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Objective: The aim of this study was to investigate the feasibility of simultaneous visualization of the cerebral macrocirculation and microcirculation, using ultrasound perfusion imaging (UPI). In addition, we studied the sensitivity of this technique for detecting changes in cerebral blood flow (CBF)., Materials and Methods: We performed an observational study in ten healthy volunteers. Ultrasound contrast was used for UPI measurements during normoventilation and hyperventilation. For the data analysis of the UPI measurements, an in-house algorithm was used to visualize the DICOM files, calculate parameter images and select regions of interest (ROIs). Next, time intensity curves (TIC) were extracted and perfusion parameters calculated., Results: Both volume- and velocity-related perfusion parameters were significantly different between the macrocirculation and the parenchymal areas. Hyperventilation-induced decreases in CBF were detectable by UPI in both the macrocirculation and microcirculation, most consistently by the volume-related parameters. The method was safe, with no adverse effects in our population., Conclusions: Bedside quantification of CBF seems feasible and the technique has a favourable safety profile. Adjustment of current method is required to improve its diagnostic accuracy. Validation studies using a 'gold standard' are needed to determine the added value of UPI in neurocritical care monitoring.

Transcranial B-mode sonography is an easy to use bedside imaging modality to monitor significant changes of the brain parenchyma such as in malignant middle cerebral infarction or intracerebral hemorrhage. The elevation of intracranial pressure can be followed with various neurosonographical techniques: Measurements of the ventricular width, midline shift, arterial resistance, and optic nerve sheath diameter. They should be viewed as complementary to each other and to other imaging modalities. Repeated cCT and MRI may be avoided in unstable patients by bedside neurosonography in the hands of an experienced physician. Monitoring of evolving hydrocephalus using serial measurements of the third and lateral ventricles can be used to guide therapeutic decisions such as the removal of a ventricular drainage. The cessation of cerebral blood flow in the case of intracranial pressure exceeding systemic arterial pressure is an important part of brain death diagnostics. Early demonstration of a sufficient temporal bone window is needed in patients in whom brain death may be expected. Cerebrovascular autoregulation is an integer component of the brain's blood supply and is compromised in a variety of neurological diseases. In neurological/neurosurgical patients in the intensive care unit, its assessment allows for extended neuromonitoring and control of therapeutic procedures.

We present 3 cases of uncommon neuro-vascular constraints in which ultrasound perfusion imaging (UPI) and pw-MRI displayed according pathological findings. The results are discussed in the light of a recapitulatory review of the literature and underline the diagnostic potential of the method and the necessity of an expanded multicentre evaluation. It would be desirable to consolidate the different approaches of UPI to achieve one commonly applicable method with the aim of gaining a novel tool for prehospital stroke diagnosis., (© 2010 by the American Society of Neuroimaging.)

Advanced applications of ultrasound in neurosurgery have been evaluated in two projects of the Ruhr Center of Excellence for Medical Engineering (KMR), Bochum, Germany. Engineers, neurologists, and neurosurgeons are cooperating within an interdisciplinary project structure, in order to practically approach neurosurgical problems by elaborating novel ultrasound-based technologies. On one hand, procedures have been implemented for an ultrasound-based registration of bone structures, applicable, amongst others, to the high-accuracy navigation of pedicle screws. On the other hand, concepts have been developed regarding a pre- and intraoperative application of ultrasound contrast agents for the detection of cerebral tumors and for the monitoring of surgery. In this article, both projects are discussed on the basis of the results obtained thus far and, furthermore, potentials of these concepts are presented that may complement or extend the scopes of the neurosurgical practice.

Background and Purpose: The purpose of this study was to assess brain perfusion with an ultrasound contrast-specific imaging mode and to prove if the results are comparable between 2 centers using a standardized study protocol., Methods: A total of 32 individuals without known cerebrovascular disease were included in the study. Perfusion studies were performed ipsilaterally in an axial diencephalic plane after intravenous administration of 0.75 mL of Optison. Offline time intensity curves (TIC) were generated in different anatomic regions. Both centers used identical study protocols, ultrasound machines, and contrast agent., Results: In both centers, the comparison of the parameter time to peak intensity (TPI) revealed significantly shorter TPIs in the main vessel structures compared with any parenchymal region of interest (ROI), whereas no significant differences were seen between the parenchymal ROIs. The parameter peak intensity (PI) varied widely interindividually in both centers, whereas the inter-ROI comparison revealed statistical significance (P < 0.05) in most of the cases according to the following pattern: (1) lentiforme nucleus > thalamus and white matter region, (2) thalamus > white matter region, and (3) main vessel > any parenchymal structure. Similar results were achieved in both centers independently., Conclusions: The study demonstrates that brain perfusion assessment with an ultrasound contrast-specific imaging mode is comparable between different centers using the same study protocol.

