Computed Tomography Effective Dose Research Articles

Computed Tomography Effective Dose and Image Quality in Deep Learning Image Reconstruction in Intensive Care Patients Compared to Iterative Algorithms.

Deep learning image reconstruction (DLIR) algorithms employ convolutional neural networks (CNNs) for CT image reconstruction to produce CT images with a very low noise level, even at a low radiation dose. The aim of this study was to assess whether the DLIR algorithm reduces the CT effective dose (ED) and improves CT image quality in comparison with filtered back projection (FBP) and iterative reconstruction (IR) algorithms in intensive care unit (ICU) patients. We identified all consecutive patients referred to the ICU of a single hospital who underwent at least two consecutive chest and/or abdominal contrast-enhanced CT scans within a time period of 30 days using DLIR and subsequently the FBP or IR algorithm (Advanced Modeled Iterative Reconstruction [ADMIRE] model-based algorithm or Adaptive Iterative Dose Reduction 3D [AIDR 3D] hybrid algorithm) for CT image reconstruction. The radiation ED, noise level, and signal-to-noise ratio (SNR) were compared between the different CT scanners. The non-parametric Wilcoxon test was used for statistical comparison. Statistical significance was set at p < 0.05. A total of 83 patients (mean age, 59 ± 15 years [standard deviation]; 56 men) were included. DLIR vs. FBP reduced the ED (18.45 ± 13.16 mSv vs. 22.06 ± 9.55 mSv, p < 0.05), while DLIR vs. FBP and vs. ADMIRE and AIDR 3D IR algorithms reduced image noise (8.45 ± 3.24 vs. 14.85 ± 2.73 vs. 14.77 ± 32.77 and 11.17 ± 32.77, p < 0.05) and increased the SNR (11.53 ± 9.28 vs. 3.99 ± 1.23 vs. 5.84 ± 2.74 and 3.58 ± 2.74, p < 0.05). CT scanners employing DLIR improved the SNR compared to CT scanners using FBP or IR algorithms in ICU patients despite maintaining a reduced ED.

Usefulness of the spectral shaping dual-source computed tomography imaging technique in posterior corrective fusion for adolescent idiopathic scoliosis.

Since childhood exposure to radiation has been demonstrated to increase cancer risk with increase in radiation dose, reduced radiation exposure during computed tomography (CT) evaluation is desired for adolescent idiopathic scoliosis (AIS). Therefore, this retrospective study aimed to investigate the radiation dose of dual-source CT using a spectral shaping technique and the accuracy of the thoracic pedicle screw (TPS) placement for posterior spinal fusion (PSF) in patients with AIS. Fifty-nine female patients with thoracic AIS who underwent PSF using CT-guided TPSs were included and divided into two groups comprised of 23 patients who underwent dual-source CT (DSCT) with a tin filter (DSCT group) and 36 who underwent conventional multislice CT (MSCT group). We assessed the CT radiation dose using the CT dose index (CTDIvol), effective dose (ED), and accuracy of TPS insertion according to the established Neo's classification. The DSCT and MSCT groups differed significantly (p < 0.001) in the mean CTDIvol (0.76 vs. 3.31mGy, respectively) and ED (0.77 vs. 3.47mSv, respectively). Although the correction rate of the main thoracic curve in the DSCT group was lower (65.7% vs. 71.2%) (p = 0.0126), the TPS accuracy (Grades 0-1) was similar in both groups (381 screws [88.8%] vs. 600 screws [88.4%], respectively) (p = 0.8133). No patient required replacement of malpositioned screws. Spectral shaping DSCT with a tube-based tin filter allowed a 75% radiation dose reduction while achieving TPS insertion accuracy similar to procedures based on conventional CT without spectral shaping.

A comparative study of the CT effective dose in whole-body 18F-FDG PET/CT for arm-raised position and arm-lowered position

