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At least 181 records · Page 10Linked to original sources

PubMed2005

Thyroid nodules: evaluation with power Doppler and duplex Doppler ultrasound.

This study purposes a new classification of thyroid nodules blood flow by power duplex Doppler ultrasound. A total of 177 nodules were studied with B-mode scanning, power Doppler, and spectral analysis. These data were compared with cytological results from ultrasound-guided fine-needle aspiration biopsy. Univariate and multivariate logistic regression analysis were performed. The power Doppler analysis of the nodules produced 5 vascular patterns: I, absence of signal blood flow; II, exclusively perinodular blood flow; III, perinodular >/= central blood flow; IV, central blood flow > perinodular blood flow; V, exclusively central blood flow. Statistical analysis revealed a significant relationship between these vascular patterns and cytological results. The spectral analysis demonstrated that the resistance index were higher in nodules with malignant versus other cytology ( P < 0.001). The results indicate that power duplex Doppler facilitates screening of thyroid nodules at high risk for malignancy with elevated sensitivity (92.3%) and specificity (88%).

Adolescent↗

PubMed2000

Hereditary haemorrhagic telangiectasia: hepatic lesions demonstrated with colour Doppler and power Doppler sonography.

Visceral vascular abnormalities in patients with hereditary haemorrhagic teleangiectasia (HHT) include teleangiectasis, arteriovenous fistula (AVF), and aneurysms. Sonographic findings and colour Doppler ultrasound (CDU) features of HHT in the liver have been described in a few reports. Presented here is the CDU finding of liver with HHT involvement in two patients, aged 52 and 29 years, respectively. Power Doppler sonography was also performed in the first patient in whom both CDU and power Doppler sonography could demonstrate the abnormal vascular channels in the liver. In the second patient, aneurysms in the left hepatic lobe and of the splenic artery were noted. Angiography was performed in both patients and confirmed the abnormal vascular lesions demonstrated by CDU and/or power Doppler sonographic findings.

Adult↗

PubMedDate not supplied

Effect of heart rate on centerline velocities of pulsatile intracardiac jets: an in vitro study with laser Doppler anemometry and pulsed Doppler ultrasound.

This article confirms a recently developed distal jet centerline technique for noninvasively quantifying regurgitant cardiac valve flows. The basic principle that allows flow rate to be calculated is conservation of momentum. As the jet entrains more mass, its centerline velocity decays inversely with distance from the orifice. Under pulsatile flow conditions, it has been shown that this technique remains applicable at peak flow for a normal resting adult heart rate of 60 to 70 beats/min. It is, however, conceivable that at higher heart rates, the same inverse relation between centerline velocity and distance is never fully established, because there is a finite time interval required for the jet to penetrate the receiving chamber. Therefore, the purpose of this study was to determine whether the inverse relationship of centerline velocity to distance develops sufficiently rapidly so that quantitative techniques based on that decay would be applicable over a wide range of heart rates. Two different techniques, an engineering tool, laser Doppler anemometry, and a clinical tool, Doppler ultrasound, were used for measuring jet centerline velocities (averaged over multiple beats). Physiologic pulsatile flows were pumped through two circular orifices, 4 and 6 mm in diameter, at 60 to 150 beats/min; peak orifice velocities ranged from 2 to 5 m/sec. Steady flow experiments were also performed with the same orifice diameters and over the same velocity range. Peak centerline velocities in the fully developed turbulent jet region decayed inversely with distance at all heart rates studied. With laser Doppler anemometry, the proportionality constant of the decay curve was found to be in the range 6.4 +/- 0.5. The pulsed Doppler results provided a jet constant in the range 6.7 +/- 0.3 with the 4-mm orifice diameter, whereas the constant was 6.5 +/- 0.3 with the 6-mm orifice diameter. In steady flow, the proportionality constant was found to be 6.1 +/- 0.2. Therefore, within a wide range of physiologic heart rates, full jet development occurs with sufficient speed so that the expected centerline velocity decay is established (jet empirical constant of 6.3). The conservation of momentum technique for calculating orifice flow rate on the basis of these centerline velocities is thus applicable under physiologic conditions.

Blood Flow Velocity↗

PubMed2003

Left ventricular mechanics during exercise: a Doppler and tissue Doppler study.

