Angle-corrected imaging transcranial doppler sonography versus imaging and nonimaging transcranial doppler sonography in children with sickle cell disease

DISPLACE study shows poor quality of transcranial doppler ultrasound for stroke risk screening in sickle cell anemia

ABSTRACT

Children with sickle cell anemia (SCA) are at increased risk of stroke when compared with their age-based counterparts. The Stroke Prevention Trial in Sickle Cell Anemia (STOP) previously demonstrated that with the use of transcranial Doppler ultrasound (TCD; Sickle Stroke Screen) and chronic red cell transfusion, the risk of stroke is reduced by over 90%. The STOP criteria detailed the type and method of measurement required; the time-averaged mean maximum velocity (TAMMV). Unfortunately, it has been difficult to adhere to the appropriate TAMMV measurements. The objectives of this study were to assess the quality of TCD and transcranial Doppler imaging (TCDi) reports to determine the report quality and accuracy. This is a subanalysis of the DISPLACE (Dissemination and Implementation of Stroke Prevention Looking at the Care Environment) study. Over 12 000 TCD/TCDi reports were collected during this study from 28 institutions; 391 TCDs were reviewed for this subanalysis. There were significant variations in the vessels being assessed, the velocities used to define abnormal results, and who was interpreting the scans. In 52% of reports, it was impossible to identify whether the TAMMV was what was measured. Similarly, it was only clear in 42% of reports that the TAMMV was used to interpret the examination as normal/abnormal. Given this inconsistency, we strongly recommend standardization of TCD/TCDi reporting, specialized training for those performing and interpreting the scans in the use of TCD/TCDi in patients with SCA, internal quality assurance, and institutional quality improvement work to ensure appropriate use of this potentially lifesaving technology.

Role of Advanced Hemodynamic Ultrasound Evaluation in the Differential Diagnosis of Middle Cerebral Artery Stenosis: Introducing Morphological Criteria

OBJECTIVE

The aim of the work described here was to determine the possible impact of the new technique advanced hemodynamic ultrasound evaluation (AHUSE) in identification of severe intracranial stenosis. Transcranial Doppler (TCD) and transcranial color-coded Doppler (TCCD) provide reliable velocimetric data, the indirect analysis of which allows us to obtain information on the patency of vessels and assumed stenosis range. However, very tight stenoses (>95%) cannot be detected with velocimetric criteria because of spectrum drops and the absence of high velocities, so that the right curve of the Spencer equation cannot be solved. Likewise, high velocities are not detected when analyzing morphologically long stenosis. Furthermore, the current classifications based on velocimetric criteria do not provide any categorization on stenoses with multiple acceleration points (MAPs).

METHODS

With this Technical Note we aim to introduce, in addition to velocimetric criteria, more morphological criteria based on TCCD with the algorithm of AHUSE to optimize the characterization of intracranial stenosis (IS). TCCD-AHUSE relies on intensity-based next-generation techniques and can be used to identify IS with MAPs and simultaneously perform a morphological assessment of the stenosis length.

RESULTS

We introduce a new technical ultrasound (U) approach that we tested in a sample of four different types of stenoses combining velocimetric data and AHUSE using Esaote Microvascularization (MicroV) technique to the M1 tract of the middle cerebral artery (MCA).

CONCLUSION

The authors believe that a multiparametric evaluation is more sensitive and supports the clinician by introducing the morphological concept, not just the velocimetric concept, to differentiate the IS pattern of MCA. The potential for developing a diagnostic/prognostic algorithm is discussed.

A Novel Patient-Specific Computational Fluid Dynamics Study of the Activation of Primary Collateral Pathways in the Circle of Willis During Vasospasm

The Circle of Willis (CoW) is a redundant network of blood vessels that perfuses the brain. The ringlike anatomy mitigates the negative effects of stroke by activating collateral pathways that help maintain physiological perfusion. Previous studies have investigated the activation of these pathways during embolic stroke and internal carotid artery occlusion. However, the role of collateral pathways during cerebral vasospasm-an involuntary constriction of blood vessels after subarachnoid hemorrhage-is not well-documented. This study presents a novel technique to create patient-specific computational fluid dynamics (CFD) simulations of the Circle of Willis before and during vasospasm. Computed tomographic angiography (CTA) scans are segmented to model the vasculature, and transcranial Doppler ultrasound (TCD) measurements of blood flow velocity are applied as boundary conditions. Bayesian analysis leverages information about the uncertainty in the measurements of vessel diameters and velocities to find an optimized parameter set that satisfies mass conservation and that is applied in the final simulation. With this optimized parameter set, the diameters, velocities, and flow rates fall within typical literature values. Virtual angiograms modeled using passive scalar transport agree closely with clinical angiography. A sensitivity analysis quantifies the changes in collateral flow rates with respect to changes in the inlet and outlet flow rates. This analysis can be applied in the future to a cohort of patients to investigate the relationship between the locations and severities of vasospasm, the patient-to-patient anatomical variability in the Circle of Willis, and the activation of collateral pathways.

