Ateneo - UPO

Fundamentals of electromagnetism. Interaction of charged particles, X rays, gamma rays and neutrons with matter.

V. Monaco, R. Sacchi, A. Solano, "Elementi di Fisica", McGrawHill
J. Kane, M. Sternheim, "Fisica Applicata", EMSI
D. Scannicchio, "Fisica Biomedica", EdiSES

J.E. Coggle, "Effetti biologici delle radiazioni", Minerva Medica
U. Amaldi, "Fisica delle Radiazioni", Boringhieri
R. Passariello, "Radiologia - Elementi di tecnologia", Idelson-Gnocchi
J.R. Greening, "Fundamentals of Radiation Dosimetry", Taylor & Francis
H.E. Johns, J.R. Cunningham, "The Physics of Radiology", C. C. Thomas Publisher
R.A. Fosbinder, C.A. Kelsey, "L'immagine radiologica", McGraw Hill

At the end of the course the student should know the basic concepts of electromagnetism, and the mechanisms of the interaction between radiation (charged particles, X and gamma rays, neutrons) and matter, with emphasis on the aspects most relevant to understand the instrumentation used in radio diagnostics and radiotherapy

The content of the Physics course (1st semester)

Formal classes

Please see Si veda http://www3.med.unipmn.it/arneodo/

Written and oral exam, aiming at assessing the degree of understanding of the subject. For examples of written tests, please see Si veda http://www3.med.unipmn.it/arneodo/

First part: electromagnetism

Electric charge, Coulomb’s law, electric field, electrostatic potential energy, potential; electron volt. Relation between field and potential difference. Electric dipole: field lines and behaviour in an electric field.

Conductors and insulators. Polarisation of a dielectric. Electric capacity; capacitor; effect of a dielectric. Relative dielectric constant. Energy stored in a capacitor. Capacitors in series and parallel.

Electric current. Drift velocity of the charge carriers. Electric resistance; resistivity. Ohm’s law. Resistors in series and parallel. Electric circuits. Power in electril circuits, Joule’s law. Ohmic and non-ohmic conductors. RC circuits.

Direct and alternating current circuits.

Effects of current through the human body. Grounding.

Magnetic field. Lorentz’s force; force on a current-carrying wire. Biot-Savart law. Field generated by a wire, field generated by a circular current loop. Solenoid. Magnetic dipoles; magnetic dipole moment; behaviour of a magnetic dipole in a magnetic field. Ferromagnetic materials, permanent magnets.

Magnetic field flux. Faraday’s law. Electric generators, transformers.

Electromagnetic waves and their spectrum. Antennas. Quantisation of energy in electromagnetic waves: the photon.

Second part: radiation physics

Structure, size and mass of atoms and nuclei. Strong nuclear interaction. Basic concepts of quantum mechanics: quantization of the energy carried by electromagnetic waves; quantisation of angular momentum of atomic electrons, wave function and its meaning, uncertainty principle, Schroedinger's equation.

Basic concepts of relativistic mechanics: invariance of peed of light, speed of light as the maximum possible, mass-energy equivalence, time dilation, length contraction; beta and gamma factors.

Particle accelerators: linac, cyclotron, synchrotron.

Generation of X rays. Cathode ray tube. Bremsstrahlung radiation; characteristic lines. X ray spectrum of a tube for radiodiagnostics. Angular distribution (thin and thick target). Current vs voltage relationship, space charge effect, saturation. X-ray tube power supply, rectifier, peak voltage. Anode cooling. Load curves.

Structure of the atomic nucleus.Isotopes and isobars. Strong nuclear interaction; weak nuclear interaction. Stable and unstable nuclei. Radioactivity. Alpha, beta and gamma decays, with examples. Activity; law of radioactive decay. Lifetime and hal-life. Initial activity vs initial number of nuclei.The physics principles of PET.

Interaction between radiation and matter:
(i) cross section;
(ii) interaction of charged particles (protons, nuclei) with matter. Stopping power. Bethe-Bloch formula; range; Bragg peak; hadron-therapy. Thickness in g/cm2, LET;
(iii)interaction of electrons and positrons with matter. Braking radiation, radiation length;
(iv) multiple scattering;
(v) interaction of X and gamma photons with matter:
- absorption coefficient;
- photoelectric effect: cross section dependence on energy and atomic number; angular distribution of photoelectrons; K-edge;
- Compton effect: cross section dependence on energy and atomic number; angular distribution of scattered electrons and photons;
- pair creation; cross section dependence on energy and atomic number;
- electromagnetic showers;
(vi) interaction of neutrons with matter: elastic, inelastic, non-elastic collisions; capture, spallation, fission.

Physics foundations of diagnostics with X rays. Principle of TC.

Physics principles of magnetic resonance imaging: proton spin, effect of magnetic fields on spin; Larmor frequency; spin flip; relaxation; gradient field. T1, T2 times. Longitudinal and transverse magnetisation. FID.

Understanding of basic electromagnetism and of the interaction between ionising radiation and matter.