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1.
Sensors (Basel) ; 21(4)2021 Feb 11.
Artículo en Inglés | MEDLINE | ID: mdl-33670276

RESUMEN

At the micrometric scale, vessels or skin capillaries network architecture can provide useful information for human health management. In this paper, from simulation to in vitro, we investigate some limits and interests of optical feedback interferometry (OFI) for blood flow imaging of skin vascularization. In order to analyze the tissue scattering effect on OFI performances, a series of skin-tissue simulating optical phantoms have been designed, fabricated and characterized. The horizontal (2D) and vertical (depth penetration) sensing resolution of the OFI sensor have been estimated. The experimental results that we present on this study are showing a very good accordance with theoretical models. In the case of a skin phantom of 0.5 mm depth with a scattering coefficient from 0 to 10.8 mm-1, the presented OFI system is able to distinguish a pair of micro fluidic channels (100 µm × 100 µm) spaced by 10 µm. Eventually, an in vivo test on human skin is presented and, for the first time using an OFI sensor, a 2D blood flow image of a vein located just beneath the skin is computed.


Asunto(s)
Interferometría , Dispositivos Ópticos , Piel/irrigación sanguínea , Simulación por Computador , Retroalimentación , Humanos , Fantasmas de Imagen
2.
AAPS PharmSciTech ; 22(3): 90, 2021 Mar 05.
Artículo en Inglés | MEDLINE | ID: mdl-33666763

RESUMEN

Contrast-enhanced X-ray computed tomography plays an important role in cancer imaging and disease progression monitoring. Imaging using radiopaque nanoparticle platforms can provide insights on the likelihood of nanoparticle accumulation and can enable image-guided therapies. Perfluorooctyl bromide (PFOB)-loaded nanocapsules designed for this purpose were stabilized using an in-house synthesized PEGylated polycaprolactone-based copolymer (PEG-b-PCL(Ch)) and compared with commercial polycaprolactone employing a Quality-by-Design approach. PFOB is a dense liquid, weakly polarizable, and immiscible in organic and aqueous solvents; thus, carefully designed formulations for optimal colloidal stabilization to overcome settling-associated instability are required. PFOB-loaded nanocapsules exhibited high PFOB loading due to the intrinsic properties of PEG-b-PCL(Ch). Settling and caking are major sources of instability for PFOB formulations. However, the PEG-b-PCL(Ch) copolymer conferred the nanocapsules enough steric impediment and polymer shell elasticity to settle without significant caking, increasing the overall colloidal stability of the formulation. Furthermore, a clear relationship between nanocapsule physical properties and X-ray attenuation was established. Nanocapsules were able to enhance the X-ray contrast in vitro as a function of PFOB loading. This nanocapsule-based platform is promising for future translational studies and image-guided tumor therapy due to its enhanced contrastability and optimal colloidal stability.


Asunto(s)
Medios de Contraste/administración & dosificación , Medios de Contraste/química , Tomografía Computarizada por Rayos X/métodos , Colesterol/química , Coloides , Composición de Medicamentos , Estabilidad de Medicamentos , Excipientes , Fluorocarburos , Hidrocarburos Bromados , Lactonas , Nanocápsulas , Tamaño de la Partícula , Fantasmas de Imagen , Polietilenglicoles
3.
Br J Radiol ; 94(1120): 20201014, 2021 Apr 01.
Artículo en Inglés | MEDLINE | ID: mdl-33733813