IntroductionThis study aimed to investigate and compare the effective dose (ED) delivered by computed tomography (CT) in whole-body positron emission tomography/CT (WB-PET/CT) scans between patients positioned with their arms-raised and those with their arms-lowered during the scan on a large population. MethodsThe retrospective study involved 785 oncology patients who underwent WB-PET/CT scans with 18F-FDG between January and June 2019. Exclusion criteria were applied, resulting in a final analysis of data from 732 adult patients. All of the patients were measured height and weight, and the ED from CT in WB-PET/CT was estimated using the dose length product value and a conversion factor. Statistical analyses were conducted to explore relationships between factors and the ED. Linear regression analysis was performed to investigate connections between weight and ED, and height and ED. Multiple linear regression was used to predict ED based on sex, weight, and arm position. ResultsThe arm-lowered group had a higher ED than the arm-raised group, and the median dose was 1.1 times higher in the arm-lowered group. The difference in ED between the two groups was found to be greater with higher body weight. Arm-position (β = 0.460), sex (β = −0.190), and weight (β = 0.057) were significant predictors of ED. ConclusionThis study demonstrated that arm position, sex, and weight were significant factors influencing the ED from CT scans in WB-PET/CT. Implications for practiceThe research underscores the importance of considering these factors when evaluating radiation exposure in clinical practice, particularly for patients undergoing WB-CT imaging. These findings contribute to a better understanding of the radiation dosimetry associated with different patient positions during WB-PET/CT scans.

Radiation exposure and cancer risk of pediatric head CT scans: Impact of age and scanning parameters

Computed tomography (CT) is a widely utilized imaging technique in various medical applications due to the advanced technology that allows the diagnosis of diseases efficiently. The aims of this study were (1) to assess the radiation dose and the probability of cancer incidence for pediatric head CT scans, and (2) to analyze the influence of age and other scanning parameters on radiation dose. A total of 224 pediatric patients, ranging in age from newborn to 18 years, were collected from three main hospitals in Saudi Arabia. The patient data were divided into four age groups: Group 1 (0 to < 1 year old), Group 2 (1 to < 5 years old), Group 3 (5 to < 10 years old), and Group 4 (10 to < 18 years old). Initially, descriptive statistics were conducted for the values of volume CT dose index (CTDIvol), dose-length product (DLP), effective dose, and probability of lifetime cancer risk. This was followed by applying the Kruskal-Wallis H and the Mann-Whitney U tests to investigate the influence of age and other scanning parameters, namely tube voltage, slice thickness, and the use of automatic tube current modulation (ATCM), on radiation dose. It has been found that as the age of patients increased, there was a corresponding increase in CTDIvol and DLP values and a decrease in effective doses and lifetime cancer risk. The patient's age accounted for 33.4% and 34.9% of the variations in CTDIvol and DLP, respectively, while tube voltage (kVp) settings accounted for 25.8% and 24.9%, respectively. There was an increase of 22.3% in CTDIvol reported for patients scanned with a slice thickness of 2 mm compared to those scanned at 2.5 mm, and a 2.2% dose increase between slice thicknesses of 2.5 mm and 5 mm. Radiation doses in the surveyed hospitals fall within acceptable limits. Further studies in Saudi Arabia should focus on evaluating patient doses based on the actual sizes, which determine radiation doses for pediatric CT imaging more accurately.

Reduced-dose CT in detecting solid liver tumors: A comparison of image quality between automatic exposure control and organ effective modulation

PurposeTo evaluate the subjective and objective image quality of solid liver tumors as well as the radiation dose using organ effective modulation (OEM) technology for abdominopelvic computed tomography (CT). Material and methodsA total of 74 patients who underwent contrast-enhanced abdominopelvic CT between January and April 2022 were prospectively enrolled in this study. Patients were randomly assigned to two groups: the non-OEM group underwent CT scans with automatic exposure control (AEC), while the OEM group underwent CT scans with OEM. The radiation dose was compared between the two groups. Objective image quality was quantitatively assessed using image noise, signal-to-noise ratio (SNR), and contrast-to-noise ratio (CNR). Two experienced radiologists independently evaluated the CT images (5, best; 1, worst) by four characteristics including sharpness, contrast, noise, and diagnostic confidence. ResultsThe OEM group presented a significant reduction in volume CT dose index (CTDIvol), dose-length product (DLP), and effective dose (ED) by 11.4%, 12.2%, and 12.2%, respectively (p < 0.05). There were no significant differences between two groups concerning image noise, SNR, and CNR (p > 0.05). Expect for the left and right liver lobes in portal images, OEM was slightly higher than the non-OEM (p < 0.05). The subjective scores of two radiologists demonstrated good agreement (kappa value = 0.84). No statistically significant differences were observed in subjective grading (p > 0.05). ConclusionOEM technology can effectively reduce the radiation dose of abdominopelvic-enhanced CT without affecting the subjective and objective image quality of solid liver tumors.

