Paulo Eduardo Pilon

Automatic measurement of carotid diameter and wall thickness in ultrasound images

Carotid vessel ultrasound imaging is a reliable noninvasive technique to measure the arterial morphology. Lumen Diameter (LD), intima-media thickness (IMT) of the far wall, and plaque presence can be reliably determined using B-mode ultrasound. In order to measure the carotid IMT as well as any other more complex quantitative indices of vessel morphology, it is necessary to identify lumen-intima and media-adventitia borders in the ultrasound images. In this paper we describe an automatic approach to measure LD and IMT based on an active contour technique improved by a multiresolution analysis. The measurements of LD and IMT were compared to manual tracing of the vessels border in terms of coefficients of variability (CV) and correlation (R). The results have shown that the method is a reliable and reproducible way of assessing the LD and far wall IMT in the carotid artery.

Assessment of carotid diameter and wall thickness in ultrasound images using active contours improved by a multiresolution technique

Carotid vessel ultrasound imaging is a reliable non-invasive technique to measure the arterial morphology. Vessel diameter, intima-media thickness (IMT) of the far wall and plaque presence can be reliably determined using B-mode ultrasound. In this paper we describe a semi-automatic approach to measure artery diameter and IMT based on an active contour technique improved by a multiresolution analysis. The operator selects a region-of-interest (ROI) in a series of carotid images obtained from B-mode ultrasound. This set of images is convolved with the corresponding partial derivatives of the Gaussian filter. The filter response is used to compute a 2D gradient magnitude image in order to refine the vessels boundaries. Using an active contour technique the vessels border is determined automatically. The near wall media-adventitia (NWMA), far wall media-adventitia (FWMA) and far wall lumen-intima (FWLI) borders are obtained by a least-square fitting of the active contours result. The distance between NWMA and FWLI (vessel diameter) and between FWLI and FWMA (far wall intima-media thickness) are obtained for all images and the mean value is computed during systole and diastole. The proposed method is a reliable and reproducible way of assessing the vessel diameter and far wall intima-media thickness of the carotid artery.

Quantitative Assessment of Peripheral Arteries in Ultrasound Images

Blood velocity vs. time graphic images, that are based on ultrasound Doppler technique, can be used to reveal relationships between data within them and the presence of cardiovascular diseases, among other applications. In clinical protocols, this kind of study involves, typically, hundreds of patients and a manual and tedious segmentation of the blood velocity curve from the images. In this paper we present a computational tool designed to extract quantitative data from these graphics. The algorithm detects the baseline and the spectrum envelope to calculate peak velocity and velocity-time integral (VTI). A comparative analysis between commercial ultrasound systems and the present methodology included measurements of carotid and brachial arteries and echocardiographic exams. The results showed small bias and high correlation for both: systolic peak velocity (bias= 0.02 m/s; r ≫ 0.998; p ≪ 0.001; n=102) and VTI (bias= 1.25 cm; r ≫ 0.998; p ≪ 0.001; n=75).

vMon-mobile provides wireless connection to the electronic patient record

This work presents the development of a set of tools to help doctors to continuously monitor critical patients. Real-time monitoring signals are displayed via a Web Based Electronic Patient Record (Web-EPR) developed at the Heart Institute. Any computer on the Hospitals Intranet can access the Web-EPR that will open a browser plug-in called vMon. Recently vMon was adapted to wireless mobile devices providing the same real-time visualization of vital signals of its desktop counterpart. The monitoring network communicates with the hospital network through a gateway using HL7 messages and has the ability to export waveforms in real time using the multicast protocol through an API library. A dedicated ActiveX component was built that establishes the streaming of the biomedical signals under monitoring and displays them on an Internet Explorer 5.x browser. The mobile version - called vMon-mobile - will parse the browser window and deliver it to a PDA device connected to a local area network. The result is a virtual monitor presenting real-time data on a mobile device. All parameters and signals acquired from the moment the patient is connected to the monitors are stored for a few days. The most clinically relevant information is added to patients EPR.

A superhighway network to exchange cardiac images in a metropolitan area

The delivery of health care and sharing of medical information over a distance using telecommunication systems involve a diverse set of clinical, educational and research applications and an equally set of diverse technologies. The technological basis and the practical issues are highly variable from one clinical application to another. Moreover, if the information to be exchanged involves images, a special problem in cardiology is how to handle full motion video echocardiograms and cine angiograms. In the metropolitan area of Sao Paulo, a number of research institutions have been working in a project as part of a national effort to provide a very high performance backbone using ATM links. This project is based on image servers which can store, send and receive images using the DICOM 3.0 protocol. This superhighway and the applications are currently being validated between the two major hospitals in the metropolitan area of Sao Paulo.

Utilization of a global data grid repository in CAD assessment of carotid wall thickness

A CAD method of calculating wall thickness of carotid vessels addresses the time-consuming issue of using B-mode ultrasound as well as inter- and intra-observer variability in results. Upon selection of a region-of-interest and filtering of a series of ultrasound carotid images, the CAD is able to measure the geometry of the lumen and plaque surfaces using a least-square fitting of the active contours during systole and diastole. To evaluate the approach, ultrasound image sequences from 30 patients were submitted to the procedure. The images were stored on an international data grid repository that consists of three international sites: Image Processing and Informatics (IPI) Laboratory at University of Southern California, USA; InCor (Heart Institute) at Sao Paulo, Brazil, and Hong Kong Polytechnic University, Hong Kong. The three chosen sites are connected with high speed international networks including the Internet2, and the Brazilian National Research and Education Network (RNP2). The Data Grid was used to store, backup, and share the ultrasound images and analysis results, which provided a large-scale and a virtual data system. In order to study the variability between the automatic and manual definition of artery boundaries, the pooled mean and the standard deviation for the difference between measurements of lumen diameter were computed. The coefficient of variation and correlation were also calculated. For the studied population the difference between manual and automatic measurement of the lumen diameter (LD) and intima-media-thickness (IMT) were 0.12 +/-0.10 and 0.09+/- 0.06, respectively.