Temporal Acoustic Bone Windows Research Articles

Design and validation of a phantom for transcranial ultrasonography.

Commercial medical ultrasound phantoms are highly specific as they simulate particular clinical scenarios. This makes them expensive to use in multi-target research and training. General approaches to human tissue and organ modeling are described in the manufacturing methodology, access to which is restricted by the manufacturer's trade secret. Our aim is to propose a reproducible methodology to design a head phantom for transcranial ultrasound training and research from widely available materials and to validate its applicability. To create an anthropomorphic phantom, we used data from real patients obtained by CT and MRI scans. We combined FDM and LCD 3D printing to achieve the desired acoustic performance and ergonomics of the phantom. We fabricated the phantom using polyvinyl chloride plastisol, photopolymer, and PLA to simulate brain tissue, temporal acoustic windows, and acoustically opaque parts of the skull, respectively. Notably, the phantom fabrication method uses only readily available materials and is easy to reproduce. We developed a basic one and anatomical one versions of the head phantom. The basic version contains a simplified brain: tissue-mimicking material is poured into the skull with needles inserted, which specific pattern is easy to recognize in B-mode images. The anatomical version has an anatomically correct brain dummy extracted from MRI data and contains multiple randomly distributed small metal, plastic, and bony objects ranging in size from 1 to 3mm each. The proposed methodology allows producing head phantoms for transcranial ultrasound training and research. The anatomical accuracy of the model is proved by ultrasonography and CT studies. Both versions of the phantom comprise the skull and the brain and are intended for ultrasound imaging through the temporal bone acoustic window. Needles and small objects serve as navigation targets during the training procedure. The basic version helps learning basic navigation skills, while the anatomical one provides a realistic setting to perform the diagnostic procedure.

The role of substantia nigra sonography in the differentiation of Parkinson\u2019s disease and multiple system atrophy

BackgroundThe differential diagnosis of Parkinson’s disease (PD) and multiple system atrophy (MSA) remains a challenge, especially in the early stage. Here, we assessed the value of transcranial sonography (TCS) to discriminate non-tremor dominant (non-TD) PD from MSA with predominant parkinsonism (MSA-P).MethodsEighty-six MSA-P patients and 147 age and gender-matched non-TD PD patients who had appropriate temporal acoustic bone windows were included in this study. All the patients were followed up for at least 2 years to confirm the initial diagnosis. Patients with at least one substantia nigra (SN) echogenic size ≥18 mm2 were classified as hyperechogenic, those with at least one SN echogenic size ≥25 mm2 was defined as markedly hyperechogenic.ResultsThe frequency of SN hyperechogenicity in non-TD PD patients was significantly higher than that in MSA-P patients (74.1% vs. 38.4%, p < 0.001). SN hyperechogenicity discriminated non-TD PD from MSA-P with sensitivity of 74.1%, specificity of 61.6%, and positive predictive value of 76.8%. If marked SN hyperechogenicity was used as the cutoff value (≥ 25 mm2), the sensitivity decreased to 46.3%, but the specificity and positive predictive value increased to 80.2 and 80.0%. Additionally, in those patients with SN hyperechogenicity, positive correlation between SN hyperechogenicity area and disease duration was found in non-TD PD rather than in MSA-P patients. In this context, among early-stage patients with disease duration ≤3 years, the sensitivity, specificity and positive predictive value of SN hyperechogenicity further declined to 69.8%, 52.2%, and 66.7%, respectively.ConclusionsTCS could help discriminate non-TD PD from MSA-P in a certain extent, but the limitation was also obvious with relatively low specificity, especially in the early stage.

