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GOAL
Our client Dr. Haughton is currently studying CSF flow during Valsalva maneuvers performed by children with Chiari I malformations. Current research suggests that CSF flow decreases during Valsalva maneuvers in these patients. The airway pressure device would help monitor the exhalation force exerted by each child during a Valsalva maneuver in the MR suite. Knowing the pressure exerted by each patient in the study would be extremely beneficial for data analysis and accuracy. This is a continuation of work done in the Fall 05 semester found here.
Design Team Members (from L to R): Kevin Johnson, Laura Sheehan, Jon Cappel, Noelle Simatic
Current Progress
We have validated our device, in MR with a volunteer. We have done testing to determine the repeatibility of our measurements in the MR enviroment and towards the development of a smooth operation protocol.
Experiment 1: MR Effects of Pressure Readings
Pressure measurements were taken using a computer controlled pump as a source, with the device out side MR, inside the MR bore, and inside the bore during imaging. The pump used controls the flow rate according to a users input. Using a squarewave input function, with a peak flow of 10 ml/s, we placed our transducer on the proximal end of a 75% stenosis phantom. Recordings were taken continously for 5 minutes at each of the three situations, leading to aproximately 240 independent pressure realizations. Each continous measurment was converted to a set of periodic functions using a trigger from the pump specifying the start of a cycle. All data was analyzed using Matlab 7.0.
Results are shown in figure 1.
Figure 1. Pressure curves obtained under several conditions. All results show high levels of correlation
Figure 2. Pressure correlation plotteded for pressures obtained outside the bore and during scanning. A linear regression fit found a slope of 1.01 with a correlation of 0.98
Experiment 2: Device effects on MR
Seperate images were taken on various conditions to determine the effects of our device on MR image quality and SNR. Initial results show, a large decrease in SNR with the introduction of our device (Figure 3). We believe this is due to the improper shielding of the transducer cable, and hope to repeat the experiements to get quanitative results, once additional shielding is in place.
Figure 3. Image taken without our device (left) and with our device (right). There is an obvious drop in SNR which must be accounted for.
Experiment 3: Device effects on MR with Shielding
The previous MR artifact images were repeated using a phantom meant to represent the geometry of a human subject. Images were acquired with a 3D GRE sequence at resolution of 512x512x128 in a coronal plane. Images were compared using a subtraction algorithm, as well as ROI analyis for SNR comparisons. Images, as shown in figure 4, show dramatic improvement over previous results and analysis found difference to be statisticall insignificant.
Figure 4. Image taken with our device (A), with our device (B), and the difference between them(C). The SNR difference between the images was insignificant (24.5 with, 23.5 without). Images value means are within 0.85% of eachother, which is less than the statistical variation of ~4%.
Experiment 4: Volunteer Testing
We have done initial testing to test the logistical feasibility of the device, and ensure acceptable waveforms are achievable in the clinical setting. A single volunteer has been imaged using a standard C-spine coil, in a 1.5T GE Sigma Scanner (Waukesha, WI). Compressed air and vaccum sources were availble in the room, allowing an operator in the room to easily close and open the valve. A 2D cine-PC exam was performed during normal breathing and during a valsalva. Recorded pressures are shown in figure 5, with the corresponding flow rates shown in figure 6.
Figure 5. Baseline (dashed-blue) and valsalva (solid-red) pressure waveforms obtained during a 2D CINE Phase Contrast exam. Pressure data was recorded for 45 seconds, starting 10 seconds before the start of the exam
Figure 6: CINE-CSF flow waveforms obtained during normal breathing and valsalva. A small net increase in flow was observed during the valsalva.
| Week | Reporting Period Beginning | Activities |
|---|---|---|
| 1 | January 20 | Formulated Research Plan, setup meeting times |
| 2 | January 27 | Met with Client, Setup IRB, created validation experiments |
| 3 | February 3 | Setup protocols for MR experiments, measure anesthizia tubing, stup K12 outreach |
| 4 | February 10 | Perfromed MR experiments, machined anesthisized patient device |
| 5 | February 17 | Analyzed Data from MR Experiments, worked on midsemester |
| 6 | February 24 | Midsemester Presentation |
| 7 | March 3 | Gathered list of things to do and timeline, contacted client/Matt Obrien, measured available source pressures |
| 8 | March 10 | Tested device with test lungs, prepared for outreach presentation |
| 9 | March 17 | Started construction on new device, outreach presentation |
| 10 | March 24 | Obtained shielding, initial testing |
| 11 | March 31 | Finished new protoype, shielding testing continued |
| 12 | April 7 | Pressure testing, image quality testing finalized |
| 13 | April 14 | Patient testing, worked on presentation |
| 14 | April 21 | Poster presentation |
| 15 | April 28 | Cognitive Studies on the effects of consumption on airway pressure |
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Midsemester Presentation (Feb 23 2006, 1809 kb) |
 |
Product Design Specifications (Mar 3 2006, 27 kb) |
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Journal Paper (Apr 28 2006, 114 kb) |
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Final Poster (May 4 2006, 721 kb) |
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Outreach Presentation Deliverable (May 10 2006, 41 kb) |
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WARF IDR (May 10 2006, 25 kb) |
