FR2587493A1 - Device for location and guidance by ultrasound - Google Patents

Abstract

The invention relates to a device for location and guidance by ultrasound. It consists of an echographic probe 1 fixed or sliding at the bottom of a spherical cap 2 representing a piezoelectric converter, the head of the probe being situated inside the cap. A second echographic probe 10 may be associated with the first 1, the second sweeping in a plane perpendicular to that of the first. This second probe is positioned as close to the target 3 as possible and it may move only in one plane, the plane of sweeping of the first probe, or alternatively perpendicular to this plane. The device according to the invention is in particular intended for location and guidance for an apparatus producing focused ultrasound for treatment.

Description

 The present invention relates to a tracking and guiding device for an apparatus producing focused ultrasound for treatment.

 The location and guidance is currently done by two x-ray machines arranged in two perpendicular planes, and with the help of a computer. This material is heavy and expensive, and the patient receives ionizing radiation.

 Another method uses a real-time sector ultrasound probe (1) fixed to the bottom of a spherical cap (2) representing a piezoelectric converter which produces focused ultrasound for treatment. The distance between this probe (1) and the target (3) to be located is large. The lateral resolution of the focal point of the probe degrades quickly away from the surface of the probe. The image of the target is therefore relatively blurred, which makes it difficult to locate.

One solution is to use a larger diameter transducer to improve the lateral resolution of the focal point away from the surface of the probe.

 The device according to the invention provides another solution to this problem. It has two different systems, which can be used jointly or separately.

 The first system consists in entering the probe (1) inside the cap (2); the probe is thus closer to the target (3). The probe can sink up to two thirds of the distance between the bottom of the spherical cap and the center of the sphere (4) without significantly hampering the path of the ultrasound (5) intended for treatment. The probe can therefore be fixed in this position instead of remaining at the bottom of the spherical cap.

 Figure 1 shows, in section, the arrangement of the probe at the bottom of the spherical cap.

 Figure 3 shows, in section, the arrangement of the probe halfway between the bottom of the spherical cap and the center of the sphere.

 By fitting a sheath, either rigid (6) or flexible (7), inside the spherical cap, the probe can be placed at will at the desired height during the location. However, during treatment, the probe head must be at a distance inside the spherical cap, equal to or less than two thirds of the radius of the sphere, so as not to impede the passage of ultrasound intended for treatment. The rigid sheath (6), remaining in place, consists of a substance having a refractive index close to the liquid which surrounds it. A rigid holding system (8) fixed to the external face of the spherical cap, and surrounding the probe (1), allows the latter to slide in a direction perfectly perpendicular to the surface of the sphere.

The same liquid which surrounds the sheath, or another having a very close refractive index, occupies the space between the probe and the sheath, and this liquid communicates freely with a reservoir which maintains constant the pressure in the sheath despite the movements of the probe. The seal is ensured by waterproof seals (9).

 Figure 7 shows, in section, the rigid sheath and the relieving system for the probe.

 Figure 8 shows, in section, the flexible sheath and the sliding system for the probe.

 FIG. 2 represents, in section, the position of the probe as close as possible to the target.

 The distance between the probe and the target being very different depending on the position of the probe, it is preferable to use a transducer equipped with a variable focusing system to improve imaging; and therefore facilitate location. To make it possible to see the ultrasound produced by the piezoelectric elements in the spherical cap, it is necessary to synchronize the stimulation of the piezoelectric elements in the cap and in the ultrasound probe for identification, correcting the difference in distance when the probe is not at the bottom of the cap and aligned with the other piezoelectric elements.

 The second system of the device according to the invention consists in using a second probe (10) next to the first. This second probe is placed as close to the target as possible to better see it, because it does not have the constraints imposed by the position of the first probe. Its only constraint is to scan in a plane perpendicular to that of the first probe.

