Accuracy and precision of a densitometric tool for jaw bone.

OBJECTIVES: To develop a digital densitometric tool for jaw bone to analyse intraoral radiographs. To assess precision and accuracy for this tool and determine the minimal detection threshold for density changes. METHODS: Bone samples deriving from the premolar region of 47 human mandibles were selected for analysis. The samples were obtained from adult cadavers in the department of anatomy (Faculty of Medicine, KULeuven) with ethical approval. Digital radiography was performed on all bone samples. Direct volumetric measurements served as gold standard density values and allowed determination of accuracy. Dual-energy X-ray absorptiometry (DXA) scans were performed on all specimens. For all radiographs, density in mm Al eq was calculated using custom-made software, Osteop. Precision and intraobserver and interobserver reliability of this method were assessed. The bone specimens were progressively decalcified. At standard time intervals the percentage of decalcification was calculated. At each decalcification step, radiographs were taken and analysed. RESULTS: CV was always lower than 3%, which points to a good precision of the method. Correlation between the density measurements in mm Al eq and the DXA results was 0.9, for the density measurements in mm Al eq and the direct density measurements r was 0.5. The custom-made software was able to detect a change in bone mineralization of 6.6%. CONCLUSIONS: The present method for bone densitometric analysis offers potentials for clinical evaluation of bone density and minute bone density changes in the jaw bone.

Dosimetry of digital panoramic imaging. Part I: Patient exposure.

OBJECTIVES: To measure patient radiation dose during panoramic exposure with various panoramic units for digital panoramic imaging. METHODS: An anthropomorphic phantom was filled with thermoluminescent dosemeters (TLD 100) and exposed with five different digital panoramic units during ten consecutive exposures. Four machines were equipped with a direct digital CCD (charge coupled device) system, whereas one of the units used storage phosphor plates (indirect digital technique). The exposure settings recommended by the different manufacturers for the particular image and patient size were used: tube potential settings ranged between 64 kV and 74 kV, exposure times between 8.2 s and 19.0 s, at fuse current values between 4 mA and 7 mA. The effective radiation dose was calculated with inclusion of the salivary glands. RESULTS: Effective radiation doses ranged between 4.7 microSv and 14.9 microSv for one exposure. Salivary glands absorbed the most radiation for all panoramic units. When indirect and direct digital panoramic systems were compared, the effective dose of the indirect digital unit (8.1 microSv) could be found within the range of the effective doses for the direct digital units (4.7-14.9 microSv). CONCLUSIONS: A rather wide range of patient radiation doses can be found for digital panoramic units. There is a tendency for lower effective doses for digital compared with analogue panoramic units, reported in previous studies.

Dosimetry of digital panoramic imaging. Part II: Occupational exposure.

OBJECTIVES: To measure occupational radiation dose during panoramic exposure from five digital panoramic X-ray units. METHODS: Exposures were made with five different digital panoramic units, of which four were equipped with a direct digital CCD (charge coupled device, "direct digital" technique), and one used storage phosphor plates ("indirect digital" technique). An anthropomorphic phantom served as the patient. An ionization chamber recorded the scattered radiation at 1 m from the phantom at five different locations around the panoramic units, both at the level of the thyroid gland and the level of the gonads, and effective organ doses were calculated. Exposure parameters were set as recommended by the manufacturers for the particular image and patient size: tube potential settings ranged between 64 kV and 74 kV, exposure times between 8.2 s and 19.0 s, tube current values between 4 mA and 7 mA. RESULTS: The maximum organ equivalent dose at 1 m from the panoramic unit was 0.60 microGy, the maximum organ effective dose was 0.10 microSv. Organ equivalent doses varied between 0.18 microGy and 0.30 microGy and organ effective doses between 0.01 microSv and 0.05 microSv for the different positions around the units (average for the different panoramic units). The variations in organ doses for the various machines were 0.04-0.53 microGy organ equivalent dose and 0.01-0.08 microSv organ effective dose. CONCLUSIONS: Assuming that 500 panoramic radiographs per year are taken by a dental practitioner at 1 m distance from the panoramic unit, he or she will receive an annual additional organ effective dose between 5 microSv and 15 microSv for the thyroid gland and between 5 microSv and 40 microSv for the gonads, depending on the type of digital panoramic unit.

