Cardiac computed tomography angiography (CCTA) studies have risen concern of radiobiological effe... more Cardiac computed tomography angiography (CCTA) studies have risen concern of radiobiological effects over the patients. Therefore, estimating radiation doses absorbed during CCTA is important. In this study, we compared radiation dose and image quality by using three different retrospective electrocardiography (ECG) protocols. A total of 123 patients undergoing CCTA were divided in three different groups. We used full-dose modulation (CareDose4D) technique in group (1); fixed tube current 200 mAs for group (2); and in group (3), chest circumference was used to adapt tube current (180-200 mAs) and tube potential (100-120 kVp). For groups (1) and (2), tube potential adapted depends on body mass index (BMI) in which it was 100 kVp for BMI < 27 kg/m2, and 120 kVp for BMI ≥ 27 kg/m2. Quantitive assessment of image quality was calculated by measuring signal intensity (SI) and image noise (IN) in the proximal segments of aorta root on left and right coronary arteries. Signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were also calculated by using SI and IN. Two experienced radiologists using a 4-point scale assessed the subjective image quality. Our results show that in group (1), the mean effective dose was 4.46 mSv (range: 1.75-8.6 mSv) and for group (2), the mean effective radiation dose was 5.07 mSv (range: 2.57-9.74 mSv) and in group (3), the mean effective dose was 5.85 mSv (range: 3.36-12.17 mSv). Group (1) representing 12% and 23% decrease in radiation dose comparing by groups (2) and (3). In multivariate analysis, adjusting for BMI, radiation dose for patients with BMI < 27 kg/m2 was significantly different; 2.53 mSv for group (1) compared to 3.54 mSv in group (2) and 5.207 in group (3) (p < 0.0001). In addition, lowering tube potential from 120 to 100 kVp in 200 mAs fixed tube current, represents 27% decrease in radiation dose. The quantitative image quality (IN, SI, SNR and CNR) was not statistically significant among the groups. To sum up, Retrospective-ECG gating may reduce radiation dose by using automatic tube current modulation and 100kVp tube potential with preservation of image quality in patient's whose BMI < 27 kg/m2.
Background: This study intended to measure radiation doses to various organs and calculate the ri... more Background: This study intended to measure radiation doses to various organs and calculate the risk of cancer incidence from neck computed tomography and head computed tomography scans of trauma patients by using a thermoluminescent dosimeter. Methods:We assessed 93 patients who presented to the Emergency Department. Based on their health conditions, different computed tomography scans were performed. We used a fixed tube current of 200 mAs and tube voltage of 120 kVp for all patients. Next, we derived the effective radiation dose by multiplying the dose length product and conversion factor of each computed tomography scan based on the International Commission on Radiological Protection 103. Organ dose estimations were calculated from the dosimeter readout. We calculated the life attributable risk for cancer incidence based on the Committee on the Biological Effects of Ionizing Radiation VII preferred models. Results: Neck computed tomography scans had a mean effective dose of 2.18 ...
Introduction: Accurate film dosimetry requires careful consideration of sources of uncertainty. S... more Introduction: Accurate film dosimetry requires careful consideration of sources of uncertainty. Some of the sources of uncertainty are dependent on the size and location of region of interest (ROI), especially in small fields. Avoiding the penumbra is often a reason for using a small ROI. In contrast, choosing very small ROIs may increase uncertainty due to the reduction of the sampling data. Using a dose profile as flat as possible for the ROI becomes more significant in small fields in which the flatness of profile is greatly affected by the penumbra. This study aims to evaluate dependency of measured dose on size and location of region of interest (ROI) in Gafchromic EBT3 film for small field dosimetry. Materials and Methods: Gafchromic EBT3 films were irradiated using the 6MV beam from a linear accelerator at 10 cm depth (100 cm SSD) of a solid water phantom for a range of field sizes of 6×6 to 100×100 mm2. For scanning, 48 bits RGB mode with a spatial resolution of 72 dpi was u...
