Diffusive Transport in the Vitreous Humor: Experimental and Analytical Studies

2019 ◽  
Vol 141 (5) ◽  
Author(s):  
Anita Penkova ◽  
Rex Moats ◽  
Mark S. Humayun ◽  
Scott Fraser ◽  
Satwindar Singh Sadhal
Keyword(s):  
Diffusion Coefficient ◽  
Drug Transport ◽  
Initial Conditions ◽  
Imaging Techniques ◽  
Vitreous Body ◽  
Vitreous Humor ◽  
Ocular Tissues ◽  
Intravitreal Drug Delivery ◽  
Magnetic Resonance Imaging Mri ◽  
Diffusive Movement

In relation to intravitreal drug delivery, predictive mathematical models for drug transport are being developed, and to effectively implement these for retinal delivery, the information on biophysical properties of various ocular tissues is fundamentally important. It is therefore necessary to accurately measure the diffusion coefficient of drugs and drug surrogates in the vitreous humor. In this review, we present the studies conducted by various researchers on such measurements over the last several decades. These include imaging techniques (fluorescence and magnetic resonance imaging (MRI)) that make use of introducing a contrast agent or a labeled drug into the vitreous and tracking its diffusive movement at various time points. A predictive model for the same initial conditions when matched with the experimental measurements provides the diffusion coefficient, leading to results for various molecules ranging in size from approximately 0.1 to 160 kDa. For real drugs, the effectiveness of this system depends on the successful labeling of the drugs with suitable contrast agents such as fluorescein and gadolinium or manganese so that fluorescence or MR imagining could be conducted. Besides this technique, some work has been carried out using the diffusion apparatus for measuring permeation of a drug across an excised vitreous body from a donor chamber to the receptor by sampling assays from the chambers at various time intervals. This has the advantage of not requiring labeling but is otherwise more disruptive to the vitreous. Some success with nanoparticles has been achieved using dynamic light scattering (DLS), and presently, radioactive labeling is being explored.

A Novel Secure and Robust encryption scheme for medical images

2020 ◽  
Vol 16 ◽  
Author(s):  
Siyamol Chirakkarottu ◽  
Sheena Mathew
Keyword(s):  
Medical Images ◽  
Technological Development ◽  
Imaging Techniques ◽  
Chaotic Map ◽  
Two Phase ◽  
Positron Emission ◽  
Medical Diagnostic ◽  
Wireless Medium ◽  
Health Care Applications ◽  
Magnetic Resonance Imaging Mri

Background: Medical imaging encloses different imaging techniques and processes to image the human body for medical diagnostic and treatment purposes. Hence it plays an important role to improve public health. The technological development in biomedical imaging specifically in X-ray, Computed Tomography (CT), nuclear ultrasound including Positron Emission Tomography (PET), optical and Magnetic Resonance Imaging (MRI) can provide valuable information unique to a person. Objective: In health care applications, the images are needed to be exchanged mostly over wireless medium. The diagnostic images with confidential information of a patient need to be protected from unauthorized access during transmission. In this paper, a novel encryption method is proposed to improve the security and integrity of medical images. Methods: Chaotic map along with DNA cryptography is used for encryption. The proposed method describes a two phase encryption of medical images. Results: Performance of the proposed method is also tested by various analysis metrics. Robustness of the method against different noises and attacks is analyzed. Conclusion: The results show that the method is efficient and well suitable to medical images.

State-of-the-art MR Imaging of Fat-containing Focal Lesions of the Liver

2019 ◽  
Vol 15 (5) ◽  
pp. 435-442
Author(s):  
Joanna Podgorska ◽  
Agnieszka Anysz-Grodzicka ◽  
Andrzej Cieszanowski
Keyword(s):  
Differential Diagnosis ◽  
Imaging Techniques ◽  
Hepatobiliary Phase ◽  
Focal Lesions ◽  
Dysplastic Nodules ◽  
Nodular Hyperplasia ◽  
Specific Finding ◽  
Magnetic Resonance Imaging Mri ◽  
Adrenal Rest ◽  
Mri Characteristics