Digital radiographic equipment in the Belgian dental office.

A survey was performed among Belgian dentists to evaluate the use and management of digital radiographic equipment. The majority of respondents work as general dental practitioners. One out of eight sets of equipment for extraoral exposures is digital. For intraoral radiography, 30% of the equipment is digital. While exposure time is reduced by about 50% for digital intraoral radiography compared with conventional radiography, no differences can be found between different conventional film speed classes. Appropriate collimation of the radiation beam is only sparingly used. Beam aiming devices to hold the film and position the radiation beam are not used by the majority of dentists. While 25% of the respondents stand behind a protective wall during exposure, 8% of dentists remain next to the patient during exposure while assisting in holding the film inside the mouth. A minority of the latter practitioners wear lead aprons.

Attitude of the Belgian dentist population towards radiation protection.

OBJECTIVES: To perform a survey of private dental offices in Belgium and gain insight in the knowledge and attitude of Belgian dentists towards quality care in radiography and radiation protection. METHODS: A questionnaire was distributed among 700 Belgian dental offices, which were included based on demographic data and the use of intraoral radiographic equipment. RESULTS: The response rate was 71%. Implementation of standards for quality care and radiation protection was suboptimal. In most offices, exposure settings of the intraoral radiation tube were 65 kV/kVp to 70 kV/kVp and 10 mA to 12 mA, with an average exposure time of 0.45 s. No reduction of exposure time was noticed when using faster film types. About one-third of the responders worked with digital image receptors. Aiming devices and rectangular collimation were used in a minority of practices (40% and 6%, respectively). The distance of the dentist to the radiation tube during exposure was on average 2.2 m, although 8% of the dentists assisted in holding the image receptor inside the patient's mouth. One quarter of the dentists were standing behind a wall when taking radiographs. Lead aprons were worn more often by female dentists. Dose estimation revealed that male dentists received a significantly larger effective dose per year than female dentists (8.3 mSv vs 3.2 mSv). CONCLUSIONS: The implementation of standards of quality care for radiography and radiation protection could be improved among Belgian dentists. An elaborate educational programme in dental radiography is a prerequisite. Furthermore, recommendations could help to attain a change in attitude towards the use of ionizing radiation in order to meet European guidelines.

Radiation doses of indirect and direct digital cephalometric radiography.

AIM: The aim of this study was to measure organ doses and calculate the effective dose for indirect and direct digital cephalometric exposures. MATERIAL AND METHODS: Indirect digital cephalometric exposures were made of a Rando phantom head using a Cranex Tome multipurpose unit with storage phosphor plates from Agfa and the direct digital (Charge Coupled Device, CCD) exposures were made with a Proline Ceph CM unit. Exposure settings were 70 kV and 4 mAs for indirect digital exposures. Direct digital exposures were made with 70 kV, 10 mA and a total scanning time of 23 s. TLD700 dosemeters were used to measure organ doses, and the effective doses were calculated with (effective dose(sal)) and without inclusion of the salivary glands. A pilot study was carried out to compare diagnostic image quality of both imaging modalities. RESULTS: Effective doses were 1.7 microSv for direct digital and 1.6 microSv for indirect digital cephalometric imaging. When salivary glands were included in the calculation, effective doses(sal) were 3.4 microSv and 2.2 microSv respectively. Organ doses were higher for direct digital imaging, except for the thyroid gland, where the organ doses were comparable. Diagnostic image quality of indirect and direct digital cephalometric images seemed comparable. CONCLUSION: Effective dose and effective dose(sal) were higher for direct digital cephalometric exposure compared with indirect digital exposure. Organ doses were higher for direct digital cephalography. From preliminary data, it may be presumed that diagnostic image quality of indirect and direct digital cephalometric images are comparable.

