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Objective: This study investigates the correlation between patient body metrics and radiation dose in abdominopelvic CT scans, aiming to identify significant predictors of radiation exposure. Methods: Employing a cross-sectional analysis of patient data, including BMI, abdominal fat, waist, abdomen, and hip circumference, we analyzed their relationship with the following dose metrics: the CTDIvol, DLP, and SSDE. Results: Results from the analysis of various body measurements revealed that BMI, abdominal fat, and waist circumference are strongly correlated with increased radiation doses. Notably, the SSDE, as a more patient-centric dose metric, showed significant positive correlations, especially with waist circumference, suggesting its potential as a key predictor for optimizing radiation doses. Conclusions: The findings suggest that incorporating patient-specific body metrics into CT dosimetry could enhance personalized care and radiation safety. Conclusively, this study highlights the necessity for tailored imaging protocols based on individual body metrics to optimize radiation exposure, encouraging further research into predictive models and the integration of these metrics into clinical practice for improved patient management.

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Computed tomography (CT) is the gold standard for diagnosing sinusitis and anatomical variations and a guide for paranasal sinus (PNS) surgeries. High doses of radiation lead to increased risk of head and neck malignancies, radiation-induced cataracts, hypothyroidism, and hyperthyroidism. The purpose of this study was to assess the effectiveness of low-dose CT as compared to standard-dose CT in the identification of anatomical variants of paranasal sinus and rhinosinusitis. This was a prospective cross-sectional study consisting of 72 patients who were divided equally into cases (underwent low-dose CT for PNS) and controls (underwent CT for PNS using standard dose protocols). Prevalence of anatomical variants and sinusitis were compared. Image quality was assessed using volume CT dose index (CTDIvol), dose length product (DLP), scan length, and noise. Subjective assessment was done by two radiologists, and scores were given. The comparison and analysis of the quantitative and qualitative variables were done. Anatomical variants were comparable among cases and controls, with post-sellar sphenoid being most common and paradoxical middle turbinate being least common surgically important variant. The difference in mean SD of CTDIvol (mGy), DLP (mGy-cm), effective dose (mSv), globe, and air noise between low and standard doses was statistically significant. A moderate agreement (with kappa 0.50) in cases and substantial agreement (with kappa 0.69) in controls was observed between both observers. Low-dose CT PNS and standard-dose CT PNS are comparable in delineating the paranasal sinus anatomy, with a 3.53× reduction of effective radiation dose to patients.

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INTRODUCTION: CT-based attenuation correction (CT-AC) plays a major role in accurate activity quantification by SPECT/CT imaging. However, the effect of kilovoltage peak (kVp) and quality-reference mAs (QRM) on the attenuation coefficient image (µ-map) and volume CT dose index (CTDIvol) have not yet been systematically evaluated. Therefore, the aim of this study was to fill this gap and investigate the influence of kVp and QRM on CT-AC in 177Lu SPECT/CT imaging. METHODS: Seventy low-dose CT acquisitions of an Electron Density Phantom (seventeen inserts of nine tissue-equivalent materials) were acquired using various kVp and QRM combinations on a Siemens Symbia Intevo Bold SPECT/CT system. Using manufacturer reconstruction software, 177Lu µ-maps were generated for each CT image, and three low-dose CT related aspects were examined. First, the µ-map-based attenuation values (µmeasured) were compared with theoretical values (µtheoretical). Second, changes in 177Lu activity expected due to changes in the µ-map were calculated using a modified Chang method. Third, the noise in the µ-map was assessed by measuring the coefficient of variation in a volume of interest in the homogeneous section of the Electron Density Phantom. Lastly, two phantoms were designed to simulate attenuation in four tissue-equivalent materials for two different source geometries (1-mL and 10-mL syringes). 177Lu SPECT/CT imaging was performed using three different reconstruction algorithms (xSPECT Quant, Flash3D, STIR), and the SPECT-based activities were compared against the nominal activities in the sources. RESULTS: The largest relative errors between µmeasured and µtheoretical were observed in the lung inhale insert (range: 18%-36%), while it remained below 6% for all other inserts. The resulting changes in 177Lu activity quantification were -3.5% in the lung inhale insert and less than -2.3% in all other inserts. Coefficient of variation and CTDIvol ranged from 0.3% and 3.6 mGy (130 kVp, 35 mAs) to 0.4% and 0.9 mGy (80 kVp, 20 mAs), respectively. The SPECT-based activity quantification using xSPECT Quant reconstructions outperformed all other reconstruction algorithms. CONCLUSION: This study shows that kVp and QRM values in low-dose CT imaging have a minimum effect on quantitative 177Lu SPECT/CT imaging, while the selection of low values of kVp and QRM reduce the CTDIvol.

