NeuroPhysics

EVALUATION OF THE HIGH RESOLUTION NEUROFOCUS SPECT DEVICE FOR SMALL ANIMAL IMAGING
 
J. P. Seibyl*, H. A. Stoddart, D. Martin, E. Smith, G. Wisniewski and H. F. Stoddart, Institute for Neurodegenerative Disorders, New Haven, CT and NeuroPhysics Corp, Shirley, MA.

Objective: Available small animal SPECT systems provide high resolution tomographic resolution at the cost of poor count sensitivity limiting the ability to perform dynamic studies for in vivo drug occupancy studies. The NeuroFocus is a novel, brain-dedicated single photon imaging device utilizing 12 scanning detector heads fitted with 1 inch NaI crystals and 800 hole focused collimators with the potential for use in small animal imaging based on ultrahigh resolution while maintaining high count rate response. A series of evaluations were performed to assess the capacity of this device.

Methods: A fillable capillary line (0.86 mm inner tube diameter) source phantom was constructed for determination of spatial resolution in the center and at the periphery of the field in x, y and z in air and water (15 cm diameter). Measurements of the FWHM of the line spread function were determined for 99mTc in all geometries. In a separate experiment, a distributed source phantom (1400 ml total volume) was filled with 3.2 mCi 99mTc and serially imaged to determine the reconstructed count rate response and linearity of the signal over a wide range of counts. Finally, a 350 gm Sprague-Dawley rat received a 300 μCi bolus injection of the dopamine transporter ligand 123-I β-CIT and imaged at 4 hours for evaluation of striatal brain uptake.

Results: FWHM measures with subtraction of the capillary tube diameter are summarized in Table 1. Reconstructed count rate response was 10,000 cps/μCi/ml with excellent linearity over the range of activities images (r= 0.98, p=0.0001). Rodent brain images of the DAT ligand cleanly separate left and right striatal structures.

Conclusion: These preliminary data suggest the NeuroFocus high-resolution single photon device provides excellent spatial resolution while maintaining good count rate capacity and is suitable for small animal imaging and high-resolution human brain imaging.

FWHM (mm)