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Biomedical subjects

R L Siegle

Publications and source records attributed to R L Siegle.

At least 19 recordsLinked to original sources
PubMed1999

Changing roles: the radiologist in management.

RATIONALE AND OBJECTIVES: Radiologists have rarely had direct administrative control of the hospital departments in which they practice. Several years ago, the administration of the medical school at the University of Texas Health Science Center at San Antonio and its county-owned principal teaching hospital agreed to integrate the physician and administrative management of the radiology department in an attempt to improve operations and reduce expenses. This integration is a pilot plan that will eventually be extended to most departments. MATERIALS AND METHODS: The authors have collected data that measure department function for the seven quarters of physician management and compared these data with those of the previous four quarters prior to physician management. RESULTS: There are substantial increases in department activity, together with reductions in expenses and waiting time for procedures. These changes have occurred while overall hospital activity has decreased. Bench-marking studies show favorable comparison with comparable radiology departments. CONCLUSION: Radiologists can have an important effect on department operations when given the responsibility and authority for managing these affairs.

Academic Medical Centers↗
PubMed1998

Rates of disagreement in imaging interpretation in a group of community hospitals.

RATIONALE AND OBJECTIVES: Prospective studies of radiologists' interpretations of selected radiographs reported 20-40 years ago indicated error rates of 30% and higher. The authors retrospectively evaluated the interpretations of groups of radiologists and determined a range of rates of disagreement in interpretation. Quality assessment or recredentialing may add to the importance of such studies in the future. MATERIALS AND METHODS: Over a 7-year period, a team of radiologists reviewed imaging interpretations in the radiology departments of six community hospitals. Each review, which lasted about 3 days, included evaluation of the interpretations of a 3%-4% sample of the images read by the radiologists at these hospitals. Reading errors were quantitated and evaluated qualitatively. RESULTS: In a review of over 11,000 images read by 35 radiologists, the authors found a 4.4% mean rate of interpretation disagreement; only one radiologist had a mean rate above 8%. Qualitative analysis of the interpretation errors revealed a mean rate of 3.0% of errors that were considered to be below an acceptable standard of care. Radiologists whose errors included a relatively high proportion of false-positive findings tended to make relatively fewer total errors. CONCLUSION: Rates of disagreement for a broad range of studies that radiologists interpret in a community hospital setting appear to be far lower than earlier studies on selective radiographs indicated.

Diagnostic Errors↗
PubMed1996

Comparison of iodixanol with iohexol in excretory urography.

RATIONALE AND OBJECTIVES: We compared the safety and efficacy of iodixanol, a nonionic, dimeric, iodinated contrast agent, with that of iohexol, a monomeric agent, in adult excretory urography. METHODS: The study used a randomized, double-blind, parallel-comparison design to evaluate image quality, vital signs, laboratory values, and adverse reactions. Seventy-five patients from each of two centers were included. One third received iodixanol at 270 mg I/ml, one third received iodixanol at 320 mg I/ml, and one third received iohexol at 300 mg I/ml. The dose for every patient was 1 ml/kg of body weight. The radiographs were interpreted and evaluated for quality by the primary investigator at each center. There were no important differences among the three groups in terms of demographics. RESULTS: Evaluation of each phase of the radiographic study showed almost uniform good-to-excellent opacification, with no significant differences among the three agents. No significant differences existed for the three groups in terms of vital signs, hematology, blood and urine chemistry, and injection discomfort. There were no deaths or serious reactions during the study, nor was there a statistically significant difference among the number of adverse events for the three agents. CONCLUSION: Iodixanol at both 270 and 320 mg I/ml proved to be a safe and effective contrast material for intravenous urography. In this study, its profile was essentially indistinguishable from that of iohexol at 300 mg I/ml.

Adolescent↗
PubMed1994

New magnetic resonance imaging techniques for the detection of breast cancer.

