Your browser doesn't support javascript.
loading
Mostrar: 20 | 50 | 100
Resultados 1 - 20 de 39.373
Filtrar
1.
Ultrasonics ; 118: 106564, 2022 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-34530395

RESUMO

Tissue-Mimicking Material (TMM) is defined on IEC International Standards and applied in assessing ultrasonic diagnostic and therapeutic equipment's basic safety and essential performance. One of the TMM that fits IEC standards specification has its recipe described at IEC 60601-2-37, and it is fabricated using glycerol (11.21 %), deionized water (82.95%), benzalkonium chloride (0.47 %), silicon carbide (0.53 %), aluminum oxide 0.3 µm (0.88%), aluminum oxide 3.0 µm (0.94 %), and agar (3.08 %). Glycerol is the component responsible for adjusting the TMM's speed of sound. Moreover, it is recommended to store TMM in a closed container immersed in a mixture of water (88.1 %)/glycerol (11.9 %) to prevent it from drying out and avoiding air contact. The literature points out TMM measurements underwater can alter the speed of sound property as TMM tends to lose glycerol. Herein, the authors proposed to assess the viability of measuring the TMM speed of sound in the water/glycerol maintenance solution. First, the authors characterized the maintenance solution's speed of sound for a temperature range of 20 °C to 45 °C. Then, the group velocity of a set of TMM was measured underwater and in the maintenance solution for the same temperature range. The respective group velocity expanded uncertainty was calculated. The results indicate it is feasible to measure TMM in the maintenance solution, achieving group velocity values with no statistical difference from the ones measured underwater in the temperature range of 20 °C to 40 °C.


Assuntos
Materiais Biomiméticos , Imagens de Fantasmas/normas , Som , Terapia por Ultrassom/instrumentação , Ultrassonografia/instrumentação , Óxido de Alumínio , Compostos de Benzalcônio , Calibragem , Compostos Inorgânicos de Carbono , Segurança de Equipamentos , Glicerol , Compostos de Silício , Temperatura , Água
2.
Sensors (Basel) ; 21(21)2021 Oct 23.
Artigo em Inglês | MEDLINE | ID: mdl-34770344

RESUMO

(1) Background: Small Animal Fast Insert for MRI detector I (SAFIR-I) is a preclinical Positron Emission Tomography (PET) insert for the Bruker BioSpec 70/30 Ultra Shield Refrigerated (USR) preclinical 7T Magnetic Resonance Imaging (MRI) system. It is designed explicitly for high-rate kinetic studies in mice and rats with injected activities reaching 500MBq, enabling truly simultaneous quantitative PET and Magnetic Resonance (MR) imaging with time frames of a few seconds in length. (2) Methods: SAFIR-I has an axial field of view of 54.2mm and an inner diameter of 114mm. It employs Lutetium Yttrium OxyorthoSilicate (LYSO) crystals and Multi Pixel Photon Counter (MPPC) arrays. The Position-Energy-Timing Application Specific Integrated Circuit, version 6, Single Ended (PETA6SE) digitizes the MPPC signals and provides time stamps and energy information. (3) Results: SAFIR-I is MR-compatible. The system's Coincidence Resolving Time (CRT) and energy resolution are between separate-uncertainty 209.0(3)ps and separate-uncertainty 12.41(02) Full Width at Half Maximum (FWHM) at low activity and separate-uncertainty 326.89(12)ps and separate-uncertainty 20.630(011) FWHM at 550MBq, respectively. The peak sensitivity is ∼1.6. The excellent performance facilitated the successful execution of first in vivo rat studies beyond 300MBq. Based on features visible in the acquired images, we estimate the spatial resolution to be ∼2mm in the center of the Field Of View (FOV). (4) Conclusion: The SAFIR-I PET insert provides excellent performance, permitting simultaneous in vivo small animal PET/MR image acquisitions with time frames of a few seconds in length at activities of up to 500MBq.


