Taeko T. Farman

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

OBJECTIVES The purpose of this study was to describe the Orthopantomograph OP 100 Digipan modification and to determine the image-layer and dosimetric characteristics of this system. RESEARCH DESIGN Image-layer contours for the Digipan were determined at resolution limits of 4.0, 3.0, and 1.5 line pairs (Ip) mm(-1) using a resolution grid positioned at intervals along the beam projection paths. A hexagonal test device was placed above the grid to determine the magnification factors at the selected resolution limits. For dosimetry, a 30 mm2 ionization chamber was placed at the beam entry points while imaging the molar, premolar, and anterior teeth using both the Digipan and conventional film receptors. RESULTS The maximum resolution exceeded 4.0 Ip mm(-1)in the center of the image layer. Using a 1.5 Ip mm(-1) resolution limit, the focal trough width was 14 mm at 0-degree horizontal angulation, 20 mm at 37 degrees, and 36 mm at 83 degrees. At 1.5 Ip mm(-1), the horizontal magnification was -21% facial and +42% lingual to the center of the image layer in the incisor region; -25% facial and +19% lingual to the center of the image layer at a horizontal angulation of 83 degrees. At 4.0 Ip mm(-1), horizontal magnifications in the incisor region were -2.0% facially and +0.5% lingually; at 83 degrees they were -3.9% facially and +1.1% lingually. The neck entrance dose for imaging the anterior and premolar regions averaged 89.5 (+/-5.6) microGy. The cheek entrance doses for imaging the molar region averaged 220.6 (+/-8.0)microGy with the Digipan. With film the average entrance doses were 297.9 (+/-8.6) microGy (anterior and premolar regions) and 682.1 (+/-16.9) microGy (molar region). CONCLUSIONS The Digipan image layer is similar, but slightly narrower than that previously reported for the Orthopantomograph OP 100 using standard film-screen combinations. The resolution at the center of the image layer exceeded 4.0 Ip mm(-1). The Digipan produced images with an entry dose savings of approximately 70% when compared with photo-timed exposures using conventional film with the Orthopantomograph OP 100.

A status report on digital imaging for dentistry

Digital radiographic systems for use in dental practice have been available for almost two decades, but internationally most dentists still use analog silver halide X-ray film. This article is a review of the presumed advantages digital radiographic systems have over conventional X-ray film with special emphasis on the costs and benefits of current intraoral and panoramic systems. It is concluded that more evaluations of time and motion for digital imaging in dental practice are needed. Moreover, evidence-based logic should be applied to the determination of the physical properties required by image detectors for the performance of the different diagnostic tasks that are needed when practicing dentistry.

A comparison of image characteristics and convenience in panoramic radiography using charge-coupled device, storage phosphor, and film receptors

This study compared the image layer characteristics, dose requirements, and convenience in use of panoramic radiography using each of four different image receptors including traditional indirect exposure x-ray film, a storage phosphor system, and two solid-state sensors. The OP 100 D (Instrumentarium Imaging, Tuusula, Finland) charge-coupled device (CCD) sensor provided an instant image with a wide focal trough, making patient positioning error unlikely, but at the same time required a patient dose higher than that used with film. While the DigiPan (Trex/Trophy, Marne-la-Vallée, France) CCD significantly reduced the patient dose to radiation and also provided an instant image, the focal trough was narrower making patient positioning error more likely. The storage phosphor system provided high resolution and a reasonable focal trough width, but the procedure took longer than traditional film radiography and did not provide a dose saving.

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 mean ratings. It was concluded that digital images are clinically equivalent to conventional film/screen images for panoramic dental radiography.

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 a skin exposure reduction exceeding 70%.

Cephalometric landmark clarity in photostimulable phosphor images using pseudo-color and emboss enhancements

AbstractObjective The conspicuity of cephalometric landmarks may be improved by pseudo color and emboss enhancements of 8 and 16 bit photostimulable phosphor (PSP) cephalograms reviewed by orthodontists. Methods PSP cephalograms of orthodontic patients were obtained. These 8 bit and 16 bit images were viewed in random order in baseline “for processing,” emboss, pseudo color and emboss/pseudo color states. Ten observers viewed the images simultaneously and idependently. Selected soft tissue and hard tissue cephalometric landmarks and of overall image clarity were rated. Repeat images were included to determine intra observer reliability in making ratings. Results Statistically significant differences were found in the preferred image state for both specific cephalometric landmark evaluation and image bit depth. The emboss state was most frequently rated highest for clarity of hard tissue landmarks. Pseudo color state was rated best for soft tissue landmarks. Interrater agreement varied between landmarks but was not altered significantly by bit depth. Intrarater agreement was high. Conclusions Post-processing enhancement of PSP cephalograms is perceived to improve clarity of selected anatomic landmarks in PSP cephalograms.

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.

Image post-processing for optimization of photostimulable phosphor cephalograms

To evaluate 16-bit PSP cephalogram images for orthodontist-perceived quality of cephalometric landmark clarity at baseline and with three different image enhancements (emboss, inverse, and inverse/emboss). This presentation concerns results limited for detection of Porion and Pronasale. These two landmarks were evaluated in view of being extremes in contrast requirements. A Sectagraph (Denar Corporation, CA) was used with the DenOptix storage phosphor system (Dentsply/Gendex, IL). Images from 48 patients (plus 12 repeats) were presented randomly and simultaneously to 10 observers engaged in orthodontics. Each observer independently rated Porion and Pronasale detection (1 = poor; 2 = satisfactory; 3 = excellent). Equal numbers of images having single and double peak histograms were included. Enhancements used in the study were: (1) emboss; (2) inverse; and (3) inverse/emboss.

Image characteristics of digital panoramic radiography—potential for computer-aided diagnosis of calcified carotid atheromatous plaque

Abstract A retrospective analysis of panoramic radiographs from patients with head and neck cancer, taken prior to radiation therapy, revealed a prevalence of carotid calcifications of 12.6% in men aged 50–59 years, but only 3.3% in women of the same age. By age 70–79 years, the prevalence of calcified carotid atheromas was similar for both genders. Evaluation of the image layer characteristics of a prototype Instrumentarium OP 100D digital panoramic X-ray machine shows this unit to be suitable for detection of calcifications, within the carotid artery at the region of the bifurcation.

The need for model generation and validation in craniofacial prosthodontics: a feasibility study

This paper reports case studies that demonstrate the problems facing the maxillofacial prosthodontist. Such cases can benefit from 3-D modeling and the use of rapid prototyping.