RESUMEN

OBJECTIVES: In real-time portal dosimetry, thresholds are set for several measures of difference between predicted and measured images, and signals larger than those thresholds signify an error. The aim of this work is to investigate the use of an additional composite difference metric (CDM) for earlier detection of errors. METHODS: Portal images were predicted for the volumetric modulated arc therapy plans of six prostate patients. Errors in monitor units, aperture opening, aperture position and path length were deliberately introduced into all 180 segments of the treatment plans, and these plans were delivered to a water-equivalent phantom. Four different metrics, consisting of central axis signal, mean image value and two image difference measures, were used to identify errors, and a CDM was added, consisting of a weighted power sum of the individual metrics. To optimise the weights of the CDM and to evaluate the resulting timeliness of error detection, a leave-pair-out strategy was used. For each combination of four patients, the weights of the CDM were determined by an exhaustive search, and the result was evaluated on the remaining two patients. RESULTS: The median segment index at which the errors were identified was 87 (range 40-130) when using all of the individual metrics separately. Using a CDM as well as multiple separate metrics reduced this to 73 (35-95). The median weighting factors of the four metrics constituting the composite were (0.15, 0.10, 0.15, 0.00). Due to selection of suitable threshold levels, there was only one false positive result in the six patients. CONCLUSION: This study shows that, in conjunction with appropriate error thresholds, use of a CDM is able to identify increased image differences around 20% earlier than the separate measures. ADVANCES IN KNOWLEDGE: This study shows the value of combining difference metrics to allow earlier detection of errors during real-time portal dosimetry for volumetric modulated arc therapy treatment.


Asunto(s)
Procesamiento de Imagen Asistido por Computador/métodos , Neoplasias de la Próstata/diagnóstico por imagen , Neoplasias de la Próstata/radioterapia , Radioterapia Guiada por Imagen/métodos , Radioterapia de Intensidad Modulada/métodos , Humanos , Masculino , Fantasmas de Imagen , Próstata/diagnóstico por imagen , Radiometría , Dosificación Radioterapéutica , Estudios Retrospectivos
4.
Biomed Eng Online ; 20(1): 29, 2021 Mar 25.
Artículo en Inglés | MEDLINE | ID: mdl-33766044

RESUMEN

BACKGROUND: As an object's electrical passive property, the electrical conductivity is proportional to the mobility and concentration of charged carriers that reflect the brain micro-structures. The measured multi-b diffusion-weighted imaging (Mb-DWI) data by controlling the degree of applied diffusion weights can quantify the apparent mobility of water molecules within biological tissues. Without any external electrical stimulation, magnetic resonance electrical properties tomography (MREPT) techniques have successfully recovered the conductivity distribution at a Larmor-frequency. METHODS: This work provides a non-invasive method to decompose the high-frequency conductivity into the extracellular medium conductivity based on a two-compartment model using Mb-DWI. To separate the intra- and extracellular micro-structures from the recovered high-frequency conductivity, we include higher b-values DWI and apply the random decision forests to stably determine the micro-structural diffusion parameters. RESULTS: To demonstrate the proposed method, we conducted phantom and human experiments by comparing the results of reconstructed conductivity of extracellular medium and the conductivity in the intra-neurite and intra-cell body. The phantom and human experiments verify that the proposed method can recover the extracellular electrical properties from the high-frequency conductivity using a routine protocol sequence of MRI scan. CONCLUSION: We have proposed a method to decompose the electrical properties in the extracellular, intra-neurite, and soma compartments from the high-frequency conductivity map, reconstructed by solving the electro-magnetic equation with measured B1 phase signals.


Asunto(s)
Imagen de Difusión por Resonancia Magnética , Conductividad Eléctrica , Procesamiento de Imagen Asistido por Computador/métodos , Tomografía , Encéfalo/diagnóstico por imagen , Encéfalo/fisiología , Mapeo Encefálico , Líquido Cefalorraquídeo , Impedancia Eléctrica , Humanos , Distribución Normal , Fantasmas de Imagen , Reproducibilidad de los Resultados
5.
Artículo en Japonés | MEDLINE | ID: mdl-33746173

