film reviewer. Actual values of the measurements were calculated taking into consideration the magnification used in PR images (130%). Measurements on CBCT images were performed using i-CAT Vision software. Statistical data analysis was performed using R software and applying Welch's t-test and the Wilcoxon test. RESULTS There was no statistically significant difference in the mean distance from the root of the second premolar and the mesial and distal roots of the first molar to the IANC between PR and CBCT images. The difference in the mean distance from the mesial and distal roots of the second and the third molars to the IANC measured in PR and CBCT images was statistically significant. CONCLUSIONS PR may be uninformative or misleading when measuring the distance from the mesial and distal roots of the second and the third molars to the IANC.

Nonsurgical Management of a Large Periapical Lesion: A Case Report

This case report describes the non-surgical management of a large cyst-like periapical lesion in the mandible of a 16-year-old female with the chief complaint of periodic swelling and pus drainage from the mandibular anterior region gingivae with no history of pain and traumatic accident in this area. Both mandibular central incisors had extensive caries. Root canals of both mandibular central incisors were filled with calcium hydroxide. After 10 days, endodontic therapy was carried out on both teeth. Clinical and radiographic re-evaluations at 3 and 12 months revealed progressing bone healing. This case report shows that appropriate diagnosis in combination with root canal treatment as a conservative non-surgical approach can lead to complete healing of large lesions without invasive treatments.

Diagnostic Index: An open-source tool to classify TMJ OA condyles

Osteoarthritis (OA) of temporomandibular joints (TMJ) occurs in about 40% of the patients who present TMJ disorders. Despite its prevalence, OA diagnosis and treatment remain controversial since there are no clear symptoms of the disease, especially in early stages. Quantitative tools based on 3D imaging of the TMJ condyle have the potential to help characterize TMJ OA changes. The goals of the tools proposed in this study are to ultimately develop robust imaging markers for diagnosis and assessment of treatment efficacy. This work proposes to identify differences among asymptomatic controls and different clinical phenotypes of TMJ OA by means of Statistical Shape Modeling (SSM), obtained via clinical expert consensus. From three different grouping schemes (with 3, 5 and 7 groups), our best results reveal that that the majority (74.5%) of the classifications occur in agreement with the groups assigned by consensus between our clinical experts. Our findings suggest the existence of different disease-based phenotypic morphologies in TMJ OA. Our preliminary findings with statistical shape modeling based biomarkers may provide a quantitative staging of the disease. The methodology used in this study is included in an open source image analysis toolbox, to ensure reproducibility and appropriate distribution and dissemination of the solution proposed.

In vitro comparison of contemporary radiographic imaging techniques for the measurement of inter-radicular width

OBJECTIVE

To assess the reliability of inter-radicular measurements taken using dental pantomograms (DPT), long cone periapical radiographs (LCPA) and cone bean computed tomography (CBCT).

MATERIALS/METHODS

A typodont simulating a hypodontia patient undergoing fixed appliance treatment was used. LCPAs, DPT, I-CAT and Accuitomo CBCT images were taken and the distances between the edentulous spans were measured at the midpoint of the roots and the cemento-enamel junctions (CEJ) of adjacent teeth. The results of each modality were compared to each other to the actual inter-radicular space.

RESULTS

The DPT overestimated inter-radicular widths by 2 mm or more [mean: 2.48; 95% confidence interval (CI): -1.09 to 6.05 mm]. The LCPA overestimated the inter-radicular widths by 1.5 mm with a 95% CI of -0.095 to 4.03 mm. The mean differences between gold standard (model) and Accuitomo was 0.57 mm (95% CI: -0.37 to 1.51 mm) for the root mean and 0.22 mm (95% CI: -0.52 to 0.96 mm) for the CEJ. This was similar to the differences between the model and I-CAT where the inter-radicular root mean difference was 0.38 mm (95% CI: -0.38 to 1.14 mm) and the CEJ mean difference was 0.21 mm (95% CI: -0.50 to 0.92 mm).

CONCLUSION

The CBCT overestimated the root distance by 0.48 mm and the CEJ width by 0.22 mm, which is clinically irrelevant for implant placement. The DPT overestimated inter-radicular width by 2 mm and the LCPA by 1.5 mm and this difference may put roots of adjacent teeth at risk during implant placement.

