Method and apparatus for detecting mental disorders

• US 6,400,978 B1
• Filed: 10/29/1999
• Issued: 06/04/2002
• Est. Priority Date: 10/29/1999
• Status: Expired due to Term

• Current Assignee: Mclean Hospital (Mass General Brigham, Inc.)
• Original Assignee: Mclean Hospital (Mass General Brigham, Inc.)
• Inventors: Maas, Luis C. III, Anderson, Carl M., Renshaw, Perry F., Teicher, Martin H.
• Primary Examiner(s): Lateef, Marvin M.
• Assistant Examiner(s): Lin, Jeoyuh
• Application Number:
  US09/430,209
• Time in Patent Office: 949 Days
• Field of Search: 600/407, 600/410, 600/425, 382/128, 324/327, 324/307, 324/309, 324/310, 324/312, 324/308, 324/318, 324/300
• US Class Current: 600/410
• CPC Class Codes: A61B 5/055 involving electronic [EMR] or nuclear [NMR] magnetic resonance, e.g. magnetic resonance imaging
• CPC Class Codes: A61B 5/168 Evaluating attention deficit, hyperactivity

Abstract

A technique for computing a T2 relaxation time (RT) and for using the so computed T2 RT to provide an output which can aid in the detection of brain dysfunction including attention-deficit hyperactivity disorder (ADHD). The technique includes the step of obtaining T*1 matched axial images through a predetermined number of axial planes in a subject and obtaining one or more spin echo, echoplanar image sets, with TE incremented by a predetermined value in each consecutive image set through the same axial planes. The images are used to generate a map of T2 for each of the T*1 matched axial images and regions of interest (ROI) are identified in the matched axial images. Median pixel intensity values in the ROI are then used to compute a T2 relaxation time.

Claims

1. An MRI system for measuring the T2 relaxation time of a sample, the system comprising:

a magnet system for generating a steady, uniform magnetic field and for generating magnetic field gradients in a chamber adapted to receive the sample;

a magnet controller for controlling the magnet system;

an RF transmitter and receiver for generating and detecting spin resonance signals;

a sampling device for sampling the generated spin resonance signals; and

a T2 RT processor for receiving the sample spin resonance signals and for computing a T2 relaxation time in one or more regions of interest (ROI) using median pixel intensity values in the one or more ROI for each of the spin resonance signals in the ROI.

2. The system of claim 1 further comprising image generating means for generating an image from the sampled spin resonance signals wherein said image generating means comprises means for obtaining one or more spin echo, echoplanar image sets with each image in the image sets taken through the same axial planes and each of the consecutive image sets having a TE incremented by a predetermined value.

3. The system of claim 2 further comprising a motion correction processor coupled to said T2 RT processor, said motion correction processor for correcting the TE-incremented images for in plane motion to provide corrected images.

4. The system of claim 3 further comprising means for comparing the T2 relaxation time for the sample with a T2 relaxation time for a reference sample.

5. The system of claim 4 wherein said T2 RT processor includes a curve fitting processor for fitting a curve to the median intensity values of the spin resonance signals in the ROI.

6. The system of claim 5 wherein:

ten axial planes through the sample are used;

thirty-two echoplanar image sets are used; and

TE is incremented by 4 msec in each consecutive image set through the same ten axial planes of the sample.

7. A method for determining a T2 relaxation time in a sample, the method comprising the steps of:

(a) obtaining one or more T*1 matched axial images through a predetermined number of axial planes of the sample;

(b) obtaining one or more spin echo, echoplanar image sets, with TE incremented by a predetermined value in each consecutive image set through the same axial planes used in step (a);

(c) generating a map of T2 for each of the T*1 matched axial images;

(d) identifying one or more regions of interest (ROI) in the images of the sample;

(e) computing the median pixel intensity values in the ROI; and

(f) determining a T2 relaxation time from the median pixel values.

8. The method of claim 7 wherein after the step of obtaining one or more spin echo, echoplanar image sets, the method further comprises the step of correcting the TE-incremented images for in plane motion to provide corrected images.

9. The method of claim 7 wherein the step of obtaining one or more T*1 matched axial images through a predetermined number of axial planes includes the step of obtaining one or more T*1 matched axial images through ten axial planes.

10. The method of claim 7 wherein the step of obtaining one or more spin echo, echoplanar image sets includes the steps of

obtaining 32 echoplanar image sets;

incrementing TE by 4 msec in each consecutive image set through the same ten axial planes;

selecting TR=10 msec;

selecting a slice thickness typically of about 7 mm; and

selecting a skip typically of about with a 3 mm.

11. The method of claim 7 wherein the step of correcting the TE incremented images for in-plane motion includes the steps of:

transferring the images to an offline workstation; and

using an image registration technique to correct for in plane motion.

12. The method of claim 7 wherein the step of identifying one or more regions of interest (ROI) in the corrected images includes the steps of:

selecting one or more brain regions as the ROIs prior to acquiring images of the brain; and

identifying specific portions of the selected ROIs on images of the brain as those regions in which the median pixel intensity is computed.

13. The method of claim 7 wherein the step of identifying one or more regions of interest in the corrected images includes the step of:

identifying an ROI in a T1 weighted brain image using anatomic boundaries observed in the T1 weighted brain image; and

circumscribing a particular brain region shown in the T1 weighted image.

14. The method of claim 7 wherein the step of computing a T2 relaxation time from the median pixel values includes the step of using linear least squares regression to compute a single T2 relaxation time measure for each pixel.