Radiation doses of collimated vs non-collimated cephalometric exposures.

OBJECTIVES: The aim of the study was to compare organ and effective radiation doses for collimated and non-collimated cephalometric radiographs made by a multipurpose extraoral radiation unit. METHODS: Cephalometric exposures were made from a Rando head phantom representing an average man with the Cranex Tome multipurpose radiation unit. A collimator was fabricated from a 3-mm thick piece of lead. The collimator was designed so that structures relevant for orthodontic diagnosis were not shielded, whereas the thyroid gland and the major part of the skull were shielded. Absorbed organ doses were measured using thermoluminescent dosimeters. The effective dose was calculated both with (E(sal)) and without (E) inclusion of the salivary glands. RESULTS: Use of a wedge-shaped lead collimator yielded a reduction in field size of 55% and a reduction in E from 3.0 micro Sv to 1.6 micro Sv (47%) and in E(sal) from 3.7 micro Sv to 2.2 micro Sv (41%). CONCLUSIONS: Use of a wedge-shaped collimator should be advocated in all cases where depiction of the thyroid gland and the neurocranium is not required. The resulting reduction in effective dose using our collimator was 47% (41% when the salivary glands are included), which is of clinical importance, especially in children.

[Preoperative radiological planning for oral implants]. / Preoperatieve röntgenologische planning voor implantaten.

For patients who lost one or more teeth, oral osseointegrating implants can offer a natural and solid solution. In order to rehabilitate (partially) edentulous patients with oral implants, a surgical intervention is inevitable. It is therefore of utmost importance that both esthetical and biomechanical demands are met in as few interventions and as little time as possible, which makes a thorough preoperative examination of the edentulous region mandatory. Radiographs of different kinds offer the possibility to evaluate bone volume and--to a lesser extent--quality of the area to be rehabilitated. It should however be kept in mind that radiography necessarily brings about a certain amount of possible detrimental radiation burden. Selection of the appropriate radiographic technique should therefore be based on a well thought-out balance between diagnostic value and risk level of the intervention on the one hand and radiation burden on the other.

Appearance, location, course, and morphology of the mandibular incisive canal: an assessment on spiral CT scan.

OBJECTIVES: To assess the appearance, location, and course of the incisive canal as compared to other anatomical landmarks on spiral CT of the mandible. METHODS: Study material included 230 spiral CT scans taken for preoperative planning of implant placement in the posterior mandible. All scanning was performed using a standard exposure and patient positioning protocol. Axial, panoramic, and reformatted cross-sectional images were carefully examined. Visibility of the incisive canal and other anatomical landmarks was scored using a four-point rating scale. The vertical and buccolingual diameter of the outer contour as well the diameter of the inner contour of the incisive canal were measured using a digital sliding caliper. RESULTS: An incisive canal was identified in 93% of the cases, with good visibility in 22% of the cases. Mean (s.d.) vertical diameter, buccolingual diameter, and inner diameter of the incisive canal were 4.7 (1.1), 3.7 (0.7), and 1.1 (0.3) mm respectively. The mandibular canal, mental foramen, lingual foramen, and anterior looping appeared in 98, 100, 82 and 7% of the images respectively. CONCLUSIONS: A well-defined incisive canal could be detected in the majority of spiral CT scans. Its radiographic detection remained lower than for the mandibular canal or mental foramen, but higher than for the visibility of the lingual foramen. Visualisation of the incisive canal and the occasional presence of an anterior looping, demonstrates the potential value of cross-sectional imaging of the anterior mandible for presurgical planning purposes.

A comparison of the effective dose from scanography with periapical radiography.

