Patent Description:
The following prior art is believed to be the current status of the art:
<CIT> describes an apparatus and method for producing a single color coded composite image from a plurality of multi-parameter magnetic resonance image sets. However, this prior art does not relate to generating multicolored images.

<CIT> describes a method and apparatus for color coding a plurality of images obtained at a plurality of pulse sequences. However, in the prior art method the monochrome colors are determined empirically according to an average pixel value of user identified regions of interest and according to required output color of these regions.

<CIT> describes color magnetic resonance imaging using both a magnetic resonance property and a function of the magnetic resonance property. This prior art system only includes determined results from a single pulse sequence.

<CIT> describes a system and method for creating and manipulating one or more color-coded magnetic resonance images. This prior art system does not relate to combining MRI images from different MRI devices taken at different magnetic field intensities. Furthermore it does not deal with the issue of images with varying resolution explicitly.

"<NPL> describes a method for fusing of registered images. However, the prior art system does not relate to different image resolutions and does not consider fusing MRI images generated by more than one MRI device.

<CIT> describes a registration between T2-weighted and T1-weighted images using a joint probability density function technique employing 2D-histograms.

However, the prior art MRI devices and methods for generating high contrast images with high spatial resolution of high signal to noise ratio (SNR) are time consuming and/or require very specific contrast agents. Thus, there is a long felt and hitherto unmet requirement for providing high contrast images with high spatial resolution and high SNR.

The present invention relates an MRI scanning assembly and method for providing high contrast images of several colors with high spatial resolution by fusing MRI images of a target taken at different magnetic field strengths. The assembly and the method of the present invention are defined in claims <NUM> and <NUM>, respectively, with the dependent claims reciting optional features.

In addition, the present invention relates to an MRI scanning device for generating a plurality of MRI images of a target, wherein each MRI scanned image is associated with at least one member of a group of MRI device parameters, such as pixel size, dwell time, T1-weigthed scan protocols and T2-weighted scan protocols.

It is known in the art, that high resolution MRI images have increased noise, since the noise increases as smaller voxels are imaged. Therefore, in MRI systems, there is often a trade-off between high SNR and high-resolution in terms of image acquisition of a particular tool. The present invention describes systems and methods for generating high resolution MRI images with high SNR by fusing MRI images generated at different resolutions and contrast and producing an enhanced single image having a superior image quality than the MRI individual images.

Typically, MRI devices which have a relatively low intensity magnetic field, of less than <NUM> Tesla, produce high resolution images with low Signal-to-Noise Ratios (SNR). However, MRI devices which have a relatively high intensity magnetic field, in the higher than <NUM> Tesla, produce high resolution images with high Signal-to-Noise Ratios (SNR).

Furthermore, tissue contrast can be considered separately from image resolution, when referring to relatively large tissue masses. The contrast is controlled by the imaging mode and can be selectively enhanced by the use of contrast agents and by reducing noise sources. In addition, fusing MRI images generated at different resolutions and contrast produces an enhanced single image having a superior image quality than the MRI individual images.

MRI devices are used for a variety of diagnostic purposes, for example, to detect and to determine the location of pathological tissues such as cancers. MRI devices are used to detect cancers that would otherwise be difficult to diagnose and to indicate the precise location and size of tumors. MRI devices provide a non-invasive method for conducting pathological examinations and studies.

In addition, MRI devices are also applicable for non-pathological purposes for providing non-invasive examinations of targets for industrial purposes. For example, MRI device are applicable for analyzing and examining non-invasively the compositions of food products for content-checking purposes and searching and investigating fluids.

MRI devices which have a relatively low intensity magnetic field, less than <NUM> Tesla, produce high resolution images with low Signal-to-Noise Ratios (SNR). MRI devices which have a relatively high intensity magnetic field, in the range of <NUM> Tesla and above, can produce high resolution images but often lack contrast for some tissues of interest.

In order to improve contrast and reducing noise in high resolution MRI images, one may exploit the property of high contrast obtainable in low intensity magnetic fields. The method adopted is combining and fusing MRI images of a target generated by an MRI device operating with a low intensity magnetic field and MRI images generated by an MRI device operating with a high intensity magnetic field. By combining and fusing the images thereof, MRI images with low noise and improved contrast between tissue masses are obtained.

