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Metal artifact reduction (MAR) algorithms are used with cone beam computed tomography (CBCT) during augmented reality surgical navigation for minimally invasive pedicle screw instrumentation. The aim of this study was to assess intra- and inter-observer reliability of pedicle screw placement and to compare the perception of baseline image quality (NoMAR) with optimized image quality (MAR). CBCT images of 24 patients operated on for degenerative spondylolisthesis using minimally invasive lumbar fusion were analyzed retrospectively. Images were treated using NoMAR and MAR by an engineer, thus creating 48 randomized files, which were then independently analyzed by 3 spine surgeons and 3 radiologists. The Gertzbein and Robins classification was used for screw accuracy rating, and an image quality scale rated the clarity of pedicle screw and bony landmark depiction. Intra-class correlation coefficients (ICC) were calculated. NoMAR and MAR led to similarly good intra-observer (ICC > 0.6) and excellent inter-observer (ICC > 0.8) assessment reliability of pedicle screw placement accuracy. The image quality scale showed more variability in individual image perception between spine surgeons and radiologists (ICC range 0.51−0.91). This study indicates that intraoperative screw positioning can be reliably assessed on CBCT for augmented reality surgical navigation when using optimized image quality. Subjective image quality was rated slightly superior for MAR compared to NoMAR.
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Tornillos Pediculares , Cirugía Asistida por Computador , Artefactos , Tomografía Computarizada de Haz Cónico/métodos , Humanos , Reproducibilidad de los Resultados , Estudios Retrospectivos , Cirugía Asistida por Computador/métodosRESUMEN
Hydrogen storage in geological formations is one of the most promising technologies for balancing major fluctuations between energy supply from renewable energy plants and energy demand of customers. If hydrogen gas is stored in a porous medium or if it leaks into a shallow aquifer, redox reactions can oxidize hydrogen and reduce electron acceptors such as nitrate, FeIII and MnIV (hydro)oxides, sulfate, and carbonate. These reactions are of key significance, because they can cause unintentional losses in hydrogen stored in porous media and they also can cause unwanted changes in the composition of protected potable groundwater. To represent an aquifer environment enclosing a hydrogen plume, laboratory experiments using sediment-filled columns were constructed and percolated by groundwater in equilibrium with high (2-15 bar) hydrogen partial pressures. Here, we show that hydrogen is consumed rapidly in these experiments via sulfate reduction (18 ± 5 µM h-1) and acetate production (0.030 ± 0.006 h-1), while no methanogenesis took place. The observed reaction rates were independent from the partial pressure of hydrogen and hydrogen consumption only stopped in supplemental microcosm experiments where salinity was increased above 35 g L-1. The outcomes presented here are implemented for planning the sustainable use of the subsurface space within the ANGUS+ project.
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Agua Subterránea , Contaminantes Químicos del Agua , Compuestos Férricos , Hidrógeno , Oxidación-Reducción , SulfatosRESUMEN
Purpose To assess the visibility of radiopaque microspheres during transarterial embolization (TAE) in the VX2 rabbit liver tumor model by using multimodality imaging, including single-snapshot radiography, cone-beam computed tomography (CT), multidetector CT, and micro-CT. Materials and Methods The study was approved by the institutional animal care and use committee. Fifteen VX2-tumor-bearing rabbits were assigned to three groups depending on the type of embolic agent injected: 70-150-µm radiopaque microspheres in saline (radiopaque microsphere group), 70-150-µm radiopaque microspheres in contrast material (radiopaque microsphere plus contrast material group), and 70-150-µm radiolucent microspheres in contrast material (nonradiopaque microsphere plus contrast material group). Rabbits were imaged with single-snapshot radiography, cone-beam CT, and multidetector CT. Three to 5 weeks after sacrifice, excised livers were imaged with micro-CT and histologic analysis was performed. The visibility of the embolic agent was assessed with all modalities before and after embolization by using a qualitative three-point scale score reading study and a quantitative assessment of the signal-to-noise ratio (SNR) change in various regions of interest, including the tumor and its feeding arteries. The Kruskal-Wallis test was used to compare the rabbit characteristics across groups, and the Wilcoxon signed rank test was used to compare SNR measurements before and after embolization. Results Radiopaque microspheres were qualitatively visualized within tumor feeding arteries and targeted tissue with all imaging modalities (P < .05), and their presence was confirmed with histologic examination. SNRs of radiopaque microsphere deposition increased after TAE on multidetector CT, cone-beam CT, and micro-CT images (P < .05). Similar results were obtained when contrast material was added to radiopaque microspheres, except for additional image attenuation due to tumor enhancement. For the group with nonradiopaque microspheres and contrast material, retained tumoral contrast remained qualitatively visible with all modalities except for micro-CT, which demonstrated soluble contrast material washout over time. Conclusion Radiopaque microspheres were visible with all imaging modalities and helped increase conspicuity of the tumor as well as its feeding arteries after TAE in a rabbit VX2 liver tumor model. (©) RSNA, 2015.