The importance of contrast agents in enhancing diagnoses from magnetic resonance images has been established in numerous cases. However, the development of a potent tissue-specific contrast agent, as a sensitive probe for early detection and investigation of the physiological characteristics of a tumor, has not yet been realized in MR imaging (MRI). In nuclear scintigraphy the technique has been demonstrated; however, the poor spacial resolution inherent to the modality and the substantial dose of radioactivity administered to the patient has hindered its widespread use. This article will review the different classes of contrast agents in MRI, with special focus on the strategies involved in the development of targeted tissue-specific MRI contrast agents for the early detection of breast cancer. The features of a new class of contrast agents for targeted MR imaging will be described. Gadolinium-containing melanin polymers (GMP's) have been synthesized as MR contrast agents in our laboratory. These GMP's demonstrate significantly higher relaxivities than any other paramagnetic contrast agents reported; consequently, they are extremely effective contrast enhancing, imaging agents by themselves. The successful coupling of these potent GMP's to a monoclonal antibody specific for breast carcinoma, the 323/A3 monoclonal antibody, suggests that in vivo tissue-specific MR imaging, at the receptor level, will become feasible in the near future.

Breast Neoplasms↗
PubMed1993

Rates of idiosyncratic reactions. Ionic versus nonionic contrast media.

RATIONALE AND OBJECTIVES: Nearly 40 years ago, investigators began collecting data regarding idiosyncratic reactions to iodinated contrast agents. The rates of idiosyncratic reactions in patients receiving ionic contrast agents are compared with those found in patients receiving nonionic agents. METHODS: A comprehensive literature review was conducted. Retrospective and prospective studies were included, as well as recent analytical multistudy reviews. RESULTS: For conventional hypermolar agents, rates are estimated to be 5% and the rate of repeat reactions, greater than 20%. Large comparative studies conducted in the late 1980s found significantly lower rates of idiosyncratic reactions with the newer, nonionic agents than with conventional agents. The results of studies evaluating the use of routine administration of steroids before the use of ionic agents have been contradictory. Two analytical reviews of earlier research find fault with the methodology of most studies, but the reviewers supported the increased safety of nonionic agents. CONCLUSIONS: All iodinated contrast media have excellent safety records. Most evidence, however, demonstrates that nonionic agents are safer than ionic agents.

Contrast Media↗
PubMed1992

Iodixanol in excretory urography: initial clinical experience with a nonionic, dimeric (ratio 6:1) contrast medium. Work in progress.

The authors report the first clinical experience in the United States with the highly water soluble, nonionic dimer (6:1 ratio) contrast medium iodixanol (5,5'-[(2-hydroxyl-1,3-propanediyl)bis(acetylimino)]bis[N,N' - bis(2,3dihydroxypropyl)-2,4,6-triodo1,3-benzenedicarbooxa mide]). Iodixanol has an osmolality less than half that of monomeric, nonionic equivalent contrast media. Sodium, calcium, and magnesium ions were added to iodixanol to make the injected solution isosmotic to blood (290 mosm/kg H2O), with levels of free calcium and magnesium equivalent to levels found in the blood. Forty patients undergoing elective excretory urography were studied after bolus injection of doses of iodixanol with either 27 or 32 g of iodine. No adverse event or idiosyncratic reaction occurred. Seven patients felt coolness at the site of injection. Diagnostically adequate urographic examinations were routinely obtained with both doses. Further clinical investigation with iodixanol is warranted to determine if its beneficial chemical properties minimize both the chemotoxic and osmotoxic side effects and the disruption of physiologic functions that are seen with use of other ionic and nonionic contrast media.

Adult↗
PubMed1991

The use of iohexol in patients with previous reactions to ionic contrast material. A multicenter clinical trial.

Patients who have had prior reactions to iodinated contrast material have increased risk for repeat reactions. Nonionic contrast agents have been reported to reduce the risk of contrast reactions. A multicenter study was undertaken to determine the repeat reaction rate using iohexol. Two hundred ninety-one repeat reactors were included in the study, of whom one-third received premedication. Sixteen patients (5.5%) experienced repeat reactions; none was severe, and only one was more serious than the prior reaction. This is in contrast to the reported 16% to 44% repeated reaction rate for ionic agents. We conclude that iohexol is effective in reducing the occurrence of repeat reactions from the level observed with ionic agents without premedication. Iohexol appears to be as effective as ionic agents plus premedication in this high-risk group of patients.

