Clinical situations for which 3D printing is considered an appropriate representation or extension of data contained in a medical imaging examination: pediatric congenital heart disease conditions

BACKGROUND

The use of medical 3D printing (focusing on anatomical modeling) has continued to grow since the Radiological Society of North America's (RSNA) 3D Printing Special Interest Group (3DPSIG) released its initial guideline and appropriateness rating document in 2018. The 3DPSIG formed a focused writing group to provide updated appropriateness ratings for 3D printing anatomical models across a variety of congenital heart disease. Evidence-based- (where available) and expert-consensus-driven appropriateness ratings are provided for twenty-eight congenital heart lesion categories.

METHODS

A structured literature search was conducted to identify all relevant articles using 3D printing technology associated with pediatric congenital heart disease indications. Each study was vetted by the authors and strength of evidence was assessed according to published appropriateness ratings.

RESULTS

Evidence-based recommendations for when 3D printing is appropriate are provided for pediatric congenital heart lesions. Recommendations are provided in accordance with strength of evidence of publications corresponding to each cardiac clinical scenario combined with expert opinion from members of the 3DPSIG.

CONCLUSIONS

This consensus appropriateness ratings document, created by the members of the RSNA 3DPSIG, provides a reference for clinical standards of 3D printing for pediatric congenital heart disease clinical scenarios.

Angiographic velocimetry analysis using contrast dilution gradient method with a 1000 frames per second photon-counting detector

Purpose

Contrast dilution gradient (CDG) analysis is a quantitative method allowing blood velocity estimation using angiographic acquisitions. Currently, CDG is restricted to peripheral vasculature due to the suboptimal temporal resolution of current imaging systems. We investigate extension of CDG methods to the flow conditions of proximal vasculature using 1000 frames per second (fps) high-speed angiographic (HSA) imaging.

Approach

We performed in-vitro HSA acquisitions using the XC-Actaeon detector and 3D-printed patient-specific phantoms. The CDG approach was used for blood velocity estimation expressed as the ratio of temporal and spatial contrast gradients. The gradients were extracted from 2D contrast intensity maps synthesized by plotting intensity profiles along the arterial centerline at each frame. In-vitro results obtained at various frame rates via temporal binning of 1000 fps data were retrospectively compared to computational fluid dynamics (CFD) velocimetry. Full-vessel velocity distributions were estimated at 1000 fps via parallel line expansion of the arterial centerline analysis.

Results

Using HSA, the CDG method displayed agreement with CFD at or above 250 fps [mean-absolute error (MAE): 2.6±6.3  cm/s, p=0.05]. Relative velocity distributions correlated well with CFD at 1000 fps with universal underapproximation due to effects of pulsatile contrast injection (MAE: 4.3 cm/s).

Conclusions

Using 1000 fps HSA, CDG-based extraction of velocities across large arteries is possible. The method is sensitive to noise; however, image processing techniques and a contrast injection, which adequately fills the vessel assist algorithm accuracy. The CDG method provides high resolution quantitative information for rapidly transient flow patterns observed in arterial circulation.

Determining 3D Distributions of Pulsatile Blood Flow Using Orthogonal Simultaneous Biplane High-Speed Angiography (SB-HSA) with 1000 fps CdTe Photon Counting Detectors for 3D X-ray Particle Image Velocimetry (3D-XPIV) compared to Results Using Computational Fluid Dynamics (CFD)

3D hemodynamic distributions are useful for the diagnosis and treatment of aneurysms. Detailed blood-flow patterns and derived velocity maps can be obtained using 1000 fps High Speed Angiography (HSA). The novel orthogonal Simultaneous Biplane High-Speed Angiography (SB-HSA) system enables flow information to be quantified in multiple planes, and with additional components of flow at depth, accurate 3D flow distributions are available. Computational Fluid Dynamics (CFD) is the current standard for derivation of volumetric flow distributions, but obtaining solution convergence is computationally expensive and time intensive. More importantly, matching in-vivo boundary conditions is non-trivial. Therefore, an experimentally derived 3D flow distribution method could offer realistic results with less computation time. Using SB-HSA image sequences, 3D X-Ray Particle Image Velocimetry (3D-XPIV) was explored as a new method for assessing 3D flow. 3D-XPIV was demonstrated using an in-vitro setup, where a patient-specific internal carotid artery aneurysm model was attached to a flow loop, and an automated injection of iodinated microspheres was used as a flow tracer. Two 1000 fps photon-counting detectors were placed orthogonally with the aneurysm model in the FOV of both planes. Frame-synchronization of the two detectors made correlation of single-particle velocity components at a given timepoint possible. With frame-rates of 1000 fps, small particle displacements between frames resolved realistic time varying flow, where accurate velocity distributions depended on near-instantaneous velocities. 3D-XPIV velocity distributions were compared to CFD velocity distributions, where the simulation boundary conditions matched the in-vitro setup. Results showed similar velocity distributions between CFD and 3D-XPIV.

