Kazuaki Kumagai

Development of Pr:LuAG Scintillator Array and Assembly for Positron Emission Mammography

Abstract-In order to detect the breast cancer at the early stage with high efficiency, we intend to develop positron emission mammography (PEM), using Pr:LuAG single crystal as a scintillator of this scanner. PEM has the same mechanism of PET, where two 511 keV annihilation gamma-rays are detected by two gamma cameras at opposite side, and reconstruction of the data shows the position of the cancer with malignancy grades. After cutting and polishing processes for each crystal to a physical dimensions of 2.1 × 2.1 × 15 mm3, Pr:LuAG array covered with BaSO4 reflector was used as a sensor head. The one camera unit consisted of 20 × 64 pixels optically coupled with three H8500-03 multi anode PMTs. Our PEM required four cameras at each side. Finally, eight cameras were installed in both sides of the prototype instrument and the spatial resolution was evaluated using the 18F in the breast phantom.

Evaluation and development for positron emission mammography based on Pr:LuAG scintillator crystals

In this report, PEM scanner using a Pr:LuAG scintillator crystal will be discussed. We have developed the PEM scanner with planer detectors which can change the angle and the distance depending on the condition of diagnosis. The planer detectors were composed of four units respectively and one unit consisted of a 20 × 64 pixels scintillator array optically coupled with three H8500 multi anode photomultipliers. As a scintillator Pr:LuAG was installed which possesses interesting properties such as a very fast decay time of 20 ns and a good energy resolution of 4.2 %. The Pr:LuAG pixel size was 2.1 mm × 2.1 mm × 15 mm and the BaSO4-type reflector was used for the array assembly. Based on this PEM system we have performed the clinical studies and compared with the images detected by the PET scanner. Because the spatial resolution of PEM is better than PET, advantages of PEM scanner were clearly shown.

Fundamental performance of a new planer PEM

A Positron Emission Mammograph (PEM) with a pair of planer detectors dedicated for breast cancer detection is developed under collaborations of Tohoku University, Kobe City Collage of Technology, and Furukawa Co., Ltd. It uses thin crystals made of a scintillator Pr:Lu3A15O12 (Pr:LuAG) of 2.1×2.1×15.0 mm in size combined with H8500 position sensitive Photo multi tubes (PMTs) from Hamamatsu. The PEM system is comprised of two opposing detectors that have 140×200 cm2 field of view (FOV). We present its basic architecture with fundamental performance, such as spatial resolution, time resolution, energy resolution, and data acquisition count rate. The Spatial resolution measured using a 22Na point sauce was found to be 1.1 mm FWHM for image planes parallel to the detector faces. Time resolution was 3.1 ns FWHM. And, energy resolution was 11.6 % FWHM (@511 keV) at the center of detector blocks. Coincident count rate was improved dramatically for optimizing energy windows level and implementation a new offset correction method.

Development of a Commercial Positron Emission Mammography (PEM)

The incidence of breast cancer is in the first place as a cause of death among Japanese women. The breast cancer is a type of cancer which can be cured relatively easily when detected early. However, it is now clear that the detection of breast cancer is difficult without imaging modalities such as X-ray mammography and/or ultrasonic echography. These imaging devices are useful, however, morphological information only are not enough for differentiating cancer from other benign diseases. Positron emission tomography (PET) for whole-body diagnosis can give us functional information regarding the degree of malignancy. But still there remain various problems such as limited spatial resolution and motion artifacts due to respiratory movement, as well as an issue of the high costs. To compensate these weak points, we have started development of the positron emission mammography (PEM) dedicated for the local diagnosis of the breast tissue.