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Embolización Terapéutica , Neoplasias Hepáticas Experimentales/diagnóstico por imagen , Animales , Tomografía Computarizada de Haz Cónico , Medios de Contraste , Aceite Etiodizado , Neoplasias Hepáticas Experimentales/irrigación sanguínea , Masculino , Microesferas , Tomografía Computarizada Multidetector , Imagen Multimodal , ConejosRESUMEN
BACKGROUND: Systemic mast cell activation disease (MCAD) is characterized by an enhanced release of mast cell-derived mediators, including eicosanoids, which induce a broad spectrum of clinical symptoms. Accordingly, the diagnostic algorithm of MCAD presupposes the proof of increased mast cell mediator release, but only a few mediators are currently established as routine laboratory parameters. We thus initiated an explorative study to evaluate in vitro typing of individual eicosanoid pattern of peripheral blood leukocytes (PBLs) as a new diagnostic tool in MCAD. METHODS: Using the "functional eicosanoid testing and typing" (FET) assay, we investigated the balance (i.e. the complex pattern of formation, release and mutual interaction) of prostaglandin E2 (PGE2) and peptido-leukotrienes (pLT) release from PBLs of 22 MCAD patients and 20 healthy individuals. FET algorithms thereby consider both basal and arachidonic acid (AA)-, acetylsalicylic acid (ASA)-, and substance P (SP)-triggered release of PGE2 and pLT. The FET assay was further supplemented by analyzing prostaglandin D2 (PGD2), as mast cell-specific eicosanoid. RESULTS: We observed marked PGE2-pLT imbalances for PBLs of MCAD patients, as indicated by a markedly enhanced mean FET value of 1.75 ± 0.356 (range: 1.14-2.36), compared to 0.53 ± 0.119 (range: 0.36-0.75) for healthy individuals. In addition, mean PGD2 release from PBLs of MCAD patients was significantly, 6.6-fold higher than from PBLs of healthy individuals (946 ± 302.2 pg/ml versus 142 ± 47.8 pg/ml; P < 0.001). In contrast to healthy individuals, PGD2 release from PBLs of MCAD patients was markedly triggered by SP (mean: 1896 ± 389.7 pg/ml; P < 0.001), whereas AA and ASA caused individually varying effects on both PGD2 and pLT release. CONCLUSIONS: The new in-vitro FET assay, supplemented with analysis of PGD2, demonstrated that the individual patterns of eicosanoid release from PBLs can unambiguously distinguish MCAD patients from healthy individuals. Notably, in our analyses, the FET value and both basal and triggered PGD2 levels were not significantly affected by MCAD-specific medication. Thus, this approach may serve as an in-vitro diagnostic tool to estimate mast cell activity and to support individualized therapeutic decision processes for patients suffering from MCAD.
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Algoritmos , Pruebas Diagnósticas de Rutina/métodos , Leucocitos/química , Mastocitosis Sistémica/diagnóstico , Prostaglandina D2/sangre , Adulto , Anciano , Análisis Químico de la Sangre/métodos , Estudios de Casos y Controles , Pruebas Diagnósticas de Rutina/tendencias , Eicosanoides/análisis , Eicosanoides/clasificación , Femenino , Humanos , Leucocitos/metabolismo , Leucocitos/patología , Leucotrienos/sangre , Masculino , Mastocitosis Sistémica/sangre , Persona de Mediana Edad , Prostaglandina D2/metabolismo , Adulto JovenRESUMEN
BACKGROUND: 4D cardiac computed tomography aims at reconstructing the beating heart from a series of 2D projections and the simultaneously acquired electrocardiogram. Each cardiac phase is reconstructed by exploiting the subset of projections acquired during this particular cardiac phase only. In these conditions, the Feldkamp, Davis and Kress method (FDK) generates large streak artifacts in the reconstructed volumes, hampering the medical interpretation. These artifacts can be substantially reduced by deconvolution methods. OBJECTIVE: The aim of this paper is to compare two 4D cardiac CT reconstruction methods based on deconvolution, and to evaluate their practical benefits on two applications: cardiac micro CT and human cardiac C-arm CT. METHODS: The first evaluated method builds upon inverse filtering. It has been proposed recently and demonstrated on 4D cardiac micro CT. The second one is an iterative deconvolution method, and turns out equivalent to an ECG-gated Iterative Filtered Back Projection (ECG-gated IFBP). RESULTS: Results are presented on simulated data in 2D parallel beam, 2D fan beam and 3D cone beam geometries. CONCLUSIONS: Both methods are efficient on the cardiac micro CT simulations, but insufficient to handle 4D human cardiac C-Arm CT simulations. Overall, ECG-gated IFPB largely outperforms the inverse filtering method.
