Exposure dose measurement during diagnostic pediatric X-ray examination using an optically stimulated luminescence (OSL) dosimeter based on precise dose calibration taking into consideration variation of X-ray spectra

Asahara, Takashi; Hayashi, Hiroaki; Goto, Sota; Tomita, Emi; Kimoto, Natsumi; Mihara, Yoshiki; Asakawa, Tsuyoshi; Kanazawa, Yuki; Katsumata, Akitoshi; Higashino, Kosaku; Yamashita, Kazuo; Okazaki, Toshiya; Hashizume, Takumi

doi:10.1016/j.radmeas.2018.10.007

Cited by 15 publications

(11 citation statements)

References 20 publications

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“…The energy chosen for the calibration of the detector is important, as it is often very different from the energy received monthly. A correction factor must be taken into account 39 . However, this factor is based on an average theoretical energy received and not on the real exposure.…”

Section: Discussionmentioning

confidence: 99%

Characterisation and mapping of scattered radiation fields in interventional radiology theatres

Nowak

Carbonez

Krauß

et al. 2020

Sci Rep

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We used the Timepix3 hybrid pixel detector technology in order to determine the exposure of medical personnel to ionizing radiation in an interventional radiology room. We measured the energy spectra of the scattered radiation generated by the patient during X-ray image-guided interventional procedures. We performed measurements at different positions and heights within the theatre. We first observed a difference in fluence for each staff member. As expected, we found that the person closest to the X-ray tube is the most exposed while the least exposed staff member is positioned at the patient’s feet. Additionally, we observed a shift in energy from head to toe for practitioners, clearly indicating a non-homogenous energy exposure. The photon counting Timepix3 detector provides a new tool for radiation field characterisation that is easier-to-use and more compact than conventional X-ray spectrometers. The spectral information is particularly valuable for optimising the use of radiation protection gear and improving dosimetry surveillance programs. We also found the device very useful for training purposes to provide awareness and understanding about radiation protection principles among interventional radiology staff.

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Section: Discussionmentioning

confidence: 99%

Characterisation and mapping of scattered radiation fields in interventional radiology theatres

Nowak

Carbonez

Krauß

et al. 2020

Sci Rep

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“…We will explain a procedure to determine dose calibration factors by taking into consideration the energy dependence of an OSL dosimeter and differences found in various x-ray spectra. Our previous study 16 aimed to derive a calibration factor used for general x-ray diagnosis, and the effects of beam hardening, scattered x-rays, and backscattering x-rays were evaluated. Namely, when an x-ray spectrum including the above effects is obtained, a proper calibration factor can be determined.…”

Section: A | Calibration Procedures Taking Into Consideration Energymentioning

confidence: 99%

“…In this section, we will describe the experimental procedure to deter- where "Counts" and "ϵ" were measured response and intrinsic detection sensitivity, respectively. 13,16 To reduce statistical uncertainty, three OSL dosimeters were individually irradiated at the above conditions, and each dosimeter was read five times using a commercially available reading device (microStar, Landauer, Inc., Illinois, USA). We adopted the mean value of Counts/ϵ for 15 readings.…”

Section: C | Experiments To Determine the Actual Calibration Factormentioning

confidence: 99%

“…Basically speaking, the energy dependence of the dosimeter is the difference of mass energy-absorption coefficients between the OSL dosimeter and air 15 ; this means that energy dependence for polychromatic x-ray distribution should be analyzed with polychromatic x-rays and should not be treated as monochromatic x-rays. 16 The dose to the eye lens is mainly caused by scattered x-rays from the patient. 3,17 This means that a person evaluating doses should pay close attention to the verifications of the polychromatic x-ray spectrum related to the scattered and penetrating x-rays.…”

Section: Introductionmentioning

confidence: 99%

“…Recently, we have proposed a precise calibration procedure in which we considered the polychromatic x-ray distribution and the energy dependence of an OSL dosimeter. 16 In this study, we applied this general method to a specific situation of eye lens dosimetry, and aimed to evaluate the precisely determined calibration factors. Because many clinical studies use a vendor-supplied calibration factor, we also investigated the applicability of this factor.…”

Section: Introductionmentioning

confidence: 99%

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Evaluation of calibration factor of OSLD toward eye lens exposure dose measurement of medical staff during IVR

