PURPOSE:There is a lack of studies on the intra- and interobserver variability of endoscopic ultrasonography (EUS) and especially endoscopic sonoelastography (ES). The aim of this study was to evaluate the intra- and interobserver agreement of EUS and ES during the evaluation of a specific lymph node in patients with upper gastrointestinal malignancies (UGIM). The ES strain ratio was used to differentiate between benign and malignant lymph nodes and the interobserver agreement was evaluated.MATERIALS AND METHODS:This study prospectively enrolled 62 patients with UGIM. EUS and ES were performed by two observers in randomized order of a specific lymph node using a linear Pentax echoendoscope and the Hitachi EUB-8500 US unit. The lymph node was classified as malignant or benign on the basis of EUS, ES, an ES scoring system, and 5 repeated strain ratio measurements. The intraobserver variation was evaluated by each observer performing 20 strain ratio measurements of the same lymph node. Finally, EUS fine needle aspiration was performed. The kappa statistic was used to test for interobserver variability.RESULTS:One patient was excluded due to inadequate ES imaging. Thus, 61 patients were included in the analysis of the interobserver agreement. Using EUS, ES, and an ES scoring system, the kappa values were 0.80, 0.58, and 0.35, respectively. An ES strain ratio of 3.81 was defined as the cut-off value between benign and malignant lymph nodes using cytology as the gold standard (n = 55). Using this modality, a kappa value of 0.59 was obtained. A t-test comparison of the measured strain ratios for the two observers found no significant differences.CONCLUSION:ES and ES strain ratio evaluation of lymph nodes were feasible and may be reproduced with good interobserver agreement in a blinded clinical setup. The predefined ES scoring system provided only poor interobserver agreement. Image selection should be part of the intra- and interobserver evaluation. ES strain ratio seemed promising but larger studies are needed to evaluate this new feature.
Ziel: Material und Methoden: Ergebnisse: Schlussfolgerung: Purpose: Materials and Methods: Results: Conclusion:
To examine separately the common carotid intima and media thicknesses in peri- and post-menopausal women by ultrasound. In this prospective observational study, 158 asymptomatic women attending our outpatient clinic for routine care were recruited (135 post- and 23 peri-menopausal). With a high-frequency linear ultrasound probe used also for breast ultrasound measurements the thickness of the intima and media layers of the common carotid arteries (both sides) were taken. Age, hypertensive status, hormone replacement therapy (HRT) and BMI were also noted and correlated with the US measurements. Intra-observer variability was also assessed in 316 still images. Reproducibility of the carotid layer measurements was good (ICC 0.8). There were no significant differences between the measurements of the left and the right sides. Overall carotid thickness increased with age (r = 0.47, P < 0.0001) and in women with hypertension (P = 0.022). Women who had stopped HRT also had thicker carotid walls than women continuing on HRT (P = 0.014). These significant results were attributable mainly to media thickness; intima thickness was only correlated with age (r = 0.34, P < 0.0001). There was no correlation with BMI. Surprisingly, ten women (10/158, 6.3%) showed atherosclerotic plaques that in three women were classified as severe; one received immediate stenting. Intima and media thickness of the common carotid artery can easily be measured in a routine setting and using the same equipment also used for breast ultrasound. Overall vessel wall correlates mostly with age and, in our study, this was determined by media thickness alone. Continuing HRT seemed to be associated with thinner media. Using this relatively easy technique, 6.3% of these asymptomatic patients were found to have relevant atherosclerotic plaques.
