[Panoramic radiographs in dental diagnostics]. / Panoramische röntgenopnamen in de tandheelkundige diagnostiek.

Panoramic radiographs are frequently used in dental practice in addition to bitewing radiographs and periapical radiographs. The way a panoramic photograph is created is different from that of a projection image, such as bitewing and periapical radiographs. As a result, the sharpness of detail is much less, and overlap of structures occurs in different areas of the image. Consequently the diagnostic utility is limited to the recognition of anomalies for which small details play a lesser role. The advantage of a panoramic radiograph is that structures over a large area are shown in their relative location. Because of the lower resolution and the higher dose of radiation to the patient compared with a series of intraoral images, the panoramic radiograph is not indicated during a periodic check-up. If clinical inspection indicates a need for it and as a supplement to an intraoral radiograph, a panoramic radiograph can, however, be appropriate in cases of abnormalities that extend over a larger area, such as tumours and developmental disorders.

[Cone beam computed tomography: is more also better?]. / Conebeamcomputertomografie: is meer ook beter?

Cone beam computed tomography (CBCT) is a radiographic technique that has now been available in dentistry for about 20 years. The ability to display three-dimensional structures is of importance for many defects in the maxillofacial area. A disadvantage, however, is that the dose of a CBCT-study is higher than the dose of more conventional imaging techniques. This should be taken into account when prescribing a CBCT-examination. Because a CBCT-image usually displays a larger area than that of conventional radiography, there is the possibility that abnormalities may be shown that are outside the direct field of experience of the dentist. For all these reasons, the user of a CBCT-device needs to have additional knowledge.

[Oral and maxillofacial radiology: laws and regulations]. / Tandheelkundige radiologie: wet- en regelgeving.

Since the discovery of X-rays, medical imaging has been one of its most important applications. In the course of years, understanding of the potentially harmful effects of radiation on tissue has substantially increased as a result of experience and scientific studies. This has led to the International Commission on Radiological Protection (ICRP), the organisation that is now regarded as the most authoritative in the field of information on radiation and radiation protection. In most countries the law governing radiation is based on the 3 principles of the ICRP: justification, ALARA and dosage limits. For the Dutch situation, these are the Nuclear Energy Act (Kernenergiewet) and the Radiation Protection Decree (Besluit stralingsbescherming). The Practice Guidelines on Radiology are available for the practical implementation of the regulations. By working according to the Practice Guidelines, the dentist satisfies the legal regulations, but, more importantly, he can apply X-ray diagnostics in a manner that is safe for him, the dental team, the patients and all other visitors of the practice.

Airway Phenotypes and Nocturnal Wearing of Dentures in Elders with Sleep Apnea.

The objective of this study was to examine to what extent the anatomic characteristics of the upper airway can influence the effect of nocturnal wearing of dentures on the sleep of edentulous elders with untreated sleep apnea. This study used the data from a randomized crossover clinical trial and an exploratory approach to address its objectives. Cone beam computed tomography scans of 65 edentulous individuals (female, n = 37; male, n = 28; mean ± SD age, 74.54 ± 6.42 y) with untreated obstructive sleep apnea (OSA) were used to identify anatomic variables. Polysomnography data were collected by means of one portable overnight recording. The respiratory variable values, including apnea-hypopnea index (AHI), with and without denture worn during sleep were used to calculate the change. Statistical analyses included multiple linear regressions, cluster analysis, and binary logistic regressions. A receiver operator characteristic curve was used to illustrate the accuracy of the statistical model. The regression model explained 15.8% (R2) of AHI change. An increase in the lateral dimension of the minimum cross-sectional area was associated with a decrease in AHI, oxygen desaturation index, and respiratory arousal index changes (P ≤ 0.041). Furthermore, an increase in the length of the hypopharynx was associated with an increase in AHI and oxygen desaturation index changes (P ≤ 0.027). An increase in the lateral dimension of the minimum cross-sectional area of the upper airway was associated with a decreased likelihood of being in the group having a worsened AHI (odds ratio = 0.85; 95% CI, 0.76 to 0.95; P = 0.006). An increase in the length of the oropharynx was associated with an increased likelihood of having increased AHI (odds ratio = 1.10; 95% CI, 1.01 to 1.20; P = 0.026). The nocturnal aggravation of respiratory variables in edentulous individuals with OSA who wear dentures at night can be linked to certain anatomic characteristics of the upper airway. Replication of these findings may open novel avenues for personalized advice regarding nocturnal wearing of dentures in edentulous individuals with OSA (ClinicalTrials.gov: NCT01868295).

From pixel to image analysis.

Over the past 50 years, computer technology has evolved enormously. This has made it possible to carry out radiography in a completely new way, allowing to process X-ray images in an advanced manner and to extract the information from the image data. This article gives an overview of some of the most important developments in dental radiology. These include capturing the images, analysing and interpreting the image information and using the images for 3D reconstruction.

