Biomedical subjects

J B Ludlow

Publications and source records attributed to J B Ludlow.

At least 55 records · Page 3Linked to original sources

PubMed1997

Characteristics of an oral and maxillofacial radiology department. Report of the ad hoc Department Characteristics Committee of the American Academy of Oral and Maxillofacial Radiology.

Oral and maxillofacial radiology is a dynamic and multifaceted discipline that plays a critical role in patient care, the education of general dentists and dental specialists, and the academic health of the dental school. Diagnostic and treatment advances in temporomandibular joint disorders (TMD), implants trauma and orthognathic surgery, and craniofacial abnormalities depend heavily on conventional and advanced imaging techniques. Oral and maxillofacial radiology contributes to the education of pre- and post-doctoral dental students with respect to biomedical and clinical knowledge, cognitive and psychomotor skills, and the professional and ethical values necessary to properly prescribe, obtain, and interpret radiographs. The development of an active and successful oral and maxillofacial radiology department, division, or section requires the committment of institutional resources. This document may serve as a guide to dental schools committed to excellence in oral and maxillofacial radiology.

Clinical Competence↗

PubMed1997

Tuned-aperture computed tomography (TACT). Theory and application for three-dimensional dento-alveolar imaging.

OBJECTIVES: To introduce a new method for creating three-dimensional (3-D) radiographic displays based on optical aperture theory known as tuned-aperture computed tomography (TACT). With a number of advantages over conventional plain film and tomographic imaging. METHODS: The TACT algorithm and some of its capabilities are explained and published with results of in vitro simulations produced from a well-tested multi-tube tomosynthetic x-ray system. Examples of TACT reconstructions of a tooth with naturally occurring caries which were produced from multiple projections and generated with a new servo-controlled single-tube prototype are illustrated. Current imaging strategies in dentistry and their shortcomings in the detection of dento-alveolar disease are reviewed. Pertinent theoretical aspects of the TACT reconstruction algorithm are described and dental applications discussed in light of these limitations. RESULTS: Results of several published in vitro investigations derived from a prototype TACT system are referenced. Sample images of a tooth with naturally occurring caries derived from an even newer system are displayed. All data are consistent with the hypothesis that TACT imaging yields diagnostic performance either comparable, or superior, to that obtainable from conventional control modalities depending on the diagnostic task. Moreover, all investigations cited demonstrated conclusively the obvious theoretical benefits associated with the acquisition of multiple projections in three dimensions. CONCLUSIONS: TACT shows promise as a supplement to film-based dental radiography and as a digital alternative to conventional tomographic systems used in dento-alveolar applications.

Algorithms↗

PubMed1997

The efficacy of caries detection using three intraoral films under different processing conditions.

This study compares the diagnostic accuracy of caries detection using Ultra-speed (Eastman Kodak), Ektaspeed (Eastman Kodak) and Ektaspeed Plus (Eastman Kodak) films after they were developed in both new and used processing solutions. Ektaspeed Plus film provided significantly better diagnostic accuracy for small proximal-surface caries limited to the outer third of the dentin than did Ektaspeed film. Ektaspeed Plus film did not differ significantly from Ultra-speed film in aiding in the diagnosis of small carious lesions, and it maintained diagnostic accuracy in used processing solutions. Dentists can offer the X-ray dose-reducing technology of Ektaspeed Plus film to their patients and maintain consistently high diagnostic quality.

Analysis of Variance↗

PubMed1996

Comparison of film, direct digital, and tuned-aperture computed tomography images to identify the location of crestal defects around endosseous titanium implants.

This study compared diagnostic performance obtained from two-dimensional and three-dimensional x-ray images. The latter were produced with a new tomosynthetic method based on aperture theory called tuned-aperture computed tomography. Seven human cadaver mandibular segments containing a total of 20 endosseous implants with a small randomly positioned alveolar crestal defect at each implant site were imaged in two dimensions with periapical film and with a charge-coupled digital detector, and digitally with the same detector in three dimensions with tuned-aperture computed tomography and subtracted tuned-aperture computed tomography techniques. Seven trained dentists viewed randomized displays of all modalities. Outcomes of the diagnostic task of identifying the locations of crestal defects were quantified with accuracy, confidence, and time performance measures. Analyses of variance demonstrated that differences between either three-dimensional technique and either two-dimensional modality were significant for all measures (p < 0.001). These findings suggest that clinically applied TACT methods hold promise as an improvement over the status quo.