Additionally, one may generate an enhanced MRI image by introducing a colored image.

It is appreciated that an MRI image of a target includes many image slices.

Although the description below relates to a single MRI image slice, this is by example only. The MRI scan measurements and analysis are performed for a plurality of slices of the target.

There is provided an MRI scanning assembly characterized by an MRI scanning device operating at a first magnetic field intensity and generating a first plurality of MRI images of a target, an MRI scanning device operating at a second magnetic field intensity and generating a second plurality of MRI images of the target, and a processing unit configured to fuse the first plurality of MRI images and the second plurality of MRI images to generate a clear image representation of at least a portion of the target.

There is further provided a method for fusing MRI images of a target including providing an MRI scanning device operating at a first magnetic field intensity providing an MRI scanning device operating at a second magnetic field intensity, generating a first plurality of MRI images of the target by the MRI scanning device operating at a first magnetic field intensity, generating a second plurality of MRI images of the target by the MRI scanning device operating at a second magnetic field intensity, and configuring a processing unit to fuse the first plurality of MRI images and the second plurality of MRI images to generate a clear image representation of at least a portion of the target.

Further, the first magnetic field intensity is less than <NUM> Tesla and the second magnetic field intensity is greater than <NUM> Tesla.

Still further the target is selected from the group consisting of a group of cancerous cell, at least one anatomical organ, at least one cancerous anatomical organ and any combination thereof.

Additionally the MRI scanning device operating at the first magnetic field intensity includes an MRD device.

Moreover an MRI selector may be provided for selecting the MRI scanning device.

Additionally, the assembly may include an image display unit for generating and displaying the at least the portion of the target.

Moreover, one may identify at least two regions of interest in the first plurality of the MRI images of the target scanned at the first magnetic field intensity.

Further in accordance with a preferred embodiment of the present invention further including determining a monochrome level scaling factor between the at least two identified regions of interest;.

Still further one may scale each image of the second plurality of images of the target scanned at the second magnetic field intensity with the monochrome level scaling factor.

Further one may generate and display a clear anatomic appearance of at least a portion of the target.

The monochrome level may be selected from a grey level, a red scale, a green scale and a blue scale.

In accordance with the present invention an MRI scanning assembly is provided in accordance with claim <NUM>, characterized by at least one MRI scanning device generating a plurality of MRI images of a target, each one of the plurality of MRI images is associated with at least one member of a group of MRI device parameters, and a processing unit configured to fuse at least one MRI image of the plurality of MRI images with at least remaining one of the plurality of MRI images to generate a clear image representation of at least a portion of the target.

In accordance with yet another preferred embodiment to the present invention a method for fusing MRI images of a target is provided in accordance with claim <NUM>. It comprises providing at least one MRI scanning device generating a plurality of MRI images of a target, each one of the plurality of MRI images is associated with at least one member of a group of MRI device parameters, generating the plurality of MRI images of the target by the at least one MRI scanning device, configuring a processing unit to fuse at least one MRI image of the plurality of MRI images with at least remaining one of the plurality of MRI images to generate a clear image representation of at least a portion of the target.

Further the group of MRI device parameters is selected from the group consisting of MRI scanning parameters and MRI scanning protocols and any combination thereof.

Additionally in accordance with a preferred embodiment of the present invention the group of MRI scanning parameters includes at least one of the following: pixel size and dwell time.

Moreover in accordance with a preferred embodiment of the present invention the group of MRI scanning protocols includes at least one of the following protocols: T1-weighted scan protocols and T2-weighted scan protocols.

Preferably the MRI scanning device includes an MRD device.

Further in accordance with a preferred embodiment of the present invention including an image display unit for generating and displaying the at least the portion of the target.

Still further the image representation is selected from the group consisting of an anatomic appearance and a non-anatomic appearance.

Further in accordance with a preferred embodiment of the present invention the MRI scans include MRI scans for searching and investigating fluids as well as investigating food products and industrial products.

A preferred embodiment of the current invention is described hereinbelow with reference to the following drawings:.

Reference is now made to <FIG>, which shows an MRI scanning assembly <NUM> for fusing scanned MRI images. The MRI scanning assembly <NUM> includes, inter alia, MRI scanning devices <NUM>i=j and <NUM>i=k, where <NUM> ≤ i ≤ N and N is the number of MRI devices available for generating the MRI scans at different magnetic field intensities.