AIMS: To study left ventricular mechanics of exercise with Doppler and tissue Doppler. METHODS AND RESULTS: Twenty-one males (mean age, 26; height, 184 cm; weight, 84 kg), exercised on a bicycle, with increasing workload, with oxygen uptake, Doppler flow and tissue Doppler recordings during exercise. There was correlation between peak systolic LVOT flow and annulus velocity; R=0.72, (p<0.001) and between peak mitral E flow and annulus E(a) velocity; R=0.68(p<0.001). Finally there was correlation between peak LVOT and mitral flow velocity; R=0.83(p<0.001) and peak systolic and early diastolic annulus velocity R=0.69(p<0.001). All intervals of the heart cycle decreased with RR-interval. There was a linear relation between diastolic filling and RR-interval, while ejection period was less increased with RR-intervals above 600 ms, and thus not a linear relationship. There was no change in E/E(a) ratio during exercise. CONCLUSIONS: Mechanism for increased filling as well as ejection during exercise seems to be increased contraction and relaxation velocity, with no evidence of Frank-Starling mechanism. Bazett's formula gives a better heart rate correction of LVET at high heart rates than Weissler's.

Adult↗

PubMed2002

Uterine and fetal cerebral Doppler predict the outcome of third-trimester small-for-gestational age fetuses with normal umbilical artery Doppler.

OBJECTIVE: To assess the value of different admission tests in predicting the outcome of small-for-gestational age (SGA) fetuses with normal Doppler waveforms in the umbilical artery. METHODS: Criteria for admission into this retrospective study included: singleton pregnancy with a birth weight < 10th centile; absence of severe maternal complications; no evidence of fetal anomalies on the sonogram; normal umbilical artery Doppler; and availability of complete follow-up. At the first antenatal sonogram classifying the fetus as SGA, Doppler analysis of the uterine and middle cerebral arteries was performed and amniotic fluid volume was assessed. Outcome variables included adverse perinatal outcome (perinatal death, severe morbidity) and emergency Cesarean section for fetal distress. RESULTS: Two hundred and thirty-one pregnancies were included in the study. The mean +/- standard deviation birth weight and gestational age at delivery were 2222 +/- 502 g and 37.3 +/- 2.9 weeks, respectively. In 37 cases (16%), an emergency Cesarean section was performed. There was one intrauterine death and three fetuses delivered by emergency Cesarean section developed severe morbidity. Logistic regression demonstrated that abnormal velocimetry of the uterine arteries and fetal middle cerebral artery were independently correlated with the occurrence of Cesarean section. CONCLUSIONS: SGA fetuses with normal umbilical artery Doppler waveforms and abnormal uterine arteries and fetal middle cerebral artery waveforms have an increased risk of developing distress and being delivered by emergency Cesarean section. Particularly when both uterine and fetal cerebral waveforms are altered at the same time, the risk is exceedingly high (86%) and delivery as soon as fetal maturity is achieved seems advisable. On the other hand, when both vessels have normal waveforms, the chances of fetal distress are small (4%) and expectant management is the most reasonable choice.

Confidence Intervals↗

PubMed2002

Noninvasive assessment of coronary flow velocity and coronary flow velocity reserve in the right coronary artery by transthoracic Doppler echocardiography: comparison with intracoronary Doppler guidewire.

The aim of this study was to evaluate whether coronary flow velocity (CFV) and coronary flow velocity reserve (CFVR) in the posterior descending right coronary artery can be reliably measured by transthoracic Doppler echocardiography (TTDE). In 17 patients, CFV in the posterior descending right coronary artery was measured with TTDE at the time of Doppler guidewire examination. CFV was measured by both methods at baseline and under hyperemic conditions. TTDE data were obtained for 12 patients. CFV and CFVR by TTDE show a good correlation with those obtained by the Doppler guidewire method (average diastolic peak velocity: r = 0.98, y = 0.85x + 5.26; diastolic peak velocity: r = 0.97, y = 0.94x + 3.39; CFVR: r = 0.97, y = 0.87x + 0.56). CFV and CFVR in the posterior descending right coronary artery obtained noninvasively by TTDE accurately reflect these values obtained by the invasive Doppler guidewire method.

Aged↗

PubMed2005

Role of duplex Doppler and power Doppler sonography in transplanted kidneys with acute renal parenchymal dysfunction.