Objective: To validate the potential of ultrasonographic depletion imaging for semiquantitatively visualizing cerebral parenchymal perfusion with contrast burst depletion imaging (CODIM) in comparison with phase inversion harmonic depletion imaging (PIDIM) in healthy volunteers., Methods: Thirteen healthy adults were examined with both CODIM and PIDIM in accordance with previously described criteria. In addition to the perfusion coefficient, the time to decrease image intensity to 10% above equilibrium intensity from the initial value and the relative error (deviation of measured data from the fitted model) were evaluated to compare the reliability of both techniques in 3 different regions of interest., Results: Perfusion coefficient values did not show significantly differing values in both groups (1.57-1.64 * 10(-2) s(-1) for CODIM and 1.42-1.58 * 10(-2) s(-1) for PIDIM). The relative error was significantly smaller in the PIDIM group (0.38-0.53 for CODIM and 0.18-0.25 for PIDIM; P < .002)., Conclusions: Phase inversion harmonic depletion imaging proved to be more reliable than CODIM because values of the relative error were significantly lower in PIDIM even in this relatively small cohort. This is of interest because the underlying technique, phase inversion harmonic imaging, is more widely available than contrast burst imaging.

Phase inversion harmonic imaging (PIHI) with newer contrast agents can display parameters of cerebral perfusion either using the established ipsilateral approach, or the novel bilateral approach in which both hemispheres are assessed in one examination. The aim of this study was to evaluate the potential of PIHI in detecting pathological perfusion in acute stroke, using the bilateral approach. Patients with a hemispheric syndrome presenting within 12 hours after symptom onset were examined with PIHI (SonoVue; bolus kinetics, fitted model function) using the bilateral approach if possible. Semi-quantitative perfusion related parameters (time to peak intensity (TPI) and peak width (PW)) were evaluated, and results correlated to follow up cerebral computed tomography (CCT) scans. In these four preliminary cases (one ipsilateral, three bilateral), PIHI was able to identify the ischaemic region because the function could not be fitted to the data. In one case, there was a difference between a core region where no perfusion was seen, and a surrounding region where hypoperfusion was detected (prolonged TPI and reduced PW). PIHI was able to predict the localisation and size of the eventual infarction even if no early CCT signs were seen. Furthermore, in one case, a surrounding hypoperfused region was identified, where tissue survived after recanalisation of the initially occluded middle cerebral artery. Using the bilateral approach, two advantages in comparison with the ipsilateral approach were obvious: cortical structures could be evaluated, and only one examination was needed to compare unaffected (ipsilateral) with affected (contralateral) tissue. These results should be confirmed by more cases, and should also be correlated to acute perfusion/diffusion weighted MRI data.

Background and Purpose: Contrast burst depletion imaging (CODIM) visualizes cerebral perfusion by destruction of microbubbles and observation of image intensity course. Because of its complexity, artifacts occur. Criteria of reliability to improve diagnostic significance were created and validated., Methods and Results: Eighteen healthy volunteers were examined with 2 echo contrast agents (ECAs) and 3 frame rates in 3 regions of interest (ROIs). Perfusion coefficient (PC), Tmin (time to decrease intensity to 10% of its max), and relative error (RE) (deviation of measured data from fitted model) were determined. PC differed significantly neither between CA nor between frame rates (overall mean = 1.60 +/- 0.21 x 10(-2) s-1). Tmin differed significantly between frame rate groups (P < .001, 33.4 +/- 11.2 s/0.5 Hz; 3.6 +/- 2.5 s/5 Hz) since it is related to destruction of microbubbles that occurs with each frame and to the perfusion rate. RE was higher in the Optison group and tended to decrease in ROIs closer to the probe., Conclusions: PC was independent of frame rate and ECA. Tmin was shorter with higher frame rates. Due to a very rapid decay at 5 Hz, the ideal frame rate should be about 1 Hz, that is, because the number of frames acquired within Tmin and therefore signal-to-noise ratio is higher at 1 Hz. Since the algorithm is complex (high RE) and more artifacts should occur in patients (insufficient bone window, etc), a triggering of the insonations by, for example, heart rate could decrease artifacts and increase diagnostic power of CODIM.

