NEUROLOGY / NEUROSURGERY
DOLPHIN product line has the market leading technology designed for ALL the TCD applications listed below!
VASOSPASM AND SAH
Cerebral Vasospasm is typically the outcome of Subarachnoid Hemorrhage (SAH) as a result of an aneurysm rupture. Early detection of vasospasm is critical since it allows timely intervention.
TCD is rather specific for this condition, and allows non-invasive, continuous bed-side monitoring. Vasospasm is characterized by increased velocities due to arterial narrowing. Severe vasospasm is defined in various international guidelines, and typically when mean velocities exceed 200 cm/sec, moderate conditions are with mean velocities between 120-200 cm/sec, and mild vasospasm is for mean velocities near 120 cm/sec. Additionally, velocities in the middle cerebral artery can be compared to internal carotid artery velocities, and the resulting ratio (Lindergaard index) can indicate cerebral vasospasm when it is greater than 3.
Typically, vasospasm is a developing pathology, and requires day by day monitoring of blood flow velocity values. The Viasonix Dolphin system provides a dedicated vasospasm protocol that allows setting velocity thresholds for immediate identification of the severity of the vasospasm condition. In addition, an immediate velocity trend analysis is provided in order to help identify the critical time whereby intracranial velocities are dramatically increased, and immediate clinical intervention is required.
The Dolphin also provides an ideal platform for the identification of the critical highest intracranial velocities. All data is saved both in the time domain and at all depths along the ultrasound beam, which allows the examiner to review the data after freeze to explore the measured blood flow velocities.
This condition is characterized by low resistance to blood flow, resulting in high volume flow rates. AVM is therefore characterized by high mean velocities – although lower then with severe vasospasm – which are coupled with a low pulsatility index (PI).
The Viasonix Dolphin multi-depth options allows to simultaneously view and measure the blood flow spectrum at different depths along the beam and quickly identify deviations from expected waveform patterns.
TCD can detect the different stages of brain death through analysis of the particular waveforms: a sharp systolic peak followed by near zero diastolic velocities; systolic spikes followed by retrograde diastolic velocities; short spikes; and ultimately, no signals at all. Note that there are countries in which the use of TCD for diagnosis of brain death is not accepted. For determination of brain death, the characteristic waveforms should be displayed in all intracranial vessels. In order to accept the absence of a Doppler signal in any vessel, a prior valid measurement must be identified in the same vessel to ensure that the access temporal window is fine.
The Viasonix Dolphin special m-mode option allows the examiner to view flows at all depths along the ultrasound beam. Thus, even after the measurement is freezed the examiner can scroll back and view signals from any depth and replay the spectrum from any depth, even if it is different than the original set depth. This significantly reduces the risk of missing a valid blood flow signal and reaching an erroneous clinical diagnosis.
VMR AND AUTOREGULATION
Typically, an increase in peak velocities above 40% during induced increase in CO2 reflects intact VMR, whereas a smaller increase reflects different degrees of impaired VMR. Absence of flow increase reflects a complete exhaustion of the autoregulatory capacity.
The Viasonix Dolphin is ideally set with dedicated Unilateral and Bilateral protocols to determine the autoregulatory capacity of the cerebral circulation of the patient. Doppler waveforms are captured automatically during baseline, and peak (hypercapnia) and minimal (hypocapnia) flows for immediate evaluation, as well as a display of the blood flow fluctuations during entire test process. The respective parameters are automatically shown in a dedicated table with the VMR index readily displayed.
TCD will easily identify a local increase in blood flow velocities, characterized by the fact that proximal or distal to the stenosis the velocities will be much lower that at the site of lesion itself. Peak focal velocities above 150 cm/sec can indicate an arterial stenosis. However, if the severity of the stenosis is beyond its' critical level, velocity signals may be diminished.
The Viasonix Dolphin ideally allows multi-depth scanning along the ultrasound beam, and display in both the m-mode and spectral domains. This allows for simultaneous analysis and evaluation of pre- and post-stenotic flows as well as in the focal region of the stenosis itself.
Similar to cerebral autoregulation and vasomotor reactivity, cerebral collateral flow reflects an alternative compensatory mechanism to pathological flow conditions. The cerebral collateral pathways include side-to-side via the anterior communicating artery, posterior-to anterior via the posterior communicating artery, and external-to-internal via the ophthalmic artery. TCD can detect reverse velocities in the collaterally perfused arteries, indicating the viability or absence of this compensatory mechanism.