PurposeTo evaluate dependence of measured dose on size and location of region of interest (ROI) i... more PurposeTo evaluate dependence of measured dose on size and location of region of interest (ROI) in Gafchromic EBT3 film dosimetry.MethodsGafchromic EBT3 films were irradiated perpendicularly using the 6MV beam from a linear accelerator at 10 cm depth (100 cm SSD) of a 30 × 30 × 20 cm3 solid water phantom for a range of field sizes of 6 × 6 to 100 × 100 mm2. ImageJ software was used for reading pieces of film. The appropriate location of ROIs in scanned films was found by two methods. First, the ROI was visually placed at the center of image. Second, the profile of pixel value versus distance was plotted and the center of profile was used for drawing ROI. Each scanned film was read using both methods and for three ROI sizes (1, 2, and 4 mm). A plastic scintillator, Exradin W1, was used as the reference dosimeter.ResultsComparing the three ROI sizes using both methods showed that there was less than 2% difference from reference in output factor measurements for field sizes larger or e...
Cardiac computed tomography angiography (CCTA) studies have risen concern of radiobiological effe... more Cardiac computed tomography angiography (CCTA) studies have risen concern of radiobiological effects over the patients. Therefore, estimating radiation doses absorbed during CCTA is important. In this study, we compared radiation dose and image quality by using three different retrospective electrocardiography (ECG) protocols. A total of 123 patients undergoing CCTA were divided in three different groups. We used full-dose modulation (CareDose4D) technique in group (1); fixed tube current 200 mAs for group (2); and in group (3), chest circumference was used to adapt tube current (180-200 mAs) and tube potential (100-120 kVp). For groups (1) and (2), tube potential adapted depends on body mass index (BMI) in which it was 100 kVp for BMI < 27 kg/m2, and 120 kVp for BMI ≥ 27 kg/m2. Quantitive assessment of image quality was calculated by measuring signal intensity (SI) and image noise (IN) in the proximal segments of aorta root on left and right coronary arteries. Signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were also calculated by using SI and IN. Two experienced radiologists using a 4-point scale assessed the subjective image quality. Our results show that in group (1), the mean effective dose was 4.46 mSv (range: 1.75-8.6 mSv) and for group (2), the mean effective radiation dose was 5.07 mSv (range: 2.57-9.74 mSv) and in group (3), the mean effective dose was 5.85 mSv (range: 3.36-12.17 mSv). Group (1) representing 12% and 23% decrease in radiation dose comparing by groups (2) and (3). In multivariate analysis, adjusting for BMI, radiation dose for patients with BMI < 27 kg/m2 was significantly different; 2.53 mSv for group (1) compared to 3.54 mSv in group (2) and 5.207 in group (3) (p < 0.0001). In addition, lowering tube potential from 120 to 100 kVp in 200 mAs fixed tube current, represents 27% decrease in radiation dose. The quantitative image quality (IN, SI, SNR and CNR) was not statistically significant among the groups. To sum up, Retrospective-ECG gating may reduce radiation dose by using automatic tube current modulation and 100kVp tube potential with preservation of image quality in patient's whose BMI < 27 kg/m2.
PurposeTo evaluate the effect of beam configuration with inaccurate or incomplete small field out... more PurposeTo evaluate the effect of beam configuration with inaccurate or incomplete small field output factors on the accuracy of dose calculations in treatment planning systems.MethodsOutput factors were measured using various detectors and for a range of field sizes. Three types of treatment machines were configured in two treatment planning systems. In the first (corrected) machine, the Exradin W1 scintillator was used to determine output factors. In the second (uncorrected) machine, the measured output factors by the A1SL ion chamber without considering output correction factors for small field sizes were utilized. In the third (clinical) machine, measured output factors by the Exradin W1 were used but not for field sizes smaller than 2 × 2 cm2. The dose computed by the anisotropic analytical algorithm (AAA), Acuros XB (AXB) and collapsed cone convolution/superposition (CCC) algorithms in the three machines were delivered using static (jaw‐, MLC‐, and jaw/MLC‐defined), and composi...
