Speaker
Dr
Nicola Belcari
(Department of Physics, University of Pisa)
Description
Objectives: The YAP-(S)PET is the only small animal scanner that combines the PET and
SPECT techniques on a single gantry. It is made up of four detector heads: each one
is composed of a 4 cm × 4 cm YAP:Ce matrix of 20 × 20 elements, 2 mm × 2 mm × 25 mm
each, coupled to a PS-PMT.
Due to the relatively large solid angle subtended by each crystal matrix the system
is subject to an appreciable pile-up probability. In order to improve the count rate
capabilities, a completely new and faster readout electronics has been installed. The
new electronics offers a reduced system dead time leading to a maximum acquisition
rate ten times higher than the previous one. The new circuitry also includes a
proprietary pile-up rejecting technique.
In this work we present the performance evaluation in terms of absolute sensitivity,
spatial resolution and count rate capability, both in PET and SPECT modalities, of
this new version of the scanner which is installed at the CNR-IFC in Pisa (Italy)
within the framework of the Center of Excellence AmbiSEN of the University of Pisa.
Methods: In PET mode a 22Na point source (1 mm Ø) was positioned at CFOV and moved
radially with 0 mm, 5 mm, 10 mm offset. For each position, the radial, transaxial and
axial FWHM and FWTM are measured. The exact methodology for measuring the scatter
fraction and count rate performance (NEC) in small animal PET scanners is still an
open question. The PET performance assessment described here are then based on the
preliminary standards proposed by the small animal PET NEMA task force.
The scatter fraction and NEC curve were evaluated using a mouse-like phantom filled
with a known quantity of activity of a 18F solution. The PET system sensitivity is
measured with a linear source placed inside a metal tubes. The measure is repeated
five times with increasing wall thickness.
The effectiveness of the new pile-up rejection technique has been evaluated by
comparing the uniformity of the reconstructed images of an uniform phantom, at
various count rates, with and without the pile-up rejection capability.
In SPECT mode a glass capillary filled with 99mTc solution was used for the
evaluation of both spatial resolution in the transaxial plane and sensitivity.
Images of a mini Derenzo phantom, with hot rods down to 1.2 mm diameter, and of the
NEMA PET image quality phantom will be presented for both PET and SPECT modalities.
Animal imaging: A new model of Parkinson disease has recently been developed on the
EnHT mice. To confirm and extend the previous analysis on the EnHT mice as a new
model for
Parkinson’s disease we evaluated the binding of DatSCAN as indicator of integrity of
dopaminergic system in asintomatic EnHT mice. SPECT image was collected 4 hours after
tail-vein injection of about 80 MBq of 123I-FP-CIT. Images was reconstructed with EM
using a dedicated procedure for 123I.
Authors
Prof.
Alberto Del Guerra
(Department of Physics, University of Pisa)
Dr
Antonietta Bartoli
(Department of Physics, University of Pisa)
Dr
Nicola Belcari
(Department of Physics, University of Pisa)
Co-authors
Prof.
Giovanni Umberto Corsini
(Department of Neuroscience, University of Pisa, Pisa, Italy)
Prof.
Giuliano Mariani
(Department of Neuroscience, University of Pisa, Pisa, Italy)
Dr
Luca Menichetti
(IFC-CNR, Pisa, Italy)
Dr
Michela Lecchi
(Ospedale S. Raffaele, Milano, Italy)
Dr
Paola Anna Erba
(Department of Neuroscience, University of Pisa, Pisa, Italy)
Dr
Paola Sgadò
(Department of Neuroscience, University of Pisa, Pisa, Italy)
