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1

Polynomial modeling of retinal vessels for tortuosity measurement

Chetia Sanyukta, Nirmala S. R.

Biocybernetics and Biomedical Engineering

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2019

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Vol. 39, no. 2

512--525

EN

Tortuosity is one of the micro vascular change that is observed in many retinopathies. Its early detection can prevent the progression of various retinopathies to a critical stage at which a person may become blind. Here, we propose a novel method for the measurement of tortuosity by polynomial modeling of retinal vessels for the analysis of hypertensive retinopathy. The proposed method is tested on a set of 30 arteries and 30 veins vessel images collected from the Retinal Vessel Tortuosity Dataset (RET-TORT). Also, 90 vessel segments from Digital Retinal Images for Vessel Extraction (DRIVE) and 149 vessel segments from High Resolution Fundus (HRF) databases are used for tortuosity evaluation. The experimental results demonstrate that the order of the polynomial increases with the increase in the tortuosity of the blood vessels. Hence, the order of the polynomial can be used as a parameter to classify vessels as non-tortuous and tortuous. The results of the method are also evaluated subjectively and the inter-rater agreement analysis is made by using Fleiss Kappa index. The Spearman's rank order correlation coefficient is used to analyze the correlation between the ranking provided by the expert in the RET-TORT database and the ranking obtained by the proposed method. The results demonstrate that this method is capable of evaluating the tortuosity and classify vessel segments into non-tortuous or tortuous effectively.

2

A generalized method for the detection of vascular structure in pathological retinal images

Kaur J., Mittal D.

Biocybernetics and Biomedical Engineering

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2017

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Vol. 37, no. 1

184--200

EN

Variations in blood vasculature morphology of retinal fundus images is one of the dominant characteristic for the early detection and analysis of retinal abnormalities. Therefore the accurate interpretation of blood vasculature is useful for ophthalmologists to diagnose patients that suffer from retinal abnormalities. A generalized method to detect and segment blood vasculature using retinal fundus images has been proposed in this work using (i) preprocessing for quality improvement of retinal fundus images, (ii) initial segmentation of vasculature map to find vascular and non vascular structures, (iii) extraction of relevant set of geometrical based features from the vasculature map and intensity based features from original retinal fundus image that differentiate vascular and non vascular structures efficiently, (iv) supervised classification of vascular and non vascular structures using the extracted features, and (v) joining of candidate vascular structures to create connectivity. The proposed method is evaluated on clinically acquired dataset and different publically available standard datasets such as DRIVE, STARE, ARIA and HRF. The clinically acquired dataset consists of 468 retinal fundus images comprising of healthy images, images with mild, intermediate and severe pathologies. Test results of the proposed method shows average sensitivity/specificity/accuracy of 85.43/97.94/95.45 on the 785 retinal fundus images. The proposed method shows an improvement of 14.01% in sensitivity without degrading specificity and accuracy in comparison to the recently published methods.

3

Development of a drug delivery system using microcapsules with ultrasound

Masuda K.

Biocybernetics and Biomedical Engineering

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2011

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Vol. 31, no. 2

23-32

EN

Micrometer-sized microcapsules collapse upon exposure to ultrasound. Use of this pheno-menon for a drug delivery system (DOS), not only for local delivery of medication but also for gene therapy, should be possible. However, enhancing of efficiency of medication is limited because the capsules in suspension diffuse in the human body after injection, since the motion of the capsules in blood flow cannot be controlled. To control behavior of the microcapsules, an acoustic radiation force was introduced. We detected local changes in the microcapsule density by producing of acoustic radiation force in an artificial blood vessel. Furthermore, we theoretically estimated the conditions required for an active path selection of the capsules at a bifurcation point in the artificial blood vessel. We observed the difference in the capsule density at both in the bifurcation point and in alternative paths downstream of the bifurcation point for the different acoustic radiation forces. We also confirmed that the microcapsules are trapped against flow with the condition when the acoustic radiation force is more than the fluid resistance of the capsules. The possibility of controlling of the capsule flow towards a specific point in a blood vessel was demonstrated.

4

Numerical modeling of heat transfer in a single blood vessel and surrounding biological tissue

Majchrzak E., Tarasek D.

Prace Naukowe Instytutu Matematyki i Informatyki Politechniki Częstochowskiej

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2010

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Vol. 9, nr 2

145-152

EN

The thermal interactions between the single blood vessel and surrounding biological tissue are analyzed. The temperature in the tissue is described by the Pennes equation, while the equation determining the change of blood temperature along the blood vessel is formulated on the basis of adequate energy balance. These equations are coupled by boundary condition given at the blood vessel wall. There are two models considered here in terms of blood vessel types. First is the supplying vessel model and the other one is traversing vessel model. Both are distinguished in the computations. The solution of the problem has been provided by means of finite difference method.

