Experiences with COMSOL Multiphysics in Medical Device R&D John F Kalafut 10/24/05 Presented at the COMSOL Multiphysics User's Conference 2005 Boston Sr Research Scientist MEDRAD Innovations Jkalafut@medrad.com
First, a word from our(my) sponsor Slide 2
MEDRAD Background Design, Manufacture, Sell and Service Medical Devices for Diagnostic Imaging and Therapy Founded 1964 by Dr.M.S.Heilman ~$400 Million in Global Sales Consistent Double Digit Revenue and Profit Growth 1500 Employees Worldwide 20 Million Medical Procedures Performed Annually with Medrad Products Subsidiary of Schering, AG since 1995. Headquarters 15 miles NE of Pittsburgh Slide 3
What We Do... Develop medical devices and services that enable or enhance diagnostic and therapeutic imaging procedures Vascular Injection MR Coils/Patient Monitoring Equipment (Multi-Vendor) Service Under three Strategic Business Units: 1. Cardiovascular (CV) 2. Magnetic Resonance (MR) 3. Computed Tomography (CT) Slide 4
We make pictures of your insides happen No Contrast With Contrast Slide 5
Medrad Innovations Innovations Business Development Product Innovation Rapid Prototyping IP Legal Staff of 30+ scientists, engineers (mechanical, electrical,biomedical) technicians, MBAs, and patent lawyers focused on new opportunities Strategic Focus: Intelligent systems for the delivery of diagnostic and therapeutic agents Slide 6
Outline Some case-studies from a day in the life type of problems for a medical device company Some hints of research applications Slide 7
FEMLAB Experience with FEMLAB Early user (v2.0+) Identified as a tool initially to add capabilities to MATLAB Systems Analysis tool Generalized research and development package used to quickly gain insight to issues (product and research) Slide 8
What kind of problems do I solve w/comsol Multiphysics? Electrostatics Heat Transfer Fluid dynamics Chemical Engineering Quasi-statics Etc. etc Slide 9
Do You do product Development? Phase I Where is and can multiphysics be used??? Concept Definition & Feasibility Phase II Requirements Development Acceptance Activities System Test Planning & Preparation Phase VI Acceptance Phase III Architecture Definition & Detailed Requirements Specification Integration Test Planning & Preparation Design Element Test Planning & Preparation Phase V System Testing Phase IV Design Element Development & Integration Slide 10
Our CAE stew Stage 0 research and concept feasibility COMSOL SPICE HFSS Labview, MATLAB used to conduct experiments and collect instrumented data System engineers translate marketing requirements MATLAB/Simulink, MathCAD, Mathematica, Excel, etc. used to define highlevel system behaviors DOORS, or other requirements management tool enlisted Maybe one package can accommodate each of these disparate areas? Mechanical engineers use ANSYS or ABAQUS to check designs. ProE SPICE/OrCAD, Remcomm Moldflow used to evaluate polymer consistency and manufacturing capabilities Slide 11
Some Specific Examples Tracking down a field failure. Design changes. Thermal problems Catheter research Drug/Body Interaction Slide 12
Early use One attractive application of FEMLAB is it s ease of use out of the box. Learning curve supported by well documented examples Easy to implement test cases.. N_Stokes for example Slide 13
Case Study 1 Addressing a field failure issue A component obsolescence forced the redesign of an optical communication channel on an MRI compatible device Failures of the comm. Link were documented by customers (with the new design). What was happening? Slide 14
An E&M/Production Issue Slide 15
Case Study 1 cont Advanced Development group called-on to assist Determined that a bias potential was inadvertently getting onto the shield of the optical comm. Box The new nir xvr chip was more susceptible to E fields than old How to mitigate? Slide 16
E&M Example cont. Slide 17
Case Study E&M Team concluded that a shielding structure around the xvr structure would be a quick, cheap solution. What dimensions to use? Trial and error FEMLAB!! Slide 18
E&M Cont. Slide 19
E&M Cont. Slide 20
E&M Case Study Cont. Slide 21
E&M Case Study Cont. Slide 22
Conclusion FEMLAB simulation reduced 5 fold (at least) the number of prototype techs. Wanted to build and test Confidence in the physical identification of the issue led to quick adoption of the solution by the program. Slide 23
Fluid performance analysisb What changes to drug fluid path occur due to changes in the outlet of a syringe design? FEMLAB used to quickly plot the effects Slide 24
Heat Transfer Case Study Design team was encountering an excessive (beyond specs) thermal build up in a system module. How to solve? Advanced engineering again asked to consult. Suggested that the design team provide holes to encourage convection. Modelled in FEMLAB (convection and conduction mode) Slide 25
Heat Transfer Example Thermocouple Readings 70 60 50 Temp F 40 30 Base no Holes - measured Case w/holes - measured Simulated - Holes Simulated From FEMLAB 20 10 0 37342.50 37342.55 37342.60 37342.65 37342.70 37342.75 37342.80 time Slide 26
Results Team converged on a design decision quicker and needed fewer empirical measurements to ensure the thermal specifications were met. Slide 27