A Study of Fixed Current and Automatic Tube Current Modulation at a Fixed Low Tube Voltage in Low-dose Computed Tomography (CT) Imaging of Infant Lungs

Background: With the development of computed tomography (CT) technology, the number of infants undergoing CT examination has increased. Recently, problems associated with radiation exposure have attracted the public attention, and low-dose CT examination has become the research focus. Objectives: This study aimed to explore the feasibility of a fixed ultralow tube current combined with iDose4 iterative reconstruction at a low tube voltage (80 kV) in low-dose CT scanning of infant lungs. Patients and Methods: Ninety infants, aged 0 - 3 years, undergoing enhanced chest CT scan (including plain CT scan and arterial scan), were included in the experimental group. In the experimental group, plain CT scan was performed at 80 kV under a fixed tube current (30 mA), and arterial phase CT scan was carried out at 80 kV with automatic tube current modulation (30 - 150 mA). Meanwhile, 90 infants, aged 0 - 3 years, undergoing non-enhanced chest CT scan, were randomly recruited as the control group. For the control group, plain CT scan was performed at 80 kV with automatic tube current modulation (30-150 mA). In each examination, the iDose4 iterative reconstruction technique was used for reconstruction. The volume CT dose index (CTDIvol), dose-length product (DLP), effective dose (ED, measured using a 32-cm diameter phantom), signal-to-noise ratio (SNR), and overall subjective quality of plain CT scans were analyzed and compared between the experimental and control groups. Results: Regarding the radiation dose in different age groups, the ED (mSv) was significantly lower in the experimental group compared to the control group (0-1-year-old subgroup: 0.48 ± 0.05 mSv in the experimental group vs. 0.91 ± 0.19 mSv in the control group, P &lt; 0.05; 1-2-year-old subgroup: 0.50 ± 0.01 mSv in the experimental group vs. 0.75 ± 0.10 mSv in the control group, P &lt; 0.05; and 2-3-year-old subgroup: 0.46 ± 0.05 mSv in the experimental group vs. 0.79 ± 0.11 mSv in the control group, P &lt; 0.05). The image SNR was higher in the control group compared to the experimental group (P &lt; 0.05), while the difference in subjective image quality was not significant between the experimental and control groups (P &lt; 0.05). Conclusion: The chest CT examination of infants, aged 0 - 3 years, at a low tube voltage (80 kV) and a fixed tube current (30 mA), combined with the iDose4 iterative reconstruction technique, and the obtained images met the diagnostic criteria...

INVESTIGATION OF RADIATION RISKS BASED ON THE CLINICAL FINDINGS FROM HEAD CT SCANS IN TRAUMA.

This study aimed to investigate the radiation risks in terms of effective dose and the cancer risk probability resulting from computed tomography (CT) scans of the head for traumatic patients and determine how often traumatic abnormalities occur. Data were collected retrospectively for 138 traumatic patients from the picture archiving and communication system, including exposure parameters and clinical findings. The mean values of the dose length product, CT dose index volume and effective dose for the CT head examinations were 787±67.7mGy•cm, 40.1±1.33mGy and 1.47±0.12mSv, respectively. Of the total cases of CT scans of the head, 57.2% (n=79) exhibited positive findings. The cancer risk probability for the patients was 6.04×10-5 per procedure, with no statistically significant differences between positive and negative findings (p=0.345). Taking into consideration the justification of the examination, the risk of missing positive findings and the radiation risks, the immediate benefit of head CT for trauma patients for guiding medical decisions outweighs the radiation risk that will probably manifest later.

Deep learning reconstruction allows low-dose imaging while maintaining image quality: comparison of deep learning reconstruction and hybrid iterative reconstruction in contrast-enhanced abdominal CT.

We aimed to compare the radiation dose and image quality of a low-dose abdominal computed tomography (CT) protocol reconstructed with deep learning reconstruction (DLR) with those of a routine-dose protocol reconstructed with hybrid-iterative reconstruction. This retrospective study enrolled 71 patients [61 men; average age, 71.9 years; mean body mass index (BMI), 24.3 kg/m2] who underwent both low-dose abdominal CT with DLR [advanced intelligent clear-IQ engine (AiCE)] and routine-dose abdominal CT with hybrid-iterative reconstruction [adaptive iterative dose reduction 3D (AIDR 3D)]. Radiation dose parameters included volume CT dose index (CTDIvol), effective dose (ED), and size-specific dose estimate (SSDE). Mean image noise and contrast-to-noise ratio (CNR) were calculated. Image noise was measured in the hepatic parenchyma and bilateral erector spinae muscles. Moreover, subjective assessment of perceived image quality and diagnostic acceptability was performed. The low-dose protocol helped reduce the CTDIvol by 44.3%, ED by 43.7%, and SSDE by 44.9%. Moreover, the noise was significantly lower and CNR significantly higher with the low-dose protocol than with the normal-dose protocol (P<0.001). In the subjective assessment of image quality, there was no significant difference between the protocols with regard to image noise. Overall, AiCE was superior to AIDR 3D in terms of diagnostic acceptability (P=0.001). The use of AiCE can reduce overall radiation dose by more than 40% without loss of image quality compared to routine-dose abdominal CT with AIDR 3D.

