Theoretic Basis and Technical Implementations of CT Perfusion in Acute Ischemic Stroke, Part 2: Technical Implementations

A−H, CTP maps calculated by using a delay-sensitive deconvolution algorithm that is affected by the delay (T_o) between arterial input and tissue curves. To simulate a range of T_o, we processed the dynamic images of a single section from a CTP study on a patient with brain tumor such that time-versus-enhancement curves from the entire left hemisphere were shifted forward in time by 2 seconds relative to the right hemisphere. The original and time-shifted CTP studies were then processed by Perfusion 3 (GE Healthcare) by using the same arterial input curve and venous curve from the right hemisphere. A and B, CBF maps for the original and the T_o = 2 second study. C and D, The corresponding CBV maps. E and F, The corresponding MTT maps. G and H, The corresponding T_o maps. As T_o increases, CBF decreases and MTT increases while CBV remains unchanged. The deconvolution algorithm is not able to estimate T_o. I−P, CTP maps calculated by using a delay-insensitive deconvolution algorithm that is unaffected by the T_o between arterial input and tissue curves. The original and time-shifted CTP studies of I−P are processed in the same way as A−H except that a delay-insensitive deconvolution algorithm (Perfusion 4, GE Healthcare) is used instead. I and J, The CBF maps for the original and T_o = 2 second study. K and L, The corresponding CBV maps. M and N, The corresponding MTT maps. O and P, The corresponding T_o maps. As T_o increases, CBF and CBV remain relatively unchanged and MTT increases slightly. The deconvolution algorithm is able to detect an increase in T_o, but the estimate of T_o is not accurate.