Alexey A. Tonyushkin, PhD

Research Assistant Professor, Physics Dept. at UMASS Boston


Research

Magnetic Particle Imaging (MPI)

Magnetic Particle Imaging (MPI) is a new noninvasive medical imaging modality. The two different types of the magnetic gradient geometries are: field-free-point (FFP) and field-free-line (FFL). The FFL-based device could potentially produce better image quality than FFP-based one at the same nanoparticles concentration. However, from a technical point of view, creation of a required high strength magnetic gradient with FFL, which is capable to encode 3D volume, is challenging thus limiting the expected resolution of such devices. In my research I explore new design of the selection coils with FFL that could overcome the major challenges of FFL MPI scanners.

Atom Interferometry and Atom Kicked Rotor

The novel implementation of the delta kicked rotor for momentum coherences in the guided atom interferometer promises practical applications. In addition, many fundamental questions still need to be addressed both theoretically and experimentally. The conventional scheme, where the dynamics of the delta kicked rotor is probed by detection of atomic momentum distribution using the time-of-flight technique, was demonstrated previously by M. Raizen and other groups. This approach, however, suffers from the intrinsic low resolution therefore making it impossible to observe many essential features of the delta kicked rotor in a single quantum system. The method also disregards a mutual phase between wave-packets in the observed signal and therefore treats the system quasi-classically. In contrast, our previous experiments revealed the interferometric nature of quantum resonances by detecting coherences between different momentum states.

Traveling wave MRI at ultra-high field

The principal advantage of MRI at ultra-high field is the concomitant increase in signal-to-noise ratio (SNR), which can be traded for higher resolution. The TW MRI is naturally associated with the propagation effects in media that offer several advantages to RF manipulations. Specifically, propagating TW can be the most effective way to deliver RF power at ultra-high fields to a large FOV and it can naturally provide variety of modes. The propagation of waves inside an electrodynamics system with cylindrical geometry of an MR scanner may be implemented by using a hollow metal waveguide, either by using the bore of the scanner, its shield or a specially constructed and dedicated waveguide. The new regimes depend critically on transmitting and receiving RF waves, specifically, by utilizing far-field excitation instead of the conventional near-field operation normally used in MRI. In my computational and experimental research with various collaborators I study the ways to overcome the constraints of various scanner geometries in order to effectively excite and couple TW RF into a subject. Among the systems of interests are small-bore ultra-high MRI systems (16.4T, 21.1T), which are normally not suitable for waves propagation; and human bore ultra-high MRI (7T, 10.5T).

Far-Field MRI at clinical field (3T) strength

The goal of Traveling wave (TW) MRI research is to demonstrate and develop a new hardware (coils) using far-fields RF effects. Conventional MRI relies on near-field inductive coils that require complicated design and most importantly high RF deposition power at the surface to achieve usable, relatively uniform field pattern in the deep region of interest. Currently, multichannel arrays of near field receive-only coils are offered for such imaging for clinical 3T MR scanners. In contrast, I study TW MRI that relies on RF transmission and reception by coupling to a metal waveguide (the scanner bore) in a far-field regime. TW MRI can be beneficial as it avoids large RF energy deposition at the body surface and instead channels RF power into a waveguide and then radiatively couples it into the region of interest. We have demonstrated a possibility of TW modality using cylindrical dielectric waveguiding system at clinical 3 T fields. We developed a new circular-polarized coil for TW excitation at 3 T. Recently we have also demonstrated a novel design for 3 T body coil that provides a more effective way to couple RF into a body.

Tractography in the Abdomen

Multiparametric MRI is a novel promising tool for staging and monitoring of prostate cancer. As reliability of Diffusion Weighted Imaging (DWI) improves we are now in a position to develop new useful quantitative parameters to provide added value besides currently used ones, such as: apparent diffusion coefficient (ADC), fractional anisotropy (FA), and other parameters available from common Diffusion Tensor Imaging (DTI). DTI becomes most relevant when the bulk motion is anisotropic. In my research I study DTI Tractography applicability to abdomen and prostate MRI exams. Prostate gland consists of various vascular, neural, and other anisotropic water paths that make the DTI applicable to it. Furthermore, I investigate a tract density parameter as a new quantitative imaging index for DTI MRI of prostate cancer. DTI Tractography of prostate offers details of the neurovascular tracts within the prostate gland, which are not visualized by conventional imaging modalities including multiparametric MRI. This new index may offer a significant improvement in performance of MRI in characterization of prostate cancer.


Teaching

Recent courses

Topics on Medical Imaging (Spring 2017)

Physics 382 (Spring 2016)


People

Collaborators

A. Weis, PhD, V. Lebedev, PhD
- Physics Department, University of Fribourg, Switzerland

M. G. Harisinghani, MD, S. S. Hedgire, MD, Maryam Moteabbed, PhD
- Radiology Department, MGH and Harvard Medical School


Publications

Recent Papers

  1. A. Tonyushkin, "Single-Sided Field-Free Line Generator Magnet for Multi-Dimensional Magnetic Particle Imaging", IEEE Transactions on Magnetics, 53(9):5300506 (2017)

  2. A. Tonyushkin, "Single-Sided Hybrid Selection Coils for Field-Free Line Magnetic Particle Imaging", Intl J. on Magnetic Particle Imaging, 3(1):1703009 (2017)

Conference Proceedings

1. A. Tonyushkin, Single-Sided Hybrid Selection Coils for Field-Free Line Magnetic Particle Imaging, IWMPI, Prague, Czech Republic (2017)

2. A. Tonyushkin, Simulation Study of Novel Selection-Focus Field Coils for Field-Free Line Magnetic Particle Imaging, IWMPI, Prague, Czech Republic (2017)