Zinc-Doped Iron Oxide Nanoparticles as a Proton-Activatable Agent for Dose Range Verification in Proton Therapy.

Proton therapy allows the treatment of specific areas and avoids the surrounding tissues. However, this technique has uncertainties in terms of the distal dose fall-off. A promising approach to studying the proton range is the use of nanoparticles as proton-activatable agents that produce detectable signals.

Peripheral Organ Equivalent Dose Estimation Procedure in Proton Therapy.

The aim of this work is to present a reproducible methodology for the evaluation of total equivalent doses in organs during proton therapy facilities. The methodology is based on measuring the dose equivalent in representative locations inside an anthropomorphic phantom where photon and neutron dosimeters were inserted. The Monte Carlo simulation was needed for obtaining neutron energy distribution inside the phantom.

CPU time optimization and precise adjustment of the Geant4 physics parameters for a VARIAN 2100 C/D gamma radiotherapy linear accelerator simulation using GAMOS.

We have verified the GAMOS/Geant4 simulation model of a 6 MV VARIAN Clinac 2100 C/D linear accelerator by the procedure of adjusting the initial beam parameters to fit the percentage depth dose and cross-profile dose experimental data at different depths in a water phantom. Thanks to the use of a wide range of field sizes, from 2  ×  2 cm to 40  ×  40 cm, a small phantom voxel size and high statistics, fine precision in the determination of the beam parameters has been achieved. This precision has allowed us to make a thorough study of the different physics models and parameters that Geant4 offers.

Calculation by GAMOS/Geant4 simulation of cellular energy distributions from alpha and lithium-7 particles created by BNCT.

Monte Carlo (MC) has demonstrated to be a suitable technique to evaluate the microdosimetric parameters at the cellular level for Boron Neutron Capture Therapy (BNCT). The objectives of the current study are first to validate GAMOS MC codes with different Geant4 physics models for the range calculations of alpha particles. Once the proper physics is selected, the second objective is to determine the distributions of deposited energy in cellular medium originated by alpha and lithium-7 particles induced by B(n,α)Li.

Production of [11C]CO2 with gas target at low proton energies.

Nowadays the demand and the installation of self-shielded low-energy cyclotrons is growing, allowing the use of (11)C in many more centers. The aim of this study was the design of a new target and the evaluation of the production of (11)C as [(11)C]CO2 at low proton energies. The target was coupled to an IBA Cyclone-18/9 and the energy was decreased to 4-16 MeV.

Postal dosimetry audit test for small photon beams.

Background And Purpose: Small radiation beams (<4 cm width) are being increasingly used in the delivery of advanced techniques as Intensity Modulated Radiotherapy (IMRT) and Stereotactic Radiosurgery (SRS). Dose measurements in small beams present challenges not encountered for larger beams. A postal audit with Thermoluminiscent Dosimeters (TLD) was developed to check the doses in small photon beams.

Uncertainty estimation in intensity-modulated radiotherapy absolute dosimetry verification.

Purpose: Intensity-modulated radiotherapy (IMRT) represents an important method for improving RT. The IMRT relative dosimetry checks are well established; however, open questions remain in reference dosimetry with ionization chambers (ICs). The main problem is the departure of the measurement conditions from the reference ones; thus, additional uncertainty is introduced into the dose determination.

Micro ionization chamber dosimetry in IMRT verification: clinical implications of dosimetric errors in the PTV.

Background And Purpose: Absolute dose measurements for Intensity Modulated Radiotherapy (IMRT) beamlets is difficult due to the lack of lateral electron equilibrium. Recently we found that the absolute dosimetry in the penumbra region of the IMRT beamlet, can suffer from significant errors (Capote et al., Med Phys 31 (2004) 2416-2422).

Microionization chamber for reference dosimetry in IMRT verification: clinical implications on OAR dosimetric errors.

Intensity modulated radiotherapy (IMRT) has become a treatment of choice in many oncological institutions. Small fields or beamlets with sizes of 1 to 5 cm2 are now routinely used in IMRT delivery. Therefore small ionization chambers (IC) with sensitive volumes 0.

An EGSnrc Monte Carlo study of the microionization chamber for reference dosimetry of narrow irregular IMRT beamlets.

Intensity modulated radiation therapy (IMRT) has evolved toward the use of many small radiation fields, or "beamlets," to increase the resolution of the intensity map. The size of smaller beamlets can be typically about 1-5 cm2. Therefore small ionization chambers (IC) with sensitive volumes < or = 0.

MLC leaf width impact on the clinical dose distribution: a Monte Carlo approach.

Purpose: The influence of the multileaf collimator (MLC) leaf width on the dose distribution in patients treated with conformal radiotherapy and intensity-modulated radiotherapy has been analyzed. This study was based on the Monte Carlo simulation with the beams generated by a linac with the double-focused MLC.

Materials And Methods: The transmission through the leaves and the exact shape of the penumbra regions are difficult to model by treatment planning system algorithms.

Total skin electron therapy treatment verification: Monte Carlo simulation and beam characteristics of large non-standard electron fields.

Total skin electron therapy (TSET) is a complex technique which requires non-standard measurements and dosimetric procedures. This paper investigates an essential first step towards TSET Monte Carlo (MC) verification. The non-standard 6 MeV 40 x 40 cm2 electron beam at a source to surface distance (SSD) of 100 cm as well as its horizontal projection behind a polymethylmethacrylate (PMMA) screen to SSD = 380 cm were evaluated.

Routine IMRT verification by means of an automated Monte Carlo simulation system.

Purpose: A tool to simulate complete intensity-modulated radiation therapy (IMRT) treatments with the Monte Carlo (MC) method has been developed. This application is based on a distribution model to employ as short processing times as possible for an operative verification.

Materials And Methods: The Clinical Primus-Siemens Linac beam was simulated with MC, using the EGS4 OMEGA-BEAM code package.