Substantia Nigra Echogenicity Associated with Clinical Subtypes of Parkinson’s Disease

It is debatable whether transcranial sonography (TCS) could be a biomarker for monitoring disease progression. Various phenotypes of Parkinson's disease (PD) may be a major reason contributing to the inconsistency. We classified PD patients into different subtypes and evaluated the correlation between SN echogenicity and disease progression. A total of 411 PD patients were included in this study. TCS evaluations of the substantia nigra (SN) were performed, and motor and non-motor symptoms were assessed by a series of rating scales in all PD patients. Three hundred and thirteen patients had appropriate temporal acoustic bone windows, and they were divided into three subgroups according to disease onset age. SN hyperechogenicity (SN+) was found to be associated with age, gender, disease duration, H-Y stage and UPDRS-II scores in 220 middle-age onset patients. Regression analysis identified both disease duration and gender as independent predictors for SN+. When this distinct group was separated into male and female subgroups, the correlation between larger SN echogenicity (SNL) and disease duration was positive in males rather than females. When these middle-age onset male patients were classified as tremor dominant (TD) and non-TD subtypes, it turned out that correlation between disease duration and SNL only existed in male non-TD PD patients. Our study demonstrated correlation between the size of SN echogenicity and disease duration in Chinese patients with PD who were male non-TD subtypes with middle-age onset, suggesting the formation of SN echogenicity might be a dynamic process following disease progression in this distinct subtype.

Simultaneous Bilateral Real-Time 3-D Transcranial Ultrasound Imaging at 1 MHz Through Poor Acoustic Windows

Ultrasound imaging has been proposed as a rapid, portable alternative imaging modality to examine stroke patients in pre-hospital or emergency room settings. However, in performing transcranial ultrasound examinations, 8%–29% of patients in a general population may present with window failure, in which case it is not possible to acquire clinically useful sonographic information through the temporal bone acoustic window. In this work, we describe the technical considerations, design and fabrication of low-frequency (1.2 MHz), large aperture (25.3 mm) sparse matrix array transducers for 3-D imaging in the event of window failure. These transducers are integrated into a system for real-time 3-D bilateral transcranial imaging—the ultrasound brain helmet—and color flow imaging capabilities at 1.2 MHz are directly compared with arrays operating at 1.8 MHz in a flow phantom with attenuation comparable to the in vivo case. Contrast-enhanced imaging allowed visualization of arteries of the Circle of Willis in 5 of 5 subjects and 8 of 10 sides of the head despite probe placement outside of the acoustic window. Results suggest that this type of transducer may allow acquisition of useful images either in individuals with poor windows or outside of the temporal acoustic window in the field.

Parkinson’s disease-like midbrain hyperechogenicity is frequent in amyotrophic lateral sclerosis

Clinical and neuroimaging data suggest impairment of the nigrostriatal system in amyotrophic lateral sclerosis (ALS). We thus hypothesized whether Parkinson's disease (PD)-like midbrain sonography findings are also present in ALS. Eighty-six patients with the diagnosis of possible or definite ALS according to revised El Escorial criteria were examined by transcranial B-mode sonography compared to 76 age- and gender-matched controls and 33 PD patients. Hyperechogenic areas of the midbrain representing the substantia nigra were measured planimetrically using standard protocols. In subjects with sufficient temporal acoustic bone windows, mean midbrain hyperechogenic areas were significantly higher in ALS (0.251 ± 0.104 cm(2)) and PD patients (0.286 ± 0.078 cm(2)) compared to controls (0.091 ± 0.054 cm(2)) with no significant difference between ALS and PD patients (one-way ANOVA: F value = 94.3; P < 0.0001). Sixty-seven percent (95 % CI 57-78 %) of ALS patients and 84 % (95 % CI 71-97 %) of PD patients displayed abnormal midbrain hyperechogenic areas (P = 0.383 for group comparison, χ(2) test). No correlations of hyperechogenic area sizes in ALS patients were found in regard to age, gender, ALS subtype (bulbar versus spinal form) or ALS-FRS-R score. In summary, we observed hyperechogenicity of the substantia nigra in patients with sporadic ALS with a frequency similar to that in PD and higher than in all other movement disorders. These findings are important for the diagnosis and differential diagnosis of PD and ALS alike.

