BACKGROUND:Bridging stent grafts (BSG) are a critical component of fenestrated and branched endovascular aortic repair (f/bEVAR) but remain prone to structural failure due to continuous biomechanical stress. Early detection of stent wire fractures is clinically relevant, yet remains challenging with conventional computed tomography (CT) because of limited effective spatial resolution and metal-related blooming artifacts. The aim of the study is to evaluate whether photon-counting detector CT (PCCT) improves the detectability of structural defects in BSG compared with dual-energy CT (DECT). METHODS:An in vitro phantom model incorporating commercially available BSGs with predefined wire fractures was examined using PCCT and DECT across multiple Siemens IQ (dose/resolution) levels. Seven experienced human observers assessed defect visibility using a five-point Likert scale. Interobserver agreement was evaluated using Fleiss' kappa. Quantitative analysis was performed using relative full width at half maximum (FWHM) measurements, expressing defect width relative to stent diameter. RESULTS:PCCT demonstrated markedly superior visibility of stent fractures compared with DECT. Mean Likert scores were 4.66±0.43 for PCCT versus 2.56±0.62 for DECT (median 4.86 vs. 2.43; P<0.001). Ratings indicating good to excellent visibility (Likert 4-5) accounted for 94.7% of PCCT assessments but only 16.9% with DECT. Interobserver agreement was substantially higher for PCCT (κ=0.295) than for DECT (κ=0.004). Quantitative analysis revealed significantly larger relative FWHM values with PCCT (0.72±0.08) compared with DECT (0.60±0.12; P<0.001), consistent across stent types and IQ levels. PCCT achieved stable high detectability already at intermediate IQ levels, whereas DECT showed a gradual dose-dependent improvement. CONCLUSIONS:In this controlled experimental setting, PCCT substantially outperformed DECT in the detection of structural bridging stent graft failure, both in subjective and quantitative analyses. These findings suggest that structural BSG defects may be substantially underdetected with conventional CT and that PCCT enables a fundamentally improved level of detectability. This has potential implications for post-f/bEVAR surveillance and warrants further in vivo evaluation.

Additively manufactured (3D-printed) anatomical bone models are used for medical education and surgical training. Manufacturing of patient-specific anatomies and rare pathologies has improved rapidly in the recent past, enabling training opportunities that were previously restricted to limitedly available anatomic specimens. However, the imitation of patient-specific trabecular bone in additively manufactured bone models remains complex and thus inadequately addressed. Test specimens in the form of Gyroid and Voronoi lattice cubes were manufactured via fused filament fabrication (FFF)-printing at varying densities with polylactide, polylactide /carbon fiber composite and polyamide /glass fiber composite filaments, and submerged in gelatin. Additionally, trabecular bone test cubes were removed from bovine femoral specimens, and the bone mineral density (BMD) was assessed utilizing quantitative computed-tomography (QCT). Subsequently, haptic drill resistance of all test cubes was evaluated by four orthopedic and trauma surgeons, and the mechanical drill resistance was assessed using a load frame. Multiple polymer lattice structures and material configurations were evaluated by the surgeons as suitable to mimic actual trabecular bone (Likert ratings between 2.60 and 3.00). Regression analyses of the surgeons’ evaluations of both the trabecular bone (R2 = 0.82) and the polymer lattice cubes (0.66 ≤ R2 ≤ 0.89) enabled the extraction of practical manufacturing parameters linking them with patient-specific BMD. The imitation of trabecular bone models via FFF-printing is feasible and could substantially enhance the haptic feedback in additively manufactured anatomical bone models. Applying the presented manufacturing framework enables the cost- and time-efficient production of patient-specific anatomical models to enhance preoperative planning and surgical training.