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OBJECTIVE: An assessment of the effective diameter of a patient's body using electron densities of tissues inside the scan area (Deffρe) was proposed to overcome challenges associated with the estimation of water-equivalent diameter (Dw), which is used for size-specific dose estimate (SSDE). The aims of this study were to (1) investigate the Deffρe method in two different forms using a wide range of patient sizes and scanning protocols, and (2) compare between four methods used to estimate the patient size for SSDE. MATERIALS AND METHODS: Under IRB approval, a total of 350 patients of varying sizes have been collected retrospectively from the Hospital. The Dw values were assessed over six different CT body protocols: (1) chest with contrast media, (2) chest High-Resolution Computed Tomography (HRCT) without contrast media, (3) abdomen-pelvis with contrast media, (4) abdomen-pelvis without contrast media, (5) chest-abdomen-pelvis with contrast media, and (6) pelvis without contrast media. A MATLAB-based code was developed in-house to assess the size of each patient using the conventional effective diameter method (Deff), Deffρe by correcting either both the lateral (LAT) and anterior-posterior (AP) dimensions (Deff,LAT+APρe) or LAT only (Deff,LATρe), and Dw at the mid-CT slice of the patient images. RESULTS: The results of Deff,LAT+APρe and Deff,LATρe provided a better estimation for the chest protocols with the averages of absolute percentage difference (PD) values in the range of 3 - 7 % for all patient sizes as compared to the Dw method, whereas the averages of PD values for the Deff method were 9 - 15 %. However, Deff gave a better estimation for Dw values for the other body protocols, with differences of 2 - 4 %, which were lower than those obtained with the Deff,LAT+APρe and Deff,LATρe methods. For the chest protocols, statistically significant differences were found between Deff and the other methods, but there were no significant differences between all the methods for the other scanning protocols. The results show that the correction of both dimensions, LAT and AP, did not improve the accuracy of the Deffρe method, and, for most protocols, Deff,LAT+APρe gave larger range differences compared to those based on correction of the LAT dimension only. CONCLUSION: If the Dw cannot be assessed, the Deff,LATρe method may only be considered for the chest protocols as an alternative approach. The Deff method may also be used for all regions taking into account the application of a correction factor for the chest protocols to avoid a significant under or overestimation of the patient dose.

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INTRODUCTION: Computed tomography urography (CTU) comprehensively evaluates the urinary tract. However, the procedure is associated with a high radiation dose due to multiple scan series and therefore requires optimisation. The study performed CTU protocol optimisation based on a reduction in tube voltage (kV) using quality assurance (QA) phantom and clinical images and evaluated image quality and radiation dose. METHODS: The study was prospectively conducted on patients referred for CTU. The patients were grouped into A and B and were scanned with the standard protocol, a protocol used for the routine CTU at the CT centre before optimisation, and optimised protocol, a protocol with reduced kV respectively. The protocols were first tried on a quality assurance (QA) phantom before being applied to patients, and image quality was assessed based on signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR). In addition, the clinical images were assessed based on the visibility of the anatomical criteria for CT images by five observers with >5 years of experience. The data were analysed using both visual grading characteristic (VGC) curves and statistical package for social sciences (SPSS) version 22.0. RESULTS: The dose was significantly lower in the optimised protocol with a 10 % reduction in both volume computed tomography dose index and (CTDIvol) and dose length product (DLP) for the phantom images, and a 26 % reduction in CTDIvol and 28 % in DLP for the clinical images. However, there was no significant difference in image quality noted between the standard and optimised protocols based on the quantitative and qualitative image quality evaluation using both the QA phantom and clinical images. CONCLUSION: The findings revealed a significant dose reduction in the optimised protocol. Further, image quality in standard and optimised protocols did not differ significantly based on quantitative and qualitative methods. IMPLICATION FOR PRACTICE: kV optimisation in contrast-enhanced procedures provides dose reduction and should be encouraged in the medical imaging departments.

