456 results on '"Tube current modulation"'
Search Results
2. A comparison of breast and lung doses from chest CT scans using organ-based tube current modulation (OBTCM) vs. Automatic tube current modulation (ATCM).
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Layman, Rick R, Hardy, Anthony J, Kim, Hyun J, Chou, Ei Ne, Bostani, Maryam, Cagnon, Chris, Cody, Dianna, and McNitt-Gray, Michael
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Breast ,Lung ,Humans ,Tomography ,X-Ray Computed ,Monte Carlo Method ,Radiation Dosage ,Phantoms ,Imaging ,Female ,Male ,breast and lung dose ,organ-based modulation ,tube current modulation ,organ‐ ,based modulation ,Nuclear Medicine & Medical Imaging ,Other Physical Sciences ,Clinical Sciences ,Medical Physiology - Abstract
PurposeThe purpose of this work was to estimate and compare breast and lung doses of chest CT scans using organ-based tube current modulation (OBTCM) to those from conventional, attenuation-based automatic tube current modulation (ATCM) across a range of patient sizes.MethodsThirty-four patients (17 females, 17 males) who underwent clinically indicated CT chest/abdomen/pelvis (CAP) examinations employing OBTCM were collected from two multi-detector row CT scanners. Patient size metric was assessed as water equivalent diameter (Dw ) taken at the center of the scan volume. Breast and lung tissues were segmented from patient image data to create voxelized models for use in a Monte Carlo transport code. The OBTCM schemes for the chest portion were extracted from the raw projection data. ATCM schemes were estimated using a recently developed method. Breast and lung doses for each TCM scenario were estimated for each patient model. CTDIvol -normalized breast (nDbreast ) and lung (nDlung ) doses were subsequently calculated. The differences between OBTCM and ATCM normalized organ dose estimates were tested using linear regression models that included CT scanner and Dw as covariates.ResultsMean dose reduction from OBTCM in nDbreast was significant after adjusting for the scanner models and patient size (P = 0.047). When pooled with females and male patient, mean dose reduction from OBTCM in nDlung was observed to be trending after adjusting for the scanner model and patient size (P = 0.085).ConclusionsOne specific manufacturer's OBTCM was analyzed. OBTCM was observed to significantly decrease normalized breast relative to a modeled version of that same manufacturer's ATCM scheme. However, significant dose savings were not observed in lung dose over all. Results from this study support the use of OBTCM chest protocols for females only.
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- 2021
3. Multimodal Contrastive Learning for Prospective Personalized Estimation of CT Organ Dose
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Imran, Abdullah-Al-Zubaer, Wang, Sen, Pal, Debashish, Dutta, Sandeep, Zucker, Evan, Wang, Adam, Goos, Gerhard, Founding Editor, Hartmanis, Juris, Founding Editor, Bertino, Elisa, Editorial Board Member, Gao, Wen, Editorial Board Member, Steffen, Bernhard, Editorial Board Member, Yung, Moti, Editorial Board Member, Wang, Linwei, editor, Dou, Qi, editor, Fletcher, P. Thomas, editor, Speidel, Stefanie, editor, and Li, Shuo, editor
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- 2022
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4. Estimating fetal dose from tube current‐modulated (TCM) and fixed tube current (FTC) abdominal/pelvis CT examinations
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Hardy, Anthony J, Angel, Erin, Bostani, Maryam, Cagnon, Chris, and McNitt‐Gray, Michael
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Medical and Biological Physics ,Physical Sciences ,Pediatric ,Biomedical Imaging ,Abdomen ,Electric Conductivity ,Female ,Fetus ,Humans ,Monte Carlo Method ,Pelvis ,Pregnancy ,Radiation Dosage ,Radiometry ,Tomography ,X-Ray Computed ,computed tomography ,conceptus dose ,embryo dose ,fetal dose ,Monte Carlo simulations ,radiation dose ,tube current modulation ,Other Physical Sciences ,Biomedical Engineering ,Oncology and Carcinogenesis ,Nuclear Medicine & Medical Imaging ,Biomedical engineering ,Medical and biological physics - Abstract
PurposeThe purpose of this work was to estimate scanner-independent CTDIvol -to-fetal-dose coefficients for tube current-modulated (TCM) and fixed tube current (FTC) computed tomography (CT) examinations of pregnant patients of various gestational ages undergoing abdominal/pelvic CT examinations.MethodsFor 24 pregnant patients of gestational age from
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- 2019
5. Estimation of Effective Doses to Patients in Whole Body Computed Tomography with Automatic Tube Current Modulation Systems
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Beganović, Adnan, Stabančić-Dragunić, Samra, Odžak, Senad, Skopljak-Beganović, Amra, Jašić, Rahima, Sefić-Pašić, Irmina, Magjarevic, Ratko, Series Editor, Ładyżyński, Piotr, Associate Editor, Ibrahim, Fatimah, Associate Editor, Lackovic, Igor, Associate Editor, Rock, Emilio Sacristan, Associate Editor, Badnjevic, Almir, editor, and Gurbeta Pokvić, Lejla, editor
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- 2021
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6. Estimating lung, breast, and effective dose from low‐dose lung cancer screening CT exams with tube current modulation across a range of patient sizes
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Hardy, Anthony J, Bostani, Maryam, McMillan, Kyle, Zankl, Maria, McCollough, Cynthia, Cagnon, Chris, and McNitt‐Gray, Michael
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Medical and Biological Physics ,Physical Sciences ,Cancer ,Biomedical Imaging ,Lung ,Breast Cancer ,Body Size ,Breast ,Female ,Humans ,Lung Neoplasms ,Male ,Mass Screening ,Monte Carlo Method ,Phantoms ,Imaging ,Radiation Dosage ,Radiometry ,Tomography ,X-Ray Computed ,breast dose ,computed tomography ,effective dose ,lung cancer screening ,lung dose ,Monte Carlo simulations ,tube current modulation ,Other Physical Sciences ,Biomedical Engineering ,Oncology and Carcinogenesis ,Nuclear Medicine & Medical Imaging ,Biomedical engineering ,Medical and biological physics - Abstract
PurposeThe purpose of this study was to estimate the radiation dose to the lung and breast as well as the effective dose from tube current modulated (TCM) lung cancer screening (LCS) scans across a range of patient sizes.MethodsMonte Carlo (MC) methods were used to calculate lung, breast, and effective doses from a low-dose LCS protocol for a 64-slice CT that used TCM. Scanning parameters were from the protocols published by AAPM's Alliance for Quality CT. To determine lung, breast, and effective doses from lung cancer screening, eight GSF/ICRP voxelized phantom models with all radiosensitive organs identified were used to estimate lung, breast, and effective doses. Additionally, to extend the limited size range provided by the GSF/ICRP phantom models, 30 voxelized patient models of thoracic anatomy were generated from LCS patient data. For these patient models, lung and breast were semi-automatically segmented. TCM schemes for each of the GSF/ICRP phantom models were generated using a validated method wherein tissue attenuation and scanner limitations were used to determine the TCM output as a function of table position and source angle. TCM schemes for voxelized patient models were extracted from the raw projection data. The water equivalent diameter, Dw, was used as the patient size descriptor. Dw was estimated for the GSF/ICRP models. For the thoracic patient models, Dw was extracted from the DICOM header of the CT localizer radiograph. MC simulations were performed using the TCM scheme for each model. Absolute organ doses were tallied and effective doses were calculated using ICRP 103 tissue weighting factors for the GSF/ICRP models. Metrics of scanner radiation output were determined based on each model's TCM scheme, including CTDIvol , dose length product (DLP), and CTDIvol, Low Att , a previously described regional metric of scanner output covering most of the lungs and breast. All lung and breast doses values were normalized by scan-specific CTDIvol and CTDIvol, Low Att . Effective doses were normalized by scan-specific CTDIvol and DLP. Absolute and normalized doses were reported as a function of Dw.ResultsLung doses normalized by CTDIvol, Low Att were modeled as an exponential relationship with respect to Dw with coefficients of determination (R2 ) of 0.80. Breast dose normalized by CTDIvol, Low Att was modeled with an exponential relationship to Dw with an R2 of 0.23. For all eight GSF/ICRP phantom models, the effective dose using TCM protocols was below 1.6 mSv. Effective doses showed some size dependence but when normalized by DLP demonstrated a constant behavior.ConclusionLung, breast, and effective doses from LCS CT exams with TCM were estimated with respect to patient size. Normalized lung dose can be reasonably estimated with a measure of a patient size such as Dw and regional metric of CTDIvol covering the thorax such as CTDIvol, Low Att , while normalized breast dose can also be estimated with a regional metric of CTDIvol but with a larger degree of variability than observed for lung. Effective dose normalized by DLP can be estimated with a constant multiplier.