Diagnostic Accuracy of Cone-Beam Computed Tomography and Periapical Radiography in Internal Root Resorption

INTRODUCTION

The aim of this study was to compare the diagnostic value of cone-beam computed tomography (CBCT) and periapical (PA) radiography in detecting internal root resorption.

METHODS AND MATERIALS

Eighty single rooted human teeth with visible pulps in PA radiography were split mesiodistally along the coronal plane. Internal resorption like lesions were created in three areas (cervical, middle and apical) in labial wall of the canals in different diameters. PA radiography and CBCT images were taken from each tooth. Two observers examined the radiographs and CBCT images to evaluate the presence of resorption cavities. The data were statistically analyzed and degree of agreement was calculated using Cohen's kappa (k) values.

RESULTS

The mean±SD of agreement coefficient of kappa between the two observers of the CBCT images was calculated to be 0.681±0.047. The coefficients for the direct, mesial and distal PA radiography were 0.405±0.059, 0.421±0.060 and 0.432±0.056, respectively (P=0.001). The differences in the diagnostic accuracy of resorption of different sizes were statistically significant (P<0.05); however, the PA radiography and CBCT, had no statistically significant differences in detection of internal resorption lesions in the cervical, middle and apical regions.

CONCLUSION

Though, CBCT has a higher sensitivity, specificity, positive predictive value and negative predictive value in comparison with conventional radiography, this difference was not significant.

Dental MRI using a dedicated RF-coil at 3 Tesla

PURPOSE

To assess the benefit of a dedicated surface coil to visualize dental structures in comparison to standard head/neck coil.

METHODS

Measurements were performed using the standard head/neck coil and a dedicated array coil for dental MRI at 3 T. As MRI methods, we used a T1-weighted spin-echo sequence with and without spectral fat saturation, a T2-weighted turbo-spin-echo sequence and a 3-dimensional T2-weighted SPACE sequence. Measurements were performed in a phantom to examine sensitivity profiles. Then the signal gain in dental structures was examined in volunteers and in a patient.

RESULTS

As expected for a surface coil, the signal gain of the dental coil was highest at the surface of the phantom and decreased with increasing distance to the coil; it was >120% even at a depth of 30 mm, measured from the centre of the coil. The signal gain within the pulp of the volunteers ranged between 236 and 413%.

CONCLUSION

The dedicated array coil offers a significantly higher signal within the region of interest for dental MR imaging thus allowing for better depiction of pathologies within the periodontium and for delineation and tracking of the branches of the maxillary and mandibular nerves.

An innovative approach in osteoporosis opportunistic screening by the dental practitioner: the use of cervical vertebrae and cone beam computed tomography with its viewer program

OBJECTIVES

To investigate the use of cone beam computed tomography (CBCT) for predicting osteoporosis based on the cervical vertebrae CBCT-derived radiographic density (RD) using the CBCT-viewer program.

STUDY DESIGN

CBCT scans (WhiteFox, de Gotzen S.r.l device, distributed by Satelec-Acteon Group, Italy) and dual-energy X-ray absorptiometry examinations of 38 women who participated in an earlier investigation were examined. A coronal slice, subjectively determined from the cervical vertebrae, was selected and the RD as gray values for the first and second vertebrae, and the dens was calculated by using CBCT-viewer software (WhiteFox imaging).

RESULTS

The CBCT-derived RD values of the dens and the left part of the first cervical vertebra showed the strongest correlation coefficients (r=0.7, 0.6; P<.001) and the highest sensitivity (76.9%, 70%), specificity (92%, 92.9%), and accuracy (90.8%, 86.4%) in predicting osteoporosis in the lumbar vertebrae and the femoral neck, respectively.

CONCLUSIONS

CBCT-derived RD of cervical vertebrae can predict osteoporosis status using a CBCT-viewer program. This finding should be confirmed on other CBCT devices.

