Biomedical subjects
Publications and source records attributed to R G Jost.
A computer-assisted system has been devised to provide objective measurements of the diagnostic efficacy of CT of the body. The diagnostic efficacy of CT is compared with that of UGI examinations for 574 patients. The potential usefulness of this system in cost effectiveness studies, diagnostic efficacy studies, and clinical efficacy studies is examined.
Computed tomography (CT) is a highly accurate method of detecting and clarifying the nature of space-occupying lesions within the liver. Obstructive (surgical) jaundice can be differentiated from nonobstructive (medical) jaundice very accurately using CT scanning; when obstruction is present, its level and cause can often be diagnosed. CT is not a sensitive method of detecting hepatocellular disease. Sources of error in CT scan interpretation are analyzed.
Retroperitoneal hemorrhage can be directly documented by computed tomography. In patients with confusing clinical findings, CT scans may provide a definite diagnoses and direct appropriate therapy. This contention is supported by seven illustrative cases.
All operating CT installations in the United States were surveyed in January 1976; data were obtained from 98 of 140 installations. Although the respondents represented 80 head units and 18 head and body units, the overwhelming experience was with head CT studies. CT equipment was installed in an average of 1.3 months, operated 64 hr per week and examined 50-55 patients per week. A downtime of 7 hr per week was reported. Radiologists are responsible for 92 of 98 installations, and 90% of installations are in a hospital. The scheduling delay averages 1.6 days for inpatients and 11.5 days for outpatients. The delay is increasing in many installations. The estimated total yearly technical cost is +325,000-+371,000 per installation, depending upon patient volume. The estimated technical cost per patient (when 50 patients per week are studied) compares favorably with the estimated net revenue per patient from the average basic technical charge (+130 compared to +138). A separate billing method is used by 59% of installations, and 76% have an extra charge for contrast injection and additional studies; 60% of patients receive contrast. The reported total charges during the last 3 months were higher in installations that (1) charged additionally for contrast, (2) were located in outpatient settings, and (3) had nonradiologists as the responsible physician. It should be emphasized that most CT installations are not independent activities and should be considered an integral part of a diagnostic radiology department or office.
Single unit recordings were obtained from 103 precentral cortical cells whose activity was related to an alternate wrist flexion-extension task in monkeys. Although the task was carried out under different loads only a weak relationship between cortical cell firing rates and static force levels was observed for force in one direction. A large change in firing rate occurred, however, when direction of force shifted as a result of a change in the predominant activity between extensor and flexor muscles. The firing patterns of the observed cortical cells suggest that the motor cortex is involved in specifying the muscles to be activated for a given movement and not the level of force to be produced by these muscles. During the dynamic phase of the movement little change in cortical cell firing pattern was observed for large changes in the rate of change of force. Motor cortex cell firing patterns appear to be unrelated to the large values of rate of change of force seen in this experiment.
A comparison of several reported methods for detection and quantitation of left-to-right shunts by radionuclides was performed in 50 children. Count ratio (C2/C1) techniques were compared with the exponential extrapolation and gamma function area ratio techniques. C2/C1 ratios accurately detected shunts and could reliably separate shunts from normals, but there was a high rate of false positives in children with valvular heart disease. The area ratio methods provided more accurate shunt quantitation and a better separation of patients with valvular heart disease than did the C2/C1 ratio. The gamma function method showed a higher correlation with oximetry than the exponential method, but the difference was not statistically significant. For accurate shunt quantitation and a reliable separation of patients with valvular heart disease from those with shunts, area ratio calculations are preferable to the C2/C1 ratio.
This report presents a case of severe dysfunction of an improved Model 104 Beall valve secondary to disc wear. This type of valve failure may be extremely difficult to detect by auscultation, echocardiography, or fluoroscopic examination. Prosthesis failure with resulting mitral insufficiency should be considered in any patient with a Teflon disc Beall mitral valve in whom there is unexplained clinical deterioration.
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Coronal CT is the definitive procedure for radiologic evaluation of sinonasal inflammatory disease, yet many clinicians rely on the less expensive plain film sinus series. We designed a limited four slice coronal CT and prospectively compared it with conventional coronal CT and plain film sinus series in 25 patients to determine whether a limited CT examination is a suitable alternative to these other radiologic procedures in screening for sinonasal inflammatory disease. The presence, amount, and location of mucous membrane disease, opacification, air fluid levels, retention cysts, erosions, and anomalies were recorded for each technique. The limited CT agreed with the complete CT in 82% of the 200 sinus compartments reviewed. Localized disease, usually mucosal thickening of 3 mm or less and missed on the limited CT, but detected on the complete CT, accounted for 22 of 36 errors of interpretation. Underestimation of mucosal disease, usually 2 mm or less, accounted for eight errors and misinterpretation of partial volume effect for three errors. Using complete CT a s the established standard, plain film missed 37 instances of disease detected on the limited CT; 73% involved an error of mucosal thickening 4 mm or greater. A limited coronal CT of the paranasal sinuses offers a potentially lower cost alternative to complete CT in screening for sinonasal inflammatory disease. It is more accurate than plain film series. Localized disease and osteomeatal disease is underestimated with the current protocol, and so a limited CT should not be used for evaluating potential cancer patients or for surgical planning.
Digital conventional tomography may be performed using a digital vascular imaging (DVI) system. Digital synthesis and removal of blur from multiple tomographic sections were accomplished by computer with a single motion of the source-receptor (x-ray tube-image intensifier) complex. Tomographic application of a DVI system was evaluated by phantom simulations.