Correlation between spatial resolution and ball distortion rate of panoramic radiography.

BACKGROUND: The purpose of this study was to analyze the correlation between spatial resolution and ball distortion rate of panoramic radiography and to elucidate the minimum criterion for ball distortion rate, which is very relevant to clinical readability. METHODS: Horizontal and vertical spatial resolution and ball distortion rates were calculated in the same position, such as the incisor, premolar, molar, and temporomandibular joint area with various object depths corresponding to 48 mm. Three devices were evaluated. A region showing spatial resolution above the reference standard was selected, and the ball distortion rate corresponding to the same region was divided into horizontal and vertical phantom groups. The mean and standard deviation of the obtained ball distortion rates were calculated. Student's t-test was used to statistically analyze the mean difference in ball distortion rates between vertical and horizontal phantom groups. RESULTS: In all devices, the horizontal line pair phantom, but not the vertical line pair phantom, was readable in all areas measured at the line pair value of at least 1.88 lp/mm. The line pair value tended to be higher toward the center and lower toward the outside. The ball distortion rate tended to decrease closer to the center and increased further away. In addition, ball distortion rates could not be measured at some areas as they were not recognized as balls due to the high degree of distortion at the outermost and innermost sides. The number of balls satisfying the reference value using the horizontal line pair phantom was 102 (mean of ball distortion rates, 20.98; standard deviation, 15.25). The number of balls satisfying the reference value using the vertical line pair phantom was 49 (mean of ball distortion rates, 16.33; standard deviation, 14.25). However, mean ball distortion rate was not significantly different between the two groups. CONCLUSIONS: Image layer of panoramic radiography could be evaluated by the spatial resolution using horizontal and vertical line pair phantoms and by assessing ball distortion rates through a ball-type panorama phantom. A ball distortion rate of 20% could be used as a threshold to evaluate the image layer of panoramic radiography.

Measurement of scattered and transmitted x-rays from intra-oral and panoramic dental x-ray equipment.

The aim of this study was to quantify the levels of transmitted radiation arising from the use of intra-oral dental x-ray equipment and scattered radiation arising from the use of both intra-oral and panoramic x-ray equipment. Levels of scattered radiation were measured at 1 m from a phantom, using an ion chamber with a volume of 1800 cm3. Transmitted radiation was measured using both (i) a phantom and dose-area product (DAP) meter and (ii) a patient and a 1800 cm3 ion chamber. For intra-oral radiography the patient study gave a maximum transmission of 1.80% (range 0.04-1.80%, mean 0.26%) and the phantom study gave a maximum transmission of 6% (range 2-6%, mean 5%). The maximum scattered radiation, per unit DAP, was 5.5 nGy (mGy cm2)-1 at 70 kVp and a distance of 1 m. For panoramic radiography the maximum scattered radiation was 9.3 nGy (mGy cm2)-1 at 80 kVp and a distance of 1 m. Dose values are presented to enable the calculation of adequate protective measures for dental radiography rooms. Previous studies have used a phantom and measured radiation doses at 1 m from the phantom to determine the radiation dose transmitted through a patient, whereas this study uses both patient and phantom measurements together with a large-area dosemeter, positioned to capture the entire x-ray beam, to ensure that more realistic dose measurements can be made.

Dosimetry analysis of panoramic-imaging devices in different-sized phantoms.

The aim of this study is to measure the radiographic dose in adult, adolescent, and child head-sized PMMA phantoms for three panoramic-imaging devices: the panoramic mode on two CBCT machines (Carestream 9300 and i-CAT NG) and the Planmeca ProMax 2D. A SEDENTEXCT dose index adult phantom and custom-built adolescent and pediatric PMMA dosimetry phantoms were used. Panoramic radiographs were performed using a Planmeca ProMax 2D and the panoramic mode on a Carestream 9300 CBCT and an i-CAT NG using the protocols used clinically. Point dose measurements were performed at the center, around the periphery and on the surface of each phantom using a thimble ionization chamber. Five repeat measurements were taken at each location. For each machine, single-factor ANOVA was conducted to determine dose differences between protocols in each phantom, as well as determine the differences in absorbed dose when the same protocol was used for different-sized phantoms. For any individual phantom, using protocols with lower kVp, mA, or acquisition times resulted in statistically significant dose savings, as expected. When the same protocol was used for different-sized phantoms, the smaller phantom had a higher radiation dose due to less attenuation of x-rays by the smaller phantom and differences in the positioning of the ion chamber relative to the focal trough. The panoramic-mode on the CBCT machines produce images suitable for clinical use with similar dose levels to the stand-alone panoramic device. Significant dose savings may result by selecting age- and size- appropriate protocols for pediatric patients, but a wider range of protocols for children and adolescents may be beneficial.