RESUMEN

PURPOSE: To evaluate image quality for chest radiography at different radiation qualities, using phantoms with scatter fractions similar to those of lungs. METHODS: Two base phantoms with 10 and 4 cm thicknesses, respectively, made of a soft tissue-equivalent material, were used to mimic the X-ray attenuation of the human lung. Two plates with soft tissue- and bone-equivalent materials, respectively, were placed on the base phantom as contrast objects. The image data were obtained with the same entrance surface dose in each radiation quality. Six radiation qualities generated using 120 and 90 kV, and additional copper filters with thicknesses 0, 0.1, and 0.2 mm were selected. The signal-difference-to-noise ratio (SdNR) and a contrast ratio of the soft tissue to the bone were measured for the six radiation qualities. RESULTS: The thicker the additional filter, the better the SdNR at both tube voltages. The SdNR values were not significantly different between 120 and 90 kV for the same filter thickness. The contrast ratio was higher at 120 than at 90 kV by approximately 8%. CONCLUSIONS: Because of the advantage of the contrast ratio and the highest SdNR, the radiation quality with 120 kV and 0.2-mm copper filtration was the best. It was indicated that the conventional tube voltage of 120 kV remains to be better than the lower tube voltage of 90 kV.


Asunto(s)
Intensificación de Imagen Radiográfica , Tórax , Humanos , Fantasmas de Imagen , Dosis de Radiación , Relación Señal-Ruido , Rayos X
6.
Artículo en Japonés | MEDLINE | ID: mdl-33746176

RESUMEN

PURPOSE: A volume scan can cover a range of 160 mm with a single gantry rotation. It can be performed sequentially (a wide volume [WV] scan) to cover more than 160 mm, and volume Xact+ (Xact+) can be used when volume scan is done to extend the reconstruction area. The purpose of this study was to investigate the dose distribution and organ doses for a WV scan during chest CT. METHOD: We arranged radiophotoluminescence glass dosimeters (RPLDs) linearly on the surface and inside of the phantom to evaluate the dose distribution along the z-axis. We also placed RPLDs at the lens, thyroid, and breast positions to evaluate organ doses. We performed WV and helical scans and WV scan using Xact+. RESULT: The absorbed doses increased at the borders of the volume scans, and dose peaks were observed there. The organ doses for the WV scan outside the acquisition range were lower than those for the helical scan. The organ doses inside the acquisition range changed by the locations of borders. CONCLUSION: The WV scan increases the absorbed doses at the overlapping scanned regions, which can be reduced by using Xact+.


Asunto(s)
Tórax , Tomografía Computarizada por Rayos X , Fantasmas de Imagen , Dosis de Radiación , Dosímetros de Radiación
7.
Br J Radiol ; 94(1119): 20200714, 2021 Mar 01.
Artículo en Inglés | MEDLINE | ID: mdl-33533635

RESUMEN

OBJECTIVE: To investigate the effects of beam hardening by the skull on the measured radiodensity of the brain. To test a hypothesis that these effects of beam hardening are decreased using a monochromatic energy source. METHODS: Selected clinical cases were reviewed in illustration. An anthropomorphic skull and brain phantom was created and scanned in a clinical CT scanner with skull, without skull, and with hemicraniectomy. The effects of beam hardening were illustrated by scanning the phantom with mono- and poly-chromatic X-ray sources. RESULTS: In clinical cases, the HU values of the brain were consistently lower when the X-ray beam traversed the skull than when it did not. An anthropomorphic skull-and-brain phantom further demonstrated these effects, which were evident with a polychromatic energy source and absent with a virtual monochromatic energy source. CONCLUSIONS: Beam hardening by the skull lowers the measured HU values of the brain. The effects, which can impact quantitative imaging, may be mitigated by a virtual monochromatic energy source. ADVANCES IN KNOWLEDGE: Beam hardening by the skull lowers the measured radiodensity of the brain. The effects may be mitigated by a virtual monochromatic energy source.


Asunto(s)
Artefactos , Encefalopatías/diagnóstico por imagen , Cráneo/diagnóstico por imagen , Tomografía Computarizada por Rayos X/métodos , Adulto , Encéfalo/diagnóstico por imagen , Femenino , Humanos , Persona de Mediana Edad , Fantasmas de Imagen , Relación Señal-Ruido
8.
Artículo en Japonés | MEDLINE | ID: mdl-33612691