Alveolar Bone Loss↗

PubMed1996

Detection of peri-implant bone changes with axial tomosynthesis.

Tuned aperture computed tomography was used to assess bone defects at implant sites that are normally obscured in conventional periapical projections. Titanium implants were placed in incisor, premolar, and molar areas of an edentulous dry human mandible. The alveolar crest adjacent to each implant was circumferentially grooved with progressively larger round burs (no. 1/4 to no. 6). After each increment of bone removal, axial tuned aperture computed tomography slice images were produced. From these, digital subtraction images were generated with incremental and baseline slices. A panel of eight dentists reviewed randomized pairs of images that showed defects that differed by a single bur size. Images were masked to limit observation to mesial, distal, facial, or lingual regions. Observers accurately identified larger lesions in 76% of the unsubtracted tuned aperture computed tomography images and in 90% of the subtracted images. Logistic regression analysis suggested significant differences as a result of lesion size (p < 0.036) and imaging modality (p < 0.020).

Alveolar Process↗

PubMed1996

Effects of focal spot size on caries diagnosis with D and E speed images.

Annual measurement of the x-ray unit focal spot size has been recommended by the American Academy of Oral and Maxillofacial radiology as part of the dental radiographic quality control program. This study compares the effects of focal spot size on caries diagnosis. Three x-ray units with small, medium, and large focal spot sizes were used to produce bite-wing images on extracted teeth mounted in acrylic bases. Randomized films were scored for lesion presence and depth by two general dentists. Weighted kappa statistics were used to evaluate the agreement of reviewer caries diagnosis by film speed and focal spot size. Comparisons of caries cells with small versus medium and small versus large focal spot size produced weighted kappa statistics = 0.72 and 0.70, respectively. Differences in caries calls were greater because of film speed rather than focal spot size. The results of this study suggest that the clinical significance of varied focal spot size is negligible. The value of annual measurement of focal spot size is questionable, and its recommendation should be revisited.

Analysis of Variance↗

PubMed1995

Densitometric comparisons of Ultra-speed, Ektaspeed, and Ektaspeed Plus intraoral films for two processing conditions.

This study compared film speed, contrast, exposure latitude, and resolution of Ultra-speed, Ektaspeed, and Ektaspeed Plus films (Eastman Kodak Co., Rochester, N.Y.). Densitometric curves were generated for each film type under processing conditions of fresh and used chemistry to observe their effect on factors associated with diagnostic quality. Ektaspeed Plus film displayed the least variability due to processing condition of any film; it also demonstrated the fastest speed and was twice as fast as Ultra-speed film. Ektaspeed exhibited the greatest relative exposure latitude followed by Ektaspeed Plus and Ultra-speed. Average gradient over a clinically useful range of densities was greatest for Ultra-speed in fresh processing solutions, but greatest for Ektaspeed Plus in used processing solutions. All film types were able to resolve more than 16.6 line pairs per millimeter regardless of processing conditions. The results of this study suggest that dental practitioners who have refrained from using E-speed film because of the sensitivity of this film to variations in processing may now consider providing this dose-reducing technology for their patients with the expectation of obtaining consistent image quality.

Absorptiometry, Photon↗

PubMed1995

Knowledge and adoption of radiographic quality assurance guidelines by general dentists in North Carolina.