5

Ocena metody zbiorów poziomicowych stosowanych do segmentacji trójwymiarowych obrazów fantomów cyfrowych oraz obrazów naczyń krwionośnych mózgu TOF-SWI rezonansu magnetycznego

Strzelecki M., Materka A., Kociński M., Szczypiński P., Deistung A., Reichenbach J.

Acta Bio-Optica et Informatica Medica. Inżynieria Biomedyczna

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2010

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Vol. 16, nr 2

167-172

PL

W pracy zbadano dokładność metody segmentacji level set stosowanej do analizy trójwymiarowych obrazów fantomów przedstawiających fragmenty naczyń oraz układ drzew krwionośnych. Badano przydatność metody do detekcji cienkich naczyń (o średnicy mniejszej niż rozmiar woksela obrazu) oraz jej odporność na zakłócenia. Oceny metody dokonano za pomocą obiektywnej miary ilościowej opisującej dokładność segmentacji. Metodę level set wykorzystano również do segmentacji rzeczywistych trójwymiarowych obrazów TOF-SWI (Time Of Flight and Susceptibility Weighted Imaging) rezonansu magnetycznego naczyń krwionośnych mózgu wraz z metodą Sato, wykorzystującą filtrację wieloskalową. Wstępne wyniki, w postaci trójwymiarowych modeli naczyń krwionośnych, są obiecujące. W pracy przedstawiono kierunki dalszych badań prowadzących do uzyskania dokładniejszych modeli układu krwionośnego, zwłaszcza dla naczyń o małych średnicach.

EN

The objective of this work is to evaluate performance of the level set approach applied to segmentation of 3D images of computer-simulated blood-vessel phantoms and artificial vascular trees. The segmentation of thin vessels with diameter smaller than voxel size and influence of noise on segmentation results, were studied. Quantitative measures of segmentation accuracy were used for the methods evaluation. The level set technique was also used for segmentation of 3D TOF-SWI MR (Time Of Flight and Susceptibility Weighted Magnetic Resonance Imaging) brain vessels images. Also, the multiscale filtering approach was applied. Preliminary results in the form of 3D vein and artery models are promising. Further work aimed at more accurate modeling of brain vasculature, focused on thin vessels detection is also addressed.

6

An automatic hybrid method for retinal blood vessel extraction

Yang Y., Huang S., Rao N.

International Journal of Applied Mathematics and Computer Science

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2008

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Vol. 18, no 3

399-407

EN

The extraction of blood vessels from retinal images is an important and challenging task in medical analysis and diagnosis. This paper presents a novel hybrid automatic approach for the extraction of retinal image vessels. The method consists in the application of mathematical morphology and a fuzzy clustering algorithm followed by a purification procedure. In mathematical morphology, the retinal image is smoothed and strengthened so that the blood vessels are enhanced and the background information is suppressed. The fuzzy clustering algorithm is then employed to the previous enhanced image for segmentation. After the fuzzy segmentation, a purification procedure is used to reduce the weak edges and noise, and the final results of the blood vessels are consequently achieved. The performance of the proposed method is compared with some existing segmentation methods and hand-labeled segmentations. The approach has been tested on a series of retinal images, and experimental results show that our technique is promising and effective.

7

Numerical simulation of pulsating blood flow through stenosed vessel

Kohge K., Minemura K.

International Journal of Applied Mechanics and Engineering

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2003

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Vol. 8, no spec.

155-161

EN

In connection with blood flow in stenosed blood vessels, Ojha and his co-workers have been measured pulsating flows in rigged pipes with a contraction using kerosene. The experiment, however, leaves something to be desired, for example, the pressure fluctuation relevant to the pulsating flow velocity is entirely unknown. To make clear the mechanism of the pulsating flow in the stenosed pipes, the flow is numerically simulated, in this paper, using a finite difference method with CIP scheme. Obtained axial velocity distributions and thickness of separation region are confirmed with Ojha's experimental results. Resultant flow brings about large periodical change of wall stress in the downstream and of pressure at the contraction, respectively, suggesting that the flow behaviour relates closely with arterial diseases.

8

Numerical model of heat transfer between blood vessel and biological tissue

Majchrzak E., Mochnacki B.

Computer Assisted Mechanics and Engineering Sciences

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1999

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Vol. 6, No. 3-4

439-447

EN

The thermal processes proceeding within a perfused tissue in the presence of a vessel are considered. The Pennes bio-heat transfer equation determines the steady state temperature field in tissue sub-domain, while the ordinary differential equation resulting from the energy balance describes the change of blood temperature along the vessel. The coupling of above equations results from the boundary condition given on the blood vessel wall. The problem is solved using the combined numerical algorithm, in particular the boundary element method (for the tissue sub-domain) and the finite differences method (for blood vessel sub-domain).