Figure5.3 Model collimator response ("beam profile") of the HEXTE field-of-view, normalized to the peak (on-axis) value. (a) Two-dimensional response, with the hexagonal cells oriented horizontally (point-to-point); contour levels are at 0 (dashed line), 10, 20...100% of peak. (b) Cross sections of the collimator response along the point-to-point (solid line) and flat-to-flat (dotted line) diameters across the hexagonal cells.§