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Biomedical subjects

O Unal

Publications and source records attributed to O Unal.

53 records · Page 3Linked to original sources
PubMed1999

Duplex and color Doppler sonographic findings in active sacroiliitis.

OBJECTIVE: The aim of this study was to describe the duplex and color Doppler sonographic findings in active sacroiliitis. SUBJECTS AND METHODS: Forty-one joints in 21 patients with active sacroiliitis, 20 sacroiliac joints in 10 patients with osteoarthritis, and 30 sacroiliac joints of 15 asymptomatic volunteers were investigated on duplex and color Doppler sonography. We investigated whether a vessel was present around the posterior portions of sacroiliac joints with color Doppler sonography. When an artery was detected, the resistive index (RI) was measured using duplex Doppler sonography in all groups and also after treatment in the patients with active sacroiliitis. RESULTS: Vascularization around the posterior portions of sacroiliac joints was seen in 41 joints of the 21 patients with active sacroiliitis, nine joints of six patients with osteoarthritis, and 13 joints of eight volunteers. The mean RI values were 0.62 +/- 0.13, 0.91 +/- 0.09, and 0.97 +/- 0.03, respectively. In the patients with active sacroiliitis, the mean RI value was 0.91 +/- 0.07 after therapy. The RI values for the patients with active sacroiliitis were significantly different from those of the patients with osteoarthritis (p < .001) and of the volunteers (p < .001). In addition, the RI values were significantly different before and after treatment in the patients with active sacroiliitis (p < .001). CONCLUSION: Vascularization around the posterior portions of sacroiliac joints increased and RI values decreased in patients with active sacroiliitis. Color and duplex Doppler sonography were able to reveal these changes and can be used in the diagnosis of active sacroiliitis and follow-up after treatment. Thus, RI values may be a quantitative indicator for clinical symptoms in patients with active sacroiliitis.

Adult↗
PubMed1999

In vitro and in vivo comparison of three MR measurement methods for calculating vascular shear stress in the internal carotid artery.

BACKGROUND AND PURPOSE: Vascular abnormalities, such as atherosclerosis and the growth and rupture of cerebral aneurysms, result from a derangement in tissue metabolism and injury that are, in part, regulated by hemodynamic stress. The purpose of this study was to establish the feasibility and accuracy of determining wall shear rate in the internal carotid artery from phase-contrast MR data. METHODS: Three algorithms were used to generate shear rate estimates from both ungated and cardiac-gated 2D phase-contrast data. These algorithms were linear extrapolation (LE), linear estimation with correction for wall position (LE*), and quadratic extrapolation (QE). In vitro experiments were conducted by using a phantom under conditions of both nonpulsatile and pulsatile flow. The findings from five healthy volunteers were also studied. MR imaging-derived shear rates were compared with values calculated by solving the fluid flow equations. RESULTS: Findings of in vitro constant-flow experiments indicated that at one or two excitations, QE has the advantage of good accuracy and low variance. Results of in vitro pulsatile flow experiments showed that neither LE* nor QE differed significantly from the predicted value of wall shear stress, despite errors of 17% and 22%, respectively. In vivo data showed that QE did not differ significantly from the predicted value, whereas LE and LE* did. The percentages of errors for QE, LE, and LE* in vivo measurements were 98.5%, 28.5%, and 36.1%, respectively. The average residual of QE was low because the residuals were both above and below baseline whereas, on average, LE* tended to be a more biased overestimator of the shear rate in volunteers. The average and peak wall shear force in five volunteers was approximately 8.10 dyne/cm2 and 13.2 dyne/cm2, respectively. CONCLUSION: Our findings show that LE consistently underestimates the shear rate. Although LE* and QE may be used to estimate shear rate, errors of up to 36% should be expected because of variance above and below the true value for individual measurements.

Biomechanical Phenomena↗
PubMed1998

A rapid 2D time-resolved variable-rate k-space sampling MR technique for passive catheter tracking during endovascular procedures.