Cardiac computed tomography angiography (CCTA) studies have risen concern of radiobiological effe... more Cardiac computed tomography angiography (CCTA) studies have risen concern of radiobiological effects over the patients. Therefore, estimating radiation doses absorbed during CCTA is important. In this study, we compared radiation dose and image quality by using three different retrospective electrocardiography (ECG) protocols. A total of 123 patients undergoing CCTA were divided in three different groups. We used full-dose modulation (CareDose4D) technique in group (1); fixed tube current 200 mAs for group (2); and in group (3), chest circumference was used to adapt tube current (180-200 mAs) and tube potential (100-120 kVp). For groups (1) and (2), tube potential adapted depends on body mass index (BMI) in which it was 100 kVp for BMI < 27 kg/m2, and 120 kVp for BMI ≥ 27 kg/m2. Quantitive assessment of image quality was calculated by measuring signal intensity (SI) and image noise (IN) in the proximal segments of aorta root on left and right coronary arteries. Signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were also calculated by using SI and IN. Two experienced radiologists using a 4-point scale assessed the subjective image quality. Our results show that in group (1), the mean effective dose was 4.46 mSv (range: 1.75-8.6 mSv) and for group (2), the mean effective radiation dose was 5.07 mSv (range: 2.57-9.74 mSv) and in group (3), the mean effective dose was 5.85 mSv (range: 3.36-12.17 mSv). Group (1) representing 12% and 23% decrease in radiation dose comparing by groups (2) and (3). In multivariate analysis, adjusting for BMI, radiation dose for patients with BMI < 27 kg/m2 was significantly different; 2.53 mSv for group (1) compared to 3.54 mSv in group (2) and 5.207 in group (3) (p < 0.0001). In addition, lowering tube potential from 120 to 100 kVp in 200 mAs fixed tube current, represents 27% decrease in radiation dose. The quantitative image quality (IN, SI, SNR and CNR) was not statistically significant among the groups. To sum up, Retrospective-ECG gating may reduce radiation dose by using automatic tube current modulation and 100kVp tube potential with preservation of image quality in patient's whose BMI < 27 kg/m2.
Background: This study intended to measure radiation doses to various organs and calculate the ri... more Background: This study intended to measure radiation doses to various organs and calculate the risk of cancer incidence from neck computed tomography and head computed tomography scans of trauma patients by using a thermoluminescent dosimeter. Methods:We assessed 93 patients who presented to the Emergency Department. Based on their health conditions, different computed tomography scans were performed. We used a fixed tube current of 200 mAs and tube voltage of 120 kVp for all patients. Next, we derived the effective radiation dose by multiplying the dose length product and conversion factor of each computed tomography scan based on the International Commission on Radiological Protection 103. Organ dose estimations were calculated from the dosimeter readout. We calculated the life attributable risk for cancer incidence based on the Committee on the Biological Effects of Ionizing Radiation VII preferred models. Results: Neck computed tomography scans had a mean effective dose of 2.18 ...
Introduction: Accurate film dosimetry requires careful consideration of sources of uncertainty. S... more Introduction: Accurate film dosimetry requires careful consideration of sources of uncertainty. Some of the sources of uncertainty are dependent on the size and location of region of interest (ROI), especially in small fields. Avoiding the penumbra is often a reason for using a small ROI. In contrast, choosing very small ROIs may increase uncertainty due to the reduction of the sampling data. Using a dose profile as flat as possible for the ROI becomes more significant in small fields in which the flatness of profile is greatly affected by the penumbra. This study aims to evaluate dependency of measured dose on size and location of region of interest (ROI) in Gafchromic EBT3 film for small field dosimetry. Materials and Methods: Gafchromic EBT3 films were irradiated using the 6MV beam from a linear accelerator at 10 cm depth (100 cm SSD) of a solid water phantom for a range of field sizes of 6×6 to 100×100 mm2. For scanning, 48 bits RGB mode with a spatial resolution of 72 dpi was u...
