Patent Application
20190029559
The present invention relates to a method for a direct positioning of a region of interest of a patient inside a scanner of a magnetic resonance imaging apparatus. Thus, the present invention relates to the technical field of performing an examination of a patient with a magnetic resonance imaging apparatus.
In a magnet resonance (MR) imaging examination, the patient is placed on a patient table and a local RF-coil, such as a local receiver coil, is placed near or on top of a region of interest of the patient, from which MR data are to be acquired. A laser pointer is usually used to designate the region of interest. The region of interest will then be moved into the isocenter of the scanner of the magnetic resonance imaging apparatus in order to achieve the best imaging quality. After this step of setting up the patient, several localizer images are usually acquired, in particular in all three spatial directions, in order to obtain an overview of the patient's anatomy and in order to plan the level of detail needed to perform the clinical imaging. If the region of interest is not located in the isocenter, a correction of the table position must be performed and new localizer images need to be acquired. Such a repeated acquisition of localizer images takes additional time, and nearly all manual steps needed for repositioning also require additional time. Thus, the time for adjustments usually takes too much time. This in turn makes the workflow for preparing a patient for an examination with a magnetic resonance imaging apparatus time-consuming, so that the utilization rate of a magnetic resonance imaging apparatus is decreased.
An exact positioning of a local RF coil relative to inner organs or to bones, such as a hip or the like, is especially challenging. Thus, repeated acquisitions are often needed because while scanning the hip, for example, it is hard to position the local RF-coil exactly on the femoral head. This means that after a first localizer acquisition, repositioning of the RF-coil as described above or repositioning of the graphical slice planning objects is often needed.
Therefore, an object of the present invention is to provide a method for shortening the time needed for the preparation step and therewith for improving a utilization rate of a magnetic resonance imaging apparatus and to provide a magnetic resonance imaging apparatus that can be used effectively.
According to the invention, a method for a direct positioning of a region of interest of a patient inside a basic field magnet of a magnetic resonance imaging apparatus is provided that has steps.
The patient is positioned on a patient table, and at least one local RF-coil is positioned on or close to the patient on a region of interest that is to be examined. A distance between the position of the at least one local RF-coil and the isocenter of the scanner is determined in a control computer of the magnetic resonance imaging apparatus. The local RF-coil, together with the patient table, moved automatically by the control computer along a z-direction in the scanner for at least the determined distance, so that the center of the local RF-coil is in or at least at z-position of the isocenter.
According to the inventive method, the patient is placed on a patient table that is designed to be movable along the z-direction of the scanner, in particular along the body length of the patient, from an exterior of the scanner into the interior of the scanner. In a next step, at least one local RF-coil for receiving diagnostic (MR) data, is positioned on or close to the patient directly on a region of interest that is to be examined. For example, the local RF-coil may be plugged into a given socket in the scanner, such as a socket on the patient table. In a next step, the distance between the position of the at least one local RF-coil and the isocenter of the scanner is determined, the latter being a fixed known point in the scanner or more precisely in the basic field magnet of the scanner. The determination of this distance can either be calculated directly if the local RF coil is plugged into a given connection, or can be detected by a detection unit and can be evaluated afterwards. After the determination of the distance between the local RF-coil and the isocenter, the local RF-coil together the patient table is moved automatically through the determined distance along the z-direction so that the center of the local RF-coil is in or at least at the z-position of the isocenter. An advantage of the inventive method is that the region of interest can be directly moved into the isocenter of the magnet. There is no need to use a laser pointer anymore. Thus the workflow for preparing the patient can be performed more quickly, and the utilization of the magnetic resonance imaging apparatus can be increased.