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OBJECTIVES: To establish local DRL (LDRL) for computed tomography (CT) examinations based on size-specific dose estimates (SSDEs), which consider patient size. The concept of diagnostic reference level (DRL) was introduced to limit patient exposure to unnecessary radiation. However, traditional DRL values do not consider patient size. METHODS: Following institutional committee approval, data were collected from CT examinations of adult patients at Madinah General Hospital, Al Madinah Al Munawwarah, Saudi Arabia from January to March 2023. The SSDE was calculated for each patient using the effective diameter (Deff). RESULTS: The LDRLs of the brain, cervical spine, chest, thoracic spine and kidneys, ureters, and bladder (KUB) examinations were 118 mGy, 12 mGy, 8 mGy, 17 mGy, and 7 mGy, respectively. A strong correlation was observed between SSDEs and the volume computed tomography dose index (CTDIvol) for all examinations except chest scans (p<0.05). Size-specific dose estimates were higher than the CTDIvol, with a greater difference for patients with smaller Deff (p<0.05). CONCLUSION: The established LDRL was within the international DRL. The use of SSDE has the potential to provide more accurate and relevant data for radiation safety practices; however, widespread adoption of SSDE in new CT scanners is necessary for promoting consistency and standardization methodologies.

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Background: The thyroid, along with the breast, lung, and bone marrow, is among the most radiosensitive organs. This study aims to assess the rate of unnecessary radiation exposure to the thyroid gland in patients who had chest Computed Tomography (CT) at a large teaching hospital. Method: Hospital-based retrospective cross-sectional study on 1,306 patients who underwent chest CT from July 2018 to January 2019. Thyroid gland inclusion along with the CT dose of the studies was evaluated. Data was collected by evaluating chest CT scans from Picture Archive and Communication System (MedWeb). Result: Out of 1306 patients, who had Chest CT scans intravenous iodinated contrast media was used in 95.4% of the CT scans. The thyroid was included in 99.8% of the scans, out of which 76.9% included the whole thyroid gland. Among the patients who had previous CT scans, 75.3% had one previous scan and 24.7% had two previous scans. DLP (Dose Length Product) in mGycm was lower in females (360.33±32) compared to males (426.45±378.4). The lowest DLP value was observed in the pediatric patients in the age range of 1-5 years which was 146.83, while the highest was observed among those above 18 years of age with mean DLP of 418.31. Conclusion: The majority of chest CT scans unnecessarily include the whole thyroid gland, which is one of the most sensitive organs for radiation-induced effects. Authors recommend optimized technique for chest scans to avoid future impacts.

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Background: In August 2017, the European Commission awarded the "European Study on Clinical Diagnostic Reference Levels (DRL) for X-ray Medical Imaging" project to the European Society of Radiology to provide up-to-date Diagnostic Reference Levels based on clinical indications. This work aimed to conduct an extensive literature review by analyzing the most recent studies published and the data provided by the National Competent Authorities to understand the current situation regarding Diagnostic Reference Levels based on clinical indications for Radiation Therapy Computed Tomography. Objective: To review the literature on established DRLs and methodologies for establishing Diagnostic reference levels in radiation therapy planning computed tomography (RTCT). Methods: Eligibility criteria: A cohort study (observational design) reporting DRLs in adult patients undergoing computed tomography (CT) for radiation therapy for the region head and neck or pelvis were included. The comprehensive literature searches for the relevant studies published between 2000 and 2021 were performed using PubMed, Scopus, CINHAL, Web of Science, and ProQuest. Results: Three hundred fifty-six articles were identified through an extensive literature search. Sixty-eight duplicate reports were removed. The title and abstract of 288 studies were assessed and excluded if they did not meet the inclusion criteria. Sixteen of 288 articles were selected for full-text screening (studies conducted between 2000 and 2021). Five articles were included in the review after the full-text screening. Conclusions: A globally approved standard protocol that includes scanning techniques, dose measurement method, and DRL percentile needs to be established to make a valuable and accurate comparison with international DRLs.

