Biomedical subjects

Orhan Unal

Publications and source records attributed to Orhan Unal.

8 recordsLinked to original sources

PubMed2006

MR-visible coatings for endovascular device visualization.

PURPOSE: To investigate the potential utility of magnetic resonance (MR)-visible coatings for passive visualization of therapeutic endovascular devices such as catheters and guidewires. MATERIALS AND METHODS: Using a multistep coating process, gadolinium-based coatings were applied to commercially available off-the-shelf catheters and guidewires. These coated devices were imaged in phantoms made of fat-free yogurt, saline, and whole blood and also in live canine aorta on a 1.5-T cardiovascular MR scanner using T1-weighted two-dimensional radiofrequency (RF)-spoiled gradient-recalled echo, two-dimensional spin echo, and three-dimensional RF-spoiled gradient-recalled echo techniques. RESULTS: Commercially available off-the shelf catheters (4, 5, and 6 French) and guidewires (0.038 inch) were clearly visualized in all phantoms and canine aorta and the coatings proved to be durable and imageable without degradation in signal intensity up to 24 hours. MR-visible coatings address some of the shortcomings that have previously limited the role of MR as a guidance tool. CONCLUSION: Both in vitro and in vivo visualization of therapeutic endovascular devices coated with MR-visible coatings are found to be clinically viable.

4-Aminopyridine↗

PubMed2005

Detection of acute renal ischemia in swine using blood oxygen level-dependent magnetic resonance imaging.

PURPOSE: To determine the feasibility and sensitivity of blood oxygen level-dependent (BOLD) magnetic resonance imaging (MRI) to detect acute renal ischemia, using a swine model, and to present the causes of variability and assess techniques that minimize variability introduced during data analysis. MATERIALS AND METHODS: BOLD MRI was performed in axial and coronal planes of the kidneys of five swine. Color R2* maps were calculated and mean R2* values and 95% confidence intervals (CIs) for the cortex and medulla were determined for baseline, renal artery occlusion and reperfusion conditions. Paired Student's t-tests were used to determine significance. RESULTS: Mean R2* measurements increased from baseline during renal artery occlusion in the cortex (axial, 13.8-24.6 second(-1); coronal, 14.4-24.7 second(-1)) and medulla (axial, 19.3-32.2 second(-1); coronal, 20.1-30.7 second(-1)). These differences were significant for both the cortex (axial, P < 0.04; coronal, P < 0.005) and medulla (axial, P < 0.02; coronal, P < 0.0005). No significant change was observed in the contralateral kidney. CONCLUSION: R2* values were significantly higher than baseline for medulla and cortex during renal artery occlusion. More variability exists in R2* measurements in the medulla than the cortex and in the axial than the coronal plane.

Animals↗

PubMed2005

Evaluation of the effects of various gestagens on insulin sensitivity, using homeostatic model assessment, in postmenopausal women on hormone replacement therapy.

The objective of the present study was to compare the effects of various gestagens on insulin sensitivity in postmenopausal women on hormone replacement therapy (HRT). This prospective study enrolled 156 postmenopausal women who had menopausal status for at least 6 months. Group 1 was treated with 17 beta-estradiol (E2; 2 mg) plus norethisterone acetate (NETA; 1 mg); Group 2 was given E2 (2 mg) plus medroxyprogesterone acetate (MPA; 2.5 mg); Group 3 was given E2 (2 mg) plus dydrogesterone (DG; 10 mg); and Group 4 was given E2 (2 mg) plus micronized progesterone (MP; 100 mg). Group 5 was the surgical menopausal group and was given only E2 (2 mg) continuously. All 156 subjects completed the 3-month follow-up on the trial. The patients were analyzed by using homeostatic model assessment (HOMA) for insulin sensitivity before treatment and 3 months after treatment, comparing the effects of various HRT regimens on insulin sensitivity. No significant differences were found in the baseline characteristics of the patients (p > 0.05). There were no significant differences in mean values of HOMA before HRT among the five groups (p > 0.05). There were statistically significant differences in mean values of HOMA only in Group 1 (E2 + NETA) and Group 3 (E2 + DG) after HRT (p > 0.05). E2 + NETA and E2 + DG were found to improve insulin sensitivity in postmenopausal women after 3 months of treatment, whereas E2 + MPA, E2 + MP and E2 only did not show such an effect in postmenopausal women.

Adult↗

PubMed2005

The effect of estradiol valerate and dienogest combination on serum homocysteine levels in postmenopausal women: a clinical trial.

Several studies have verified that hormone replacement therapy (HRT) has protective effects on postmenopausal women's cardiovascular condition. However, highly significant recent studies have reported that women treated with HRT have more cardiovascular events than untreated women. An elevated homocysteine level is one important risk factor for cardiovascular disease (CVD). As a good indicator of CVD risk, we examined the changes in plasma homocysteine levels of postmenopausal women treated with HRT. In our study, we administered estradiol valerate (2 mg) and dionegest (2 mg) to 34 postmenopausal women recruited randomly from our menopause clinic, and measured plasma homocysteine levels of patients at baseline and after 3 and 6 months of therapy. The changes in plasma homocysteine levels of treated patients were not statistically significant (p = 0.241). Our results indicate that 6 months of estradiol valerate and dionegest therapy does not change homocysteine levels in postmenopausal women.

Adult↗

PubMed2003

Diagnosis of premature rupture of membranes by identification of beta-HCG in vaginal washing fluid.

