Surgery – Diagnostic testing – Detecting nuclear – electromagnetic – or ultrasonic radiation
Reexamination Certificate
2001-08-28
2004-02-03
Smith, Ruth S. (Department: 3737)
Surgery
Diagnostic testing
Detecting nuclear, electromagnetic, or ultrasonic radiation
C324S318000
Reexamination Certificate
active
06687527
ABSTRACT:
BACKGROUND OF THE INVENTION
The present invention relates to the magnetic resonance arts, and more particularly to user interfaces for clinical imaging systems. The invention is particularly suitable for user interfacing with a magnetic resonance imaging (MRI) apparatus in a clinical setting, and will be described with particular reference thereto. However, it will be appreciated that the invention will also find application in conjunction with other MRI applications, other medical imaging methods and apparatus, in medical technologist training, and the like.
A magnetic resonance imaging (MRI) apparatus excites magnetic nuclear resonances in a subject, e.g. a patient, and manipulate and detect the resultant magnetic resonance signal. By limiting the spatial volume of the magnetic excitations and by spatially- and/or phase-encoding the magnetic resonance signal, usually through the use of applied magnetic field gradients, image representations of body parts, blood flow, injected radiopharmeceutical distributions, and the like are reconstructed from the magnetic resonance measurements.
MRI apparatus are operated in a multitude of imaging modes, for example SE, FE/CBASS, FSE, EPI (DWI/PWI), GRASE, and other modes. The choice of operating mode is based upon the body part to be imaged and the clinical aspects under study. By appropriately selecting MRI operational parameters the conditions can be selectively weighted to produce images that are proton density (&rgr;) weighted, T
1
, weighted, T
2
weighted, et cetera. Scan parameters can also be optimized for imaging a particular body part and for using particular RF coils or coil arrays.
These various imaging capabilities are effectuated through appropriate selection of a large number of quantitative input parameters, such as the scan repeat time, the scan resolution, the interecho spacing, the bandwidth, the time-to-echo, and so forth. In all, twenty to forty input parameters are typically available for operator manipulation. These parameters are not, however, fully independent insofar as the setting of one parameter, e.g. the bandwidth, typically changes or limits the dynamic range of other parameters, e.g. the scan time.
The vast quantitative input parameter space often introduces practical limitations on the obtained image quality. Clinical MRI systems are usually operated by technologists who often have limited knowledge of the physical interrelations between the various parameters. Clinical MRI systems are also usually operated under significant time constraints in which patient throughput is an important consideration. Imaging under these conditions is often performed using sub-optimal parameter values, and these sub-optimized imaging conditions lead to degraded image quality that can limit the clinical value of the results. Thus, a critical area of clinical MRI development is the user interface design.
Prior art user interfaces (UI) typically provide the operator with a large number of input parameters, e.g. typically twenty to forty input parameters. Operator guidance in user selection of these parameters is usually limited to providing pre-designed parameter value sets for specific imaging tasks. Thus, for example, a technologist who wants to acquire a T
2
weighted brain scan using an EPI imaging mode retrieves a pre-designed parameter value set corresponding to that type of image. The retrieved parameters are displayed by the UI. The operator typically either executes the scan using the pre-designed parameter values in unmodified form, or makes parameter adjustments through the UI based upon the operator's prior experience and knowledge prior to acquiring the image.
In the latter case, the prior art UI systems usually provide only limited operator assistance in making the adjustments. Typically, feedback includes only a signal-to-noise ratio (SNR) value and a pixel or voxel size. A specific absorption ratio (SAR) value is usually calculated as a safety check, but the SAR user feedback is often limited to an overrange alarm indicator which indicates that the patient would be subject to unacceptably high energy fields during image scanning using the presently selected parameter values.
Importantly, the prior art UI systems typically provide no user guidance with respect to parameter interrelations and tradeoffs, beyond generally unhelpful parameter-out-of-range errors. In view of the demanding time constraints often imposed on clinical MRI, the technologist often finds these complex prior art UI systems overly complicated and contributory to operator errors and to sub-optimal acquired images. Only a limited amount of information about the interrelations which connect the MRI operational parameters is provided.
The present invention contemplates an improved system and method which overcomes the aforementioned limitations and others.
SUMMARY OF THE INVENTION
According to one aspect of the invention, a method for providing guidance to a magnetic resonance imaging (MRI) apparatus operator is disclosed. A desirability factor function is calculated, which depends upon a plurality of MRI operating parameters. Optimized values are obtained for the plurality of MRI operating parameters through analysis of the desirability factor function.
Preferably, the calculating of a desirability factor function includes calculating a monitor function, calculating a penalty function corresponding to a first parameter selected from the plurality of MRI operating parameters, and calculating the desirability factor function by mathematically combining the monitor function and the penalty function.
Preferably, the calculating of a monitor function includes calculating an estimated signal-to-noise ratio value. The mathematical combining preferably includes additively or subtractively combining the estimated signal-to-noise ratio with the penalty function.
The calculating of the penalty function preferably includes calculating a barrier function that has a prohibitively undesirable value within a pre-selected range of the first parameter.
The calculating of the penalty function preferably includes calculating a function whose value becomes less desirable as the value of the first parameter increasingly deviates from a default range.
The obtaining of optimized values for the plurality of MRI operating parameters through analysis of the desirability factor function preferably includes optimizing the desirability factor function with respect to at least one of the plurality of MRI operating parameters using an iterative optimization algorithm.
The obtaining of optimized values for the plurality of MRI operating parameters through analysis of the desirability factor function preferably includes graphically displaying a plot of the desirability factor function plotted against at least one of the plurality of MRI operating parameters on a display area of an associated interactive display device. A selection of the optimized values is received from the MRI apparatus operator via the associated interactive display device.
The method preferably further comprises: receiving initial values for the plurality of MRI operating parameters; calculating limit values corresponding to the MRI operating parameters; calculating values for a set of monitor parameters; displaying values of a sub-set of the MRI operating parameters; displaying the limit values for the sub-set of MRI operating parameters; and displaying the calculated monitor parameter values.
According to another aspect of the invention, a method for providing guidance to a magnetic resonance imaging (MRI) apparatus operator is disclosed. An operating curve is calculated indicating allowable combinations of values for a plurality of MRI operating parameters. An optimized combination of values for the plurality of MRI operating parameters is obtained by analyzing the operating curve.
Preferably, the obtaining of an optimized combination of values for the plurality of MRI operating parameters includes graphically displaying the operating curve on a display area of an associated interactive display devi
Havens Troy K.
Wu Dee H.
Fay Sharpe Fagan Minnich & McKee LLP
Koninklijke Philips Electronics , N.V.
Smith Ruth S.
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