OBJECTIVES/STUDY DESIGN: A random survey of equal proportions of urban and rural North Carolina general dentists was conducted to assess their knowledge and adoption of radiographic quality assurance guidelines of the American Dental Association. RESULTS: A total of 159 surveys were returned representing a response rate of 51%. A majority of respondents answered "don't know" to questions dealing with intraoral and panoramic radiography units and darkroom monitoring. Higher levels of knowledge (58% to 77%) and adoption (63% to 86%) of guidelines were seen with film-processing activities. Linear regression demonstrated substantial positive association between knowledge and adoption of guidelines (R = 0.50). Stepwise multiple regression revealed positive associations of the demographic variables of years in practice, urban location, and age with greater knowledge of guidelines (R2 = 0.33, p < 0.05). Urban location was associated with increased likelihood of adoption of guidelines (R2 = 0.09, p < 0.05).

Health Knowledge, Attitudes, Practice↗

PubMed1995

Teaching radiographic localization in dental schools in the United States and Canada.

Although radiographic localization is an essential element of the practices of radiography and radiology, its incorporation into the dental curriculum has not previously been studied. This project surveyed dental schools in the United States and Canada on the relative amount of time that was given to instruction in various localization techniques and instructor opinion of the adequacy of training in localization skills. Ninety-eight percent of all dental schools returned questionnaires. Respondents who felt that teaching time was inadequate had mean rank time scores that were 40% less for total localization instruction and 57% less for teaching anatomic clues of the Buccal Object Rule than those who felt that teaching time was adequate. Because the Buccal Object Rule, cues, and cues represent the definitive dose-reducing approach to radiographic localization and because the Buccal Object Rule is readily applied across a broad range of clinical disciplines and activities, we recommend that this concept be incorporated into the curricula of all dental schools.

Algorithms↗

PubMed1995

Temporomandibular joint imaging: a comparative study of diagnostic accuracy for the detection of bone change with biplanar multidirectional tomography and panoramic images.

This in vitro investigation compares biplanar (sagittal and coronal) temporomandibular joint images produced by multidirectional tomographic and panoramic techniques for diagnostic accuracy in the detection of simulated degenerative lesions. A series of dentin chips placed at four locations on the head of a temporomandibular joint condyle in a dried human skull were imaged with tomographic and panoramic modalities. Equal numbers of images with and without chips were scored by four examiners with the use of confidence levels for presence or absence of the lesion. To assess intra-examiner reliability, each examiner viewed one of the modalities twice. Responses were assessed by generating receiver operating characteristic curves and analyzing the area (A(z)) under the curves with analysis of variation methods. Biplanar tomography provided significantly more accurate assessment of condylar lesions than biplanar panoramic images (p = 0.007). No statistical difference by location (p = 0.592) was found. The effects of observer and repeated observation were marginally significant at p = 0.046 and p = 0.030, respectively.

Analysis of Variance↗

PubMed1995

Radiographic evaluation of implant-obscured bone. Comparison of digitally subtracted tomographic and periapical techniques.

This study evaluated the diagnostic accuracy of digitized and substracted periapical and tomographic film images in the assessment of facial and lingual bone loss at implant-obscured sites. An edentulous dried human mandible was prepared with implants in the incisor, premolar, and molar regions. Successive bur sizes from quarter round to no. 6 were used to create circumferential infrabony periodontal defects in the alveolar crest adjacent to the implants. Periapical radiographs were made with the use of custom stents. Linear tomograms imaged sites in a cross-sectional orientation. An equal number of radiographs with and without lesions were digitized and subtracted from baseline images. Radiographic anatomy on the mesial and distal aspects of each implant was electronically masked before the evaluation by a series of eight observers. Receiver operating characteristics analysis and analysis of variance were used to evaluate accuracy of interpretation of the presence or absence of crestal defects. Observer accuracy in detecting facial or lingual bone defects was significantly greater with subtracted tomographic images than with substracted periapical images (p < 0.001).

Alveolar Bone Loss↗

PubMed1995

Radiographic evaluation of alveolar crest obscured by dental implants.