Background: The use of photon-counting detector computed tomography (PCD-CT) has improved image quality in cardiac, pulmonary, and musculoskeletal imaging. Abdominal imaging research, especially about the use of PCD-CT in hepatocellular carcinoma (HCC), is sparse. Objectives: We aimed to compare the image quality of tumors, the liver parenchyma, and the vasculature in patients with HCC using PCD-CT reconstructions at different slice thicknesses and kernels to identify the most appropriate settings for the clinical routine. Methods: CT exams from twenty adult patients with HCC performed with a clinically approved, first-generation PCD-CT scanner (Naeotom Alpha®, Siemens Healthineers), were retrospectively reviewed. For each patient, images were reconstructed at four different sharp kernels, designed for abdominal imaging (Br40; Br44; Br48; Br56) and at three slice thicknesses (0.4 mm; 1 mm; 3 mm). The reconstruction with the Br40 kernel at 3 mm (Br403 mm) was used as a clinical reference. Three readers independently assessed the image quality of different anatomical abdominal structures and hypervascular HCC lesions using a five-point Likert scale. In addition, image sharpness was assessed using line-density profiles. Results: Compared with the clinical reference, the Br441 mm and Br481 mm reconstructions were rated superior for the assessment of the hepatic vasculature (median difference +0.67 [+0.33 to +1.33], p < 0.001 and +1.00 [+0.67 to +1.67], p < 0.001). Reconstructions for Br401 mm (+0.33 [−0.67 to +1.00], p < 0.001), and Br443 mm (+0.0 [0.0 to +1.00], p = 0.030) were scored superior for overall image quality. The noise demonstrated a continuous increase when using sharper kernels and thinner slices than Br403 mm (p < 0.001), leading to a decrease in contrast-to-noise ratio. Although there was a trend toward increased image sharpness using the slope analysis with higher kernels, this was not significantly different compared with the reference standard. Conclusion: PCD-CT reconstruction Br401 mm was the most suitable setting for overall image quality, while reconstructions with sharper kernels (Br441 mm and Br481 mm) can be considered for the assessment of the hepatic vasculature in patients with HCC.

Fractures of the odontoid process are associated with high non-union rates, challenging treatment, and high incidence of screw-related complications. The aim of this study was to compare the biomechanical competence of a single biointegrative bone allograft screw versus two conventional cannulated screws for odontoid fracture fixation. The odontoid process of intact C2 vertebral specimens was subjected to quasi-static loading until fracture. Specimens with an Anderson and d’Alonzo type II or III fracture (n = 47) were fixated with either two conventional cannulated screws or with a single bone allograft screw. The constructs were biomechanically tested to failure in the same fashion as in their intact state. Stiffness, yield, and ultimate load were evaluated. The results were adjusted by age, sex, volumetric bone mineral density (vBMD), and the cross-sectional area ratio of cortical bone to total bone measured at the junction of the odontoid process with the vertebral body (Ct.Ar/Tt.Ar). Stiffness, yield and ultimate load were restored in the cannulated screws group by 44 ± 10

OBJECTIVES:Surgical ablation for treating atrial fibrillation (AF) is currently performed mostly without preoperative electrophysiological imaging. This study aimed to investigate the use of non-invasive surface mapping as a preoperative tool to explore potential mechanisms and patterns involved in the electrophysiology of persistent and long-standing persistent AF. METHODS:This prospective, observational study included cardiac surgery candidates without previous ablation. Bi-atrial epicardial activation sequences were obtained with electrocardiographic imaging and analysed in an independent core lab. Statistical analyses included hierarchical clustering, which quantified 3 clusters based on the number of drivers to identify specific characteristics. RESULTS:All 51 patients [14 (27%) persistent; 37 (73%) long-standing persistent; AF, duration 42 months (interquartile range 14-120)] had bi-atrial electrophysiological abnormalities. Most rotors were harbored in the upper half of the right atrium, involved in almost all patients (50/51, 98%), followed by the pulmonary vein areas and left-atrial backwall (48/51, 94%). Longer AF duration showed no association towards fewer rotor and focal activity (r = -0.08, P = 0.42; r = -0.06, P = 0.56, respectively). A significant correlation existed between larger left atrial (LA) size and fewer rotors (r = -0.33, P < 0.001), but not focal activity (r = 0.01, P = 0.92). The clusters differed in AF duration and LA size, and in their number of rotor and focal activities (P = 0.005, P < 0.001, respectively). CONCLUSIONS:The underlying electrophysiological mechanism was identified in all patients and consistently showed bi-atrial involvement irrespective of AF duration, LA size, or concomitant heart disease. In larger left atria and longer AF duration, the observed lower number of rotors might be related to atrial tissue fibrosis and lower amplitudes. The results demonstrate the potential role of preoperative mapping to improve procedural planning and our understanding of patients' electrophysiology. CLINICAL REGISTRATION:ClicalTrials.gov NCT06803615.