Validation of Osteoarthritis synthetic defect database via non-rigid registration

Temporomandibular joint (TMJ) disorders are a group of conditions that cause pain and dysfunction in the jaw joint and the muscles controlling jaw movement. However, diagnosis and treatment of these conditions remain controversial. To date, there is no single sign, symptom, or test that can clearly diagnose early stages of osteoarthritis (OA). Instead, the diagnosis is based on a consideration of several factors, including radiological evaluation. The current radiological diagnosis scores of TMJ pathology are subject to misdiagnosis. We believe these scores are limited by the acquisition procedures, such as oblique cuts of the CT and head positioning errors, and can lead to incorrect diagnoses of flattening of the head of the condyle, formation of osteophytes, or condylar pitting. This study consists of creating and validating a methodological framework to simulate defects in CBCT scans of known location and size, in order to create synthetic TMJ OA database. User-generated defects were created using a non-rigid deformation protocol in CBCT. All segmentation evaluation, surface distances and linear distances from the user-generated to the simulated defects showed our methodological framework to be very precise and within a voxel (0.5 mm) of magnitude. A TMJ OA synthetic database will be created next, and evaluated by expert radiologists, and this will serve to evaluate how sensitive the current radiological diagnosis tools are.

Osteoporosis prediction from the mandible using cone-beam computed tomography

PURPOSE

This study aimed to evaluate the use of dental cone-beam computed tomography (CBCT) in the diagnosis of osteoporosis among menopausal and postmenopausal women by using only a CBCT viewer program.

MATERIALS AND METHODS

Thirty-eight menopausal and postmenopausal women who underwent dual-energy X-ray absorptiometry (DXA) examination for hip and lumbar vertebrae were scanned using CBCT (field of view: 13 cm×15 cm; voxel size: 0.25 mm). Slices from the body of the mandible as well as the ramus were selected and some CBCT-derived variables, such as radiographic density (RD) as gray values, were calculated as gray values. Pearson's correlation, one-way analysis of variance (ANOVA), and accuracy (sensitivity and specificity) evaluation based on linear and logistic regression were performed to choose the variable that best correlated with the lumbar and femoral neck T-scores.

RESULTS

RD of the whole bone area of the mandible was the variable that best correlated with and predicted both the femoral neck and the lumbar vertebrae T-scores; further, Pearson's correlation coefficients were 0.5/0.6 (p value=0.037/0.009). The sensitivity, specificity, and accuracy based on the logistic regression were 50%, 88.9%, and 78.4%, respectively, for the femoral neck, and 46.2%, 91.3%, and 75%, respectively, for the lumbar vertebrae.

CONCLUSION

Lumbar vertebrae and femoral neck osteoporosis can be predicted with high accuracy from the RD value of the body of the mandible by using a CBCT viewer program.

Advances in diagnostic imaging for pathologic conditions of the jaws

Advances in dental and maxillofacial imaging are delineated along with the advantages and disadvantages of each imaging modality. The imaging modalities that are included are intraoral radiography, panoramic radiography, cone-beam computed tomography, multidetector computed tomography, magnetic resonance imaging, nuclear medicine, and ultrasound.

Impact of voxel size variation on CBCT-based diagnostic outcome in dentistry: a systematic review

The objective of this study was to make a systematic review on the impact of voxel size in cone beam computed tomography (CBCT)-based image acquisition, retrieving evidence regarding the diagnostic outcome of those images. The MEDLINE bibliographic database was searched from 1950 to June 2012 for reports comparing diverse CBCT voxel sizes. The search strategy was limited to English-language publications using the following combined terms in the search strategy: (voxel or FOV or field of view or resolution) and (CBCT or cone beam CT). The results from the review identified 20 publications that qualitatively or quantitatively assessed the influence of voxel size on CBCT-based diagnostic outcome, and in which the methodology/results comprised at least one of the expected parameters (image acquisition, reconstruction protocols, type of diagnostic task, and presence of a gold standard). The diagnostic task assessed in the studies was diverse, including the detection of root fractures, the detection of caries lesions, and accuracy of 3D surface reconstruction and of bony measurements, among others. From the studies assessed, it is clear that no general protocol can be yet defined for CBCT examination of specific diagnostic tasks in dentistry. Rationale in this direction is an important step to define the utility of CBCT imaging.

