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ROT-SLIT

ROT-SLIT. Padova - Genova collaboration. PINHOLE SCINTIGRAPHY WITH ROTATING SLIT. PARALLEL HOLE SCINTIGRAPHY. Gamma source. Poor spatial resolution Steady sensitivity. Parallel hole lead collimator. Scintillator. Gamma source. PINHOLE SCINTIGRAPHY. Improved sensitivity.

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ROT-SLIT

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

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

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

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

  5. BACK-PROJECTION IMAGING 4 2 1 • Rejected gamma ray • Detected brackground gamma ray • Detected gamma ray • Compton scattered gamma ray • Compton scattered gamma ray in the detector 3 5 first scan BACK-PROJECTED IMAGE[b(r)] second scan third scan fourth scan

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

  7. 50 mm 20 mm 70 mm SPATIAL RESOLUTION (L= 70 mm) Detector resolution (mm) 0.5 1 2 Source diameter 50 mm 1.36 – 2.1 1.4 – 2.3 1.5 – 2.9 Source diameter 25 mm 1.18 - 1.5 1.2 – 1.6 1.23 – 1.8 Side-view of one-dimensional imaging (parallax-error rejection) 50 mm 25 mm 25 mm Effective pinhole width = 1 mm L= 70 mm

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

  9. MONTECARLO TEST (minimum FOV) one projection 2 mm diameter sources zero spurious - 1000 gammas / projection - 100 projections - 1 mm widthslit

  10. Spurious rejection capability (minimum FOV) 2 mm diameter sources one projection 10000 spurious - 1000 gammas / projection - 100 projections - 1 mm width slit

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

  12. EXPERIMENTAL SET-UP 18 mm internal diameter of 1mm tick glass vessel gamma source rotating system 1mm diameter two holes 2 mm thick lead 20 25 20 scintillating fiber bundle 1 mm slit holes- gamma source asymmetry

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

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

  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. 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

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

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

  19. 4 mm 6 mm Gamma image of two 1 mm-diameter holes (SSV bundle - 36 projections - 1s exposure/projection - minimum FOV – evidence of spurious rejection)

  20. 4 mm 6 mm Thresholded gamma image of two 1 mm-diameter holes (SSV bundle - 36 projections - 1s exposure/projection - minimum FOV – evidence of spurious rejection)

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

  23. Sistema di sostegno, avanzamento e rotazione della bacchetta di vetro (~ 10 giri/min) Bacchetta iniziale di vetro (diametro 6-12 mm) Alimentazione automatica del forno tramite termocoppia Isolamento del forno in fibra ceramica Fornovisto dall’alto Forno elettrico (crogiolo di platino) Bacchetta stirata Rulli in gomma dura per la tiratura della fibra. La velocità di tiratura dipende dal diametro della fibra Rulli vistI dall’alto

  24. FIBER- DRAWING EQUIPMENT (without crucible)

  25. 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 delleimmagini. • 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. Composizione del gruppo Padova: P.Pavan (50%) , G.Zanella (100%) responsabile nazionale e locale, R.Zannoni (100%). Genova: G.Rottigni (100%) responsabile locale P.Ottonello (30%)

  27. ROT-SLIT (Padova – Genova collaboration) Piano finanziario globale di spesa (k€) interno Totale consumo 6.00 7.00 13.00 2011 13.00 7.00 2012 6.00 Richiesta all’O.M. della Sezione di Padova: 2 mesi / uomo

  28. 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. (Submitted to NIM A)

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