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PURPOSE: We developed X-ray dose monitoring and optimization software for computed tomography (CT) by using a spreadsheet software. METHODS: The analysis was carried out on 1,212 patients using 2,128 CT examinations at our institution, in the period of April 2020 to April 2022. These cases were extracted in the limitation of patient's weight in the range of 50 to 70 kg. The individual radiation report, including CTDIvol and DLP, on the console displayed by a CT system was used and manually transferred to our software. The X-ray dose distribution was evaluated by using a boxplot chart and a scatter plot, and the data were referred to Japan DRLs 2020 (National Diagnostic Reference Levels in Japan 2020). RESULTS: Almost all patient's doses in our institution were distributed in the acceptable ranges in comparison with the Japan DRLs 2020. Neither extremely high nor low dose data were recorded. However, seven cases recorded outlier dose values. Three cases were caused by errors during manually inputting the data. Four from seven cases were explored the reason to record outlier dose values. CONCLUSION: Our software on a spreadsheet software worked well to explore the CT dose data, such as CTDIvol and DLP. Our software was able to find cases that were recorded as outlier dose values, but their values were not extremely high/low values. The cautionary notice of either high or low dose, as a function of our software, will be able to keep our patient's CT dose in the universal-standard "justification and optimization" level.

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The aim of this study is to measure the volumetric computed tomography dose index (CTDIvol) for different tube voltages for a polyester-resin (PESR) phantom, and to compare it to values for a standard polymethyl methacrylate (PMMA) phantom. Both phantoms are head phantoms with a diameter of 16 cm. The phantoms were scanned by a CT scanner (GE Revolution EVO 64/128 slice) with tube voltages of 80, 100, 120, and 140 kV. The other scan parameters were constant (i.e. tube current of 100 mA, rotation time of 1 s, and collimation width of 10 mm). The CTDI100,c and CTDI100,p were obtained by measuring the dose with an ionization chamber inserted into five holes within the phantoms. The CTDIvol was calculated based on the CTDI100,c and CTDI100,p values. The measurements were repeated three times for each hole. It was found that the CTDIvol values for the PESR phantom were dependent on tube voltage value, and were similar to the dependency in a PMMA phantom. The maximum CTDIvol difference between the PESR and PMMA phantoms was 7.5%. We conclude that the dose measured in the PESR phantom is similar to that in the PMMA phantom and that the PESR phantom can be used as an alternative if the PMMA phantom is not available.

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OBJECTIVE: This study aimed to investigate the feasibility of low-dose chest CT acquisition protocol for the imaging of COVID 19 disease or suspects of this disease in adults. METHODS: In this retrospective case-control study, the study group consisted of 141 patients who were imaged with low dose chest CT acquisition protocol. The control group consisted of 92 patients who were imaged with standard protocol. Anteroposterior and lateral diameters of chest, effective diameter and scan length, qualitative and quantitative noise levels, volumetric CT dose index (CTDIvol), dose length product (DLP), and size-specific dose estimations were compared between groups. RESULTS: Radiation dose reduction by nearly 90% (CTDIvol and DLP values 1.06 mGy and 40.3 mGy.cm vs. 8.07 mGy and 330 mGy.cm, respectively; p < 0.001) was achieved with the use of low-dose acquisition chest CT protocol. Despite higher image noise with low-dose acquisition protocol, no significant effect on diagnostic confidence was encountered. Cardiac and diaphragm movement-related artifacts were similar in both groups (p=0.275). Interobserver agreement was very good in terms of diagnostic confidence assessment. CONCLUSION: For the imaging of COVID-19 pneumonia or suspects of this disease in adults, lowdose chest CT acquisition protocol provides remarkable radiation dose reduction without adversely affecting image quality and diagnostic confidence.

