Experimental studies of SPECT scintimammography with combined cone-beam and parallel-beam collimators

2003 ◽  
Author(s):  
Andrzej Krol ◽  
David H. Feiglin ◽  
K. R. Gangal ◽  
Ioana L. Coman ◽  
Roberto B. Salgado ◽  
...  
Keyword(s):  
Experimental Studies ◽  
Cone Beam ◽  
Parallel Beam

Combined cone-beam and parallel-beam approach to SPECT

2004 ◽  
Author(s):  
A. Krol ◽  
R.B. Salgado ◽  
D.H. Feiglin ◽  
K.R. Gangal ◽  
A.S. Hardikar ◽  
...  
Keyword(s):  
Cone Beam ◽  
Parallel Beam

scholarly journals Revisit of combined parallel-beam/cone-beam or fan-beam/cone-beam imaging

2013 ◽  
Vol 40 (10) ◽  
pp. 100701 ◽  
Author(s):  
Gengsheng L. Zeng
Keyword(s):  
Cone Beam ◽  
Parallel Beam

scholarly journals Tomographic evaluation of atrophic maxilla rehabilitated with autogenous and xenogeneic block grafts

2017 ◽  
Vol 4 (4) ◽  
pp. 112
Author(s):  
Julio Cesar Lara Sawada ◽  
Luis Eduardo Marques Padovan ◽  
Bernardo Mattos Da Silveira ◽  
Fernando Gianzanti Peres ◽  
Marcela Claudino
Keyword(s):  
Computed Tomography ◽  
Bone Graft ◽  
Dimensional Stability ◽  
Experimental Studies ◽  
Cone Beam ◽  
Autogenous Bone ◽  
Linear Measurements ◽  
Atrophic Maxilla ◽  
The Mean

Aim: The aim of this study was to evaluate the dimensional stability of autogenous and xenogenous bone blocks after grafting procedures using cone beam computed tomography Material and Methods: Autogenous (n=6) and xenogeneic (n=7) bone graft blocks were evaluated after 8 (T1) and 16 (T2) months. A dimensional analysis was carried using linear measurements of the height and thickness of the blocks in the tomographic exam.Results: For the autogenous bone blocks, there was a reduction in height of 1.42mm (10.06%) and a reduction in mean thickness of 1.24mm (29.60%). For the xenogeneic bone blocks, the mean height reduction was 1.38mm (10.02%) and the mean thickness reduction was 0.97mm (18.81%) with remodeling (26.62%). However, there were no significant differences between the xenogeneic and autogenous bone blocks (p=0.366).Conclusions: The results showed no differences in the dimensional stability of autogenous or xenogenous bone graft blocks. However, clinical and experimental studies with longer follow up periods are needed to elucidate the mechanisms involved in the remodeling process of bone grafts.

scholarly journals An Efficient Estimation Method for Reducing the Axial Intensity Drop in Circular Cone-Beam CT

2008 ◽  
Vol 2008 ◽  
pp. 1-11 ◽  
Author(s):  
Lei Zhu ◽  
Jared Starman ◽  
Rebecca Fahrig
Keyword(s):  
Correction Term ◽  
Circular Cone ◽  
Efficient Estimation ◽  
Superior Performance ◽  
Cone Beam ◽  
Parallel Beam ◽  
Beam Geometry ◽  
Computation Efficiency ◽  
Parallel Beam Geometry ◽  
Radon Space

