Low-dose high-resolution chest CT in adults with cystic fibrosis: intraindividual comparison between photon-counting and energy-integrating detector CT

Photon-counting detectors offer the potential for improved image quality for brain CT but have not yet been evaluated in vivo. The purpose of this study was to compare photon-counting detector CT with conventional energy-integrating detector CT for human brains. Radiation dose-matched energy-integrating detector and photon-counting detector head CT scans were acquired with standardized protocols (tube voltage/current, 120 kV(peak)/370 mAs) in both an anthropomorphic head phantom and 21 human asymptomatic volunteers (mean age, 58.9 ± 8.5 years). Photon-counting detector thresholds were 22 and 52 keV (low-energy bin, 22-52 keV; high-energy bin, 52-120 keV). Image noise, gray matter, and white matter signal-to-noise ratios and GM-WM contrast and contrast-to-noise ratios were measured. Image quality was scored by 2 neuroradiologists blinded to the CT detector type. Reproducibility was assessed with the intraclass correlation coefficient. Energy-integrating detector and photon-counting detector CT images were compared using a paired t test and the Wilcoxon signed rank test. Photon-counting detector CT images received higher reader scores for GM-WM differentiation with lower image noise (all P < .001). Intrareader and interreader reproducibility was excellent (intraclass correlation coefficient, ≥0.86 and 0.79, respectively). Quantitative analysis showed 12.8%-20.6% less image noise for photon-counting detector CT. The SNR of photon-counting detector CT was 19.0%-20.0% higher than of energy-integrating detector CT for GM and WM. The contrast-to-noise ratio of photon-counting detector CT was 15.7% higher for GM-WM contrast and 33.3% higher for GM-WM contrast-to-noise ratio. Photon-counting detector brain CT scans demonstrated greater gray-white matter contrast compared with conventional CT. This was due to both higher soft-tissue contrast and lower image noise for photon-counting CT.

This study aims to investigate the qualitative and quantitative image quality of low-dose high-resolution (LD-HR) lung CT scans acquired with the first clinical approved photon counting CT (PCCT) scanner. Furthermore, the radiation dose used by the PCCT is compared to a conventional CT scanner with an energy-integrating detector system (EID-CT). Twenty-nine patients who underwent a LD-HR chest CT scan with dual-source PCCT and had previously undergone a LD-HR chest CT with a standard EID-CT scanner were retrospectively included in this study. Images of the whole lung as well as enlarged image sections displaying a specific finding (lesion) were evaluated in terms of overall image quality, image sharpness and image noise by three senior radiologists using a 5-point Likert scale. The PCCT images were reconstructed with and without a quantum iterative reconstruction algorithm (PCCT QIR+/−). Noise and signal-to-noise (SNR) were measured and the effective radiation dose was calculated. Overall, image quality and image sharpness were rated best in PCCT (QIR+) images. A significant difference was seen particularly in image sections of PCCT (QIR+) images compared to EID-CT images (p < 0.005). Image noise of PCCT (QIR+) images was significantly lower compared to EID-CT images in image sections (p = 0.005). In contrast, noise was lowest on EID-CT images (p < 0.001). The PCCT used significantly less radiation dose compared to the EID-CT (p < 0.001). In conclusion, LD-HR PCCT scans of the lung provide better image quality while using significantly less radiation dose compared to EID-CT scans.

