Objectives: Bilateral lung transplantation might require venoarterial extracorporeal membrane oxygenation for intraoperative support. However, the impact of extracorporeal life support modalities on right ventricular function and pulmonary ischemia-reperfusion injury remains poorly understood. This study aimed to compare the effects of passive and active extracorporeal life support strategies on right ventricular performance, pulmonary injury, and systemic inflammation. Methods: By using a validated porcine surrogate bilateral lung transplantation model, animals were divided into 3 groups: no extracorporeal life support group (clamping, n = 9), passive extracorporeal circuit group without a mechanical pump but with a low-resistance oxygenator (pulmonary artery to left atrium bypass strategy, n = 7) between the pulmonary artery and left atrium, and a centrally cannulated venoarterial extracorporeal membrane oxygenation group (n = 7). Pulmonary injury, hemodynamic parameters, and inflammatory markers were comprehensively assessed. Results: Pulmonary edema was greater in extracorporeal membrane oxygenation versus a pulmonary artery to left atrium bypass strategy (wet-to-dry weight ratio, P = .0315). Right ventricular failure occurred in 5 of 9 animals in the clamping group but was absent in both pulmonary artery to left atrium bypass and extracorporeal membrane oxygenation groups. Extracorporeal membrane oxygenation led to significantly higher right ventricular afterload compared with clamping and pulmonary artery to left atrium bypass (arterial elastance, P = .0001 and P < .0001, respectively). Systemic inflammation appeared highest in extracorporeal membrane oxygenation, as reflected by interleukin-6 levels (clamping vs pulmonary artery to left atrium bypass strategy P = .0004; clamping vs extracorporeal membrane oxygenation P < .0001; pulmonary artery to left atrium bypass strategy vs extracorporeal membrane oxygenation P = .0004). Conclusions: Both pulmonary artery to left atrium bypass and extracorporeal membrane oxygenation prevented right ventricular failure in a setting of severe pulmonary ischemia-reperfusion injury. Our results suggest that pulmonary artery to left atrium bypass might provide better pulmonary protection and cause less inflammation than extracorporeal membrane oxygenation. These findings may guide further investigation of pumpless extracorporeal life support strategies for lung transplantation.

To propose and validate a personalized iodine delivery rate (IDR) based injection protocol for coronary CT angiography (cCTA) on photon-counting CT. First, ideal IDR (IDRIDEAL) was retrospectively calculated for a HU target of 500 in 55 keV image reconstructions. Next, linear regression analysis was performed with IDRIDEAL and demographic parameters to derive a candidate IDR formula. This was implemented in two validation groups characterized by injection rate (3.5 and 5.0 mL/s). Here, coronary enhancement was quantified and equivalence assessed for a predefined HU range (500 ± 50). Additionally, a reader study assessed perceived enhancement of the coronary tree. This IRB-approved study used a retrospective cohort of 162 patients (group A: 58 ± 12 years; 81 men) and two prospective cohorts of 51 patients (group B1: 60 ± 13 years; 22 men and group B2: 59 ± 12 years; 30 men). IDRIDEAL correlated best with fat-free mass (FFM) (r = 0.67) and was integrated for contrast personalization. Prospectively, mean coronary enhancement was 533 ± 97 HU and 528 ± 68 HU for both groups (p = 0.79) with mean IDR values of 1.01 ± 0.11 gI/s and 1.07 ± 0.14 gI/s. However, distribution variances were significantly different (p = 0.015). Subjective scoring showed no differences between the two groups on overall and per-vessel level (p > 0.05). A personalized, IDR-based injection protocol for cCTA was proposed and validated. FFM was best for IDRIDEAL prediction. Higher injection rates provided more precise coronary enhancement. Question Virtual mono-energetic images lead to low iodine delivery rate settings, but the impact on coronary enhancement is not clear. Findings An iodine delivery rate-based injection protocol implementing personalized contrast volume dilutions with set injection duration and high injection rate improved coronary enhancement. Clinical relevance Iodine delivery rate fine-tuning is a promising approach for coronary CT angiography with low iodine volumes. High injection rates provide more accurate and precise coronary enhancement.

