Fig. 1.

a) The inverse of the sample covariance for a gamma-variate regressor in a design matrix including drift terms. Initially, CNR increases as the area of the response increases, but CNR decreases for long values of the time-to-peak (τ) as the response becomes more difficult to separate from baseline drift. b) Three response shapes with the same CNR based upon differences in sample variance. Optimal sampling continues until the response returns to baseline (dark solid line). If sampling is terminated during the response, then a long response will have no larger CNR than a very short response (gray solid lines).