VFI Technology to Change the Way You Work

Transcription

1 Technology to Change the Way You Work Vascular Ultrasound Made Easier Vector Flow Imaging VFI VFI is a ground-breaking technology that can revolutionize the workflow for many Doppler ultrasound applications. In addition to revealing flow pattern details, it saves valuable time and makes the exam much easier. The new proprietary VFI method visualizes blood flow in all directions, independent of imaging angle. VFI and VFI Assist A good overview of flow Visual representation of flow in all directions including turbulence and transverse flow Angle-independence Faster gives an overall hemodynamic view without having to steer More consistent results less clinician dependent Streamlined vascular procedures to potentially save time. Automatic functions include: Placing PW Doppler gate at highest velocity Selecting best steering angle Showing real-time Flow Velocity Showing real-time Volume Flow Conventional CFM before angling and steering of the beams VFI

2 Measuring Flow Velocity VFI Assist Flow Velocity Measurements Flow velocity information is often needed in exams, e.g. to exclude carotid artery stenosis and plaque, or leg exams to exclude DVT (Deep Vein Thrombosis). Measuring flow velocity requires a skilled sonographer and usually needs the following 5 steps (and 3 for every new location). Using the automated functions in VFI Assist, the workflow only requires 2 steps and it is updated at all times, even when the transducer is moved. Easy as 1, 2, 3 Scan Long Axis of Artery Press Color On Press PW Doppler On Page 2

3 Measuring Volume Flow VFI Assist Volume Flow Measurements The benefits of VFI Assist are even more pronounced when measuring volume flow (VF). In this situation, the workflow to obtain VF is reduced from 12 steps (for a VF on a frozen image - and 12 more for every new location) to 2 steps (and one for every new location) shown in real-time. VFI Assist Volume Flow Page 3

4 A Clinical Use Hemodialysis Monitoring the flow at vascular access site The increase in number of patients undergoing hemodialysis highlights the need for improved methods of monitoring vascular flow. Thrombosis is a common complication of hemodialysis; it is essential to monitor the flow in the vascular access to ensure that it is below 600ml/min for a fistula and 400ml/min for a graft. Vascular access failure is the most frequent cause of hospitalization for patients with chronic renal disease (Cairoli OM 2004). One popular way to assess the patency of the dialysis graft is to use ultrasound and measure the volume flow. VFI Assist streamlines the process of obtaining flow data and can minimize time consuming adjustments. VF measurements can easily be made at different locations to potentially increase the quality of the evaluation. Hemodialysis Terms Hemodialysis: Treatment for renal failure in which circulating blood is diverted through a dialyzer that acts as an artificial kidney to filter out toxins before the blood is returned to the body. Vascular access: Site where blood leaves and reenters the body. There are two main types of AV (arteriovenous) vascular access: 1. Fistula - Artery connected directly to vein 2. Graft - Artery connected to vein by a tube VFI Assist guides you through the workflow. You can also override any of the automatic adjustments, if changes to the diameter or the angle of flow need to be made. It is an alternative to other flow measurement methods and supports the trend of increased use of ultrasound in daily clinical practice. The measurement calipers for the diameter can also be adjusted manually Color coding and/or arrows are used to show the size and direction of the flow VFI Volume Flow AV Fistula Page 4

5 VFI Advanced Vascular Imaging Dialysis graft with VFI Assist Volume Flow VFI turbulence in arm vein and tributaries VFI turbulence at carotid bulb VFI turbulence in popliteal artery and branch VFI Assist with PW at the internal carotid artery VFI Assist with PW at the common carotid artery Page 5

6 VFI Transverse Oscillation Technology VFI uses a technique called transverse oscillation to overcome the angle limitations of ordinary Doppler ultrasound. It creates an effective component of the ultrasound oscillation perpendicular to the transmitting beam an oscillation in the transverse direction (Jensen JA 2001; Jensen JA, Munk P 1998). VFI generates a 2D interference pattern in the received ultrasound signal. This allows the system to calculate not only the axial component of the velocity (as traditional Color Doppler), but also the transverse component. This eliminates the angle dependence and enables both the detection and visualization of complex flows. Traditional Color Doppler Oscillations in the axial direction gives a frequency shift in this direction VFI Oscillations both in the axial and the transverse directions gives frequency shifts in both directions V axial Blood flow V axial Blood flow V transverse Page 6

7 VFI Why and How Angle Limitations of Doppler Flow Measurements Ordinary Color and Spectral Doppler ultrasound measure the velocity of flow components toward or away from the transducer. It uses the angle of the ultrasound beam relative to the flow direction to calculate the actual flow velocity through the vessel. The accuracy of this computation depends on precise knowledge of the direction of the ultrasound beam and direction of the flow in the vessel (and the angle α between them). Doppler Velocity Calculation When the ultrasound beam is perpendicular to the vessel (90 ), this computation is impossible, because there is no flow component in the direction of the beam. D = In effect, the measurement is impossible when the insonation angle is over , because then small errors in measuring the two directions lead to large discrepancies in the results. VFI frees you from angle dependence The groundbreaking new VFI technology addresses this problem by eliminating angle-dependence. f 0 = Transmitted frequency f D = Doppler frequency (received) c = Speed of sound in blood α = Doppler angle (when α=90, cos α=0) Vector Flow Imaging is an excellent method for revealing the full complexity of human hemodynamics. Clinical scans have in real-time given us a wealth of information about vortices and other complex flow in the human circulation Jørgen Arendt Jensen, Professor, Ph.D., Dr. Techn. VFI was developed in conjunction with the Center for Fast Ultrasound Imaging at the Technical University of Denmark. Page 7

8 References Cairoli, OM Routine Ultrasound Studies of the Vascular Access in a Dialysis Center: A Review. Hemodial Int 2004; 8: doi: /j b.x Jensen JA A new estimator for vector velocity estimation IEEE Trans Ultrason Ferroelectr Freq Control 2001; 48 (4): Jensen JA, Munk P A new method for estimation of velocity vectors. IEEE Trans Ultrason Ferroelectr Freq Control 1998; 45 (3): Page 8 BG0536-A