OBJECTIVE:Photon-counting computed tomography (PCCT) represents a major innovation in X-ray detection technology, offering improved signal efficiency and reduced electronic noise compared with cone-beam computed tomography (CBCT), which can enhance image quality. This study aimed to evaluate the diagnostic performance of PCCT in detecting vertical root fractures (VRF), in comparison with four CBCT devices. METHODOLOGY:Eighteen single-rooted teeth were endodontically treated, and VRF was induced in eight of them. Each tooth was individually placed into the mandibular first premolar empty socket of an anthropomorphic phantom and scanned under three conditions: without a metal post, with a nickel-chromium metal post (Ni-Cr), and with a cobalt-chromium metal post (Co-Cr) in five CT devices: the NAEOTOM Alpha PCCT (Siemens Healthineers) device and four CBCT devices (3D Accuitomo 170-Morita, Veraview X800-Morita, NewTom VGi evo-NewTom, and Carestream 9600-Carestream). The highest-resolution protocol available on each device was used, resulting in a total of 270 scans. Five experienced dentomaxillofacial radiologists independently and blindly evaluated the scans using a five-point confidence scale. Diagnostic accuracy was assessed by calculating the area under the ROC curve (AUC), sensitivity, and specificity, with results compared by two-way ANOVA with post hoc Tukey's test (α = 0.05). RESULTS:NewTom VGi and PCCT devices showed significantly higher AUC values than the Veraview X800, regardless of the metal post material (p < 0.05). CS9600 and PCCT devices exhibited significantly higher sensitivity values in diagnosing with Ni-Cr posts than the Accuitomo 3D and Veraview X800 devices (p < 0.05). With the Co-Cr metal post, the NewTom VGi, CS9600, and PCCT devices showed significantly higher sensitivity values compared to the Veraview X800 device (p < 0.05). There were no statistically significant differences in specificity, regardless of the CT device or metal post material (p > 0.05). CONCLUSIONS:The NEAOTOM Alpha PCCT showed high diagnostic accuracy for VRF detection in an ex vivo model, comparable to high-resolution CBCT devices, highlighting its diagnostic performance under controlled ex vivo conditions.

BACKGROUND:Post-infectious bronchiolitis obliterans (PIBO) may occur following childhood infections. Subsequent dysanaptic lung growth, with differential development of the alveolar compartment over the airways, remains elusive. We performed a morphological characterization of the whole airway tree in PIBO compared to bronchiolitis obliterans syndrome (BOS) after lung transplantation. METHODS:Lungs from matched PIBO (n=5), BOS (n=5), and non-diseased donors (n=5) were evaluated using ex vivo high-resolution computed tomography (CT) scans followed by three-dimensional (3D)-airway segmentation. Matched lung tissue samples (n=4 locations/lung) were scanned with micro-CT (resolution: 5-10 µm) for 3D terminal bronchiole assessment and histology. RESULTS:No significant difference in the number of airways per generation (until generation 11) was observed between groups (p=0.86). Airway diameters in PIBO (generations 6-11) and BOS (generations 7-10) were increased compared to controls (overall p=0.018), without significant differences between PIBO and BOS. More obstructed airways were present in BOS versus PIBO (p=0.016), but airway obstructions were larger in PIBO versus BOS (p=0.032). There were significantly fewer terminal bronchioles in PIBO compared to BOS and controls (PIBO: median 2934 terminal bronchioles/lung (IQR:2247-4115), BOS 8424 terminal bronchioles/lung (IQR:6207-10480), controls 10 903 terminal bronchioles/lung (IQR:7583-12 820), p=0.0009), but terminal bronchiole diameters were not significantly different (p=0.37). Obstruction of pre-terminal bronchioles was segmental (i.e., focal with normal distal terminal bronchiole) in BOS, but partly non-focal (non-reopening bronchiole) in PIBO. CONCLUSIONS:PIBO lungs display an almost threefold decrease in terminal bronchioles compared to BOS, with morphological differences in the type and location of airway obstructions, providing structural evidence supporting dysanaptic lung growth.

