Signal Processing for Maternal Fetal Medicine

In collaboration with the medical doctors at the University of Utah Hospitals and researchers at Erasmus University, Rotterdam, The Netherlands, we have been developing the tools necessary to facilitate engineering model based practice of maternal fetal medicine. We are particularly interested in the evolution of the placenta with gestation since many pregnancy-related diseases can be traced to placental dysfunction. Examples of such diseases include preeclampsia, intra-uterine growth restriction and some cases of prematurity. Our long-term goal involves building digital placenta models that are specifically tuned to characteristics of the pregnant woman under observation. Such models may depend on many factors that affect the development of the placenta including maternal phenotype, nutrition, medication and genetic influences. Accomplishing this goal will allow the identification of pregnancies that are destined to develop a variety of abnormalities much earlier and more accurately than currently possible, which would in turn allow the care givers to better prepare for the possibility of subsequent pregnancy complications. This may take the form of closer and more frequent observations, transfer of the patient from a low risk to high risk clinic/hospital, and initiation of therapy as needed.

In recent years, we have concentrated on developing tools for understanding the evolution of the placental circulation system and possible relationships between maternal and fetal circulation systems. We have used Doppler ultrasound as one of the primary means of data acquisition because it is easy to use and easily available, non-intrusive, can be used as early as during the eight week of human pregnancy, and is relatively inexpensive. Some of our recent accomplishments include:

1. We have developed methods for non-invasively estimating the blood pressure waveforms and shear stress in fetal arteries using Doppler ultrasound, and characterized the evolution of their properties with gestational age.
2. We have developed a method for estimating fetal heart rate variability using Doppler ultrasound techniques. Our method is robust to variations in the angle of insonation as well as ambient noise levels, and thus has made Doppler ultrasound feasible for practical measurement of fetal heart rate variability. Using this approach, we have developed a method for detecting certain congenital heart diseases during the early stages of human pregnancy by measuring fetal heart rate variability. About 8 in 1000 pregnancies are affected by some form of congenital heart defects.
3. We have developed a system for characterizing the relationship between maternal and fetal circulation systems, and the evolution of this relationship with fetal age. We have used this system for early detection (late first through early second trimester) of pregnancies that are destined to later develop preeclampsia. Preeclampsia is a disease that affects between 6 and 8% of all pregnant women in the United States and their fetuses, and is one of the major causes of maternal and fetal death in the USA. At present, there exist no reliable means of predicting during the early stages of pregnancy, whether a woman will later develop preeclampsia.
4. In addition to developing markers of placental deficiency using parameters of the circulation system, we recently developed what appear to be reliable proteomic markers for preeclampsia.

Our work in this area was supported by the Primary Children’s Medical Center Foundation, Salt Lake City and the American Heart Association and the University of Utah Research Foundation. This work has also been supported by federal grants awarded to the School of Medicine at the University of Utah.

Students With Research Emphasis in Biomedical Signal Processing

• Lanka Fernando, Prediction of Maternal-Fetal Diseases Using Ultrasound Signal Processing, Ph. D., University of Utah, August 2003.
• Piet Struijk, Assessment of Hemodynamic Parameters in the Fetal and Utero-placental Circulation using Doppler Ultrasound, Ph. D., Erasmus University (Visiting Scholar at the University of Utah), 2006.

Publications and Presentations in Biomedical Signal Processing

1. K. A. East, T. D. East, V. J. Mathews and B. T. Waterfall, "Computerized Artifact Rejection for Respiratory Inductance Plethysmography Apnea Monitor,''  J. Clinical Monitoring, Vol. 5, No. 3, pp. 170-176, July 1989.
2. P. C. Struijk, N. T. C. Ursem, V. J.Mathews, E. B. Clark, B. B. Keller and J. W. Wladimiroff, " Power Spectrum Analysis of Heart Rate and Blood Flow Velocity Variability Measured in Umbilical Artery and Uterine Artery in Early Pregnancy. A Comparative Study ,'' Ultrasound in Obstetrics and Gynecology, Vol. 17, No. 4, pp. 316-321, April 2001.
3. K. L. Fernando, V. J. Mathews, M. W. Varner and E. B. Clark, "Robust Estimation of Fetal Heart Rate Variability Using Doppler Ultrasound," IEEE Trans. Biomedical Engineering, Vol. 50, No. 8, pp. 950-957, August 2003.
4. K. L. Fernando, V. J. Mathews, and E. B. Clark,  "Mean Frequency Estimation of Narrowband Signals," IEEE Signal Processing Letters, Vol. 11, No. 2 , pp. 175-178, Feb. 2004.
5. K. L. Fernando, V. J. Mathews, and E. B. Clark,  "A mathematical basis for the application of the modified geometric method to maximum frequency estimation," IEEE Trans. Biomedical Engineering, vol. 51, no. 11, pp. 2085-2088, November 2004.
6. P. C. Struijk, P.A. Stewart, K. L. Fernando, V.J. Mathews, T.Loupas, E.A.P. Steegers, J.W. Wladimiroff, "Wall shear stress and related hemodynamic parameters in the fetal descending aorta derived from high spatio-temporal resolution color Doppler velocity profiles,"  Ultrasound in Medicine and Biology, vol. 11, pp. 1441-1450, Nov. 2005.
7. P. C. Strujik, K. L. Fernando, V. J. Mathews,  E.A.P. Steegers, J. W. Wladimiroff, E.B. Clark and M.W. Varner, "Application of the Magnitude-Squared Coherence Function Between Uterine and Umbilical Flow Velocity Waveforms for Predicting Placental Dysfunction: A Preliminary Study," Ultrasound in Medicine and Biology, vol. 33, no. 7, pp. 1057-1063, 2007.

8. K. L. Fernando, V. J. Mathews and E. B. Clark, "Mean Frequency Estimation of Narrowband Signals and its Application to Doppler
   Ultrasound Blood Velocity Waveform Estimation," IEEE International Conference on Acoustics, Speech and Signal Processing, Vol. 2, pp. 1317-1320, May 2002.
9. K. L. Fernando, V. J. Mathews, and E. B. Clark, "Reconstruction of Maximum Blood Velocity Waveforms from Doppler Ultrasound Measurements," Proc. Engineering in Medicine and Biology, 2002, 24th Annual Conference and the Annual Fall Meeting of the Biomedical Engineering Society, vol 1, pp. 124-125, October 2002.
10. K. L. Fernando, V. J. Mathews M. W. Varner and E. B. Clark, "Robust Estimation of Fetal Heart Rate Variability Using Doppler Ultrasound," Proc. IEEE International Conf. Acoustics, Speech, and Signal Processing, pp. II - 257-260, Hong Kong, April 2003.
11. K. L. Fernando, V. J. Mathews M. W. Varner and E. B. Clark, "Prediction of pregnancy-induced hypertension using coherence analysis," Proc. IEEE International Conf. Acoustics, Speech, and Signal Processing, vol. 5, pp. 433-436, Montreal, Canada, May 2004.
12. V. J. Mathews, "Signal Processing for Maternal-Fetal Medicine," European Signal Processing Conference (EUSIPCO), Florence Italy, September 2007 (Plenary Talk)