Computed Tomography Scanning Protocols Research Articles

Lifetime Attributable Breast Cancer Risk Related to Lung CT Scan in Women with Covid19

Abstract
 Purpose: Organ, effective dose, and Lifetime Attributable Risk (LAR) of breast cancer incidence related to lung Computed Tomography (CT) scans were evaluated. Seven hundred thirty-five female patients (20-50 years old) with Coronavirus (COVID-19) in four medical imaging centers in Tehran, Iran, were surveyed. Patients’ data, including age, sex, and exposure information (Kilovoltage (KVp), milliampere-second (mAs), pitch factor, Computed Tomography Dose Index (CTDIvol), and Dose Length Product (DLP)) were extracted from dose report pages in picture archiving and communication systems (PACS).
 Materials and Methods: Patients were divided into six age groups of 20-25, 25-30, 30-35, 35–40, 40-45, and 45–50 years. Breast, thyroid, lung, and heart absorbed doses, and also effective doses, were calculated by National Cancer Institute (NCICT) software, and LAR of breast cancer incidence has been evaluated by the Biological Effect of Ionizing Radiation (BEIR) VII in phase 2 report.
 Results: The average doses of breast, thyroid, lung, the heart were 3.97, 4.75, 4.10, and 3.37 mGy, respectively. Also, the average effective dose was 2.56 mSv. The average LAR of breast cancer in female patients was 7.45 per 100,000 exposures, decreasing dramatically with age. It was clear that exposure parameters and organ absorbed dose were significantly different between medical imaging centers (P value<0.05).
 Conclusion: Although the CT scan is a useful instrument in the diagnosis of Corona disease, it should be suggested with caution due to the increased risk of breast cancer, especially in younger women and pediatrics. Also, low-dose CT scan protocols are recommended to minimize radiation effective and absorbed doses.

CT number calibration audit in photon radiation therapy.

Inadequate computed tomography (CT) number calibration curves affect dose calculation accuracy. Although CT number calibration curves registered in treatment planning systems (TPSs) should be consistent with human tissues, it is unclear whether adequate CT number calibration is performed because CT number calibration curves have not been assessed for various types of CT number calibration phantoms and TPSs. The purpose of this study was to investigate CT number calibration curves for mass density (ρ) and relative electron density (ρe ). A CT number calibration audit phantom was sent to 24 Japanese photon therapy institutes from the evaluating institute and scanned using their individual clinical CT scan protocols. The CT images of the audit phantom and institute-specific CT number calibration curves were submitted to the evaluating institute for analyzing the calibration curves registered in the TPSs at the participating institutes. The institute-specific CT number calibration curves were created using commercial phantom (Gammex, Gammex Inc., Middleton, WI, USA) or CIRS phantom (Computerized Imaging Reference Systems, Inc., Norfolk, VA, USA)). At the evaluating institute, theoretical CT number calibration curves were created using a stoichiometric CT number calibration method based on the CT image, and the institute-specific CT number calibration curves were compared with the theoretical calibration curve. Differences in ρ and ρe over the multiple points on the curve (Δρm and Δρe,m , respectively) were calculated for each CT number, categorized for each phantom vendor and TPS, and evaluated for three tissue types: lung, soft tissues, and bones. In particular, the CT-ρ calibration curves for Tomotherapy TPSs (ACCURAY, Sunnyvale, CA, USA) were categorized separately from the Gammex CT-ρ calibration curves because the available tissue-equivalent materials (TEMs) were limited by the manufacturer recommendations. In addition, the differences in ρ and ρe for the specific TEMs (ΔρTEM and Δρe,TEM , respectively) were calculated by subtracting the ρ or ρe of the TEMs from the theoretical CT-ρ or CT-ρe calibration curve. The mean±standard deviation (SD) of Δρm and Δρe,m for the Gammex phantom were -1.1±1.2g/cm3 and -0.2±1.1, -0.3±0.9g/cm3 and 0.8±1.3, and -0.9±1.3g/cm3 and 1.0±1.5 for lung, soft tissues, and bones, respectively. The mean±SD of Δρm and Δρe,m for the CIRS phantom were 0.3±0.8g/cm3 and 0.9±0.9, 0.6±0.6g/cm3 and 1.4±0.8, and 0.2±0.5g/cm3 and 1.6±0.5 for lung, soft tissues, and bones, respectively. The mean±SD of Δρm for Tomotherapy TPSs was 2.1±1.4g/cm3 for soft tissues, which is larger than those for other TPSs. The mean±SD of Δρe,TEM for the Gammex brain phantom (BRN-SR2) was -1.8±0.4, implying that the tissue equivalency of the BRN-SR2 plug was slightly inferior to that of other plugs. Latent deviations between human tissues and TEMs were found by comparing the CT number calibration curves of the various institutes.