Multi-angled simultaneous biplane High-Speed Angiography (HSA) of patient-specific 3D-printed aneurysm phantoms using 1000 fps CdTe Photon-Counting Detectors (PCD's)

1000 fps HSA enables visualization of flow details, which may be important in accurately guiding interventional procedures; however, single-plane imaging may lack clear visualization of vessel geometry and flow detail. The previously presented high-speed orthogonal biplane imaging may overcome these limitations but may still result in foreshortening of vessel morphology. In certain morphologies, acquiring two non-orthogonal biplane projections at multiple angles can provide better flow detail rather than a standard orthogonal biplane acquisition. Flow studies of aneurysm models were performed, where simultaneous biplane acquisitions at various angles separating the two detector views allowed for better evaluation of morphology and flow. 3D-printed, patient-specific internal carotid artery aneurysm models were imaged with various non-orthogonal angles between the two high-speed photon-counting detectors (7.5 cm x 5 cm FOV) to provide frame-correlated simultaneous 1000-fps image sequences. Fluid dynamics were visualized in multi-angled planes of each model using automated injections of iodine contrast media. The resulting dual simultaneous frame-correlated 1000-fps acquisitions from multiple planes of each aneurysm model provided improved visualization of complex aneurysm geometries and flow streamlines. Multi-angled biplane acquisitions with frame correlation allows for further understanding of aneurysm morphology and flow details: additionally, the ability to recover fluid dynamics at depth enables accurate analysis of 3D flow streamlines, and it is expected that multiple-planar views will enable better volumetric flow visualization and quantification. Such better visualization has the potential to improve interventional procedures.

Investigating Angiographic Injection Parameters for Cerebral Aneurysm Hemodynamic Characterization Using Patient-Specific Simulated Angiograms

Cerebral aneurysm (CA) rupture is one of the major causes of hemorrhagic stroke. During endovascular therapy (ET), neurointerventionalists rely on qualitative image sequences and do not have access to crucial quantitative hemodynamic information. Quantifying angiographic image sequences can provide vital information, but it is not possible to perform this in a controlled manner in vivo. Computational fluid dynamics (CFD) is a valuable tool capable of providing high fidelity quantitative data by replicating the blood flow physics within the cerebrovasculature. In this work, we use simulated angiograms (SA) to quantify the hemodynamic interaction with a clinically utilized contrast agent. SA enables extraction of time density curves (TDC) within the desired region of interest to analyze hemodynamic parameters such as time to peak (TTP) and mean transit time (MTT) within the aneurysm. We present on the quantification of several hemodynamic parameters of interest for multiple, clinically-relevant scenarios such as variable contrast injection duration and bolus volumes for 7 patient-specific CA geometries. Results indicate that utilizing these analyses provides valuable hemodynamic information relating vascular and aneurysm morphology, contrast flow conditions and injection variability. The injected contrast circulates for multiple cardiac cycles within the aneurysmal region, especially for larger aneurysms and tortuous vasculature. The SA approach enables determination of angiographic parameters for each scenario. Together, these have the potential to overcome the existing barriers in quantifying angiographic procedures in vitro or in vivo, and can provide clinically valuable hemodynamic insights for CA treatment.

Use of 1000fps High Speed X-ray Angiography (HSAngio) to quantify differences in flow diversion effects of three stents with different coverage densities in a cerebral aneurysm invitro model

High temporal resolution images acquired using 1000fps HSAngio can be used to visualize blood flow patterns and derive flow velocities during neurointerventional procedures. In this work we use this technology to quantify the changes in the blood flow velocities inside a cerebral aneurysm after treatment with three different stents with varying degrees of metal coverage density; stent A : <2%, stent B: 23% and stent C: 40%. A 3D printed in-vitro model of internal carotid artery aneurysm was connected to a flow loop (60% water, 40% glycerol solution used as circulation fluid, circulation flow rate 8 L/s). An automatic programmable injector (KD Scientific Legato 110) was used to inject iodine contrast agent at a rate of 88 mL/min in 3secs. 1000 fps HSAngio sequences of the contrast injection were acquired using an Aries single photon counting detector (Direct Conversion Inc., Stockholm). From these images blood flow velocities were calculated using an optical flow algorithm. As expected the biggest reduction in blood flow velocity inside the aneurysm was 32.4% after deployment of stent C. However, the velocity profile distribution indicated there was still a significant inflow jet into the aneurysm which could be caused by a endoluminal leak between the stent and the vessel wall. The average reduction was only 14% after placement of stent B and 3% after placement of stent A. Blood velocity distribution maps derived using 1000fps HSAngiography technology can be used to evaluate the quality of flow diversion within the aneurysm after placement of stent. Critical information such as endo luminal leakage which can cause treatment failure can also be detected.

Simultaneous Biplane High Speed 1000 fps X-ray Angiography (HSAngio)

High-speed 1000-fps x-ray Angiography (HSAngio) images can be used to visualize blood-flow patterns and derive flow velocities during neurointerventional procedures. In this work, we present for the very first-time, orthogonal views of contrast injection in an aneurysm model acquired simultaneously using biplane HSAngio imaging. 3-D printed in-vitro models A and B of two different internal carotid-artery aneurysms were connected to a flow loop (circulation fluid: 60% water, 40% glycerol solution, circulation flow rate: 8 L/s). An automatic programmable injector (KD Scientific Legato 110) injected iodine contrast agent at a rate of 88 mL/min for a duration of 3 sec. With an RQA5 spectrum, 1000 fps HSAngio sequences of the contrast injection were acquired simultaneously on the frontal plane using the Actaeon detector (Direct Conversion, Stockholm) and on the lateral plane using the Aries (Direct Conversion, Stockholm) detector. The start of contrast injection and simultaneous biplane x-ray exposures and detector image acquisitions were manually synchronized to capture the initial inflow of contrast into the aneurysm region. For model A the frontal plane images gave a better visualization of the flow streamlines in the parent artery in the inflow (average velocity 28 cm/s) and outflow (average velocity 24 cm/s) region of the aneurysm. The vortices within the aneurysm region especially within the aneurysm dome were better visualized in the lateral plane images (average velocity 27 cm/s). Biplane HSAngio imaging techniques can give more accurate representations of 3-D blood flow within the complex vascular pathology of the human brain, compared to single-plane imaging.

