Quantification of temporal resolution improvement factor in SMART-RECON based time-resolved C-arm Cone beam computed tomography angiography (TR-CBCTA)

Abstract

In a recently published paper by Li et al (2018 Phys. Med. Biol. 63 075001), reconstruction parameters were optimized for the so-called synchronized multiArtifact reduction with tomographic reconstruction (SMART-RECON) method to enable time-resolved Cone beam computed tomography angiography (TR-CBCTA) from a single short-scan CBCT data set. However, the paper did not quantitatively address how much temporal resolution can be improved by using the SMART-RECON algorithm in TR-CBCTA. The purpose of this note was to present a method to quantify this temporal resolution improvement factor and to use that method to quantify the improvement in temporal resolution using SMART-RECON and optimized reconstruction parameters. In the method proposed in this note, the potential temporal blurring caused by SMART-RECON was modeled as a convolution between a temporal Gaussian blurring kernel and the ground truth temporal enhancement curve. The width parameter of the resulting Gaussian blurring kernel was used as a surrogate metric for temporal resolution to quantify the achievable temporal resolution for the conventional filtered backprojection (FBP) and SMART-RECON methods. The ratio of the surrogate temporal resolutions for the two reconstruction methods was calculated to quantify the factor of temporal resolution improvement. The quantitative results show that the temporal resolution is improved by a factor of 4.5 using SMART-RECON compared with FBP.

An Enhanced SMART-RECON Algorithm for Time-Resolved C-Arm Cone-Beam CT Imaging

“…As shown in Fig. 6, for all vessel segments, SMART-RECON provides an achievable frame rate of about 1 fps which has been quantified to be 4.5 times better than that of the conventional FBP reconstruction [23]. For eSMART-RECON, the achievable frame rate is about 4 fps measured at proximal-end artery and about 7.5 fps measured at middle, distalend artery or vein.…”

“…Specifically, up to five image frames with clear temporal variation can be reconstructed without introducing limited-view artifacts from a single short-scan data acquisition. Therefore, the best performance of the current SMART-RECON is to obtain a temporal resolution of about one frame per second (1.0 fps) which is 4.5 times better than that offered by the conventional FBP reconstruction [23]. With the constraint of a single short-scan cone beam CT acquisition, it would be very difficult to further improve of temporal resolution using SMART-RECON since it is difficult to balance the need to eliminate limited-view artifacts while maintaining the needed temporal fidelity simultaneously.…”

“…For a given ground truth temporal curve, the measured temporal curve from the reconstructed image volumes can be considered as the convolution between the ground truth curve and Gaussian function with a kernel width, σ w , as shown in [23]. After the optimal width is determined, the achievable frame rate can then be calculated in the following equation.…”