A survey of patient contact shielding in dental teaching hospitals in the UK.

A high volume of dental imaging is carried out each year. In the UK, guidance on the use of patient contact shielding for these investigations is published by the British Institute of Radiology (BIR) and in a document jointly produced by the Faculty of General Dental Practice and Public Health England (FGDP/PHE). Both these sources of guidance have been updated recently and patient contact shielding is no longer recommended for most imaging settings in dental radiology. It is unclear whether radiology departments at dental teaching hospitals in the UK are aware of these sources of guidance, and how this relates to clinical practice within these departments. A survey was carried out exploring the awareness of current guidelines and clinical practice at dental teaching hospitals in the UK. The survey was sent to a representative at 17 different dental teaching hospital radiology departments. Responses were received from 11 departments. The range of intra-oral and extra-oral imaging carried out at these departments was comparable. Ten departments were aware of the existence of national guidelines for patient contact shielding, however only four were specifically aware of the recent BIR guidelines and only four were specifically aware of the FGDP/PHE guidelines. No department was aware of both sets of guidelines. No departments used thyroid protection for bitewing, periapical, lower 45 degree occlusal, panoramic or lateral cephalometric radiographs. Six departments sometimes or always used thyroid protection for upper standard occlusal imaging. Two departments used thyroid protection for cone beam CT imaging. No departments routinely used lead aprons on patients for dental imaging. In conclusion, radiology departments at dental teaching hospitals in the UK do not use patient contact shielding for most imaging situations in dental radiology. There is mixed awareness of current national guidelines, but the reported clinical practice aligns well with the current guidelines.

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

Cone-beam computed tomography (CBCT) was first used in dental and maxillofacial radiology (DMFR) at the end of the 1990s. Since then, it has been successfully established as the standard three-dimensional radiographic imaging technique in DMFR, with a wide variety of applications in this field. This manuscript briefly reviews the background information on the technology and summarises available data on effective dose and dose optimisation. In addition, typical clinical applications and indications of the technique in DMFR are presented.

Imaging patients with cancer of the oral cavity.

The staging of oral cavity tumours as with all other malignancy subsites is undergoing a revision in the line with the updated American Joint Committee on Cancer guidelines. Of note, the new guidelines incorporate more emphasis on clinical and histopathological data. The aim of the new guidelines is to increase prognostic concordance between stage and survival. This article aims to review the multimodality approach to imaging of oral cavity malignancy. In addition, it will also review the multidisciplinary approach to diagnosis and management of these tumours as multiple specialities are crucial for effective treatment.

An investigation in to the impact of acquisition location on error type and rate when undertaking panoramic radiography.

INTRODUCTION: Panoramic radiography is a common radiographic examination carried out in the UK. This study was carried out to determine if acquisition site has an impact on image quality. METHODS: An image quality audit was carried out in South Wales across a number of dental and general radiology settings. The image quality was assessed retrospectively against national standards. A total of 174 radiographs were assessed from general radiology departments and 141 from dental radiology units. Chi-squared analysis was used to investigate whether there were differences in the grading between dental radiology units and general radiology departments. Differences between the two settings in terms of the number of errors in the radiographs was analysed using the Mann-Whitney test. Chi-squared analysis was used to see if there were differences between the types of errors in the two clinical settings. RESULTS: There was a significant association (p = 0.021) between the quality of the radiograph grading and type of radiology department. However when excellent and diagnostically acceptable radiographs were grouped together there was no significant difference between the two clinical settings. Although the vast majority of radiographs were diagnostic (89% for general radiology and 92% for dental radiology units), neither reached the required standards. The most common errors were patient positioning errors (54.6% radiographs affected) and preparation/instructional errors (47.9% radiographs affected). CONCLUSION: Errors in panoramic radiography are relatively high and further instruction to staff undertaking these procedures is required to ensure the targets are reached.

Sebaceous carcinoma of the lip: Comparing normal lip and cheek anatomy with the imaging features of a rare cutaneous malignancy.

Sebaceous carcinoma is a rare cutaneous malignancy, commonly affecting the eyelids. This case highlights a patient who presented with sebaceous carcinoma of the right upper lip with extensive involvement of the soft tissues of the head and neck. As part of the initial investigation, ultrasound was requested. This case demonstrates the ultrasound features of sebaceous carcinoma as well as revising the normal ultrasound anatomy of the upper lip and muscles of the cheek.