OBJECTIVE:Implant removal is a common method to quantify the level of osseointegration in small animal studies. Due to small implant sizes, precise alignment in removal experiments is crucial to obtain accurate and reproducible results. This study proposes a novel approach using photon counting detector computed tomography (PCD-CT) data and additive manufacturing to improve implant alignment. METHODS:A simplified finite element model was designed to investigate the effect of implant misalignment in removal tests. Additionally, the geometry of 43 rat tibiae was assessed utilizing PCD-CT scans, and subsequently specimen-specific positioning fixtures were designed and manufactured using computer-aided design and tabletop 3D printers. The accuracy and precision of the specimen alignment within the fixtures were assessed both visually (current state of the art) and through projectional radiography in both cranial-caudal (CC) and anterior-posterior (AP) projections to quantify true misalignment. RESULTS:Finite element analysis demonstrated that stresses and displacements are sensitive to misalignment, potentially leading to substantial inaccuracies in the implant removal measurements. Statistical analysis of visual assessments revealed poor to moderate inter- and intra-operator variability (0.336 ≤ ICC ≤ 0.625) and low correlation with true misalignment (0.024 ≤ R2 ≤ 0.204). Specimen alignment within the fixtures (CC: 0.23 ± 0.46°, AP: 1.00 ± 0.82°) showed improvement in accuracy and precision compared to visual assessments (CC: 0.88 ± 0.92°, AP: 1.11 ± 1.15°). CONCLUSION:The proposed specimen fixation and alignment, which relies on clinical imaging data and inexpensive 3D printers, offers a cost- and time-effective alternative to visual assessments, which could considerably improve the accuracy and precision in osseointegration assessment.

OBJECTIVES:In cardiac amyloidosis (CA) protein misfolding and consecutive storage into the extracellular myocardial compartment causes left ventricular hypertrophy and, in later stages of the disease, heart failure. The aim of this study was to compare extracellular volume (ECV) measurements obtained from photon-counting CT (PCCT) to the imaging reference cardiac magnetic resonance imaging (CMR) and to evaluate coronary artery disease (CAD) in a CA cohort. MATERIALS AND METHODS:Thirty CA patients (mean age 77.5 +/- 7.9 years) underwent clinically indicated coronary CT angiography (CCTA) for the evaluation of CAD on a first-generation PCCT including a late-phase scan for assessment of ECV. ECV in PCCT was derived using 2 different techniques: (I) a single-energy (SE) technique, based on attenuation changes between the precontrast calcium scoring scan and delayed CCTA in the equilibrium phase (II) a dual-energy (DE) technique, based on iodine density maps from the delayed scan. Both methods were compared with CMR-derived ECV. Statistical analysis included repeated-measures analysis of variance (RM-ANOVA) with Bonferroni-adjusted pairwise comparisons. Correlations between methods were assessed using Pearson's correlation coefficient, and agreement was evaluated using Bland-Altman analysis. RESULTS:CMR exhibited the highest mean ECV value (42.93 ± 10.14), followed by the SE method (42.5 ± 9.1), while the DE method yielded the lowest ECV values (40.7 ± 9.2). When compared with CMR, ECV obtained via the DE method was significantly lower ( MDiff  = -2.24, P =  0.04). In contrast, no significant difference was observed between CMR and the SE method ( MDiff  = 0.43, P  = 1.00). Differences between the DE and SE methods were significant ( MDiff  = -1.82, P <  0.001). Despite these differences, all 3 methods demonstrated excellent positive correlations. The strongest correlation was observed between the DE and SE methods ( r  = 0.98, P  < 0.001), indicating high consistency in their measurements. Comparatively, the correlation between CMR and DE ( r  = 0.892, P  < 0.001) was slightly stronger than that between CMR and SE methods ( r  = 0.882, P  < 0.001). CAD was present in 29 (97.0%) CA patients with a mean Agatston score of 1086 ± 1398 (range 0-6848.5). Despite this high mean plaque burden and 14 (47.6%) patients presenting with atrial fibrillation, image quality was preserved in 29 (97.0%) patients with 17 (57.6%) of the patients having nonobstructive CAD. CONCLUSIONS:Compared to the imaging reference standard CMR, ECV derived from the DE and SE methods via PCCT demonstrated excellent positive correlations with CMR. The DE method exhibited minor differences compared to CMR, which were clinically not relevant. CAD with an extensive burden of calcified plaque was highly prevalent in CA; however, 57.6% of patients presented with nonobstructive CAD. Therefore, PCCT is a valuable tool for imaging both the coronary arteries and myocardial structure in CA.

