Technical Solution for an Interactive Functional MR Imaging Examination: Application to a Physiologic Interview and the Study of Cerebral Physiology
Joseph A. Frank, MD1,3,
John L. Ostuni, PhD1,
Yihong Yang, PhD1,
Yoseph Shiferaw, PhD1,2,
Anand Patel, BS1,
Jiangning Qin, PhD1,
Venkata S. Mattay, MD3,
Bobbi K. Lewis, BA1,
Ronald L. Levin, PhD1 and
Jeff H. Duyn, PhD1
1 Laboratory of Diagnostic Radiology Research, Clinical Center (J.A.F., J.L.O., Y.Y., B.K.L., A.P., J.Q., R.L.L., J.H.D.)
2 in Vivo NMR Research Center, National Institute of Neurological Disorders and Stroke (Y.S.)
3 Clinical Brain Disorders Branch, National Institute for Mental Health (J.A.F., V.S.M.), National Institutes of Health, Bldg 10, Rm B1N256, 10 Center Dr, MSC 1074, Bethesda, MD 20892-1074.
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Figure 1. Schematic diagram of the hardware interface between the MR unit and the computational server and display system. BAM = bulk access memory.
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Figure 2. Schematic diagram of four-processor computational server with respect to interactive functional MR imaging system. P1–P4 represent processor numbers. For a blood-oxygenation-level–dependent study, the statistics and display steps take 20 seconds after the completion of the raw data acquisition. For a dynamic contrast-enhanced study, the statistics step takes about 29 seconds, during which the changes in signal intensity for each voxel in the brain are fitted with a gamma variate function to determine the relative cerebral blood volume. The maximum change in signal intensity over time is used to determine the map of time to peak intensity. A search is performed for the arterial input function, and the deconvolution is performed with the singular-value decomposition algorithm to determine the relative cerebral blood flow (29,30). It takes another 17 seconds to display the maps, for a total time of 49 seconds after the completion of the raw data acquisition. DEC = Digital Equipment Corp (computational server), SUN = Sparc 20 Unix workstation.
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Figure 3a. Blood-oxygenation-level–dependent functional MR imaging study. (a) Activated voxels in red are superimposed on top of axial spiral images for the five motor regions (primary sensorimotor, lateral premotor, parietal, supplementary motor, and ipsilateral cerebellum) associated with right-handed, finger-tapping paradigm with a threshold of 4.8. Images were obtained within 20 seconds after completion of acquisition of the raw data. (Fig 3 continues.)
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Figure 3b. Figure 3 (continued). (b) Plot of normalized SEM histograms for all voxel signal intensities over time. In experiment 2, the control subject was asked to move to simulate an uncooperative patient; results were plotted with the registration algorithm for the correspondence of closest gradient voxels applied to the data. Note the spread of the histograms for the second experiment as compared with that for the first and third experiments. (c) Graph displays the degree of rotation detected and corrected with the registration algorithm for the correspondence of closest gradient voxels for each experiment.
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Figure 3c. Figure 3 (continued). (b) Plot of normalized SEM histograms for all voxel signal intensities over time. In experiment 2, the control subject was asked to move to simulate an uncooperative patient; results were plotted with the registration algorithm for the correspondence of closest gradient voxels applied to the data. Note the spread of the histograms for the second experiment as compared with that for the first and third experiments. (c) Graph displays the degree of rotation detected and corrected with the registration algorithm for the correspondence of closest gradient voxels for each experiment.
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Figure 4. Dynamic contrast-enhanced study. Six representative maps from a 36-section whole-brain study performed in a 25-year-old male control subject after administration of 0.1 mmol of gadopentetate dimeglumine as a bolus at 10 mL/sec. A, Relative cerebral blood volume. B, Relative cerebral blood flow. C, Time to peak intensity. These maps were produced from 80 whole-brain spiral images and were displayed in 49 seconds after the completion of the study. Differences in gray and white matter in parts A and B can be clearly appreciated. The high signal intensity observed in part C indicates a delayed arrival (up to 5 seconds) of the bolus in the white matter, the choroid plexus, and the larger vessels such as sinuses compared to that in the arteries.
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Copyright © 1999 by the Radiological Society of North America.