Assuntos
Imageamento por Ressonância Magnética , Tomografia por Emissão de Pósitrons , Animais , Desenho de Equipamento , Cinética , Camundongos , Imagens de Fantasmas , Fótons , Ratos
3.
Sensors (Basel) ; 21(21)2021 Oct 30.
Artigo em Inglês | MEDLINE | ID: mdl-34770534

RESUMO

Positron emission tomography (PET) can provide functional images and identify abnormal metabolic regions of the whole-body to effectively detect tumor presence and distribution. The filtered back-projection (FBP) algorithm is one of the most common images reconstruction methods. However, it will generate strike artifacts on the reconstructed image and affect the clinical diagnosis of lesions. Past studies have shown reduction in strike artifacts and improvement in quality of images by two-dimensional morphological structure operators (2D-MSO). The morphological structure method merely processes the noise distribution of 2D space and never considers the noise distribution of 3D space. This study was designed to develop three-dimensional-morphological structure operators (3D MSO) for nuclear medicine imaging and effectively eliminating strike artifacts without reducing image quality. A parallel operation was also used to calculate the minimum background standard deviation of the images for three-dimensional morphological structure operators with the optimal response curve (3D-MSO/ORC). As a result of Jaszczak phantom and rat verification, 3D-MSO/ORC showed better denoising performance and image quality than the 2D-MSO method. Thus, 3D MSO/ORC with a 3 × 3 × 3 mask can reduce noise efficiently and provide stability in FBP images.


Assuntos
Algoritmos , Artefatos , Animais , Processamento de Imagem Assistida por Computador , Imagens de Fantasmas , Tomografia por Emissão de Pósitrons , Ratos
4.
Sensors (Basel) ; 21(21)2021 Oct 30.
Artigo em Inglês | MEDLINE | ID: mdl-34770558

RESUMO

For ultra-high field and frequency (UHF) magnetic resonance imaging (MRI), the associated short wavelengths in biological tissues leads to penetration and homogeneity issues at 10.5 tesla (T) and require antenna transmit arrays for efficiently generated 447 MHz B1+ fields (defined as the transmit radiofrequency (RF) magnetic field generated by RF coils). Previously, we evaluated a 16-channel combined loop + dipole antenna (LD) 10.5 T head array. While the LD array configuration did not achieve the desired B1+ efficiency, it showed an improvement of the specific absorption rate (SAR) efficiency compared to the separate 8-channel loop and separate 8-channel dipole antenna arrays at 10.5 T. Here we compare a 16-channel dipole antenna array with a 16-channel LD array of the same dimensions to evaluate B1+ efficiency, 10 g SAR, and SAR efficiency. The 16-channel dipole antenna array achieved a 24% increase in B1+ efficiency in the electromagnetic simulation and MR experiment compared to the LD array, as measured in the central region of a phantom. Based on the simulation results with a human model, we estimate that a 16-channel dipole antenna array for human brain imaging can increase B1+ efficiency by 15% with similar SAR efficiency compared to a 16-channel LD head array.


Assuntos
Imageamento por Ressonância Magnética , Ondas de Rádio , Encéfalo/diagnóstico por imagem , Desenho de Equipamento , Humanos , Imagens de Fantasmas
5.
J Biomed Opt ; 27(7)2021 11.
Artigo em Inglês | MEDLINE | ID: mdl-34725995

