Teb Medical Inc. Simon Fraser University Burnaby, BC V7C 5T5

Transcription

1 Teb Medical Inc. Simon Fraser University Burnaby, BC V7C 5T5 December 18, 2004 Dr. Andrew Rawicz School of Engineering Science Simon Fraser University Burnaby, British Columbia V5A 1S6 Re: ENSC 340 Post Mortem for a Venipuncture Site Locator (Teeka ) Dear Dr. Rawicz: The attached document, Teb Medical Inc. Post Mortem, describes the design, implementation, and testing process of the veinpuncture site locator. The document describes the prototype, states the deviations from the proposed design, and highlights the future plans for the designed device. In addition, the document outlines the budgetary and time constraints encountered and explains the inter-personal and technical experience gained during the system development process. We have built the prototype for our future product, Teeka, to improve tedious and painful circumstances in locating veins of patients. Teeka collects data by using a near-infrared transmitter and detector, processes the data with a microprocessor, and finally locates the optimal venipuncture site. Teb Medical Inc. consists of four dedicated fourth and fifth-year engineering students who love to incorporate their knowledge and experience to assist others: Ameneh Atai, Amir Goldan, Ida Khodami, and Balraj Mattu. Please do not hesitate to contact us for any questions or concerns via , ensc340-vein@sfu.ca. Sincerely, Amir H. Goldan Amir H. Goldan Chief Executive Officer Teb Medical Inc. Enclosure: Post Mortem for a Venipuncture Site Locator

2 Post Mortem for the Venipuncture Site Locator Project Team: Contact Person: Submitted to: Ameneh Atai Amir Goldan Ida Khodami Balraj Mattu Balraj Mattu Dr. Andrew Rawicz, Mr. Steve Whitmore, Mr. Mike Joerdsma, and Mr. Scott Logie School of Engineering Science Simon Fraser University Date: December 18, 2004

3 Table of Contents 1. Introduction Acknowledgement Description of System Operation Scanning Mode Detection Mode Problems Encountered in Design Ambient Light Coupling Effect Reflection of the skin Demodulation Group Dynamics Future Work Hardware Optimization Software Optimization Marketing Plans Budget (Estimated Vs. Actual) Schedule (Estimated Vs. Actual) Individual Experiences Conclusion Copyright 2004 Teb Medical Inc. Page ii

4 List of Figures Figure 1, The functional system block diagram... 1 Figure 2, The coupling capacitance introduces the coupling effect... 3 Figure 3, The Estimated Timeline Figure 4, The Actual Timeline List of Tables Table 1, The tentative budget... 7 Table 2, The actual costs incurred... 7 Table 3, The funding require for the second prototype... 8 Copyright 2004 Teb Medical Inc. Page iii

5 1. Introduction In past five months, Teb Medical team - Ameneh Atai, Amir Goldan, Ida Khodami, and Balraj Mattu - has designed and implemented a prototype for a Venipuncture site locator and has successfully overcome the obstacles and challenges in completion of the task. The included report re-examines the process of design and implementation, reports on the description of the current device operation, any deviations from our original plans, and our future plans for the venipuncture site locator. Figure 1, illustrates and overview of the system. The detailed description of the transmission, receiver, and processor stages were discussed in the design specification document. Figure 1, The functional system block diagram. 1.1 Acknowledgement We would like express our gratitude to Dr. Andrew H. Rawicz for his guidance and motivation throughout the entire project. We would also like to thank Mr. Mike Joerdsma, and Mr. Scott Logie for their contribution with documentation and inspirational work to this project. Copyright 2004 Teb Medical Inc. Page 1

