Medical applications of UWB radars : 8/29/2010 1 Enrico M. Staderini, MD, PhD
School of Medicine - Medical Physics
“Tor Vergata” University of Rome
firstname.lastname@example.org Medical applications of UWB radars Tip: this document has hyperlinks to related documentation on the web, use them for further information. This is the physician’s view on(and a review about)UWB radars in medicine : 8/29/2010 2 This is the physician’s view on(and a review about)UWB radars in medicine The medical radar history halted 20 years ago... : 8/29/2010 3 The medical radar history halted 20 years ago... 1971: A contactless apnoea detector based on radar presented (Lancet 1971 Oct 30;2(7731):959-61) .
1976: Radar respiration monitor for infants described (Med. Biol. Eng. 1976 May;14(3):306-318) .
1980: Respiratory patterns in infants detected using radar (Arch. Dis. Child 1980 Aug;55(8):595-603) . The possible reasons for a failure : 8/29/2010 4 The possible reasons for a failure Microwave radiation safety concerns.
Cumbersome, bulky apparatuses.
Power supply concerns.
Pneumology limited applications.
Not a strong rationale for using. Rejection. The medical radarhistory restarted with UWB technology in 1994 : 8/29/2010 5 The medical radarhistory restarted with UWB technology in 1994 Image from LLNL MIR website, Livermore, USA
http://lasers.llnl.gov/lasers/idp/mir/cardio.html The medical UWB radar history : 8/29/2010 6 The medical UWB radar history Aug. 9, 1994: first US Patent application filed for a medical UWB radar.
Mar. 23, 1995: MIT educational project for the Radar Stethoscope. Image from MIT website, Cambridge, USA
http://me.mit.edu/courses/2.744/s95/prj2/SketchModels.html The medical UWB radar history : 8/29/2010 7 The medical UWB radar history Jan. 1996: The biomedical use of UWB radars is better described with photo and sample tracings (Science and Technology Review, UCRL-52000-96-1/2, Jan. 1996).
Nov. 12, 1996: US Patent (no. 5,573,012) awarded. Image from US Patent #5,573,012 The medical UWB radar history : 8/29/2010 8 The medical UWB radar history Nov. 12, 1996: second US Patent application filed.
1998: UWB radar application in medicine first described on a paper in a scientific journal (J. Acoust. Soc. Am. 103 (1), January 1998).
Jun. 16, 1998: US Patent (no. 5,766,208 ) awarded.
1999: Works in progress for UWB radar applications in cardiology, obstetrics, breath pathways and arteries. The medical UWB radar history : 8/29/2010 9 The medical UWB radar history UWB radar applications in medicine are being studied here (list may be incomplete):
Lawrence Livermore National Laboratory
(heart, breath, speech)
University of California Davis
University of California Berkeley
University of Iowa
Tor Vergata University of Rome
(heart) Could misunderstanding destroy a promising technology ? : 8/29/2010 10 Could misunderstanding destroy a promising technology ? As early as March 1995 a project was assigned to the students of the Mechanical Engineering Department of MIT. The purpose was the “Design of a product concept: the Radar Stethoscope” *.
It was the very first attempt to test the feasibility of a real product for the biomedical market using UWB radar technology. Follow the link above. * Woody C. Flowers - Pappalardo Professor of Mechanical Engineering, MIT
David R. Wallace - Assistant Professor of Mechanical Engineering, MIT Could misunderstanding destroy a promising technology ? : 8/29/2010 11 Could misunderstanding destroy a promising technology ? Unfortunately, the project was too much prone to the stethoscope concept and it appears to be a misunderstanding of the real strength of the technology and an opportunity lost.
