Calculation of CT MTF and NPS using the ACR accreditation phantom

This code enables measurements of CT MTF and NPS from images of an ACR accreditation phantom.

This code is intended to accompany the paper:

S. N. Friedman, G. S. K. Fung, J. H. Siewerdsen, and B. M. W. Tsui. "A simple approach to measure computed tomography (CT) modulation transfer function (MTF) and noise-power spectrum (NPS) using the American College of Radiology (ACR) accreditation phantom," Med. Phys. 40, 051907-1 - 051907-9 (2013).
http://dx.doi.org/10.1118/1.4800795

Purpose:
To calculate the 1D radial (axial) MTF and 3D NPS using CT data of the American College of Radiology (ACR) accreditation phantom.

Input:
Two consecutive scans of the phantom are needed. The program requires a data directory to be selected in which there are only two subdirectories containing only CT slices corresponding to the third module of the phantom. Be careful of partial volume effects with surrounding modules.
i.e., datadir
|-> scan 1 dir
| | -> only module 3 slices
|
|-> scan 2 dir
|-> only module 3 slices