Background:Dual-source photon-counting detector computed tomography (PCDCT) offers the opportunity to perform cardiac examinations within one beat and simultaneously the acquisition of spectral information. This study, evaluated subjective and objective image quality of virtual monoenergetic image (VMI) reconstructions using data from a first-generation, dual-source PCDCT scanner, operated in high-pitch scanning mode. Methods:We retrospectively included 30 patients who underwent a clinically indicated CTA of the coronary arteries. VMI were reconstructed at five different energy levels. Subjective image quality was assessed by three radiologists according to a four-point Likert scale for four different quality features. To evaluate objective image quality, SNR and CNR were calculated via ROIs placed in the aorta, coronary arteries, myocardium, pectoral muscle, and epicardial fat. Results:VMI at 40, 50, 60, and 70 keV showed equal mean scores (4/4) for subjective vascular contrast, followed by 80 keV reconstructions with a mean score of 3/4. The 40 keV reconstruction yielded the lowest range (3-4) in Likert scores and highest percentage of reader agreement (80 %). Minor differences in subjective image noise, sharpness, and plaque visualization were observed with positive trends toward higher keV levels. SNR and CNR were superior for 40 keV, with a mean of 34.8 ± 1.7HU and 45.4 ± 2.7HU, respectively. Mean applied contrast volume was 65 ml, resulting in a mean CT value of 1150HU for 40 keV VMI. Conclusion:First-generation PCDCT-derived VMI at 40 and 50 keV offer satisfying subjective and objective image quality, even when acquired in high-pitch scanning mode.

In forensic medicine, maceration is often essential for examining bone surfaces, serving purposes such as identifying cut marks, making geometric measurements, and determining the victim’s age. While hot water maceration removes soft tissue effectively, it is known to cause bone surface shrinkage. This raises the question of whether this effect is permanent or if it can be partially reversed through rehydration, considering the presence of soft tissue. Computed tomography (CT) scans were conducted on the radii of 20 paired human anatomic forearm specimens. Subsequently, the radii were extracted, macerated in 60 °C water, CT-scanned in an air environment, rehydrated, re-implanted into the forearms, and CT-scanned again. Maceration resulted in a mean shrinkage of 0.12 mm on the outer bone surface. This shrinkage was nearly fully recoverable for the diaphysis after rehydration and accounting for soft tissue surrounding the bone. In contrast, the epiphysis showed permanent shrinkage, likely due to the loss of small bone fragments. Analysis of the inner bone surface indicated a smaller effect, but with significant standard deviations, especially for the epiphysis, possibly related to the less well-defined nature of the inner bone surface. The epiphyseal surface of hot water-macerated bone will, on average, be approximately 0.15 mm deflated and cannot retain the original surface. On the other hand, the diaphyseal surface is less affected and can be nearly completely restored after rehydration and accounting for soft tissue surrounding the bone.

