Characterization of OSL dosimeters for use in dose assessment in Computed Tomography procedures

Giansante, Louise; Santos, João; Umisedo, Nancy K.; Terini, Ricardo Andrade; Costa, Paulo Roberto

doi:10.1016/j.ejmp.2018.02.009

Cited by 16 publications

(10 citation statements)

References 19 publications

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“…20 In order to correlate the TL value to the Air Kerma (K Air ), calibration curves were constructed using both an RQT 9 X ray beam quality 21 generated by a Philips MCN 421 equipment (Philips, Germany) and a Philips Brilliance 64 CT scanner. 22 Two SSDL calibrated ion chambers (30 cc from PTW, Freiburg, Germany, and 0.6 cc from Radcal Corporation, Monrovia, CA, USA) were used to measure the air kerma. These calibration curves were adopted for the organ doses estimations with the anthropomorphic phantoms.…”

Section: A | Thermoluminescent Dosimetersmentioning

confidence: 99%

Organ doses evaluation for chest computed tomography procedures with TL dosimeters: Comparison with Monte Carlo simulations

Giansante

Martins

Nersissian

et al. 2018

J Applied Clin Med Phys

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PurposeTo evaluate organ doses in routine and low‐dose chest computed tomography (CT) protocols using an experimental methodology. To compare experimental results with results obtained by the National Cancer Institute dosimetry system for CT (NCICT) organ dose calculator. To address the differences on organ dose measurements using tube current modulation (TCM) and fixed tube current protocols.MethodsAn experimental approach to evaluate organ doses in pediatric and adult anthropomorphic phantoms using thermoluminescent dosimeters (TLDs) was employed in this study. Several analyses were performed in order to establish the best way to achieve the main results in this investigation. The protocols used in this study were selected after an analysis of patient data collected from the Institute of Radiology of the School of Medicine of the University of São Paulo (InRad). The image quality was evaluated by a radiologist from this institution. Six chest adult protocols and four chest pediatric protocols were evaluated. Lung doses were evaluated for the adult phantom and lung and thyroid doses were evaluated for the pediatric phantom. The irradiations were performed using both a GE and a Philips CT scanner. Finally, organ doses measured with dosimeters were compared with Monte Carlo simulations performed with NCICT.ResultsAfter analyzing the data collected from all CT examinations performed during a period of 3 yr, the authors identified that adult and pediatric chest CT are among the most applied protocol in patients in that clinical institution, demonstrating the relevance on evaluating organ doses due to these examinations. With regards to the scan parameters adopted, the authors identified that using 80 kV instead of 120 kV for a pediatric chest routine CT, with TCM in both situations, can lead up to a 28.7% decrease on the absorbed dose. Moreover, in comparison to the standard adult protocol, which is performed with fixed mAs, TCM, and ultra low‐dose protocols resulted in dose reductions of up to 35.0% and 90.0%, respectively. Finally, the percent differences found between experimental and Monte Carlo simulated organ doses were within a 20% interval.ConclusionsThe results obtained in this study measured the impact on the absorbed dose in routine chest CT by changing several scan parameters while the image quality could be potentially preserved.

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Section: A | Thermoluminescent Dosimetersmentioning

confidence: 99%

Organ doses evaluation for chest computed tomography procedures with TL dosimeters: Comparison with Monte Carlo simulations

Giansante

Martins

Nersissian

et al. 2018

J Applied Clin Med Phys

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“…In addition, this kind of OSL dosimeter (Al 2 O 3 :C) has a linear response with the radiation exposure that was subdued. The linearity and energy response of the OSL dosimeters had been investigated previously by Giansante et al 66 . The uncertainties associated to the OSL reading process were evaluated resulting in values lower than 5%.…”