Solitary fibrous tumour of the cheek: An unusual presentation of a rare soft tissue tumour.

This case report discusses the unusual presentation and ultrasound features of a solitary fibrous tumour of the face. Solitary fibrous tumour is an uncommon form of soft tissue tumour which, although seen predominantly within the lung pleura, can occur throughout the body in sites such as the peritoneum, mediastinum and head and neck. Ultrasound is an excellent imaging modality in the assessment of soft tissue masses in the head and neck. The ultrasound features demonstrated by this example of solitary fibrous tumour are reviewed. This report also highlights that ultrasound alone is ultimately limited in reaching a definitive diagnosis. The roles of other investigations such as ultrasound-guided biopsy and cross-sectional imaging are discussed.

A pitfall in the reconstruction of fibre ODFs using spherical deconvolution of diffusion MRI data.

Diffusion weighted (DW) MRI facilitates non-invasive quantification of tissue microstructure and, in combination with appropriate signal processing, three-dimensional estimates of fibrous orientation. In recent years, attention has shifted from the diffusion tensor model, which assumes a unimodal Gaussian diffusion displacement profile to recover fibre orientation (with various well-documented limitations), towards more complex high angular resolution diffusion imaging (HARDI) analysis techniques. Spherical deconvolution (SD) approaches assume that the fibre orientation density function (fODF) within a voxel can be obtained by deconvolving a 'common' single fibre response function from the observed set of DW signals. In practice, this common response function is not known a priori and thus an estimated fibre response must be used. Here the establishment of this single-fibre response function is referred to as 'calibration'. This work examines the vulnerability of two different SD approaches to inappropriate response function calibration: (1) constrained spherical harmonic deconvolution (CSHD)--a technique that exploits spherical harmonic basis sets and (2) damped Richardson-Lucy (dRL) deconvolution--a technique based on the standard Richardson-Lucy deconvolution. Through simulations, the impact of a discrepancy between the calibrated diffusion profiles and the observed ('Target') DW-signals in both single and crossing-fibre configurations was investigated. The results show that CSHD produces spurious fODF peaks (consistent with well known ringing artefacts) as the discrepancy between calibration and target response increases, while dRL demonstrates a lower over-all sensitivity to miscalibration (with a calibration response function for a highly anisotropic fibre being optimal). However, dRL demonstrates a reduced ability to resolve low anisotropy crossing-fibres compared to CSHD. It is concluded that the range and spatial-distribution of expected single-fibre anisotropies within an image must be carefully considered to ensure selection of the appropriate algorithm, parameters and calibration. Failure to choose the calibration response function carefully may severely impact the quality of any resultant tractography.

Evaluation of three imaging techniques for the detection of vertical root fractures in the absence and presence of gutta-percha root fillings.

AIM: To compare the accuracy of digital radiography (DR), multidetector computed tomography (MDCT) and cone beam computed tomography (CBCT) in detecting vertical root fractures (VRF) in the absence and presence of gutta-percha root filling. METHODOLOGY: The root canals of 100 extracted human single-rooted teeth were prepared and randomly divided into four groups: two experimental groups with artificially fractured root and two intact groups as controls. In one experimental and one control group, a size 40, 0.04 taper gutta-percha cone was inserted in the root canals. Then DR, MDCT and CBCT were performed and the images evaluated. Statistical analyses of sensitivity, specificity and accuracy of each imaging technique in the presence and absence of gutta-percha were calculated and compared. RESULTS: In the absence of gutta-percha, the specificity of DR, MDCT and CBCT was similar. CBCT was the most accurate and sensitive imaging technique (P < 0 .05). In the presence of gutta-percha, the accuracy of MDCT was higher than the other imaging techniques (P < 0.05). The sensitivity of CBCT and MDCT was significantly higher than that of DR (P < 0.05), whereas CBCT was the least specific technique. CONCLUSIONS: Under the conditions of this ex vivo study, CBCT was the most sensitive imaging technique in detecting vertical root fracture. The presence of gutta-percha reduced the accuracy, sensitivity and specificity of CBCT but not MDCT. The sensitivity of DR was reduced in the presence of gutta-percha. The use of MDCT as an alternative technique may be recommended when VRF are suspected in root filled teeth. However, as the radiation dose of MDCT is higher than CBCT, the technique could be considered at variance with the principles of ALARA.

