Imaging Physics Group | Institutes for Quantum Medical Science

News

Our workshop for Next Generation PET held on Jan.25 has been completed successfully

​                 Our latest annual report "Reports on PET Imaging Physics Research" is now available

2024/11/18
Won the Encouragement Award at JSNM

2024/6/25
Won two awards at SNMMI

2024/5/9
Won the Certificate of Merit Award at the 3rd ICRPT
Taiga Yamaya et al.
Hideaki Tashima et al.

Recipient of Hal Anger Lectureship Award

The Imaging Physics Research Group has developed innovative and unique instrumentation such as OpenPET, small animal PET, and brain PET and has promoted research and development toward practical applications.

Receiving the Hal Anger Lectureship Award from the American Society of Nuclear Medicine and Molecular Imaging is a recognition of our achievements over the years.

While celebrating the harvest, we continue to create the seeds for the next generation.

“Application-Specific PET Systems Expanding the Potential of Nuclear Medicine”

Over view

The Imaging Physics Research Group has prototyped 23 innovative systems between 2009 and 2023, which is believed to be a world record. We are proposing innovative concepts and promoting development with the aim of practical application. The more novel the idea, the more critical it is to prove it ourselves.

OpenPET

OpenPET is the world's first open-type PET that enables PET-guided particle therapy, including beam range verification within the body and target tumor tracking. Particle beam range verification by PET is performed by imaging the distribution of PET nuclides (positron-emitting nuclides) produced by nuclear fragmentation reactions. OpenPET has a full-ring detector arrangement, which is important for imaging, although having enough open space to pass the treatment beam. We established a ¹⁵O beam irradiation method in the HIMAC physics experiment room, showing that by using the beam as a PET nuclide, the difference between the dose peak position and the PET image peak position is less than 1 mm.

In July 2023, we started an OpenPET clinical trial for patients undergoing carbon-ion cancer therapy. Even when irradiated with a standard heavy ion beam (¹²C beam), a small amount of positron-emitting nuclides is generated in the body. With OpenPET, measurements can be made while irradiating, so the slight radioactivity can be captured before it decays. By imaging this, it is expected that we will be able to confirm on the spot how the actual irradiation was performed.

Helmet-type PET

Life extension is now causing another issue of rising numbers of dementia cases. Many prototypes of brain PET scanners have been developed to satisfy the potential demand for brain imaging. However, all previous prototypes were based on a cylindrical geometry, which is not the most efficient for brain imaging. Making the detector ring as small as possible improves PET sensitivity. In addition, a hemispherical detector arrangement detectors can further improve the sensitivity with a limited number of detectors. 
Furthermore, making detectors closer mitigates the angular deviation effects, which is a limiting factor of PET spatial resolution. As a result, the hemispherical arrangement offers the potential for higher resolution, enabling more accurate brain imaging.

First, we prototyped the world's first helmet-type PET device with DOI detectors arranged in a hemispherical shape, paving the way for the widespread use of small, highly sensitive, high-resolution head PET devices. Then, TOF MPPC modules appeared that could significantly improve effective sensitivity by measuring time information with high precision. We then created a custom model that optimized the TOF MPPC module for a hemispherical arrangement and moved on to developing a practical device.

(The PET images are reprinted from Takahashi et al. 2022 EJNMMI Phys under CC BY 4.0 license​)

After developing a practical production model, Atox Co., Ltd. obtained approval as a medical device and successfully commercialized helmet-type PET. Clinical trials showed that it was possible to separate small structures in the brain that could not be separated using a whole-body PET scanner.

Add-on PET for MRI

One of the significant innovations made in recent years is the combined PET/MRI, but utilization of DOI detectors has not been studied well. DOI measurements are essential for PET to exploit improved spatial resolution and sensitivity and reduce production costs. Therefore, we proposed an add-on PET, an RF coil combined with DOI-PET detectors.