Are children's dental panoramic tomographs and lateral cephalometric radiographs sufficiently optimized?

OBJECTIVES: Children are especially vulnerable to harmful effects of ionizing radiation. Cutting down the dimensions of the X-ray beam is the most effective way to reduce the patient dose. We evaluated the appropriateness of field-size in the most frequent radiographs, dental panoramic tomographs (DPTs) and lateral cephalometric radiographs (LCRs) among 7- to 12-year-olds. MATERIALS AND METHODS: The image field-size of 241 DPTs and 118 LCRs was analysed. The image field was considered appropriate when it did not include anatomic structures beyond the area of clinical interest. The image field was compared with factors such as the age of the patient, the radiographic equipment used and the programme selected. Moreover, we assessed the use of thyroid shield in LCR. RESULTS: The field-size was too large in 70% of the DPTs horizontally and in 96% vertically. None of the DPTs were segmented. Every LCR showed appropriate limitation anteriorly, but the image field was too large in 54% posteriorly, in 86% superiorly, and in 76% inferiorly. A thyroid shield had been used in only 71% of cases. CONCLUSION: Most DPTs and LCRs had been performed sub-optimally. An abundancy of DPTs had been taken using an adult programme, and the field-size had not been sufficiently adjusted in LCRs, possibly for technical reasons. To facilitate adherence to radiological best practice the equipment used for DPTs and LCRs should facilitate the adjustment of field-size in both the vertical and horizontal planes. In addition, those involved in taking radiographs should maintain their skills through regular update courses.

A tomographic study of the mandibular condyle position in partially edentulous population.

BACKGROUND AND OBJECTIVES: The Influence of the loss of teeth on the condylar position and on temporomandibular joint (TMJ) dysfunction syndrome remains a c ontroversial issue. This study analyses the condylar position by means of a tomogram in partially dentate subjects which serves as a guide to predict which of the partially dentate statuses is prone to develop TMJ dysfunction syndrome in personnel without symptoms of the same. METHODOLOGY: Eighty personnel were enrolled in this study consisting of Kennedy's class I, II, III, IV and control to analyze the condylar position by means of a tomogram. In all the five groups TMJ sectional tomogram programmed in a panoramic radiographic machine (PLANMECA PM 2002 CC PROLINE) was taken with the subjects at maximal intercuspal position and rest position. Tomograms were evaluated using linear measurements of the anterior and posterior intra-articular joint spaces on the basis of drawings and tracings. RESULTS: The results of the study revealed a predominance of reduced posterior condylar space in Kennedy's class I and II. A disparity was seen between the maximum intercuspal position and rest position, where the posterior joint space was reduced in the rest position. CONCLUSION: Within the limitations of this study, it has been revealed that in Kennedy's classes I and II, for partially dentate personnel, a posterior displacement of the c ondyles was seen. This predisposition would suggest towards the necessity of restoring the missing dentition in order to maintain the har mony of the stomatognathic system.

Guide to Digital Radiographic Imaging.

This is a resource for clinicians who are considering purchasing a digital imaging system or those already using one who want to optimize its use. It covers selected topics in digital imaging fundamentals, detector technology, image processing and quality assurance. Through a critical appraisal of the strengths and limitations of digital imaging components, the goal of this guide is to contribute to the appropriate use of these systems to maximize the health benefit for patients.

Dry skull positioning device for extra-oral radiology and cone-beam CT.

Extra-oral radiographs of dry skulls on scientific or forensic context have head position as a critical procedure. The aims of this article are to present a multi-purposed head-positioning device, and to describe the new method of image acquirement using the device to adequately keep the head in a correct and safe position during radiological or tomographic exam. The design was created from an average-sized skull and then tested in 20 others with different morphologies, sizes, weights, and structural state of preservation. A series of digital and analog orthopantomographies followed by a cone-beam computer tomography were obtained to assure that the correct positioning standards and anatomical visualization were achievable. The developed device properly kept adult skulls in position for all extra-oral radiographic exams, providing to operators a secure and facilitated way to achieve the proper position standards. The device did not impair the visualization of the anatomical structures neither on radiographs nor in cone-beam computer tomography.

