Post-mortem computed tomography: Technical principles and recommended parameter settings for high-resolution imaging

Post-mortem computed tomography (PMCT) has become a standard procedure in many forensic institutes worldwide. However, the standard scan protocols offered by vendors are optimised for clinical radiology and its main considerations regarding computed tomography (CT), namely, radiation exposure and motion artefacts. Thus, these protocols aim at low-dose imaging and fast imaging techniques. However, these considerations are negligible in post-mortem imaging, which allows for significantly increased image quality. Therefore, the parameters have to be adjusted to achieve the best image quality. Several parameters affect the image quality differently and have to be weighed against each other to achieve the best image quality for different diagnostic interests. There are two main groups of parameters that are adjustable by the user: acquisition parameters and reconstruction parameters. Acquisition parameters have to be selected prior to scanning and affect the raw data composition. In contrast, reconstruction parameters affect the calculation of the slice stacks from the raw data. This article describes the CT principles from acquiring image data to post-processing and provides an overview of the significant parameters for increasing the image quality in PMCT. Based on the CT principles, the effects of these parameters on the contrast, noise, resolution and frequently occurring artefacts are described. This article provides a guide for the performance of PMCT in morgues, clinical facilities or private practices.

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Magnetic resonance imaging and computed tomography of equine cheek teeth and adjacent structures: comparative study of image quality in horses in vivo, post-mortem and frozen-thawed

Acta Veterinaria Scandinavica ◽

10.1186/s13028-019-0495-8 ◽

2019 ◽

Vol 61 (1) ◽

Author(s):

Christin Röttiger ◽

Maren Hellige ◽

Bernhard Ohnesorge ◽

Astrid Bienert-Zeit

Keyword(s):

Computed Tomography ◽

Image Quality ◽

Post Mortem ◽

Mr Images ◽

Adjacent Structures ◽

Group A ◽

Group B ◽

The Impact ◽

Ct And Mri

Abstract Background The use of cadavers for radiology research methodologies involving subjective image quality evaluation of anatomical criteria is well-documented. The purpose of this method comparison study was to evaluate the image quality of dental and adjacent structures in computed tomography (CT) and high-field (3 T) magnetic resonance (MR) images in cadaveric heads, based on an objective four-point rating scale. Whilst CT is a well-established technique, MR imaging (MRI) is rarely used for equine dental diagnostics. The use of a grading system in this study allowed an objective assessment of CT and MRI advantages in portraying equine cheek teeth. As imaging is commonly performed with cadaveric or frozen and thawed heads for dental research investigations, the second objective was to quantify the impact of the specimens’ conditions (in vivo, post-mortem, frozen-thawed) on the image quality in CT and MRI. Results The CT and MR images of nine horses, focused on the maxillary premolar 08s and molar 09s, were acquired post-mortem (Group A). Three observers scored the dental and adjacent tissues. Results showed that MR sequences gave an excellent depiction of endo- and periodontal structures, whereas CT produced high-quality images of the hard tooth and bony tissues. Additional CT and MRI was performed in vivo (Group B) and frozen-thawed (Group C) in three of these nine horses to specify the condition of the best specimens for further research. Assessing the impact of the specimens’ conditions on image quality, specific soft tissues of the maxillary 08s and 09s including adjacent structures (pulps, mucosa of the maxillary sinuses, periodontal ligament, soft tissue inside the infraorbital canal) were graded in group B and C and analysed for significant differences within CT and MR modalities in comparison to group A. Results showed that MRI scores in vivo were superior to the post-mortem and frozen-thawed condition. Conclusions On comparing the imaging performance of CT and MRI, both techniques show a huge potential for application in equine dentistry. Further studies are needed to assess the clinical suitability of MRI. For further research investigations it must be considered, that the best MR image quality is provided in live horses.