6 2. Description of System Operation TMI is proud to announce that the first phase of the prototype development cycle was completed as scheduled on December 15 of The venipuncture site locator transmits a near-infrared modulated pulsating beam, detects the reflected infrared photons, and processes the detector output signal. The detector signal is first digitized using an A/D converter, and is then processed with the vein detection algorithm which is programmed into the microprocessor. For the optimal vein detection, the device operates in two functionally distinct modes: 1) the Scanning Mode, and 2) the Detection Mode. 2.1 Scanning Mode Scanning mode is activated by pressing the switch located on the device. During scanning mode, the operator scans the veinpuncture area while the device records the variation of reflection intensities. The recorded data are processed by detection algorithm within the processor to recognize the tissue underneath. the operator scans the venipuncture site by pressing the switch located on the device. 2.2 Detection Mode The detection mode is activated by the release of the switch. The operator shall scan the same venipuncture site once more, during which the optimal vein is referenced by an LED mounted on the board. The optimal vein is the one with the maximum diameter and highest blood flow in the scanning area. Copyright 2004 Teb Medical Inc. Page 2

7 3. Problems Encountered in Design A description of several problems encountered during the design process is provided in this section. Note that our prototype was delivered on time and as proposed. 3.1 Ambient Light The presence of the ambient light is a major source of error in the detection process; therefore, the design must ensure the phototransistor s output is resulted from the incident near-infrared photons only. Recalling that the ambient light adds a dc offset to the output signal, it can be eliminated by appropriate filtering of the signal. The filtering can be achieved by modulating the signal by a higher carrier frequency followed by filtering of the lower frequencies through a simple analog filter. This was achieved by transmitting a modulated pulsating beam, using a near-infrared LED, and passing the signal through a high order bandpass filter in the signal retrieval stage. The suggested method reduces the detector s sensitivity to stray light dramatically and ensures a higher signal to noise ratio. The useful data can then be extracted from the carrier wave through downshifting. 3.2 Coupling Effect Ideally, when no reflective surface is present within the OPB745 sensor s field-of-view, the output voltage of the BPF is zero; however, due to the coupling effect, the output voltage is a sinusoidal signal with the same frequency as the carrier. As shown in Figure 2, the input to pin A is a square wave and the presence of the coupling capacitor between pins A and E induces a current pulse. The magnitude of the current pulse is proportional to both the value of the coupling capacitor and the slew rate of the square wave. Figure 2, The coupling capacitance introduces the coupling effect. Timer feedthrough, caused by the coupling capacitor, imposes a major constraint on the amount of amplification and the sensitivity of the detector. Therefore, minimizing the coupling effect is critical in designing the detector circuit. The coupling effect can be Copyright 2004 Teb Medical Inc. Page 3

8 minimized by choosing a small value high-pass resistance, R HP. The coupling effect can be entirely eliminated by the proper shielding of the reflective object sensor s wires. 3.3 Reflection of the skin Using empirical data, about 65% of the transmitted near-infrared photons will be reflected of the skin, 25% will be absorbed by soft tissue, and only 10% will be transmitted inside. Again, out of the 10% transmitted inside the body, only a small percentage will be reflected but this time the intensity of the reflected photons varies with different medians present within sensor s field of view. To reveal these small changes in intensity, the analog circuit must have a high sensitivity. 3.4 Demodulation As mentioned before, the transmitter transmits a modulated pulsating beam. In the signal retrieval stage, demodulation is necessary to extract the useful information imposed on the carrier. To demodulate the received signal, we first employed the Double-Sideband Modulation (DSM) technique but our attempt was unsuccessful simply because we approximated the sinusoidal carrier wave with a square wave. Later on we managed to demodulate the signal using a precision peak-detector. Copyright 2004 Teb Medical Inc. Page 4

9 4. Group Dynamics In all the years of studying engineering science and taking numerous courses we have learned theories and means of applying them to real life applications. During ENSC 340 and ENSC 305, we gained experience on how to manage a project, co-ordinate work between several people, perform our absolute best as a team and to meet deadlines. No major group dynamic issues were experienced in Teb Medical Inc group. During our weekly meeting we discussed what had to be done in the following week and assigned tasks to individuals. In certain stages of the project assigning tasks to member individually was difficult, as the other stages strongly depended on the outcome and performance of another stage. (i.e. the software design could have not been started before the completion of the hardware design). This allowed us to work together as a team. Several excellent advantages were experienced in working together as a team. Working in a team allows frequent updates on the project; furthermore four talents together can achieve a lot more. Working as a team did not constrain us on testing their individual ideas on the project. However, if we were to undertake a similar project again we would assign task to each person as well as working together when needed. Also we would have different members of group to manage the group for one week and give a progress report on all other members at the end of each week. This also helps to keep all the group members on the same page. Copyright 2004 Teb Medical Inc. Page 5

