A practical sparse-view ultra-low dose CT acquisition scheme for PET attenuation correction

For PET imaging, CT scans are often used for PET attenuation correction and can be acquired at greatly reduced CT radiation dose levels. Techniques as low tube voltage/current have been used to obtain adequate attenuation maps in medium size patients. These techniques usually employ a smooth filter before backprojection to reduce CT image noise which can introduce bias in the conversion from HU to attenuation values. Due to the heaviness of the smooth filter and advancement of CT reconstruction algorithm, the CT dose can be further reduced while providing the same attenuation estimation. In this work, we propose an ultra-low dose CT technique for PET attenuation correction based on sparse-view acquisition. That is, instead of an acquisition of full amount of views, only a fraction of views are acquired. We tested this technique on a 256-slice GE Revolution CT scanner using a whole-body anthropomorphic phantom. An FBP reconstruction with Q.AC on 492 views (10 mA, 120 kV, 0.5 s) and an FBP reconstruction with standard filter on 984 views (150 mA, 120 kV, 0.5s) produced similar attenuation uniformity. We also simulated sparse-view acquisition by skipping views in an interleaved manner from the fully-acquired data. FBP reconstruction with Q.AC filter on simulated 246 views (20 mA, 120 kV, 0.5 s) looks similarly to the reconstruction on acquired 984 views (20 mA, 120 kV, 0.5 s), showing a further potential for dose reduction compared to the full acquisition. With the proposed sparse-view method, this work can bring at least 2× more CT dose reduction to the current Ultra-Low Dose (ULD) PET/CT protocol.