Evaluation of Low-Dose 3D skull CT images in craniosynostosis

Introduction: Computed Tomography (CT) is nowadays used widely to differentiate normal brain cranium sutures from abnormal ones in pediatric patients with the aim of early treatment. This study tried to develop a low-dose CT protocol with acceptable image quality of skull bone in order to evaluate craniosynostosis. Materials and Methods: In this study a cranium bone of human cadaver was scanned with standard and reduced dose protocols. Two radiologists verified the quality of skull bone image acquired from the protocol in which there had been 60% dose reduction to scan pediatric patients. The quality of low dose protocol of three dimensional (3D) CT images of skull bone of 57 pediatric subjects suspected of craniosynostosis were compared with standard-dose skull CT images of 44 patients of the same age range. Volume CT dose index (CTDIvol), dose-length product (DLP), and effective dose (ED) were used to evaluate CT dose protocols. Comparison was made by two sample t-test. Results: Mean and standard deviations of CTDIvol, DLP, and ED of standard and reduced doses were 12.4±2.7 mGy, 191.5±54 mGy.cm, 1.94±0.58 mSv and 5.4±0.2 mGy, 85±9 mGy.cm, 0.77±0.17 mSv, respectively, which had statistically significant difference (α=0.05). The quality of skull bone views obtained from low-dose CT protocol were found to be as good as in standard dose. Conclusion: Standard-dose 3D CT protocol of skull bone can be replaced by a 60%-reduced-dose 3D CT protocol with comparable image quality in pediatric patients suspected of craniosynostosis.

Application of 70 kVp tube voltage combined with the FLASH in low-dose CT of pediatric paranasal sinus

Objective To evaluate the feasibility of dual-source low-dose computed tomography (CT) of the paranasal sinus in children, with acquisition at an ultra-low tube voltage (70 kVp) combined with the Flash scan. Methods CT scans of the paranasal sinus were performed on 80 pediatric patients who were divided into two groups according to different protocols (70 kVp protocol with Flash scan mode and the iterative reconstruction, pitch 3, the experimental group (group A), n = 40; 80 kVp protocol with conventional spiral mode, pitch 1.5, control group (group B), n = 40). For each examination, the CT dose index (CTDIvol), dose-length product (DLP) and effective dose (ED) were estimated. The image noise, signal-to-noise ratio (SNR) and overall subjective diagnostic image quality were also evaluated. Results The images of these two groups were all satisfied for the clinical diagnosis. For radiation dose, the CTDIvol (mGy), DLP (mGycm) and ED (mSv) values of the 70 kVp protocol were significantly lower than those of the 80 kVp protocol [CTDIvol: 0.39 ± 0.004 vs 1.57 ± 0.009 mGy, P < 0.001; DLP: 6.31 ± 0.52 vs 19.88 ± 2.01 mGycm, P < 0.001; ED: 0.024 ± 0.005 vs 0.079 ± 0.016 mSv, P < 0.001. Compared with those of the 80-kVp protocol, the image noise and the SNR bone increased, the SNR soft-tissue decreased. There was no statistical difference in the subjective scores of the two groups of image quality by the two physicians ( P > 0.05). Conclusion When diagnosing the paranasal sinus in children, an ultralow tube voltage (70 kVp) combined with the Flash scan technique can reduce the radiation dose significantly while maintaining diagnostic image quality with clinically acceptable image noise. 摘要: 目的 探讨双源CT超低管电压(70 kVp)联合FLASH的扫描技术在儿童鼻旁窦检查中的可行性。 方法 选 取80例临床怀疑鼻旁窦炎的患儿随机分成A、B两组, 实验组 (A组) 40 例: 管电压70 kVp, 螺距3.0,所得数据采用迭 代算法(SAFIRE)重建;对照组(B 组) 40例: 管电压80 kVp, 螺距1.5,所得数据采用滤波反投影算法(FBP)重建。分析 比较2组不同扫描方式的主、客观图像质量以及辐射剂量, 包括容积CT剂量指数(CTDIvol)、剂量长度乘积(DLP), 并计算有效辐射剂量(ED)。 结果 患者所受的辐射剂量, 实验组的CTDIvol (mGy)、DLP (mGycm)和ED (mSv)较 对照组显著降低 (CTDIvol: 0.39 ± 0.004 vs 1.57 ± 0.009 mGy, P < 0.001; DLP: 6.31 ± 0.52 vs 19.88 ± 2.01 mGycm, P < 0.001; ED: 0.024 ± 0.005 vs 0.079 ± 0.016 mSv, P < 0.001)。较对照组, 试验组的图像噪声及SNR硬组织均有所增加, SNR软组织则有所下降。2名医师对2组图像质量的主观评分无统计学差异 ( P > 0.05)。 结论 超低管电压 (70 kVp) 联 合FLASH扫描技术可明显降低儿童鼻旁窦CT扫描剂量, 且图像质量均满足诊断要求。