Typically, in the MRI scanning assembly <NUM>, the MRI scans of a target <NUM> are performed at different magnetic field intensities, such that the MRI devices <NUM>i=j and <NUM>i=k scan the target <NUM> at a different magnetic field intensities. In order for the devices <NUM>i=j and <NUM>i=k to scan the target <NUM>, the target <NUM> is located on a moving platform <NUM> which transports the target <NUM> from a scanning location <NUM> at the device <NUM>i=j to a scanning location <NUM> at the device <NUM>i=k.

The MRI scanning assembly <NUM> also includes an MRI selector <NUM> which selects the MRI devices <NUM>i=j or <NUM>i=k for scanning the target <NUM> at the scanning locations <NUM> and <NUM>, respectively. Thus, for example, the selector <NUM> instructs the MRI device <NUM>i=j to scan the target at the low magnetic field intensity.

Typically, for example, the low magnetic field intensity is in a range of approximately <NUM> Tesla to approximately <NUM> Tesla. The device <NUM>i=j scans the target <NUM> and generates a plurality of MRI target scans <NUM>.

Following the "low-field scan", the target <NUM> is transported to the location <NUM> and the magnetic field selector <NUM> instructs device 12i=k to scan the target <NUM> at a higher magnetic field intensity scan. For example, for the "high-field scan", the high magnetic field intensity is typically in a magnetic field intensity range of approximately <NUM> Tesla to <NUM> Tesla. The device <NUM>i=k scans the target <NUM> and generates a plurality of MRI target scans <NUM>.

It is appreciated that the MRI devices <NUM>i=j and <NUM>i=k generate a plurality of MRI scans of the target <NUM> at each magnetic field intensity, as required. The plurality of scans is generated by changes in the MRI device parameters, such as the pulse sequence or a scanning protocol. The pulse sequence determines the dynamics of the magnetic moments and therefore determines the measured signal intensity.

On completion of the respective MRI scans of the target <NUM>, the MRI devices <NUM>i=j and <NUM>i=k transfer the scanned MRI data <NUM> and <NUM>, respectively, to a processing unit <NUM> for processing, analyzing and interpretation by an operator. The processing unit <NUM> allows the operator to reconstruct the MRI scans, which are taken in "k-space" and convert the MRI images into "real-space". The analysis of the reconstructed MRI scans is conducted in accordance with an analysis tool, as discussed below. The operator manually or with the aid of a computing device (semi-automatically), analyzes the reconstructed MRI scans. The analysis involves, for example, the operator outlining and segmenting a region of the reconstructed scan, such as an organ or a pathological feature. In addition, the operator, typically, makes measurements of the segmented region, such as the volume of region and the average signal strength.

The processing unit <NUM> forwards the results of the analysis to an MRI image display device <NUM>.

Alternatively, the plurality of MRI scans <NUM> and <NUM> are generated by a single MRI scanning device <NUM>i=<NUM>, which includes a typical device is the MRD scanning device, as described in <CIT>.

In the single MRI device. different MRI images are generated by using different device parameters, such as pixel size and dwell time and different scanning parameters, such as a T1-weighted scanning protocol and a T2-weighted protocol.

<FIG> compares the MRI the resolution of MRI images obtained at a magnetic field intensity of approximately <NUM> Tesla with the resolution of MRI images obtained at a magnetic field intensity of approximately <NUM> Tesla, respectively, in accordance with a preferred embodiment of the present invention;.

Reference is now made to <FIG>, which compares generated MRI scans of the rodent at the low magnetic field intensity and the high magnetic field intensity, respectively, in accordance with a preferred embodiment of the present invention. <FIG> shows a scan slice <NUM> of the small rodent with a tumor <NUM>, taken at a magnetic field intensity of approximately <NUM> Tesla. <FIG> shows a scan slice <NUM> of the rodent with a tumor <NUM> at a magnetic field intensity of approximately <NUM> Tesla, at a different slice of the rodent.

The scan slices <NUM> and <NUM> in <FIG>, respectively, are not the same scan slice. Thus, the scan slices <NUM> and <NUM> are non-coherent. The MRI slices <NUM> and <NUM> do not include the same content and portion of the rodent. Thus, pixel-wise registration is not possible. The low resolution scan includes a higher SNR level than that of the high resolution scan (<FIG>). In order to enhance and improve the contrast between tissue masses of the high resolution scan, preferably, the low resolution scan (<FIG>) is fused with the high resolution scan of <FIG> thereby enhancing the contrast in <FIG>.