Background: Transcranial sonography (TCS) identifies hyperechogenic basal ganglia in extrapyramidal disorders such as Parkinson's disease or dystonia and reveals brain atrophy reflecting the stage of degeneration in Huntington's disease. Aim of the present study was to evaluate the diagnostic potential of TCS in spinocerebellar ataxia type 3 (SCA3), a neurodegenerative disease affecting the cerebellum, multiple pontine nuclei, substantia nigra, pallidum, putamen, caudate nucleus and long spinal tracts., Methods: 15 patients with a molecular diagnosis of SCA3 and 15 age- and sex-matched healthy control individuals were examined with TCS. Echogenicity of the substantia nigra, caudate nucleus, pallidum, putamen, dentate nucleus and cerebellar white matter were determined quantitatively (substantia nigra by measuring the area of incresed echogenicity) or semiquantitatively (0 = none, 1 = mild, 2 = marked) on both sides and compared with the echotexture of defined brain structures. Additionally, the width of the lateral ventricles, the 3rd and 4th ventricle was measured in both groups., Results: SCA3 patients exhibited hyperechogenicities of the cerebellar white matter (57%), substantia nigra (40%), the dentate nucleus (54%), putamen (40%) and pallidum (40%) significantly more frequently (p <0.05) than controls (20%, 13%, 9%, 0%, and 0% in the corresponding areas). In none of the healthy individuals a marked signal increase could be observed, whereas 53% of SCA3 subjects had at least one region with marked echogenicity. Cerebellar atrophy as demonstrated by an enlarged 4th ventricle was observed in all SCA3 patients whereas this structure could not be differentiated from surrounding parenchyma due to its small size in healthy individuals. 3rd and lateral ventricles were significantly larger in SCA patients as compared to controls (p < 0.05)., Conclusions: TCS is a suitable and non-invasive bed-side method to detect basal ganglia hyperechogenic lesions and posterior fossa abnormalities in SCA3 patients. The pattern of echotexture alterations and brain atrophy most likely reflects distribution and morphology of the neurodegenerative process.

Background and Purpose: Contrast burst imaging (CBI) and time variance imaging (TVI) are new ultrasonic imaging modes enabling the visualization of intravenously injected echo contrast agents in brain parenchyma. The aim of this study was to compare the quantitative ultrasonic data with corresponding perfusion-weighted MRI data (p-MRI) with respect to the assessment of brain perfusion., Methods: Twelve individuals with no vascular abnormalities were examined by CBI and TVI after an intravenous bolus injection of 4 g galactose-based microbubble suspension (Levovist) in a concentration of 400 mg/mL. Complementary, a dynamic susceptibility contrast MRI, ie, p-MRI, of each individual was obtained. In both ultrasound (US) methods and p-MRI, time-intensity curves were calculated offline, and absolute time to peak intensities (TPI), peak intensities (PI), and peak width (PW) of US investigations and TPI, relative cerebral blood flow (CBF) and relative cerebral blood volume (CBV) of p-MRI examinations were determined in the following regions of interest (ROIs): lentiform nucleus (LN), white matter (WM), posterior (PT), and anterior thalamus (AT). In addition, the M(2) segment of the middle cerebral artery (MCA) was evaluated in the US, and the precentral gyrus (PG) was examined in the p-MRI examinations. In relation to a reference parenchymal ROI (AT), relative TPIs were compared between the US and p-MRI methods and relative PI of US investigations with the ratio of CBF (rCBF) of p-MRI examinations in identical ROIs., Results: Mean TPIs varied from 18.3+/-5.0 (AT) to 20.1+/- 5.8 (WM) to 17.2+/-4.9 (MCA) seconds in CBI examinations and from 19.4+/-5.3 (AT) to 20.4+/-4.3 (WM) to 17.3+/-4.0 (MCA) seconds in TVI examinations. Mean PIs were found to vary from 581.9+/-342.4 (WM) to 1522.9+/-574.2 (LN) to 3400.9+/- 621.7 arbitrary units (MCA) in CBI mode and from 7.5+/-4.6 (WM) to 17.5+/-4.9 (LN) to 46.3+/-7.1 (MCA) arbitrary units in TVI mode. PW ranged from 7.3+/-4.5 (AT) to 9.1+/-4.0 (LN) to 24.3+/-12.8 (MCA) seconds in CBI examinations and from 7.1+/-3.9 (AT) to 8.7+/-3.5 (LN) to 26.7+/-18.2 (MCA) seconds in TVI examinations. Mean TPI was significantly shorter and mean PI and mean PW were significantly higher in the MCA compared with all other ROIs (P<0.05). Mean TPI of the p-MRI examinations ranged from 22.0+/-6.9 (LN) to 23.0+/-6.8 (WM) seconds; mean CBF ranged from 0.0093+/- 0.0041 (LN) to 0.0043+/-0.0021 (WM). There was no significant difference in rTPI in any ROI between US and p-MRI measurements (P>0.2), whereas relative PIs were significantly higher in areas with lower insonation depth such as the LN compared with rCBF., Conclusions: In contrast to PI, TPI and rTPI in US techniques are robust parameters for the evaluation of cerebral perfusion and may help to differentiate physiological and pathological perfusion in different parenchymal regions of the brain.