The radar stethoscope is NOT a stethoscope, so a different name (and claims!) should have had to be devised. Could misunderstanding destroy a promising technology ? : 8/29/2010 12 Could misunderstanding destroy a promising technology ? Most of the students developed clever prototypes just too much resembling a conventional electronic stethoscope. Images from MIT website, Cambridge, USA
http://me.mit.edu/courses/2.744/s95/prj2/RhondaMassie.html Could misunderstanding destroy a promising technology ? : 8/29/2010 13 Could misunderstanding destroy a promising technology ? A few of them quite attractive, indeed! Images from MIT website, Cambridge, USA
http://me.mit.edu/courses/2.744/s95/prj2/FrancisPahng.html Could misunderstanding destroy a promising technology ? : 8/29/2010 14 Could misunderstanding destroy a promising technology ? The bioengineering approach was probably wrong
the “sounds” obtained with a radar stethoscope are too much different from conventional acoustic sounds.
The new device appeared not just a new way to explore what is already known
indeed it is a new, and unknown, modality of probing the human body. Could misunderstanding destroy a promising technology ? : 8/29/2010 15 Could misunderstanding destroy a promising technology ? The project is not known having reached the market
(a first batch of 1000 was initially considered).
5 years after the filing of the first patent, commercial medical applications are still missing.
Many new technologies has to fight against conservative approaches. A suitable model for UWB radar interaction with the human body is missing : 8/29/2010 16 A suitable model for UWB radar interaction with the human body is missing “When you can measure what you are speaking about, and express it in numbers, you know something about it; but when you cannot measure it, when you cannot express it in numbers, your knowledge is of a meager and unsatisfactory kind: it may be the beginning of knowledge, but you have scarcely, in your thoughts, advanced to the stage of science.”
William Thomson, Lord Kelvin (1824-1907) ? : 8/29/2010 17 ? Is UWB really a golden egg tech in medicine Key questions : 8/29/2010 18 Key questions What can be reasonably devised?
What kind of medical problems really deserve UWB radar technology for their solution?
Is UWB radar technology able to address yet unresolved medical problems?
What should have to be the role of medical and bioengineering research? Most wanted technical features for any electrical medical instrumentation : 8/29/2010 19 Most wanted technical features for any electrical medical instrumentation Non invasiveness.
Non contact remote operation.
Intrinsic electrical transducer. UWB radar features them all! Most wanted clinical features for any electrical medical instrumentation : 8/29/2010 20 Most wanted clinical features for any electrical medical instrumentation User friendliness.
Technical understandability by the users.
Hardly to get physiological measurements.
High specificity. UWB radar needs more research! Useful tips for any medical device inventor/designer : 8/29/2010 21 Useful tips for any medical device inventor/designer Look for a solid rationale before reinventing/modifying the wheel.
Don’t fall in love with technology.
Aim to credible, clear, understandable objectives.
Consider medical specificity. UWB radar needs more research! The magic of seeingliving internal organs : 8/29/2010 22 The magic of seeingliving internal organs “But John Castorp’s attention was drawn by something sack-shaped, a sort of formless animal, dark and visible almost in the middle of the thorax, and mostly on the right side as seen by an observer, - it was contracting and relaxing with a regular alternation between the two, like a swimming jellyfish.
“ Can you see his heart ? ” … My God! It was the heart, John’s aspiring heart …
“ I am seeing your heart ! ”
he said with repressed voice.”
Thomas Mann* - The enchanted mountain
* Nobel Laureate German writer Cardiology : 8/29/2010 23 Cardiology Applications for heart monitoring were the first devised for UWB radar technology.
Heart related research has a high impact on the general public.
Unfortunately UWBtech had no visibility in the medical research area, although the situation is about to change. Cardiology : 8/29/2010 24 Cardiology The first Mc Ewan’s patent on the “radar stethoscope” Cardiology : 8/29/2010 25 Cardiology heart echoes Images from US Patent #5,573,012 Cardiology : 8/29/2010 26 Cardiology What we are looking at ? cardiology The Visible Human Project
http://www.dhpc.adelaide.edu.au/projects/vishuman2/ Cardiology : 8/29/2010 27 Cardiology EKG vs. UWB UWB vs. US Research needed! Image from US Patent #5,573,012 Cardiology : 8/29/2010 28 Cardiology Intensive Care Unit monitoring (avoiding a few more wires) Cardiovascular research : 8/29/2010 29 Cardiovascular research Bio-mechanics of circulation Image from US Patent #5,573,012 Cardiology : 8/29/2010 30 Cardiology Advantages over current instrumentation:
No need for cleaning.