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The volumetric computed tomography (CT) dose index (CTDIvol) is the measure of output displayed on CT consoles relating to dose within a standard phantom. This gives a false impression of doses levels within the tissues of smaller patients in Southeast Asia. A size-specific dose estimate (SSDE) can be calculated from the CTDIvolto provide an assessment of doses at specific positions within a scan using size-specific conversion factors. SSDE is derived using the water equivalent diameter (Dw) of the patient, but calculation ofDwrequires sophisticated computer software. This study aimed to evaluate relationships betweenDWand effective diameter (DEff), which can be measured more readily, in order to estimate SSDE at various positions within a routine clinical abdomen and pelvis CT examination for Thai patients. An in-house ImageJ algorithm was developed to measureDw, effective diameter (DEff), and SSDE on CT slices located at the heart, liver, kidneys, colon, and bladder, on 181 CT examinations of abdomen and pelvis. Relationships betweenDEffandDwwere determined, and values of organ absorbed dose usingDEffwere estimated. This approach was validated using a second cohort of 54 patients scanned on a different CT scanner. The results revealed that ratios betweenDEffandDwat the heart level were 1.11-1.13 and those for the others were about 1.00. Additionally, the SSDE/CTDIvolratio was estimated for each organ in terms of exponential functions using the relationships betweenDwandDEfffor individual organs. In summary, this study proposed a simple method for estimation of organ absorbed doses for Southeast Asian patients undergoing abdomen and pelvis CT examinations where sophisticated computer software is not available.

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BACKGROUND & AIMS: Retrospective cross-sectional studies linked sarcopenia and myosteatosis with metabolic dysfunction-associated fatty liver disease (MAFLD). Here, we wanted to clarify the dynamic relationship between sarcopenia, myosteatosis, and MAFLD. METHODS: A cohort of 48 obese patients was randomised for a dietary intervention consisting of 16 g/day of inulin (prebiotic) or maltodextrin (placebo) supplementation. Before and after the intervention, we evaluated liver steatosis and stiffness with transient elastography (TE); we assessed skeletal muscle index (SMI) and skeletal muscle fat index (SMFI) (a surrogate for absolute fat content in muscle) using computed tomography (CT) and bioelectrical impedance analysis (BIA). RESULTS: At baseline, sarcopenia was uncommon in patients with MAFLD (4/48, 8.3%). SMFI was higher in patients with high liver stiffness than in those with low liver stiffness (640.6 ± 114.3 cm2/ Hounsfield unit [HU] vs. 507.9 ± 103.0 cm2/HU, p = 0.001). In multivariate analysis, SMFI was robustly associated with liver stiffness even when adjusted for multiple confounders (binary logistic regression, p <0.05). After intervention, patients with inulin supplementation lost weight, but this was not associated with a decrease in liver stiffness. Remarkably, upon intervention (being inulin or maltodextrin), patients who lowered their SMFI, but not those who increased SMI, had a 12.7% decrease in liver stiffness (before = 6.36 ± 2.15 vs. after = 5.55 ± 1.97 kPa, p = 0.04). CONCLUSIONS: Myosteatosis, but not sarcopenia, is strongly and independently associated with liver stiffness in obese patients with MAFLD. After intervention, patients in which the degree of myosteatosis decreased reduced their liver stiffness, irrespective of body weight loss or prebiotic treatment. The potential contribution of myosteatosis to liver disease progression should be investigated. CLINICAL TRIALS REGISTRATION NUMBER: NCT03852069. LAY SUMMARY: The fat content in skeletal muscles (or myosteatosis) is strongly associated with liver stiffness in obese patients with MAFLD. After a dietary intervention, patients in which the degree of myosteatosis decreased also reduced their liver stiffness. The potential contribution of myosteatosis to liver disease progression should be investigated.

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A method for estimating peak skin dose (PSD) from CTDIvol has been published but not validated. The objective of this study was to validate this method during CT-guided ablation procedures. Radiochromic film was calibrated and used to measure PSD. Sixty-eight patients were enrolled in this study, and measured PSD were collected for 46 procedures. CTDIvol stratified by axial and helical scanning was used to calculate an estimate of PSD using the method [1.2 × CTDIvol (helical) + 0.6 × CTDIvol (axial)], and both calculated PSD and total CTDIvol were compared to measured PSD using paired t-tests on the log-transformed data and Bland-Altman analysis. Calculated PSD were significantly different from measured PSD (P < 0.0001, bias, 18.3%, 95% limits of agreement, -63.0% to 26.4%). Measured PSD were not significantly different from total CTDIvol (P = 0.27, bias, 3.97%, 95% limits of agreement, -51.6% to 43.7%). Considering that CTDIvol is reported on the console of all CT scanners, is not stratified by axial and helical scanning modes, and is immediately available to the operator during CT-guided interventional procedures, it may be reasonable to use the scanner-reported CTDIvol as an indicator of PSD during CT-guided procedures. However, further validation is required for other models of CT scanner.