Adult↗
PubMed1989

Findings on chest radiographs after prophylactic pulmonary surfactant treatment of premature infants.

Clinical trials are underway that use pulmonary surfactant replacement therapy in an attempt to prevent respiratory distress syndrome (RDS) in premature infants. This study was undertaken to determine the relationship between the clinical course of infants receiving prophylactic "first-breath" endotracheal surfactant and their initial posttreatment radiographs. The study population consisted of 80 premature infants of 24-32 weeks gestational age. All received 3 ml of calf-lung surfactant extract via endotracheal tube at birth. Anteroposterior chest radiographs taken within 1 hr of treatment were reviewed and correlated with gestational age, birth weight, days of endotracheal intubation, mean airway pressure, and days of oxygen requirement greater than 30%. Three distinct patterns of radiographic abnormality were encountered: typical RDS with hypoinflation, diffuse granularity, and air bronchograms (30%); central clearing of RDS (14%); and disproportionate clearing of RDS in the right lung (8%). No significant differences in ventilator requirements or clinical course were seen among these three groups. A fourth group (49%), whose posttreatment radiographs showed no evidence of RDS, required significantly less ventilatory support. Prophylactic first-breath surfactant treatment of premature infants occasionally results in radiographic patterns that are atypical for RDS. Familiarity with these patterns and their clinical significance will be important if surfactant augmentation becomes prevalent.

Humans↗
PubMed1988

The hemodynamic effects of the administration of ionic and nonionic contrast materials into the pulmonary arteries of a canine model of acute pulmonary hypertension.

Clinical studies have shown pulmonary and right ventricular hypertension to be important factors increasing the risk to patients during pulmonary angiography. This experiment was undertaken to define the hemodynamic changes induced by the administration of contrast material into the pulmonary arteries of dogs with embolic pulmonary hypertension, and to compare the effects of ionic and nonionic agents. Ten closed-chest dogs under light halothan anesthesia were subjected to pulmonary embolization with sephadex microspheres until severe pulmonary hypertension occurred and the cardiac output decreased to 50%-60% of the pre-embolization baseline. Intra-pulmonary injections of contrast material were performed in eight animals while hemodynamic indices were measured. Sodium methylglucamine diatrizoate induced severe, transient, hypotension associated with a large decrease in systemic vascular resistance and little change in the cardiac output. Hypotension is especially undesirable in the presence of pulmonary hypertension because it worsens the preexisting coronary ischemia and compromised right ventricular function. No elevation in mean pulmonary artery pressure was seen, and pulmonary vascular resistance decreased. Iohexol induced milder effects, perhaps because it exerts a less severe systemic vasodilatory effect and is not a negative inotrope. These findings suggest iohexol may be safer in the high risk patient, however, these data may not be directly applied to unanesthetized humans.

Acute Disease↗
PubMed1986

Excretory urography with iohexol: evaluation in children.

A multicenter clinical study was conducted using iohexol, a second-generation nonionic contrast medium, for excretory urography performed in 130 children. Doses of iohexol (300 mg iodine/ml) ranged between 150 and 660 mgI/kg (0.5 and 2.2 ml/kg). Iohexol was tolerated well, and no significant adverse reactions occurred. Sixty-five iohexol urograms were evaluated to determine the minimum dose for adequate visualization of the kidneys and collecting systems. A dose greater than 300 mgI/kg (1.0 ml/kg) always resulted in a urogram of diagnostic quality, while visualization was insufficient for diagnosis in 10% of studies done with doses of 150-300 mgI/kg (0.5-1.0 ml/kg). Another 65 iohexol urograms were compared in a blinded manner with a similar number of studies performed using iothalamate meglumine at comparable iodine concentration and dose. Visualization of calyces and pelvoinfundibular structures achieved with iohexol was rated better with statistical significance, but there was no difference in visualization of the renal parenchyma or ureters. Use of iohexol in excretory urography may be advantageous in children who are at greatest risk for an adverse reaction to contrast media or in those most likely to benefit from use of a low osmolality contrast agent.

Adolescent↗