The first-generation photon-counting detector CT was recently introduced into clinical practice and represents a promising innovation in high-resolution CT imaging. The purpose of this study was to assess the image quality of ultra-high-resolution photon-counting detector CT compared with energy-integrating detector CT and to explore different reconstruction kernel sharpness levels for the evaluation of intracranial aneurysms. Ten patients with intracranial saccular aneurysms who had previously undergone conventional energy-integrating detector CT were prospectively enrolled. CT angiograms were acquired on a clinical dual-source photon-counting detector CT in ultra-high-resolution mode and reconstructed with 4 vascular kernels (Bv36, Bv40, Bv44, Bv48). Quantitative and qualitative image-quality parameters of the intracranial arteries were evaluated. For the quantitative analysis (image noise, SNR, contrast-to-noise ratio), ROIs were manually placed at standard anatomic intracranial and extracranial locations by 1 author. In addition, vessel border sharpness was evaluated quantitatively. For the qualitative analysis, 3 blinded neuroradiologists rated photon-counting detector CT and energy-integrating detector CT image quality for the evaluation of the intracranial vessels (ie, the aneurysms and 9 standard vascular branching locations) on a 5-point Likert-type scale. Additionally, readers independently selected their preferred kernel among the 4 kernels evaluated on photon-counting detector CT. In terms of quantitative image quality, Bv48, the sharpest kernel, yielded increased image noise and decreased SNR and contrast-to-noise ratio parameters compared with Bv36, the smoothest kernel. Compared with energy-integrating detector CT, the Bv48 kernel offered better quantitative image quality for the evaluation of small intracranial vessels (P < .001). Image-quality ratings of the Bv48 were superior to those of the energy-integrating detector CT and not significantly different from ratings of the B44 reconstruction kernel. When comparing side by side all 4 photon-counting detector reconstruction kernels, readers selected the B48 kernel as the best to visualize the aneurysms in 80% of cases. Ultra-high-resolution photon-counting detector CT provides improved image quality for neurovascular imaging. Although the less sharp kernels provided superior SNR and contrast-to-noise ratio, the sharpest kernels delivered the best subjective image quality on photon-counting detector CT for the evaluation of intracranial aneurysms.

BackgroundPeople diagnosed with cystic fibrosis (pwCF) who have chronic rhinosinusitis undergo low-dose computed tomography (LDCT) scans of the paranasal sinuses as a crucial component of their disease management.PurposeTo assess and compare the intra-individual image quality and radiation dose between photon-counting CT (PCCT) and CT scanners utilizing an energy-integrating detector system (EID-CT) with LD protocols for pwCF.Material and MethodsIn this retrospective study, 23 pwCF who underwent LD paranasal sinuses PCCT and who had previously undergone LD paranasal sinuses EID-CT were included. An intra-individual comparison of image quality and radiation dose was carried out. Three blinded radiologists rated overall image quality, image sharpness, and image noise using a 5-point Likert scale. The study measured the dose length product, the volumetric CT dose index, the effective dose, and the signal to noise ratio (SNR).ResultsThe cohort comprised 23 individuals (6 women [26%], 17 men [74%]; mean age = 36.7 years). PCCT achieved superior evaluations for image quality in comparison to EID-CT (mean = 5 vs. 3; P <0.001). Furthermore, PCCT exhibited diminished image noise (mean = 4 vs. 3; P <0.001). The mean SNR of the paranasal sinuses demonstrated an increase in PCCT as opposed to EID-CT (P <0.001). PCCT demonstrated a reduction of approximately 36% in effective dose compared to EID-CT (mean = 0.09 vs. 0.15 mSv; P <0.001).ConclusionPCCT scans of the paranasal sinuses offer superior image quality and substantially reduce radiation dose compared to EID-CT scans in pwCF, offering a safer and more effective imaging alternative compared to EID-CT for managing cystic fibrosis.

BACKGROUND: Photon-counting CT (PCCT) may improve dose efficiency compared with energy-integrating detector CT (EID-CT), but evidence remains limited in very young children undergoing non-contrast preoperative chest CT under real-world clinical protocols. OBJECTIVE: To provide a size-aware matched comparison of radiation dose and image quality between PCCT and EID-CT in infants and toddlers (≤ 36 months) undergoing non-contrast preoperative chest CT, and to examine whether the main findings remained directionally consistent across prespecified strata of age, BMI, and water-equivalent diameter (DW). METHODS: In this single-center matched cohort study, a prospective PCCT cohort and a retrospective EID-CT cohort were propensity score–matched 1:1 (49 pairs). Dose metrics (CTDIvol, DLP, SSDE) and objective and subjective image quality were evaluated, with subgroup analyses stratified by age (< 12 vs. ≥ 12 months), BMI tertiles, and DW tertiles. RESULTS: The PCCT group showed significantly lower radiation dose metrics (CTDIvol, DLP, and SSDE) compared to the EID-CT group (P < 0.001). In terms of objective image quality, PCCT significantly reduced image noise in all lung lobes and consistently demonstrated higher signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) (all P < 0.001). Subjective image quality assessments showed no significant difference between PCCT and EID-CT (P > 0.05). Across prespecified age, BMI, and DW strata, PCCT remained associated with lower dose metrics and favorable objective image-quality trends, although these subgroup findings should be interpreted as exploratory. CONCLUSION: In this matched cohort of infants and toddlers undergoing non-contrast preoperative chest CT, PCCT was associated with substantially lower radiation dose and improved objective image quality compared with EID-CT, and no statistically significant difference was detected in subjective image quality scores between PCCT and EID-CT.