RESUMO

SIGNIFICANCE: Gas in scattering media absorption spectroscopy (GASMAS) enables noninvasive gas sensing in the body. It is developing as a tool for diagnosis and monitoring of respiratory conditions in neonates. Phantom models with relevant features to the clinical translation of GASMAS technology are necessary to understand technical challenges and potential applications of this technique. State-of-the-art phantoms designed for this purpose have focused on the optical properties and anthropomorphic geometry of the thorax, contributing to the source-detector placement, design, and optimization. Lung phantom mimicking the alveolar anatomy has not been included in the existent models due to the inherent complexity of the tissue. We present a simplified model that recreates inflated alveoli embedded in lung phantom. AIM: The goal of this study was to build a lung model with air-filled structures mimicking inflated alveoli surrounded by optical phantom with accurate optical properties (µa = 0.50 cm - 1 and µs'=5.4 cm-1) and physiological parameters [37°C and 100% relative humidity (RH)], and to control the air volume within the phantom to demonstrate the feasibility of GASMAS in sensing changes in pulmonary air volume. APPROACH: The lung model was built using a capillary structure with analogous size to alveolar units. Part of the capillaries were filled with liquid lung optical phantom to recreate scattering and absorption, whereas empty capillaries mimicked air filled alveoli. The capillary array was placed inside a custom-made chamber that maintained pulmonary temperature and RH. The geometry of the chamber permitted the placement of the laser head and detector of a GASMAS bench top system (MicroLab Dual O2 / H2O), to test the changes in volume of the lung model in transmittance geometry. RESULTS: The lung tissue model with air volume range from 6.89 × 10 - 7 m3 to 1.80 × 10 - 3 m3 was built. Two measurement sets, with 10 different capillary configurations each, were arranged to increase or decrease progressively (in steps of 3.93 × 10 - 8 m3) the air volume in the lung model. The respective GASMAS data acquisition was performed for both data sets. The maximum absorption signal was obtained for configurations with the highest number of air-filled capillaries and decreased progressively when the air spaces were replaced by capillaries filled with liquid optical phantom. Further studies are necessary to define the minimum and maximum volume of air that can be measured with GASMAS-based devices for different source-detector geometries. CONCLUSIONS: The optical properties and the structure of tissue from the respiratory zone have been modeled using a simplified capillary array immersed in a controlled environment chamber at pulmonary temperature and RH. The feasibility of measuring volume changes with GASMAS technique has been proven, stating a new possible application of GASMAS technology in respiratory treatment and diagnostics.


Assuntos
Pulmão , Oxigênio , Humanos , Umidade , Recém-Nascido , Pulmão/diagnóstico por imagem , Imagens de Fantasmas , Temperatura
6.
Nihon Hoshasen Gijutsu Gakkai Zasshi ; 77(11): 1317-1324, 2021.
Artigo em Japonês | MEDLINE | ID: mdl-34803112

RESUMO

PURPOSE: We applied deviceless, positron emission tomography/computed tomography(PET/CT) data-driven respiratory gating (DDG) to validate the effects of misalignment between PET and CT at various respiratory phases. METHODS: A lung lesion was simulated using an NEMA IEC body phantom in which the background comprised hot spheres containing polystyrene foam beads. We acquired PET images as the phantom moved downwards and then stopped. Attenuation on computed tomography images acquired at the inspiratory, stationary, and expiratory phases was corrected after the phantom stopped moving. Normalized mean square error (NMSE), recovery coefficients (RCmax and RCmean) and volume were analyzed on DDG-PET images using CT-based attenuation correction. RESULTS: The NMSE was closest to 0 in PET images corrected using the expiratory CT image. The RCmax was<1.0, and the RCmean was closest to 1.0 only in PET images corrected using the expiratory CT image. Volume was either underestimated or overestimated more according to the size of the spheres when the alignment of CT and PET images was greater. CONCLUSION: We recommend using the expiratory but not the inspiratory phase when using DDG for PET/CT correction.


Assuntos
Tomografia por Emissão de Pósitrons combinada à Tomografia Computadorizada , Tomografia por Emissão de Pósitrons , Artefatos , Imagens de Fantasmas , Tomografia Computadorizada por Raios X
7.
J Biomed Opt ; 27(7)2021 11.
Artigo em Inglês | MEDLINE | ID: mdl-34796707

