Biomedical subjects
George A Taylor
Publications and source records attributed to George A Taylor.
Removal of dust and scratches from electronic image files.
Explore the source record for details and available documents.
Correlation of contrast-enhanced power Doppler sonography and conventional angiography of abduction-induced hip ischemia in piglets.
OBJECTIVE: The purpose of this study was to determine if enhanced power Doppler sonography can detect early ischemia of the capital femoral epiphysis induced by hip hyperabduction in piglets and to correlate these findings with angiography. MATERIALS AND METHODS: Proximal femoral perfusion was evaluated in 18 studies of 10 piglet hips with unenhanced power Doppler sonography, enhanced power Doppler sonography with IV contrast agent, and digital angiography, in neutral position, hyperabduction, and after release to neutral position. Enhancement ratios between pixel intensities of power Doppler sonography and enhanced power Doppler images in each position were calculated. Angiograms were analyzed for differences in flow with changes in hip position. RESULTS: With the piglet in neutral position, power Doppler sonography revealed few vessels in the femoral head. Contrast administration resulted in a temporary marked increase in the visualization of vessels in the femoral head. Quantitative enhanced power Doppler sonography revealed a marked decrease in pixel intensity with abduction (p < 0.001) that was not apparent on unenhanced studies (p = 0.28). The enhancement ratio decreased from 0.45 (mean +/- SD, +/- 0.26) in neutral position to 0.10 (+/- 0.21) after abduction; it returned to 0.41 (+/- 0.14) after release of abduction (p < 0.001 for each comparison). Angiographic studies in hyperabduction revealed a variable level of ischemia. CONCLUSION: Enhanced power Doppler sonography can be used to visualize the vascular supply to the cartilaginous femoral head in piglets and can detect reversible ischemia induced by hip hyperabduction. These differences correlate with digital angiographic evidence of ischemia.
Color correction and automating repetitive tasks.
Explore the source record for details and available documents.
The effects of lidocaine and adrenergic agonists on rat sciatic nerve and skeletal muscle blood flow in vivo.
UNLABELLED: It has been proposed that epinephrine prolongs lidocaine nerve blockade duration by exerting a local vasoconstrictive effect on tissues at the injection site, slowing lidocaine's local clearance. However, previous studies have failed to demonstrate consistent effects of lidocaine and epinephrine, injected alone and in combination, on vascular tone or regional blood flow. To reinvestigate this idea, in this study we used the radiolabeled microsphere technique to measure in vivo tissue blood flow before and at several time points after perisciatic nerve and intramasseter muscle injection of lidocaine alone, epinephrine, the selective alpha(1)-adrenergic receptor agonist phenylephrine, or lidocaine combined with these adrenergic receptor agonists. Repeated-measures analyses of variance were used to assess significant changes in blood flow over time. Lidocaine (2, 10, and 20 mg/mL) and epinephrine (10 micro g/mL or 1:100,000) injected alone did not alter blood flow in sciatic nerve, perisciatic muscle, or masseter muscle. Injections of lidocaine (10 mg/mL) combined with epinephrine (10 micro g/mL) did not affect adjacent muscle blood flow but caused a mild reduction in sciatic nerve blood flow, which was significant 30 min after injection. However, phenylephrine (10 micro g/mL), a potent vasoconstrictor, combined with lidocaine (10 mg/mL) significantly reduced blood flow in all three tissues. Our findings suggest that mechanisms other than local vasoconstriction may contribute to the prolongation of lidocaine nerve blocks by epinephrine. IMPLICATIONS: Accepting that the microsphere technique may be limited in its sensitivity to detect small but clinically relevant changes in tissue blood flow, our findings suggest that mechanisms other than local vasoconstriction may contribute to the prolongation of lidocaine nerve blocks by epinephrine.
Tumor vascularity: evaluation in a murine model with contrast-enhanced color Doppler US effect of angiogenesis inhibitors.
PURPOSE: To determine the ability of contrast material-enhanced ultrasonography (US) to depict tumor growth and vascularity in a murine model of prostate carcinoma treated with an angiogenic inhibitor. MATERIALS AND METHODS: Thirty-five genetically engineered mice with spontaneously occurring prostate tumors were monitored on a weekly basis with gray-scale and color Doppler US with a 15-MHz linear transducer. Eighteen mice were treated with an adenoviral vector to deliver a soluble form of the Flk1 receptor (VEGFR-2), a vascular endothelial growth factor receptor designed to block tumor angiogenesis. The remaining 17 animals were injected with saline and used as controls. Tumor volumes were calculated on the basis of serial US measurements. Color Doppler US was performed in every tumor before and after intravenous injection of 0.1 mL per kilogram of body weight of a US contrast agent. US images were evaluated for tumor size, pattern of vascularity, and extent of vascularity (vascularity index). Findings at US were correlated with findings at autopsy in 30 animals. RESULTS: Estimates of tumor volume at US correlated well with tumor measurements at autopsy (r =.89, P <.001). Marked differences in tumor size and slope of increasing tumor volume were evident at US between treated and control mice after treatment (P <.016, analysis of variance). The US contrast agent markedly increased color Doppler US signal intensity with an 800% (from 10% to 12,700%) change in the mean number of color pixels per imaging field, and showed vascularity in areas of tumor not identified on precontrast images in 70% (109 of 156 studies). No correlation was found between the pattern of vascularity or vascularity index before or after contrast material administration and tumor size, treatment status, or histologic assessment of tumor vascularity. CONCLUSION: Contrast-enhanced US improves visualization of tumor vascularity. However, histologic patterns of tumor vascularity do not correlate with Doppler US depiction of blood flow in these vessels.
