An investigation of the depth dose in the build-up region, andsurface dose for a 6-MV therapeutic photon beam: Monte Carlo simulation and measurements

Apipunyasopon, Lukkana; Srisatit, Somyot; Phaisangittisakul, N.

doi:10.1093/jrr/rrs097

Cited by 51 publications

(39 citation statements)

References 26 publications

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“…17 Although dosimetry of actual skin doses is difficult, ceasing bolus usage may decrease actual doses by 5% to 10%. 24 With respect to soft-tissue necrosis, we may have overdiagnosed the toxicities in our study compared with the results from previous studies. 6,[9][10][11]23 Grade 3/4 necrosis or dermatitis was previously reported to develop in 6% to 15% of patients.…”

Section: Discussionmentioning

confidence: 55%

Hypofractionated Stereotactic Radiotherapy for Auditory Canal or Middle Ear Cancer

et al. 2016

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Section: Discussionmentioning

confidence: 55%

Hypofractionated Stereotactic Radiotherapy for Auditory Canal or Middle Ear Cancer

et al. 2016

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“…There have been several studies comparing different detector types for measurements including the buildup region . The scintillator Exradin W1 was shown to produce depth dose curves in water in close agreement to Monte Carlo calculated curves .…”

Section: Introductionmentioning

confidence: 71%

Detector response in the buildup region of small MV fields

2020

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Purpose The model used to calculate dose distributions in a radiotherapy treatment plan relies on the data entered during beam commissioning. The quality of these data heavily depends on the detector choice made, especially in small fields and in the buildup region. Therefore, it is necessary to identify suitable detectors for measurements in the buildup region of small fields. To aid the understanding of a detector's limitations, several factors that influence the detector signal are to be analyzed, for example, the volume effect due to the detector size, the response to electron contamination, the signal dependence on the polarity used, and the effective point of measurement chosen. Methods We tested the suitability of different small field detectors for measurements of depth dose curves with a special focus on the surface‐near area of dose buildup for fields sized between 10 × 10 and 0.6 × 0.6 cm2. Depth dose curves were measured with 14 different detectors including plane‐parallel chambers, thimble chambers of different types and sizes, shielded and unshielded diodes as well as a diamond detector. Those curves were compared with depth dose curves acquired on Gafchromic film. Additionally, the magnitude of geometric volume corrections was estimated from film profiles in different depths. Furthermore, a lead foil was inserted into the beam to reduce contaminating electrons and to study the resulting changes of the detector response. The role of the effective point of measurement was investigated by quantifying the changes occurring when shifting depth dose curves. Last, measurements for the small ionization chambers taken at opposing biasing voltages were compared to study polarity effects. Results Depth‐dependent correction factors for relative depth dose curves with different detectors were derived. Film, the Farmer chamber FC23, a 0.13 cm3 scanning chamber CC13 and a plane‐parallel chamber PPC05 agree very well in fields sized 4 × 4 and 10 × 10 cm2. For most detectors and in smaller fields, depth dose curves differ from the film. In general, shielded diodes require larger corrections than unshielded diodes. Neither the geometric volume effect nor the electron contamination can account for the detector differences. The biggest uncertainty arises from the positioning of a detector with respect to the water surface and from the choice of the detector's effective point of measurement. Depth dose curves acquired with small ionization chambers differ by over 15% in the buildup region depending on sign of the biasing voltage used. Conclusions A scanning chamber or a PPC40 chamber is suitable for fields larger than 4 × 4 cm2. Below that field size, the microDiamond or small ionization chambers perform best requiring the smallest corrections at depth as well as in the buildup region. Diode response changes considerably between the different types of detectors. The position of the effective point of measurement has a huge effect on the resulting curves, therefore detector specific rather than general shifts of half th...

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“…The increased surface dose observed with the sheet in place corresponds to a water depth of approximately 2 mm. 26 The increase in surface dose needs to be carefully considered prior to clinical implementation, but we expect that by reducing the thickness and/or scintillator concentration in the film, the equivalent thickness can be reduced to half of its current value. The camera utilized in this study was a simple CMOS camera with a cost of approximately $1500.…”

Section: Discussionmentioning

confidence: 99%

Monitoring external beam radiotherapy using real‐time beam visualization

Jenkins

Naczynski

et al. 2015

Medical Physics

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Purpose: To characterize the performance of a novel radiation therapy monitoring technique that utilizes a flexible scintillating film, common optical detectors, and image processing algorithms for real-time beam visualization (RT-BV). Methods: Scintillating films were formed by mixing Gd 2 O 2 S:Tb (GOS) with silicone and casting the mixture at room temperature. The films were placed in the path of therapeutic beams generated by medical linear accelerators (LINAC). The emitted light was subsequently captured using a CMOS digital camera. Image processing algorithms were used to extract the intensity, shape, and location of the radiation field at various beam energies, dose rates, and collimator locations. The measurement results were compared with known collimator settings to validate the performance of the imaging system. Results: The RT-BV system achieved a sufficient contrast-to-noise ratio to enable real-time monitoring of the LINAC beam at 20 fps with normal ambient lighting in the LINAC room. The RT-BV system successfully identified collimator movements with sub-millimeter resolution. Conclusions: The RT-BV system is capable of localizing radiation therapy beams with sub-millimeter precision and tracking beam movement at video-rate exposure. C 2015 American Association of Physicists in Medicine. [http://dx

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An investigation of the depth dose in the build-up region, andsurface dose for a 6-MV therapeutic photon beam: Monte Carlo simulation and measurements

Cited by 51 publications

References 26 publications

Hypofractionated Stereotactic Radiotherapy for Auditory Canal or Middle Ear Cancer

Hypofractionated Stereotactic Radiotherapy for Auditory Canal or Middle Ear Cancer

Detector response in the buildup region of small MV fields

Monitoring external beam radiotherapy using real‐time beam visualization

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