Transcranial sonography: Brazilian experience

entitled “Transcranial sonography as a diagnostic tool for Parkinson’s disease”. These authors aimed to establish the per-centage of subjects with adequated temporal bone windows for transcranial sonography (TCS) studies and also to revisit in a Brazilian sample the hypothesis that increased echogenic size of substantia nigra (SN) might distinguish Parkinson’s disease (PD) patients from healthy individuals. We would like to congratu -late the authors for the original idea to assess the Brazilian sub -jects with a case-control study. The authors found that 10.8% of the subjects had insufficient temporal acoustic bone windows, which is in line with previous data. Also, they identified hyper -echogenicity of the SN in 88.2% of PD patients, against 14.2% of control group individuals. In addition, the authors pointed out that “in Brazil there is no systematic study on transcranial sonography”. Actually, this is an appropriate opportunity to report that our group has sys -tematically studied TCS findings in some neurological dis -eases, such as spinocerebellar ataxias (SCA) and restless legs syndrome (RLS) (Figure). We have recently published a study entitled “Transcranial sonography findings in spinocerebellar ataxia type 3 (Machado-Joseph disease): a cross sectional study”, in which we conducted TCS studies in 30 patients with clinical and molecular proven Machado-Joseph disease (MJD), and used 44 healthy subjects as control group, and found that hiperecho -genicity of the SN was more frequent in MJD patients (75%) than in the control group subjects (18%), and that brain atrophy and lenticular nucleus hyperechogenicity occurred more frequently in MJD group. Two out of 30 MJD patients were excluded from the study due to limitation of acoustic temporal bone windows

Transcranial sonography as a diagnostic tool for Parkinson's disease: a pilot study in the city of Rio de Janeiro, Brazil

In Brazil there is no systematic study on Transcranial Sonography (TCS), a neuroimaging method that depicts echogenic deep brain structures using ultrasound. To establish the percentage of subjects with permissive temporal windows and to address the ability of TCS of the substantia nigra (SN) to distinguish parkinsonian patients in a Brazilian sample. We performed TCS using the Acuson X300 (Siemens, Germany) in 37 individuals: 23 with Parkinson's disease (PD) and 14 healthy controls. 10.8% of subjects had insufficient temporal acoustic bone windows. SN echogenic areas were larger in patients (mean ± SD, 0.31 ± 0.08 cm(2)) compared to controls (mean ± SD, 0.17 ± 0.02 cm(2)). TCS accurately identified 88.2% of PD patients. A large proportion of Brazilians seem to be eligible for TCS. An expressive number of PD patients could be diagnosed by TCS based on an expanded SN echogenic area. However, the current data is preliminary and must be corroborated by larger studies.

Perioperative Transorbital Doppler Flow Imaging Offers an Alternative to Transcranial Doppler Monitoring in Those Patients Without a Temporal Bone Acoustic Window

Transcranial Doppler has been used to identify microembolic signals before, during and after carotid endarterectomy, but 10% to 15% of patients are reported not to have suitable temporal bone window. The aim of this study was to assess the feasibility of transorbital Doppler monitoring of patients with absent temporal bone acoustic window. Between 2005 and 2008, those patients with absent temporal bone acoustic window were assessed for a transorbital acoustic window. During the study period, 318 carotid endarterectomy were performed. In the 29 (9.1%) with absent temporal bone acoustic window, 25 (86%) had satisfactory transorbital acoustic windows, consequently only four (1.2%) of patients could not be monitored postoperatively. One patient required postoperative transorbital acoustic windows directed glycoprotein IIb/IIIa receptor antagonist infusion due to excessive carotid microembolisation to prevent stroke. This is the first description of the use of transorbital flow imaging to determine postoperative cerebral blood flow, microembolic load and to direct the use of intravenous antiplatelet agents.(E-mail: chrisimray@aol.com)

