The OP 100 Digipan: evaluation of the image layer, magnification factors, and dosimetry

Reliability of panoramic radiographs for the assessment of mandibular elongation after distraction osteogenesis procedures

To determine whether panoramic radiographs could be used for evaluation of changes in the vertical and horizontal dimensions following internal curvilinear mandibular distraction osteogenesis.

STUDY DESIGN

A retrospective cohort study included 25 patients who underwent bilateral mandibular distraction surgery. Three panoramic radiographs and lateral cephalograms from each patient were available: before distraction, immediately upon termination of the distraction process, and at the end of the follow-up period. The radiographs were traced by plotting Condylion, Gonion, and Menton. The linear distances between Condylion and Gonion and between Gonion and Menton were measured on each side, and the correlation was calculated.

RESULTS

No significant differences were found between the values of the linear measurements determined by lateral cephalograms and panoramic radiographs (p ≥ 0.079), excluding one measurement. The correlation test for these radiographs showed very high, positive and statistically significant correlations, for both sides of the internal mandibular distraction (r > 0.77, p ≤ 0.0001), apart from three measurements.

CONCLUSION

Panoramic radiographs, with mandibular length (Co-Go and Go-Me) measurements, can be used as an alternative to lateral cephalograms, i.e. as a reliable tool for assessing vertical and horizontal dimensional changes resulting from internal mandibular distraction achieved by a curvilinear distractor.

Effective dosages for recording Veraviewepocs dental panoramic images: analog film, digital, and panoramic scout for CBCT

OBJECTIVE

The aim of this study was to evaluate the effective doses from analog film, panoramic digital, and panoramic scout for cone-beam computerized tomography (CT).

STUDY DESIGN

Three different types of Veraviewepocs machines were investigated: Veraviewepocs Conventional, Veraviewepocs Digital, and Veraviewepocs 3D (Morita, Kyoto, Japan). Organ absorbed doses were measured using an anthropomorphic phantom loaded with thermoluminescent dosimeters (TLD 100H) at 16 sites located in sensitive organs. The resulting effective organ doses (muSv) were compared by descriptive statistics.

RESULTS

The highest value (5.2 muSv) was for Veraviewepocs Conventional. The Veraviewepocs Digital (2.7 muSv) and Veraviewepocs 3D (2.95 muSv) presented low effective doses in the same range.

CONCLUSIONS

The panoramic digital system delivered the least radiation dose. The use of the panoramic scout for cone-beam CT was marginally higher in dose than its 2D counterpart.

Determination of the resolution of a digital system for panoramic radiography based on CCD technology

OBJECTIVES

To determine Line Spread Functions (LSFs) and Modulation Transfer Functions (MTFs) for a digital system for panoramic radiography: the Dimax I (Planmeca Oy, Helsinki, Finland) based on Charge-Coupled Device (CCD) technology.

STUDY DESIGN

A test object was specially designed having a gold foil positioned vertically. Images of the gold foil created edge functions that were used to determine LSFs and MTFs. The design of the test object made it possible to move the gold foil forward and backward relative to the central plane of the image layer by means of a micrometer screw. The experiment was carried out for different object depths in 5 different regions: the anterior, the canine, the premolar, the molar, and the TMJ regions. LSFs and MTFs were calculated using specially designed software.

RESULTS

The results are presented graphically. LSFs and MTFs for the central plane were essentially the same for all regions. The MTFs for different object depths in the 5 investigated regions exhibited typical characteristics of MTFs for panoramic radiography with the exception for the functions for the molar region.

CONCLUSIONS

The present findings indicate that the resolution of the Dimax I CCD system is comparable to that of film-based panoramic radiography.

Fundamentals of image acquisition and processing in the digital era

OBJECTIVES

To review the historic context for digital imaging in dentistry and to outline the fundamental issues related to digital imaging modalities.