Objectives:As an often-young population with regular CT follow-up, lung transplant (LTX) patients could benefit from both high spatial resolution and lower radiation dose. We compared the image quality of ultra-high-resolution photon-counting CT (UHR-PCCT) with high-resolution energy-integrating-detector CT (HR-EIDCT) at both a normal (IQ100) and a reduced radiation dose (IQ40) in patients after LTX. Methods:Hundred patients post-LTX, with an UHR-PCCT (0.4 mm) between Dec-2021 and Aug-2022, and prior HR-EIDCT (1.0 mm) <14 months apart, were included. In 49 patients, PCCT-IQ100 images were compared with previous HR-EIDCT; in 51 patients, PCCT-IQ40 images were compared with previous HR-EIDCT. Image quality was scored using a 5-point Liker scale (-2 to +2) for 7 relevant entities (peripheral airways, micronodules, reticulations, pleural thickening, consolidation, ground glass opacities (GGO), and air-trapping) plus an overall quality impression score. Results:For PCCT-IQ100, the median visual grading analysis (VGA) score was significantly better than EIDCT for all structures/abnormalities (median < 0; p < 0.005) and for most structures/abnormalities in PCCT-IQ40 (p < 0.023). There was no perceived diagnostic impact in either group (median = 2; p ≥ 0.039). Mean dose length product (DLP) was reduced by 33% in PCCT-IQ100 and 73% in PCCT-IQ40 compared to EIDCT (p < 0.0001). Conclusions:A significant dose reduction was achieved using the PCCT-IQ40 protocol. Although image quality was best in PCCT-IQ100, image quality in PCCT-IQ40 was non-inferior to EIDCT. Therefore, a significant radiation dose reduction is feasible without compromising image quality. Clinical relevance statement:PCCT offers improved image quality while reducing radiation dose significantly.For lung transplant patients, who are often younger and require lifelong, regular follow-up with CT, both improved image quality and lowered radiation dose would be very beneficial. Key Points:- LTX patients require long-term follow-up with high-resolution imaging to detect often subtle abnormalities and would benefit from both improved image quality and radiation dose reduction.- Perceived image quality was significantly higher in IQ100-PCCT than EIDCT; a significant further radiation dose reduction was feasible (IQ40-PCCT) without compromising image quality compared to EIDCT.

Photon-counting computed tomography (PCCT) represents a major innovation in X-ray detection technology, offering improved signal efficiency and reduced electronic noise compared with cone-beam computed tomography (CBCT), which can enhance image quality. This study aimed to evaluate the diagnostic performance of PCCT in detecting vertical root fractures (VRF), in comparison with four CBCT devices. Eighteen single-rooted teeth were endodontically treated, and VRF was induced in eight of them. Each tooth was individually placed into the mandibular first premolar empty socket of an anthropomorphic phantom and scanned under three conditions: without a metal post, with a nickel-chromium metal post (Ni-Cr), and with a cobalt-chromium metal post (Co-Cr) in five CT devices: the NAEOTOM Alpha PCCT (Siemens Healthineers) device and four CBCT devices (3D Accuitomo 170—Morita, Veraview X800—Morita, NewTom VGi evo—NewTom, and Carestream 9600—Carestream). The highest-resolution protocol available on each device was used, resulting in a total of 270 scans. Five experienced dentomaxillofacial radiologists independently and blindly evaluated the scans using a five-point confidence scale. Diagnostic accuracy was assessed by calculating the area under the ROC curve (AUC), sensitivity, and specificity, with results compared by two-way ANOVA with post hoc Tukey's test ( α = 0.05). NewTom VGi and PCCT devices showed significantly higher AUC values than the Veraview X800, regardless of the metal post material ( p < 0.05). CS9600 and PCCT devices exhibited significantly higher sensitivity values in diagnosing with Ni-Cr posts than the Accuitomo 3D and Veraview X800 devices ( p < 0.05). With the Co-Cr metal post, the NewTom VGi, CS9600, and PCCT devices showed significantly higher sensitivity values compared to the Veraview X800 device ( p < 0.05). There were no statistically significant differences in specificity, regardless of the CT device or metal post material ( p > 0.05). The NEAOTOM Alpha PCCT showed high diagnostic accuracy for VRF detection in an ex vivo model, comparable to high-resolution CBCT devices, highlighting its diagnostic performance under controlled ex vivo conditions.

