Search results for "beam [electron]"
showing 10 items of 433 documents
SU-E-J-69: Evaluation of the Lens Dose On the Cone Beam IGRT Procedures
2014
Purpose: With the establishment of the IGRT as a standard technique, the extra dose that is given to the patients should be taken into account. Furthermore, it has been a recent decrease of the dose threshold in the lens, reduced to 0.5 Gy (ICRP ref 4825-3093-1464 on 21st April, 2011).The purpose of this work was to evaluate the extra dose that the lens is receive due to the Cone-Beam (CBCT) location systems in Head-and-Neck treatments. Methods: The On-Board Imaging (OBI) v 1.5 of the two Varian accelerators, one Clinac iX and one True Beam, were used to obtain the dose that this OBI version give to the lens in the Head-and-Neck location treatments. All CBCT scans were acquired with the Sta…
Dental CBCT equipment and performance issues
2012
Dental cone beam computed tomography (CBCT), also known as digital volumetric tomography was developed in the late 1990s and is now increasingly available in clinical practice. It can provide high resolution cross-sectional images of teeth and the maxillofacial region with applications in all branches of dentistry. As a new imaging modality, there were no established suspension levels at a European level. A literature review, encompassing scientific, professional publications and existing national guidelines was performed in an attempt to develop a set of suspension levels for dental CBCT, using additional expert opinion from the members of the European Academy of dento-maxillo-facial radio…
Editorial 1/2018
2017
Mandibular incisive canal-related prevalence, morphometric parameters, and implant placement implications : a multicenter study of 847 CBCT scans
2020
Background This study evaluated the epidemiological and morphological features of the mandibular incisive canal (MIC) using cone beam computed tomography (CBCT) in a significant sample of subjects in Brazil. Material and Methods This retrospective, multicenter study assessed 847 CBCT scans performed at four oral imaging centers. The sample comprised CBCT images acquired from dentate individuals who presented at least from tooth 35 to tooth 45 in the anterior mandible region. Data regarding patient sex and age, and MIC linear measurements (length and diameter in mm), anatomical distances (to the alveolar, buccal and lingual cortexes, inferior border of the mandible, and adjacent teeth apexes…
Evaluation of horizontal ridge augmentation using beta tricalcium phosphate and demineralized bone matrix: A comparative study
2013
Objectives: To evaluate the effectiveness of beta tricalcium phosphate (Beta-TCP) alone compared to Beta-TCP and Demineralized Bone Matrix (DBM) in regenerating localized horizontal maxillary alveolar ridge deficiencies prior to implant placement. Study Design: The study included 20 patients with horizontal maxillary ridge deficiencies limited to one or more neighbouring teeth and initial ridge width of . 5mmm. Patients were divided equally into two equal groups. Ridge augmentation was performed using Guided Bone Regeneration (GBR) principals. In group I GBR was performed using Beta-TCP only, while in group II both Beta-TCP and DBM were used. Following a 6 months healing period, bone cores …
On cone-beam computed tomography artifacts induced by titanium implants
2010
Objectives: To briefly review the mathematical background of beam-hardening artifacts in cone-beam computed tomography (CBCT)-reconstruction and to investigate geometrical properties relevant for these reconstruction errors. By means of simulated and experimental results, beam-hardening effects caused by titanium implants are evaluated. Materials and methods: The geometrical and physical properties of the acquisition process of the projections used for 3D reconstruction are investigated and their effects on the CBCT images in the presence of titanium implants are derived. Beam-hardening effects are computed for a simplified polychromatic situation (three energy subsets of 80 and 110 kV) and…
Effect of amount of biomaterial used for maxillary sinus lift on volume maintenance of grafts
2020
Background Regardless of the kind of biomaterial used for the graft, it is clear that, over time, the graft undergoes dimensional changes that could influence the final bone volume obtained, which could alter the stability of the installed implants. The aim of the present study was to compared and correlated the graft behavior with the amount (in grams) of xenogeneic and alloplastic biomaterials used in grafts for maxillary sinus lift. Material and Methods This retrospective cohort study used 148 CBCT images of 74 grafts from 68 maxillary sinuses lift patients in a university, post-graduate clinic. The weights of biomaterials, categorized in intervals according to amount used, were correlat…
What is the frequency of anatomical variations and pathological findings in maxillary sinuses among patients subjected to maxillofacial cone beam com…
2016
Background When considering dental implant rehabilitation in atrophic posterior sectors, the maxillary sinuses must be evaluated in detail. Knowledge of the anatomical variations and of the potential lesions found in these structures conditions the outcome of sinus lift procedures and therefore of the dental implants. A systematic review is made to determine the frequency of anatomical variations and pathological findings in maxillary sinuses among patients subjected to cone beam computed tomography (CBCT). Material and Methods A PubMed (MEDLINE) literature search was made of articles published up until 20 December 2015. The systematic review was conducted based on the Preferred Reporting I…
Cone-beam computed tomography analysis of root and canal morphology of mandibular premolars in a Spanish population
2014
Purpose: This study aimed to investigate the clinical anatomy of lower premolar roots in a Spanish population by using cone-beam computed tomography (CBCT), correlating findings with patient gender and tooth type. Materials and Methods: Using 70 CBCT images, we evaluated 126 healthy, untreated, well-developed lower premolars. The number and morphology of roots and root canals, and the foramina number were assessed. Results for gender and tooth type were compared using the chi-squared and ANOVA tests. Results: The average length of teeth and roots was significantly higher in men (p=0.00). All 126 premolars had a single root. One canal was found in 83.3% of the premolars, with no gender or to…
Alignment of cone beam computed tomography data using intra-oral fiducial markers.
2009
This article illustrates a new method to align and merge two partially overlapping volumes each of them generated by cone beam computed tomography (CBCT). The aggregate volume covers a larger area of investigation and is determined by localizing one fixed LEGO brick in both of the primal volumes. Based on the LEGO brick an approximate registration of the volumes is determined. Afterwards we improve the transformation by minimizing the difference in overlapping space. In this paper we present a method which automates these two steps and provides an aligned volume.