Reinventing ventilation/perfusion lung scanning with SPECT
Department of Nuclear Medicine, Royal North Shore Hospital, Sydney, NSW, Australia. Nuclear Medicine Communications
(Impact Factor: 1.67).
01/2009; 29(12):1023-5. DOI: 10.1097/MNM.0b013e328315efa1
Available from: Maria E Lyra
- "SPECT techniques were, up to few years ago, used in clinical diagnosis only by a limited number of centers. Given the improvements in sensitivity and diagnostic accuracy that has generally accompanied the transition from two-dimensional planar to three-dimensional (3D) imaging, SPECT technique in ventilation/perfusion (V/P) scintigraphy historically, one of the most commonly performed diagnostic studies in nuclear medicine, is superior in contrast resolution and improved anatomical detail compared with V/P perfusion scintigraphy, in the diagnosis of perfusion embolism . "
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ABSTRACT: Single photon emission computed tomography (SPECT) imaging is widely implemented in nuclear medicine as its clinical role in the diagnosis and management of several diseases is, many times, very helpful (e.g., myocardium perfusion imaging). The quality of SPECT images are degraded by several factors such as noise because of the limited number of counts, attenuation, or scatter of photons. Image filtering is necessary to compensate these effects and, therefore, to improve image quality. The goal of filtering in tomographic images is to suppress statistical noise and simultaneously to preserve spatial resolution and contrast. The aim of this work is to describe the most widely used filters in SPECT applications and how these affect the image quality. The choice of the filter type, the cut-off frequency and the order is a major problem in clinical routine. In many clinical cases, information for specific parameters is not provided, and findings cannot be extrapolated to other similar SPECT imaging applications. A literature review for the determination of the mostly used filters in cardiac, brain, bone, liver, kidneys, and thyroid applications is also presented. As resulting from the overview, no filter is perfect, and the selection of the proper filters, most of the times, is done empirically. The standardization of image-processing results may limit the filter types for each SPECT examination to certain few filters and some of their parameters. Standardization, also, helps in reducing image processing time, as the filters and their parameters must be standardised before being put to clinical use. Commercial reconstruction software selections lead to comparable results interdepartmentally. The manufacturers normally supply default filters/parameters, but these may not be relevant in various clinical situations. After proper standardisation, it is possible to use many suitable filters or one optimal filter.
Available from: york.ac.uk
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ABSTRACT: This paper describes a new modeling methodology that allows to derive systematically behavioral signal path models of operational amplifiers. Combined with symbolic simulation, these models provide high qualitative insight into the small-signal functioning of a circuit. The behavioral signal path model provides compact interpretable expressions for the poles and zeros that constitute the signal path. These expressions show which design parameters have dominant influence on the position of a pole/zero and thus enable a designer to control a manual interactive sizing process. The methodology consists of the application of a sequence of abstractions, so that one gradually progresses from a full device to a full behavior circuit representation. During this translation, qualitative insight and design requirements are obtained. The methodology is implemented in an open tool called EF2ef. The behavioral signal path model is also used for optimization based sizing in order to achieve pole placement in an efficient way. For optimization based siting, a new strategy for hierarchical penalty function composition is proposed, which allows sequential pruning of the design space. Combined with an operating point driven DC formulation and local minimax optimization, a fast sizing method is obtained which can be used for interactive design space exploration. Experimental results of both modeling and siting are shown
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