Biomedical subjects
Publications and source records attributed to M S Pastel.
The advent of computed tomography (CT) has initiated a technological revolution which continues to the present time. A brief review of basic principles of CT scanning is presented, and the evolution of modern CT scanner systems is traced. Some early indications of future trends are also presented.
Although computed tomography (CT) delineation of normal white matter of the cerebral hemispheres has been well documented, there has been no description of white matter within the cerebellum. Through the use of phantom studies, CT number correlations between cerebellum and cerebral hemispheres, and anatomic correlation with in vitro specimens, the ability to visualize cerebellar white matter is demonstrated. Thin sections decrease volume averaging and enable consistent imaging of these structures. Size and shape of the corpus medullaris on CT scan may vary with the scan angle and level of section. Representative examples of various normal appearances are illustrated.
The imaging process has two fundamental stages: detection and display. The detection stage can be quantified rigourously using Shannon's information theory. This requires the contrast scale (CS), modulation transfer function (MTF), and noise power spectrum [N(f)] to be combined into a signal-to-noise ratio (SNR). This results in two fundamental summary figures of merit: the density of noise equivalent quanta (NEQ) in the image and the information bandwidth integral (IBWI). These algorithm-independent measures are used to quantify the recording stage. The display stage is less well understood since it couples to an external observer. Several types of decision makers are treated. Examples are drawn from first and second generation CT, demonstrating that thye are nearly quantum limited for large signals, indicating how their algorithms are matched or mismatched to the geometry, and calculating the contrast-detail diagrams for those decision makers.