GSO single crystal is used as a scintillator in medical imaging equipment like PET (Positron Emission Tomography) scanners and other radiation detection equipment. Its superior energy resolution, fast decay time, large light output support quick and high precision radiation detection.

Features

Stopping power	: Dense and high absorption coefficient for gamma-ray.
Scintillation properties	: High light output and short decay time.
Uniformities	: Excellent energy resolution and uniform light output.
Temperature response	: Small decrease in light output at 100°C.
Radiation hardness	: Almost no degradation in scintillation properties at 106 gray.

Characteristics

Crystal scintillators	GSO	BGO	LSO	YSO	YAP	CWO	NaI:Tl
Density (g/cm3)	6.71	7.13	7.4	4.45	5.55	7.9	3.67
Radiation length (cm)	1.38	1.11	1.14	2.75	2.67	1.06	2.6
Decay constant (ns)	30 - 60	300	40	40	28	5000	230
Light yield (relative)	20	7 - 12	40 - 75	30 - 45	40	30 - 40	100
Peak emission λem (nm)	430	480	420	420	347	480	415
Index of refraction (at λem)	1.85	2.15	1.82	1.8	1.94	2.25	1.85
Radiation hardness (gray)	106	102-3	105	104	104	103	10
Hygroscopicity	no	no	no	no	no	no	Strong
Melting point (°C)	1950	1050	2050	1980	1850	1300	651

Application

• Gamma-ray and X-ray detectors such as PET, well logging and high energy physics.

GSO Single Crystal	Crystal growth furnace for GSO

GSO Single Crystal for PET

About PET

A PET, which can find out a small cancer with a few mm, is a new diagnostic imaging technique different from traditional diagnostic techniques, such as X-ray CT (X-ray transmission computed tomography) and MRI (magnetic resonance imaging).
Mechanism of the PET is based on a principle that the cancer consumes sugars as many times more than normal tissues. Compounds of specific sugar are labeled with positron-emitting tracer and are injected into the patient. These tracers collect to the cancers while emitting positrons. The positron will then combine with an electron from surroundings and convert to two gamma-rays flying off at 180 degrees from each other.
An array of radiation detectors is located around the human body as a cylinder in the PET equipment for detecting these gamma-rays. We can assume that the tracer is on a line connecting the centers of the two detectors detecting each of gamma-ray in coincidence. Lines of response connecting the coincidence detectors detecting gamma-rays come from numbers of tracers distributed in the human body and are used in the image reconstruction.

Function of GSO single crystal

In the PET, scintillation crystals are used for the radiation detectors. The scintillation detector consists of a scintillating material which emits photons following interaction with ionizing radiation such as gamma-ray. The photons are detected by one or more photomultiplier tubes (PMT). A Ce-doped Gd₂SiO₅ single crystal (GSO) is an excellent scintillator material applied for the detectors in the PET.
There are some single crystal scintillators that have been used in PET applications including Bi₄Ge₃O₁₂ (BGO) and Ce-doped Lu₂SiO₅ (LSO). GSO single crystal scintillators made by Hitachi Chemical have superior energy resolution, fast decay time and large light output for gamma-ray detection and meet the requirements of fast and high sensitivity PET.

PET equipment	Principle of PET	GSO single crystal scintillators