Figure 4.

Cross-sections of the physical phantoms used in the experiments. (a) Uniform cylinder phantom shifted upwards 1.4 cm from isocenter for the system model validation experiment; (b) enlarged diagram of the spherical tumor phantom positioned inside the half-ring insert for the resolution and contrast study (scanner not shown). See the text for a complete description of the phantom properties. The three cross-hatched circles are solid plastic support structures, the white circles do not contain activity, and the dark circles resemble hot tumors.