The limited work published on the comparison of power Doppler sonography (PDS) and duplex Doppler sonography (DDS) in the assessment of acute renal allograft dysfunction has shown contradictory results. We compared the role of DDS and PDS in renal transplant recipients developing acute renal parenchymal dysfunction and correlated these findings with kidney biopsy, which was taken as the gold standard. Thirty post-renal transplant patients with acute graft dysfunction underwent Doppler sonography, DDS and PDS using an HDI 5000 ATL machine. Patients who developed graft dysfunction as a result of vascular, obstructive or other non-parenchymal causes were excluded. All patients underwent an allograft biopsy within 72 h of the sonography. Based on the biopsy findings, 24 patients were categorized as having acute rejection, and six patients as having no rejection. The overall sensitivity, specificity and accuracy of DDS for evaluation of graft dysfunction were 54.17, 33.33, and 50.00%, respectively, and that for PDS were superior with 87.50, 33.30, and 76.67%, respectively. The low specificity can be partially attributed to the small number of cases without rejection in our study population. We conclude that PDS is superior to DDS in screening patients with acute parenchymal renal dysfunction post-transplant. However, a normal PDS examination does not exclude the presence of acute rejection. Power Doppler sonography is a useful screening test for diagnosing acute rejection but a renal allograft biopsy remains the gold standard for diagnosis of this condition.

Adolescent↗

PubMed1990

Problems and pitfalls in the performance and interpretation of color Doppler flow imaging: observations based on the influences of technical and physiological factors on the color Doppler examination of mitral regurgitation.

Color Doppler flow imaging has become an integral part of the echocardiographic examination. By providing real-time, two-dimensional spatial maps of normal and abnormal cardiac blood flows, this technique provides important information that may be used to guide patient management. The acquisition and display of color Doppler flow information may be influenced by technical factors, by the physiological condition of the patient, by abnormalities of cardiac morphology, and, on occasion, by artifact. In this article, the results of a study performed to evaluate the influence of technical factors on the color Doppler assessment of mitral regurgitation are reported. Mitral regurgitation jet area size changed significantly with variation in the control settings for color gain, color process, color map, color image resolution, and sector width. A review of those factors that influence the performance and interpretation of the color Doppler flow examination is provided and their significance discussed.

Echocardiography, Doppler↗

PubMed2006

The impact of marathon running upon ventricular function as assessed by 2D, Doppler, and tissue-Doppler echocardiography.

The impact of prolonged exercise upon right ventricular (RV) function is poorly understood and to date no studies have utilized tissue-Doppler imaging (TDI). Thirty-five marathon runners (age range 18-50 years) volunteered for the study. Two-dimensional, pulsed Doppler, and TDI studies were performed one day before and immediately following race completion. Right and left ventricular (LV) longitudinal TDI myocardial velocities were acquired from the tricuspid annulus and mitral annulus, providing velocity data during systole (S'), early diastole (E'), and late diastole (A'). Transtricuspid and transmitral, early diastolic (E), and late diastolic (A) velocities and ratios were assessed using conventional pulsed-wave Doppler. RV and LV fractional area changes (FAC) were calculated from RV and LV end-diastolic and end-systolic areas recorded from 2D scans in a subsample (n = 23). RV myocardial velocities were unchanged pre-post race in S' (21.1 +/- 2.7 to 21.7 +/- 4.5 cm s(-1), P > 0.05), reduced in E' (23.3 +/- 3.5 to 19.9 +/- 5.3 cm s(-1), P < 0.05), increased in A' (19.1 +/- 3.6 to 23.7 +/- 6.8 cm s(-1), P < 0.05) with a resultant decline in E'/A' (1.28 +/- 0.36 to 0.94 +/- 0.45, P < 0.05). This pattern of data was mirrored in the LV. Similarly both pulsed-Doppler tricuspid and mitral E/A ratios decreased from pre- to postrace (P < 0.05). FAC for the RV and LV were unaltered postrace (P > 0.05). The impact of differing age, finishing time (173-330 min), hemodynamic loading and heart rate upon RV and LV function pre- to postrace was negligible. In conclusion, TDI and 2D data, for both the RV and LV demonstrated little change in systolic function after a marathon race. Conversely, a reduction in diastolic function was observed in both ventricles for which a mechanism has yet to be deduced.