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Artefactos , Electrocardiografía/métodos , Tomografía Computarizada Cuatridimensional/métodos , Procesamiento de Imagen Asistido por Computador/métodos , Algoritmos , Simulación por Computador , Humanos , Fantasmas de ImagenRESUMEN
PURPOSE: Cone-beam CT in the interventional suite could be an alternative to CT to shorten door-to-thrombectomy time. However, image quality in cone-beam CT is limited by artifacts and poor differentiation between gray and white matter. This study compared non-contrast brain dual-layer cone-beam CT in the interventional suite to reference standard CT in stroke patients. METHODS: A prospective single-center study enrolled consecutive participants with ischemic or hemorrhagic stroke. The hemorrhage detection accuracy, per-region ASPECTS accuracy and subjective image quality (Likert scales for gray-white matter differentiation, structure perception and artifacts) were assessed by three neuroradiologists blinded to clinical data on dual-layer cone-beam CT 75â¯keV monoenergetic images compared to CT. Objective image quality was assessed by region-of-interest metrics. Non-inferiority for hemorrhage detection and ASPECTS accuracy was determined by the exact binomial test with a one-sided lower performance boundary prospectively set to 80% (98.75% CI). RESULTS: 27 participants were included (74 years⯱ 9; 19 female) in the hyperacute or acute stroke phase. One reader missed a small bleeding, but all hemorrhages were detected in the majority analysis (100% accuracy, CI lower boundary 86%, pâ¯= 0.002). ASPECTS majority analysis showed 90% accuracy (CI lower boundary 85%, pâ¯< 0.001). Sensitivity was 66% (individual readers 67%, 69%, and 76%), specificity was 97% (97%, 96%, 89%). Subjective and objective image quality were inferior to CT. CONCLUSION: In a small single-center cohort, dual-layer cone-beam CT showed non-inferior hemorrhage detection and ASPECTS accuracy to CT. Despite inferior image quality, the technique may be useful for stroke evaluation in the interventional suite. TRIAL REGISTRATION NUMBER: NCT04571099 (clinicaltrials.gov). Prospectively registered 2020-09-04.
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INTRODUCTION: C-Arm CT (CACT) is a new imaging modality in liver oncology therapy that allows for the acquisition of 3D images intra-procedurally. CACT has been used to enhance intra-arterial therapies for the liver by improving lesion detection, avoiding non-target embolization, and allowing for more selective delivery of agents. However, one of the limitations of this technology is image artifacts created by respiratory motion. PURPOSE: To determine in this preliminary study improvements in image acquisition, motion compensation, and high resolution 3D reconstruction that can improve CACT image quality (IQ). MATERIAL AND METHODS: Three adult male New Zealand white rabbits were used for this study. First, a control rabbit was used to select the best x-ray acquisition imaging protocol and then two rabbits were implanted with liver tumor to further develop 3D image reconstruction and motion compensation algorithms. RESULTS: The best IQ was obtained using the low 80 kVp protocol with motion compensated reconstruction with high resolution and fast acquisition speed (60 fps, 5 s/scan, and 312 images). CONCLUSION: IQ improved by: (1) decreasing acquisition time, (2) applying motion-compensated reconstruction, and (3) high resolution 3D reconstruction. The findings of this study can be applied to future animal studies and eventually could be translated into the clinical environment.