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BACKGROUND: Internationally, the typical allowed difference between the measured radiation dose and dose reported by a computed tomography (CT) scanner is ±20 %. The objective is to describe a method in order to analyse this difference in a CT scanner in the Emergency Department of Kanta-Häme Central Hospital, and to calculate a correction factor for more comparable radiation dose values in further studies. METHODS: Ten intra-day radiation dose measurements were performed with undisturbed setting. Measurement reports on differences between measured and displayed dose were gathered from the vendor maintenance and supervising authority over a 12-year period. Additionally, two in-house measurements were made. A total of 18 datapoints were collected, with some differences in measurement settings. Data were also analysed against imaging parameters, ambient air pressure and time to identify trends or associations in the variation of the discrepancy. RESULTS: Measured doses were generally lower than displayed doses. Differences between displayed and measured doses varied between -3.46 and -0.10 %, with a mean of -1.26 % in the intra-day measurements, and between +4.65 and -17.3 %, with a mean of -7.53 % in the long-term data. There were no trends nor connections in the variations. CONCLUSION: Since the acceptable difference between the radiation dose display and the measured dose is relevant, the average difference for every CT scanner should be determined before radiation dose studies, especially when comparing multiple scanners.

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OBJECTIVES: CT is an essential diagnostic tool in health care. However, CT delivers relatively high levels of radiation which has been associated with an increased risk of childhood cancer. To address this, we evaluated patterns and time trends of CT use among children in Finland during the period in which changes in pediatric CT imaging practices were reported in several countries. METHODS: Data on CTs performed on children younger than 15 years were obtained from Finland's largest eight hospitals. CT data included the period 1996-2010 with an estimated coverage of more than 80 % of pediatric CT imaging in Finland. Joinpoint regression was used for trends analysis. CT radiation doses were estimated based on a Finnish dosimetry survey. RESULTS: A total of 48,807 pediatric CTs were performed in 1996-2010. More boys (55.5 %) were scanned than girls (42.8 %). CT numbers increased up to 2002, then decreased significantly (-6.9 % per year, 95 % CI: -10.4 to -3.2) towards 2005 and to a lesser extent thereafter, particularly among younger children. All CT types decreased in recent years, except for chest, spine, and extremities. The frequency of head CTs related to the diagnoses of intracranial injury, migraine and headache decreased towards the end of the study period. The estimated annual average effective dose from the three most common CT examinations was 0.004 mSv per child in the population. CONCLUSIONS: The frequency of pediatric CTs in Finland started to decrease after 2002. Apart from chest and orthopedic CTs, the utilization of pediatric CT imaging declined in recent years, most likely explained by improved awareness of medical radiation risks and reliance on alternative modalities such as MRI and ultrasound.

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PURPOSE: It is well known that there is a trade-off relationship between image noise and exposure dose in X-ray computed tomography (CT) examination. Therefore, CT dose level was evaluated by using the CT image noise property. Although noise power spectrum (NPS) is a common measure for evaluating CT image noise property, it is difficult to evaluate noise performance directly on clinical CT images, because NPS requires CT image samples with uniform exposure area for the evaluation. In this study, various noise levels of CT phantom images were classified for estimating dose levels of CT images using convolutional neural network (CNN). METHOD: CT image samples of water phantom were obtained with a combination of mAs value (50, 100, 200 mAs) and X-ray tube voltage (80, 100, 120 kV). The CNN was trained and tested for classifying various noise levels of CT image samples by keeping 1) a constant kV and 2) a constant mAs. In addition, CT dose levels (CT dose index: CTDI) for all exposure conditions were estimated by using regression approach of the CNN. RESULT: Classification accuracies for various noise levels were very high (more than 99.9%). The CNN-estimated dose level of CT images was highly correlated (r=0.998) with the actual CTDI. CONCLUSION: CT image noise level classification using CNN can be useful for the estimation of CT radiation dose.