OBJECTIVE:Long term patient and re-intervention free survival outcomes after aortic endografting are scarce. In this study, long term outcomes of patients initially presenting with an aortic or aorto-iliac aneurysm and treated with the Zenith endograft were assessed. METHODS:This single centre, retrospective, observational study examined overall survival (OS), re-intervention free survival, and occurrence of adverse events during follow up of patients treated with Zenith endografts. Data of 209 patients who underwent endovascular aneurysm repair with the Zenith Endoprosthesis between January 1998 and December 2009 in an academic, tertiary care centre for aortic disease were analysed. Follow ups were analysed until January 2024 to ensure a follow up time of at least 14 years. The primary end points were OS and re-intervention free survival. Secondary end points were endograft related complications, endoleaks, and re-interventions. RESULTS:OS at two, five, ten, and 15 year follow up was 89%, 71%, 40%, and 18%, respectively. Re-intervention free survival was 83%, 76%, 69%, and 66% at two, five, ten, and 15 year follow up, respectively; 87 re-interventions in 60 patients were performed in the zero to eight year follow up period. After ten years or more of follow up, there were 15 re-interventions performed in ten patients. Freedom from type I and III endoleaks at five and 15 years were 93% and 86%, respectively. The vast majority of type I (n = 29 of 37) and type III endoleaks (n = 3 of 4) occurred in the first eight years of post-operative follow up. CONCLUSION:Endovascular aneurysm repair using the Zenith Endoprosthesis is effective and durable on long term follow up, with acceptably low endograft related complications and re-interventions. The number of re-interventions for type I and III endoleaks is low after eight years of follow up.

Objectives: To evaluate the impact of patient-specific contrast volume adjustments on preoperative aortic computed tomography angiography (CTA) image quality after adjusting and reducing the total, injected contrast volume based on patients' body surface area (BSA) and heart rate (HR) and after adapting the CT-scanner's kilovoltage (kV). Methods: Prospective study included 80 surgery-naive patients. Three study groups were included: Group 1 (n = 56 patients): the injected contrast dose, calculated from BSA and HR, was reduced by 50%; Group 2 (n = 11 patients): the injected contrast dose, calculated from BSA and HR, was reduced by 50%, and an additional volume reduction was based on the kV values; Group 3 (n = 13 patients): the injected contrast dose, calculated from BSA and HR, was reduced by 50% and additionally diluted to 80% contrast and 20% saline. Image quality was evaluated by quantitative analysis (Hounsfield units) and qualitative analysis (five-point visual score). Results: The mean injected contrast dose was 46.1 ml, 28.3 ml, and 35.0 ml in Groups 1, 2, and 3, respectively, with a significant difference between Group 1 vs Group 2 (P < 0.001) and between Group 1 vs Group 3 (P < 0.001). A linear relationship between the Hounsfield units and the given contrast dose for all study groups was observed. The mean image quality score for Group 1 was 4.34/5. The mean image quality score for Group 2 was 2.8/5 and for Group 3 was 3.5/5. Conclusions: Significant contrast dose reduction, based on HR and BSA, in preoperative aortic CTA is associated with acceptable diagnostic quality.

