Deoxyhemoglobin Concentration Changes and Cerebral Perfusion Imaging
Stenosis, Carotid, Stroke, Neurovascular Disorder
About this trial
This is an interventional diagnostic trial for Stenosis, Carotid
Eligibility Criteria
Inclusion Criteria:
- Clinical suspicion of a disorder that affects the control of brain blood flow.
- Previous investigations that indicate the presence of a vascular disorder including history, physical examination, laboratory testing, and imaging.
Exclusion Criteria:
- Unwilling or unable to co-operate with breathing manoeuvers
- Respiratory or cardiac limitations to breathing at 20 L/min
- Exercise limitation on history of inability to climb one flight of stairs or walk a city block due to shortness of breath
- Medical contra-indications to limited hypercapnia or hypocapnia (known increased intracerebral pressure, metabolic acidosis or alkalosis)
- Standard contraindications for MRI scanning (see consent form)
- Non compliance with prescribed anti-seizure medication
- Ingestion of caffeine, or smoking within 6 hours of the test
- Pregnancy
- Baseline SaO2 < 95%,
- Propensity of right to left shunt: lung AVM, patent foramen ovale, atrial-septal defect, ventricular septal defect.
- History of congestive heart failure, myocardial infarction
- known coronary artery disease, congenital heart lesion, valvular heart lesion other than mild mitral regurgitation, cardiomyopathy with ejection fraction < 50%
Sites / Locations
- Joseph Fisher
Arms of the Study
Arm 1
Experimental
dHb contrast compared to gadolinium contrast imaging
Subjects will be referred for a clinical gadolinium contrast perfusion exam. Gas manipulation will be supplied by a programmable computer-controlled gas delivery system while subjects are in the MRI scanner. In addition to their prescribed clinical scans, two additional scans will be obtained: 1) a structural sequence (, followed by 2) a BOLD-EPI sequence while inducing changes of PO2. PO2 will be held at a baseline of 45-50 mmHg for 60s. For 10 s, the lung PO2 will be transiently raised to peak PO2 of 90-120 mmHg (normoxia) within 2 s transition, and then returned to baseline. Alternatively, the baseline may be at normoxia and the gas challenges will target PO2 of 45-50 mmHg. A total of 4 such ventilatory challenges will be applied over 6 min while maintaining normocapnia.