This study evaluated the diagnostic accuracy of periapical, tomographic, and cross-sectional occlusal radiographic techniques in the assessment of facial and lingual bone loss at implant obscured sites. An edentulous dry human mandible was prepared with implants in the incisor, premolar, and molar regions. Successive round bur sizes (No. 1 to 6) were used to create circumferential infrabony periodontal defects in the alveolar crest adjacent to the implants. Periapical radiographs were made with custom stents and imaged each site in a conventional parasagittal orientation. Linear tomograms imaged sites in a cross-sectional coronal orientation. Cross-sectional occlusal radiographs imaged anatomy in the axial plane. Radiographic anatomy mesial and distal to each implant was masked with opaque tape before evaluation by a panel of six observers. Images were displayed in pairs consisting of an image at baseline and a second image having an equal chance of displaying an increment of bone removal or no bone removal. Image pairs were displayed in random order. A five-point scale was used to evaluate accuracy of detection of the presence or absence of changes in bone density as well as observer confidence in that assessment. ANOVA demonstrated significant variation due to image modality and increment of bone removal. Cross-sectional occlusal views provided significantly greater mean observer confidence scores than either periapical images or tomograms (P < .01). However, tomograms may provide greater utility in actual clinical practice.

Alveolar Bone Loss↗

PubMed1995

A comparison of zonography, multidirectional tomography, and biplanar panoramic images for detection of simulated condylar arthropathy of the temporomandibular joint.

Three imaging modalities were compared for diagnostic efficacy in the detection of simulated osteoarthritic lesions created by a series of dentin chips placed at four locations on the head of a temporomandibular joint condyle in a dry human skull. The modalities included panoramic-based biplanar temporomandibular joint views, parasagittal linear zonography, and sagittal-view, computer-controlled, multidirectional tomography. Equal numbers of images with and without chips were viewed by six examiners. Observers recorded the presence or absence of lesions on a 100-point confidence scale. Responses were used to construct ROC curves. Pooled data sorted by modality produced areas under the curves of 0.7421 (zonography), 0.6627 (panoramic imaging), and 0.7478 (tomography). No statistically significant difference in lesion detection was found among the three modalities, between observers, or within observers.

Analysis of Variance↗

PubMed1994

Comparison of stent versus laser- and cephalostat-aligned periapical film-positioning techniques for use in digital subtraction radiography.

Digital subtraction radiography is a sensitive diagnostic technique that allows detection of subtle calcific changes in the jaws and teeth that would otherwise not be radiographically visible. However, a high failure rate associated with stent-based periapical film-positioning strategies combined with the complexity, expense, and time of image acquisition has limited the clinical utility of this technique. This study compares a new technique that uses film-positioning instruments, laser alignment beams, and a cephalostat with a previously validated method that used film positioners and elastic impression material. Two series of periapical radiographs were taken of six different anatomic areas of six phantoms using both techniques. Film pairs were digitally subtracted twice and analyzed. A paired t test for difference in standard deviation of mean pixel values revealed no difference in repositioning accuracy between the two techniques (p = .68). The new technique eliminates problems that are associated with the use of elastomeric impression materials.

Alveolar Bone Loss↗

PubMed1994

Analysis of condylar position changes: a test of validity of posteroanterior cephalometric and 20-degree lateral cephalometric techniques enhanced by digital subtraction.

This preclinical study was designed to evaluate 20-degree lateral cephalometric and posteroanterior cephalometric techniques with digital subtraction enhancement for their ability to detect 1-, 2-, and 3-mm shifts in condylar position in two of three planes of space (horizontal or transverse and vertical). The model used was a dry human skull with a complete mandible mounted on a microscopic stage with positioning accuracy to 0.1 mm in x, y, and z planes. Analysis of variance showed no significant difference from expected values in the transverse plane (posteroanterior cephalogram only). There were significant differences in the sagittal plane (20-degree lateral cephalogram only) for the 2- and 3-mm shifts (P < .001). There were no significant differences among expected values in the vertical plane for individual increments or for increment comparisons. The magnitude of standard deviations and of the absolute value of differences indicates markedly increased variability for both techniques as compared to tomograms produced with cephalostat repositioning. The authors conclude that even with precise repositioning and digital subtraction enhancement, cephalometric radiographs are inadequate for clinical monitoring of condylar position.

