Jeffrey H. Walton

Bio: Jeffrey H. Walton is an academic researcher from University of California, Davis. The author has contributed to research in topics: Nuclear magnetic resonance spectroscopy & Imaging phantom. The author has an hindex of 24, co-authored 63 publications receiving 1947 citations. Previous affiliations of Jeffrey H. Walton include Florida State University & University of California, Berkeley.

Performance Test of an LSO-APD Detector in a 7-T MRI Scanner for Simultaneous PET/MRI

Abstract: PET combined with CT has proven to be a valuable multimodality imaging device revealing both functional and anatomic information. Although PET/CT has become completely integrated into routine clinical application and also has been used in small-animal imaging, CT provides only limited soft-tissue contrast and, in preclinical studies, exposes the animal to a relatively high radiation dose. Unlike CT, MRI provides good soft-tissue contrast even without application of contrast agents and, furthermore, does not require ionizing radiation. Methods: This project focused on combining a high-resolution PET scanner with a 7-T MRI system for animal research. Because classic PET detectors based on photomultiplier tubes cannot be used in high magnetic fields, we used a detector technology based on 10 × 10 lutetium oxyorthosilicate crystal arrays and 3 × 3 avalanche photodiode arrays. A ring of such PET detectors will ultimately be used as an insert for the 119-mm-diameter MRI bore. Results: Initial measurements with 1 PET detector module in the 7-T field during application of MRI sequences were encouraging. Position profiles from the PET detectors and a first MR image of a mouse could be acquired simultaneously. Conclusion: Further work will concentrate on the construction of a full PET detector ring with compact, integrated electronics.

A smart and versatile theranostic nanomedicine platform based on nanoporphyrin

Abstract: Multifunctional nanoparticles with combined diagnostic and therapeutic functions show great promise towards personalized nanomedicine. However, attaining consistently high performance of these functions in vivo in one single nanoconstruct remains extremely challenging. Here we demonstrate the use of one single polymer to develop a smart 'all-in-one' nanoporphyrin platform that conveniently integrates a broad range of clinically relevant functions. Nanoporphyrins can be used as amplifiable multimodality nanoprobes for near-infrared fluorescence imaging (NIRFI), magnetic resonance imaging (MRI), positron emission tomography (PET) and dual modal PET-MRI. Nanoporphyrins greatly increase the imaging sensitivity for tumour detection through background suppression in blood, as well as preferential accumulation and signal amplification in tumours. Nanoporphyrins also function as multiphase nanotransducers that can efficiently convert light to heat inside tumours for photothermal therapy (PTT), and light to singlet oxygen for photodynamic therapy (PDT). Furthermore, nanoporphyrins act as programmable releasing nanocarriers for targeted delivery of drugs or therapeutic radio-metals into tumours.

Microwave combination heating: Coupled electromagnetics‐ multiphase porous media modeling and MRI experimentation

Abstract: The work includes development of a multiphase porous media model and magnetic resonance imaging (MRI) experiments to study microwave combination heating. Combination of electromagnetic, convective and radiant heating was considered. The material being heated was modeled as a hygroscopic porous medium with different phases: solid matrix, water and gas, and included pressure driven flow, binary diffusion and phase change. The three-dimensional transport model was fully coupled with electromagnetics to include the effect of variable properties. MRI was used to obtain spatial temperature and moisture distributions to validate the model. The model demonstrated that high and low moisture materials behave differently under different combinations of heating and general guidelines for combining heating modes were obtained. Low moisture materials can be heated effectively using higher microwave power which is not possible in high moisture material. Cycling of microwave was found to be useful in distribution of excessive volumetric heat generated by microwaves. © 2011 American Institute of Chemical Engineers AIChE J, 2012

Xylella fastidiosa Infection and Ethylene Exposure Result in Xylem and Water Movement Disruption in Grapevine Shoots

Abstract: It is conventionally thought that multiplication of the xylem-limited bacterium Xylella fastidiosa ( Xf ) within xylem vessels is the sole factor responsible for the blockage of water movement in grapevines ( Vitis vinifera ) affected by Pierce9s disease. However, results from our studies have provided substantial support for the idea that vessel obstructions, and likely other aspects of the Pierce9s disease syndrome, result from the grapevine9s active responses to the presence of Xf , rather than to the direct action of the bacterium. The use of magnetic resonance imaging (MRI) to observe the distribution of water within the xylem has allowed us to follow nondestructively the development of vascular system obstructions subsequent to inoculation of grapevines with Xf . Because we have hypothesized a role for ethylene produced in vines following infection, the impact of vine ethylene exposure on obstruction development was also followed using MRI. In both infected and ethylene-exposed plants, MRI shows that an important proportion of the xylem vessels become progressively air embolized after the treatments. The loss of xylem water-transporting function, assessed by MRI, has been also correlated with a decrease in stem-specific hydraulic conductivity ( K S ) and the presence of tyloses in the lumens of obstructed water conduits. We have observed that the ethylene production of leaves from infected grapevines is greater than that from healthy vines and, therefore, propose that ethylene may be involved in a series of cellular events that coordinates the vine9s response to the pathogen.