[Radiodiagnostics: between looking and observing]. / Röntgendiagnostiek: tussen kijken en waarnemen.

The quality of radiodiagnostics is crucial because of its important role in general diagnostics and the subsequent treatment planning. Nowadays, digital radiology is providing many new opportunities, such as optimization of contrast and brightness of the radiographic image. Nevertheless, it is a fact that not every abnormality is discovered and recognized, in spite of the technological advancements. The perceptive abilities of the observer is in many circumstances the limiting factor. The question is how crucial an incorrect observation of the presence or absence of an abnormality on the radiograph is and what the clinician can do to minimize the chance of mistakes as much as possible. The decision to make a radiograph and the choice of imaging technique are essential. An oral health care provider can take advise with several guidelines, indicating what is currently considered good practice by the profession.

Spatial orientation in bone samples and Young's modulus.

Bone mass is the most important determinant of the mechanical strength of bones, and spatial structure is the second. In general, the spatial structure and mechanical properties of bones such as the breaking strength are direction dependent. The mean intercept length (MIL) and line frequency deviation (LFD) are two methods for quantifying directional aspects of the spatial structure of bone. Young's modulus is commonly used to describe the stiffness of bone, which is also a direction-dependent mechanical property. The aim of this article is to investigate the relation between MIL and LFD on one hand and Young's modulus on the other. From 11 human mandibular condyles, 44 samples were taken and scanned with high-resolution computer tomography equipment (micro-CT). For each sample the MIL and LFD were determined in 72602 directions distributed evenly in 3D space. In the same directions Young's modulus was determined by means of the stiffness tensor that had been determined for each sample by finite element analysis. To investigate the relation between the MIL and LFD on one hand and Young's modulus on the other, multiple regression was used. On average the MIL accounted for 69% of the variance in Young's modulus in the 44 samples and the LFD accounted for 72%. The average percentage of variance accounted for increased to 80% when the MIL was combined with the LFD to predict Young's modulus. Obviously MIL and LFD to some extent are complementary with respect to predicting Young's modulus. It is known that directional plots of the MIL tend to be ellipses or ellipsoids. It is speculated that ellipsoids are not always sufficient to describe Young's modulus of a bone sample and that the LFD partly compensates for this.

Preliminary images from an adaptive imaging system.

I-ImaS (Intelligent Imaging Sensors) is a European project aiming to produce real-time adaptive X-ray imaging systems using Monolithic Active Pixel Sensors (MAPS) to create images with maximum diagnostic information within given dose constraints. Initial systems concentrate on mammography and cephalography. In our system, the exposure in each image region is optimised and the beam intensity is a function of tissue thickness and attenuation, and also of local physical and statistical parameters in the image. Using a linear array of detectors, the system will perform on-line analysis of the image during the scan, followed by optimisation of the X-ray intensity to obtain the maximum diagnostic information from the region of interest while minimising exposure of diagnostically less important regions. This paper presents preliminary images obtained with a small area CMOS detector developed for this application. Wedge systems were used to modulate the beam intensity during breast and dental imaging using suitable X-ray spectra. The sensitive imaging area of the sensor is 512 x 32 pixels 32 x 32 microm(2) in size. The sensors' X-ray sensitivity was increased by coupling to a structured CsI(Tl) scintillator. In order to develop the I-ImaS prototype, the on-line data analysis and data acquisition control are based on custom-developed electronics using multiple FPGAs. Images of both breast tissues and jaw samples were acquired and different exposure optimisation algorithms applied. Results are very promising since the average dose has been reduced to around 60% of the dose delivered by conventional imaging systems without decrease in the visibility of details.

Automated osteoporosis risk assessment by dentists: a new pathway to diagnosis.

General dental practitioners use a vast amount of panoramic radiography in their routine clinical work, but valuable information about patients' osteoporotic status is not collected. There are many reasons for this, but one of the prime reasons must be the disruption involved in clinical routine with lengthy manual radiographic assessment. We have developed computer software, based on active shape modeling that will automatically detect the mandibular cortex on panoramic radiographs, and then measure its width. Automatic or semi-automatic measurement of the cortical width will indicate the osteoporotic risk of the patient. The aim of our work was to assess the computer search technique's ability to measure the mandibular cortical width and to assess its potential for detection of osteoporosis of the hip, spine and femoral neck. Mandibular cortical width was measured using the manually initialized (semi-automatic) method and, when assessed for diagnosing osteoporosis at one of the three measurement sites, gave an area under the ROC curve (A(z))=0.816 (95% CI=0.784 to 0.845) and for the automatically initialized searches, A(z)=0.759 (95% CI=0.724 to 0.791). The difference between areas=0.057 (95% Confidence interval=0.025 to 0.089), p<0.0001. For diagnosing osteoporosis at the femoral neck, mandibular cortical width derived from the manually initialized fit gave an area under the ROC curve (A(z))=0.835 (95% CI=0.805 to 0.863) and for the automatically initialized searches A(z)=0.805 (95% CI=0.773 to 0.835). The difference in A(z) values between active shape modeling search methods=0.030 (95% CI=-0.010 to 0.070), and this was not significant, p=0.138. We concluded that measurement of mandibular cortical width using active shape modeling is capable of diagnosing skeletal osteoporosis with good diagnostic ability and repeatability.