Background: Fat can be identified in numerous liver lesions, and usually is not a specific finding. Distinguishing between different kinds of fatty deposits is an important part of differential diagnosis. Magnetic Resonance Imaging (MRI) is superior to other imaging techniques because it allows distinguishing intracellular from macroscopic fat. Discussion: Intracellular lipid may be found in focal hepatic steatosis, hepatic adenoma, hepatocellular carcinoma and, less commonly, in focal nodular hyperplasia as well as regenerative and dysplastic nodules. Macroscopic fat is seen in angiomyolipoma, lipoma, metastases from fatcontaining neoplasms, primary or metastatic liposarcoma, hydatid cyst, pseudolipoma of the Glisson capsule, pericaval fat collection, lipopeliosis, hepatic teratoma, focal hepatic extramedullary haematopoiesis and adrenal rest tumour. Conclusion: Liver nodules should be characterised with regard to underlying liver condition, MRI characteristics and contrast enhancement pattern, including hepatobiliary phase. In many cases, identification of fatty content may help narrowing the differential diagnosis.

scholarly journals Design and Synthesis of Luminescent Lanthanide-Based Bimodal Nanoprobes for Dual Magnetic Resonance (MR) and Optical Imaging

Nanomaterials ◽  
2021 ◽  
Vol 11 (2) ◽  
pp. 354
Author(s):  
Walid Mnasri ◽  
Mahsa Parvizian ◽  
Souad Ammar-Merah
Keyword(s):  
Magnetic Resonance ◽  
Optical Imaging ◽  
Imaging Technique ◽  
Imaging Techniques ◽  
Design And Synthesis ◽  
Bimodal Imaging ◽  
Successive Image ◽  
Complete Set ◽  
Magnetic Resonance Imaging Mri ◽  
Physical And Chemical

Current biomedical imaging techniques are crucial for the diagnosis of various diseases. Each imaging technique uses specific probes that, although each one has its own merits, do not encompass all the functionalities required for comprehensive imaging (sensitivity, non-invasiveness, etc.). Bimodal imaging methods are therefore rapidly becoming an important topic in advanced healthcare. This bimodality can be achieved by successive image acquisitions involving different and independent probes, one for each mode, with the risk of artifacts. It can be also achieved simultaneously by using a single probe combining a complete set of physical and chemical characteristics, in order to record complementary views of the same biological object at the same time. In this scenario, and focusing on bimodal magnetic resonance imaging (MRI) and optical imaging (OI), probes can be engineered by the attachment, more or less covalently, of a contrast agent (CA) to an organic or inorganic dye, or by designing single objects containing both the optical emitter and MRI-active dipole. If in the first type of system, there is frequent concern that at some point the dye may dissociate from the magnetic dipole, it may not in the second type. This review aims to present a summary of current activity relating to this kind of dual probes, with a special emphasis on lanthanide-based luminescent nano-objects.

scholarly journals Malformations of cortical development: current concepts and advanced neuroimaging review

2011 ◽  
Vol 69 (1) ◽  
pp. 130-138 ◽  
Author(s):  
Celi Santos Andrade ◽  
Claudia da Costa Leite
Keyword(s):  
Imaging Techniques ◽  
Cortical Development ◽  
Motor Dysfunction ◽  
Malformations Of Cortical Development ◽  
Neurodevelopmental Delay ◽  
Complex Process ◽  
Magnetic Resonance Imaging Mri ◽  
Specific Disorders ◽  
Patients With Epilepsy ◽  
Work Up

Malformations of cortical development (MCD) result from disruptions in the complex process of the human brain cortex formation and are highly associated to severe epilepsy, neurodevelopmental delay and motor dysfunction. Nowadays, magnetic resonance imaging (MRI) is the cornerstone of the work-up of patients with epilepsy and modern advanced imaging techniques have improved not only our ability to detect and characterize cortical malformations, but also in identifying associated functional abnormalities that are far beyond the structural visualized lesions. Herein, we address the most currently used classifications of MCD and make a concise review of the embryological process of cortical development. Our main goal is to summarize recent advances and new trends in diagnostic imaging techniques concerning MCD. Thereafter, follows a brief discussion of specific disorders and their radiological features.

scholarly journals Study of Osteocyte Behavior by High-Resolution Intravital Imaging Following Photo-Induced Ischemia

Molecules ◽  
2018 ◽  
Vol 23 (11) ◽  
pp. 2874
Author(s):  
Hengfeng Yuan ◽  
Wen Jiang ◽  
Yuanxin Chen ◽  
Betty Kim
Keyword(s):  
Imaging Techniques ◽  
Avascular Osteonecrosis ◽  
Functional Changes ◽  
Cellular Processes ◽  
Non Invasive ◽  
Behavioral Dynamics ◽  
Bony Anatomy ◽  
Magnetic Resonance Imaging Mri