Development of a Flow Phantom for Transcranial Doppler Ultrasound Quality Assurance

Anecdotal evidence was recently brought to our attention suggesting a potential difference in velocity estimates between transcranial Doppler (TCD) systems when measuring high velocities (∼200 cm/s) close to the threshold for sickle cell disease stroke prevention. As we were unable to identify a suitable commercial TCD phantom, a middle cerebral artery (MCA) flow phantom was developed to evaluate velocity estimates from different devices under controlled conditions. Time-averaged velocity estimates were obtained using two TCD devices: a Spencer Technologies ST³ Doppler system (ST³ PMD150, Spencer Technologies, Seattle, WA, USA) and a DWL Dopplerbox (DWL Compumedics, SN-300947, Singen, Germany). These were compared with velocity estimates obtained using a Zonare duplex scanner (Zonare Medical Systems, Mountain View, CA, USA), with timed collection of fluid as the gold standard. Bland-Altman analysis was performed to compare measurements between devices. Our tests confirmed that velocities measured with the DWL TCD system were +4.1 cm/s (+3.7%; limits of agreement [LoA]: 2%, 5%; p = 0.03) higher than the Spencer system when measuring a velocity 110 cm/s and +12 cm/s higher (+5.7 %; LoA: 4.8%, 6.6%; p = 0.03) when measuring velocities of 210 cm/s, close to the diagnostic threshold for stroke intervention. We found our MCA phantom to be a valuable tool for systematically quantifying differences in TCD velocity estimates between devices, confirming that the DWL system gave consistently higher readings than the Spencer ST³ system. Differences become more pronounced at high velocities, which explains why they were not identified earlier. Our findings have clinical implications for centers using TCD to monitor patients with sickle cell disease, as extra care may be needed to adjust for bias between manufacturers when making treatment decisions about children with sickle cell with velocities close to the diagnostic threshold.

Transcranial Doppler Screening in a Current Cohort of Children With Sickle Cell Anemia: Results From the DISPLACE Study

Stroke prevention guidelines for sickle cell anemia (SCA) recommend transcranial Doppler (TCD) screening to identify children at stroke risk; however, TCD screening implementation remains poor. This report describes results from Part 1 of the 28-site DISPLACE (Dissemination and Implementation of Stroke Prevention Looking at the Care Environment) study, a baseline assessment of TCD implementation rates. This report describes TCD implementation by consortium site characteristics; characteristics of TCDs completed; and TCD results based on age. The cohort included 5247 children with SCA, of whom 5116 were eligible for TCD implementation assessment for at least 1 study year. The majority of children were African American or Black, non-Hispanic and received Medicaid. Mean age at first recorded TCD was 5.9 and 10.5 years at study end. Observed TCD screening rates were unsatisfactory across geographic regions (mean 49.9%; range: 30.9% to 74.7%) independent of size, institution type, or previous stroke prevention trial participation. The abnormal TCD rate was 2.9%, with a median age of 6.3 years for first abnormal TCD result. Findings highlight real-world TCD screening practices and results from the largest SCA cohort to date. Data informed the part 3 implementation study for improving stroke screening and findings may inform clinical practice improvements.

Practice patterns for stroke prevention using transcranial Doppler in sickle cell anemia: DISPLACE Consortium

BACKGROUND

Children with sickle cell anemia (SCA) are at increased risk for stroke. In 2014, the National Heart, Lung, and Blood Institute (NHLBI) developed guidelines for stroke prevention in SCA informed by the Stroke Prevention Trial in Sickle Cell Anemia (STOP) and Optimizing Primary Stroke Prevention in Sickle Cell Anemia (STOP II) trials. The guidelines specify the use of transcranial Doppler (TCD) screening and intervention with chronic red cell transfusions (CRCT) in children with SCA who have TCD indication of high stroke risk. The purpose of this study was to describe real-world practice patterns of stroke risk screening and intervention in sites that participated in the Dissemination and Implementation of Stroke Prevention Looking at the Care Environment (DISPLACE) Consortium.

