| 1. |
- Achilles, Silvio, et al.
(författare)
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GPU-Accelerated Coupled Ptychographic Tomography
- 2022
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Ingår i: Developments in X-Ray Tomography XIV. - : SPIE. - 0277-786X .- 1996-756X. - 9781510654686 ; 12242
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Konferensbidrag (refereegranskat)abstract
- Scanning coherent X-ray microscopy (ptychography) has gained considerable interest during the last decade since the performance of this indirect imaging technique does not necessarily rely on the quality of the X-ray optics and, in principle, can achieve highest spatial resolution in X-ray imaging. The method can be easily extended to 3D by adding standard tomographic reconstruction schemes. However, the tomographic reconstruction is often applied in a subsequent step using a sequence of aligned ptychographic 2D projections. In this contribution, we outline current developments of a GPU-accelerated framework for direct 3D ptychography, coupling 2D ptychography and tomography. The program utilizes a custom GPU-accelerated framework for ptychography that offers three distinct ptychographic reconstruction algorithms. The tomographic reconstruction runs simultaneously and uses numerical routines of the ASTRA Toolbox. This parallel-computing approach results in a high performance increase considerably reducing the reconstruction time of 3D ptychographic datasets.
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| 2. |
- Correa, Leticia, et al.
(författare)
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Planning of dental implant size with digital panoramic radiographs, CBCT-generated panoramic images, and CBCT cross-sectional images
- 2014
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Ingår i: Clinical Oral Implants Research. - : Blackwell Munksgaard. - 0905-7161 .- 1600-0501. ; 25:6, s. 690-695
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Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVES: To compare the implant size (width and length) planned with digital panoramic radiographs, cone beam computed tomography (CBCT)-generated panoramic views, or CBCT cross-sectional images, in four implant systems. MATERIAL AND METHODS: Seventy-one patients with a total of 103 implant sites in the upper premolar and/or lower molar regions were examined with digital panoramic radiography (D-PAN) and (CBCT). A metal ball 5 mm in diameter was placed in the edentulous area for the D-PAN. CBCT data sets were reformatted to a 10-mm thick CBCT panoramic view (CBCT-pan) and 1-mm cross-sections (CBCT-cross). Measurements were performed in the images using dedicated software. All images were displayed on a monitor and assessed by three observers who outlined a dental implant by placing four reference points in the site of the implant-to-be. Differences in width and length of the implant-to-be from the three modalities were analyzed. The implant size selected in the CBCT-cross images was then compared to that selected in the other two modalities (D-PAN and CBCT-pan) for each of the implant systems separately. RESULTS: The implant-to-be (average measurements among observers) was narrower when measured in CBCT-cross compared with both D-PAN and CBCT-Pan. For premolar sites, the width also differed significantly between D-PAN and CBCT-pan modalities. The implant-to-be was also significantly shorter when recorded in CBCT-cross than in D-PAN. In premolar sites, there were no significant differences in implant length among the three image modalities. It mattered very little for the change in implant step sizes whether CBCT-cross was compared to D-PAN or CBCT-pan images. CONCLUSION: Our results show that the selected implant size differs when planned on panoramic or cross-section CBCT images. In most cases, implant size measured in cross-section images was narrower and shorter than implant size measured in a panoramic image or CBCT-based panoramic view
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| 3. |
- Domic, Danijel, et al.
(författare)
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Accuracy of cone beam computed tomography is limited at implant sites with a thin buccal bone : A laboratory study
- 2021
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Ingår i: Journal of Periodontology. - : John Wiley & Sons. - 0022-3492 .- 1943-3670. ; 92:4, s. 592-601
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Tidskriftsartikel (refereegranskat)abstract
- Background: To evaluate whether buccal bone thickness (BBT), implant diameter, and abutment/crown material influence the accuracy of cone beam computed tomography (CBCT) to determine the buccal bone level at titanium implants.Methods: Two implant beds (i.e., narrow and standard diameter) were prepared in each of 36 porcine bone blocks. The implant beds were positioned at a variable distance from the buccal bone surface, thus resulting in 3 BBT groups (i.e., > 0.5-1.0; > 1.0-1.5; > 1.5-2.0 mm). In half of the blocks, a buccal bone dehiscence of random extent ("depth") was created and implants were mounted with different abutment/crown material (i.e., titanium abutments with a metal-ceramic crown and zirconia abutments with an all-ceramic zirconia crown). The distance from the implant shoulder to the buccal bone crest was measured on cross-sectional CBCT images and compared to the direct measurements at the bone blocks.Results: While abutment/crown material and implant diameter had no effect on the detection accuracy of the buccal bone level at dental implants in CBCT scans, BBT had a significant effect. Specifically, when BBT was ≤ 1.0 mm, a dehiscence was often diagnosed although not present, i.e., the sensitivity was high (95.8%), but the specificity (12.5%) and the detection accuracy (54.2%) were low. Further, the average measurement error of the distance from the implant shoulder to the buccal bone crest was 1.6 mm.Conclusions: Based on the present laboratory study, BBT has a major impact on the correct diagnosis of the buccal bone level at dental titanium implants in CBCT images; in cases where the buccal bone is ≤ 1 mm thick, detection of the buccal bone level is largely inaccurate. This article is protected by copyright. All rights reserved.