Leaflet thrombosis (LT) is a multifaceted and underexplored condition that can manifest following transcatheter aortic valve implantation (TAVI). The objective of this study was to formulate a prediction model based on laboratory assessments and clinical parameters, providing additional guidance and insight into this relatively unexplored aspect of post-TAVI complications. The present study was an observational prospective hypothesis-generating study, including 101 patients who underwent TAVI and a screening for LT (the primary endpoint) by multidetector computed tomography (MDCT). All images were acquired on a third-generation dual-source CT system. Levels of von Willebrand factor (vWF) activity, hemoglobin (Hb), and lactate dehydrogenase (LDH) were measured among other parameters. A predictive score utilizing binary logistic regression, Kaplan–Meier time-to-event analysis, and receiver operating characteristics (ROC) analysis was established. LT (11 subclinical and 2 clinical) was detected in 13 of 101 patients (13

Background Additively manufactured (AM) anatomical bone models are primarily utilized for training and preoperative planning purposes. As such, they must meet stringent requirements, with dimensional accuracy being of utmost importance. This study aimed to evaluate the precision and accuracy of anatomical bone models manufactured using three different AM technologies: digital light processing (DLP), fused deposition modeling (FDM), and PolyJetting (PJ), built in three different part orientations. Additionally, the study sought to assess surgeons’ perceptions of how well these models mimic real bones in simulated osteosynthesis. Methods Computer-aided design (CAD) models of six human radii were generated from computed tomography (CT) imaging data. Anatomical models were then manufactured using the three aforementioned technologies and in three different part orientations. The surfaces of all models were 3D-scanned and compared with the original CAD models. Furthermore, an anatomical model of a proximal femur including a metastatic lesion was manufactured using the three technologies, followed by (mock) osteosynthesis performed by six surgeons on each type of model. The surgeons’ perceptions of the quality and haptic properties of each model were assessed using a questionnaire. Results The mean dimensional deviations from the original CAD model ranged between 0.00 and 0.13 mm with maximal inaccuracies < 1 mm for all models. In surgical simulation, PJ models achieved the highest total score on a 5-point Likert scale ranging from 1 to 5 (with 1 and 5 representing the lowest and highest level of agreement, respectively), (3.74 ± 0.99) in the surgeons’ perception assessment, followed by DLP (3.41 ± 0.99) and FDM (2.43 ± 1.02). Notably, FDM was perceived as unsuitable for surgical simulation, as the material melted during drilling and sawing. Conclusions In conclusion, the choice of technology and part orientation significantly influenced the accuracy and precision of additively manufactured bone models. However, all anatomical models showed satisfying accuracies and precisions, independent of the AM technology or part orientation. The anatomical and functional performance of FDM models was rated by surgeons as poor.

Background Data on the diagnostic accuracy of ultralow-dose (ULD) CT protocols for periodic surveillance in recipients of lung transplant are lacking. Purpose To assess the potential for radiation dose reduction using ULD photon-counting CT (PCT) to detect lung abnormalities in recipients of lung transplant during repeat CT follow-up. Materials and Methods Consecutive adult recipients of lung transplant undergoing same-day standard-of-care low-dose (LD) and ULD PCT from March 2023 to May 2023 were prospectively included. The ULD protocols were performed with two target effective doses comprising 20% (hereafter, ULD1) and 10% (hereafter, ULD2) of the standard LD protocol. The 1-mm reconstructions were reviewed by three readers. Subjective image quality, the visibility of certain anatomic structures (using a five-point Likert scale), and the presence of lung abnormalities were independently assessed. The χ2 or t tests were used to evaluate differences between the ULD1 and ULD2 protocols. Results A total of 82 participants (median age, 64 years [IQR, 54-69 years]; 47 male) were included (41 participants for each ULD protocol). The mean effective doses per protocol were 1.41 mSv ± 0.44 (SD) for LD, 0.26 mSv ± 0.08 for ULD1, and 0.17 mSv ± 0.04 for ULD2. According to three readers, the subjective image quality of the ULD images was deemed diagnostic (Likert score ≥3) in 39-40 (ULD1) and 40-41 (ULD2) participants, and anatomic structures could be adequately visualized (Likert score ≥3) in 33-41 (ULD1) and 34-41 (ULD2) participants. The detection accuracy for individual lung anomalies exceeded 70% for both ULD protocols, except for readers 1 and 3 detecting proximal bronchiectasis and reader 3 detecting bronchial wall thickening and air trapping. No evidence of a statistically significant difference in noise (P = .96), signal-to-noise ratio (P = .77), or reader accuracy (all P ≥ .05) was noted between the ULD protocols. Conclusion ULD PCT was feasible for detecting lung abnormalities following lung transplant, with a tenfold radiation dose reduction. © RSNA, 2024 Supplemental material is available for this article. See also the editorial by Ciet in this issue.