Accuracy in osteoporosis diagnosis of a combination of mandibular cortical width measurement on dental panoramic radiographs and a clinical risk index (OSIRIS): the OSTEODENT project.

Clinical questionnaires and dental radiographic findings have both been suggested as methods of identifying women at risk of having osteoporosis and who might benefit from bone densitometry. The aim of this study was to measure the diagnostic accuracy of a combination of mandibular cortical width (MCW) measured from dental panoramic radiographs (DPRs) and the osteoporosis index of risk (OSIRIS) in the diagnosis of osteoporosis. 653 women (age range 45-70 years, mean age 54.95 years) in four European centres underwent standardised dual X-ray energy absorptiometry (DXA) to provide reference data on osteoporosis status. Each subject was interviewed to derive OSIRIS scores and underwent DPR examination. MCW was measured directly by five observers. Receiver Operating Characteristic (ROC) curve analysis was used to calculate sensitivities and specificities of the clinical and radiographic tests for the diagnosis of osteoporosis. 512 (78.4%) of the study population were classified as having normal BMD and 141 (21.6%) as having osteoporosis. Using ROC analysis, OSIRIS gave a ROC curve area (A(z)) of 0.838, with a sensitivity of 70.9% and a specificity of 79.5% at a diagnostic threshold of

Prediction of bone mineral density with dental radiographs.

There is consensus to use the bone mineral density (BMD) for the operational definition of the degree of osteoporosis and the risk of osteoporotic fractures. Dual X-ray absorptiometry (DXA) is the common technique to determine BMD. Because of high costs and limited availability of DXA equipment it is worthwhile to look for alternative diagnostic techniques. As part of a larger study, the Osteodent project, we investigated if the trabecular pattern on dental radiographs can be used to predict BMD and to identify the subjects with osteoporosis and increased risk of osteoporotic fractures. In four clinical centers 671 women with an average age of 55 years were recruited. BMD values were measured by DXA equipment at the femoral neck, total hip, and spine. One panoramic and two intraoral radiographs were made. From 525 women a complete set of BMD values and radiographs was obtained. Four regions of interest on the radiographs were selected manually and then processed automatically. On all regions of interest mean and standard deviation of the gray values were measured and several features describing the shape of the binarized trabecular pattern. Multiple regression was used to predict BMD of total hip and spine by means of the radiographic measurements combined with age. It was found that age accounts for 10% of the variation in total hip BMD and 14% of the variation in spinal BMD. When all measurements on the dental radiographs are used the explained variation increases to 22% and 23%. The areas under the ROC curves are comparable to those of commonly used screening instruments for osteoporosis. It is concluded that prediction of DXA measurements of BMD by means of quantitative analysis of the trabecular pattern on dental radiographs is feasible.

Detection of proximal caries in vitro using standard and task-specific enhanced images from a storage phosphor plate system.

Eight dentists evaluated 72 proximal surfaces of premolars with respect to all caries lesions and to lesions into dentine in digital images from a storage phosphor plate system. The images were processed in four different ways: (1) the default algorithm of the standard imaging system (DF); (2) an algorithm correcting for attenuation and visual response (AV), and two proprietary caries-specific enhancement algorithms (3) K1, and (4) K2, respectively. The lesions were validated by histological examination. There were no significant differences in the areas under the receiver operating characteristic curves between differently processed radiographs for the categories of all caries lesions and caries into dentine.

[Research methods in dentistry. 8. Methods for longitudinally detecting differences in bone density: digital subtraction radiography]. / Onderzoeksmethoden in de tandheelkunde. 8. Methoden om longitudinale verschillen in botdensiteit te detecteren: digitale subtractie.

Subtraction radiography has been developed in 1934 by the Dutch radiologist B. Ziedses des Plantes. The technique is based on the subtraction of two radiographic images. As a result, only the differences remain visible, and structures which have been unaltered in between both exposures, are suppressed. The technique was introduced also in dental radiology in the eighties in the last century. Since then, many studies have been performed showing the benefit of this technique in dental diagnosis. A requirement for reliable results is that the two radiographs which are used for the subtraction have equal brightness and contrast, as well as a completely identical projective geometry. Since radiographic images can be acquired digitally, methods have been developed to make density and contrast equal for both images used for the subtraction process even after the images have been taken, using dedicated software programs. The projection geometry of two images can be made identical in this way as well. Because of this, the technique can also be applied in general dental practice.