Derivation of vascular wall shear stress from 1000 fps high-speed angiography (HSA) velocity distributions

Pathological changes in blood flow lead to altered hemodynamic forces, which are responsible for a number of conditions related to the remodeling and regeneration of the vasculature. More specifically, wall shear stress (WSS) has been shown to be a significant hemodynamic parameter with respect to aneurysm growth and rupture, as well as plaque activation leading to increased risk of stroke. In-vivo measurement of shear stress is difficult due to the stringent requirements on spatial resolution near the wall boundaries, as well as the deviation from the commonly assumed parabolic flow behavior at the wall. In this work, we propose an experimental method of in-vitro WSS calculations from high-temporal resolution velocity distributions, which are derived from 1000 fps high-speed angiography (HSA). The high-spatial and temporal resolution of our HSA detector makes such high-resolution velocity gradient measurements feasible. Presented here is the methodology for calculation of WSS in the imaging plane, as well as initial results for a variety of vascular geometries at physiologically realistic flow rates. Further, the effect of spatial resolution on the gradient calculation is explored using CFD-derived velocity data. Such angiographic-based analysis with HSA has the potential to provide critical hemodynamic feedback in an interventional setting, with the overarching objective of supporting clinical decision-making and improving patient outcomes.

Initial evaluation of 2D and 3D simulated high-speed 1000 fps vascular contrast-flow image sequences using computational fluid dynamics (CFD)

Digital subtraction angiography (DSA) remains the clinical standard for detailed visualization of the neurovasculature due to its high-spatial resolution; however, detailed blood-flow quantification is impaired by its low-temporal resolution. Advances in photon-counting detector technology have led us to develop High-Speed Angiography (HSA), where x-ray images are acquired at 1000 fps for more accurate visualization and quantification of blood flow. We have implemented a physics-based optical flow method to extract such information from HSA, but validation of the angiography-derived velocity distributions is not straightforward. Computational fluid dynamics (CFD) is widely regarded as the benchmark for hemodynamic analysis, as it provides a multitude of quantitative flow parameters throughout the volume of interest. However, there are several limitations with this method related to over-simplification of boundary conditions and suboptimal meshing (spatial resolution), that make CFD simulation results an inexact criterion for validation. To overcome this issue for HSA validation, CFD was used to generate both simulated high-speed angiograms and the corresponding ground-truth 3D flow fields to better understand the relationship between the 3D volumetric-flow distribution and the 2D projected-flow distribution as is obtained with angiography, and the subsequent 2D approximation of flow velocity. Several geometries were investigated, ranging from simple pipe models to complex patient-specific aneurysms. Simulated datasets were analyzed with the optical flow algorithm, and the effects of flow divergence, quantum mottle, and intensity gradient on the calculation were evaluated. From these simulations, we can evaluate whether flow fields reconstructed from HSA are representative of significant flow patterns in the 3D vasculature.

Leveraging Patient-Specific Simulated Angiograms to Characterize Cerebral Aneurysm Hemodynamics using Computational Fluid Dynamics

Cerebral aneurysms (CA) affect nearly 6% of the US population and its rupture is one of the major causes of hemorrhagic stroke. Neurointerventionalists performing endovascular therapy (ET) to treat CA rely on qualitative image sequences obtained under fluoroscopy guidance alone, and do not have access to crucial quantitative information regarding blood flow before, during and after treatment - partially contributing to a failure rate of up to 30%. Computational fluid dynamics (CFD) is a powerful tool that can provide a wealth of quantitative data; however, CFD has found limited utility in the clinic due to the challenges in obtaining hemodynamic boundary conditions for each patient. In this work, we present a novel CFD-based simulated angiogram approach (SAA) that resolves the blood flow physics and interaction between blood and injected contrast agent to extract quantitative hemodynamic parameters which can be used to design real-time parametric imaging analysis. The SAA enables correlating contrast agent transport to the underlying hemodynamic conditions via time-density curves (TDC) obtained at several points in the region of interest. The ability of the TDC and the SAA to provide critical hemodynamic parameters in and around CA anatomies, such as washout and local flow changes is explored and presented. This provides invaluable quantitative data to the clinician at the time of intervention, since it incorporates the physics of blood flow and correlates the contrast transport to hemodynamic parameters quantitatively - thereby enabling the clinician to take informed decisions that improve treatment outcomes.

Realistic computer modelling of stent retriever thrombectomy: a hybrid finite-element analysis-smoothed particle hydrodynamics model

Stent retriever thrombectomy is a pre-eminent treatment modality for large vessel ischaemic stroke. Simulation of thrombectomy could help understand stent and clot mechanics in failed cases and provide a digital testbed for the development of new, safer devices. Here, we present a novel, in silico thrombectomy method using a hybrid finite-element analysis (FEA) and smoothed particle hydrodynamics (SPH). Inspired by its biological structure and components, the blood clot was modelled with the hybrid FEA-SPH method. The Solitaire self-expanding stent was parametrically reconstructed from micro-CT imaging and was modelled as three-dimensional finite beam elements. Our simulation encompassed all steps of mechanical thrombectomy, including stent packaging, delivery and self-expansion into the clot, and clot extraction. To test the feasibility of our method, we simulated clot extraction in simple straight vessels. This was compared against in vitro thrombectomies using the same stent, vessel geometry, and clot size and composition. Comparisons with benchtop tests indicated that our model was able to accurately simulate clot deflection and penetration of stent wires into the clot, the relative movement of the clot and stent during extraction, and clot fragmentation/embolus formation. In this study, we demonstrated that coupling FEA and SPH techniques could realistically model stent retriever thrombectomy.