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Imagenología Tridimensional/métodos , Neoplasias Hepáticas Experimentales/diagnóstico , Tomografía Computarizada por Rayos X/métodos , Algoritmos , Animales , Neoplasias Hepáticas Experimentales/patología , Masculino , Movimiento (Física) , Conejos , Factores de TiempoRESUMEN
PURPOSE: Conventional cone-beam computed tomography CT (CBCT) provides limited discrimination between low-contrast tissues. Furthermore, it is limited to full-spectrum energy integration. A dual-energy CBCT system could be used to separate photon energy spectra with the potential to increase the visibility of clinically relevant features and acquire additional information relevant in a multitude of clinical imaging applications. In this work, the performance of a novel dual-layer dual-energy CBCT (DL-DE-CBCT) C-arm system is characterized for the first time. METHODS: A prototype dual-layer detector was fitted into a commercial interventional C-arm CBCT system to enable DL-DE-CBCT acquisitions. DL-DE reconstructions were derived from material-decomposed Compton scatter and photoelectric base functions. The modulation transfer function (MTF) of the prototype DL-DE-CBCT was compared to that of a commercial CBCT. Noise and uniformity characteristics were evaluated using a cylindrical water phantom. Effective atomic numbers and electron densities were estimated in clinically relevant tissue substitutes. Iodine quantification was performed (for 0.5-15 mg/ml concentrations) and virtual noncontrast (VNC) images were evaluated. Finally, contrast-to-noise ratios (CNR) and CT number accuracies were estimated. RESULTS: The prototype and commercial CBCT showed similar spatial resolution, with a mean 10% MTF of 5.98 cycles/cm and 6.28 cycles/cm, respectively, using a commercial standard reconstruction. The lowest noise was seen in the 80 keV virtual monoenergetic images (VMI) (7.40 HU) and the most uniform images were seen at VMI 60 keV (4.74 HU) or VMI 80 keV (1.98 HU), depending on the uniformity measure used. For all the tissue substitutes measured, the mean accuracy in effective atomic number was 98.2% (SD 1.2%) and the mean accuracy in electron density was 100.3% (SD 0.9%). Iodine quantification images showed a mean difference of -0.1 (SD 0.5) mg/ml compared to the true iodine concentration for all blood and iodine-containing objects. For VNC images, all blood substitutes containing iodine averaged a CT number of 43.2 HU, whereas a blood-only substitute measured 44.8 HU. All water-containing iodine substitutes measured a mean CT number of 2.6 in the VNC images. A noise-suppressed dataset showed a CNR peak at VMI 40 keV and low at VMI 120 keV. In the same dataset without noise suppression applied, a peak in CNR was obtained at VMI 70 keV and a low at VMI 120 keV. The estimated CT numbers of various clinically relevant objects were generally very close to the calculated CT number. CONCLUSIONS: The performance of a prototype dual-layer dual-energy C-arm CBCT system was characterized. Spatial resolution and noise were comparable with a commercially available C-arm CBCT system, while offering dual-energy capability. Iodine quantifications, effective atomic numbers, and electron densities were in good agreement with expected values, indicating that the system can be used to reliably evaluate the material composition of clinically relevant tissues. The VNC and monoenergetic images indicate a consistent ability to separate clinically relevant tissues. The results presented indicate that the system could find utility in diagnostic, interventional, and radiotherapy planning settings.
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Yodo , Imagen Radiográfica por Emisión de Doble Fotón , Tomografía Computarizada de Haz Cónico , Fantasmas de Imagen , Estudios Retrospectivos , Relación Señal-RuidoRESUMEN
The current need for bone grafts in orthopedic and reconstructive surgery cannot be satisfied by autologous tissue transplant due to its limited availability and significant associated morbidity. Tissue engineering approaches could supply sufficient amounts of bone substitutes by exploiting the ability to harvest autologous osteogenic progenitors associated with suitable porous materials. However, the generation of clinically relevant-sized constructs is critically hampered by limited vascularization, with consequent engraftment and survival only of a thin outer shell, upon in vivo implantation. To overcome this limitation, different non-mutually exclusive approaches have recently been developed to promote or accelerate graft vascularization, from angiogenic growth factor gene delivery to surgical pre-vascularization of the construct before implantation. A simple, promising strategy involves the co-culture of vasculogenic cells to form an intrinsic vascular network inside the graft in vitro, which can rapidly anastomose with the host blood vessels in vivo. Recent data have shown that adipose tissue-derived stromal vascular fraction (SVF) may provide an efficient, convenient, and autologous source for both osteogenic and endothelial cells. When SVF progenitors were cultured in appropriate bioreactor systems and ectopically implanted, a functional vascular network connected to the host was formed concomitantly to bone formation. Future studies should aim at demonstrating that this approach effectively supports survival of scaled up cell-based bone grafts at an orthotopic site. The procedure should also be adapted to become compatible with an intra-operative timeline and complemented with the definition of suitable potency markers, to facilitate its development into a simplified, reproducible, and cost-effective clinical treatment.
