Patent Issued for Systems And Methods For Multi-Echo, Background Suppressed Magnetic Resonance Angiography (USPTO 10,401,458)

2019 SEP 12 (NewsRx) -- By a News Reporter-Staff News Editor at Insurance Daily News -- According to news reporting originating from Alexandria, Virginia, by NewsRx journalists, a patent by the inventor Edelman, Robert R. (Highland Park, IL), filed on September 19, 2017, was published online on September 16, 2019.

The assignee for this patent, patent number 10,401,458, is Northshore University Health System (Evanston, Illinois, United States).

Reporters obtained the following quote from the background information supplied by the inventors: “The field of the disclosure is systems and methods for magnetic resonance imaging (‘MRI’). More particularly, the disclosure relates to systems and methods for multi-echo background-suppressed magnetic resonance angiography (MRA).

“Peripheral vascular disease (PVD) has an age-adjusted prevalence of 12% in the United States, causes significant morbidity, and is often associated with excess cardiovascular mortality. Contrast-enhanced (CE) magnetic resonance angiography (MRA) often substitutes for the more invasive ‘gold standard’ procedure of digital subtraction angiography. Given the frequency of renal functional impairment in patients with PVD and concerns about nephrogenic systemic fibrosis, there is growing interest in non-contrast-enhanced MRA.

“Quiescent-interval slice-selective (QISS) MRA has is an efficient and accurate non-contrast technique for the evaluation of peripheral arterial disease. In QISS MRA, the MRI system acquires data using a modified single shot two-dimensional balanced steady-state free precession (bSSFP) pulse sequence. Unlike subtractive non-contrast-enhanced three-dimensional MRA methods, the imaging parameters for QISS MRA require minimal if any tailoring for individual patients. However, compared with CE-MRA, the bSSFP readout used for QISS is more sensitive to susceptibility effects.

“For example, in certain circumstances such as imaging near a metallic hip prosthesis or at 3 Tesla near an air-containing bowel loop, the image quality may be degraded by susceptibility artifacts due to the use of a bSSFP readout. A high bandwidth and short TE may reduce artifacts at the expense of worsening small vessel conspicuity on projection images.

“It would therefore be desirable to provide MRI systems and methods with enhanced background suppression to overcome the above limitations.”

In addition to obtaining background information on this patent, NewsRx editors also obtained the inventor’s summary information for this patent: “The present disclosure overcomes the aforementioned drawbacks by providing a method for producing an image of a subject using a magnetic resonance imaging (‘MRI’) system, in which data is acquired from a subject by directing the MRI system to perform a pulse sequence that forms echoes at least at two different echo times. The MRI system acquires first echo image data at a first echo time and second echo image data at a second echo time. A first image is reconstructed from the first echo image data and a second image is reconstructed from the second echo image data. A mask image is generated using the first and second image. A first scale factor (SF1) is computed by calculating a first ratio of a selected tissue signal in the first image and the mask image, and a first scaled mask image is generated by multiplying the mask image by SF1. A second scale factor (SF2) is computed by calculating a second ratio of the selected tissue signal in the second image and the mask image, and a second scaled mask image is generated by multiplying the mask image by SF2. A first processed image is generated by subtracting the first scaled mask image from the first image, and a second processed image is generated by subtracting the second scaled mask image from the second image. A projection angiogram is then generated from the processed images.

“The foregoing and other aspects and advantages of the disclosure will appear from the following description. In the description, reference is made to the accompanying drawings that form a part hereof, and in which there is shown by way of illustration a preferred embodiment of the disclosure. Such embodiment does not necessarily represent the full scope of the disclosure, however, and reference is made therefore to the claims and herein for interpreting the scope of the disclosure.”

The claims supplied by the inventors are:

“The invention claimed is:

“1. A method for generating a magnetic resonance angiogram, comprising: (a) acquiring, using a magnetic resonance imaging (MRI) system, first echo image data at a first echo time and second echo image data at a second echo time while applying a pulse sequence that forms echoes at least at the first echo time and the second echo time in a given repetition time period; (b) reconstructing, with a computer system, a first image from the first echo image data and a second image from the second echo image data; © generating, with the computer system, a mask image using the first image and the second image; (d) computing, with the computer system, a first scale factor by calculating a first ratio of a selected tissue signal in the first image and the mask image, and (e) generating, with the computer system, a first scaled mask image by multiplying the mask image by the first scale factor; (f) computing, with the computer system, a second scale factor by calculating a second ratio of the selected tissue signal in the second image and the mask image (g) generating, with the computer system, a second scaled mask image by multiplying the mask image by the second scale factor; (h) generating, with the computer system, a first processed image by subtracting the first scaled mask image from the first image; (i) generating, with the computer system, a second processed image by subtracting the second scaled mask image from the second echo image; and (j) generating, with the computer system, a projection angiogram from each of the first and second processed images.