In an embodiment of the invention, the position of the at least one local RF-coil is predetermined, or is detected by a detection unit. The position of the at least one local RF-coil is predetermined if the at least one local RF-coil is plugged into a given socket connection, so that the magnetic resonance imaging apparatus detects the RF-coil automatically. Alternatively the RF-coil can be detected by a detection unit, so that the distance between the position of the RF-coil and the isocenter can be calculated. The detection unit has a camera, and/or a sensor inside the RF-coil. If a camera system is used, it is preferably a 2D or a 3D camera, which produces optical images. If a sensor is used, the sensor is preferably located inside the RF-coil and is preferably designed as a Hall sensor. The information about the depth is important in order to know the exact position of the RF-Coil. Such parameters are used for graphical slice planning. The determination and the evaluation of the position of the RF-coil within regard to the isocenter can be performed automatically. This has the advantage that the preparation steps can be performed quickly, in particular, without losing time for adjustment or repositioning work steps.
In a further embodiment of the invention, localizer data are acquired by the magnetic resonance imaging apparatus while the at least one local RF-coil is moved into the isocenter. As the patient table is moved into the isocenter, localizer images can be detected, in particular along the z-direction, and/or the x-direction along which the RF-coil extends. This means the acquisition of the localizer images can be focused along the extent of the RF coil. In particular the localizer images are obtained in the z- and the x-directions along the at least local RF-coil. This means that the localizer images can be acquired with as many slices as are necessary in order to obtain a detailed overview of the region of interest, and can be acquired restricted to the extent of the RF coil. This has the advantage that the localizer images can be acquired with a high image quality while the patient table is being moved into the isocenter, without losing time.
According to a further embodiment of the invention, the localizer data are acquired upon the determined position of the local RF-coil and/or the known geometry of the local RF-coil. As mentioned, because of the known position of the coil, the detection of the localizer images can be restricted to the extension and/or the geometry of the RF-coil. This means that the localizer images are acquired over the region of interest and also that the regions next to the region of interest can be neglected. This has the advantage that the localizer images can be acquired with a high image quality, in particular during the initial patient table movement into the isocenter, without losing time.
According to a further embodiment of the invention, the localizer data are acquired along the x-direction perpendicular to the z-direction, and perpendicular to the longitudinal extent of the at least one local RF-coil. As also mentioned, because of the known position of the coil, the detection of the localizer images is restricted to the extent and/or the geometry of the RF-coil. This means that the localizer images are acquired solely in the region of interest and the regions next to the region of interest are neglected. This has the advantage that the localizer images can be acquired with a high image quality, in particular during the patient table is moved into the isocenter, without losing time.
In a further embodiment of the invention, the localizer data are acquired by execution of a computer program according to the known DICOM (Digital Imaging and
Communication in Medicine) standard, in particular the program FastView/TimCT. The localizer data are visually shown to an operator as soon as they are acquired, so that the operator, if necessary, can create a robust localizer that will include all relative anatomies, i.e. regions of interest, from patient-to-patient, or the operator can terminate the localizer when enough data have been obtained to continue with the study thereby minimizing extra effort. The FastView/TimCT is a 3D imaging acquisition, so all orientations are displayed. This enables the operator to quickly begin diagnostic imaging as the operator need not perform several 2D localizers. By using the DICOM standard, like FastView/TimCT, the diagnostic examination can be planned easily.
According to a further embodiment of the invention, the localizer data are reproduced as a localizer image or localizer images, in which at least one landmark is detectable, so that the patient table is re-adjustable, if necessary, such that a special region of interest is in the isocenter, even if the local RF-coil is not positioned exactly over the region of interest. The localizer data are visually presented to the operator so that the landmark can be detected easily within the localizer image. If an adjustment of the patient table is necessary, such as if the region of interest is not exactly in the isocenter along the z-direction, the patient table can be moved there easily, even if the local RF-coil is not exactly positioned on the region of interest. Such off-center imaging techniques are required if the region of interest is a region of a hip, or a region of an arm, or a region of a shoulder, or a region of a foot of a patient, or the like.