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- 2018
7. Patient‐specific radiation risk‐based tube current modulation for diagnostic CT.
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Klein, Laura, Liu, Chang, Steidel, Jörg, Enzmann, Lucia, Knaup, Michael, Sawall, Stefan, Maier, Andreas, Lell, Michael, Maier, Joscha, and Kachelrieß, Marc
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- *
RADIATION exposure , *RADIATION , *TUBES , *COMPUTED tomography , *REDUCTION potential , *MACHINE learning - Abstract
Purpose: Modern CT scanners use automatic exposure control (AEC) techniques, such as tube current modulation (TCM), to reduce dose delivered to patients while maintaining image quality. In contrast to conventional approaches that minimize the tube current time product of the CT scan, referred to as mAsTCM in the following, we herein propose a new method referred to as riskTCM, which aims at reducing the radiation risk to the patient by taking into account the specific radiation risk of every dose‐sensitive organ. Methods: For current mAsTCM implementations, the mAs product is used as a surrogate for the patient dose. Thus, they do not take into account the varying dose sensitivity of different organs. Our riskTCM framework assumes that a coarse CT reconstruction, an organ segmentation, and an estimation of the dose distribution can be provided in real time, for example, by applying machine learning techniques. Using this information, riskTCM determines a tube current curve that minimizes a patient risk measure, for example, the effective dose, while keeping the image quality constant. We retrospectively applied riskTCM to 20 patients covering all relevant anatomical regions and tube voltages from 70 to 150 kV. The potential reduction of effective dose at same image noise is evaluated as a figure of merit and compared to mAsTCM and to a situation with a constant tube current referred to as noTCM. Results: Anatomical regions like the neck, thorax, abdomen, and the pelvis benefit from the proposed riskTCM. On average, a reduction of effective dose of about 23% for the thorax, 31% for the abdomen, 24% for the pelvis, and 27% for the neck has been evaluated compared to today's state‐of‐the‐art mAsTCM. For the head, the resulting reduction of effective dose is lower, about 13% on average compared to mAsTCM. Conclusions: With a risk‐minimizing TCM, significant higher reduction of effective dose compared to mAs‐minimizing TCM is possible. [ABSTRACT FROM AUTHOR]
- Published
- 2022
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8. Evaluation of automatic tube current modulation of CT scanners using a dedicated and the CTDI dosimetry phantoms.
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Tsalafoutas, Ioannis A., AlKhazzam, Shady, AlNaemi, Huda, and Kharita, Mohammed Hassan
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IMAGING phantoms ,SCANNING systems ,COMPUTED tomography ,MEDICAL protocols ,CURRENT transformers (Instrument transformer) - Abstract
Purpose: To investigate the operation principles of the automatic tube current modulation (ATCM) of a CT scanner, using a dedicated phantom and the CT dosimetry index (CTDI) phantom. Material and methods: The Mercury 4.0 phantom and three different configurations of the CTDI dosimetry phantom were employed. A frequently used clinical scanning protocol was employed as a basis for the acquisitions performed with all phantoms, using both scanning directions. Additional acquisitions with different pitch and examination protocols were performed with Mercury phantom, to further explore their effect on ATCM and the resulting image quality. Different software named DICOM Info Extractor, ImageJ, and imQuest, were used to derive CTDIvol and table position, image noise, and water equivalent diameter (WED) of each phantom CT image, respectively. ImQuest was also used to derive the detectability index (d') of five different materials (air, solid water, polystyrene, iodine, and bone) embedded in the Mercury phantom. Results: It was exhibited with all four phantoms that the scanning direction greatly affects the modulation curves. The fitting of the dose modulations curves suggested that for each table position what determines the CTDIvol value is the WED values of the phantom structures laying ahead towards the scanning direction, for a length equal to the effective width of the X‐ray beam. Furthermore, it was also exhibited that ATCM does not fully compensate for larger thicknesses, since images of larger WED phantom sections present more noise (larger SD) in all four phantoms and in Mercury 4.0 phantom smaller detectability (d'). Conclusion: Mercury 4.0 is a dedicated phantom for a complete and in‐depth evaluation of the ATCM operation and the resulting image quality. However, in its absence, different CTDI configurations can be used as an alternative to investigate and comprehend some basic operation principles of the CT scanners' ATCM systems. [ABSTRACT FROM AUTHOR]
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- 2022
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9. Estimating patient dose from CT exams that use automatic exposure control: Development and validation of methods to accurately estimate tube current values.
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McMillan, Kyle, Bostani, Maryam, Cagnon, Christopher, Yu, Lifeng, Leng, Shuai, McCollough, Cynthia, and Mcnitt-Gray, Michael
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Monte Carlo simulations ,computed tomography ,organ dose ,radiation dose ,tube current modulation ,Adult ,Child ,Female ,Germany ,Humans ,Male ,Monte Carlo Method ,Phantoms ,Imaging ,Radiation Dosage ,Tomography ,X-Ray Computed - Abstract
PURPOSE: The vast majority of body CT exams are performed with automatic exposure control (AEC), which adapts the mean tube current to the patient size and modulates the tube current either angularly, longitudinally or both. However, most radiation dose estimation tools are based on fixed tube current scans. Accurate estimates of patient dose from AEC scans require knowledge of the tube current values, which is usually unavailable. The purpose of this work was to develop and validate methods to accurately estimate the tube current values prescribed by one manufacturers AEC system to enable accurate estimates of patient dose. METHODS: Methods were developed that took into account available patient attenuation information, user selected image quality reference parameters and x-ray system limits to estimate tube current values for patient scans. Methods consistent with AAPM Report 220 were developed that used patient attenuation data that were: (a) supplied by the manufacturer in the CT localizer radiograph and (b) based on a simulated CT localizer radiograph derived from image data. For comparison, actual tube current values were extracted from the projection data of each patient. Validation of each approach was based on data collected from 40 pediatric and adult patients who received clinically indicated chest (n = 20) and abdomen/pelvis (n = 20) scans on a 64 slice multidetector row CT (Sensation 64, Siemens Healthcare, Forchheim, Germany). For each patient dataset, the following were collected with Institutional Review Board (IRB) approval: (a) projection data containing actual tube current values at each projection view, (b) CT localizer radiograph (topogram) and (c) reconstructed image data. Tube current values were estimated based on the actual topogram (actual-topo) as well as the simulated topogram based on image data (sim-topo). Each of these was compared to the actual tube current values from the patient scan. In addition, to assess the accuracy of each method in estimating patient organ doses, Monte Carlo simulations were performed by creating voxelized models of each patient, identifying key organs and incorporating tube current values into the simulations to estimate dose to the lungs and breasts (females only) for chest scans and the liver, kidney, and spleen for abdomen/pelvis scans. Organ doses from simulations using the actual tube current values were compared to those using each of the estimated tube current values (actual-topo and sim-topo). RESULTS: When compared to the actual tube current values, the average error for tube current values estimated from the actual topogram (actual-topo) and simulated topogram (sim-topo) was 3.9% and 5.8% respectively. For Monte Carlo simulations of chest CT exams using the actual tube current values and estimated tube current values (based on the actual-topo and sim-topo methods), the average differences for lung and breast doses ranged from 3.4% to 6.6%. For abdomen/pelvis exams, the average differences for liver, kidney, and spleen doses ranged from 4.2% to 5.3%. CONCLUSIONS: Strong agreement between organ doses estimated using actual and estimated tube current values provides validation of both methods for estimating tube current values based on data provided in the topogram or simulated from image data.
