Low-dose CT Perfusion with Sparse-view Filtered Back Projection in Acute Ischemic Stroke

Published:March 14, 2022DOI:

      Rationale and Objectives

      Radiation dose associated with computed tomography (CT) perfusion (CTP) may discourage its use despite its added diagnostic benefit in quantifying ischemic lesion volume. Sparse-view CT reduces scan dose by acquiring fewer X-ray projections per gantry rotation but is contaminated by streaking artifacts using filtered back projection (FBP). We investigated the achievable dose reduction by sparse-view CTP with FBP without affecting CTP lesion volume estimations.

      Materials and Methods

      Thirty-eight consecutive patients with acute ischemic stroke and CTP were included in this simulation study. CTP projection data was simulated by forward projecting original reconstructions with 984 views and adding Gaussian noise. Full-view (984 views) and sparse-view (492, 328, 246, and 164 views) CTP studies were simulated by FBP of simulated projection data. Cerebral blood flow (CBF) and time-to-maximum of the impulse residue function (Tmax) maps were generated by deconvolution for each simulated CTP study. Ischemic volumes were measured by CBF<30% relative to the contralateral hemisphere and Tmax > 6 s. Volume accuracy was evaluated with respect to the full-view CTP study by the Friedman test with post hoc multiplicity-adjusted pairwise tests and Bland-Altman analysis.


      Friedman and multiplicity-adjusted pairwise tests indicated that 164-view CBF < 30%, 246- and 164-view Tmax > 6 s volumes were significantly different to full-view volumes (p < 0.001). Mean difference ± standard deviation (sparse minus full-view lesion volume) ranged from –1.0 ± 2.8 ml to –4.1 ± 11.7 ml for CBF < 30% and –2.9 ± 3.8 ml to –12.5 ± 19.9 ml for Tmax > 6 s from 492 to 164 views, respectively.


      By ischemic volume accuracy, our study indicates that sparse-view CTP may allow dose reduction by up to a factor of 3.

      Key Words


      ANOVA (analysis of variance), CBF (cerebral blood flow), CBV (cerebral blood volume), CT (computed tomography), CTP (computed tomography perfusion), FBP (filtered back projection), GM (grey matter), ICC (intraclass correlation coefficient), MD (mean difference), MSE (Mean squared error), mTICI (modified thrombolysis in cerebral infarction), NRMSE (normalized root mean squared error), PSNR (peak to signal to noise ratio), ROI (region of interest), SNR (Signal to noise ratio), SSIM (structural similarity index), T0 (delay in contrast arrival time), TDC (time-density curve), Tmax (time-to-maximum of the impulse residue function), WM (white matter)
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