RESUMEN

OBJECTIVES: While computed tomography colonography (CTC) has become a non-invasive alternative to traditional colonoscopy, superficial lesions tend to be harder to detect, with reports of lesions <2 mm in height being missed. Therefore, for the evaluation of lesion detectability using CTC, optimizing scan parameters becomes important. In this study, we investigate the effect of the reconstructed matrix size from CTC on the lesion conspicuity. METHODS: A CTC phantom was scanned, and images were reconstructed with 512, 768 and 1024 matrix sizes with the same raw data. The image data in each matrix size were compared in terms of physical assessment of the task-transfer function (TTF) and the noise power spectrum (NPS), and of visual assessment using Scheffé's paired comparison. RESULTS: Comparing 768 and 1024 matrix sizes with that of 512, NPS was higher in high-frequency components. On the other hand, TTF was improved using these larger matrix sizes along with significant statistical differences in the visual assessment. CONCLUSION: Larger matrix sizes (768 and 1024) improve the lesion conspicuity, thereby helping to detect superficial and small lesions (size<2 mm) in CTC.


Asunto(s)
Colonografía Tomográfica Computarizada , Análisis por Apareamiento , Fantasmas de Imagen , Dosis de Radiación , Interpretación de Imagen Radiográfica Asistida por Computador
9.
Artículo en Japonés | MEDLINE | ID: mdl-33612692

RESUMEN

PURPOSE: This study investigated whether real-time variable shape tungsten rubber (STR) could be applied for nail radiation protection in total skin electron beam (TSEB) therapy. METHODS: Simulated finger phantoms were made from syringes filled with physiological saline of volumes 5, 10, 20, and 30 ml (inner diameters of 14.1, 17.0, 21.7, and 25.3 mm, respectively). Gafchromic film was applied to the phantom, and lead (thickness 1-3 mm) or STR (thickness 1-4 mm) with an area of 4´1.5 cm was used to cover the film. A 6 MeV electron beam with an 8 mm acrylic board was then used to irradiate the phantom. The source-surface distance (SSD) was 444 cm, the field size was 36´36 cm at SSD of 100 cm without an electron applicator, and the monitor unit was 2000 MU. The shielding rates were obtained from the dose profiles. RESULTS: The mean values of the shielding rate values for all phantoms were 50.1, 97.6, and 98.7% for 1, 2, and 3 mm of lead, respectively, and -13.6, 53.9, 91.2, and 99.4% for 1, 2, 3, and 4 mm of STR, respectively. CONCLUSION: STR with a thickness of 4 mm had the same shielding properties as lead with a thickness of 3 mm, which was an approximately 100% shielding rate. STR could therefore be used in TSEB therapy instead of lead.


Asunto(s)
Protección Radiológica , Electrones , Fantasmas de Imagen , Dosificación Radioterapéutica , Goma , Tungsteno
10.
Artículo en Japonés | MEDLINE | ID: mdl-33612696

RESUMEN

We studied the image resolution properties in digital mammography using the variance and edge response function methods. The associated measurements were made using a polymethylmethacrylate phantom of 0-40 mm thickness while maintaining the incident dose to the detector constant, as well as with and without using the phantom but by varying the level of exposure to the detector. The results obtained using the two methods were compared on the object plane of the mammography unit with compensation for the magnification and rejection of the scattered radiation. In this unit, the imaging process of resolution enhancement may be performed according to the phantom thickness, shape of test device, exposure level, and so on. The modulation transfer function values of the variance method were slightly higher than those of the edge method, approximately 6% at 2 cycles/mm and 8% at 4 cycles/mm without resolution enhancement processing. We concluded that the variance method is more suitable than the edge method for the constancy test or quality control because of its lower coefficient of variation.


Asunto(s)
Mamografía , Intensificación de Imagen Radiográfica , Fantasmas de Imagen , Control de Calidad , Reproducibilidad de los Resultados
11.
Ultrasonics ; 113: 106357, 2021 May.
Artículo en Inglés | MEDLINE | ID: mdl-33548756