Adolescent↗

PubMed1999

Power Doppler improves the diagnostic accuracy of color Doppler ultrasonography in cold thyroid nodules: follow-up results.

The usefulness of a recent color Doppler (CD) ultrasonography technique, named power Doppler (PD), was evaluated in the diagnosis of thyroid nodules showing low or absent uptake of (99m)Tc-pertechnetate, in order to investigate the possibility to improve the diagnostic accuracy of ultrasonography. The rationale was the evidence that at PD the color map displays the total integrated Doppler power in color, while CD generally displays an estimate of the mean Doppler shift. The vascular patterns recorded at PD and CD evaluation of 322 thyroid nodules were compared to the results of cytology and/or histology, when surgery was performed. In respect to the results of cytology, PD has a higher sensitivity (100 vs. 91%) and specificity (95.1 vs. 86.2%) than CD. A similar result was found when PD and CD were compared to the results of histology, sensitivity being 100 vs. 89% and specificity 98.1 vs. 93.7%, respectively. During the follow-up the 2 nodules considered false positive at PD resulted to be tumoral lesions. On this basis, the final specificity of PD in our series was 100%. In conclusion, in the current series including 322 thyroid nodules characterized by a low or absent uptake of (99m)Tc-pertechnetate, PD seems to provide a better characterization of thyroid nodules, possibly allowing a more accurate selection of the patients to subject to fine-needle biopsy.

Adenoma↗

PubMed2006

Thoraco-omphalopagus conjoined twins detected at as early as 9 weeks of gestation: transvaginal two-dimensional ultrasound, color Doppler and fetoplacental Doppler velocity waveform findings.

Here we report a case of conjoined twins that were diagnosed antenatally by routine two-dimensional transvaginal ultrasound examination at as early as the 9th week of gestational age. The fetuses were of the thoraco-omphalopagus type and were sharing the liver, as confirmed by color Doppler. There was a reversed flow in the single ductus venosus of the twins. Umbilical arterial and venous blood flow waveform did not show any abnormality for this gestational age. This case demonstrated the possibility of making an accurate diagnosis of conjoined twins in the first trimester by transvaginal two-dimensional ultrasound and color Doppler examination. Although conjoined twins were described at first trimester before, fetoplacental Doppler waveform findings at this gestational age have been described very rarely. This case demonstrated the possibility of making an accurate diagnosis of conjoined twins and delineating the extent of organ sharing in the first trimester, and early diagnosis can help the parents with the option for pregnancy termination. The importance of expert early vaginal sonography and color Doppler findings is emphasized.

Adult↗

PubMed1999

Closure of the ductus venosus in premature infants: findings on real-time gray-scale, color-flow Doppler, and duplex Doppler sonography.

OBJECTIVE: Our objective was to use gray-scale, color-flow, and duplex Doppler sonography to study the anatomy, flow pattern, and time of closure of the ductus venosus in healthy premature infants. SUBJECTS AND METHODS: We prospectively examined the ductus venosus in 130 premature infants whom we divided into two groups: Group I comprised 27 neonates of gestational age 28-32 weeks, and group II comprised 103 neonates of gestational age 33-36 weeks. Neonates who had undergone umbilical vessel manipulation were excluded from the study. All examinations included gray-scale, color-flow, and duplex Doppler sonography. Patency, length, color flow, and Doppler characteristics of the ductus venosus were recorded. Neonates were examined 1-2 days after birth, 6-7 days after birth, and subsequently every 3-4 days until ductus closure was observed. The time of closure of the ductus for the two groups was compared using the chi-square test. RESULTS: The ductus venosus was patent during the initial examination in 128 of the 130 neonates. Doppler waveform was venous with little variation in velocity. Ductus length slightly exceeded 1 cm in both groups. We found a statistically significant difference in the percentage of infants having a patent ductus venosus after the initial examination: At 1 week after birth, ductus patency was shown in 85% of the infants in group I and in 56% of the infants in group II; at 2 weeks, the respective percentages were 42% and 14%; and at 3 weeks, 27% and 0%. CONCLUSION: The ductus venosus is patent 1-2 days after birth in virtually all premature infants. From 6 days after birth and onward, a significantly greater percentage of smaller premature infants (i.e., 28-32 weeks' gestational age) have a patent ductus venosus than do larger premature infants (i.e., 33-36 weeks' gestational age).