RESUMO

SIGNIFICANCE: The polymer, polydimethylsiloxane (PDMS), has been increasingly used to make tissue simulating phantoms due to its excellent processability, durability, flexibility, and limited tunability of optical, mechanical, and thermal properties. We report on a robust technique to fabricate PDMS-based tissue-mimicking phantoms where the broad range of scattering and absorption properties are independently adjustable in the visible- to near-infrared wavelength range from 500 to 850 nm. We also report on an analysis method to concisely quantify the phantoms' broadband characteristics with four parameters. AIM: We report on techniques to manufacture and characterize solid tissue-mimicking phantoms of PDMS polymers. Tunability of the absorption (µa ( λ ) ) and reduced scattering coefficient spectra (µs'(λ)) in the wavelength range of 500 to 850 nm is demonstrated by adjusting the concentrations of light absorbing carbon black powder (CBP) and light scattering titanium dioxide powder (TDP) added into the PDMS base material. APPROACH: The µa ( λ ) and µs'(λ) of the phantoms were obtained through measurements with a broadband integrating sphere system and by applying an inverse adding doubling algorithm. Analyses of µa ( λ ) and µs'(λ) of the phantoms, by fitting them to linear and power law functions, respectively, demonstrate that independent control of µa ( λ ) and µs'(λ) is possible by systematically varying the concentrations of CBP and TDP. RESULTS: Our technique quantifies the phantoms with four simple fitting parameters enabling a concise tabulation of their broadband optical properties as well as comparisons to the optical properties of biological tissues. We demonstrate that, to a limited extent, the scattering properties of our phantoms mimic those of human tissues of various types. A possible way to overcome this limitation is demonstrated with phantoms that incorporate polystyrene microbead scatterers. CONCLUSIONS: Our manufacturing and analysis techniques may further promote the application of PDMS-based tissue-mimicking phantoms and may enable robust quality control and quality checks of the phantoms.


Assuntos
Dimetilpolisiloxanos , Humanos , Imagens de Fantasmas
8.
Dentomaxillofac Radiol ; 50(8): 20210276, 2021 Dec 01.
Artigo em Inglês | MEDLINE | ID: mdl-34739304

RESUMO

The mathematical theory of CT was proposed by J. Radon in 1917. It was declared that the projection of whole data sets was needed to reconstruct CT images. Therefore, according to J. Radon's original theory, local cone beam CT (local CBCT) was impossible to achieve.In this paper, I discuss how local CBCT was discovered and developed. Its development required many technical elements, such as a turntable and X-ray television system, for basic experiments such as those on which narrow collimation theory and multifunctional panoramic tomography were based. These experiments endured many failures during development.Now, local CBCT is extremely popular in dental practice because local CBCT has a low radiation dose and high resolution. This paper introduces the technical elements and outlines the important stages during the development of local CBCT in the 1990s.


Assuntos
Tomografia Computadorizada de Feixe Cônico , Imagens de Fantasmas , Raios X
9.
J Int Med Res ; 49(11): 3000605211053281, 2021 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-34743631

RESUMO

OBJECTIVE: Technological developments have made it possible to create simulation models to educate clinicians on surgical techniques and patient preparation. In this study, we created an inexpensive lumbar spine phantom using patient data and analyzed its usefulness in clinical education. METHODS: This randomized comparative study used computed tomography and magnetic resonance imaging data from a single patient to print a three-dimensional (3D) bone framework and create a mold. The printed bones and structures made from the mold were placed in a simulation model that was used to train residents. The residents were divided into two groups: Group L, which received only an audiovisual lecture, and Group P, which received an additional 1 hour of training using the 3D phantom. The performance of both groups was evaluated using pretest and post-test analyses. RESULTS: Both the checklist and global rating scores increased after training in both groups. However, some variables improved significantly only in Group P. The overall satisfaction score was also higher in Group P than in Group L. CONCLUSIONS: We have described a method by which medical doctors can create a spine simulation phantom and have demonstrated its efficiency for procedural education.


Assuntos
Vértebras Lombares , Impressão Tridimensional , Humanos , Vértebras Lombares/diagnóstico por imagem , Vértebras Lombares/cirurgia , Modelos Anatômicos , Dor , Imagens de Fantasmas , Tomografia Computadorizada por Raios X
10.
J Biomed Opt ; 26(10)2021 10.
Artigo em Inglês | MEDLINE | ID: mdl-34643072