Shall I go digital?

UNLABELLED: Dental radiographic imaging is slowly transferring to digital format. The decision to invest in this new technology should be based on a good understanding of the different types of digital imaging available within the dental field. This article outlines its use in general dental practice, highlighting the pros and cons of the various systems both for intra-oral and extra-oral radiography. CLINICAL RELEVANCE: An understanding of the mechanisms of digital imaging and their associated potential problems are required by any clinician moving to film-less imaging.

Position of the mental foramen on panoramic radiographs and its relation to the horizontal course of the mandibular canal: a computed tomographic analysis.

AIM: The purposes of this study were (1) to investigate the bucco-lingual course of the mandibular canal in the bony structure and (2) to figure out the relationship between the position of mental foramen on panoramic radiographs and the horizontal course of the mandibular canal. MATERIALS AND METHODS: A database of panoramic radiography and spiral computed tomography (CT) scans was searched and 100 subjects were selected based on the criteria. Mental foramina were classified into four groups according to its antero-posterior position. Three measurements were made on each slice of coronal CT scans at three different points: (1) apex of second premolar; (2) median point of two root apexes of first molar; and (3) median point of two root apexes of second molar. The bucco-lingual ratios were calculated to access the relative bucco-lingual position of the mandibular canal. RESULTS: The distribution of subjects according to the type of mental foramen was: (1) type 3, 67%; (2) type 2, 26%; (3) type 4, 5%; and (4) type 1, 2%. The overall horizontal course of the mandibular canal was relatively constant from the second molar to first molar, whereas much significant directional change was found on the remaining course. Between types 2 and 3, no statistically significant differences were found at the level of the second molar and first molar (P = 0.461 and 0.965, respectively). Only below the second premolar, significant differences were found (P = 0.001). CONCLUSIONS: Based on the findings of our computed tomographic image analysis, the position of mental foramen on panoramic radiographs was affected by its horizontal course of inferior alveolar nerve. The significant horizontal direction change of the course was found after the canal passing below the mandibular first molar regardless of the antero-posterior position of mental foramen.

Comparison of ionisation chamber and semiconductor detector devices for measurement of the dose-width product for panoramic dental units.

Doses for panoramic dental radiography are assessed in terms of the dose-width product (DWP) or dose-area product, which gives a measure of the radiation through a whole exposure. The DWP can be measured using a pencil ionisation chamber (IC) similar to that used for computed tomography dose assessment. However, ICs are sensitive to radiation incident from all directions and so backscatter from the image receptor may increase the recorded dose. This study compares measurements performed using four options: a pencil IC mounted straight on the image receptor, the IC mounted with a steel plate to the rear to standardise scatter conditions, the IC mounted with a steel plate and lead collimators in front to minimise the effect of extra-focal radiation, and a Quart Dido employing a one square centimetre semiconductor detector (SD) designed for panoramic measurements. The results indicate that modification of the current method by incorporating a steel plate reduced the measurement dose by 7% on average, but the reduction was greater for units with semiconductor imaging plates. The measurements with the SD agree more closely with the IC with the steel plate to the rear. An IC with a backing plate to standardise scatter or a suitable SD is recommended for measurement on panoramic dental units.

Dosimetry of a cone-beam computed tomography machine compared with a digital x-ray machine in orthodontic imaging.

INTRODUCTION: Cone-beam computed tomography (CBCT) has become a routine imaging modality for many orthodontic clinics. However, questions remain about the amount of radiation patients are exposed to during the scans. This study determined the amounts of radiation potentially absorbed by a patient during orthodontic imaging with a CBCT machine with various scan settings compared with a conventional 2-dimensional digital x-ray machine. METHODS: The radiation exposures delivered by a next generation i-CAT CBCT machine (Imaging Sciences International, Hatfield, Pa) at various scan settings and orthopantomograph OP100/OC100 digital x-ray machine (Instrumentarium Dental, Tuusula, Finland) during panoramic and cephalometric radiography were recorded using thermoluminescent dosimeters placed inside a head and neck phantom. The manufacturer-recommended settings for an average adult male were used for both types of machines. Effective doses were calculated using the tissue-weighting factors recommended by the 2007 International Commission on Radiological Protection. RESULTS: The effective doses at various voxel sizes and field of view settings ranged from 64.7 to 69.2 µSv for standard resolution CBCT scans (scan time 8.9 s) and 127.3 to 131.3 µSv for high resolution full field of view scans (scan time 17.8 s), and measured 134.2 µSv for a high-resolution landscape scan with a voxel size as would be used for SureSmile (OraMetrix, Richardson, Tex) therapy (scan time 26.9 s). The effective doses for digital panoramic and lateral cephalometric radiographs measured 21.5 and 4.5 µSv, respectively. CONCLUSIONS: CBCT, although providing additional diagnostic and therapeutic benefits, also exposes patients to higher levels of radiation than conventional digital radiography.