Evaluation of organ and effective doses using anthropomorphic phantom: A comparison between experimental measurement and a commercial dose calculator

IntroductionThe aim of this study was to experimentally measure organ doses for computed tomography (CT) procedures using thermoluminescence dosimeters (TLDs) on a RANDO anthropomorphic phantom and verify the measured doses using CT-Expo software. MethodsThe phantom was irradiated using clinical CT scan protocols routinely used for specific procedures in the radiology department. Fifty TLD chips were used in this study. The scanning parameters (kVp, mA, s) used to scan the phantom were used as input parameters for CT-Expo dose estimations. ResultsThe TLD measured organ doses varied between 3.97 mGy for the esophagus and 56.22 mGy for the brain. High doses were recorded in the brain (37.80–56.22 mGy) and the eye lens (29.94–36.16 mGy). Comparing the organ dose measurements between TLD and CT-Expo, the maximum organ dose difference was obtained for the eye lens. A comparison between the two methods for the other organs were all less than 32 %. The effective doses from the TLD measurements for the head, chest, and abdominopelvic CT examinations were 2.78, 6.67, and 17 mSv, respectively and CT-Expo were 2.20, 10.30, and 16.70 mSv, respectively. ConclusionThe experimental and computational results are comparable, and the reliability of the TLD measurements and CT-Expo dose calculator has been proven. Implications for studyA reason for the difference in dose measurements between the two methods has been attributed to the dissimilarity in the organ position in the Rando anthropomorphic phantom and the standard mathematical phantom used by CT-Expo. The experimental and computational results have been found to be comparable.

A Kinematic Analysis of Wrist and Carpal Function Using Four-Dimensional Computed Tomography Technology: A Dynamic Perspective

An emerging imaging modality, four-dimensional computed tomography, can provide dynamic evaluation of carpal motion, which allows for a better understanding of how the carpals work together to achieve range of motion. The objective of this work was to examine kinematic motion of the carpus through a flexion/extension arc of motion using four-dimensional computed tomography. A convenience sample of 20 uninjured participants underwent a four-dimensional computed tomography scanning protocol through a complete arc of flexion/extension motion. Kinematic changes in motion were quantified using helical axes motion data for each carpal. Rotation angles were compared between bones to identify differences in kinematic motion between bones. The bones within the proximal carpal row, the lunate, scaphoid, and triquetrum, rotate significantly to differing magnitudes at the ends of motion (40° of flexion and 40° of extension). The scaphoid rotates to the highest magnitude, followed by the triquetrum, and lastly, the lunate. The distal carpal row bones rotate to similar magnitudes throughout the entire range of motion. This work describes the kinematics of the carpals throughout dynamic invivo flexion and extension. This study adds to an understanding of wrist mechanics and the possible clinical implications of pathological deviation from baseline kinematics.

Technical comparison of continuous versus intermittent perfusion computed tomography computed tomography scans of the human pancreas.

