Design of a novel multi slit-slat collimator for a conventional gamma camera

Objectives Previously we have investigated design of a multi-slit-slat collimator system to be used with an idealized cylindrical detector system with 1mm intrinsic resolution to provide optimized system sensitivity and resolution by allowing mixed multiplxed (MX) and non-MX data to be acquired. Now we have designed a slit-slat collimator for a standard gamma camera for application to brain SPECT which will soon be available to us.

Methods In the transaxial direction the collimator designed consists of up to 7 slits with an opening angle of 105 degrees, slit width 1.6mm and focal length of 100mm. In the axial direction the collimator consists of multiple parallel slats with slat height, spacing and thickness of 95, 3.7 and 0.25mm respectively. A shutter system is included in the design to allow one or more of the slits to be covered in order to study the effect of multiplexing as well as truncation of the object FOV.

Results The system resolution for a point source at the centre of the FOV is 7mm in all directions and system sensitivity with 3 slits uncovered (non-MX case) is 1.2x10-4. In comparison to a standard fan-beam collimator used for brain SPECT, this provides an improvement in both resolution (9mm) and sensitivity (0.83×10-4). Our simulations show that by using a combination of MX and non-MX data an increase in SNR of 15% can be obtained. Further optimization of the system is possible by permitting partial truncation of the data which has proven to be beneficial especially for studies of sub-cortical structures.

Conclusions The designed system facilitates acquisition with varied multiplexing on a standard gamma camera, with performance superior to fan-beam collimation and potential for further improvements.