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ROT-SLIT

Padova - Genova collaboration

PINHOLE SCINTIGRAPHY WITH ROTATING SLIT

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PARALLEL HOLE SCINTIGRAPHY

Poor spatial resolutionSteady sensitivity

Parallel hole lead collimator

Scintillator

Gamma source

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Pinhole collimator

Magnification

Improved sensitivity

Parallax error

Gamma source PINHOLE

SCINTIGRAPHY

Scintillator

Trade-off spatial resolution vs sensitivity

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Scintillating fiber bundle

Rotating-slit collimator

Gamma source

ICCD readout

ROTATING SLIT SCINTIGRAPHSET-UP

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BACK-PROJECTION IMAGING

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1. Rejected gamma ray

2. Detected brackground gamma ray

3. Detected gamma ray

4. Compton scattered gamma ray

5. Compton scattered gamma ray in the detector

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4

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BACK-PROJECTED IMAGE

[b(r)]first scan

second scan

third scan

fourth scan

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SPURIOUS REJECTION

[f*(r)] = [b(r)]/[(1/r)]

f(r) 1/r b(r)

f*(r)= [f*(r)] -1

(convolution)

(Fourier transform)

Virtual impulse response

Real image with random spurious in

space and time

Repetitive gamma source

Back-projected image

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20 mm

50 mm

50 mm

L= 70 mm

70 mm

25 mm

25 mm

Effective pinhole width = 1 mm

Detector resolution (mm)

SPATIAL RESOLUTION (L= 70 mm) 0.5 1 2

Source diameter 50 mm

Source diameter 25 mm 1.18 - 1.5 1.2 – 1.6 1.23 – 1.8

1.36 – 2.1 1.4 – 2.3 1.5 – 2.9

Side-view of one-dimensional imaging (parallax-error rejection)

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CCD

FOV (70 mm diameter)

Image intensifier(25 mm diameter)

Fiber optics guide

FOV (140 mm diameter)

SCINTILLATING FIBER-PLATE READ-OUT

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MONTECARLO TEST(minimum FOV)

2 mm diameter sources one projection

zero spurious - 1000 gammas / projection - 100 projections -

1 mm width slit

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2 mm diameter sources one projection

Spurious rejection capability(minimum FOV)

10000 spurious - 1000 gammas / projection - 100 projections -1 mm width slit

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gammasource

fiberbundle

slit

ICCD camera

Scintigraph-prototipe set-up

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20

25

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1 mm slit

2 mm thick lead

1mm diameter two holes

scintillating fiber bundle

EXPERIMENTAL SET-UP

rotating systemgamma source

18 mm internal diameter of 1mm tick glass vessel

holes- gamma source asymmetry

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UNCLADDED SSV FIBER BUNDLES WITH EXTRAMURAL ABSORBER (EMA)

without EMAstrips of EMA statistical EMAwith dark fibers

loss of transmission due to air bubbles within the fibers

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SSV scintillating glass fiber bundle

The fibers are manufactured by SSV (Stazione Sperimentale del Vetro – Murano) using a silicate, terbium doped, barium charged, LKH-6 scintillating glass (effective atomic number 30, maximum of emission 550 nm, decay time = 3÷5 ms, light yield 40 ph/keV, refraction index 1.59).

SSV fiber-bundle vs Collimated Holes fiber-bundle

Fibers with air cladding improve the collection efficiency of the scintillating light, in one direction, from 3.46 % to 18.55 % (1: 5.36) [1].

[1] A. Bertuola, Il ruolo del campo evanescente in strutture di fibre ottiche scintillanti per la rivelazione di immagini di radiazioni, Tesi di laurea in fisica (relatori: G. Zanella, R. Zannoni) Università di Padova -

2004.

Scintillating fiberswithout cladding(0.5 mm diameter, 105 mm length)

Strips of EMA(dark plastic 120 µm thick)

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Side-view of two-hole gamma image by SSV fiber-bundle (exposure time 5 s)

SSV fiber-bundle actually improves the collection efficiency,vs the Collimated Holes bundle, of

3.3 ± 10%

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Sideview of two-hole gamma image by Collimated Holes fiber-bundle (same exposure of previous SSV bundle)

Collimated Holes LKH–6 scintillating glass fiber bundle

- Fiber stack geometry = Hexagonal - Core diameter = 10 μm- Cladding diameter = 10.7 μm- 1 EMA fiber every 11 normal- Fiber lenght = 120 mm- Refractive index of the core glass = 1.59- Refractive index of the cladding glass = 1.48