Radiation dose, contrast enhancement, image noise and heart rate variability of ECG-gated CT volumetry using 3D threshold-based segmentation: Comparison between conventional single scan and dual focused scan methods

ObjectiveTo compare radiation dose, contrast enhancement, image noise and heart rate variability in electrocardiography (ECG)-gated computed tomography (CT) ventricular volumetry using a three-dimensional (3D) threshold-based segmentation between the conventional single scan and dual focused scan methods in patients with congenital heart disease. MethodsAfter matching for age, sex, heart rate during the CT examination, and tube voltage, 96 patients (age range, 7 − 36 years; male:female = 63:33) who underwent ECG-gated CT volumetry using a 3D threshold-based segmentation, were divided into 32 patients who underwent a conventional single scan (group 1) and 64 who underwent dual focused scans (group 2). CT radiation dose, contrast enhancement, image noise, and heart rate variability were compared between the two groups. ResultsVolume CT dose index, dose-length product, and effective dose estimates, in group 1 were significantly higher than those in group 2 (28.4 ± 24.6 mGy vs. 9.7 ± 4.5 mGy, 636.5 ± 572.9 mGy cm vs. 379.5 ± 192.4 mGy cm, 8.9 ± 8.0 mSv vs. 5.3 ± 2.7 mSv, 8.2 ± 6.4 mSv vs. 5.0 ± 2.2 mSv, respectively; p values < 0.019). No significant differences in right and left ventricular contrast enhancement were found between the two groups (470.2 ± 152.4 HU vs. 481.0 ± 139.2 HU and 428.6 ± 97.8 HU vs. 429.3 ± 106.7 HU, respectively; p values > 0.05). Image noise measured in the air showed no significant differences between groups 1 and 2 (5.6 ± 1.9 HU vs. 5.5 ± 1.1 HU; p > 0.05). The proportion of heart rate variability ≥ 20 beats per minute in group 1 (15.6 %, 5/32) was significantly higher than that in group 2 (3.1 %, 2/64; p < 0.040). ConclusionCompared with the conventional single scan method, the dual focused scan method can provide a lower radiation dose with comparable contrast enhancement and image noise for ECG-gated CT ventricular volumetry using a 3D threshold-based segmentation in patients with congenital heart disease.

Development of CT Effective Dose Conversion Factors from Clinical CT Examinations in the Republic of Korea

The aim of this study was to determine the conversion factors for the effective dose (ED) per dose length product (DLP) for various computed tomography (CT) protocols based on the 2007 recommendations of the International Commission on Radiological Protection (ICRP). CT dose data from 369 CT scanners and 13,625 patients were collected through a nationwide survey. Data from 3793 patients with a difference in height within 5% of computational human phantoms were selected to calculate ED and DLP. The anatomical CT scan ranges for 11 scan protocols (adult-10, pediatric-1) were determined by experts, and scan lengths were obtained by matching scan ranges to computational phantoms. ED and DLP were calculated using the NCICT program. For each CT protocol, ED/DLP conversion factors were calculated from ED and DLP. Estimated ED conversion factors were 0.00172, 0.00751, 0.00858, 0.01843, 0.01103, 0.02532, 0.01794, 0.02811, 0.02815, 0.02175, 0.00626, 0.00458, 0.00308, and 0.00233 mSv∙mGy−1∙cm−1 for the adult brain, intra-cranial angiography, C-spine, L-spine, neck, chest, abdomen and pelvis, coronary angiography, calcium scoring, aortography, and CT examinations of pediatric brain of <2 years, 4–6 years, 9–11 years, and 13–15 years, respectively. We determined ED conversion factors for 11 CT protocols using CT data obtained from a nationwide survey in Korea and Monte Carlo-based dose calculations.

