Showing papers in "Investigative Radiology in 1968"

Echocardiography of the aortic root.

Abstract: The echo pattern of the aortic root is elicited by locating the typical echo of the mitral valve and then angulating the transducer medially and sometimes cephalically. The characteristic echo pattern of the aortic root consists of paired undulating signals three to five cm apart. These signals move

Precision and Accuracy of Bone Mineral Determination by Direct Photon Absorptiometry

Abstract: Bone mineral was determined using a radiologic absorptiometric method. The attenuation of a low-energy beam from a well-collimated radionuclide source (125I or 241Am) was measured using a collimated scintillation detectorpulse height analyzer system. The absorption of the photon beam by bone, as shown by this scanning method, was highly correlated with the weight of standard sections on excised bones (r = 0.97 to 0.99). Even scans on tissue covered cadaver forearms were highly correlated (r = 0.96) with the weight of underlying bone components and single scans on human ulnae were highly correlated (r= 0.96) with total ulna weight. The precision (2%) and accuracy (4 to 7%error) were the highest ever demonstrated for a radiologic method of bone determination and the large inaccuracies (more than 20 to 30% error) of older methods, which used photodensitometry of radiographs, were eliminated by the present method. Improved techniques allow even higher precision (1 to 2%) and accuracy (2 to 4%); therefore, the radionuclide absorption method is potentially useful for diagnostic, clinical and normative evaluation of appendicular skeletal mineralization where older photodensitometric methods cannot be used.

Renal hemodynamic effects of contrast media.

Abstract: Dye dilution measurements of renal blood flow were made before and immediately following selective injections (0.3 ml/kg) of contrast media into the renal artery of anesthetized dogs. The materials studied were 50% sodium diatrizoate, 60% meglumine diatrizoate and 60% meglumine iothalamate. NaCl solutions served as isotonic (0.9%) and hypertonic controls (4.5%). The data show a transient 10 to 20% decrease in renal blood flow after each of the contrast media and 4.5% NaCl, whereas physiologic saline produced no significant change. Aortic and renal artery pressure did not change significantly. It is concluded that injection of a hypertonic solution into the renal artery is sufficient to cause a lowering of renal blood flow. The bolus effect, sodium content and pH of the injected agents were eliminated as major determinants of this phenomenon. The extent to which the N-methylglucamine cation and the organic triiodinated molecule contributed to the response was not established. Measurements of appearance time and mean transit time revealed no evidence of major intrarenal shunting.

Effect of contrast media on renal extraction of PAH.

Abstract: The effect of contrast media on renal extraction of para-aminohippurate (PAH) was studied experimentally in dogs. Fifty per cent sodium diatrizoate, 60% meglumine diatrizoate and 60% meglumine iothalamate at a dose of 0.3 ml/kg body wt., delivered into the renal artery, produce a consistent fall in EPAH measured at 30 sec after injection with return to control levels several minutes thereafter. Similar volumes of physiologic saline resulted in no consistent change in EPAH. Mannitol, 26.5% and sodium chloride (hypertonic), 4.5% caused a diminished EPAH, comparable to the contrast agents, as did 12% meglumine diatrizoate (isotonic). The data indicate that the bolus effect, pH, and sodium content are not important in the genesis of the fall in EPAH. For the contrast media in current use, it appears that the N-methylglucamine cation and/or organic iodinated molecule is capable of inducing a decrease in EPAH, exclusive of the effect of hypertonicity, but it is likely that the latter plays a significant role. Further experiments are outlined to resolve this question.

Evaluation of a Television Image Processing System

Abstract: An image processing device using television and a scanning contrast enhancer has been evaluated by study of error rates of 13 observers viewing a standard series of chest x-rays A technique for creating artificial lesions which simulate parenchymal masses was developed, allowing known densities to be put in known locations in otherwise normal chest x-rays Detection was chosen as the criterion of performance An image processor can be considered useful if percentage error is decreased Observers were shown a series of 54 chest x-rays on a conventional viewbox and on the television monitors of the image processor A statistical comparison of error rates was used to evaluate the system The results show that the unprocessed television display degraded performance considerably The addition of contrast enhancement improved error rates but direct viewing was still superior to image processing A detailed study of error distribution showed that, using image processing, observers made considerably poorer judgments on lesions in the lower chest areas than in the upper In the upper areas there was a trend toward lower error rates with image processing than with direct viewing although a statistically significant difference could not be demonstrated The possible reasons for the error rate variations are discussed

Intracranial Anatomy Visualized in Vivo by Ultrasound

Abstract: Ultrasonic visualization in vivo of anatomic features of the ventricles, cisterns, sulci and major blood vessels of the brain and the internal surface configuration of the cranial vault of the rhesus monkey, using recently developed instrumentation; incorporating omnidirectional scanning, relief presentation and computer control of transducer positioning, data handling and display parameters, is illustrated. Results are presented in cross-sectional views of the tissue. In this study the acoustic energy had access to intracranial structures via an opening in the skull, but traversed the intact scalp, thus achieving separation of the problems associated with the traversal of bone from those concerned with identification of interfaces detectable by examining pulses alone. A resolution capability of 1 mm and an accuracy of localization of ±0.5 mm are achieved. All definitive echoes in the echograms are identified, and quantitative comparison of the anatomic information obtained with brain atlases is presented. The analytic determination of length scaling factors and relative angular orientation values for the subject's ultrasonically-viewed tissue cross sections and those of an atlas are also illustrated.