OBJECTIVE:To define alterations in the blood flow velocities of the ophthalmic artery (OA), central retinal artery (CRA), posterior ciliary artery (PCA) in essential hypertension and to evaluate the effect of a new antihypertensive drug, candesartan which is an angiotensin II receptor antagonist, on the blood flow velocity in hypertensive patients. METHODS:Blood flow velocity and resistive index (RI) of the OA, CRA, and PCA were measured in 22 hypertensive patients off medication and 15 controls by color Doppler imaging. After treatment with candesartan, blood flow velocity and RI were again measured in the hypertensive patients. RESULTS:In controls (n=15), the OA had a mean peak systolic flow velocity (PSFV) of 48.1+/-2.6 cm/s, mean end diastolic flow velocity (EDFV) of 16+/-1.0 cm/s, and RI of 0.65+/-0.01; the CRA had a PSFV of 20.8+/-0.4 cm/s, EDFV of 9.4+/-0.3 cm/s, and RI of 0.54+/-0.01; the PCA had a PSFV of 23.6+/-0.7 cm/s, EDFV of 11.2+/-0.3 cm/s, and RI of 0.52+/-0.01. There was a significant decrease in the PSFV and EDFV of the vessels in the medication free hypertensive patients when compared with controls (P<0.05). In the hypertensive patients off medication (n=22), the OA had a PSFV of 29.4+/-1.2 cm/s, EDFV of 10.4+/-0.5 cm/s, and RI of 0.71+/-0.01; the CRA had a PSFV of 15.1+/-0.6 cm/s, EDFV of 5.4+/-0.3 cm/s, and RI of 0.65+/-0.02; the PCA had a PSFV of 17.2+/-0.6 cm/s, EDFV of 6.7+/-0.3 cm/s, and RI of 0.61+/-0.01. RI measured in the OA, CRA, PCA were significantly increased in the hypertensive patients when compared with the controls (P<0.05). In hypertensive patients after medication (n=22), OA had a PSFV of 38.3+/-2.5 cm/s, EDFV of 12.3+/-0.7 cm/s, and RI of 0.68+/-0.01; CRA had a PSFV of 19.2+/-0.5 cm/s, EDFV of 7.8+/-0.3 cm/s, and RI of 0.59+/-0.01; PCA had a PSFV of 20.8+/-0.8 cm/s, EDFV of 9.2+/-0.4 cm/s, and RI of 0.56+/-0.01. There was a significant increase in the blood flow velocities of the OA, CRA, PCA (P<0.05) and significant decrease in the RI values in the treated hypertensive patients when compared with the controls (P<0.05). But blood flow velocities and RI values did not reach the control level. CONCLUSION:The increase in the RI values and the decrease in the blood flow velocity of extraocular vessels in the hypertensive patients are thought to be caused by increased peripheral resistance in the vessels of the eye and orbit. Although, it increases blood flow velocity and decreases RI significantly, candesartan treatment in the hypertensive patients cannot increase blood flow velocity and decrease RI to the control level.
Background and purpose: Until now the assessment of intracranial pressure (ICP) requires invasive methods. A previously introduced mathematical model allowed the non-invasive estimation of ICP (nICP) from arterial blood pressure (ABP) and blood flow velocity (FV). In various studies we have investigated the accuracy of this method and possible clinical applications. Methods and results: Selected hemodynamic parameters, calculated from the cerebral blood FV and the ABP curves, were used to express the relationship between ABP input and ICP output by linear transformation rules. In several clinical studies the accuracy and possible benefits of this method of non-invasive ICP (nICP) assessment were investigated. Assessment of ICP plateau waves: In 17 severely head injured patients we verified this model by comparison of nICP and measured ICP during generation of plateau waves, recorded in seven of these patients. In all simulations plateau elevations of ICP were well replicated. The correlation coefficient between increase of nICP and real ICP was R=0.98; P<0.001. Lumbar infusion tests: Twenty one hydrocephalic patients were studied. Parallel increases in real ICP and nICP during lumbar infusion tests were evidently visible. Resistance of cerebrospinal fluid outflow (Rcsf) was computed using nICP and compared with Rcsf computed from real ICP. The mean error between real and non-invasive Rcsf was 4.1±2.2 mmHg min/ml. Cerebral autoregulation: One hundred and forty five patients were studied after severe head injuries. The state of autoregulation was assessed by moving correlation of cerebral perfusion pressure (CPP=ABP−ICP) and FV (Mx index). nICP instead of ICP was used to continuously estimate the state of autoregulation and to dynamically adapt the nICP procedure to this state. A median error between ICP and nICP of 6.0 mmHg was observed. Directly and non-invasively assessed Mx indices correlated highly significantly (R=0.9; P<0.001). Conclusions: The results demonstrate that the nICP assessment model constitutes a reliable method to monitor ICP and may therefore provide various useful clinical applications.
As an object rotates with respect to a stationary planar ultrasonic beam, the scattering centres within the object return echoes that are Doppler-shifted in frequency by amounts depending on the velocities of the individual scatterers. The backscattered echo amplitude at any particular frequency is the line integral of the scattered radiation at the cross-range corresponding to that frequency. The amplitude as a function of frequency can be interpreted as a tomographic projection. A tomographic reconstruction algorithm can produce an image of the distribution of scattering centres in the insonified object from these projections. This paper describes the development and characterisation of a microscanner to investigate the approach of using continuous wave ultrasound for three-dimensional cross-sectional imaging. The results of preliminary tissue investigation, conducted using bovine coccygeal intervertebral discs, are described. The radial imaging resolution improves as the Doppler frequency resolution improves but the circumferential resolution degrades proportionally. As the number of projections increases, there is a finite increase in image quality. Two- and three-dimensional images of the intervertebral disc reveal an alternate light and dark banding pattern that is characteristic of the laminar structure of the annulus fibrosus.