Low-dose CT of paediatric paranasal sinus using an ultra-low tube voltage (70 kVp) combined with the flash technique

To evaluate the radiation dose and diagnostic image quality of low-dose computed tomography (CT) of the paranasal sinus in children, with acquisition at an ultra-low tube voltage (70 kVp) combined with the Flash technique. Eighty paediatric patients underwent CT of the paranasal sinus and were divided into two groups according to different protocols (group A: 80 kVp protocol with conventional spiral mode [n=40] and group B: 70 kVp protocol with Flash scan mode [n=40]). For each examination, the CT dose index (CTDIvol), dose-length product (DLP), and effective dose (ED) were estimated. The image noise, signal-to-noise ratio (SNR), and overall subjective diagnostic image quality were also evaluated. For radiation dose, the CTDIvol (mGy), DLP (mGy·cm), and ED (mSv) values of the 70 kVp protocol were significantly lower than those of the 80 kVp protocol (CTDIvol: 1.57±0.009 versus 0.39±0.004 mGy, p<0.001; DLP: 19.88±2.01 versus 6.31±0.52 mGy·cm, p<0.001; ED: 0.079±0.016 versus 0.024±0.005 mSv, p<0.001). Compared with those of the 80-kVp protocol, the image noise increased by 40.7% (p=0.113), the SNRsoft-tissue decreased by 48.9%, and the SNRbone increased by 10.1% with the 70-kVp protocol (p=0.176 and 0.227, respectively). There was no significant difference in the overall subjective image quality grades between these two groups (p=0.15). When imaging the paranasal sinus in children, an ultra-low tube voltage (70 kVp) combined with the Flash CT technique can reduce the radiation dose significantly while maintaining diagnostic image quality with clinically acceptable image noise.

Dual-energy CT angiography-derived virtual non-contrast images for follow-up of patients with surgically clipped aneurysms: a retrospective study.

To evaluate the diagnostic performance, image quality, artifacts, and radiation doses of virtual non-contrast (VNC) images, relative to true non-contrast (TNC) images, in patients with surgically clipped aneurysms. Seventy-six patients who underwent unenhanced computed tomography (CT) and dual-energy (DE)-CT angiography after surgical clipping of 85 intracranial aneurysms were included in the study. Diagnostic performances of VNC and TNC images were compared with respect to sensitivity, specificity, and positive and negative predictive values. The results of quantitative and qualitative analyses were compared between VNC and TNC images. Radiation doses were also compared between VNC and TNC images. Diagnostic performance of VNC images was lower than that of TNC images; however, addition of contrast-enhanced images improved diagnostic performance. Image noise and mean attenuation of VNC images were significantly higher than those of TNC images in the centrum semiovale, cerebellum, and pons. The quality of VNC images was excellent or sufficient (85.5% for observer 1, 85.5% for observer 2), and complete acceptance of VNC images was achieved in 64.5% for observer 1 and in 71.0% for observer 2; however, the addition of contrast-enhanced images increased the level of acceptance (92.0% for observer 1, 90.9% for observer 2). Clip artifacts were significantly lower in VNC images than in TNC images. CT dose index, dose-length product, and effective dose were significantly lower without TNC images. VNC images showed lower diagnostic performance and image quality, and higher image noise than TNC images; however, VNC images could reduce clip artifacts and radiation doses.

