Proc. SPIE. 6920, Medical Imaging 2008: Ultrasonic Imaging and Signal Processing
KEYWORDS: Human-machine interfaces, Digital signal processing, Foam, Detection and tracking algorithms, Ultrasonography, Interfaces, Arteries, Signal processing, Video processing, Algorithm development
Analyzing the artery mechanics is a crucial issue because of its close relationship with several cardiovascular risk
factors, such as hypertension and diabetes. Moreover, most of the work can be carried out by analyzing image sequences
obtained with ultrasounds, that is with a non-invasive technique which allows a real-time visualization of the observed
structures. For this reason, therefore, an accurate temporal localization of the main vessel interfaces becomes a central
task for which the manual approach should be avoided since such a method is rather unreliable and time consuming.
Real-time automatic systems are advantageously used to automatically locate the arterial interfaces. The automatic
measurement reduces the inter/intra-observer variability with respect to the manual measurement which unavoidably
depends on the experience of the operator. The real-time visual feedback, moreover, guides physicians when looking for
the best position of the ultrasound probe, thus increasing the global robustness of the system. The automatic system
which we developed is a stand-alone video processing system which acquires the analog video signal from the
ultrasound equipment, performs all the measurements and shows the results in real-time. The localization algorithm of
the artery tunics is based on a new mathematical operator (the first order absolute moment) and on a pattern recognition
approach. Various clinical applications have been developed on board and validated through a comparison with gold-standard
techniques: the assessment of intima-media thickness, the arterial distension, the flow-mediated dilation and
the pulse wave velocity. With this paper, the results obtained on clinical trials are presented.
The characterization of the endothelial function is one of the most attractive research topics in modern vascular medicine. The evaluation of the flow-mediated vasodilation (FMD) of the brachial artery is a widely used measurement technique. Despite its widespread use, this technique has some limitations due to the difficulties in obtaining an accurate measurement of such a small vessel (3 to 5 mm) by using ultrasounds. The system we present in this paper can automatically measure the diameter of the artery with high accuracy on each image of a video sequence. Furthermore, it processes the data in real-time, thus providing the physician with an immediate response while the examination is still in progress. The main part of the system is a video processing board based on a state-of-the-art digital signal processor (DSP). The board acquires the video signal generated by the ultrasound equipment which furnishes a longitudinal section of the artery vessel. For each image, the DSP automatically locates the two borders of the vessel and subsequently computes the diameter. The algorithm used to automatically locate the borders of the vessel is based on a new operator of edge detection which was derived from the first absolute central moment. Tests in many clinical centers proved that the system provides very accurate measurements and is a remarkable step forward toward a more systematic evaluation of the FMD.