Biomedical subjects

W C Scarfe

Publications and source records attributed to W C Scarfe.

At least 19 recordsLinked to original sources

PubMed2000

Diagnostic accuracy of film-based, TIFF, and wavelet compressed digital temporomandibular joint images.

The purpose of this research was to determine if digitization and the application of various compression routines to digital images of temporomandibular joint (TMJ) radiographs would diminish observer accuracy in the detection of specific osseous characteristics associated with TMJ degenerative joint disease (DJD). Nine observers viewed 6 cropped hard-copy radiographic films each of 34 TMJs (17 radiographic series). Regions of interest measuring 2 in x 2 in were digitized using an 8-bit scanner with transparency adapter at 300 dpi. The images were placed into a montage of 6 images and stored as tagged image file format (TIFF), compressed at 4 levels (25:1, 50:1, 75:1, and 100:1) using a wavelet algorithm, and displayed to the observers on a computer monitor. Their observations regarding condylar faceting, sclerosis, osteophyte formation, erosion, and abnormal shape were analyzed using ROC. Kappa values were determined for relative condylar size and condylar position within the glenoid fossa. Indices were compared using ANOVA at a significance level of P < .05. Although significant and substantial observer variability was demonstrated, there were no statistically significant differences between image modalities, except for condylar position, in which TIFF and wavelet (at all compression ratios) performed better than the original image. For faceting, wavelet 100:1 performed better than radiographic film images. Little actual image file reduction was achieved at compression ratios above 25:1.

Analysis of Variance↗

PubMed1999

In vivo accuracy and reliability of color-coded image enhancements for the assessment of periradicular lesion dimensions.

OBJECTIVE: The purpose of this study was to compare dimensions on charge-coupled device-acquired images under various enhancements with dimensions on film radiographs and in vivo dimensions with respect to the linear measurement of periradicular radiolucent lesions. STUDY DESIGN: The dimensions of 25 lesions imaged by means of a charge-coupled device-based digital receptor and Ektaspeed Plus radiographic film were measured and compared with dimensions as actually measured on impressions of the lesions taken during surgery. Digital images were displayed in unenhanced, equalized, and equalized/color-coded modes. The color-coding protocol was repeated to determine the method error, and each image treatment was also remeasured to determine intrarater reliability. Differences were compared through use of a Friedman 2-way analysis of variance with a follow-up Wilcoxon signed rank test (alpha = 0.01). RESULTS: Actual lesion dimensions were larger than dimension estimates obtained with digital images (range, 23% to 35%) and film radiographs (range, 29% to 43%). Color-coded images were significantly less accurate than equalized images and unenhanced images. Images equalized through use of the measurement algorithm of the resident software provided estimates that were more accurate than estimates made with film radiographs and a standard millimeter rule. Intrarater variability was low. The application of color coding was found to be unreliable. CONCLUSIONS: When applied to intraoral images, color-coded image processing of digital images had limited value in the estimation of periradicular lesional dimensions.

Analysis of Variance↗

PubMed1998

In vivo comparison of Visualix-2 and Ektaspeed Plus in the assessment of periradicular lesion dimensions.

UNLABELLED: Accurate assessment of intraosseous lesion dimensions is useful in determining strategies for treatment of periradicular pathoses of dental causation. OBJECTIVES: To compare the efficacy of digital versus analog imaging for the measurement of mesiodistal and vertical dimensions of periapical lesions in patients that require apical surgery. METHODS: Fourteen examiners assessed the dimensions of 28 lesions with a millimeter ruler and Ektaspeed Plus radiographs (Eastman Kodak, Rochester, N.Y.), and with the Visualix-2 (Gendex/Dentsply, Milan, Italy) in unenhanced, contrast-stretched and equalized modes with proprietary software mouse-driven measurement algorithm. Impregum F (Premier Dental Products) impressions at surgery were used as the "gold standard." Ten randomly chosen images were reread 2 weeks later to assess intra-operator reliability. As the Mauchly sphericity test was significant for all tests, a multivariate analysis of variance was used to assess accuracy. To explain the exact difference between means, the Bonferroni test was applied. Intra-observer reliability was assessed with Friedman's two-way analysis of variance; inter-observer effects were determined with Cronbach's alpha. RESULTS: For accuracy in measurement, the closest to the "gold standard" were achieved with the Visualix-2 with image equalization. The contrast-stretched Visualix-2 and unenhanced Visualix-2 measurements were less accurate; conventional film was consistently the least accurate (p < 0.002). On the other hand, subjective preference placed film radiographs above the unenhanced Visualix-2 images; contrast-stretched Visualix-2 images were preferred over all other modalities. CONCLUSIONS: Charge-coupled device-based images with the Visualix-2 are preferable to film-based radiographs for measuring periapical lesion dimensions.

