Photon-Counting Detector CT Allows Abdominal Virtual Monoenergetic Imaging at Lower Kiloelectron Volt Level with Lower Noise Using Lower Radiation Dose: A Prospective Matched Study Compared to Energy-Integrating Detector CT.

Our study aimed to assess the image quality of lower kiloelectron volt (keV) level abdominal virtual monoenergetic imaging (VMI) with lower radiation dose on photon-counting detector computed tomography (PCD-CT), in comparison to energy-integrating detector computed tomography (EID-CT). We prospectively included three matched groups, each with 59 participants, to undergo contrast-enhanced abdominal CT scans using EID-CT with full-dose (EID_FD), PCD-CT with full-dose (PCD_FD), and PCD-CT with low-dose (PCD_LD) protocols, respectively. The data of portal-venous phase were reconstructed into VMI at 40, 50, 60, and 70 keV, respectively. The standard deviation of CT values in liver parenchyma was measured as image noise. The signal-to-noise ratio (SNR) of liver parenchyma and contrast-to-noise ratio (CNR) of liver-portal vein were calculated. Three radiologists assessed the image noise, vessel sharpness, and overall quality, and rated the hepatic lesion conspicuity if possible. Our study found that the PCD_LD significantly reduced the radiation dose than EID_FD or PCD_FD (p < 0.001). The noise was significantly decreased by PCD_FD and PCD_LD compared to EID_FD, but SNR values were significantly increased (p ≤ 0.006). The CNR values were significantly increased by PCD_FD and PCD_LD compared to EID_FD in VMI at 40 keV and 50 keV (p ≤ 0.010). The ratings of image noise, vessel sharpness, overall quality, and lesion conspicuity were significantly greater in PCD_FD and PCD_LD compared to EID_FD (p ≤ 0.001). There was no significant difference detected in rating of lesion conspicuity between PCD_FD and PCD_LD (p ≥ 0.259). In conclusion, PCD-CT allows abdominal VMI with lower keV and lower noise using lower radiation dose, to provide better visualization of the hepatic lesions.