Because of the very high chip rate of global positioning system (GPS), P-code acquisition at GPS receiver will be challenging. A variety of methods for increasing the probability of detection and reducing the average time of acquisition have been provided, among which the method of Zero Padding (ZP) is the most essential and the most widely used. The method using the Fast Fourier Transform (FFT), searches phase codes of the uncertainty region in a parallel method to find the desired code for correct acquisition. ZP method is sensitive to Doppler frequency so that the increase in Doppler frequency drastically reduces the probability of detection and consequently the average time of acquisition increases. The presented method in this paper, that called Segmented Zero Padding (SZP), reduces the Doppler effects on probability of detection at the acquisition of GPS receiver. Also, it will be shown that using the proposed algorithm proper mean acquisition time at high Doppler frequencies is achievable. Based on the comparisons made in this paper, we prove that the proposed algorithm in comparison to ZP algorithm, maintains the capability of parallel search and finally has a lower average acquisition time.

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Accurate assessment of gestational age, fetal growth, and the detection of fetal and placental abnormalities are major benefits of sonography. Color Doppler can be used to assist in the identification of vascular architecture, detection of vascular pathology and visualization of blood flow changes associated with physiologic processes and disease states.The clinical applications of obstetrical Doppler are Intrauterine Growth Restriction, diagnosis of fetal anemia and twin-twin transfusion syndrome.The use of Doppler during antenatal fetal surveillance has involved assessment of (1) the umbilical arterial and venous flow velocity waveforms, (2) the fetal cerebral circulation, and (3) the fetal venous circulation, in particular the ductus venosus.Doppler studies of the fetal circulation in intrauterine growth retardation and hypoxia have demonstrated increased resistance to flow in the umbilical arteries and redistribution in the fetal circulation with reduced resistance and increased velocity in the internal carotid and middle cerebral artery and the opposite in the descending thoracic aorta.Assessment of placental function using umbilical artery Doppler velocimetry: Placental insufficiency can be quantified based on the reduction of end-diastolic Doppler flow velocity into (1) reduced end diastolic flow velocity, (2) absent end-diastolic flow velocity, and (3) reversed end-diastolic flow velocity.Use of middle cerebral artery velocimetry to detect fetal hypoxia: an increase in pCO2 or a reduction in pO2 will cause an increase in fetal cerebral arterial Doppler end-diastolic flow velocity, likely related to cerebral vasodilatation.This phenomenon has been described as the “brain sparing” effect.Use of Doppler to detect fetal anemia: The MCA-PSV is an accurate predictor of severe fetal anemia in pregnancies complicated by red cell alloimmunization.Use of uterine artery Doppler to detect maternal complications of pregnancy: The uterine artery Doppler reflects fetal response to stress of hostile intrauterine environment (pregnancy induced hypertension, re-eclamptic toxemia).Fetal venous flow: The umbilical vein, ductus venosus and the inferior vena cava are the main areas of interest in the investigation of venous blood return to the fetal heart.Pulsatile umbilical vein flow and back flow in ductus venosus and IVC are indications advanced cardiac decompensation.

Considering that more than 85 percent of ischemic strokes take place in the territory of middle cerebral artery and Transcranial Doppler Sonography (TCD) is a sensitive and non aggressive method for detection of flow of cranial vessels, the aim was assessing flow alterations of these arteries in ischemic strokes of middle cerebral artery (MCA) to enable an accurate and quick method to for cast happening of any stroke and it's Prognosis. In this study, designed in descriptive method, the anterior circulation arteries of 44 patients who suffered ischemic infarction in the territory of MCA were insonated by TCD. Patients with first stroke were included and sampling was non probability testing on consecutive patients. Brain axial CTS can was performed on all patients on first and third days of stroke and TCD was performed on days 3 to 6 and the results were as following: Peak Systolic Velocity (PSV) and Mean Flow Velocity (MFV) of ipsilateral MCA were reduced resulting in asymmetry of flow more than 15% in 61.4% of cases (P value <0.005) . PSV and MFV of ACA were increased resulting in increased ratio of ipsilateral to contralateral ACA (ACAVR) in 72.2% of cases. (P value < 0.005) Pulsatility index (PI) of ipsilateral MCA to contralateral MCA had a significant increase. (P value=p.005) indicating distal vascular resistance. Resistance Index (RI) of ipsilateral MCA and contralateral MCA didn't have any significant difference (P value = 0.05) 1- Ischemic MCA infarcts reduce PSV, MFV in ipsilateral MCA and increase PSV, MFV in ipsilateral ACA, resulting in increased ipsilateral ACAYR. 2- The most valuable parameter in determining MCA infarct is ACAVR (Sensitivity=72.2%), the next one being MCA flow asymmetry> 15% (Sensitivity=61.4%) 3- RI Value had no relation to the final size of infarct. Further studies evaluating normal values of TCD parameters in Iranian people are recommended to compare these indexes with normal ones.  