OBJECTIVES: To compare organ and effective doses from analogue scanographic and periapical radiography. METHODS: Thermoluminescent dosimeters (TLD-700) were inserted in the parotid glands (bilateral), submandibular glands (bilateral) and bone marrow (left ascending ramus) of three human cadavers. Dosimeters were also attached to the skin, thyroid gland and lens of both eyes. Central, left lateral and left posterior scanograms were obtained with a Cranex Tome (Soredex, Helsinki, Finland) multimodal imaging system. A similar procedure was applied for periapical radiographs of the midline, left lateral and left molar regions using E-speed film both with and without rectangular collimation. Organ and effective doses were calculated for scanograms and periapical radiographs. RESULTS: The effective doses for the scanograms were 0.001 mSv (central), 0.011 mSv (lateral) and 0.015 mSv (posterior). The effective doses for periapical radiographs were 0.001 mSv (anterior), 0.001 mSv (lateral) and 0.003 mSv (posterior) for rectangular collimation and 0.001 mSv (anterior), 0.002 mSv (lateral) and 0.005 mSv (posterior) for round collimation. CONCLUSIONS: When a larger area of the upper or lower jaw needs to be visualised, scanograms might be considered as an alternative to periapical radiography since the effective dose is lower.

The accuracy and reliability of radiographic methods for the assessment of marginal bone level around oral implants.

OBJECTIVES: To determine the accuracy and reliability of radiographic methods for assessment of the marginal bone level around oral implants in human cadavers. METHODS: In three human cadavers two implants were placed according to the Instruction Manual for the Brånemark System. One implant was installed in the canine and one in the premolar region of the left mandible. For each implant, conventional and digital intra-oral paralleling radiography were performed. Digital images were printed with a Kodak 1200 Distributed Medical Imaging printer on blue transparent film, glossy and plain paper. Furthermore, digital scanographic, panoramic and tomographic images were taken with the Cranex Tome multimodal X-ray unit and printed on Agfa Drystar TM 1 B transparent films. All images were evaluated by five dental specialists. Data were statistically compared with real measurements of the marginal bone level on the human cadavers, performed by the same group of observers. Intra- and inter-observer variability were determined. RESULTS: Digital intra-oral images on glossy paper showed the smallest absolute difference between real and measured bone level, followed by digital intra-oral images on film and on plain paper, conventional intra-oral images on analogue film, panoramic, scanographic and tomographic images on film. The difference between real and radiographic measurements was not statistically significant (P>0.05) for all radiographic techniques. Intra- and inter-observer reproducibility was high for all techniques. CONCLUSIONS: The selected imaging techniques showed an acceptable accuracy for peri-implant bone level measurements with an overall error of less than 0.5 mm. Intra-oral images showed the smallest absolute differences.

Organ doses and subjective image quality of indirect digital panoramic radiography.

OBJECTIVES: To determine if slight variations in exposure will affect diagnostic image quality and absorbed radiation doses for digital and analogue panoramic radiography. METHODS: Thermoluminescent dosimeters were placed in the thyroid gland, eyes, submandibular glands, parotid glands and skin of two human cadaver heads. Three different exposure settings were used: 70 kV, 120 mAs; 77 kV, 75 mAs; and 81 kV, 60 mAs. Subjective image quality was assessed using a phantom head. Storage phosphor (SP) images were printed on film and both analogue and SP images were assessed for their subjective image quality on a five-point rating scale. The results were statistically analysed using logistic regression analysis and chi(2) tests. RESULTS: Highest organ doses were measured for the submandibular glands, followed by the parotid glands. Salivary gland doses tended to be higher at lower kV settings. Image quality was not statistically different for the different exposure settings. Imaging technique did not seem to influence diagnostic image quality, except for the periapical status of upper premolars where SP was better. The main reason for any differences appeared to be interobserver variation. CONCLUSIONS: Analogue and SP panoramic radiography performed equally well for subjective diagnostic image quality. No significant differences could be found at the exposure settings used in this study. Radiation doses were highest for the salivary glands, especially at lower kV settings.