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Tejido Adiposo/citología , Vasos Sanguíneos , Trasplante Óseo , Células Madre/fisiología , Ingeniería de Tejidos/métodos , Animales , Vasos Sanguíneos/crecimiento & desarrollo , Técnicas de Cultivo de CélulaRESUMEN
PURPOSE: Three-dimensional (3-D) reconstruction of the coronary arteries during a cardiac catheter-based intervention can be performed from a C-arm based rotational x-ray angiography sequence. It can support the diagnosis of coronary artery disease, treatment planning, and intervention guidance. 3-D reconstruction also enables quantitative vessel analysis, including vessel dynamics from a time-series of reconstructions. METHODS: The strong angular undersampling and motion effects present in gated cardiac reconstruction necessitate the development of special reconstruction methods. This contribution presents a fully automatic method for creating high-quality coronary artery reconstructions. It employs a sparseness-prior based iterative reconstruction technique in combination with projection-based motion compensation. RESULTS: The method is tested on a dynamic software phantom, assessing reconstruction accuracy with respect to vessel radii and attenuation coefficients. Reconstructions from clinical cases are presented, displaying high contrast, sharpness, and level of detail. CONCLUSIONS: The presented method enables high-quality 3-D coronary artery imaging on an interventional C-arm system.
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Vasos Coronarios/patología , Imagenología Tridimensional/métodos , Radiología Intervencionista/métodos , Algoritmos , Inteligencia Artificial , Enfermedad de la Arteria Coronaria/diagnóstico por imagen , Enfermedad de la Arteria Coronaria/radioterapia , Diagnóstico por Imagen/métodos , Humanos , Procesamiento de Imagen Asistido por Computador/métodos , Movimiento (Física) , Reconocimiento de Normas Patrones Automatizadas/métodos , Fantasmas de Imagen , Radiografía , Planificación de la Radioterapia Asistida por Computador/métodos , Reproducibilidad de los Resultados , Rayos XRESUMEN
Rotational coronary angiography provides a multitude of x-ray projections of the contrast agent enhanced coronary arteries along a given trajectory with parallel ECG recording. These data can be used to derive motion information of the coronary arteries including vessel displacement and pulsation. In this paper, a fully automated algorithm to generate 4D motion vector fields for coronary arteries from multi-phase 3D centerline data is presented. The algorithm computes similarity measures of centerline segments at different cardiac phases and defines corresponding centerline segments as those with highest similarity. In order to achieve an excellent matching accuracy, an increasing number of bifurcations is included as reference points in an iterative manner. Based on the motion data, time-dependent vessel surface extraction is performed on the projections without the need of prior reconstruction. The algorithm accuracy is evaluated quantitatively on phantom data. The magnitude of longitudinal errors (parallel to the centerline) reaches approx. 0.50 mm and is thus more than twice as large as the transversal 3D extraction errors of the underlying multi-phase 3D centerline data. It is shown that the algorithm can extract asymmetric stenoses accurately. The feasibility on clinical data is demonstrated on five different cases. The ability of the algorithm to extract time-dependent surface data, e.g. for quantification of pulsating stenosis is demonstrated.
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Vasos Coronarios/fisiología , Procesamiento de Imagen Asistido por Computador/métodos , Movimiento , Rotación , Algoritmos , Automatización , Constricción Patológica/diagnóstico por imagen , Angiografía Coronaria , Vasos Coronarios/fisiopatología , Estudios de Factibilidad , Humanos , Fantasmas de Imagen , Respiración , Sensibilidad y Especificidad , Programas Informáticos , Propiedades de Superficie , Factores de TiempoRESUMEN
BACKGROUND: Back pain and knee pain are typical secondary degeneration symptoms after hip ankylosis. Take down of hip ankylosis and implantation of a total hip arthroplasty (THA) is believed to be a promising treatment option. METHODS: A total of 22 hip ankylosis patients [15 men, mean age 53.7 years (range 30-72 years); 7 women, mean age 50.8 years (range 42-61 years)] underwent THA during 1980-2000 after spontaneous (n = 10) or surgical (n = 12) fusion of the hip joint. The mean duration of ankylosis prior to THA was 32.5 years (range 2-61 years). RESULTS: At the mean follow-up of 13.2 years (range 2-19 years), the Harris hip score averaged 84.9 points (range 70.1-99.0 points). All patients (100%) confirmed that they would undergo conversion surgery again. Aseptic loosening of two stems (one cemented, one cementless; 9.5%) and two deep infections (9.5%) required revision surgery. CONCLUSIONS: THA is a promising option for treatment of secondary long-term hip ankylosis sequelae. A conversion operation after spontaneous ankylosis provides better functional outcome than after surgical fusion. However, full function with complete pain relief and a negative Trendelenburg sign might be not attainable in all cases.