10 5. Future Work Our goal in the first prototype was to make a device that accurately locates veins. Now that we have achieved it, for the next prototype our goal would be to optimize both the hardware circuit and the software 5.1 Hardware Optimization To optimize the hardware circuit, we have to make the analog circuits smaller and also cheaper. If we make our own transmitter LED and photo detector we would be able to reduce the cost and also area used by the analog circuit. Also in our current design for filtering the received signal we are using one op-amp chip and many capacitors, which can be reduced with further research on better filtering methods. 5.2 Softwa re Optimization For optimizing the software, we need to improve the vein detection algorithm. Mainly we can have only one mode of operation instead of two that we currently have, by improving the vein detection algorithm and coming up with new methods. 5.3 Marketing Plans We are in process of patenting our design with the help of UILO in Simon Fraser University. In addition the final product shall have a marking mechanism. The size of the final product shall be reduced to the size of a pen. Also as the next step we can insert a syringe into the device, so that whenever the best vein is detected the venipuncture operation is done by pushing a button, reliably and efficiently. Copyright 2004 Teb Medical Inc. Page 6

11 6. Budget (Estimated Vs. Actual) Table 1 outlines the estimated expenditures to develop the prototype for the venipuncture site locator at September Table 1, The tentative budget Materials Estimated Cost Lasers/Sensors $50 Microcontrollers/Comparators $50 Miscellaneous Components $20 Batteries $15 Prototyping/Casing $80 Cables & Wires $10 Total $225 Table 2 outlines the costs incurred to develop the first prototype for the venipuncture site locator. Table 2, The actual costs incurred Materials Actual Cost Reflective Object Sensor $ Instrumentation Amplifier $52.02 PCB $ Prototyping/Casing $80.00 Miscellaneous Components $ Batteries $12.99 Cables & Wires $10.00 Total $ The above costs were generally on target for this project. A major problem in the design was to obtain a very flexible shielded wire. This would have been a costly addition to the prototype, which was compromised by employing a less quality wire provided for free in the engineering lab. Another cost overrun was with the reflective object sensors, since testing was perform on numerous amounts of them. The actual cost was around $ to purchase several types of sensors. Since several sensors had to be tested, the cost of components also increased as circuitry for each sensor was different. The overall miscellaneous component (i.e. TL071 op-amp, 555 timers, potentiometers, resistors, capacitors, sockets, headers, etc) cost came to $ Once a final analog circuit was composed, the circuit was converted to a PCB (printed circuit board). The cost of this was $142. The board has not yet been tested. The funding required for the second prototype is shown in the Table 3. Copyright 2004 Teb Medical Inc. Page 7

12 Table 3, The funding require for the second prototype. Rough Casing for prototype model for testing purposes $1000 Printed Circuit boards of prototype $2000 PCB Surface Mount Parts $1000 Texas Instruments MSP430F1132 Microcontroller w10bit A/D for precision $50 (Current Microcontroller is not accurate enough) Texas Instruments MC Programmer and Manuals $800 (Manuals required to learn programming language) Hardware analysis of the existing system by external engineer $1500 (Need to ensure ha rdware is optimized before designing final prototype, this price may fluctuate depending of professional that is hired) Software analysis of the existing system by external engineer (Need to ensure hardware is optimized before designing final prototype, this price may fluctuate depending of professional that is hired) $1500 TOTAL $7850 All funding as of yet has been provided by the members of TMI. Funding for the second prototype has been applied for through the UILO (university industry/liason office). Approval for the funding which is projected to be $7,850 is to be determined by early January Copyright 2004 Teb Medical Inc. Page 8

