Description
(covering the III School on Medical Physics)
Optimization of chest radiography aims to ensure that image quality remains adequate for the clinical tasks undertaken, while patient exposure is kept as low as possible. Establishing good image quality is a complex subject as this is strongly linked to clinical task. Additionally, the evaluation of a large number of system parameters is necessary. While clinical trials offer the gold standard...
The methodology of Risk Matrices has been used extensively for safety assessments in the risk industry. The method characterized by being systematic and simple, features that allow considering its application in hospitals. The practice of radiotherapy, where fatal accidents have occurred, needs to apply methodologies to anticipate and prevent potential accidents. The Ibero-American Forum of...
Among the most used methods of risk analysis for medical practices with ionizing radiations are the Risk Matrix and the Failures Modes and Effects Analysis. Two large projects represent these methods. The first corresponds to the Forum of Radiological and Nuclear Regulatory Agencies (FORO-IAEA) and the second to the TG-100, of the American Association of Medical Physicists (AAPM). The...
Mammography is the gold standard to diagnose breast anomalies at the present; nevertheless, the automatized methods using PC interface are increasing today. They help physicians to give a Breast Imaging Reporting and Data System (BIRADS) classification.
The comparison of some automated methods is presented in this work to detect breast anomalies with good sensibility and specificity on PC,...
Electrons generated by photons during their interaction with matter produce significant ionization through electron-electron Coulomb interactions along their track. The absorbed dose deposited along these tracks is defined as the product of the electron fluence generated and the linear energy transfer, LET, or the restricted mass stopping power averaged over the electron energy spectrum....
$^{67}$Cu is a promising isotope for theranostics, the innovative medical strategy that allows the selection of patients prior treatment and the optimisation of therapy throught a personal dosimetry. The γ-radiation of $^{67}$Cu (E$_γ$ = 184.58 keV, I$_γ$ = 48.6%) is suitable for SPECT/CT imaging, while its β-emission (mean E$_{β^-}$ = 141 keV) and relatively long half-life (61.83 h) permits...
In medical physics, conventional machine learning uses “hand designed” feature extractors which require great domain expertise. Deep learning has dramatically improved state-of-the-art machine learning in a variety of domains - including speech recognition, visual object recognition, and object detection. Deep learning networks do not need “hand designed” features, but they usually require...
This work presents an integral description of electron beam deflection control as required for novel radiotherapy technique based on convergent photon beam production [1,2]. Conventional radiotherapy is mainly applied by linear accelerators. Although linear accelerators provide dual (electron/photon) radiation beam modalities, both of them are intrinsically produced by a megavoltage electron...
The massive development of photon radiation treatment techniques as well as the increase use of Hadron therapy has led to a difficult treatment evaluation since many parameters are in play. At the same time, there has been an increase of cancer clinical data generation in the form of clinical records and imaging data. As a response, biophysical models based on clinical data mining and machine...
During more than 60 years of Hyperthyroidism radioiodine treatment has been no general agreement on the applied dose or calculus methodology. The EANM Dosimetry Committee recommend in 2013 an “Standard Operational Procedures for Pre-Therapeutic Dosimetry (SOP)” based on the assessment of the individual $^{131}$I uptake and kinetics. To estimate the 3D dose delivery deviations from prescribed...
Machine learning algorithms that are both interpretable and accurate are essential in applications such as medicine where errors can have a dire consequence. Unfortunately, there is currently a tradeoff between accuracy and interpretability among state-of-the-art methods. Decision trees are interpretable and are therefore used extensively throughout medicine for stratifying patients. Current...
Metal artifacts are common in clinical images. Many methods for artifact reduction have been published to overcome this problem. In this work, three well-known methods and a new one were evaluated, compared and enhanced to achieve artifact suppression (linear interpolation (LI), normalized metal artifact reduction (NMAR) and Frequency split metal artifact reduction (FSMAR)). Furthermore, a new...
While pre-treatment VMAT QA is currently a clinical mainstay, there is growing interest in the use of QA methods that are more relevant to the actual patient treatment and are, in fact, capable of providing in vivo dosimetry. To this end, I will present a newly developed methodology for Monte Carlo based VMAT QA, which simultaneously provides the dose deposited in both the patient CT data set...
Introduction: Fiber-coupled plastic organic scintillator detectors are exceptional for the measurement of the absorbed dose to water in small MV photon beams. This is mostly because of their high degree of water equivalence which results in an almost negligible perturbation of the radiation field. However, these detectors are less ideal when the signal generation and detection is considered....
The first phase I/II clinical trial involving the application of particle beam radiation therapy (PBRT) with ions heavier than protons up were initiated at the University of California, San Francisco / Lawrence Berkeley National Laboratory (UCSF-LBNL) in 1975 [1–4]. This trial prospectively evaluated tumor responses to PBRT and collected information on the late effects. The last trial...
Fiber-coupled scintillators are known to exhibit a nonlinear response to high-LET beams, i.e. ionization quenching. Although corrections may be applied using e.g. Birks’ empirical formula such procedures are challenging and may even introduce errors.
Recent studies suggest that Cerenkov light produced in optical fiber cables may be used to circumvent the ionization quenching. The...
Purpose: This study is devoted to optimize and characterize the response of a multipoint plastic scintillator detector (mPSD) for in vivo dosimetry.
Methods: A 3 points mPSD was constructed and characterized in terms of response to interacting ionizing photons.The detector was composed of BCF-60, BCF-12 and BCF-10 scintillating fibers, separated from each other by segments of clear optical...
Magnetic Resonance (MR) Imaging is a powerful noninvasive diagnostic technique based on the interaction of the nuclear spins in the biological medium with external magnetic fields. MR signal is affected by several physical properties or phenomena including nuclear relaxation times (T1, T2, T1rho), nuclear density, magnetic susceptibility, diffusion, perfusion, etc. However, MR images are...
Methods and results for commissioning and verification of the VMAT delivery chain at NPL are presented. The VMAT parameters for the combination of Pinnacle v9.8 with with Elekta’s Mosaiq® v1.6 record and verify system and Synergy and Versa HD linacs are discussed. Commissioning verification and gamma analysis results for three stablished IMRT QA deliveries are presented and compared, based on...
At INFN-LNL the SPES facility for the production of radioactive ion beams is constructing. This RIB new facility, besides being operated for nuclear physics studies, may play a pivotal role in the production of medically relevant radionuclides by means of the ISOL (Isotope Separation On-Line) technique.
The production of the radioactive isotopes will be obtained by nuclear reactions induced by...
In this review lecture, we will explore the physics behind the contemporary codes of practice for dosimetry based on standards of absorbed dose to water, such as the widely used protocols TRS 398 of the IAEA or TG 51 of the AAPM. In particular, we will review the basic concepts of cavity theory and take a pedagogic approach to understanding its role as an essential component of the formalism...
One of the main challenges of proton therapy today is to produce an equipment that, because of its size and cost, is accessible for general health centers. This way, this therapy will not only be possible in a few centers in developed countries. For this purpose, new equipment has been developed for a single treatment room and equipped with small size cyclotrons with modern technology...
The computational approach, also known as computational radiobiology, to study biological effects induced by ionizing radiations on living beings has being commonly used by many research groups in several applications like micro and nanodosimetry, radiotherapy, radiation protection, and space radiation. A group led by Bernal at University of Campinas, Sao Paulo, developed a biophysical model...