The visualization of peripheral in-stent restenosis using energy-integrating detector CT is challenging due to deficient spatial resolution and artifact formation. This study compares the first clinically available photon-counting detector CT to third-generation dual-source energy-integrating detector CT. Nylon cylinders with central bores (4 mm, 2 mm), mimicking 75

The introduction of three-dimensional (3D) printed anatomical models has garnered interest in pre-operative planning, especially in orthopedic and trauma surgery. Identifying potential error sources and quantifying their effect on the model dimensional accuracy are crucial for the applicability and reliability of such models. In this study, twenty radii were extracted from anatomic forearm specimens and subjected to osteotomy to simulate a defined fracture of the distal radius (Colles’ fracture). Various factors, including two different computed tomography (CT) technologies (energy-integrating detector (EID) and photon-counting detector (PCD)), four different CT scanners, two scan protocols (i.e., routine and high dosage), two different scan orientations, as well as two segmentation algorithms were considered to determine their effect on 3D model accuracy. Ground truth was established using 3D reconstructions of surface scans of the physical specimens. Results indicated that all investigated variables significantly impacted the 3D model accuracy (p < 0.001). However, the mean absolute deviation fell within the range of 0.03 ± 0.20 to 0.32 ± 0.23 mm, well below the 0.5 mm threshold necessary for pre-operative planning. Intra- and inter-operator variability demonstrated fair to excellent agreement for 3D model accuracy, with an intra-class correlation (ICC) of 0.43 to 0.92. This systematic investigation displayed dimensional deviations in the magnitude of sub-voxel imaging resolution for all variables. Major pitfalls included missed or overestimated bone regions during the segmentation process, necessitating additional manual editing of 3D models. In conclusion, this study demonstrates that 3D bone fracture models can be obtained with clinical routine scanners and scan protocols, utilizing a simple global segmentation threshold, thereby providing an accurate and reliable tool for pre-operative planning.

Background Thoracic computed tomography scans (CT) are used by several study groups to investigate the circulatory structures (heart and vessels) located behind the pressure point for chest compressions. Yet, it remains unclear how the positioning of these structures is influenced by factors such as intubation, the respiratory cycle and arm positioning. Methods We retrospectively analyzed data of adult patients with in- or out-of-hospital cardiac arrest who underwent thoracic CT imaging within one year before or up to six months after arrest. A region of interest (ROI) behind the pressure point was defined. The largest structure within this region was defined as “leading circulatory structure”, which was the primary outcome. Airway status (intubated versus spontaneous breathing), respiratory cycle (inspiration, expiration, resting expiratory position), and arm position (up over the head versus down beside the trunk) served as covariates in an ordinal regression model. Results Among 500 initially screened patients, 411 (82.2%) were included in the analysis. There was a significant association between the arm position and the leading circulatory structure behind the pressure point. However, no association was found with airway status or respiratory cycle. The most frequently identified leading circulatory structure was the left atrium (arms up: 41.8%, down: 50.7%), followed by the ascending aorta (up: 23.8% vs. down: 16.7%). The left ventricle was the leading structure in only one case (0.2%, arms down). Conclusion This study shows that arm position is significantly associated with the leading circulatory structure behind the pressure point for chest compressions in cardiac arrest.

