155,248 research outputs found
A Model for a Linear a-Se Detector in Simulated X-Ray Breast Imaging With Monte Carlo Software
No full textIn-silico clinical trials with digital patient models and simulated devices are an alternative to expensive and long clinical trials on patient population for testing X-ray breast imaging apparatuses. In this work, we simulated a linear-response a-Se detector as an X-ray absorber, neglecting some physical processes, such as electro-hole tracking and thermal noise. In order to tune characteristics of the simulated images toward those of the clinical scanners, the detector response curve, modulation transfer function (MTF), and normalized noise power spectrum (NNPS) were measured on a clinical mammographic unit. The same tests were replicated in-silico via a custom-made Monte Carlo code in order to define a suitable model to modify simulated images and to have realistic pixel values, noise, and spatial resolution. The proposed approach resulted to restore the slope and the magnitude of the NNPS in simulated images toward curves evaluated on a clinical scanner. Similarly, the proposed strategy for tuning noise and spatial resolution in simulated images led to a contrast-to-noise ratio (CNR) evaluated on a custom-made phantom which differed from those in measured images less than 16% in absolute value
A new dose index in mammography: innovative experimental method to assess the average absorbed breast dose
No full textBreast cancer is the principal cause of death from cancer among women worldwide. Nevertheless, early detection of breast cancer through adequate screening
programs can save many lives, reducing the overall mortality. The best diagnostic
tool for early detection of breast cancer is Full Field Digital Mammography (FFDM). However, in a mammographic screening program healthy people are exposed to
ionizing radiation, thus special care is required in the evaluation of the patient absorbed
dose. In addition, the new European Directive 59/2013/EURATOM highlights the
importance of monitoring the doses delivered during radiological procedures and requires
that dosimetric data referred to exposure should be part of the radiological report.
For these reasons, the aim of this work is to introduce a simple method for evaluating
the absorbed dose in mammography. We propose a quantitative and personalized dose
index (Average Absorbed Breast Dose, 2ABD) that could be easy computed and inserted
in the radiological reports.
This work is part of the RADIOMA project (RADiazioni IOnizzanti in MAmmografia,
ionizing radiation in mammography), funded by "Fondazione Pisa"
A Model for a Linear a-Se Detector in Simulated X-Ray Breast Imaging With Monte Carlo Software
No full textIn-silico clinical trials with digital patient models and simulated devices are an alternative to expensive and long clinical trials on patient population for testing X-ray breast imaging apparatuses. In this work, we simulated a linear-response a-Se detector as an X-ray absorber, neglecting some physical processes, such as electro-hole tracking and thermal noise. In order to tune characteristics of the simulated images toward those of the clinical scanners, the detector response curve, modulation transfer function (MTF), and normalized noise power spectrum (NNPS) were measured on a clinical mammographic unit. The same tests were replicated in-silico via a custom-made Monte Carlo code in order to define a suitable model to modify simulated images and to have realistic pixel values, noise, and spatial resolution. The proposed approach resulted to restore the slope and the magnitude of the NNPS in simulated images toward curves evaluated on a clinical scanner. Similarly, the proposed strategy for tuning noise and spatial resolution in simulated images led to a contrast-to-noise ratio (CNR) evaluated on a custom-made phantom which differed from those in measured images less than 16% in absolute value
A single-photon CCD-based setup for in situ measurement of the X-ray spectrum of mammographic units
No full textA technique enabling in situ measurements of the spectrum of X-ray tubes employed in mammographic screenings is described. The technique involves the use of a commercially available CCD camera and a set of metal foils and is particularly useful to perform a fast evaluation of the spectral properties of a Mo anode mammographic system operating at standard flux levels. A description of the detector calibration procedure is first given, followed by a discussion of the study and choice of an appropriate set of X-ray attenuation foils. Finally, the use of the system for a spectroscopic characterization of a mammographic system is reported. (C) 2007 Elsevier B.V. All rights reserved
A new method to evaluate the average absorbed dose in mammography and breast tomosynthesis
No full textDigital mammography represents the most sensitive technique to detect and diagnose breast cancer and is hence the preferred method for clinical and screening diagnostic tests. Nevertheless, the absorbed dose in a mammographic procedure can not be neglected even due to the highly radiosensitivity of the breast. In this work we developed a practical method to assess the average absorbed dose both in digital mammography and digital breast tomosynthesis. A new dose index is here proposed as an easily evaluable dosimetric quantity according to the requests of the European Directive 2013/59 EURATOM
Tc99m-Sestamibi scintimammography in the differentiation of benign and malignant breast microcalcifications
No full text
A Model for a Linear a-Se Detector in Simulated X-Ray Breast Imaging with Monte Carlo Software
No full textAs alternative to high-cost and long clinical trials on patient population for testing x-ray breast imaging techniques, the AGATA project proposes the use of in-silico clinical trials with digital patient models and simulated devices. In the in-silico reproductions, the detector model assumes great importance, and its performance should reflect that of the real detector. In this work, we simulated a linear-response a-Se area detector as a pure X-ray absorber of known thickness. The detector response curve, modulation transfer function (MTF) and noise power spectrum (NPS) were measured on a clinical mammographic unit. The same tests were replicated in-silico via the AGATA Geant4 Monte Carlo software. The relations between the measured energy-dependent detector response curves (pixel value vs air kerma) and the simulated ones (pixel dose vs air kerma) will permit to convert simulated pixel values to practical scale values. The comparison between simulated and measured MTF, will permit to define a linear filter for spatial resolution tuning in simulated projections. The comparison between simulated and measured NPS will support strategies for defining a suitable noise model, specifically for the estimates of neglected white noise due to electrons and electro-hole pairs tracking, as well as due to the (not simulated) thermal noise
A computer program for customized recommendations to radioiodine-treated patients [Studio e realizzazione di un programma computerizzato per prescrizioni personalizzate a pazienti iodiotrattati in dimissione]
No full textINTRODUCTION: Iodine-131 (131I) therapy is widely used to treat some thyroid diseases such as hyperthyroidism and thyroid carcinoma. The discharge of a radioiodine treated patient is a potential problem for the radiation protection of the general population. To keep the absorbed dose to the general population as low as possible, patients are given some recommendations, on discharge usually a quite standard list of behaviors to avoid for an amount of time depending only on the administered activity. Thus, recommendations usually consider neither the individual kinetics of 131I nor disease type, while both factors account for major differences in iodine uptake and retention. We investigated the feasibility of customizing recommendations according to recent Euratom guidelines. MATERIAL AND METHODS: Individual 131I kinetics can be evaluated from previous work characterizing dose rate decay as a function of time for different thyroid diseases, together with measurements of iodine uptake or dose rate to the patient. Based on individual kinetics, the committed effective dose to the general population is calculated according to the kind of relationship with the patient, resulting in different amounts of time spent near him/her. RESULTS: The calculation procedure was implemented in a user-friendly software which requires input of few data and measurements to give each patient a customized list of precautions. Using the program on patient's discharge takes no longer than 10 minutes. The precautions are in good agreement with those reported in the literature. CONCLUSIONS: We have been using our program for nine months. Data show that most patients treated for thyroid cancer must follow the recommendations for a shorter time than hyperthyroid patients. The program is suitable for routine use in a nuclear medicine department
Sviluppo e validazione di un sistema integrato per dosimetria fotoneutronica basato su rivelatori ad emulsioni surriscaldate
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