Minor Blunt Thoracic Trauma in the Emergency Department: Sensitivity and Specificity of Chest Ultralow-Dose Computed Tomography Compared With Conventional Radiography

To evaluate the diagnostic performance of chest ultralow-dose computed tomography (CT) compared with chest radiograph for minor blunt thoracic trauma. One hundred sixty patients with minor blunt thoracic trauma were evaluated first by chest radiograph and subsequently with a double-acquisition nonenhanced chest CT protocol: reference CT and ultralow-dose CT with iterative reconstruction. Two study radiologists independently assessed injuries with a structured report and subjective image quality and calculated certainty of diagnostic confidence level. Ultralow-dose CT had a sensitivity and specificity of 100% compared with reference CT in the detection of injuries (187 lesions) in 104 patients. Chest radiograph detected abnormalities in 82 patients (79% of the population), with lower sensitivity and specificity compared with ultralow-dose CT (P<.05). Despite an only fair interobserver agreement for ultralow-dose CT image quality (κ=0.26), the diagnostic confidence level was certain for 95.6% of patients (chest radiograph=79.3%). Ultralow-dose CT effective dose (0.203 mSv [SD 0.029 mSv]) was similar (P=.14) to that of chest radiograph (0.175 mSv [SD 0.155 mSv]) and significantly less (P<.001) than that of reference CT (1.193 mSv [SD 0.459 mSv]). Ultralow-dose CT with iterative reconstruction conveyed a radiation dose similar to that of chest radiograph and was more reliable than a radiographic study for minor blunt thoracic trauma assessment. Radiologists, regardless of experience with ultralow-dose CT, were more confident with chest ultralow-dose CT than chest radiograph.

Computed tomography portography of patients with cirrhosis with normal body mass index: Comparison between low-tube-voltage CT with low contrast agent dose and conventional CT.

This study is to investigate the computed tomography (CT) image quality of the low- tube-voltage protocol with low contrast agent dose.CT portography was performed in 118 cirrhosis patients with body mass index (BMI) less than 25 kg/m2 under 2 protocols: Protocol A, tube voltage of 90 kVp/395 mAs and contrast agent dosage of 1.2 mL/kg, and, Protocol B, tube voltage of 120 kVp/200 mAs and contrast agent dosage of 1.5 mL/kg.The number of patients in each protocol was 59. The CT value noise, signal-to-noise ratio (SNR), and contrast-to-noise ratio (CNR) in portal veins was comparatively analyzed between the 2 protocols. The subjective image quality was further assessed on 5-point scales. Radiation dose was also recorded and statistical analysis was performed.The CT value, CNR, and SNR of the images were higher at 90 kVp than those at 120 kVp (P < .05). There was no significant difference in image noise between the 2 protocols (P > .05). The CT dose index volume, dose-length product, and effective dose at 90 kVp were 18.2%, 16.0%, and 16.0% less than that at 120 kVp, respectively. There was no difference in image quality score between the 2 protocols (P > .05). The average amount of contrast agent was decreased by 17.8% when the 90 kVp protocol was used.CT portography at 90 kVp combined with low-dosage contrast agent leads to a significant reduction in radiation dose and improved SNR and CNR, without deterioration of image quality.

Combination of Adaptive Statistical Iterative Reconstruction-V and Lower Tube Voltage During Craniocervical Computed Tomographic Angiography Yields Better Image Quality with a Reduced Radiation Dose

To evaluate image quality and radiation exposure when using the adaptive statistical iterative reconstruction-V (ASIR-V) algorithm for reconstructing craniocervical computed tomographic angiography images acquired at 100 kVp. We randomly divided 121 patients into three groups: group A (conventional protocol), 120 kVp with filtered back projection; group B, 120 kVp with 50% ASIR-V; and group C, 100 kVp with 50% ASIR-V. All patients underwent scans in a 256-slice computed tomography (CT) scanner. Radiation dose (volume CT dose index), dose-length product, and effective dose, objective parameters such as arterial attenuation value, signal-to-noise ratio, contrast-to-noise ratio, and noise obtained at head, neck, and shoulder levels were compared among the groups. Subjective image quality was independently assessed by two radiologists, and interobserver reliability was assessed using kappa analysis. The radiation dose in group C was the lowest (p < 0.01) with a 40% reduction in volume CT dose index, dose-length product, and effective dose values compared to group A, and group C showed higher arterial attenuation than either group A or B (p < 0.01). Additionally, signal-to-noise ratio and contrast-to-noise ratio were higher and noise was lower in groups B and C than group A. Group C had better subjective image quality than groups A and B (p < 0.05), and the interobserver reliability between the two radiologists was high (k = 0.783). Compared to the conventional protocol, using 50% ASIR-V and the 100 kVp protocol during craniocervical computed tomographic angiography yields better objective and subjective image quality at lower radiation doses.