No need for disposables.
Remote and continuous operation.
Easier use. New New New New Cardiology : 8/29/2010 31 Cardiology Summary of cardio applications:
Heart rate monitoring.
Heart movements recording.
Ambulatory cardiac output monitoring.
Blood vessel movements recording.
Blood pulse pressure celerity measurement.
Shock diagnosis in emergency patients. New New New New Pneumology : 8/29/2010 32 Pneumology Respiratory patterns monitor.
Apnea monitor in infants.
Obstructive sleep apnea monitor.
Polysomnography (sleep studies).
Dynamic chest diameters measurement.
Allergy and asthma crisis monitoring.
Chest imaging (?). Obstetrics : 8/29/2010 33 Obstetrics Great concern regarding RF safety for the newborn (but, why is ultrasound generally considered safe?).
Very useful and common use devices might be produced (even for large scale sales). Italian 16th century
pregnancy ring Obstetrics : 8/29/2010 34 Obstetrics Conventional (octopus) ultrasound-based fetal monitor. An ultrasound fetal monitor is a device designed to transmit and receive ultrasonic energy into and from the pregnant woman, usually by means of continuous wave (doppler) echoscopy. The device is used to represent some physiological condition or characteristic in a measured value over a period of time (e.g. perinatal monitoring during labor) or in an immediately perceptible form (e.g. use of the ultrasonic stethoscope). Obstetrics : 8/29/2010 35 Obstetrics A comprehensive obstetrical UWB radar-based monitor. Unfortunately, “emissions” from the device make this a “fear generating” situation! Obstetrics : 8/29/2010 36 Obstetrics Advantages over current instrumentation:
Unimpaired mother and child care.
Easier use. New New New New New Ear-Nose-Throat : 8/29/2010 37 Ear-Nose-Throat Medical applications of the throat microphone
In principle the throat microphone is a device able to monitor vocal chords movements by means of UWB radar. Image from LLNL MIR website, Livermore, USA
http://lasers.llnl.gov/lasers/idp/mir/throatmic.html ENT : 8/29/2010 38 ENT medical uses may not be concerned with voice at all, as in:
vocal chords diseases
for medical purposes, a vocal chords’ movements monitor is much more valuable than a “simple” throat microphone. New ENT : 8/29/2010 39 ENT The University of Iowa’s National Center for Voice and Speech and the UC Davis Voice/Speech/Swallowing Center are actively working on speech sensors using UWB radar technology.
Correlations were found between UWB radar signature and other conventional tracings while recording the movements of lips, tongue, glottis and tracheal wall. Rehabilitation medicine : 8/29/2010 40 Rehabilitation medicine Biofeedback-based rehabilitation protocols:
Artificial prosthesis control and actuation:
wheelchair driving systems
smart-home systems New New Other medical areas of application : 8/29/2010 41 Other medical areas of application Underwater medicine measurements.
Space medicine measurements.
Sport medicine measurements.
Rubble Rescue Radar New The optical UWB radar : 8/29/2010 42 The optical UWB radar IR pulse and echo Fast pulse IR laser Fast PIN photodiode Target Neurology : 8/29/2010 43 Neurology Brain studies.
IR spectral imaging.
