Method and apparatus for providing pulses inhalation of 17 O 2 for magnetic resonance imaging of cerebral metabolism
First Claim
1. A method of administering 17O2 to a patient for magnetic resonance imaging a region of interest remote from the patient'"'"'s lungs, comprising:
- providing 16O2 to the patient by inhalation;
a ventilator applying a pulse of 17O2 by inhalation comprising an approximately step increase in 17O2, a duration of said pulse selected so as to be shorter than a diffusion time lag of metabolized H217O in the patient from the patient'"'"'s lungs to the region of interest; and
imaging the region of interest during the duration of said pulse.
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Accused Products
Abstract
Prior approaches have delivered 17O2 to a subject by inhalation, but the relationship between local signal changes and metabolism has been complicated by H217O created in non-cerebral tissues. During a brief pulse of 17O2 inhalation, this arterial input function for H217O is negligible due to convective transport delays. Additional delays in the arterial input function due to restricted diffusion of water makes pulsed inhalation of 17O2 even more effective. Accordingly, ventilator system are provided to deliver 17O2 as a brief pulse to a subject. Subsequent MR imaging demonstrates delayed appearance of H217O in the cerebral ventricles, suggesting that the arterial input function of H217O is delayed by restricted water diffusion in addition to convective transit delays. Delivery as a brief pulse therefore offers significant advantages in relating MR signal changes directly to metabolism.
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Citations
12 Claims
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1. A method of administering 17O2 to a patient for magnetic resonance imaging a region of interest remote from the patient'"'"'s lungs, comprising:
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providing 16O2 to the patient by inhalation; a ventilator applying a pulse of 17O2 by inhalation comprising an approximately step increase in 17O2, a duration of said pulse selected so as to be shorter than a diffusion time lag of metabolized H217O in the patient from the patient'"'"'s lungs to the region of interest; and imaging the region of interest during the duration of said pulse. - View Dependent Claims (2, 3, 4, 5, 6)
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7. A ventilation apparatus, comprising:
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means for selecting either a source of 16O2 or 17O2; an inhalation pump for pumping the selected source to a patient at a first pressure; an exhalation pump for pumping exhaled gases at a second pressure; and means for controlling said selecting means so as to apply a pulse of 17O2 to the patient, said pulse comprising an approximately step increase in 17O2 for a duration selected by the means for controlling said selecting means so as to be shorter than a diffusion time lag of metabolized H217O in the patient from the patient'"'"'s lungs to a region of interest in the patient'"'"'s body, said region of interest being remote from the patient'"'"'s lungs. - View Dependent Claims (8, 9, 10, 11, 12)
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Specification