Alveolar Bone Loss↗

PubMed1998

Characteristics of the Orthopantomograph OP 100.

OBJECTIVE: To investigate empirically the imaging characteristics of the Orthopantomograph OP 100 and compare them to the average form of the dental arch. METHODS: Repeatable radiographs were taken of a lead resolution grid positioned at 1 mm increments along known angular intervals of the projected X-ray beam. Focal trough thickness was determined by visibility of the 1.5 lp mm-1 resolution limits. The path of the effective rotation center was determined using a film positioned at right angles to the slit beam. The vertical magnification and horizontal magnification and distortion index, corrected for the position of the tomographic layer, were calculated using a reference object placed at various resolution limits of the focal trough. The beam projection angle was calculated with respect to the central plane of the focal trough and the average dental arch shape compared with the average proximal contact angle. RESULTS: The maximum resolution observed at the central plane of the focal trough was 5 lp mm-1. The width of the focal trough varied from 17 mm in the anterior region to 44 mm in the posterior region. The path of the effective rotation center was found to translate between three fixed centers of rotation, with the effective anterior projection radius of 24 mm. The vertical magnification factor within the focal trough showed a linear increase along the beam path from 1.24-1.37 and the horizontal magnification varied from 1.01-1.63. The distortion index varied from 0.84-1.24. The beam projection angle increased from 90 degrees anteriorly to 115 degrees in the premolar area with respect to the central plane of the focal trough and from 90 degrees anteriorly to 110 degrees in the premolar area compared with the average dental arch. CONCLUSIONS: The OP 100 provides a focal trough conforming well to the overall geometry of the dental arch and provides adequate spatial resolution.

Dental Arch↗

PubMed1998

Panoramic radiographic patterns of the infraorbital canal and anterior superior dental plexus.

OBJECTIVE: To describe and classify the presentations of the infra-orbital canal/groove (IOC/G) complex and anterior superior dental plexus (ASDP) on panoramic radiographs. METHODS: The frequency of occurrence and variations in appearance of the IOC/G were determined on 246 random panoramic radiographs. A classification system consisting of Types I, II and III was developed to describe the radiographic patterns of the IOC/G. RESULTS: Two hundred radiographs (81.3%) demonstrated evidence of the IOG/C. The most frequent appearance of the IOC was Type III (44.75%) closely followed by Type I (42%) and Type II (13.25%), with only minor differences in prevalence between right and left sides. Sixty one percent were bilateral. Radiologic evidence of the ASDP was noted in 29% of radiographs demonstrating an IOG/C with 12% of cases being bilateral. Three distinct radiographic patterns of the anterior superior dental plexus (ASDP) were also observed. CONCLUSION: A classification of the appearance of the IOC/G and ASDP on panoramic radiographs has been presented.

Adolescent↗

PubMed1998

A meta-analysis of mandibular intercanine width in treatment and postretention.

