Tuned aperture computed tomography (TACT) : an investigation on the factors associated with its image quality for caries detection

De Abreu, Murillo Jose Nunes (2001-03)

Dissertation (PhD)--University of Stellenbosch, 2001.

Thesis

ENGLISH ABSTRACT: The purpose of this investigation was to explore the multiple variables involved in TACT® image generation in an attempt to optimize this imaging modality for the diagnostic task of primary dental caries detection. The work is divided in seven phases in which the variables are evaluated individually. Teeth from the study samples were mounted in dental stone and imaged with a solid state digital radiography sensor. As a requisite of TACT® imaging, multiple images of the teeth were acquired from different projection angles. These resulting basis images were then used to generate TACT® slices. Variables tested in the investigation included the number of iterative restorations to which the slices were submitted, the number of basis images, the angle formed between the basis images, the two- and three-dimensional distribution of the basis projections in space, and the method through which the slices were reconstructed. For all phases, observers were asked to assess the presence or absence of primary caries in the teeth imaged using the TACT® slices treated with the different variables. Finally, to determine whether the best combination of variables produced a significant improvement in diagnostic performance, a comparison with conventional digital radiography images was carried out. No statistically significant differences were found in caries detection between TACT® slices submitted to different numbers of iterative restorations, reconstructed from basis images bearing different angular disparities, spatial distributions (in both two and three dimensions), or through different reconstruction methods. A statistically significant difference was detected between TACT® slices reconstructed from different numbers of basis projections. The final comparison showed that TACT® was not statistically superior to conventional digital radiography for the task of caries detection. The results of this investigation suggest that, although TACT® has been shown to be useful in many tasks performed in dentistry, its application in caries detection is not essential inasmuch as there are modalities that are simpler, more practical, less expensive, and that submit the patient to smaller radiation doses. Keywords: TACT, tomosynthesis, image reconstruction, digital radiography, caries detection, ROC analysis, analysis of variance

AFRIKAANSE OPSOMMING: Die doel van hierdie proefskrif was om die veelvuldige veranderlikes wat betrokke is by gewysigde spleet rekenaartomografie (Tuned Aperture Computed Tomography (TACT)) te ondersoek in 'n poging om die beeldingsmodaliteit te optimaliseer in die diagnostiese opsporing van primere karies. Die proefskrif bestaan uit 'n ekstensiewe literatuur oorsig en word in 7 fases aangebied waarin die veranderlikes individueel geevalueer word. Tande is in gips ingebed en radiografiese opnames is gemaak met behulp van 'n digitale radiografiese sensor. As 'n voorvereiste vir TACT beelding is veelvuldige beelde uit verskillende projeksiehoeke van die tande gemaak. Die resulterende basisbeelde is dan gebruik om TACT snitte te produseer. Veranderlikes wat in die proefskrif getoets is, sluit die volgende in: 'n aantal herhalende herstellings waaraan die snitte blootgestel is, die aantal basisbeelde, die hoek gevorm tussen die basisbeelde, die 2 en 3 dimensionele verspeiding van die basis projeksies in die ruimte en die metodes waardeur die snitte gerekonstrueer is. In aIle fases is waarnemers gevra om die teenwoordigheid of afwesigheid van primere karies te evalueer wat met TACT afgeneem is met in ag neming van die verskillende veranderlikes. Ten slotte, om te bepaal of die beste kombinasie van veranderlikes 'n aansienlike verbetering in diagnostiese prestasies sou meebring, is 'n vergelyking met konvensionele digitale radiografiese beelding uitgevoer. Geen statistiese beduidende verskille is waargeneem in die opsporing van karies tussen TACT snitte wat blootgestel is aan verskillende aantal herhalende herstellings, rekonstruksie van basis beelding met verskillende hoek veranderinge, ruimtelike verspreiding (beide 2 en 3 dimensioneel) of deur verskillende rekonstruksie metodes nie. 'n Statistiese beduidende verskil is waargeneem tussen TACT snitte wat van 'n verskeidenheid basis projeksies gerekonstrueer is. Die finale vergelyking het aangetoon dat TACT nie statisties beter is as konvensionele radiografie in die opsporing van karies nie. Die resultate van hierdie proefskrif het getoon dat alhoewel TACT bruikbaar is in vele prosedures wat in die tandheelkunde uitgevoer word, is die toepassing daarvan in die diagnose van karies nie noodsaaklik nie, omdat daar in die tandheelkunde modaliteite beskikbaar is, wat meer eenvoudig, meer prakties en goedkoper is, met 'n laer stralingsdosis vir die pasient.

Please refer to this item in SUNScholar by using the following persistent URL: http://hdl.handle.net/10019.1/52594
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