Rationale: The precise nature of small airway obstructions in chronic obstructive pulmonary disease (COPD) remains poorly understood, especially at early disease stages. Objectives: This study aimed to characterize small airway obstructions and numbers up to the terminal bronchioles (TBs) in smokers with limited emphysema and end-stage COPD. We hypothesized that obstruction subtypes would differ in morphology, nature, and number from early to end-stage COPD. Methods: Whole lungs were inflated and processed from seven control donors (control: declined for extrapulmonary reasons); from eight donors with a history of smoking, of whom three had <5% emphysema (smokers with no emphysema) and five had >5% emphysema (smokers with emphysema); and from eight patients with end-stage COPD. Micro-computed tomography of tissue was used to assess number of TBs, aerated TBs, and number and type of obstructions and was cross-correlated with histopathology. Measurements and Main Results: Obstructions were mainly present in smokers with emphysema and patients with COPD, resulting in less aerated TBs. On the basis of emphysema extent, more nonaerated TBs were present in regions with no emphysema than in regions with mild emphysema; however, destruction was more prominent in mild emphysema. Multiple types of obstructions were identified, comprising occlusions, webs, and collapses. In smokers with emphysema, obstructions primarily comprised webs and occlusions, whereas all obstruction types were present in COPD. On histopathology, obstructions were identified as mucus plugs. Conclusions: Multiple types of obstruction characterized as mucus plugs were identified in smokers with emphysema and patients with end-stage COPD. Their morphology, nature, and number evolved from smokers with emphysema to end-stage COPD. A shift from obstruction-dominant dysfunction to destruction-dominant pathology was found in smokers on the basis of emphysema presence.

Bone structural and mechanical properties predict fragility fractures, but unexplained variance remains. A better quantification of the anisotropic nature of bone, and an improved model-based prediction of bone failure load could fill in this gap. Yet, quantifying mechanical anisotropy requires high-resolution imaging modalities, which are often lacking in clinical practice. This study used voxel-based finite element (FE) models from high-resolution photon-counting CT (PCCT) and conventional energy-integrating detector CT (EIDCT) to mechanically characterize trabecular bone samples from vertebrae. Ten trabecular cubical samples from bovine lumbar vertebrae were scanned with PCCT, EIDCT and micro-CT (μCT), calibrated to bone mineral density values, and images were converted to voxel-based FE meshes. A density-scaled linear-elastic material model was employed to calculate the apparent stiffness tensor in the orthotropic direction, and results from PCCT and EIDCT were compared to μCT-based reference values. Anisotropy of the resulting linear-elastic material parameters was quantified as the ratio of axial to transverse moduli. Next, a non-linear density-scaled material model that included a plastic and strain-softening phase was used to quantify failure load. Anisotropy of failure load in the orthotropic directions was compared between PCCT and EIDCT, and axial failure load was compared to experimental measurements. For PCCT, all apparent Young's and shear moduli showed no systematic bias with respect to μCT; in contrast, EIDCT systematically overestimated all transverse moduli, and underestimated the axial Young's modulus. As a result, the anisotropic nature of bone was better quantified with PCCT (1.71 ± 0.28) than with EIDCT (1.22 ± 0.14). Similarly, PCCT demonstrated higher anisotropy of failure loads in the orthotropic directions (1.75 ± 0.27) than EIDCT did (1.28 ± 0.17). Compared to experimental measurements, all voxel-based FE models underestimated failure load, yet, adjusted R2 was higher for PCCT (0.91) than for EIDCT (0.84). For multivariate linear models that incorporated both FE failure load and trabecular bone microarchitecture, adjusted R2 increased to 0.98 for PCCT, and 0.91 for EIDCT. We conclude that the increased resolution of PCCT enables a better linear-elastic characterization as compared to EIDCT, and that PCCT is more predictive of failure load than EIDCT. This could aid in clinically relevant fracture risk predictions.