The meta-analysis technique of literature review was applied to a total of 26 previous studies to assess the longitudinal stability of postretention mandibular intercanine width. Weighted averages and standard deviations for the means of 1,233 subjects were compared for linear changes in intercanine transverse dimensions during treatment (T1), immediately after treatment (T2), and after removal of all retention (T3). Net change was defined as the difference between means at T3 and T1. Dimensional changes were also evaluated on the basis of patient pretreatment Angle classification, extraction, and nonextraction treatment modalities of each group. Paired two-tail t-tests were performed between T3 and T1 means on all groups at the a priori level of significance set at a < or = 0.05. Statistically significant differences were observed for the following groups: all patients; nonextraction; extraction; Class I; Class I extraction; Class II extraction; and, Class I Division 1 nonextraction. The findings of this study indicate that regardless of patient diagnostic and treatment modalities, mandibular intercanine width tends to expand during treatment on the order of one to two millimeters, and to contract postretention to approximately the original dimension. While statistically significant differences could be demonstrated within various groups, the magnitudes of the differences were not considered clinically important.

Dental Arch↗

PubMed1998

A common sense approach to TMJ and implant imaging.

During the last two decades, computer-based imaging technology has contributed significantly to our assessment of patients with head and neck anomalies. For instance, magnetic resonance imaging has given us a modality for visualizing the hard and soft tissues of the temporomandibular joint. We are fortunate that this has led to the refinement of the concepts of normality and the characterization of non-normal conditions. In the pre-surgical assessment of alveolar bone prior to implant placement, tomography in its various forms has provided the possibility of three dimensional bony assessment thus potentially optimizing fixture placement and minimizing potential failure. Unfortunately, there has been a reluctance to employ these techniques as they are either not available or both the equipment and the cost of image acquisition time is too expensive. Until recently, there has been a lack of consensus as to the selection of imaging modalities appropriate to patient presentation and the clinical value of the information obtained. The more recent development of computer-controlled panoramic imaging has made available to us many special projections which are capable of producing hard tissue images of either the TMJ or a potential implant site in multiple dimensions at lower cost (both financially and in terms of X-ray dose) than the more advanced modalities. These projections can now be incorporated into a clinically determined patient-based protocol and thus provide the clinician with both an economical and common sense approach to diagnostic imaging.

Dental Implantation, Endosseous↗

PubMed1997

Evaluation of XD/A Plus and ST8G films for cephalometric radiography with Grenex G8 and BH-III screens.

OBJECTIVES: Sensitometric properties, clinical image quality, and patient dose requirements are important considerations when selecting film for cephalometrics. Two recently released films, XD/A Plus and ST 8G green sensitive films, were studied. METHODS: The films were each combined with Grenex G8 (Fuji Medical) green-fluorescing matched and BH-III (Kasei Optonix) blue-fluorescing mismatched intensifying screens. The density response and resolution for each screen-film combination were evaluated by use of the characteristic curve and modulation transfer function. The kilovoltage settings providing clinically acceptable images were assessed individually by 12 observers. Clinically acceptable images for each combination were also compared, and the skin entrance doses in the temporomandibular joint region were determined. RESULTS: The average contrast at the most effective density range was found to be slightly higher for the BH-III group than for the G8 group. The modulation transfer function for the BH-III group was inferior to that for the G8 screens. There were no significant differences in diagnostically acceptable image quality among the four combinations; nevertheless the BH-III screen group required two to three times more exposure than the G8 screen group. CONCLUSIONS: XD/A Plus and ST8G films provide acceptable image detail for cephalometrics. To minimize the patient dose they should be used with green-emitting screens.

Analysis of Variance↗

PubMed1997

Sensitometric effects of varying the intensifying screens used with Agfa Dentus ST8G and RP6 panoramic radiographic films.

OBJECTIVES: To compare the sensitometric effects and information yield of varying the intensifying screens used with both Dentus ST8G and RP6 Agfa Gevaert, Dormagen, Germany panoramic radiographic films. MATERIAL AND METHODS: Four screen-film combinations were employed for each of the two film types. The screens used were blue fluorescing PX-III (Kasei Optonix, Tokyo, Japan) and Special (Siemens AG, Bensheim, Germany), as well as green fluorescing Lanex Regular (Eastman Kodak, Rochester, NY, USA) and Trimax T16 (3M, Mineapolis, Minnesota, USA). The density response for each screen-film combination was evaluated using the characteristic curves generated. Information yield, as determined by the radiographic detection of defects in an aluminium test object, was evaluated by nine observers. RESULTS: The characteristic curves for ST8G were different when green and blue fluorescing screens were used; however, those for RP6 varied little irrespective of the choice of intensifying screens. Observers were able to perceive defects at significantly lower radiation exposures for ST8G combined with green fluorescing screens compared with blue emitting screens. RP6 with all screen combinations provided similar image detail perceptibility at comparable exposures with ST8G with green-fluorescing screens. CONCLUSIONS: RP6 is suitable for use with either the spectrally matched blue emitting screens or green-emitting screens. ST8G radiographic film should always be matched to rare earth screens.

