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K Kouris

Publications and source records attributed to K Kouris.

41 records · Page 3Linked to original sources
PubMed1981

Sampling properties of stationary and half-rotation rings in positron emission tomography.

The aim in positron emission tomography is to provide quantitative information about the uptake, localization, and turnover of labeled molecules in the human body. Instruments designed for this purpose are based on the coincidence detection of the emitted annihilation photons. In this paper, we examine those instruments that use a ring of detectors. We investigate such instruments with respect to their sampling properties in the stationary and half-rotation modes. It is shown that, although the half-rotation motion provides an improvement if the data are treated as a set of parallel projections, there is no improvement when divergent projections are assumed by the reconstruction procedure. The effects on reconstruction quality of the radial and the angular sampling in ring collected data are discussed and illustrated.

Data Collection↗
PubMed1980

Coherent scattering and the assessment of mineral concentration in trabecular bone.

The number of 103.2 keV (153Sm) gamma-rays scattered coherently and incoherently from the os calcis of three cadaver feet has been measured using a high purity Ge detector. The ratio of the intensities of coherent to incoherent scattered photons is dependent on elemental composition while the number scattered incoherently is dependent on density. The results indicate that techniques for the assessment of mineral status in the skeleton may be based on either of these measurements and each will exhibit a similar sensitivity to a given biological change. It is shown that a method based entirely on the detection of coherently scattered photons will be more sensitive to changes in mineral composition than either of the above. Such a system is proposed and optimised with respect to incident beam energy and scattering angle. For a dose of 4 mSV, coherent intensity measurements with a precision of 3% are anticipated.

Cadaver↗
PubMedDate not supplied

The value of parenchymal transit time index of Tc-99m DTPA diuretic renography in the evaluation of surgery in chronic bilharzial obstructive uropathy.

Selection of patients with chronic bilharzial uropathy (CBU) for surgery is a difficult problem due to the presence of grossly dilated urinary tracts without a significant obstruction in most of the cases. In this prospective study of 40 patients with CBU, the time-activity curve (TAC) patterns of the pre- and postoperative Tc-99m DTPA diuretic renography (RDR) studies were compared with the corresponding parenchymal transit time indices (PTTI). The aims were to find out which of these renographic parameters was more accurate in identifying obstruction and which was better in predicting the outcome of surgery. PTTI was more sensitive than TAC in identifying obstruction (96% and 92%, respectively) but it was less specific (78% and 98%). The detection accuracy of RDR for obstruction using TAC patterns was 96% compared to 84% using PTTI. Being independent of renal uptake function, PTTI could not predict the outcome of surgery as TAC could. In contrast to PTTI, TAC patterns could differentiate obstructed kidneys from severely nephropathic kidneys. However, PTTI was useful in identifying kidneys with residual nephropathy.

Adult↗
PubMedDate not supplied

Implementation of the T4/5 left ventricular functional image on a VAX-based Lexidata image processing station.

A VAX-based Lexidata image processing station has been used for the development and application of image processing and data analysis techniques in nuclear medicine. Within the area of cardiac multigated equilibrium blood-pool scintigraphy, the computational implementation of the T4/5 functional image, a new left ventricular functional image, is presented. This image reflects myocardial compliance. The versatility of the implementation is demonstrated. Examples of the T4/5 functional image are presented. The VAX-based Lexidata image processing station is a useful tool for parameter, feature, and image extraction from nuclear medicine images.

Coronary Disease↗