VOL.211 JANUARY 2026
JAPAN AND UME [SCIENCE＆TECHNOLOGY―The Next Generation of Young Leaders] The Development of Diffusion MRI: A Less Invasive Diagnostic Technology for Cancer

An example of MRI equipment

Since 1981, cancer has been the leading cause of death among Japanese. Cancer is still a major threat to human beings, even in today’s medically advanced era. Among the various diagnostic methods for cancer, diffusion MRI is considered as a breakthrough biomedical technology innovation that has become a mainstay of modern medical imaging. Diffusion MRI had a transformative effect on diagnostic medicine. The method has been adopted by MRI system manufacturers and is now used worldwide. The success of diffusion MRI is based on its roots: It is a completely non-invasive¹ that can reveal intimate features of tissue microstructure, especially in cancer lesions. We interviewed IIMA Mami, who has worked on diffusion MRI R&D and aims to establish global standards for diagnostic technology.

“There are many different types of cancer, and they differ in where they originate and how quickly they spread,” says IIMA Mami, a Designated Professor at Nagoya University Graduate School of Medicine. “Therefore, treatment methods are diverse. Diagnostic technology that can clarify the cancer properties is crucial for selecting the best course of treatment.” In 2014, while a graduate student at Kyoto University, IIMA received the 4th JSPS Ikushi Prize for her work “Development of a New Non-Invasive Cancer Diagnostic Method Using Diffusion MRI,” which became the starting point of her current research field (see box for details on the Ikushi Prize).

MRI stands for Magnetic Resonance Imaging, a diagnostic imaging method that uses powerful magnets and electromagnetic waves to examine the movement of hydrogen atoms contained in the bodily fluids of living things, thereby creating cross-sectional images of the body’s interior, enabling the detection of lesions. Conventional MRI often involves injecting a contrast agent² into the body to make it easier to find lesions. However, such agents cannot be used for individuals with allergies, and side effects may also occur. That is why IIMA continues her research on diffusion MRI as a less invasive approach that does not use contrast agents.

This method, which relies on the monitoring of molecular diffusion³ of water molecules, has been commonly used for diagnosing stroke at the acute phase and neurological disorder since the mid-1990s. Application to cancer diagnosis came around 2000, building on the observation that water diffusion is hindered by proliferating cells in cancer lesions. Tumors typically exhibit altered vasculature, disrupted extracellular matrix organization,⁴ heterogeneous cellularity and cell proliferation, features to which diffusion MRI is exquisitely sensitive. However, its widespread clinical use has been hampered for a number of reasons: the difficulty of obtaining stable images of internal organs other than the brainbecause they are easily affected by motion artifacts⁵ from breathing, heartbeats and other movements; the lack of standard protocols resulting in values fluctuating depending on the scanner and imaging parmeters; and the fact that advanced detailed analysis requires some modeling software not always available on the MRI vendor consoles.

Still, IIMA and her research group took on these hurdles. They analyzed a mountain of data obtained from diffusion MRI and made efforts at quantification⁶ to evaluate its usefulness in diagnosing breast tumors in over 200 clinical cases. They analyzed diffusion MRI signal values to establish usable quantitative diagnostic values and developed and patented a semi-automated tumor evaluation system that can visualize, in color, regions with higher degrees of malignancy—a tool that shows promise for guiding diagnosis and biopsies of malignant lesions.

“Improvements in the imaging capabilities of MRI equipment have significantly impacted the development of diffusion MRI diagnostic technology,” says IIMA. “We are getting more vivid images, and it is becoming easier to understand changes in tumor properties brought on by drug therapy.” IIMA adds that currently, in addition to research, she is involved with the European Society of Breast Imaging and other international conferences, and working toward formulating guidelines and standardizing diagnostic technologies using diffusion MRI for breast cancer. She hopes to enable more medical professionals to use diffusion MRI in clinical settings, thereby connecting basic research with clinical research, and contributing to early cancer detection and treatment optimization.

JSPS Ikushi Prize
The JSPS Ikushi Prize was established to foster the development of young researchers by recognizing outstanding doctoral students who can be expected to contribute to the future advancement of academic research in Japan, thereby enhancing their motivation for study and research. On the 20th year of his ascending to the throne, Emperor Emeritus Akihito provided the endowment for this Prize to support and encourage young researchers who are diligently pursuing their studies and research within an economically challenging environment. This Prize was established in FY 2010 by the Japan Society for the Promotion of Science (JSPS)⁷ For more information, see website JSPS Ikushi Prize.

• 1. A term that describes a method or technology for medical treatment or examination that does not damage living tissue and minimizes strain on the body.
• 2. A special substance that is used to make lesions easier to find by adding black-and-white contrast to blood vessels, organs, and other internal tissues in MRI and other diagnostic imaging. It is administered intravenously or orally.
• 3. The movement of a substance from an area of higher concentration to an area of lower concentration to become evenly distributed.
• 4. A complex structure made of proteins and carbohydrates that fills the gaps between cells and in tissues, maintaining the shape and elasticity of tissues and controlling cell function.
• 5. Image distortion and noise caused by the subject's body movements and breathing.
• 6. The act of expressing a thing in numerical form using objective criteria, making comparison and analysis easier.
• 7. Established in 1932 with an endowment from Emperor Showa, JSPS is today Japan’s only independent funding agency with a mission to advance science. JSPS carries out a wide variety of programs in pursuit of this mission. They include programs to fund scientific research, foster researchers, promote international scientific exchange, and reform university systems.

By FUKUDA Mitsuhiro
Photo: Bioindustry Encouragement Project; PIXTA