Compton imaging with liquid xenon and 44SC: recent progress toward 3 gamma imaging

Abstract

BACKGROUND: Subatech has initiated research works in view of
qualifying a new medical imaging technique, thanks to the presence
of the Arronax cyclotron, which is located in the outskirts of
Nantes, France. This new technique is called 3g imaging.

MATERIAL AND METHODS: The main idea is to detect the three
g-rays emitted indirectly or directly by specified radionuclide
(Sc44) and reconstruct its position in three-dimension in real
time, with a spatial resolution around one centimeter. To make
a g-ray detector with high sensitivity, good spatial resolution and
homogeneous volume, ultra-pure liquid xenon is a good choice
to be selected as a detector media due to its excellent properties
for particle detection (liquid, high atomic number, high density,
high stopping power).

RESULTS: XEMIS (Xenon Medical Imaging System), which is
a prototype of high sensitive liquid xenon Compton telescope,
is used to demonstrate this 3 g imaging. With an ultra-low noise
front-end electronics operating at liquid xenon temperature
(around 100 electrons NEC) and a fast UV sensitive PMT, high
spatial resolution in three-dimension and high energy resolution
are achievable. This is particularly important for Compton imaging since all interactions in the medium have to be identified to
reconstruct the direction of incident g-ray.
A prototype with an active area of 1’’x1’’ is now in test at Subatech
and shows promising results with a 511keV source from
22Na. All the cryogenic system is fully operational with a high
purification rate and shows a very good stability.