Pancreatic perfusion computed tomography (CT) imaging is increasingly used for neoplastic grading, predicting prognosis, and evaluating the response to therapy. To optimize the clinical pancreatic CT perfusion imaging methods, we evaluated 2 different CT scanning protocols concerning pancreas perfusion parameters. A retrospective study was conducted on 40 patients who underwent whole pancreas CT perfusion scanning in The First Affiliated Hospital of Zhengzhou University. Of these 40 patients, 20 patients in group A underwent continuous perfusion scanning, while 20 patients in group B underwent intermittent perfusion scanning. For group A, continuous axial scanning was performed 25 times, and the total scan time was 50 s. For group B, arterial phase helical perfusion scanning was performed 8 times, and then venous phase helical perfusion scanning was performed 15 times, with a total scan time of 64.6 to 70.0 s. A comprehensive list of perfusion parameters between different parts of the pancreas and the 2 groups were compared. The effective radiation dose for the 2 scanning methods was analyzed. The parameter of the mean slope of increase (MSI) at different pancreatic parts in group A differed (P=0.028). The pancreas head had the lowest value, and the tail had the highest (about a 20% difference). In group A compared to group B, the blood volume of the pancreatic head was smaller (15.256±2.925 vs. 16.953±3.602), the positive enhanced integral was smaller (0.307±0.050 vs. 0.344±0.060) and the permeability surface was larger (34.205±9. 612 vs. 24.377±8.413); the blood volume of the pancreatic neck was smaller (13.940±2.691 vs. 17.173±3.918), the positive enhanced integral was smaller (0.304±0.088 vs. 0.361±0.051) and the permeability surface was larger (34.898±11.592 vs. 25. 794±8.149); the blood volume of the pancreatic body was smaller (16.142±4.006 vs. 18.401±2.513), the positive enhanced integral was smaller (0.305±0.093 vs. 0.342±0.048) and the permeability surface was larger (28.861±10.448 vs. 22.158±6. 017); the blood volume of the pancreatic tail was smaller (16.446±3.709 vs. 17.374±3.781), the positive enhanced integral was smaller (0.304±0.057 vs. 0.350±0.073) and the permeability surface was larger (27.823±8.228 vs. 21.509±7.768) (P<0.05). The effective radiation dose in the intermittent scan mode was slightly lower at 16.657±2.259 mSv than in the continuous scan mode (17.973±3.698 mSv). Different CT scanning intervals had a significant influence on whole pancreas blood volume, permeability surface, and positive enhanced integral. These demonstrate the high sensitivity of intermittent perfusion scanning for identifying perfusion abnormalities. Therefore, for the diagnosis of pancreatic diseases, intermittent pancreatic CT perfusion may be more advantageous.

Combining the advantages of 3-D and 2-D templating of total hip arthroplasty using a new tin-filtered ultra-low-dose CT of the hip with comparable radiation dose to conventional radiographs

BackgroundInaccurately scaled radiographs for total hip arthroplasty (THA) templating are a source of error not recognizable to the surgeon and may lead to inaccurate reconstruction and thus revision surgery or litigation. Planning based on computed tomography (CT) scans is more accurate but associated with higher radiation exposure. The aim of this study was (1) to retrospectively assess the scaling deviation of pelvic radiographs; (2) to prospectively assess the feasibility and the radiation dose of THA templating on radiograph-like images reconstructed from a tin-filtered ultra-low-dose CT dataset.Methods120 consecutive patients were retrospectively analyzed to assess the magnification error of our current THA templates. 27 consecutive patients were prospectively enrolled and a radiographic work-up in the supine position including a new tin-filtered ultra-low-dose CT scan protocol was obtained. THA was templated on both images. Radiation dose was calculated.ResultsScaling deviations between preoperative radiographs and CT of ≥ 5% were seen in 25% of the 120 retrospectively analyzed patients. Between the two templates trochanter tip distance differed significantly (Δ2.4 mm, 0–7 mm, p = 0.035)), predicted femoral shaft size/cup size was the same in 45%/41%. The radiation dose of the CT (0.58 mSv, range 0.53–0.64) was remarkably low.ConclusionScaling deviations of pelvic radiographs for templating THA may lead to planning errors of ≥ 3 mm in 25% and ≥ 6 mm in 2% of the patients. 2-D templating on radiograph-like images based on tin-filtered ultra-low-dose CT eliminates this source of error without increased radiation dose.Level of evidenceRetrospective and prospective comparative study, Level III.

Noise Characteristics Modeled Unsupervised Network for Robust CT Image Reconstruction.

Deep learning (DL)-based methods show great potential in computed tomography (CT) imaging field. The DL-based reconstruction methods are usually evaluated on the training and testing datasets which are obtained from the same distribution, i.e., the same CT scan protocol (i.e., the region setting, kVp, mAs, etc.). In this work, we focus on analyzing the robustness of the DL-based methods against protocol-specific distribution shifts (i.e., the training and testing datasets are from different region settings, different kVp settings, or different mAs settings, respectively). The results show that the DL-based reconstruction methods are sensitive to the protocol-specific perturbations which can be attributed to the noise distribution shift between the training and testing datasets. Based on these findings, we presented a low-dose CT reconstruction method using an unsupervised strategy with the consideration of noise distribution to address the issue of protocol-specific perturbations. Specifically, unpaired sinogram data is enrolled into the network training, which represents unique information for specific imaging protocol, and a Gaussian mixture model (GMM) is introduced to characterize the noise distribution in CT images. It can be termed as GMM based unsupervised CT reconstruction network (GMM-unNet) method. Moreover, an expectation-maximization algorithm is designed to optimize the presented GMM-unNet method. Extensive experiments are performed on three datasets from different scan protocols, which demonstrate that the presented GMM-unNet method outperforms the competing methods both qualitatively and quantitatively.

