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Biomedical subjects

S Pizer

Publications and source records attributed to S Pizer.

5 recordsLinked to original sources
PubMed1997

Does intensity windowing improve the detection of simulated calcifications in dense mammograms?

This study attempts to determine whether intensity windowing (IW) improves detection of simulated calcifications in dense mammograms. Clusters of five simulated calcifications were embedded in dense mammograms digitized at 50-microns pixels, 12 bits deep. Film images with no windowing applied were compared with film images with nine different window widths and levels applied. A simulated cluster was embedded in a realistic background of dense breast tissue, with the position of the cluster varied. The key variables involved in each trial included the position of the cluster, contrast level of the cluster, and the IW settings applied to the image. Combining the ten IW conditions, four contrast levels and four quadrant positions gave 160 combinations. The trials were constructed by pairing 160 combinations of key variables with 160 backgrounds. The entire experiment consisted of 800 trials. Twenty student observers were asked to detect the quadrant of the image in which the mass was located. There was a statistically significant improvement in detection performance for clusters of calcifications when the window width was set at 1024 with a level of 3328, and when the window width was set at 1024 with a level of 3456. The selected IW settings should be tested in the clinic with digital mammograms to determine whether calcification detection performance can be improved.

Breast Neoplasms↗
PubMed1997

The effect of intensity windowing on the detection of simulated masses embedded in dense portions of digitized mammograms in a laboratory setting.

The purpose of this study was to determine whether intensity windowing (IW) improves detection of simulated masses in dense mammograms. Simulated masses were embedded in dense mammograms digitized at 50 microns/pixel, 12 bits deep. Images were printed with no windowing applied and with nine window width and level combinations applied. A simulated mass was embedded in a realistic background of dense breast tissue, with the position of the mass (against the background) varied. The key variables involved in each trial included the position of the mass, the contrast levels and the IW setting applied to the image. Combining the 10 image processing conditions, 4 contrast levels, and 4 quadrant positions gave 160 combinations. The trials were constructed by pairing 160 combinations of key variables with 160 backgrounds. The entire experiment consisted of 800 trials. Twenty observers were asked to detect the quadrant of the image into which the mass was located. There was a statistically significant improvement in detection performance for masses when the window width was set at 1024 with a level of 3328. IW should be tested in the clinic to determine whether mass detection performance in real mammograms is improved.

Analysis of Variance↗
PubMedDate not supplied

Quantitative digital fluorography. Computer vs. human estimation of vascular stenoses.

Digital subtracted images of iodinated rods, incorporating accurately measured areas of eccentric stenosis were obtained. The average subjective estimations of fractional area reduction (211 readings each) by three experienced angiographers were compared with values obtained using an interactive computer algorithm using the densitometric data. Results were analyzed to identify major influences on accuracy, including iodine concentration, vessel width, absolute severity of the stenosis, and vessel orientation. While no single factor appeared to seriously affect human accuracy, computer readings were significantly influenced by the tilt of the vessel in relation to the x-ray beam. Various potential sources of error including beam hardening, stenosis geometry, and scattering are discussed and appropriate algorithm corrections suggested. The importance of the availability of a reliable and accurate method to quantify vascular stenosis and volume of stenotic material is stressed.

Absorptiometry, Photon↗
PubMedDate not supplied

Examination of the extracranial carotid bifurcation by thin-section dynamic CT: direct visualization of intimal atheroma in man (Part 2).

Examination of the extracranial carotid bifurcation by thin-section computed tomographic (CT) scans after bolus, high-volume contrast enhancement allowed detection of more disease than did arteriograms in six of eight consecutive patients with transient ischemic attacks. In four patients this was on the clinical side of the lesion; in two the disease was in the asymptomatic carotid artery. One patient appeared to show a carotid ulcer; the ulcer was detected on CT. However, at surgery and subsequent histology, the surface of the lesion was endothelialized. The carotid CT examination is performed in the scanner "dead time" between unenhanced and enhanced head CT scans using the same contrast material for both studies. The examinations covers 3-3.6 cm of the carotid bifurcation region. Thin-section CT of the extracranial carotid arteries is a noninvasive examination that on preliminary evaluations appears to have sensitivity at least equal to that of carotid angiography in the detection of intimal disease.

Adult↗