Author Correction: Proton range verification with MACACO II Compton camera enhanced by a neural network for event selection (vol 11, 23903, 2021)

The applicability extent of hadron therapy for tumor treatment is currently limited by the lack of reliable online monitoring techniques. An active topic of investigation is the research of monitoring systems based on the detection of secondary radiation produced during treatment. MACACO, a multi-layer Compton camera based on LaBr3 scintillator crystals and SiPMs, is being developed at IFIC-Valencia for this purpose. This work reports the results obtained from measurements of a 150 MeV proton beam impinging on a PMMA target. A neural network trained on Monte Carlo simulations is used for event selection, increasing the signal to background ratio before image reconstruction. Images of the measured prompt gamma distributions are reconstructed by means of a spectral reconstruction code, through which the 4.439 MeV spectral line is resolved. Images of the emission distribution at this energy are reconstructed, allowing calculation of the distal fall-off and identification of target displacements of 3 mm

Advanced radiation measurement techniques in diagnostic radiology and molecular imaging.

This paper reports some technological advances recently achieved in the fields of micro-CT and small animal PET instrumentation. It highlights a balance between image-quality improvement and dose reduction. Most of the recent accomplishments in these fields are due to the use of novel imaging sensors such as CMOS-based X-ray detectors and silicon photomultipliers (SiPM). Some of the research projects carried out at the University of Pisa for the development of such advanced radiation imaging technology are also described

Performance evaluation of a very high resolution small animal PET imager using silicon scatter detectors

A very high resolution positron emission tomography (PET) scanner for small animal imaging based on the idea of inserting a ring of high-granularity solid-state detectors into a conventional PET scanner is under investigation. A particularly interesting configuration of this concept, which takes the form of a degenerate Compton camera, is shown capable of providing sub-millimeter resolution with good sensitivity. We present a Compton PET system and estimate its performance using a proof-of-concept prototype. A prototype single-slice imaging instrument was constructed with two silicon detectors 1 mm thick, each having 512 1.4 mm × 1.4 mm pads arranged in a 32 × 16 array. The silicon detectors were located edgewise on opposite sides and flanked by two non-position sensitive BGO detectors. The scanner performance was measured for its sensitivity, energy, timing, spatial resolution and resolution uniformity. Using the experimental scanner, energy resolution for the silicon detectors is 1%. However, system energy resolution is dominated by the 23% FWHM BGO resolution. Timing resolution for silicon is 82.1 ns FWHM due to time-walk in trigger devices. Using the scattered photons, time resolution between the BGO detectors is 19.4 ns FWHM. Image resolution of 980 µm FWHM at the center of the field-of-view (FOV) is obtained from a 1D profile of a 0.254 mm diameter 18F line source image reconstructed using the conventional 2D filtered back-projection (FBP). The 0.4 mm gap between two line sources is resolved in the image reconstructed with both FBP and the maximum likelihood expectation maximization (ML-EM) algorithm. The experimental instrument demonstrates sub-millimeter resolution. A prototype having sensitivity high enough for initial small animal images can be used for in vivo studies of small animal models of metabolism, molecular mechanism and the development of new radiotracers.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/58094/2/pmb7_10_012.pd

Dispositivo de adquisición de datos para dispositivos detectores de diferentes tipos

