Browsing by Subject "Contrast enhancement"

Now showing 1 - 8 of 8

Open Access
Advances in nanoparticle‐based medical diagnostic and therapeutic techniques
(John Wiley & Sons, 2016-03-11) Sardan, Melis; Özkan, Alper Devrim; Zengin, Aygül; Tekinay, Ayşe B.; Güler, Mustafa O.; Güler, Mustafa O.; Tekinay, Ayşe B.
Advances in modern medicine have eliminated several major causes of human mortality and considerably extended life expectancies around the world; however, this increase in the global age average has also boosted the incidences of age‐associated disorders. These conditions, such as cancer, neurodegenerative disorders, and cardiovascular disease, severely decrease the quality of life for the affected but are highly polymorphic and often difficult to treat. This chapter describes the characteristics of nanoparticle (NP) contrast agents (CAs) proposed for use in medical imaging, and details the surface modification methods used to designate specific targets for their attachment. It then compares their effectiveness and toxicity compared to conventional methods of contrast enhancement, and discusses the contribution that nanoscience has had, and will have, on medical imaging and disease diagnosis at large.
Open Access
Contrast enhancement using phase transition information and total variation
(Institute of Electrical and Electronics Engineers, 2018) Çakır, Serdar; Çetin, A.Enis
Contrast enhancement is an important preprocessing step for the analysis of images. The main aim of contrast enhancement techniques is to increase the visibility of the objects by modifying the spatial characteristics of the image. In this paper, phase transition based contrast enhancement framework is proposed to overcome the limitations of existing image enhancement techniques. The proposed image enhancement framework transforms the changes in image phase into the variations of magnitude to enhance the structural details of the image and to improve visibility. In addition, the concept of Selective Variation (SV) technique is introduced and enhancement parameters are optimized using SV. The experimental studies that were carried out on TID2008 dataset, show that the proposed scheme obtains promising results on contrast enhancement.
Open Access
Current constrained voltage scaled reconstruction (CCVSR) algorithm for MR-EIT and its performance with different probing current patterns
(Institute of Physics Publishing, 2003) Birgül, Ö.; Eyüboğlu, B. M.; İder, Y. Z.
Conventional injected-current electrical impedance tomography (EIT) and magnetic resonance imaging (MRI) techniques can be combined to reconstruct high resolution true conductivity images. The magnetic flux density distribution generated by the internal current density distribution is extracted from MR phase images. This information is used to form a fine detailed conductivity image using an Ohm's law based update equation. The reconstructed conductivity image is assumed to differ from the true image by a scale factor. EIT surface potential measurements are then used to scale the reconstructed image in order to find the true conductivity values. This process is iterated until a stopping criterion is met. Several simulations are carried out for opposite and cosine current injection patterns to select the best current injection pattern for a 2D thorax model. The contrast resolution and accuracy of the proposed algorithm are also studied. In all simulation studies, realistic noise models for voltage and magnetic flux density measurements are used. It is shown that, in contrast to the conventional EIT techniques, the proposed method has the capability of reconstructing conductivity images with uniform and high spatial resolution. The spatial resolution is limited by the larger element size of the finite element mesh and twice the magnetic resonance image pixel size.
Open Access
In vivo magnetic resonance imaging of mesenchymal stem cells in myocardial infarction
(Lippincott Williams & Wilkins, 2003) Kraitchman, D. L.; Heldman, A. W.; Atalar, Ergin; Amado, L. C.; Martin, B. J.; Pittenger, M. F.; Hare, J. M.; Bulte, J. W. M.
Background - We investigated the potential of magnetic resonance imaging (MRI) to track magnetically labeled mesenchymal stem cells (MR-MSCs) in a swine myocardial infarction (MI) model. Methods and Results - Adult farm pigs (n=5) were subjected to closed-chest experimental MI. MR-MSCs (2.8 to 16×107 cells) were injected intramyocardially under x-ray fluoroscopy. MRIs were obtained on a 1.5T MR scanner to demonstrate the location of the MR-MSCs and were correlated with histology. Contrast-enhanced MRI demonstrated successful injection in the infarct and serial MSC tracking was demonstrated in two animals. Conclusion - MRI tracking of MSCs is feasible and represents a preferred method for studying the engraftment of MSCs in MI.
Open Access
Intravascular MR-monitored balloon angioplasty: An in vivo feasibility study
(Elsevier Inc., 1998) Yang, Xiaoming; Bolster Jr., B. D.; Kraitchman, D. L.; Atalar, Ergin
PURPOSE: To develop a new method for monitoring balloon angioplasty by using an intravascular magnetic resonance (MR) imaging technique. MATERIALS AND METHODS: Nine New Zealand White rabbits were used: seven for technique refinement, including surgery, device insertion, stenosis creation, and MR protocol development; and two for the final MR imaging of the balloon angioplasty. The in vivo experimental method involved insertion of a catheter antenna and a balloon catheter, via femoral arteriotomies bilaterally, into the target site of the upper abdominal aorta, where a stenosis was artificially created by binding a plastic cable tie. Then, the entire process of the dilation of the stenosis with balloon inflation was monitored under MR fluoroscopy. RESULTS: Catheter insertions were successful, and a 5-mm-long stenosis of the aorta was produced in all nine rabbits. Eight complete balloon angioplasty procedures were satisfactorily monitored and recorded, showing clearly the stenosis of the aorta at the beginning of the procedure, the dilation of the stenosis during the balloon inflation, and the complete opening of the stenosis after balloon dilation. CONCLUSION: Preliminary results of in vivo balloon angioplasty monitored with intravascular MR imaging are presented. MR fluoroscopy, based on the intravascular MR imaging technique, may represent a potential alternative to x-ray fluoroscopy for guiding interventional treatment of cardiovascular diseases.