TCD Diastolic Velocity Decay and Pulsatility Index Increment in PVS Cases

Functional neuroimaging has provided new insights for assessing cerebral function in persistent vegetative state patients (PVS). Compared to controls, positron emission tomography and single photon emission tomography have shown a substantial reduction of global brain cerebral glucose metabolism and perfusion in PVS. Doppler ultrasonography (TCD) assesses local blood flow velocity and direction in the proximal portions of large intracranial arteries; it is a noninvasive technique, and it can be carried out at the bedside. To date, few studies have applied TCD to study PVS. We assessed intracranial circulation by TCD in five PVS patients. The cause of brain insult was hypoxic encephalopathy in four cases, and the other suffered an embolic cerebral infarct causing a top of the basilar artery syndrome. The sample volume was set at 12 mm; power output and gain settings were maximized as needed. The temporal bone acoustic window was not suitable for intracranial vessel insonation in all patients. As an alternative, the internal carotid artery siphon was assessed by orbital insonation between 55-70 mm. Systolic velocity was within a normal range, between 44 and 62 cm/second in all cases. However, the diastolic amplitude was reduced, as well as the end diastolic velocity, and the pulsatility index was increased in all patients. We conclude that TCD diastolic velocity decrement and PI augmentation in our cases might be related to uncoupling of cerebral blood flow and cerebral metabolic rate, arising from reduced cerebral glucose consumption and oxygen uptake, after extensive brain injury.

Bedside detection of acute epidural hematoma by transcranial sonography in a head-injured patient

Sir: A 24 year-old boy was brought to the ED with head injury after a motorcycle accident. On his arrival, he was alert, and his GCS was 14 (V5, M5, E4). A head CT scan was performed, and a small (max width 0.9 cm) temporal epidural hematoma was observed. Since its small dimension, it was not scheduled for surgery, and a new CT scan after 4 h was planned. Transcranial echography (TCE) was performed with a 2.0 MHz transducer insonating in a transverse plane through the temporal acoustic bone window: after identifying the arteries of the circle of Willis, the depth of the insonation window was adjusted (usually 16 cm), so that the butterfly-shaped mesencephalic brainstem and the contralateral skull became visible [1]. In these conditions an epidural hematoma was observed as an hyperechogenic image just inside the skull (Fig. 1). One hour later, the clinical condition was unchanged. TCE was repeated, and an enlargement of the hematoma with a maximum width of 2.5 cm (Fig. 1). CT scan was immediately performed, and the enlargement was confirmed. The hematoma was promptly evacuated, and 7 days later the patient was discharged from the hospital with no neurological deficit. Recently, transcranial sonography of brain parenchyma in adults has been proposed by several authors for the evaluation of the ventricular system, monitoring of midline shift, diagnosis and follow-up of intracranial mass lesions. Seidel G et al. [2] found a good correlation between CT and TCE in the measurements of third (r = 0.83, P \ 0.0001) and lateral ventricles (r = 0.73, P \ 0.0001). Similar agreement between these two imaging techniques were observed by Tang et al. [3] in the measurement of midline shift (gamma = 0.91, P \ 0.01). Maurer et al. [4] used TCE to differentiate ischemic from hemorrhagic stroke. On 151 patients, 18 (12%) had no sufficient acoustic bone window. Of the remaining 133 patients, they observed that a correct sonographic diagnosis was made in the 95% of the cases (126 patients). To our knowledge, this is the first report that shows echographical finding of acute epidural hematoma in adults. Actually, we found that, thanks to the improvement of technology of ultrasound machines, high resolution images of the contralateral skull may be often obtained by the transtemporal approach, so that epidural mass lesion can be rapidly detected by trained physicians. According with recent guidelines [5], morphologic criteria for surgery are based on the volume and thickness of the hematoma, and on the extent of midline shift. All these data may be obtained by transcranial sonography that can be used bedside, together with CT scan, to monitor these patients in case of non-operative management. In conclusion, in our opinion transcranial echography may be a useful tool to monitor epidural hematomas before clinical conditions deteriorate. In all patients with a sufficient acoustic window in the temporal bone, it is a rapid and noninvasive neuroimaging technique that can complement the results of CT scan, and may help to reduce delays in surgical management. Further prospective studies are needed to evaluate sensitivity, specificity and accuracy of this technique

Suitability of Temporal Bone Acoustic Window: Conventional TCD Versus Transcranial Color‐Coded Duplex Sonography

