Patent Application
20160169996
The subject matter disclosed herein relates to Magnetic Resonance Imaging (MRI), and more particularly, to a method of scan plane prescription for cardiac MRI.
For cardiac MRI scanning, a user typically acquires oblique plane images such as short-axis images, four-chamber images, and two-chamber images. Because the planes are oblique, neither normal nor parallel to any axis of mechanical coordinate system or patient coordinate system, a complex procedure is performed to determine each plane location and orientation. The procedure is time-consuming, typically taking more than several minutes. Additionally, the plane prescription procedure is difficult for a novice user to perform. It requires training and experience to do so competently and efficiently. Therefore, automation of scan plane orientation and location has been desired.
To address this problem, automatic scan plane computation techniques have been explored. These techniques typically start acquiring low resolution “localizer” images. In the case of cardiac imaging, the localizer image contains the whole heart volume in its field of view. The software then processes the input localizer image and computes scan plane location and orientation based on image processing techniques and machine learning.
However, there are known problems with this technology and method. For example, the success rate of automatically computing the correct plane prescription is not as high as desired. Achieving correct scan plane prescription at a success rate of 95% or higher is quite difficult. Additionally, the user is not aware of the failure of the scan plane prescription until after the higher resolution images are acquired, and manual manipulation of the higher resolution images is required. This can be very time consuming and difficult for novice users. Therefore, there is a need for a method and system to determine whether computed scan plane prescription is successful or not, and to correct plane prescription quickly and effectively when automatic scan plane prescription fails.
The above-mentioned shortcomings, disadvantages and problems are addressed herein which will be understood by reading and understanding the following specification.
In an embodiment a method of prescribing a scan plane during Magnetic Resonance Imaging (MRI) of an anatomy comprises acquiring a volume image of the anatomy at a first resolution and simultaneously displaying three planar images representing cross-sections through the anatomy. The three images are orthogonal to each other and intersecting at a common point in the volume. The method also comprises further displaying a pair of axes on each image showing a correspondence of the image with each of the other two images, and receiving a manipulation of one at least one of the axes on at least one of the images and automatically updating the other images to maintain the correspondences. The method also comprises acquiring a volume of the anatomy at a second resolution that is higher than the first resolution.
In another embodiment, a MRI system comprises an apparatus configured to acquire an MRI volume image of an anatomy and a processing unit configured to prescribe a scan plane. The system also comprises an operator console comprising a display and an input device. The display is configured to display the prescribed scan plane comprising three planar images representing cross-sections through the anatomy, the three images being orthogonal to each other and intersecting at a common point in the volume, and a pair of axes on each image showing a correspondence of the image with each of the other two images. The processing unit is configured to receive manipulation of at least one of the axes on at least one of the images by the input device in order to modify the prescribed scan plane.
Various other features, objects, and advantages of the invention will be made apparent to those skilled in the art from the accompanying drawings and detailed description thereof.
In the following detailed description, reference is made to the accompanying drawings that form a part hereof, and in which is shown by way of illustration specific embodiments that may be practiced. These embodiments are described in sufficient detail to enable those skilled in the art to practice the embodiments, and it is to be understood that other embodiments may be utilized and that logical, mechanical, electrical and other changes may be made without departing from the scope of the embodiments. The following detailed description is, therefore, not to be taken as limiting the scope of the invention.
The system control computer 32 includes a set of modules in communication with each other via electrical and/or data connections 32a. Data connections 32a may be direct wired links, or may be fiber optic connections or wireless communication links or the like. In alternative embodiments, the modules of computer system 20 and system control computer 32 may be implemented on the same computer system or a plurality of computer systems. The modules of system control computer 32 include a CPU module 36 and a pulse generator module 38 that connects to the operator console 12 through a communications link 40. The pulse generator module 38 may alternatively be integrated into the scanner equipment (e.g., resonance assembly 52). It is through link 40 that the system control computer 32 receives commands from the operator to indicate the scan sequence that is to be performed. The pulse generator module 38 operates the system components that play out (i.e., perform) the desired pulse sequence by sending instructions, commands and/or requests describing the timing, strength and shape of the RF pulses and pulse sequences to be produced and the timing and length of the data acquisition window. The pulse generator module 38 connects to a gradient amplifier system 42 and produces data called gradient waveforms that control the timing and shape of the gradient pulses that are to be used during the scan. The pulse generator module 38 may also receive patient data from a physiological acquisition controller 44 that receives signals from a number of different sensors connected to the patient, such as ECG signals from electrodes attached to the patient. The pulse generator module 38 connects to a scan room interface circuit 46 that receives signals from various sensors associated with the condition of the patient and the magnet system. It is also through the scan room interface circuit 46 that a patient positioning system 48 receives commands to move the patient table to the desired position for the scan.