Asahara

Hayashi

Goto

et al. 2020

J Applied Clin Med Phys

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The eye lens is a sensitive organ of which an x-ray exposure dose should be managed during interventional radiology (IVR). In the actual situations, the eye lens is exposed to scattered x-rays; they have different from the standard x-ray energies which are used for general dose calibration of the dosimeter. To perform precise dose measurement, the energy dependence of the dosimeter should be properly accounted for when calibrating the dosimeter. The vendor supplies a calibration factor using 80-kV diagnostic x-rays under a free-air condition. However, whether it is possible to use this calibration factor to evaluate the air kerma during the evaluation of the eye lens dose is unclear. In this paper, we aim to precisely determine calibration factors, and also examine the possible application of using a vendor-supplied calibration factor. First, the x-ray spectrum at the eye lens position during fluoroscopy was measured with a CdTe x-ray spectrometer. We mimicked transfemoral cardiac catheterization using a human-type phantom. Second, we evaluated the doses and calibration factors at three dosimetric points: front and back of protective goggles, and the front of the head (eye lens position). We used the measured x-ray spectrum to determine the incident photon distribution in the eye lens regions, and x-ray spectra corresponding to the dosimetric points around the eye lens were estimated using Monte Carlo simulation. Although the calibration factors varied with dosimetric positions, we found that the factors obtained were similar to the vendorsupplied calibration factor. Furthermore, based on the experiment, we propose a practical way to calibrate an OSL dosimeter in an actual clinical situation. A person evaluating doses can use a vendor-supplied calibration factor without any corrections for energy dependences, only when they add a systematic uncertainty of 5%. This evidence will strongly support actual exposure dose measurement during a clinical study.

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A disposable OSL dosimeter for in vivo measurement of rectum dose during brachytherapy

et al. 2021

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Purpose We aimed to develop a disposable rectum dosimeter and to demonstrate its ability to measure exposure dose to the rectum during brachytherapy for cervical cancer treatment using high‐dose rate 192Ir. Our rectum dosimeter measures the dose with an optically stimulated luminescence (OSL) sheet which was furled to a catheter. The catheter we used is 6 mm in diameter; therefore, it is much less invasive than other rectum dosimeters. The rectum dosimeter developed in this study has the characteristics of being inexpensive and disposable. It is also an easy‐to‐use detector that can be individually sterilized, making it suitable for clinical use. Methods To obtain a dose calibration curve, phantom experiments were performed. Irradiation was performed using a cubical acrylic phantom, and the response of the OSL dosimeter was calibrated with the calculation value predicted by the treatment planning system (TPS). Additionally, the dependence of catheter angle on the dosimeter position and repeatability were evaluated. We also measured the absorbed dose to the rectum of patients who were undergoing brachytherapy for cervical cancer (n = 64). The doses measured with our dosimeters were compared with the doses calculated by the TPS. In order to examine the causes of large differences between measured and planned doses, we classified the data into common and specific cases when performing this clinical study. For specific cases, the following three categories were considered: (a) patient movement, (b) gas in the vagina and/or rectum, and (c) artifacts in the X‐ray image caused by applicators. Results A dose calibration curve was obtained in the range of 0.1 Gy–10.0 Gy. From the evaluation of the dependence of catheter angle on the dosimeter position and repeatability, we determined that our dosimeter can measure rectum dose with an accuracy of 3.1% (k = 1). In this clinical study, we succeeded in measuring actual doses using our rectum dosimeter. We found that the deviation of the measured dose from the planned dose was derived to be 12.7% (k = 1); this result shows that the clinical study included large elements of uncertainty. The discrepancies were found to be due to patient motion during treatment, applicator movement after planning images were taken, and artifacts in the planning images. Conclusions We present the idea that a minimally invasive rectum dosimeter can be fabricated using an OSL sheet. Our clinical study demonstrates that a rectum dosimeter made from an OSL sheet has sufficient ability to evaluate rectum dose. Using this dosimeter, valuable information concerning organs at risk can be obtained during brachytherapy.

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Exposure dose measurement during diagnostic pediatric X-ray examination using an optically stimulated luminescence (OSL) dosimeter based on precise dose calibration taking into consideration variation of X-ray spectra

Cited by 15 publications

References 20 publications

Characterisation and mapping of scattered radiation fields in interventional radiology theatres

Characterisation and mapping of scattered radiation fields in interventional radiology theatres

Evaluation of calibration factor of OSLD toward eye lens exposure dose measurement of medical staff during IVR

A disposable OSL dosimeter for in vivo measurement of rectum dose during brachytherapy

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