Low‐dose CT perfusion with projection view sharing

Abstract

Purpose: CT Perfusion (CTP) is a widely used clinical imaging modality. However, CTP typically involves the use of substantial radiation dose (CTDI vol ≥~200 mGy). The purpose of this study is to present a low-dose CTP technique using a projection view-sharing reconstruction algorithm originally developed for dynamic MRI -"K-space Weighted Image Contrast" (KWIC). Methods: The KWIC reconstruction is based on an angle-bisection scheme. In KWIC, a Fourier transform was performed along each projection to form a "k-space"-like CT data space, based on the central-slice theorem. As a projection view-sharing technique, KWIC preserves the spatiotemporal resolution of undersampled CTP data by progressively increasing the number of projection views shared for more distant regions of "k-space". KWIC reconstruction was evaluated on a digital FOR-BILD head phantom with numerically simulated time-varying objects. The numerically simulated scans were undersampled using the angle-bisection scheme to achieve 50%, 25%, and 12.5% of the original dose (288, 144, and 72 projections, respectively). The area-under-the-curve (AUC), time-topeak (TTP), and full width half maximum (FWHM) were measured in KWIC recons and compared to fully sampled filtered back projection (FBP) reconstructions. KWIC reconstruction and dose reduction was also implemented for three clinical CTP cases (45 s, 1156 projections per turn, 1 s/ turn, CTDI vol 217 mGy). Quantitative perfusion metrics were computed and compared between KWIC reconstructed CTP data and those of standard FBP reconstruction. Results: The AUC, TTP, and FWHM in the numerical simzulations were unaffected by the undersampling/dose reduction (down to 12.5% dose) with KWIC reconstruction compared to the fully sampled FBP reconstruction. The normalized root-mean-square-error (NRMSE) of the AUC in the FORBILD head phantom is 0.04, 0.05, and 0.07 for 50%, 25%, and 12.5% KWIC, respectively, as compared to FBP reconstruction. The cerebral blood flow (CBF) and cerebral blood volume had no significant difference between FBP and 50%, 25%, and 12.5% KWIC reconstructions (P > 0.05). Conclusions: This study demonstrates that KWIC preserves perfusion metrics for CTP with substantially reduced dose. Clinical implementation will require further investigation into methods of rapid switching of a CT x-ray source.

Early Diagnosis of Acute Ischemic Stroke by Brain Computed Tomography Perfusion Imaging Combined with Head and Neck Computed Tomography Angiography on Deep Learning Algorithm

“…Besides, the TTP was significantly lower than that in the corresponding healthy side area. The difference was statistically significant ( P < 0.05), indicating that the cerebral perfusion parameters CBF, CBV, MTT, and TTP can predict the occurrence of acute cerebral infarction to a certain extent [ 26 ]. Further analysis showed that the cerebral perfusion parameters CBF, TTP, and MTT in the penumbra were significantly different from the infarct central area and the corresponding contralateral area.…”

Low Dose CT Perfusion With K-Space Weighted Image Average (KWIA)

“…By converting the CT sinogram into “k-space” data, we can adapt many innovative MRI reconstruction algorithms to preserve high spatial and temporal resolutions of undersampled CT data. In a previous study, we introduced an innovative image reconstruction algorithm based on k-space weighted image contrast (KWIC) [ 23 ], [ 41 ] for radiation dose reduction of CTP [ 24 ]. Our preliminary results showed that KWIC was able to reduce the radiation dose of existing CTP methods by 50–75% without compromising imaging speed or quality.…”

“…Based on the central slice theorem, CT sinogram data can be converted to 2D Fourier space (equivalent to k-space in MRI), making it feasible for the adaptation of KWIC to CT perfusion with reduced dose through the sparse sampling of projections followed by view-sharing. In our proof-of-concept study, a specific sparse sampling scheme was employed to achieve up to 75% dose reduction while maintaining both high image quality and quantification accuracy of CTP scans [ 24 ]. However, the implementation of the KWIC algorithm requires rapid-switching pulsed X-ray at pre-specified rotation angles–a hardware capability yet to be implemented by commercial CT vendors.…”

The effect of patellofemoral pain syndrome on patellofemoral joint kinematics under upright weight-bearing conditions

“…In total, 248 and 496 images were acquired in the upright (WB) and supine (NWB) positions, respectively. Two-dimensional projection images were reconstructed into a volumetric CT image using a filtered-backprojection method [ 28 – 30 ] implemented in our in-house reconstruction package, named CONRAD (Radiological Sciences Laboratory, Stanford University, Stanford, CA, USA) [ 31 , 32 ]. A pipeline for the CONRAD software framework for cone-beam imaging is shown in Fig 2 .…”