Abstract:
An MR image especially useful for computer-guided diagnostics uses at least one programmed computer to acquire an MR-image of T1 values for a patient volume containing at least one predetermined tissue type having a respectively corresponding predetermined range of expected T1 values. A color-coded T1-image is generated from the MR-image by (a) assigning a first color or spectrum of colors to those pixels having a T1 value falling within a predetermined range of expected T1 values and (b) assigning a second color or spectrum of colors to those pixels having a T1 value falling outside a predetermined range of expected T1 values. The color-coded T1-image is then displayed for use in computer-aided diagnosis of patient tissue.

Description:
FIELD 
       [0001]    The subject matter below relates generally to magnetic resonance imaging (MRI) processes. Preferably, the MRI processes described below involve enhancements to T1 images of tissue for computer-aided diagnostics (CAD) of imaged patient tissue. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0002]      FIG. 1  is a high-level schematic block diagram of an MRI system adapted to acquire and process data for MRI using color-coding of T1 values in a T1 image to enhance computer-aided diagnosis; 
           [0003]      FIG. 2  is a schematic flow chart of exemplary computer program code structure that may be utilized for practicing an exemplary embodiment; and 
           [0004]      FIG. 3  is a schematic illustration of a possible screen display of an MRI T1 image showing a targeted organ that has been displayed with two distinguishable color spectra. 
       
    
    
     DETAILED DESCRIPTION 
       [0005]    The MRI system shown in  FIG. 1  includes a gantry  10  (shown in schematic cross-section) and various related system components  20  interfaced therewith. At least the gantry  10  is typically located in a shielded room. One MRI system geometry depicted in  FIG. 1  includes a substantially coaxial cylindrical arrangement of the static field B 0  magnet  12 , a G x , G y  and G z  gradient coil set  14  and an RF coil assembly  16 . Along the horizontal axis of this cylindrical array of elements is an imaging volume  18  shown as substantially encompassing the head of a patient  9  supported by a patient table  11 . 
         [0006]    An MRI system controller  22  has input/output ports connected to display  24 , keyboard/mouse  26  and printer  28 . As will be appreciated, the display  24  may be of the touch-screen variety so that it provides control inputs as well. 
         [0007]    The MRI system controller  22  interfaces with MRI sequence controller  30  which, in turn, controls the G x , G y  and G z  gradient coil drivers  32 , as well as the RF transmitter  34  and the transmit/receive switch  36  (if the same RF coil is used for both transmission and reception). The MRI sequence controller  30  includes suitable program code structure  38  for implementing MRI data acquisition sequences already available in the repertoire of the MRI sequence controller  30  to generate T1-parameter valued image pixels (e.g., by capturing plural MR images at different TR intervals to calculate T1 values for each pixel in an image of tissue). 
         [0008]    The MRI system  20  includes an RF receiver  40  providing input to data processor  42  so as to create processed image data to display  24 . The MRI data processor  42  is also configured for access to T 1 -image reconstruction program code structure  44  and to MR T1 image memory  46  (e.g., for storing MR T1 image data derived from processing in accordance with the exemplary embodiments and the image reconstruction program code structure  44 ). 
         [0009]    Also illustrated in  FIG. 1  is a generalized depiction of an MRI system program/data store  50  where stored program code structures (e.g., for generation of color-coded T1-images, operator inputs to same, etc.) are stored in computer-readable storage media accessible to the various data processing components of the MRI system. As those in the art will appreciate, the program store  50  may be segmented and directly connected, at least in part, to different ones of the system  20  processing computers having most immediate need for such stored program code structures in their normal operation (i.e., rather than being commonly stored and connected directly to the MRI system controller  22 ). 
         [0010]    Indeed, as those in the art will appreciate, the  FIG. 1  depiction is a very high-level simplified diagram of a typical MRI system with some modifications so as to practice exemplary embodiments to be described hereinbelow. The system components can be divided into different logical collections of “boxes” and typically comprise numerous digital signal processors (DSP), microprocessors, special purpose processing circuits (e.g., for fast A/D conversions, fast Fourier transforming, array processing, etc.). Each of those processors is typically a clocked “state machine” wherein the physical data processing circuits progress from one physical state to another upon the occurrence of each clock cycle (or predetermined number of clock cycles). 
         [0011]    Not only does the physical state of processing circuits (e.g., CPUs, registers, buffers, arithmetic units, etc.) progressively change from one clock cycle to another during the course of operation, the physical state of associated data storage media (e.g., bit storage sites in magnetic storage media) is transformed from one state to another during operation of such a system. For example, at the conclusion of an MR-imaging reconstruction process, an array of computer-readable accessible data value storage sites in physical storage media will be transformed from some prior state (e.g., all uniform “zero” values or all “one” values) to a new state wherein the physical states at the physical sites of such an array vary between minimum and maximum values to represent real world physical events and conditions (e.g., the tissues of a patient over an imaging volume space). As those in the art will appreciate, such arrays of stored data values represent and also constitute a physical structure—as does a particular structure of computer control program codes that, when sequentially loaded into instruction registers and executed by one or more CPUs of the MRI system  20 , cause a particular sequence of operational states to occur and be transitioned through within the MRI system. 
         [0012]    The exemplary embodiments described below provide improved ways to process data acquisitions and/or to generate and display MR-images. 
         [0013]    Even if contrast materials are injected into a patient&#39;s imaged anatomy, thus highlighted MRI signals may still be missed when the image is used for diagnostic purposes. However, as may be ascertained from the following Table 1, different organs and/or tissues can be expected to have a wide range of differing T1 values (both at 1.5 Tesla and 3.0 Tesla imaging parameters). At the same time, as can be ascertained from the following Table 2, the MR T2 values for different tissue/organs may be relatively similar and with overlapping ranges that make it difficult to differentiate. 
         [0014]    The following tables are taken from de Bazelaire, et al., “MR Imaging Relaxation Times of Abdominal and Pelvic Tissues Measured in Vivo at 3.0T: Preliminary Results,”  Radiology  230:3, pages 652-659, March 2004. As those in the art will appreciate, there are other sources of similar data readily available in the literature. For example, see Stanisz, et al, “T 1 , T 2  Relaxation and Magnetization Transfer in Tissue at 3T,” MRIM 54:507-512 (2005). 
         [0000]    
       