The MRI scan in <FIG> is a low-resolution image of approximately <NUM> pixel size and with high contrast between certain tissues. <FIG> also shows a corresponding grey level scale <NUM>. <FIG> shows a high resolution scan of approximately <NUM> resolution with a high SNR and low contrast between the corresponding high contrast tissues of <FIG> and a corresponding grey level scale <NUM>.

If, for example, the operator wishes to improve the contrast of a tumor area <NUM> (<FIG>), relative to the surrounding regions, thereby distinguishing and classifying the tumour area <NUM>. The operator decides to enhance the contrast of the tumor area <NUM> and selects a corresponding area <NUM> in <FIG>.

In operation, the operator and/or processing unit <NUM> identifies two corresponding regions of interest in <FIG> that are required to be enhanced in <FIG>. For example, the operator and/or processing unit <NUM> selects the tumor <NUM> and a fatty white portion <NUM> in <FIG>. Similarly, preferably, the operator and/or processing unit selects corresponding regions <NUM> and <NUM> (white region) in <FIG>.

In operation, a tissue (or tissues) which require enhancing the contrast thereof, is selected. The entire tissue region thereof is identified, typically, by a segmentation algorithm based on a previously defined seed voxel, as is known in the art. It is appreciated that the tissue region can also be identified manually by the operator. This identification procedure is performed separately for the images <NUM>, (<FIG>) and <NUM> (<FIG>), since the images <NUM> and <NUM> cannot be registered. The images <NUM> and <NUM> are MRI images of different slices of the target <NUM>. Now a reference region must be segmented in each of the images 3A and 3B. A reference region, such as a marker reference or a tissue reference, such as muscle portion <NUM> in <FIG> and a muscle portion <NUM> in <FIG> is identified and selected. It is appreciated that the reference tissues <NUM> and <NUM> are selected since these reference tissues images appear relatively similar in both spatial extent and in terms of signal strength.

It is appreciated that for determining the reference regions the segmentation need not be accurate and does not have to include the entire spatial area of "reference object". For each image, the reference object is used to generate a mean reference signal strength by averaging the signals of its included voxels.

For the MRI scan images <NUM> and <NUM>, a ratio between the mean grey levels of the segment to be enhanced with a reference segment is calculated from:<MAT> wherein im <NUM> is image <NUM> in <FIG>.

For the MRI scan image <NUM>, a second ratio is calculated as a mean of the grey values:<MAT> wherein im <NUM> is image <NUM> in <FIG>.

From <FIG>, Ratio_1 is approximately <NUM> and from <FIG>, Ratio_2 is approximately <NUM>.

A Scaling Factor SF is calculated from:<MAT>.

Based on the mean grey values determined for the segments <NUM> and <NUM>, SF is determined to be approximately <NUM> for the tumor segment.

The grey values of the voxels included in segment <NUM> of the MRI scan image shown in <NUM> of <FIG> will be scaled by a value of <NUM> to form an enhanced high resolution as in <FIG>. Similar scaling is performed on other high contrast segments of image <NUM> of <FIG>. Reference is now made to <FIG>, which compare histograms of MRI images of the target taken at a low magnetic field intensity of approximately <NUM> Tesla and MRI images taken at a high magnetic field intensity of approximately <NUM> Tesla, respectively, in accordance with a preferred embodiment of the present invention.

In <FIG>, the pixel populations of the image <NUM> are shown as a function of the Grey Level (GL) for two different portions of the rodent in the low-field scan. In <FIG>, the grey level histograms for a tumor <NUM> (<FIG>) and the reference rodent muscle region <NUM> (<FIG>) are identified by the respective shaded portions <NUM> and <NUM>, respectively. The y-axis is the proportion of each GL relative to the overall population of pixels in the studied segment (regions <NUM> and <NUM>).

<FIG> shows that the tumor <NUM> and muscle regions <NUM> are clearly distinguishable by their different grey level values. The separable regions <NUM> and <NUM>, due to the high contrast of the MRI scans obtained at the low magnetic field intensity.