Knowledge of the minimal detectable bone fracture gap is essential in three-dimensional (3D) models, particularly in pre-operative planning of osteosynthesis to avoid overlooking gaps. In this study, defined incisions and bony displacements ranging from 100 to 400 µm were created in diaphyseal radii in 20 paired forearm specimens and verified with light microscopy. The specimens were scanned utilizing different computed tomography (CT) technologies/scanners, specimen positionings, scan protocols, image segmentations, and processing protocols. Inter- and intra-operator variabilities were reported as coefficient kappa. In CT images, fracture gaps of 100 µm and bone lamellae of 300 µm and 400 µm width were identified at a rate of 80 to 100

In cardiac transplant recipients, non-invasive allograft surveillance for identifying patients at risk for graft failure remains challenging. The fat attenuation index (FAI) of the perivascular adipose tissue in coronary computed tomography angiography (CCTA) predicts outcomes in coronary artery disease in non-transplanted hearts; however, it has not been evaluated in cardiac transplant patients. We followed 39 cardiac transplant patients with two or more CCTAs obtained between 2010 and 2021. We performed FAI measurements around the proximal 4 cm segments of the left anterior descending (LAD), right coronary artery (RCA), and left circumflex artery (LCx) using a previously validated methodology. The FAI was analyzed at a threshold of − 30 to − 190 Hounsfield units. FAI measurements were completed in 113 CCTAs, obtained on two same-vendor CT models. Within each CCTA, the FAI values between coronary vessels were strongly correlated (RCA and LAD R = 0.67 (p < 0.0001), RCA and LCx R = 0.58 (p < 0.0001), LAD and LCx R = 0.67 (p < 0.0001)). The FAIs of each coronary vessel between the patient’s first and last CCTA completed at 120 kV were also correlated (RCA R = 0.73 (p < 0.0001), LAD R = 0.81 (p < 0.0001), LCx R = 0.55 (p = 0.0069). Finally, a high mean FAI value of all three coronary vessels at baseline (mean ≥ − 71 HU) was predictive of cardiac mortality or re-transplantation, however, not predictive of all cause-mortality. High baseline FAI values may identify a higher-risk cardiac transplant population; thus, FAI may support the implementation of CCTA in post-transplant surveillance. • Perivascular fat attenuation measured with coronary CT is feasible in cardiac transplant patients and may predict cardiac mortality or need for re-transplantation.

Odontoid fracture of the second cervical vertebra (C2) is the most common spinal fracture type in elderly patients. However, very little is known about the biomechanical fracture mechanisms, but could play a role in fracture prevention and treatment. This study aimed to investigate the biomechanical competence and fracture characteristics of the odontoid process. A total of 42 human C2 specimens (14 female and 28 male, 71.5 ± 6.5 years) were scanned via quantitative computed tomography, divided in 6 groups (n = 7) and subjected to combined quasi-static loading at a rate of 0.1 mm/s until fracturing at inclinations of −15°, 0° and 15° in sagittal plane, and −50° and 0° in transverse plane. Bone mineral density (BMD), specimen height, fusion state of the ossification centers, stiffness, yield load, ultimate load, and fracture type according to Anderson and d'Alonzo were assessed. While the lowest values for stiffness, yield, and ultimate load were observed at load inclination of 15° in sagittal plane, no statistically significant differences could be observed among the six groups (p = 0.235, p = 0.646, and p = 0.505, respectively). Evaluating specimens with only clearly distinguishable fusion of the ossification centers (n = 26) reveled even less differences among the groups for all mechanical parameters. BMD was positively correlated with yield load (R² = 0.350, p < 0.001), and ultimate load (R² = 0.955, p < 0.001), but not with stiffness (p = 0.070). Type III was the most common fracture type (23.5%). These biomechanical outcomes indicate that load direction plays a subordinate role in traumatic fractures of the odontoid process in contrast to BMD which is a strong determinant of stiffness and strength. Thus, odontoid fractures appear to result from an interaction between load magnitude and bone quality.