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- 2017
10. Estimating organ doses from tube current modulated CT examinations using a generalized linear model
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Bostani, Maryam, McMillan, Kyle, Lu, Peiyun, Kim, Grace Hyun J, Cody, Dianna, Arbique, Gary, Greenberg, S Bruce, DeMarco, John J, Cagnon, Chris H, and McNitt‐Gray, Michael F
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Medical and Biological Physics ,Physical Sciences ,Biomedical Imaging ,Bioengineering ,Adult ,Child ,Female ,Humans ,Linear Models ,Male ,Monte Carlo Method ,Radiometry ,Reference Standards ,Tomography ,X-Ray Computed ,CT ,generalized linear model ,Monte Carlo simulations ,organ dose estimation ,tube current modulation ,CT ,Other Physical Sciences ,Biomedical Engineering ,Oncology and Carcinogenesis ,Nuclear Medicine & Medical Imaging ,Biomedical engineering ,Medical and biological physics - Abstract
PurposeCurrently, available Computed Tomography dose metrics are mostly based on fixed tube current Monte Carlo (MC) simulations and/or physical measurements such as the size specific dose estimate (SSDE). In addition to not being able to account for Tube Current Modulation (TCM), these dose metrics do not represent actual patient dose. The purpose of this study was to generate and evaluate a dose estimation model based on the Generalized Linear Model (GLM), which extends the ability to estimate organ dose from tube current modulated examinations by incorporating regional descriptors of patient size, scanner output, and other scan-specific variables as needed.MethodsThe collection of a total of 332 patient CT scans at four different institutions was approved by each institution's IRB and used to generate and test organ dose estimation models. The patient population consisted of pediatric and adult patients and included thoracic and abdomen/pelvis scans. The scans were performed on three different CT scanner systems. Manual segmentation of organs, depending on the examined anatomy, was performed on each patient's image series. In addition to the collected images, detailed TCM data were collected for all patients scanned on Siemens CT scanners, while for all GE and Toshiba patients, data representing z-axis-only TCM, extracted from the DICOM header of the images, were used for TCM simulations. A validated MC dosimetry package was used to perform detailed simulation of CT examinations on all 332 patient models to estimate dose to each segmented organ (lungs, breasts, liver, spleen, and kidneys), denoted as reference organ dose values. Approximately 60% of the data were used to train a dose estimation model, while the remaining 40% was used to evaluate performance. Two different methodologies were explored using GLM to generate a dose estimation model: (a) using the conventional exponential relationship between normalized organ dose and size with regional water equivalent diameter (WED) and regional CTDIvol as variables and (b) using the same exponential relationship with the addition of categorical variables such as scanner model and organ to provide a more complete estimate of factors that may affect organ dose. Finally, estimates from generated models were compared to those obtained from SSDE and ImPACT.ResultsThe Generalized Linear Model yielded organ dose estimates that were significantly closer to the MC reference organ dose values than were organ doses estimated via SSDE or ImPACT. Moreover, the GLM estimates were better than those of SSDE or ImPACT irrespective of whether or not categorical variables were used in the model. While the improvement associated with a categorical variable was substantial in estimating breast dose, the improvement was minor for other organs.ConclusionsThe GLM approach extends the current CT dose estimation methods by allowing the use of additional variables to more accurately estimate organ dose from TCM scans. Thus, this approach may be able to overcome the limitations of current CT dose metrics to provide more accurate estimates of patient dose, in particular, dose to organs with considerable variability across the population.
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- 2017
11. The determination of coefficients for size specific effective dose for adult and pediatric patients undergoing routine computed tomography examinations.
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Sookpeng S and Martin CJ
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- Humans, Child, Adult, Radiation Dosage, Tomography, X-Ray Computed, Phantoms, Imaging, Monte Carlo Method, Body Size
- Abstract
The effective dose resulting from computed tomography (CT) scans provides an assessment of the risk associated with stochastic effects but does not account for the patient's size. Advances in Monte Carlo simulations offer the potential to obtain organ dose data from phantoms of varying stature, enabling derivation of a size-specific effective doses (SEDs) representing doses to individual patients. This study aimed to compute size-specific k-conversion factors for SED in routine CT examinations for adult and pediatric patients of different sizes. Radiation interactions were simulated for adult and pediatric phantom models of various sizes using National Cancer Institute CT version 3.0.20211123. Subsequent calculations of SED were performed, and coefficients for SED were derived, considering the variations in body sizes. The results revealed a strong correlation between effective diameter and weight, observed with size-specific k-conversion factors for adult and pediatric phantoms, respectively. While size-specific k-conversion factors for CT brain remained constant in adults, values for pediatric cases varied. When using the tube current modulation (TCM) system, size-specific k-conversion factors increased in larger phantoms and decreased in smaller ones. The extent of this increase or decrease correlated with the set TCM strength. This study provides coefficients for estimating SEDs in routine CT exams. Software utilizing look-up tables of coefficients can be used to provide dose information for CT scanners at local hospitals, offering guidance to practitioners on doses to individual patients and improving radiation risk awareness in clinical practice., (© 2024 Society for Radiological Protection. Published on behalf of SRP by IOP Publishing Limited. All rights, including for text and data mining, AI training, and similar technologies, are reserved.)
- Published
- 2024
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12. Estimating Specific Patient Organ Dose for Chest CT Examinations with Monte Carlo Method.