PurposeTo evaluate dependence of measured dose on size and location of region of interest (ROI) i... more PurposeTo evaluate dependence of measured dose on size and location of region of interest (ROI) in Gafchromic EBT3 film dosimetry.MethodsGafchromic EBT3 films were irradiated perpendicularly using the 6MV beam from a linear accelerator at 10 cm depth (100 cm SSD) of a 30 × 30 × 20 cm3 solid water phantom for a range of field sizes of 6 × 6 to 100 × 100 mm2. ImageJ software was used for reading pieces of film. The appropriate location of ROIs in scanned films was found by two methods. First, the ROI was visually placed at the center of image. Second, the profile of pixel value versus distance was plotted and the center of profile was used for drawing ROI. Each scanned film was read using both methods and for three ROI sizes (1, 2, and 4 mm). A plastic scintillator, Exradin W1, was used as the reference dosimeter.ResultsComparing the three ROI sizes using both methods showed that there was less than 2% difference from reference in output factor measurements for field sizes larger or e...
Cardiac computed tomography angiography (CCTA) studies have risen concern of radiobiological effe... more Cardiac computed tomography angiography (CCTA) studies have risen concern of radiobiological effects over the patients. Therefore, estimating radiation doses absorbed during CCTA is important. In this study, we compared radiation dose and image quality by using three different retrospective electrocardiography (ECG) protocols. A total of 123 patients undergoing CCTA were divided in three different groups. We used full-dose modulation (CareDose4D) technique in group (1); fixed tube current 200 mAs for group (2); and in group (3), chest circumference was used to adapt tube current (180-200 mAs) and tube potential (100-120 kVp). For groups (1) and (2), tube potential adapted depends on body mass index (BMI) in which it was 100 kVp for BMI < 27 kg/m2, and 120 kVp for BMI ≥ 27 kg/m2. Quantitive assessment of image quality was calculated by measuring signal intensity (SI) and image noise (IN) in the proximal segments of aorta root on left and right coronary arteries. Signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) were also calculated by using SI and IN. Two experienced radiologists using a 4-point scale assessed the subjective image quality. Our results show that in group (1), the mean effective dose was 4.46 mSv (range: 1.75-8.6 mSv) and for group (2), the mean effective radiation dose was 5.07 mSv (range: 2.57-9.74 mSv) and in group (3), the mean effective dose was 5.85 mSv (range: 3.36-12.17 mSv). Group (1) representing 12% and 23% decrease in radiation dose comparing by groups (2) and (3). In multivariate analysis, adjusting for BMI, radiation dose for patients with BMI < 27 kg/m2 was significantly different; 2.53 mSv for group (1) compared to 3.54 mSv in group (2) and 5.207 in group (3) (p < 0.0001). In addition, lowering tube potential from 120 to 100 kVp in 200 mAs fixed tube current, represents 27% decrease in radiation dose. The quantitative image quality (IN, SI, SNR and CNR) was not statistically significant among the groups. To sum up, Retrospective-ECG gating may reduce radiation dose by using automatic tube current modulation and 100kVp tube potential with preservation of image quality in patient's whose BMI < 27 kg/m2.
PurposeTo evaluate the effect of beam configuration with inaccurate or incomplete small field out... more PurposeTo evaluate the effect of beam configuration with inaccurate or incomplete small field output factors on the accuracy of dose calculations in treatment planning systems.MethodsOutput factors were measured using various detectors and for a range of field sizes. Three types of treatment machines were configured in two treatment planning systems. In the first (corrected) machine, the Exradin W1 scintillator was used to determine output factors. In the second (uncorrected) machine, the measured output factors by the A1SL ion chamber without considering output correction factors for small field sizes were utilized. In the third (clinical) machine, measured output factors by the Exradin W1 were used but not for field sizes smaller than 2 × 2 cm2. The dose computed by the anisotropic analytical algorithm (AAA), Acuros XB (AXB) and collapsed cone convolution/superposition (CCC) algorithms in the three machines were delivered using static (jaw‐, MLC‐, and jaw/MLC‐defined), and composi...
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