PROCEDURE

Site investigators completed a survey during the formative stages of the study to evaluate their TCD practices relative to the STOP studies. Descriptive statistics and analysis of free-text comments for more complex practices were evaluated.

RESULTS

Results suggested universal acceptance of annual TCD screening and initiation of CRCT following an abnormal result among the DISPLACE Consortium, consistent with NHLBI recommendations. However, there was wide variation in methods for conducting TCD screenings (eg, dedicated Doppler vs TCD imaging), classifying TCD results, and actions taken for conditional and inadequate results.

CONCLUSIONS

Annual TCD screening and initiation of CRCT are critical stroke prevention practices that were universally embraced in the consortium. Additional research would be beneficial for informing clinical practices for areas in which guidelines are absent or unclear.

An Educational Study Promoting the Delivery of Transcranial Doppler Ultrasound Screening in Paediatric Sickle Cell Disease: A European Multi-Centre Perspective

Background: Effective stroke prevention in sickle cell disease (SCD) is recommended for children with sickle cell anaemia. Effective implementation relies on the correct stratification of stroke risk using Transcranial Doppler Ultrasound (TCD), prior to committing children to long-term treatment with transfusion. Nevertheless, less than 50% of children with SCD in Europe receive annual TCD—one of the reasons being a lack of trained personnel. The present European multi-centre study was designed to promote the standardisation and delivery of effective screening. Methods: Fifty-five practitioners from differing professional backgrounds were recruited to the TCD training program. The impact of the training programme was evaluated in three European haematology clinics by comparing stroke risk classification and middle cerebral artery time-averaged maximum velocity (TAMMV) obtained from a cohort of 555 patients, before and after training. Results: 42% (23/55) of trainees successfully completed the program. The TAMMV, used to predict stroke risk at each Centre, demonstrated the highest values in Centre 3 (p < 0.0001) before training. The imaging-TCD TAMMV was also higher in Centre 3 (p < 0.001). Following training, the TAMMV showed closer agreement between centres for both imaging-TCD and non-imaging TCD. The stroke risk distribution of children at each centre varied significantly before training (p < 0.001), but improved after training (Fisher’s Exact: no treatment = 5.6, p = 0.41, treatment = 13.8, p < 0.01). The same consistency in stroke risk distribution following training was demonstrated with both non-imaging and imaging-TCD data. Conclusion: The attainment of competency in stroke screening using transcranial Doppler scanning (TCD) in sickle cell disease is more feasible for professionals with an ultrasound imaging background. A quality assurance (QA) system is required to ensure that standards are maintained. Further work is in progress to develop an achievable and reproducible QA program.

Transcranial Doppler in the Diagnosis of Cerebral Vasospasm: An Updated Meta-Analysis

OBJECTIVES

To evaluate the performance of transcranial Doppler and transcranial color-coded duplex Doppler in patients with cerebral vasospasm due to aneurysm rupture. Angiography was considered as the gold standard comparator.

DATA SOURCES

Search in MEDLINE, Embase, and Central from January 2001 to October 2017, without language restriction. Bibliographies of retrieved articles were screened for additional studies.

STUDY SELECTION

Randomized studies comparing transcranial Doppler or transcranial color-coded duplex Doppler with angiography in adults.

DATA EXTRACTION

Data were extracted independently by several investigators. Sensitivity and specificity were combined across studies using a bivariate model. Preferred Reporting Items for Systematic Reviews and Meta-Analyses was used for reporting and Quality Assessment of Diagnostic Accuracy Studies-2 for quality assessment.

DATA SYNTHESIS

We included 18 studies. Fifteen tested transcranial Doppler. For the middle cerebral artery (10 studies, 1,408 tests), the pooled sensitivity was 66.7% (95% CI, 55.9-75.9) and specificity was 89.5% (80.3-94.7). Three studies (278 tests) tested transcranial color-coded duplex Doppler for the middle cerebral artery. The pooled sensitivity was 81.5% (66.0-90.0), and specificity was 96.6% (93.0-98.0). For an arbitrarily chosen prevalence of vasospasm of 70%, positive and negative predictive values were 93.7% (88.9-96.6) and 53.4% (46.7-60.9) for transcranial Doppler and 98.2% (96.4-99.1) and 69.1% (56.1-80.9) for transcranial color-coded duplex Doppler.

