Image-based arterial input function estimation for cerebral blood flow measurement on a PET/MR scanner

Objectives The study objective was to accurately measure the arterial input function (AIF) using PET list file and co-registered MR Angiography (MRA) images for cerebral blood flow (CBF) measurement on the GE SIGNA PET/MR.

Methods Six subjects were injected with 15O-H2O (activity levels between 14 to 25 mCi) and scanned on a simultaneous time-of-flight enabled PET/MR scanner (GE SIGNA PET/MR, Waukesha, WI). The time interval of 15O arrival to the carotid artery and before entering the brain tissue was identified from the PET list file. PET angiograms of carotid arteries were reconstructed over this time interval and arteries were masked. PET images were reconstructed every 1s using a 3s sliding window for the first minute and a 5s sliding window for the second minute after the arrival of 15O to the carotid artery. 10s and 30s reconstruction windows were used for 2-4 and 4-10 min after 15O arrival to the carotid artery. AIF was estimated using activity measured from PET images over the arteries’ mask corrected for the MRA-based arterial volume, in order to take into account the effect of spill-over. A separate correction for spill-in effect using brain tissue counts was also applied. CBF and permeability coefficient maps were created using the corrected image-based AIF.

Results The measured CBF from PET images for 5 healthy volunteers was 72±13, 41±10 and 55±11 ml/min/100g for gray matter, white matter and whole brain, respectively. The permeability coefficient was measured at 0.90±0.08, 0.75±0.09 and 0.80±0.08 ml/g for gray matter, white matter and whole brain, respectively.

Conclusions A simultaneous time-of-flight enabled PET/MR was used to estimate AIF with 1s time resolution for the first 2 minutes after 15O arrival to carotid artery. The arteries’ volume was measured with high-resolution MR angiography and both spill-in and spill-over effects were corrected to estimate AIF accurately. CBF and permeability coefficient measurements were consistent with literature values. $$graphic_BE7F4EB6-1451-4A6D-B005-573B40383BF3$$