Dose reduction in orthodontic lateral cephalography: dosimetric evaluation of a novel cephalographic thyroid protector (CTP) and anatomical cranial collimation (ACC).

OBJECTIVES: To test the dose-reducing capabilities of a novel thyroid protection device and a recently introduced cranial collimator to be used in orthodontic lateral cephalography. METHODS: Cephalographic thyroid protector (CTP) was designed to shield the thyroid while leaving the cervical vertebrae depicted. Using a RANDO(®) head phantom (The Phantom Laboratory, Salem, NY) equipped with dosemeters and a Proline XC (Planmeca, Helsinki, Finland) cephalograph, lateral cephalograms were taken, and the effective dose (ED) was calculated for four protocols: (1) without shielding; (2) with CTP; (3) with CTP and anatomical cranial collimator (ACC); and (4) with a thyroid collar (TC). RESULTS: The ED for the respective protocols was (1) 8.51; (2) 5.39; (3) 3.50; and (4) 4.97 µSv. The organ dose for the thyroid was reduced from 30.17 to 4.50 µSv in Protocols 2 and 3 and to 3.33 µSv in Protocol 4. CONCLUSIONS: The use of just the CTP (Protocol 2) resulted in a 36.8% reduction of the ED of a lateral cephalogram. This was comparable to the classical TC (Protocol 4). A 58.8% reduction of the ED was obtained when combining CTP and ACC (Protocol 3). The dose to the radiosensitive thyroid gland was reduced by 85% in Protocols 2 and 3 and by 89% in Protocol 4.

Reducing an already low dental diagnostic X-ray dose: does it make sense? Comparison of three cost-utility analysis methods used to assess two dental dose-reduction measures.

OBJECTIVES: To find a method that is suitable for providing an objective assessment of the cost effectiveness of a dose-reducing measure used for diagnostic dental X-ray exposures. METHODS: Three cost-utility analysis (CUA) methods were evaluated by comparing their assessments of two dose-reduction measures, a rectangular collimator and the combination of two devices that reduce the radiation dose received during orthodontic lateral cephalography. The following CUA methods were used: (1) the alpha value (AV), a monetary valuation of dose reduction used in the nuclear industry; (2) the value of a statistical life for valuation of the reduction in stochastic adverse effects; and (3) the time-for-time method, based on the postulate that risk reduction is effective when the number of years of life gained is more than the years that an average worker must work to earn the costs of the risk-reducing measure. The CUA methods were used to determine the minimum number of uses that was required for the dose-reducing device to be cost effective. The methods were assessed for coherence (are comparable results achieved for comparable countries?) and adaptability (can the method be adjusted for age and gender of specific patient groups?). RESULTS: The performance of the time-for-time method was superior to the other methods. Both types of dose-reduction devices tested were assessed as cost effective after a realistic number of uses with all three methods except low AVs. CONCLUSIONS: CUA for the methods of X-ray dose reduction can be performed to determine if investment in low dose reduction is cost effective. The time-for-time method proved to be a coherent and versatile method for performing CUA.

Enhancement of tomosynthetic images in dental radiology.

In conventional projection radiography, anatomical structures superimposed on details of interest increase the difficulty of visual interpretation. Part of this problem can be resolved by tomographic reconstruction of specific "tissue" slices. Computer-aided tomosynthesis is one method which can reduce the superposition problem, but the reconstruction can benefit from further enhancement. In this investigation, we studied two such enhancement schemes: high-pass spatial-frequency filtration and iterative deconvolution. The performance of each technique was judged qualitatively in terms of the depiction of specific details of diagnostic interest, and quantitatively in terms of the degree of success afforded by each in rendering adjacent tissue slices independent. Both techniques demonstrated improved performance over the status quo.

Computer-aided interpretation and quantification of angular periodontal bone defects on dental radiographs.

Capabilities of human observers to detect and describe small bone defects objectively are limited. Digital image processing can provide a useful contribution to the diagnostic process. This paper describes the evaluation of a computer-aided procedure for the interpretation and quantification of angular periodontal bone defects on dental radiographs. The computer-aided procedure was able to rank series of artificial periodontal bone lesions as accurate as experienced clinicians. Comparison of data from clinical inspection of lesions during surgery and quantitative results of the digitized procedure shows that the latter produced reliable information on the lesions size. Reproducibility is satisfactory. It was concluded that computer-aided detection and description of periodontal bone defects decreases the interobserver variability in general and the time-dependent variability in repeated assessments of a single observer.