Biomedical subjects

W C Scarfe

Publications and source records attributed to W C Scarfe.

34 records · Page 2Linked to original sources

PubMed1996

Technical report. Processing to achieve high-contrast images with computed dental radiography.

OBJECTIVES: To determine the effects of equalization on image contrast and signal-to-noise ratio (SNR) with Computed Dental Radiography (CDR). METHODS: Pixel value distributions were measured for various tissue thicknesses of a dental quality assurance jaw phantom and the average pixel values and SNR calculated. RESULTS: Equalization resulted in enhanced image contrast of underexposed images by effecting pixel value adjustment with little change in SNR. Overexposed images demonstrated minimal difference in contrast or SNR when equalization was applied. CONCLUSION: The equalize function of CDR is a convenient method to provide high-contrast images from underexposed images without detriment to the SNR. As it does not compensate for overexposure, the function will not lead to inappropriate overdosage of the patient.

Humans↗

PubMed1996

Identification of the temporomandibular joint and adjacent cephalometric landmarks using a dual sensitivity screen-cassette system.

OBJECTIVES: Clinical evaluation of a cassette with dual speed screens for cephalometric radiography. METHODS: Two lateral cephalometric radiographs were taken on 20 consenting subjects using the TMJ Orthoceph Slimline Cassette System (TOSCS), incorporating circular Trimax 12 screens in the area adjacent to the temporomandibular joint, and a control cassette (Trimax 8 screens). Ten pairs of radiographs with optimal image quality were randomly presented to 10 observers trained in cephalometric interpretation. Observers rated the overall diagnostic quality of each radiograph and of the TMJ region on an ordinal scale. They then located specific landmarks and traced the TMJ anatomy using acetate overlays. Overlays were digitized by a single operator who repeated tracing placements and digitizations to determine the error of recording method. Landmark variability was compared in the x- and y-axis by the Wilcoxon matched-pairs signed ranks test (p < 0.05). Six repeat tracings were performed and assessed by percentage of repeated observations above the maximum affordable error. Fossa space values were analyzed by the coefficient of variation (CV). The variability of the angular and linear values was also compared. RESULTS: TOSCS image quality was perceived as significantly better than the control. Method error was 0.34 mm in the x-axis and 0.4 mm in the y-axis. Interobserver variability was 2 to 3 times greater than intraobserver. There was less variability with TOSCS for identification of basion (x-axis), center-of-rotation (x-axis) and condyle (posterior) (x-axis). However, this was clinically insignificant. Accurate determination of the fossa space was not possible as CV varied from 23 to 84%. No differences in the variability of angular or linear values variability were found. CONCLUSIONS: While observers preferred TOSCS, no significant clinical differences could be demonstrated between the two systems.

Cephalometry↗

PubMed1996

Technical note. Modulation transfer function analysis of a newly revised rotational panoramic machine.

OBJECTIVES: To determine the modulation transfer function (MTF) and noise equivalent passband (NE) values for a newly revised rotational panoramic X-ray machine, the PC-1000 (Panoramic Corp., Fort Wayne, Indiana, USA). METHODS: Images of a 10 microns test slit were taken at various locations along the X-ray beam projection path using a Lanex Regular/T-Mat G image receptor. Line spread functions were obtained at specific beam paths by scanning slit images with a microdensitometer. RESULTS: MTF values were highest around the central plane of the image layer, with a maximum near the centre of 0.25 at 4 cycles/mm. The NE values near the central plane of image layer were 1.4 cycles/mm. MTF and NE values in the anterior region were low, 0.2 and 1.2, respectively. The width of the image layer was narrower in the anterior and wider in the posterior segments. Rapid decreases in MTF and NE values were found on the X-ray tube side compared with the receptor side of the central plane. Using a spatial frequency of 0.25 MTF the shape of the image layer was coincident with that determined visually. CONCLUSION: On the basis of the MTF and NE values the image resolution produced by this machine is considered acceptable for panoramic dental radiography.

Mathematics↗

PubMed1995

Radiographic detection of accessory/lateral canals: use of RadioVisioGraphy and Hypaque.

