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Biomedical subjects

K J Taylor

Publications and source records attributed to K J Taylor.

At least 73 records · Page 4Linked to original sources
PubMed1991

Ultrasound imaging of pancreatico-duodenal transplants.

A preliminary investigation of the role of ultrasound, including color and duplex Doppler, was performed in recipients of cadaveric pancreatico-duodenal transplants. Twenty such examinations were done on three patients. Three different complications were noted: rejection, pancreatitis, and peripancreatic abscess. The mean normal resistive index (RI) was 0.71 +/- 0.12. The normal allograft anteroposterior (AP) dimension ranged from 1.5 to 2.0 cm. Intraparenchymal and main feeding vessels were demonstrated easily. RI calculations alone were not helpful in diagnosing graft rejection. However, this diagnosis can be made using a new biochemical marker, serum anodal trypsinogen. We conclude that when used in conjunction with a reliable biochemical marker for rejection (serum anodal trypsinogen), ultrasound, including color and duplex Doppler, provides an important adjunct for the rapid, inexpensive, and complete evaluation of patients with pancreatico-duodenal transplants.

Cadaver↗
PubMed1991

New techniques in the diagnosis of ectopic pregnancy.

Pulse and color Doppler studies have provided a potent method for the investigation of functional changes and pathologic conditions in the female pelvis, both in the gravid and nongravid state. Combined with transvaginal sonography, which optimizes the imaging capability, the transvaginal color Doppler ultrasonography provides a new major modality for reproductive flow studies that have hitherto been possible only in animal models because of the invasiveness of the technique. Apart from these potential applications of the technique for research purposes, however, transvaginal imaging and the Doppler technique have become major modalities in all patients suspected of ectopic pregnancy at our institution.

Fallopian Tubes↗
PubMed1991

Evaluation of postprandial hyperemia in superior mesenteric artery and portal vein in healthy and cirrhotic humans: an operator-blind echo-Doppler study.

In an operator-blind design, we used an echo-Doppler duplex system to examine superior mesenteric artery and portal vein hemodynamics on two consecutive mornings in 12 fasting cirrhotic patients and 12 matched controls, randomized to a standardized 355 kcal mixed-liquid meal vs. water. Cross-sectional area and mean velocity were recorded from the portal vein and superior mesenteric artery at 30 min intervals, from 0 min to 150 min after ingestion. Flows were calculated. Pulsatility index, an index related to vascular resistance, was obtained for the mesenteric artery. Baseline flows did not differ between cirrhotic patients and control patients, but pulsatility index was reduced in the cirrhotic subjects. Maximal postprandial hyperemia was attained at 30 min. Cirrhotic patients showed a blunted hyperemic response to food. In normal controls, portal vein area increased significantly after the meal from 30 min to 150 min, whereas in cirrhotic patients a significant difference occurred only at 30 min. Pulsatility index in both groups was significantly reduced after eating, and this reduction persisted up to 150 min. No changes after ingestion of water were observed. Echo-Doppler was very sensitive in detecting postprandial splanchnic hemodynamic changes and differences between cirrhotic patients and normal subjects. Mesenteric artery pulsatility index was more sensitive than flow in detecting baseline hemodynamic differences. In cirrhotic patients, portal postprandial hyperemia was mainly related to the increase in mean velocity.

Aged↗
PubMed1990

Observer variability in echo-Doppler measurements of portal flow in cirrhotic patients and normal volunteers.

The intraobserver and interobserver variability in measuring the portal vein flow by the echo-Doppler technique was evaluated in a blind controlled study. A total of 22 cirrhotic patients and 14 normal volunteers were examined by two skilled operators using duplex Doppler within a period of 1-3 mo (6 cirrhotics and 7 normal volunteers by both observers). Area, mean velocity, and flow were measured (4 measurements: A, B on day 1; C, D on day 2). The intraclass correlation coefficient was used to assess both the statistical and clinical significance of intraobserver and interobserver agreement for the measurements of these three parameters. The level of intraobserver agreement for each parameter on normal subjects and cirrhotics was obtained from the two measurements on the same day and from the two measurements at the same time on consecutive days. Overall agreement between the four measurements was also calculated. Levels of interobserver agreement were obtained by calculating separately the intraclass correlation coefficient from each of the four pairs by measurements made on the same subject by the two observers over the same period of 2 days. The coefficient of variation was also used to compare the variability in these measurements. Overall, intraobserver agreement on normal subjects varied from good to excellent for observer 1, and from fair to good for observer 2. On cirrhotic patients, observer 1 was excellent at all times for all parameters. Observer 2 had lower intraclass correlation coefficient values, especially for velocity on consecutive days. For the best of the two observers on the portal flow, the coefficient of variation in cirrhotic patients ranged from 2%-30% with a mean +/- SEM of 12% +/- 4%. No acceptable interobserver agreement was found between the two observers in either of the two samples of subjects. These results support the use of this technique mainly for the determination of rapid and large changes in portal hemodynamics within a short period of time. The technique seems to have low precision in monitoring chronic changes in portal hemodynamics.