Ischemic injuries and local hypoxia can result in osteocytes dysfunction and play a key role in the pathogenesis of avascular osteonecrosis. Conventional imaging techniques including magnetic resonance imaging (MRI) and computed tomography (CT) can reveal structural and functional changes within bony anatomy; however, characterization of osteocyte behavioral dynamics in the setting of osteonecrosis at the single cell resolution is limited. Here, we demonstrate an optical approach to study real-time osteocyte functions in vivo. Using nicotinamide adenine dinucleotide (NADH) as a biomarker for metabolic dynamics in osteocytes, we showed that NADH level within osteocytes transiently increase significantly after local ischemia through non-invasive photo-induced thrombosis of afferent arterioles followed by a steady decline. Our study presents a non-invasive optical approach to study osteocyte behavior through the modulation of local environmental conditions. Thus it provides a powerful toolkit to study cellular processes involved in bone pathologies in vivo.

scholarly journals Perfusion Magnetic Resonance Imaging to Assess Brain Tumor Responses to New Therapies

1998 ◽  
Vol 5 (2) ◽  
pp. 115-123 ◽  
Author(s):  
Michael H. Lev ◽  
Fred Hochberg
Keyword(s):  
Magnetic Resonance Imaging ◽  
Brain Tumor ◽  
Magnetic Resonance ◽  
Imaging Techniques ◽  
Perfusion Mri ◽  
Perfusion Magnetic Resonance Imaging ◽  
Normal Brain ◽  
Resonance Imaging ◽  
New Therapies ◽  
Magnetic Resonance Imaging Mri

Background: Although magnetic resonance imaging (MRI) is effective in detecting the location of intracranial tumors, new imaging techniques have been studied that may enhance the specificity for the prediction of histologic grade of tumor and for the distinction between recurrence and tumor necrosis associated with cancer therapy. Methods: The authors review their experience and that of others on the use of perfusion magnetic resonance imaging to evaluate responses of brain tumors to new therapies. Results: Functional imaging techniques that can distinguish tumor from normal brain tissue using physiological parameters. These new approaches provide maps of tumor perfusion to monitor the effects of novel compounds that restrict tumor angiogenesis. Conclusions: Perfusion MRI not only may be as effective as radionuclide-based techniques in sensitivity and specificity in assessing brain tumor responses to new therapies, but also may offer higher resolution and convenient co-registration with conventional MRI, as well as time- and cost-effectiveness. Further study is needed to determine the role of perfusion MRI in assessing brain tumor responses to new therapies.

scholarly journals In Vivo Experimental and Analytical Studies for Bevacizumab Diffusion Coefficient Measurement in the Rabbit Vitreous Humor

2020 ◽  
Author(s):  
Shuqi Zhang ◽  
Anita Penkova ◽  
Mark Humayun ◽  
Juan Carlos Martinez-Camarillo ◽  
Abegail C. Tadle ◽  
...  
Keyword(s):  
Diffusion Coefficient ◽  
Effective Diffusion ◽  
Drug Distribution ◽  
Vitreous Humor ◽  
Contour Method ◽  
Experimental Result ◽  
Coefficient Measurement ◽  
A New Technique ◽  
Best Fit

Abstract In order to measure the effective diffusion coefficient of Bevacizumab (Avastin, Genentech) in the vitreous humor, a new technique is developed based on the 'contour method' and in vivo OCT measurements. After injection of Bevacizumab-fluorescein conjugated compound solution into the rabbit eye, the contours of drug concentration distribution at the subsurface of injection were tracked over time. The 2D contours were extrapolated to 3D contours using reasonable assumptions and a numerically integrated analytical model was developed for the theoretical contours for the irregularly shaped drug distribution in the experimental result. By floating the diffusion coefficient, different theoretical contours were constructed and the least-squares best fit to the experimental contours was performed at each time point to get the best fit solution. The approach generated consistent diffusion coefficient values based on the experiments on four rabbit eyes over a period of 3 hours each, which gave , D=1.2±0.6×(?10?^(-6) ?cm?^2)/s and the corresponding theoretical contours matched well with the experimental contours. The quantitative measurement of concentration using OCT and fluorescein labeling gives a new approach for the "non-contact" in vivo drug distribution measurement within vitreous and other ocular tissues.

scholarly journals Reasons for discordances between ultrasonography and magnetic resonance imaging in the evaluation of the ankle, hindfoot and heel of the patients with rheumatoid arthritis

2019 ◽  
Vol 21 (4) ◽  
pp. 405 ◽  
Author(s):  
Oana Șerban ◽  
Daniela Fodor ◽  
Iulia Papp ◽  
Mihaela Cosmina Micu ◽  
Dan Gabriel Duma ◽  
...  
Keyword(s):  
Rheumatoid Arthritis ◽  
Magnetic Resonance Imaging ◽  
Magnetic Resonance ◽  
Disease Activity ◽  
Activity Index ◽  
Imaging Techniques ◽  
Disease Activity Index ◽  
Resonance Imaging ◽  
Magnetic Resonance Imaging Mri ◽  
Definition Of