The diagnostic accuracy of RadioVisioGraphy (RVG-S) and conventional film images with and without the use of a radiopaque contrast media were compared for the detection of accessory/lateral canals. Forty-nine root canals, 13 with verified lateral canals, were endodontically prepared and imaged using both conventional intraoral dental film (E-speed) and three modes of RVG-S digital radiography (normal, inverse, zoom) before and after introduction of Hypaque-M, 90%. Images were presented to seven viewers; however, three demonstrated only fair intrarater reliability and were excluded. Overall sensitivity was low. RVG images were slightly more sensitive than conventional film images. Specificities, positive predictive values, and negative predictive values were low and showed no differences between modalities. It was concluded that the diagnostic accuracy of both film and RVG-S digital radiographic images for the detection of accessory/lateral canals, either alone or in combination with radiopaque contrast material, is low.

Contrast Media↗

PubMed1995

Longitudinal predictability of AF-BF value in Angle Class I patients.

AF-BF is a linear cephalometric measure of the anteroposterior jaw relationship in the sagittal plane. A retrospective, longitudinal study was made to determine the mean Caucasian American AF-BF values at ages 8 and 18 years for 30 male and 32 female participants of the Bolton Growth Study. Mean AF-BF values (+/- s.d.) for males were 7.3 +/- 2.7 mm at 8 years and 6.5 +/- 4.2 mm at 18 years. Mean AF-BF values (+/- s.d.) for females were 6.7 +/- 2.1 mm at 8 years and 5.2 +/- 2.9 mm at 18 years. No significant difference was found between the mean AF-BF values for males and females at either age group (P < 0.05). The decrease in AF-BF mean values with increasing age both for males and females was statistically significant. The correlation (r) for the AF-BF values was 0.49 (P < 0.05) for females and 0.86 (P < 0.05) for males. With increasing age, the mean difference between ANB values for females was 1.40 +/- 1.60 and 1.10 +/- 1.40 for males. The correlation of ANB angle and AF-BF provides a clinically useful tool for the cephalometric assessment of anteroposterior sagittal discrepancies of maxillary and mandibular denture bases.

Adolescent↗

PubMed1995

A dual sensitivity screen system for TMJ image enhancement in cephalometric radiography: sensitometric evaluation.

OBJECTIVES: An in vitro evaluation of the image quality of the TMJ OrthoCeph Slimline Cassette System (TOSCS). METHODS: The density response, resolution and clarity of the system were evaluated by use of the characteristic curve, modulation transfer function and root mean square quantum mottle. Relative sharpness was evaluated qualitatively by five observers. RESULTS: Increased density with Trimax 12 gave almost the same contrast as that with Trimax 8 in the diagnostic range, whereas MTF and RMS for Trimax 12 were inferior. CONCLUSIONS: The dual-sensitivity screen system should lead to improved radiographic contrast of the TMJ region in cephalometric radiography. The reduction in sharpness is probably clinically insignificant.

Absorptiometry, Photon↗

PubMed1995

Perceptibility of defects in an aluminum test object: a comparison of the RVG-S and first generation VIXA systems with and without added niobium filtration.

OBJECTIVE: To compare the first generation VIXA (Gendex, Milan, Italy) and the RVG-S (Trophy Radiologie, Vincennes, France) for detection of defects in an aluminium test object at various exposures both with and without added niobium filtration. METHODS: Images of a 7 mm aluminium test object with defects ranging from 0.1 to 1.5 mm with standardized projection geometry. Seven dentists acted as observers. Perceptibility curves were developed for both sensors under the various filtration conditions and exposures. RESULTS: At optimum exposures both the VIXA and the RVG-S permitted the same number of defects to be observed. The optimum exposures were similar for the two systems, but the dynamic range was greater for the RVG-S. Addition of niobium filtration did not appreciably alter the radiation dose required to perceive a given number of defects using either system. CONCLUSIONS: The two systems performed equally at optimum exposure when the dose is approximately the same irrespective of the presence or absence of niobium filtration. Beyond the optimal level, the RVG-S outperformed the VIXA system.

Aluminum↗

PubMed1995

Measurement accuracy: a comparison of two intra-oral digital radiographic systems, RadioVisiography-S and FlashDent, with analog film.

