The diagnostic value of ~ (13)N-ammonia PET in ischemic cerebrovascular disorders

Objective To evaluate the feasibility of ~ 13N-ammonia PET in diagnosing ischemic cerebrovascular disorders. Methods A total of 25 subjects were investigated. Five healthy volunteers served as normal control. Twenty patients included 13 with transient ischemic attack(TIA), 6 with brain infarction and 1 with moyamoya disease. 740～925 MBq of ~ 13N-ammonia was injected intravenously. 3～5 min later, PET imaging was performed with T+E 2D acquisition with Siemens ECAT EXACT HR~+ PET scanner. Image analysis was done by visual and semiquantitative estimating. Standardized uptake value(SUV) was measured in mirror regions of cerebrum with autocopy methods. Nine patients underwent drug stress with oral acetazolamide (ACZ). Images were compared before and after oral ACZ intervention. Results Physiological brain uptake with SUV ratio of 0.99±0 15 (n=5, left/right) was observed in healthy volunteers. L/N0.85 was defined as hypoperfusion whereas L/N0.7 was infarct area(L/N represents the lesioned to normal in the symmetric area of cerebral cortex). Of the 20 patients, the positive rate in PET was 53.8%. Compared with other modalities, the positive rate with MRI and CT was 25.0% and 16.7%(P0.05). Twenty-nine hypoperfusion focuses were found in TIA cases, the average SUV was 1.78±0.41 which was much lower than that of normal controls (2.51±0.52,t=8.78,P0 05),13 infarct focuses were found in patients with brain infarction. The average SUV was 1.05±0.23 which was significantly lower than that of normal controls and TIA patients(t=5.9,P0.001). The number of identified focus was increased from 29 to 35 after oral ACZ stress, positive rate for lesion detection was increased by 17 1%; which enabled positive rate for cases to escalate from 53.8% to 62.5%. The SUV ratio in rest imaging was 0.87±0.11,the mean SUV was decreased to 0.77±0.07 in focuses after stress(t=6.47,P0.05). Conclusions The results show that PET with ~ 13N-ammonia as radioactive tracer was a safe and noninvasive, sensitive and accurate functional imaging modality for brain perfusion. The oral ACZ stress is a safe, simple and reliable diagnostic method for ischemic cerebrovascular disorders. It is of important uses in detecting the potential reserve of cerebral blood flow.