Preverjanje kakovosti slik pri napravah za zobno računalniško tomografijo : magistrsko delo

Vidmar, Anja (author), Škrk, Damijan (mentor), Drolc, Boštjan (comentor)

Uvod: Preverjanje kakovosti pomembno prispeva k optimizaciji radioloških posegov tako, da pridobimo zadostno količino diagnostičnih informacij, pri čim nižji izpostavljenosti pacienta. Evropska komisija je za preverjanje kakovosti slik CBCT aparatov predlagala šest parametrov, ki bi morali biti vključeni v program preverjanja kakovosti in sicer: prikaz nizkokontrastnih elementov, homogenost in prisotnost artefaktov, šum, prostorska ločljivost, geometrijska popačenost in sivinska lestvica. Namen: Namen magistrske naloge je ocena sprejemljivosti fantoma PRO-DENT CT mk II za preverjanje kakovosti slik CBCT aparatov. Metode dela: Preverjanje kakovosti slik smo izvajali na Vatechovem, Sironinem in Instrumentarium aparatu s fantomom Pro-Dent CT mk II, ki je sestavljen iz PMMA ohišja, v katerega so vstavljeni objekti različnih specifikacij. Po opravljenih meritvah preverjanja kakovosti slik CBCT aparatov smo opravili analizo homogenosti in šuma, artefaktov, geometrijske popačenosti, kontrastne in prostorske ločljivosti. Slike smo analizirali s programom ImageJ. Rezultati in razprava: V svoji raziskavi homogenosti s pomočjo fantoma smo ugotovili, da so slike pridobljene s CBCT aparati zelo nehomogene. Robne vrednosti sivin močno odstopajo od vrednosti v sredini. Artefakti zaradi prisotnosti kovin so pri višjih ekspozicijskih pogojih izrazitejši. Zato nekateri proizvajalci uporabljajo filtre, ki ta učinek zmanjšajo. Pri določanju geometrijske popačenosti nismo zaznali nobenih posebnosti. Za kontrastno ločljivost smo ugotovili, da so najmanjši vsadki, ki jih vidimo pri vizualni oceni merili 1 ali 2 mm. Aparati prav tako niso bili umerjeni na Hounsfieldovo lestvico. Razmerje CNR je bilo za večino materialov nizko. Prostorska ločljivost je bila med 1 in 1,7 lp/mm, oz. pri Endo programu 2,5 lp/mm. Zaključek: Glede na vse ugotovitve lahko zaključimo, da so fantom in testi primerni za letne QC teste, saj smo lahko na vseh treh zelo različnih aparatih uporabili fantom PRO-DENT CT mk II, prav tako nam je omogočal izvedbo vseh priporočenih testov preverjanje kakovosti slike.

• Language: Slovenian
• Keywords: CBCT, preverjanje kakovosti slik, homogenost, geometrijska popačenost, kontrastna ločljivost, prostorska ločljivost
• Work type: Master's thesis/paper
• Organization: ZF - Faculty of Health Sciences
• Year: 2018
• PID: 20.500.12556/RUL-105161
• COBISS.SI-ID: 5524331
• Publication date in RUL: 31.10.2018

VIDMAR, Anja, 2018, Preverjanje kakovosti slik pri napravah za zobno računalniško tomografijo : magistrsko delo [online]. Master’s thesis. [Accessed 13 June 2025]. Retrieved from: https://repozitorij.uni-lj.si/IzpisGradiva.php?lang=eng&id=105161

Secondary language

• Language: English
• Title: Image quality control in dental CBCT : master thesis

Abstract

Introduction: Quality control is important because it contributes to gather a sufficient amount of diagnostic information, with the lowest exposure of the patient. The European Commission has recommended six parameters that should be included in the quality control program for CBCT images: display of low-contrast elements, homogeneity and the presence of artefacts, noise, spatial resolution, geometric resolution and grayscale. Purpose: The purpose is to assess the acceptability of the PRO-DENT CT mk II phantom for quality control of images of CBCT machine. Methods: We assessed the quality of the images on the Vatech, Sirona and Instrumentarium apparatus with the Pro-Dent CT mk II phantom, which consists of PMMA 1.19 g/cm3 and has inserted objects of different specifications. After the quality control measurements were performed, we analysed the homogeneity and noise, artefacts, geometric distortion, contrast and spatial resolution. We analysed the images with the ImageJ program. Results and discussion: In our homogeneity research, we discovered that CBCT images are highly non-homogeneous. The peripheral values vary greatly from the values in the centre. Due to the presence of metals, artefacts are more visible under higher exposition conditions. That is why some manufacturers use filters to reduce this effect. We did not detect any issues in determining geometric distortion. For contrast resolution, we found that the smallest implants visible were of 1 or 2 mm. The appliances were not calibrated on the Hounsfield scale. The CNR ratio was low for most materials. Spatial resolution was between 1 and 1,7 lp/mm, or in Endo program 2,5 lp/mm. Conclusion: Based on all the findings we can conclude that the phantom and tests would be aplicable for annual QC tests, because we could use the PRO-DENT CT mk II phantom on all three different apparatus, and it allowed us to carry out all the recommended image quality control tests.

• Keywords: CBCT, image quality control, homogeneity, geometric distortion, contrast resolution, spatial resolution