A new, fast, 2D MR imaging technique allowing passive catheter visualization adequate for use as a tool for guiding the movement of a catheter during endovascular procedures is described. This imaging technique samples low spatial frequencies more often than high spatial frequencies; it also uses both k-space view sharing and temporal interpolation. Unlike other techniques for passive visualization that exploit magnetic-susceptibility-induced artifacts, we have adopted a strategy that takes advantage of the T1-shortening effect of paramagnetic contrast agents, such as Gd-DTPA and a projection dephaser. This not only permits visualization of the entire catheter length but also minimizes the risk of intravascular heating. Using this method, a temporal frame rate of up to eight images per second and a tip localization accuracy of +/- 1mm (root mean square difference) can be achieved.

Angioplasty, Balloon↗
PubMed1998

The role of power Doppler sonography in the evaluation of superficial soft tissue abscesses.

OBJECTIVE: To evaluate the efficacy of power doppler ultrasonography in depicting increased vasculature and hyperemia around the superficial soft tissue abscess. MATERIALS AND METHODS: 21 patients with soft tissue abscess were evaluated with gray scale imaging, color doppler sonography, power doppler sonography and computed tomography. In each case attempts were made using power doppler sonography to demonstrate any areas of increased vascularity around the lesion. The results were compared with computed tomographic findings. RESULTS: Peripheral hyperemia and increased vasculature were demonstrated with power doppler sonography in 19 of 21 patients with soft tissue abscess. The hyperemic area demonstrated around the wall of the abscess by power doppler sonography was similar to the enhanced area shown by computed tomography performed after contrast administration. CONCLUSION: Power doppler sonography shows increased vasculature and hyperemia in the wall of abscesses. Therefore, power doppler sonography can be used to assist with the diagnosis of superficial soft tissue abscess.

Abscess↗
PubMed1998

The role of power Doppler ultrasonography in the diagnosis of prostate cancer: a preliminary study.

OBJECTIVE: To determine the role of transrectal power Doppler ultrasonography (PDU) in the diagnosis of prostate cancer. PATIENTS AND METHODS: Thirty-six patients (mean age 66.4 years, SD 7.7, range 59-82) with possible prostate cancer, suspected from an abnormal digital rectal examination or elevated prostate specific antigen level, underwent transrectal ultrasonography, transrectal PDU and biopsy. The vascularity on PDU was graded on a scale of 0-2, where grade 1-2 was considered positive and grade 0 negative. RESULTS: The vascularity was grade 2 in 11 patients, grade 1 in 11 and grade 0 in 14; 20 of the 36 (56%) patients had prostate cancer. Of the 22 patients positive on PDU, 18 had malignant disease and four benign; two of 20 patients with histopathologically confirmed malignancy had a normal PDU. The sensitivity of PDU was 90%, the specificity 75% and the positive predictive value 82%. CONCLUSION: Focal hypervascularity on PDU was associated with an increased likelihood of prostate cancer. Although ultrasonography alone cannot detect all cancers, even using PDU, the technique appears to increase the sensitivity and to help identify appropriate sites for biopsy.

Aged↗
PubMed1990

Preparation of cross-sectional specimens of ceramic thermal barrier coatings for transmission electron microscopy.

During the microstructural examination of ceramic thermal barrier coatings by transmission electron microscopy (TEM), initial efforts for the preparation of cross-sectional thin foils from interface regions by conventional means were mostly failures. Delamination of the Y2O3-stabilized ZrO2 ceramic coating from the nickel-base alloy substrate sometimes occurred during fine polishing at around 80 microns thickness but mostly occurred during dimpling. Because of this sensitivity, special techniques for mechanical handling were developed so that ion milling could give thin enough regions of the metal-ceramic interface. TEM showed convincingly that the highly fragile nature of the coatings is in fact due to the extensive porosity at the interface developed as a result of heat treatment.

Ceramics↗
PubMed1989

Characterization of potassium channels in respiratory cells. I. General properties.