To determine whether the proportion of patients with suitable temporal bone acoustic windows is different for conventional transcranial Doppler sonography (TCD) and transcranial color-coded duplex sonography (TCCS), based on a head-to-head comparison in the same population of patients. Ninety patients, age 22-88 years (mean 57.1 +/- 11.7 years), 46 women and 44 men, 66 Caucasian, 19 African-American, and five Hispanic, underwent routine conventional TCD and the TCCS examination close in time to each other. Suitability of temporal bone acoustic window was defined by ability to insonate the middle and posterior and/or anterior cerebral arteries, while partial suitability was defined by ability to detect the posterior cerebral artery but not the middle cerebral artery. To compare proportions of suitable temporal bone windows for both sonographic methods, exact sign test by Liddell was used. Bilateral absence of temporal bone acoustic window was reported in six patients when studied with both conventional TCD and TCCS, whereas at least unilateral absence was reported in 10 patients. Partial, at least unilateral, suitability was reported in 11 patients with conventional TCD, and in 7 with TCCS. All differences in proportions were not significant (two-sided P>0.05). This study suggests that success rate of insonating the intracranial vessels through the temporal bone acoustic window is the same for conventional TCD and imaging TCCS.

Contrast-Enhanced Transcranial Color-Coded Duplex Sonography Versus Computed Tomography and Magnetic Resonance Angiography in the Follow-up of Basilar Stenting

The annual risk of stroke in patients with basilar artery stenosis is 2.5% to 11%, and even despite aggressive medical treatment, the prognosis of basilar artery thrombosis is fatal. For these reasons, invasive therapeutic approaches have been developed for cases of stroke due to vertebrobasilar circulation stenosis and occlusion. 1 In specialized centers, both intra-arterial thrombolysis performed in cases of basilar occlusion and intracranial stenting nowadays are becoming available suitable procedures to restore vascularization in cases of vertebrobasilar stenosis. 2,3 Nonetheless, restenosis is the major complication, with rates of 30% to 41% and an overall annual periprocedural complication rate of 6.6%. 4,5 It is therefore important to perform an accurate postprocedural follow-up to determine stent lumen patency. Conventional digital subtraction angiography (DSA) is still the most sensitive technique for visualizing the residual lumen after stenting, but it is invasive and not free of complications. Postprocedural follow-up is then usually performed by computed tomographic angiography (CTA) or magnetic resonance angiography (MRA). These techniques are both expensive and have limitations due to stent-induced artifacts, which may hide the residual lumen. 2 Transcranial color-coded duplex sonography (TCCD) has been a well-established diagnostic tool for visualization of the basal cerebral arteries since the early 1990s, although it is limited by the quality of the temporal acoustic bone window.6 With the introduction of sonographic contrast agents, vessel visualization has become easier and feasible in daily practice, at the bedside of the patient, with low costs and excellent results. 7 We report a case of a patient with a stroke and basilar artery stenosis who underwent a stenting procedure and follow-up studies with MRA, CTA, DSA, and TCCD.

Detection of Cardiac Right-to-Left Shunts by Contrast-Enhanced Harmonic Carotid Duplex Sonography

Paradoxical embolization by cardiac right-to-left shunts (RLS) is increasingly recognized as an important factor for embolic stroke. Contrast-enhanced transcranial Doppler sonography (ce-TCDS) is an established diagnostic tool for RLS detection but is frequently limited because of an inadequate temporal acoustic bone window. The purpose of this study was to determine whether extracranial sonography (ECS) using harmonic frequencies improves detection of RLS. Extracranial color duplex sonography using harmonic frequencies enables visualization of even single ultrasound contrast agent microbubbles because of oscillation. Patients with stroke and positive RLS findings on transesophageal echocardiography underwent a simultaneous extracranial and transcranial sonographic examination of the proximal common carotid artery (CCA) and middle cerebral artery (MCA) on the same side. A Valsalva strain was performed for 10 seconds after intravenous bolus injection of a galactose-based nontranspulmonary contrast agent. The B-mode frame sequences of the transverse plane of the CCA obtained by harmonic ECS and the ce-TCDS recordings of high-intensity transient signals from the MCA were analyzed offline. In all patients with RLS, the shunts could be identified by harmonic ECS. A close correlation could be seen between the count of visualized microbubbles in the CCA and the number of high-intensity transient signals detected on ce-TCDS in the ipsilateral MCA. The results of this study indicate that contrast-enhanced ultrasound harmonic imaging of the CCA using a Valsalva strain might be an optional screening tool for detection of cardiac RLS in patients with insufficient acoustic bone windows.

