Calibration of a multi-pinhole SPECT system without pre-knowledge of point source markers 3D coordinates

A single photon emission computed tomography system comprising:

• a machine-readable storage medium;
• and
• a system controller connected to and in communication with a gamma camera detector provided with a pinhole collimator and the machine-readable storage medium, wherein the machine-readable storage medium is encoded with a computer program code such that, when the computer program code is executed by the system controller, the system controller performs a method for reconstructing single photon emission computed tomography data acquired with a pinhole collimator without pre-knowledge of 3D coordinates of point source markers, the method comprising:
• reiteratively applying a downhill simplex process to determine a first parameter and a second parameter;
• keeping a lowest vertex from a previous iteration;
• randomly resetting starting values for rest vertexes for a current iteration, wherein the lowest vertex is prevented from performing a last iteration;
• determining whether at least one of a first threshold and a second threshold has been reached, wherein the first threshold comprises a cost function value and the second threshold comprises a predetermined number of iterations of the downhill simplex process;
• acquiring projection data from the first parameter;
• determining locations of 2D data from the projection data of the first parameter;
• and
• estimating the second parameter by fitting the forward projected data locations to the measured data locations.

A machine-readable storage medium, tangibly embodying a program of instructions executable by a processor to perform method steps for reconstructing single photon emission computed tomography data acquired with a pinhole collimator without pre-knowledge of 3D coordinates of point source markers, the method comprising:

• reiteratively applying a downhill simplex process to determine a first parameter and a second parameter;
• keeping a lowest vertex from a previous iteration;
• randomly resetting starting values for rest vertexes for a current iteration, wherein the lowest vertex is prevented from performing a last iteration;
• determining whether at least one of a first threshold and a second threshold has been reached, wherein the first threshold comprises a cost function value and the second threshold comprises a predetermined number of iterations of the downhill simplex process;
• acquiring projection data from the first parameter;
• determining locations of 2D data from the projection data of the first parameter;
• and
• estimating the second parameter by fitting the forward projected data locations to the measured data locations.