         
               
             
               
               
               
               
             
               
               
               
               
               
               
             
           
               
                 TABLE 1 
               
             
             
               
                   
               
               
                 Average T1 Relaxation Times at 1.5 Tesla and 3.0 Tesla 
               
             
          
           
               
                   
                 1.5 Tesla 
                 3.0 Tesla 
                   
               
             
          
           
               
                   
                 T1 
                   
                 T1 
                   
                   
               
               
                   
                 Relaxation 
                 R 2   
                 Relaxation 
                 R 2   
                 Differ- 
               
               
                   
                 Time 
                 Value 
                 Time 
                 Value 
                 ence 
               
               
                 Tissue 
                 (msec) 
                 (%) 
                 (msec) 
                 (%) 
                 (%) 
               
               
                   
               
               
                 Kidney 
                   
                   
                   
                   
                   
               
               
                 Cortex 
                  966 ± 58 
                 0.999 
                 1,142 ± 154 
                 0.990 
                 18 
               
               
                 Medulla 
                 1,412 ± 58  
                 0.997 
                 1,545 ± 142 
                 0.999 
                  9 
               
               
                 Liver 
                  586 ± 39 
                 0.995 
                  809 ± 71 
                 0.987 
                 38 
               
               
                 Spleen 
                 1,057 ± 42  
                 0.998 
                 1,328 ± 31  
                 0.998 
                 26 
               
               
                 Pancreas 
                  584 ± 14 
                 0.982 
                  725 ± 71 
                 0.976 
                 24 
               
               
                 Paravertebral 
                  856 ± 61 
                 0.988 
                  898 ± 33 
                 0.988 
                  5 
               
               
                 muscle 
                   
                   
                   
                   
                   
               
               
                 Bone marrow 
                  549 ± 52 
                 0.991 
                  586 ± 73 
                 0.994 
                  7 
               
               
                 (L4 vertebra) 
                   
                   
                   
                   
                   
               
               
                 Subcutaneous fat 
                  343 ± 37 
                 0.997 
                  382 ± 13 
                 0.999 
                 11 
               
               
                 Uterus 
                   
                   
                   
                   
                   
               
               
                 Myometrium 
                 1,309 ± 35  
                 0.998 
                 1,514 ± 156 
                 0.999 
                 16 
               
               
                 Endometrium 
                 1,274 ± 64  
                 0.997 
                 1,453 ± 123 
                 0.998 
                 14 
               
               
                 Cervix 
                 1,135 ± 154 
                 0.998 
                 1,616 ± 61  
                 0.998 
                 42 
               
               
                 Prostate 
                 1,317 ± 85  
                 0.999 
                 1,597 ± 42  
                 0.998 
                 21 
               
               
                   
               
             
          
         
       
     
         [0000]    
       
         
               
             
               
               
               
               
             
               
               
               
               
               
               
             
           
               
                 TABLE 2 
               
             
             
               
                   
               
               
                 Average T2 Relaxation Times at 1.5 Tesla and 3.0 Tesla 
               
             
          
           
               
                   
                 1.5 Tesla 
                 3.0 Tesla 
                   
               
             
          
           
               
                   
                 T2 
                   
                 T2 
                   
                   
               
               
                   
                 Relaxation 
                 R 2   
                 Relaxation 
                 R 2   
                 Differ- 
               
