Usage tips

  • Although only a "reference-region" overlay is required in principle, also use a "target-region" overlay corresponding to a high-binding region. At the beginning of analysis ("unix% srtm glm.dat"), the reference region is analyzed to give the chi-squared per degree of freedom and other parameters. This enables one to adjust parameters to minimize the chi2/DOF, which is important when using a time variation in a parameter such as k2a.
  • Add odd "feature" of this GLM is that BP is in the denominator of k2a, so how does one define "BP" (or "DBP" for "dynamic binding potential") from a condition that tests more than one value of k2a? The answer is that the "BP" value corresponding to a condition is found by first calculating the net k2a, which be the sum or difference of several k2a values, and then calculating BP as k2/k2a - 1.  When a gamma function or a sigmoidal function is employed in addition to a constant in challenge design, then the minimum (assuming displacement) DBP value is assigned to the summed condition. So, in the "MRTM2+gamma" example on this page, the condition "AB" outputs a file named BP-AB that contains the value of DBP evaluated at the t=tau location of the time-dependent term. Note that condition "A" gives the baseline BP prior to the challenge, but condition "B" by itself is not useful.
Joseph B. Mandeville, Athinoula A. Martinos Center for Biomedical Imaging at MGH/MIT/Harvard