Potassium channels present in the basolateral membrane of respiratory epithelial cells play an important role in the process of chloride secretion. Utilizing the patch clamp technique, we examined human cultured respiratory epithelial cells derived from patients with cystic fibrosis (CF) and normals individual (N) for the existence of and for the properties of K+ channels. We obtained qualitatively and quantitatively identical results for both preparations (CF and N). K+ channels were spontaneously present in cell attached patches. The channels showed burst appearance with rapid flickering within the bursts. When the pipette was filled with 145 mmol/l KCl, a mean conductance of 131 +/- 25 pS (n = 15) was read from the I/V-curve at a clamp voltage (Vc) of 0 mV. After excision, the conductance read from the I/V-curve at Vc = 0 mV was 212 +/- 11 pS (Pipette: 145 mmol/l KCl, bath: 145 mmol/l NaCl) (n = 61). With NaCl in the pipette and KCl in the bath, a similar conductance was obtained (g = 210 pS; n = 2). When both, pipette and bath contained KCl, the conductance was increased to 302 +/- 19 (n = 7). The channel was highly selective for potassium over sodium: PK + /PNa + greater than 40. The channel open probability was only slightly voltage dependent i.e. the open probability increased slightly with depolarisation. For most of the channels one open time constant (to = 6.3 +/- 1.6 ms; n = 22) and one closed time constant (tc = 1.8 +/- 0.3 ms; n = 21) was obtained.(ABSTRACT TRUNCATED AT 250 WORDS)

Cell Membrane↗
PubMedDate not supplied

Evaluation of diaphragmatic movement with MR fluoroscopy in chronic obstructive pulmonary disease.

The aim of this study was to show reduction of the diaphragmatic excursion with MR fluoroscopy in patients with chronic obstructive pulmonary disease (COPD) and to compare the results with pulmonary function test (PFT). The study included 13 men and 10 women (average age 56.2) with COPD, and 9 men and 6 women (average age 55.8) as a control group. MR fluoroscopy images with Spoiled Gradient-echo pulse sequence was obtained during deep inspiration and expiration. After examination, over cine-loop display, the highest and lowest positions of the diaphragm were identified and the distance of excursion was measured. Differences in the diaphragmatic excursion between patient and healthy subjects were compared. We have also compared MR fluoroscopy results with PFT. In each person of both groups, excursion of the diaphragm was demonstrated clearly in cine-loop display. Differences of excursion between deepest and highest point of diaphragm were on average 26 and 20 mm, respectively, in the right and left side in patients and 69 and 56 mm in healthy group. Significant correlation was found between expiratory volume in 1 s and MR fluoroscopy results. MR fluoroscopy study showed that there were significant statistical differences in diaphragmatic excursion between patients with COPD and healthy subjects. Expiratory volume in 1 s is closely associated with the diaphragmatic excursion. MR fluoroscopy would seem to be a useful method for showing diaphragmatic excursion.

Adult↗
PubMedDate not supplied

Brucellar spondylodiscitis: MRI diagnosis.

Early diagnosis of brucellar spondylodiscitis is often difficult because of the long latent period. Radiographs of the spine, bone scan, and computed tomography (CT) scan provide insufficient data. Among 25 patients with brucellar spondylodiscitis studied by magnetic resonance imaging (MRI), 9 were in the acute stage and 16 were in the chronic stage. MRI is the investigation method of choice in diagnosing brucellar spondylodiscitis.

Adolescent↗
PubMedDate not supplied

The role of power Doppler sonography in the prenatal evaluation of fetal renal vasculature.

This study was performed to determine whether power Doppler sonography is superior to color Doppler sonography in the depiction of the normal fetal intrarenal vasculature during pregnancy. Twenty-five fetal kidneys in 22 healthy fetuses between 22 and 40 weeks of gestation (mean 32.6 weeks) were studied with color and power Doppler sonography with a 3.75 MHz transducer. The efficacy of power and color Doppler sonography were compared in assessing fetal renal vasculature. Power Doppler sonography demonstrated diffuse "blush" in almost the entire cortex in 21 of 25 fetal kidneys, whereas it was demonstrated in half of the cortex in the other four kidneys. Color Doppler sonography failed to demonstrate a cortical blush in fetal kidneys. Power Doppler sonography has been shown to be superior to color Doppler sonography in the depiction of normal fetal intrarenal vasculature during pregnancy by demonstrating vascular blood flow better than color Doppler sonography.

Female↗
PubMedDate not supplied

Determination of optimal injection parameters for intraarterial gadolinium-enhanced MR angiography.

