Dose monitoring methods in medical linear accelerators

Wh, Sutherland

doi:10.1259/0007-1285-42-503-864-a

Cited by 4 publications

(2 citation statements)

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“…A sensitivity change in one of these plates can result in the flatness control system not detecting a tilt of the beam and thus a patient can be treated with an undesirable tilt of the dose distribution. A tilted beam may also have impact on the dose calibration level (Sutherland 1969).…”

Section: Introductionmentioning

confidence: 99%

The influence of air humidity on an unsealed ionization chamber in a linear accelerator

Blad

Nilsson²,

Knöös³

1996

Phys. Med. Biol.

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The safe and accurate delivery of the prescribed absorbed dose is the central function of the dose monitoring and beam stabilization system in a medical linear accelerator. The absorbed dose delivered to the patient during radiotherapy is often monitored by a transmission ionization chamber. Therefore it is of utmost importance that the chamber behaves correctly. We have noticed that the sensitivity of an unsealed chamber in a Philips SL linear accelerator changes significantly, especially during and after the summer season. The reason for this is probably a corrosion effect of the conductive plates in the chamber due to the increased relative humidity during hot periods. We have found that the responses of the different ion chamber plates change with variations in air humidity and that they do not return to their original values when the air humidity is returned to ambient conditions.

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Section: Introductionmentioning

confidence: 99%

The influence of air humidity on an unsealed ionization chamber in a linear accelerator

Blad

Nilsson²,

Knöös³

1996

Phys. Med. Biol.

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“…Error components include variations of focal spot positioning over the flattening filter during the exposure, and inherently poor dose resolution of the inbuilt dose-terminating ion chambers. This poor resolution may in part be due t o lack of chamber saturation making the delivered dose output dependent and in part to the influence of unstable peripheral rays on the dose measured (Sutherland 1969). It should also be noted that in the absence of build-up material, these chambers are most sensitive to the low end of the bremsstrahlung energy spectrum.…”

Section: (P1)mentioning

confidence: 99%

Generation of 8MV Modified Tissue-Phantom Ratios by Pivotal Unfolding of Central Axis Depth Dose Data

Sherlock

Swincer

1978

Australas Radiol

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Modified Tissue‐Phantom Ratios are an analogous quantity to Tissue‐Air Ratios for beam energies greater than 2MV. Direct measurement of Modified Tissue‐Phantom Ratios is a tedious and error prone process, and may be avoided by applying an unfolding procedure to Central Axis Depth Dose Data. The method requires that a small range of Modified Tissue‐Phantom Ratios be obtained by direct measurement. Summary A method for generating MTPR data from PDD has been described. Results of the application of the method to an 8MV X‐ray beam have been tabulated. The principal areas in which experimental errors exist have been indicated, and their magnitude given as a between classes error histogram. The method of pivotal unfolding is recommended as an accurate and time saving procedure for the generation of Modified Tissue‐Phantom Ratios.

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Design and performance criteria for medical electron accelerators

Nunan

1985

Nuclear Instruments and Methods in Physics Research Section B:

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Dose monitoring methods in medical linear accelerators

Cited by 4 publications

References 0 publications

The influence of air humidity on an unsealed ionization chamber in a linear accelerator

The influence of air humidity on an unsealed ionization chamber in a linear accelerator

Generation of 8MV Modified Tissue-Phantom Ratios by Pivotal Unfolding of Central Axis Depth Dose Data

Design and performance criteria for medical electron accelerators

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