Factors Associated With Decreased Accuracy of Modified Thrombolysis in Cerebral Infarct Scoring Among Neurointerventionalists During Thrombectomy

Background and Purpose

The modified Thrombolysis in Cerebral Infarct (mTICI) score is used to grade angiographic outcome after endovascular thrombectomy. We sought to identify factors that decrease the accuracy of intraprocedural mTICI.

Methods

We performed a 2-center retrospective cohort study comparing operator (n=6) mTICI scores to consensus scores from blinded adjudicators. Groups were also assessed by dichotomizing mTICI scores to 0–2a versus 2b–3.

Results

One hundred thirty endovascular thrombectomy procedures were included. Operators and adjudicators had a pairwise agreement in 96 cases (73.8%). Krippendorff α was 0.712. Multivariate analysis showed endovascular thrombectomy overnight (odds ratio [OR]=3.84 [95% CI, 1.22–12.1]), lacking frontal (OR, 5.66 [95 CI, 1.36–23.6]), or occipital (OR, 7.18 [95 CI, 2.12–24.3]) region reperfusion, and higher operator mTICI scores (OR, 2.16 [95 CI, 1.16–4.01]) were predictive of incorrectly scoring mTICI intraprocedurally. With dichotomized mTICI scores, increasing number of passes was associated with increased risk of operator error (OR, 1.93 [95 CI, 1.22–3.05]).

Conclusions

In our study, mTICI disagreement between operator and adjudicators was observed in 26.2% of cases. Interventions that took place between 22:30 and 4:00, featured frontal or occipital region nonperfusion, higher operator mTICI scores, and increased number of passes had higher odds of intraprocedural mTICI inaccuracy.

Evaluation of methods to derive blood flow velocity from 1000 fps high-speed angiographic sequences (HSA) using optical flow (OF) and computational fluid dynamics (CFD)

Digital Subtraction Angiography (DSA) is considered the gold standard for imaging and guiding treatment of neurovascular lesions, such as cerebral aneurysms and carotid stenoses. Though DSA can show high-resolution morphology, it remains difficult to extract temporal physiological information, because higher frame-rates are necessary to accurately quantify neurovascular flow details. Recent advances in photon-counting detector technology have led us to develop High-Speed Angiography (HSA), where X-ray images are acquired at 1000 fps for more accurate visualization and quantification of blood flow. Blood flow was imaged using HSA under constant flow conditions within various 3D printed patient-specific phantoms. Blood velocity was quantified using an open source Optical Flow algorithm, OpenOpticalFlow, to perform velocity estimation based on the spatio-temporal intensity changes of iodinated contrast wavefronts. The results of these algorithms are then compared with Computational Fluid Dynamics (CFD) simulations, using the same inlet boundary conditions and model geometries. The performance of these algorithms at lower temporal resolution was then also assessed by simulating lower frame rates from the acquired 1000 fps data. It is important to ascertain the hemodynamic effect of abnormal neurovascular conditions, as well as their effect on treatment of such conditions during the actual clinical interventional procedure. While theoretical CFD results requiring considerable computer capability are delayed for hours or more, it is expected that clinical results from multiple HSA sequences will be available almost immediately while the patient is still under treatment, and even right after flow conditions are changed beneficially by the intervention.

Characterization of velocity patterns produced by pulsatile and constant flows using 1000 fps high-speed angiography (HSA)

In order to accurately quantify rapidly changing blood flow velocities, as typically seen in the neurovasculature, high temporal resolution is necessary. Current methods to extract velocity data from angiographic image sequences are generally limited to 30 fps or less. High-speed angiography (HSA) with a maximal frame rate of 1000 fps can be used to evaluate time-dependent flow details normally averaged out with lower frame rates. For new HSA image sequences, two different quantitative methods were utilized to extract high-temporal resolution velocity changes: X-Ray Particle Image Velocimetry (X-PIV) and optical flow (OF). A variety of flow conditions were examined in a range of patient-specific 3D-printed phantoms. Both pulsatile and constant flow settings were investigated. X-PIV was performed using radiopaque sub-millimeter microspheres, which were tracked throughout the image sequence to provide accurate, but limited sampling of the velocity field within the 3D-printed models. Also, an open source optical flow algorithm, OpenOpticalFlow, was used to perform velocity estimation based on the spatio-temporal intensity changes of iodinated contrast wavefronts. Periodic changes in velocity within each phantom ROI can be illustrated throughout the pulsatile cycle capture by the high-speed detector. In the constant flow sequences, changes in velocity across the phantom geometry can be seen. The ability to accurately measure detailed velocity distributions and velocity changes throughout various flow conditions at high temporal resolution enables further insight into the evaluation and treatment of neurovascular disease states.

Semi-automated measurement of vascular tortuosity and its implications for mechanical thrombectomy performance

PURPOSE

Few studies have examined the geometry of endovascular mechanical thrombectomy pathways. Here we examine the tortuosity and angulations of catheter pathways from the aortic arch to the termination of the internal carotid artery (ICA) and its association with thrombectomy performance.

METHODS

We included 100 consecutive anterior circulation large vessel occlusion thrombectomy patients over 12 months. Computed tomography angiograms (CTA) were used for 3D segmentation of catheter pathway from the aortic arch to ICA termination. Tortuosity index (TI) and angulations of the catheter pathway were measured in a semi-automated fashion. TI and angulation degree were compared between sides and correlated with age and procedural measures.

