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Biomedical subjects

A Pogany

Publications and source records attributed to A Pogany.

6 recordsLinked to original sources
PubMed2002

Quantitative X-ray projection microscopy: phase-contrast and multi-spectral imaging.

We outline a new approach to X-ray projection microscopy in a scanning electron microscope (SEM), which exploits phase contrast to boost the quality and information content of images. These developments have been made possible by the combination of a high-brightness field-emission gun (FEG)-based SEM, direct detection CCD technology and new phase retrieval algorithms. Using this approach we have been able to obtain spatial resolution of < 0.2 micro m and have demonstrated novel features such as: (i) phase-contrast enhanced visibility of high spatial frequency image features (e.g. edges and boundaries) over a wide energy range; (ii) energy-resolved imaging to simultaneously produce multiple quasi-monochromatic images using broad-band polychromatic illumination; (iii) easy implementation of microtomography; (iv) rapid and robust phase/amplitude-retrieval algorithms to enable new real-time and quantitative modes of microscopic imaging. These algorithms can also be applied successfully to recover object-plane information from intermediate-field images, unlocking the potentially greater contrast and resolution of the intermediate-field regime. Widespread applications are envisaged for fields such as materials science, biological and biomedical research and microelectronics device inspection. Some illustrative examples are presented. The quantitative methods described here are also very relevant to projection microscopy using other sources of radiation, such as visible light and electrons.

Journal Article↗
PubMed2000

Quantitative methods in phase-contrast x-ray imaging.

A new method for extracting quantitative information from phase-contrast x-ray images obtained with microfocus x-ray sources is presented. The proposed technique allows rapid noninvasive characterization of the internal structure of thick optically opaque organic samples. The method does not generally involve any sample preparation and does not need any x-ray optical elements (such as monochromators, zone plates, or interferometers). As a consequence, samples can be imaged in vivo or in vitro, and the images are free from optical aberrations. While alternative techniques of x-ray phase-contrast imaging usually require expensive synchrotron radiation sources, our method can be implemented with conventional, albeit microfocus, x-ray tubes, which greatly enhances its practicality. In the present work, we develop the theoretical framework, perform numerical simulations, and present the first experimental results, demonstrating the viability of the proposed approach. We believe that this method should find wide-ranging applications in clinical radiology and medical research.

Animals↗
PubMed1985

Septic endarteritis after percutaneous transluminal angioplasty.

A case of septic endarteritis leading to septic arthritis and septic emboli occurred after percutaneous transluminal angioplasty. To our knowledge, this is the first reported instance of arterial wall infection potentially caused by percutaneous transluminal angioplasty. Treatment consisted of long-term intravenous antibiotics and drainage of the septic joint.

Angioplasty, Balloon↗
PubMed1984

Marked hepatic congestion caused by a thoracoabdominal aneurysm.

A 70-yr-old man with a large thoracoabdominal aortic aneurysm developed marked congestive hepatomegaly. Evaluation by arteriography, venography, and computed tomography revealed compression and venous obstruction at the confluence of the hepatic veins and inferior vena cava. Although obstruction of the inferior vena cava caused by rupture of an abdominal aortic aneurysm is known to occur, obstruction without rupture and involving the hepatic veins has not been previously reported.

Aged↗
PubMedDate not supplied

Phase-contrast radiography.

For the past 100 years, the paradigm for radiography has been premised on absorption as the sole means of contrast formation and on ray optics as the basis for image interpretation. A new conceptual approach to radiography has been developed that includes phase (ie, refractive) contrast and requires wave optics for proper treatment. This new approach greatly increases the amount of information that can be obtained with radiographic techniques and is particularly well suited to the imaging of soft tissue and of very small features in biologic samples. A key feature of the present technique of phase-contrast radiography is the use of a microfocus x-ray source about an order of magnitude (< or = 20 microm) smaller than that used in conventional radiography. Phase-contrast radiography offers a number of improvements over conventional radiography in a clinical setting, especially in soft-tissue imaging. These improvements include increased contrast resulting in improved visualization of anatomic detail, reduced absorbed dose to the patient, inherent image magnification and high spatial resolution, use of harder x rays, and relative ease of implementation. More technologically advanced detectors are currently being developed and commercialized, which will help fully realize the considerable potential of phase-contrast imaging.

Animals↗