RESUMEN

This study describes the development and characterization of an agar-based soft tissue-mimicking material (TMM) doped with wood powder destined for fabricating MRgFUS applications. The main objective of the following work was to investigate the suitability of wood powder as an inexpensive alternative in replacing other added materials that have been suggested in previous studies for controlling the ultrasonic properties of TMMs. The characterization procedure involved a series of experiments designed to estimate the acoustic (attenuation coefficient, absorption coefficient, propagation speed, and impedance), thermal (conductivity, diffusivity, specific heat capacity), and MR properties (T1 and T2 relaxation times) of the wood-powder doped material. The developed TMM (2% w/v agar and 4% w/v wood powder) as expected demonstrated compatibility with MRI scanner following images artifacts evaluation. The acoustic attenuation coefficient of the proposed material was measured over the frequency range of 1.1-3 MHz and found to be nearly proportional to frequency. The measured attenuation coefficient was 0.48 dB/cm at 1 MHz which was well within the range of soft tissue. Temperatures over 37 °C proved to increase marginally the attenuation coefficient. Following the transient thermoelectric method, the acoustic absorption coefficient was estimated at 0.34 dB/cm-MHz. The estimated propagation speed (1487 m/s) was within the range of soft tissue at room temperature, while it significantly increased with higher temperature. The material possessed an acoustic impedance of 1.58 MRayl which was found to be comparable to the corresponding value of muscle tissue. The thermal conductivity of the material was estimated at 0.51 W/m K. The measured relaxation times T1 (844 ms) and T2 (66 ms) were within the range of values found in the literature for soft tissue. The phantom was tested for its suitability for evaluating MRgFUS thermal protocols. High acoustic energy was applied, and temperature change was recorded using thermocouples and MR thermometry. MR thermal maps were acquired using single-shot Echo Planar Imaging (EPI) gradient echo sequence. The TMM matched adequately the acoustic and thermal properties of human tissues and through a series of experiments, it was proven that wood concentration enhances acoustic absorption. Experiments using MR thermometry demonstrated the usefulness of this phantom to evaluate ultrasonic thermal protocols by monitoring peak temperatures in real-time. Thermal lesions formed above a thermal dose were observed in high-resolution MR images and visually in dissections of the proposed TMM.


Asunto(s)
Materiales Biomiméticos , Ultrasonido Enfocado de Alta Intensidad de Ablación , Fantasmas de Imagen , Agar , Artefactos , Diseño de Equipo , Polvos , Temperatura , Madera
12.
J Vis Exp ; (167)2021 01 18.
Artículo en Inglés | MEDLINE | ID: mdl-33522517

RESUMEN

Catheter-based interventions are standard treatment options for cardiovascular pathologies. Therefore, patient-specific models could help training physicians' wire-skills as well as improving planning of interventional procedures. The aim of this study was to develop a manufacturing process of patient-specific 3D-printed models for cardiovascular interventions. To create a 3D-printed elastic phantom, different 3D-printing materials were compared to porcine biological tissues (i.e., aortic tissue) in terms of mechanical characteristics. A fitting material was selected based on comparative tensile tests and specific material thicknesses were defined. Anonymized contrast-enhanced CT-datasets were collected retrospectively. Patient-specific volumetric models were extracted from these datasets and subsequently 3D-printed. A pulsatile flow loop was constructed to simulate the intraluminal blood flow during interventions. Models' suitability for clinical imaging was assessed by x-ray imaging, CT, 4D-MRI and (Doppler) ultrasonography. Contrast medium was used to enhance visibility in x-ray-based imaging. Different catheterization techniques were applied to evaluate the 3D-printed phantoms in physicians' training as well as for pre-interventional therapy planning. Printed models showed a high printing resolution (~30 µm) and mechanical properties of the chosen material were comparable to physiological biomechanics. Physical and digital models showed high anatomical accuracy when compared to the underlying radiological dataset. Printed models were suitable for ultrasonic imaging as well as standard x-rays. Doppler ultrasonography and 4D-MRI displayed flow patterns and landmark characteristics (i.e., turbulence, wall shear stress) matching native data. In a catheter-based laboratory setting, patient-specific phantoms were easy to catheterize. Therapy planning and training of interventional procedures on challenging anatomies (e.g., congenital heart disease (CHD)) was possible. Flexible patient-specific cardiovascular phantoms were 3D-printed, and the application of common clinical imaging techniques was possible. This new process is ideal as a training tool for catheter-based (electrophysiological) interventions and can be used in patient-specific therapy planning.