Objectives: to determine (1) a target Hounsfield unit (HU) for portal venous phase iodinated contrast media enhanced abdominal CT scans, (2) an equation for a personalized total contrast agent volume, and (3) the best/most appropriate time between injection and plateau/peak in HU enhancement. Material and methods: from an original dataset of 5,000 cases, a weight representative subset of 370 cases was sampled for detailed HU measurements. An additional 90 cases were used for visual grading to define the minimal HU required for diagnostic quality, which led to the proposed target HU. This study uses the fact that in a first approach, the injected contrast agent volume and HU correlate linearly. Based on the injected contrast agent volumes and HU measurements in the patient scans, it was then calculated which (ideal) volume would have reached the target value. The ideal volumes and patient data (weight, height, heart rate, age, and gender) were correlated by means of a regression analysis, to determine a new patient-specific contrast volume calculation equation. The best scan delay time was derived from the start of the injection to the HU enhancement plateau/peak evaluated from manually triggered venous phase scans. Results: The target HU value was 125. This can be achieved with a personalized contrast agent volume (ml), equal to - 108.5 + ∗ weight(kg) + 0.40 ∗ heart rate(bpm) + 0.61 ∗ height(cm). The time delay between injection and HU plateau/peak was found to be, on average, 102 s. Conclusion: this study proposes a comprehensive protocol for contrast enhanced venous phase scans, including a target HU, a personalized contrast volume, and a scan delay.

The quantification of bone microarchitecture provides insight into bone health and the effects of disease or treatment, and is therefore highly relevant clinical information. Nonetheless, in vivo quantification of bone microarchitecture is mostly limited to high-resolution peripheral quantitative CT (HR-pQCT). This is a small field of view CT modality of which the gantry size only allows scanning of distal radius and tibia. Photon-counting CT (PCCT) is a novel clinical full-body CT with improved image resolution and quality compared to other clinical CT modalities, yet data on its capabilities in quantifying bone microarchitecture are limited. The aim of this study was to quantify the accuracy of two methods for trabecular bone segmentation on PCCT images as compared to the segmentations on micro-CT (μCT) and to use these segmentations to quantify the accuracy and agreement of trabecular bone morphometry measurements as compared to μCT, as well as the short-term precision. This study analysed multimodal CT data, obtained from eight cadaveric forearms; the data includes two repeated PCCT scans, as well as a single HR-pQCT scan from the forearm, and μCT scans of all individual carpal bones. For each carpal bone, trabecular volumes of interest (VOI) were delineated on the μCT images, and the μCT reference segmentations and VOIs were resampled onto the PCCT and HR-pQCT images. HR-pQCT images were segmented with a global threshold of 320 mgHA/cm3; PCCT images were segmented with either an identical global threshold or with an adaptive thresholding algorithm. Trabecular bone-volume fraction (Tb.BV/TV), trabecular thickness (Tb.Th), trabecular number (Tb.N) and trabecular separation (Tb.Sp) were quantified for all segmented VOIs. Accuracy and agreement were calculated relative to μCT as the gold standard, short-term precision was calculated from the repeated PCCT scan. For PCCT, adaptive threshold segmentation had significantly increased sensitivity compared to global threshold segmentation, along with a lower variance in its sensitivity and specificity. Concerning the microarchitecture quantification, for global threshold segmentation of PCCT images, correlations with μCT were significant, except for Tb.Sp. Correlation coefficients of Tb.BV/TV and Tb.N were not significantly different from those between HR-pQCT and μCT. Adaptive threshold segmentation led to higher correlation coefficients between PCCT and μCT of Tb.Th, Tb.N and Tb.Sp, although correlations of Tb.N remained poor for both PCCT and HR-pQCT. Moreover, adaptive thresholding led to a constant bias of Tb.BV/TV, Tb.Th and Tb.Sp, unlike the bias of HR-pQCT which was proportionally increasing with the size of the measurement. Finally, adaptive threshold segmentation led to a higher short-term precision than global threshold segmentation, with a root-mean-squared coefficient of variation below 0.65 % for all parameters. We conclude that adaptive threshold segmentation is well-suited for the segmentation of PCCT images. Despite measurement error, our results indicate that these segmentations can be used for bone microarchitecture analyses of carpal bones with agreement and short-term precision comparable to HR-pQCT.

