Cranial Computer Tomography with Photon Counting and Energy-Integrated Detectors: Objective Comparison in the Same Patients

Abstract

This study provides an objective comparison of cranial computed tomography (CT) imaging quality and radiation dose between photon counting detectors (PCCTs) and energy-integrated detectors (EIDs). We retrospectively analyzed 158 CT scans from 76 patients, employing both detector types on the same individuals to ensure a consistent comparison. Our analysis focused on the Computed Tomography Dose Index and the Dose-Length Product together with the contrast-to-noise ratio and the signal-to-noise ratio for brain gray and white matter. We utilized standardized imaging protocols and consistent patient positioning to minimize variables. PCCT showed a potential for higher image quality and lower radiation doses, as highlighted by this study, thus achieving diagnostic clarity with reduced radiation exposure, underlining its significance in patient care, particularly for patients requiring multiple scans. The results demonstrated that while both systems were effective, PCCT offered enhanced imaging and patient safety in neuroradiological evaluations.

Keywords: computer tomography; neurocranium; photon counting; radiation dose.

Figure 1

(a) PCCT scan; (b) EID scan with ROI markings of white matter in green and gray matter in red. Please note that macroscopically, there is no difference in the imaging from either scanner for the same patient due to the good quality of both scanners.

Figure 2

Graphical comparison between photon counting detectors (PCCTs) shown in blue and energy-integrated detectors (EIDs) in milligray (mGy). The graphic highlights the differences in the average Computed Tomography Dose Index (CTDI) values. The boxplot visually contrasts the CTDI values for PCCT and EID CT. It reveals that the median CTDI for EID is higher compared to PCCT, and EID’s interquartile range is narrower, suggesting that its CTDI values have less variability than those of PCCT. The maximum CTDI values are observed in PCCT, while the minimum values are found in EID. Whiskers: these lines extend from the box edges to the smallest and largest values in the dataset, excluding any outliers. For the blue box representing PCCT, the whiskers range from approximately 34.6 to 68.3 mGy. In contrast, the whiskers for the orange box representing EID extend from approximately 32.3 to 57.3 mGy. Boxes: these delineate the interquartile range (IQR), encompassing the middle 50% of the data. The blue box stretches from roughly 39.1 to 49.1 mGy. Meanwhile, the orange box spans from about 42.9 to 50.98 mGy. Horizontal line inside boxes: this line represents the median value within the dataset. For PCCT, the median is approximately 41.6 mGy, indicated by the line within the blue box. For EID, the median is around 50.98 mGy, also marked with an “X”.

Figure 3

The boxplot contrasts the Dose-Length Product (DLP) in milligray–centimeters (mGy*cm) between photon counting CT (PCCT) in blue and energy-integrated detectors (EID) in orange. For PCCT, the interquartile range (IQR) spans from approximately 658.57 to 826 mGy*cm, with a median value indicated by the line inside the box at approximately 781 mGy*cm. Notably, there is an outlier at 1184 mGy*cm, which is significantly higher than the rest of the data points. The whiskers extend from about 512 to 1184 mGy*cm, defining the overall spread of the PCCT data. In comparison, EID’s IQR ranges from roughly 679.75 to 748.15 mGy*cm, with a median value marked by the “X” at approximately 769.87 mGy*cm. The EID data also include an outlier at 160 mGy*cm, which is well below the lower quartile. The whiskers for EID show data points ranging from approximately 547.51 to 974.27 mGy*cm. This comparison indicates a wider spread of values for PCCT, while EID presents a narrower distribution of DLP values with the median closer to the third quartile, suggesting a higher average DLP for EID than for PCCT.

Figure 4

Comparison of signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) in photon counting CT (PCCT) and energy-integrated detectors CT (EID CT). The graph illustrates SNR values for white matter (WM) and gray matter (GM) using both PCCT and EID technologies, as well as the CNR values achieved with each technique. The SNR for WM and GM is depicted by the X marks, with horizontal error bars representing the range of measurements. The comparison indicates that WM SNR is higher in PCCT compared to EID. For CNR, PCCT demonstrates a higher value than EID, suggesting better tissue contrast differentiation with PC technology. The data collectively suggest that PCCT may offer superior noise management and tissue contrast, potentially leading to more accurate diagnoses.