               
                   
                 Time 
                 Value 
                 Time 
                 Value 
                 ence 
               
               
                 Tissue 
                 (msec) 
                 (%) 
                 (msec) 
                 (%) 
                 (%) 
               
               
                   
               
               
                 Kidney 
                   
                   
                   
                   
                   
               
               
                 Cortex 
                 87 ± 4 
                 0.993 
                 76 ± 7  
                 0.993 
                 −13 
               
               
                 Medulla 
                  85 ± 11 
                 0.992 
                 81 ± 8  
                 0.996 
                  −5 
               
               
                 Liver 
                 46 ± 6 
                 0.992 
                 34 ± 4  
                 0.984 
                 −26 
               
               
                 Spleen 
                  79 ± 15 
                 0.998 
                 61 ± 9  
                 0.996 
                 −23 
               
               
                 Pancreas 
                 46 ± 6 
                 0.989 
                 43 ± 7  
                 0.977 
                  −7 
               
               
                 Paravertebral 
                 27 ± 8 
                 0.925 
                 29 ± 4  
                 0.867 
                    7 
               
               
                 muscle 
                   
                   
                   
                   
                   
               
               
                 Bone marrow 
                 49 ± 8 
                 0.997 
                 49 ± 4  
                 0.994 
                    1 
               
               
                 (L4 vertebra) 
                   
                   
                   
                   
                   
               
               
                 Subcutaneous fat 
                 58 ± 4 
                 0.995 
                 68 ± 4  
                 0.999 
                   17 
               
               
                 Uterus 
                   
                   
                   
                   
                   
               
               
                 Myometrium 
                 117 ± 14 
                 0.995 
                 79 ± 10 
                 0.993 
                 −33 
               
               
                 Endometrium 
                 101 ± 21 
                 0.987 
                 59 ± 1  
                 0.999 
                 −42 
               
               
                 Cervix 
                  58 ± 20 
                 0.993 
                 83 ± 7  
                 0.992 
                   43 
               
               
                 Prostate 
                 88 ± 0 
                 0.997 
                 74 ± 9  
                 0.995 
                 −16 
               
               
                   
               
             
          
         
       
     