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Yang, Yang, Zhuo, Weihai, Zhao, Yiyang, Xie, Tianwu, Wang, Chuyan, and Liu, Haikuan
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COMPUTED tomography ,MONTE Carlo method ,LUNGS ,CHEST examination ,ADULTS ,ESTIMATES - Abstract
Purpose: The purpose of this study was to preliminarily estimate patient-specific organ doses in chest CT examinations for Chinese adults, and to investigate the effect of patient size on organ doses. Methods: By considering the body-size and body-build effects on the organ doses and taking the mid-chest water equivalent diameter (WED) as a body-size indicator, the chest scan images of 18 Chinese adults were acquired on a multi-detector CT to generate the regional voxel models. For each patient, the lungs, heart, and breasts (glandular breast tissues for both breasts) were segmented, and other organs were semi-automated segmented based on their HU values. The CT scanner and patient models simulated by MCNPX 2.4.0 software (Los Alamos National LaboratoryLos Alamos, USA) were used to calculate lung, breast, and heart doses. CTDI
vol values were used to normalize simulated organ doses, and the exponential estimation model between the normalized organ dose and WED was investigated. Results: Among the 18 patients in this study, the simulated doses of lung, heart, and breast were 18.15 ± 2.69 mGy, 18.68 ± 2.87 mGy, and 16.11 ± 3.08 mGy, respectively. Larger patients received higher organ doses than smaller ones due to the higher tube current used. The ratios of lung, heart, and breast doses to the CTDIvol were 1.48 ± 0.22, 1.54 ± 0.20, and 1.41 ± 0.13, respectively. The normalized organ doses of all the three organs decreased with the increase in WED, and the normalized doses decreased more obviously in the lung and the heart than that in the breasts. Conclusions: The output of CT scanner under ATCM is positively related to the attenuation of patients, larger-size patients receive higher organ doses. The organ dose normalized by CTDIvol was negatively correlated with patient size. The organ doses could be estimated by using the indicated CTDIvol combined with the estimated WED. [ABSTRACT FROM AUTHOR]- Published
- 2021
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13. Attenuation‐based size metric for estimating organ dose to patients undergoing tube current modulated CT exams
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Bostani, Maryam, McMillan, Kyle, Lu, Peiyun, Kim, Hyun J, Cagnon, Chris H, DeMarco, John J, and McNitt-Gray, Michael F
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Medical and Biological Physics ,Physical Sciences ,Bioengineering ,Biomedical Imaging ,Lung ,Patient Safety ,Adult ,Female ,Humans ,Male ,Monte Carlo Method ,Phantoms ,Imaging ,Radiation Dosage ,Radiography ,Abdominal ,Radiography ,Thoracic ,Radiometry ,Tomography ,X-Ray Computed ,CT ,Monte Carlo ,dosimetry ,tube current modulation ,water equivalent diameter ,Other Physical Sciences ,Biomedical Engineering ,Oncology and Carcinogenesis ,Nuclear Medicine & Medical Imaging ,Biomedical engineering ,Medical and biological physics - Abstract
PurposeTask Group 204 introduced effective diameter (ED) as the patient size metric used to correlate size-specific-dose-estimates. However, this size metric fails to account for patient attenuation properties and has been suggested to be replaced by an attenuation-based size metric, water equivalent diameter (DW). The purpose of this study is to investigate different size metrics, effective diameter, and water equivalent diameter, in combination with regional descriptions of scanner output to establish the most appropriate size metric to be used as a predictor for organ dose in tube current modulated CT exams.Methods101 thoracic and 82 abdomen/pelvis scans from clinically indicated CT exams were collected retrospectively from a multidetector row CT (Sensation 64, Siemens Healthcare) with Institutional Review Board approval to generate voxelized patient models. Fully irradiated organs (lung and breasts in thoracic scans and liver, kidneys, and spleen in abdominal scans) were segmented and used as tally regions in Monte Carlo simulations for reporting organ dose. Along with image data, raw projection data were collected to obtain tube current information for simulating tube current modulation scans using Monte Carlo methods. Additionally, previously described patient size metrics [ED, DW, and approximated water equivalent diameter (DWa)] were calculated for each patient and reported in three different ways: a single value averaged over the entire scan, a single value averaged over the region of interest, and a single value from a location in the middle of the scan volume. Organ doses were normalized by an appropriate mAs weighted CTDIvol to reflect regional variation of tube current. Linear regression analysis was used to evaluate the correlations between normalized organ doses and each size metric.ResultsFor the abdominal organs, the correlations between normalized organ dose and size metric were overall slightly higher for all three differently (global, regional, and middle slice) reported DW and DWa than they were for ED, but the differences were not statistically significant. However, for lung dose, computed correlations using water equivalent diameter calculated in the middle of the image data (DW,middle) and averaged over the low attenuating region of lung (DW,regional) were statistically significantly higher than correlations of normalized lung dose with ED.ConclusionsTo conclude, effective diameter and water equivalent diameter are very similar in abdominal regions; however, their difference becomes noticeable in lungs. Water equivalent diameter, specifically reported as a regional average and middle of scan volume, was shown to be better predictors of lung dose. Therefore, an attenuation-based size metric (water equivalent diameter) is recommended because it is more robust across different anatomic regions. Additionally, it was observed that the regional size metric reported as a single value averaged over a region of interest and the size metric calculated from a single slice/image chosen from the middle of the scan volume are highly correlated for these specific patient models and scan types.
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- 2015
14. Validation of a Monte Carlo model used for simulating tube current modulation in computed tomography over a wide range of phantom conditions/challenges
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Bostani, Maryam, McMillan, Kyle, DeMarco, John J, Cagnon, Chris H, and McNitt-Gray, Michael F
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Medical and Biological Physics ,Physical Sciences ,Bioengineering ,Biomedical Imaging ,Humans ,Monte Carlo Method ,Phantoms ,Imaging ,Radiation Dosage ,Tomography ,Spiral Computed ,CT ,tube current modulation ,Monte Carlo simulations ,validation of Monte Carlo model ,Other Physical Sciences ,Biomedical Engineering ,Oncology and Carcinogenesis ,Nuclear Medicine & Medical Imaging ,Biomedical engineering ,Medical and biological physics - Abstract
PurposeMonte Carlo (MC) simulation methods have been widely used in patient dosimetry in computed tomography (CT), including estimating patient organ doses. However, most simulation methods have undergone a limited set of validations, often using homogeneous phantoms with simple geometries. As clinical scanning has become more complex and the use of tube current modulation (TCM) has become pervasive in the clinic, MC simulations should include these techniques in their methodologies and therefore should also be validated using a variety of phantoms with different shapes and material compositions to result in a variety of differently modulated tube current profiles. The purpose of this work is to perform the measurements and simulations to validate a Monte Carlo model under a variety of test conditions where fixed tube current (FTC) and TCM were used.MethodsA previously developed MC model for estimating dose from CT scans that models TCM, built using the platform of mcnpx, was used for CT dose quantification. In order to validate the suitability of this model to accurately simulate patient dose from FTC and TCM CT scan, measurements and simulations were compared over a wide range of conditions. Phantoms used for testing range from simple geometries with homogeneous composition (16 and 32 cm computed tomography dose index phantoms) to more complex phantoms including a rectangular homogeneous water equivalent phantom, an elliptical shaped phantom with three sections (where each section was a homogeneous, but different material), and a heterogeneous, complex geometry anthropomorphic phantom. Each phantom requires varying levels of x-, y- and z-modulation. Each phantom was scanned on a multidetector row CT (Sensation 64) scanner under the conditions of both FTC and TCM. Dose measurements were made at various surface and depth positions within each phantom. Simulations using each phantom were performed for FTC, detailed x-y-z TCM, and z-axis-only TCM to obtain dose estimates. This allowed direct comparisons between measured and simulated dose values under each condition of phantom, location, and scan to be made.ResultsFor FTC scans, the percent root mean square (RMS) difference between measurements and simulations was within 5% across all phantoms. For TCM scans, the percent RMS of the difference between measured and simulated values when using detailed TCM and z-axis-only TCM simulations was 4.5% and 13.2%, respectively. For the anthropomorphic phantom, the difference between TCM measurements and detailed TCM and z-axis-only TCM simulations was 1.2% and 8.9%, respectively. For FTC measurements and simulations, the percent RMS of the difference was 5.0%.ConclusionsThis work demonstrated that the Monte Carlo model developed provided good agreement between measured and simulated values under both simple and complex geometries including an anthropomorphic phantom. This work also showed the increased dose differences for z-axis-only TCM simulations, where considerable modulation in the x-y plane was present due to the shape of the rectangular water phantom. Results from this investigation highlight details that need to be included in Monte Carlo simulations of TCM CT scans in order to yield accurate, clinically viable assessments of patient dosimetry.
- Published
- 2014
15. Methods for CT Automatic Exposure Control Protocol Translation Between Scanner Platforms
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McKenney, Sarah E, Seibert, J Anthony, Lamba, Ramit, and Boone, John M
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Biomedical and Clinical Sciences ,Clinical Sciences ,Biomedical Imaging ,Algorithms ,Calibration ,Equipment Design ,Equipment Failure Analysis ,Guidelines as Topic ,Radiation Dosage ,Radiation Protection ,Radiographic Image Enhancement ,Tomography ,X-Ray Computed ,United States ,CT protocols ,automatic exposure control ,tube current modulation ,phantoms ,Public Health and Health Services ,Nuclear Medicine & Medical Imaging ,Clinical sciences - Abstract
PurposeAn imaging facility with a diverse fleet of CT scanners faces considerable challenges when propagating CT protocols with consistent image quality and patient dose across scanner makes and models. Although some protocol parameters can comfortably remain constant among scanners (eg, tube voltage, gantry rotation time), the automatic exposure control (AEC) parameter, which selects the overall mA level during tube current modulation, is difficult to match among scanners, especially from different CT manufacturers.MethodsObjective methods for converting tube current modulation protocols among CT scanners were developed. Three CT scanners were investigated, a GE LightSpeed 16 scanner, a GE VCT scanner, and a Siemens Definition AS+ scanner. Translation of the AEC parameters such as noise index and quality reference mAs across CT scanners was specifically investigated. A variable-diameter poly(methyl methacrylate) phantom was imaged on the 3 scanners using a range of AEC parameters for each scanner. The phantom consisted of 5 cylindrical sections with diameters of 13, 16, 20, 25, and 32 cm. The protocol translation scheme was based on matching either the volumetric CT dose index or image noise (in Hounsfield units) between two different CT scanners. A series of analytic fit functions, corresponding to different patient sizes (phantom diameters), were developed from the measured CT data. These functions relate the AEC metric of the reference scanner, the GE LightSpeed 16 in this case, to the AEC metric of a secondary scanner.ResultsWhen translating protocols between different models of CT scanners (from the GE LightSpeed 16 reference scanner to the GE VCT system), the translation functions were linear. However, a power-law function was necessary to convert the AEC functions of the GE LightSpeed 16 reference scanner to the Siemens Definition AS+ secondary scanner, because of differences in the AEC functionality designed by these two companies.ConclusionsProtocol translation on the basis of quantitative metrics (volumetric CT dose index or measured image noise) is feasible. Protocol translation has a dependency on patient size, especially between the GE and Siemens systems. Translation schemes that preserve dose levels may not produce identical image quality.
