Abstract
We investigated a projection interpolation method for reconstructing dynamic contrast-enhanced (DCE) heart images from undersampled x-ray projections with filtered backprojecton (FBP). This method may facilitate the application of sparse-view dynamic acquisition for ultralow-dose quantitative computed tomography (CT) myocardial perfusion (MP) imaging. We conducted CT perfusion studies on 5 pigs with a standard full-view acquisition protocol (984 projections). We reconstructed DCE heart images with FBP from all and a quarter of the measured projections evenly distributed over 360°. We interpolated the sparse-view (quarter) projections to a full-view setting using a cubic-spline interpolation method before applying FBP to reconstruct the DCE heart images (synthesized full-view). To generate MP maps, we used 3 sets of DCE heart images, and compared mean MP values and biases among the 3 protocols. Compared with synthesized full-view DCE images, sparse-view DCE images were more affected by streak artifacts arising from projection undersampling. Relative to the full-view protocol, mean bias in MP measurement associated with the sparse-view protocol was 10.0 mL/min/100 g (95%CI: −8.9 to 28.9), which was >3 times higher than that associated with the synthesized full-view protocol (3.3 mL/min/100 g, 95% CI: −6.7 to 13.2). The cubic-spline-view interpolation method improved MP measurement from DCE heart images reconstructed from only a quarter of the full projection set. This method can be used with the industry-standard FBP algorithm to reconstruct DCE images of the heart, and it can reduce the radiation dose of a whole-heart quantitative CT MP study to <2 mSv (at 8-cm coverage).
Highlights
Computed tomography (CT) myocardial perfusion (MP) imaging is a technique used to quantitatively measure myocardial blood flow through tracer kinetic modeling of the timeenhancement curves acquired from dynamic contrast-enhanced (DCE) CT scanning of the heart
Our findings showed that the number of projections required for reconstructing relatively streak-free DCE heart images with the conventional filtered backprojecton (FBP) algorithm could be reduced to 25% of the full-view projection set, as evident by the subtle image difference with respect to the reference full-view protocol
The findings of this study suggest that ultra-low-dose quantitative CT MP measurement can be attained with sparse-view dynamic contrast-enhanced acquisition, provided the missing projections can be properly estimated using a cubicspline interpolation method before image reconstruction
Summary
Computed tomography (CT) myocardial perfusion (MP) imaging is a technique used to quantitatively measure myocardial blood flow (perfusion) through tracer kinetic modeling of the timeenhancement curves acquired from dynamic contrast-enhanced (DCE) CT scanning of the heart. As this technique requires repeated scanning of the heart following a short bolus injection of contrast solution, the associated radiation dose is higher than that required for a standard chest CT scan. The CT detector electronic noise becomes dominant at the extremely low milliampere level, which is difficult to model and correct for with Poisson statistics alone
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