CONCLUSIONS

Assuming a high prevalence of vasospasm of the middle cerebral artery, both transcranial Doppler and transcranial color-coded duplex Doppler are likely to detect it, but neither is useful to exclude it. There is no convincing evidence that the accuracy of transcranial color-coded duplex Doppler is any better than that of transcranial Doppler. For arteries other than middle cerebral artery, there is a lack of evidence of the usefulness of transcranial Doppler.

Transcranial Doppler screening for stroke risk in children with sickle cell disease: a systematic review

Background Sickle cell disease (SCD) is one of the most common causes of stroke in children worldwide. Based on the results of the Stroke Prevention Trial in Sickle Cell Anemia (STOP), annual transcranial Doppler ultrasound (TCD) screening for affected children is standard practice. However, the need for TCD surveillance programs could override the accuracy of the screening, affecting the correct stratification of stroke risk and subsequent clinical management of the target population. Aims To shed light on this issue, a systematic review of the literature on TCD screening for children and adolescents with SCD was carried out (CRD42016050549), according to a list of clinically relevant questions, with a particular focus on screening practices in European countries. Quality of the evidence was rated using the grading of recommendations assessment, development and evaluation. Summary of review Thirty-three studies published in English or French were included (5 randomized controlled trials, 8 experimental non-randomized, and 20 observational studies). The quality of the retrieved evidence ranged between low and high, but was rated as moderate or high most of the times. TCD is effective as a screening tool for the primary prevention of stroke in SCD children. There is no high-quality evidence on the effectiveness of alternative screening methods, such as imaging-TCD with or without angle correction or magnetic resonance angiography. No evidence was found on effectiveness of the screening on children on hydroxyurea and with genotypes other than HbSS and HbS/β0. No European data were found on screening rates or adherence of screening practices to the STOP protocol. Conclusions High-quality studies on alternative screening methods that are currently used in real-world practice, and on screening applicability to specific subgroups of patients are urgently needed. Considering the low awareness of the disease in European countries and the lack of data on screening practices and adherence, clinicians need up-to-date guidelines for more uniform and evidence-based surveillance of children with SCD.

Cerebral blood flow velocity underestimates cerebral blood flow during modest hypercapnia and hypocapnia

To establish the accuracy of transcranial Doppler ultrasound (TCD) measures of middle cerebral artery (MCA) cerebral blood flow velocity (CBFV) as a surrogate of cerebral blood flow (CBF) during hypercapnia (HC) and hypocapnia (HO), we examined whether the cross-sectional area (CSA) of the MCA changed during HC or HO and whether TCD-based estimates of CBFV were equivalent to estimates from phase contrast (PC) magnetic resonance imaging. MCA CSA was measured from 3T magnetic resonance images during baseline, HO (hyperventilation at 30 breaths/min), and HC (6% carbon dioxide). PC and TCD measures of CBFV were measured during these protocols on separate days. CSA and TCD CBFV were used to calculate CBF. During HC, CSA increased from 5.6 ± 0.8 to 6.5 ± 1.0 mm2 ( P < 0.001, n = 13), while end-tidal carbon dioxide partial pressure (PetCO2) increased from 37 ± 3 to 46 ± 5 Torr ( P < 0.001). During HO, CSA decreased from 5.8 ± 0.9 to 5.3 ± 0.9 mm2 ( P < 0.001, n = 15), while PetCO2 decreased from 36 ± 4 to 23 ± 3 Torr ( P < 0.001). CBFVs during baseline, HO, and HC were compared between PC and TCD, and the intraclass correlation coefficient was 0.83 ( P < 0.001). The relative increase from baseline was 18 ± 8% greater ( P < 0.001) for CBF than TCD CBFV during HC, and the relative decrease of CBF during HO was 7 ± 4% greater than the change in TCD CBFV ( P < 0.001). These findings challenge the assumption that the CSA of the MCA does not change over modest changes in PetCO2.

Brazilian Guidelines for transcranial doppler in children and adolescents with sickle cell disease

BACKGROUND

Sickle cell disease is the most common monogenic hereditary disease in Brazil. Although strokes are one of the main causes of morbidity and mortality in these patients, the use of transcranial Doppler to identify children at risk is not universally used.

OBJECTIVE

To develop Brazilian guidelines for the use of transcranial Doppler in sickle cell disease children and adolescents, so that related health policies can be expanded, and thus contribute to reduce morbidity and mortality.