RESULTS

We analyzed 188 catheter pathways in 100 patients. Severe angulation (≤ 30°) was present in 5.8% and 39.4% of common carotid artery (CCA) and extracranial ICA segments, respectively. Five pathways (2.6%) had 360° loop. CCA and extracranial ICA tortuosity had a weak but significant correlation with age (r = 0.17, 0.21, p value = 0.05, 0.02 respectively), time from groin puncture to the site of occlusion (r = 0.29, 0.25, p values = 0.008, 0.026 respectively), and fluoroscopy time (r = 0.022, 0.31, p values = 0.016, 0.001 respectively). There was a significant difference in the pattern of angulation (p value = 0.04) and tortuosity between right and left side in CCA segment (TI = 0.20 ± 0.086 vs. 0.15 ± 0.82, p value < 0.001).

CONCLUSIONS

There was a significant difference in CCA angulation between right and left sides. TI of extracranial CCA and ICA correlated with age and influenced time from groin puncture to the occlusion site and total fluoroscopy time.

Determination of Fat,Moisture, and Protein in Meat and Meat Products by Using the FOSS FoodScan Near-Infrared Spectrophotometer with FOSS Artificial Neural Network Calibration Model and Associated Database: Collaborative Study

A collaborative study was conducted to evaluate the repeatability and reproducibility of the FOSS FoodScan near-infrared spectrophotometer with artificial neural network calibration model and database for the determination of fat, moisture, and protein in meat and meat products. Representative samples were homogenized by grinding according to AOAC Official Method 983.18. Approximately 180 g ground sample was placed in a 140 mm round sample dish, and the dish was placed in the FoodScan. The operator ID was entered, the meat product profile within the software was selected, and the scanning process was initiated by pressing the start button. Results were displayed for percent (g/100 g) fat, moisture, and protein. Ten blind duplicate samples were sent to 15 collaborators in the United States. The within-laboratory (repeatability) relative standard deviation (RSDr) ranged from 0.22 to 2.67% for fat, 0.23 to 0.92% for moisture, and 0.35 to 2.13% for protein. The between-laboratories (reproducibility) relative standard deviation (RSDR) ranged from 0.52 to 6.89% for fat, 0.39 to 1.55% for moisture, and 0.54 to 5.23% for protein. The method is recommended for Official First Action.

High-Definition Zoom Mode, a High-Resolution X-Ray Microscope for Neurointerventional Treatment Procedures: A Blinded-Rater Clinical-Utility Study

BACKGROUND AND PURPOSE

Quality of visualization of treatment devices during critical stages of endovascular interventions, can directly impact their safety and efficacy. Our aim was to compare the visualization of neurointerventional procedures and treatment devices using a 194-μm pixel flat panel detector mode and a 76-μm pixel complementary metal oxide semiconductor detector mode (high definition) of a new-generation x-ray detector system using a blinded-rater study.

MATERIALS AND METHODS

Deployment of flow-diversion devices for the treatment of internal carotid artery aneurysms was performed under flat panel detector and high-definition-mode image guidance in a neurointerventional phantom simulating patient cranium and tissue attenuation, embedded with 3D-printed intracranial vascular models, each with an aneurysm in the ICA segment. Image-sequence pairs of device deployments for each detector mode, under similar exposure and FOV conditions, were evaluated by 2 blinded experienced neurointerventionalists who independently selected their preferred image on the basis of visualization of anatomic features, image noise, and treatment device. They rated their selection as either similar, better, much better, or substantially better than the other choice. Inter- and intrarater agreement was calculated and categorized as poor, moderate, and good.

RESULTS

Both raters demonstrating good inter- and intrarater agreement selected high-definition-mode images with a frequency of at least 95% each and, on average, rated the high-definition images as much better than flat panel detector images with a frequency of 73% from a total of 60 image pairs.

CONCLUSIONS

Due to their higher resolution, high-definition-mode images are sharper and visually preferred compared with the flat panel detector images. The improved imaging provided by the high-definition mode can potentially provide an advantage during neurointerventional procedures.

Survival Rates and Complications for Zirconia-Based Fixed Dental Prostheses in a Period up to 10 Years: A Systematic Review

AIMS

The purpose of this study was to methodically review the literature concerning the success and survival rates of zirconia fixed dental prostheses (FDPs).

METHODS

A systematic search was conducted of MEDLINE, Elsevier and the Cochrane Library to identify relevant articles about zirconia FDPs. In order to obtain suitable articles, rigorous criteria were applied. The minimum follow-up period was five years.

RESULTS

From a total of 986 articles identified in the first electronic search, only 10 matched the inclusion criteria. A total of 368 patients with 430 zirconia FDPs were included in this systematic review. The survival rate was 89.43% ± 10.01% and chipping of the veneering ceramic occurred in 16.97% of the cases.

CONCLUSION

Zirconia-based fixed dental prostheses perform reasonably well and can serve as an alternative to metal-ceramic fixed dental prostheses.

9.4T Magnetic Resonance Imaging of the Mouse Circle of Willis Enables Serial Characterization of Flow-Induced Vascular Remodeling by Computational Fluid Dynamics

BACKGROUND

The neurovasculature dynamically responds to changes in cerebral blood flow by vascular remodeling processes. Serial imaging studies in mouse models could help characterize pathologic and physiologic flow-induced remodeling of the Circle of Willis (CoW).

