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Biomedical subjects

L Hutton

Publications and source records attributed to L Hutton.

35 records · Page 2Linked to original sources
PubMed1984

Oleothorax: expanding pleural lesion.

Oleothorax is a method of therapy for pulmonary tuberculosis that was largely abandoned in the 1950s. Its purpose was to cause collapse of the adjacent lung by mechanical means. In the absence of either reactivation of tuberculosis or the development of an empyema, an oleothorax may expand to such an extent as to cause respiratory distress and require removal. The mechanism for this expansion is the stimulation of pleural fluid production by the oil. It is also thought that it may act in a manner similar to a chronic subdural hematoma. This expansion may occur after the oleothorax has been stable for many years, and frequently it is asymptomatic. Four patients were reviewed: one in whom the expansion was so great as to cause respiratory distress, one in whom the enlargement was less rapid and asymptomatic, and two with longstanding oleothoraces in whom the enlargement was more subtle.

Female↗
PubMed1984

Computed tomographic diagnosis of distal radio-ulnar joint disruption.

Distal radio-ulnar joint dislocation may be a difficult diagnosis using standard wrist radiographs. We report a patient in whom standard films did not convincingly demonstrate a dislocation which was well seen with computed tomographic scans of the wrist. Computed tomography may be the method of choice for demonstrating distal radio-ulnar joint dislocation when this is suspected clinically but not seen with standard films.

Adult↗
PubMed1984

Cardiac pacemaker leads--a radiographic perspective.

To comment on the adequacy of positioning of single- or dual-chambered pacemaker leads requires some knowledge of the type of electrode used. Earlier leads relied upon force transmitted along the body of the lead to the electrode-myocardial interface to maintain positioning. These relatively large stiff leads were placed almost exclusively near the apex of the right ventricle to prevent dislodgement. More recent leads incorporate mechanical fixation devices to maintain position, commonly either tined or screw-in electrodes (or variations of these) representing passive and active fixation mechanisms respectively. The tines are not radiopaque; the screw-in devices are metallic. Such newer electrodes permit the use of smaller, more flexible leads, reduce the necessity for precise positioning, and reduce the frequency of lead dislodgement.

Adult↗
PubMed1983

Unusual presentations of benign intrathoracic neurogenic tumors.

Three patients with benign neural sheath tumors (two neurofibromata, one schwannoma) are reported here. One is known to have von Recklinghausen's disease. All presented in an atypical manner providing a diagnostic challenge. The series comprises one patient with a schwannoma of the left vagus nerve, one with submucosal neurofibromata of the lower one-third of the esophagus and one with an endobronchial neurofibroma. The plain film findings suggested aortic aneurysm, esophageal varices and endobronchial carcinoma respectively.

Adult↗
PubMed1983

Pitfalls in ultrasonographic diagnosis with fatty infiltration of the liver.

Problems in ultrasonography in patients with fatty infiltration of the liver include the possible misinterpretation of small, solid, focal lesions within the liver as being cystic; attributing the relative sonolucency of the pancreas to pancreatitis in the absence of pancreatic disease; and an inability to display normal right renal anatomy using the liver as a "window." Recognition of these problems and careful attention to equipment settings and scanning techniques should prevent errors.

Adult↗
PubMed1983

The non-visualized gallbladder by ultrasonography implications and differential diagnosis.

The findings in 42 consecutive patients in whom the gallbladder or its lumen were not visualized ultrasonographically were reviewed retrospectively for evidence of gallbladder disease. The series contains two groups of patients--the larger comprised 32 patients in whom the gallbladder was represented only by a dense echogenic focus, with acoustic shadowing, in the right upper quadrant, thought to be due to cholelithiasis in a small contracted gallbladder. The accuracy of this finding in predicting gallbladder disease was 96%. The smaller group consisted of eight patients in whom the gallbladder was not visualized. In seven patients with follow-up, the accuracy of this finding in predicting gallbladder disease was only 71%. Dense echoes in the right upper quadrant were not always due to cholelithiasis but to emphysematous cholecystitis in one patient, porcelain gallbladder in a second, and agenesis of the gallbladder in a third.

Calcinosis↗
PubMed1982

Halo around the gallbladder--a prognostic sign?