Analysis of Variance↗

PubMed1997

Tissue radiation dosages using the RVG-S with and without niobium filtration.

Tissue doses for a modified Rando head- and-neck phantom were measured for imaging with speed group E film with standardized aluminium filtration and the RVG-S both with and without added niobium filtration. Cylindrical holes drilled into the phantom's tissue-equivalent material permitted the placement of a small ionization chamber into anatomically correct sites representing the thyroid, parotid, submandibular and sublingual glands. To establish the necessary cone positions, angulations and time settings for each exposure, diagnostically acceptable images of six teeth, representative of different intraoral regions, were made for a DXXTR mannequin. Entrance and exit points were marked and transferred to the phantom to allow reproducible repeat exposures. The RVG-S provided reductions in average skin entrance dose of 31 per cent to 39 per cent with standard aluminium filtration and 51 per cent to 60 per cent with the addition of niobium filtration to attenuate the beam. While dose reductions relative to E-speed film usage were found for deep tissue sites, these were site and projection specific. The cumulative reduction from use of the RVG-S without niobium filtration was 32 per cent. It was 42 per cent with additional niobium filtration. It should be noted, however, that adding niobium filtration resulted in increased dosages to the deeper soft tissues such as the thyroid gland.

Aluminum↗

PubMed1996

Measurement algorithm accuracy of the RVG-PCi in vertical and diagonal assessments at various beam energies.

The Trophy RadioVisioGraphy model PCi was compared to Kodak Ektaspeed Plus film for accurate recording and estimation of the length of size 15 files placed vertically and diagonally across the receptor surface. Variations in kilovoltage (50, 70, and 75) and exposure were also factored. Eight observers estimated file lengths using the proprietary software measurement algorithm for the RVG-PCi and a millimeter rule for the film-based radiographs. Both modalities resulted in slight magnification for vertically oriented files; however, the RVG-PCi caused overestimation in the order of 6 to 8% with diagonally oriented instruments. Measurement interobserver variability was least when using the RVG-PCi. It was concluded that the proprietary software supplied with RVG-PCi is not sufficiently accurate for endodontic assessment. Furthermore, exposures above 0.15 s at 75 kVp resulted in pixel saturation resulting in apparent shortening of the instrument; hence, length calculations are particularly sensitive to overexposure when using the RVG-PCi.

Algorithms↗

PubMed1996

Observer differentiation of proximal enamel mechanical defects versus natural proximal dental caries with computed dental radiography.