In <FIG>, the grey level histograms for the tumor <NUM> and the reference rodent muscle region <NUM> are identified by the respective shaded portions <NUM> and <NUM>, respectively.

In <FIG>, the pixel fractions are compared as a function of the Grey Level (GL) for the tumor <NUM> (<FIG>) and the reference muscle region <NUM> (<FIG>) of the rodent. In <FIG>, the grey level histograms for the tumor <NUM> and the reference rodent muscle region <NUM> are identified by the respective shaded portions <NUM> and <NUM>, respectively.

<FIG> shows that the tumor and muscle regions are not clearly distinguishable by their different grey level values, due to the relatively low relative contrast of the MRI scans obtained at the high magnetic field intensity.

Reference is now made to <FIG>, which compares the high resolution high-field MRI scan and the enhanced high resolution high-field scan, respectively, in accordance with a preferred embodiment of the present invention.

<FIG> shows the image <NUM> from the high-field scan and indicates regions of interest <NUM> and <NUM> as well as a reference region <NUM>. <FIG> shows the results of scaling the image <NUM> (<FIG>) with the SF's determined from the low field and high field MRI scans. A tumor region <NUM>, a white region <NUM> and a reference region <NUM> are clearly distinguishable and have a high level of contrast with the remaining portions of the image <NUM>.

<FIG> shows the contrast enhancement of the two regions, namely, the tumor region and the fat tissue region (white region).

Thus, using this method a clear image of rodent slice is obtained with the tumor and fatty region being well distinguished from other tissues imaged in the slice.

Reference is now made to <FIG>, which show MRI images of a cross sectional slice of a cucumber typically generated by the low intensity magnetic field device at different in-slice pixel sizes, respectively, in accordance with a preferred embodiment of the present invention;.

<FIG> shows the cross section image of the cucumber <NUM> generated at an in-slice pixel size of <NUM> (high resolution) and a group of cucumber seeds <NUM> are clearly distinguishable from a cucumber background <NUM>. However, due to the low SNR, the image of the cucumber seeds <NUM> is not clearly distinguishable from the cucumber background <NUM>. A group of seeds <NUM> are not clearly distinguishable from the background <NUM>. In addition, <FIG> shows a group of seeds <NUM> located on the periphery of the cucumber <NUM>.

<FIG> shows a cross section image of the cucumber <NUM> generated at an in-slice pixel size of <NUM> (medium resolution) and the group of seeds <NUM> is clearly imaged. The image of the group of seeds <NUM> is clearer. Due to edge effects, the border between the cucumber flesh <NUM> and the group of cucumber seeds <NUM> is not clearly defined. The group <NUM> is not clearly distinguishable from the cucumber background <NUM>. Due to the decrease in the resolution, <FIG> does not clearly identify a group of seeds located on the periphery of the cucumber <NUM>.

<FIG> shows a cross section image of the cucumber <NUM> generated at an in-slice pixel size of <NUM> (low resolution) and groups of cucumber seeds <NUM> and <NUM> are not clearly seen and the image is very blurred. Due to the further decrease in the resolution, <FIG> does not clearly identify a group of seeds located on the periphery of the cucumber <NUM>.

<FIG> shows a combined image <NUM> of the high resolution (<NUM> in-slice pixel size) and medium resolution (<NUM> in-slice pixel size). The group of seeds <NUM> is distinguishable from the cucumber background <NUM> and the group of seeds <NUM> is barely distinguishable from the cucumber background <NUM>. However, due to noise, the edges of the seeds <NUM> and <NUM> are not clearly discernible. <FIG> shows a group of seeds <NUM> located on the periphery of the cucumber <NUM>. To summarize the the resolution in <NUM> in <FIG> has the full resolution of cucumber <NUM> in <FIG>.

Reference is now made to <FIG>, which presents a flow chart of a typical procedure <NUM> for fusing multiple sets of images of a given volume of the target <NUM>, into a single enhanced image, in accordance with a preferred embodiment of the present invention. The procedure <NUM> is controlled by the processing unit <NUM>, wherein the images are taken at the same slice of the target <NUM>.

In step <NUM>, the MRI scanned images are interpolated in order to generate voxels of the same geometrical voxel size, as is known in the art.

In step <NUM>, registration of the images acquired from the same acquisition mode is performed. The registration procedure ensures that the voxel representations of the images to be fused represent the same region of interest of the target.