The Viasonix Dolphin’s highly sensitive M-mode display identifies forward or reversed blood flow, throughout the depth range, for analysis of this brain protection mechanism.
Cerebral monitoring can be critical for identification of neurological complications. Relative and/or sudden changes in cerebral blood flow velocities can become a powerful diagnostic tool and effect the immediate clinical intervention.
Bilateral cerebral monitoring is particularly useful during cardiac surgery for identification of embolic events, which may be the source of post-surgery neurological deficiencies.
The Viasonix Dolphin supports both unilateral and bilateral cerebral blood flow monitoring with a dedicated and easy to use monitoring headset. A variety of monitoring tools allow to view the complete duration of the monitored procedure, as well as zoom in or out on specific regions of interest. A variety of automatically inserted event markers, as well as user defined markers, help in post-monitoring analysis.
In addition, the Dolphin supports the display of data obtained from external channels for close correlation with the cerebral blood flow information.
PATENT FORAMEN OVALE (PFO)
TCD can easily identify the existence of PFO by injecting micro-bubbles (air mixed saline) to the patient vein (typically the antecubital vein), while the Doppler signal is recorded during the Valsalva maneuver. If embolic events are found in the recorded cerebral blood flow, typically the middle cerebral artery (MCA), then this is an indication of the existence of PFO in the patient.
The Viasonix Dolphin is ideal for PFO examinations, with a dedicated PFO protocol. The test can be performed unilaterally or bilaterally, with automatic count of high intensity transient signals (HITS) which are considered as embolic events. Each embolic event can be further analyzed with extremely high temporal and depth resolutions, and the specifications of each event displayed in a special screen. Furthermore, the embolic travel in the depth and time domains can be viewed for additional discrimination from artifact events.
SICKLE CELL DISEASE
Sickle cell disease is a disorder of the blood caused by abnormal hemoglobin which causes distorted (sickled) red blood cells. It is associated with a high risk of stroke, particularly in the early years of childhood.
Transcranial Doppler (TCD) can be significant in the prevention of stroke under this condition. Mean of maximum cerebral velocity readings are obtained, and results are classified as normal, conditional, abnormal or inadequate based on the measurements. Clinical treatment based on the findings can be significant in stroke prevention.
The Viasonix Dolphin is ideal for sickle cell disease diagnosis and monitoring, with a dedicated sickle cell protocol. Special markers, which can also be configured by the examiner, clearly mark the velocity thresholds according to international guidelines, help in the identification and documentation of the pathology.
TCD can detect the embolic signals in the blood flow velocity waveforms, which are characterized by high intensity, short duration and unidirectional signals. High intensity transient signals (HITS) are often considered as embolic events.
The Viasonix Dolphin has the most advanced HITS detection and analysis platform. Dedicated screens show the specific embolic characteristics, such as its’ energy, velocity and duration patterns, as well as display its’ travel route in the time and depth domains.
Furthermore, the Dolphin can detect embolic events that are even not within the measured spectrum of the central depth, due to its’ powerful multi-range and multi-depth analysis capabilities.
EVALUATION OF ICP CHANGES
Intracranial pressure (ICP) is the pressure inside the skull and thus in the brain tissue and cerebrospinal fluid. Elevated ICP has a direct effect on the cerebral blood flow velocity and its’ pulsatility, which can be detected with simple transcranial Doppler (TCD) measurements.
The Viasonix Dolphin has the ability for multi-parameter analysis which allows close evaluation of cerebral condition. In addition, dedicated trend analysis displays help to closely monitor changes in cerebral condition for timely identification of deterioration of cerebral perfusion.
The Breath Holding (BH) test is a specific test for evaluation of Vasomotor Reactivity (VMR) and cerebral autoregulatory capacity.
Identification of exhausted VMR can be a good indication for high risk for stroke. Breath holding induces and increase in CO2, which in turn results in cerebral vasodilation. An increase in peak velocities during breath holding indicates different levels of patent autoregulatory capacity, While the absence of flow increase during the BH test indicates diminished physiological vasodilatory capacity and potentially high risk for stroke.
The Viasonix Dolphin is ideal for BH test with a dedicated breath holding protocol. This protocol leads the examiner with the different stages of the test, and provides automatically the breath holding index (BHI) for clinical determination.
A large timer displayed during the test helps both the patient and the examiner in keeping track of the duration of the procedure. Automatically placed markers identify the peak and minimal velocities measured during the procedure.