Abstract
ObjectivesPhoton-counting detector CT (PCD-CT) promises a leap in spatial resolution due to smaller detector pixel sizes than implemented in energy-integrating detector CTs (EID-CT). Our objective was to compare the visualization of smallest bone details between PCD-CT and EID-CT using a mouse as a specimen.Materials and methodsTwo euthanized mice were scanned at a 20-slice EID-CT and a dual-source PCD-CT in single-pixel mode at various CTDIVol values. Image noise and signal-to-noise ratio (SNR) were evaluated using repeated ROI measurements. Edge sharpness of bones was compared by the maximal slope within CT value plots along sampling lines intersecting predefined bones of the spine. Two readers evaluated bone detail visualization at four regions of the spine on a three-point Likert scale at various CTDIVol’s. Two radiologists selected the series with better detail visualization among each of 20 SNR-matched pairs of EID-CT and PCD-CT series.ResultsIn CTDIVol-matched scans, PCD-CT series showed significantly lower image noise (NoiseCTDI=5 mGy: 16.27 ± 1.39 vs. 23.46 ± 0.96 HU, p < 0.01), higher SNR (SNRCTDI=5 mGy: 20.57 ± 1.89 vs. 14.00 ± 0.66, p < 0.01), and higher edge sharpness (Edge Slopelumbar spine: 981 ± 160 vs. 608 ± 146 HU/mm, p < 0.01) than EID-CT series. Two radiologists considered the delineation of bone details as feasible at consistently lower CTDIVol values at PCD-CT than at EID-CT. In comparison of SNR-matched reconstructions, PCD-CT series were still considered superior in almost all cases.ConclusionsIn this head-to-head comparison, PCD-CT showed superior objective and subjective image quality characteristics over EID-CT for the delineation of tiniest bone details. Even in SNR-matched pairs (acquired at different CTDIVol’s), PCD-CT was strongly preferred by radiologists.Key Points• In dose-matched scans, photon-counting detector CT series showed significantly less image noise, higher signal-to-noise ratio, and higher edge sharpness than energy-integrating detector CT series.• Human observers considered the delineation of tiny bone details as feasible at much lower dose levels in photon-counting detector CT than in energy-integrating detector CT.• In direct comparison of series matched for signal-to-noise ratio, photon-counting detector CT series were considered superior in almost all cases.
Highlights
Computed tomography (CT) is the most widely used tomographic imaging modality worldwide due to its short acquisition times, high technical reliability, and ubiquitous1 3 Vol.:(0123456789)European Radiology availability
This study reports our comprehensive analyses of bone detail visualization on a novel dual-source Photon-counting detector CT (PCD-CT) in comparison with a modern energy-integrating detector CTs (EID-CT) at various CTDIVol values using a mouse as a specimen
Image noise was significantly lower in photon-counting detectors (PCDs)-CT reconstructions compared to energy-integrating detectors (EID)-CT reconstructions at all CTDIVol values
Summary
Computed tomography (CT) is the most widely used tomographic imaging modality worldwide due to its short acquisition times, high technical reliability, and ubiquitous1 3 Vol.:(0123456789)European Radiology availability. Detecting charge separation in semiconductors induced by X-ray photons, PCDs directly convert X-rays into an electric signal This confers substantial theoretical benefits such as improved spatial resolution due to smaller detector pixel size, elimination of electronic noise, and intrinsic spectral sensitivity [1, 2]. A single-pixel acquisition mode is routinely available on the latest PCD-CT models. This mode discerns individual detector pixels and should considerably improve visualization of finest anatomic details such as in bone or in the lungs beyond that reported for earlier PCD-CT prototypes which aggregated two pixels for ultra-high-resolution (UHR) acquisitions [3, 4]. Uncertainty remains, to what extent this SNR advantage translates into improved visualization of anatomic details and whether there is a dose-dependency of this effect
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