METHODS

The guidelines were formulated in a consensus meeting of experts in transcranial Doppler and sickle cell disease. The issues discussed were previously formulated and scientific articles in databases (MEDLINE, SciELO and Cochrane) were carefully analyzed. The consensus for each question was obtained by a vote of experts on the specific theme.

RESULTS

Recommendations were made, including indications for the use of transcranial Doppler according to the sickle cell disease genotype and patients age; the necessary conditions to perform the exam and its periodicity depending on exam results; the criteria for the indication of blood transfusions and iron chelation therapy; the indication of hydroxyurea; and the therapeutic approach in cases of conditional transcranial Doppler.

CONCLUSION

The Brazilian guidelines on the use of transcranial doppler in sickle cell disease patients may reduce the risk of strokes, and thus reduce the morbidity and mortality and improve the quality of life of sickle cell disease patients.

Vertebral and Basilar Arteries: Transcranial Color-Coded Duplex Ultrasonography versus Conventional TCD in Detection of Narrowings

We prospectively compared the accuracies of conventional transcranial Doppler ultrasound (TCD) and transcranial color-coded duplex sonography (TCCS) in the diagnosis of narrowing of the basilar (BA) and vertebral arteries (VA). Fifty-six consecutive patients (mean age 55.8 years; 34 women) after subarachnoid hemorrhage (n=46), stroke or transient ischemic attack (n=5), and for other reasons (n=5) underwent on the same day TCD, TCCS and the intra-arterial digital subtraction angiography (DSA) – the reference standard. The accuracy of peak-systolic (VPS), mean (VM), and end-diastolic velocities (VED) in detection of any arterial narrowing was estimated using the receiver operator characteristic (ROC) curve methodology and the total area (Az) under the curve. Accuracy of TCCS in detection of VA narrowing based on VPS and VM measurements was significantly higher than accuracy of TCD (Az =0.65 for VPS and Az =0.62 for VM versus Az =0.51 and Az =0.50, respectively, p<0.05 for both). Accuracy of TCCS in detection of BA narrowing was also higher than accuracy of TCD based on VPS measurements (Az =0.69 versus Az =0.50, respectively), with a trend toward significant difference, p=0.085. The accuracy of TCCS is superior to accuracy of TCD in detection of narrowings of vertebral and basilar arteries, thus TCCS should be preferred in routine clinical practice.

Sickle cell disease in children: accuracy of imaging transcranial Doppler ultrasonography in detection of intracranial arterial stenosis

This study aimed to determine the accuracy of imaging transcranial Doppler sonography in detection of intracranial arterial stenosis in children with sickle cell disease using three-dimensional MR angiography as a reference standard. Sixty-one children (mean age 102±39 months, 30 males), who had no history of overt stroke, and were classified as at lowest risk of stroke by mean flow velocity criterion <170 cm/s, underwent conventional and imaging transcranial Doppler ultrasonographic examinations. We employed the area under the receiver operating characteristic curve (AUC) to determine the accuracy of flow velocity measurements obtained with imaging ultrasonography with and without correction for the angle of insonation as well as with conventional ultrasonography. We also established the most efficacious velocity thresholds for detection of the stenosis. We found ten intracranial stenoses in six patients on MR angiography, but we calculated AUC only for detection of stenosis (n=6) of the left intracranial internal carotid artery. The accuracy of flow velocity with angle correction was lower than the accuracy of velocity without angle correction (AUC=0.73, 95% CI, 0.53-0.93 versus AUC=0.87, 95% CI, 0.74-1.00; p=0.017). The accuracy of flow velocity obtained with conventional ultrasonography (AUC=0.82, 95% CI, 0.67-0.97) was not different from the accuracy of flow velocities obtained with imaging ultrasonography. We found that the threshold of 165 cm/s of mean velocity without angle correction is associated with highest efficiency for imaging (92%) and conventional ultrasonography (90%). Velocity measurements without angle-correction provide good accuracy in detection of stenosis of the terminal internal carotid artery, whereas angle-corrected velocities have lower accuracy.

