MRI Gradient Power Supply Capacitance Management

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Solution Overview

Problem

Conventional MRI systems face challenges in maintaining image quality over time due to capacitance degradation of electrolytic capacitors in gradient magnetic field power supplies, leading to increased manufacturing costs and larger equipment sizes to account for capacitance margin, which affects the load on the power supply during high-image-quality imaging.

Innovation Solution

An MRI apparatus and method that includes a charge/discharge controlling unit, a judging unit, and a condition restricting unit to monitor and manage the capacitance of the electrolytic capacitor, adjusting the power supply to the gradient magnetic field coil based on the capacitor's capacitance levels, thereby maintaining image quality without excessive margin design.

Engineering Contradictions & Design Principles

VSEngineering Contradiction Analysis

1Reliability

If circuits of gradient magnetic field power supply are designed with margin for capacitance degradation, then reliability is improved, but manufacturing cost increases

Engineering Contradiction:

ImprovereliabilityVSAvoidmanufacturing cost

Core Design Contradiction:

ReliabilityVSEase of manufacture

Solution Approach 1:

The patent applies dynamics by making the power supply circuit characteristics adjustable rather than fixed. The control unit dynamically changes the output voltage waveform characteristics (rise time, fall time, duration) based on the measured capacitance value, allowing the system to adapt to capacitor degradation over time without requiring excessive initial design margin.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent changes operational parameters (voltage waveform characteristics) based on the capacitance value. By measuring the actual capacitance and adjusting the power supply output parameters accordingly, the system maintains reliable operation even with degraded capacitors, reducing the need for oversized initial design margin.

Inventive Principle:

Principle #35Parameter changes

2Reliability

If electrolytic capacitor is grown in size and capacitance to provide sufficient margin, then reliability is improved, but device volume increases

Engineering Contradiction:

ImprovereliabilityVSAvoiddevice volume

Core Design Contradiction:

ReliabilityVSVolume of moving object

Solution Approach 1:

Instead of using a statically oversized capacitor, the system dynamically adjusts power supply parameters based on the actual capacitance value. This allows smaller capacitors to provide sufficient margin through adaptive control, reducing the volume required for the power supply unit.

Inventive Principle:

Principle #15Dynamics

Solution Approach 2:

The patent replaces the mechanical approach of increasing capacitor size with a control system approach. By using measurement and adjustment of electrical parameters, the system achieves the same reliability goal without the physical bulk of oversized capacitors.

Inventive Principle:

Principle #28Mechanics substitution (Replace mechanical system)

3Ease of manufacture

If circuits of gradient magnetic field power supply are designed without capacitance margin, then manufacturing cost is reduced, but image quality degrades over time

Engineering Contradiction:

Improvemanufacturing costVSAvoidimage quality

Core Design Contradiction:

Ease of manufactureVSManufacturing precision

Solution Approach 1:

The patent implements feedback by measuring the actual capacitance value and using this information to adjust the power supply output parameters. This closed-loop approach ensures that image quality is maintained over time by compensating for capacitor degradation, allowing economical design without margin while preserving quality.

Inventive Principle:

Principle #23Feedback

Solution Approach 2:

The system performs preliminary measurement of capacitance value before imaging operations. Based on this preliminary information, the control unit pre-adjusts the power supply parameters to ensure optimal image quality throughout the capacitor's operational life, preventing quality degradation before it occurs.

Inventive Principle:

Principle #10Preliminary action

4Reliability

If capacitance of electrolytic capacitor is increased to provide margin, then reliability is improved, but power supply unit size increases

Engineering Contradiction:

ImprovereliabilityVSAvoidpower supply unit size

Core Design Contradiction:

ReliabilityVSVolume of stationary object

Solution Approach 1:

The patent changes the operational parameters of the power supply (voltage waveform characteristics) based on capacitance measurement. This allows the system to achieve reliable operation with smaller capacitors by optimizing the electrical parameters, thereby reducing the overall power supply unit size.

Inventive Principle:

Principle #35Parameter changes

Data Source

PatentUS9726734B2Magnetic resonance imaging apparatus and magnetic resonance imaging method

Publication Date: 2017.08.08 TOSHIBA MEDICAL SYST CORP

AI summary

An MRI apparatus includes a charge/discharge controlling unit, a judging unit and a condition restricting unit. The charge/discharge controlling unit includes a charge/discharge element, receives electric power, and charges the charge/discharge element by using the received electric power. The charge/discharge controlling unit also supplies a gradient magnetic field coil with electric power discharged from the charge/discharge element at a time of performance of magnetic resonance imaging. The judging unit judges whether capacitance of the charge/discharge element falls below a threshold value or not. The condition restricting unit restricts electric power amount supplied to the gradient magnetic field coil by restricting conditions of an imaging sequence, when the capacitance of the charge/discharge element falls below the threshold value.