The reliability of high resolution ultrasound in the identification of pus collections in head and neck swellings.

Head and neck swellings often present to oral and maxillofacial surgeons. It is often unclear whether a collection of pus is present. This information is essential for decisions regarding surgical intervention. Although ultrasound scanning (USS) is widely used to investigate the presence of a collection, the reliability and validity of this investigation in this context is uncertain. A retrospective review of 4000 consecutive head and neck USS reports over a 4 year period in the Cardiff University Health Board produced 43 cases in which ultrasound had been used to look for evidence of pus collection. The management and treatment outcome of these patients were reviewed and the data analysed. 36 of 43 patients had their swelling incised in theatre, and in 92% of these cases USS and clinical findings corresponded. Of the seven not taken to theatre, four were USS negative and three USS positive; in all seven cases the swelling resolved with antimicrobial therapy. Sensitivity and specificity of USS imaging to identify pus collection were very high, 96% and 82%, respectively. The evidence in this study indicates that USS is a very reliable diagnostic tool in the diagnosis of a collection as well as providing evidence that small collections of pus can resolve without surgical drainage.

Continuing dental education in radiation protection: knowledge retention following a postgraduate course.

OBJECTIVE: To evaluate medium-term knowledge retention of dental personnel following attendance at a postgraduate course in radiation protection. SUBJECTS AND METHODS: Knowledge was measured using identical pre- and post-course validated single best-answer multiple-choice instruments, administered immediately before and after training and at follow-up at 6 or 12 months. These comprise 16 questions each with 5 choices. The range of possible scores was from 0 to 16, and scores were scaled to percentages. Participants were predominantly dental practitioners, but a minority consisted of dental care professionals (dental nurses, hygienists and therapists). Of 285 participants, 272 (95.4%) completed both pre- and post-course questionnaires. One hundred and seventeen (43%) of these also completed the follow-up test, but only 109 (40%) individuals could be linked to the original course. RESULTS: Mean (standard deviation) pre-, post-course and follow-up-corrected percentage scores were 39.1 (16.1), 74.6 (16.9) and 58.9 (22.7), respectively. There was attrition in knowledge at follow-up: the average increase in adjusted score after training was 35.5 points, but only 56% of this was retained at follow-up. Paired t-tests confirmed that the mean score at follow-up was firmly intermediate between the pre- and post-course scores. Of the 109 participants, 7 (6%) achieved a satisfactory score pre-training, 82 (75%) immediately post-training and 41 (38%) at follow-up. There were gross differences between the levels of performance achieved for the eight subject areas tested. CONCLUSION: Immediate post-course assessments have indicated that current postgraduate courses in radiation protection are effective. However, a substantial amount of knowledge is lost by 6-12 months following course attendance. To achieve long-term knowledge retention, early or repeated reinforcement may be necessary.

A comparative study of image quality and radiation exposure for dental radiographs produced using a charge-coupled device and a phosphor plate system.

AIM: To investigate the quality of periapical radiographic images produced by two digital dental radiography systems, a charge-coupled device (CCD) and a photostimulable phosphor (PSP) image plate system, and to examine the overall radiation exposure when using these systems in a clinical setting. METHODOLOGY: Patients were randomly allocated to both systems and the resultant radiographs rated for quality. The expected radiation exposure for an investigation was calculated. RESULTS: Overall, 98 images were acquired using the CCD system and 108 with the PSP system. The PSP system produced significantly higher quality (P < 0.001) periapical images compared with the CCD system. The CCD system required significantly more (P < 0.001) repeat exposures to obtain a diagnostic image than the PSP system but at a lower expected radiation exposure. CONCLUSIONS: The image quality was superior using the phosphor plate system. Although more repeat radiographs were required using the CCD system, the images were produced with a lower expected radiation exposure.

Cone beam computed sialography of sialoliths.

Cone beam CT is an emerging imaging modality used in maxillofacial imaging. This paper describes the use of cone beam sialography in two patients with salivary gland obstruction. In both cases, the obstruction was identified. The dose is comparable with conventional fluoroscopic techniques and has the advantage that the data may be viewed in a series of fine slices and in three dimensions, which may help in diagnosis and further management of the patient.