15. A system for determining a T2 relaxation time, the system comprising:

(a) an MRI scanner for acquiring brain images;

(b) means for obtaining one or more T*1 matched axial images through a predetermined number of axial planes;

(c) means for obtaining one or more spin echo, echoplanar image sets, with TE incremented by a predetermined value in each consecutive image set through the predetermined number of axial planes;

(d) means for generating a map of T2 for each of the T*1 matched axial images;

(e) means for correcting the TE-incremented images for in plane motion to provide corrected images;

(f) means for identifying one or more regions of interest (ROI) in the corrected images;

(g) means for computing the median pixel intensity values in the ROI; and

(h) means for determining a T2 relaxation time from the median pixel values.

16. The system of claim 15 wherein said means for obtaining one or more T*1 matched axial images through a predetermined number of axial planes includes means for obtaining one or more T*1 matched axial images through each of 1 to 40 axial planes.

17. The system of claim 16 wherein said means for obtaining one or more spin echo, echoplanar image sets comprises:

means for obtaining a number of echo planar in the range of 16-48 echoplanar image sets; and

means for incrementing TE by a predetermined value in each consecutive image set through the axial planes.

18. The system of claim 17 wherein said means for correcting comprises:

means for transferring the images to an offline workstation; and

means for using an image registration technique to correct for in-plane movement.

19. The system of claim 15 wherein said means for identifying one or more regions of interest (ROI) in the corrected images comprises:

means for selecting each of the one or more brain regions as the ROIs prior to acquiring images of the brain; and

means for identifying specific portions of the selected ROIs on images of the brain as those regions in which the median pixel intensity is computed.

20. The system of claim 15 wherein said means for identifying one or more regions of interest in the corrected images comprises:

means for identifying an ROI in a T1 weighted brain image using anatomic boundaries observed in the T1 weighted brain image; and

means for circumscribing a particular brain region shown in the T1 weighted image.

21. The system of claim 15 wherein said means for computing a T2 relaxation time from the median pixel values comprises means for performing a linear least squares regression to compute a single T2 relaxation time measure for each pixel.

22. A method for aiding the detection of ADHD in a subject, the method comprising the steps of:

(a) exposing the subject to one or more pulses of electromagnetic energy so as to cause a time-varying response in the subject;

(b) determining a relaxation time T2 of the time varying response in the subject, wherein the median values of the time varying response in the subject are used to compute the relaxation time T2;

(c) providing an output which can be used to compare the detected relaxation time T2 with a reference relaxation time T2 such that a determination can be made as to whether the subject has ADHD.

23. The method of claim 22 wherein the step of exposing the subject to one or more pulses of electromagnetic energy comprises the step of exciting nuclear spins in the subject in the presence of a steady magnetic field in order to generate a spin resonance signal.

24. The method of claim 22 wherein the step of detecting the relaxation time T2 of the response in the subject comprises the steps of:

(b1) sampling the spin resonance signal in the presence of a magnetic field gradient which is superposed on the steady magnetic field and which has a first direction;

(b2) transforming the sampled resonance signals to generate a distribution;

(b3) performing motion correction on the sampled signals;

(b4) identifying regions of interest;

(b5) selecting median values of the resonance signals in the region of interest; and

(b6) computing a T2 relaxation time based on the median values of the resonance signals in the region of interest.

25. The method of claim 22 wherein the step of computing a T2 relaxation time based on the median values in the region of interest comprises the step of fitting a curve to the median values in the region of interest.

26. The method of claim 25 wherein the step of fitting a curve to the median values in the region of interest includes the step of performing a linear least squares regression technique.

27. The method of claim 26 wherein the region of interest corresponds to at least a portion of a putamen of the subject.

28. An apparatus for aiding the detection of ADHD in a subject, the apparatus comprising:

(a) an NMR device for exposing the subject to one or more pulses of electromagnetic energy so as to cause a time-varying response in the subject;

(b) a detector for detecting in the subject a response to each of the one or more pulses of electromagnetic energy; and

(c) a T2 RT processor for computing median values of the responses detected in the subject and for determining a T2 relaxation time and for providing an output such that the computed T2 relaxation time can be compared with a reference T2 relaxation time.

29. The apparatus of claim 28 further comprising:

means for identifying a region of interest

means for comparing the determined T2 relaxation time with a reference T2 relaxation time.

30. The apparatus of claim 28 wherein said NMR device comprises means for exciting nuclear spins in the subject in the presence of a steady magnetic field in order to generate a spin resonance signal.

31. The apparatus of claim 30 wherein said detector comprises means for sampling the spin resonance signal in the presence of a magnetic field gradient which is superposed on the steady magnetic field and which has a first direction.

32. The apparatus of claim 31 wherein said T2 RT processor comprises:

means for performing motion correction on the sampled resonance signals to provide motion corrected sampled resonance signals;

means for transforming the motion corrected sampled resonance signals to generate an MRI image;

means for computing median pixel intensity values in a region of interest in the MRI image; and

means for determining a T2 relaxation time based on the median pixel intensity values in the region of interest; and

means for fitting a curve to the median pixel intensity values in the region of interest.

33. The apparatus of claim 32 wherein said means for fitting a curve to the median pixel intensity values in the region of interest includes means for performing a linear least squares regression technique.

34. The apparatus of claim 33 wherein the region of interest corresponds to at least a portion of a putamen of the subject.