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This feature is fully documented on our Detector page.
This has been implemented. For more information, see the phg section of the user's guide for using positron range modelling.
| The original version of SimSET assumed that the angle between the direction vectors of the photons produced by a positron-electron annihilation was exactly 180°. In fact, there is a slight deviation from collinearity caused by the momentum of the positron-electron pair relative to the tomograph reference frame.
Model the deviation from non-collinearity as a Gaussian random variable, theta, with mean m, m = 0, and standard deviation s, s = 0.0037059 radians (= 0.5 degrees FWHM, Phelps and Hoffman, JNM 17:8:757-8.) Choose the location of the annihilation and initial photon directions as before. However, before doing any tracking or forcing of the photons, randomly choose one of the photons (i.e., generate a random number, r, and if r < 0.5 then choose the pink photon, else choose the blue photon). Determine theta as specified above, and calculate a deflection angle as follows: mu = cos(theta). Use mu to compute a new direction for the chosen photon. |
This feature is full documented on our Collimator page.
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