2005
DOI: 10.1118/1.2128086
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Determination of penumbral widths from ion chamber measurements

Abstract: We have investigated methods of reconstructing beam profiles in the penumbral region using a set of axially symmetric chambers, differing only in the detector radius. In principal, the transfer functions, or kernels, of such chambers should be functions of radius only. Three chambers of radii 0.297, 0.556, and 0.714 cm have been used. The transfer functions of the chambers can be determined by deconvolving the profiles measured with each detector with the PPMC profile. The results indicate that the transfer fu… Show more

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Cited by 17 publications
(29 citation statements)
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“…It has been proven definitively that the broadening of the measured penumbra due to the detector size could be explained by the detector convolution kernel. [70][71][72][73][74][75][76] It is possible to extrapolate the true penumbra using the detector convolution kernel. Deconvolution algorithms are susceptible to noise and require tuning to eliminate the noise effect.…”
Section: Iie4 Detector Response and Correctionsmentioning
confidence: 99%
“…It has been proven definitively that the broadening of the measured penumbra due to the detector size could be explained by the detector convolution kernel. [70][71][72][73][74][75][76] It is possible to extrapolate the true penumbra using the detector convolution kernel. Deconvolution algorithms are susceptible to noise and require tuning to eliminate the noise effect.…”
Section: Iie4 Detector Response and Correctionsmentioning
confidence: 99%
“…Direct measurement of the photon fluence is difficult as it usually requires a build-up cap when using an air chamber detector for MV photon energies and the volume of the chamber cavity and build-up cap can blur the fluence profiles. Several alternative methods, such as the deconvolution algorithm or deblurring algorithm to eliminate the detector volume effect, [22][23][24][25] have been proposed, but these methods entail extra measurements and complex data processing. Film dosimetry is another option, but it suffers from a tedious process and limited reliability.…”
Section: Iie Determination Of Oar Of Photon Fluence By Using Optimimentioning
confidence: 99%
“…This effect is also clinically demonstrated by Yan and colleagues (10) . With emphasis placed on the penumbra, methods for reconstructing beam profiles to account for the overestimation of the penumbra are available for ion chambers 10 , 11 , 12 . However, dosimetric modeling accuracy is not attributed solely to the maintenance of penumbral fidelity.…”
Section: Introductionmentioning
confidence: 85%