According to a further embodiment of the invention, the distance between the position of the at least one local RF-coil and the isocenter is determined by a camera system and/or a sensor system, in particular, by a sensor positioned inside the local RF-coil. If a camera system is used, it is preferably an optical camera system taking 2D or 3D images. In such an optical 2D or 3D image, a landmark can be easily identified. In case of a sensor which is alternatively or additionally used the sensor is preferably arranged inside or close to the RF-coil. Preferably, a Hall sensor is used which is a transducer that varies its output voltage dependent on a magnetic field. Thus, the RF coil is detected visually or by a Hall sensor and, because the dimensions of the RF coil are known, the localizer, i.e. the localizer data, needs to be scanned only from where the RF coil starts and ends.
The present invention also encompasses a medical imaging apparatus, specifically a magnetic resonance apparatus having a scanner with a basic field magnet and a patient table for placing a patient thereon, and at least one local RF-coil, which is positionable on or close to the patient on a region of interest which is to be examined. The apparatus also has a detector that detects distance between the position of the at least one local RF-coil and the isocenter of the scanner.
The apparatus has a control computer configured to automatically move the local RF-coil together with the patient table along the z-direction of the scanner for at least the determined distance, so that the center of the local RF-coil is in or at least at the z-position of the isocenter.
The inventive magnetic resonance imaging apparatus has a patient table onto which a patient is placed for an examination. The patient table is designed to be movable along the z-direction, in particular along a body length of a patient, from an exterior of the scanner of the magnetic resonance imaging apparatus into an interior of the scanner of the magnetic resonance imaging apparatus. Furthermore, at least one local RF-coil for receiving diagnostic data positionable on or close to the patient directly on a region of interest that is to be examined. For example, the local RF-coil may be plugged into a given connection socket at a predetermined location at the scanner. The distance between the position of the at least one local RF-coil and the isocenter of the basic field magnet, if the position is a fixed known point in the scanner, is determined automatically by the detection unit. However, the detection unit can be operated, if the position of the local RF-coil is not a predetermined position, to detect the position and the distance can then be calculated, such as the local RF coil is not directly plugged into a given connection. The detection unit may have the predetermined positions stored therein or may be operable to actively detect the position of the local RF-coil. The determination of the distance between the local RF-coil and the isocenter allows for movement of the local RF-coil together the patient table into the isocenter, such that the center of the local RF-coil is in or at least at the z-position of the isocenter. An advantage of the inventive magnetic resonance imaging apparatus is that it is configured to move the region of interest directly into the isocenter of the scanner. Using a laser pointer for adjustment is not needed anymore. This means the utilization of the magnetic resonance imaging apparatus can be increased.
According to an embodiment of the inventive magnetic resonance imaging apparatus, the magnetic resonance imaging apparatus has at least one predetermined position into which the at least one local RF-coil is pluggable such that the position of the least one local RF-coil is predetermined automatically. When the RF-coil is plugged into one of the predetermined positions, control computer of the magnetic resonance imaging apparatus directly and automatically detects which position is occupied. Since the pluggable positions and the isocenter are respectively fixed positions, the distance is stored as a function of the position of the patient table in the scanner in a control computer of the magnetic resonance imaging apparatus. The advantage of the predetermined positions is that the RF-coil used for a particular examination can be moved quickly into the isocenter without needing to determine the distance that the patient table needs to be moved.
According to an embodiment of the inventive magnetic resonance imaging apparatus, the magnetic resonance imaging apparatus has at least one detection unit that detects the least one local RF-coil. The at least one detection unit may be a camera system and/or a sensor located inside the at least one local RF-coil. Preferably, the detection unit is designed as a camera system which detects optical images. The optical images are either 2D or 3D images from which the distance between the RF-coil and the isocenter can be reliably calculated. Alternatively or additionally, the detection unit may be a sensor. Preferably, such sensor is arranged inside the RF-coil and is configured to measure an output voltage in response to a magnetic field, i.e., is configured as a Hall sensor. The advantage of the detection unit is that the RF-coil can be detected automatically even if the RF-coil is not arranged in a predetermined position.
According to another embodiment of the inventive magnetic resonance imaging apparatus, the magnetic resonance imaging apparatus is configured to acquire localizer data in the x-direction along the at least one local RF-coil, the x direction being perpendicular to the z-direction. Preferably, the localizer data are acquired along the longitudinal extent of the RF-coil, which is sufficient since the RF-coil is positioned over the region of interest to be examined. Therefore, it is sufficient to acquire a localizer image that primary reproduces the region of interest mainly in order to plan the diagnostic acquisition of imaging data in detail.