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| 4. |
- Liedke, Gabriela Salatino, et al.
(författare)
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Accuracy of detecting and measuring buccal bone thickness adjacent to titanium dental implants-a cone beam computed tomography in vitro study
- 2018
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Ingår i: Oral surgery, oral medicine, oral pathology and oral radiology. - : Elsevier. - 2212-4403 .- 2212-4411. ; 126:5, s. 432-438
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Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVES: The aim of this study was to assess the accuracy of detecting and measuring buccal bone thickness (BBT) adjacent to titanium implants in cone beam computed tomography (CBCT) images. STUDY DESIGN: Titanium implants (1, 2, or 3), abutments, and metal-ceramic crowns were inserted into 40 bone blocks with various BBTs. CBCT images were acquired in various settings: Voxel sizes (0.2 and 0.13 mm) and reconstruction section thicknesses (2.0 and 5.0 mm) were assessed by 3 examiners. True BBT was measured in digital photographs of the bone blocks. Buccal bone detection was evaluated by sensitivity and specificity. BBT was evaluated by 1-way analysis of variance (ANOVA) between the true and the CBCT measurements and by calculating the difference between the true measurement and the CBCT measurement (Di-BBT). RESULTS: Detection of buccal bone exhibited high sensitivity (0.86-1) and low specificity (0.14-1). More implants in the field of view, large voxel size, and thick image reconstruction sections had a negative impact on buccal bone detection. ANOVA showed statistically significantly larger BBT for the CBCT measurements in all settings (1.07-1.21 mm) compared with the true measurements (0.85 mm). Di-BBT was mostly within 0.5 mm. CONCLUSIONS: BBT adjacent to titanium implants is overestimated when evaluated on CBCT cross-sectional images.
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| 5. |
- Liedke, Gabriela S., et al.
(författare)
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Factors affecting the possibility to detect buccal bone condition around dental implants using cone beam computed tomography
- 2017
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Ingår i: Clinical Oral Implants Research. - : John Wiley & Sons. - 0905-7161 .- 1600-0501. ; 28:9, s. 1082-1088
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Tidskriftsartikel (refereegranskat)abstract
- OBJECTIVES: To evaluate factors with impact on the conspicuity (possibility to detect) of the buccal bone condition around dental implants in cone beam computed tomography (CBCT) imaging. MATERIAL AND METHODS: Titanium (Ti) or zirconia (Zr) implants and abutments were inserted into 40 bone blocks in a way to obtain variable buccal bone thicknesses. Three combinations regarding the implant-abutment metal (TiTi, TiZr, or ZrZr) and the number of implants (one, two, or three) were assessed. Two CBCT units (Scanora 3D - Sc and Cranex 3D - Cr) and two voxel resolutions (0.2 and 0.13 mm) were used. Reconstructed sagittal images (2.0 and 5.0 mm thickness) were evaluated by three examiners, using a dichotomous scale when assessing the condition of the buccal bone around the implants. A multivariate logistic regression was performed using examiners' detection of the buccal bone condition as the dependent variable. Odds ratio (OR) were calculated separately for each CBCT unit. RESULTS: Implant-abutment combination (ZrZr) (OR Sc = 19.18, OR Cr = 11.89) and number of implants (3) (OR Sc = 12.10, OR Cr = 4.25) had major impact on buccal bone conspicuity. The thinner the buccal bone, the higher the risk that the condition of the buccal bone could not be detected. The use of lower resolution protocols increased the risk that buccal bone was not properly detected (OR Sc = 1.46, OR Cr = 2.00). For both CBCT units, increasing the image reconstruction thickness increased the conspicuity of buccal bone (OR Sc = 0.33, OR Cr = 0.31). CONCLUSIONS: Buccal bone conspicuity was impaired by a number of factors, the implant-abutment material being the most relevant. Acquisition and reconstruction factors had minor impact on the detection of the buccal bone condition.
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| 6. |
- Nilsson, Daniel, et al.
