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Real-time Visualization of Clot Dissolution Using Doppler
UltrasoundGroup 38
Teammates: Debra Yen, Taylor Tso, Vera XiaoPresenter: Vera Xiao
Client: Michael Sabo, Pulse Therapeutics, Inc.
Background and Client Need Design Specifications and Concept Overview The Chosen Design Material, Manufacturing, and Cost Safety Conclusion
Outline
795,000 strokes / year in US ( 87% are ischemic stroke )
Time is critical: - 1.9 million neuron die per minute - 7.5 miles of myelinated fiber damaged per minute tPA (tissue plasminogen activator) is only drug
approved Limited access to clot due to lack of blood flow
Background
Client: Pulse Therapeutics Inc. Magnetically-Enhanced Diffusion (MED)
therapy for ER use tPA coded magnetite directed to clot location
under magnetic effect real-time visualization of lysis: - monitor therapy - detect successful
Client and Client Needs
TCD Probe - Phased Array
Headset - Ball and socket mechanism - Adhesive and three elastic straps Algorithm
- Compare affected and unaffected middle cerebral artery mean full velocity
Design Overview
Phased Array - All crystals are excited simultaneously - Electronic steering of beam provides different lines of sight
Advantages - Variable focal lengths, high resolution, high line density - Electronic steering and focusing enhanced with delay times
- Small size
The Chosen Design : TCD Probe (1)
Manufacturer: Sonosite M-Turbo P-21X with custom-made case
Frequency range: 5 – 1 MHz 21 mm broadband phased array Scan depth: 35 cm Dimension: cylindrical case with length =
120 mm, diameter = 31 mm. Probe body is threaded for probe insertion
The Chosen Design: TCD Probe (2)
The Chosen Design : Headset (1)
Ball and Socket Mechanism
70° full range of insonation angle
Single Thumb screw to lock mechanism
Probe screws in the ball
Adhesive and Elastic Straps
Probe positioned perpendicular to patient’s temporal window
Three elastic strips across patient’s forehead, back head, and chin
Adhesive : Collodion
The Chosen Design : Headset (2)
Physical constraints on pedestal size: <70 mm diameter
Socket size < 60mm Probe diameter = 31
mm Allow 70° insonation
angle Result: ball radius = 25 mm
The Chosen Design: Headset (4)
Straps
Primary fixture mechanism
Three straps 120° apart
Material: Nylon Young’s Modulus: 2-4
GPa
Adhesive
Prevent Minor disturbance
Material: Collodion - 5 minutes to dry - acetone to clean up Position most on
zygoma, squamous portion of the temporal bone
Safe for medical use
Headset material: polyvinyl chloride (PVC) Strong, stiff, and head and weather resistant Density: 1.35-1.45 g/ Volume: 36324 Headset weight: volume x density ~ 52.67g Headset + Probe weight ~ 250 g 2.45 N Strap across sections: 30 816.7 Pa
Nylon straps and collodion strength >> gravity force
The Chosen Design : Headset (6)
The Chosen Design: Probe & Headset Usage Workflow
1. Apply gel, and locate temporal window with probe while pedestal is locked at middle of the probe body
2. Twist down the pedestal and apply adhesives
3. Attach straps to pedestal, and allow adhesive to dry
4. Unlock the ball and socket, and alter probe insonation angle till optimal
The Chosen Design: Algorithm (3)
Created algorithm based only on MFV
- Neglects effects of magnetite particles Ultrasound signal from
particles must be filtered out before applying algorithm
- Need experimental data
Values to detect beginning of clot dissolution can differentiate completely occluded signal from partially occluded signal.
If MCA is originally partially occluded, threshold may not apply
Algorithm is therefore targeted towards severe cases involving initial completely occluded flow
The Chosen Design : Algorithm (4)
LCD Monitor from Industrial Image, Inc.
6.4” Open Frame LCD Monitor - Contrast Ratio: 400:1 - Display Color: 262, 144 colors - Viewing Angle: -50~50 (H); 35~15 (V) - Resolution: 640x480 pixels - Input: VGA - Touchscreen: Resistive
Material, Manufacturing and Cost (1)
Prototype
Component Material Method Lead Time Cost
Probe (M-Turbo P-21X)
Phased Array single probe 3 Weeks 11,500
PVC 3D Printing 8 Days 4070.4
Headset -- Ball PVC 3D Printing 8 Days 489.4
Headset -- Pedestal PVC 3D Printing 8 Days 1726.4Headset -- Thumb Screw Nylon Direct Purchase 1 Week 9.5
Headset -- Flat Hook PVC 3D Printing 8 Days 3.5
Headset -- Straps Nylon Elastic Strap Direct Purchase 1 Week 9.11
Headset -- Adhesive Collodion Direct Purchase 1 Week 6
Algorithm -- Coding N/A Coding 3 Days 480
Algorithm -- LCD N/A N/A N/A N/A
Total 18294.31
Material, Manufacturing, and Cost (2)
Note: 1st year cost includes initial tooling and 50 units of the imaging systems.
Manufacturing
Component Material Method manufacterLead Time Cost (1st Year)
Probe (M-Turbo P-21X) Phased Array Duplex Sonosite 3 weeks 1150000
PVC Injection Mold ICOMold 2 weeks 2875
Headset -- Ball PVC Injection Mold ICOMold 2 weeks 3025.5Headset -- Pedestal PVC Injection Mold ICOMold 2 weeks 5389Headset -- Thumb Screw Nylon Direct Purchase
plastic nuts and bolts 1 week 19
Headset -- Flat Hook PVC Injection Mold ICOMold 2 weeks 502.5Headset -- Straps
Nylon Elastic Strap Direct Purchase McMaster-Carr 2 days 152
Headset -- Adhesive Collodion Direct Purchase Mehron 1 week 2400Algorithm -- Coding N/A
Modification and Test N/A 2 weeks 1600
Algorithm -- LCD N/A Direct PurchaseIndustrial Image 2 weeks 65800
Total N/A N/A N/A N/A 1231762.8
DesignSafe ReportSummary
Item Counts
Total Users 2
Total Tasks 9
Total Hazards (Task-Hazard pairs) 21
Residual Risks
Number of residual risks that are:
High 0
Moderate 0
Low 20
Unspecified 1
Initial Risks
Number of initial risks that are:
High 2
Moderate 15
Low 4
Unspecified 0
Change in risk levels
High to Low 2
Moderate to Low 15
Low to Unspecified 1
No change in risk level 3
Conclusions
Our device and algorithm will function well for severe cases of ischemic stroke from MCA occlusion
- Algorithm may detect false positives in milder cases - We did not consider cases arising from occlusion in other arteries
10-20% of patients have too thick temporal windows to properly insonate
Future Direction
Conduct experiments comparing visibility of magnetite particles to that of blood - May use a contrast agent
Develop a digital filter for the algorithm Ultrasound affect clot-dissolution?
Take-away
Learned about the foundations of ultrasound and design dynamics
We should manage our time better We should try to work in teams with a
diverse technical background
References
Burgin, S. “TCD Criteria for Recanalization.” Stroke. Oct. 20 1999.
Halsey, J. and Tan, MJ. “Evaluation of Acute Stroke.” Transcranial Doppler, New York 1992.
http://www.industrialimage.net/openframe/openframe6-1.php
http://sentryair.com/blog/collodion-fumes/collodion-adhesive-possible-health-effects-fume-extraction-recommendations/
DesignSafe software http://www.designsafe.com/
Ball and socket mechanism