The gradient waveforms produced by the pulse generator module 38 are applied to gradient amplifier system 42 which is comprised of Gx, Gy and Gz amplifiers. Each gradient amplifier excites a corresponding physical gradient coil in a gradient coil assembly generally designated 50 to produce the magnetic field gradient pulses used for spatially encoding acquired signals. The gradient coil assembly 50 forms part of a resonance assembly 52 that includes a polarizing superconducting magnet with superconducting main coils 54. Resonance assembly 52 may include a whole-body RF coil 56, surface or parallel imaging coils 76 or both. The coils 56, 76 of the RF coil assembly may be configured for both transmitting and receiving or for transmit-only or receive-only. A patient or imaging subject 70 may be positioned within a cylindrical patient imaging volume 72 of the resonance assembly 52. A transceiver module 58 in the system control computer 32 produces pulses that are amplified by an RF amplifier 60 and coupled to the RF coils 56, 76 by a transmit/receive switch 62. The resulting signals emitted by the excited nuclei in the patient may be sensed by the same RF coil 56 and coupled through the transmit/receive switch 62 to a preamplifier 64. Alternatively, the signals emitted by the excited nuclei may be sensed by separate receive coils such as parallel coils or surface coils 76. The amplified MR signals are demodulated, filtered and digitized in the receiver section of the transceiver 58. The transmit/receive switch 62 is controlled by a signal from the pulse generator module 38 to electrically connect the RF amplifier 60 to the RF coil 56 during the transmit mode and to connect the preamplifier 64 to the RF coil 56 during the receive mode. The transmit/receive switch 62 can also enable a separate RF coil (for example, a parallel or surface coil 76) to be used in either the transmit or receive mode.
The MR signals sensed by the RF coil 56 or parallel or surface coil 76 are digitized by the transceiver module 58 and transferred to a memory module 66 in the system control computer 32. Typically, frames of data corresponding to MR signals are stored temporarily in the memory module 66 until they are subsequently transformed to create images. An array processor 68 uses a known transformation method, most commonly a Fourier transform, to create images from the MR signals. These images are communicated through the link 34 to the computer system 20 where it is stored in memory. In response to commands received from the operator console 12, this image data may be archived in long-term storage or it may be further processed by the image processor 22 and conveyed to the operator console 12 and presented on display 16.
Referring to
In the depicted embodiment, each image 104, 106, 108 is comprised in a viewport 94, 96, 98, respectively. It should be appreciated that the distinct viewports 94, 96, 98 for each image 104, 106, 108 could be eliminated while also operating within the scope of the present disclosure. For example, all three images 104, 106, 108 may be comprised in a single viewport.
Each planar image 104, 106, 108 represents a cross-section through the heart 102. For example, image 104 represents a short-axis view of the heart 102. The short-axis view depicts the left ventricle and the right ventricle. In another example, image 106 represents a 2-chamber view of the heart 102. The 2-chamber view depicts the left ventricle and the left atrium. In yet another example, image 108 represents the 4-chamber view of the heart 102 and it depicts the left ventricle, left atrium, right ventricle and the right atrium.
Each of the three images 104, 106, 108, are orthogonal to each other and intersect at a common point P in the volume of the anatomy 102. For the purpose herein, the term orthogonal may be defined as perpendicular. For example, three planes that are orthogonal to one another may be the axial, sagittal and coronal planes, wherein the axial plane divides the superior and inferior parts of the body, the sagittal plane divides the right side of the body from the left, and the coronal plane divides the anterior (front) of the body from the posterior (back) of the body.
A pair of axes 116, 118, 120, may be superimposed on each image 104, 106, 108, respectively. The pair of axes 116 comprises axis 116b and axis 116c. The pair of axes 118 comprises axis 118a and axis 118c. The pair of axes 120 comprises axis 120a and axis 120b. The pairs of axes 116, 118, 120 show a correspondence of the image with each of the other two images. For example, image 104 has axis 116b which represents the intersection of the plane of image 104 with the plane of image 106. Axis 116c represents the intersection of the plane of image 104 with the plane of image 108. In another example, image 106 has axis 118a which represents the intersection of the plane of image 106 with the plane of image 104. Axis 118c represents the intersection of the plane of image 106 with the plane of image 108. In yet another example, image 108 has axis 120a which represents the intersection of the plane of image 108 with the plane of image 104. Axis 120b represents the intersection of the plane of image 108 with the plane of image 106.
