A filtration method for improving film dosimetry in photon radiation therapy

Yeo, I; Wang, C. K. Chris; Burch, Sandra E.

doi:10.1118/1.598108

Cited by 38 publications

(29 citation statements)

References 17 publications

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“…Furthermore, energy absorption coefficients for film emulsions and water differ significantly in the low energy region bellow 400 keV, as the data calculated according to Seltzer have shown 10. Since there is an enhanced contribution of scattered radiation to the total dose in modulated photon beams, a disadvantage of the film which shows over-response to low energy photons may become important 11–13…”

Section: Introductionmentioning

confidence: 99%

Dosimetric verification of compensated beams using radiographic film

Jurković¹,

Žauhar²,

Faj³

et al. 2011

Radiology and Oncology

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IntroductionExternal photon beam modulation using compensators in order to achieve a desired dose distribution when brachytherapy treatment is followed by external beam radiation is a well-established technique. A compensator modulates the central part of the beam, and the dose beneath the thickest part of the compensator is delivered mostly by scattered, low energy photons. A two-dimensional detector with a good spatial resolution is needed for the verification of those beams. In this work, the influence of different types of detectors on the measured modulated dose distributions was examined.Materials and methodsDosimetric verification was performed using X-Omat V, Eastman Kodak radiographic films at different depths in a solid water phantom. The film measurements were compared with those made by ionization chambers. Photon beams were also modelled using EGSnrc Monte Carlo algorithm to explain the measured results.ResultsMonte Carlo calculated over-response of the film under the thickest part of the compensator was over 15%, which was confirmed by measurements. The magnitude of over-response could be associated with changes in the spectra of photon energy in the beam.ConclusionsThe radiographic film can be used for the dosimetry of compensated high energy photon beams, with limitations in volumes where photon spectra are hardly degraded.

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Section: Introductionmentioning

confidence: 99%

Dosimetric verification of compensated beams using radiographic film

Jurković¹,

Žauhar²,

Faj³

et al. 2011

Radiology and Oncology

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“…In addition, films have an increased sensitivity to x rays below 200 keV, so that the response varies with the field size and the depth in the phantom. 2,3 The response of the film also depends on the orientation of the film with respect to the incident radiation. 4 Finally, it was shown that the envelope material also has a slight influence on the dosimetric results obtained with films.…”

Section: Introductionmentioning

confidence: 99%

Evaluation of GafChromic EBT prototype B for external beam dose verification

et al. 2006

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The capability of the new GafChromic EBT prototype B for external beam dose verification is investigated in this paper. First the general characteristics of this film (dose response, postirradiation coloration, influence of calibration field size) were derived using a flat-bed scanner. In the dose range from 0.1 to 8 Gy, the sensitivity of the EBT prototype B film is ten times higher than the response of the GafChromic HS, which so far was the GafChromic film with the highest sensitivity. Compared with the Kodak EDR2 film, the response of the EBT is higher by a factor of 3 in the dose range from 0.1 to 8 Gy. The GafChromic EBT almost does not show a temporal growth of the optical density and there is no influence of the chosen calibration field size on the dose response curve obtained from this data. A MatLab program was written to evaluate the two-dimensional dose distributions from treatment planning systems and GafChromic EBT film measurements. Verification of external beam therapy (SRT, IMRT) using the above-mentioned approach resulted in very small differences between the planned and the applied dose. The GafChromic EBT prototype B together with the flat-bed scanner and MatLab is a successful approach for making the advantages of the GafChromic films applicable for verification of external beam therapy.

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“…To reduce the low energy scatter to the film, 0.5-mm lead sheets were placed at 1.2 cm on both sides. (11) Film dosimetry was used only for relative measurements. An automatic film processor (FPM 2800, FUJI Photo Film Co., Tokyo, Japan) was used to develop the film.…”

Section: Methodsmentioning

confidence: 99%

Commissioning and quality assurance for intensity‐modulated radiotherapy with dynamic multileaf collimator: Experience of the Pontificia Universidad Católica de Chile

Venencia

Besa

2004

J Applied Clin Med Phys

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The objective of this paper is to present our experience in the commissioning and quality assurance (QA) for intensity-modulated radiotherapy (IMRT) using the dynamic multileaf collimator (dMLC), sliding window technique. The connectivity and operation between all IMRT chain components were checked on the Varian equipment. Then the following tests were performed: stability of leaf positioning and leaf speed, sensitivity to treatment interruptions (acceleration and deceleration), evaluation of standard field patterns, stability of dMLC output, segmental dose accuracy check, average leaf transmission, dosimetric leaf separation, effects of lateral disequilibrium between adjacent leaves in dose profiles, and multiple carriage field verification. Standard patterns were generated for verification: uniform field, pyramid, hole, wedge, peaks, and chair. Weekly QA protocol includes sweeping gap output, garden fence test (narrow bands, 2 mm wide, of exposure spaced at 2-cm intervals), and segmental dose accuracy check. Monthly QA includes sweeping gap output at multiple gantry and collimator angles, sweeping gap off-axis output, picket fence test (eight consecutive movements of a 5-cm wide rectangular field spaced at 5-cm intervals), stability of leaf speed and leaf motor current test (PWM test). Our patient QA procedure consists of an absolute dose measurement for all treatment fields in the treatment condition, analysis of actual leaf position versus planned leaf position (dynalog files) for each treatment field, film relative dose determination for each field, film relative dose determination for the plan (all treatment fields) in two axial planes, and patient positioning verification with orthogonal films. The tests performed showed acceptable results. After over one year of IMRT treatment, the routine QA machine checks confirmed the precision and stability of the IMRT system.

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A filtration method for improving film dosimetry in photon radiation therapy

Cited by 38 publications

References 17 publications

Dosimetric verification of compensated beams using radiographic film

Dosimetric verification of compensated beams using radiographic film

Evaluation of GafChromic EBT prototype B for external beam dose verification

Commissioning and quality assurance for intensity‐modulated radiotherapy with dynamic multileaf collimator: Experience of the Pontificia Universidad Católica de Chile

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