The aim of this study was to evaluate whether volumetric changes in persistent periapical lesions can be detected in follow-ups six months to five years after apicoectomy using cone-beam computed tomography. Patients with a previous treatment history of apicoectomy and for whom a pre-surgical CBCT scan was taken between November 2010 and December 2015 were invited to participate in the study. A post-surgical CBCT image of the treated tooth was obtained at the recall visit. Volumetric and linear measurements of periapical lesions on initial and postoperative CBCT images were performed using DiThreshGUI software and two calibrated examiners—a board-certified endodontist and a board-certified oral radiologist. Repeated-measures ANOVA were used to estimate the magnitude of reduction and to test for differences (at alpha=0.05). A total of 20 patients with 27 surgically treated teeth were recalled at an average interval of 37 months. Reduction in the size of lesions was observed in 24 teeth (88%); overall, the volumes significantly decreased as detected by software-assisted measurement of volume (P = .0002) and by calculation from linear measurements (P < .0001). Volumetric analysis detected a reduction of 86% in lesions while the linear-derived volume measurements yielded an average reduction of 96%. These two methods of lesion assessment were strongly correlated with one another in pre-surgical scans (r>0.88) when apical lesions are measurable.

Mémoire numérisé par la Division de la gestion de documents et des archives de l'Université de Montréal.

AIM: Extraction of a tooth can lead to alveolar ridge resorption which can be minimized by socket preservation. The aim of this study is to analyze vertical and horizontal alveolar ridge dimensions clinically and by CBCT immediately following extraction and 3-4 months following socket preservation. METHODS: The preserved group (P) consisted of 20 patients with1-2 non-molar teeth requiring extraction with socket preservation, while the control group (C) consisted of 5 patients requiring extraction alone. An acrylic stent was fabricated presurgically in order to measure vertical and horizontal ridge dimensions clinically and radiographically immediately following extraction and 3-4 months following socket preservation. RESULTS: Overall, P sites gained ridge height and lost minimal ridge width over 3-4 months, while C sites lost both ridge height and width. Preserved sites in which the teeth were extracted due to caries had the most significant gain in the radiographic vertical occlusal dimension (RVO). Overall, high correlations were found between the clinical and radiographic measurements at the initial surgery and at the 3-4 month follow up. CONCLUSIONS: The preserved group had minimal ridge resorption and more socket bony fill when compared to the non-preserved group 3-4 months following tooth extraction, especially when the tooth was extracted due to caries. Additionally, the CBCT can be a useful diagnostic tool to evaluate socket preservation healing, as it compares well to clinical assessments of socket healing.

BACKGROUND: The use of three-dimensional imaging has shown to provide advantages to the clinician in assessing bone morphology. The aim of this study will be to compare the diagnostic efficacy of cone beam computed tomography (CBCT) versus diagnostic clinical measurements in patients presenting with furcation involved maxillary first molars. METHODS: The study population included 20 patients with 34 maxillary first molar teeth with furcation involvement. Clinical horizontal and vertical probing measurements were compared to CBCT measurements taken by two calibrated examiners. RESULTS: Horizontal measurements showed a significant difference between Glickman class II and class III. There were no statistical significant differences with the horizontal measurements between clinical probing, bone sounding and CBCT measurements. CBCT vertical measurements were statistically greater than clinical probing measurements. CONCLUSION: The CBCT can provide similar horizontal measurements to standard clinical horizontal probing measurements and will provide a greater vertical dimension of a furcation defect to standard vertical probing measurements.

