Search research articles

ABOUT JoVE

Overview Leadership Blog JoVE Help Center

AUTHORS

Publishing Process Editorial Board Scope & Policies Peer Review FAQ Submit

LIBRARIANS

Testimonials Subscriptions Access Resources Library Advisory Board FAQ

RESEARCH

JoVE Journal Methods Collections JoVE Encyclopedia of Experiments Archive

EDUCATION

JoVE Core JoVE Business JoVE Science Education JoVE Lab Manual Faculty Resource Center Faculty Site

Terms & Conditions of Use

Related Concept Videos

Controlled-Current Coulometry: Overview

Controlled-Current Coulometry: Overview

Controlled current coulometry, also known as amperostatic coulometry, is a technique used in electrochemical analysis to measure the quantity of a substance through the controlled passage of current. It involves the application of a constant current to an electrochemical cell containing the analyte of interest. As the current flows through the cell, the analyte undergoes a redox reaction at the electrode surface, resulting in a charge transfer. By monitoring the time required for a certain...

Biasing of P-N Junction

Biasing of P-N Junction

The operation of a p-n junction diode involves various biasing conditions, including forward bias, reverse bias, and equilibrium.
In equilibrium, no external voltage is applied across the p-n junction. The depletion region is formed at the junction interface due to the diffusion of carriers, which leaves behind charged dopants, acceptors on the p-side, and donors on the n-side. These immobile charges create an electric field that prevents further diffusion of carriers. The related energy band...

Controlled-Potential Coulometry: Electrolytic Methods

Controlled-Potential Coulometry: Electrolytic Methods

Controlled-potential coulometry, also known as potentiostatic coulometry, employs a three-electrode system in which the working electrode's potential is precisely regulated using a potentiostat. Platinum working electrodes are utilized for positive potentials, while mercury pool electrodes are favored for extremely negative potentials. The platinum counter electrode is separated from the analyte using a membrane or salt bridge to avoid interference in the analysis.
The chosen potential ensures...

Controlled-Current Coulometry: Coulometric Titration

Controlled-Current Coulometry: Coulometric Titration

Coulometric titrations are a form of titrimetric analysis where the reagent is generated electrically, and its amount is evaluated based on current and generating time. The electron serves as the standard reagent. The procedure is similar to conventional titrations, such as endpoint detection.
The fundamental requirements for coulometric titrations are (1) 100% efficiency in the reagent-generating electrode reaction and (2) a stoichiometric and preferably rapid reaction between the generated...

Source Transformation for AC Circuits

Source Transformation for AC Circuits

The process of source transformation in the frequency domain entails the conversion of a voltage source, positioned in series with an impedance, into a current source that is parallel to an impedance, or the other way around. It is essential to maintain the following relationships while transitioning from one source type to another.

Phasor Relationships for Circuit Elements

Phasor Relationships for Circuit Elements

Phasor representation is a powerful tool used to transform the voltage-current relationship for resistors, inductors, and capacitors from the time domain to the frequency domain. This transformation simplifies the analysis of alternating current (AC) circuits.
In the time domain, Ohm's law provides a fundamental relation between the current flowing through a resistor and the voltage across it:

You might also read

Related Articles

Articles linked to this work by shared authors, journal, and citation graph.

Sort by

Same author

Coffee Consumption and Improved Liver Outcomes: Clinical, Imaging, and Proteomic Evidence From the UK Biobank.

Clinical gastroenterology and hepatology : the official clinical practice journal of the American Gastroenterological Association·2026

Same author

The "Brain's Traffic Map" Reveals Neural Pathways Linked to Coronary Microvascular Dysfunction in Women.

Brain and behavior·2026

Same author

Refined liver MRI-derived cT1 thresholds capturing hepatic fat fraction enhance mortality risk prediction.

JHEP reports : innovation in hepatology·2026

Same author

Hierarchical organ aging signatures from routine abdominal CT add incremental disease risk stratification beyond blood biomarkers.

medRxiv : the preprint server for health sciences·2026

Same author

Functional brain growth trajectories across the first decade of life from a single longitudinal cohort.

Research square·2026

Same author

A 20-minute, free-running, whole-heart cardiac MRI to image myocardial injury following reperfused myocardial infarction: demonstration in a large animal model.

Radiology advances·2026

Same journal

Localization-driven exchange contrast in diffusion exchange spectroscopy.

Journal of magnetic resonance (San Diego, Calif. : 1997)·2026

Same journal

4.5 Tesla superconducting miniature magnet in liquid nitrogen.

Journal of magnetic resonance (San Diego, Calif. : 1997)·2026

Same journal

Folding and unfolding dynamics of a DNA aptamer studied by heteronuclear <sup>1</sup>H-<sup>13</sup>C correlation zz-exchange spectroscopy.

