How Gamma Camera's Head-Tilts Affect Image Quality of a Nuclear Scintigram?

Mechanical calibration of camera plays an important role in nuclear imaging to acquire a more qualified and quantized scintigram. The objective of this work was to quantitatively evaluate planar resolution and sensitivity of a tilted Anger camera using a Monte Carlo simulation. For this purpose, spatial resolution and system sensitivity of a tilted-head, LEHR collimated gamma-camera were evaluated using Monte Carlo simulation. To do so, tilt-angle of camera’s head was considered to vary from -10 to 10 degrees from the baseline. The Monte Carlo simulated data were validated by means of a comparison with experimental data. In addition, the performance of the system was analyzed both in spatial and frequency domains. Spatial resolution, in terms of FWHM, for simulated and measured point-spread functions (PSFs), at the rest-position has a value of 7.22 mm and 7.43 mm, respectively. The results also show that the spatial resolution monotonically increases as the absolute value of tilt angles increases, up to a degradation factor of 2.02 for a typical scintillation-camera. System sensitivity exhibits a constant behavior for all tilt-angles with a maximum statistical fluctuation of 2%. While a head tilt has no effect on the sensitivity of the camera, it can result in a poor and spatially variable planar spatial resolution and contrast of the images provided by the tilted-scanner.