Development and characterization of an innovative ASIC pixel detector for imaging based on chromatic photon counting technology

The purpose of this work is to characterize Pixirad (INFN spin-off) detector system, an innovative X-ray imaging sensor with intrinsic digital characteristics, based on Chromatic Photon Counting technology. The system counts individually the incident X-ray photons and selects them according to their energy to produce two color images per exposure. The energy selection occurs in real time and at radiographic imaging speed (GHz global counting rate). Photon counting, color mode and a very fine spatial resolution allow to obtain a high ratio between image quality and absorbed dose. The individual building block of the imaging system is a two-side buttable semiconductor radiation detector made of a thin pixellated CdTe crystal coupled to a Very Large Scale Integration (VLSI) CMOS pixel ASIC (Application Specific Integrated Circuits). The first chapter is devoted to introduce the basic processes of interaction of photons with matter. In the second chapter the most common radiographic metrics are described with an introduction to the imager systems. The third chapter focuses on the pixel detectors, describing the physical mechanism of charge collection involved in the CdTe sensor and explaining the principal components of the front-end electronic chain. In the fourth chapter the general features of Pixirad detector system are described. The chapter five is focused on the characterization of the Pixirad-1 detector system from the spectroscopic point of view: an energy calibration and resolution has been carried out using different X-ray sources and the charge sharing fraction has been evaluated by exploiting the monochromatic Elettra synchrotron beam. The aim of chapter six is the characterization of the imaging performance of the detector with monochromatic synchrotron radiation at different energies, investigating the linearity of the system, the ratio between detector counts and number of impinging photons, as a function of energy and discriminator thresholds, the pixel noise and the spatial resolution. In the chapter seven are showed some last measurements with PIXIE III: the third and last generation of Pixirad ASIC. In particular the full recovering of the charge sharing effect is demonstrated at 62 micron pixel pitch allowing the sharp spectral separation between the color images

Un metodo ibrido deterministico-stocastico per la soluzione dell'equazione del trasporto.

Lo scopo di questa tesi è quello di presentare il metodo ibrido stocastico-deterministico per la risoluzione dell'equazione del trasporto, sviluppato presso il Dipartimento d'Ingegneria Meccanica Nucleare e della Produzione dell'Università di Pisa. Nel primo capitolo si è descritto la teoria generale del trasporto neutronico soffermandosi in particolare sulle diverse formulazioni di questa: integro-differenziale, integrale e alle armoniche sferiche. L'obiettivo del secondo capitolo è di trasformare la soluzione esatta dell'equazione del trasporto, nelle sue varie forme trattate nel capitolo precedente, in formulazioni spendibili per la risoluzione numerica attraverso codici di calcolo. Si è cercato di descrivere quei metodi che discretizzano la dipendenza continua del flusso angolare che rappresenta, com'è noto, la direzione di moto dei neutroni. Per maggiore semplicità espositiva, si è scelto di trattare il caso mono-energetico stazionario che senza molte difficoltà può essere espanso a casi più generali. Il terzo capitolo spiega la profonda differenza del metodo stocastico nella risoluzione dell'equazione del trasporto rispetto a quelli deterministici, attraverso la presentazione delle caratteristiche principali del metodo Monte Carlo. Il quarto capitolo descrive il metodo ibrido determistico-stocastico in principio fornendo il background teorico sul quale è poggiato il metodo AN, dimostrandone la sua derivazione dal metodo delle armoniche sferiche semplificato SP(2N-1), analizzando le sue proprietà e dimostrando il fondamentale teorema di equivalenza tra AN e P(2N-1). Poi si farà cenno ai metodi della Matrice di Risposta e BIE (Boundary Integral Equation) utilizzati nel codice deterministico. Infine si è trattato il Monte Carlo sviluppato ad hoc per il calcolo del flusso incolliso, che genera la sorgente di prima collisione inserita come input nella parte deterministica del codice. Verranno presentati e commentati i risultati numerici di questa nuova tecnica confrontandoli con un calcolo per così dire diretto di Monte Carlo tradizionale attraverso l'MCNP. In appendice vi sono dei richiami alle funzioni matematiche speciali, delle quali si è fatto largamente uso in questa tesi, inoltre vi è anche il listato del codice di calcolo elaborato con il linguaggio di programmazione FORTRAN 77 riferito alla parte stocastica

Re-testing the JET-X Flight Module No. 2 at the PANTER facility

The Joint European X-ray Telescope (JET-X) was the core instrument of the Russian Spectrum-X-gamma space observatory. It consisted of two identical soft X-ray (0.3 - 10 keV) telescopes with focusing optical modules having a measured angular resolution of nearly 15 arcsec. Soon after the payload completion, the mission was cancelled and the two optical flight modules (FM) were brought to the Brera Astronomical Observatory where they had been manufactured. After 16 years of storage, we have utilized the JET-X FM2 to test at the PANTER X-ray facility a prototype of a novel X-ray polarimetric telescope, using a Gas Pixel Detector (GPD) with polarimetric capabilities in the focal plane of the FM2. The GPD was developed by a collaboration between INFN-Pisa and INAF-IAPS. In the first phase of the test campaign, we have re-tested the FM2 at PANTER to have an up-to-date characterization in terms of angular resolution and effective area, while in the second part of the test the GPD has been placed in the focal plane of the FM2. In this paper we report the results of the tests of the sole FM2, using an unpolarized X-ray source, comparing the results with the calibration done in 1996.Comment: Author's accepted manuscript posted to arXiv.org as permitted by Springer's Self-Archiving Policy. The final publication is available at http://rd.springer.com/article/10.1007%2Fs10686-013-9365-