Purpose: To assess the diagnostic value of Levovist in the ultrasound imaging of visceral arteries in patients with clinical symptoms of abdominal angina, before and after percutaneous transluminal angioplasty (PTA). Material and method: During a 12-month period (2000/2001) five patients with visceral arterial stenoses had ultrasound examinations and a subsequent PTA procedure. Indications for ultrasound examination were abdominal angina symptoms persisting for 3–5 years, (postprandial abdominal pain, diarrhea, and vomiting). In all patients ultrasound examinations were performed using color and spectral Doppler before and after Levovist injections. Color Doppler images and maximum blood flow velocity in stenosed visceral arteries were assessed. Patients underwent control Doppler examinations with Levovist injections to assess the effect of PTA. Results: In three patients conventional Doppler examination did not allow proper evaluation of visceral arteries, because of weak color and spectral Doppler signal and in two remaining patients visceral arteries were not visualized at all. In all five patients strong enhancement of color and spectral Doppler signal was observed after Levovist administration. In all these cases a hemodynamically significant stenosis was diagnosed: coeliac trunk-2 and superior mesenteric artery-3. PTA was performed successfully in these patients. In one of them ultrasound examination done before Levovist injection allowed good visualization of treated SMA and showed good PTA result. In the remaining four patients Doppler examination with the use of Levovist demonstrated visceral arteries well and confirmed successful PTA procedures. Conclusions: The use of Levovist makes the diagnostic efficiency of Doppler examinations much higher. In most cases it allows an unequivocal diagnosis of visceral artery stenosis in patients with abdominal angina symptoms. The Doppler examination with the use of Levovist is the method of choice in follow-up after PTA.
Objective: Among other factors, the cerebral blood flow (CBF) is regulated in accordance to the arterial CO2 tension and the cortical activity. The CO2 test is commonly used to measure the vascular reserve capacity. Most functional imaging studies rely on the activity-flow coupling (AFC). We aimed to combine both challenges in order to increase the insight into mechanisms of CBF regulation. Methods: Fifteen healthy students underwent a functional transcranial Doppler test using a visual stimulation paradigm: firstly under normocapnia and secondly under conditions of hypercapnia. Hypercapnia was induced by breathing a carbogene gas mixture of 5% CO2 and 95% O2. The entire time course of flow velocity adaptation in the posterior cerebral artery (PCA) was analyzed mathematically using a control system approach. Results: Resting CBF velocities increased by nearly 26% under conditions of hypercapnia, whereas the slight increase in arterial blood pressure (ABP) and the decrease in the Pourcelot–Pulsatility index (PI) were statistically not significant. From the control system parameters which were time delay, rate time, gain, attenuation and natural frequency, only the parameter rate time, indicative for the initial steepness of flow velocity increase, showed a statistically significant decrease, consistently for the peak systolic and enddiastolic flow velocity data. As concluded from the unchanged gain parameter the absolute amount of blood flow evoked by the same visual stimulus increased also by 26%. Conclusion: Evaluated by Doppler measurements hypercapnia seems to influence the AFC in two ways: It decreases the steepness of the initial increase in blood flow velocity and enhances the absolute amount of blood flow evoked by the same stimulus.
Objectives: The aim of this study was to investigate whether ultrasonography can characterise plaque morphology and surfaces independent of the observer. Methods: Computer-assisted image analysis of the grey scales of B-mode scans from 15 patients with stenoses of the internal carotid artery was performed and compared with the histopathological reports. In vitro angioscopy, was used to visualise the plaque surfaces of the thromboendarterectomy specimens. Result: Assessment of the internal plaque structure by ultrasound showed close agreement between the two observers (P<0.01) without correlation with the histopathological results. Ultrasonography was able to characterise the plaque surfaces in 93% of cases. Conclusion: This investigation showed that standardised computer-assisted analysis of the internal plaque structure correlates less closely than histological investigation, but agrees closely with the surface structure of the plaque. The exclusive use of digital image processing and standardisation of the investigative technique are expected to provide even better results.
