Dissertation (PhD)--University of Stellenbosch, 2001. / 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.
| Identifer | oai:union.ndltd.org:netd.ac.za/oai:union.ndltd.org:sun/oai:scholar.sun.ac.za:10019.1/52594 |
| Date | 03 1900 |
| Creators | De Abreu, Murillo Jose Nunes |
| Contributors | Nortje, C. J., Tyndall, D. A., Stellenbosch University. Faculty of Medicine and Health Sciences. Dept. of Medical Imaging and Clinical Oncology. Radiodiagnosis. |
| Publisher | Stellenbosch : Stellenbosch University |
| Source Sets | South African National ETD Portal |
| Language | en_ZA |
| Detected Language | English |
| Type | Thesis |
| Format | 112 p. : ill. |
| Rights | Stellenbosch University |
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