Method of generating multiple sets of experimental phantom data.
Currently, 2 types of phantoms (physical and computer generated) are used for testing and comparing tomographic reconstruction methods. Data from physical phantoms include all physical effects associated with the detection of radiation. However, with physical phantoms it is difficult to control the number of detected counts, simulate the dynamics of uptake and washout, or create multiple noise realizations of an acquisition. Computer-generated phantoms can overcome some of the disadvantages of physical phantoms, but simulation of all factors affecting the detection of radiation is extremely complex and in some cases impossible. To overcome the problems with both types of phantoms, we developed a physical and computer-generated hybrid phantom that allows the creation of multiple noise realizations of tomographic datasets of the dynamic uptake governed by kinetic models.


METHODS
The method is phantom and camera specific. We applied it to an anthropomorphic torso phantom with a cardiac insert, using a SPECT system with attenuation correction. First, real data were acquired. For each compartment (heart, blood pool, liver, and background) of the physical phantom, large numbers of short tomographic projections were acquired separately for each angle. Sinograms were built from a database of projections by summing the projections of each compartment of the phantom. The amount of activity in each phantom compartment was regulated by the number of added projections. Sinograms corresponding to various projection times, configurations and numbers of detector heads, numbers of noise realizations, numbers of phantom compartments, and compartment-specific time-activity curves in MBq/cm3 were assembled from the database.


RESULTS
The acquisition produced a database of 120 projection angles ranging over 360 degrees . For each angle, 300 projections of 0.5 s each were stored in 128 x 128 matrices for easy access. The acquired database was successful in the generation of static and dynamic sinograms for which the myocardial uptake and washout was governed by a compartment kinetic model.


CONCLUSIONS
A method has been developed that allows creation of sinograms of physical phantoms with the capacity to control the number of noise realizations, the level of noise, the dynamics of uptake in the phantom compartments, and the acquisition parameters and acquisition modes.
Sitek
Arkadiusz
A
Nuclear Medicine and Functional Imaging Department, E.O. Lawrence Berkeley National Laboratory, Berkeley, California 94720, USA. ASitek@lbl.gov
Reutter
Bryan W
BW
Huesman
Ronald H
RH
Gullberg
Grant T
GT
D000465:Algorithms; D003201:Computers; D003627:Data Interpretation, Statistical; D006801:Humans; D007700:Kinetics; D019047:Phantoms, Imaging; D011874:Radiometry / Q000379:methods*; D012984:Software; D013997:Time Factors; D015899:Tomography, Emission-Computed, Single-Photon / Q000379:methods