Two-piece sensor assembly

Details Two-piece sensor assembly Two-piece sensor assembly

2001-08-22

2003-09-16

Dunn, Drew A. (Department: 2882)

X-ray or gamma ray systems or devices

Nonphotographic detector support

Fluoroscope

C378S189000, C378S204000, C378S208000

Reexamination Certificate

active

06619838

ABSTRACT:

TECHNICAL FIELD OF INVENTION
The present invention relates to an assembly for securely mounting a sensor to an image-acquisition device capable of pivoting, and, in particular for securely mounting a sensor to a C-arm or some other C-shaped fluoroscope.
BACKGROUND OF INVENTION
Referring to
FIG. 1
, an image-acquisition device
100
can be used for simultaneous real-time image acquisition and intrabody navigation of a probe, such as a catheter
105
. Catheters may be employed for diagnostic purposes, e.g., by retrieving samples of tissue, or for therapeutic purposes, e.g., ablation by radiofrequency waves emitted by at least one electrode contained in the catheter. In either case, tracking of the catheter
105
as it is navigated through the body of a patient is of great importance.
To this end, the image-acquisition device
100
comprises a C-arm fluoroscope
110
that may pivot about three orthogonal axes to allow imaging of a patient from several different angles. Typically, such a fluoroscope
110
includes an X-ray source
115
and an image acquisition module
120
mounted on opposite ends of a C-arm
125
, as well as a table
130
where the patient lies. The portion of the patient's body being imaged, typically the chest, is positioned between the ends of the C-arm
125
. The image-acquisition module
120
converts x-rays that transit through the patient on the table
130
into electronic signals representative of 2-D images of the patient. The pivotable feature provides images from various perspectives, thereby allowing the reconstruction of a 3-D image of the patient from a series of successive 2-D images. This function is performed by a controller/processor
135
, which is coupled to the image-acquisition module
120
.
Tracking of the catheter
105
is accomplished by using a fixed transmitter
140
to transmit to a sensor
145
located on the catheter
105
, thereby locating the catheter
105
relative to the transmitter
140
. Optionally, a reference sensor can be placed on the patient, preferably the chest, to create a “fixed” space in combination with the transmitter
140
relative to other moving sensors. In this manner, the device
100
compensates for any movement of the patient, such as chest movement during the respiratory cycle. The sensor
145
typically comprises a housing that contains three pairs of electromagnetic sensing elements for the three orthogonal axes. In any event, the continuously changing position and orientation of the catheter
105
can be inferred from the electromagnetic signals transmitted by the transmitter
140
and received by the sensor
145
. This tracking function is performed by driving circuitry
150
and reception circuitry
155
, which are respectively coupled to the transmitter
140
and sensor
145
, and the controller/processor
135
, which controls the driving circuitry
150
and processes the signals received by the reception circuitry
155
.
Thus, by determining the position and orientation of the catheter
105
relative to the frame of reference defined by the transmitter
140
and the optional reference sensor, the controller/processor
135
determines the position and orientation of the catheter
105
relative to the 2-D image acquired by the fluoroscope
110
. The controller/processor
135
then synthesizes a combined image that includes both the 3-D image of the patient and an icon representing the catheter
105
positioned and oriented with respect to the 3-D image, and then displays this combined image on a monitor
158
. In order to synchronize the acquired location of the catheter
105
with each 2-D image, the orientation of which changes as the C-arm
125
is rotated around the patient, another sensor
160
, which is similar to the sensor
145
located in the catheter
105
, is mounted on the C-arm
125
. Electromagnetic signals received by the sensor
160
from the transmitter
140
are sent to reception circuitry
165
, which is identical to the reception circuitry
155
. The controller/processor
135
is coupled to this reception circuitry
155
and acquires the data therefrom to determine the orientation of the C-arm
125
, and thus the orientation of the 2-D image, at any given time, so as to provide a means to synchronize the image of the catheter
105
with that of each 2-D image. Further details on the image-acquisition device
105
are described in PCT publication WO 00/10456, entitled “Intrabody Navigation System for Medical Applications,” and published on Mar. 2, 2000, which publication is fully and expressly incorporated herein by reference.
In order to securely mount the sensor
160
to the C-arm
125
, certain constraints must be considered. First, as the sensor
160
serves as a fixed point of reference, it must be sufficiently secured to the C-arm
125
, such that it does not move relative to the C-arm
125
when the C-arm
125
pivots. The sensor
160
, however, should be easily engageable and disengageable from the C-arm
125
in order to replace the sensor
160
if desired. Secondly, as the sensor
160
functions by the reception of electromagnetic waves, it must not contact or be placed in proximity to any ferromagnetic material, such as steel or any other material or alloy containing iron, which would disrupt the magnetic field of the sensor
160
.
Thus, an objective of this invention is to provide for a sensor assembly that detachably secures the sensor onto a C-arm, or some other pivotable image-acquisition device, without disrupting the sensor's magnetic field.
SUMMARY OF THE INVENTION
The present inventions are directed to medical sensor assemblies that include sensors that can be detachably mounted onto a fluoroscopic mount, such as a C-arm. In accordance with a general aspect of the present inventions, a medical sensor assembly for use with a fluoroscopic mount comprises an electromagnetic sensor that is configured for outputting positional data relating to the fluoroscopic mount. The sensor includes a mount engaging element, and the sensor mount includes a sensor engaging element, both of which are configured to be removably mounted in an interference relationship with each other. The mount engaging element of the sensor can be a sensor housing, or alternatively, an element that is separate from the sensor housing. The sensor mount, which is composed of a non-ferromagnetic material, further includes a spacer for maintaining the sensor at a prescribed distance from the ferromagnetic fluoroscopic mount, thereby minimizing any adverse ferromagnetic effects on the sensor.
The sensor mount may be configured, e.g., in a front-mount arrangement, such that the sensor is mounted to the sensor mount in a direction perpendicular to the plane in which the sensor mount is mounted to the fluoroscopic mount. Alternatively, the sensor mount may be configured, e.g., in a side-mount arrangement, such that the sensor is mounted to the sensor mount in a direction parallel to the plane in which the sensor mount is mounted to the fluoroscopic mount.
The spacer can be configured to be permanently mounted to the fluoroscopic mount, e.g., by bonding or welding thereto. In this case, the sensor engaging element of the sensor mount can be permanently mounted to the spacer. For example, the sensor engaging element can be bonded or welded thereto, or can be formed with the spacer as a unibody structure. Thus, the sensor with the mount engaging element can be repeatedly attached to and detached from the fluoroscopic mount. Alternatively, the sensor engaging element, rather than the spacer, is configured to be permanently mounted to the fluoroscopic mount, e.g., by bonding or welding thereto. In this case, the spacer acts as the mount engaging element, in that it is configured to be removably mounted to the sensor engaging element, e.g., by using a hook-in-loop material, such as Velcro®. The mount engaging element of the sensor can be permanently mounted to the spacer, e.g., by bonding or welding thereto. Thus, the sensor with the spacer can be repeatedly attached to and detached from the fluoroscopic

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