Effective dose from cone beam CT examinations in dentistry.

Cone beam CT (CBCT) is becoming an increasingly utilized imaging modality for dental examinations in the UK. Previous studies have presented little information on patient dose for the range of fields of view (FOVs) that can be utilized. The purpose of the study was therefore to calculate the effective dose delivered to the patient during a selection of CBCT examinations performed in dentistry. In particular, the i-CAT CBCT scanner was investigated for several imaging protocols commonly used in clinical practice. A Rando phantom containing thermoluminescent dosemeters was scanned. Using both the 1990 and recently approved 2007 International Commission on Radiological Protection recommended tissue weighting factors, effective doses were calculated. The doses (E(1990), E(2007)) were: full FOV head (92.8 microSv, 206.2 microSv); 13 cm scan of the jaws (39.5 microSv, 133.9 microSv); 6 cm high-resolution mandible (47.2 microSv, 188.5 microSv); 6 cm high-resolution maxilla (18.5 microSv, 93.3 microSv); 6 cm standard mandible (23.9 microSv, 96.2 microSv); and 6 cm standard maxilla (9.7 microSv, 58.9 microSv). The doses from CBCT are low compared with conventional CT but significantly higher than conventional dental radiography techniques.

Case report: segmental odontomaxillary dysplasia--a rare disorder.

BACKGROUND: Segmental odontomaxillary dysplasia (SOD) is a rare developmental disorder of the maxilla characterised by abnormal growth and maturation of bone, teeth and gingival of the affected segment. Due to the rarity of the disorder, the full range of clinical manifestations is unknown. Since there are concerns that cases may be subject to misdiagnosis, this report aims to increase awareness of the condition among paediatric dentists. CASE REPORT: A 7-year-old boy was initially referred regarding failure of eruption of maxillary primary molars. Characteristic clinical and radiographic findings led to the diagnosis of SOD. Interestingly, the patient presented with unilateral ectopic eyelashes, a finding previously unreported in association with this condition. TREATMENT: Reassurance was provided regarding the benign nature of the condition. While no active intervention was needed at the time of diagnosis, close monitoring is essential. Future management may require surgical, orthodontic and prosthetic input. FOLLOW-UP: A period of four years elapsed between initial presentation of the condition and its definitive diagnosis. No significant increase in the unilateral maxillary swelling was noted. The patient will continue to be monitored on a regular basis. CONCLUSION: SOD is a rare cause of facial asymmetry. Prompt diagnosis can reassure both patient and healthcare professionals. Reporting of cases is encouraged to help determine the full range of clinical manifestations and establish a management protocol.

Study of the scan uniformity from an i-CAT cone beam computed tomography dental imaging system.

OBJECTIVES: As part of an ongoing programme to improve diagnosis and treatment planning relevant to implant placement, orthodontic treatment and dentomaxillofacial surgery, a study has been made of the spatial accuracy and density response of an i-CAT, a cone beam CT (CBCT) dental imaging system supplied by Imaging Sciences International Inc. METHODS: Custom-made phantoms using acrylic sheet and water were used for measurements on spatial accuracy, density response and noise. The measurements were made over a period of several months on a clinical machine rather than on a machine dedicated to research. RESULTS: Measurements on a precision grid showed the spatial accuracy to be universally within the tolerance of +/-1 pixel. The density response and the noise in the data were found to depend strongly on the mass in the slice being scanned. CONCLUSIONS: The density response was subject to two effects. The first effect changes the whole slice uniformly and linearly depends on the total mass in the slice. The second effect exists when there is mass outside the field of view, dubbed the "exo-mass" effect. This effect lowers the measured CT number rapidly at the scan edge furthest from the exo-mass and raises it on the adjacent edge. The noise also depended quasi-linearly on the mass in the slice. Some general performance rules were drafted to describe these effects and a preliminary correction algorithm was constructed.

Mid-line clefts of the cervical vertebrae - an incidental finding arising from cone beam computed tomography of the dental patient.

Cone beam computed tomography (CBCT) is a rapidly emerging imaging modality in dentistry that offers the advantages of high diagnostic yield with short scanning times and a radiation dose significantly lower than conventional CT. Clinical applications of CBCT are numerous and they are being used both within the hospital and the primary care setting. The need for complete interpretation of CBCT images is essential. This report presents two patients for whom CBCT was carried out for orthodontic related purposes and incidental findings of cervical vertebrae clefts diagnosed. CBCT wherever they are undertaken should be reported by someone who has undergone adequate training in their interpretation particularly when machines using a large field of view are employed.