PURPOSE: Rapid vascular depiction with use of a minimum of gadolinium (Gd) contrast agent will be required to generate road-map vascular images for magnetic resonance (MR) imaging-guided endovascular interventions. The objective of this study was to optimize intraarterial injections of MR contrast agent during magnetic resonance angiography (MRA), obtained during interventions, by determining the optimal Gd vascular concentration ([Gd]) for vessel depiction. MATERIALS AND METHODS: The authors derived theoretical expressions to estimate the [Gd] resulting in maximal signal in blood. A model was developed to account for flow dilution to estimate [Gd] given the injected Gd concentration, injection rate, and the blood flow rate. Experiments in four animals (three dogs, one pig) were conducted to verify this model with use of both time-resolved two-dimensional (2D) thick-slab and single-phase three-dimensional (3D) MRA acquisitions. The authors also determined the optimal [Gd] required for vessel depiction in animal models. RESULTS: The theoretical expressions yielded optimal [Gd] of 10.2 mmol/L in blood. The animal experiments used the flow dilution model and examined signal enhancement in the aorta and the renal and iliac arteries. Maximal enhancement occurred at [Gd] = 16.2 +/- 4.0 mmol/L (mean +/- SE). CONCLUSIONS: The theoretically predicted values for [Gd]optimal and the flow dilution model were successfully validated. The relationship between injected [Gd], injection rate, and blood flow rate permits rapid intraarterial administration of contrast material, using less overall contrast material than with standard intravenous Gd-enhanced MRA.

Animals↗
PubMedDate not supplied

Intraarterial gadolinium-enhanced 2D and 3D MR angiography: a preliminary study.

PURPOSE: To evaluate, in phantom and canine models, intraarterial gadolinium-enhanced two-dimensional (2D) and three-dimensional (3D) magnetic resonance angiography (MRA). MATERIALS AND METHODS: The in vitro experiments examined gadodiamide solutions ranging in gadolinium (Gd) concentration from 0.1% to 100%. A spoiled gradient-recalled echo (SPGR) sequence was used with various repetition time/echo time (TR/TE) parameters. Signal was measured to determine which concentration yielded the highest signal. For in vivo experiments, pigtail catheters were placed in the abdominal aortae of two dogs. Intraarterial injections of 20-30 mL of 0.5%-25% Gd solutions were performed. We acquired images with use of 2D and 3D SPGR techniques. Depiction of the abdominal aortae and renal vessels was assessed qualitatively and quantitatively. RESULTS: Phantom experiments demonstrated that a 2%-6% solution of Gd produced the highest MR signal, depending on the imaging parameters. In the canine model, a 2% Gd solution was best for 2D techniques, whereas 7%-14% Gd solutions were optimal for 3D techniques. CONCLUSIONS: Intraarterial contrast material-enhanced 2D and 3D MRA can be successfully implemented with use of dilute Gd. Dilution permits the administration of more intraarterial injections per day, without exceeding the dose limit, compared with intravenous Gd-enhanced MRA. Intraarterial injections also limit scan synchronization and contrast material dispersion issues. This technique may have application in MR-guided endovascular procedures.

Animals↗
PubMedDate not supplied

Effect of different types of intrauterine devices on intrauterine activity.

OBJECTIVE: To compare the effects of various IUDs on intrauterine activity. PATIENTS AND METHODS: 57 women volunteers aged 18 to 25 in the outpatient clinic of the Department of Obstetrics and Gynecology at Cerrahpasa Medical Faculty of Istanbul University were included in the study. All were in good health and menstruating normally. The subjects were introduced to different types of IUDs on the fifth to eighth days of their menstrual cycle. Intrauterine activities with and without naproxen were recorded, for at least 20 minutes each time, with a micro-tip transducer before insertion, just after insertion, and 1 month later. RESULTS: Intrauterine activity increased just after insertion of both IUDs and disappeared 1 month later in copper-T wearing women, but persisted in multiload wearers. Naproxen seemed to be useful in preventing intrauterine activity caused by the IUD. CONCLUSIONS: The IUD itself causes an increase in intrauterine activity which is preventable by naproxen, suggesting the possible role of prostaglandins. Persistence of intrauterine activity depends upon the type of device. Optimal designing of IUDs is required to decrease side effects and make them more acceptable.

Adolescent↗