Evaluation of the ventricular system in children using transcranial ultrasound: reference values for routine diagnostics

In children, evaluation of the size of the ventricular system is important. Transcranial Doppler sonography (TCD), a broadly available and easily applicable method that is not hampered by side effects, such as radiation, is a valuable tool for routine examinations. However, standard TCD values of the ventricular system are lacking. In this study, we performed TCD through the temporal acoustic bone window in a large cohort of 1693 healthy children. Of these, 157 had to be excluded because of insufficient bone windows. In the remaining children, a mean width of 1.4 ± 0.8 mm for the third ventricle, 14.4 ± 0.8 mm for the right and 14.6 ± 0.7 mm for the left cella media, and 1.6 ± 0.7 mm for the right and 1.9 ± 0.8 mm for the left temporal horn were measured. Side differences are indicated and values are given in relation to age and gender. Inter-rater reproducibility obtained in 25 children was adequate, with no significant difference between the two measurements in any of the parts of the ventricular system measured, rendering these values suitable for reference. (E-mail: deniela.berg@uni-tuebingen.de)

Assessment of intracranial collateral flow by transcranial color-coded duplex sonography using a temporal and frontal axial insonation plane.

The insonation of the posterior communicating artery (PcomA) is often hampered by the unfavorable insonation angle when the temporal acoustic bone window (TBW) is used. This problem may be ameliorated by a lateral frontal bone window (LFBW). This study evaluated the TBW and LFBW for the assessment of collateral intracranial flow conditions and aimed at defining diagnostic transcranial color-coded duplex sonography (TCCS) criteria that do not need compression maneuvers. The A1 segment of the anterior cerebral artery (ACA), the PcomA, and the P1 segment of the posterior cerebral artery (PCA) were insonated by TCCS in 40 controls and 20 patients (16 internal carotid artery [ICA] occlusions or high grade stenoses, 3 middle cerebral artery stenoses or occlusions, 1 PCA stenosis). Detection rates for the A1 ACA and P1 PCA were higher for the TBW (94%, 98%) compared to the LFBW (86%, 81%) in controls. The PcomA was identified more frequently through the LFBW (86%) compared to the TBW (80%). Through the LFBW angle, corrected flow velocity (FV) measurements were possible for the PcomA with an average correction of 6.5 degrees. In controls, in > 80% of identified PcomAs, flow was directed towards the ICA. Side to side differences were below 7% for peak systolic FVs. In the patients with ICA disease, a flow reversal in the ipsilateral A1 ACA and a FV difference of > 30% seemed feasible for diagnosis of anterior communicating artery crossflow. Criteria for PcomA crossflow were side differences of FVs in the PcomA of > or = 30% and in the P1 PCA of > or = 20%. The LFBW proved useful as a complementary insonation plane to assess intracranial crossflow conditions, especially via the PcomA. We were able to define TCCS criteria for functional relevant collateralization without the need of compression maneuvers.

Cerebral Microembolus Detection in an Unselected Acute Ischemic Stroke Population

Objective: The aims of this study were firstly to determine prevalence, frequency, and clinical significance of cerebral microemboli in an unselected acute ischemic stroke population and secondly to examine how this information may improve ischemic stroke subtype classification. Methods: We intended to perform transcranial Doppler (TCD) microembolus monitorings of the middle cerebral artery (MCA) in the symptomatic hemisphere for 45 min in 120 consecutive patients with internal carotid artery territory ischemia. The first examination was performed within 72 h from start of symptoms and the second 5 ± 1 days later. Platelet and coagulation system activation were measured following TCD monitoring in 38 patients. The strokes were subtyped using the TOAST classification criteria, and the patients’ clinical status was assessed at discharge using the Scandinavian Stroke Scale and the Barthel Index. Results: Microembolus monitoring was technically possible in 83 (69.2%) of the 120 patients. Thirty-two (26.6%) patients had an inadequate temporal bone acoustic window or were too restless to allow long-time monitoring. In 5 (4.2%) patients the relevant MCA was occluded. Twenty-two (26.5%) of the 83 patients had microemboli despite the fact that over 90% were receiving an antiplatelet or an anticoagulant treatment. The mean frequency of microemboli was 6.7 ± 13.6 per 45 min. Microemboli were more prevalent in assumed cardioembolic stroke than in other subtypes of ischemic stroke (p = 0.047). We found no association between the presence of cerebral microemboli and the clinical outcome or the parameters for platelet or coagulation system activation. The presence of microemboli was not associated with in-hospital deaths (p = 0.17), whereas MCA occlusion was (p = 0.01). Conclusions: Cerebral microemboli are frequent in unselected acute ischemic stroke patients despite antiplatelet or anticoagulant treatment. TCD detection of microemboli provides valuable pathophysiological information and may, therefore, improve current ischemic stroke subtype classification.