Master of Science in Dentistry / Objectives: The aims of this study were: • to evaluate the exact level of the mandibular canal using Cone Beam Volumetric Tomography (CBVT) using measurements taken on images from the NewTom3G and i-CAT machines and manually • to determine the course of the mandibular canal in the regions of the first, second , and third molars • to compare the course of the mandibular canals bilaterally • to compare variables measured between the CBVT and panoramic units • to determine appropriate positions for the implant placement at the region of the mandibular molars in relation to the mandibular canal. Methods: Ten mandibles were selected, including seven edentulous and three dentate ones. They were marked at four positions from the distal border of the mental foramina in the posterior direction at intervals of 10.00 mm. On each dry mandible, at four sites namely M0, M1, M2, and M3, Gutta Percha (GP) points, known as markers, were attached to the mandible so that they were parallel to the midline of the mandible on both buccal and lingual sides. On the NewTom 3G and i-CAT, variables of cross-sectional images were measured from the alveolar crest of the mandible to the superior border of the mandibular canal (AC); the lingual rim of the canal to the lingual margin of the mandible (LC); the buccal rim of the canal to the buccal margin of the mandible (BC); the inferior rim of the canal to the lower border of the mandible (IC), and from the lingual margin to the buccal margin of the mandible (BW: Bone Width). Dry mandibles were subsequently sacrificed by cutting at the four marked sites. On each cross-section of mandibles, distances AC, BC, LC, IC, and BW were measured using a caliper as the manual measurement. IC distances on a conventional OrthophosIII panoramic machine were also measured to compare with the CBVT. Data were managed by Microsoft Office Excel 2003 and transferred to the software of Statistics Package for Social Sciences (SPSS) version 15.0 for Windows for analysis. Data were presented as Mean, Standard Deviation (SD), and Mean Difference, and Standard Error of Mean (SEM) with decimal at 0.00. T-test and One-way ANOVA were used to analyse variables measured in which T-test was used to analyse variables with paired samples and One-way ANOVA was used with adjustment for multiple comparisons of Bonferroni. Statistical significance has an assumed P- value of 0.05 or less. Results: The findings showed that there was no significant difference among measured variables from the NewTom 3G, i-CAT and manual measurement (P>0.05). There was significant statistical difference between the Orthophos OPG machine and CBVT system (P=0.00<0.05). There was no significant difference in the course of the mandibular canals bilaterally (P>0.05). On average, Distances AC, BC, LC, and IC were obtained for reference purposes. The bone width of the mandible on the right side was slightly different from that on the left side. Conclusions: The findings implied CBVT was an accurate diagnostic tool for locating the course of the mandibular canal and for placing dental implants in the region of the mandibular molars. The course of the mandibular canal on the left and right sides was variable. The distances measured at the region of the first, second, and third mandibular molars should be considered as a valuable reference. The bone width of the mandible on the right and left sides was slightly different. The accuracy of the NewTom3G and i-CAT was superior to the panoramic Orthophos machine. However, a panoramic radiograph is still valuable in the daily dental clinic.

<p>The daily uncertainty concerning tumor localization is one of the major problems during the course of radiation therapy. Image guided-radiation therapy (IGRT) can be used to improve the localization and adjustment of the planning target volume. The aim of this work was to evaluate both the IGRT technique used for prostate cancer patients at the department of the Karolinska University Hospital and an alternative on-line adaptive radiation therapy (ART) method with an On-Board Imager (OBI).</p><p>In the first part of the thesis 2D and 3D image registration with an OBI were compared. Ten prostate cancer patients were involved in the analyses. Two different statistical tests were used to determine significant systematic deviations between the two methods. The second part concerns daily dose verifications and dose plan reoptimization of one intensity modulated radiation therapy (IMRT) prostate cancer patient treated with IGRT. The study was based on cone-beam computed tomography (CBCT) images acquired at 6 different treatment fractions. The risk of developing late rectal and bladder toxicity was quantified using normal tissue complication probability (NTCP) calculations. Additional measurements on an Alderson phantom were performed to verify the accuracy of using the CBCT images for dose calculations.</p><p>A statistically significant difference between the 2D-2D and the 3D-3D match applications could be observed in lateral and longitudinal direction. However, the effect differed among the patients. The phantom measurements showed small dose deviations between the CT and CBCT image, with a mean dose increase to the prostate and seminal vesicles (SV) of 2.5 %. The daily dose to the prostate and SV of the IMRT patient showed to be satisfactory. The daily dose to the rectum did not exceed the prescribed rectal dose except at one treatment fraction and the highest risk of developing late rectal toxicity was about 10.4 %. Large daily bladder dose variations were observed and at two treatment fractions the bladder dose restrictions were exceeded. With a reoptimization process of the dose plan, the dose to the bladder could be reduced while conserving the dose to the target.</p><p>This work shows that for these specific patient cases appropriate doses to the prostate and SV can be delivered with IGRT. However, introducing a suitable ART method could lead to a reduction of inter-fractional rectal and bladder dose variations.</p>