Background: The purpose of our study was to assess the potential of color Doppler (CD) and Power Doppler Imaging (PDI) to differentiate benign from malignant solid breast masses. Materials and Methods: Seventy-one biopsy proven solid breast masses were evaluated with CD and PDI using 7.5MHz Transducer. Vascularity, Resistive Index (RI) and patterns of vascular distribution of masses were assigned before biopsy. Results: There were 22 cancers and 49 benign lesions. All malignant masses had vascularity in some degrees, except 3 cancers which were less than 10 mm in diameter. Most of cancers were hypervascular (15 cancers) and had penetrating or diffuse vessels (14 cancers). Most of benign lesions and fibro adenomas were avascular (35 masses). 12 cancers, 2 fibro adenomas and all vascular benign lesions had RI>0.6. 7 cancers and 6 fibro adenomas had RI<0.6. By using hypervascularity to indicate malignancy sensitivity for CD and PDI was 68 percent and specificity was 90 percent and by using penetrating and diffuse vessels sensitivity was 64 percent and specificity was 82 percent. By using RI<0.6 sensitivity was 32 percent and specificity was 88 percent and by using these three criteria together sensitivity was 73 percent and specificity was 82 percent (p<0.00001). Conclusion: The vascularity and pattern of distribution and morphology of blood vessels in solid breast masses seen at PDI and CD is a potentially important feature to predict the likelihood of malignancy. But RI appears to be of limited value.

Background: Classically, one's heart function is mostly based upon its systolic function, whereas the diastolic function steps on second order. In recent years it has been revealed that diastolic function plays an important role in both cardiac mortality and cardiac morbidity. On the other hand is hypertension which due to increasing the afterload, interferes with these functions of heart. In this study we assessed the diastolic function of hypertensive patients using pulse tissue Doppler.Materials and Methods: 30 patients with high blood pressure that had not consumed antihypertensive agents and along with 30 healthy control ones enrolled in our survey, all of whom had normal sinus rhythm without detectable symptoms corresponding to congestive heart failure, ischemia, valvular diseases and pulmonary problems. 2D echocardiography was performed in both groups as well asM Mode and Doppler echo The PTD echo was performed by the lateral annulus of both tricuspid and mitral valves. Systolic and diastolic findings were measured by PTD.Results: Hypertensive patients had negative diastolic findings but no negative systolic ones. PTS illustrated that E/A ratio (early peak velocity / late peak velocity) in right ventricle had significantly decreases (P<0.01) among these patients. In right ventricle, both RT (relaxation time) (P<0.01), DT (decelation time)(P<0.04) and Am (Late Peak Velocity) (P<0.03) were conversely increased. Right ventricular E/A ratio had a significant correlation with that of left ventricl (P<0.005, r =0.5).Conclusion: It seems that hypertension is longitudinally related with diastolic dysfunction of right ventricle. This disturbance would be represented by the lengthened RT and decreasing of E/A ratio which are both resulted from interfering of two ventricle's function and increased pressure of left ventricle. Therefore, PTD can be applied to evaluate the right ventricular diastolic function among patients with high blood pressure.

In continuous wave (CW) radar systems, the efficiency of semi-active chaser receiver in the tracking of target is of paramount importance. In a situation where the target and chaser have variable speed (accelerated motion) relative to one another, in the semi-active chaser receiver, the received signal has time varying Doppler frequency shifts. In this paper, semi-active receiver with hierarchical features first acquires an estimation of the parameters of the received signal using the short time-frequency transform (STFT) at the time of the acceleration of the target or chaser. Then, mono-pulse angular tracking accuracy is tested using a matched filter based on the estimated parameters of the received signal. Eventually, providing the required simulation, the proposed method is compared with “ maximum signal spectrum” and “ average signal spectrum” methods. The results imply that the matched filter-based algorithm has a better performance than other algorithms.