3-dimensional echo-enhanced transcranial Doppler ultrasound diagnosis

Echo-enhancing agents improve the signal intensity of transcranial Doppler signals, enabling a novel approach of three-dimensional transcranial vascular imaging by Doppler ultrasound. The basic principle, system requirements and early clinical results with a custom built system are described. Transcranial color Doppler imaging was performed through the temporal bone acoustic window. During i.v. administration of the transpulmonary stable, galactose-based echo-enhancer Levovist (Schering) the video output of the ultrasound scanner was digitized and the spatial position of the recorded frames was simultaneously registered using a mechanical position sensor. After automatic segmentation of the color information, the 3D datasets were reconstructed offline using a Unix-based workstation (Silicon Graphics). Visualization was achieved by maximum intensity projection or surface visualization techniques. Administration of Levovist resulted in good enhancement of the vascular Doppler signal intensity, enabling acquisition of a 3D dataset of the complete circle of Willis with an imaging window of approximately 3-5 min for one i.v. injection. The vascularity of tumors could be recorded as a 3D dataset and further analyzed. The power Doppler technique with echoenhancement proved a valuable tool for 3D dataset recording. 3D datasets clearly facilitated the diagnosis of the vascular anatomy and lesion vascularity and provided additional information on localization of feeders, vascular displacement and extent of tumor vascularity.

Use of intravenous contrast material in transcranial sonography.

The appearance of the intracranial vasculature was compared on power and color Doppler ultrasound (US) scans obtained with and without a microbubble contrast agent. Nine patients (three men, six women) aged 42-70 years (mean age, 53 years) participated in the study. Seven patients underwent both color Doppler US and power Doppler US before and after intravenous administration of contrast agent, and two underwent only color Doppler US. All patients had previously undergone cerebral angiography. Before contrast material was administered, power Doppler US was more sensitive than color Doppler US in the detection of intracranial vessels (P < .05); neither technique depicted the entire circle of Willis in eight of nine patients. Postcontrast power Doppler US depicted more vascular segments than postcontrast color Doppler US (P < .01) or precontrast power Doppler US (P < .01). Use of intravenous contrast material enabled the entire circle of Willis to be evaluated from a single temporal bone acoustic window with both power Doppler US and color Doppler US in all patients. Contrast-enhanced power Doppler US depicted vessels not shown by enhanced color Doppler US. Contrast-enhanced power Doppler US depicted more vessels, better demonstrated specific vascular segments, and provided better vascular definition of the intracranial vasculature than contrast-enhanced color Doppler US or unenhanced power Doppler US.

Transcranial color-coded real-time sonography in adults.

We investigated the diagnostic potential of transcranial color-coded real-time sonography in 52 individuals using a phased-array ultrasound system with color-coded blood flow representation. Ultrasound scans in the axial and coronal planes were feasible through temporal acoustic bone windows in 49 subjects, enabling depiction of the main parenchymal and vascular structures as well as the ventricular system. Color-coded representation of blood flow in the cerebral vessels allowed unequivocal identification of the circle of Willis within the anatomic black-and-white B-mode image of the parenchymal structures. In Doppler mode, vascular blood flow phenomena may be analyzed semiquantitatively using the Doppler frequency spectrum. This noninvasive, serially applicable, mobile beside method may complement conventional neuroradiologic imaging methods, allowing on-line studies of functional processes within the adult brain.