Molecular Breast Imaging – state of art of design, analysis and optimization processes in industrial context F. Cirillo 1, F. Garibaldi 2,3, S. Gioia 1, G. Peretta 1, A. Fabbri 4, F. de Angelis 1 and L. Perez Metaltronica SpA (Italy) 2 - Istituto Superiore di Sanità (Italy) 3 - Istituto Nazionale di Fisica Nucleare, Sezione di Roma (Italy) 4 - Università degli Studi Roma Tre (Italy) 5 th September 2014

Molecolar Breast Imaging Molecular Breast Imaging (MBI) is a new FDA cleared technology and is emerging as a critical tool in the fight against breast disease. Dilon 6800 Acella Gamma Medica Lumagem 3200s The inadequacy of breast compression and the inability to position the detector close to the breast considerably degrade image quality and limit the detection of small lesions. Molecolar Breast Imaging

Our Design and Modality

Collimator In order to get the needed, sub-millimetric, spatial resolution, pinhole collimators have to be used. The aperture has to be small (2 mm). It will be a compromise between spatial resolution and detection efficiency, according to the specific application. The source can be placed close to the hole; so reasonable counting rates can be obtained, comparable to what one can get with other collimators. Segmented scintillators coupled to segmented photo detectors, with parallel collimators are used in this phase. At equal distance of the source, Resolution is better for a collimator with smaller holes and septa longer Resolution is not stationary: it depends on distance from the source Efficiency independent of distance from the source The thickness of the septa may be decided once established the condition of penetration acceptable, ie the level of penetration of the photons that is considered acceptable (5%) Collimator

In order to maintain a good spatial resolution along the process of conversion of the gamma-ray photon into optical photons, we intend to use a matrix of segmented scintillators properly sealed on the backside of the detector The systems presently use NaI(Tl) scintillators arrays coupled to MPPS for large detector. NaI(Tl), being igroscopic has to be encapsulated into glass (light pool enlargement and partial absorption). It can be produced with pixel size as low as 1.25 x 1.25 mm2 (1.5 mm pitch). For spot compressor LaBr3(Ce) is used. The use of crystals of LaBr3(Ce) allows to go below the millimetric resolution with crystal of 5 mm thickness, obtaining also a considerable improvement in energy resolution. Continuous scintillator and centroid reconstruction can be considered. Very thin scintillators have to be used for this to do not reduce the spatial resolution (light pool enlargement) Scintillators Continuous scintillatorPixellated scintillator

Detector The MPPC is a new type of photon counting device made up of multiple APD (avalanche photodiode) pixels operated in Geiger mode and available in room temperature operation. The MPPC is essentially an opto-semiconductor device with excellent photon counting capability and which also possesses great advantages such as low voltage operation and insensitivity to magnetic fields. TSV MPPC array is a COB (Chip on board) type MPPC array with a 3x3mm2 effective photosensitive, using the TSV (Through Silicon Via) technology. There is no wire bonding, so the package outline is very close to the MPPC array. The outer gap from active area edge to package edge is only 0.2mm. This package realizes the 4- side buttable arrangement. Detector The choice of the 16x16 detector allows: better coupling with the scintillator a reduction of the dead zone a greater sensitive area

Wire bonding for Front End board equipped with MAROC3 Detector Assembly Thickness ~ 20 mm Low process temperature High level of dependability Saves space High degree of design flexibility Ideal repair option Versatile substrate- component combination Simplification of complex circuits

Setup 1: - Hamamatsu photomultiplier tubes in 8 x 8 channels - Electronics Maroc3 + FPGA - Source Cobalt (57C) - Optical compound Saint Gobain - Pin-hole collimator with a hole diameter of 5 mm - Duration of test 10 minutes Result: Energy resolution over the area REt = 18% Energy resolution resp single pixel REsp = 14-15% Dedicated Electronics Commercial Electronics Setup 2: - Hamamatsu photomultiplier tubes in 8 x 8 channels - Commercial Electronics - Source Cobalt (57C) - Optical compound Saint Gobain - Pin-hole collimator with a hole diameter of 5 mm - Duration of test 10 minutes Result: Energy resolution over the area REt = 15% Energy resolution single pixel REsp = % Preliminary Test with dedicated electronics

with the dedicated electronics and mechanics, still under evaluation, it may be possible to integrate the system MBI with the unit for digital mammography and / or tomosynthesis, in order to merge metabolic information with anatomic lesions detected