METHOD

We induced flow-driven pathologic cerebral vascular remodeling in the CoW of mice (n=3) by ligation of the left Common Carotid Artery (CCA), and the right external carotid and pterygopalatine arteries, increasing blood flow through the basilar and the right internal carotid arteries. One additional mouse was used as a wild-type control. Magnetic Resonance Imaging (MRI) at 9.4 Tesla (T) was used to serially image the mouse CoW over three months, and to obtain threedimensional images for use in Computational Fluid Dynamic (CFD) simulations. Terminal vascular corrosion casting and scanning electron microscope imaging were used to identify regions of macroscopic and microscopic arterial damage.

RESULTS

We demonstrated the feasibility of detecting and serially measuring pathologic cerebral vascular changes in the mouse CoW, specifically in the anterior vasculature. These changes were characterized by bulging and increased vessel tortuosity on the anterior cerebral artery and aneurysm- like remodeling at the right olfactory artery origin. The resolution of the 9.4T system further allowed us to perform CFD simulations in the anterior CoW, which showed a correlation between elevated wall shear stress and pathological vascular changes.

CONCLUSION

In the future, serial high-resolution MRI could be useful for characterizing the flow environments corresponding to other pathologic remodeling processes in the mouse CoW, such as aneurysm formation, subarachnoid hemorrhage, and ischemia.

The Impact of Socioeconomic Status and Nutritional Biochemical Markers on Quality of Life of Chronic Dialysis Patients?

AIM

This cross-sectional study aimed to determine the relationship between socio-economic status and laboratory values with mental and physical components of QoL (quality of life) in chronic dialysis patients.

MATERIAL AND METHODS

254 patients were included in the study and divided into two groups: 243 hemodialysis (HD) patients and 11 peritoneal dialysis (PD) patients. QoL was measured by the Short Form 36(SF-36). Scores for all dimensions are expressed on a 0-100 scale. Higher score indicates better health status. Two more questions related to monthly food expenditure and the presence/or lack of family support were added. Laboratory investigations included the following nutritional parameters: serum albumin and creatinine.

RESULTS

Our study results showed that compared to PD group in HD patients QoL was compromised in all SF-36 subscale except physical functioning, role limitations due to physical functioning and role limitations due to emotional functioning. Also, the presence of supportive family members/ caregivers showed a significant improvement of all QoL scores. HD patients who spend at least 90 euros monthly on groceries/food had higher values of SF-36 items. Better QoL is associated with high pre-dialysis serum creatinine and serum albumin levels.

CONCLUSIONS

Future work should incorporate larger and more balanced sample sizes and patient recruitment from multiple dialysis centers to truly capture the variability in patient characteristics.

Bunker probe: A plasma potential probe almost insensitive to its orientation with the magnetic field

Due to their ability to suppress a large part of the electron current and thus measuring directly the plasma potential, ion sensitive probes have begun to be widely tested and used in fusion devices. For these probes to work, almost perfect alignment with the total magnetic field is necessary. This condition cannot always be fulfilled due to the curvature of magnetic fields, complex magnetic structure, or magnetic field reconnection. In this perspective, we have developed a plasma potential probe (named Bunker probe) based on the principle of the ion sensitive probe but almost insensitive to its orientation with the total magnetic field. Therefore it can be used to measure the plasma potential inside fusion devices, especially in regions with complex magnetic field topology. Experimental results are presented and compared with Ball-Pen probe measurements taken under identical conditions. We have observed that the floating potential of the Bunker probe is indeed little affected by its orientation with the magnetic field for angles ranging from 90° to 30°, in contrast to the Ball-Pen probe whose floating potential decreases towards that of a Langmuir probe if not properly aligned with the magnetic field.

Profile measurements of the electron temperature on the ASDEX Upgrade, COMPASS, and ISTTOK tokamak using Thomson scattering, triple, and ball-pen probes

The ball-pen probe (BPP) technique is used successfully to make profile measurements of the electron temperature on the ASDEX Upgrade (Axially Symmetric Divertor Experiment), COMPASS (COMPact ASSembly), and ISTTOK (Instituto Superior Tecnico TOKamak) tokamak. The electron temperature is provided by a combination of the BPP potential (ΦBPP) and the floating potential (Vfl) of the Langmuir probe (LP), which is compared with the Thomson scattering diagnostic on ASDEX Upgrade and COMPASS. Excellent agreement between the two diagnostics is obtained for circular and diverted plasmas and different heating mechanisms (Ohmic, NBI, ECRH) in deuterium discharges with the same formula Te = (ΦBPP - Vfl)/2.2. The comparative measurements of the electron temperature using BPP/LP and triple probe (TP) techniques on the ISTTOK tokamak show good agreement of averaged values only inside the separatrix. It was also found that the TP provides the electron temperature with significantly higher standard deviation than BPP/LP. However, the resulting values of both techniques are well in the phase with the maximum of cross-correlation function being 0.8.

Measurement of pion, kaon and proton production in proton-proton collisions at [Formula: see text] TeV

The measurement of primary [Formula: see text], [Formula: see text], [Formula: see text] and [Formula: see text] production at mid-rapidity ([Formula: see text] 0.5) in proton-proton collisions at [Formula: see text][Formula: see text] 7 TeV performed with a large ion collider experiment at the large hadron collider (LHC) is reported. Particle identification is performed using the specific ionisation energy-loss and time-of-flight information, the ring-imaging Cherenkov technique and the kink-topology identification of weak decays of charged kaons. Transverse momentum spectra are measured from 0.1 up to 3 GeV/[Formula: see text] for pions, from 0.2 up to 6 GeV/[Formula: see text] for kaons and from 0.3 up to 6 GeV/[Formula: see text] for protons. The measured spectra and particle ratios are compared with quantum chromodynamics-inspired models, tuned to reproduce also the earlier measurements performed at the LHC. Furthermore, the integrated particle yields and ratios as well as the average transverse momenta are compared with results at lower collision energies.

