WGI is a new imaging technique for nuclear medicine diagnosis based on the concept of “utilizing all detectable gamma rays for imaging”. Adding Compton camera function to PET enables to use radionuclides that have not been widely used for imaging. In order to realize the full potential of WGI, the key point is to improve the performance of the scatterer detector ring, which is inserted into the PET detector ring. The first half of this paper focuses on the principle of WGI and the development of the scatterer detector and the prototype for the proof of concept. The second half of this paper introduces the applications of WGI, such as new imaging methods that effectively utilize radionuclides such as ⁸⁹Zr and ⁴⁴Sc, which emit high energy gamma rays in addition to positron emission, and C-type Compton PET, which has the potential to upgrade existing MRI to PET/MRI.

Simultaneous multi-nuclide imaging in nuclear medicine is highly expected that visualize the metabolism of multiple molecules in individual on the same coordinates and time axis. In this review paper, Compton-PET hybrid imaging system combining PET and Compton imaging technology is introduced. The possibility of active collimators for multi-nuclide imaging, the improvement of Compton camera and multi-photon time-space correlated imaging are also discussed as future imaging methods. We expect the development of novel nuclear medicine imaging based on those new concepts in Japan.

We have been developing a medical Compton camera in collaboration with Japan Aerospace Exploration Agency (JAXA) and National Institutes for Quantum and Radiological Science and Technology (QST) Takasaki Advanced Radiation Research Institute. Our Compton camera uses Si and CdTe semiconductor detectors as scatterers and absorbers, and has high energy and spatial resolutions. The Compton camera is especially suitable for low energy 𝛾-ray measurements and can image ^99mTc, which is most widely used in the field of nuclear medicine diagnosis. We have conducted various experiments and succeeded in human trials. In addition, since carbon ion radiotherapy is performed at Gunma university heavy ion medical center, we have studied on the measurement of the range of carbon beams. In this paper, I introduce our research and discuss the research issues that have arisen.

Electron-Tracking Compton Camera is one of the gamma-ray imaging devices, and the gamma-ray direction and energy can be determined event by even with this camera. I show the camera structure, short history of the camera, improvement of each part and medical application.

In the 1970s, the Compton camera was proposed both for space physics and nuclear medicine as an innovative method for imaging gamma-rays, but there has been no mutual communication between the two fields since then. On the other hand, the advanced technology developed in satellite experiments, where the power, space and weight are extremely limited, will surely be useful in medical imaging. In this paper, we introduce “active” dynamic imaging based on an inexpensive and ultra-compact Compton camera using a high-performance scintillator coupled with MPPC arrays. In particular, we propose a technological innovation through the collaboration of space/nuclear (basic science) and medical (clinical/therapeutic imaging, etc.), as well as novel “active radiation imaging” of drugs as a new idea obtained from space satellite experiments.

We report a chest X-ray (CXR) anomaly detection method based on models of normal anatomical structures (ASs). Conventional computer-aided diagnosis (CAD) methods for CXR involve machine learning of predetermined target lesions; thus, these methods are unable to detect and diagnose unknown lesions. As such, we are building a new CAD system to model normal ASs and detect anomalies based on changes in ASs due to disease. The method consists of AS segmentation by U-Net, index calculation from the segmented AS region, and anomaly detection compared with the distribution of normal indices. The position, size, and continuity of the segmented ASs were used as indices. Six structures near the central shadow, which tend to be easily overlooked on CXR, were used as the target ASs. For the anomaly detection evaluation, 240 normal cases and 255 abnormal cases were used, and an average sensitivity of 0.774 and specificity of 0.827 for each AS were obtained. However, abnormalities that do not affect the currently used indices cannot be detected. In the future, we plan to apply this method to other ASs and the entire lung and adopt other indices, such as features that directly reflect image patterns.