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.

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.

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.

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.

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.

Ectopic submandibular gland presenting as a swelling in the floor of mouth.

The authors describe a patient who presented with a left sublingual swelling. Ultrasonic and sialographic investigation showed no salivary tissue in the expected left submandibular region, but a large salivary gland in the left floor of the mouth deep to the mylohyoid muscle. This is likely to represent an ectopically positioned submandibular gland.

Staple diet: a foreign body in a tooth.

The chance discovery of a foreign object embedded in a tooth is uncommon, and requires radiographic examination to determine the composition and location of the object. The authors describe the case of an 11-year-old boy who presented with a staple lodged in the root canal of the maxillary left permanent central incisor. This staple was localized using parallax techniques and successfully removed from the canal. The radiographic techniques of localization and possible methods of removal of foreign bodies are discussed.

Ultrasound-guided basket retrieval of salivary stones: a new technique.

We describe the successful use of ultrasound-guided retrieval of a submandibular stone with a basket in two patients.

Haemangioma of the body of the mandible: a case report.

We present a case of haemangioma of the mandible in a 46-year-old woman. The radiological appearance was of a unilocular radiolucency that looked similar to other more common lesions of the mandible. This case shows that a potentially life-threatening haemangioma can present as an apparently benign cyst-like unilocular radiolucency, and highlights the need to include haemangioma in many differential diagnoses, and the importance of taking all radiological features into account.

Extracorporeal shockwave lithotripsy in the management of salivary calculi.

BACKGROUND: The aim was to investigate the results of extracorporeal shockwave lithotripsy in the management of salivary calculi using a dedicated sialolithotriptor. METHODS: Some 122 salivary calculi (84 submandibular and 38 parotid) were treated in an experimental study using a sialolithotriptor. RESULTS: Complete success was achieved in 40 procedures (33 per cent), 27 of 84 submandibular and 13 of 38 parotid calculi. A further 43 patients (35 per cent) were rendered asymptomatic although some stone debris remained in the duct (26 submandibular and 17 parotid). Failure (retention of stone debris and continued symptoms) occurred in 39 patients (32 per cent), 30 submandibular and eight parotid glands. The chance of failure increased with the size of the calculus and increasing duration of symptoms. CONCLUSION: Extracorporeal shockwave lithotripsy provides a useful option for the management of salivary calculi, particularly for stones less than 7 mm in diameter.

Differential diagnosis and treatment of autosomal dominant osteosclerosis of the mandible.

A 20-year-old patient who presented with concerns about her large mandible was found to have a generalized mild cortical sclerosis. She was treated successfully with staged orthognathic surgery, despite the dense sclerosis of the jaws.

Pain and swelling after sialography: is it a significant problem?

OBJECTIVES: This study investigated the incidence of pain and swelling after sialography and quantified the duration and severity of these symptoms. STUDY DESIGN: Sialography was performed on 92 patients who were then given a questionnaire to complete. Seventy-two questionnaires were returned and completed in a satisfactory manner. The patients were asked to assess pain and swelling before and after the sialogram was performed by using a Visual Analogue Scale (VAS). Comparisons between postsialographic measurements and baseline measures were carried out by using Friedman repeated measures analysis of variance on ranks. RESULTS: VAS scores increased significantly for both pain and swelling 1 hour after the sialogram (T1). The scores for swelling returned to baseline levels after 1 day (T2). The VAS for pain showed a similar pattern, but 2 days after the sialogram (T3), the scores were significantly lower, compared with those before the sialogram (P <. 05). CONCLUSIONS: Sialography is a safe procedure. Patients should be advised that minor effects may last approximately 1 day. A reduction in pain to below baseline levels was noted 2 days after sialography, which may suggest an unexpected benefit of sialography.

Interventional radiology in the removal of salivary calculi.

PURPOSE: To prospectively investigate the efficacy of a wire basket extractor in the retrieval of salivary calculi and establish selection criteria for suitable cases. MATERIALS AND METHODS: Twenty-five consecutive patients (14 male, 11 female; age range, 13-69 years) with salivary calculi (20 submandibular, five parotid) were treated by using a commercially available wire basket extractor with intermittent fluoroscopic guidance. RESULTS: Elimination of calculi was accomplished in 10 (40%) cases. In an additional seven (28%) cases, either part of the calculus was removed or whole calculi were removed with others remaining. Failure to retrieve any stone occurred in eight (32%) cases. The most common cause of failure was attachment of the calculus to the duct wall. CONCLUSION: Interventional radiology provides a useful adjuvant method of calculus removal and complements extracorporeal lithotripsy. Basket retrieval of calculi has low morbidity and is rapid and less invasive than traditional surgery. It is most effective in retrieving mobile stones in the extraglandular parotid and submandibular ducts.