Facial growth and development are dynamic processes influenced by intrinsic and extrinsic factors. Predicting these changes is essential in forensic science and clinical dentistry. While AI-driven age progression tools like Remini AI (a mobile application) and SAM (open-source software) may offer innovative solutions, their clinical applicability remains underexplored. To evaluate the accuracy and clinical feasibility of AI-driven age progression tools: using a mobile application (Remini AI) and an open-source software (SAM). This retrospective observational study used the FG-NET aging database and additional personal images. Remini AI and SAM processed 18 images each, generating 180 age-progressed images in total for predefined age groups (5, 11, 15, 18, and 26 years). Subjective assessments involved dental experts performing reordering, categorization, and accuracy tasks, while objective assessments used an age estimation model (MiVolo) to estimate the age of the AI-generated images. Statistical analyses included t-tests and chi-square tests with a significance level of 5%. Remini AI achieved higher results for the categorization task (55%, P < .001), whereas SAM demonstrated superior accuracy in generating realistic age progressions between 11 and 18 years old, with a lower mean absolute error (2.7 years vs. 3.7 years, P < .001). Neither tool performed effectively for younger (age 5) or older (age 26) age groups. SAM outperformed Remini AI in processing speed, generating images in an average of 9 seconds versus 5 minutes per image (P < .001). Remini AI excels in categorization tasks, while SAM demonstrates greater accuracy and efficiency for realistic age progressions, particularly in mid-childhood and young adulthood. Both tools require refinement for younger and older populations. These findings emphasize the potential of AI-driven tools in forensic investigations and clinical dentistry, including orthodontic planning and reconstructive procedures. This study is retrospective and observational, and no trial registration is applicable.

Hybrid depth electrodes are increasingly being used for epilepsy monitoring and human neurophysiology research. Microwires extending from the tip of the Behnke-Fried (BF) electrode into (sub)cortical areas allow to isolate single neurons and perform microstimulation. Conventional CT or MRI visualize the entire microwire bundle as an artifact extending from the BF electrode tip with low resolution, without proper identification of individual microwires. We illustrate the first direct visualization method of individual microwires using high-resolution photon-counting CT (PCCT). Coregistration of the PCCT scan with a preoperative MRI can visualize individual wires directly in cortex, which is an advantage as it provides feedback on the accuracy of the implantation method and can guide future implantations. This PCCT technique allows for accurately depicting individual microwires which could be relevant for neuroscientific research through improved visualization and implantation of specific cortical and subcortical brain areas. PLAIN LANGUAGE SUMMARY: Researchers are using hybrid depth electrodes to study epilepsy and brain activity. These electrodes, called Behnke-Fried (BF) electrodes, have microwires at the tip that can record single neurons and stimulate brain areas. Regular CT or MRI scans do not show the individual microwires clearly. The authors use a new high-resolution photon-counting CT (PCCT) technique, which can show each individual microwire in the brain. By combining PCCT with MRI, the authors can precisely see where the microwires are located. This could improve future implantation surgeries and brain research.

Visualization and quantification of bone microarchitecture in the human knee allows gaining insight into normal bone structure, and into the structural changes occurring in the onset and progression of bone diseases such as osteoporosis and osteoarthritis. However, current imaging modalities have limitations in capturing the intricacies of bone microarchitecture. Photon counting computed tomography (PCCT) is a promising imaging modality that presents high-resolution three-dimensional visualization of bone with a large field of view. However, the potential of PCCT in assessing trabecular microstructure has not been investigated yet. Therefore, this study aimed to evaluate the accuracy of PCCT in quantifying bone microstructure and bone mechanics in the knee. Five human cadaveric knees were scanned ex vivo using a PCCT scanner (Naetom alpha, Siemens, Germany) with an in-plane resolution of 146.5 μm and slice thickness of 100 μm. To assess accuracy, the specimens were also scanned with a high-resolution peripheral quantitative computed tomography (HR-pQCT; XtremeCT II, Scanco Medical, Switzerland) with a nominal isotropic voxel size of 60.7 μm as well as with micro-computed tomography (micro-CT; TESCAN UniTOM XL, Czech Republic) with a nominal isotropic voxel size of 25 μm which can be considered gold standards for in vivo and ex vivo scanning, respectively. The thickness and porosity of the subchondral bone and the microstructure of the underlying trabecular bone were assessed in the load bearing regions of the proximal tibia and distal femur. The apparent Young's modulus was determined by micro-finite element (μFE) analysis of subchondral trabecular bone (STB) in the load bearing regions of the proximal tibia using PCCT, HR-pQCT and micro-CT images. The correlation between PCCT measurements and micro-CT and HR-pQCT, respectively, was calculated. The coefficients of determination (R2) between PCCT and micro-CT based parameters, ranged from 0.69 to 0.87. The coefficients of determination between PCCT and HR-pQCT were slightly higher and ranged from 0.71 to 0.91. Apparent Young's modulus, assessed by μFE analysis of PCCT images, correlated well with that of micro-CT (R2 = 0.80, mean relative difference = 19 %). However, PCCT overestimated the apparent Young's modulus by 47 %, but the correlation (R2 = 0.84) remained strong when compared to HR-pQCT. The results of this study suggest that PCCT can be used to quantify bone microstructure in the knee.