13 7. Schedule (Estimated Vs. Actual) The following two Figures outline our estimated and actual schedules for the first prototype development cycle. The first prototype was estimated to be completed by November 30, However due to the challenges faced in the design process, the completion of the prototype was delayed to December 15, Copyright 2004 Teb Medical Inc. Page 9

14 Figure 3, The Estimated Timeline. Figure 4, The Actual Timeline. Copyright 2004 Teb Medical Inc. Page 10

15 8. Individual Experiences Amir Goldan Chief Executive Officer I had a blast working with my team members on this exciting project. It was five months of untiring team effort but every minute of it was an adventure worth exploring. ENSC 340 and 305 gave me the opportunity to employ all the assets at my disposal toward creating a device that would help ease the pain of the venipuncture procedure. However, the journey was not without obstacles and had its pitfalls. It was after a couple times redesigning the analog circuit that we recognized the importance of the type of the reflective object sensor s photodetector. Also minimizing the coupling effect was of paramount importance in order to improve detector sensitivity. It was extremely fascinating, and at the same time rewarding, when we overcame these obstacles as a team and that boosted our confidence. I must say that all the hard work throughout my five years of studying at SFU paid off by my accomplishments in this project course. I hope to continue the journey even further along with my group members and finish what we started. Ameneh Atai Chief Technical Officer ENSC 340 and 305, unlike most other courses taught in university, encourage students to think laterally rather than linearly. Creativity is not only a requirement; it is the most important factor; furthermore, the courses force student to go beyond their limits. These courses, reminded of me of how much I don t know and how much I am capable of learning within such a short period of time. I am very proud of our achievement, and am very pleased with everyone I worked with. The team members were amazing and I look forward to further our research and design with them in the future. Ida Khodami Chief Operation Officer During the past five months I have learned many valuable criteria, not only from the project but also from my group members who are among my best friends. For this project We worked together for a common goal, and all survived through this extraordinary experience. From the first days researching for different methods of doing this project to the final prototype I have gained many valuable experiences in optical system design. I got familiar particularly with optical emitters, receivers. Also, I gained a lot of experiences with programming a microprocessor. Now that I look back at these five months I know that every second of it was worth all the challenge. Balraj Mattu Chief Financial Officer This course provided a good opportunity to combine and apply some of the knowledge acquired through the many engineering courses I have taken at SFU. It also provided a setting that is very similar to real life corporations. I am fortunate to be a part of this process where we started out with a great idea in mind and ended up with a completion of our product and possibly even a product that will be available in the market shortly. Copyright 2004 Teb Medical Inc. Page 11

16 Through this completion, we faced many challenges and learned how to deal with and handle each of them as a group. A real challenge in terms of the scope of the project is our inadequate biological background. Fortunately, the amount of knowledge needed for this project was not rigorous and was easily learned in a short amount of time. Furthermore, I have leaned how to write professional project documents such as functional and design specifications, as well as how and where to obtain financial help for projects. I have truly enjoyed being a part of this team. Even though it has been stressful at times, we have had many fun moments, which have made the stressful times worthwhile. Copyright 2004 Teb Medical Inc. Page 12

17 9. Conclusion We are proud to announce that Teb Medical Inc. s (TMI) has developed the first prototype (displaying proof of concept) of an accurate, safe, and inexpensive device that will allow doctors and nurses to locate a venipuncture site on any patient quickly and effortlessly. The trauma some patients go through in this procedure can therefore be reduced or even eliminated. Moreover, we managed to complete the project approximately within the planned budget and managed to meet all deliverable deadlines, along with the final project deadline. The successful completion of the first prototype has enabled us to realize the value of this project and to proceed with the second phase of design. Together as a team, TMI will go on to the next phase of development with the valuable leadership and organizational skills attained during this four month period. Overall, this project has equipped us to become better team members and development engineers for the future. Ever tried? Ever failed? No matter. Try Again. Fail again. Fail better. --- Samuel Beckett Copyright 2004 Teb Medical Inc. Page 13