Treatment Planning for Image-Guided Neuro-Vascular Interventions Using Patient-Specific 3D Printed Phantoms

Minimally invasive endovascular image-guided interventions (EIGIs) are the preferred procedures for treatment of a wide range of vascular disorders. Despite benefits including reduced trauma and recovery time, EIGIs have their own challenges. Remote catheter actuation and challenging anatomical morphology may lead to erroneous endovascular device selections, delays or even complications such as vessel injury. EIGI planning using 3D phantoms would allow interventionists to become familiarized with the patient vessel anatomy by first performing the planned treatment on a phantom under standard operating protocols. In this study the optimal workflow to obtain such phantoms from 3D data for interventionist to practice on prior to an actual procedure was investigated. Patient-specific phantoms and phantoms presenting a wide range of challenging geometries were created. Computed Tomographic Angiography (CTA) data was uploaded into a Vitrea 3D station which allows segmentation and resulting stereo-lithographic files to be exported. The files were uploaded using processing software where preloaded vessel structures were included to create a closed-flow vasculature having structural support. The final file was printed, cleaned, connected to a flow loop and placed in an angiographic room for EIGI practice. Various Circle of Willis and cardiac arterial geometries were used. The phantoms were tested for ischemic stroke treatment, distal catheter navigation, aneurysm stenting and cardiac imaging under angiographic guidance. This method should allow for adjustments to treatment plans to be made before the patient is actually in the procedure room and enabling reduced risk of peri-operative complications or delays.

A Combination of Spatial and Recursive Temporal Filtering for Noise Reduction when Using Region of Interest (ROI) Fluoroscopy for Patient Dose Reduction in Image Guided Vascular Interventions with Significant Anatomical Motion

Because x-ray based image-guided vascular interventions are minimally invasive they are currently the most preferred method of treating disorders such as stroke, arterial stenosis, and aneurysms; however, the x-ray exposure to the patient during long image-guided interventional procedures could cause harmful effects such as cancer in the long run and even tissue damage in the short term. ROI fluoroscopy reduces patient dose by differentially attenuating the incident x-rays outside the region-of-interest. To reduce the noise in the dose-reduced regions previously recursive temporal filtering was successfully demonstrated for neurovascular interventions. However, in cardiac interventions, anatomical motion is significant and excessive recursive filtering could cause blur. In this work the effects of three noise-reduction schemes, including recursive temporal filtering, spatial mean filtering, and a combination of spatial and recursive temporal filtering, were investigated in a simulated ROI dose-reduced cardiac intervention. First a model to simulate the aortic arch and its movement was built. A coronary stent was used to simulate a bio-prosthetic valve used in TAVR procedures and was deployed under dose-reduced ROI fluoroscopy during the simulated heart motion. The images were then retrospectively processed for noise reduction in the periphery, using recursive temporal filtering, spatial filtering and a combination of both. Quantitative metrics for all three noise reduction schemes are calculated and are presented as results. From these it can be concluded that with significant anatomical motion, a combination of spatial and recursive temporal filtering scheme is best suited for reducing the excess quantum noise in the periphery. This new noise-reduction technique in combination with ROI fluoroscopy has the potential for substantial patient-dose savings in cardiac interventions.

Influence of cryopreservation and mechanical stimulation on equine Autologous Conditioned Plasma (ACP®)

OBJECTIVE

To determine the influence of cryopreservation at two different temperatures on platelet concentration, growth factor (GF) levels and platelet activation parameters in equine ACP®; moreover, to determine if adding mechanical ACP® stimulation to freeze-thaw activation amplifies GF release from platelets.

MATERIAL AND METHODS

Firstly, blood from five horses was used to prepare ACP®. Platelet, platelet derived growth factor BB (PDGF-BB) and transforming growth factor β1 (TGF-β1) concentrations as well as mean platelet volume (MPV) and mean platelet component (MPC) were determined in fresh and corresponding ACP® samples after 2 months cryopreservation at -20 °C and -80 °C, respectively. Secondly, ACP® was prepared from blood of nine horses. Half of ACP® was activated using one freeze-thaw-cycle at -20 °C, whereas the rest was first vortexed. Their PDGF-BB and TGF-β1 concentrations were subsequently determined.

RESULTS

Platelet concentration significantly decreased after -80 °C cryopreservation. PDGF-BB level augmented significantly after both storage methods, whereas TGF-β1 concentration was not significantly altered. MPV significantly increased after -20 °C cryopreservation. Both storage regimens induced a significant MPC decrease. No significant differences in GF concentrations between the vortexed and non-vortexed samples were detected.

DISCUSSION

Both cryopreservation methods induced platelet activation, but storage at -80 °C apparently harmed the platelets without generating higher GF release than -20 °C. The mechanical stimulation process could not enhance GF release in subsequently frozen-thawed ACP®.

CONCLUSION AND CLINICAL RELEVANCE

Storage of ACP® at -20 °C could be useful in equine practice, but, before this procedure can be recommended, further qualitative tests are needed. The mechanical stimulation technique should be adjusted in order to increase platelet activation.