This is ensured by a particular fixing of the probe to the spherical cap (11). This attachment (11) keeps the probe (10) in one plane: it can move forward, backward, up, down, and pivot, but only in this plane. It makes it easier to spot the target because it is closer. It allows you to see the target in a section perpendicular to that of the first probe. If the axis of movement of the spherical cap when locating by the second probe is transverse, the axis of movement of the spherical cap during locating by the first probe is then longitudinal. This is important, because when the target is located by the second probe, it is enough to block the transverse movement of the cap, and by moving the cap longitudinally, the first probe will not fail to fall directly on the target.

 Part of the probe can be found in the flexible bag (12) containing a liquid, which covers the concave face of the spherical cap. Waterproof seals (9) prevent any leakage of liquid. The bag is flexible enough to allow movement of the probe. The probe can also be located entirely outside of this bag. In this case, the bevel shape (13) of the probe head allows for closer contact with the patient's body.

 If, during tracking, part of the second probe (10) enters the path of the ultrasound intended for treatment, it suffices to withdraw the probe a little at the time of treatment.

 Figure 4 shows, in section, the arrangement of the second probe, part of which is in the flexible bag (12).

 Figure 5 shows, in section, the arrangement of the second probe, located entirely outside the bag.

 Figure 6 shows the two scanning planes of the two ultrasound probes. The two planes are perpendicular to each other.

 The device according to the invention is particularly intended for locating and guiding for an apparatus producing acoustic waves for treatment.

Claims (9)

 1) Locating and guiding device for an apparatus producing focused ultrasound for the treatment having the shape of a spherical cap (2) representing a piezoelectric converter, characterized in that the real-time sector ultrasound probe ( 1) used for location and guidance is fixed to the bottom of the spherical cap (2) and the probe head is located inside the cap at a distance less than two thirds of the radius of the sphere; or the probe (1) can slide perpendicular to the surface of the sphere to enter the cap to a desired depth.  2) Device according to claim 1 characterized in that a rigid holding system (8) fixed to the spherical cap (2) and surrounding the probe (1) allows the latter to slide in a direction perfectly perpendicular to the surface of the sphere.  3) Device according to claim 1 characterized in that a sheath (6 or 7) is arranged inside the spherical cap (2) to isolate the probe (1) from the liquid covering the internal face of the spherical cap, this sheath can be rigid (6) or flexible (7), and waterproof joints ensuring the tightness of the sheath.  4) Device according to claim 3 characterized in that if the sheath is rigid (6), it consists of a substance having an index of refraction close to the liquid which surrounds it, and the same liquid or another having an index of very close refraction, occupies the space between the probe (1) and the sheath (6) and this liquid communicates freely with a reservoir which keeps the pressure in the sheath constant despite the movements of the probe.  5) Device according to claim 1 characterized in that a synchronized system of stimulation of the piezoelectric elements in the spherical cap (2) and in the ultrasound probe (1) corrects the difference in distance when the probe is not at the bottom of the shell and aligned on the other piezoelectric elements, so that the probe can see the path of the ultrasound coming from the shell, without distortion.  6) Device according to claim 1 characterized in that a second ultrasound probe (10) used alone or next to the first (1) is held by a particular attachment (11) to the spherical cap (2) and this fixing allows all movements of the probe but in a plane, perpendicular to the scanning plane of the first probe, or in the scanning plane of the first probe (1).  7) Device according to claims 1 and 6, characterized in that the second probe (10) is positioned as close as possible to the target (5), and it is located entirely outside the flexible bag (12) containing a liquid, which covers the concave face of the spherical cap (2), is partly in this bag.  8) Device according to claim 7 characterized in that if the second probe (10) is outside the flexible bag (12), the probe head can have a bevel shape to allow closer contact with the body of the patient.  9) Device according to claim 7 characterized in that if the second probe (10) is partly in the flexible bag (12), waterproof seals (9) ensure the sealing of the bag (12) and the bag is enough flexible to allow movement of the probe.