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Biomedical subjects

B A Carroll

Publications and source records attributed to B A Carroll.

115 records · Page 7Linked to original sources
PubMedDate not supplied

Sonographic estimates of vein size in the lower extremities: subjective assessment compared with direct measurement.

PURPOSE: We studied whether subjective impression of vein size is a valid means of assessment during sonographic evaluation for deep vein thrombosis. METHODS: Diameter was assessed at 5 predetermined venous segments on 975 legs of 721 patients referred for evaluation for lower extremity deep vein thrombosis. The sonographer recorded a subjective assessment of whether the venous segment was enlarged, normal, or narrowed based on a visual impression of sonographic images obtained without compression. This subjective impression was then compared with the absolute measurements of vein diameter and vein diameter:artery diameter ratio at each segment. RESULTS: A significant correlation was found between the subjective characterization of vein size as enlarged, normal, and narrowed and both the absolute vein diameter and the vein:artery ratio at all 5 segments. CONCLUSIONS: Vein size can be reliably categorized by the subjective impression of experienced sonographers. Therefore, actual measurement of the vein diameter is not necessary in the evaluation for deep vein thrombosis in the majority of patients.

Analysis of Variance↗
PubMedDate not supplied

Color flow and image-directed Doppler ultrasound evaluation of iatrogenic arteriovenous fistulas in the groin.

Color flow image-directed Doppler ultrasound was used to image 9 iatrogenic arteriovenous (AV) fistulas in the groin following femoral artery catheterization. Characteristic findings in the color images and spectral waveforms seen in most patients included (1) visible connection between the artery and vein (8 cases); (2) a multicolored speckled mass at the fistula site (7 cases); (3) spreading of color pixels into the extraluminal soft tissues (7 cases); (4) high diastolic flow in the arterial waveform proximal to the fistula site (7 cases); (5) decreased flow in the artery caudal to the fistula (5 cases); and (6) high velocity turbulent flow, sometimes with a pulsatile component, in the vein near the fistula (9 cases). The authors conclude that color flow imaging is useful in differentiating an AV fistula from other complications of femoral artery catheterization, such as pseudoaneurysm or hematoma.

Adult↗
PubMedDate not supplied

Detection of deep venous thrombosis: prospective comparison of MR imaging and sonography.

Seventy-five patients (41 women and 34 men, 20-85 years old) with clinically suspected deep venous thrombosis (DVT) were examined with MR imaging and sonography. In 26 patients, the final diagnosis was acute femoropopliteal DVT. The sensitivity of MR imaging for detecting this disease was 100% with a 95% confidence interval (CI) of 87-100%; the specificity was 100% with a CI of 92-100%; and the accuracy was 96% with a CI of 89-99%. The correspond-ing sensitivity of sonography was 77% with a CI of 53-92%; the specificity was 98% with a CI of 89-100%; and the accuracy was 83% with a CI of 72-90%. In four of the 75 patients, MR images revealed thrombus of the pelvis (n = 1) or calf (n = 3) without femoropopliteal involvement. The estimated prevalence of isolated calf and/or pelvic DVT was 5% with a CI of 1-13%. MR imaging is significantly more sensitive (P = .02) and accurate (P < .01) than sonography in the detection of lower extremity DVT, but there was no difference in the specificity of MR imaging and that of sonography (P = .31).

Adult↗
PubMedDate not supplied

Gelatin encapsulated nitrogen microbubbles as ultrasonic contrast agents.

Gelatin encapsulated nitrogen microbubbles were effective ultrasonic contrast agents in in vitro phantom and in vivo rabbit V2 carcinoma studies. Intra-arterial injection of 80-micrometer gelatin encapsulated nitrogen microbubbles appeared to improve tumor visualization by rim enhancement, which persisted for several minutes.

Aerosols↗
PubMedDate not supplied

The harmful effects of aqueous contrast agents on the gastrointestinal tract: a study of mechanism and means of counteraction.

The effect of mildly and strongly hypertonic solutions on intestinal tone and motility was tested with aqueous contrast solutions and with mannitol as a control in 15 dogs. These experiments were repeated in animals premedicated with atropine sulfate and/or methysergide maleate. Intestinal motility was recorded on serial x-ray films. Tone and motility were estimated by variations of intestinal caliber and rate of transit of contrast solution, respectively. The results obtained contradict the currently accepted mechanism of action of iodinated contrast media on the intestinal tract, which assumes that the effect is osmotic like that of a saline laxative. Solutions of different osmolarity produce hyperperistalsis of the same magnitude. This effect begins rapidly after the onset of gastric emptying and much sooner than a significant osmotic fluid shift occurs. Atropine sulfate and methysergide maleate (serotonin blocker), when given individually, are incapable of completely inhibiting hyperperistalsis induced by hypertonic solutions. However, when these agents are given in combination, motility is completely inhibited. The evidence supports a serotonin role in the hyperperistalsis induced by hypertonic solutions, partly by direct action of serotonin on the smooth muscle cells and partly by indirect action on the intramural cholinergic ganglion cells. This concept offers a possible means of eliminating one of the adverse effects of aqueous contrast media on the gastrointestinal tract.

Animals↗
PubMedDate not supplied

MR imaging with surface coils in primary hyperparathyroidism.

The use of magnetic resonance (MR) to preoperatively evaluate patients with primary hyperparathyroidism was assessed using a 1.5 T system and surface coil reception. Twenty-five patients with primary hyperparathyroidism were studied before surgical exploration. Axial images, 5 mm thick, were obtained from the thyroid cartilage to the sternal notch. Both T1-weighted [short repetition time (TR), short echo time (TE)] and T2-weighted (long TR, long TE) spin echo sequences were performed in most cases. Parathyroid adenomas typically demonstrated greater signal than surrounding tissues on T2-weighted sequences, yet demonstrated signal intensity that was less than or equal to normal thyroid tissue on T1-weighted sequences. Using these criteria, MR correctly identified 17 of 20 surgically proven parathyroid adenomas in the neck. Magnetic resonance appeared less sensitive in two patients with parathyroid hyperplasia, identifying only one of six hyperplastic glands. We conclude that MR with surface coils provides high contrast, anatomic delineation of the neck and is useful for preoperative localization of parathyroid tumors.

Adenoma↗