Clinical impact of hemodynamic parameter measurement for cerebrovascular disease using positron emission tomography and 15O-labeled tracers

Abstract

Positron emission tomography (PET) measurement of cerebral blood flow and metabolism has been a basic and standard method for evaluation of hemodynamics in patients with cerebral vascular disease (CVD). Despite the recent rapid spread of PET and PET/CT facilities, the number of patient examinations with (15)O-gas PET scans is declining because most facilities are used for cancer studies. They avoid (15)O-gas PET study because it is time consuming and the technique and calculation methods appear to be complicated. However, reconsidering the benefits and usefulness of conventional (15)O-gas PET study is a good opportunity to understand its potential possibility. Physiological evaluation of cerebral perfusion and metabolism provided the basic concept of hemodynamics in impaired circulation and the development of evidence-based medicine in neurosurgical treatment for CVD. This method can be used for two major objectives, clinical examination with a less-invasive simplified method, and quantitative precise measurements with model analysis for research purposes. Both are important for developing further practical and investigational approaches using (15)O-gas PET.

Clinical implication and prognosis of normal baseline cerebral blood flow with impaired vascular reserve in patients with major cerebral artery occlusive disease

“…This result may indicate impairment of hemodynamic auto-regulation in type 2 patients, which would be the cause of CVR reduction [7,15]. A previous study also reported that the most critical factor for a CVR reduction is insufficient collateral circulation from regions with an adequate blood supply [16].…”

“…For 15 O-gas PET, a nasal cannula was placed in the nose of each patient, and an oxygen mask was used to cover the nose and mouth [7,9]. 15 O-gas was administered from the tube, and radioactive gas in the expired air was vacuumed from the mask. Details for the steady-state method were described elsewhere [7].…”

“…In brief, each subject inhaled a single dose of C 15 O (1000 MBq) at first to obtain a cerebral blood volume (CBV) image (mL/100 g). Ten minutes after the C 15 O scan, 15 O 2 (740 MBq/min) and C 15 O 2 (370 MBq/min) were inhaled continuously for approximately 8 min, followed by static data acquisition for 5 min to obtain images of the CBF (mL/100 g/min), OEF, and cerebral metabolic rate of oxygen (CMRO 2 ) (mL/100 g/min). The interval of the two scans was at least 10 min.…”

“…In terms of impaired hemodynamics, patients with normal CBF and reduced CVR are classified as type 2 and those with CBF and CVR reduction as type 3. Overlap of type 3 ischemia and misery perfusion in 15 O-gas PET measurement is relatively high, and the specificity of this type 3 classification for misery perfusion was reported as 88.2% [7]. Since reduced CBF and CVR is also one of the high risk factors for subsequent ischemic stroke [5], type 3 patients should be treated by any surgical treatment such as carotid endoatherectomy, carotid artery stenting (CAS) or extracranialintracranial (EC-IC) bypass surgery.…”

“…Decay of radioactivity from PET and blood data was corrected to the starting point of each scan. After 15 O-gas scans and baseline CBF measurement, 1 g ACZ in 10 mL of saline was injected from a venous line over 1 min, and H 2 15 O-PET was started 10 min after ACZ administration to evaluate changes in CBF. CBF images for the two conditions of pre-and post-ACZ administration were calculated from the H 2 15 O-PET data and arterial input functions, as described previously [9].…”