RESUMO

SIGNIFICANCE: The Cherenkov emission spectrum overlaps with that of ambient room light sources. Choice of room lighting devices dramatically affects the efficient detection of Cherenkov emission during patient treatment. AIM: To determine optimal room light sources allowing Cherenkov emission imaging in normally lit radiotherapy treatment delivery rooms. APPROACH: A variety of commercial light sources and long-pass (LP) filters were surveyed for spectral band separation from the red to near-infrared Cherenkov light emitted by tissue. Their effects on signal-to-noise ratio (SNR), Cherenkov to background signal ratio, and image artifacts were quantified by imaging irradiated tissue equivalent phantoms with an intensified time-gated CMOS camera. RESULTS: Because Cherenkov emission from tissue lies largely in the near-infrared spectrum, a controlled choice of ambient light that avoids this spectral band is ideal, along with a camera that is maximally sensitive to it. An RGB LED light source produced the best SNR out of all sources that mimic room light temperature. A 675-nm LP filter on the camera input further reduced ambient light detected (optical density > 3), achieving maximal SNR for Cherenkov emission near 40. Reduction of the room light signal reduced artifacts from specular reflection on the tissue surface and also minimized spurious Cherenkov signals from non-tissue features such as bolus. CONCLUSIONS: LP filtering during image acquisition for near-infrared light in tandem with narrow band LED illuminated rooms improves image quality, trading off the loss of red wavelengths for better removal of room light in the image. This spectral filtering is also critically important to remove specular reflection in the images and allow for imaging of Cherenkov emission through clear bolus. Beyond time-gated external beam therapy systems, the spectral separation methods can be utilized for background removal for continuous treatment delivery methods including proton pencil beam scanning systems and brachytherapy.


Assuntos
Raios Infravermelhos , Radiometria , Humanos , Imagem Óptica , Imagens de Fantasmas , Razão Sinal-Ruído
11.
Nihon Hoshasen Gijutsu Gakkai Zasshi ; 77(10): 1196-1202, 2021.
Artigo em Japonês | MEDLINE | ID: mdl-34670927

RESUMO

PURPOSE: This study aims to evaluate the fat suppression effect on images of the head and neck region using chemical shift selective (CHESS), and iterative decomposition of water and fat with echo asymmetry and least-squares estimation (IDEAL). METHOD: A self-made phantom containing oil around the simulated bone marrow and muscle was scanned. The signal-to-noise ratio (SNR) was calculated using the National Electrical Manufacturers Association (NEMA) subtraction and pixel shift methods. Thereafter, the fat suppression effect and SNR were calculated in clinical images using the pixel shift method. RESULT: In both phantom and clinical images, the fat suppression effect was higher using IDEAL. In addition, the SNR of the NEMA subtraction method and the pixel shift method in phantom images was higher in the simulated bone marrow than in the simulated muscle. The SNR of the vertebral body was higher than that of the tongue in the clinical images using IDEAL, and the same tendency was observed in the phantom image evaluation. However, there was a difference in SNR between the phantom and clinical images. CONCLUSION: In the head and neck region, fat-suppressed images using IDEAL showed the same higher fat-suppressing effect as that in a previous study. The SNR for the phantom and the clinical images was different. The SNR calculated using the pixel shift method for the phantom images with IDEAL and the clinical images showed the same tendency. Although there is a difference between the SNRs of phantom and clinical images calculated by the pixel shift method, it is suggested that the method can be used to compare the SNR between tissues such as the vertebral body and the tongue.


Assuntos
Cabeça , Imageamento por Ressonância Magnética , Pescoço/diagnóstico por imagem , Imagens de Fantasmas , Razão Sinal-Ruído
12.
In Vivo ; 35(6): 3147-3155, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-34697145

RESUMO

BACKGROUND/AIM: The quantitative evaluation of fat tissue, mainly for the determination of liver steatosis, is possible by using dual-energy computed tomography. Different photon energy acquisitions allow for estimation of attenuation coefficients. The effect of variation in radiation doses and reconstruction kernels on fat fraction estimation was investigated. MATERIALS AND METHODS: A six-probe-phantom with fat concentrations of 0%, 20%, 40%, 60%, 80%, and 100% were scanned in Sn140/100 kV with radiation doses ranging between 20 and 200 mAs before and after calibration. Images were reconstructed using iterative kernels (I26,Q30,I70). RESULTS: Fat fractions measured in dual-energy computed tomography (DECT) were consistent with the 20%-stepwise varying actual concentrations. Variation in radiation dose resulted in 3.1% variation of fat fraction. Softer reconstruction kernel (I26) underestimated the fat fraction (-9.1%), while quantitative (Q30) and sharper kernel (I70) overestimated fat fraction (10,8% and 13,1, respectively). CONCLUSION: The fat fraction in DECT approaches the actual fat concentration when calibrated to the reconstruction kerneö. Variation of radiation dose caused an acceptable 3% variation.