Aim: To compare the ultrasonography (US) performance with magnetic resonance imaging (MRI) in identifying pathology in ankles, hindfeet and heels of rheumatoid arthritis (RA) patients and to evaluate the reasons for discordances between the two imaging methods.Material and methods: RA patients were enrolled and evaluated using the Clinical Disease Activity Index (CDAI) and the Disease Activity Score 28 with C-reactive Protein (DAS28-CRP). The ankle (tibiotalar joint, tendons), hindfoot (talonavicular, subtalar joints) and heel of the most symptomatic or dominant foot (for the asymptomatic patient)were evaluated by two pairs of examiners using US and contrast-enhanced MRI.Results: Totally, 105 joints, 245 tendons and 35 heels in 35 patients [mean age 59.2±11.25 years old, median disease duration 36 (16.5-114), mean CDAI 19.87±12.7] were evaluated. The interobserver agreements between the two sonographers, and the two radiologists were good and very good (k=0.624-0.940). The overall agreement between US and MRI was very good for subcalcaneal panniculitis (k=0.928, p<0.001), moderate for synovitis (k=0.463, p<0.001) and tenosynovitis (k=0.514, p<0.001), fair for osteophytes (k=0.260, p=0.004), and poor for erosions (k=0.063, p=0.308) and heel’s structures. MRI found more erosions, synovitis, osteophytes,tenosynovitis and retrocalcaneal bursitis, but US found more enthesophytes and plantar fasciitis. Many of the discordancesbetween the two imaging techniques have explanations related to the technique itself or definition of the pathologic findings.Conclusions: US is comparable to MRI for the evaluation of ankle, hindfoot and heel in RA patients and discordances in theinterpretation of the pathological findings/normal structures must be carefully analyzed.

scholarly journals In vivo imaging techniques: a new era for histochemical analysis

2016 ◽  
Author(s):  
A. Busato ◽  
P. Fumene Feruglio ◽  
P.P. Parnigotto ◽  
P. Marzola ◽  
A. Sbarbati
Keyword(s):  
Magnetic Resonance ◽  
In Vivo Imaging ◽  
Diffusion Tensor ◽  
Technological Development ◽  
Imaging Techniques ◽  
Resonance Spectroscopy ◽  
Preclinical Research ◽  
Tissue Contrast ◽  
Magnetic Resonance Imaging Mri

In vivo imaging techniques can be integrated with classical histochemistry to create an actual histochemistry of water. In particular, Magnetic Resonance Imaging (MRI), an imaging technique primarily used as diagnostic tool in clinical/preclinical research, has excellent anatomical resolution, unlimited penetration depth and intrinsic soft tissue contrast. Thanks to the technological development, MRI is not only capable to provide morphological information but also and more interestingly functional, biophysical and molecular. In this paper we describe the main features of several advanced imaging techniques, such as MRI microscopy, Magnetic Resonance Spectroscopy, functional MRI, Diffusion Tensor Imaging and MRI with contrast agent as a useful support to classical histochemistry.

scholarly journals Effect of Thermophysical Properties on Coupled Heat and Mass Transfer in Porous Material during Forced Convective Drying

2014 ◽  
Vol 6 ◽  
pp. 830387 ◽  
Author(s):  
Wei Cai ◽  
Lexian Zhu ◽  
Shilin Dong ◽  
Guozhen Xie ◽  
Junming Li
Keyword(s):  
Porous Medium ◽  
Diffusion Coefficient ◽  
Temperature Distribution ◽  
Moisture Content ◽  
Initial Conditions ◽  
Positive Impact ◽  
Soret Effect ◽  
Convective Drying ◽  
Large Temperature ◽  
Kinetics Of

The convective drying kinetics of porous medium was investigated numerically. A mathematical model for forced convective drying was established to estimate the evolution of moisture content and temperature inside multilayered porous medium. The set of coupled partial differential equations with the specified boundary and initial conditions were solved numerically using a MATLAB code. An experimental setup of convective drying had been constructed and validated the theoretical model. The temperature and moisture content of the potato samples were dynamically measured and recorded during the drying process. Results indicate that thermal diffusion coefficient has significant positive impact on temperature distribution and mass diffusion coefficient might directly affect the moisture content distribution. Soret effect has a significant impact on heat flux and temperature distribution in the presence of large temperature gradient.

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