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OBJECTIVES: Computed tomography (CT) scanning is an essential part of diagnostic and treatment plans, providing swift and accurate diagnostic images. The aim of this study is to develop diagnostic reference levels (DRLs) for the adult common CT examination in the United Arab Emirates (UAE). METHODS: This study presents results of the survey of CT dose indices. The data were collected from 91% of the scanners registered at the Ministry of Health and Prevention (MOHAP) for five common examinations: head, chest, and abdomen-pelvis with and without CM. RESULTS: CT dose index, dose-length product, and patient weight were analyzed; the reference dose was calculated on the 75th percentile, and an achievable dose was proposed from the median value. The results were compared with the UAE initial National Dose Report as well as the international reports. The proposed dose for CTDIvol (mGy) and DLP (mGy cm) is as follows: head without CM 40 and 695, head with CM 48 and 820, chest 10 and 275, abdomen-pelvis without CM 14 and 810, and abdomen-pelvis with CM 20 and 1025. CONCLUSIONS: The results show low dose variations between the MOHAP scanners. The data also revealed CTDIvol and DLP values comparable to those in the initial NDRL report and international standards. The establishment of diagnostic reference levels will require a continuous dose monitoring system.

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PURPOSE: Most clinical computed tomography (CT) protocols use helical scanning; however, the traditional method for CTDIvol measurement replaces the helical protocol with an axial scan, which is not easily accomplished on many scanners and may lead to unmatched collimation settings and bowtie filters. This study assesses whether CTDIvol can be accurately measured with a helical scan and determines the impact of pitch, collimation width, and excess scan length. METHODS: CTDIvol was measured for 95 helical protocols on 31 CT scanners from all major manufacturers. CTDIvol was measured axially, then again helically, with the scan range set to the active area of the pencil chamber seen on the localizer image. CTDIvol measurements using each method were compared to each other and to the scanner-displayed CTDIvol . To test the impact of scan length, the study was repeated on four scanners, with the scan range set to the phantom borders seen on the localizer. RESULTS: It was not possible to match the collimation width between the axial and helical modes for 12 of the 95 protocols tested. For helical and axial protocols with matched collimation, the difference between the two methods averaged below 1 mGy with a correlation of R2  = 0.99. The difference between the methods was not statistically significant (P = 0.81). The traditional method produced four measurements that differed from the displayed CTDIvol by >20%; no helical measurements did. The accuracy of the helical CTDIvol was independent of protocol pitch (R2  = 0.0) or collimation (R2  = 0.0). Extending the scan range to the phantom borders increased the measured CTDIvol by 2.1%-9.7%. CONCLUSION: There was excellent agreement between the two measurement methods and to the displayed CTDIvol , without protocol or vendor dependence. The helical CTDIvol measurement can be accomplished more easily than the axial method on many scanners and is reasonable to use for QC purposes.

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PURPOSE: To compare CT pulmonary angiographies (CTPAs) as well as phantom scans obtained at 100 kVp with a conventional CT (C-CT) to virtual monochromatic images (VMI) obtained with a spectral detector CT (SD-CT) at equivalent dose levels as well as to compare the radiation exposure of both systems. MATERIAL AND METHODS: In total, 2110 patients with suspected pulmonary embolism (PE) were examined with both systems. For each system (C-CT and SD-CT), imaging data of 30 patients with the same mean CT dose index (4.85 mGy) was used for the reader study. C-CT was performed with 100 kVp and SD-CT was performed with 120 kVp; for SD-CT, virtual monochromatic images (VMI) with 40, 60 and 70 keV were calculated. All datasets were evaluated by three blinded radiologists regarding image quality, diagnostic confidence and diagnostic performance (sensitivity, specificity). Contrast-to-noise ratio (CNR) for different iodine concentrations was evaluated in a phantom study. RESULTS: CNR was significantly higher with VMI at 40 keV compared to all other datasets. Subjective image quality as well as sensitivity and specificity showed the highest values with VMI at 60 keV and 70 keV. Hereby, a significant difference to 100 kVp (C-CT) was found for image quality. The highest sensitivity was found using VMI at 60 keV with a sensitivity of more than 97 % for all localizations of PE. For diagnostic confidence and subjective contrast, highest values were found with VMI at 40 keV. CONCLUSION: Higher levels of diagnostic performance and image quality were achieved for CPTAs with SD-CT compared to C-CT given similar dose levels. In the clinical setting SD-CT may be the modality of choice as additional spectral information can be obtained.