Production of [Formula: see text] and [Formula: see text] in proton-proton collisions at [Formula: see text] 7 TeV

The production of the strange and double-strange baryon resonances ([Formula: see text], [Formula: see text]) has been measured at mid-rapidity ([Formula: see text][Formula: see text]) in proton-proton collisions at [Formula: see text] [Formula: see text] 7 TeV with the ALICE detector at the LHC. Transverse momentum spectra for inelastic collisions are compared to QCD-inspired models, which in general underpredict the data. A search for the [Formula: see text] pentaquark, decaying in the [Formula: see text] channel, has been carried out but no evidence is seen.

Three-dimensional printing to facilitate anatomic study, device development, simulation, and planning in thoracic surgery

BACKGROUND

The development and deployment of new technologies in additive 3-dimensional (3D) printing (ie, rapid prototyping and additive manufacturing) in conjunction with medical imaging techniques allow the creation of anatomic models based on patient data.

OBJECTIVE

To explore this rapidly evolving technology for possible use in care and research for patients undergoing thoracic surgery.

METHODS

Because of an active research project at our institution on regional lung chemotherapy, human pulmonary arteries (PAs) were chosen for this rapid prototyping project. Computed tomography (CT) and CT angiography in combination with segmentation techniques from 2 software packages were used for rapid generation and adjustment of the 3D polygon mesh and models reconstruction of the PAs. The reconstructed models were exported as stereolithographic data sets and further processed by trimming, smoothing, and wall extrusion.

RESULTS

Flexible 3D printed replicas of 10 patient PAs were created successfully with no print failures; however, 1 initial test print with a 1 mm mural thickness was too fragile so the whole group was printed with a 1.5 mm wall. The design process took 8 hours for each model (CT image to stereolithographic) and printing required 97 hours in aggregate. Useful differences in anatomy were defined by this method, such as the expected greater number of proximal branches on the left versus right (2.5 ± 1.1 vs 1.0 ± 0.0; P = .001).

CONCLUSIONS

Reconstructed models of pulmonary arteries using 3D rapid prototyping allow replication of sophisticated anatomical structures that can be used to facilitate anatomic study, surgical planning, and device development.

Exclusive J/ψ photoproduction off protons in ultraperipheral p-Pb collisions at √(s(NN))=5.02 TeV

We present the first measurement at the LHC of exclusive J/ψ photoproduction off protons, in ultraperipheral proton-lead collisions at sqrt[s_{NN}]=5.02  TeV. Events are selected with a dimuon pair produced either in the rapidity interval, in the laboratory frame, 2.5<y<4 (p-Pb) or -3.6<y<-2.6 (Pb-p), and no other particles observed in the ALICE acceptance. The measured cross sections σ(γ+p→J/ψ+p) are 33.2±2.2(stat)±3.2(syst)±0.7(theor)  nb in p-Pb and 284±36(stat)_{-32}^{+27}(syst)±26(theor)  nb in Pb-p collisions. We measure this process up to about 700 GeV in the γp center of mass, which is a factor of two larger than the highest energy studied at HERA. The data are consistent with a power law dependence of the J/ψ photoproduction cross section in γp energies from about 20 to 700 GeV, or equivalently, from Bjorken x scaling variable between ∼2×10^{-2} and ∼2×10^{-5}, thus indicating no significant change in the gluon density behavior of the proton between HERA and LHC energies.

Measurement of prompt D-meson production in p-Pb collisions at √(s(NN))=5.02 TeV

The p_{T}-differential production cross sections of the prompt charmed mesons D^{0}, D^{+}, D^{*+}, and D_{s}^{+} and their charge conjugate in the rapidity interval -0.96<y_{cms}<0.04 were measured in p-Pb collisions at a center-of-mass energy sqrt[s_{NN}]=5.02  TeV with the ALICE detector at the LHC. The nuclear modification factor R_{pPb}, quantifying the D-meson yield in p-Pb collisions relative to the yield in pp collisions scaled by the number of binary nucleon-nucleon collisions, is compatible within the 15%-20% uncertainties with unity in the transverse momentum interval 1<p_{T}<24  GeV/c. No significant difference among the R_{pPb} of the four D-meson species is observed. The results are described within uncertainties by theoretical calculations that include initial-state effects. The measurement adds experimental evidence that the modification of the momentum spectrum of D mesons observed in Pb-Pb collisions with respect to pp collisions is due to strong final-state effects induced by hot partonic matter.

Measurement of quarkonium production at forward rapidity in [Formula: see text] collisions at [Formula: see text]TeV

The inclusive production cross sections at forward rapidity of [Formula: see text], [Formula: see text], [Formula: see text](1S) and [Formula: see text](2S) are measured in [Formula: see text] collisions at [Formula: see text] with the ALICE detector at the LHC. The analysis is based on a data sample corresponding to an integrated luminosity of 1.35 pb[Formula: see text]. Quarkonia are reconstructed in the dimuon-decay channel and the signal yields are evaluated by fitting the [Formula: see text] invariant mass distributions. The differential production cross sections are measured as a function of the transverse momentum [Formula: see text] and rapidity [Formula: see text], over the ranges [Formula: see text] GeV/c for [Formula: see text], [Formula: see text] GeV/c for all other resonances and for [Formula: see text]. The measured cross sections integrated over [Formula: see text] and [Formula: see text], and assuming unpolarized quarkonia, are: [Formula: see text] [Formula: see text]b, [Formula: see text] [Formula: see text]b, [Formula: see text] nb and [Formula: see text] nb, where the first uncertainty is statistical and the second one is systematic. The results are compared to measurements performed by other LHC experiments and to theoretical models.