Low-Dose Computed Tomography Scanning Protocols for Online Adaptive Proton Therapy of Head-and-Neck Cancers.

Simple SummaryAdaptive proton therapy requires taking images over the course of treatment to correct the plan for anatomy changes. Most workflows assume daily imaging for this purpose. The associated imaging doses can be significant, which may compromise one of the proton therapy aims: minimizing the dose to healthy tissue. Low-dose scanning protocols address this problem. In this paper, we evaluate the influence of low-dose CT protocols on adaptation. We used a head phantom to define the protocols and simulated adaptive treatments of 10 head-and-neck patients with our established adaptation framework. We assessed the influence of lower image quality on the contour propagation and dose calculation. We demonstrated that decreasing the imaging dose by a factor of 40 with respect to our standard CT scanning protocol does not affect the adaptation performance.Purpose: To evaluate the suitability of low-dose CT protocols for online plan adaptation of head-and-neck patients. Methods: We acquired CT scans of a head phantom with protocols corresponding to CT dose index volume CTDIvol in the range of 4.2–165.9 mGy. The highest value corresponds to the standard protocol used for CT simulations of 10 head-and-neck patients included in the study. The minimum value corresponds to the lowest achievable tube current of the GE Discovery RT scanner used for the study. For each patient and each low-dose protocol, the noise relative to the standard protocol, derived from phantom images, was applied to a virtual CT (vCT). The vCT was obtained from a daily CBCT scan corresponding to the fraction with the largest anatomical changes. We ran an established adaptive workflow twice for each low-dose protocol using a high-quality daily vCT and the corresponding low-dose synthetic vCT. For a relative comparison of the adaptation efficacy, two adapted plans were recalculated in the high-quality vCT and evaluated with the contours obtained through deformable registration of the planning CT. We also evaluated the accuracy of dose calculation in low-dose CT volumes using the standard CT protocol as reference. Results: The maximum differences in D98 between low-dose protocols and the standard protocol for the high-risk and low-risk CTV were found to be 0.6% and 0.3%, respectively. The difference in OAR sparing was up to 3%. The Dice similarity coefficient between propagated contours obtained with low-dose and standard protocols was above 0.982. The mean 2%/2 mm gamma pass rate for the lowest-dose image, using the standard protocol as reference, was found to be 99.99%. Conclusion: The differences between low-dose protocols and the standard scanning protocol were marginal. Thus, low-dose CT protocols are suitable for online adaptive proton therapy of head-and-neck cancers. As such, considering scanning protocols used in our clinic, the imaging dose associated with online adaption of head-and-neck cancers treated with protons can be reduced by a factor of 40.

Dual-energy CT scan protocol optimization to monitor transient fluid saturation distributions during three-phase flow in sand columns

Surfactant foam injection is a promising in situ remediation technique for aquifers impacted by Non-Aqueous Phase Liquids (NAPL). Though the viscous properties of foam can promote immiscible displacement, pore plugging by foam is a concern in an environmental remediation (ER) context, as maintaining flow conditions may require the application of pressures that exceed soil matrix failure thresholds. Optimization of the technology for ER may be furthered by gaining a better understanding of the relationship between foam morphology and NAPL desaturation. This relationship is poorly understood, partly because the interactions between organic phases and foam occurring at specific positions within the flow field at any given time are difficult to assess quantitatively. A Dual-energy X-ray Computed Tomography (CT) technique was developed to enable the measurement of sand column characteristics, as well as transient fluid saturation profiles within the porous medium during foam injection. The available settings of a medical CT scanner were systematically explored in order to identify the acquisition and reconstruction parameters best suited to image the fluids of interest: 0.4 mm slice thickness, a medium kernel (U40u), peak tube voltages of 140 kVp and 80 kVp, and the addition of a doping agent to the NAPL at a concentration of 20 wt%. Using datasets produced by imaging sand columns at various stages of foam injection experiments, an algorithm was developed in order to extract saturation profiles from CT images. The algorithm included multiple scan averaging to reduce image noise, image registration, and specific matrix operations required for calculating fluid saturation values in two- and three-phase systems. The accuracies of the CT-extracted porosity and fluid saturation data were compared to, and found to be in good agreement with, experimentally determined average porosity and saturation values. The scan parameter optimization method developed here can be applied to future studies involving any combination of site-specific natural materials.

Pragmatic Approaches to Reducing Radiation Dose in Brain Computed Tomography Scan using Scan Parameter Modification.