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Comparison of quantitative image quality of cardiac computed tomography between raw-data-based and model-based iterative reconstruction algorithms with an emphasis on image sharpness

Pediatric Radiology ◽

10.1007/s00247-020-04741-x ◽

2020 ◽

Vol 50 (11) ◽

pp. 1570-1578

Author(s):

Ki Baek Lee ◽

Hyun Woo Goo

Keyword(s):

Computed Tomography ◽

Image Quality ◽

Iterative Reconstruction ◽

Cardiac Computed Tomography ◽

Reconstruction Algorithms ◽

Image Sharpness ◽

Raw Data ◽

Model Based ◽

Quantitative Image

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Post-mortem analysis of gunshot wounds to the head and thorax in dogs by computed tomography, radiography and forensic necropsy

Medicine Science and the Law ◽

10.1177/0025802420971176 ◽

2020 ◽

pp. 002580242097117

Author(s):

Małgorzata Grela ◽

Kinga Panasiuk-Flak ◽

Piotr Listos ◽

Magdalena Gryzińska ◽

Grzegorz Buszewicz ◽

...

Keyword(s):

Computed Tomography ◽

Foreign Bodies ◽

Imaging Techniques ◽

Gunshot Wounds ◽

Bone Lesions ◽

X Rays ◽

Post Mortem ◽

Additional Information ◽

Different Types ◽

Post Traumatic

In view of the scarcity of literature data on the use of radiological imaging techniques in forensic veterinary medicine, while at the same time the number of reported crimes against animals involving the use of firearms is rising, this paper attempts to assess the usefulness of radiography and computed tomography (CT) in the post-mortem diagnosis of gunshot wounds (GSW) in comparison to classic necropsy. The design of the experiment was as follows: preparation of the research material (13 dog carcasses), shooting of the material from different distances (1.5 and 12 m, plus one contact shot to the head) and using different types of ammunition, followed by X-rays and CT scans in each case to examine the injuries resulting from the shot. The final steps of the experiment were photographic documentation and autopsy by the Virchow method. In the examined material, post-traumatic bone lesions and the presence of metallic foreign bodies were successfully imaged by both radiography and CT. GSW analysis using CT provided much better data quality and some additional information. Two general conclusions can be drawn from the results of the experiment. First, damage caused by gunshots is correlated with the calibre, initial velocity and kinetic energy of the projectile, as well as the distance from the muzzle of the gun to the object shot. Second, radiological examination is useful in preparing forensic veterinary opinions. Used as a complement to classic necropsy, they increase the possibility of an accurate post-mortem diagnosis of shooting victims.

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Synthesizing Dental Radiographs for Human Identification

Journal of Dental Research ◽

10.1177/154405910708601107 ◽

2007 ◽

Vol 86 (11) ◽

pp. 1057-1062 ◽

Cited By ~ 22

Author(s):

S. Tohnak ◽

A.J.H. Mehnert ◽

M. Mahoney ◽

S. Crozier

Keyword(s):

Computed Tomography ◽

Image Quality ◽

Human Remains ◽

Geometric Distortion ◽

Post Mortem ◽

X Ray ◽

X Ray Computed ◽

Dental Radiographs ◽

Ct Data ◽

Comparison Algorithms

The task of identifying human remains based on dental comparisons of post mortem (PM) and ante mortem (AM) radiographs is labor-intensive, subjective, and has several drawbacks, including: inherently poor image quality, difficulty matching the viewing angles in PM radiographs to those taken AM, and the fact that the state of the dental remains may entirely preclude the possibility of obtaining certain types of radiographs PM. The aim of the present study was to investigate the feasibility of using radiograph-like images reconstructed from PM x-ray computed tomography (CT) data to overcome the shortcomings of conventional radiographic comparison. Algorithms for computer synthesis of panoramic, periapical, and bitewing images are presented. The algorithms were evaluated with data from clinical examinations of two persons. The results demonstrate the efficacy of the CT-based approach and that, in comparison with conventional radiographs, the synthesized images exhibit minimal geometric distortion, reduced blurring, and reduced superimposition of oral structures.