PET detector modules were placed between the spokes of the birdcage RF coil to make the PET detector ring as small as possible while placing electronic parts such as photodetectors and front-end circuits outside the RF coil. For each detector module, electronic parts were covered with a shielding box with a hole in front of the photodetectors, and scintillators were stuck out of the shielding box to allow their placement inside the birdcage coil. In February 2023, the first clinical trial was conducted using the developed prototype, and simultaneous PET and MRI imaging was successfully achieved. In the future, we will make the PET-integrated birdcage coil a variation of the RF coil to easily upgrade any existing MRI to PET/MRI.

Whole Gamma Imaging (WGI)

PET is recognized as a successful imaging method, but to meet emerging demands such as in-situ single-level cell tracking, we need to break through an inherent limitation in the principle of PET itself. Therefore, in collaboration with Prof. Katia Parodi at Ludwig-Maximilians-Universität München and colleagues, with support from the NIRS International Open Laboratory program and the QST President Grant, Imaging Physics Group started the realization of the new concept of whole gamma imaging (WGI) in 2016.

WGI is a concept utilizing all detectable gamma rays for imaging by combining PET and Compton imaging. An additional detector ring used as the scatterer is inserted in a conventional PET ring to detect single gamma rays with the Compton imaging method. As a wide range of radioisotopes can be visualized, WGI is expected to enable imaging of the targeted radioisotope therapy. In addition, triple gamma emitters, such as ⁴⁴Sc, which emits a pair of 511 keV photons and an 1157 keV gamma ray almost at the same time, are selected as imaging targets. In theory, localization from a single decay is possible by identifying the intersection point between a coincidence line and a Compton cone.

So far, we have developed small prototypes No. 1 to No. 3 and have succeeded in proving the concept, but there were still issues with the energy resolution of the scattering detector. We have completed the housing development for No. 4 and are proceeding with detector calibration and software optimization. In addition, we are also developing clinical WGI with the support of the Nakatani Foundation.

Small-animal PET

Small animal PET plays an essential role in the field of drug discovery. Labeling a candidate drug with a PET nuclide and administering it makes it possible to efficiently investigate how well it is taken up by the target organ in the animal's body, how it acts, and even to predict side effects. Small animal PET requires a higher resolution than human PET. The Imaging Physics Research Group is developing high-resolution PET detectors and high-resolution PET scanners using these detectors.

Mirai-PET: CLS detector-equipped PET

The CLS (Crosshair Light Sharing) detector is a next-generation high-resolution PET detector that can highly accurately measure TOF and DOI. Based on the first small animal prototype device developed using the CLS detector in 2021, it was commercialized as Mirai-PET by Mirai Imaging Inc. in 2023. The scintillator pitch is 1.6 mm, achieving a spatial resolution of less than 1 mm. The model introduced to QST as the successor to the MicroPET Focus 220, which was a best-selling small animal PET scanner, has a detector ring diameter of 16 cm and a body axis length of 15.4 cm to enable multi-mouse imaging but has unparalleled flexibility in that the detector ring size can be freely customized and designed under conditions of up to 128 detectors.

Super high-resolution small-animal PET

Using a detector capable of three-layer DOI identification with a 1mm scintillator pitch, we developed a super high-resolution small-animal PET system with the world's highest spatial resolution (as of 2024), approaching 0.55 mm. We also succeeded in imaging mouse brain functions at submillimeter resolution, and this system is expected to be useful in future brain research using model mice.