CONTEXT

Digital dental X-ray images can be achieved by scanning analog film radiographs (secondary capture), with photostimulable phosphors, or using solid-state detectors (e.g. charge-coupled device and complementary metal oxide semiconductor). There are four characteristics that are basic to all digital image detectors; namely, size of active area, signal-to-noise ratio, contrast resolution and the spatial resolution. To perceive structure in a radiographic image, there needs to be sufficient difference between contrasting densities. This primarily depends on the differences in the attenuation of the X-ray beam by adjacent tissues. It is also depends on the signal received; therefore, contrast tends to increase with increased exposure. Given adequate signal and sufficient differences in radiodensity, contrast will be sufficient to differentiate between adjacent structures, irrespective of the recording modality and processing used. Where contrast is not sufficient, digital images can sometimes be post-processed to disclose details that would otherwise go undetected. For example, cephalogram isodensity mapping can improve soft tissue detail.

CONCLUSIONS

It is concluded that it could be a further decade or two before three-dimensional digital imaging systems entirely replace two-dimensional analog films. Such systems need not only to produce prettier images, but also to provide a demonstrable evidence-based higher standard of care at a cost that is not economically prohibitive for the practitioner or society, and which allows efficient and effective workflow within the business of dental practice.

Panoramic radiographs: a tool for investigating skeletal pattern

The objective of this study was to investigate the possibility of enhancing the clinical versatility of the panoramic radiograph, which is an indispensable tool for dental diagnosis. The material of this study consisted of lateral cephalograms and panoramic radiographs obtained from 30 patients. A correlation test was performed between the parametric measurements, and the predictability level of the cephalometric measurements from panoramic radiograms was determined by using regression equations. The equations showed that the Go-Gn/S-N, ANS-PNS/Go-Me (palatal plane/mandibular plane), and Co-Go/Go-Me parameters could be predicted from panoramic radiographs within statistically significant levels, and their predictability levels were 20.6%, 15.6%, and 11.2%, respectively. Statistically significant correlations and predictability levels were also determined for the cephalometric and corresponding panoramic parameters in which Frankfort horizontal plane was used. It can be concluded that even though panoramic radiographs provide information on the vertical dimensions of craniofacial structures, clinicians should be vigilant when predicting skeletal cephalometric parameters from panoramic radiographs, because of their lower predictability percentages.

The accuracy of dental panoramic tomographs in determining the root morphology of mandibular third molar teeth before surgery

OBJECTIVE

The objective of this study was to assess the accuracy of dental panoramic tomograph (DPT) in the presurgical assessment of mandibular third molar teeth by correlating the radiologic interpretation with surgical findings.

STUDY DESIGN

DPTs of 300 mandibular third molar teeth were assessed by 9 staff oral surgeons for root morphology and proximity to the inferior alveolar neurovascular bundle. Detailed records were made at surgery.

RESULTS

The sensitivity and specificity for observation of root curvatures (+/-15%) were 29% and 94%, respectively. The sensitivity and specificity of determining an intimate relationship between the root and the neurovascular bundle were 66% and 74%, respectively. Kappa analysis demonstrated poor levels of agreement between radiologic interpretation and surgical findings when the number of roots was determined (0.191) and also when the roots were fused or separate (0.466).

CONCLUSION

Using DPTs to assess mandibular third molar teeth before surgery gives poor diagnostic accuracy of anatomic form and structures.

Image quality of two solid-state and three photostimulable phosphor plate digital panoramic systems, and treatment planning of mandibular third molar removal

OBJECTIVES

The purpose was to evaluate image quality of two solid-state (charge-coupled device (CCD)) and three photostimulable phosphor (PSP) plate digital panoramic systems, and to assess their utility for treatment planning before mandibular third molar removal.

METHODS

433 patients were randomly allocated to five digital systems: Dimax2 and Orthophos Plus (both CCD systems) and DenOptix, DigiDent and Digora (all PSP systems). Image quality was evaluated in six regions on a 4-point scale by three independent observers. In addition, an oral surgeon evaluated image quality in the mandibular third molar region only as well as the utility of the image for treatment planning before removal of that molar.