Cone beam CT evaluation of the presence of anatomic accessory canals in the jaws

OBJECTIVES

To assess the prevalence, location and anatomical course of accessory canals of the jaws using cone beam CT.

METHODS

A retrospective analysis of 4200 successive cone beam CT scans, for patients of both genders and ages ranging from 7 to 88 years, was performed. They were exposed at the School of Dentistry, University of Michigan, Ann Arbor, MI. After applying the exclusion criteria (the presence of severe ridge resorption, pre-existing implants, a previously reported history of craniofacial malformations or syndromes, a previous history of trauma or surgery, inadequate image quality and subsequent scans from the same individuals), 4051 scans were ultimately included in this study.

RESULTS

Of the 4051 scans (2306 females and 1745 males) that qualified for inclusion in this study, accessory canals were identified in 1737 cases (42.9%; 1004 females and 733 males). 532 scans were in the maxilla (13.1%; 296 females and 236 males) and 1205 in the mandible (29.8%; 708 females and 497 males).

CONCLUSIONS

A network of accessory canals bringing into communication the inner and outer cortical plates of the jaws was identified. In light of these findings, clinicians should carefully assess for the presence of accessory canals prior to any surgical intervention to decrease the risk for complications.

Surfing the spectrum - what is on the horizon?

Diagnostic imaging techniques have evolved with technological advancements - but how far? The objective of this article was to explore the electromagnetic spectrum to find imaging techniques which may deliver diagnostic information of equal, or improved, standing to conventional radiographs and to explore any developments within radiography which may yield improved diagnostic data. A comprehensive literature search was performed using Medline, Web of Knowledge, Science Direct and PubMed Databases. Boolean Operators were used and key-terms included (not exclusively): terahertz, X-ray, ultraviolet, visible, infra-red, magnetic resonance, dental, diagnostic, caries and periodontal. Radiographic techniques are primarily used for diagnostic imaging in dentistry, and continued developments in X-ray imaging include: phase contrast, darkfield and spectral imaging. Other modalities have potential application, for example, terahertz, laser doppler and optical techniques, but require further development. In particular, infra-red imaging has regenerated interest with caries detection in vitro, due to improved quality and accessibility of cameras. Non-ionising imaging techniques, for example, infra-red, are becoming more commensurate with traditional radiographic techniques for caries detection. Nevertheless, X-rays continue to be the leading diagnostic image for dentists, with improved diagnostic potential for lower radiation dose becoming a reality.

Dilemmas pertaining to three canals in the mesiobuccal root of a maxillary second molar: a case report

The mesiobuccal root of the maxillary molars is well known to pose a hindrance during endodontic therapy. Presented here is a case of a maxillary left second molar where three canals were located in its mesiobuccal root with the use of visual and diagnostic aids. Difficulties encountered during the process of unveiling the tooth's internal anatomy were discussed. The dilemmas encountered pertained to the root canal configuration, the nomenclature of the extra canals, and the justification for the presence of a third canal. The root canal configuration of 3-2-1 was confirmed for the mesiobuccal root using information gained from clinical, radiographic, and multi-detector computed tomography (MDCT) scan findings. This case demonstrates the need for efforts to locate extra canals in the mesiobuccal root of the maxillary molars as their internal anatomy remains a mystery.

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.

Using GafChromic film to estimate the effective dose from dental cone beam CT and panoramic radiography

OBJECTIVES

To demonstrate the feasibility of GafChromic(®) XR-QA2 (ISP Corp., Wayne, NJ) as a dosemeter when performing measurements of the effective dose from three cone beam CT (CBCT) units and to compare the doses from examinations of three common dental clinical situations. A second aim was to compare the radiation doses for three digital panoramic units with the doses for the CBCT units.

METHODS

The CBCT units used were Veraviewepocs 3De(®) (J Morita MFG Corp., Kyoto, Japan), ProMax(®) 3D (Planmeca, Helsinki, Finland) and NewTom VGi(®) (Quantitative Radiology, Verona, Italy). GafChromic XR-QA2 films were placed between the selected layers of the head and neck of a tissue-equivalent human skull (RANDO(®) phantom; The Phantom Laboratory, Salem, NY). The exposure parameters were set using the automatic exposure control function of the units. Depending on the availability, medium and smaller field of view (FOV) scanning modes were used. The effective dose was estimated using the 2007 International Commission on Radiological Protection formalism.

