An evaluation of the effectiveness of adaptive histogram equalization for contrast enhancement.

Adaptive histogram equalization (AHE) and intensity windowing have been compared using psychophysical observer studies. Experienced radiologists were shown clinical CT (computerized tomographic) images of the chest. Into some of the images, appropriate artificial lesions were introduced; the physicians were then shown the images processed with both AHE and intensity windowing. They were asked to assess the probability that a given image contained the artificial lesion, and their accuracy was measured. The results of these experiments show that for this particular diagnostic task, there was no significant difference in the ability of the two methods to depict luminance contrast; thus, further evaluation of AHE using controlled clinical trials is indicated.

Intravenous digital subtraction angiography of orbital and ocular circulation. A preliminary experimental study.

In serial experiments on cats, intravenous digital subtraction angiography (DSA) was utilized to observe orbital and ocular circulation. Images of the orbital arterial system as well as normal ocular vasculature were obtained, utilizing dosage of contrast material acceptable for human study. Images obtained after intra-arterial DSA had no advantage over those obtained with intravenous DSA. After retrobulbar injection of 3 ml of saline, intravenous DSA demonstrated straightening of the external ophthalmic arteries showing the potential of this method for identifying orbital vascular pathology.

Image communications. What is needed and why.

Better communications are essential in the new medical environment. Methods to make more efficient the throughput in an existing department, foster confidence of patients, and improve the communications and efficiency of referring physicians are needed. The most difficult and thus the driving component of the new communications environment is image transmission. Concepts of picture archiving and communications systems, or PACS, arising from digital technology make possible unique and ubiquitous solutions to image communications. Better quality control and improved interpretation throughout the system, including the offices of referring physicians, will be possible. Radiologists are in a position to mold this new medical industry.

Increased in blood flow to ischemic myocardium caused by a new dopamine analog.

In the anesthetized, open-chest dog, intravenous infusion 8-13 microgram . kg-1. min-1) of a new dopamine analog 5,6-dihydroxy-2-methylaminotetralin hydrobromide (M-8) demonstrated potent coronary vasodilator properties. Blood flow to normal myocardium was increased an average of 53% above control flow values and this was associated with a decrease in coronary vascular resistance of 50%. The increase in blood flow was distributed uniformly to all portions of the myocardium (left ventricular free wall, right ventricular free wall, and septum). Subendocardial/subepicardial (endo/epi) flow ratios of the left ventricle, right ventricle, and septum were not significantly changed from control. In dog hearts subjected to acute, sudden occlusion of portions of the left anterior branch of the left coronary artery, M-8 produced a 93% increase in flow to the whole heart over postocclusion flow values. Flow to tissues of the heart made ischemic by the occlusive procedure in creased by an average of 94% during M-8 administration despite the fact that the occlusive ligatures remained in place. The vasodilation produced by M-8 was accompanied by a 22-24% increase in myocardial capillary surface area available for exchange of lipid-insoluble substances, fructose and sucrose. Hemodynamic changes associated with M-8 include a transient decrease in aortic pressure, but no change in heart rate, left ventricular (dP/dt)/P, or central venous pressure. Propranolol blocked the vasodilator activity of M-8. It was concluded that M-8 is a beta2-adrenergic receptor agonist having potent coronary vasodilator properties which also has the ability to open preexisting collateral blood flow channels and provide nutritive flow to ischemic, marginally ischemic, and normal myocardium. The cardiovascular actions of M-8 increase blood flow and oxygen delivery to the myocardium while decreasing the work and oxygen utilization by the heart, suggesting that it may have important antianginal characteristics.