Speaker
Dr
Raffaele Scafè
(Casaccia Research Center, ENEA, Rome, Italy)
Description
This paper is aimed to describe a sub-miniature scintillation detector suitable for
functional inspection of bronchi inside a bronchoscope. The device is made by a
probe having diameter adequate for insertion in a bronchial catheter and an
external electronics for signal’s analysis. The probe is composed of a
scintillation crystal for high-efficiency photon detection and a Si-avalanche
photodiode for high quantum-efficiency scintillation readout. The device can be
adequately shielded to select a field of view reducing the background and operates
in single-photon mode giving the possibility of good energy discrimination.
The localization technique takes mainly advantage (i) from the inverse dependence
of crystal efficiency on the square of crystal-to-radiation source distance, (ii)
the lesion-to-background uptake ratio and (iii) from the exponential absorption of
radiation coming from distant locations, eventually reduced by additional selective
shielding.
Furthermore, the pulmonary environment is characterized, with respect to the
surrounding organs, by a reduced specific density of tissues (about 0.7 g cm-3 at
maximum expiration and about 0.3 g cm-3 at maximum inspiration). This produces an
advantage in terms of lesion visibility due to high lesion-to-background ratio.
A somatostatin-analogue depreotide, labelled with 99mTc, is currently used for
detection and characterization of pulmonary nodule that means 140keV single photons
have to be detected.
Previous measurements concerning a laboratory setup made by a 57Co point-source and
a 2.85x2.85x5.00mm3 CsI:Tl scintillator have been made at different distances.
Furthermore, the limits of the technique have been assessed by Monte Carlo
simulations. The considered geometry, reproducing a very severe clinical situation,
consisted of a duct positioned at the centre of a homogeneous cylindrical
background-source (40cm diameter, 30cm height) adjacent to a homogeneous lesion-
source 0.2cm diameter. Results gave a very small lesion to background factor which
has to be enhanced 103 times to obtain a good detectability.
New Monte Carlo cases are presented concerning pulmonary configurations and nodule
diameter in the range from 1cm to 4cm. Si-avalanche photodiodes with reduced
peripheral dead zones customized by Hamamatsu are used for new measurements with
phantoms simulating clinical conditions. Experimental results are compared with
simulated data.
Author
Dr
Raffaele Scafè
(Casaccia Research Center, ENEA, Rome, Italy)
Co-authors
Dr
Dario Della Sala
(Casaccia Research Center, ENEA, Rome, Italy)
Dr
Fabrizio Pisacane
(Casaccia Research Center, ENEA, Rome, Italy)
Dr
Giorgia Iurlaro
(Casaccia Research Center, ENEA, Rome, Italy)
Dr
Giuseppe Alonge
(Portici Research Center, ENEA, Portici, Naples, Italy)
Dr
Giuseppe De Vincentis
(Dept of Radiological Sciences, University of Rome “La Sapienza”, Rome, Italy)
Dr
Livia Montani
(Casaccia Research Center, ENEA, Rome, Italy)
Prof.
Roberto Pani
(Dept of Experimental Medicine, University of Rome “La Sapienza”, Rome, Italy)
Dr
Rosanna Pellegrini
(Dept of Experimental Medicine, University of Rome “La Sapienza”, Rome, Italy)
