Fast and Furious: Optimizing Clinical Blood Pool SPECT

Introduction
Imaging the blood pool activity imaging allows to demonstrate inflammation associated with osteomyelitis, yet traditional planar imaging methods present challenges in accurately identifying focal regions of increased activity. Integrating SPECT imaging into bone scintigraphy protocols would enhance localization accuracy and eliminate superposition artifacts. Therefore, we aimed to optimize a fast SPECT imaging acquisition specifically tailored for blood pool imaging.
Materials & Methods
A Jaszczak phantom filled with 550MBq of 99mTc-MDP, a standard activity for bone scintigraphy, was scanned using various SPECT acquisition setups. The standard bone scintigraphy SPECT consisting of 60p (projections per detector head) of 18 seconds and a matrix size of 128x128 served as baseline. Setup variations included: 30p x 18s, 30p x 9s, 12p x 30s, 12p x 18s, and 8p x 30s. All acquisitions were processed using OSEM iterative reconstruction. The same reconstruction parameters of the baseline SPECT were maintained with 8 iterations and 8 subsets, utilizing a Gaussian filter of 9mm FWHM.
Results
The acquisitions of 30 projections demonstrated good performance in discerning hot rods, while those based on 8 or 12 projections struggled to delineate the hot rods clearly. Cold sphere contrast was reduced notably. A balance between acquisition time and image quality was achieved with 30 projections of 9 seconds, resulting in a total acquisition time of 4.5 minutes.
Conclusion
A SPECT protocol suitable for blood pool imaging was obtained, showcasing a preference for acquiring more projections using shorter acquisition times over a limited number of projections. The protocol offers improved accuracy in localizing inflammatory sites over traditional planar imaging, while still being able to image the blood pool activity. Because of this, the protocol was introduced in clinical routine.