Asunto(s)
Sistema Cardiovascular/diagnóstico por imagen , Fantasmas de Imagen , Impresión Tridimensional , Animales , Aorta Torácica/diagnóstico por imagen , Humanos , Imagen por Resonancia Magnética , Estudios Retrospectivos , Porcinos , Tomografía Computarizada por Rayos X , Ultrasonografía
14.
Medicine (Baltimore) ; 100(4): e24473, 2021 Jan 29.
Artículo en Inglés | MEDLINE | ID: mdl-33530260

RESUMEN

ABSTRACT: Tomoscintigraphic reconstruction in nuclear medicine assumes that the distribution of the tracer is unchanged in the volume of interest throughout the duration of the acquisition. This condition is however not met in early-phase bone scintigraphy and early-phase pelvic SPECT may display helical artifacts due to the filling of the bladder. Those artifacts may hamper proper interpretation of surrounding bone areas. The aim of this study was to construct a 4D digital pelvic phantom to simulate different acquisition protocols and optimize the acquisition.A 4D digital pelvic phantom was generated with a dynamic component consisting in an expanding bladder with 2 ureters and a static part consisting in the 2 kidneys, bone structures, and soft tissues. Projection data were obtained using an attenuated Radon transform function. Four acquisitions protocols were tested: 32 projections of 16 seconds (32-16-1), 32 projections of 8 seconds (32-8-1), 2 consecutive SPECT of 32 projections of 4 seconds (32-4-2) and 2 consecutive SPECT of 16 projections of 8 seconds (16-8-2). The optimal protocol was then tested on one patient.The amplitude of the artifacts was reduced with the 32-8-1, 32-4-2, and 16-8-2 protocols. The 16-8-2 protocol had the highest signal to noise ratio among those 3 protocols. The bladder artifact was visually markedly reduced on the patient acquisition with a 16-8-2 protocol.Two successive early-phase bone SPECT, with a lower number of projection than the usual protocol reduce the impact of the helical artifacts around the bladder.


Asunto(s)
Artefactos , Huesos Pélvicos/diagnóstico por imagen , Tomografía Computarizada de Emisión/métodos , Vejiga Urinaria/diagnóstico por imagen , Humanos , Procesamiento de Imagen Asistido por Computador/métodos , Fantasmas de Imagen , Mejoramiento de la Calidad
15.
Br J Radiol ; 94(1119): 20191004, 2021 Mar 01.
Artículo en Inglés | MEDLINE | ID: mdl-33507818

RESUMEN

OBJECTIVES: To investigate the feasibility of accurately quantifying the concentration of MRI contrast agent in flowing blood by measuring its T1 in a large vessel. Such measures are often used to obtain patient-specific arterial input functions for the accurate fitting of pharmacokinetic models to dynamic contrast enhanced MRI data. Flow is known to produce errors with this technique, but these have so far been poorly quantified and characterised in the context of pulsatile flow with a rapidly changing T1 as would be expected in vivo. METHODS: A phantom was developed which used a mechanical pump to pass fluid at physiologically relevant rates. Measurements of T1 were made using high temporal resolution gradient recalled sequences suitable for DCE-MRI of both constant and pulsatile flow. These measures were used to validate a virtual phantom that was then used to simulate the expected errors in the measurement of an AIF in vivo. RESULTS: The relationship between measured T1 values and flow velocity was found to be non-linear. The subsequent error in quantification of contrast agent concentration in a measured AIF was shown. CONCLUSIONS: The T1 measurement of flowing blood using standard DCE- MRI sequences are subject to large measurement errors which are non-linear in relation to flow velocity. ADVANCES IN KNOWLEDGE: This work qualitatively and quantitatively demonstrates the difficulties of accurately measuring the T1 of flowing blood using DCE-MRI over a wide range of physiologically realistic flow velocities and pulsatilities. Sources of error are identified and proposals made to reduce these.