Open Access
A new class of cubic SPIONs as a dual-mode T1 and T2 contrast agent for MRI
(Elsevier, 2018) Alipour, Akbar; Soran-Erdem, Zeliha; Utkur, Mustafa; Sharma, Vijay Kumar; Algın, Oktay; Sarıtaş, Emine Ülkü; Demir, Hilmi Volkan
Superparamagnetic iron oxide nanoparticles (SPIONs) are widely used as a robust negative contrast agent on conventional MRI. In this study, we (a) synthesized a new class of cubic SPIONs as a dual-mode contrast agent in MRI and (b) showed the in-vivo feasibility of these nanaoparticles as a simultaneous positive and negative contrast agent. Relaxation properties and contrast enhancement analysis of the synthesized SPIONs with two different shapes (cubic vs. spherical) and three different sizes 7 nm, 11 nm, and 14 nm were investigated to evaluate contrast enhancement in-vitro. In-vivo MRI experiments were performed on a 3T MR scanner, where a healthy anesthetized rat was imaged before, and from 20 to 80 min after intravenous injection of 1 mg/kg of contrast agent. Representative transmission electron microscopy (TEM) images of the synthesized nanoparticles reveal that the particles are well dispersed in a solvent and do not aggregate. The in-vitro relaxivity and contrast enhancement analysis show that, among all six SPIONs tested, 11-nm cubic SPIONs possess optimal molar relaxivities and contrast enhancement values, which can shorten the spin-lattice and spin-spin relaxation times, simultaneously. No noticeable toxicity is observed during in-vitro cytotoxicity analysis. In-vivo T1-and T2-weighted acquisitions at 60-min post-injection of 11-nm cubic SPIONs result in 64% and 48% contrast enhancement on the T1-and T2-weighted images, respectively. By controlling the shape and size of SPIONs, we have introduced a new class of cubic SPIONs as a synergistic (dual-mode) MRI contrast agent. 11-nm cubic SPIONs with smaller size and high positive and negative contrast enhancements were selected as a promising candidate for dual-mode contrast agent. Our proof-of-concept MRI experiments on rat demonstrate the in-vivo dual-mode contrast enhancement feasibility of these nanoparticles.
Open Access
Spatial mutual information and PageRank-Based contrast enhancement and Quality-Aware relative contrast measure
(Institute of Electrical and Electronics Engineers Inc., 2016) Celik, T.
This paper proposes a novel algorithm for global contrast enhancement using a new definition of spatial mutual information (SMI) of gray levels of an input image and PageRank algorithm. The gray levels are used to represent nodes in PageRank algorithm, and the weights between the nodes are computed according to their dependence and spatial spread over the image, which is quantified by using SMI. The rank vector of gray levels resulted from PageRank algorithm is used in mapping input gray levels to output. The damping factor of the PageRank algorithm is utilized to control the level of perceived global contrast on the output image. Furthermore, a new metric is proposed for image quality-Aware relative contrast measurement between input and output images. Experimental results show that the proposed algorithm consistently produces good results. © 1992-2012 IEEE.
Open Access
System for MR image-guided prostate interventions: Canine study
(Radiological Society of North America, Inc., 2003) Susil, R. C.; Krieger, A.; Derbyshire, J. A.; Tanacs, A.; Whitcomb, L. L.; Fichtinger, G.; Atalar, Ergin
The purpose of this study was to demonstrate the use of a transrectal system that enables precise magnetic resonance (MR) image guidance and monitoring of prostate interventions. The system used a closed-bore 1.5-T MR imaging unit and enables one to take advantage of the higher signal-to-noise ratio achieved with traditional magnet designs, which is crucial for accurate targeting and monitoring of prostate interventions. In the first of the four canine studies, reliable needle placement, with all needles placed within 2 mm of the desired target site, was achieved. In two other studies, MR imaging was used to monitor distribution of injected contrast agent solution (gadopentetate dimeglumine mixed with trypan blue dye) in and around the prostate, thereby confirming that solution had been delivered to the desired tissue and also detecting faulty injections. In the final study, accurate placement and MR imaging of brachytherapy seeds in the prostate were demonstrated. The described system provides a flexible platform for a variety of minimally invasive MR image-guided therapeutic and diagnostic prostate interventions. © RSNA, 2003.