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Raw-data-based iterative reconstruction versus filtered back projection: image quality of low-dose chest computed tomography examinations in 87 patients

Clinical Imaging ◽

10.1016/j.clinimag.2013.06.004 ◽

2013 ◽

Vol 37 (6) ◽

pp. 1024-1032 ◽

Cited By ~ 20

Author(s):

Haiyan Wang ◽

Bingyi Tan ◽

Bin Zhao ◽

Changhu Liang ◽

Zhuodong Xu

Keyword(s):

Computed Tomography ◽

Image Quality ◽

Iterative Reconstruction ◽

Low Dose ◽

Back Projection ◽

Filtered Back Projection ◽

Raw Data ◽

Chest Computed Tomography ◽

Projection Image

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SEM/FESEM imaging of lamellar structures in melt extruded polyethylene films

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100130341 ◽

1992 ◽

Vol 50 (2) ◽

pp. 1142-1143

Author(s):

R.T. Chen ◽

M.G. Jamieson ◽

R. Callahan

Keyword(s):

Imaging Techniques ◽

Membrane Surface ◽

High Stress ◽

Extrusion Direction ◽

Polymeric Membranes ◽

Scanning Tunneling ◽

Tunneling Microscopy ◽

Crystalline Polymers ◽

Lamellar Structures ◽

Resolution Imaging

“Row lamellar” structures have previously been observed when highly crystalline polymers are melt-extruded and recrystallized under high stress. With annealing to perfect the stacked lamellar superstructure and subsequent stretching in the machine (extrusion) direction, slit-like micropores form between the stacked lamellae. This process has been adopted to produce polymeric membranes on a commercial scale with controlled microporous structures. In order to produce the desired pore morphology, row lamellar structures must be established in the membrane precursors, i.e., as-extruded and annealed polymer films or hollow fibers. Due to the lack of pronounced surface topography, the lamellar structures have typically been investigated by replica-TEM, an indirect and time consuming procedure. Recently, with the availability of high resolution imaging techniques such as scanning tunneling microscopy (STM) and field emission scanning electron microscopy (FESEM), the microporous structures on the membrane surface as well as lamellar structures in the precursors can be directly examined.The materials investigated are Celgard® polyethylene (PE) flat sheet membranes and their film precursors, both as-extruded and annealed, made at different extrusion rates (E.R.).

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Quantitative nano-characterization of heterogeneous catalysts

Proceedings, annual meeting, Electron Microscopy Society of America ◽

10.1017/s0424820100138361 ◽

1995 ◽

Vol 53 ◽

pp. 398-399

Author(s):

P.A. Crozier ◽

M. Pan

Keyword(s):

Heterogeneous Catalysts ◽

Low Dose ◽

Imaging Techniques ◽

Structural Features ◽

Catalyst Characterization ◽

New Developments ◽

Double Phase ◽

Phase Systems ◽

Dose Imaging

Heterogeneous catalysts can be of varying complexity ranging from single or double phase systems to complicated mixtures of metals and oxides with additives to help promote chemical reactions, extend the life of the catalysts, prevent poisoning etc. Although catalysis occurs on the surface of most systems, detailed descriptions of the microstructure and chemistry of catalysts can be helpful for developing an understanding of the mechanism by which a catalyst facilitates a reaction. Recent years have seen continued development and improvement of various TEM, STEM and AEM techniques for yielding information on the structure and chemistry of catalysts on the nanometer scale. Here we review some quantitative approaches to catalyst characterization that have resulted from new developments in instrumentation.HREM has been used to examine structural features of catalysts often by employing profile imaging techniques to study atomic details on the surface. Digital recording techniques employing slow-scan CCD cameras have facilitated the use of low-dose imaging in zeolite structure analysis and electron crystallography. Fig. la shows a low-dose image from SSZ-33 zeolite revealing the presence of a stacking fault.

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