OBJECTIVES: To compare the accuracy of measurement algorithms incorporated into the software provided with two CCD-based digital radiographic systems and compare assessments using intra-oral film. METHODS: A test object with three radiopaque reference points was imaged using Ektaspeed intra-oral film, both with and without an overlaid 1 mm reference grid, the RVG-S, the measurement software of which overlays a 2 mm grid, and the FlashDent, which uses a mouse-driven cursor to estimate distances. Geometric factors, including source-to-object and receptor-to-object distances, vertical and horizontal cone angulation, and vertical angulation of receptor, were successively altered. Six viewers estimated vertical, horizontal and diagonal distances for each image. RESULTS: Increased source-to-object distance resulted in a 5-10% reduction in image dimensions, whereas increased receptor-to-object distance produced a magnification of 15-20% with all techniques. Increased vertical and horizontal cone angulation resulted in slight increases in magnification (0-5%) whereas greater receptor angulation resulted in noticeable magnification under all test conditions (10-15%). Estimated values for vertical, horizontal and diagonal measurements were approximately 5-10% higher than the actual dimensions, irrespective of the technique used. The FlashDent mouse-driven cursor system and direct measurement of distances from conventional film were more accurate in horizontal and diagonal dimension estimates than using an overlaid grid. Intra-observer and inter-observer differences were found for specific situations. CONCLUSION: The mouse-driven computerized measurement cursor and intra-oral film assessment using a ruler provided the most accurate, reliable and consistent dimensional measurements.

Analysis of Variance↗

PubMed1995

Accuracy of dimensional and angular measurements from panoramic and lateral oblique radiographs.

OBJECTIVES: Dimensional and angular measurements from radiographs can be used in clinical dentistry to determine the inclination of impacted teeth, the relative position of roots and restorative abutments, and for implant site assessment. This study was carried out to assess the in-vitro accuracy of such measurements obtained from three rotational panoramic systems and two standardized lateral oblique projections (45 degrees and 60 degrees) using two cephalometric systems. METHODS: Acrylic test models with wires positioned to represent the position and angulations of the teeth were used. Ten images were taken with Oralix Pan DC/1, Panelipse and Orthophos panoramic machines. Fourteen lateral oblique radiographs were also taken using two cephalometric units: an Orthophos and a Quint Sectograph. The models were repositioned between each exposure. Horizontal, vertical and angular dimensions of every tooth position on each radiograph were measured by three evaluators and compared using ANOVA at an a priori significance level of alpha = 0.05. RESULTS: Assessment of vertical dimensions was consistently more accurate on lateral oblique projections than on the panoramic radiographs. In general, the most accurate horizontal measurements could also be made with the lateral oblique projections. No differences in angular measurement accuracy were found between any of the projections. The use of statistical means and standard deviations can be misleading in ranking accuracy where a consistent conversion factor can be applied. CONCLUSIONS: While panoramic radiography is convenient for dimensional and angular assessments, lateral oblique radiographs taken with a standard cephalometric apparatus are an alternative when greater clinical accuracy is needed.

Analysis of Variance↗

PubMed1995

Computed dental radiography: evaluation of a new charge-coupled device-based intraoral radiographic system.

Computed dental radiography is a filmless system of dental x-ray imaging. It features multiple sensors with receptive areas and image quality that approach the size and resolution of film. The system is able to match the utility of film on levels such as multiple-sized images and printing output. It approaches film in quality of image and diagnostic capacity. In features such as speed of image acquisition, reduction in radiation dose, retrieval of data, and organization and storage of images, the computed dental radiography system surpasses traditional x-ray film.

Evaluation Studies as Topic↗

PubMed1995

Three-dimensional CT scan of hemimandibular hyperplasia: case report.

Three-dimensional images of craniofacial structures are reconstructed from conventional CT scans with the use of special computer software. These reconstructed images do not exhibit magnification nor superimposition of CT scans of structures. Quantitative measurements of three-dimensional craniofacial structures can be very precise. This technique has broad applications in the field of special patient care and is demonstrated in a case report of hemimandibular hyperplasia.

Adolescent↗

PubMed1994

Clinical comparison of two panoramic modalities and posterior bite-wing radiography in the detection of proximal dental caries.

A clinical study was designed to examine whether the Philips OrthOralix SD (Gendex Dental Systems, Monza, Italy) orthogonal panoramic projection could improve diagnostic accuracy over standard projections in the detection of proximal surface caries. Thirty-five sets of radiographs that demonstrated optimal image characteristics were selected. Using a five-point scale, 18 viewers evaluated whether specified lesions were present or absent. Viewer data was then compared with a consensus radiographic assessment of the state of the proximal areas. Receiver operating characteristic curves were generated with the use of a maximum-likelihood method of fit. The area under the receiver operating characteristic curve was used as the index of diagnostic accuracy. The mean receiver operating characteristic areas for orthogonal and standard projection panoramic and bite-wing radiography to detect the presence of proximal dental caries were 0.68 +/- 0.03, 0.69 +/- 0.03, and 0.79 +/- 0.03 respectively. Critical ratio analysis was used to compare the means for all possible pairings of imaging modalities. In overall performance, conventional bite-wing radiographs gave a significantly greater diagnostic yield for proximal caries than the Philips OrthOralix SD orthogonal or standard panoramic modalities (p > 0.05). The orthogonal projection did not improve diagnostic accuracy in the detection of proximal carious lesions compared with the standard projection.

