A poster has been presented at 2016 IEEE Nuclear Science Symposium and Medical Imaging Conference

1. Comparison of columnar and pixelated scintillators for small field of
view hybrid gamma camera imaging
1 Space Research Centre, University of Leicester, Leicester, LE1 7RH, UK
2 Imaging Clinical Group, Sandwell and West Birmingham NHS Hospital Trust, West Bromwich B71 4HJ, UK
3 Radiological and Imaging Sciences, Medical Physics and Clinical Engineering, Medical School, University of Nottingham and Nottingham University Hospitals NHS Trust, NG7 2UH, UK
INTRODUCTION
In intraoperative medical imaging, the
development of small field of view (SFOV)
hybrid gamma cameras is considered an
expanding area of research. A new innovation
combining both gamma and optical imaging in
a co-aligned configuration, the Hybrid Gamma
Camera (HGC), could provide intraoperative
imaging with superior spatial resolution and
may enhance the physical localisation of
radiopharmaceutical uptake during critical
surgical procedures such as in head and neck
sentinel node biopsies [1].
The aim of this study was to compare the
performance characteristics of the HGC with
either a thallium doped caesium iodide (CsI:TI)
columnar scintillator or a pixelated gadolinium
oxysulfide (GOS) ceramic scintillator installed.
MATERIALS AND
METHODS
The hybrid gamma camera (HGC) consists of
an electron multiplying CCD coupled to a
1500µm thick scintillator (in this study both
CsI:TI and GOS scintillators were used). A fused
gamma optical image is achieved using a
tungsten pinhole collimator co-aligned with a
mirror and optical camera.
A performance characterisation of the HGC has
been evaluated using a columnar CsI:TI and a
pixelated gadolinium oxysulfide GOS ceramic
scintillator. Characteristics investigated include
spatial resolution (both intrinsic and extrinsic),
intrinsic uniformity, sensitivity (both intrinsic
and extrinsic) and count rate capability [2].
DISCUSSION
In this study, the characterisation of
the HGC has been evaluated and
compared. The results in table 1
indicate that the HGC has
significantly better spatial resolution
when using CsI:TI columnar
scintillator. However, the HGC is
more sensitive when using
pixelated GOS scintillator but with a
poorer spatial resolution and count
rate capability.
CONCLUSION
The choice of material and its
structure are key parameters when
deciding which scintillator to use
for particular imaging applications.
For the current application of the
HGC where spatial resolution is a
priority CsI:TI has significant
advantages over the evaluated
GOS scintillator.
Reference
[1] J E Lees, S L Bugby, B S Bhatia, L K Jambi, M S Alqahtani, W R McKnight, A H Ng and A C Perkins,
A small field of view camera for hybrid gamma and optical imaging, Journal of Instrumentation 9 (2014) C12020
[2] S L Bugby, L K Jambi and J E Lees,
A comparison of CsI:TI and GOS in a scintillator-CCD detector for nuclear medicine imaging , Journal of Instrumentation 11(2016) P09009
Figure 2. Scanning electron microscope images of: GOS scintillator (top) each
pixel is 400µm x 400µm, with an individual pixels separated by a 40µm wide
boundary material coated with TiO2 and CsI:TI scintillator (bottom) tightly
packed columns with approximately 1µm diameter.
Figure 1. Schematic of Hybrid Gamma Camera
HGC.
Contact:
Lj97@le.ac.uk
The performance characteristics of the HGC fitted with each scintillator are summarised in table 1
RESULTS
SCINTILLATOR STURUCTURE
Table 1. Performance characteristics for HGC with either 1500 µm thick CsI:TI or 1500 µm thick GOS scintillator
installed.
Parameters CsI:TI GOS
Intrinsic spatial resolution FWHM 230 ± 25 µm 1090 ± 200 µm
FWHM
(no scattering material)
1.8 ± 0.027 mm 1.97 ± 0.34 mm
FWHM
(including scattering material)
2.02 ± 0.09 mm 2.13 ± 0.46 mm
Intrinsic uniformity Co-efficient of variation 20 ± 15 % 17 ± 9 %
Intrinsic sensitivity At 140.5 keV 40 ± 3 % 54 ± 4 %
At 50 mm
(no scattering material)
6.6 ± 0.5 cps/MBq 18.5 ± 0.3 cps/MBq
At 50 mm
(including scattering material)
3.3 ± 0.5 cps/MBq 8.1 ± 0.3 cps/MBq
Count rate capability Maximum recorded count rate 35700 ± 200 cps 3170 ± 30 cps
L.K. Jambi1, J.E. Lees1, S.L. Bugby1, M.S. Alqahtani1, B.S. Bhatia1,2,
W.R. McKnight1, N.S. Dawood1 , A.H. Ng3 and A.C. Perkins3
Extrinsic spatial resolution
Extrinsic sensitivity