Intrafraction Motion in Surface-Guided Breast Radiation Therapy and its Implications on a Single Planning Target Volume Margin Strategy.

Purpose: This study quantifies intrafraction motion in surface-guided radiation therapy (SGRT) for breast cancer and considers the need for individualized intrafraction motion measures when calculating planning target volume (PTV) margins.

Methods And Materials: SGRT was used to assess intrafraction motion in consecutive patients according to (1) site irradiated (whole-breast/chest wall vs whole-breast/chest wall + regional lymph nodes) and (2) the use of deep inspiration breath hold versus free breathing. Intrafraction motion variation was evaluated throughout the treatment course for all cases.

Estimation of the relative biological effectiveness for double strand break induction of clinical kilovoltage beams using Monte Carlo simulations.

Background: The Relative Biological Effectiveness (RBE) of kilovoltage photon beams has been previously investigated in vitro and in silico using analytical methods. The estimated values range from 1.03 to 1.

Clinical treatment planning for kilovoltage radiotherapy using EGSnrc and Python.

Kilovoltage radiotherapy dose calculations are generally performed with manual point dose calculations based on water dosimetry. Tissue heterogeneities, irregular surfaces, and introduction of lead cutouts for treatment are either not taken into account or crudely approximated in manual calculations. Full Monte Carlo (MC) simulations can account for these limitations but require a validated treatment unit model, accurately segmented patient tissues and a treatment planning interface (TPI) to facilitate the simulation setup and result analysis.

Performance of a low gain avalanche detector in a medical linac and characterisation of the beam profile.

Low gain avalanche detectors can measure charged particle fluences with high speed and spatial precision, and are a promising technology for radiation monitoring and dosimetry. A detector has been tested in a medical linac where single particles were observed with a time resolution of 50 ps. The integrated response is similar to a standard ionising chamber but with a spatial precision twenty times finer, and a temporal precision over 100 million times better, with the capability to measure the charge deposited by a single linac pulse.

Energy and dose dependence of GafChromic EBT3-V3 film across a wide energy range.

Aim: To determine the energy and dose dependence of GafChromic EBT3-V3 film over an energy range 0.2 mm Al HVL to 6 MV.

Background: The decay scheme of a brachytherapy source may be complex and the spectrum of energy can be wide.

Determination of MLC model parameters for Monaco using commercial diode arrays.

Multileaf collimators (MLCs) need to be characterized accurately in treatment planning systems to facilitate accurate intensity-modulated radiation therapy (IMRT) and volumetric-modulated arc therapy (VMAT). The aim of this study was to examine the use of MapCHECK 2 and ArcCHECK diode arrays for optimizing MLC parameters in Monaco X-ray voxel Monte Carlo (XVMC) dose calculation algorithm. A series of radiation test beams designed to evaluate MLC model parameters were delivered to MapCHECK 2, ArcCHECK, and EBT3 Gafchromic film for comparison.

Photon beam quality variations of a flattening filter free linear accelerator.

Purpose: Recently, there has been an increasing interest in operating conventional linear accelerators without a flattening filter. The aim of this study was to determine beam quality variations as a function of off-axis ray angle for unflattened beams. In addition, a comparison was made with the off-axis energy variation in flattened beams.

Dosimetric characteristics of 6 and 10MV unflattened photon beams.

Purpose: To determine dosimetric properties of unflattened megavoltage photon beams.

Materials And Methods: Dosimetric data including depth dose, profiles, output factors and phantom scatter factors from three different beam qualities provided by Elekta Precise linacs, operated with and without flattening filter were examined. Additional measurements of leaf transmission, leakage radiation and surface dose were performed.

Experimental investigation of the response of an a-Si EPID to an unflattened photon beam from an Elekta Precise linear accelerator.

The characteristics of an Elekta amorphous silicon (a-Si) electronic portal imaging device (EPID) in response to a 6 MV photon beam generated without a flattening filter, an unflattened beam, have been determined. The characteristics were then compared to those for a conventional photon beam generated with a flattening filter in the beam, a flattened beam, in order to determine the suitability of an a-Si EPID for transit dosimetry. The response of the EPID to the unflattened beam increased by 7.

A modified method of calculating the lateral build-up ratio for small electron fields.

This note outlines an improved method of calculating dose per monitor unit values for small electron fields using Khan's lateral build-up ratio (LBR). This modified method obtains the LBR directly from the ratio of measured, surface normalized, electron beam percentage depth dose curves. The LBR calculated using this modified method more accurately accounts for the change in lateral scatter with decreasing field size.