Case report of a neonate presenting within 1 h of birth with right side scrotal swelling and a dusky skin discoloration thought clinically to be a hydrocele or testicular torsion. Ultrasound examination demonstrated bilateral hydroceles, more prominent on the right, scrotal oedema and a perinephric loculated fluid collection secondary to right adrenal hemorrhage. We review the ultrasound appearance of the normal and haemorrhagic neonatal adrenal and discuss the differential diagnosis of both neonatal adrenal lesions and scrotal swellings. The role and benefits of ultrasound in the primary diagnosis and management of neonatal adrenal hemorrhage is emphasized.
The Authors evaluate the diagnostic accuracy of echography in hepatic echinococcosis, particularly in the completely liquid types of cysts without septa or hydatid sand and in the solidified forms where the differential diagnosis with other hepatic pathologies can be difficult. The study was carried out with a 7.5 MHz probe and the results were compared with those from the use of a 3.5 MHz probe and from CT, serology for hydatidosis and echoguided sampling. Seventy one patients, 36 with liquid hepatic lesions and 35 with solid hepatic lesions (31 hydatid and 40 non-parasitic), were evaluated echographically, first with a 3.5 MHz probe and subsequently with a 7.5 MHz probe. All the patients underwent serology for hydatidosis. All the liquid lesions were subjected to percutaneous echoguided aspiration and all the solid lesions to CT; echoguided biopsy was performed in only 24 of the latter lesions. With the 7.5 MHz probe, a wall was revealed in 96.77% of parasitic cysts but in only 5% of non-hydatid ones. Moreover, using the 7.5 MHz probe, it was possible to see a triple-layered aspect of the wall in the hydatid cysts. The results obtained with the 7.5 MHz probe demonstrate a high diagnostic accuracy comparable to that of MR.
Background: The value of color Doppler sonography in thyroid disease continues to be a matter of debate. Over the past few years, several studies have proved unable to yield unequivocal results. Only a few studies concerning color Doppler sonography in patients with hypothyroidism have been published. Methods: 89 patients with hypothyroidism have been evaluated. They were examined clinically; laboratory tests on thyroid function and color Doppler sonography have been performed. The color flow distribution and intensity were estimated and the fastest flow velocity (PSV) detectable with a pw-doppler was registered. The color pattern was graded from 0 to III as has been described by others and the color Doppler findings were then correlated to both the clinical picture and the laboratory results. Results: 56 of the 89 hypothyroid patients showed pattern 0 with a PSV of 22 cm/s. In 33 patients different degrees of increased parenchymal color could be found with a concordant PSV: 16 patients showed pattern I with a PSV of 39 cm/s; 11 showed pattern II with PSV 58 cm/s, and 6 showed pattern III with PSV 63 cm/s. Regarding the corresponding clinical and laboratory variables, there was a very close correlation between color intensity and anti-Tg/anti-TPO antibody levels: pattern 0: anti-Tg 474 IU/ml, anti-TPO-Ab 810 IU/ml; pattern I: 1053/1733; pattern II: 1774/2432; pattern III: 1951/2633. Some correlation could also be found for the TSH values and the calculated volume of the thyroid gland, whereas the duration of hypothyroidism showed an inverse correlation to color intensity. (Pattern 0: TSH 3.1 mE/ml, volume 9.2 ml, duration 43 months; pattern I: 4.2 mE/l, 15.7 ml, 24 mos.; pattern II: 11.5 mE/l, 22.3 ml, 16 mos.; pattern III: 38.2 mE/l, 34.3 ml, 10 mos, respectively). Conclusions: The color Doppler pattern of intense hypervascularization of the thyroid gland formerly attributed only to the hyperthyroid state of active Graves’ Disease can also be seen in hypothyroidism. Our data support the concept that the color flow appearance is not the result of stimulated thyroid hormone production, but a measure of the activity of an autoimmune process.