An investigation into dental digital radiography in dental practices in West Kent following the introduction of the 2006 NHS General Dental Services contract.

AIMS: The primary aims of the study were to investigate the use of digital radiography within primary dental care practices in the West Kent Primary Care Trust (PCT) area and general dental practitioners' (GDPs) self-reported change in radiographic prescribing patterns following the introduction of the nGDS contract in 2006. METHODS: Data were gathered via a piloted, self-completed questionnaire, and circulated to all GDPs listed on the National Health Service (NHS) Choices website as practising in the West Kent PCT area. There were three mailings and follow-up telephone calls. The resulting data were entered into a statistical software database and, where relevant, statistically tested, using the chi-square test and Pearson correlation coefficient. RESULTS: Of 223 GDPs, 168 (75%) responded. There were 163 usable questionnaires. The respondents represented 85% of the general dental practices in West Kent. Eighty (49%) respondents were using digital intra-oral radiography. Of those who used digital radiography, 44 (55%) reported that they used phosphor plate systems and 36 (45%) that they used direct digital sensors. Eighty-three (51%) had a panoramic machine in their practice, 46 of whom (55%) were using digital systems; of these, 32 (67%) were using a direct digital system. Seventy-one GDPs reported that they worked exclusively or mainly in private practice. Forty (56%) of these 'mainly private' GDPs reported that they used digital radiographic systems, whereas only 40 (44%) of the 89 'mainly NHS' GDPs reported using digital radio-graphic systems. On average, mainly private GDPs made the transition to a digital radiographic system six months before mainly NHS GDPs. Of those who provided NHS dentistry before and after April 2006, only 18 (14%) reported taking fewer radiographs and seven (6%) taking more. CONCLUSIONS: In February 2010, of the West Kent GDPs who responded to the questionnaire, just under 50% used digital radio graphy. Mainly private GDPs were more likely to use digital radiography than their mainly NHS counterparts. A link between digital radiography and increased prescription of radiographs was not specifically apparent from this study. There was no evidence that West Kent GDPs were taking fewer radiographs than they did prior to the introduction of the new GDS contract in April 2006. Research is needed to investigate whether the uptake of digital radiography by GDPs in the rest of the country is similar to that in West Kent.

Panoramic radiography: digital technology fosters efficiency.

Panoramic imaging continues to be a clinically popular tool in the diagnosis and assessment of dental patients. Digital technology improves the efficiency of the imaging system, may reduce overall costs and radiation risk, and aids in optimal interpretation of the image.

[Digital volume tomography in ENT medicine]. / Die digitale Volumentomographie in der HNO-Heilkunde.

Digital volume tomography (DVT) is an advancement of panoramic tomography used in dentistry. DVT enables precise display of fine osseous structures without any disturbing artefacts. This makes its application interesting in the field of the lateral, anterior skull base and paranasal sinuses, as well as for the diagnosis of nasal bone fractures. The tomograms can be completed according to need by volume rendering or panoramic slices within a short time. Assuming they have the appropriate technical qualifications in radiation protection, ENT specialists are even able to perform tomography independently using DVT.

Artefact in a panoral radiograph: a short communication.

Artefacts in dental radiographs are not uncommon findings. In some cases, however, such film faults might lead to difficult or even wrong diagnoses. In this brief report, the authors present a case where a small piece of paper cast a foreign body-like image onto a panoral radiograph. The importance of proper techniques and film handling when taking radiographs cannot be over-emphasised.

Automatic human identification based on dental X-ray radiographs using computer vision.