Brain hemoglobin O2 % sat Research directions : 8/29/2010 44 Research directions Research directions : 8/29/2010 45 Research directions To validate UWB radar as a viable technology to be used in medicine we need to better know the genesis of the UWB radar signal, so to correlate it with already known electro/mechano biological phenomena. UNDERSTAND WHAT WE GET Research directions : 8/29/2010 46 Research directions UWB echos coming from the structures inside the human body are mainly explained in the framework of the time domain reflectometry (TDR) theory (see McEwan’s patents on body movements monitoring). A MODEL OF UWB PULSE INTERACTION WITH THE LIVING TISSUES IS REQUIRED Research directions : 8/29/2010 47 Research directions According to McEwan’s model
(as presented in US Patent # 5,573,012) Research directions : 8/29/2010 48 Research directions A more appropriate model for the echoes from the frontal heart wall: UWB radar device right lung left lung left ventricle Picture from the Visible Human Project impedance attenuation wave speed thickness beam path echo generating surfaces Research directions : 8/29/2010 49 Research directions Electromagnetic data obtained from:
Camelia Gabriel, PhD., Sami Gabriel, MSc.
“Compilation of the Dielectric Properties of Body Tissues at RF and Microwave Frequencies” Physics Department King's College London London WC2R 2LS, UK.
Armstrong Laboratory (AFMC) Occupational and Environmental Health Directorate - Radiofrequency Radiation Division
2503 D Drive Brooks Air Force Base TX, 78235-5102
Report: AL/OE-TR-1996-0037 Research directions : 8/29/2010 50 Research directions The pulse propagation model: Research directions : 8/29/2010 51 Research directions The echo propagation model: The results from the model : 8/29/2010 52 The results from the model Time delay: pulse-echo flight time = 1.74 ns The results from the model : 8/29/2010 53 The results from the model Echo decay: pulse-echo decay = -35.6 dB Power losses balance:
echoes from non-target surfaces = -10 dB
attenuation from layers in the pulse-echo path = -10 dB
useful echo from target surface = -15 dB Limitations of the model : 8/29/2010 54 Limitations of the model Although more accurate, the new model of pulse-echo behavior in the thorax is all but correct. As the dielectric properties used were those measured on actual living tissues using a continuous wave at 1500 MHz, the model remains intrinsically wrong.
Indeed, for an effective model to be developed, we need ultra wide-band dielectric properties, not narrow band ones (although in the microwave region). This means that a convolution method, or a Finite Differences Time Domain technique, like that already employed in UWB antenna calculations, should be used. Limitations of the model : 8/29/2010 55 Limitations of the model Also, both the real part and the imaginary one of the reflection coefficients at the boundaries should be considered, as the UWB receiving correlator, working in the time domain, is by design strongly sensitive to phase errors.
Another point to be addressed is that of the receiving correlator itself to assess what amount is actually its phase sensitivity. Research directions : 8/29/2010 56 Research directions In a nutshell: we know that a heart-related signal is obtained out of a UWB radar device aimed at the thorax, but what are we actually measuring? To what extent do correlator performances, pulse shape and tissues properties affect the intensity and morphology of the recovered signal?
These problems ask for some clear answers to reach an adequate physical understanding of medical UWB radar and subsequent clinical viability and acceptability of the technique. Accurate modeling of the phenomena with correct and extended electromagnetic measures should help advancement of science in this field. Research directions : 8/29/2010 57 Research directions The SARA prototype (1997) Tor Vergata University of Rome, 1997
http://www.uniroma2.it/fismed/UWBradar Just an amateur prototype, it was initially built for fun.
It actually detects heart beats from a distance of 1/2 inch to the thorax using a simple dipole antenna. Research directions : 8/29/2010 58 Research directions The CASTORP prototype (1999) Tor Vergata University of Rome, 1999 Improvements over SARA:
µP controlled range gating using dual channel VCDG (Voltage Controlled Delay Generator with Dtmax = 35 ns).
higher pulse power (Peak power = 2W Mean power = 2mW).
higher CMRR in the UWB receiver.
ADC conversion and direct RS-232 connection to host PC.
software elaboration of UWB heart signature using FWT (fast wavelet transform). Research directions : 8/29/2010 59 Research directions What next ? Studies “in the medical domain” to correlate UWB heart signature signals with:
ultrasound heart M-Mode tracings.
external phonocardiogram and apexcardiogram tracings.
external ballistocardiogram tracings.
invasive pressure pulse recordings.
better understanding and modeling of RF pulse propagation in the living tissues My card : 8/29/2010 60 My card