Blood Flow Velocity↗

PubMed2001

B-mode, power Doppler and contrast-enhanced power Doppler ultrasonography in the diagnosis of breast tumors.

PURPOSE: To investigate the role of B-mode and unenhanced and enhanced power Doppler ultrasonography (US) in differentiating solid breast lesions, and to find out whether morphologically different tumors differ in terms of vascularity. MATERIAL AND METHODS: Sixty-five lesions, indeterminate or suggestive of malignancy after mammography were prospectively examined with B-mode and unenhanced and enhanced power Doppler US. The lesions were classified as benign, indeterminate or malignant at B-mode, and as benign or malignant at power Doppler US. The results were compared to the histologic diagnoses. Vascularity was analyzed also quantitatively to find out whether threshold values for differential diagnostics could be set. RESULTS: The sensitivity, specificity, and overall accuracy of the morphologic evaluation were 100%, 10%, and 57%, respectively. Rounded lesions were more vascular than spiculated lesions, but vascular assessment was only helpful when it supported a benign morphology. In quantitative analysis, due to the overlap between the benign and malignant lesions, no threshold values could be set. CONCLUSION: Morphologic criteria were useful in characterizing malignant lesions, but the large proportion of indeterminate findings decreased the specificity of US. Neither unenhanced, nor enhanced power Doppler US was able to improve diagnostic accuracy.

Adult↗

PubMed2003

[Contrast enhanced power Doppler and color Doppler ultrasound in breast masses: Efficiency in diagnosis and contributions to differential diagnosis].

PURPOSE: To compare ability of detection of vascular structures by utilizing ultrasonographic contrast agent (Levovist) prior to and following power Doppler ultrasound (PDUS) and colour Doppler ultrasound (CDUS) and to determine useful parameters in the differentiation of malignant and benign breast masses by means of verified data. MATERIALS AND METHODS: Vascularisation characteristics of 38 breast masses (22 malignant, 16 benign) which were confirmed by mammography and B-mode sonography were evaluated by both CDUS and PDUS following and prior to intravenous contrast application. In addition, Vmax and RI values of vascular structures were calculated by Doppler spectral evaluation. RESULTS: Malignant lesions showed more vascularity than benign lesions both with and without contrast enhancement. With both methods, by utilizing contrast agent, central, penetrating and tortuous vascular structures became more significant in malignant lesions when compared with benign lesions. PDUS was able to detect vascular structures better than CDUS; however, the difference was not statistically significant. Presence of peripheral vascularity was not useful in differentiating malignant from benign lesions. Vmax and RI values were higher in malignant lesions and the difference was statistically significant. In both methods, Vmax > 15 cm/sec and RI > 0.80 (CDUS), and RI > 0.70 (PDUS) were accepted as malignancy parameters. CONCLUSION: Vascular patterns of breast masses as determined with PDUS and CDUS with contrast enhancement and Doppler spectral examinations enabled differentiation of malignant and benign breast lesions. Thus, it is possible to decrease the number of unnecessary surgical interventions.

Adult↗

PubMed1980

[Cerebrovascular Doppler ultrasound studies (cv-Doppler)].

With the cv-Doppler examination, obstructions in the extracranial cerebral arteries can be detected with high reliability. The method can be used - if properly applied - to determine the further diagnostic and therapeutic procedure in cerebrovascular patients. Carotid artery Doppler is based on measurement of blood flow in the teminal branches of the ophthalmic artery and the common carotid atery with and without additional compression manoeuvers of the common carotid artery and branches of the external carotid artery. With direct measurements over the carotid artery, external and internal carotid artery can be differentiated, and stenoses as well as major ulcerated lesions can be localized by pathological flow patterns in the vicinity of these obstructions. In Vertebral-/Subclavian artery Doppler blood flow of the vertebral artery is picked up with the probe placed through the mouth on the locally anesthesized mucous membrane of the oropharynx. By compression of the common carotid artery at the site and opposite to the vessel under examination, the vertebral artery is differentiated from branches of the carotid artery. Blood flow in the central portion of the subclavian artery is picked up by placing the probe in the supraclavicular fossa over the target vessel. - The cv-Doppler examination was used in 3961 patients of whom 570 underwent cerebral angiography. The findings of the noninvasive and invasive method corresponded in more than 94% of the cases.