Contact-force monitoring increases accuracy of right ventricular voltage mapping avoiding "false scar" detection in patients with no evidence of structural heart disease

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Contact-force monitoring increases accuracy of right ventricular voltage mapping avoiding “false scar” detection in patients with no evidence of structural heart disease

Purpose: Electroanatomical mapping (EAM) could increase cardiac magnetic resonance imaging (CMR) sensitivity in detecting ventricular scar. Possible bias may be scar over-estimation due to inadequate tissue contact. Aim of the study is to evaluate contact-force monitoring influence during EAM, in patients with idiopathic right ventricular arrhythmias. Methods: 20 pts (13 M; 43 ± 12 y) with idiopathic right ventricular outflow tract (RVOT) arrhythmias and no structural abnormalities were submitted to Smarttouch catheter Carto3 EAM. Native maps included points collected without considering contact-force. EAM scar was defined as area ≥1 cm2 including at least 3 adjacent points with signal amplitude (bipolar <0.5 mV, unipolar 3,5 mV), surrounded by low-voltage border zone. EAM were re-evaluated offline, removing points collected with contact force <5 g. Finally, contact force-corrected maps were compared to the native ones. Results: An EAM was created for each patient (345 ± 85 points). After removing poor contact points, a mean of 149 ± 60 points was collected. The percentage of false scar, collected during contact force blinded mapping compared to total volume, was 6.0 ± 5.2% for bipolar scar and 7.1 ± 5.9% for unipolar scar, respectively. No EAM scar was present after poor contact points removal. Right ventricular areas analysis revealed a greater number of points with contact force < 5 g acquired in free wall, where reduced mean bipolar and unipolar voltage were recorded. Conclusions: To date this is the first work conducted on structurally normal hearts in which contact-force significantly increases EAM accuracy, avoiding “false scar” related to non-adequate contact between catheter and tissue

Long-Term Follow-Up In Paroxysmal Atrial Fibrillation Patients With Documented Isolated Trigger

AimsSupraventricular tachycardias may trigger atrial fibrillation (AF). The aim of the study was to evaluate the prevalence of supraventricular tachycardia (SVT) inducibility in patients referred for AF ablation and to evaluate the effects of SVT ablation on AF recurrences.Methods and results249 patients (mean age: 54 ± 14 years) referred for paroxysmal AF ablation were studied. In all patients, only AF relapses had been documented in the clinical history. 47 patients (19%; mean age: 42 ± 11 years) had inducible SVT during the electrophysiological study and underwent an ablation targeted only at SVT suppression. Ablation was successful in all 47 patients. The ablative procedures were: 11 slow-pathway ablations for atrioventricular nodal re-entrant tachycardia; 6 concealed accessory pathway ablations for atrioventricular re-entrant tachycardia; 17 focal ectopic atrial tachycardia ablations; 13 with only one arrhythmogenic pulmonary vein. No recurrences of SVT were observed during the follow-up (32 ± 18 months). 4 patients (8.5%) showed recurrence of at least one episode of AF. Patients with inducible SVT had less structural heart disease and were younger than those without inducible SVT.ConclusionA significant proportion of candidates for AF ablation are inducible for an SVT. SVT ablation showed a preventive effect on AF recurrences. Those patients should be selected for simpler ablation procedures tailored only to the triggering arrhythmia suppression

XIPE: the x-ray imaging polarimetry explorer

XIPE, the X-ray Imaging Polarimetry Explorer, is a mission dedicated to X-ray Astronomy. At the time of writing XIPE is in a competitive phase A as fourth medium size mission of ESA (M4). It promises to reopen the polarimetry window in high energy Astrophysics after more than 4 decades thanks to a detector that efficiently exploits the photoelectric effect and to X-ray optics with large effective area. XIPE uniqueness is time-spectrally-spatially- resolved X-ray polarimetry as a breakthrough in high energy astrophysics and fundamental physics. Indeed the payload consists of three Gas Pixel Detectors at the focus of three X-ray optics with a total effective area larger than one XMM mirror but with a low weight. The payload is compatible with the fairing of the Vega launcher. XIPE is designed as an observatory for X-ray astronomers with 75 % of the time dedicated to a Guest Observer competitive program and it is organized as a consortium across Europe with main contributions from Italy, Germany, Spain, United Kingdom, Poland, Sweden

Clinical Efficacy of an Eyedrop Containing Hyaluronic Acid and Ginkgo Biloba in the Management of Dry Eye Disease Induced by Cataract Surgery