Displacement encoding for the measurement of cartilage deformation

Abstract: Articular cartilage is a load bearing and lubricating tissue inanimal joints. Heterogeneous deformations arise in the struc-turedandzonaltissueundertheapplicationofmechanicalload.The character of these deformations is altered by degenerativejoint disease. Here, we document an MRI-based technique fordetermining deformations throughout the volume of the tissuebased on displacement encoding with stimulated echoes(DENSE) and a fast spin echo (FSE) readout. A DENSE-FSEtechnique was designed to image cartilage at 9.4 Tesla in adeformed state during the application of cyclic mechanicalloading. Artifact elimination arising from stimulated echoes andFSE was accomplished by radio frequency pulse phase cycling.The error of the technique was random and was quantified interms of precision as better than 0.17% strain. Heterogeneousdeformation field patterns in axial, transverse, and shear direc-tions were quantified in a single tissue explant loaded in simpleuniaxial compression. The technique is appropriate for docu-menting tissue deformations during applied physiologically rel-evant stress levels and loading rates. It may also be applied tocharacterize the micromechanical strain environment in nor-mal, diseased, or regenerated cartilage in response to appliedmechanical loading. Magn Reson Med 59:149–155, 2008.© 2007 Wiley-Liss, Inc.Key words: articular cartilage; deformation fields; stimulatedechoes; MRI; strain precision

Reactive Oxygen Species (ROS)-Based Nanomedicine.

Abstract: Reactive oxygen species (ROS) play an essential role in regulating various physiological functions of living organisms. The intrinsic biochemical properties of ROS, which underlie the mechanisms ne...

Magnetism and microfluidics

Abstract: Magnetic forces are now being utilised in an amazing variety of microfluidic applications. Magnetohydrodynamic flow has been applied to the pumping of fluids through microchannels. Magnetic materials such as ferrofluids or magnetically doped PDMS have been used as valves. Magnetic microparticles have been employed for mixing of fluid streams. Magnetic particles have also been used as solid supports for bioreactions in microchannels. Trapping and transport of single cells are being investigated and recently, advances have been made towards the detection of magnetic material on-chip. The aim of this review is to introduce and discuss the various developments within the field of magnetism and microfluidics.

Nanochemistry and Nanomedicine for Nanoparticle-based Diagnostics and Therapy

Abstract: Diagnostics and Therapy Guanying Chen,‡,† Indrajit Roy,†,§ Chunhui Yang,*,‡ and Paras N. Prasad*,† †Institute for Lasers, Photonics, and Biophotonics and Department of Chemistry, University at Buffalo, State University of New York, Buffalo, New York 14260, United States ‡School of Chemical Engineering and Technology, Harbin Institute of Technology, Harbin, Heilongjiang 150001, China Department of Chemistry, University of Delhi, Delhi 110007, India

Simultaneous PET-MRI: a new approach for functional and morphological imaging

Abstract: Noninvasive imaging at the molecular level is an emerging field in biomedical research. This paper introduces a new technology synergizing two leading imaging methodologies: positron emission tomography (PET) and magnetic resonance imaging (MRI). Although the value of PET lies in its high-sensitivity tracking of biomarkers in vivo, it lacks resolving morphology. MRI has lower sensitivity, but produces high soft-tissue contrast and provides spectroscopic information and functional MRI (fMRI). We have developed a three-dimensional animal PET scanner that is built into a 7-T MRI. Our evaluations show that both modalities preserve their functionality, even when operated isochronously. With this combined imaging system, we simultaneously acquired functional and morphological PET-MRI data from living mice. PET-MRI provides a powerful tool for studying biology and pathology in preclinical research and has great potential for clinical applications. Combining fMRI and spectroscopy with PET paves the way for a new perspective in molecular imaging.

Nanomaterials for In Vivo Imaging

Abstract: In vivo imaging, which enables us to peer deeply within living subjects, is producing tremendous opportunities both for clinical diagnostics and as a research tool. Contrast material is often required to clearly visualize the functional architecture of physiological structures. Recent advances in nanomaterials are becoming pivotal to generate the high-resolution, high-contrast images needed for accurate, precision diagnostics. Nanomaterials are playing major roles in imaging by delivering large imaging payloads, yielding improved sensitivity, multiplexing capacity, and modularity of design. Indeed, for several imaging modalities, nanomaterials are now not simply ancillary contrast entities, but are instead the original and sole source of image signal that make possible the modality’s existence. We address the physicochemical makeup/design of nanomaterials through the lens of the physical properties that produce contrast signal for the cognate imaging modality—we stratify nanomaterials on the basis of thei...