- Published
- 2014
16. Quality control of angular tube current modulation
- Author
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Redžić, M., Beganović, A., Čiva, L., Jašić, R., Skopljak-Beganović, A., Vegar-Zubović, S., Magjarevic, Ratko, Editor-in-chief, Ładyżyński, Piotr, Series editor, Ibrahim, Fatimah, Series editor, Lacković, Igor, Series editor, Rock, Emilio Sacristan, Series editor, and Badnjevic, Almir, editor
- Published
- 2017
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17. Improving linac integrated cone beam computed tomography image quality using tube current modulation.
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Stankovic, Uros, Ploeger, Lennert S., and Sonke, Jan‐Jakob
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CONE beam computed tomography , *LINEAR accelerators , *PULSE width modulation , *ARDUINO (Microcontroller) , *ANATOMICAL planes , *POWER spectra , *TUBES - Abstract
Purpose: Linac integrated cone beam CT (CBCT) scanners have become widespread tool for image guidance in radiotherapy. The current implementation uses constant imaging fluence across all the projection angles, which leads to anisotropic noise properties and suboptimal image quality for noncircular symmetric objects. Tube current modulation (TCM) is widely used in conventional CT. The purpose of this work was to implement TCM on a linac integrated CBCT scanner and evaluate its impact on image quality under varying scatter conditions and scatter correction strategies. Methods: We have implemented TCM on a nonclinical Elekta Versa HD linear accelerator with enhanced x‐ray generator functionality including pulse width modulation. The pulse width was modulated using two Arduino programmable microcontrollers: one placed on the kV arm to measure the projection angle and the other connected to the kV generator control board to vary x‐ray pulse width as function of gantry angle and precalculated transmission. An in‐house developed phantom with a ratio of the left–right to anterior–posterior path length of 1.85:1 was scanned. Image quality was determined using the anisotropicity of the 2D noise power spectra (NPS) in the transverse plane and the contrast‐to‐noise ratio (CNR). In addition, to determine the impact of scatter on the applicability of the TCM method we have modified the generated scatter using three different collimators in the cranio‐caudal direction as well as with and without an antiscatter grid (ASG). Results: Application of the TCM led to 30–78% reduction of the angular anisotropicity of the NPS in the transverse plane. The amount of reduction depended on the scatter conditions, with lower values corresponding to higher scatter conditions. The same was true for the CNR: when scatter contribution was low (presence of an ASG or very aggressive collimation) the CNR was improved by about 30%, while in high scatter conditions the CNR was improved by about 12%. Conclusions: TCM has the potential to improve CBCT image quality, but this depends on the amount of detected x‐ray scatter. [ABSTRACT FROM AUTHOR]
- Published
- 2021
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18. Technical Note: Evaluating automatic tube current modulation in CT using the standard CTDI dosimetry phantom.
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Papadakis, Antonios E. and Damilakis, John
- Abstract
Purpose: To assess the utility of the standard body CTDI phantom in characterizing the operation scheme of tube current modulation (TCM) systems in CT. Methods: The body CDTI phantom was used to characterize two TCM systems: TCM1 and TCM2, implemented in scanners from different vendors. The phantom was aligned at the gantry isocenter in two configurations. In configuration A, the facet planes of the phantom were parallel to the patient table, while in configuration B they were vertical to the patient table and parallel to the patient's long axis. Acquisitions were performed using the routine abdominal examination protocol. mA(z) profiles were recorded from images' DICOM header. The water equivalent diameter (dw) and oval ratio (OR) were calculated as a function of z‐axis location. Image noise was defined as the standard deviation (SD) of the mean Hounsfield unit value measured in a region of interest at the center of the phantom's image. Regression analysis was performed to modulated mA and SD vs dw and OR. The spatial concordance between the change in phantom size and change in mA (SCmA) was calculated as the percent difference in the slope of mA(z) change between the 1st and 2nd half of the phantom. The corresponding spatial concordance between the change in phantom size and change in image noise (SCnoise) was calculated. Results: Modulated mA(z) along the z‐axis did not substantially differentiate between configurations A and B. Correlation between ln(mA) and OR was found to be higher compared to correlation between ln(mA) and dw. SCmA was 48% for TCM1 and 33% for TCM2. The corresponding SCnoise was 29% for TCM1 and 16% for TCM2. Conclusion: Apart from routine CT dosimetry evaluations, the standard CTDI phantom positioned in configuration A or B may additionally be used by medical physicists to evaluate the performance of TCM operational characteristics. [ABSTRACT FROM AUTHOR]
- Published
- 2021
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19. Image Quality Assessment of Deep Learning Image Reconstruction in Torso Computed Tomography Using Tube Current Modulation
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Takeuchi, Kazuhiro, Ide, Yasuhiro, Mori, Yuichiro, Uehara, Yusuke, Sukeishi, Hiroshi, and Goto, Sachiko
- Subjects
tube current modulation ,object size ,deep learning ,computed tomography ,image reconstruction - Abstract
Novel deep learning image reconstruction (DLIR) reportedly changes the image quality characteristics based on object contrast and image noise. In clinical practice, computed tomography image noise is usually controlled by tube current modulation (TCM) to accommodate changes in object size. This study aimed to evaluate the image quality characteristics of DLIR for different object sizes when the in-plane noise was controlled by TCM. Images acquisition was performed on a GE Revolution CT system to investigate the impact of the DLIR algorithm compared to the standard reconstructions of filtered-back projection (FBP) and hybrid iterative reconstruction (hybrid-IR). The image quality assessment was performed using phantom images, and an observer study was conducted using clinical cases. The image quality assessment confirmed the excellent noise- reduction performance of DLIR, despite variations due to phantom size. Similarly, in the observer study, DLIR received high evaluations regardless of the body parts imaged. We evaluated a novel DLIR algorithm by replicating clinical behaviors. Consequently, DLIR exhibited higher image quality than those of FBP and hybrid-IR in both phantom and observer studies, albeit the value depended on the reconstruction strength, and proved itself capable of providing stable image quality in clinical use.
- Published
- 2023
20. Effect of scan projection radiography coverage on tube current modulation in pediatric and adult chest CT.
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Perisinakis, Kostas, Ntoufas, Nikos, Velivassaki, Mary, Tzedakis, Antonis, Myronakis, Marios, Hatzidakis, Adam, and Damilakis, John
- Abstract
To investigate the effect of scan projection radiography (SPR) coverage on tube current modulation in pediatric and adult thoracic CT examinations. Sixty pediatric and 60 adult chest CT examinations were retrospectively studied to determine the incidence rate of examinations involving SPRs that did not include the entire image volume (IV) or the entire primarily exposed body volume (PEBV). The routine chest CT acquisition procedure on a modern 64-slice CT system was imitated on five anthropomorphic phantoms of different size. SPRs of varying length were successively acquired. The same IV was prescribed each time and the computed tube current modulation plan was recorded. The SPR boundaries were altered symmetrically by several steps of ±10 mm with respect to the IV boundaries. The upper IV boundary was found to be excluded from SPR in 52% of pediatric and 40% adult chest CT examinations. The corresponding values for the lower boundary were 15% and 20%, respectively. The computed tube current modulation was found to be considerably affected when the SPR did not encompass the entire IV. SPR deficit of 3 cm was found to induce up to 46% increase in the computed tube current value to be applied during the first tube rotations over lung apex. The tube current modulation mechanism functions properly only if the IV set by the operator is entirely included in the localizing SPR image. Operators should cautiously set the SPR boundaries to avoid partial exclusion of prescribed IV from SPRs and thus achieve optimum tube current modulation. [ABSTRACT FROM AUTHOR]
- Published
- 2020
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21. Correlation analysis of organ doses determined by Monte Carlo simulation with dose metrics for patients undergoing chest-abdomen-pelvis CT examinations.