Background:High radiation dose of patients has become a concern in the computed tomography (CT) examinations. The aim of this study is to guide the radiology technician in modifying or optimizing the underlying parameters of the CT scan to reduce the patient radiation dose and produce an acceptable image quality for diagnosis.Methods:The body mass measurement device phantom was repeatedly scanned by changing the scan parameters. To analyze the image quality, software-based and observer-based evaluations were employed. To study the effect of scan parameters such as slice thickness and reconstruction filter on image quality and radiation dose, the structural equation modeling was used.Results:By changing the reconstruction filter from standard to soft and slice thickness from 2.5 mm to 5 mm, low-contrast resolution did not change significantly. In addition, by increasing the slice thickness and changing the reconstruction filter, the spatial resolution at different radiation conditions did not significantly differ from the standard irradiation conditions (P > 0.05).Conclusion:In this study, it was shown that in the brain CT scan imaging, the radiation dose was reduced by 30%–50% by increasing the slice thickness or changing the reconstruction filter. It is necessary to adjust the CT scan protocols according to clinical requirements or the special conditions of some patients while maintaining acceptable image quality.

Poor practice and governance in Lebanese national diagnostic reference levels of adult head and body computed tomography: A nationwide study

Lebanon has one of the highest number of computed tomography (CT) scanners per capita in the world which could likely be one of the causative factors of its high cancer incidence. In this study, we aimed to establish a national diagnostic reference level (NDRL) in adult CT examinations of the head and body in Lebanon. Dose Length Product (DLP) (n = 2730) were recorded in 91 hospitals/centers in Lebanon for head, chest, and abdomen-pelvis CT. Data was obtained from adult patients (≥18 years) with a weight range of 75–80 kg, from January 2018 until December 2019. Then, the median, mean and 75th percentile of the DLP was calculated for each anatomical region. NDRL was reported as the 75th percentile. Then, the established NDRL was benchmarked with international countries as the USA, UK, and Australia. In our study, data were collected from imaging departments (n = 91), with a response rate of 65% of the national total. All CT scanners ranged from 1 to 256 slices. The 75th percentile for the DLP of the head, chest, and abdomen-pelvis CT scan in Lebanon was 1426, 646, and 967 mGy cm respectively. A significant difference in mean DLP of the chest and abdomen-pelvis CT in different governorates was noted with north Lebanon having the highest levels (604 and 882 mGy cm respectively) (p < 0.05). When benchmarked with 18 different countries, Lebanon ranked 2nd, 3rd, and 4th highest in 75th percentile DLP for head, chest, and abdomen-pelvis CT scans respectively. In conclusion, the established Lebanese NDRL for adult routine CT scans of head, chest, and abdomen-pelvis were significantly higher than the reported international radiation dose thresholds. This demonstrates a great scope for radiation dose reduction and the need for urgent intervention of DRL to optimize CT scanning procedures and protocols in Lebanon.

Multi-Length Scale X-Ray CT and Thermal Analysis for Battery Safety Assessment

Lithium-ion battery failure occurs across multiple length and time scales. This work presents the properties of thermal and mechanical failure in batteries of cylindrical, pouch and coin cell format by using a combination of Accelerating Rate Calorimetry (ARC) and X-ray Computed Tomography (CT) at various length scales; from whole cell (macro) to bulk electrode (micro) to particle (nano).Typical features of a thermal runaway (TR) sequence in a commercial 18650 cell, such as the onset temperature of TR, the order of and rate of heat generation from cell component breakdown, such as SEI layer deformation, are shown using a heat-wait-search protocol in an ARC. Alongside this, pre- and post-mortem X-ray CT images reveal the effects of thermal failure on the bulk electrode structure within the cell, such as deformations due to gas formation and release. Electrode material characteristics, such as porosity, particle size distribution, tortuosity, and particle cracking, are also quantified and compared before and after cell failure in the bulk electrode (micro–X-ray CT) and individual particles (nano-X-ray CT)[1].A novel X-ray CT scanning protocol is also demonstrated for characterising bespoke pouch cells (single and multi-layer) with sufficient resolution to reconcile electrode morphology, for example to evaluate the morphology changes during thermal abuse by nail penetration.Furthermore, this work investigates the sequence of reactions leading up to thermal runaway using a novel coin cell Differential Scanning Calorimeter (DSC). Heat flux signals are used to quantify the contribution of various exothermic and endothermic reactions to the overall heat generated by a cell as it undergoes failure. Some key features of early-stage TR reactions, such as the decomposition of the SEI layer are revealed for NMC111, NMC622 and NMC811. Some of the typical thermal characteristics of cells as they undergo ‘normal’ charge and discharge are also shown and compared to abnormal operating conditions such as, temperatures up to 60 °C, high C-rates, and cycle numbers.[1] D. Patel, J. B. Robinson, S. Ball, D. J. L. Brett, and P. R. Shearing, J. Electrochem. Soc., 167, 090511 (2020). Figure 1

What is the Orbital Volume of African-Americans?

