LeedsTor MTF potential inconsistency


I am studying the planar imaging module, trying to calculate some things by hand. When the highcontrast is plotted for the LeedsTOR phantom the graph is not consistent with the 80 % MTF calculation in the report. This is from the plotting part:


plot the high contrast MTF

if high_contrast:
hicon_ax = next(axes)
hc_rois = [roi.mtf for roi in self.hc_rois]
hc_rois.insert(0, 1)
self._plot_highcontrast(hicon_ax, hc_rois, self.hi_contrast_threshold)


However, this causes an inconsistency when MTF 80 % is calculated with this function:

def _mtf(self, x=50): norm = max(roi.mtf for roi in self.hc_rois) ys = [roi.mtf / norm for roi in self.hc_rois] xs = np.arange(len(ys)) f = interp1d(ys, xs) try: mtf = f(x / 100) except ValueError: mtf = min(ys) return float(mtf)

In the attached image the 80 % MTF, I think, should be 4.8 by my calculation.