It may be desirable to use a color-coding scheme to quickly and efficiently aid the user to identify the corresponding axes with image or viewport. In one embodiment, the viewports 94, 96, 98 and/or images 104, 106, 108 are color coded and the axes 116b, 116c, 118a, 118c, 120a, 120b are colored to correspond to the intersecting image. The viewports 94, 96, 98 and/or images 104, 106, 108 may be color coded in a variety of ways. For example, in one embodiment, the viewport 94 may be outlined in a color such as red, for example, and axes 118a and 120a would also be colored red to show a correspondence to viewport 94. In another embodiment, there is a blue-colored symbol, for example, in viewport 96 and axes 116b and 120b would also be colored blue. In yet another embodiment, text appearing in viewport 98 may be in a green-colored font and axes 116c and 118c would be in green. It should be appreciated that other embodiments of the color-coding of viewports 94, 96, 98 and/or images 104, 106, 108 with axes 116b, 116c, 118a, 118c, 120a, 120b may be envisioned.
Each axis 116b, 116c, 118a, 118c, 120a, 120b may be manipulated via the input device 13. The manipulation may include rotating, shifting or a combination thereof. Rotating may comprise the movement of one axis about the intersection point P. Shifting may comprise movement of one axis such that the intersection point P is modified.
Having described exemplary components of the MRI system 10, a method 200 of prescribing a scan plane will now be described in accordance with an embodiment. Referring to
The method 200 may include a step 220 comprising simultaneously displaying the three planar images 104, 106, 108 on the display 16. For purposes herein, simultaneously may be defined as concurrent. As described above with respect to
The method 200 may include a step 230 comprising displaying the pair of axes 116, 118, 120 on each image 104, 106, 108. The pairs of axes 116, 118, 120 may be superimposed on each image 104, 106, 108. The pair of axes 116 comprises axis 116b and axis 116c. The pair of axes 118 comprises axis 118a and axis 118c. The pair of axes 120 comprises axis 120a and axis 120b.
Each pair of axes 116, 118, 120 represents a correspondence of the image with the other two images. For example, image 104 has axis 116b which represents the intersection of the plane of image 104 with the plane of image 106. Axis 116c represents the intersection of the plane of image 104 with the plane of image 108. In another example, image 106 has axis 118a which represents the intersection of the plane of image 106 with the plane of image 104. Axis 118c represents the intersection of the plane of image 106 with the plane of image 108. In yet another example, image 108 has axis 120a which represents the intersection of the plane of image 108 with the plane of image 104. Axis 120b represents the intersection of the plane of image 108 with the plane of image 106.
In one embodiment, the images and/or viewports may be color coded with the axes 116b, 116c, 118a, 118c, 120a, 120b may be color-coded in order to show the correspondences between axes and images.
The method 200 may include a step 240 comprising receiving manipulation of at least one of the axes 116b, 116c, 118a, 118c, 120a, 120b on at least one of the images 104, 106, 108, and automatically updating the other images to maintain correspondences. Each axis 116b, 116c, 118a, 118c, 120a, 120b may be manipulated via the input device 13. The manipulation may include rotating, shifting or a combination thereof. Rotating may comprise the movement of one axis about the intersection point P. Shifting may comprise the movement of one axis such that the intersection point P is altered.
In one embodiment, the step 240 may be performed substantially in real time. For the purpose herein, substantially in real time may be defined as without intentional delay. For example, the images may be updated within one to two seconds of receipt of the manipulation.
The method 200 may include a step 250 comprising acquiring a volume of the anatomy 102 at a second resolution that is higher than the first resolution. In one embodiment, the second resolution may be between 1 mm and 2 mm.
The method 200 and apparatus 10 provide numerous benefits. For example, the refinement and adjustment of an automatically calculated scan plane allows for more efficient, faster, scan plane prescription, especially where the automatically calculated prescription fails. It also makes scan plane prescription more accessible for novice users as it eliminates the need for entirely manual prescription.
This written description uses examples to disclose the invention, including the best mode, and also to enable any person skilled in the art to practice the invention, including making and using any devices or systems and performing any incorporated methods. The patentable scope of the invention is defined by the claims, and may include other examples that occur to those skilled in the art. Such other examples are intended to be within the scope of the claims if they have structural elements that do not differ from the literal language of the claims, or if they include equivalent structural elements with insubstantial differences from the literal language of the claims.