Member

	Taiga Yamaya	Deputy Director Department of Advanced Nuclear Medicine Sciences, Institute for Quantum Medical Science, QST Imaging Physics Group Leader Future PET Development Unit Leader
	Eiji Yoshida	Principal Researcher Imaging Physics Group, Department of Advanced Nuclear Medicine Sciences, Institute for Quantum Medical Science, QST
	Miwako Takahashi	Group Leader of Diagnostic and Therapeutic Nuclear Medicine Group, Department of Molecular Imaging and Theranostics Principal Researcher Imaging Physics Group, Department of Advanced Nuclear Medicine Sciences, Institute for Quantum Medical Science, QST
	Hideaki Tashima	Principal Researcher Imaging Physics Group, Department of Advanced Nuclear Medicine Sciences, Institute for Quantum Medical Science, QST
	​Chie Toramatsu	Principal Researcher Imaging Physics Group, Department of Advanced Nuclear Medicine Sciences, Institute for Quantum Medical Science, QST
	Fumihiko Nishikido	Senior Researcher Imaging Physics Group, Department of Advanced Nuclear Medicine Sciences, Institute for Quantum Medical Science, QST
	​Akram Hamato (Akram Mohammadi)	Visiting Collaborative Researcher Imaging Physics Group, Department of Advanced Nuclear Medicine Sciences, Institute for Quantum Medical Science, QST
	Md Shahadat Hossain Akram	Senior Researcher Imaging Physics Group, Department of Advanced Nuclear Medicine Sciences, Institute for Quantum Medical Science, QST
	Go Akamatsu	Senior Researcher Imaging Physics Group, Department of Advanced Nuclear Medicine Sciences, Institute for Quantum Medical Science, QST
	Han Gyu Kang	Senior Researcher Imaging Physics Group, Department of Advanced Nuclear Medicine Sciences, Institute for Quantum Medical Science, QST
	Sodai Takyu	Senior Researcher Imaging Physics Group, Department of Advanced Nuclear Medicine Sciences, Institute for Quantum Medical Science, QST
	Yuma Iwao	Researcher Imaging Physics Group, Department of Advanced Nuclear Medicine Sciences, Institute for Quantum Medical Science, QST
	Hidekatsu Wakizaka	Senior Technical Staff Imaging Physics Group, Department of Advanced Nuclear Medicine Sciences, Institute for Quantum Medical Science, QST
	Fujino Obata	Technical Staff Imaging Physics Group, Department of Advanced Nuclear Medicine Sciences, Institute for Quantum Medical Science, QST
	Ryotaro Ohashi	QST Research Assistant Imaging Physics Group, Department of Advanced Nuclear Medicine Sciences, Institute for Quantum Medical Science, QST Yamaya Lab, Chiba University
	Taiyo Ishikawa	QST Research Assistant Imaging Physics Group, Department of Advanced Nuclear Medicine Sciences, Institute for Quantum Medical Science, QST Haneishi Lab, Chiba University
	Tomoya Kikuchi	QST Research Assistant Imaging Physics Group, Department of Advanced Nuclear Medicine Sciences, Institute for Quantum Medical Science, QST Suga Lab, Chiba University
​	Madoka Ohno	Secretary Imaging Physics Group, Department of Advanced Nuclear Medicine Sciences, Institute for Quantum Medical Science, QST
​	Risa Kitamura	Secretary Imaging Physics Group, Department of Advanced Nuclear Medicine Sciences, Institute for Quantum Medical Science, QST
​	Yuki Ochi	Secretary Imaging Physics Group, Department of Advanced Nuclear Medicine Sciences, Institute for Quantum Medical Science, QST
​	Miki Honda	Secretary Imaging Physics Group, Department of Advanced Nuclear Medicine Sciences, Institute for Quantum Medical Science, QST
​	Kurumi Narita	Assistant Imaging Physics Group, Department of Advanced Nuclear Medicine Sciences, Institute for Quantum Medical Science, QST Yamaya Lab, Chiba University
​	Nobuyoshi Hosotani	Assistant Imaging Physics Group, Department of Advanced Nuclear Medicine Sciences, Institute for Quantum Medical Science, QST Yamaya Lab, Chiba University
​	Makoto Kakegawa	Visiting Researcher Imaging Physics Group, Department of Advanced Nuclear Medicine Sciences, Institute for Quantum Medical Science, QST
​	Norio Arai	Visiting Researcher Imaging Physics Group, Department of Advanced Nuclear Medicine Sciences, Institute for Quantum Medical Science, QST