Comparison of proton and x-ray conformal dose distributions for radiosurgery applications

The purpose of this study was to apply Monte Carlo (MC) based simulations to design a new collimation system to achieve a larger beam size (2 ± 0.1 cm) and tight penumbra (< 1 mm) with a kV X-ray small animal irradiator. The BEAMnrc and DOSXYZnrc MC-based programs were adapted to simulate the system. First the aperture of the primary collimator was expanded until the desired size of the beam was obtained. Subsequently, the beam was trimmed by reducing the aperture size of the secondary collimator in order to eliminate low energy scattered photons and sharpen the penumbra. Finally, the new collimator was constructed and the resultant dose distributions were evaluated with EBT2 film measurements. From the MC computed dose profiles, a 2.1 cm FWHM (1.9 cm width at 95% of the dose) and a sharp penumbra (< 1.0 mm) at 1.0 cm depth in water were obtained. Dose distribution comparisons between the EBT2 film measurements and the MC calculations showed acceptable agreement. MC-based calculation is an effective tool to expedite the creation of new collimator designs and avoid costly machining.

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PROPOSAL FOR LOCAL DIAGNOSTIC REFERENCE LEVELS IN GENERAL RADIOGRAPHY IN JAPAN

Radiation Protection Dosimetry ◽

10.1093/rpd/ncz172 ◽

2019 ◽

Author(s):

Yasuki Asada ◽

Koji Ono ◽

Yuya Kondo ◽

Kazuma Sugita ◽

Takuma Ichikawa ◽

...

Keyword(s):

Radiation Dose ◽

Diagnostic Reference Levels ◽

Reference Levels ◽

Dose Distributions ◽

X Ray ◽

Non Invasive ◽

Air Kerma ◽

Aichi Prefecture

Abstract The present study aimed to propose local diagnostic reference levels (DRLs) formulated by calculating entrance surface doses for general radiography at 20 facilities of Aichi prefecture in Japan, by comparing these values with DRLs established in Japan in 2015 (DRLs 2015) and assessing radiation dose differences among facilities. X-ray outputs (half-value layer and air kerma) of each facility were measured with a non-invasive type of detector. The results were employed to formulate local DRLs based on the 75th percentiles of dose distributions. These local DRLs were lower than the DRLs 2015 for all examinations. If proposed local DRLs from other 46 prefectures can be collected, this paper can be used to benefit the next effort to draft better DRL for Japan.

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Effects of Finite Angular Steps and Extent of Profile Data on the Calculation of Rotational X-Ray Dose Distributions

Medical Dosimetry ◽

10.1016/s0958-3947(98)90142-x ◽

1988 ◽

Vol 13 (1) ◽

pp. 44

Author(s):

R.G. Kurup ◽

K.R. Hogstrom ◽

C.C. Hwang

Keyword(s):

Profile Data ◽

Dose Distributions ◽

X Ray

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EPID – a useful interfraction QC tool

Polish Journal of Medical Physics and Engineering ◽

10.2478/pjmpe-2019-0029 ◽

2019 ◽

Vol 25 (4) ◽

pp. 221-228 ◽

Cited By ~ 1

Author(s):

Aleksandra Klimas ◽

Aleksandra Grządziel ◽

Dominika Plaza ◽

Barbara Bekman ◽

Bożena Woźniak ◽

...

Keyword(s):

Treatment Session ◽

Measured Signal ◽

Dose Distributions ◽

Imaging Device ◽

Detector Arrays ◽

X Ray ◽

Gamma Index ◽

Field Geometry ◽

Two Parameters ◽

Delivered Dose

Abstract Biomedical accelerators used in radiotherapy are equipped with detector arrays which are commonly used to obtain the image of patient position during the treatment session. These devices use both kilovolt and megavolt x-ray beams. The advantage of EPID (Electronic Portal Imaging Device) megavolt panels is the correlation of the measured signal with the calibrated dose. The EPID gives a possibility to verify delivered dose. The aim of the study is to answer the question whether EPID can be useful as a tool for interfraction QC (quality control) of dose and geometry repeatability. The EPID system has been calibrated according to the manufacturer’s recommendations to obtain a signal and dose values correlation. Initially, the uncertainty of the EPID matrix measurement was estimated. According to that, the detecting sensitivity of two parameters was checked: discrepancies between the planned and measured dose and field geometry variance. Moreover, the linearity of measured signal-dose function was evaluated. In the second part of the work, an analysis of several dose distributions was performed. In this study, the analysis of clinical cases was limited to stereotactic dynamic radiotherapy. Fluence maps were obtained as a result of the dose distribution measurements with the EPID during treatment sessions. The compatibility of fluence maps was analyzed using the gamma index. The fluence map acquired during the first fraction was the reference one. The obtained results show that EPID system can be used for interfraction control of dose and geometry repeatability.

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Analysis of a novel X-ray lens for converging beam radiotherapy

Scientific Reports ◽

10.1038/s41598-021-98888-8 ◽

2021 ◽

Vol 11 (1) ◽

Author(s):

Dirk A. Bartkoski ◽

Aharon Bar-David ◽

Michael Kleckner ◽

Dragan Mirkovic ◽

Ramesh Tailor ◽

...

Keyword(s):

Focal Spot ◽

Treatment Approach ◽

Target Volume ◽

Optimal Placement ◽

Radiation Beam ◽

Dose Distributions ◽

X Ray ◽

Radiation Delivery ◽

Novel Approach ◽

Physical Principles

AbstractWe describe the development and analysis of a new teletherapy modality that, through a novel approach to targeted radiation delivery, has the potential to provide greater conformality than conventional photon-based treatments. The proposed system uses an X-ray lens to reflect photons from a conventional X-ray tube toward a focal spot. The resulting dose distributions have a highly localized peak dose, with lower doses in the converging radiation cone. Physical principles governing the design of this system are presented, along with a series of measurements analyzing various characteristics of the converging beam. The beam was designed to be nearly monoenergetic (~ 59 keV), with an energy bandwidth of approximately 10 keV allowing for treatment energies lower than conventional therapies. The focal spot was measured to be approximately 2.5 cm long and 4 mm wide. Mounting the proposed X-ray delivery system on a robotic arm would allow sub-millimeter accuracy in focal spot positioning, resulting in highly conformal dose distribution via the optimal placement of individual focal spots within the target volume. Aspects of this novel radiation beam are discussed considering their possible clinical application as a treatment approach that takes maximum advantage of the unique properties afforded by converging X-ray beam therapy.

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