Assuntos
Fígado Gorduroso , Tomografia Computadorizada por Raios X , Humanos , Imagens de Fantasmas , Fótons , Doses de Radiação
13.
In Vivo ; 35(6): 3521-3526, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-34697190

RESUMO

BACKGROUND/AIM: Auto-activation positron emission tomography (AAPET) is one of the most promising methods to verify beam range in carbon ion radiotherapy (C-ion RT). We aimed to confirm this for the first time in a clinical setting by performing AAPET in a patient with pancreatic cancer previously receiving coil embolisation of hepatic artery pseudoaneurysm. MATERIALS AND METHODS: A 70-year-old pancreatic head cancer patient was treated with C-ion RT on a clinical dose of 4.6 Gy (RBE), followed by AAPET, to verify beam ranges in C-ion RT. RESULTS: Positron emission tomography (PET) revealed low positron emitter concentrations at the distal side of the internal metals and in the aorta compared to the dose distribution of the treatment plan, indicating range shortening by internal metals in C-ion beams and positron emitter transportation by biofluids. CONCLUSION: AAPET may detect range shortening by internal metals in the trajectory and washout of intravascular positron emitter compared to plan dose distribution.


Assuntos
Elétrons , Radioterapia com Íons Pesados , Idoso , Carbono , Humanos , Imagens de Fantasmas , Tomografia por Emissão de Pósitrons
14.
Anticancer Res ; 41(10): 5053-5058, 2021 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-34593454

RESUMO

BACKGROUND/AIM: Investigation of the influence of different ultra-low dose computed tomography (ULDCT) protocols on the detection of solid and subsolid nodules in a phantom study. PATIENTS AND METHODS: A chest phantom with pulmonary nodules was scanned with different CT protocols ranging from ultra-low dose settings with spectral shaping to a standard low dose lung cancer screening protocol. Image analysis was performed with different reconstruction algorithms and dedicated computer aided detection (CAD), which was compared to manual readout. RESULTS: The highest sensitivity rates (83%) were achieved for the 90 mAs and 120 mAs protocols when reconstructed with ADMIRE 3 or 5 and manual readout. The only statistically significant difference was found for subsolid nodules with preference of manual readout compared to CAD (p<0.05). Dose levels for the mAs settings ranged from 0.029 to 0.2 mSv. CONCLUSION: Reliable detectability rates for solid nodules were achieved; CAD software did not prove reliable for subsolid nodules.


Assuntos
Detecção Precoce de Câncer/métodos , Processamento de Imagem Assistida por Computador/métodos , Neoplasias Pulmonares/diagnóstico , Nódulos Pulmonares Múltiplos/diagnóstico , Imagens de Fantasmas , Interpretação de Imagem Radiográfica Assistida por Computador/métodos , Tomografia Computadorizada por Raios X/métodos , Algoritmos , Seguimentos , Humanos , Neoplasias Pulmonares/diagnóstico por imagem , Nódulos Pulmonares Múltiplos/diagnóstico por imagem , Prognóstico , Estudos Prospectivos , Doses de Radiação
15.
Zhongguo Yi Liao Qi Xie Za Zhi ; 45(5): 568-572, 2021 Sep 30.
Artigo em Chinês | MEDLINE | ID: mdl-34628775

RESUMO

Virtual monochromatic images (VMI) that reconstructed on dual-energy computed tomography (DECT) have further application prospects in radiotherapy, and there is still a lack of clinical dose verification. In this study, GE Revolution CT scanner was used to perform conventional imaging and gemstone spectral imaging on the simulated head and body phantom. The CT images were imported to radiotherapy treatment planning system (TPS), and the same treatment plans were transplanted to compare the CT value and the dose distribution. The results show that the VMI can be imported into TPS for CT value-relative electron density conversion and dose calculation. Compared to conventional images, the VMI varies from 70 to 140 keV, has little difference in dose distribution of 6 MV photon treatment plan.


