Glossar

Alanine Electron Paramagnetic Resonance (EPR) dosimetry

The EPR dosimetry provides information about the absorbed dose to a medium through measuring the concentration of the free radicals produced by ionizing radiation. From the early sixties the development of alanine/EPR dosimetry has reached a level that makes it competitive with classical methods of dosimetry such as thermoluminescence, chemical and ionization methods, at least at the higher dose range (above 5 Gy). The alanine detectors in form of pellets are provided by the National Physical Laboratory (NPL). The detectors have a nominal diameter of 5.0 mm and a thickness of about 2.3 mm. The pellets consist of 90.9% by weight L-α-alanine and 9.1% high melting point paraffin wax. The average density is around 1.22 g cm3 actually close to PMMA (density 1.19 g cm3), but varies slightly from batch to batch.

Beam Parameters

The beam parameters characterise an accelerated ion beam. Typical beam parameters are for example particle type, beam energy, beam intensity or size.

Carbon Ions

Carbon ions are carbon atoms in which at least one electron or even all six electrons have been removed. Just like protons, carbon ions are used in medicine for ion beam therapy.

Chemotherapy

Chemotherapy is a drug treatment for cancer using substances that exert their effects in a targeted manner on certain disease-causing microorganisms or cells and kill them or inhibit their growth. In the treatment of malignant tumours most of these substances affect the rapid proliferative potential of tumour cells, as these respond more sensitively than normal cells to disturbance in cell division. However, on healthy cells with similar proliferative potential they have a comparable effect, resulting in side effects such as blood disorders or diarrhoea.

Dosimetry

Dosimetry is a measuring technique using dosimeters for the determination of the dose created by ionising radiation in matter.

End-to-end testing

The purpose of end-to-end testing is to confirm that the entire logistic chain of radiation treatment starting from imagining, treatment planning, monitor calibration, patient positioning and verification and beam delivery is efficient and leads to the desired results with sufficient accuracy. End-to-end tests are performed with the anthropomorphic phantoms that allow to place detectors in different locations over the irradiation area and thus perform simultaneous verification of delivery accuracy of planned absorbed dose at many points. Successful completion of dosimetric end-to-end tests is a prerequisite for starting clinical activity at a PBS radiotherapy facility and may also serve as a dosimetric credentialing for clinical trials in the near future.

Equivalent Dose

An equivalent dose is defined as the product of absorbed dose and a factor, dependent on type and energy of the radiation, i.e. the quality factor. The value of this factor is determined by biological insights and ranges from 1 for photons to 20 for heavy nuclei. The equivalent dose is measured in Sievert, ie 1 Sv = 1 J/kg, due to the fact that the quality factor has no dimension.

Experimental Physics

Experimental physics tries to gain qualitative and quantitative insights into physical processes using planned scientific tests carried out in exactly the same way in reproducible and interference-avoiding conditions. An important prerequisite of experimental physics is the repeatability of the experiments. This alone can guarantee objectivity of statements. On the one hand, experimental physics acts as an engine for theoretical physics, given the fact that surprising experimental results must be integrated in the intellectual edifice of physics. On the other hand, experimental physics is driven by theoretical physics, as new theories must always be tested in order to develop their obviousness, borders and relationships.

Helium

Helium is the second lightest chemical element in the periodic table of elements after hydrogen and is a noble gas. It is colourless, odourless and tasteless and liquefies only close to absolute zero.

Horizontal Beam Line

A horizontal beam is defined as a fixed beam line, reaching horizontally into the irradiation room at a certain height. In order to gain radiation fields from different directions the area targeted for irradiation must be moved around such a horizontal beam line.

Immunotherapy

Immunotherapy is a collective term for various different treatment approaches aiming to influence the activity of the human immune system. Oncology distinguishes between two different types of immunisation: active and passive immunisation. In active immunisation the patient receives administered substances to induce an immune response in their immune system. The immune response ideally leads to the death of the tumour cells, or at least to reduced tumour growth. In contrast, in passive immunisation the patient receives antibodies or antibody fragments. These selectively bind to tumour cells and so lead to their demise. In adoptive immunotherapy the patient’s leukocytes are removed and cultured ex vivo to be re-injected.

Indication

The medical term indication describes the medical procedure that should be used for a certain disease.

Ion Beam Therapy

Ion beam therapy (particle therapy) is part of an external radiotherapy where instead of photon and electron beams, ion beams are used. Compared to conventional radiotherapy, the energy output of the ion beams can be controlled much more effectively. As a result, the unwanted dose on healthy tissue can be reduced, leading to a reduction of treatment-related side effects.

Ion Beams

Ion beams (particles or particle beams) are defined as rapidly moving ions designated with non-zero rest mass. When passing through matter, these ions lose their energy due to scattering processes, until the kinetic energy of the ions has finally sunk to the value of thermal energy. The route the particles cover in order to get to this level is called range. The range depends on the particle type, the initial energy and the material the particle passes through. The energy transfer per distance unit on the matter also is determined by the particle type, the material and the energy of the moment. The energy transfer generally increases per distance unit travelled by the particle. The curve describing this increase of energy transfer is known as the Bragg curve, named after William Henry Bragg. Shortly before the end of the route the energy transfer achieves a maximum and then drops abruptly to zero. This effect is made use of in ion beam therapy in order to focus the attack on the tumour and spare the surrounding tissue.

Ionising Radiation

Ionising radiation is the name given to every particle radiation or electromagnetic radiation that can remove electrons from atoms or molecules, resulting in a residue of positively charged ions or molecule particles (ionisation). In direct ionising radiation, the energy transfer takes place by the Coulomb interaction, i.e. the invading primary charged electrons, protons, etc. give their energy to the electrons of the absorber medium. Indirectly ionising radiation, however, is produced by electrically neutral particles like photons and neutrons and the energy release is a two-step process: first charged particles (electrons, protons, etc.) are released from the atoms of the absorbing medium and then these charged secondary particles – similar to the direct ionising radiation – pass their energy to the electrons of the absorber medium.

Ions

An ion is an electrically charged atom or molecule. In the neutral state atoms or molecules have exactly as many electrons as protons. The electric charge, and thus the ion, is created when an atom or molecule has either more or less electrons compared to the neutral condition. Ions are positively charged if they have an electron deficiency and negatively charged if they have more electrons. Because of their electrical charge, ions can be bundled and accelerated to high speeds in an ion beam using ion sources and particle accelerators.

Light Ions

In ion beam therapy particles with a low mass number such as protons or helium ions are called light ions. Heavy ions are, for example, carbon or oxygen ions.

Linac

Linac is the abbreviation for linear accelerator. In contrast to circular accelerators, in a linear accelerator the particles to be accelerated pass the accelerator unit only once and no magnetic fields deflecting the particle beam are necessary. Therefore, no synchrotron radiation is generated.

Local Recurrence

In general, recurrence is a relapse after treatment of an illness. A local recurrence in the treatment of cancer refers to the re-appearance of a tumour at the source.

Medical Radiation Physics

Medical radiation physics is concerned with the use of radiation beam therapy and/or diagnosing diseases. These include inter alia dosimetry, treatment planning and the use of radiation beam therapy and diagnostic imaging.