CT of appendicitis in children.
Appendicitis is the most common condition requiring intraabdominal surgery in infancy and childhood. Yet, despite its common occurrence, accurate diagnosis remains challenging. Acute appendicitis may be missed at initial clinical examination in 28%-57% of children aged 12 years and younger and in nearly 100% of children under the age of 2 years. Diagnostic imaging has an ever-increasing role in the prompt and accurate diagnosis of acute appendicitis in the pediatric population. At the authors' institution, helical computed tomography (CT) is the primary tool for diagnosing or excluding appendicitis in children. Since its inception in 1998, helical CT with rectally administered contrast material has been shown to reduce the total number of inpatient observation days, laparotomies with negative findings, and per-patient cost. Helical CT is a highly sensitive and specific tool for diagnosing pediatric appendicitis and has resulted in a beneficial change in patient care in 68.5% of all patients seen in the authors' emergency department for suspected appendicitis. This includes both those patients who receive an eventual diagnosis of appendicitis and those who do not have the disease. Major strengths of limited helical CT with rectal contrast material include producing uniformly high published sensitivity and specificity values for diagnosis of appendicitis and enabling diagnosis of alternative conditions of acute abdominal pain in children. In contrast, limitations of graded-compression ultrasonography in children include highly operator-dependent sensitivity and specificity values and relative infrequency with which the normal appendix can be visualized in this population. Although there have been many exciting diagnostic advancements for the diagnosis of acute appendicitis in the pediatric population, the role of helical CT is far from clear. The purpose of this article is to describe a helical CT approach to imaging in children suspected of having acute appendicitis at a large urban pediatric teaching hospital and its effects on patient outcomes and hospital costs.
Effect of an imaging protocol on clinical outcomes among pediatric patients with appendicitis.
OBJECTIVE: In 1998, we implemented a clinical imaging protocol in which children with suspected appendicitis underwent ultrasonography (US) followed by computed tomography (CT). We sought to determine the impact of the US-CT protocol on changes in perforation and negative appendectomy rates. METHODS: Children with unequivocal presentations for appendicitis went to the operating room without entering the imaging protocol. Using a modified time series design, we analyzed a prospective and retrospective cohort of consecutive patients who were admitted from the emergency department for suspected appendicitis. The perforation and negative appendectomy rates were computed for the periods before and after implementation of the imaging protocol and adjustment for time trends was made. RESULTS: A total of 1338 children were identified. Eight hundred ten (60.5%) children had equivocal clinical findings. A total of 920 patients were admitted for suspected appendicitis before the protocol was implemented; 526 (57.2%) of the 920 children had appendicitis, and 186 (35.4%) of them had perforation. A total of 91 (14.7%) of 617 had negative appendectomies. After the protocol was implemented, 418 patients were admitted for suspected appendicitis; 328 (78.5%) had appendicitis with 51 (15.5%) perforated. There were 14 (4.1%) of 342 cases of negative appendectomies. After implementation of the imaging protocol, the perforation rate decreased from 35.4% to 15.5%, and the negative appendectomy rate decreased from 14.7% to 4.1%. After secular time trends were adjusted for, the imaging protocol continued to have a strong association with a reduction in perforation rate and negative appendectomy rate. CONCLUSION: The implementation of an imaging protocol using US and CT resulted in a marked decrease in the perforation and negative appendectomy rates in children with suspected appendicitis.
Initial steps in image preparation.
Explore the source record for details and available documents.
Gene therapy of prostate cancer with the soluble vascular endothelial growth factor receptor Flk1.
A variety of novel therapeutic approaches have emerged recently for the treatment of human cancers. We have coupled two of these therapeutic approaches, gene therapy and antiangiogenic therapy and tested them in two murine prostate cancer models Recombinant adenovirus encoding the ligand-binding ectodomain of the VEGF receptor 2 (Flk1) fused to an Fc domain was administered to SCID mice carrying orthotopic human LNCaP tumors as well as to transgenic (TRAMP) mice with spontaneous prostate tumors. Ad Flk1-Fc injection reduced tumor growth by 66% for orthotopic LNCaP tumors and by 42% for spontaneous tumors in TRAMP mice. Microvessel density in the primary tumors was reduced by 68% and 40% in the two models respectively. A decrease in microvessel density was also observed in lymphatic metastases in Ad Flk1-Fc-treated TRAMP mice and was correlated with a decrease in the frequency of regional metastases in the treated animals. Survival time was also extended in the Ad Flk1-Fc-treated TRAMP mice relative to the control-treated animals. Our results suggest that adenoviral delivery of soluble Flk1 receptor can reduce vascular density and prostate tumor growth and prolong survival time in orthotopically implanted tumors as well as in spontaneous prostate tumors in transgenic animals.