BackgroundA positive PET scan at diagnosis was associated with a greater yearly increase in ascending and descending aortic diameter and thoracic aortic volume in patients with giant cell arteritis (GCA). Radiologic and histopathologic vascular abnormalities persist in a subset of treated patients despite clinical remission. The aim of this study was to evaluate the association between vascular FDG uptake during follow-up and the development of thoracic aortic aneurysms.MethodsWe recently performed a prospective cohort study of 106 GCA patients, who underwent FDG PET and CT imaging at diagnosis and CT imaging yearly for a maximum of 10 years. In this post hoc analysis, GCA patients who also have had FDG PET imaging during follow-up were included. PET scans were visually scored (0–3) at 7 vascular areas. PET scans were considered positive in case of FDG uptake ≥grade 2 in any large vessel.ResultsEighty-eight repeat PET scans were performed in 52 out of 106 GCA patients, who were included in the original prospective cohort. Fifty-five (63%) PET scans were done at the time of a relapse and 33 (38%) were done while in remission. Nine out of ten patients with an incident thoracic aortic aneurysm had both a positive PET scan at diagnosis and during follow-up.ConclusionIn addition to the intensity and extent of the initial vascular inflammation, ongoing aortic inflammation may contribute to the development of thoracic aortic aneurysms in GCA. However, this hypothesis should be confirmed in a large prospective trial with repeat PET scans at predefined time points during follow-up.

HR-pQCT has become standard practice when quantifying volumetric BMD (vBMD) in vivo. Yet, it is only accessible to peripheral sites, with small fields of view and lengthy scanning times. This limits general applicability in clinical workflows. The goal of this study was to assess the potential of photon counting CT (PCCT) in quantitative bone imaging. Using the European Forearm Phantom, PCCT was calibrated to hydroxyapatite (HA) density. Eight cadaveric forearms were scanned twice with PCCT and once with HR-pQCT. The dominant forearm of two volunteers was scanned twice with PCCT. In each scan, the carpals were delineated. At bone level, accuracy was assessed with a paired measurement of total vBMD (Tt.vBMD) calculated with PCCT and HR-pQCT. At voxel-level, repeatability was assessed by image registration and voxel-wise subtraction of the ex vivo PCCT scans. In an ideal scenario, this difference would be zero; any deviation was interpreted as falsely detected remodeling. For clinical usage, the least detectable remodeling was determined by finding a threshold in the PCCT difference image that resulted in a classification of bone formation and resorption below acceptable noise levels (<0.5%). The paired measurement of Tt.vBMD had a Pearson correlation of 0.986. Compared to HR-pQCT, PCCT showed a bias of 7.46 mgHA/cm3. At voxel-level, the repeated PCCT scans showed a bias of 17.66 mgHA/cm3 and a standard error of 96.23 mgHA/cm3. Least detectable remodeling was found to be 250 mgHA/cm3, for which 0.37% of the voxels was incorrectly classified as newly added or resorbed bone. In vivo, this volume increased to 0.97%. Based on the cadaver data, we conclude that PCCT can be used to quantify vBMD and bone turnover. We provided proof of principle that this technique is also accurate in vivo, hence, that it has high potential for clinical applications.