Objective: Ultrasound (US) measurement of thyroid volume is used in diagnosis and follow-up of patients with thyroid disease. We assessed a new formula and technique for thyroid volume calculation, based on an automatically continuous trace transverse surface area (aTSA) calculation, to ascertain where this technique could reduce inter-observer variation. Methods: Three observers with a different level of US expertise, using a 12–5 MHz linear transducer, examined 25 volunteers. Inter-observer variations were calculated for diameter measurements and for the thyroid lobe volume calculations using the single factor ANOVA method. Results: Using the new technique and formula, no statistically significant differences existed, in contradistinction to using the classical formula for an ellipsoid (P=0.02). Conclusion: When thyroid volume measurements are required, we recommend using a new method of thyroid volume calculation based on the use of an automatically calculated continuous trace aTSA measurement to avoid significant inter-observer variation in calculation of thyroid lobe volumes
OBJECTIVE:To assess the heating caused by selected pulsed Doppler and physiotherapy ultrasound beams by measurements made using thermal test objects. METHOD:Thermal test objects were used to measure temperature rises in selected ultrasound fields. These were compared with theoretical predictions based on standard exposure measurements. A separate thermocouple was used to measure heating at the transducer surface. RESULTS:Temperature rises of up to 6 degrees C were measured for Doppler fields using a thermal test object. The attenuation-corrected temperature rises that were measured generally agreed with calculated Thermal Indices. Temperature rises of up to 2 degrees C were observed for physiotherapy ultrasound fields in pulsed operation. CONCLUSION:Significant overlap between the measured temperature rises of selected pulsed Doppler and physiotherapy ultrasound fields was observed.
Background: Patients with colorectal metastases confined to the liver may be cured by resection. Combined bimanual palpation and intraoperative ultrasound (IOUS) augment the detection of colorectal hepatic metastases. The importance of IOUS in the surgical management of hepatic tumors has been demonstrated and should arguably be considered the final diagnostic procedure. Objective: To determine the relevance of routine IOUS prior to hepatic resection compared with improved preoperative Magnetic resonance imaging (MRI). Patients and methods: Eighty patients with metastatic colorectal adenocarcinoma underwent hepatic resection between 1998 and 2001. The IOUS results were compared with preoperative MRI, bimanual palpation, and resection histopathology. The preoperative surgical plan was compared with the surgical procedure performed. Data were retrospectively analyzed. Results: IOUS provided additional useful information not available preoperatively for 37 (47%) patients, including the identification of subcentimetre metastatic lesions, characterization of the lesion, and the anatomy of the hepatic vasculature. The preoperative surgical plan was changed secondary to the IOUS findings alone in 14/80 (18%) patients. IOUS did not provide any additional useful information for 43 (53%) patients. A correlation was demonstrated between the preoperative diagnosis, intraoperative findings, and resection histopathology. Conclusion: Accurate diagnostic studies facilitate critically decisive actions during planned hepatic resection(s). The current findings suggest that IOUS provide the most useful additional information for hepatic lesions, despite recent improvements in preoperative MRI scanning. Furthermore, routine IOUS should be employed during hepatic resection for colorectal metastases.
Objective: Ultrasonography is an established diagnostic modality in the follow-up of thyroid cancer. Color flow Doppler has been proposed by some authors as an additional tool for differentiating benign from malignant cervical lesions in various types of head and neck cancer. Over the last few years, a new generation of high-resolution ultrasound platforms with the ‘power-mode’ feature has become available, that also enables the imaging of small vessel blood flow. The objective of our study was to find ways of optimizing the differentiation of benign and malignant cervical tumors in thyroid cancer follow-up by means of sonography. Methods: Hundred and twelve cervical lesions in 90 patients with thyroid cancer were evaluated by high-end ultrasonography (Sonoline™ Elegra, Siemens) using a small-part transducer (7.5 L 40, Siemens). B-mode sonography was performed at a frequency of 8 MHz. The Solbiati index (SI= ratio of largest to smallest diameter), configuration, echogenicity, intranodular structures, and margins were assessed. Perinodular and intranodular blood flow was evaluated by color flow Doppler (PRF 1250 Hz for conventional color flow Doppler, 868 Hz for power-mode Doppler). Possible malignancy was validated by histology, cytology, scintigraphy, and follow-up. Thirty five lesions were benign (diameter 0.4–3.0 cm) and 77 were malignant (0.4–5.4 cm). The patients were randomized into a test group and a learning group to determine the diagnostic value of various ultrasound criteria by means of statistical analysis. In the learning group, decision rules based on the dichotomized criteria were developed using a logistic regression model. Sensitivity and specificity of these decision rules were then evaluated in the test group. Results: The presence of an echocomplex pattern or irregular hyperechoic small intranodular structures (criterion A) and the presence of an irregular diffuse intranodular blood flow (criterion B) are the best indicators of malignancy, whereas an SI≫2 is highly indicative of benign changes. Color flow Doppler is a useful addition to B-mode scanning for distinguishing benign and malignant neoplasms in the follow-up of thyroid cancer. Power-mode Doppler sonography significantly improves imaging of perinodular and intranodular blood flow when compared with conventional color flow Doppler. Conclusion: We propose the following decision rules based on a combination of the criteria above: (A) and (B) fulfilled: malignant, if SI≤4; (B) but not (A) fulfilled: malignant, if SI≤3; (A) but not (B) fulfilled: malignant, if SI≤2; neither (A) nor (B) fulfilled: malignant, if SI≈1 (sensitivity: 90%; specificity: 82%; accuracy 88%).