Stenosis or hyperperfusion in sickle cell disease--ultrasound assessment of cerebral blood flow volume

Increased blood flow velocity (BFV) in basal cerebral arteries measured by transcranial color-coded sonography (TCCS) is a stroke risk factor in sickle cell disease (SCD). Raised BFV may be caused by vessel narrowing or by hyperperfusion. In 44 SCD patients and 14 controls, intracranial arterial BFVs and global cerebral blood flow (CBF) were analyzed by TCCS and extracranial duplex ultrasound, respectively. Magnetic resonance imaging and magnetic resonance angiography were performed in all patients with pathologic intracranial BFV rise. Intracranial BFVs and CBF in SCD were significantly higher than in controls. CBF in SCD correlated with BFV in all intracranial arteries and correlated inversely with age and hemoglobin values. Magnetic resonance angiography failed to demonstrate any stenosis in our SCD patients, thus raised intracranial BFVs must be interpreted as an anemia-dependent cerebral hyperperfusion. These findings suggest that the pathomechanism of stenosis-derived arterio-arterial embolism might be less relevant in SCD-related ischemic stroke, and other factors like small vessel disease or sickle cell-induced microvascular blood clotting have to be considered.

Association of Pulsatility Index in the Middle Cerebral Artery with Intelligence Quotient in Children with Sickle Cell Disease

The aim of this study was to explore whether intellectual performance in children with Sickle Cell Disease and with low risk of stroke as determined with conventional transcranial Doppler ultrasonography (TCD) criteria was associated with hemodynamic parameters in imaging TCD, when controlling for hematological and socio-economical variables and presence of silent infarcts. We performed neuropsychological testing with Kaufman Brief Intelligence Test (K-BIT-IQ) and imaging TCD examinations to measure blood flow velocities and pulsatility indexes (PI) in the middle cerebral arteries (MCA) In 46 children with homozygous HbSS (mean age 108±34 months, range limits: 47–166 months; 24 females), without a history of stroke or transient ischemic attack, with no stenosis on magnetic resonance angiography and with velocities below 170 cm/s in screening conventional TCD. Mean K-BIT IQ Composite and Vocabulary scores (91±13 and 86±14 respectively) were significantly below the average scores of 100 for the age-matched population (one sample t-test=5.21, p<0.001). Using univariate and multivariate regression models, we found that lower PI in the right MCA was associated with lower K-BIT-IQ Composite and Vocabulary scores. Furthermore, we found that interhemispheric differences in PIs were even more strongly associated with neuropsychological performance, whereas flow velocities were not associated with the K-BIT-IQ score. Using a model of chronic anemia, we found that cognitive functioning was associated with cerebral hemodynamics.

Problems with implementing a standardised transcranial Doppler screening programme: impact of instrumentation variation on STOP classification

BACKGROUND

The Stroke Prevention Trial in Sickle Cell Anaemia (STOP) demonstrated the value of selective transfusion based on transcranial Doppler (TCD) US screening. This facilitated widespread surveillance, but due to reported differences with non-imaging TCD, imaging velocity thresholds have been reduced in some centres.

OBJECTIVE

(1) Retrospectively review velocity measurements obtained by non-imaging and imaging TCD, using a standardised protocol. (2) Determine the impact on STOP classification of different velocity thresholds.

MATERIALS AND METHODS

TCD data from 23 children (2-19 years of age) were reviewed. The TCD protocol focused on obtaining the velocity corresponding to the highest audible Doppler frequency. STOP velocity thresholds were the recommended for non-imaging TCD and values reduced by 5-15%.

RESULTS

Non-imaging and imaging TCD velocities were correlated closely with little overall bias. Reducing imaging TCD velocity thresholds increased the number of abnormal and conditional classifications. Abnormal TCD imaging classifications ranged from 1.9% to 37% depending on the degree of correction applied to the velocity data.

CONCLUSION

The current approach for applying STOP thresholds to imaging TCD data may not be required. Centres need to validate their imaging TCD practice to avoid inappropriate selection of patients for transfusion therapy.

Sickle cell disease and transcranial Doppler imaging: inter-hemispheric differences in blood flow Doppler parameters

BACKGROUND AND PURPOSE

to establish reference values of interhemispheric differences and ratios of blood flow Doppler parameters in the terminal internal carotid artery, middle cerebral artery, and anterior cerebral artery in children with sickle cell anemia.

METHODS

fifty-seven out of 74 recruited children (mean age, 7.8 ± 3.4 years; range limits, 3-14 years), who were free of neurological deficits and intracranial narrowing detectable by MRA and had flow velocities <170 cm/s by conventional transcranial Doppler ultrasound, underwent transcranial color-coded duplex ultrasonography. Reference limits of flow parameters corrected and uncorrected for the angle of insonation were estimated using tolerance intervals, with P=0.90 for all possible data values from 95% of a population.