1. Dispositivo de adquisición de datos para dispositivos detectores de diferentes tipos, comprende: una primera placa auxiliar (P_AUX) que incluye: - un primer dispositivo detector (1), de un primer tipo; - una pluralidad de chips de lectura (2) operativamente conectada a dicho primer dispositivo detector (1) para adquirir dichos datos proporcionando una única señal de salida de los datos adquiridos; y - una unidad de conexión (5); y - una placa principal (P_PRIN) que incluye: - una unidad de control (14) adaptada para procesar datos; y - una unidad de conexión (10), para conexión de la placa principal (P_PRIN) con un dispositivo de computación remoto para transmitir a este último los datos procesados y recibir de él diferentes comandos, caracterizado porque el dispositivo comprende, además: - al menos una segunda placa auxiliar (P_AUX) que incluye: - un segundo dispositivo detector (1), de un segundo tipo, diferente del primer tipo; - una pluralidad de chips de lectura (2) operativamente conectada a dicho segundo dispositivo detector (1) para adquirir dichos datos proporcionando una única señal de salida de los datos adquiridos, y - una unidad de conexión (5), estando conectada al menos una de las placas auxiliares (P_AUX) a una placa intermedia (P_INT), conectada a su vez a la placa principal (P_PRIN), en donde dicha placa intermedia (P_INT), que es al menos una, incluye: - una primera unidad de conexión (6) configurada para recibir la señal única de salida de los datos adquiridos, de su placa auxiliar correspondiente; - una unidad de ajuste (7) configurada para adaptarla señal única de salida recibida a un protocolo de comunicación de la placa principal (P_PRIN); y - una segunda unidad de conexión (8) configurada para transmitir la señal adaptada a la placa principal (P_PRIN) y para recibir de esta última diferentes comandos; y porque - la placa principal (P_PRIN) incluye además un dispositivo de disparo (13) configurado para detectar cuando las señales únicas de salida de los datos adquiridos están disponibles, - la unidad de control (14) de la placa principal (P_PRIN) está adaptada para procesar las señales recibidas, de la placa intermedia (P_INT) y/o de una placa auxiliar (P_AUX), proporcionándoles además una etiqueta temporal y un identificador que permita distinguirlas.Peer reviewedConsejo Superior de Investigaciones Científicas (España), Universitat de València, Alibava Systems S.L.U Solicitud de modelo de utilida

A dedicated Gate versatile module for Compton camera imaging

International audienc

Recent Developments on Silicon Photomultipliers produced at FBK-irst

In this contribution, new developments on the silicon photomultipliers (SiPM) fabricated at FBK-irst (Trento, Italy) are reported. With respect to the first series of devices produced in 2005/2006, there have been major improvements on both the layout and the technology. Concerning the first aspect we fabricated SiPMs with increased fill factor and with different geometries (square/circular devices, arrays and matrices of SiPMs) to meet the requirements of different applications. Concerning the technology, we identified a process technique able to reduce significantly the dark count rate. In this paper we will describe the main electro-optical characteristics of these devices

Energy and Timing Resolution Studies With Silicon Photomultipliers (SiPMs) and 4-Pixel SiPM Matrices for PET

A high performance detector head with matrices of silicon photomultipliers (SiPMs) as photodetectors is under development at the University of Pisa and INFN Pisa. The silicon photomultipliers fabricated at FBK-irst (Trento, Italy) are being evaluated for this purpose. Single SiPM detectors of 1mm x 1 mm size and the first SiPM test matrices composed of four (2 x 2) pixel elements in a common substrate have been tested with LYSO crystals. The energy and timing resolution of single SiPMs have been evaluated, obtaining an energy resolution of 20% FWHM at 511 keV, and a coincidence timing resolution of 1.4 ns FWHM. In addition, the first tests performed with the SiPM matrices prove the feasibility of such devices

Performance of MACACO Compton telescope for ion-beam therapy monitoring: First test with proton beams

In order to exploit the advantages of ion-beam therapy in a clinical setting, delivery verification techniques are necessary to detect deviations from the planned treatment. Efforts are currently oriented towards the development of devices for real-time range monitoring. Among the different detector concepts proposed, Compton cameras are employed to detect prompt gammas and represent a valid candidate for real-time range verification. We present the first on-beam test of MACACO, a Compton telescope (multi-layer Compton camera) based on lanthanum bromide crystals and silicon photo-multipliers. The Compton telescope was first characterized through measurements and Monte Carlo simulations. The detector linearity was measured employing Na-22 and Am-Be sources, obtaining about 10% deviation from linearity at 3.44 MeV. A spectral image reconstruction algorithm was tested on synthetic data. Point-like sources emitting gamma rays with energy between 2 and 7 MeV were reconstructed with 3-5 mm resolution. The two-layer Compton telescope was employed to measure radiation emitted from a beam of 150 MeV protons impinging on a cylindrical PMMA target. Bragg-peak shifts were achieved via adjustment of the PMMA target location and the resulting measurements used during image reconstruction. Reconstructed Bragg peak profiles proved sufficient to observe peak-location differences within 10 mm demonstrating the potential of the MACACO Compton Telescope as a monitoring device for ion-beam therapy