A discussion of random number generation is given, and the connection between Monte Carlo methods and random numbers is indicated. Outlines of two well established Monte Carlo sampling techniques are given together with examples illustrating their use. The general techniques for improving the efficiency of Monte Carlo calculations are discussed. Monte Carlo literature pertinent to medical physics is reviewed.

https://iopscience.iop.org/article/10.1088/0031-9155/21/2/001/pdf

Monte Carlo principles and applications.

The irradiation of staff in diagnostic radiology was simulated for conditions commonly encountered in fluoroscopy. Scattered radiation distributions were produced from diagnostic X-ray beams generated at tube potentials in the range 60-120 kVp, using the abdomen sections of a Rando phantom. Doses to a number of organs in the head and neck were measured using a Rando phantom loaded with lithium fluoride thermoluminescent dosemeters. The torso sections were placed on a water phantom on top of a stand, with film badge dosemeters positioned on the surface of the phantom at the forehead, neck, chest and waist, and the phantom was placed in the radiation field. The effective dose equivalent (EDE) to the phantom was calculated for various X-ray beam qualities and lead apron thicknesses and compared with the film badge doses. The results indicate that a dosemeter worn at the waist/chest level under a lead apron generally underestimates the EDE. Conversely, dosemeters worn at the forehead/neck tend to overestimate the EDE. It is recommended that a dosemeter is positioned under a lead apron, if worn.

https://iopscience.iop.org/article/10.1088/0031-9155/33/1/008/pdf

Estimation of effective dose equivalent to staff in diagnostic radiology.

CaSO4:Dy and CaSO4:Tm are highly sensitive phosphors used in the thermoluminescence (TL) dosimetry of the ionizing radiations. It is shown that, by using P, Mo or SO3 as co-dopants, the TL sensitivities can be increased by 40-100%. The increase in sensitivity originates in various processes, which are discussed. P acts as a charge compensator, allowing the incorporation of Dy in higher concentration without causing quenching. Mo increases the efficiency of trap filling. It is claimed that use of Mo as a co-dopant will improve the sensitivities without disturbing the other dosimetric characteristics.

Effective co-dopants for CaSO4:Dy and CaSO4:Tm phosphors

The thermal neutron response and gamma -ray sensitivity of CaSO4:Dy as a function of Dy concentration were studied in detail. CaSO4 with 0.2% Dy has maximum gamma -ray sensitivity. The thermal neutron response of CaSO4:Dy increases rapidly with concentration beyond 0.1% Dy. CaSO4:0.05% Dy (or Tm) has high gamma -ray sensitivity coupled with low thermal neutron response and hence is useful for gamma -ray dosimetry in mixed fields. A mixture of LiF TLD-100 and TLD-700 was arrived at for rem equivalent dosimetric purposes in a mixed field consisting of thermal and intermediate energy neutrons and gamma -rays. Mixtures of CaSO4:Dy with various lithium based materials were also selected for the same purpose. The thermal neutron response and glow peak temperature of CaSO4:(Dy, 6Li) were studied as a function of 6Li concentration.

https://iopscience.iop.org/article/10.1088/0031-9155/19/5/006/pdf

Mixed field dosimetry with CaSO4:Dy

phosphors find applications in dosimetry of ionizing radiations. Phosphors having Dy or Tm activators are high-sensitivity thermoluminescence dosimetry materials, while the phosphors with Eu or Sm activators are the proposed materials for radio-photoluminescence dosimetry. Mechanisms of several processes related to various luminescence phenomena, however, are not yet properly understood. Usually, all phosphors are prepared under identical conditions and comparative studies are carried out. It is shown here that the form in which the impurity is incorporated and the nature of defects produced is quite different in than in . The results presented throw light on the mechanism for thermoluminescence, radio-photoluminescence, incorporation of the impurity and conversion.

https://iopscience.iop.org/article/10.1088/0953-8984/9/39/015/pdf

Redox reactions, radio-photoluminescence and thermoluminescence in ?

A Monte Carlo code was used to study dose and LET distributions, in a specially designed tissue-equivalent cylindrical phantom, due to cylindrical beams of neutrons collimated to diameters of 5 cm. Dose due to ions produced by neutron interactions and dose due to (n, gamma) interactions for neutrons of energy 0.025 eV and 1, 5, 7 and 14 MeV are determined separately and are compared with broad-beam results. LET spectra are given for selected regions inside the phantom. Doses at the front of the phantom, in the center of the restricted beam, were found to approximate those of a broad beam for 14 MeV neutrons and to decrease with decreasing neutron energy, converging to a value of 80–85% of those for broad beams at 1 MeV. Dose from recoil ions averaged over a region 1 cm thick, immediately outside the volume of the incident beam, was found to be lower by- about an order of magnitude (for all energies except thermal, where a factor of 4 was observed) as compared with dose at comparable depths within the beam.

Snyder Ws

Papers

Absorbed dose, dose equivalent and LET distributions in cylindrical phantoms irradiated by a collimated beam of monoenergetic neutrons.

Dose to standard reference man from external sources of monoenergetic photons.