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Conventional, unsharp masking, and slit-mask (combining slit radiography and unsharp masking) techniques were compared in a clinical nodule detection study in cancer patients who were at risk for metastatic lung disease. Unsharp masking improved detection rates for nodules located in poorly penetrated areas of the chest (25% vs. 52%), with no difference in detection rates for other areas of the image and no change in false-positive detection rates. Results with the slit-mask technique did not differ significantly from those obtained with conventional techniques. In general, the differences in nodule detection rates noted between different techniques in the clinical study were less than had been observed in earlier phantom-nodule detection studies. Possible reasons for these findings are discussed.

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The kinetics of iopanoate metabolism have been examined using a physiologic and pharmacokinetic model in rats. The kinetics of iopanoic acid concentration in blood and in eight other major tissue distribution compartments have been determined and fitted to computer-generated concentrations based on a well-established pharmacokinetic model. The results of these studies in nonfasted, conscious rats revealed that after gastric administration of the contrast material tissue concentrations never exceed 30 microgram/g even in the liver. In addition, a clear-cut enterohepatic circulation of the drug was noted in the experimental setting and had to be incorporated into a computer-generated model to account for differences in the predicted model as compared to the experimental data. Such data point out the importance of knowledge of pharmacokinetics of a drug for development of more appropriate dosage regimens of older compounds, theoretical design and testing of new compounds, or to explain clinically observed drug-related phenomenon.

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Thick bile may appear as a nonshadowing, dependent, echogenic layer within the gallbladder. In vivo sonographic imaging of the canine gallbladder showed that highly viscous, desiccated bile appeared echogenic and could potentially prevent imaging an enlarged gallbladder or dilated bile ducts. Selected clinical cases demonstrated that multiple nonshadowing calculi, pus, cholesterol crystals, and possibly abnormal mucous in the gallbladder may be sonographically indistinguishable from thick bile.

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Successful opacification of the gallbladder during oral cholecystography depends on adequate absorption of the contrast agent from the intestine. The present studies were undertaken to define the specific characteristics of the intestinal mucosa and the properties of the various contrast agents which determine their rates of intestinal absorption. The polarity of the compounds was established by determining the ratios of their distribution between bulk solvents (benzene and water). In addition, the maximum aqueous solubility of each compound was determined. Using in vivo cannulated segments of dog jejunum, apparent passive permeability coefficients were measured. From these data, the apparent maximal rate of intestinal absorption was calculated. The six cholecystopaques studied differed markedly in polarity as judged by their varying ratios of distribution between benzene and water. The permeability coefficients varied inversely with the polarity of the compounds. However, the incremental changes in the coefficients were considerably less than the corresponding changes observed in the partition ratios. The rates of absorption of the more polar contrast agents (tyropanoate, iopronic acid, and iocetamic acid) were greater than the less polar compounds (iopanoic acid, sodium ipodate, and calcium ipodate) under the conditions in which the resistance of the unstirred water layer is not rate limiting and where bile acid micelles are not present.

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The use of steerable catheter for replacement of a U-tube following its accidental removal in a patient with incurable cholangiocarcinoma is described. The simplicity of the technique, and the advantages for prevention of further surgery in these patients are emphasized.

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The criteria for the diagnosis of minimal obstructive jaundice (i.e., bilirubin less than 11.0 mg/100 ml) using sonography have not been established. A reliable diagnosis of obstructive jaundice with mild dilation of the bile ducts can be made by sonography when the "parallel channel" sign is seen. This sign is due to the simultaneous imaging of the dilated right or left main hepatic duct and the adjacent contiguous main portal vein branch. A prospective study of 86 patients showed this to be a highly reliable means of differentiating obstructive from nonobstructive jaundice when minimal duct dilation is present.

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Examples of diverticulitis of the colon associated with fistulae to the left hip, inferior mesenteric vein, and portal vein resulting in the demonstration of intrahepatic abscesses, the vermiform appendix, and the skin are presented with a review of the literature. A case of a fistula to the epidural space is included.

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The effect of fasting on gallbladder opacification during oral cholecystography was studied in 10 normal volunteers using 2 oral cholecystographic agents, iopanoic acid and sodium tryopanoate. Radiographs made 15 hours after ingestion of the contrast agents revealed good opacification of the gallbladder in all subjects when iopanoic acid was administered with a meal and when sodium tyropanoate was administered in the fasting state; in only 2 subjects when iopanoic acid was given in the fasting state; in 3 when given in the fasting state with ox bile; and in 3 when sodium tyropanoate was given with a meal.

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