PurposeMeasurements of orbital volume (OV) are important for reconstructive operations of orbits such as congenital deformities, trauma, and pathology. Successful orbital reconstruction relies on an accurate restoration of OV. The purpose of this study was to identify the OV in the African-American (AA) population. The specific aims were to compare OV of AAs to Caucasians and right-to-left OV in the same racial group. This is the first project in available literature that calculates these OVs. Materials and methodsThe authors implemented a retrospective observational study of successive subjects who received a maxillofacial computed tomography (CT) scan at Grady Memorial Hospital between 2017 and 2020. The primary predictor variable was race. The primary outcome was orbital volume. Two independent examiners calculated OV with an open access OsiriX MD software (version 10.0.5; Pixmeo, Switzerland). All CT scans were acquired using a departmental-based max-face CT scan protocol; 0.6mm slice thickness, 0.5mm slice increment, 100-120kV, 80-440mA, 200-220 FOV, 0.656 Pitch, and a 512 × 512 image matrix. All CT scan data sets were anonymized. The CT images was exported in the digital imaging and communication in medicine (DICOM) format file from Philips Intellispace PACS Enterprise 4.4 software to an external hard drive WD My Passport for Mac. Computer-assisted manual segmentation of OV was performed using an open-access OsiriX MD (software version 10.0.5 [Pixmeo, Switzerland]). The anterior and posterior boundary of the orbit was defined by posterior lacrimal crest and anterior aspect of the optic canal, respectively. Inter-rater reliability was calculated. Differences in means between races, genders, and sides were tested using an independent samples T-test. ResultsSixty subjects (120 orbits) with an average age of 36.7 years (range 22 to 78) met the inclusion criteria. Male-to-female ratio was 1:1. Racial distribution represented 30 AA (50%) and 30 Caucasian patients (50%). Inter-examiner reliability was 0.973. The mean OV of AA and Caucasians was 22.375 cm3 and 23.225 cm3, respectively (P = .07). The mean OV in AA and Caucasian males was 23.919 cm3 and 24.168 cm3, respectively (P = .71). The mean OV in AA and Caucasian females was 20.832 cm3 and 22.282cm3, respectively (P = .013). Gender analysis revealed that AA males had a statistically significant larger OV than AA females (P = <.0001). ConclusionIn conclusion, this study showed that the mean OV for AAs was 22.38 cm3 (male 23.919 cm3; female 20.832 cm3). Caucasian males and females had a larger OV than AA males and females. Caucasian and AA males had a larger OV than Caucasian and AA females. The study findings provide normative values for race and gender between AA and Caucasians. Understanding the average value for OV based on race and gender will assist in preoperative surgical planning of orbital trauma repair and therefore will improve surgical outcome.

Radiation dose levels in chest computed tomography scans of coronavirus disease 2019 pneumonia: A survey of 2119 patients in Chongqing, southwest China.

To investigate computed tomography (CT) diagnostic reference levels for coronavirus disease 2019 (COVID-19) pneumonia by collecting radiation exposure parameters of the most performed chest CT examinations and emphasize the necessity of low-dose CT in COVID-19 and its significance in radioprotection.The survey collected RIS data from 2119 chest CT examinations for 550 COVID-19 patients performed in 92 hospitals from January 23, 2020 to May 1, 2020. Dose data such as volume computed tomography dose index, dose-length product, and effective dose (ED) were recorded and analyzed. The radiation dose levels in different hospitals have been compared, and average ED and cumulative ED have been studied.The median dose-length product, volume computed tomography dose index, and ED measurements were 325.2 mGy cm with a range of 6.79 to 1098 mGy cm, 9.68 mGy with a range of 0.62 to 33.80 mGy, and 4.55 mSv with a range of 0.11 to 15.37 mSv for COVID-19 CT scanning protocols in Chongqing, China. The distribution of all observed EDs of radiation received by per patient undergoing CT protocols during hospitalization yielded a median cumulative ED of 17.34 mSv (range, 2.05–53.39 mSv) in the detection and management of COVID-19 patients. The average number of CT scan times for each patient was 4.0 ± 2.0, and the average time interval between 2 CT scans was 7.0 ± 5.0 days. The average cumulative ED of chest CT examinations for COVID-19 patients in Chongqing, China greatly exceeded public limit and the annual dose limit of occupational exposure in a short period.For patients with known or suspected COVID-19, a chest CT should be performed on the principle of rapid-scan, low-dose, single-phase protocol instead of routine chest CT protocol to minimize radiation doses and motion artifacts.

