A SYSTEM AND METHOD TO MEASURE DISPLACEMENT OF PATIENT TRANSPORT BOARD IN A MAGNETIC RESONANCE IMAGING MRI SYSTEM
Publication Date: 2015-Nov-11
The IP.com Prior Art Database
A non invasive laser based technique is disclosed that measures displacement of a patient board or cradle into a magnet bore of a magnetic resonance imaging MRI system Two sources of laser point lasers towards the cradle According to one embodiment the two sources of laser are provided at a side of the MRI system proximal to the cradle and in another embodiment the two sources of laser are provided at a side of the MRI system proximal to the cradle actuator The lasers point at a rear section of the cradle so that an operator can visually observe and track the cradle The cradle is in touch with an air damper When the cradle enters the bore the cradle gets connected to the air damper and remains in contact with the air damper till the time the cradle is in the bore As the cradle moves into the bore to facilitate scanning of a patient the two lasers track the cradle movement The movement is constantly resolved into X and Y directions Any component of the movement that is along the Y axis is rejected The average of the two components along the X axis is reported as the displacement of the cradle
The present invention relates generally to magnetic resonance imaging (MRI) system and more particularly to a technique of measuring displacement of a patient transport board in the MRI system.
Generally, magnetic environment of a magnetic resonance imaging (MRI) system requires elements used for actuating a cradle to be made of non-magnetic material such as plastic. These elements are compliant as compared to their metallic counterparts and have a good amount of spring action. Also, a joint between a cradle actuator and the cradle has its own compliance and clearances. Further, contact type linear displacement sensors are assembled in the magnetic resonance imaging (MRI) system to measure linear position of the cradle. However, contact type linear displacement sensors are not effective as range of measurement of the sensors is in meters and desired accuracy is in the range of fraction of a millimeter.
Some conventional techniques involve measurement of rotational movement of a motor shaft or linear measurement of a cradle actuation unit. However, such measurements provide an indirect measure of cradle displacement.
A conventional technique includes adjusting scanning region of a computed tomography (CT) scanner. The technique utilizes a distance sensor that is mounted at a reference point of a patient examination table to measure a distance from the at least one edge point to a reference point. From the measured distance, position of the at least one edge point relative to the patient examination table is determined, and a corresponding edge of a CT scanning region of the CT scanner is conformed to the derived position.
Another conventional technique includes an MRI scanner which has an optical measuring device. The optical measuring device includes a distance sensor for determining surface of a patient and for determining a setting signal for a setting mechanism. One other conventional technique includes determining a puncture insert position and a puncture insert angle of a puncture needle from result of simulation measurements on a CT image. Such simulation measurements are displayed by a laser beam from a laser projector.
The above mentioned conventional techniques utilize sensor or detector or optical (laser) means for determining puncture insert or patient surface or edge point relative to patient examination table. However, the above mentioned conventional techniques are not used to track patient board or cradle displacement.
It would be desirable to have a technique for correct displacement measurement of the patient board or cradle to obtain correct images of a desired anatomy at a desired cross section.
BRIEF DESCRIPTION OF DRAWINGS
Figure 1 depicts front view and top view of an MRI system utilizing laser based technique for measuring displacement of the patient board or cradle in a magnet bore.