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Fujii, Keisuke, Nomura, Keiichi, Muramatsu, Yoshihisa, Goto, Takahiro, Obara, Satoshi, Ota, Hiroyuki, and Tsukagoshi, Shinsuke
- Abstract
• Organ doses for the patients in CT with TCM increased with patient size. • Organ doses exhibited stronger linear relationships with organ-specific SSDE. • The linear regression fits will be useful for organ dose evaluation for patients in CT. This study aimed to determine organ doses based on Monte Carlo (MC) simulations for individual patients undergoing routine adult chest abdomen-pelvis computed tomography (CT) examinations and to evaluate the correlations of organ doses with patient size and dose metrics. MC simulations were performed by reading detailed descriptions of the CT scanner, scanning parameters, and CT images of phantoms and patients into the simulation software. The simulation models were validated by comparing the simulated doses with the doses measured by in-phantom dosimetry using radiophotoluminescent glass dosimeters and an adult anthropomorphic phantom, and organ doses for 80 patients were determined from the simulation results. To obtain patient size and dose metrics, body mass index and volume computed tomography dose index (CTDIvol) data were collected. Water equivalent diameter (WED) was calculated from the CT images of each patient. Size-specific dose estimates (SSDE) were calculated using CTDIvol and average WED over the scan range, and organ specific SSDE were calculated using the average CTDIvol and WED over each organ position. The correlations of organ doses with dose metrics were evaluated using coefficients of determination. Organ doses increased with patient size, and the doses for obese were approximately two to three times higher than those for underweight patients. Organ doses exhibited stronger linear relationships with organ specific SSDE (R
2 ≥ 0.82) than other dose metrics. The linear regression fits between organ doses determined by MC simulation and organ-specific SSDE are valuable for simplified and accurate organ dose estimation for individual patients undergoing CT examinations. [ABSTRACT FROM AUTHOR]- Published
- 2020
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22. Patient size matters: Effect of tube current modulation on size‐specific dose estimates (SSDE) and image quality in low‐dose lung cancer screening CT.
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Barreto, Izabella, Verma, Nupur, Quails, Nathan, Olguin, Catherine, Correa, Nathalie, and Mohammed, Tan‐Lucien
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EARLY detection of cancer ,LUNG cancer ,CONE beam computed tomography ,TUBES ,RADIATION doses - Abstract
Purpose: We compare the effect of tube current modulation (TCM) and fixed tube current (FTC) on size‐specific dose estimates (SSDE) and image quality in lung cancer screening with low‐dose CT (LDCT) for patients of all sizes. Methods: Initially, 107 lung screening examinations were performed using FTC, which satisfied the Centers for Medicare & Medicaid Services' volumetric CT dose index (CTDIvol) limit of 3.0 mGy for standard‐sized patients. Following protocol modification, 287 examinations were performed using TCM. Patient size and examination parameters were collected and water‐equivalent diameter (Dw) and SSDE were determined for each patient. Regression models were used to correlate CTDIvol and SSDE with Dw. Objective and subjective image quality were measured in 20 patients who had consecutive annual screenings with both FTC and TCM. Results: CTDIvol was 2.3 mGy for all FTC scans and increased exponentially with Dw (range = 0.96–4.50 mGy, R2 = 0.73) for TCM scans. As patient Dw increased, SSDE decreased for FTC examinations (R2 = 1) and increased for TCM examinations (R2 = 0.54). Image quality measurements were superior with FTC for smaller sized patients and with TCM for larger sized patients (R2 > 0.5, P < 0.005). Radiologist graded all images acceptable for diagnostic evaluation of lung cancer screening. Conclusion: Although FTC protocol offered a consistently low CTDIvol for all patients, it yielded unnecessarily high SSDE for small patients and increased image noise for large patients. Lung cancer screening with LDCT using TCM produces radiation doses that are appropriately reduced for small patients and increased for large patients with diagnostic image quality for all patients. [ABSTRACT FROM AUTHOR]
- Published
- 2020
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23. Protocols for Cardiac Studies with Computed Tomography
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Leta, Rubén, Barros, Antonio, and Pons-Lladó, Guillem, editor
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- 2016
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24. Dose Optimisation in CT Colonography
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Trauernicht, Christoph, Bortz, Joel H., editor, Ramlaul, Aarthi, editor, and Munro, Leonie, editor
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- 2016
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25. Dose-Lowering Strategies in Computed Tomography Imaging of the Lung and Heart
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Euler, André, Szucs-Farkas, Zsolt, Mayo, John R., Schindera, Sebastian T., Hodler, J., editor, von Schulthess, G. K., editor, Kubik-Huch, R. A., editor, and Zollikofer, Ch. L., editor
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- 2015
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26. Physics Background and Radiation Exposure
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Geleijns, J., Dewey, M., and Dewey, Marc
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- 2014
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27. Cardiac Function
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Wolf, F., Feuchtner, G., and Dewey, Marc
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- 2014
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28. Clinical Expansion of CT and Radiation Dose
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Meeson, Stuart, Patel, Rajesh, Golding, Stephen, Tack, Denis, editor, Kalra, Mannudeep K., editor, and Gevenois, Pierre Alain, editor
- Published
- 2012
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29. Practical Approaches to Dose Reduction: Toshiba Perspective
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Geleijns, Jacob, Irwan, R, Tack, Denis, editor, Kalra, Mannudeep K., editor, and Gevenois, Pierre Alain, editor
- Published
- 2012
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30. Multi-Detector Row CT–Recent Developments, Radiation Dose and Dose Reduction Technologies
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Flohr, Thomas, Tack, Denis, editor, Kalra, Mannudeep K., editor, and Gevenois, Pierre Alain, editor
- Published
- 2012
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31. Dose Reduction in Screening Programs: Colon Cancer Screening
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Boellaard, Thierry N., Venema, Henk W., Stoker, Jaap, Tack, Denis, editor, Kalra, Mannudeep K., editor, and Gevenois, Pierre Alain, editor
- Published
- 2012
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32. Software for Calculating Dose and Risk
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Stamm, Georg, Tack, Denis, editor, Kalra, Mannudeep K., editor, and Gevenois, Pierre Alain, editor
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- 2012
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33. Automatic Exposure Control in Multidetector-row CT
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Kalra, Mannudeep K., Tack, Denis, editor, Kalra, Mannudeep K., editor, and Gevenois, Pierre Alain, editor
- Published
- 2012
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34. Dose Optimization and Reduction in CT of the Brain and Head and Neck Region
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Mulkens, Tom, Salgado, Rodrigo, Bellinck, Patrick, Tack, Denis, editor, Kalra, Mannudeep K., editor, and Gevenois, Pierre Alain, editor
- Published
- 2012
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35. Cardiac Function
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Wolf, F., Feuchtner, G., and Dewey, Marc
- Published
- 2011
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36. Monte Carlo simulation of eye lens dose reduction from CT scan using organ based tube current modulation.