Quality control of radiomic features using 3D-printed CT phantoms.

.Purpose: The lack of standardization in quantitative radiomic measures of tumors seen on computed tomography (CT) scans is generally recognized as an unresolved issue. To develop reliable clinical applications, radiomics must be robust across different CT scan modes, protocols, software, and systems. We demonstrate how custom-designed phantoms, imprinted with human-derived patterns, can provide a straightforward approach to validating longitudinally stable radiomic signature values in a clinical setting.Approach: Described herein is a prototype process to design an anatomically informed 3D-printed radiomic phantom. We used a multimaterial, ultra-high-resolution 3D printer with voxel printing capabilities. Multiple tissue regions of interest (ROIs), from four pancreas tumors, one lung tumor, and a liver background, were extracted from digital imaging and communication in medicine (DICOM) CT exam files and were merged together to develop a multipurpose, circular radiomic phantom (18 cm diameter and 4 cm width). The phantom was scanned 30 times using standard clinical CT protocols to test repeatability. Features that have been found to be prognostic for various diseases were then investigated for their repeatability and reproducibility across different CT scan modes.Results: The structural similarity index between the segment used from the patients’ DICOM image and the phantom CT scan was 0.71. The coefficient variation for all assessed radiomic features was across 30 repeat scans of the phantom. The percent deviation (pDV) from the baseline value, which was the mean feature value determined from repeat scans, increased with the application of the lung convolution kernel, changes to the voxel size, and increases in the image noise. Gray level co-occurrence features, contrast, dissimilarity, and entropy were particularly affected by different scan modes, presenting with .Conclusions: Previously discovered prognostic and popular radiomic features are variable in practice and need to be interpreted with caution or excluded from clinical implementation. Voxel-based 3D printing can reproduce tissue morphology seen on CT exams. We believe that this is a flexible, yet practical, way to design custom phantoms to validate and compare radiomic metrics longitudinally, over time, and across systems.

Bismuth breast-shield use in chest computed tomography for efficient dose reduction and sufficient image quality.

Background:Radiosensitivity in the breasts increases the risk of carcinogenesis from exposure to the ionizing radiation of computed tomography (CT) administered in the course of medical attention. Bismuth shielding techniques have been used to reduce radiation, but image noise increased, degrading image quality.Purpose:The aim of this study was to investigate how the use of iterative reconstruction (IR) combined with bismuth shielding influences image quality.Materials and Methods:Women aged at least 20 years with body mass indexes <28 were recruited and randomly assigned to 1 of 3 CT scanning protocols without shielding, with a bismuth breast shield before the scout view, or with a bismuth breast shield after the scout view. All obtained images were reconstructed using an IR algorithm. To evaluate radiation dose, 2 Gafchromic films were placed over the clothes, 1 near each nipple.Results:Average dose reduction was significant (27.99%, P < .05) when bismuth shielding was applied after the scout view. Using the contrast-to-noise ratio, the image quality was found to be superior when the IR algorithm was applied. Using quantitative evaluations by 2 radiologists applying a 4-point Likert scale, significant differences in image quality were not found among the 3 protocols.Conclusion:Bismuth breast shields, particularly when used after acquiring scout images, are effective at reducing radiation dose without undermining the diagnostic value of the images when the IR technique is applied.

Conservative management of grade 4 and 5 renal injuries: A high-volume trauma center experience.

