Browsing by Author "Muthupillai, Raja"

Now showing 1 - 4 of 4
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    A New High-Performance Gadonanotube-Polymer Hybrid Material for Stem Cell Labeling and Tracking by MRI
    (Hindawi, 2018) Moghaddam, Sakineh E.; Hernández-Rivera, Mayra; Zaibaq, Nicholas G.; Ajala, Afis; Cabreira-Hansen, Maria da Graça; Mowlazadeh-Haghighi, Saghar; Willerson, James T.; Perin, Emerson C.; Muthupillai, Raja; Wilson, Lon J.
    A gentle, rapid method has been developed to introduce a polyacrylic acid (PAA) polymer coating on the surface of gadonanotubes (GNTs) which significantly increases their dispersibility in water without the need of a surfactant. As a result, the polymer, with its many carboxylic acid groups, coats the surface of the GNTs to form a new GNT-polymer hybrid material (PAA-GNT) which can be highly dispersed in water (ca. 20 mg·mL−1) at physiological pH. When dispersed in water, the new PAA-GNT material is a powerful MRI contrast agent with an extremely short water proton spin-lattice relaxation time (T1) which results in a T1-weighted relaxivity of 150 mM−1·s−1 per Gd3+ ion at 1.5 T. Furthermore, the PAA-GNTs have been used to safely label porcine bone-marrow-derived mesenchymal stem cells for magnetic resonance imaging. The labeled cells display excellent image contrast in phantom imaging experiments, and transmission electron microscopy images of the labeled cells reveal the presence of highly dispersed PAA-GNTs within the cytoplasm with 1014 Gd3+ ions per cell.
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    Cardiac MRI: Improved Assessment of Left Ventricular Function, Wall Motion, and Viability
    (2013-09-16) Krishnamurthy, Ramkumar; Drezek, Rebekah A.; Muthupillai, Raja; Jacot, Jeffrey G.; Clark, John W., Jr.
    Heart failure is the clinical syndrome accompanying the inability of the heart to maintain a cardiac output required to meet the metabolic requirements and accommodate venous return, and is one of the leading causes of mortality in United States. Accurate imaging of the heart and its failure is important for successful patient management and treatment. Multiple cardiac imaging modalities provide complementary information about the heart – LV function and wall motion, anatomy, myocardial viability and ischemia. In many instances, it is necessary for a patient to undergo multiple imaging sessions to obtain diagnostic clinical information with confidence. It would be beneficial to the individual and the health care system if a single imaging modality could yield reliable clinical information about the heart, leading to a reduced cost, anxiety and an increased diagnostic confidence. This thesis proposes methods that would make cardiac MRI perform an improved assessment of LV function, wall motion, and viability, such that cardiac MRI is taken one step closer to being a single stop solution for imaging of heart. Conventional cardiac MR imaging is performed at a temporal resolution of around 40 ms per cardiac phase. While the global left ventricular (LV) function can be reliably established at this temporal resolution, functional metrics characterizing transient function like peak filling and ejection rates are not accurately assessed. A high temporal resolution is necessary to characterize such transient LV function and wall motion mechanics. This thesis proposes methods to acquire cine-images of the heart at a higher temporal resolution (~ 6 ms) and algorithms to acquire the LV volume across all cardiac phases that would yield functional metrics characterizing LV function and wall motion mechanics. The validation of these algorithms was performed on human subjects. Cardiac MR imaging is the current gold standard of myocardial viability imaging, in which scarred regions of the heart following myocardial infarction are visualized. However viability imaging faces image quality challenges in patients with severe arrhythmias and in cases where a higher spatial resolution, and hence a longer acquisition time, is desired. This thesis also proposes an arrhythmia insensitive inversion recovery (AIIR) algorithm that would significantly reduce artifacts that degrade image quality, thereby extending viability imaging to higher spatial resolution and in patients with severe arrhythmia. Simulations, experimental validation on phantoms and clinical verification on patients are performed. Results from high temporal resolution imaging reveal that obtaining cine cardiac MR images at a temporal resolution of 6 ms per cardiac phase is feasible. Appropriate validated algorithms yield LV time-volume curve from which LV functional metrics are reliably extracted. A dependence on temporal resolution is revealed, and a temporal resolution cut-off of 12 ms is proposed to reliably capture the temporal dynamics of the LV. Also, results from cardiac viability imaging show that the AIIR algorithm performs significantly better than conventional imaging methods in both phantoms and human subjects, as shown by the blinded expert scores, leading to a better image quality. In conclusion, this thesis proposes and implements methods that help cardiac MRI yield 1) a better function and wall motion assessment of the heart through high temporal resolution imaging and 2) a better assessment of myocardial viability through the AIIR algorithm.
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    Enhanced MRI relaxivity of aquated Gd3+ﾠions by carboxyphenylated water-dispersed graphene nanoribbons
    (Royal Society of Chemistry, 2014) Gizzatov, Ayrat; Keshishian, Vazrik; Guven, Adem; Dimiev, Ayrat M.; Qu, Feifei; Muthupillai, Raja; Decuzzi, Paolo; Bryant, Robert G.; Tour, James M.; Wilson, Lon J.; Richard E. Smalley Institute for Nanoscale Science and Technology
    The present study demonstrates that highly water-dispersed graphene nanoribbons dispersed by carboxyphenylated substituents and conjugated to aquated Gd3+ﾠions can serve as a high-performance contrast agent (CA) for applications inﾠT1- andﾠT2-weighted magnetic resonance imaging (MRI) with relaxivity (r1,2) values outperforming currently-available clinical CAs by up to 16 times forﾠr1ﾠand 21 times forﾠr2.
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    Surfactant-free Gd3+-ion-containing carbon nanotube MRI contrast agents for stem cell labeling
    (Royal Society of Chemistry, 2015) Gizzatov, Ayrat; Hernández-Rivera, Mayra; Keshishian, Vazrik; Mackeyev, Yuri; Law, Justin J.; Guven, Adem; Sethi, Richa; Qu, Feifei; Muthupillai, Raja; Cabreira-Hansen, Maria da Graça; Willerson, James T.; Perin, Emerson C.; Ma, Qing; Bryant, Robert G.; Wilson, Lon J.; Richard E. Smalley Institute for Nanoscale Science and Technology
    There is an ever increasing interest in developing new stem cell therapies. However, imaging and tracking stem cells in vivo after transplantation remains a serious challenge. In this work, we report new, functionalized and high-performance Gd3+-ion-containing ultra-short carbon nanotube (US-tube) MRI contrast agent (CA) materials which are highly-water-dispersible (ca. 35 mg ml−1) without the need of a surfactant. The new materials have extremely high T1-weighted relaxivities of 90 (mM s)−1 per Gd3+ ion at 1.5 T at room temperature and have been used to safely label porcine bone-marrow-derived mesenchymal stem cells for MR imaging. The labeled cells display excellent image contrast in phantom imaging experiments, and TEM images of the labeled cells, in general, reveal small clusters of the CA material located within the cytoplasm with 109 Gd3+ ions per cell.