Antoine Collet-Billon

System and method for viewing three-dimensional echographic data

A system useful echographic examination simulation and training includes an ultrasonic echograph (31) equipped with a TV monitor (32), a 3D probe (33) for analyzing a subject, acquisition means (39), a memory card (42) storing the detected acoustic lines and a workstation (34) with central processing unit (35) and 3D echography memory (38). For reading the latter memory (38), the system includes a viewing device including a dummy (56) simulating the subject, and a 3D orientation sensor (52) connected to the workstation via a 3D coordinate indicator (54) and display means (29) of the workstation, which make the sectional plane which the sensor defines on the dummy correspond to the equivalent plane contained in the form of voxels in the echography memory (38), and display this plane on the screen of the TV monitor (32).

Reproducibility of Two 3-D Ultrasound Carotid Plaque Quantification Methods

Compared with single 2-D images, emerging 3-D ultrasound technologies hold the promise of reducing variability and increasing sensitivity in the quantification of carotid plaques for individual cardiovascular risk stratification. Inter- and intra-observer agreement between a manual, cross-sectional, 2-D freehand sweep and a mechanical 3-D ultrasound investigation of 62 carotid artery plaques is reported with intra-class correlation coefficients (with 95% confidence intervals). Inter-observer agreement was 0.60 (0.29-0.77) for the freehand method and 0.89 (0.83-0.93) for the mechanical 3-D acquisition. The use of semi-automated computerized planimetric measurements of plaque burden has high intra-observer repeatability, but is vulnerable to systematic inter-observer differences. For the 2-D freehand sweep, a considerable contribution to variation is introduced by the scanning procedure itself, that is, the lack of controlled motion along the third dimension. Future implementation of 3-D ultrasound quantification in large-scale studies of inter-individual cardiovascular risk assessment seems justified using the methods described.

Scalable compression of 3D medical datasets using a (2D+T) wavelet video coding scheme

Nowadays the all-digital solution in hospitals is becoming widespread. The formidable increase of medical data to be processed, transmitted and stored, requires some efficient compression systems and innovative tools to improve data access, while ensuring a sufficient visualization quality for diagnosis. Medical image sequences can benefit from advanced video coding techniques when adapted to their specific constraints. Scalability, or the capability to partly decode a video bitstream and to get a reconstruction quality proportional to the decoded amount of information, is a key functionality. We have developed a video codec based on a 3D motion-compensated subband decomposition, which provides a combination of temporal, spatial and SNR scalabilities together with a very competitive compression ratio. We show that, when applied to medical sequences, it outperforms JPEG-2000 on coding efficiency aspects and offers new functionalities.

Inter-Scan Reproducibility of Carotid Plaque Volume Measurements by 3-D Ultrasound

We tested a novel 3-D matrix transducer with respect to inter-scan reproducibility of carotid maximum plaque thickness (MPT) and volume measurements. To improve reproducibility while focusing on the largest plaque/most diseased part of the carotid artery, we introduced a new partial plaque volume (PPV) measure centered on MPT. Total plaque volume (TPV), PPV from a 10-mm segment and MPT were measured using dedicated semi-automated software on 38 plaques from 26 patients. Inter-scan reproducibility was assessed using the t-test, Bland-Altman plots and Pearsons correlation coefficient. There was a mean difference of 0.01 mm in MPT (limits of agreement: -0.45 to 0.42 mm, Pearsons correlation coefficient: 0.96). Both volume measurements exhibited high reproducibility, with PPV being superior (limits of agreement: -35.3 mm3 to 33.5 mm3, Pearsons correlation coefficient: 0.96) to TPV (limits of agreement: -88.2 to 61.5 mm3, Pearsons correlation coefficient: 0.91). The good reproducibility revealed by the present results encourages future studies on establishing plaque quantification as part of cardiovascular risk assessment and for follow-up of disease progression over time.