Dose optimization for pediatric chest CT: a comparative study of energy-integrating and photon-counting detector CT using 70kV and 100kV protocols with tin filtration regarding image quality and dose exposure.

Photon Counting CT of the Head: Retrospective Analysis of Image Quality and Dose in Comparison to Energy Integrating Detector CT.

Photon counting detector (PCD) CT benefits from reduced noise compared with conventional energy-integrating detector (EID) CT, which should translate to improved image quality and reduced radiation exposure for pediatric patients undergoing chest CT with IV contrast. To determine the differences in radiation exposure and image quality of PCD CT and EID CT in pediatric chest CT with intravenous (IV) contrast. In this institutional review board-approved retrospective observational study, 20 scan pairs (20 PCD CT; 20 EID CT) for children who underwent chest CT with IV contrast on both a PCD CT (Siemens NAEOTOM Alpha) and an EID CT (Siemens SOMATOM Definition Edge or Force) within 12months were reviewed independently by three pediatric radiologists for three subjective quality features on 5-point Likert scales: overall quality, small structure delineation, and motion artifact. Objective measures of image quality (image noise, signal-to-noise ratio, and contrast-to-noise ratio) were assessed by a single radiologist in several locations in the chest through region of interest measurement of Hounsfield units (HU) and standard deviation. Patient-related and radiation exposure parameters were collected for each scan and summarized with median and interquartile range (IQR). The Wilcoxon rank-sum test was utilized to compare groups. A P < 0.05 indicated statistical significance. Inter-observer agreement of subjective image quality metrics was analyzed using weighted kappa. Age (14.2years vs 13.8years, P= 0.15), height (P= 0.13), weight (P= 0.21), and BMI (P = 0.24) did not significantly differ between groups. There were 10 male and 3 female patients. Compared to EID CT, PCD CT showed lower radiation exposure parameters including volumetric CT dose index, 1.7mGy (IQR 1.1-2.4mGy) vs 3.8mGy (IQR 2.0-4.7mGy) (P< 0.01), and size-specific dose estimate, 2.6mGy (IQR 1.8-3.1mGy) vs 5.0mGy (IQR 3.3-6.2mGy) (P< 0.01). Objective image quality of lung parenchyma was improved on the PCD CT scanner, including image noise 119.5 HU (IQR 95.4-135.7 HU) vs 143.1 HU (IQR 125.4-169.8 HU) (P < 0.01), signal-to-noise ratio (SNR) -6.1 (IQR -8.4 to -4.8) vs -4.9 (IQR -5.6 to -3.8) (P= 0.01), and contrast-to-noise ratio -63.9 (-84.1 to -57.5) vs -60.5 (-76.3 to -52.5) (P = 0.01). Motion artifact was improved on the PCD CT scanner (P< 0.01). No significant differences in overall image quality or small structure delineation were identified (P= 0.06 and P= 0.31). PCD CT pediatric chest CT had significantly reduced radiation exposure, improved image quality, and reduced motion artifact compared with EID CT.