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Anquilosis/cirugía , Artroplastia de Reemplazo de Cadera/métodos , Adulto , Anciano , Anquilosis/complicaciones , Dolor de Espalda/etiología , Dolor de Espalda/terapia , Femenino , Estudios de Seguimiento , Humanos , Masculino , Persona de Mediana Edad , Recuperación de la FunciónRESUMEN
BACKGROUND: Total contact casting (TCC) has become established as standard treatment for Wagner grades 1 and 2 diabetic foot ulcers. However, the recurrence rate after TCC is unacceptably high, and a clear concept to prevent recurrences is still lacking. The purpose of this study was to evaluate recurrences and the effectiveness of preventive measures in a group of diabetic patients treated with TCC. METHODS: From January of 1999, to June of 2004, 28 patients (20 men and 8 women; average age 63 years) with 34 ulcers were treated using TCC. Thereafter, orthopaedic shoes were provided and patients were followed regularly. Recurrences were treated first by TCC, and operative correction was carried out in patients with an underlying foot deformity. Mean followup was 2.8 (1 to 5) years. RESULTS: Primary TCC treatment lasted 4 (1 to 17) months. Complete healing was achieved in 85% of ulcers; 57% of patients had a total of 26 recurrences, and 18 new ulcers were found in a different area or on the other foot. Sixteen recurrences were treated successfully by TCC, but the rate of new recurrences during followup was 50%. Eight recurrences were treated by operative correction of foot deformities. Most patients stayed ulcer-free thereafter. An unloading shoe was applied twice. No amputations were required. CONCLUSIONS: The first TCC showed an effective healing rate of 85%. The high recurrence rate of 57% in the presence of optimal instruction, shoes, and followup suggests that these measures are not sufficient. However, because patients who had operative corrections stayed ulcer-free thereafter, it is suggested that foot deformities should be operatively corrected immediately after primary healing rather than waiting until further recurrences occur.
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Moldes Quirúrgicos , Pie Diabético/prevención & control , Adulto , Anciano , Anciano de 80 o más Años , Pie Diabético/complicaciones , Pie Diabético/terapia , Femenino , Deformidades del Pie/complicaciones , Deformidades del Pie/prevención & control , Humanos , Masculino , Persona de Mediana Edad , Recurrencia , Factores de TiempoRESUMEN
The cyclooxygenase-2 isoform (COX-2) was found recently to be constitutively expressed in the guinea pig inner ear. To gain knowledge about its role in sound perception, alterations in the COX-2 level of moderate noise-stimulated cochleae were determined. Staining intensities were quantified in different regions using an immunohistochemical staining procedure and computer-assisted system. After 70 dB and 90 dB noise exposure for 1 h at 8000 Hz, COX-2 downregulation was observed in the organ of Corti, which was most prominent in Deiters' cells near Hensen cells and outer hair cells. In pillar cells, COX-2 levels were only slightly reduced after 70 dB but strongly diminished after 90 dB exposure. In Hensen cells, COX-2 was downregulated after 70 dB stimulation, revealing a decreasing COX-2 content from the third to the first turn of the cochlea and a homogeneously reduced enzyme expression in all three turns after 90 dB. The COX-2 content in inner hair cells was nearly identical to unexposed cochleae after 70 dB exposure but significantly reduced after 90 dB stimulation. In spiral ganglion cells, stria vascularis, spiral ligament and limbus, COX-2 expression was unchanged after 70 dB and 90 dB. We suggest that alterations in COX-2 expression might contribute to diminished sensitivity at the cochlea after noise exposure to reduce subsequent noise distress, termed sound conditioning.