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Gamma image of two 1 mm diameter holes( 4 projections - SSV bundle – minimum FOV)

4 mm

6 mm

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One side-view (with spurious) of the two-hole gamma image by SSV fiber-bundle (exposure time 1s)

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6 mm

Gamma image of two 1 mm-diameter holes(SSV bundle - 36 projections - 1s exposure/projection - minimum

FOV – evidence of spurious rejection)

4 mm

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Thresholded gamma image of two 1 mm-diameter holes(SSV bundle - 36 projections - 1s exposure/projection - minimum FOV –

evidence of spurious rejection)

6 mm

4 mm

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Gamma image (without spurious) of the two 1 mm-diameter holes using the parallel-hole scintimammograph MAMMOCAM 1000

(lead collimator depth = 35 mm, hole diameter = 1.8 mm, pixellated CI(Tl), pixel size 2x2 mm, PSPMT read-out, 36s exposure time)

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SSV bundle irradiated uniformly by a 137 Cs source(see the irregular response of the fibers due to the presence of

micro-bubbles)

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Rulli in gomma dura per la tiratura della fibra.

La velocità di tiratura dipende dal diametro della fibra

Fiber-drawing system set-up

(Design Staz. Sper. Vetro – Murano)

Sistema di sostegno, avanzamento e rotazione della bacchetta di vetro (~ 10 giri/min)

Bacchetta iniziale di vetro (diametro 6-12 mm)

Forno elettrico (crogiolo di platino)

Forno visto dall’alto

Isolamento del forno in fibra ceramica

Rulli vistI dall’alto

Alimentazione automatica del forno tramite termocoppia

Bacchetta stirata

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FIBER- DRAWING EQUIPMENT

(without crucible)

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Milestones 2011-2012

– GENNAIO-GIUGNO 2011: Progetto di un prototipo di scintigrafo "rotating slit" con movimentazione automatica. Completamento e test dell'attrezzatura per il tiraggio da "pre-form" delle fibre di vetro scintillante. Sviluppo software di simulazione ricostruzione tomografica delle immagini.

– LUGLIO-DICEMBRE 2011: Test di tiraggio delle fibre da "pre-form". Test scintigrafici con le nuove fibre. Progetto e parziale costruzione di un prototipo di scintigrafo "rotating-slit" automatico. Sviluppo di software di ricostruzione delle immagini.

– GENNAIO-GIUGNO 2012: Realizzazione del prototipo definitivo di scintigrafo automatico e sua caratterizzazione rispetto a scintigrafi tradizionali.

– LUGLIO-DICEMBRE 2012: Sperimentazione con fantocci e "in vivo". Confronto con scintigrafi tradizionali. Analisi per applicazioni astrofisiche.

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Padova: P.Pavan (50%) , G.Zanella (100%) responsabile nazionale e locale,

R.Zannoni (100%). Genova: G.Rottigni (100%) responsabile locale P.Ottonello (30%)

Composizione del gruppo

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ROT-SLIT (Padova – Genova collaboration)

Piano finanziario globale di spesa (k€)

2011

2012

interno consumo Totale

6.00

6.00

7.00

7.00

13.00

13.00

Richiesta all’O.M. della Sezione di Padova: 2 mesi / uomo

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arXiv.org > physics > arXiv:1004.3681

Rotating-slit scintigraphy using scintillating glass fibers: First results

Authors: P. Ottonello, P. Pavan, G. Rottigni, G. Zanella, R. Zannoni

(Submitted on 21 Apr 2010)

Abstract: In this paper we propose to perform the scintigraphy of small organ using a rotating-slit collimator and a bundle of scintillating glass fibers, put in parallel with the slit and rotating with it. An intensified CCD, coupled to the end of the fibers, acquires an integrated image of the events per each rotation angle. The final image is computed by a back-projection procedure. The advantages of this method, with respect to conventional scintigraphy, are the improvement of the detection efficiency of one-two order of magnitude without counting rate limitations, the improvement of the spatial resolution, the elimination of the parallax error and the rejection of the spurious events, without energy analysis. Simulations and first experimental results are showed.

(19 pages, 15 figures)

Subjects: Instrumentation and Detectors (physics.ins-det)

Cite as: arXiv:1004.3681v1 [physics.ins-det]

(Submitted to NIM A)