Interior photon counting computed tomography for quantification of coronary artery calcium: pre-clinical phantom study

Abstract

Computed tomography (CT) is the reference method for cardiac imaging, but concerns have been raised regarding the radiation dose of CT examinations. Recently, photon counting detectors (PCDs) and interior tomography, in which the radiation beam is limited to the organ-of-interest, have been suggested for patient dose reduction. In this study, we investigated interior PCD-CT (iPCD-CT) for non-enhanced quantification of coronary artery calcium (CAC) using an anthropomorphic torso phantom and ex vivo coronary artery samples. We reconstructed the iPCD-CT measurements with filtered back projection (FBP), iterative total variation (TV) regularization, padded FBP, and adaptively detruncated FBP and adaptively detruncated TV. We compared the organ doses between conventional CT and iPCD-CT geometries, assessed the truncation and cupping artifacts with iPCD-CT, and evaluated the CAC quantification performance of iPCD-CT. With approximately the same effective dose between conventional CT geometry (0.30 mSv) and interior PCD-CT with 10.2 cm field-of-view (0.27 mSv), the organ dose of the heart was increased by 52.3% with interior PCD-CT when compared to CT. Conversely, the organ doses to peripheral and radiosensitive organs, such as the stomach (55.0% reduction), were often reduced with interior PCD-CT. FBP and TV did not sufficiently reduce the truncation artifact, whereas padded FBP and adaptively detruncated FBP and TV yielded satisfactory truncation artifact reduction. Notably, the adaptive detruncation algorithm reduced truncation artifacts effectively when it was combined with reconstruction detrending. With this approach, the CAC quantification accuracy was good, and the coronary artery disease grade reclassification rate was particularly low (5.6%). Thus, our results confirm that CAC quantification can be performed with the interior CT geometry, that the artifacts are effectively reduced with suitable interior reconstruction methods, and that interior tomography provides efficient patient dose reduction.

Optimizing iterative reconstruction for quantification of calcium hydroxyapatite with photon counting flat-detector computed tomography: a cardiac phantom study

“…Future research should investigate the possible dose reductions when using a torso phantom and interior tomography imaging geometry. 57 This geometry can induce further dose reductions, 5 but it requires additional image processing, such as sinogram extension techniques, 58 to reduce the characteristic truncation artifacts originating from the limited field-of-view. Further research is also needed to expand these results for more realistic cardiac PC-FDCT and clinical CT studies with the torso and a moving heart rather than a cylindrical cardiac rod phantom.…”

Self-attention network for weak-supervised learning multi-material decomposition in dual energy CT

“…Dual energy computed tomography (DECT) utilizes two X-ray spectra to obtain two CT datasets and offers the possibility to exploit spectral information for diagnostic purposes. Compared with conventional CT, DECT is able to discriminate and qualify different materials such as soft tissues, bone and contrast agents in clinical application, for calcium density measurement, kidney stone composition determination, fragile plaques characterization and virtual non-contrast imaging [1][2][3][4] . Meanwhile, it is difficult for DECT to obtain multi-material decomposition (MMD) because the number of spectra is limited to two.…”

Virtual monochromatic imaging reduces beam hardening artefacts in cardiac interior photon counting computed tomography: a phantom study with cadaveric specimens

“…In interior computed tomography (CT), the field-ofview (FOV) is focused on the studied organ, e.g., in cardiac imaging applications, the x-ray beam is collimated to the heart (Wang and Yu 2013). This results in a reduced radiation dose to the surrounding tissues (Wang et al 2019, Juntunen et al 2020b. Also, cost savings to the imaging hardware can be attained, as the detector size can be reduced.…”

“…A few studies focus on performing CAC scoring with PCD-CT using human or anthropomorphic phantoms (Symons et al 2019, Juntunen et al 2020b. Symons et al (2019) showed the CAC scoring performance is similar as with the conventional CT, and further, the image quality can be improved with the PCDtechnology.…”