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Estimulación Acústica , Cóclea/efectos de la radiación , Ciclooxigenasa 2/metabolismo , Expresión Génica/efectos de la radiación , Neuronas/efectos de la radiación , Animales , Cóclea/citología , Cóclea/enzimología , Cóclea/metabolismo , Relación Dosis-Respuesta en la Radiación , Cobayas , Inmunohistoquímica/métodos , Neuronas/clasificación , Neuronas/enzimología , Neuronas/metabolismoRESUMEN
This paper presents a method to reconstruct moving objects from cone beam X-ray projections acquired during a single rotational run using a given motion vector field. The method is applicable to voxel driven cone-beam filtered back-projection reconstruction approaches. Here, a formulation based on the algorithm of Feldkamp, Davis, and Kress (FDK) is presented. The motion correction is applied during the back-projection step by shifting the voxel to be reconstructed according to the motion vector field. The method is applied to three-dimensional (3-D) rotational X-ray angiography. Projections from a beating coronary heart phantom are simulated. Motion-compensated reconstructions with varying accuracy of the applied motion field are carried out for a late diastolic heart phase and compared to the reconstruction obtained with the standard FDK-method from projections of the corresponding motion-free model in the same heart phase. Furthermore, gated reconstructions are calculated by weighting the projections according to their cardiac phase without using a motion vector field. Different gating window widths are applied, and the reconstructions are compared. Using the correct motion field with the motion-compensated reconstruction, the image quality of the standard reconstruction from the corresponding motion-free coronary model can almost be recovered. The reconstructed image quality stays acceptable if the accuracy of the motion field sampling points is better than 1 mm. The gated reconstructions with a window width of 15%-20% of the cardiac cycle lead to superior results compared to nearest neighbor gating, especially for histogram based visualization and analysis. The motion-compensated reconstructions provide sharp images of the coronaries far surpassing the image quality of gated reconstructions.
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Artefactos , Angiografía Coronaria/métodos , Imagenología Tridimensional/métodos , Movimiento , Intensificación de Imagen Radiográfica/métodos , Interpretación de Imagen Radiográfica Asistida por Computador/métodos , Tomografía Computarizada Espiral/métodos , Algoritmos , Angiografía Coronaria/instrumentación , Humanos , Fantasmas de Imagen , Reproducibilidad de los Resultados , Rotación , Sensibilidad y Especificidad , Tomografía Computarizada Espiral/instrumentaciónRESUMEN
RATIONALE AND OBJECTIVES: For the reconstruction of the coronary arteries from rotational angiography data, a crucial point is the selection of the optimal cardiac phase for data reconstruction. To avoid time-consuming interactive selection of the optimal cardiac phase by visual inspection of multiple high-resolution data sets reconstructed at different cardiac phases, an automatic approach for deriving optimal reconstruction windows is attractive. MATERIALS AND METHODS: This paper presents a new approach to fully automatic selection of the optimal cardiac phase for image reconstruction. It is based on the analysis of a four-dimensional data set of the region of interest reconstructed at low-spatial resolution utilizing an image quality index, which quantifies the image quality of a single three-dimensional reconstructed volume. The derived image quality index utilizes the histogram information of a single temporal snapshot as a quality measure for the vessel reconstruction. The proposed technique was applied to 16 projection data sets obtained in eight pigs. RESULTS: Experiments to evaluate the proposed method based on user-defined image quality parameters serving as ground truth, showed a relatively high correlation (>84%) for high-quality (c(phi) > 0.95) images. CONCLUSION: An image-based technique is introduced, which is able to determine the optimal cardiac phase for 3D-RCA fully automatically. The proposed method was successfully applied to 16 data sets obtained in a total of 8 porcine models.
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Algoritmos , Inteligencia Artificial , Angiografía Coronaria/métodos , Electrocardiografía/métodos , Imagenología Tridimensional/métodos , Reconocimiento de Normas Patrones Automatizadas/métodos , Interpretación de Imagen Radiográfica Asistida por Computador/métodos , Animales , Almacenamiento y Recuperación de la Información/métodos , Intensificación de Imagen Radiográfica/métodos , Reproducibilidad de los Resultados , Sensibilidad y Especificidad , PorcinosRESUMEN
RATIONALE AND OBJECTIVES: Three-dimensional high-spatial-resolution angiograms of the coronary arteries were acquired with an electrocardiogram-gated three-dimensional rotational angiography technique on an interventional X-ray system. MATERIALS AND METHODS: During selective injection of contrast material in the left and right coronary artery, projection images were obtained in eight pigs during a continuous rotation of the X-ray gantry over an angular range of 180 degrees within 8 seconds. RESULTS: Three-dimensional tomographic reconstruction depicted the proximal, medial, and distal sections of the main arteries as well as the main bifurcations in multiple cardiac phases in all animals. CONCLUSIONS: For the first time, this feasibility study shows that a three-dimensional angiogram of the coronary arteries can be obtained intraprocedurally in a conventional interventional suite by means of tomographic reconstruction from projection images.