Reconstruction algorithms for circular cone-beam (CB) scans have been extensively studied in the literature. Since insufficient data are measured, an exact reconstruction is impossible for such a geometry. If the reconstruction algorithm assumes zeros for the missing data, such as the standard FDK algorithm, a major type of resulting CB artifacts is the intensity drop along the axial direction. Many algorithms have been proposed to improve image quality when faced with this problem of data missing; however, development of an effective and computationally efficient algorithm remains a major challenge. In this work, we propose a novel method for estimating the unmeasured data and reducing the intensity drop artifacts. Each CB projection is analyzed in the Radon space via Grangeat's first derivative. Assuming the CB projection is taken from a parallel beam geometry, we extract those data that reside in the unmeasured region of the Radon space. These data are then used as in a parallel beam geometry to calculate a correction term, which is added together with Hu’s correction term to the FDK result to form a final reconstruction. More approximations are then made on the calculation of the additional term, and the final formula is implemented very efficiently. The algorithm performance is evaluated using computer simulations on analytical phantoms. The reconstruction comparison with results using other existing algorithms shows that the proposed algorithm achieves a superior performance on the reduction of axial intensity drop artifacts with a high computation efficiency.

A novel extension of the parallel-beam projection-slice theorem to divergent fan-beam and cone-beam projections

2005 ◽  
Vol 32 (3) ◽  
pp. 654-665 ◽  
Author(s):  
Guang-Hong Chen ◽  
Shuai Leng ◽  
Charles A. Mistretta
Keyword(s):  
Cone Beam ◽  
Parallel Beam ◽  
Slice Theorem ◽  
Beam Projection

scholarly journals Artifacts related to cone beam computed tomography technology (CBCT) and their significance for clinicians: illustrated review of medical literature.

NEMESIS ◽  
2020 ◽  
Vol 11 (1) ◽  
pp. 1-29
Author(s):  
Raphael Olszewski
Keyword(s):  
Computed Tomography ◽  
Dental Implants ◽  
Cone Beam Computed Tomography ◽  
Experimental Studies ◽  
Field Of View ◽  
Cone Beam ◽  
Beam Hardening ◽  
Exclusion Criteria ◽  
Ring Artifact ◽  
Pubmed Database

Objective: to explain the meaning and to illustrate technical artifacts (aliasing as well as the ring artifact) and beam hardening (metal artifact) that can be present in the dentomaxillofacial cone beam computed tomography (CBCT), and to check the accessibility of free illustrations of these artifacts in medical publications. Material and methods: One observer applied five search equations using database PubMed. The exclusion criteria were: experimental studies, animal studies, studies not related to dentomaxillofacial area, and articles with closed access. There was no time limit for the search of articles. We limited our search to English and French language. Results: Only 3 articles out of 434 publications were retained after application of inclusion/exclusion criteria. In these articles only 4 annotated figures were freely accessible in medical publications from PubMed. In this paper we presented examples of aliasing, ring artifact, and beam artifacts from I-CAT, Carestream 9000 3D (Kodak), and Planmeca Promax 3D Mid CBCT. The intensity of beam hardening artifact varies from major degradation of image (i.e., subperiosteal implants, bridges, crowns, dental implants, and orthodontic fix appliances), through mean degradation (screws securing titanium mesh, head of mini-implant) to no beam hardening on metallic devices (orthodontic anchorage, orthodontic contention wire) or on dense objects (endodontic treatments, impression materials, Lego box). Some beam hardening artifacts arising from nasal piercing, hairs, or hearing aid device may be present on the image but they will not disturb the evaluation of the field of view. Conclusions: reduction of aliasing artifact is related with the improvement of detectors quality. The presence of ring artifact means that CBCT device has lost its calibration. The field of view (FOV) needs to be reduce in order to avoid scanning regions susceptible to beam hardening (e.g., metallic restorations, dental implants). Finally, the accessibility to open knowledge on technique -related CBCT artifacts seems extremely limited when searching at PubMed database.

Three-dimensional SPECT reconstruction of combined cone beam and parallel beam data

1992 ◽  
Vol 37 (3) ◽  
pp. 535-548 ◽  
Author(s):  
R J Jaszczak ◽  
J Li ◽  
J Wang ◽  
R E Coleman
Keyword(s):  
Three Dimensional ◽  
Cone Beam ◽  
Parallel Beam ◽  
Spect Reconstruction
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