Asunto(s)
Arterias/fisiología , Medios de Contraste , Hemodinámica/fisiología , Aumento de la Imagen/métodos , Imagen por Resonancia Magnética/métodos , Estudios de Factibilidad , Fantasmas de Imagen , Reproducibilidad de los Resultados
16.
Sensors (Basel) ; 21(2)2021 Jan 15.
Artículo en Inglés | MEDLINE | ID: mdl-33467627

RESUMEN

In this paper, a computer-aided training method for hyperparameter selection of limited data X-ray computed tomography (XCT) reconstruction was proposed. The proposed method employed the ant colony optimisation (ACO) approach to assist in hyperparameter selection for the adaptive-weighted projection-controlled steepest descent (AwPCSD) algorithm, which is a total-variation (TV) based regularisation algorithm. During the implementation, there was a colony of artificial ants that swarm through the AwPCSD algorithm. Each ant chose a set of hyperparameters required for its iterative CT reconstruction and the correlation coefficient (CC) score was given for reconstructed images compared to the reference image. A colony of ants in one generation left a pheromone through its chosen path representing a choice of hyperparameters. Higher score means stronger pheromones/probabilities to attract more ants in the next generations. At the end of the implementation, the hyperparameter configuration with the highest score was chosen as an optimal set of hyperparameters. In the experimental results section, the reconstruction using hyperparameters from the proposed method was compared with results from three other cases: the conjugate gradient least square (CGLS), the AwPCSD algorithm using the set of arbitrary hyperparameters and the cross-validation method.The experiments showed that the results from the proposed method were superior to those of the CGLS algorithm and the AwPCSD algorithm using the set of arbitrary hyperparameters. Although the results of the ACO algorithm were slightly inferior to those of the cross-validation method as measured by the quantitative metrics, the ACO algorithm was over 10 times faster than cross-Validation. The optimal set of hyperparameters from the proposed method was also robust against an increase of noise in the data and can be applicable to different imaging samples with similar context. The ACO approach in the proposed method was able to identify optimal values of hyperparameters for a dataset and, as a result, produced a good quality reconstructed image from limited number of projection data. The proposed method in this work successfully solves a problem of hyperparameters selection, which is a major challenge in an implementation of TV based reconstruction algorithms.


Asunto(s)
Algoritmos , Tomografía Computarizada por Rayos X , Procesamiento de Imagen Asistido por Computador , Análisis de los Mínimos Cuadrados , Fantasmas de Imagen
17.
Methods Mol Biol ; 2216: 75-85, 2021.
Artículo en Inglés | MEDLINE | ID: mdl-33475995

RESUMEN

Here we describe a simple and inexpensive protocol for preparing ex vivo rodent phantoms for use in MR imaging studies. The experimental animals are perfused and fixed with formaldehyde, and then wrapped with gauze and sealed with liquid latex. This yields a phantom that preserves all organs in situ, and which avoids the need to keep fixed animals and organs in containers that have dimensions very different from living animals. This is especially important for loading in MR detectors, and specifically the RF coils, they are usually used with. The phantom can be safely stored and conveniently reused, and can provide MR scientists with a realistic phantom with which to establish protocols in preparation for preclinical in vivo studies-for renal, brain, and body imaging. The phantom also serves as an ideal teaching tool, for trainees learning how to perform preclinical MRI investigations of the kidney and other target organs, while avoiding the need for handling living animals, and reducing the total number of animals required.This protocol chapter is part of the PARENCHIMA initiative "MRI Biomarkers for CKD " (CA16103), a community-driven Action of the European Cooperation in Science and Technology (COST) program of the European Union, which aims to improve the reproducibility and standardization of renal MRI biomarkers.