Optimal tube potential and tube current for radiation dose reduction in routine adult head computed tomography scanning

ABSTRACTWe proposed a new, optimised scanning parameter that can reduce the patient’s radiation dose while maintaining image quality in a head computed tomography (CT) scan. We evaluated the clinical CT scan parameters (tube voltage, tube current, slice thickness pitch, scan range, rotation time, and CT dose index) for brain CT examination in a total of 52 multi-detector row spiral CTs (SOMATOM Definition AS+, Siemens Healthcare, Germany). The data were analysed, and the range of valid scan parameters was determined clinically using quartile distribution within the 95% confidence interval. The American Association of Physicists in Medicine performance evaluation phantom was used to acquire images using these scan parameters, and new, optimised CT scan parameters were proposed by analysing CT number accuracy, noise, uniformity, spatial resolution, and contrast resolution. The new CT scan parameters proposed were determined as tube voltage 100 kVp and tube current 300 mAs. Compared with conventional clinical scan parameters, tube voltage was reduced by 16.7% and tube current was decreased by 33.3%. Loss in imaging accuracy and uniformity of CT number was less than 20%, loss in noise was less than 40%, and no change in resolution was observed. Conversely, the CT dose index and effective dose was 20%–50%. A new systematic method for clinically assessing the optimised CT scan parameters were proposed, and the effective dose was decreased, with changing exposure conditions.

Radiation dose metrics in multidetector computed tomography examinations: A multicentre retrospective study from seven tertiary care hospitals in Kerala, South India.

Background:Presently, computed tomography (CT) is the most important source of medical radiation exposure. CT radiation doses vary considerably across institutions depending on the protocol and make of equipment. India does not yet have national or region-specific CT diagnostic reference levels.Aim:To evaluate radiation doses of consecutive multidetector CT (MDCT) examinations based on anatomic region, performed in 1 month, collected simultaneously from seven tertiary care hospitals in Kerala.Settings and Design:Descriptive study.Materials and Methods:We collected the CT radiation dose data of examinations from the seven collaborating tertiary care hospitals in Kerala, performed with MDCT scanners of five different makes. The data included anatomic region, number of phases, CT dose index (CTDIvol), dose-length product (DLP), and effective dose (ED) of each examinations and patient demographic data.Statistical Analysis:We calculated the 25th, 50th, and 75th percentiles of the CTDIvol, DLP, and ED according to anatomic region. We made descriptive comparisons of these results with corresponding data from other countries.Results:Of 3553 patients, head was the most frequently performed examination (60%), followed by abdomen (19%). For single-phase head examinations, 75th percentile of CTDIvol was 68.1 mGy, DLP 1120 mGy-cm, and ED 2.1 mSv. The 75th percentiles of CTDIvol, DLP, and ED for single-phase abdomen examinations were 10.6, 509.3, and 7.7, and multiphase examinations were 14.6, 2666.9, and 40.8; single-phase chest examinations were 23.4, 916.7, and 13.38, and multiphase examinations were 19.9, 1737.6, and 25.36; single-phase neck were 24.9, 733.6, and 3.814, and multiphase neck were 24.9, 2076, and 10.79, respectively.Conclusion:This summary CT radiation dose data of most frequently performed anatomical regions could provide a starting point for institutional analysis of CT radiation doses, which in turn leads to meaningful optimization of CT.

Reduced Radiation in Children Presenting to the ED With Suspected Ventricular Shunt Complication.

Ventricular shunt complications in children can be severe and life-threatening if not identified and treated in a timely manner. Evaluation for shunt obstruction is not without risk, including lifetime cumulative radiation as patients routinely receive computed tomography (CT) scans of the brain and shunt series (multiple radiographs of the skull, neck, chest, and abdomen). A multidisciplinary team collaborated to develop a clinical pathway with the goal of standardizing the evaluation and management of patients with suspected shunt complication. The team implemented a low-dose CT scan, specifically tailored for the detection of hydrocephalus and discouraged routine use of shunt series with single-view radiographs used only when specifically indicated. There was a reduction in the average CT effective dose (millisievert) per emergency department (ED) encounter of 50.6% (confidence interval, 46.0-54.9; P ≤ .001) during the intervention period. There was a significant reduction in the number of shunt surveys obtained per ED encounter, from 62.4% to 5.32% (P < .01). There was no significant change in the 72-hour ED revisit rate or CT scan utilization rate after hospital admission. There were no reports of inadequate patient evaluations or serious medical events. A new clinical pathway has rapidly reduced radiation exposure, both by reducing the radiation dose of CT scans and eliminating or reducing the number of radiographs obtained in the evaluation of patients with ventricular shunts without compromising clinical care.