Noise reduction of radiochromic film: median filter processing of subtraction image

Katsuda, Toshizo; Gotanda, Tatsuhiro; Gotanda, Rumi; Akagawa, Takuya; Tanki, Nobuyoshi; Kuwano, Tadao; Yabunaka, Koichi

doi:10.1007/978-3-319-19387-8_188

Cited by 2 publications

(1 citation statement)

References 3 publications

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“…A 2D 5 × 5 median filter was applied across the scanned film to reduce the inherent noise and statistical fluctuations. 5 The scanned 2D film intensity distribution was converted to the equivalent dose distribution by using the calibration film-dose response curve. The primary dose distribution was deducted from the transmitted dose distribution which includes the forward scatter, to obtain a forward scatter dose distribution.…”

Section: Methodsmentioning

confidence: 99%

Calculation of forward scatter dose distribution at the skin entrance from the patient table for fluoroscopically guided interventions using a pencil beam convolution kernel

Vijayan¹,

Xiong²,

Guo³

et al. 2018

Medical Imaging 2018: Physics of Medical Imaging

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The forward-scatter dose distribution generated by the patient table during fluoroscopic interventions and its contribution to the skin dose is studied. The forward-scatter dose distribution to skin generated by a water table-equivalent phantom and the patient table are calculated using EGSnrc Monte-Carlo and Gafchromic film as a function of x-ray field size and beam penetrability. Forward scatter point spread function’s (PSFn) were generated with EGSnrc from a 1×1 mm simulated primary pencil beam incident on the water model and patient table. The forward-scatter point spread function normalized to the primary is convolved over the primary-dose distribution to generate scatter-dose distributions. The utility of PSFn to calculate the entrance skin dose distribution using DTS (dose tracking system) software is investigated. The forward-scatter distribution calculations were performed for 2.32 mm, 3.10 mm, 3.84 mm and 4.24 mm Al HVL x-ray beams for 5×5 cm, 9×9 cm, 13.5×13.5 cm sized x-ray fields for water and 3.1 mm Al HVL x-ray beam for 16.5×16.5 cm field for the patient table. The skin dose is determined with DTS by convolution of the scatter dose PSFn’s and with Gafchromic film under PMMA “patient-simulating” blocks for uniform and for shaped x-ray fields. The normalized forward-scatter distribution determined using the convolution method for water table-equivalent phantom agreed with that calculated for the full field using EGSnrc within ±6%. The normalized forward-scatter dose distribution calculated for the patient table for a 16.5×16.5 cm FOV, agreed with that determined using film within ±2.4%. For the homogenous PMMA phantom, the skin dose using DTS was calculated within ±2 % of that measured with the film for both uniform and non-uniform x-ray fields. The convolution method provides improved accuracy over using a single forward-scatter value over the entire field and is a faster alternative to performing full-field Monte-Carlo calculations.

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Section: Methodsmentioning

confidence: 99%

Calculation of forward scatter dose distribution at the skin entrance from the patient table for fluoroscopically guided interventions using a pencil beam convolution kernel

Vijayan¹,

Xiong²,

Guo³

et al. 2018

Medical Imaging 2018: Physics of Medical Imaging

View full text Add to dashboard Cite

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Correction of nonuniformity error of Gafchromic EBT2 and EBT3

Katsuda

Gotanda

et al. 2016

J Applied Clin Med Phys

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This study investigates an X‐ray dose measurement method for computed tomography using Gafchromic films. Nonuniformity of the active layer is a major problem in Gafchromic films. In radiotherapy, nonuniformity error is reduced by applying the double‐exposure technique, but this is impractical in diagnostic radiology because of the heel effect. Therefore, we propose replacing the X‐rays in the double‐exposure technique with ultraviolet (UV)‐A irradiation of Gafchromic EBT2 and EBT3. To improve the reproducibility of the scan position, Gafchromic EBT2 and EBT3 films were attached to a 3‐mm‐thick acrylic plate. The samples were then irradiated with a 10 W UV‐A fluorescent lamp placed at a distance of 72 cm for 30, 60, and 90 minutes. The profile curves were evaluated along the long and short axes of the film center, and the standard deviations of the pixel values were calculated over large areas of the films. Paired t‐test was performed. UV‐A irradiation exerted a significant effect on Gafchromic EBT2 (paired t‐test; p=0.0275) but not on EBT3 (paired t‐test; p=0.2785). Similarly, the homogeneity was improved in Gafchromic EBT2 but not in EBT3. Therefore, the double‐exposure technique under UV‐A irradiation is suitable only for EBT2 films.PACS number(s): 87.53 Bn

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Noise reduction of radiochromic film: median filter processing of subtraction image

Cited by 2 publications

References 3 publications

Calculation of forward scatter dose distribution at the skin entrance from the patient table for fluoroscopically guided interventions using a pencil beam convolution kernel

Calculation of forward scatter dose distribution at the skin entrance from the patient table for fluoroscopically guided interventions using a pencil beam convolution kernel

Correction of nonuniformity error of Gafchromic EBT2 and EBT3

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