D-SPECT: A new solid state camera for high speed molecular imaging

Abstract

542 Objectives: For 50 years, physicists have been struggling with the inherent trade-off between spatial resolution and sensitivity associated with radionuclide imaging. A novel technology (D-SPECT) constituting a radical departure from the conventional Anger camera (A-SPECT) has been developed. The aim of this study was to demonstrate the order of magnitude increase in sensitivity and improved spatial resolution of D- SPECT ( Spectrum-Dynamics, Haifa, Israel), as compared to Anger camera SPECT (A-SPECT). Methods: The novel technology employs ten detector columns, tungsten collimators with large holes and an acceptance angle of nearly five times that of the standard parallel-hole collimator in front of cadmium zinc telluride (CZT) crystals. The detector columns rotate and concentrate on the object of interest viewing it from thousands of different angles. The acquired data are processed by innovative iterative algorithms. A NEMA phantom with three 2.7 mCi Co-57 line sources, each of 1 mm diameter and 20cm in length, was employed to demonstrate the inherent resolution of the two systems. With each system, time of acquisition and resolution was measured (FWHM). Mapping of the usable field of view (UFOV) was carried out by imaging a 2.7 mCi Co-57 point source of 1mm moved on a 30 x 29 x 12 cm grid in 150 x 145 x 60 mm steps throughout the UFOV by a robotic arm. Results: For the NEMA phantom, total scan time for D-SPECT was 128 seconds and a resolution of 7 mm in the x-axis and 6.5 mm in the y-axis was demonstrated for the central rod. Total scan time for A-SPECT (GE Millenium VG) with a high resolution collimator was 900 seconds and demonstrated a resolution of 12.6 mm in the x-axis and 13.6 mm in the y-axis for the central rod. Mapping of the UFOV demonstrated an average resolution of 8.4 mm, 7.9 mm and 5.8 mm (std. dev. 2.6mm, 2.7mm, 2.1mm) in the x,y,and z axis. The most centrally located point demonstrated a sensitivity of 1407 counts/µCi/min; as opposed to 160-240 counts/µCi/min range generally observed with standard cameras. Conclusions: D-SPECT has demonstrated an order of magnitude improvement in sensitivity and ~2-fold improvement in spatial resolution. The marked increase in sensitivity and spatial resolution could enable the use of low-dose radiopharmaceuticals, dynamic imaging with absolute measurements of tissue perfusion, as well as parametric representation of molecular function.