Biomaterial Database

Digitally subtracted linear tomograms: three techniques for measuring condylar displacement. 1991

J B Ludlow, and R Soltmann, and D Tyndall, and J J Grady

Department of Diagnostic Sciences, University of North Carolina School of Dentistry, Chapel Hill.

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)

UI	MeSH Term	Description	Entries
D008335	Mandibular Condyle	The posterior process on the ramus of the mandible composed of two parts: a superior part, the articular portion, and an inferior part, the condylar neck.	Condyle, Mandibular,Condyles, Mandibular,Mandibular Condyles
D011856	Radiographic Image Enhancement	Improvement in the quality of an x-ray image by use of an intensifying screen, tube, or filter and by optimum exposure techniques. Digital processing methods are often employed.	Digital Radiography,Image Enhancement, Radiographic,Radiography, Digital,Enhancement, Radiographic Image,Enhancements, Radiographic Image,Image Enhancements, Radiographic,Radiographic Image Enhancements
D006801	Humans	Members of the species Homo sapiens.	Homo sapiens,Man (Taxonomy),Human,Man, Modern,Modern Man
D000704	Analysis of Variance	A statistical technique that isolates and assesses the contributions of categorical independent variables to variation in the mean of a continuous dependent variable.	ANOVA,Analysis, Variance,Variance Analysis,Analyses, Variance,Variance Analyses
D001175	Arthrography	Roentgenography of a joint, usually after injection of either positive or negative contrast medium.	Arthrographies
D013382	Subtraction Technique	Combination or superimposition of two images for demonstrating differences between them (e.g., radiograph with contrast vs. one without, radionuclide images using different radionuclides, radiograph vs. radionuclide image) and in the preparation of audiovisual materials (e.g., offsetting identical images, coloring of vessels in angiograms).	Subtraction Technic,Subtraction Technics,Subtraction Techniques,Technic, Subtraction,Technics, Subtraction,Technique, Subtraction,Techniques, Subtraction
D013704	Temporomandibular Joint	An articulation between the condyle of the mandible and the articular tubercle of the temporal bone.	TMJ,Joint, Temporomandibular,Joints, Temporomandibular,Temporomandibular Joints
D014056	Tomography, X-Ray	Tomography using x-ray transmission.	Tomography, Transmission,X-Ray Tomography,Zonography,Radiographic Tomography,Tomography, Radiographic,Tomography, X Ray,Tomography, Xray,Transmission Tomography,X Ray Tomography,Xray Tomography
D015203	Reproducibility of Results	The statistical reproducibility of measurements (often in a clinical context), including the testing of instrumentation or techniques to obtain reproducible results. The concept includes reproducibility of physiological measurements, which may be used to develop rules to assess probability or prognosis, or response to a stimulus; reproducibility of occurrence of a condition; and reproducibility of experimental results.	Reliability and Validity,Reliability of Result,Reproducibility Of Result,Reproducibility of Finding,Validity of Result,Validity of Results,Face Validity,Reliability (Epidemiology),Reliability of Results,Reproducibility of Findings,Test-Retest Reliability,Validity (Epidemiology),Finding Reproducibilities,Finding Reproducibility,Of Result, Reproducibility,Of Results, Reproducibility,Reliabilities, Test-Retest,Reliability, Test-Retest,Result Reliabilities,Result Reliability,Result Validities,Result Validity,Result, Reproducibility Of,Results, Reproducibility Of,Test Retest Reliability,Validity and Reliability,Validity, Face
D015588	Observer Variation	The failure by the observer to measure or identify a phenomenon accurately, which results in an error. Sources for this may be due to the observer's missing an abnormality, or to faulty technique resulting in incorrect test measurement, or to misinterpretation of the data. Two varieties are inter-observer variation (the amount observers vary from one another when reporting on the same material) and intra-observer variation (the amount one observer varies between observations when reporting more than once on the same material).	Bias, Observer,Interobserver Variation,Intraobserver Variation,Observer Bias,Inter-Observer Variability,Inter-Observer Variation,Interobserver Variability,Intra-Observer Variability,Intra-Observer Variation,Intraobserver Variability,Inter Observer Variability,Inter Observer Variation,Inter-Observer Variabilities,Inter-Observer Variations,Interobserver Variabilities,Interobserver Variations,Intra Observer Variability,Intra Observer Variation,Intra-Observer Variabilities,Intra-Observer Variations,Intraobserver Variabilities,Intraobserver Variations,Observer Variations,Variabilities, Inter-Observer,Variabilities, Interobserver,Variabilities, Intra-Observer,Variabilities, Intraobserver,Variability, Inter-Observer,Variability, Interobserver,Variability, Intra-Observer,Variability, Intraobserver,Variation, Inter-Observer,Variation, Interobserver,Variation, Intra-Observer,Variation, Intraobserver,Variation, Observer,Variations, Inter-Observer,Variations, Interobserver,Variations, Intra-Observer,Variations, Intraobserver,Variations, Observer