“2. The method as recited in claim 1, wherein the MRI system acquires the first and second echo image data using different readout bandwidths.

“3. The method as recited in claim 1, wherein the MRI system acquires the first echo image data using a readout bandwidth greater than 400 Hz/pixel.

“4. The method as recited in claim 3, wherein the first echo time is less than 2 milliseconds.

“5. The method as recited in claim 1, wherein the MRI system synchronizes data acquisition to a diastolic phase of the cardiac cycle.

“6. The method as recited in claim 1, wherein the pulse sequence further comprises applying flow compensation along at least one direction.

“7. The method as recited in claim 1, wherein generating the mask image includes compute a difference between the first image and the second image.

“8. The method as recited in claim 1, wherein the MRI system acquires additional echo image data, at least one additional image is reconstructed from the additional echo image data, and the mask image is generated based at least in part on a standard deviation calculated using the first image, the second image, and the at least one additional image.

“9. The method as recited in claim 1, wherein the pulse sequence implemented by the MRI system uses one of a Cartesian, radial, and spiral k-space trajectory while acquiring the first and second echo image data.

“10. The method as recited in claim 1, wherein the pulse sequence further comprises applying a multiband radio frequency (RF) excitation to excite more than one slice simultaneously.

“11. The method as recited in claim 1, further comprising applying one or more acceleration techniques to acquire the first and second echo image data and to reconstruct the first and second images therefrom.

“12. The method as recited in claim 1, further comprising calculating at least one of a T2* map and a magnetic susceptibility map using the first and second echo image data.

“13. The method as recited in claim 1, wherein the selected tissue signal is a fat signal.

“14. A magnetic resonance imaging (MRI) system comprising: a magnet system configured to generate a polarizing magnetic field about at least a region of interest (ROI) in a subject arranged in the MRI system; a plurality of gradient coils configured to apply a gradient field to the polarizing magnetic field; a radio frequency (RF) system configured to apply an excitation field to the subject and acquire echo image data from the ROI; a computer system programmed to: acquire first echo image data at a first echo time and second echo image data at a second echo time while controlling the RF system and the plurality of gradient coils to apply a pulse sequence that forms echoes at least at the first echo time and the second echo time; reconstruct a first image from the first echo image data and a second image from the second echo image data; generate a mask image using the first image and the second image; compute a first scale factor by calculating a first ratio of a selected tissue signal in the first image and the mask image generate a first scaled mask image by multiplying the mask image by the first scale factor; compute a second scale factor by calculating a second ratio of the selected tissue signal in the second image and the mask image generate a second scaled mask image by multiplying the mask image by the second scale factor; generate a first processed image by subtracting the first scaled mask image from the first image; generate a second processed image by subtracting the second scaled mask image from the second image; and generate a projection angiogram from each of the first and second processed images.

“15. The MRI system of claim 14, wherein the MRI system acquires the first and second echo image data using different readout bandwidths.

“16. The MRI system of claim 14, wherein the MRI system acquires the first echo image data using a readout bandwidth greater than 400 Hz/pixel.

“17. The MRI system of claim 16, and wherein the first echo time is less than 2 milliseconds.

“18. The MRI system of claim 14, wherein the MRI system synchronizes data acquisition to a diastolic phase of a cardiac cycle.

“19. The MRI system of claim 14, wherein the selected tissue signal is a fat signal.”

For more information, see this patent: Edelman, Robert R. Systems And Methods For Multi-Echo, Background Suppressed Magnetic Resonance Angiography. U.S. Patent Number 10,401,458, filed September 19, 2017, and published online on September 16, 2019. Patent URL: http://patft.uspto.gov/netacgi/nph-Parser?Sect1=PTO1&Sect2=HITOFF&d=PALL&p=1&u=%2Fnetahtml%2FPTO%2Fsrchnum.htm&r=1&f=G&l=50&s1=10,401,458.PN.&OS=PN/10,401,458RS=PN/10,401,458

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