Clinical value of PET/CT imaging of cerebral blood flow and metabolism in patients with chronic disorders of consciousness

Objective To investigate the value of PET/CT imaging of cerebral glucose metabolism (CGM) and cerebral blood flow (CBF) in evaluating chronic disorders of consciousness (CDC). Methods A total of 10 CDC patients (5 males, 5 females, age (50.9±17.2) years) and 10 healthy controls (5 males, 5 females, age (52.0±10.3) years) from January 2016 to March 2017 were recruited to perform brain PET/CT of CGM and CBF. The brain PET imaging using 13N-Ammonia was performed and followed by 18F-fluorodeoxyglucose (FDG) PET. The mean standardized uptake values (SUVmean) of frontal, parietal, temporal and occipital lobes as well as basal ganglia, thalamus were obtained. The SUVmean of cerebral regions/SUVmean of cerebellum ratios (SUVr) were acquired. The SUVr were compared between the patients and controls. The imaging characteristics of CGM and CBF were investigated, and their relationships with clinical scores were further analyzed. Two-sample t test and Pearson correlation analysis were used to analyze the data. Results The radioactive distribution in the brain of healthy controls was symmetrical. SUVr of cerebral regions in the affected side of patients were significantly lower than those of the controls both in CGM imaging and CBF imaging (t values: 2.90-5.19, all P<0.05). In 10 CDC patients, there were 9 with hypometabolism in basal ganglia and thalamus, 8 with hypometabolism in frontal and parietal lobes, and 7 with hypometabolism in temporal and occipital lobes. At the same time, there were 7 with parietal hypoperfusion and 6 with hypoperfusion in other cerebral regions in the CDC patients. In the frontal, parietal lobes and basal ganglia, the CGM and CBF were both correlated with the clinical scores (r values: 0.473-0.606, all P<0.05). Abnormal metabolism-perfusion patterns were divided into 3 types. Type Ⅰ included 2 patients and their hypometabolism and hypoperfusion were mismatched completely. Type Ⅱ included 3 patients and their hypometabolism and hypoperfusion were matched in frontal, parietal, occipital and temporal lobes, while mismatched in basal ganglia and thalamus. Type Ⅲ included 5 patients and their hypometabolism and hypoperfusion were matched completely. The clinical scores of typeⅠ, Ⅱand Ⅲ were 10.5, 8.3 and 5.6, respectively. Conclusion The PET/CT imaging of cerebral blood flow and metabolism is useful in evaluating the disorders of consciousness. Key words: Consciousness disorders; Positron-emission tomography; Tomography, X-ray computed; Deoxyglucose; Ammonia