Traumatic renal injuries represent a major public health issue concerning mostly young men. Over the last decades there is growing debate regarding the management of high-grade renal injuries due to the emerging role of conservative treatment. The aim of this study is to present our experience in the conservative management of patients presenting with grade 4 or grade 5 renal injuries in our department. In this retrospective, single center study we evaluated data from a total of 57 hemodynamically stable patients who were managed conservatively for grade 4 or grade 5 renal injuries from 2015 to 2019 in our high-volume trauma center. Grading was based on contrast enhanced abdominal computed tomography (CT) scans. Patients managed with immediate nephrectomy due to hemodynamic instability and patients who underwent immediate laparotomy due to concomitant injuries or penetrating wounds were excluded from the study. A total of 54 patients diagnosed either with grade 4 or grade 5 renal trauma were finally successfully managed conservatively and included in the study. Median age was 34 years. Most patients presented with grade 4 renal trauma while five patients presented with grade 5 renal injury. Concomitant injuries not requiring surgical intervention were present in 48 patients. Continuous renal bleeding was detected in 15 patients (27.8%) and subsequent arterial embolization was performed with no further intervention required. Urine leak was diagnosed in 12 patients treated either by double j stent or by nephrostomy tube. Grade 4 and selected cases of grade 5 renal trauma can be treated conservatively with close monitoring and CT scan protocols in hemodynamic stable patients. In cases of continuous bleeding, arterial embolization can be performed. In cases of severe urine leak conservative management is also feasible either by inserting a double j stent or a nephrostomy tube.

Mixed reality models based on low-dose computed tomography technology in nephron-sparing surgery are better than models based on normal-dose computed tomography.

Nephron-sparing surgery has been widely applied in the treatment of renal tumors. Previous studies have confirmed the advantages of mixed reality technology in surgery. The study aimed to explore the optimization of mixed reality technology and its application value in nephron-sparing surgery. In this prospective study of 150 patients with complex renal tumors (RENAL nephrometry score ≥7) who underwent nephron-sparing surgery, patients were randomly divided into Group A (the normal-dose mixed reality group, n=50), Group B (the low-dose mixed reality group, n=50), and Group C (the traditional computed tomography image group, n=50). Group A and Group C received the normal-dose computed tomography scan protocol: 120 kVp, 400 mA, and 350 mgI/mL, while Group B received the low-dose computed tomography scan protocol: 80 kVp, automatic tube current modulation, and 320 mgI/mL. All computed tomography data were transmitted to a three-dimensional visualization workstation and underwent modeling and mixed reality imaging. Two senior surgeons evaluated mixed reality quality. Objective indexes and perioperative indexes were calculated and compared. Compared with Group A, the radiation effective dose in Group B was decreased by 39.6%. The subjective scores of mixed reality quality in Group B were significantly higher than those of Group A (Z=-4.186, P<0.001). The inter-observer agreement between the two senior surgeons in mixed reality quality was excellent (K=0.840, P<0.001). The perioperative indexes showed that the mixed reality groups were significantly different from the computed tomography image group (all P<0.017). More cases underwent nephron-sparing surgery in the mixed reality groups than in the computed tomography image group (P<0.0017). Low-dose computed tomography technology can be effectively applied to mixed reality optimization, reducing the effective dose and improving mixed reality quality. Optimized mixed reality can significantly increase the cases of successful nephron-sparing surgery and improve perioperative indexes.

A new phantom developed to test the ATCM performance of chest CT scanners

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.

Evaluation of Volume CT Dose Index (CTDIvol) and Dose Length Product (DLP) in Routine CT scan Protocols among Children under 15 Years of Age Admitted to Imam Khomeini Hospital in Ahvaz, Iran, during 2019

Background The computed tomography (CT) scan is a valuable tool in the diagnosis of various diseases, but the absorbed dose causes concern, especially for children. The present study aimed to evaluate the absorbed dose of volume CT dose index (CTDIvol) and dose length product (DLP) in routine CT scan protocols in children under 15 years of age admitted to Imam Khomeini Hospital of Ahvaz, Iran. Materials and Methods The present descriptive-analytical epidemiological study was carried out on children under 15 years of age admitted to Imam Khomeini Hospital of Ahvaz during the first 6 months of 2019. CTDIvol and DLP values ​​were measured using a pencil ionization chamber. Universal dosimeter fire ware 2, 20, and single scan standard phantoms were done on children in a single scan for several routine CT scan protocols. Data were analyzed using SPSS software version 16.0. Results Significantly different (P < 0.05) CTDIvol values were obtained for head, chest, and pelvis (2.14 ± 0.93, 0.93 ± 0.07, and 1.20 ± 0.53, respectively). The obtained DLP values for head, chest, and pelvis (28.46 ± 0.93, 23.91 ± 2.26, and 38.14 ±2.52, respectively) were significantly different (P <0.05). Mean CTDIvol and DLP values calculated for head, chest, and pelvic protocols were significantly different by month. Conclusion The mean CTDIvol and DLP values for the head, chest, and pelvic protocols, which are within the allowable range and will not be associated with the risks mentioned in this test on children, are less than the values ​​suggested by various guidelines and other studies.