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Huang, Ying, Zhuo, Weihai, Gao, Yiming, and Liu, Haikuan
- Abstract
Purpose To investigate lens dose reduction with organ based tube current modulation (TCM) using the Monte Carlo method. Methods To calculate lens dose with organ based TCM, 36 pairs of X-ray sources with bowtie filters were placed around the patient head using a projection angle interval of 10° for one rotation of Computed Tomography (CT). Each projection was simulated respectively. Both voxelized and stylized eye models and Chinese reference male phantoms were used in the simulation, and tube voltages 80, 100, 120 and 140 kVp were used. Results Dose differences between two eye models were less than 20%, but large variations were observed among dose results from different projections of all tube voltages investigated. Dose results from 0° (AP) directions were 60 times greater than those from 180° (PA) directions, which enables organ based TCM reduce lens doses by more than 47%. Conclusions Organ based TCM may be used to reduce lens doses. Stylized eye models are more anatomically realistic compared with voxelized eye models and are more reliable for dose evaluation. [ABSTRACT FROM AUTHOR]
- Published
- 2018
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37. Automatic Exposure Control Systems and Current Modulations: Comparison of Different 64-Slice CT Scanners
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Colli, V., Strocchi, S., Vite, C., Cacciatori, M., Rizzi, E., Conte, L., Magjarevic, Ratko, editor, Dössel, Olaf, editor, and Schlegel, Wolfgang C., editor
- Published
- 2009
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38. Dose Reduction in Chest CT
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Mayo, John R., Aldrich, John, Baert, A. L., editor, Knauth, M., editor, Sartor, K., editor, Rémy-Jardin, Martine, editor, Rémy, Jacques, editor, Aldrich, J., Editor, Alkadhi, H., Editor, Becker, C. R., Editor, Bonomo, L., Editor, Boroto, K., Editor, Boussel, L., Editor, Bouvier, E., Editor, Cademartiri, F., Editor, Camus, C., Editor, Camus, P., Editor, Caulo, A., Editor, Couvreur, T., Editor, Douek, P., Editor, Dupont, M., Editor, Elicker, B., Editor, Faivre, J.-B., Editor, Feignoux, J., Editor, Fleischmann, D., Editor, Flohr, T., Editor, Foucher, P., Editor, Gamondès, D., Editor, Ghaye, B., Editor, B. Gorgos, A., Editor, Hachulla, A.-L., Editor, Hamoir, X., Editor, Hansell, D. M., Editor, Kirsch, J., Editor, Klotz, E., Editor, La Grutta, L., Editor, Laissy, J.-P., Editor, Larici, A. R., Editor, Laurent, F., Editor, Lin, M. C. C., Editor, Macis, G., Editor, Maffei, E., Editor, Maggi, F., Editor, Marincek, B., Editor, Mayo, J. R., Editor, Menchini, L., Editor, Mollet, N. R., Editor, Montaudon, M., Editor, Ohnesorge, B., Editor, Palumbo, A. A., Editor, Pansini, V., Editor, Pontana, F., Editor, Prokop, M., Editor, Qanadli, S. D., Editor, Rémy, J., Editor, Rémy-Jardin, M., Editor, Revel, D., Editor, Rizzo, E., Editor, Rutten, A., Editor, Sablayrolles, J.-L., Editor, Stolzmann, P., Editor, Storto, M. L., Editor, Sverzellati, N., Editor, Tacelli, N., Editor, Trautenaere, J. M., Editor, White, C. S., Editor, and Yoo, S. M., Editor
- Published
- 2009
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39. Dynamic Volume CT with 320-Detector Rows: Technology and Clinical Applications
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Rogalla, Patrik, Reiser, Maximilian F., editor, Becker, C.R., editor, Nikolaou, Konstantin, editor, and Glazer, Gary, editor
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- 2009
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40. MDCT in Children: Scan Techniques and Contrast Issues
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Frush, Donald P., Kalra, Mannudeep K., editor, Saini, Sanjay, editor, and Rubin, Geoffrey D., editor
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- 2008
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41. Body: Obese Mode
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McDonald, Elizabeth, Hartman, Robert P., McCollough, Cynthia, Seidensticker, Peter R., editor, and Hofmann, Lars K., editor
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- 2008
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42. Evaluating Size‐Specific Dose Estimate (SSDE) as an estimate of organ doses from routine CT exams derived from Monte Carlo simulations
- Author
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Maria Zankl, Grace Kim, Chris H. Cagnon, Maryam Bostani, Anthony J. Hardy, and Michael F. McNitt-Gray
- Subjects
education.field_of_study ,Phantoms, Imaging ,business.industry ,education ,Population ,Monte Carlo Dose Simulations ,Size-specific Dose Estimate ,Tcm ,Routine Ct Exams ,General Medicine ,Radiation Dosage ,Water equivalent ,Tolerance limit ,Imaging phantom ,medicine.anatomical_structure ,Abdomen ,Dose estimation ,Tube current modulation ,medicine ,Humans ,Child ,Tomography, X-Ray Computed ,Nuclear medicine ,business ,Monte Carlo Method - Abstract
Purpose Size-specific dose estimate (SSDE) is a metric that adjusts CTDIvol to account for patient size. While not intended to be an estimate of organ dose, AAPM Report 204 notes the difference between the patient organ dose and SSDE is expected to be 10-20%. The purpose of this work was therefore to evaluate SSDE against estimates of organ dose obtained using Monte Carlo (MC) simulation techniques applied to routine exams across a wide range of patient sizes. Materials and methods Size-specific dose estimate was evaluated with respect to organ dose based on three routine protocols taken from Siemens scanners: (a) brain parenchyma dose in routine head exams, (b) lung and breast dose in routine chest exams, and (c) liver, kidney, and spleen dose in routine abdomen/pelvis exams. For each exam, voxelized phantom models were created from existing models or derived from clinical patient scans. For routine head exams, 15 patient models were used which consisted of 10 GSF/ICRP voxelized phantom models and five pediatric voxelized patient models created from CT image data. For all exams, the size metric used was water equivalent diameter (Dw ). For the routine chest exams, data from 161 patients were collected with a Dw range of ~16-44 cm. For the routine abdomen/pelvis exams, data from 107 patients were collected with a range of Dw from ~16 to 44 cm. Image data from these patients were segmented to generate voxelized patient models. For routine head exams, fixed tube current (FTC) was used while tube current modulation (TCM) data for body exams were extracted from raw projection data. The voxelized patient models and tube current information were used in detailed MC simulations for organ dose estimation. Organ doses from MC simulation were normalized by CTDIvol and parameterized as a function of Dw . For each patient scan, the SSDE was obtained using Dw and CTDIvol values of each scan, according to AAPM Report 220 for body scans and Report 293 for head scans. For each protocol and each patient, normalized organ doses were compared with SSDE. A one-sided tolerance limit covering 95% (P = 0.95) of the population with 95% confidence (α = 0.05) was used to assess the upper tolerance limit (TU ) between SSDE and normalized organ dose. Results For head exams, the TU between SSDE and brain parenchyma dose was observed to be 12.5%. For routine chest exams, the TU between SSDE and lung and breast dose was observed to be 35.6% and 68.3%, respectively. For routine abdomen/pelvis exams, the TU between SSDE and liver, spleen, and kidney dose was observed to be 30.7%, 33.2%, and 33.0%, respectively. Conclusions The TU of 20% between SSDE and organ dose was found to be insufficient to cover 95% of the sampled population with 95% confidence for all of the organs and protocols investigated, except for brain parenchyma dose. For the routine body exams, excluding the breasts, a wider threshold difference of ~30-36% would be needed. These results are, however, specific to Siemens scanners.