Journal of magnetic resonance (San Diego, Calif. : 1997)·2026

Same journal

Multi-spin control from one-spin pulses.

Journal of magnetic resonance (San Diego, Calif. : 1997)·2026

Same journal

Altering MRI rotating frame relaxations by changing the truncation level of Hyperbolic Secant pulse.

Journal of magnetic resonance (San Diego, Calif. : 1997)·2026

Same journal

Effects of proton exchange on the lifetimes of long-lived states in aliphatic chains.

Journal of magnetic resonance (San Diego, Calif. : 1997)·2026

See all related articles

Search research articles

Related Experiment Video

Updated: May 8, 2026

A Photonic System for Generating Unconditional Polarization-Entangled Photons Based on Multiple Quantum Interference

A Photonic System for Generating Unconditional Polarization-Entangled Photons Based on Multiple Quantum Interference

Published on: September 5, 2019

Improved PHIP polarization using a precision, low noise, voltage controlled current source.

Jose Agraz¹, Alexander Grunfeld, Karl Cunningham

¹Department of Bioengineering, University of California, Los Angeles, United States; Biomedical Imaging Research Institute, Cedars Sinai Medical Center, Los Angeles, United States.

Journal of Magnetic Resonance (San Diego, Calif. : 1997)

|August 31, 2013

Summary

This summary is machine-generated.

A novel voltage controlled current source (VCCS) significantly improves para-hydrogen induced polarization (PHIP) for molecular-level MRI. This low-noise circuit stabilizes magnetic fields, enhancing hyperpolarized substance signals compared to traditional methods.

Keywords:

(13)C HEA HEP Hyperpolarization PHIP instrumentation VCCS VCVS

More Related Videos

Merging Ion Concentration Polarization between Juxtaposed Ion Exchange Membranes to Block the Propagation of the Polarization Zone

Merging Ion Concentration Polarization between Juxtaposed Ion Exchange Membranes to Block the Propagation of the Polarization Zone

Published on: February 23, 2017

Automation of Mode Locking in a Nonlinear Polarization Rotation Fiber Laser through Output Polarization Measurements

Automation of Mode Locking in a Nonlinear Polarization Rotation Fiber Laser through Output Polarization Measurements

Published on: February 28, 2016

Related Experiment Videos

Last Updated: May 8, 2026

A Photonic System for Generating Unconditional Polarization-Entangled Photons Based on Multiple Quantum Interference

A Photonic System for Generating Unconditional Polarization-Entangled Photons Based on Multiple Quantum Interference

Published on: September 5, 2019

Merging Ion Concentration Polarization between Juxtaposed Ion Exchange Membranes to Block the Propagation of the Polarization Zone

Merging Ion Concentration Polarization between Juxtaposed Ion Exchange Membranes to Block the Propagation of the Polarization Zone

Published on: February 23, 2017

Automation of Mode Locking in a Nonlinear Polarization Rotation Fiber Laser through Output Polarization Measurements

Automation of Mode Locking in a Nonlinear Polarization Rotation Fiber Laser through Output Polarization Measurements

Published on: February 28, 2016

Area of Science:

Medical Imaging
Physics
Electrical Engineering

Background:

Para-hydrogen induced polarization (PHIP) enhances MRI signals over 10,000-fold for molecular-level imaging.
Current instrumentation uses voltage-controlled voltage sources (VCVS) for magnetic field generation, which lack precise current regulation, leading to signal instability.
Fluctuations in magnetic fields generated by VCVS limit the achievable PHIP polarization.

Purpose of the Study:

To design and implement a low-noise, high-stability voltage controlled current source (VCCS) for generating a stable static magnetic field (Bo).
To improve the polarization efficiency in PHIP by minimizing magnetic field variations.
To demonstrate the superiority of VCCS over VCVS in PHIP applications.

Main Methods:

Developed a VCCS using a precision voltage reference and a MOSFET-based current sink for stable solenoid current control.
Analyzed current stability using transfer functions (TF) for both VCVS and VCCS models.
Characterized the thermal and 1/f noise of the VCCS design.
Compared hydroxyethyl-propionate (HEP) polarization using both VCVS and VCCS in a PHIP instrument.

Main Results:

The VCCS design provides superior current regulation, resulting in a more stable Bo compared to VCVS.
Noise measurements confirmed the low-noise characteristics of the developed VCCS.
Hydroxyethyl-propionate (HEP) hyperpolarization using the VCCS showed a statistically significant increase in polarization magnitude compared to using a VCVS.

Conclusions:

A low-noise, high-stability VCCS is crucial for optimizing PHIP performance by ensuring a stable magnetic field.
The developed VCCS design offers a significant advancement for hyperpolarization techniques in MRI.
This work provides a practical solution for enhancing MRI sensitivity through improved PHIP instrumentation.