Dental Caries↗

PubMed1994

Flash Dent: an alternative charge-coupled device/scintillator-based direct digital intraoral radiographic system.

The Flash Dent digital intraoral radiographic system is yet to be described in the scientific literature. A Windows operating environment, a lens based optical scintillator charge-coupled device (CCD) and 'IMG' image format are the major features which distinguish this from other available systems. In this paper we describe the component of the Flash Dent system, investigate the validity of the X-ray generator specifications, determine comparative image doses and assess the performance of the intraoral sensor. Although we found Flash Dent software facilitates image processing, X-ray generator operation, sensor performance and dimensional measurements, inconsistencies between sensors and the use of a non-standard image format require further consideration for improvements on the part of the manufacturer.

Humans↗

PubMed1994

Pixel perception and voxel vision: constructs for a new paradigm in maxillofacial imaging.

With the introduction of multimedia computed systems, a revolution equal in magnitude to the introduction of the air-turbine handpiece is presently under way in general dental practice. Alongside the introduction of new direct digital radiographic devices, dental imaging is expanding to include video, and optical impressions for Cad-Cam, all of which have common image processing needs. Hence, it is time for maxillofacial radiologists to decide what their role should be both during and after the change. This has major ramifications in terms of assignment of responsibilities between disciplines as the dental curriculum is redesigned to train the modern dentist.

Humans↗

PubMed1993

Radiographic interproximal angulations: implications for rotational panoramic radiography.

Axial radiographs were taken on 160 subjects at the screening clinic of the Dental School, University of Texas Health Science Center at San Antonio. Intermeatal and midsagittal lines, together with coordinate axes and polynomial curves that represent the average dental arch form, were overlaid on each radiograph. Coordinate references for interproximal tangents at 3154 contacts along the average dental arch form were digitized and angulations between the arch form and midsagittal plane calculated. Interproximal angulations at the average arch form were found to vary greatly but the average fluctuated around 90 degrees over the length of the arch. Optimal beam angulations were shown to be considerably different from central ray angulations of current panoramic machines, and although most machines demonstrated favorable interproximal beam angulation in the anterior region, discrepancy in the premolar region ranged from 15 degrees to over 40 degrees. Overall the OrthOralix SD (Gendex Dental Systems, S.r.l., Monza, Italy) orthogonal projection and PM 2002 CC (Planmeca Inc. Helsinki, Finland) deviate least from optimal interproximal angulation over most of the dental arch. However, the Planmeca gives a better angulation in the canine/premolar region, whereas the OP5/10 (Palomex Instrumentarium Corp., Helsinki, Finland) is comparable with the OrthOralix SD in the molar region.

Analysis of Variance↗

PubMedDate not supplied

Optical densities of dental resin composites: a comparison of CCD, storage phosphor, and Ektaspeed plus radiographic film.

Density versus exposure was determined for digital and film radiographic images of various thicknesses of six dental resin composites. The curves were relatively parallel; saturation at the black end of the contrast scale occurred at lower exposures with Computed Dental Radiography (CDR, Schick Industries, Long Island City, NY) than with the Sens-A-Ray (Regam AB, Sundsvall, Sweden). Ektaspeed Plus film (Kodak Dental Products, Rochester, NY) was the least sensitive modality tested. The DIGORA storage phosphor system (Soredex-Orion, Helsinki) had a wide exposure latitude with significantly less steep characteristic slopes than for images from the charge-coupled devices (CCDs). Slopes generated for the Sens-A-Ray and the CDR were not significantly different. Slopes generated for each resin composite were not significantly different for each of the modalities. Relative radiopacities of the resin materials with respect to each other were constant across all modalities; hence, in these systems, sensor type is unlikely to affect differentiation between resin composites and dental enamel or recurrent caries.

Absorptiometry, Photon↗