Adult↗
PubMed1990

Doppler US. Part I. Basic principles, instrumentation, and pitfalls.

This article reviews some of the important physical principles involved in Doppler ultrasound (US) in the context of modern diagnostic US technology. Methods of quantitative Doppler US data analysis used to distinguish normal hemodynamics from disturbed flow conditions are discussed with the aid of numerous examples. Definitions and measurement techniques are presented for determining from Doppler signals such indicators of arterial disease as velocity, volume flow rate, flow impedance, and pulsatility. Spectral analysis and its utility in Doppler signal analysis are described. The various options available on modern Doppler US instrumentation are reviewed, including duplex Doppler techniques and color Doppler flow mapping. Finally, the authors discuss artifacts and pitfalls likely to be encountered in the routine clinical use of Doppler US for diagnostic purposes.

Doppler Effect↗
PubMed1990

Doppler US. Part II. Clinical applications.

Duplex and color Doppler ultrasound (US) are noninvasive techniques capable of providing much information about the condition of blood vessels and flow within them throughout the body. Doppler US provides more than noninvasive angiography. Besides assessment of blood vessel patency and direction of flow, analysis of the flow velocity waveform allows quantitation of arterial stenoses and evaluation of both physiologic and pathologic changes in impedance. In certain situations, Doppler US can aid in tissue characterization and estimation of absolute flow volume. Color Doppler flow imaging may both expedite and clarify the duplex Doppler examination. In addition, color Doppler imaging can demonstrate flow orientation and improve the identification of turbulence and soft plaque. Color and duplex Doppler US are complementary, with color Doppler techniques providing spatial orientation and pulse Doppler techniques providing the time-velocity spectrum for quantitation.

Humans↗
PubMed1990

Hepatoblastoma: detection of tumor vascularity with duplex Doppler US.

The evaluation of pediatric abdominal masses commonly includes computed tomography, ultrasound (US), and, more recently, magnetic resonance imaging. A previous study suggested that duplex US is of use in further tissue characterization of hepatic lesions in adults. The authors describe the Doppler signals arising from hepatoblastomas in three infants. Peak systolic Doppler frequency shifts in the neoplasms of these three patients were all equal to or greater than 4 kHz, well above the normal range for hepatic arteries. Each neoplasm also exhibited antegrade diastolic flow. The detection of high Doppler frequency shifts associated with neovascularity may prove useful in future evaluation of pediatric hepatic masses.

Carcinoma, Hepatocellular↗
PubMed1990

Pseudogestational sacs: Doppler US differentiation from normal or abnormal intrauterine pregnancies.

Doppler ultrasound (US) evaluation of 40 empty intrauterine sac-like structures was performed to evaluate the ability of this technique to permit distinction between intrauterine pregnancy and pseudogestational sac associated with ectopic pregnancy. Proof of the location of the pregnancy was available in all cases. There were 31 intrauterine pregnancies, of which 23 were missed or incomplete abortions and eight were early normal pregnancies. With an insonating frequency of 3 MHz, the average frequency shift detected from these intrauterine pregnancies was 1.7/1.0 kHz (peak systolic/end diastolic ratio). Nine pseudogestational sacs were evaluated, of which seven demonstrated no flow and two demonstrated minimal flow that averaged 0.4/0.1 kHz. Defining intrauterine peritrophoblastic flow as a peak systolic frequency shift of 0.8 kHz or greater (equivalent to 21 cm/sec with an angle of 0 degree) correctly classifies 26 of the 31 intrauterine pregnancies and all of the nine pseudosacs. The sensitivity of the Doppler technique for the detection of intrauterine pregnancies was 84%, and the specificity was 100%.

Abortion, Incomplete↗
PubMed1990

Renal masses: characterization with Doppler US.

The vascularity of indeterminate renal masses in 70 patients was investigated prospectively with duplex ultrasound. The peak-systolic Doppler shift frequency obtained from the renal mass was utilized to attempt distinction between benign and malignant lesions. With use of the criterion of a peak-systolic Doppler shift frequency of 2.5 kHz or greater as evidence of neovascularity, 26 of 37 malignant lesions demonstrated tumor signals (70% sensitivity). Thirty-one of 33 benign lesions lacked tumor signals (94% specificity). Both of the false-positive lesions were infections with inflammatory masses, with peak frequencies of 3.0 and 3.7 kHz. Tumor vascularity in most malignant renal mass lesions gives rise to abnormal, high-frequency, Doppler-shifted signals that can aid the differential diagnosis of renal masses.