In step <NUM>, the registered images are averaged to form a single image for each acquisition mode. This image includes a multiplicity of slices.

In step <NUM>, the combined images from the distinct acquisition modes used to image the registered target. A typical registration method is "The Lukas-Kanade Optical Flow Method", as is known in art and described in "<NPL>. Since the distinct image acquisition modes may have a different appearance, other methods known in the art for registering multi-modality images may be used. These can be based on maximizing mutual information of images patches as is known in the art.

In step <NUM>, the registered MR images of different acquisition modes are fused according to any of the well know fusion methods. In the following steps of <FIG>, a method that is suited to variable resolution images acquisitions is outlined:
In order to fuse the different acquisition modes of averaged images, they are divided into two types: high resolution images and low resolution images. The high resolution images are combined to form a single monochrome image as follows:
The pixel values are combined using some weighting which can be assigned by a variety of methods, such as a principal component analysis. The method is known in the art and described in "<NPL>. This combined monochrome image controls the brightness and/or intensity of the fused colored image while the low resolution images will control the spectral resolution of the fused image.

The steps for fusing these high resolution and low resolution images to colored image are further outlined in <FIG>.

In step <NUM>, each low-resolution image acquisition mode is assigned a color channel: for example, red, green and blue for three acquisition modes. The low resolution image is transformed to the HSV (hue,saturation,value) basis.

In step <NUM>, the intensity channel (value) is associated with the high resolution monochrome image and/or combined with the low-resolution intensity channel, for example by the Brovey method, as is known in the art.

In step <NUM>, the resulting image is transformed back to RGB space to form a colored fused final image of the target.

Reference is now made to <FIG>, which compare in grey and color, the results of combining multi-resolutions images as grey and color images, in accordance with a preferred embodiment of the present invention.

<FIG> shows a high resolution image <NUM> of a cross section of a cucumber <NUM> and groups of cucumber seeds <NUM> and <NUM>. <FIG> is similar to the high resolution scan shown in <FIG>.

<FIG> shows a high resolution image <NUM> of a cross section of the cucumber <NUM> and groups of cucumber seeds <NUM> and <NUM>. In the image <NUM>, the high resolution image (<FIG>), the medium resolution image (<FIG>) and the low resolution image (<FIG>) are combined by a IHS method as described in "<NPL>. ), The image <NUM> is clearer than the colored image <NUM>.

<FIG> shows a high resolution image <NUM> of a cross section of the cucumber <NUM> and groups of cucumber seeds <NUM> and <NUM>. In the image <NUM>, the high resolution image (<FIG>), the medium resolution image (<FIG>) and the low resolution image (<FIG>) are combined by the Brovey method, as is known in the art (step <NUM>, <FIG>). The image <NUM> clearly distinguishes between the groups of cucumbers <NUM> and <NUM> and the groups of cucumbers <NUM> and <NUM> are clearly distinguishable from the cucumber background.

Claim 1:
An MRI scanning assembly (<NUM>) including:
at least one MRI scanning device (<NUM>) configured to generate a plurality of MRI images of a target (<NUM>), wherein:
each one of said plurality of MRI images is associated with at least one member of a group of MRI device parameters, and
the at least one MRI device parameter is one of: an MRI scanning parameter, e.g. pixel size or dwell time, and an MRI scanning protocol;
a processing unit (<NUM>) configured to fuse at least one MRI image of said plurality of MRI images with at least one remaining MRI image of said plurality of MRI images to generate a clear image representation of at least a portion of said target,
wherein the fusing comprises:
identifying a region of interest in said at least one MRI image and a region of interest in said at least one remaining MRI image,
determining a monochrome level scaling factor between said regions of interest based on a ratio of a first ratio of monochrome levels associated with the at least MRI image and a second ratio of monochrome levels associated with said at least one remaining MRI image wherein:
the first ratio is a ratio of a mean monochrome level associated with the region of interest in said at least MRI image and a mean monochrome level associated with a reference region in said at least MRI image, and
the second ratio is a ratio of a mean monochrome level associated with the region of interest in said at least one remaining MRI image and a mean monochrome level associated with a reference region in said at least one remaining MRI image, and
scaling said at least one remaining MRI image of said plurality of MRI images with the monochrome level scaling factor.