Dynamic Reconstruction with Statistical Ray Weighting for C-Arm CT Perfusion Imaging

Abstract—Tissue perfusion measurement using C-arm angiography systems is a novel technique with potential high benefit for catheter-guided treatment of stroke in the interventional suite. However, perfusion C-arm CT (PCCT) is challenging: the slow C-arm rotation speed only allows measuring samples of contrast time attenuation curves (TACs) every 5 – 6 s if reconstruction algorithms for static data are used. Furthermore, the peaks of the tissue TACs typically lie in a range of 5 – 30 HU, thus perfusion imaging is very sensitive to noise. Recently we presented a dynamic, iterative reconstruction (DIR) approach to reconstruct TACs described by a weighted sum of linear spline functions with a regularization based on joint bilateral filtering (JBF). In this work we incorporate statistical ray weighting into the algorithm and show how this helps to improve the reconstructed cerebral blood flow (CBF) maps in a simulation study with a realistic dynamic brain phantom. The Pearson correlation of the CBF maps to ground truth maps increases from 0.85 (FDK), 0.87 (FDK with JBF), and 0.90 (DIR with JBF) to 0.92 (DIR with JBF and ray weighting). The results suggest that the statistical ray weighting approach improves the diagnostic accuracy of PCCT based on DIR. I

Iterative denoising algorithms for perfusion C-arm CT with a rapid scanning protocol

Tissue perfusion measurement using C-arm angiography sys-tems capable of CT-like imaging (C-arm CT) is a novel tech-nique with potentially high benefit for catheter-guided treat-ment of stroke in the interventional suite. New rapid scan-ning protocols with increased C-arm rotation speed enable fast acquisitions of C-arm CT volumes and allow for sampling the contrast flow with improved temporal resolution. How-ever, the peak contrast attenuation values of brain tissue lie typically in a range of 5–30 HU. Thus perfusion imaging is very sensitive to noise. In this work we compare different denoising algorithms based on the algebraic reconstruction technique (ART) and introduce a novel denoising technique, which requires only iterative filtering in volume space and is computationally much more attractive. Our evaluation using a realistic digital brain phantom shows that all methods im-prove the perfusion maps perceptibly compared to Feldkamp-type (FDK) reconstruction. The volume-based technique per-forms similarly to the ART-based methods: the Pearson cor-relation of reference and reconstructed blood flow maps in-creases from 0.61 for the FDK method to 0.81 for the best ART method and to 0.79 for the volume-based method. Fur-thermore results from a canine stroke model study are shown. Index Terms — Perfusion imaging, iterative reconstruc-tion, C-arm CT, stroke treatmen

Quantitative Liver Tumor Blood Volume Measurements by A C-Arm Ct Post-Processing Software Before and After Hepatic Arterial Embolization Therapy: Comparison with Mdct Perfusion

PURPOSE We aimed to determine whether the C-arm computed tomography (CT) blood volume (BV) imaging of hepatic tumors performed with a new prototype software is capable of measuring the BV changes in response to hepatic arterial treatments and to validate these quantitative measurements with commercially available multidetector computed tomography (MDCT) perfusion software. METHODS A total of 34 patients with hepatic tumors who underwent either radioembolization (RE, n=21) or transarterial chemoembolization (TACE, n=13) were included in the study. Using a prototype software by Siemens Healthcare, 74 C-arm CT BV measurements were obtained in both pre- and postembolization settings (three patients had additional BV measurements before and after work-up angiography for RE). Ten of 34 patients underwent MDCT perfusion study before embolization, enabling comparison of BV measurements using C-arm CT versus MDCT methods. RESULTS The mean BV of 14 tumor lesions in 10 patients on MDCT perfusion was highly correlated with the BV values on C-arm CT (r=0.97, P < 0.01). The BV values obtained by C-arm CT decreased from 140.6 +/- 28.3 mL/1000 mL to 45.9 +/- 23.5 mL/1000 mL after TACE (66.37% reduction) and from 175.6 +/- 29.4 mL/1000 mL to 84.1 +/- 22.5 mL/1000 mL after RE (53.75% reduction). DISCUSSION Quantitative BV measurement with C-arm CT is well-correlated with MDCT BV measurements, and it is a promising tool to monitor perfusion changes during hepatic arterial embolization.Wo