Image quality and dose reduction with photon counting detector CT: Comparison between ultra-high resolution mode and standard mode using a phantom study - 08/04/25

Doi : 10.1016/j.diii.2025.03.009

Joël Greffier ^a,^⁎ , Claire Van Ngoc Ty ^b, Skander Sammoud ^a, Cédric Croisille ^c, Jean-Paul Beregi ^a, Djamel Dabli ^a, Isabelle Fitton ^b
^a IMAGINE UR UM 103, Montpellier University, Department of Medical Imaging, Nîmes University Hospital, 30029 Nîmes, France
^b Université Paris Cité, 75006 Paris, France; Department of Radiology, Assistance Publique-Hôpitaux de Paris, Hôpital Européen Georges Pompidou, 75015 Paris, France
^c Department of Computed Tomography, Siemens Healthineers AG, 91301 Forchheim, Germany

^⁎Corresponding author.

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Highlights

•	Image quality and dose reduction obtained with a commercially available photon-counting detector computed tomography (PCCT) system were compared between the ultra-high resolution mode and the standard mode using a phantom.
•	Using PCCT, the ultra-high resolution mode reduces the image noise and improves the detectability of simulated abdominal and bone lesions without altering the spatial resolution by comparison with the standard mode.
•	By comparison with the standard mode, the images obtained with the ultra-high resolution mode may offer great potential for dose reduction in patients undergoing abdominal and/or bone PCCT examination.

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Abstract

Purpose

The purpose of this study was to assess the image quality and dose reduction potential of ultra-high resolution (UHR) mode compared with standard mode, both available on a commercial photon-counting detector computed tomography (PCCT) scanner.

Materials and methods

Images were acquired on a PCCT with a phantom using UHR and standard modes at three dose levels (3/6/12 mGy). Raw data were reconstructed using soft tissue (Br36) and bone (Br68) reconstruction kernels and 0.4-mm slice thickness. Noise power spectrum (NPS) and task-based transfer function (TTF) were calculated to assess noise magnitude, noise texture (f_av), and spatial resolution (f₅₀), respectively. Detectability indexes (d’) were calculated to model the detection of two abdominal lesions for a Br36 soft tissue reconstruction kernel and three bone lesions for a Br68 bone reconstruction kernel.

Results

At all dose levels, noise magnitude values were lower with UHR than with standard mode (mean difference, -18.0 ± 2.6 [standard deviation (SD)] % for Br36 and -33.9 ± 2.3 [SD] % for Br68). Noise texture was lower with UHR than with standard mode (mean difference, -4.2 ± 0.9 [SD] % for Br36 and -16.0 ± 1.8 [SD] % for Br68). For the solid water insert and Br36, f₅₀ values were similar for both UHR (0.34 ± [SD] 0.04 mm^-1) and standard (0.33 ± [SD] 0.04 mm^-1) modes. For Br68, f₅₀ values were greater with UHR than with standard for iodine (mean difference, 18.5 ± 1.9 [SD] %) and bone (11.7 ± 5.7 [SD] %) inserts. For all simulated lesions, d’ values were greater with UHR than with standard and, compared to standard, the dose reduction potential with UHR was -32.9 ± 0.0 (SD) % for abdominal lesions and -68.7 ± 3.2 (SD) % for bone lesions.

Conclusion

Compared to the standard mode, the UHR mode offers lower noise levels and better detectability of abdominal and bone lesions, paving the way for potential dose reduction with PCCT in clinical applications.

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Keywords : Dose optimization, Phantom imaging, Photon counting CT, Task-based image quality assessment, Ultra-high resolution