A person may be identified by comparison between ante- and post-mortem dental panoramic radiographs (DPR). However, it is difficult to find reference material if the person is unknown. This is often the case when victims of crime or mass disaster are found. Computer vision can be a helpful solution to automate the finding of reference material in a large database of images. The purpose of the present study was to improve the automated identification of unknown individuals by comparison of ante- and post-mortem DPR using computer vision. The study includes 61,545 DPRs from 33,206 patients, acquired between October 2006 and June 2018. The matching process is based on the Speeded Up Robust Features (SURF) algorithm to find unique corresponding points between two DPRs (unknown person and database entry). The number of matching points found is an indicator for identification. All 43 individuals (100%) were successfully identified by comparison with the content of the feature database. The experimental setup was designed to identify unknown persons based on their DPR using an automatic algorithm system. The proposed tool is able to filter large databases with many entries of potentially matching partners. This identification method is suitable even if dental characteristics were removed or added in the past.

Interpreting an orthopantomogram.

BACKGROUND: An orthopantomogram (OPG) is a common radiograph used to identify the hard tissues of the oral cavity and surrounding skeletal structures. It is an extra-oral radiograph that approximates the focal trough of the mandible. Although resolution is not as detailed as intra-oral radiographs for examination of the teeth, gross changes in calcification of the dental structures, and changes in ossification of the underlying mandible and maxilla can aid in identification of dental disease such as caries (decay), periodontal bone loss, and abscess and cyst formation. OBJECTIVE: This article outlines key anatomical features identifiable in an OPG and illustrates some common pathology that may be seen. DISCUSSION: The large amount of data visible on an OPG may appear daunting to the viewer unless a systematic approach is used to examine structures present. Distortion due to flattening of the curve of the mandible and dentition will give an overall view of these structures and requires the viewer to reinterpret these in their mind for a three-dimensional appreciation of the image.

Calibration of radiographs by a reference metal ball affects preoperative selection of implant size.

The aim was to evaluate the impact of a reference ball for calibration of periapical and panoramic radiographs on preoperative selection of implant size for three implant systems. Presurgical digital radiographs (70 panoramic, 43 periapical) from 70 patients scheduled for single-tooth implant treatment, recorded with a metal ball placed in the edentulous area, were evaluated by three observers with the intent to select the appropriate implant size. Four reference marks corresponding to the margins of the metal ball were manually placed on the digital image by means of computer software. Additionally, an implant with proper dimensions for the respective site was outlined by manually placing four reference marks. The diameter of the metal ball and the unadjusted length and width of the implant were calculated. Implant size was adjusted according to a "standard" calibration method (SCM; magnification factor 1.25 in panoramic images and 1.05 in periapical images) and according to a reference ball calibration method (RCM; true magnification). Based on the unadjusted as well as the adjusted implant dimensions, the implant size was selected among those available in a given implant system. For periapical radiographs, when comparing SCM and RCM with unadjusted implant dimensions, implant size changed in 42% and 58%, respectively. When comparing SCM and RCM, implant size changed in 24%. For panoramic radiographs, comparing SCM and RCM changed implant size in 48%. The use of a reference metal ball for calibration of periapical and panoramic radiographs when selecting implant size during treatment planning might be advantageous.

[A new modality for dentomaxillofacial imaging: cone beam CT]. / Nouveauté en radiologie dento-maxillofaciale: la tomographie volumétrique à faisceau conique.

Cone beam CT is an imaging technique used worldwide. It is a reliable and credible alternative to CT scan for dentomaxillofacial imaging. Radiation exposure may vary from one machine to another, but it remains definitely lower than CT dose levels. This technique is compatible with dental implant software. The major diagnostic advantage is the exquisite spatial resolution. The main pitfall is the poor contrast of face and neck soft tissues, due to a lower density resolution compared to CT scan.

[Diagnostic means using oral and maxillofacial cone beam computed tomography: results]. / Moyens diagnostiques en imagerie odonto-stomatologique cone beam: résultats.

Every imaging test is justified by clinical facts and optimized to reduce the X-rays dose delivered to patients. If results from orthopantomogram are inadequate, a cross-sectional tomographic technique is indicated. Today, cone beam computed tomography yields images comparable to CT scan or even better. Some dedicated cone beam machines allow the study of small volumes with a very high definition. Dental and maxillofacial imaging as a whole, including endodontic imaging, formerly dreaded by imagers, is now accessible to cross-sectional imaging.