Analysis of Variance↗

PubMed1992

Accuracy of quantification of mandibular condyle displacement in digitally subtracted linear tomograms.

Using a TMJ skeletal phantom, we assessed validity and reliability of digitally subtracted linear tomographic images to quantify condylar position changes. Horizontally corrected frontal and lateral tomographic images were made with the condyle in a 'centred' position and displaced by 1, 2 and 3 mm increments in two of three directions (inferior, and posterior, or lateral). Film images were sequentially subtracted and then randomized so that observers were blinded to the amount and direction of condylar movement. Averages of three measurements of the dark bands representing condylar shifts were made using a digitizing tablet. The study utilized a nested design where the series of film images was subtracted twice and each subtraction was read twice by two examiners. We repeated the study with a second series of films treated in an identical manner. Average differences from expected values were similar for frontal and lateral techniques and all directions and increments of displacement. Typical average difference for any increment was less than 0.1 mm. Standard deviations in measures were similar across techniques and increments and were typically less than 0.1 mm. Significant variation in the absolute value of differences between measured and expected values by direction of condylar displacement was attributed to greater accuracy of registration on the vertical axis for frontal images. A significant source of variation in the study design element 'film set' was attributed to errors in repositioning the phantom.(ABSTRACT TRUNCATED AT 250 WORDS)

Analysis of Variance↗

PubMed1991

Accuracy of measures of temporomandibular joint space and condylar position with three tomographic imaging techniques.

Fourteen temporomandibular joints in seven dry skulls, representing the distribution of horizontal and vertical condylar axis inclinations of a larger population, were imaged with three tomographic projection techniques. Closest anterior and posterior joint spaces were measured on radiographs, and sectioned plaster casts were made from impressions of actual joint space, Individualized horizontal and vertical correction of the condylar axis produced significantly more accurate (p less than 0.005) measures of condylar space than either standard 20-degree horizontal correction (SHC) or individualized horizontal correction (IHC) of the axis. Representations of joint space by SHC and IHC were not significantly different from each other. Numbers of uninterpretable images displayed a similar pattern of 9.5% for individualized horizontal and vertical correction, 14% for IHC, and 17% for SHC. This study supports the use of fully individualized condylar axis correction with temporomandibular joint tomography for increased accuracy of visualization of the osseous anatomy of the joint.

Humans↗

PubMed1991

Digitally subtracted linear tomograms: three techniques for measuring condylar displacement.

Using digital subtraction enhancement, we compared the accuracy of three tomographic technique variations for quantifying small changes of condylar position. A phantom made of skeletal material and an adjustable mechanical stage provided 0.1 mm positioning accuracy of the condylar segment. Linear tomographic images were made with the condyle in a centered position and at each of three 1 mm increments of displacement in two of three directions (inferior, and posterior or lateral). Variations for frontal views included arbitrary (+20 degrees) and individualized (+10 degrees) horizontal correction of the condylar axis. Variations for lateral views included the arbitrary and individualized correction and a fully corrected vertical (+5 degrees) and horizontal (+10 degrees) adjustment. Blinded observers made repeated measurements on randomized subtraction images with a digitizing tablet. Film images were subtracted twice, and each subtraction was read twice by two examiners. The study was repeated with a second series of films treated in an identical manner. Mean values for measurements, standard deviations, and absolute values of differences between measured and expected values were calculated for each subtraction. Analysis of variance identified statistically significant sources of variation in repositioning the phantom and producing exact displacements of the condyle. Average absolute value of differences from expected values were similar for the three techniques and for frontal and lateral orientations and increments of displacement. Typical absolute value of difference for any technique was 0.2 mm for posterior, 0.2 mm for lateral, and 0.1 mm for inferior displacements. Significantly greater accuracy of inferior displacement measures was attributed to greater accuracy of registration of the fossa in its cranio-caudal dimension.(ABSTRACT TRUNCATED AT 250 WORDS)

Analysis of Variance↗