: Purpose: To evaluate the prevalence of dry eye disease (DED) after cataract surgery, and the impact of hyaluronic acid and ginkgo biloba eyedrops (HA-GB). Methods: Forty patients with no DED received Ocular Surface Disease Index (OSDI) questionnaire, assessment of conjunctival hyperemia and epithelial damage, fluorescein tear break-up time (TBUT) at baseline, day 1, week 1, and 4; adherence and tolerability were checked at weeks 1 and 4. At day 0 patients underwent cataract surgery and were randomized to standard postoperative care (control group) or standard postoperative care + HA-GB 3 times a day for 4 weeks (HA-GB group). Results: At baseline, TBUT was 9.6 ± 2.6 sec in controls and 9.0 ± 1.6 in HA-GB; thereafter it was higher in HA-GB group: 5.8 ± 2.3 versus 7.8 ± 3.2 (week 1, P = 0.03) and 6.4 ± 2.3 versus 8.5 ± 2.5 (week 4, P = 0.009). OSDI and conjunctival hyperemia were better in HA-GB group at week 4; respectively, 9.0 ± 5.7 versus 14.8 ± 7.3 (P = 0.004) and 5% versus 35% (P = 0.04). In the last 2 visits 50% of controls were symptomatic (OSDI of 13 or higher) compared with 16% on HA-GB group (P < 0.001). In addition, tolerability was higher in HA-GB group (week 1: 0.81 ± 0.20 versus 0.70 ± 0.24, P = 0.007; week 4: 0.93 ± 0.17 versus 0.80 ± 0.28, P = 0.001). Conclusion: Treatment with HA-GB is effective in reducing DED signs and symptoms in patients receiving cataract surgery, with high tolerability and safety profiles. clinicaltrials.gov (ID number NCT05002036)

Inter-Eye Comparison of the Ocular Surface of Glaucoma Patients Receiving Surgical and Medical Treatments

Background: Ocular surface frequently affects glaucoma patients. In this paper we aimed at evaluating the impact of glaucoma surgery on the ocular surface of patients who received unilateral trabeculectomy. Methods: 26 consecutive patients successfully treated with trabeculectomy on one eye (Trab Eye) and under control with topical treatments on the fellow eye (Med Eye) were included in this observational study. They received IDEEL and OSDI questionnaires, Tear Film Osmolarity (TFO), grading of conjunctival hyperemia, fluorescein tear break-up time (tBUT), grading of corneal staining and Schirmer test. Results: IDEEL and OSDI scores were 48 ± 38 and 11 ± 12, respectively, with moderate correlation (r = 0.50, p = 0.03). Compared with Med eyes, Trab Eyes had higher tBUT (6.5 ± 3.5 vs. 5.1 ± 2.7 s, p = 0.004), lower conjunctival hyperemia (0.8 ± 0.9 and 1.7 ± 1.1 respectively, p < 0.001) and lower corneal staining (0.3 ± 0.5 and 0.6 ± 0.5, respectively, p = 0.03). Correlation between corneal staining and conjunctival hyperemia was 0.55 in Trab Eyes (p = 0.01) and 0.44 in Med Eyes (p > 0.05). Patients with bilateral corneal staining had had threefold worse questionnaire scores (p < 0.05). The duration of treatment and the daily exposure to preservatives did not directly affect OS parameters in this cohort of patients. Conclusions: Patients receiving successful trabeculectomy showed better OS homeostasis (higher TBUT, lower grading of conjunctival hyperemia and corneal staining) than fellow medically treated eyes. Presence of corneal epithelial damage in both eyes is the factor more consistently affecting questionnaire scores

The implantable cardiac monitor in heart failure patient: a possible new indication?

International audienceAbstract Implantable cardiac monitors (ICMs) have found increasing use in clinical practice over the years, proving, when used in high-risk populations, to facilitate the diagnosis of bradyarrhythmias and tachyarrhythmias requiring treatment. Experience with heart failure patients undergoing pacemaker (PMK) or implantable defibrillator (ICD) implantation, which allow for continuous electrocardiographic monitoring and transthoracic impedance assessment, has made it possible to identify predictors of heart failure flare-ups. In this context, the use of telemonitoring has been shown to ensure better management of patients with heart failure. These benefits cannot be assessed to date in patients with heart failure and left ventricular ejection fraction (LVEF) > 35% who have no indication for PMK or ICD implantation. This population has been shown to have a significant incidence of ventricular arrhythmias and bradyarrhythmias. In addition, a significant number of cerebrovascular events are observed in this population, largely attributable to the high incidence of atrial fibrillation (AF). In this population, the occurrence of AF has also been shown to have a negative impact on patients’ prognosis; at the same time, a rhythm control strategy has been shown to be more beneficial in this area than a rate control strategy. Studies also suggest arrhythmias have a negative impact on the cognitive status and quality of life of heart failure patients. These reasons could justify the implantation of ICMs equipped with telemonitoring systems in heart failure patients. The information provided by the monitoring system, if properly managed, could bring benefits in terms of prognosis and quality of life along with a reduction in economic costs. We will try here, by answering a few questions, to assess whether there is an indication for ICM in heart failure, which patients should be candidates and how these patients should be managed