Resorption: within or without? The benefit of cone-beam computed tomography when diagnosing a case of an internal/external resorption defect.

Maxillary canines are the second most common teeth to become impacted, following third molars. Variable levels of incidence have been reported but roughly fall between 1-2.5%. The aetiology of impaction is unknown but both environmental and genetic factors have been suggested. The majority of impacted canines are palatally displaced and such ectopic teeth can be associated with various complications. Rarely this may include cystic or tumourous lesions of the dental follicle or, more commonly, resorption of adjacent teeth. This has a reported incidence of between 12% and 68% depending on the modality of diagnosis and the population sampled. With overlapping teeth causing superimposition on developed images, the diagnostic accuracy of intra-oral radiographs may be reduced. Conventional tomography also exhibits blurring of images and this again reduces its sensitivity. For this reason, Cone Beam Computed Tomography may be beneficial in selected cases of tooth resorption.

Salivary duct strictures: nature and incidence in benign salivary obstruction.

OBJECTIVES: The aim of this study was to establish the incidence and character of salivary duct strictures by carrying out a 10 year retrospective review. Salivary gland obstruction is most commonly caused either by salivary calculi or duct strictures. These strictures or stenoses develop secondarily to inflammation in the duct wall and may be single or multiple. METHODS: All reports of sialographic examinations performed on patients referred to the Dental Radiology Department in a London Dental Hospital between 1995 and 2004 were reviewed and those patients with symptoms of salivary obstruction identified. In total, 1362 sialograms using the conventional hand injection technique with water-soluble contrast media were performed on 1349 patients with obstructive symptoms during the 10-year period. RESULTS: Of the 1362 sialograms performed, the reports revealed that 877 (64.4%) showed evidence of benign intraductal obstruction. The remaining 485 (35.6%) were normal. 642 of the cases (73.2%) revealing obstruction were reported to be due to salivary calculi, 198 due to duct strictures (22.6%) and the remaining 37 (4.2%) were considered to be due to mucous plugs. Detailed analysis of the patients with strictures showed they were more common in women with a mean age of 52 years. Single strictures were evident in 66.7% of cases while 33.3% showed multiple stenoses. Strictures were more common in the parotid duct (75.3%). 7% of patients presented with bilateral stenoses. CONCLUSION: This is the largest review of duct strictures to be reported. It has shown that ductal stricture formation accounts for almost 25% of cases of benign salivary obstruction and appears to have been an under-recognized condition. Strictures more commonly affect parotid ducts and are typically found in the fourth, fifth or sixth decades, particularly in women.

The effectiveness of dental postgraduate courses--are we doing the right thing?

OBJECTIVE: To evaluate the effectiveness of dental postgraduate one-day courses in radiation protection in Wales. DESIGN: Analysis of dentists' performance pre- and immediately post-course training. SUBJECTS AND METHODS: Two hundred and eighty-five general dental practitioners took part in eight courses. Identical, validated multiple choice questionnaires were completed anonymously at the start and at the end of each course. Fifty (+62.5%) or above was regarded as a satisfactory standard. Two hundred and fifty-three (89%) paired morning-afternoon records were completed and analysed. Data was compared to that of similar courses five years earlier. RESULTS: The mean (SD) pre- and post-course percentage scores were 33.8 (13.5) and 63.6 (14.6). The mean improvement was 29.8 percentage points (SD 11.7). The pre-post correlation was +0.66. At baseline only six (2.4%) of the 253 practitioners achieved the preset standard. After the course, 146 (57.7%) did so, an improvement of 55.3% (95% CI 48.9-61.3%). The final score and score gain were slightly higher in more recent graduates. The increase in proportion attaining the standard following training was 11.9% higher for IRMER than for POPUMET (p <0.001). CONCLUSION: The level of knowledge in radiation protection was very low at baseline. Whilst attending the approved course led to considerable improvement, it did not invariably result in a satisfactory level of knowledge in fundamental radiation physics and regulations. The prescribed standard was achieved by less than 60% of the attendees. The IRMER course was significantly more effective than its POPUMET predecessor.