OBJECTIVE: To evaluate the reliability of vaginal washing fluid beta-HCG for the diagnosis of premature rupture of membranes (PROMs) and to determine a cut-off value. STUDY DESIGN: A total of 141 pregnant women were recruited. The first group consisted of 73 pregnant women between 14 and 41 weeks of gestation with the complaint of vaginal fluid leakage. These were further subdivided into two subgroups. Group 1-confirmed PROM group (amniotic fluid pooling (+) and nitrazine paper test (+); 34 patients). Group 2-suspected but unconfirmed PROM group (amniotic fluid pooling (+/-) and/or nitrazine paper test (+/-); 39 patients). The control group (Group 3) consisted of 68 pregnant women between 14 and 41 weeks of gestation without any complaint or complication. All patients underwent speculum examination for amniotic fluid pooling, nitrazine paper test, vaginal washing fluid beta-HCG sampling and ultrasonographic examination for gestational age determination, amniotic fluid index calculation. One-way ANOVA test, Scheffe multiple comparison test and receiver operating characteristic (ROC) curve analysis were used. RESULTS: Geometric mean values of beta-HCG was found to be 95 for Group 1, 14 for Group 2, 10 for Group 3 (P<0.0001). The optimal cut-off was a beta-HCG value of 65 mIU/ml (sensitivity 68%, specificity 95%, positive predictive value 82%, negative predictive value 90%, accuracy 87%). CONCLUSION: Vaginal washing fluid beta-HCG determination for the diagnosis of PROM is reliable, simple and rapid test.

Adult↗

PubMed2002

Validation of injection parameters for catheter-directed intraarterial gadolinium-enhanced MR angiography.

RATIONALE AND OBJECTIVES: Catheter-directed intraarterial (IA) injections of gadolinium contrast agents may be used during endovascular interventions with magnetic resonance (MR) imaging guidance. Injection protocols require further validation. Using a flow phantom and swine, the authors aimed to (a) measure the optimal arterial gadolinium concentration ([Gd]) required for MR angiography and (b) validate a proposed IA injection protocol for gadolinium-enhanced MR angiography. MATERIALS AND METHODS: For in vitro experiments, the authors placed a catheter in the aorta of an aorto-renal-iliac flow phantom. Injected [Gd], injection rates, and aortic blood flow rates were varied independently for 36 separate IA gadolinium injections. The authors performed 2D and 3D MR angiography with a fast spoiled gradient-recalled echo sequence. For subsequent in vivo experiments, they selectively placed catheters within the aorta, renal artery, or common iliac artery of three pigs. Injection rate and injected [Gd] were varied. The authors performed 32 separate IA gadolinium injections for 2D MR angiography. Signal-to-noise ratios (SNRs) were compared for the various combinations of injection rate and injected [Gd]. RESULTS: In vitro, an arterial [Gd] of 2%-4% produced an optimal SNR for 2D MR angiography, and 3%-5% was best for 3D MR angiography. In swine, an arterial [Gd] of 1%-4% produced an optimal SNR. In the phantom and swine experiments, SNR was maintained at higher injection rates by inversely varying the injected [Gd]. CONCLUSION: Dilute arterial [Gd] is required for optimal IA gadolinium-enhanced MR angiography. To maintain an optimal SNR, injection rates and injected [Gd] should be varied inversely. The postulated injection protocol was validated.

Animals↗

PubMed2002

Comparison of intraarterial and IV gadolinium-enhanced MR angiography with digital subtraction angiography for the detection of renal artery stenosis in pigs.

OBJECTIVE: Catheter-based intraarterial injections of gadolinium are useful during MR imaging-guided endovascular procedures to generate rapid vascular road maps. Using an animal model of renal artery stenosis, we tested the hypothesis that intraarterial gadolinium-enhanced MR angiography is as accurate as IV gadolinium-enhanced MR angiography and digital subtraction angiography (DSA). We also tested the hypothesis that intraarterial MR angiography uses less gadolinium than IV MR angiography. MATERIALS AND METHODS: We induced bilateral renal artery stenosis in five pigs. All pigs underwent comparative imaging with DSA, IV MR angiography, and aortic catheter-directed intraarterial MR angiography. For IV and intraarterial MR angiography, we used the same three-dimensional acquisition. We assessed differences in quantitative stenosis measurements among DSA, IV MR angiography, and intraarterial MR angiography using the Wilcoxon's signed rank test. RESULTS: Mean stenosis measurements (+/-SD) were as follows: DSA, 58% +/- 12%; IV MR angiography, 63% +/- 9.3%; and intraarterial MR angiography, 64% +/- 11%. There were no statistically significant differences in accuracy between DSA and IV MR angiography (p = 0.06), DSA and intraarterial MR angiography (p = 0.16), or IV and intraarterial MR angiography (p = 0.70). Intraarterial MR angiography used a mean gadolinium dose of 5.6 mL, compared with 9 mL for IV MR angiography. CONCLUSION: In swine, IV and intraarterial MR angiography have a similar accuracy for detecting renal artery stenosis. Intraarterial MR angiography uses smaller doses of injected gadolinium.

Angiography, Digital Subtraction↗

PubMedDate not supplied

Brain damage to the survivor within 30 min of co-twin demise in monochorionic twins.

Single fetal death in a twin pregnancy in the late second or early third trimester is associated with significant morbidity and mortality rate in the surviving co-twin, especially in monochorionic twin pregnancies. The common causes are twin-to-twin transfusion syndrome, chromosomal abnormalities, and congenital anomalies of the fetus or anomalies of the umbilical cord-placenta. Here we report a case of monochorionic twin pregnancy in which one fetus had a single umbilical artery (SUA) while the co-twin had two umbilical arteries. The twin with SUA died in utero at the 30th week of gestation and the other fetus was delivered by cesarean section immediately due to fetal distress diagnosed by cardiotocography. Disseminated intravascular coagulation and multicystic encephalomalacia have been observed in the surviving neonate. This case and review of the literature suggest that neurologic complication rates are also increased in monochorionic twin pregnancies with single fetal demise despite the immediate delivery as in our case.

Adult↗