Raoul Mallart

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).

Improved imaging rate through simultaneous transmission of several ultrasound beams

The main requirement of pulsed-echo ultrasound applications such as cardiac imaging, 3-D imaging, or blood flow imaging can be identified as frame rate. Currently, frame rate is limited by the imaging depth range and the number of ultrasonic fires. For example, a 15 cm imaging range gives rise to 200 microsecond(s) lines or to a 2 s acquisition time for 100 planes of 100 lines in 3-D medical applications. The only way to increase frame rate is parallel beam formation in the receive mode. Simultaneous parallel beam forming allows us to divide the acquisition time by a factor proportional to the number of beam formed lines. In the technique developed by S. W. Smith, an increase frame rate of 16 is achieved. However, this technique is limited by a loss in lateral resolution due to the requirement for a wide illumination beam of the explored medium in the transmit mode. We propose an alternate illumination scheme that minimizes the loss in resolution in the transmit mode. In this technique, ultrasonic energy is transmitted simultaneously in several narrow beams. This technique works in pulsed mode and we have built the hardware needed for the simultaneous production of several beams. Each transducer is connected to a transmitter able to generate a sequence of excitation pulses. If n beams are to be transmitted, the excitation signal is the sum of n cylindrical wave fronts. For those, among elements where the n wave fronts are disjoint, the excitation signal is thus the succession of n pulses with specific time positions with respect to the system synchronization. For the others, the excitation signal is more complex since it consists in a (n - 1) level signal (0, 1, 2, ... n - 1 times the basic excitation signal). We show the performances of such a parallel transmit scheme based on beam plots as well as on tissue phantom images. This leads to an evaluation of the maximal number of beams compatible with current medical imaging quality standards. It is shown that a gain of 16 in the acquisition time can be achieved without any loss in lateral resolution.

Apparatus for examining objects by ultrasonic echography

An apparatus for examining objects by ultrasonic echography includes an array of m ultrasonic transducer elements and a transmission stage having n transmission channels for causing n of the m transducer elements associated with an ultrasonic aperture to radiate echographic signals to the object and a receiving and processing stage having n receiving channels for receiving and processing echographic signals returned by the object being examined. The transmission and the receiving and processing stages include transmission-mode and receiving-mode circuits, respectively, for focusing by the provision of suitable focusing delays in the n channels of each. The receiving and processing stage includes a stage for determine after a first burst, (n-1)correction values for the focusing delays, and a circuit for correcting the focusing delays as a function of the (n-1) correction values thus determined. The stage for determining focusing delay correction values includes, in parallel, (n-1) correction determining circuits, each separately receiving two focused echographic signals in adjoining channels for determining a focusing delay correction value for one of the two channels.