To evaluate the diagnostic quality of photon-counting detector (PCD) computed tomography (CT) in patients undergoing lung cancer screening compared with conventional energy-integrating detector (EID) CT in a prospective multireader study. Patients undergoing lung cancer screening with conventional EID-CT were prospectively enrolled and scanned on a PCD-CT system using similar automatic exposure control settings and reconstruction kernels. Three thoracic radiologists blinded to CT system compared PCD-CT and EID-CT images and scored examinations using a 5-point Likert comparison score (-2 [left image is worse] to +2 [left image is better]) for artifacts, sharpness, image noise, diagnostic image quality, emphysema visualization, and lung nodule evaluation focusing on the border. Post hoc correction of Likert scores was performed such that they reflected PCD-CT performance in comparison to EID-CT. A nonreader radiologist measured objective image noise. Thirty-three patients (mean, 66.9 ± 5.6 years; 11 female; body mass index; 30.1 ± 5.1 kg/m 2 ) were enrolled. Mean volume CT dose index for PCD-CT was lower (0.61 ± 0.21 vs 0.73 ± 0.22; P < 0.001). Pooled reader results showed significant differences between imaging modalities for all comparative rankings ( P < 0.001), with PCD-CT favored for sharpness, image noise, image quality, and emphysema visualization and lung nodule border, but not artifacts. Photon-counting detector CT had significantly lower image noise (74.4 ± 10.5 HU vs 80.1 ± 8.6 HU; P = 0.048). Photon-counting detector CT with similar acquisition and reconstruction settings demonstrated improved image quality and less noise despite lower radiation dose, with improved ability to depict pulmonary emphysema and lung nodule borders compared with EID-CT at low-dose lung cancer CT screening.

The aim was to compare the image quality of photon-counting detector CT (PCD-CT) and energy-integrating detector CT (EID-CT) in patients with tibial plateau fractures treated with metallic osteosynthesis material, and to identify optimal reconstruction parameters for PCD-CT. After ethical approval, twelve patients underwent PCD-CT and EID-CT scans. Images were reconstructed using bone and soft-tissue kernels with metal artifact reduction (iMAR). PCD-CT virtual monoenergetic images (VMI) at 70, 110, and 150 keV were generated. Five radiologists assessed metal artifact severity and bone and soft-tissue visualization using a 7-point Likert scale. Visual grading characteristics analysis was performed. Noise levels were quantified and compared using Wilcoxon's signed-rank test. EID-CT was rated superior in reducing metal-artifact streaks (AUC: 0.10-0.21). No significant difference was found between EID-CT iMAR and PCD-CT VMI at 110 keV and 150 keV (AUC: 0.40-0.49) concerning the metal-bone interface. An ultra-high-resolution PCD-CT kernel outperformed its EID-CT counterpart in bone visualization, with AUC values of 0.67-0.92 across all bone criteria, including those incorporating artifact-affected regions. PCD-CT showed lower noise. Metal artifact reduction was superior in EID-CT iMAR images compared to PCD-CT iMAR and VMI 110/150 keV, except at the metal-bone interface, where EID-CT iMAR images and PCD-CT VMI 110/150 keV performed comparably. The ultra-high-resolution PCD-CT kernel provided the best bone visualization, even when artifact-affected areas were included. Noise levels were lower in PCD-CT. This is the first in vivo comparison of photon-counting and energy-integrating CT for postoperative knee imaging with metallic osteosynthesis material. These findings highlight the need for improved metal artifact reduction in PCD‑CT, while demonstrating superior bone visualization, and support a complementary interpretation strategy in postoperative knees using high‑energy VMI and MAR‑corrected reconstructions. Photon-counting CT demonstrated excellent bone visualization. Conventional EID-CT achieved better metal artifact reduction than photon-counting CT. The metal-bone interface was rated similarly for energy-integrating CT and photon-counting CT virtual monoenergetic images. These findings indicate that further improvements in metal artifact reduction algorithms for PCD-CT are warranted.