The possibilities and the limits of transabdominal ultrasonography (US) in the diagnosis of bilio-pancreatic diseases are reviewed here in the light of the last 10 years’ research. US remains the method of choice for the diagnosis of gallstones and is generally accepted as an initial imaging technique in gallstone complications, such as acute cholecystitis. Moreover the method can be useful for the detection of the biliary complications after laparoscopic cholecystectomy and after liver transplantation. US is still considered the first diagnostic procedure when stones are suspected in the common bile duct. The use of color Doppler can provide a differential diagnosis of gallbladder cancer with respect to other benign inflammatory or polypoid lesions. Color Doppler US allows to detect vascular complications of acute pancreatitis such as pseudoaneurysms. US is still considered useful for the initial screening of the pancreatic cancer. However, for staging other imaging techniques must be employed. With US useful informations are obtained in the diagnosis of cystic tumors of the pancreas and of pancretic metastases. US is generally of little use for the diagnosis of endocrine tumors.
Objectives: The objectives are to study the correlation between the women's perception of transvaginal sonography (TVS) and the gender of the examiner and the state of the pregnancy. Methods: The population studied was unselected women attending the early assessment unit at Sharoe Green Hospital with various complications of early pregnancy. All the women were in the first trimester. Only women who had TVS and who gave informed consent were included. Results: Four hundred and twenty five (425) women were recruited. A male doctor examined 215 (50.6%), while a female doctor examined the remaining 210 (49.4%). Two hundred and ninety eight (70.1%) of the pregnancies were viable and 127 (29.9%) were non-viable. About 98.1% of the women found TVS acceptable. There was no statistically significant difference in the women's perception of the procedure with regard to the gender of the examiner or the state of the pregnancy. Conclusions: The majority of women (98.1%) perceived TVS favourably. The gender of the examiner and the state of the pregnancy have no influence on the women's perception of the procedure.
Advances in neurosonology have generated several techniques of ultrasonic perfusion imaging employing ultrasound echo contrast agents (ECAs). Doppler imaging techniques cannot measure the low flow velocities that are associated with parenchymal perfusion. Ultrasonic perfusion imaging, therefore, is a combination of a contrast agent-specific ultrasound imaging technique (CAI) mode and a data acquisition and processing (DAP) technique that is suited to observe and evaluate the perfusion kinetics. The intensity in CAI images is a measure of ECA concentration but also depends on various other parameters, e.g. depth of examination. Moreover, ECAs can be destroyed by ultrasound, which is an artifact but can also be a feature. Thus, many different DAPs have been developed for certain CAI techniques, ECAs and target organs. Although substantial progress in ECA and CAI technology can be foreseen, ultrasound contrast imaging has yet to reliably differentiate between normal and pathological perfusion conditions. Destructive imaging techniques, such as contrast burst imaging (CBI) or time variance imaging (TVI), in combination with new DAP techniques provide sufficient signal-to-noise ratio (SNR) for transcranial applications, and consider contrast agent kinetics and destruction to eliminate depth dependency and to calculate semi-quantitative parameters. Since ultrasound machines are widely accessible and cost-effective, ultrasonic perfusion imaging techniques should become supplementary standard perfusion imaging techniques in acute stroke diagnosis and monitoring. This paper gives an overview on different CAI and DAP techniques with special focus on recent innovations and their clinical potential.
During the past 15 years several paradigms to study dynamic cerebral autoregulation (CA) were developed by measuring cerebral blood flow (CBF) velocity with transcranial Doppler (TCD) in response to blood pressure changes. As a more indirect approach to measure autoregulation, vasomotor reactivity (VMR) can be determined by the use of vasodilatory stimuli. CA or VMR are often severely disturbed in occlusive carotid artery disease. Several prospective studies have shown that reduced VMR is an important risk factor for stroke or TIA in patients with symptomatic and asymptomatic carotid artery stenosis or occlusion. Future randomized intervention studies will show whether asymptomatic patients with carotid artery stenosis and pathological autoregulation or VMR will benefit from revascularization therapy.
