The Current Research Projects
of Prof. Zhenyu Guo
at the Laboratory of Biomedical Engineering

Project1: Three-dimensional Power Doppler Angiography

(Click on images for larger views)

The therapeutic options for patients having lower-extremity arterial occlusive diease requires vascular imaging that can accurately quantify the severety of stenosis and reveal all distall runoff vessels suitable for bypass grafting. Currently, contrast angiography is the standard technique for this purpose. However, this invasive technique has failed to demonstrate suitable distall vessels for reconstructive surgery in up to 70% of patients with severe occlusive diease. Although duplex ultrasound scanning is today the most widely used noninvasive technique to quantify arterial stenoses, recent studies showed that there are significant limitations to use it in situations invloving multiple stenoses. Magnetic resonance angiography has been considered as a potential technique to replace contrast angiography, but its avaiability to accurately diagnose the arterial occlusive disease is limited by the signal loss due to flow turbulence encountered in the stenotic jets.

In this project, we use three-dimensional (3D) power Doppler angiography (PDA) for quantifying lower-extremity arterial stenoses and revealing distall runoff vessels. This technique has high sensitivity to map flowing blood. It is nearly flow velocity and Doppler angle independent and essentially alsising- free. With this technique, physicians should be able to analyze the lower- extremity arteries for anatomic and pathological purpose in 3D. This will significantly increase the accuracy for quantifying stenoses and facilitate the salvaging limbs surgery planning. we have done substantial research on 3D PDA. Attached figures show some of our 3D power Doppler angiograms.

The general objective of the current project is to extend 3D PDA to routine clinical practice by improving the current mothod. This project will result in a clinical relevant 3D PDA system for quantifying lower-extremity arterial stenoses and revealing run-off vessels. Successfully completion of this project will produce a great impact on reducing the health care cost on cardiovascular disease as this technique can be expended to diagnose stenoses of other arterial beds, to monitor bypass graft patency, and to diagnose deep vein thrombosis.

Project2: Medical Virtual Instrumentation

In normal clinical practice, several medical instruments are required for the measurement and monitoring of various physical and physiological data. These instruments function as single, stand-alone devices capable of performing individual tasks and lack the flexibility required to perform multiple tests and kinds of monitoring. In addition, small medical clinics may not have all the required instruments, meaning that patients have to be referred to medical centers for simple physiological tests. It is thus of great value to develop a general purpose instrument with the cost of a single-functional instrument which can measure different biomedical data.

The current clinically applied monitoring instruments mainly perform simple monitoring and measurement functions, without the ability to perform advanced signal processing to extract valuable diagnostic information. In addition, conventional medical instruments do not perform remote(i.e.. tele-medicine) measurements or be controlled remotely. It is thus of great value to develop a medical instrument which has the abilities to conduct advanced signal processing for biopotentials and to perform remote measurements.

The general objectives of this medical virtual instrumentation research are: 1- to embed the functions of various medical monitoring instruments in a single location, the personal computer, by using virtual instrumentation technology to develop a multi-functional medical virtual instrument; 2- to integrate advanced signal processing techniques into this medical virtual instrument to facilitate the extraction of diagnostic information; and 3- to connect this medical virtual instrument to the World Wide Web (WWW) and remotely control this instrument from any Web Browser for tele-medicine practice and home medical care delivery.

Through the use of suitable transducers, this instrument can be used to monitor and measure physiological data such as blood pressure, heart sounds, respiratory flow, body temperature, muscle force as well as many other parameters. It can also be used with electrodes for monitoring and diagnosing biopotentials such as electrocardiogram (ECG), the electromyogram (EMG), and the electroencephalogram (EEG). Such an instrument is also ideal for physiology education. This medical virtual instrument include a micro-controller controlled multi-channel signal conditioner, plug-in data acquisition boards, software modules used to create instrument front panels on the computer monitor with which to conduct various tasks, as well as algorithms used to perform signal processing and Internet communication.

Comparing with the conventional medical instruments, our instrument has the following advantages: 1- Patient management. Since a PC is the core of the instrument, patients can be managed using patient data base. 2- Reduce the health care cost. Multiple functional virtual instrument will have a cost of a stand-alone instrument due to the fact that software is the instrument. 3- Capture and display current signals while saving or analyzing the previous signals using inherent multiprocessing of the Pentium PC. This is very important as the traditional instrument can only perform one task at a time. 4- Advanced signal processing can be performed to the medical data recorded. For example, modern spectral analysis techniques and time-frequency analysis can be applied to extract useful diagnostic information which is not possible in the traditional instruments. 5- A key function of this instrument is the ability to connect to the Internet. All front panels of this instrument are viewable and controllable from any browser via the Internet, providing a means to deliver home medical care.

In summary, this project will provide the most advanced and cost-effective technology for medical instrumentation. The multi-functional medical virtual instrument can be used in routine clinical pratice and tele-medicine, it can also be used in physiological and biomedical engineering laboratories for teaching and research.

Project3: Three-dimensional Image Compression using Iterated Function Systems (under construction)