Adult↗

PubMed1997

[A comparative study of the Doppler methods for evaluation of the degree of carotid artery stenosis. Continuous, pulsed, color Doppler].

OBJECTIVE: Compare various Doppler methods for the quantification of the degree of stenosis on 85 patients. METHOD: the following parameters were measured: maximal velocity (Vmax) inside the stenosis (PW), grades of spectral disturbances at the outlet of the stenosis (PW-CW), index of spectral disturbance (STI) at the outlet of the stenosis (PW-CW), ratio of velocities I(IC/CC) in internal and common carotid (PW), ratio of vessel cross section and residual lumen area (% STEN) by color Doppler. The reference method was the Grades of spectral disturbance and the index of stenosis measured post stenosis. (Method validated against angiography and pieces of endarterectomy.) The following comparisons were done; grades and STI by CW against grades and STI by PW, Vmax (PW) against grade and STI, % STEN (color) against grade and STI, % STEN (color) against Vmax (PW), I(IC/CC) (PW) against grade and STI, I(IC/CC) (PW) against Vmax. CONCLUSION: (a) grades or stenosis index : showed the best reproductibility; (b) a high correlation was found between the grades or stenosis index post stenosis measured by CW or PW; (c) Vmax was not proportional to the stenosis degree and showed large fluctuations for the same stenosis degree; (d) the I(IC/CC) showed large fluctuations for the same stenosis degree, the correlation was poor for this velocity ratio. Both Vmax and I(IC/CC) allow to detect only 2 groups of stenosis > 75% or > 90% in area; (e) color doppler over-estimate stenosis degree by approximately 20% but was more accurate and reproducible than Vmax. An appropriate procedure was designed to avoid this over estimation.

Blood Flow Velocity↗

PubMed1988

Comparison of blood velocity waveform indices recorded by pulsed Doppler and continuous wave Doppler in the umbilical artery.

A comparison was made between the AB ratio, resistance index (RI), and pulsatility index (PI), calculated from tracings obtained by pulsed Doppler (PD) and continuous wave (CW) Doppler devices in 14 uncomplicated singleton pregnancies. The AB ratio, RI, and PI were a slightly higher for the CW Doppler compared to the PD system, although not significantly (p = 0.18, p = 0.21, and p = 0.44, respectively). The difference in signal to noise ratio (S/N ratio) between the PD and CW Doppler systems was felt to be the reason for the discrepancy in the calculated velocity waveform indices.

Blood Flow Velocity↗

PubMed1985

[Doppler sonography in intracranial circulation disorders of the internal carotid artery. A comparative Doppler sonography-angiography study].

During the past 33 months we have investigated 6,587 patients using directional continuous-wave Doppler sonography of the carotid arteries. On the basis of 1,671 retrograde brachial and direct carotid angiograms we have developed criteria for demonstrating a significant increase in the peripheral resistance of the internal carotid artery. We distinguished stenoses proximal (15 cases) and distal (4) to the origin of the ophthalmic artery, supraclinoid internal carotid artery occlusions (8), stenoses (2) and obliterations (10) of the middle cerebral artery that developed suddenly. Stenoses in the carotid siphon (proximal or distal to the origin of the ophthalmic artery) showed a reduction of more than 40% in the relative end-diastolic flow velocity (modified Pourcelot's index); in addition, stenoses proximal to the origin of the ophthalmic artery exhibited an alternating flow, or flow reversal, in the supratrochlear artery to a variable extent. Stenoses distal to the origin of the ophthalmic artery only rarely revealed the increase in orthograde flow velocity that had been theoretically expected in the supratrochlear artery. Stenoses of the middle cerebral artery exceeding the extent of atherosclerotic irregularities proved to be an exception. Supraclinoid obliterations of the internal carotid artery were reliably demonstrated by Doppler sonography. However, the reliably demonstrated by Doppler sonography. However, the majority of the occlusions of the middle cerebral artery that developed suddenly could not be detected by this means, probably due to anastomoses between the anterior and middle cerebral arteries, which were detected by means of angiography. Thus, we believe that continuous-wave Doppler sonography is a reliable tool for detecting stenoses of the carotid siphon of more than 60% reduction in lumen diameter as well as supraclinoid carotid artery occlusions. Resistance to the cerebral blood flow that is located more peripherally cannot be diagnosed reliably by this method.

Brain Ischemia↗