RESULTS

The lowest effective dose of a CBCT unit was observed for ProMax 3D, FOV 4 × 5 cm (10 μSv), the highest for NewTom VGi, FOV 8 × 8 cm-high resolution (129 μSv). The range of effective doses for digital panoramic machines measured was 8-14 μSv.

CONCLUSIONS

This study demonstrates the feasibility of using radiochromic films for dental CBCT and panoramic dosimetry.

Technical assessment of a cone-beam CT scanner for otolaryngology imaging: image quality, dose, and technique protocols

PURPOSE

As cone-beam CT (CBCT) systems dedicated to various imaging specialties proliferate, technical assessment grounded in imaging physics is important to ensuring that image quality and radiation dose are quantified, understood, and justified. This paper involves technical assessment of a new CBCT scanner (CS 9300, Carestream Health, Rochester, NY) dedicated to imaging of the ear and sinuses for applications in otolaryngology-head and neck surgery (OHNS). The results guided evaluation of technique protocols to minimize radiation dose in a manner sufficient for OHNS imaging tasks.

METHODS

The technical assessment focused on the imaging performance and radiation dose for each of seven technique protocols recommended by the manufacturer: three sinus protocols and four ear (temporal bone) protocols. Absolute dose was measured using techniques adapted from AAPM Task Group Report No. 111, involving three stacked 16 cm diameter acrylic cylinders (CTDI phantoms) and a 0.6 cm(3) Farmer ionization chamber to measure central and peripheral dose. The central dose (D(o)) was also measured as a function of longitudinal position (z) within and beyond the primary radiation field to assess, for example, out-of-field dose to the neck. Signal-difference-to-noise ratio (SDNR) and Hounsfield unit (HU) accuracy were assessed in a commercially available quality assurance phantom (CATPHAN module CTP404, The Phantom Laboratory, Greenwich, NY) and a custom phantom with soft-tissue-simulating plastic inserts (Gammex RMI, Madison, WI). Spatial resolution was assessed both qualitatively (a line-pair pattern, CATPHAN module CTP528) and quantitatively (modulation transfer function, MTF, measured with a wire phantom). Imaging performance pertinent to various OHNS imaging tasks was qualitatively assessed using an anthropomorphic phantom as evaluated by two experienced OHNS specialists.

RESULTS

The technical assessment motivated a variety of modifications to the manufacturer-specified protocols to provide reduced radiation dose without compromising pertinent task-based imaging performance. The revised protocols yielded D(o) ranging 2.9-5.7 mGy, representing a ∼30% reduction in dose from the original technique chart. Out-of-field dose was ∼10% of D(o) at a distance of ∼8 cm from the field edge. Soft-tissue contrast resolution was fairly limited (water-brain SDNR ∼0.4-0.7) while high-contrast performance was reasonably good (SDNR ∼2-4 for a polystyrene insert in the CATPHAN). The scanner does not demonstrate (or claim to provide) accurate HU and exhibits a systematic error in CT number that could potentially be addressed by further calibration. The spatial resolution is ∼10-16 lp∕cm as assessed in a line-pair phantom, with MTF exceeding 10% out to ∼20 lp∕cm. Qualitative assessment by expert readers suggested limited soft-tissue visibility but excellent high-contrast (bone) visualization with isotropic spatial resolution suitable to a broad spectrum of pertinent sinus and temporal bone imaging tasks.

CONCLUSIONS

The CBCT scanner provided spatial and contrast resolution suitable to visualization of high-contrast morphology in sinus, maxillofacial, and otologic imaging applications. Rigorous technical assessment guided revision of technique protocols to reduce radiation dose while maintaining image quality sufficient for pertinent imaging tasks. The scanner appears well suited to high-contrast sinus and temporal bone imaging at doses comparable to or less than that reported for conventional diagnostic CT of the head.