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1 ROT-SLIT Padova - Genova collaboration PINHOLE SCINTIGRAPHY WITH ROTATING SLIT.

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Presentazione sul tema: "1 ROT-SLIT Padova - Genova collaboration PINHOLE SCINTIGRAPHY WITH ROTATING SLIT."— Transcript della presentazione:

1 1 ROT-SLIT Padova - Genova collaboration PINHOLE SCINTIGRAPHY WITH ROTATING SLIT

2 2 PARALLEL HOLE SCINTIGRAPHY Poor spatial resolution Steady sensitivity Parallel hole lead collimator Scintillator Gamma source

3 3 Pinhole collimator Magnification Improved sensitivity Parallax error Gamma source PINHOLE SCINTIGRAPHY Scintillator Trade-off spatial resolution vs sensitivity

4 4 Scintillating fiber bundle Rotating-slit collimator Gamma source ICCD readout ROTATING SLIT SCINTIGRAPH SET-UP

5 5 1 BACK-PROJECTION IMAGING 2 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 BACK-PROJECTED IMAGE [b(r)] first scan second scan third scan fourth scan

6 6 SPURIOUS REJECTION  [f*(r)] =  [b(r)]/  [(1/r)] f(r) 1/r b(r) f*(r)=  [f*(r)] (convolution) (Fourier transform) Virtual impulse response Real image with random spurious in space and time Repetitive gamma source Back-projected image

7 7 20 mm 50 mm L= 70 mm 70 mm 25 mm Effective pinhole width = 1 mm Detector resolution (mm) SPATIAL RESOLUTION (L= 70 mm) Source diameter 50 mm Source diameter 25 mm – – – – – 2.9 Side-view of one-dimensional imaging (parallax-error rejection)

8 8 CCD FOV (70 mm diameter) Image intensifier (25 mm diameter) Fiber optics guide FOV (140 mm diameter) SCINTILLATING FIBER- PLATE READ-OUT

9 9 MONTECARLO TEST (minimum FOV) 2 mm diameter sources one projection zero spurious gammas / projection projections - 1 mm width slit

10 10 2 mm diameter sources one projection Spurious rejection capability (minimum FOV) spurious gammas / projection projections - 1 mm width slit

11 11 gamma source fiber bundle slit ICCD camera Scintigraph-prototipe set-up

12 mm slit 2 mm thick lead 1mm diameter two holes scintillating fiber bundle EXPERIMENTAL SET-UP rotating system gamma source 18 mm internal diameter of 1mm tick glass vessel holes- gamma source asymmetry

13 13 UNCLADDED SSV FIBER BUNDLES WITH EXTRAMURAL ABSORBER (EMA) without EMA strips of EMA statistical EMA with dark fibers loss of transmission due to air bubbles within the fibers

14 14 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 % (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 Scintillating fibers without cladding (0.5 mm diameter, 105 mm length) Strips of EMA (dark plastic 120 µm thick)

15 15 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%

16 16 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 = Refractive index of the cladding glass = 1.48

17 17 Gamma image of two 1 mm diameter holes ( 4 projections - SSV bundle – minimum FOV) 4 mm 6 mm

18 18 One side-view (with spurious) of the two-hole gamma image by SSV fiber-bundle (exposure time 1s)

19 19 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

20 20 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

21 21 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)

22 22 SSV bundle irradiated uniformly by a 137 Cs source (see the irregular response of the fibers due to the presence of micro-bubbles)

23 23 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

24 24 FIBER- DRAWING EQUIPMENT (without crucible)

25 25 Milestones –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.

26 26 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

27 27 ROT-SLIT (Padova – Genova collaboration) Piano finanziario globale di spesa (k€) interno consumo Totale Richiesta all’O.M. della Sezione di Padova: 2 mesi / uomo

28 28 arXiv.orgarXiv.org > physics > arXiv: physics Rotating-slit scintigraphy using scintillating glass fibers: First results Authors: P. Ottonello, P. Pavan, G. Rottigni, G. Zanella, R. Zannoni P. OttonelloP. PavanG. RottigniG. ZanellaR. 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: v1arXiv: v1 [physics.ins-det] (Submitted to NIM A)


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