Stopping‐power ratios for electron beams used in total skin electron therapy

The motion of electrons as determined by the field acceleration and the elastic and inelastic collisions with the gas atoms is calculated from the BOLTZMANN equation. We derive the average velocity and the scattering ellipsoid as a function of time. For particles starting from rest there exists always a critical electric field Ec depending on pressure and temperature. Below this critical value electrons approach the stationary drift process. Above the critical value the electrons do not reach a stationary state, they “run away”. For a finite initial velocity ν0 and a field below the critical value Ec the particles are either accelerated to drift, or decelerated to drift, or “run away”, depending on the value ν0. From a calculation of the scattering parameters we find for E > Ec a focussing effect in the velocity space which increases with field strength. Also the relaxation time for the drift process and the stopping power for electron beams can be calculated. Applications to the glow discharge are discussed.

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Practical lookup tables for ensuring target coverage in a clinical setup for skin cancer electron therapy

Journal of Radiotherapy in Practice ◽

10.1017/s1460396917000607 ◽

2017 ◽

Vol 17 (2) ◽

pp. 205-211

Author(s):

Yongsook C. Lee ◽

Yongbok Kim

Keyword(s):

Skin Cancer ◽

Maximum Dose ◽

Electron Beams ◽

Target Coverage ◽

Electron Beam Therapy ◽

Surface Distance ◽

Depth Dose ◽

Electron Therapy ◽

Lookup Tables ◽

Output Factors

AbstractAimTo create practical lookup tables containing percent depth dose (PDD) and profile parameters of electron beams and to demonstrate clinical application of the lookup tables to skin cancer treatment to ensure target coverage in a clinical setup.Materials and methodsFor 6 and 9 MeV electron energies, PDDs and profiles at clinically relevant depths [i.e., R95 (distal depth of 95% maximum dose), R90, R85 and R80] were measured in water at 100 cm source-to-surface distance for an 10×10 cm2 open field and circular cutouts with diameters of 4, 5, 6, 7 and 8 cm. Then PDD parameters along with profile parameters such as width of isodose lines and penumbra at the clinically relevant depths were determined. Output factors for the cutouts were measured at dmax in water and solid water.ResultsWith PDD and profile parameters, dosimetry lookup tables were generated. Based upon the lookup tables, target coverage at prescribed depths was retrospectively reviewed for three skin cancer cases. The lookup tables suggested larger cutouts for adequate target coverage.FindingsDosimetry lookup tables for electron beam therapy should include profile parameters at clinically relevant depths and be provided to clinicians to ensure target coverage in a clinical setup.

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Measurements of output factors with different detector types and Monte Carlo calculations of stopping-power ratios for degraded electron beams

Physics in Medicine and Biology ◽

10.1088/0031-9155/49/19/004 ◽

2004 ◽

Vol 49 (19) ◽

pp. 4493-4506 ◽

Cited By ~ 21

Author(s):

Peter Björk ◽

Tommy Knöös ◽

Per Nilsson

Keyword(s):

Monte Carlo ◽

Electron Beams ◽

Stopping Power ◽

Monte Carlo Calculations ◽

Output Factors

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Stopping-power ratios for clinical electron beams from a scatter-foil linear accelerator

Physics in Medicine and Biology ◽

10.1088/0031-9155/44/9/317 ◽

1999 ◽

Vol 44 (9) ◽

pp. 2321-2341 ◽

Cited By ~ 12

Author(s):

Ajay Kapur ◽

Chang-Ming Ma

Keyword(s):

Linear Accelerator ◽

Electron Beams ◽

Stopping Power

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RANGE AND STOPPING POWER ENERGY RELATIONSHIPS FOR 0.5–30 keV ELECTRON BEAMS SLOWING DOWN IN SOLIDS: ANALYTICAL MODEL

Modern Physics Letters B ◽

10.1142/s0217984914500067 ◽

2013 ◽

Vol 28 (01) ◽

pp. 1450006 ◽

Cited By ~ 1

Author(s):

A. BENTABET

Keyword(s):

Analytical Model ◽

Electron Beams ◽

Geometric Model ◽

Mathematical Expression ◽

Low Energy ◽

Stopping Power ◽

Slowing Down ◽

Energy Relationships ◽

Slight Discrepancy ◽

Good Agreement

The development of an analytical model for calculating the electron stopping power (SP) converging with the experimental data at lower energies is still not completed. The purpose of this work is to suggest a mathematical expression of the range and the stopping power of electrons impinging in solid targets in the energy range up to 30 keV based on the spherical geometric model [A. Bentabet, Vacuum86 (2012) 1855]. The results are in good agreement with those of the literature. The slight discrepancy between the obtained and both the theoretical and experimental results regarding the stopping power at very low energy (E<0.5 keV) is discussed.

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