Magnetic particle imaging device capable of producing images of human brain

Date: 11/09/2023
Mitsubishi Electric, Okayama University, and Osaka University have together developed world's first high-sensitivity imaging device capable of operating at low frequencies with compact power supply, will facilitate diagnosis of pre-Alzheimer's new magnetic particle imaging device (prototype). This magnetic particle imaging device capable of sensitive imaging of magnetic particles in an area equivalent in size to that of the human brain, in a project supported by the Japan Agency for Medical Research and Development (AMED). The device operates at low frequencies of 1 kHz or less, a world-first, allowing the use of a significantly smaller power supply unit. The utilization of this device to image magnetic particles that bind to amyloid-▀, 2 the causative agent of Alzheimer's, will allow the accumulation and distribution of amyloid-▀ to be quantified. The aim is to allow imaging-based assessments of the likelihood of Alzheimer's developing prior to the onset of the disease.
Magnetic image

Magnetic image

The number of dementia patients aged 65 and older in Japan is expected to reach 7 million in 2025. Significant statistical findings indicate that Alzheimer's accounts for 67.6% of these dementia cases. Japan enacted the Dementia Basic Law, aimed at advancing dementia prevention efforts. In August, a panel of experts from Japan's Ministry of Health, Labour and Welfare gave a green light for the manufacture and sale of a drug that targets the accumulation of amyloid-▀ in the brain, a potential factor in the development of Alzheimerĺs, thereby inhibiting the progression of the disease. Initiating medication early during a phase of low amyloid-▀ accumulation in the brain has been shown to help suppress the onset of the disease. This underscores the necessity for technology capable of measuring both the accumulation and distribution of amyloid▀.

The magnetic particle imaging device deploys an alternating magnetic field generated by a coil to induce magnetic signals from magnetic particles injected into the body; it then uses these signals to produce a three dimensional image. A higher frequency alternating magnetic field enhances the sensitivity of signal detection.
In compact devices designed for testing on small animals such as mice, which have already been commercialized, frequencies of approximately 25 kHz are used. One of the factors that hitherto hindered the practical application of this system in the treatment of humans was the extremely large size of the power supply unit needed to drive the much larger coil.

By leveraging its extensive electromagnetic technology know-how acquired through the development of various devices, and by fine-tuning the configuration of the coils that generate alternating magnetic fields and those dedicated to signal detection, Mitsubishi Electric has developed a process that minimizes extraneous signals (noise) that hinder the detection of magnetic signals. This has allowed the three participating organizations to successfully develop a magnetic particle imaging device capable of sensitively capturing images of magnetic particles across an area equivalent to the size of the human brain; while operating at low frequencies below 1 kHz, a world-first, significantly reducing the size of the power supply unit required. This accomplishment marks a significant stride toward the realization of imaging tests that can assess the likelihood of the development of Alzheimer's prior to its onset.
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Future Plans and Prospects:
In order to use a magnetic particle imaging device to conduct imaging tests that can assess the likelihood of the development of Alzheimerĺs prior to the onset of the disease, it is essential to enhance the sensitivity and resolution of the device. Clinical trials to confirm its safety and effectiveness as a diagnostic tool are required before it can be put to practical use. With the goal of achieving commercialization by around 2030, the three organizations behind the development of this solution will continue to study the possibility of collaborating with other companies.
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Key Features:

The world's first "magnetic particle imaging device" capable of highly sensitive imaging of magnetic particles of an area equivalent to the size of the human brain, operating at low frequencies of 1 kHz or less, and with a much smaller power supply unit:

- By advancing the electromagnetic technology of Mitsubishi Electric, the three participating organizations have succeeded in creating a process that minimizes noise interference during signal detection. This is achieved through precise adjustments to the arrangement of the coils generating alternating magnetic fields and those used for signal detection. This innovation has enabled the pioneering achievement of highly sensitive detection and imaging of magnetic signals in samples comparable to the size of a human brain, even at frequencies as low as 1 kHz or less.
- The participating organizations have developed a magnetic particle imaging device capable of imaging areas the size of the human brain with a miniaturized power supply, achieved by reducing imaging frequency and thereby minimizing the capacity of the power supply required.
The sensitivity of the magnetic signal detection is directly related to the frequency of the alternating magnetic field. Magnetic particle imaging devices designed for testing on small animals, which are currently in production, can only operate at high frequencies of around 25 kHz. However, scaling up the magnetic particle imaging device from one that produces images of small animals (coil inner diameter 30 mm) to one that can produce images the size of a human head (coil inner diameter 300 mm), while maintaining the same frequency, would lead to a significant increase in coil load, equivalent to the square of both the coil radius and the frequency. This tenfold increase in coil diameter would necessitate around a hundred fold increase in loading and power supply capacity, with a correspondingly huge power supply. However, reducing the frequency of the alternating magnetic field to minimize power supply size would diminish the strength of the signals emanating from the magnetic particles, rendering these undetectable.

In order to improve signal detection sensitivity while simultaneously reducing frequency, the focus of the participating organizations shifted towards addressing the extraneous signals (noise) that impede magnetic signal detection. Significant progress has been achieved through the development of a coil structure specifically designed to minimize these noise effects. By precisely adjusting the layout of the AC excitation coil and the signal reception coil - both used to generate the alternating magnetic field using a rail-type slide structure, they have effectively reduced the voltage induced by the alternating magnetic field on the signal reception coil, thus minimizing noise interference. Consequently, they have been able to detect and image the magnetic signals from samples equivalent in size to the human brain, even at frequencies of 1 kHz or less, with high sensitivity. In addition, by optimizing the power supply capacity to four times that of a magnetic particle imaging device designed for small animals, they have been able to substantially reduce the dimensions of the power supply. As a result, we have been able to develop the world's first magnetic particle imaging device with a coil inner diameter of 300 mm and a diagnostic area diameter of 180 mm capable of imaging objects the size of the human brain at low frequencies and with a small power supply. This constitutes significant progress toward the realization of imaging tests that can assess the likelihood of the development of Alzheimerĺs prior to the onset of the disease.
Magnetic image

Magnetic image

This project was developed with the support of AMED's Advanced Measurement Analysis Technology and Equipment Development Program.

News Source: Mitsubishi Electric