INTRODUCTION: Photon-counting detector (PCD) CT represents a major advancement in CT imaging, offering improved image quality and reduced radiation dose compared to traditional energy-integrating detector (EID) CT. This study compared image quality and radiation dose using a self-controlled approach, while evaluating the impact of patient positioning. METHODS: This retrospective study analyzed data from 200 patients who underwent abdominal CT scans on both EID (Somatom Definition Flash) and PCD (Naeotom Alpha) scanners. After applying inclusion criteria for proper positioning (within ±20 mm) and stable anatomical conditions, 119 patients were included. Radiation doses were assessed using CTDIvol, and image quality was evaluated via CT numbers, noise levels, signal-to-noise ratio (SNR), SNR to dose (SNRD), and contrast-to-noise ratio to dose (CNRD). RESULTS: The study found a median radiation dose reduction of 37 % with PCD CT compared to EID CT (p < 0.05). Image quality assessments revealed significant improvements with PCD CT, including reduced noise levels (up to 31 % in contrast-enhanced organs) and enhanced SNRD (33-51 % increase). CNRD improved by 60-76 %, indicating superior imaging performance of PCD CT. However, 36 % of patients on EID were positioned outside the ±20 mm range, which could adversely affect image quality and radiation dose, underscoring the need for more precise patient positioning. CONCLUSION: This study confirms that PCD CT achieves substantial reductions in radiation dose while enhancing image quality. However, accurate patient positioning is crucial to fully optimize these benefits. Automated tools that ensure proper positioning may be necessary to consistently maintain image quality and reduce radiation exposure. IMPLICATIONS FOR PRACTICE: PCD CT offers improved patient safety and diagnostic imaging. Automated positioning tools are essential to optimize and consistently maintain image quality and minimize radiation exposure.

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