OBJECTIVES: Various models have been used to study the accuracy of imaging systems for detection of dental caries. This study compares the ability of dentists to detect mechanically created defects versus natural dental caries cavitations on the proximal surfaces of extracted teeth with Computed Dental Radiography (Schick Industries, Long Island City, N.Y.). Detection rates are investigated according to lesion depth to permit comparisons to be made between studies in the literature with other mechanical defects or natural caries models. Discrimination of natural caries versus artificial defects with Computed Dental Radiography is also compared with a previous report that used standard dental film. STUDY DESIGN: Fifty-two extracted molar and premolar teeth were mounted into representative sets of maxillary and mandibular posterior arches for bite-wing radiography. There were 16 proximal surfaces with natural caries and 28 proximal surfaces with mechanical defects. An optical bench was used to ensure constant beam geometry. A 1.8 cm acrylic soft tissue equivalent attenuator was placed in front of the receptor. Thirty dentists acted independently as observers to differentiate between sound proximal tooth surfaces, natural dental caries, and mechanical defects. Evaluation of intra- and interobserver variability was made with use of the kappa statistic. The Zelen test of odds ratios was used to test for homogeneity, and the Mantel-Haenszel analysis plus stratified logistic regression were used for inference about the common odds ratio. Significance was set at p < 0.05. RESULTS AND CONCLUSIONS: Ignoring stipulation of cavity type, detection was 74% for mechanical defects and 67% for natural caries. The odds of detecting a mechanical defect were 1.40 times the odds of finding natural dental caries cavitation of the same depth. Lesion depth did influence the probability of correctly identifying the presence of a lesion; the odds of identifying cavitation increased 1.41 times with every 0.1 mm increase in lesion depth. Correct designation of lesion type was 1.42 times more likely with mechanical defects than with natural caries (p = 0.003). Intraobserver (kappa = 0.65) and interobserver (kappa = 0.43) agreements were fair to good. Discrimination between natural and artificial lesions was less with the Computed Dental Radiography than that found in our previous study with standard direct emulsion x-ray film.

Bicuspid↗

PubMed1996

RVG-S, VIXA, and Ektaspeed film in detection of proximal enamel defects under orthodontic bands.

An in vitro investigation was carried out to compare CCD-based intraoral radiographic systems with E-speed film for the detection of proximal enamel defects beneath orthodontic bands, with and without added niobium filtration to attenuate the x-ray beam. Twenty caries-free extracted teeth were randomly divided into five groups. Fifteen of 30 contacting proximal surfaces remained lesion free; the other 15 received a small, medium large mechanically induced enamel defect. Images were made with and without the addition of 30 microns niobium filtration, and with and without orthodontic bands. Six dentists were viewers. Receiver operating characteristic (ROC) curves were developed for each modality under each test situation. The area under the curve (Az) was used as an index of diagnostic accuracy, and the critical ratio was used for statistical comparisons. In the absence of orthodontic bands, the Az values for E-speed film and for nonenhanced RVG-S were greater than for all other modalities tested, indicating that they have the greatest diagnostic accuracy. With orthodontic bands, the RVG-S with steep gradient enhancement (X-function) had a higher Az value than all other modalities. Addition of niobium had no significant effect on defect detection. CCD-based devices hold no diagnostic advantage over conventional film for detecting changes in the density of enamel not covered by orthodontic bands. Contrast enhancement of digital images (RVG-S X-function) holds promise for the detection of such changes beneath orthodontic bands.

Bicuspid↗

PubMed1996

Mechanical defects in dental enamel vs. natural dental caries: observer differentiation using Ektaspeed Plus film.

The value of imaging modalities in enabling the observer to detect proximal dental caries has been tested previously using both natural carious cavitations and mechanical defects. This study compared the ability of dentists to detect mechanically created defects and natural dental carious cavitations on the proximal surfaces of extracted teeth, and to differentiate between the two. Detection rates according to lesion depth were also investigated. There was a difference in the ability of readers to detect natural proximal dental carious cavities and mechanical defects in the proximal enamel. The odds of detecting artificial cavities was 2.92 times the odds of diagnosing natural caries cavitations. There was great variation in the ability of the dentists to identify natural and artificial lesions. According to logistic regression, when the cavity depths are equal, the mechanical defects in the proximal dental enamel are easier to identify than are natural enamel dental caries cavitations. The odds ratio charts provided from this study show the depths of mechanical and natural lesions that are comparable in diagnostic challenge. These charts might permit rough approximations to be made when comparing previously published papers that variously use both mechanical defects and natural caries. Use of poorly designed in vitro models for testing can produce a false guide to the clinical performance of diagnostic systems.

Dental Caries↗

PubMed1996

Teledentistry: protocols for the transmission of digitized radiographs of the temporomandibular joint.