- Published
- 2021
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43. Dose Optimization and Reduction in CT of the Musculoskeletal System Including the Spine
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Blum, Alain, Noël, Alain, Winninger, Daniel, Batch, Toufik, Ludig, Thomas, Ferquel, Gilles, Sauer, Benoît, Baert, A. L., editor, Knauth, M., editor, Sartor, K., editor, Tack, Denis, editor, and Gevenois, Pierre Alain, editor
- Published
- 2007
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44. Optimization of Radiation Dose in Cardiac and Vascular Multirow-Detector CT
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Paul, Jean-François, Abada, Hicham T., Baert, A. L., editor, Knauth, M., editor, Sartor, K., editor, Tack, Denis, editor, and Gevenois, Pierre Alain, editor
- Published
- 2007
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45. Automatic Exposure Control in Multidetector-Row Computed Tomography
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Kalra, Mannudeep K., Baert, A. L., editor, Knauth, M., editor, Sartor, K., editor, Tack, Denis, editor, and Gevenois, Pierre Alain, editor
- Published
- 2007
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46. Techniques and Protocols for Acquisition and Display of Contrast-Enhanced CT Angiography
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Becker, Christoph R., Cannon, Christopher P., editor, and Schoepf, U. Joseph, editor
- Published
- 2005
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47. A new phantom developed to test the ATCM performance of chest CT scanners
- Author
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Weihai Zhuo, Bo Chen, Wenliang Ren, Shunqi Lu, Haikuan Liu, Pei Zhou, and Yang Yang
- Subjects
Male ,Tomography Scanners, X-Ray Computed ,Materials science ,Phantoms, Imaging ,Detector ,Monte Carlo method ,Public Health, Environmental and Occupational Health ,Chest ct ,Dose profile ,General Medicine ,Radiation Dosage ,Imaging phantom ,030218 nuclear medicine & medical imaging ,03 medical and health sciences ,Radiation Protection ,0302 clinical medicine ,030220 oncology & carcinogenesis ,Tube current modulation ,Ct scanners ,Image noise ,Humans ,Tomography, X-Ray Computed ,Waste Management and Disposal ,Biomedical engineering - Abstract
In this study, a new ATCM phantom was developed to test the performance of the automatic tube current modulation (ATCM) of computed tomography (CT) scanners.. Based on the Chinese reference man and Monte Carlo simulations of x-ray attenuation, a more realistic ATCM phantom made of polymethyl methacrylate was developed. The phantom has a length of 20 cm, and it can be used to measure the dose profile along the central axis using 19 real-time MOSFET detectors. The image noise can be calculated slice by slice in the phantom’s center. Test experiments showed that the phantom could initiate tube current modulation under different modulation levels of CT scans, and the actual effects of ATCM could be evaluated with the aid of the dose profile measurements. Using the measured dose profiles and image noise, the preferred dose can easily be identified from a choice of different modulation levels. The new phantom developed in this study can be used to test the ATCM performance of CT scanners, and is useful for further studies of the optimization of CT scan protocols with ATCM.
- Published
- 2021
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48. Computed tomography colonography and radiation risk: How low can we go?
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Ivan Balen, Jelena Popić, Sandra Tipuric, and Anna Mrzljak
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Opinion Review ,medicine.medical_specialty ,Colorectal cancer ,Iterative reconstruction ,Critical Care Nursing ,Pediatrics ,03 medical and health sciences ,Radiation risk ,0302 clinical medicine ,Computed Tomography Colonography ,Tube current modulation ,computed tomography colonography ,colorectal cancer ,radiation risk ,image quality ,image noise ,iterative reconstruction ,Medicine ,Image quality ,Patient compliance ,neoplasms ,Image noise ,business.industry ,medicine.disease ,digestive system diseases ,Optical colonoscopy ,030220 oncology & carcinogenesis ,Imaging technology ,030211 gastroenterology & hepatology ,Radiology ,Computed tomography colonography ,business - Abstract
Computed tomography colonography (CTC) has become a key examination in detecting colonic polyps and colorectal carcinoma (CRC). It is particularly useful after incomplete optical colonoscopy (OC) for patients with sedation risks and patients anxious about the risks or potential discomfort associated with OC. CTC's main advantages compared with OC are its non-invasive nature, better patient compliance, and the ability to assess the extracolonic disease. Despite these advantages, ionizing radiation remains the most significant burden of CTC. This opinion review comprehensively addresses the radiation risk of CTC, incorporating imaging technology refinements such as automatic tube current modulation, filtered back projections, lowering the tube voltage, and iterative reconstructions as tools for optimizing low and ultra-low dose protocols of CTC. Future perspectives arise from integrating artificial intelligence in computed tomography machines for the screening of CRC.
- Published
- 2021
49. Vertical off-centering affects organ dose in chest CT: Evidence from Monte Carlo simulations in anthropomorphic phantoms.
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Saltybaeva, Natalia and Alkadhi, Hatem
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- *
LUNGS , *RADIATION doses , *COMPUTED tomography , *MONTE Carlo method , *IMAGING phantoms - Abstract
Purpose The objective of our study was to assess the effect of patient vertical off-centering on organ dose in chest CT with tube current modulation. Methods For this purpose, anthropomorphic phantoms representing adult male, female, and overweight male were scanned on 192-slice CT scanner at 11 different vertical positions (maximal off-centering ± 5 cm). Monte Carlo simulations were performed for each of the investigated setup, using tube current values extracted from the raw data, in order to obtain 3D dose distributions. Organ doses were calculated as a function of vertical off-centering and compared with the reference values, calculated for the phantoms positioned in the gantry isocenter. Image noise was also calculated as a function of phantoms vertical position using few circular regions of interest. Pearson statistical analysis was used to determine the correlation coefficient between image noise and organ dose values with vertical off-centering. Results Results of our study showed a significant difference in tube currents applied by the CT scanner when the phantom was scanned in off-centered vertical positions compared to those obtained when the phantom was positioned in the gantry isocenter ( P < 0.005). For all investigated phantom configurations the vertical off-centering below 20 mm in both directions resulted in relative organ dose differences below 7%, while the off-centering above 40 mm was associated with higher organ dose changes of about 20%. The highest relative dose difference of 38% was observed for the thyroid gland at the lowest table positions. A significant correlation between organ doses for breasts, heart, lungs, thyroid, and liver, and vertical off-centering (R2 = 0.909-0.998, P < 0.005) was found. The relative dose increase associated with lower table position was more pronounced in peripheral organs: breast and thyroid gland. Image noise behaved opposite to the tube current and organ doses and increased at higher table positions. Conclusion Strong vertical off-centering in chest CT with tube current modulation results in misoperation of the TCM function affecting both radiation dose and image noise. Therefore, special attention must be paid to a correct patient positioning in order to optimize organ doses and image quality of the respective CT examination. [ABSTRACT FROM AUTHOR]
- Published
- 2017
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50. Relationship between the radiation doses at nonenhanced CT studies using different tube voltages and automatic tube current modulation during anthropomorphic phantoms of young children.
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Masuda, Takanori, Funama, Yoshinori, Kiguchi, Masao, Osawa, Kazuaki, Suzuki, Syouichi, Oku, Takayuki, Sugisawa, Koichi, Shouji, Tomokazu, and Awai, Kazuo
- Subjects
ANTHROPOMORPHISM ,ANALOGY (Religion) ,RADIATION ,DIAGNOSTIC imaging ,RADIOTHERAPY - Abstract
To compare the radiation dose and image noise of nonenhanced CT scans performed at 80, 100, and 120 kVp with tube current modulation ( TCM) we used anthropomorphic phantoms of newborn, 1-year-old, and 5-year-old children. The noise index was set at 12. The image noise in the center of the phantoms at the level of the chest and abdomen was measured within a circumscribed region of interest. We measured the doses in individual tissues or organs with radio-photoluminescence glass dosimeters for each phantom. Various tissues or organs were assigned and the radiation dose was calculated based on the international commission on radiological protection definition. With TCM the respective radiation dose at tube voltages of 80, 100, and 120 was 29.71, 31.60, and 33.79 mGy for the newborn, 32.00, 36.79, and 39.48 mGy for the 1-year-old, and 32.78, 38.11, and 40.85 mGy for the 5-year-old phantom. There were no significant differences in the radiation dose among the tube voltages and phantoms ( P > 0.05). Our comparison of the radiation dose using anthropomorphic phantoms of young children showed that the radiation dose of nonenhanced CT performed at different tube voltages with TCM was not significantly different. [ABSTRACT FROM AUTHOR]
- Published
- 2017
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