The implications of the finding of a sonolucent zone around the gallbladder, characterized on ultrasonography by loss of definition of the outer (serosal) aspect of the gallbladder wall with a moderately well defined inner (mucosal) surface in patients with signs and symptoms of acute cholecystitis, are described. Of the nine consecutive patients with this finding, five were found to have gangrenous cholecystitis and/or perforation of the gallbladder at surgery. Four of these patients were operated upon within 24 hours of the ultrasound study, one 19 days later. The pathologic basis for this finding is thought to represent massive thickening of the gallbladder wall, with a possible contribution from adherent edematous omentum in the region of the fundus of the gallbladder. Thus this finding of a sonolucent halo about the gallbladder was important in our series, being frequently an indicator of acute cholecystitis complicated by gangrene with or without perforation of the gallbladder.

Acute Disease↗
PubMed1981

Pseudomembranous colitis in renal transplant recipients; plain film findings.

The plain abdominal film findings in nine renal transplant patients with pseudomembranous colitis were characteristic of but not specific for this entity and most commonly showed "thumb-printing" reflecting submucosal edema (five patients) and a persisting localized segmental ileus in the colon (five patients). Based on the plain film findings, the differential diagnosis will include the acute stages of ulcerative colitis, granulomatous colitis, ischemic colitis and other inflammatory colitides, but the radiologist is in a position to suggest the correct diagnosis in the appropriate clinical setting. A barium study of the colon is not indicated, as diagnosis is usually accomplished by endoscopy. The etiology of this colitis has recently been shown to be a cytopathic toxin of the anaerobic bacterium, Clostridium difficile.

Adult↗
PubMed1979

Effects of response-independent negative reinforcers on negatively reinforced key pecking.

Previous research has shown that presenting response-independent positive reinforcers reduces the response rate of an operant maintained by positive reinforcement. The present experiment investigated a similar effect using shock-free time as a negative reinforcer. Brief shocks were delivered in the presence of a distinctive stimulus, and pigeon's key pecks were reinforced by the occasional presentation of a 2-minute shock-free period. Extra 2-minute shock-free periods were added independently of behavior. For each of three pigeons, response rate during shock-on periods declined with added shock-free periods; the more frequently the extra shock-free periods occurred the greater the decline in response rate. This outcome is predicted by extending the Law of Effect to include negative reinforcement.

Journal Article↗
PubMed1979

Percutaneous pulmonary aspiration biopsy using the Chiba needle.

The Chiba needle was used for percutaneous needle aspiration of lung lesions in 35 patients. Two separate needles were used for each patient at the same sitting. The aspirate was true positive for malignancy in 23 patients and true negative for malignancy in eight patients. Two aspirates were false negative for malignancy and two aspirates, negative for malignancy, were classified as inconclusive due to inadequate patient follow-up. The overall accuracy rate was 94%. Six patients had small pneumothoraces but only one required a chest tube. Appreciable hemoptysis did not occur. The Chiba needle provided an adequate aspirate for cytologic diagnosis. The complication rate using two needles appears to be entirely acceptable.

Adult↗
PubMed1978

Matching with a key-peck response in concurrent negative reinforcement schedules.

In the absence of responding, pigeons were shocked under a variable-time schedule. Responses on either of two keys occasionally produced one minute of shock-free time. That is, pigeons' key pecks were reinforced with shock-free time under concurrent variable-interval schedules. The relative frequency of access to the one-minute shock-free periods was systematically manipulated. Pigeons tended to match both relative response rate and proportion of time spent on each key to the relative frequency of the shock-free periods. A best-fit linear regression equation accounted for over 95% of the variance in both relative response rate and time allocation. The data paralleled closely the results of concurrent schedules of positive reinforcement. These findings are consistent with a description of reinforcement as a transition to a higher-valued situation and suggest that common laws govern choice for both positive and negative reinforcement.

Journal Article↗
PubMed1976

Integrated delays to shock as negative reinforcement.

Rats were shocked at the rate of two per minute until they pressed a lever. In Experiment I, shocks were delivered at variable-time intervals averaging 30 sec; in Experiment II, shocks were delivered at fixed-time intervals of 30 sec. A response produced an alternate condition for a fixed-time period. The shock frequency following a response, calculated over the whole alternate condition, was two per minute. The pattern of shocks in the alternate condition was controlled so that the first shock occurred at the same time as it would have occurred had the response not been emitted; the remaining shocks were delayed until near the end of the alternate condition. Bar pressing was acquired in both experiments. This finding is not explained by two-factor theories of avoidance and is inconsistent with the notion that overall shock-frequency reduction is necessary for negative reinforcement. The data imply that responding is determined by the integrated delays to each shock following a response versus the integrated delays to shock in the absence of a response.

Journal Article↗