Assuntos
Elétrons , Tomografia Computadorizada por Raios X , Imagens de Fantasmas , Tomógrafos Computadorizados
16.
Sensors (Basel) ; 21(19)2021 Sep 28.
Artigo em Inglês | MEDLINE | ID: mdl-34640807

RESUMO

We developed a new mobile ultrasound device for long-term and automated bladder monitoring without user interaction consisting of 32 transmit and receive electronics as well as a 32-element phased array 3 MHz transducer. The device architecture is based on data digitization and rapid transfer to a consumer electronics device (e.g., a tablet) for signal reconstruction (e.g., by means of plane wave compounding algorithms) and further image processing. All reconstruction algorithms are implemented in the GPU, allowing real-time reconstruction and imaging. The system and the beamforming algorithms were evaluated with respect to the imaging performance on standard sonographical phantoms (CIRS multipurpose ultrasound phantom) by analyzing the resolution, the SNR and the CNR. Furthermore, ML-based segmentation algorithms were developed and assessed with respect to their ability to reliably segment human bladders with different filling levels. A corresponding CNN was trained with 253 B-mode data sets and 20 B-mode images were evaluated. The quantitative and qualitative results of the bladder segmentation are presented and compared to the ground truth obtained by manual segmentation.


Assuntos
Processamento de Imagem Assistida por Computador , Bexiga Urinária , Humanos , Aprendizado de Máquina , Imagens de Fantasmas , Ultrassonografia , Bexiga Urinária/diagnóstico por imagem
17.
Curr Protoc ; 1(10): e264, 2021 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-34679245

RESUMO

As a major application focus of vascular ultrasonography, the carotid artery has long been the subject of phantom design and procedure focus. It is therefore important to devise procedures that are minimally invasive and informative, initially using a physiologically accurate anthropomorphic phantom to validate the methodology. In this article, a novel phantom design protocol is presented that enables the efficient production of a pulsatile ultrasound phantom consisting of soft and vascular tissue mimics, as well as a blood surrogate fluid. These components when combined give the phantom high acoustic compatibility and lifelike mechanical properties. The phantom was developed using "at-home" purchasable components and 3D printing technology. The phantom was subsequently used to develop a 4D reconstruction algorithm of the pulsing vessel in MATLAB. In pattern with recent developments in medical imaging, the 4D reconstruction enables clinicians to view vessel wall motion in a 3D space without the need for manual intervention. The reconstruction algorithm also produces measured inner luminal areas and vessel wall thickness, providing further information relating to structural properties and stenosis, as well as elastic properties such as arterial stiffness, which could provide helpful markers for disease diagnosis. © 2021 Wiley Periodicals LLC. Basic Protocol 1: Constructing a pulsatile ultrasound phantom model Support Protocol: Creating a vascular mimic mold Basic Protocol 2: Creating a 4D reconstruction from ultrasound frames.


Assuntos
Estenose das Carótidas , Algoritmos , Artérias Carótidas/diagnóstico por imagem , Estenose das Carótidas/diagnóstico por imagem , Humanos , Imagens de Fantasmas , Ultrassonografia
18.
Sheng Wu Yi Xue Gong Cheng Xue Za Zhi ; 38(5): 951-959, 2021 Oct 25.
Artigo em Chinês | MEDLINE | ID: mdl-34713663

RESUMO

In order to suppress the geometrical artifacts caused by random jitter in ray source scanning, and to achieve flexible ray source scanning trajectory and meet the requirements of task-driven scanning imaging, a method of free trajectory cone-beam computed tomography (CBCT) reconstruction is proposed in this paper. This method proposed a geometric calibration method of two-dimensional plane. Based on this method, the geometric calibration phantom and the imaging object could be simultaneously imaged. Then, the geometric parameters could be obtained by online calibration method, and then combined with the geometric parameters, the alternating direction multiplier method (ADMM) was used for image iterative reconstruction. Experimental results showed that this method obtained high quality reconstruction image with high contrast and clear feature edge. The root mean square errors (RMSE) of the simulation results were rather small, and the structural similarity (SSIM) values were all above 0.99. The experimental results showed that it had lower image information entropy (IE) and higher contrast noise ratio (CNR). This method provides some practical value for CBCT to realize trajectory freedom and obtain high quality reconstructed image.