This study evaluates the feasibility of photon-counting detector CT (PCD-CT)-based coronary CT angiography (CCTA) using ultra-low flow contrast rate while maintaining diagnostic image quality. In this prospective trial, 292 patients underwent CCTA assigned to one of three protocols: ultra-low (1.5-1.8 mL/s) or routine (4.0-5.0 mL/s) contrast injection with PCD-CT, or routine injection with EID-CT. All scans utilized a high-pitch prospective electrocardiogram-triggering acquisition. PCD-CT images were reconstructed at 45 keV (ultra-low) or 60 keV (routine). Objective image quality was quantitatively assessed by measuring vessel attenuation, signal-to-noise ratio (SNR), and contrast-to-noise ratio (CNR). Subjective image quality parameters (vascular contrast, image noise, artifacts, and vessel clarity) were independently evaluated by two blinded readers using a 4-point Likert scale (1: non-diagnostic; 2: adequate; 3: good; 4: excellent). Objective image quality demonstrated comparable attenuation, CNR, and SNR in proximal coronary segments across all groups (all p > 0.05). The ultra-low PCD-CT protocol significantly lowers attenuation in the distal LAD (373.20 ± 49.58 HU) compared to routine protocols (PCD-CT: 393.52 ± 49.38 HU; EID-CT: 396.72 ± 47.55 HU; p = 0.01). While distal vessel clarity scores were modestly reduced in distal vessel clarity (ultra-low PCD-CT: 2.91 ± 0.81 versus routine PCD-CT: 3.58 ± 0.50 versus routine EID-CT: 3.54 ± 0.50; p < 0.01). For patients with difficulty establishing venous access routes, ultra-low contrast agent flow rates in PCD-CT maintain objective image quality comparable to that of standard protocols, with acceptable diagnostic performance despite slight reductions. Photon-counting detector CT (PCD-CT) maintains objective coronary CT angiography image quality comparable to standard protocols even at ultra-low contrast flow rates (1.5-1.8 mL/s), offering a clinically acceptable and safer alternative for patients with challenging venous access. First validation of ultra-low flow contrast rate CCTA using photon-counting CT (PCD-CT). Ultra-low flow rates maintain objective image quality (CNR/SNR) versus routine protocols. PCD-CT enables 50% contrast reduction without diagnostic compromise.

Comparison of radiation dose and image quality for abdominal CT exams using photon-counting and energy-integrating CT: A self-controlled study including optimized patient positioning.

Photon counting computed tomography (PCCT) employs direct and spectrally resolved counting of individual x-ray quanta, enhancing image quality compared to the standard energy-integrating CT (EICT). To evaluate the quantitative improvements in CT image quality metrics by comparing the first medical PCCT with a state-of-the-art EICT. The PCCT versus EICT noise improvement ratio R was derived from the quantum statistics of the measurement process and measured across the clinical x-ray flux range for both systems. Detector and system modulation transfer functions (MTFs) were obtained using tilted-slit and wire phantom measurements. Image root mean square (RMS) noise, noise power spectrum (NPS), and x-ray patient dose were compared using a CatPhan phantom at two identical clinical target resolutions. The measurement of the PCCT noise improvement ratio R showed an elimination of electronic noise and a 10% noise transfer advantage. The PCCT detector MTF exhibited 3x higher angular resolution limits in comparison to EICT and close to ideal sinc behavior due to the electromagnetic formation of pixels in the PCCT semiconductor detector. This translated to 3.5x enhancements in CT system MTF ratios at 10 LP/cm, reflecting a significant improvement in millimeter range CT imaging. Both the improved quantum detection and the system MTF ratio improvement contribute to the measured 3x enhancements in image NPS at 10 LP/cm for identical image target resolution. An improvement of up to 1.7x in RMS image noise was observed accordingly. For low and ultra-low dose imaging with image filtering, dose efficiency increased between 2x and 10x, demonstrating the PCCT's capability to advance CT ultra-low dose imaging. The direct counting detection in PCCT has been shown to significantly improve sinogram noise and detector MTF ratios compared to energy integrating EICT. The observed translations into CT system MTF, image NPS, image noise, and dose ratios reflect a paradigm shift for CT image quality and dose efficiency.