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Algoritmos , Inteligencia Artificial , Angiografía Coronaria/métodos , Imagenología Tridimensional/métodos , Reconocimiento de Normas Patrones Automatizadas/métodos , Interpretación de Imagen Radiográfica Asistida por Computador/métodos , Animales , Estudios de Factibilidad , Almacenamiento y Recuperación de la Información/métodos , Intensificación de Imagen Radiográfica/métodos , Reproducibilidad de los Resultados , Sensibilidad y Especificidad , PorcinosRESUMEN
OBJECTIVE: Correction of genu varum and unloading of the medial compartment using a proximal osteotomy, callus distraction. INDICATIONS: Symptomatic genu varum due to post-medial-meniscectomy syndrome, medial compartment osteoarthritis, articular cartilage lesions of medial compartment, avascular necrosis of medial femoral condyle, osteoarthritis dissecans of medial femoral condyle, posterolateral and/or anteromedial rotatory instability. CONTRAINDICATIONS: Advanced articular cartilage lesions of lateral compartment. Advanced osteoarthritis of patellofemoral compartment. Extension lag > 10 degrees. Patients > 60 years with low physical demands. SURGICAL TECHNIQUE: Installation of an external fixator under image intensification as close to the joint as possible. Skin incision medial to the tibial tuberosity. Osteotomy between proximal fixator screw and tibial tuberosity leaving the lateral cortex intact. Control of desired distraction under image intensification. Closure of distraction gap. POSTOPERATIVE MANAGEMENT: Start of distraction (1 mm/day) on day 5. Radiographs on day 5-7, after 6 weeks, and after 8-10 weeks. Removal of only the fixator rods once desired correction has been reached and sufficient callus has formed. If correction is maintained after full weight bearing, removal of screws. RESULTS: Between 1998 and 2000, 34 callus distractions were done in 24 patients (six women, 18 men, age 24-64 years). Follow-up of 21 patients after an average of 23 months (6-36 months). Exclusion of one patient after total knee replacement. Pre- and postoperative femorotibial angle 179 degrees (172-183 degrees) and 185 degrees (179-191 degrees), respectively. Median correction was 6 degrees (3-12 degrees). 20 patients would accept the procedure again. Using the score developed by the authors, improvement from 15 points preoperatively to 10 points postoperatively. Complications in 15 corrections, eight of these needing a surgical revision.
Asunto(s)
Deformidades Adquiridas de la Articulación/cirugía , Articulación de la Rodilla/anomalías , Articulación de la Rodilla/cirugía , Osteogénesis por Distracción/métodos , Osteotomía/métodos , Tibia/anomalías , Tibia/cirugía , Adulto , Fijadores Externos , Femenino , Humanos , Masculino , Persona de Mediana Edad , Osteogénesis por Distracción/instrumentación , Osteotomía/instrumentación , Resultado del TratamientoRESUMEN
The authors developed a mathematical model of arachidonic acid (AA) degradation to prostaglandins (PGs) and leukotrienes (LTs), which are implicated in the processes of inflammation and hypersensitivity to non-steroidal anti-inflammatory drugs (NSAIDs). The model focuses on two PGs (PGE2 and PGD2) and one LT (LTC4), their % increases and their ratios. Results are compared with experimental studies obtained from non-asthmatics (NAs), and asthmatics tolerant (ATA) or intolerant (AIA) to aspirin. Simulations are carried out for predefined model populations NA, ATA and three AIA, based on the differences of two enzymes, PG E synthase and/or LTC4-synthase in two states, that is, no-inflammation and inflammation. Their model reveals that the model population with concomitant malfunctions in both enzymes is the most sensitive to NSAIDs, since the duration and the capacity for bronchoconstriction risk are highest after simulated oral dosing of indomethacin. Furthermore, inflammation prolongs the duration of the bronchoconstriction risk in all AIA model populations, and the sensitivity analysis reveals multiple possible scenarios leading to hypersensitivity, especially if inflammatory processes affect the expression of multiple enzymes of the AA metabolic pathway. Their model estimates the expected fold-changes in enzyme activities and gives valuable information for further targeted transcriptomic/proteomic and metabolomic studies.