Micrometer‐resolved film dosimetry using a microscope in microbeam radiation therapy

Bartzsch, Stefan; Lott, Johanna; Welsch, Katrin; Bräuer-Krisch, Elke; Oelfke, Uwe

doi:10.1118/1.4922001

Cited by 40 publications

(55 citation statements)

References 30 publications

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“…Close to the collimator beam, penumbras are sharp and approximately equal to those measured at the ESRF. The 10% to 90% penumbra definition yields 29 μ m penumbra width in film dosimetry measurements at the ESRF 23 . However, x‐ray tube generated microbeams had clearly wider penumbras when moving away from the collimator.…”

Section: Discussionmentioning

confidence: 99%

“…Exposure times were chosen such that peak or valley doses respectively fell into a range between 1 and 10 Gy. Readout of the exposed films was carried out with microscopy using the methods described previously 23 . Calibration of the films was performed in an open field, i.e., without collimator, and reference dosimetry by a semiflex TW31010 and farmer TW30002‐1 ionization chamber (PTW, Darmstadt, Germany).…”

Section: Methodsmentioning

confidence: 99%

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A preclinical microbeam facility with a conventional x‐ray tube

et al. 2016

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Purpose:Microbeam radiation therapy is an innovative treatment approach in radiation therapy that uses arrays of a few tens of micrometer wide and a few hundreds of micrometer spaced planar x‐ray beams as treatment fields. In preclinical studies these fields efficiently eradicated tumors while normal tissue could effectively be spared. However, development and clinical application of microbeam radiation therapy is impeded by a lack of suitable small scale sources. Until now, only large synchrotrons provide appropriate beam properties for the production of microbeams.Methods:In this work, a conventional x‐ray tube with a small focal spot and a specially designed collimator are used to produce microbeams for preclinical research. The applicability of the developed source is demonstrated in a pilot in vitro experiment. The properties of the produced radiation field are characterized by radiochromic film dosimetry.Results:50 μm wide and 400 μm spaced microbeams were produced in a 20 × 20 mm2 sized microbeam field. The peak to valley dose ratio ranged from 15.5 to 30, which is comparable to values obtained at synchrotrons. A dose rate of up to 300 mGy/s was achieved in the microbeam peaks. Analysis of DNA double strand repair and cell cycle distribution after in vitro exposures of pancreatic cancer cells (Panc1) at the x‐ray tube and the European Synchrotron leads to similar results. In particular, a reduced G2 cell cycle arrest is observed in cells in the microbeam peak region.Conclusions:At its current stage, the source is restricted to in vitro applications. However, moderate modifications of the setup may soon allow in vivo research in mice and rats.

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Section: Discussionmentioning

confidence: 99%

Section: Methodsmentioning

confidence: 99%

A preclinical microbeam facility with a conventional x‐ray tube

et al. 2016

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“…A method of obtaining 2D relative dose distributions of microbeams was developed by Bartzsch et al 24 using optical microscopy and EBT3 films, 25 which when using a microscope is technically capable of spatial resolutions better than 1 µm. Due to film grain inhomogeneities this is reduced to 5 µm in practice.…”

Section: B Current Verification Methodsmentioning

confidence: 99%

“…The objective was to quantify microbeam parameters and to compare the results of the analysis of the same deliveries to EBT3 films, using the optical microscopy method. 24…”

Section: B Current Verification Methodsmentioning

confidence: 99%

“…This investigation was carried out to evaluate the suitability of the newly developed vM1212 detector for its use in the analysis of preclinical radiotherapy microbeams, using the custom built multi‐slit collimator at the Helmholtz Zentrum München, Germany. The objective was to quantify microbeam parameters and to compare the results of the analysis of the same deliveries to EBT3 films, using the optical microscopy method …”

Section: Introductionmentioning

confidence: 99%

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Evaluation of a pixelated large format CMOS sensor for x‐ray microbeam radiotherapy

et al. 2020

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Purpose Current techniques and procedures for dosimetry in microbeams typically rely on radiochromic film or small volume ionization chambers for validation and quality assurance in 2D and 1D, respectively. Whilst well characterized for clinical and preclinical radiotherapy, these methods are noninstantaneous and do not provide real time profile information. The objective of this work is to determine the suitability of the newly developed vM1212 detector, a pixelated CMOS (complementary metal‐oxide‐semiconductor) imaging sensor, for in situ and in vivo verification of x‐ray microbeams. Methods Experiments were carried out on the vM1212 detector using a 220 kVp small animal radiation research platform (SARRP) at the Helmholtz Centre Munich. A 3 x 3 cm2 square piece of EBT3 film was placed on top of a marked nonfibrous card overlaying the sensitive silicon of the sensor. One centimeter of water equivalent bolus material was placed on top of the film for build‐up. The response of the detector was compared to an Epson Expression 10000XL flatbed scanner using FilmQA Pro with triple channel dosimetry. This was also compared to a separate exposure using 450 µm of silicon as a surrogate for the detector and a Zeiss Axio Imager 2 microscope using an optical microscopy method of dosimetry. Microbeam collimator slits with range of nominal widths of 25, 50, 75, and 100 µm were used to compare beam profiles and determine sensitivity of the detector and both film measurements to different microbeams. Results The detector was able to measure peak and valley profiles in real‐time, a significant reduction from the 24 hr self‐development required by the EBT3 film. Observed full width at half maximum (FWHM) values were larger than the nominal slit widths, ranging from 130 to 190 µm due to divergence. Agreement between the methods was found for peak‐to‐valley dose ratio (PVDR), peak to peak separation and FWHM, but a difference in relative intensity of the microbeams was observed between the detectors. Conclusions The investigation demonstrated that pixelated CMOS sensors could be applied to microbeam radiotherapy for real‐time dosimetry in the future, however the relatively large pixel pitch of the vM1212 detector limit the immediate application of the results.

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Synchrotron Radiation X‐ray Imaging in Biomedical Research

Wang

Yang

2018

Synchrotron Radiation in Materials Science

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Micrometer‐resolved film dosimetry using a microscope in microbeam radiation therapy

Cited by 40 publications

References 30 publications

A preclinical microbeam facility with a conventional x‐ray tube

A preclinical microbeam facility with a conventional x‐ray tube

Evaluation of a pixelated large format CMOS sensor for x‐ray microbeam radiotherapy

Synchrotron Radiation X‐ray Imaging in Biomedical Research

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