Section: Methodsmentioning

confidence: 99%

A comprehensive Monte Carlo study of CT dose metrics proposed by the AAPM Reports 111 and 200

et al. 2021

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Purpose: A Monte Carlo (MC) modeling of single axial and helical CT scan modes has been developed to compute single and accumulated dose distributions. The radiation emission characteristics of an MDCT scanner has been modeled and used to evaluate the dose deposition in infinitely long head and body PMMA phantoms. The simulated accumulated dose distributions determined the approach to equilibrium function, H(L). From these H(L) curves, doserelated information was calculated for different head and body clinical protocols. Methods: The PENELOPE/penEasy package has been used to model the single axial and helical procedures and the radiation transport of photons and electrons in the phantoms. The bowtie filters, heel effect, focal-spot angle, and fan-beam geometry were incorporated. Head and body protocols with different pitch values were modeled for x-ray spectra corresponding to 80, 100, 120, and 140 kV. The analytical formulation for the single dose distributions and experimental measurements of single and accumulated dose distributions were employed to validate the MC results. The experimental dose distributions were measured with OSLDs and a thimble ion chamber inserted into PMMA phantoms. Also, the experimental values of the CTDI 100 along the center and peripheral axes of the CTDI phantom served to calibrate the simulated single and accumulated dose distributions. Results: The match of the simulated dose distributions with the reference data supports the correct modeling of the heel effect and the radiation transport in the phantom material reflected in the tails of the dose distributions. The validation of the x-ray source model was done comparing the CTDI ratios between simulated, measured and CTDosimetry data. The average difference of these ratios for head and body protocols between the simulated and measured data was in the range of 13-17% and between simulated and CTDosimetry data varied 10-13%. The distributions of simulated doses and those measured with the thimble ion chamber are compatible within 3%. In this study, it was demonstrated that the efficiencies of the CTDI 100 measurements in head phantoms with nT = 20 mm and 120 kV are 80.6% and 87.8% at central and peripheral axes, respectively. In the body phantoms with nT = 40 mm and 120 kV, the efficiencies are 56.5% and 86.2% at central and peripheral axes, respectively. In general terms, the clinical parameters such as pitch, beam intensity, and voltage affect the D eq values with the increase of the pitch decreasing the D eq and the beam intensity and the voltage increasing its value. The H(L) function does not change with the pitch values, but depends on the phantom axis (central or peripheral). Conclusions: The computation of the pitch-equilibrium dose product, Deq , evidenced the limitations of the CTDI 100 method to determine the dose delivered

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“…where D 0 is the air kerma, K s,i is the relative sensitivity correction factor between the individual elements of OSLD, and K Q is the energy correction factor in CT (Al-Senan and Hatab 2011; Giansante et al 2018).…”

Section: Methodsmentioning

confidence: 99%

Evaluation of Radiation Protection Methods for Assistant Staff during CT Imaging in High-energy Trauma: Lens Dosimetry with a Phantom Study

Ota¹,

Yokota

Kawasaki

et al. 2021

Health Physics

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Staff are exposed to radiation in the scanning room when assisting with CT scans of patients requiring ventilatory support during procedures. We measured lens doses using a phantom during a high-energy trauma protocol. Dosimetry showed that the unprotected lens received 2.02 mGy on the right and 1.91 mGy on the left, which are not negligible doses. Respective exposures to the right and left lens were 53.6% and 55.1% when wearing 0.07 mm Pb protective glasses with side covers; 53.7% and 64.2% when wearing 0.7 mm Pb glasses without side covers when facing away from the patient couch; and 92.1% and 91.2% using protective shielding in the gantry. Since the face direction may change during assistance with CT imaging, it is desirable that the protective glasses have a shape with a side cover. The protective shielding had a major radiation reduction effect, although it is expensive to acquire, install, and maintain.

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Characterization of OSL dosimeters for use in dose assessment in Computed Tomography procedures

Cited by 16 publications

References 19 publications

Organ doses evaluation for chest computed tomography procedures with TL dosimeters: Comparison with Monte Carlo simulations

Organ doses evaluation for chest computed tomography procedures with TL dosimeters: Comparison with Monte Carlo simulations

A comprehensive Monte Carlo study of CT dose metrics proposed by the AAPM Reports 111 and 200

Evaluation of Radiation Protection Methods for Assistant Staff during CT Imaging in High-energy Trauma: Lens Dosimetry with a Phantom Study

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