High resolution polymer gel dosimetry for small beam irradiation using a 7T micro-MRI scanner

Ding, Xuanfeng; Olsen, John O.; Best, Ryan; Bennett, Michael; McGowin, I; Dorand, Jennifer E.; Link, Kerry M.; Bourland, J. Daniel

doi:10.1088/1742-6596/250/1/012094

Cited by 6 publications

(7 citation statements)

References 3 publications

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“…1 When a volume of gel is irradiated, the radiation sensitive material undergoes a measurable change in the magnetic relaxation, density, and optical density, which is directly related to the radiation dose received, potentially providing a high-resolution three-dimensional measurement of the dose absorbed by the gel. [2][3][4][5][6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21] An important consideration for any dosimeter prior to clinical use is the spatial resolution and the accuracy in the measurement of the absorbed dose. Many authors have investigated gel dosimetry as a solution.…”

Section: Introductionmentioning

confidence: 99%

“…Many authors have investigated gel dosimetry as a solution. [2][3][4][5][6][7] One of the challenges in gel dosimetry is the extraction of the dose information once the gel has been irradiated. Various techniques have been employed for gel dose readout, including magnetic resonance imaging (MRI), [11][12][13] optical CT scanning (OCT), 15,16 x-ray computed tomography (CT), 20,21 and ultrasound.…”

Section: Introductionmentioning

confidence: 99%

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Improved image quality for x‐ray CT imaging of gel dosimeters

et al. 2011

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Section: Introductionmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

Improved image quality for x‐ray CT imaging of gel dosimeters

et al. 2011

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“…12 The importance of extending the investigations to higher magnetic field strengths (above 3 T) was underscored by Hassani et al 7 The dose distribution imaging at increased spatial resolution achievable at these fields could open new possibilities for small beam dosimetry. However, apart of several published works, 8,9 application of high magnetic field microimaging in polymer gel dosimetry remains an unexplored area of research.…”

Section: Introductionmentioning

confidence: 99%

Application of high field magnetic resonance microimaging in polymer gel dosimetry

et al. 2020

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The purpose of this work was to examine the suitability of VIPAR nd polymer gel-9.4 T magnetic resonance microimaging system for high spatial resolution dose distribution measurements. Methods: The VIPAR nd samples (3 cm in outside diameter and 12 cm in height) were exposed to ionizing radiation by using a linear accelerator (Varian TrueBeam, USA; 6 MV x-ray beam). In the calibration stage, nine gel dosimeter vials were irradiated in a water phantom homogenously to the doses from 1.5 to 30 Gy in order to obtain R2-dose relation. In the verification stage, two gel dosimeter vials were irradiated in the half beam penumbra area of 10 9 10 cm radiation field using the amount of monitor units appropriate to deliver 20 Gy at the field center. The gels were imaged on a vertical 9.4 T magnetic resonance (MR) microimaging scanner using single slice and multislice (9 slices) multiecho (90 9 7 ms) sequences at the spatial resolutions of 0.2-0.4 9 0.2-0.4 9 3 mm 3 and 0.2-0.4 9 0.2-0.4 9 1 mm 3 respectively. The gels were subjected to microimaging during the period of two weeks after irradiation. The reference data consisted of the dose profiles measured using the diode dosimetry, radiochromic film, ionization chamber, and the water phantom system. Results: The VIPAR nd-9.4 T MR microimaging system was characterized by the dose sensitivity of 0.067 AE 0.002 Gy À1 s À1 at day 3 after irradiation. The dose resolution at 10 Gy (at P = 95%) was equal to 0.42 Gy at day 3 after irradiation using a single slice sequence (0.2 9 0.2 9 3 mm 3) and 2.0 Gy at day 4 after irradiation using a multislice sequence (0.2 9 0.2 9 1 mm 3) for one signal acquisition (measurement time: 15 min). These values were improved by~1.4-fold when using four signal acquisitions in the single slice sequence, and by~2.78-fold for 12 signal acquisitions in the multislice sequence. Furthermore, decreasing the in-plane resolution from 0.2 9 0.2 mm 2 to 0.4 9 0.4 mm 2 resulted in a dose resolution of 0.3 Gy and 1 Gy at 10 Gy (at P = 95%) for one signal acquisition in the single slice and multislice sequences respectively (measurement time: 7.5 min). As reveals from the gamma index analysis the dose distributions measured at days 3-4 postirradiation using both VIPAR nd verification phantoms agree with the data obtained using a silicon diode, assuming 1 mm/5% criterion. A good interphantom reproducibility of the polymer gel dosimetry was proved by monitoring of two phantoms up to 10 days after irradiation. However, the agreement between the dose distributions measured using the diode and polymer gel started to get worse from day 5 after irradiation. Conclusion: The VIPAR nd-9.4T MR microimaging system allows to obtain dose resolution of 0.42 Gy at 10 Gy (at P = 95%) for a spatial resolution of 0.2 9 0.2 9 3 mm 3 (acquisition time:

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“…Readout of dose information from polymer gel dosimeters can be undertaken with imaging techniques, such as magnetic resonance imaging (MRI) (2‐4) and optical computed tomography (CT), (5‐7) though these modalities are not available at all radiation oncology clinics. X‐ray CT, which is commonly available in radiotherapy departments, is a viable alternative for scanning gel images, despite suffering from poor signal‐to‐noise ratio owing to a relatively small increase in gel density (8,9) .…”

Section: Introductionmentioning

confidence: 99%

A feasibility study of multislice X‐ray CT imaging of gel dosimeters using the “zero scan” method

Kakakhel

Kairn²,

Charles³

et al. 2014

J Applied Clin Med Phys

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This study extends the ‘zero scan’ method for CT imaging of polymer gel dosimeters to include multislice acquisitions. Multislice CT images consisting of 24 slices of 1.2 mm thickness were acquired of an irradiated polymer gel dosimeter and processed with the zero scan technique. The results demonstrate that zero scan‐based gel readout can be successfully applied to generate a three‐dimensional image of the irradiated gel field. Compared to the raw CT images, the processed figures and cross‐gel profiles demonstrated reduced noise and clear visibility of the penumbral region. Moreover, these improved results further highlight the suitability of this method in volumetric reconstruction with reduced CT data acquisition per slice. This work shows that 3D volumes of irradiated polymer gel dosimeters can be acquired and processed with X‐ray CT.PACS number: 87.57.Q‐, 87.57.nf, 87.55.‐x

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High resolution polymer gel dosimetry for small beam irradiation using a 7T micro-MRI scanner

Cited by 6 publications

References 3 publications

Improved image quality for x‐ray CT imaging of gel dosimeters

Improved image quality for x‐ray CT imaging of gel dosimeters

Application of high field magnetic resonance microimaging in polymer gel dosimetry

A feasibility study of multislice X‐ray CT imaging of gel dosimeters using the “zero scan” method

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