Carcinoma, Renal Cell↗
PubMed1990

Feasibility spectrum for Doppler flowmetry of splanchnic vessels. In normal and cirrhotic populations.

The calculation of absolute blood flow by Doppler flowmetry requires adequate visualization of a vessel in both transverse and longitudinal planes and an insonating angle less than 60 degrees. The percentage of the splanchnic vessels in a given population in which these criteria could be fulfilled (ie, the feasibility spectrum) is not known. To identify this spectrum in our patient sample, 100 consecutive nonselected patients (58 female, 42 male) and 34 cirrhotics (31 male, three female) were prospectively studied. In addition, from the group of 42 nonselected patients, 31 males with no evidence of liver disease were matched for age, weight, and height with the 31 male cirrhotics. The echo-Doppler feasibility (EDF; success percentage) was determined for the hepatic, superior mesenteric, and splenic arteries and portal, superior mesenteric, and splenic veins. In the nonselected sample, the EDF varied from 86% for the portal vein to 60% for the superior mesenteric artery. In cirrhotics, the EDF ranged from 88% for portal vein to 29% in splenic artery. The total EDF for the nonselected sample (68%) was significantly higher than the EDF for cirrhotics (54%; P less than .001). Physical factors (weight, age, height, and sex) affected the EDF in the nonselected patient sample but not in cirrhotics. We conclude that analysis of EDF of splanchnic vessels in these groups clearly demonstrates that the composition of the patient sample has an important bearing on the feasibility spectrum of Doppler study. Female subjects who are thin, young, and short and lighter male patients are better candidates for abdominal Doppler flowmetry.

Adolescent↗
PubMed1989

Tissue characterisation.

Many attempts have been made in the past 20 years to derive more quantitative information relating to tissue structure from the returned ultrasound beam. The qualitative method of characterising tissue from visual inspection of the image with interpretation of artifacts remains the most successful one. Potential quantitative methods include estimation of: attenuation, speed of sound, acoustic impedance, scattering characteristics, non-linearity of propagation, tissue motion and the specific perfusion patterns detected by the Doppler shift. The authors conclude that only image inspection and Doppler techniques have shown progress toward the concept of telehistology expressed in the 1970s. Further advances in quantitation of the Doppler signals and development of contrast agents appear promising for the future.

Humans↗
PubMed1989

Pseudoportal Doppler signal in the partially obstructed inferior vena cava.

The Doppler spectrum of the normal inferior vena cava (IVC) shows a majority of flow toward the right atrium, with wide variations in flow velocity and direction owing to effects of the cardiac and respiratory cycles. Seventeen subjects underwent duplex sonography: nine children after liver transplantation, two children with right upper quadrant neuroblastoma, and six healthy control subjects. In six children the spectrum obtained from the IVC bore a strong resemblance to the unidirectional, low-velocity, continuous-flow pattern associated with the portal vein; these children included two children with biliary atresia and cirrhosis, two liver transplant recipients, and two children with IVC compression by neoplasm. In healthy children and adults, a pseudoportal Doppler signal in the IVC can be generated by subcostal right upper quadrant compression. The pseudoportal IVC appears to be a sign of partial IVC obstruction. Knowledge of this potential pitfall and meticulous morphologic imaging can help prevent mistaking the IVC for a patent portal vein.

Adult↗
PubMed1989

Ectopic pregnancy: duplex Doppler evaluation.

Of 398 patients in whom there was a clinical suspicion of ectopic pregnancy, 96 (24%) were found to have the condition. Of the 96, 70 underwent duplex Doppler imaging. A viable ectopic fetus was seen in 10 of 70 (14%), and an extrauterine sac without an identifiable fetus was seen in an additional 27, giving a sensitivity for imaging alone of 53%. Fetal heart activity was detected with Doppler in 13 (19%). High-velocity flow, which suggested the presence of an ectopic pregnancy, was detected in 38 of 70 (54%) patients (total preoperative sensitivity, 73%). In the 91 patients who did not have an ectopic pregnancy, duplex Doppler imaging of the intrauterine contents alone allowed an ectopic pregnancy to be excluded in 29 (32%) on the first examination and in a further 21 on the second scan (specificity, 55%). Nine vascular adnexal masses were falsely considered to be ectopic pregnancies (specificity, 90%). The positive predictive values were 47% for imaging alone and 85% for Doppler. The negative predictive values were 60% for imaging alone and 81% for Doppler.

Adult↗