Assuntos
Algoritmos , Processamento de Imagem Assistida por Computador , Calibragem , Tomografia Computadorizada de Feixe Cônico , Imagens de Fantasmas
19.
Anal Chem ; 93(42): 14138-14145, 2021 10 26.
Artigo em Inglês | MEDLINE | ID: mdl-34649431

RESUMO

Free radicals, such as metabolic intermediates, reactive oxygen species, and metal enzymes, are key substances in organisms, although they can also cause various oxidative diseases. Thus, in vivo free radical imaging should be considered as the ultimate form of metabolic imaging. Unfortunately, electron spin resonance (ESR) imaging has inherent disadvantages, such as free radicals with large linewidths generating blurred images and the presence of two or more free radicals resulting in a complicated imaging procedure. Dynamic nuclear polarization-magnetic resonance imaging (DNP-MRI) is a noninvasive imaging method to visualize in vivo free radicals, theoretically, with the same resolution as the MRI anatomical resolution, and fixed low-field DNP-MRI provides unique information on oxidative diseases and cancer. However, the large gyromagnetic ratio of the electron spin, which is 660-fold greater than that of a proton, requires field cycling, wherein the external magnetic field should be varied during DNP-MRI observations. This causes difficulties in developing a DNP-MRI system for clinical purposes. We developed a novel field-cycling DNP-MRI system for a preclinical study. In the said system, the magnetic field is switched by rotationally moving two magnets, with a magnetic flux density of 0.3 T for MRI and 5 mT for ESR. The image quality was examined using various pulse sequences and ESR irradiation using nitroxyl radical as the phantom, and the optimum conditions were established. Using the system, we performed a preclinical study involving free radical imaging by placing the free radicals under the palm of a human hand.


Assuntos
Imageamento por Ressonância Magnética , Espectroscopia de Ressonância de Spin Eletrônica , Radicais Livres , Humanos , Oxirredução , Imagens de Fantasmas
20.
Phys Med ; 90: 150-157, 2021 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-34662818

RESUMO

PURPOSE: MRI for radiotherapy planning requires spatial referencing using immobilization devices and markers. Clinical images of a difficult-to-interpret artifact are presented, resembling a metastasis, which occurs when combining CAIPIRINHA k-space-based parallel imaging (PI), 3D distortion correction, and external markers. METHODS: A 3D variable flip angle Turbo Spin Echo sequence was used on a 1.5 T and 3 T MRI using flexible and head and neck coils. Two types of markers were tested: Liquimark LM1 and Spee-D-Mark. A silicone oil phantom was used that represents low signal intensity, such as gray matter. 3D Fourier transforms were also used to show the issue's origin. RESULTS: The markers can appear in an unexpected region of a patient, not in the same original or reconstructed slice nor in a rectilinear direction in a slice, especially when using CAIPIRINHA acceleration with 3D distortion correction. The probability of occurrence was respectively 13% and 80% for distances of <=2 mm and >2 mm between marker and patient, for example when using thermoplastic masks. Clinical cases are shown where this semi-randomly occurring artifact appears post contrast only, and thus can be interpreted as metastases. The artifact did not appear when using compressed sensing acceleration. CONCLUSION: Markers used for radiotherapy MRI application can introduce additional artifacts that can be interpreted as metastases. However, other high signal intensity structures on the surface of a patient, such as the ear, can lead to an equivalent error.


Assuntos
Artefatos , Imageamento Tridimensional , Análise de Fourier , Humanos , Imageamento por Ressonância Magnética , Imagens de Fantasmas
SELEÇÃO DE REFERÊNCIAS
DETALHE DA PESQUISA
...