The aims of this study were to determine the objective and subjective image quality of high-pitch computed tomography (CT) angiography of the aorta in clinical dual-source photon-counting detector CT (PCD-CT) and to compare the image quality to conventional dual-source energy-integrating detector CT (EID-CT) in the same patients at equal radiation dose. Patients with prior CT angiography of the thoracoabdominal aorta acquired on third-generation dual-source EID-CT in the high-pitch mode and with automatic tube voltage selection (ATVS, reference tube voltage 100 kV) were included. Follow-up imaging was performed on a first-generation, clinical dual-source PCD-CT scanner in the high-pitch and multienergy (QuantumPlus) mode at 120 kV using the same contrast media protocol as with EID-CT. Radiation doses between scans were matched by adapting the tube current of PCD-CT. Polychromatic images for both EID-CT and PCD-CT (called T3D) and virtual monoenergetic images at 40, 45, 50, and 55 keV for PCD-CT were reconstructed. Computed tomography attenuation was measured in the aorta; noise was defined as the standard deviation of attenuation; contrast-to-noise ratio (CNR) was calculated. Subjective image quality (noise, vessel attenuation, vessel sharpness, and overall quality) was rated by 2 blinded, independent radiologists. Forty patients were included (mean age, 63 years; 8 women; mean body mass index [BMI], 26 kg/m2). There was no significant difference in BMI, effective diameter, or radiation dose between scans (all P's > 0.05). The ATVS in EID-CT selected 70, 80, 90, 100, 110, and 120 kV in 2, 14, 14, 7, 2, and 1 patients, respectively. Mean CNR was 17 ± 8 for EID-CT and 22 ± 7, 20 ± 6, 18 ± 5, 16 ± 5, and 12 ± 4 for PCD-CT at 40, 45, 50, 55 keV, and T3D, respectively. Contrast-to-noise ratio was significantly higher for 40 and 45 keV of PCD-CT as compared with EID-CT (both P's < 0.05). The linear regression model (adjusted R2, 0.38; P < 0.001) revealed that PCD-CT reconstruction (P < 0.001), BMI group (P = 0.007), and kV of the EID-CT scan (P = 0.01) were significantly associated with CNR difference, with an increase by 34% with PCD-CT for overweight as compared with normal weight patients. Subjective image quality reading revealed slight differences between readers for subjective vessel attenuation and sharpness, whereas subjective noise was rated significantly higher for 40 and 45 keV (P < 0.001) and overall quality similar (P > 0.05) between scans. High-pitch PCD-CT angiography of the aorta with VMI at 40 and 45 keV resulted in significantly increased CNR compared with EID-CT with ATVS at matched radiation dose. The CNR gain of PCD-CT increased in overweight patients. Taking into account the subjective analysis, VMI at 45 to 50 keV is proposed as the best trade-off between objective and subjective image quality.

To investigate the image quality and the performance of photon-counting detector (PCD) CT compared to conventional energy-integrating detector (EID) CT in identifying subsolid nodule (SSN) characteristics. Participants with SSNs who underwent same-day EID CT and PCD CT between October 2023 and April 2024 were prospectively included. The 1.0 mm EID CT images and, subsequently, 1.0 mm, 0.4 mm, and 0.2 mm PCD CT images were reviewed to assess image noise and subjective image quality on a 5-point Likert scale. SSN characteristics, including lobulation, spiculation, pleural retraction, air cavities, intra-nodular vessel signs, internal vascular changes, and heterogeneous solid components, were evaluated. Additionally, a step-by-step observation and comparison method was used to determine the presence of any additional characteristics. Forty-eight participants (mean age: 56 ± 11 years; 16 males) with 89 SSNs were included. PCD CT significantly reduced radiation dose when using matched scans (1.79 ± 0.39 vs 2.17 ± 0.57 mSv, p < 0.001). Compared to 1.0 mm EID CT, 1.0 mm PCD CT images exhibited significantly lower objective image noise and higher subjective image quality (all p < 0.001). Compared to EID CT, PCD CT demonstrated enhanced visualization of subtle characteristics, except for lobulation, with a 0.4 mm section thickness offering a favorable balance between ultra-high resolution and perceived image quality for radiologists. PCD CT facilitated radiation dose reduction and outperformed conventional EID CT in terms of image quality and visualization of SSN characteristics. Question PCD CT, featuring ultra-high-resolution mode acquisition and a thinner reconstruction, has not been fully explored for characterizing SSNs. Findings Compared to EID CT, PCD CT was associated with lower objective image noise, higher subjective image quality, and superior SSN characterization. Clinical relevance PCD CT effectively reduced the radiation dose delivered to the patients and enabled more precise SSN characterization.