An investigation into factors affecting the precision of CT radiation dose profile width measurements using radiochromic films

Li, Baojun; Behrman, Richard H.

doi:10.1118/1.4914396

Cited by 5 publications

(3 citation statements)

References 22 publications

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“…The reconstructed images were 1.0 mm thick with a reconstruction interval of 1.0 mm. The film dosimeter [ 19 , 20 , 21 , 22 , 23 , 24 ] used to measure surface dose distribution in the z-axis direction comprised a Gafchromic film (XR-SP2, Ashland Ltd., Wilmington, NJ, USA) and a film scanner (Epson Expression 11000G flat-table document scanner and “DD-system,” R-Tech Inc., Tokyo, Japan). Surface dose distributions were analyzed using software (DD-Analysis Ver.10.33, R-Tech Inc., Tokyo, Japan) on a personal computer (Windows 7; R-Tech Inc., Tokyo, Japan).…”

Section: Methodsmentioning

confidence: 99%

Influence of Pitch on Surface Dose Distribution and Image Noise of Computed Tomography Scans

Yamada

Kawata

Amano

et al. 2023

Sensors

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This study evaluated the effect of pitch on 256-slice helical computed tomography (CT) scans. Cylindrical water phantoms (CWP) were measured using axial and helical scans with various pitch values. The surface dose distributions of CWP were measured, and reconstructed images were obtained using filtered back-projection (FBP) and iterative model reconstruction (IMR). The image noise in each reconstructed image was decomposed into a baseline component and another component that varied along the z-axis. The baseline component of the image noise was highest at the center of the reconstructed image and decreased toward the edges. The normalized 2D power spectra for each pitch were almost identically distributed. Furthermore, the ratios of the 2D power spectra for IMR and FBP at different pitch values were obtained. The magnitudes of the components varying along the z-axis were smallest at the center of the reconstructed image and increased toward the edge. The ratios of the 3D power spectra on the fx axis for IMR and FBP at different pitch values were obtained. The results showed that the effect of the pitch was related to the component that varied along the z-axis. Furthermore, the pitch had a smaller effect on IMR than on FBP.

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Section: Methodsmentioning

confidence: 99%

Influence of Pitch on Surface Dose Distribution and Image Noise of Computed Tomography Scans

Yamada

Kawata

Amano

et al. 2023

Sensors

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“…Measurement of effective beam width is a component of routine CT quality assurance (ACR 2012). A number of methods exist in the literature for measuring effective beam width (Liu et al 2005, Hansson et al 2010, Jackson et al 2013, Li and Behrman 2015. In the study by Jackson et al (2013), the authors compared effective beam width (i.e.…”

Section: Photon Path Lengths Through the Bowtie Filtermentioning

confidence: 99%

Analysis of uncertainties in Monte Carlo simulated organ and effective dose in chest CT: scanner- and scan-related factors

et al. 2017

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In Monte Carlo simulation of CT dose, many input parameters are required (e.g. bowtie filter properties and scan start/end location). Our goal was to examine the uncertainties in patient dose when input parameters were inaccurate. Using a validated Monte Carlo program, organ dose from a chest CT scan was simulated for an average-size female phantom using a reference set of input parameter values (treated as the truth). Additional simulations were performed in which errors were purposely introduced into the input parameter values. The effects on four dose quantities were analyzed: organ dose (mGy/mAs), effective dose (mSv/mAs), CTDI-normalized organ dose (unitless), and DLP-normalized effective dose (mSv/mGy · cm). At 120 kVp, when spectral half value layer deviated from its true value by ±1.0 mm Al, the four dose quantities had errors of 18%, 7%, 14% and 2%, respectively. None of the dose quantities were affected significantly by errors in photon path length through the graphite section of the bowtie filter; path length error as large as 5 mm produced dose errors of ⩽2%. In contrast, error of this magnitude in the aluminum section produced dose errors of ⩽14%. At a total collimation of 38.4 mm, when radiation beam width deviated from its true value by ± 3 mm, dose errors were ⩽7%. Errors in tube starting angle had little impact on effective dose (errors ⩽ 1%); however, they produced organ dose errors as high as 66%. When the assumed scan length was longer by 4 cm than the truth, organ dose errors were up to 137%. The corresponding error was 24% for effective dose, but only 3% for DLP-normalized effective dose. Lastly, when the scan isocenter deviated from the patient's anatomical center by 5 cm, organ and effective dose errors were up 18% and 8%, respectively.

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“…Li et al . 14 used radiochromic films to record CT dose profiles and investigate the impact of X-ray energy and spatial resolution. Some physical phantoms for image quality assurance, e.g.…”

Section: Introductionmentioning

confidence: 99%

Dose and slice thickness evaluation with nMAG gel dosimeters in computed tomography

Chuang

2018

Sci Rep

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Computed tomography (CT) has been widely used in clinical diagnosis. It is important to estimate radiation dose and perform image quality assurance procedures for CT scans. In this study, nMAG gel dosimeters were used to simultaneously measure the 300-mm weighted CT dose index (CTDI) and slice sensitivity profile (SSP) for multiple detector CT (MDCT). Magnetic resonance imaging (MRI) was performed on the irradiated gel to create R2‒dose response curves for the tube voltages of 120 and 140 kVp. The gel dosimeters were loaded in three home-made cylindrical phantoms to obtain CTDI100 and CTDI300. The full width at half maximum (FWHM) for 2, 5, 10, 14.4, and 38.4-mm slice thicknesses was measured and compared with the result obtained by radiochromic films. The difference in weighted CTDI100 obtained by the gel dosimeter and ionization chamber was less than 1%. The CTDI efficiency at 120 and 140 kVp was in the range of 80.1%–82.5%. The FWHM of SSP measured by the gel dosimeter matched very well with the nominal slice thickness. The use of nMAG gel dosimeters combined with the home-made cylindrical phantoms can provide 300-mm weighted CTDI and slice thickness information, showing potential for quality assurance and clinical applications in MDCT.

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An investigation into factors affecting the precision of CT radiation dose profile width measurements using radiochromic films

Cited by 5 publications

References 22 publications

Influence of Pitch on Surface Dose Distribution and Image Noise of Computed Tomography Scans

Influence of Pitch on Surface Dose Distribution and Image Noise of Computed Tomography Scans

Analysis of uncertainties in Monte Carlo simulated organ and effective dose in chest CT: scanner- and scan-related factors

Dose and slice thickness evaluation with nMAG gel dosimeters in computed tomography

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