Objective : To determine the relationship of tongue volume as determined from Cone Beam Computed Tomography (CBCT) scan reconstructions with maxillary and mandibular arch width, axial cross-sectional palatal perimeter, palatal index and axial inclination of upper and lower first premolars and molars. Method: Thirty subjects without prior orthodontic treatment swished barium sulfate to coat the tongue prior to CBCT imaging. The scan reconstructions were analyzed with three after-market softwares and intra-examiner reliability was assessed. Results: Absolute agreement intra-class correlation coefficients were used to determine reliability of the measurements. Pearson correlation coefficients and regression analysis were used to determine relationships. Conclusions: Tongue volume was strongly correlated with upper inter-molar width and palatal perimeter at the molar level, and least correlated with lower inter-molar width and axial inclination of the upper and lower first premolars and molars. The differences in measurements obtained from the three softwares were not statistically significant.

This thesis aims at introducing a methodology for clinical evaluation of orthodontic treatments using three-dimensional dento-maxillofacial images. Since complementary information is achieved by integrating multiple modalities, cone-beam computed tomography (CBCT) and stereophotogrammetry technologies are used to develop a methodology for tracking bone and facial skin variations over time. Our proposed methodology consists of a two-phase registration procedure. In the first phase, the multimodal images are registered using an extrinsic landmark-based registration followed by a robust Iterative Closest Points (ICP) method. In the second phase, by utilizing specific anatomical landmarks, single modal images of the skull and the mandible are registered over time using an intrinsic landmark-based registration method followed by the robust ICP algorithm. The results of registrations show that the signed error distribution of both mandible and skull registrations follow a normal distribution while all the errors fall within the CBCT precision range.

The daily uncertainty concerning tumor localization is one of the major problems during the course of radiation therapy. Image guided-radiation therapy (IGRT) can be used to improve the localization and adjustment of the planning target volume. The aim of this work was to evaluate both the IGRT technique used for prostate cancer patients at the department of the Karolinska University Hospital and an alternative on-line adaptive radiation therapy (ART) method with an On-Board Imager (OBI). In the first part of the thesis 2D and 3D image registration with an OBI were compared. Ten prostate cancer patients were involved in the analyses. Two different statistical tests were used to determine significant systematic deviations between the two methods. The second part concerns daily dose verifications and dose plan reoptimization of one intensity modulated radiation therapy (IMRT) prostate cancer patient treated with IGRT. The study was based on cone-beam computed tomography (CBCT) images acquired at 6 different treatment fractions. The risk of developing late rectal and bladder toxicity was quantified using normal tissue complication probability (NTCP) calculations. Additional measurements on an Alderson phantom were performed to verify the accuracy of using the CBCT images for dose calculations. A statistically significant difference between the 2D-2D and the 3D-3D match applications could be observed in lateral and longitudinal direction. However, the effect differed among the patients. The phantom measurements showed small dose deviations between the CT and CBCT image, with a mean dose increase to the prostate and seminal vesicles (SV) of 2.5 %. The daily dose to the prostate and SV of the IMRT patient showed to be satisfactory. The daily dose to the rectum did not exceed the prescribed rectal dose except at one treatment fraction and the highest risk of developing late rectal toxicity was about 10.4 %. Large daily bladder dose variations were observed and at two treatment fractions the bladder dose restrictions were exceeded. With a reoptimization process of the dose plan, the dose to the bladder could be reduced while conserving the dose to the target. This work shows that for these specific patient cases appropriate doses to the prostate and SV can be delivered with IGRT. However, introducing a suitable ART method could lead to a reduction of inter-fractional rectal and bladder dose variations.

3d αναπαράσταση με παράλληλη επεξεργασία μέσω Matlab / 3D cone beam representation using Matlab