RESULTS

Images from the DenOptix and DigiDent systems had a significantly lower overall quality than images from the Digora, Dimax2 and Orthophos Plus systems (P < 0.005). The oral surgeon's assessment of image utility resulted in rejection rates of 0% for Orthophos Plus, 2% for Digora, 8% for Dimax2, 12% for DigiDent and 14% for DenOptix images. The rates for the DigiDent and DenOptix images were significantly higher than those for the other systems (P < 0.001), and the rate for Dimax2 was significantly higher than that for Orthophos Plus (P = 0.002).

CONCLUSIONS

The quality of DenOptix and DigiDent digital panoramic images was found to be inferior to the quality found in images obtained with the Digora, Dimax2 and Orthophos Plus systems. Images from the Digora and Orthophos Plus systems were regarded to be the most useful for treatment planning before mandibular third molar removal.

Panoramic and cephalometric extraoral dental radiograph systems

The basic unit is the Orthopantomograph OP100, which is a computer-controlled extraoral imaging system capable of producing panoramic radiographs using either film or digital technology. This unit has automatic exposure control, automatic spine compensation, a patented V-shaped X-ray beam and a built-in quality assurance program. The OP100 is available with cephalometrics (the OC100 model), linear tomography (the Ortho Trans model), identification film marking (the Ortho ID model) and imaging software (the Ortho Zone and Ortho TMJ models). The addition of a cephalometric arm to the Orthopantomograph makes the unit an Orthoceph. The image receptor sizes are as follows: Panorama OP100: cassette 15 x 30 centimeters; Cephalometric image receptor OC100: 24 x 30 cm, 18 x 24 cm, 8 x 10 inches; Panoramic image receptor OP100D: CCD camera, image pixel size 90 x 90 micrometers; Cephalometric image receptor OC100D: CCD camera, image pixel size 90 x 90 microm.

A comparison of conventional panoramic radiographs with volumetric computed tomography images in the preoperative assessment of impacted mandibular third molars

PURPOSE

In the present study, we evaluated the geometric, topographic, and anatomic reliability of volumetric computed tomography (VCT) images by comparing conventional panoramic radiographs with reconstructed VCT panoramic and paraxial images before performing third molar surgery.

PATIENTS AND METHODS

A total of 6 anatomic sites on 10 patients who showed a topographic relationship between the apices of the third molar root and the mandibular canal were preoperatively assessed by 5 oral surgeons using conventional panoramic radiographs; these were complemented and compared with secondary reconstructed paraxial and panoramic VCT images.

RESULTS

The position of the apices in relation to the mandibular canal could be revealed on 94% of VCT reconstructed paraxial images. Assessment of VCT paraxial images could be facilitated by using a toolbar marker in 70% of the paraxial images. In 90% of the paraxial images, it was possible to assess the relationship of the mandibular canal and its adjacent anatomy. The visual grading scores for conventional panoramic images were significantly better on all 7 assessed anatomic sites compared with the reconstructed VCT panoramic images.

CONCLUSION

The results showed that the VCT paraxial images gave a significantly clearer perception of the mandibular nerve than conventional panoramic radiographs. However, conventional panoramic radiographs were shown to be better than the VCT reconstructed panoramic images and were therefore an invaluable tool in the "expert-derived" assessment and posed the potential for identifying the need for further VCT diagnostic procedures.

Temporomandibular joint pantomography using charge-coupled device, photostimulable phosphor, and film receptors: a comparison