RESULTS

reference limits for left-to-right differences in cm/s in the mean angle-corrected and uncorrected flow velocities were -56 to 53 and -72 to 75 for middle cerebral artery, -49 to 57 and -81 to 91 for anterior cerebral artery, and -55 to 64 and -73 to 78 for terminal internal carotid artery, respectively. Respective reference limits for left-to-right velocity ratios were 0.31 to 1.84 and 0.38 to 1.75 for middle cerebral artery, 0.48 to 2.99 and 0.46 to 2.89 for anterior cerebral artery, and 0.61 to 2.56 and 0.56 to 2.23 for terminal internal carotid artery.

CONCLUSIONS

the study provides reference limits of interhemispheric differences and ratios of blood flow Doppler parameters that may be helpful in identification of intracranial arterial narrowing in children with sickle cell disease undergoing ultrasound screening for stroke prevention.

Transcranial color-coded duplex sonography allows to assess cerebral perfusion pressure noninvasively following severe traumatic brain injury

OBJECTIVE

Assess optimal equation to noninvasively estimate intracranial pressure (eICP) and cerebral perfusion pressure (eCPP) following severe traumatic brain injury (TBI) using transcranial color-coded duplex sonography (TCCDS).

DESIGN AND SETTING

This is an observational clinical study in a university hospital.

PATIENTS

A total of 45 continuously sedated (BIS < 50), normoventilated (paCO(2) > 35 mmHg), and non-febrile TBI patients.

METHODS

eICP and eCPP based on TCCDS-derived flow velocities and arterial blood pressure values using three different equations were compared to actually measured ICP and CPP in severe TBI patients subjected to standard treatment. Optimal equation was assessed by Bland-Altman analysis.

RESULTS

The equations: ICP = 10:927 x PI(pulsatility index) - 1:284 and CPP = 89:646 - 8:258 PI resulted in eICP and eCPP similar to actually measured ICP and CPP with eICP 10.6 +/- 4.8 vs. ICP 10.3 +/- 2.8 and eCPP 81.1 +/- 7.9 vs. CPP 80.9 +/- 2.1 mmHg, respectively. The other two equations, eCPP = (MABP x EDV)/mFV + 14 and eCPP = mFV / (mFV - EDV)] x (MABP - RRdiast), resulted in significantly decreased eCPP values: 72.9 +/- 10.1 and 67 +/- 19.5 mmHg, respectively. Superiority of the first equation was confirmed by Bland-Altman revealing a smallest standard deviations for eCPP and eICP.

CONCLUSIONS

TCCDS-based equation (ICP = 10.927 x PI - 1.284) allows to screen patients at risk of increased ICP and decreased CPP. However, adequate therapeutic interventions need to be based on continuously determined ICP and CPP values.

Neuroimaging in assessment of risk of stroke in children with sickle cell disease

PURPOSE

Stroke and subclinical "silent infarcts" are major causes of morbidity in children with Sickle Cell Disease (SCD). Ischemic strokes are more common in younger children while hemorrhagic strokes are more frequent in adults. The goal of neuroimaging in acute stroke is to document whether the stroke is ischemic or hemorrhagic, to assess the extent of parenchymal abnormalities and to determine the presence of other cerebrovascular lesions. Computed Tomography (CT) is the primary modality for the assessment of acute stroke patients because of its 24/7 availability and ability to exclude hemorrhagic causes. Magnetic resonance imaging (MRI) and MR angiography (MRA) are recommended to determine precisely extent of infarction and detect cerebrovascular abnormalities. The goal of neuroimaging in patients with hemorrhagic stroke is to identify an arteriovenous malformation or aneurysm(s) amenable to surgery or catheter intervention.The risk of first stroke is very high in asymptomatic children with intracranial arterial mean velocities over 200 cm/s on transcranial Doppler (TCD) examination. The risk can be substantially reduced if chronic blood transfusions are timely implemented. Large cerebral vessel disease detected by TCD can be confirmed or excluded by MRI/MRA. Those with evidence of parenchymal and/or cerebrovascular lesions should be followed by preventive therapy. In patients with neurologic symptoms and negative MRI/MRA findings Positron Emission Tomography or single photon emission CT is recommended. There are no specific neuroimaging findings that suggest that blood transfusions can be safely halted in children with SCD.