Asunto(s)
Biomarcadores/análisis , Encéfalo/fisiología , Procesamiento de Imagen Asistido por Computador/métodos , Riñón/fisiología , Imagen por Resonancia Magnética/métodos , Monitoreo Fisiológico/métodos , Fantasmas de Imagen , Animales , Ratones , Ratas , Programas Informáticos
18.
Methods Mol Biol ; 2216: 241-256, 2021.
Artículo en Inglés | MEDLINE | ID: mdl-33476004

RESUMEN

Magnetic Resonance Imaging (MRI) has been actively explored in the last several decades for assessing renal function by providing several physiological information, including glomerular filtration rate, renal plasma flow, tissue oxygenation and water diffusion. Within MRI, the developing field of chemical exchange saturation transfer (CEST) has potential to provide further functional information for diagnosing kidney diseases. Both endogenous produced molecules as well as exogenously administered CEST agents have been exploited for providing functional information related to kidney diseases in preclinical studies. In particular, CEST MRI has been exploited for assessing the acid-base homeostasis in the kidney and for monitoring pH changes in several disease models. This review summarizes several CEST MRI procedures for assessing kidney functionality and pH, for monitoring renal pH changes in different kidney injury models and for evaluating renal allograft rejection.This chapter is based upon work from the COST Action PARENCHIMA, a community-driven network funded by the European Cooperation in Science and Technology (COST) program of the European Union, which aims to improve the reproducibility and standardization of renal MRI biomarkers. This introduction chapter is complemented by two separate chapters describing the experimental procedure and data analysis.


Asunto(s)
Biomarcadores/análisis , Medios de Contraste/química , Procesamiento de Imagen Asistido por Computador/métodos , Riñón/fisiología , Imagen por Resonancia Magnética/métodos , Monitoreo Fisiológico/métodos , Fantasmas de Imagen , Animales , Humanos , Concentración de Iones de Hidrógeno , Programas Informáticos
19.
Methods Mol Biol ; 2216: 455-471, 2021.
Artículo en Inglés | MEDLINE | ID: mdl-33476017

RESUMEN

Chemical exchange saturation transfer (CEST) is recognized as one of the premier methods for measuring pH with this environmental variable expected to be an excellent biomarker for kidney diseases. Here we describe step-by-step CEST MRI experimental protocols for producing pH and perfusion maps for monitoring kidney pH homeostasis in rodents after administering iopamidol as contrast agent. Several CEST techniques, acquisition protocols and ratiometric approaches are described. The impact of length of acquisition time on the quality of the maps is detailed. These methods may be useful for investigating progression in kidney disease in vivo for rodent models.This chapter is based upon work from the COST Action PARENCHIMA, a community-driven network funded by the European Cooperation in Science and Technology (COST) program of the European Union, which aims to improve the reproducibility and standardization of renal MRI biomarkers. This experimental protocol is complemented by two separate chapters describing the basic concepts and data analysis.


Asunto(s)
Medios de Contraste/química , Procesamiento de Imagen Asistido por Computador/métodos , Riñón/fisiología , Imagen por Resonancia Magnética/métodos , Monitoreo Fisiológico/métodos , Fantasmas de Imagen , Animales , Concentración de Iones de Hidrógeno , Ratones , Ratones Endogámicos C57BL , Programas Informáticos
20.
Methods Mol Biol ; 2216: 473-480, 2021.
Artículo en Inglés | MEDLINE | ID: mdl-33476018

RESUMEN

Sodium handling is a key physiological hallmark of renal function. Alterations are generally considered a pathophysiologic event associated with kidney injury, with disturbances in the corticomedullary sodium gradient being indicative of a number of conditions. This experimental protocol review describes the individual steps needed to perform 23Na MRI; allowing accurate monitoring of the renal sodium distribution in a step-by-step experimental protocol for rodents.This chapter is based upon work from the PARENCHIMA COST Action, a community-driven network funded by the European Cooperation in Science and Technology (COST) program of the European Union, which aims to improve the reproducibility and standardization of renal MRI biomarkers. This experimental protocol chapter is complemented by two separate chapters describing the basic concept and data analysis.


Asunto(s)
Procesamiento de Imagen Asistido por Computador/métodos , Riñón/fisiología , Imagen por Resonancia Magnética/métodos , Monitoreo Fisiológico/métodos , Isótopos de Sodio/análisis , Animales , Fantasmas de Imagen , Ratas , Ratas Endogámicas Lew , Ratas Sprague-Dawley , Ratas Wistar , Programas Informáticos
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