First experimental results from a prototype rotating slit-slat collimator
We have previously found and validated expressions for slit-slat (SS) geometric efficiency and resolution. These xpressions have suggested that SS may be a good choice for imaging mid-size objects or objects that are long axially since (i) the geometric efficiency increases near the slit as h -1 (instead of h-2for pinhole (PIN) and either decreasing near the collimator for fan-beam (FB) or constant for parallel-beam (PB», where is the distance from a point to the slit plane; (ii) the transverse resolution is comparable to PIN, which is better than FB and PB for small objects; (iii) the axial resolution is worse than PIN since there is no axial magnification; (iv) there is a large axial FOV, unlike PIN, which is likely to be useful when imaging mid-size or long objects; and (v) there is no need for 3D orbits (e.g., helical) since each slice is complete (like PB and FB). We have developed a rotating prototype SS collimator that is capable of single-slit or multi-slit acquisition of data. The design seeks to maximize the height of the slats for improved efficiency. The focal length (FL) is shorter than a typical PIN since increasing the FL requires taller slats to maintain resolution; taller slats reduce geometric efficiency. Construction used a lead rectangular box. Lead slats, spaced with Rohacell, were mounted in an assembly with 3 mm pitch. We have performed preliminary characterization with point sources and acquired micro hot- and cold-rod phantoms and a Deluxe Jaszczak phantom. The projections have been reconstructedusing an MLEM algorithm and show good resolution. ©2008 IEEE.