         [0015]    To provide improved computer-aided diagnostic (CAD) images in MRI (magnetic resonance imaging), especially for areas of the body outside intra-cranial MRA and breast tissues, images of T1-valued pixels can now be used to help guide differentiation between different tissues and/or organs. T1-weighted and/or T1-valued images can be obtained in various ways. For example, two or more MR images can be obtained with different TR intervals so as to permit exponential fitting processes to determine T1 values. Different inversion times (TI) can be used, as can different inversion recovery (IR) sequences or different values of TE (time to echo) so as to obtain requisite data for calculating T1 values (or at least T1-weighted values) for each pixel. 
         [0016]    It is believed that a color-coded display of T1 values within a T1-image will make display of normal and irregular organ/tissue signals more easily differentiated by human eyes during diagnostic processes. In addition, rough ranges of expected T1 values using inversion recovery (IR) pulses can be accumulated over time to allow even better tissue characterization (e.g., so as to differentiate cancerous tumor cells from other tissues). 
         [0017]    As shown by Table 1 above of published T1-parameter values for various tissues (including ranges of expected variation), it is possible to determine threshold ranges of T1 values so as to distinguish between various organs and/or tissues. It is now proposed that such ranges of T1 values be color-coded (e.g., with a given color for a certain range of T1 values or for a whole spectrum of colors to be assigned to a particular range of T1 values). Display of such color-coded images will permit one to achieve better visual recognition of a target organ/tissue even without the use of contrast agents. However, in addition, such color-coding of T1-valued images can be used in conjunction with contrast agents (e.g., which can be expected to further change the T1-parameter values for cancerous tumor tissues, as well as normal tissues). 
         [0018]    Two or more T1-weighted images may be acquired so as to provide T1-image guides and/or reference images. A range of T1 values associated with a target organ/tissue may be used as a threshold range in which one or more colors are assigned to particular sub-ranges/values of the T1 parameter. For example, a first spectrum A of colors may be assigned to a first spectrum of T1-parameter values, while a second different spectrum B of color values may be assigned to a different spectrum of T1-parameter values (e.g., as might correspond to expected cancerous tissues that may be located within a target organ or body area). 
         [0019]    If an injected contrast agent is to be utilized in conjunction with such color-coding of T1-valued images, then a CAD-guided image display may usefully be obtained both before and after the contrast injection so that comparisons may be made therebetween to enhance detection of possibly abnormal tissue. 
         [0020]    If abnormal tissues are detected (e.g., possibly due to concentration of injected contrast agents or otherwise), then such abnormal T1-valued areas may be highlighted with a notable distinguishing color or color spectrum (e.g., a red-colored spectrum or possibly a single red color value). 
         [0021]    An MRI system configured to provide such color-coded T1 image displays may provide a reference image of the same target area with conventional display parameters (e.g., contrast, gray scales, etc.). However utilized, it is believed that color-coded T1 images can provide a useful diagnostic tool for computer-aided diagnosis that better differentiates abnormal tissues from normal tissues based on such different tissues having respectively different T1-parameter values. 
         [0022]    The set of color-coded T1-parameter valued images also can be used for CAD in conjunction with X-ray mammography and breast dynamic contrast enhancement (DCE). 
         [0023]    Two or more T1-weighted images (or T1 with IR pulse) can be acquired to make the T1-valued guide or reference images. Different threshold ranges of T1 values can then be utilized to make corresponding color assignments to different ranges of T1 values. Such thresholding of ranges allows one to present tissue within a normal range in one color (or spectrum of colors) and abnormal signals in a different color (or spectrum of colors). 
         [0024]    Besides published data showing ranges of T1 values to be expected for different tissues, a T1 range with rough T1 values can be expected due to the measurement methods, such as imaging sequences, BO and/or B1 inhomogeneities, etc. 
         [0025]    A CAD-guided image display taken before injection of contrast media may be compared to one taken after the injection of contrast media so as to better notice T1-parameter values then being displayed in different colors. As will be appreciated, the T1 value ranges for different abnormal tissues can be stored in system databases and used as reference data for identifying particular types of tumors or cancerous tissues. 
         [0026]    A color-coded T1-imaged CAD module as depicted in  FIG. 2  may be entered at  80  by any suitable operator-entry or system-entry mode. For example, the operator might click on a mouse-selected icon, a touch-sensitive icon, a keyboard command or the like. Alternatively, the system may, in fact, select entry to this module based upon some other criteria. 
         [0027]    At box  82 , a T1-valued MR image of the patient region of interest (ROI) is acquired. Such a T1-valued image may be acquired by retrieving such from memory or may be originally acquired in real time by suitable MRI data acquisition using suitable MRI sequences, calculations, etc., so as to produce an MR image of the patient ROI having pixels with T1-values or at least T1-weighted values. 
         [0028]    At decision box  84  in  FIG. 2 , a wait loop is entered, if necessary, to permit operator/system selection of an organ/tissue of interest. For example, based on the entries in Table 1 noted above, the operator and/or system may have access to previously stored expected ranges of T1 values for many different organs and/or tissues of possible interest. Those pre-stored expected ranges of values may be used “as is”. However, the operator/system may also have the option of modifying the ranges somewhat (e.g., so as to broaden or narrow the ranges and/or to weight the ranges in accordance with desired criteria). The operator/system may also have the option to select “other” as shown in box  86  where complete freedom is given to identify any desired particular range of T1 values that may be of interest for a particular target anatomy. 
         [0029]    As already mentioned, the operator/system may have an option for approving the nominal or modified T1 ranges to be color-coded as depicted in the optional wait loop  88  of  FIG. 2 . 
         [0030]    Similarly, the operator/system may have an optional wait loop  90  as indicated in  FIG. 2  for approving and/or modifying color values, spectra, etc., to be used for different T1 values and/or ranges of values. At step  92 , particular color values are assigned to particular T1-valued pixels. In conjunction therewith, or possibly before or after step  92 , a test may be made as depicted at  94  in  FIG. 2  for abnormal out-of-range T1-valued pixels (e.g., possibly being bounded by normal-valued ranges of pixels). If such abnormal collections of T1-valued pixels are discovered, then as depicted at  96 , a different color (or color spectra) code may be assigned to such abnormal pixels. 
         [0031]    As depicted at  98  in  FIG. 2 , the color-coded T1 image is displayed for CAD purposes. It may also be stored and/or output (e.g., to a printer or remote site) as depicted at  100  in  FIG. 2  before exit from this module is taken at  102 . 
         [0032]    As a result of the module in  FIG. 2 , an image may be displayed as is schematically depicted at  FIG. 3 . Here, within the anatomy of a patient  300 , an organ  302  is depicted with normal expected T1-valued pixels being assigned a color spectrum A. However, within the boundaries of organ  302 , unexpected, abnormally valued pixels are discovered in area  304  and assigned a different contrasting color spectrum B. As explained previously, the system may be configured so as to permit the operator/system to assign different color spectra to different ranges of T1-valued pixels so as to optimize a CAD display for particular applications. 
         [0033]    While certain embodiments of the inventions have been described, these embodiments have been presented by way of example only, and are not intended to limit the scope of the inventions. Indeed, the novel methods and systems described herein may be embodied in a variety of other forms. Furthermore, various omissions, substitutions and changes in the form of the methods and systems described herein may be made without departing from the spirit of the inventions. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the inventions.