Absorbed doses from spiral CT and conventional spiral tomography: a phantom vs. cadaver study.

For several radiological examinations, a clinician can select between conventional and spiral computed tomography. Using both techniques, this study aimed at evaluating the difference in absorbed doses when examining a single lateral jaw segment in a human cadaver head and Rando phantom. The present study involved the placement of thermoluminescent dosimeter (TLD) chips (GR-200) in the thyroid gland, and bilaterally, in the parotid and submandibular glands and the lenses of the eyes in both a human cadaver and a Rando phantom at corresponding locations. Consecutive conventional spiral tomographic examinations were carried out in both the left upper and lower premolar area, using a Cranex TOME multifunctional unit. Each examination consisted of 4 slices with a 2 mm slice thickness and exposure parameters of 57 kV, 56 seconds and 1.6-2.0 mA. Regarding spiral computed tomography (CT), a Somatom Plus S scanner (Siemens, Erlangen, Germany), with a slice thickness of 1 mm with settings at 120 kV and 165 mA, was used on both phantoms and separately in the upper and lower jaw. With conventional tomography, the findings of the present study showed that the parotid and submandibular glands on the side near the X-ray tube received the highest dose, both for the cadaver head (doses ranging from 0.5 to 1.3 mGy) and the phantom (doses ranging from 0.6 to 2.6 mGy). For CT of the upper jaw, the highest doses were delivered to the parotid glands with an average absorbed dose of 9.2 and 10.6 mGy for the cadaver head and phantom, respectively. The submandibular glands received the highest doses during CT examination of the lower jaw with an average of 7.8 and 12.9 mGy for the cadaver head and phantom, respectively. It appears from the present investigation that if small edentulous regions are examined, radiation doses during conventional tomography remain much lower than during CT imaging. However, when multiple tomographic cuts are required, a spiral CT examination can replace a series of conventional examinations, especially in cases such as the rehabilitation of an edentulous upper jaw or a more complex surgery.

Diagnostic yield of conventional and digital cephalometric images: a human cadaver study.

OBJECTIVES: To compare the clinical efficacy of digital and conventional cephalometric imaging. METHODS: Conventional and photostimulable phosphor cephalometric radiographs were obtained from three human cadavers at nine different exposure settings. Subjective image quality was assessed by six observers who evaluated six cephalometric landmarks. Organ doses were measured with TLDs and effective doses calculated. RESULTS: Compared with conventional cephalometric images, digital images had a consistently better subjective image quality for all exposure settings which was significant (P<0.05) for all but two. Organ doses were comparable. Higher kV and lower mAs settings yielded the lowest effective dose, which was highly dependent on the position of the thyroid gland in the beam. CONCLUSION: Relatively small variations in exposure settings do not influence subjective diagnostic image quality of digital cephalometric radiographs. Higher kV and lower mAs settings have the lowest effective dose and should therefore be preferred.

The subjective image quality of direct digital and conventional panoramic radiography.

One of the main advantages of digital imaging is the possibility of altering display options for improved image interpretation. The aim of the present study was to evaluate the subjective image quality of direct digital panoramic images and compare the results with those obtained from conventional images. Furthermore, the effect of various filter settings on image interpretation was assessed. Panoramic images were obtained with three different types of panoramic equipment (one direct digital and two conventional units) from three groups of 54 patients with a natural dentition in all quadrants. The first series of panoramic images consisted of 54 unprocessed digital images; conventional film images (n = 108) comprised the second and third series. A final series consisted of the digital images treated with three different filters ("smoothening," "sharpening," and "contrast enhancement"). All images were scored randomly by four experts in oral radiology on a 4-point rating scale. The results showed a statistically significant difference in scorings between the conventional and digital panoramic units. The main reason for poor image quality appeared to be a combination of blurring and overlapping in the panoramic image. The premolar region in the upper jaw was the region where most additional radiographs were needed.