(författare)
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Ronchi test for characterization of nanofocusing optics at a hard x-ray free-electron laser
- 2012
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Ingår i: Optics Letters. - : Optical Society of America. - 0146-9592 .- 1539-4794. ; 37:24, s. 5046-5048
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Tidskriftsartikel (refereegranskat)abstract
- We demonstrate the use of the classical Ronchi test to characterize aberrations in focusing optics at a hard x-ray free-electron laser. A grating is placed close to the focus and the interference between the different orders after the grating is observed in the far field. Any aberrations in the beam or the optics will distort the interference fringes. The methodis simple to implement and can provide single-shot information about the focusing quality. We used the Ronchi test to measure the aberrations in a nanofocusing Fresnel zone plate at the Linac Coherent Light Source at 8.194 keV.
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| 7. |
- Schroer, Christian G, et al.
(författare)
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Hard x-ray nanofocusing with refractive x-ray optics : full beam characterization by ptychographic imaging
- 2013
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Ingår i: Proceedings of SPIE. - : SPIE. - 9780819496980 ; , s. 884807-
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Konferensbidrag (refereegranskat)abstract
- Hard x-ray scanning microscopy relies on small and intensive nanobeams. Refractive x-ray lenses are well suited to generate hard x-ray beams with lateral dimensions of 100 nm and below. The diffraction limited beam size of refractive x-ray lenses mainly depends on the focal length and the attenuation inside the lens material. The numerical aperture of refractive lenses scales with the inverse square root of the focal length until it reaches the critical angle of total reflection. We have used nanofocusing refractive x-ray lenses made of silicon to focus hard x-rays at 8 and 20 keV to (sub-)100 nm dimensions. Using ptychographic scanning coherent diffraction imaging we have characterized these nanobeams with high accuracy and sensitivity, measuring the full complex wave field in the focus. This gives access to the full caustic and aberrations of the x-ray optics.
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| 8. |
- Schropp, Andreas, et al.
(författare)
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Full spatial characterization of a nanofocused x-ray free-electron laser beam by ptychographic imaging
- 2013
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Ingår i: Scientific Reports. - : Springer Science and Business Media LLC. - 2045-2322. ; 3, s. 1633-
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Tidskriftsartikel (refereegranskat)abstract
- The emergence of hard X-ray free electron lasers (XFELs) enables new insights into many fields of science. These new sources provide short, highly intense, and coherent X-ray pulses. In a variety of scientific applications these pulses need to be strongly focused. In this article, we demonstrate focusing of hard X-ray FEL pulses to 125 nmusing refractive x-ray optics. For a quantitative analysis of most experiments, the wave field or at least the intensity distribution illuminating the sample is needed. We report on the full characterization of a nanofocused XFEL beam by ptychographic imaging, giving access to the complex wave field in the nanofocus. From these data, we obtain the full caustic of the beam, identify the aberrations of the optic, and determine the wave field for individual pulses. This information is for example crucial for high-resolution imaging, creating matter in extreme conditions, and nonlinear x-ray optics.
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| 9. |
- Schropp, Andreas, et al.
(författare)
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PtyNAMi : Ptychographic nano-analytical microscope
- 2020
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Ingår i: Journal of Applied Crystallography. - 0021-8898. ; 53, s. 957-971
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Tidskriftsartikel (refereegranskat)abstract
- Ptychographic X-ray imaging at the highest spatial resolution requires an optimal experimental environment, providing a high coherent flux, excellent mechanical stability and a low background in the measured data. This requires, for example, a stable performance of all optical components along the entire beam path, high temperature stability, a robust sample and optics tracking system, and a scatter-free environment. This contribution summarizes the efforts along these lines to transform the nanoprobe station on beamline P06 (PETRAIII) into the ptychographic nano-analytical microscope (PtyNAMi).
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| 10. |
- Schropp, Andreas, et al.
(författare)
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Scanning coherent x-ray microscopy as a tool for XFEL nanobeam characterization
- 2013
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Ingår i: Proceedings of SPIE. - : SPIE. - 9780819496997
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Konferensbidrag (refereegranskat)abstract
- During the last years, scanning coherent x-ray microscopy, also called ptychography, has revolutionized nanobeam characterization at third generation x-ray sources. The method yields the complete information on the complex valued, nanofocused wave field with high spatial resolution. In an experiment carried out at the Matter in Extreme Conditions (MEC) instrument at the Linac Coherent Light Source (LCLS) we successfully applied the method to an attenuated nanofocused XFEL beam with a size of 180(h) × 150(v) nm2 (FWHM) in horizontal (h) and vertical direction (v), respectively. It was created by a set of 20 beryllium compound refractive lenses (Be-CRLs). By using a fast detector (CSPAD) to record the diffraction patterns and a fast implementation of the phase retrieval code running on a graphics processing unit (GPU), the applicability of the method as a real-time XFEL nanobeam diagnostic is highlighted.
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