Narrowing of the middle cerebral artery: artificial intelligence methods and comparison of transcranial color coded duplex sonography with conventional TCD

The goal of the study was to compare performances of transcranial color-coded duplex sonography (TCCS) and transcranial Doppler sonography (TCD) in the diagnosis of the middle cerebral artery (MCA) narrowing in the same population of patients using statistical and nonstatistical intelligent models for data analysis. We prospectively collected data from 179 consecutive routine digital subtraction angiography (DSA) procedures performed in 111 patients (mean age 54.17+/-14.4 years; 59 women, 52 men) who underwent TCD and TCCS examinations simultaneously. Each patient was examined independently using both ultrasound techniques, 267 M1 segments of MCA were assessed and narrowings were classified as < or =50% and >50% lumen reduction. Diagnostic performance was estimated by two statistical and two artificial neural networks (ANN) classification methods. Separate models were constructed for the TCD and TCCS sonographic data, as well as for detection of "any narrowing" and "severe narrowing" of the MCA. Input for each classifier consisted of the peak-systolic, mean and end-diastolic velocities measured with each sonographic method; the output was MCA narrowing. Arterial narrowings less or equal 50% of lumen reduction were found in 55 and >50% narrowings in 26 out of 267 arteries, as indicated by DSA. In the category of "any narrowing" the rate of correct assignment by all models was 82% to 83% for TCCS and 79% to 81% for TCD. In the diagnosis of >50% narrowing the overall classification accuracy remained in the range of 89% to 90% for TCCS data and 90% to 91% for TCD data. For the diagnosis of any narrowing, the sensitivity of the TCCS was significantly higher than that of the TCD, while for diagnosis of >50% MCA narrowing, sensitivity of the TCCS was similar to sensitivity of the TCD. Our study showed that TCCS outperforms conventional TCD in detection of < or =50% MCA narrowing, whereas no significant difference in accuracy between both methods was found in the diagnosis of >50% MCA narrowing. (E-mail: jaroslaw.krejza@uphs.upenn.edu).

Sickle cell disease: ratio of blood flow velocity of intracranial to extracranial cerebral arteries--initial experience

PURPOSE

To establish reference values of the ratios of flow velocity in the middle cerebral artery (V(MCA)) and the terminal portion of the internal carotid artery (V(tICA)) to flow velocity in the extracranial portion of internal carotid artery (V(ICA)) in children with sickle cell disease (SCD).

MATERIALS AND METHODS

Institutional ethics committee approval and parental informed consent were obtained for this prospective HIPAA-compliant study. Sixty-eight children (38 female; mean age, 7.7 years +/- 3.3; range, 2-14 years) with HbSS genotype, without neurologic deficits and no history of stroke, were enrolled. Final study population comprised 56 (mean age 8.0 +/- 3.3 years, 26 females) children who underwent magnetic resonance (MR) angiography, which excluded intracranial arterial narrowing, transcranial color-coded duplex ultrasonography (US), and carotid US to determine V(MCA)/V(ICA) and V(tICA)/V(ICA) ratios from angle-corrected and uncorrected velocities. Tolerance interval estimates were used to calculate reference ranges and linear regression was used to quantify associations of Doppler parameters with age adjusted for hemoglobin and hematocrit.

RESULTS

Reference ranges in centimeters per second for mean angle-corrected V(MCA) on the left and right sides were 62-198 and 69-153; those for V(tICA) were 30-196 and 36-175; and those for V(ICA) were 18-116 and 15-95, respectively. Reference ranges for mean angle-corrected V(MCA)/V(ICA) ratio on the left and right sides were 1.2-4.0 and 0.4-3.4 and those for V(tICA)/V(IC)(A) ratio were 0.5-2.9 and 0.5-2.7, respectively. V(MCA), V(tICA), and V(tICA)/V(ICA) ratio were not age dependent, contrary to V(ICA) and V(MCA)/V(ICA) ratio, after controlling for hematocrit and hemoglobin.

CONCLUSION

The study provides reference limits for V(MCA), V(tICA), V(ICA), and velocity ratios obtained from children with SCD.

Comparison of duplex and nonduplex transcranial Doppler ultrasonography

Transcranial Doppler ultrasonography is essential in the management of children with sickle cell anemia and is a valuable adjunct to the evaluation of a variety of intracranial pathologies in children and adults, including vasoconstriction caused by subarachnoid hemorrhage, demonstration of major intracranial vessel stenoses or occlusion, determination of brain death, demonstration of the nidus of arteriovascular malformations, and assessment of cerebral hemodynamics after trauma, stroke, or migraine. There are 2 types of transcranial Doppler equipment currently available: nonduplex (nonimaging) and duplex (imaging). The purpose of this review is to compare and contrast the clinically relevant differences between these 2 types of equipment.