Our objective was to compare the accuracy and practicality in use of three available imaging receptors for temporomandibular joint (TMJ) imaging; namely, two computer-assisted and one traditional analog x-ray film system. A standardized tissue-equivalent encased human skull specimen was imaged using lateral and posteroanterior (PA) pantomographic projections with the Orthopantomograph OP 100 (Instrumentarium Imaging, Tuusula, Finland) and three different receptor modalities: (1) Ektavision film with Ektavision screens (Eastman Kodak, Rochester, NY); (2) DenOptix photostimulable phosphor screens (Dentsply/Gendex, Chicago, IL); and (3) the charge-coupled device (CCD) receptor, DigiPan (TREX/Trophy Radiology, Marne-la-Vallée, France). The effective focal trough was found for each receptor using lead resolution grids placed at fractional millimeter distances along empirically determined beam projection angulations. The time to acquire and process images was also established. We found that the CCD system permitted real-time display, whereas the use of traditional film took 2 minutes to load the cassette in a darkroom and perform the exposure, and then a further 2 minutes to unload and process. The storage phosphor took 3 minutes to unload the cassette and process the image and a further 20 seconds to clear the plate following laser scanning. Film produced the greatest maximum resolution followed by the storage phosphor and the CCD. In conclusion, CCD-based TMJ pantomography provided an instant image. The photostimulable phosphor system used was the least satisfactory in terms of the time expended to obtain an image, but provided better spatial resolution than the CCD. Ektavision film/screens provided the best spatial resolution in this investigation.

Panoramic dental radiography using a charge-coupled device receptor

Panoramic radiography using a slit beam and film/screen receptor is standard for the emergency room evaluation of mandibular fractures and also in dentistry. This study compared the spatial resolution, area distortion factors, and the dosage considerations for a panoramic system where standard film/screen and a charge-coupled device were alternatively employed as the image receptor. Resolution and image contours were determined using a lead resolution grid positioned at selected beam projection angulations. Exposure measurements were carried out using a RANDO average man phantom and a 3 cc beryllium-windowed ionization chamber. The maximum spatial resolution with film approached 5 lp mm-1 whereas with the CCD the maximum resolution was just above 4 lp mm-1. Consequently, the image layer was reduced slightly in width when using the CCD receptor. The use of the CCD resulted in skin exposure reduction exceeding 70%.

Clinical trial of panoramic dental radiography using a CCD receptor

The objective of this study was to evaluate the perceived clinical efficacy of a charge-coupled device (CCD) detector for panoramic radiography by comparing the images produced to conventional film/screen radiographs using the same machine and patient population. For clinical evaluation, 18 criteria were selected. These included overall assessment of the area of coverage, clarity of dental structures, clarity of bony outlines, specific anatomic details such as the maxillary sinus floor, mandibular canal and mandibular condyle, and region-by-region assessment of the dentition. Observers acted independently using identical optimal viewing conditions. Film and digital radiographs were evaluated separately. A five interval Likert rating scale was used. Digital images were rated superior to the conventional film radiographs for 14 criteria. Film radiographs marginally outperformed digital images for three criteria. For one criterion (periodontal bone status) the two modalities showed no difference in terms of the means ratings. It was concluded that digital images are clinically equivalent to conventional film/screen images for panoramic dental radiography.

Charge-coupled device panoramic radiography: effect of beam energy on radiation exposure

OBJECTIVE

To determine the consequences for entrance exposure of varying the beam energy and operating current for panoramic radiography using a charge-coupled device receptor.

MATERIAL AND METHODS

Images were made of a RANDO average man phantom (Alderson Research Laboratories, Stamford, CT) at kVcp settings of 60, 66, 70 and 80 and an mA of 2.0, 3.2, 6.4 and 10.0. The exposure cycle was set as recommended by the manufacturer at 17.6 s. Diagnostic image quality was rated by a panel of two oral and maxillofacial radiologists and one oral and maxillofacial pathologist. Entrance exposures were assessed using a 3 cc ionization chamber placed at the beam entry points while imaging the molar, premolar, and anterior teeth both using the DigiPan (Trophy Radiologie, Vincennes, France) CCD receptor and conventional T-Mat G film/Lanex Regular screens (Eastman Kodak, Rochester, NY, USA).

RESULTS

Acceptable image quality was attained with combinations of 60 kVcp and 3.2, 6.4 or 10 mA, 70 kVcp and 2.0, 3.2 or 6.4 mA; at 80 kVcp irrespective of the mA it was unacceptable. The maximum reduction in entrance dose was 77%, averaged over the three sites, at 70 kVcp and 2 mA.

CONCLUSION

The DigiPan receptor produces satisfactory images with saving in entry exposure saving of approximately 70% when compared with a conventional film/rare earth screen combination.