Tomograms of the temporomandibular joint were digitized in three different formats using a PC-based system. The image resolution for various projections was determined at different camera-film distances. Three series of images were transmitted by telephone, and transmission times were measured. The original radiographs, the digitized images, the transmitted images and the transmitted-and-printed images were presented to 10 observers, who were asked to rate image quality. No difference in image quality was found between the initial digitized and the transmitted images. However, transmitted and transmitted-and-printed images were of significantly lower quality than the original radiographs or the digitized images viewed on a computer monitor. Transmission time was reduced significantly (50%) by cropping the images before transmission. The image quality of individual radiographs was better than radiographs formatted as a series.

Analog-Digital Conversion↗

PubMed1996

Sensitometric response of the Sens-A-Ray, a charge-coupled imaging device, to changes in beam energy.

OBJECTIVES: To evaluate image density (pixel values) and image contrast due to variations in beam energy (kVp) for the Sens-A-Ray intra-oral radiographic sensor. METHOD: Images of an aluminium step wedge were made at 50, 70 and 90 kVp. Mean pixel values (with standard deviations) for representative attenuator thicknesses were measured using region-of-interest histogram analysis. Corresponding entrance doses were measured using a beryllium-windowed ionization chamber. RESULTS: The steepest response slopes were found with the lowest kVp settings; hence the CCD results mimic the behaviour of standard radiographic film, with the high contrast being found with low kVp. The entrance dose resulting in pixel saturation was less with low kVp than high kVp. It is suggested that this is due to the CCD receptor being most sensitive to X-ray photons of relatively low keV. CONCLUSION: While the kVp needs to be selected in relation to both tissue and receptor characteristics, it is possible to use low kVp techniques with the Sens-A-Ray without increasing the entrance dosage.

Electricity↗

PubMed1996

Optimum exposure ranges for computed dental radiography.

OBJECTIVE: Computed dental radiography (CDR; Schick Technologies Inc, Lond Island City, NY, USA) can be used with any dental X-ray generator. The optimum exposure at various tube voltage settings was studied. METHODS: Images were made of a dental QA jaw phantom and a standard aluminium stepwedge. Exposures were made between 50 and 90 kVp at 10 kVp intervals. Two contrast indices were calculated from the bone stepwedge pixel values: CI(1), the ratio between the highest and lowest pixel values, and CI(2), the difference between them. RESULTS: Contrast indices were greatest at low kVp. The gradual decrease in CI(1) with increased exposure demonstrated that the optimum exposure range was always relatively wide. Maximum CI(2) values were found at exposures of 27, 17, 15, 11 and 9microC kg-1 at 50, 60, 70, 80 and 90 kVp, respectively, at the centre of the optimum exposure range. Pixel values for each aluminium step increased both with increased exposure and with increased kVp. The longest contrast scale was obtained at 11.0, 9.6, 8.7, 7.2 and 7.0 microC kg-1 at 50, 60, 70, 80 and 90 kVp. The steepest slopes were obtained either with thin aluminium steps or at low kVp. CONCLUSIONS: CDR is a fast CCD-based system and is capable of operating at a wide range of kVp settings.

Aluminum↗

PubMed1996

Effects of instruction on the knowledge, attitudes and beliefs of dental students towards digital radiography.

OBJECTIVE: To investigate the effects of a course of instruction in intraoral digital radiology on the knowledge, attitudes and beliefs of dental students. METHODS: A questionnaire was administered to dental students at two institutions with (UL) and without (MCG) formal instruction in digital dental radiology, investigating their understanding of the principles of digital radiography, their attitudes to its use in the near future, and on the timing and suitability of the topic in the undergraduate dental curriculum. Differences in the responses between preclinical and clinical students at the two institutions were statistically assessed. RESULTS: The overall response rate was 66% (277) with rates of 52% (103) at MCG and 76% (174) at UL. UL students knew significantly more about digital radiography but they also had some significant misconceptions and differed in their perception of its future role. Most students (93%) believed that digital radiography should be included in the curriculum or offered as an elective course. CONCLUSIONS: Dental students want digital radiology to be introduced into the dental radiology curriculum, regardless of whether it is examined or not. The teaching methods and content of such a course need careful consideration.

Attitude of Health Personnel↗