Shalom Michaeli

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Postmortem demonstration of increased iron in the substantia nigra (SN) is a well-appreciated finding in Parkinson's disease (PD). Iron facilitates generation of free radicals, which are thought to play a role in dopamine neuronal loss. To date, however, magnetic resonance imaging (MRI) has failed to show significant in vivo differences in SN iron levels in(More)
Carr-Purcell and Hahn spin-echo (SE) measurements were used to estimate the apparent transverse relaxation time constant (T2) of water and metabolites in human brain at 4T and 7T. A significant reduction in the T2 values of proton resonances (water, N-acetylaspartate, and creatine/phosphocreatine) was observed with increasing magnetic field strength and was(More)
The rotating frame longitudinal relaxation magnetic resonance imaging (MRI) contrast, T(1 rho), obtained with on-resonance continuous wave (CW) spin-lock field is a sensitive indicator of tissue changes associated with hyperacute stroke. Here, the rotating frame relaxation concept was extended by acquiring both T(1 rho) and transverse rotating frame (T(2(More)
Apparent transverse-relaxation rate constants (R₂⁺ = 1/T₂⁺) were measured in various regions of the healthy human brain using a multiecho adiabatic spin-echo sequence at five different magnetic fields, 1.5, 1.9, 3, 4.7, and 7 T. The R₂⁺ values showed a clear dependence on magnetic field strength (B(0) ). The regional distribution of the R ₂⁺ was well(More)
A high-resolution spin-echo imaging method is presented (called CP-LASER) which exploits the spin refocusing capability of an adiabatic Carr-Purcell (CP) pulse sequence to measure apparent 1H2O transverse relaxation (T2+) and generate contrast based on microscopic tissue susceptibility. High-resolution CP-LASER images of the human occipital lobe were(More)
Calculations and experiments were used to examine the B(1) field behavior and signal intensity distribution in a 16-cm diameter spherical phantom excited by a 10-cm diameter surface coil at 300 MHz. In this simple system at this high frequency very complex RF field behavior exists, resulting in different excitation and reception distributions. Included in(More)
Spin relaxation taking place during radiofrequency (RF) irradiation can be assessed by measuring the longitudinal and transverse rotating frame relaxation rate constants (R(1rho) and R(2rho)). These relaxation parameters can be altered by utilizing different settings of the RF irradiation, thus providing a useful tool to generate contrast in MRI. In this(More)
The feasibility of performing quantitative T(1rho) MRI in human brain at 4 T is shown. T(1rho) values obtained from five volunteers were compared with T2 and adiabatic Carr-Purcell (CP) T2 values. Measured relaxation time constants increased in order from T2, CP-T2, T(1rho) both in white and gray matter, demonstrating differential sensitivities of these(More)
Longitudinal and transverse relaxations in the rotating frame, with characteristic time constants T1rho and T2rho, respectively, have potential to provide unique MRI contrast in vivo. On-resonance spin-lock T1rho with different spin-lock field strengths and adiabatic T2rho with different radiofrequency-modulation functions were measured in BT4C gliomas(More)
Recent developments in brain imaging methods are on the verge of changing the evaluation of people with Parkinson's disease (PD). This includes an assortment of techniques ranging from diffusion tensor imaging (DTI) to iron-sensitive methods such as T2(*), as well as adiabatic methods R1ρ and R2ρ, resting-state functional MRI, and magnetic resonance(More)