In another embodiment of the inventive magnetic resonance imaging apparatus, the magnetic resonance imaging apparatus is configured to acquire the localizer data at and/or near to the determined position of the local RF-coil and/or the known geometry of the local RF-coil. Because of the predetermined position of the local RF-coil and/or the known geometry of the local RF-coil, the localizer images can directly be acquired over the region of interest.
In an embodiment of the inventive magnetic resonance imaging apparatus, a computer program is executable by the control computer of the magnetic resonance imaging apparatus that uses the known DICOM (Digital Imaging and Communication in Medicine) standard, known as FastView/TimCT. This has the advantage that the proposed magnetic resonance imaging apparatus complies with such a standard.
The present invention also encompasses a non-transitory, computer-readable data storage medium encoded with programming instructions that, when the storage medium is loaded into a computer or computer system of medical imaging apparatus, such as magnetic resonance apparatus, cause the computer or computer system to operate the medical imaging apparatus in order to implement any or all of the embodiments of the method according to the invention, as described above.
The present invention is explained in the following with respect to
The RF-coil 2 has an information element 5, including an information code 6. The information code 6 provides a coil identification. For example, the identifications code 6 can be a series of numbers such as 124, which identify an RF-coil used in the examination of hips.
Furthermore, a display unit 8 and an input unit 9 are both connected with the control computer 4. The display unit 8 displays, for example, the localizer data in the form of localizer images or the like.
The method disclosed herein is preferably implemented as a computer program, i.e., software, in the control computer 4.
In order to perform a diagnostic examination, for example, of a patient's hip 14, the patient 12 is placed on the patient table 10 in a first step 51 as shown in
In a second step S2, the control computer 4 evaluates a distance d between the position of the local RF-coil 16 and an isocenter 20 of the scanner 1. After determination of the distance d according to a third step S3 indicated in
As the patient table 10 is moved the distance d along the z-direction, localizer data are acquired along an x-direction, which is perpendicular to the z-direction. Preferably, the x-direction extends in parallel to a width 22 of the patient table 10. In particular, the localizer imaging is started when the patient table 10 is moved along the z-direction. Because of the determined position of the local RF-coil 16 and/or its known geometry, the localizer data acquisition starts at a position x before the local RF-coil 16 and ends a position x behind the local RF-coil 16, such that the localizer data are preferably acquired in the region of interest 24 (compare with
Preferably, the localizer image or the localizer images will be acquired until a position x after the local RF-coil 16 or the local RF-coils 16 to obtain a good overview. It is also possible that more than one local RF-coil 16 is positioned in the z-direction and/or x-direction (not shown). Since the information corresponding to a region 30 of a left and a right position of the local RF-coil 16 is usually taken into account, it is possible to reduce the localizer data acquired to the region of interest 24, i.e., to one side. In case of a hip examination, the one side corresponds to the hip which is to be examined. In particular, such a procedure is useful for off-center imaging techniques, for example if a hip, an arm, a foot, a shoulder or the like shall be examined.
After the acquisition of localizer data, in particular in the region of interest 24, the patient table 10 is moved back into the isocenter 20, or at least to the z-coordinate of the isocenter 20.
After the image acquisition, landmarks can be detected inside the image and the patient table 10 can be moved along the z-direction such that a particular anatomy of the patient is in the isocenter which refers to an optional work step S4 (compare with
Thus, a particularly preferred inventive method can be summarized as follows:
Advantages of the disclosed method are
Although modifications and changes may be suggested by those skilled in the art, it is the intention of the Applicant to embody within the patent warranted hereon all changes and modifications as reasonably and properly come within the scope of the Applicant's contribution to the art.
| Number | Date | Country | Kind |
|---|---|---|---|
| 17183011 | Jul 2017 | EP | regional |
