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Efficient method for radiochromic film dosimetry

A radiation dose and film technology, which is applied in the field of radiation-sensitive film dosimetry, can solve the problem of reducing the spatial resolution of array devices, and achieve the effect of eliminating influence and high spatial resolution

Active Publication Date: 2015-05-27
ISP INVESTMENTS INC
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  • Summary
  • Abstract
  • Description
  • Claims
  • Application Information

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Problems solved by technology

[0008] As mentioned above, while a single ion chamber or diode has a spatial resolution of about 1 mm, array devices may contain hundreds or even thousands of devices, but in order to cover large areas (typically 400–1000 cm 2 ), individual sensors may be spaced 5–10mm apart, severely reducing the spatial resolution of the array device

Method used

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  • Efficient method for radiochromic film dosimetry
  • Efficient method for radiochromic film dosimetry
  • Efficient method for radiochromic film dosimetry

Examples

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Embodiment approach

[0039] According to certain aspects, the present application provides methods and systems for improved radiation dosimetry. According to one aspect, the present application illustrates how a universal calibration function can be generated using any calibration function determined for radiation sensitive films on a given scanner, and more particularly EBT2 and EBT3 radiochromic films. According to one embodiment, the method comprises:

[0040] 1) Expose film from a single batch of film to a number of known doses of radiation. The number of doses is preferably 3 or more.

[0041] 2) Along with the unexposed film, scan the exposed film on a scanner to obtain a digital image. To minimize errors from post-exposure time differences, these scans should be performed at least 24 hours post-exposure.

[0042] 3) Taking measurements on the portions of the digital image corresponding to the exposed film and the unexposed film. The measured values ​​for each film in each color channel ...

Embodiment 1

[0077] This embodiment relates to the scan-to-scan variability of an optical scanner. A piece of Gafchromic EBT3 radiochromic film was placed on the glass scanning window of an Epson 10000XL scanner. The film was scanned in transmission mode at intervals throughout the day to obtain a 48 bit rgb digital image of the radiochromic film with a spatial resolution of 72 dpi. The area corresponding to the radiochromic film in the digital image was measured using the software application FilmQA Pro. The measured values ​​are shown in Table 1 below. Inspection of these values ​​shows that they have a mean variability of about 0.5%.

[0078]

[0079] Table 1

[0080] Similar results were obtained from similar measurements made in the green and blue channels. Differences between scanned images are believed to occur for a number of reasons, including temperature variations over the day, instability of the scanner's light source, and variability within the scanner's individual opto...

Embodiment 2

[0082]This example demonstrates the error in dose measurement due to the type of variability demonstrated in Example 1. Three pieces of Gafchromic EBT3 radiochromic film lot A101711 were exposed to calibrated X-ray radiation doses of 501.1 cGy, 253.2 cGy, and 123.7 cGy. Along with a piece of unexposed film from the same batch, and about two weeks after the film had been exposed, they were placed on an Epson V700 scanner and spaced with 72dpi was obtained from time to time throughout the day for about 16 hours 48-bit RGB digital image resolution. The purpose of waiting two weeks after film exposure is to allow the film to equalize. Gafchromic EBT3 radiochromic film is known to continue to darken after exposure, but the rate of change decreases rapidly over time. After two weeks, the rate of change was too small to be measured over the 16 hour period as used in data acquisition.

[0083] The area corresponding to the radiochromic film sample in the digital image was measured ...

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Abstract

The present invention provides a method for measuring a two-dimensional distribution of ionizing radiation doses with high spatial resolution. The method comprises exposing radiation sensitive film to a pattern of ionizing radiation to form a measurement film, exposing areas of radiation sensitive film to a plurality of known doses of the ionizing radiation to form a calibration film(s), scanning all the exposed films together with an unexposed radiation sensitive film at a single time to produce a digital image, measuring those areas of the digital image corresponding to the unexposed film and the calibration film(s) exposed to different known doses, associating the measured responses in the areas to the known doses and using the association to convert the values in the scanned image corresponding to the measurement film from scanner response values to dose values. In a preferred embodiment, all of the radiation sensitive films are the same type of film.

Description

Background technique [0001] The present invention relates to efficient methods for dosimetry of radiation-sensitive films, and in particular to methods for measuring ionizing radiation dose distributions. [0002] Radiation therapy has been used for many years as a method for irradiating and selectively killing cancer cells while minimizing radiation exposure to adjacent tissues. The effectiveness of radiation therapy depends on the absorbed dose or the amount of energy deposited within the tissue mass. Absorbed dose is usually measured in centigray or cGy units. [0003] Radiation detection media can be used to determine the amount and location of radiation experienced by a patient during radiation therapy. Particularly useful are two-dimensional radiation detection media that can measure radiation dose over an area. Examples are radiographic films, radiochromic films, phosphor panels, two-dimensional arrays of diodes or ion chambers, etc. Radiation detection media typica...

Claims

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Application Information

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IPC IPC(8): G01T1/08
CPCG01T1/02G01T7/005G01T1/04A61N5/1048G01T1/08
Inventor D·F·刘易斯A·米奇克X·于
Owner ISP INVESTMENTS INC
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