CFD Case Study A product Design team was encountering difficulties with bubble formation and nonideal flow through a key, disposable element of a new product. Could FEMLAB be used to help address the problems? Slide 28
CFD Case Study O utlet O utlet Inlet Figure 1 Cross section through the PIV valve. Input flow is defined on the boundary at the bottom right. The boundaries at the top left and right were defined as outlets. The rem aining boundaries were treated as "no-slip" boundary conditions. The fluid had physical properties of saline density = 1kg/m l, viscosity ~ 1 cp. The colormap indicates the m agnitude of fluid velocity within the geom etry (unscaled units because of the norm alized geom etry). The input velocity was uniform not assum ed to be developed, Poiesuelle flow). Slide 29
CFD Case Study Slide 30
CFD Case Study Slide 31
CFD Case Study Slide 32
CFD Case Study Slide 33
CFD Results Team was provided with quick results and direction regarding geometries to modify so as to rectify issues FEMLAB results tracked well with empirical data Slide 34
Fluid delivery research MEDRAD is a fluid delivery company (core competency) Innovations group investigating novel catheter designs and applications FEMLAB a natural choice to support concept feasibility, IP due diligence, and research. Slide 35
Catheter technologies Slide 36
Drug/Blood interaction research Slide 37
CT Imaging with Contrast Computed Tomography imaging is a form of X-Ray imaging that enables high resolution 2D,3D and (somewhat) 4D images of human anatomy.images created based on attenuation of X-Rays through dense materials: X-Ray sources and detectors are positioned in a ring around the patient, allowing for multiplanar imaging. Because blood, blood vessels, soft tissue and organs are radioopaque, X-Rays pass through them mostly unaffected. Solution: Add to the circulation liquid that attenuates X-Ray energy! I( x) = I e 0 μ Δx ρ Slide 38
Contrast Medium in CT Molecule of X-Ray Contrast Modern CT Contrast Injection System Medrad Inc. Stellant tm Modern CT contrast medium is a watersoluble drug injected via a peripheral vein injection site. Contrast is provided by 3 Iodine atoms attached to a Benzene structure Agent is hyperosmolar (typically), and quickly diffuses through capillary endothelia and is excreted by the kidneys via glomerular filtration Open-Loop Control paradigm Slide 39
Problems With Delivery Improved CT scanners allow for the acquisition of volumetric scans in seconds. Injection timing and delivery becomes challenging because of the fast scan times. Fast injections causes a peak enhancement curve whose structure can confuse a radiologist X-Ray Slice CM Bolus propagation Blood vessel (ie: Descending Aorta) Ideal Bolus of contrast medium in blood vessel Red Blood Cells Pictorial of actual CM transit in blood vessel. Notice the CM spreading Slide 40
Example Typical Vessel Enhancement Curve Ideally want the enhancement curve to be flat (~ at this level) Peak Enhancement How to get rid of the peak? Contrast injection: 2ml/s of 80 ml. Time to peak enhancement Slide 41
Drug Propagation Modelling Using FEMLAB and the Chemical Engineering module to better understand the early-time dynamics of the injection event Couple N-Stokes with Convectionvection- Diffusion (concentration affecting viscosity) to gain insight to the distribution of drug through the peripheral vasculature (into the heart) Can lead to better use of the drug, better scans and images, and better diagnoses. Slide 42
Governing Equations v ρ( + ) = + μ t v = 0 2 v v p v C v C k 2 C + = t μ( C) Similar to Calamante et al., Estimation of bolus dispersion effects in perfusion MRI using image-based computation fluid dynamics, NeuroImage, 19(2003) 341-353 Slide 43
Drug Blood Interaction Slide 44
Why Care? P1- Diagnostic Enhancement 280 230 w/ saline w/o saline enh_meas 180 130 80 30 0 10 20 30 40 50 60 70-20 Time (sec) Differences in patient-patient physiology presents as different flow profiles (timedensity curves) complicate rational drug delivery schemes Slide 45
Check against empirical evidence Fluid Dynamics in Cerebral Angiography, Mabon RF, Soder PD, Carpenter WA, Giddens DP., Radiology. 1978 Sep;128(3):669-76 Slide 46
Peripheral Venous System Slide 47
Simplified 3D Slide 48
Concentration profile Slide 49
Streamline Slide 50
Local injection characterisitcs Slide 51
Drug/Body Discussion Insight leading to better controlled and designed lab experiments Ultimately leading to better design and delivery of diagnostic imaging agents. Slide 52
COMSOL Multiphysics The Good!! Very easy to use Intuitive interface User-modes Capability exists to go under the hood Extension and interaction with MATLAB/Simulink nice Priced VERY reasonably GREAT support EXCELLENT documentation Some Areas for improvement Importing of 3D geometries * Quirkiness while solver active (mostly solved in 3.1) * Multi-processor support Units * Some engineery enhancements (like easily plotted S params) * Slide 53
Conclusion COMSOL Multiphysics is a very powerful tool for the corporate biomedical engineer (in research and development) True multiphysics capabilities means the sky s the limit COMSOL Multiphysics allows for the quick investigation of complex interactions ant a very affordable $$ Slide 54