Computed Tomography Scanner Type Research Articles

Phantom and Animal Study of a Robot-Assisted, CT-Guided Targeting System using Image-Only Navigation for Stereotactic Needle Insertion without Positional Sensors

PurposeTo evaluate the feasibility and accuracy of a robotic system to integrate and map computed tomography (CT) and robotic coordinates, followed by automatic trajectory execution by a robotic arm. The system was hypothesized to achieve a targeting error of <5 mm without significant influence from variations in angulation or depth. Materials and MethodsAn experimental study was conducted using a robotic system (Automated Needle Targeting device for CT [ANT-C]) for needle insertions into a phantom model on both moving patient table and moving gantry CT scanners. Eight spherical markers were registered as targets for 90 insertions at different trajectories. After a single ANT-C registration, the closed-loop software targeted multiple markers via the insertion of robotically aligned 18-gauge needles. Accuracy (distance from the needle tip to the target) was assessed by postinsertion CT scans. Similar procedures were repeated to guide 10 needle insertions into a porcine lung. A regression analysis was performed to test the effect of needle angulation and insertion depth on the accuracy of insertion. ResultsIn the phantom model, all needle insertions (median trajectory depth, 64.8 mm; range, 46.1–153 mm) were successfully performed in single attempts. The overall accuracy was 1.36 mm ± 0.53, which did not differ between the 2 types of CT scanners (1.39 mm ± 0.54 [moving patient table CT] vs 1.33 mm ± 0.52 [moving gantry CT]; P = .54) and was not significantly affected by the needle angulation and insertion depth. The accuracy for the porcine model was 9.09 mm ± 4.21. ConclusionsRobot-assisted needle insertion using the ANT-C robotic device was feasible and accurate for targeting multiple markers in a phantom model.

Abstract 9425: Coronary Artery Calcium Measurement and Prediction of Cardiovascular Disease by Different Ct Scanner Types: The Multi-Ethnic Study of Atherosclerosis

Introduction: Coronary artery calcium (CAC) scoring is a powerful tool for cardiovascular disease (CVD) risk prediction. The Agatston score weighs lesion area upward for density, and is consistent across computed tomography (CT) scanner type. Considering volume and density separately improves risk prediction, but has not been evaluated by CT scanner type. Hypothesis: Our hypothesis was that the predictive value of volume and density scoring would be superior to the Agatston score across CT scanner types. Methods: We used data from MESA (Multi-Ethnic Study of Atherosclerosis), a prospective cohort study of participants free of baseline clinical cardiovascular disease. CAC was measured using either EBCT (electron beam CT) or MDCT (multi-detector CT). We compared risk prediction for coronary heart disease (CHD) and CVD events using the Agatston method and the volume and density scores by scanner type using Cox proportional hazards models with multivariable adjustment among those with baseline CAC &gt; 0. HRs are presented as per standard deviation. Results: The 3,362 MESA participants with CAC &gt;0 were studied. Using the Agatston method, the HR [95% CI] for CHD was 1.28 [1.16-1.42] for EBCT and 1.22 [1.12-1.34] for MDCT. Using the volume score adjusted for density, the HR for CHD was 2.11 [1.70-2.63] for EBCT and 1.71 [1.41-2.07] for MDCT. Density was strongly and inversely associated with CHD. Similar results were seen for CVD risk and in analyses stratified by sex, BMI, age, and baseline statin use. The volume score demonstrated higher areas under the curve (AUC) than the Agatston score with EBCT (0.702, 95% CI 0.665-0.738 vs 0.677, 95% CI 0.638-0.715, p=0.013) and MDCT (0.669, 95% CI 0.632-0.705 vs 0.653, 95% CI 0.616-0.690, p=0.107). Conclusions: Compared with the Agatston score, the CAC volume score, adjusted for density, provides better risk prediction for CHD and CVD events, regardless of CT scanner type. CAC density was strongly and inversely associated with CVD risk.

Prediction of Human Papillomavirus (HPV) Association of Oropharyngeal Cancer (OPC) Using Radiomics: The Impact of the Variation of CT Scanner.

Simple SummaryRecent studies exploring the application of radiomics features in medicine have shown promising results. However, variation in imaging parameters may impact the robustness of these features. Feature robustness may then in turn affect the prediction performance of the machine learning models built upon these features. While numerous studies have tested feature robustness against a variety of imaging parameters, the extent to which feature robustness affects predictions remains unclear. A particularly notable application of radiomics in clinical oncology is the prediction of Human Papillomavirus (HPV) association in Oropharyngeal cancer. In this study we explore how CT scanner type affects the performance of radiomics features for HPV association prediction and highlight the need to implement precautionary approaches so as to minimize this effect.Studies have shown that radiomic features are sensitive to the variability of imaging parameters (e.g., scanner models), and one of the major challenges in these studies lies in improving the robustness of quantitative features against the variations in imaging datasets from multi-center studies. Here, we assess the impact of scanner choice on computed tomography (CT)-derived radiomic features to predict the association of oropharyngeal squamous cell carcinoma with human papillomavirus (HPV). This experiment was performed on CT image datasets acquired from two different scanner manufacturers. We demonstrate strong scanner dependency by developing a machine learning model to classify HPV status from radiological images. These experiments reveal the effect of scanner manufacturer on the robustness of radiomic features, and the extent of this dependency is reflected in the performance of HPV prediction models. The results of this study highlight the importance of implementing an appropriate approach to reducing the impact of imaging parameters on radiomic features and consequently on the machine learning models, without removing features which are deemed non-robust but may contain learning information.

Use of bismuth shield for protection of superficial radiosensitive organs in patients undergoing computed tomography: a literature review and meta-analysis.

The study aimed to assess the effect of bismuth (Bi) shielding on dose reduction and image quality in computed tomography (CT) through a literature review. A search was conducted in the following databases: Web of Science, PubMed, Google Scholar, and Scopus. Studies that reported estimated dose reduction with bismuth shielding during imaging of the eye, thyroid, and breast were included, and a meta-regression analysis was used to examine the influence of the CT scanner type on the dose reduction. The studies included a total of 237 patients and 34 pediatric and adult anthropomorphic phantoms for whom the radiation dose was reported. Bismuth shielding was recommended in 88.89% of the studies based on the maintenance of appropriate image quality under shielding. Noise associated with Bi shielding was 7.5%, 263%, and 23.5% for the eye, thyroid, and breast, respectively. The fixed-effects pooled estimate of dose reduction was 34% (95% CI: 13-55; p < 0.001) for the eye, 37% (95% CI 14-61; p < 0.001) for the thyroid, and 36% (95% CI 36-55; p < 0.001) for the breast. The image quality, usage of foams, CT scanner type, beam energies, and backscatter radiation were important factors that directly affected the efficacy of Bi shielding to reduce the radiation dose at the superficial radiosensitive organs.

Inter-scanner variability in Hounsfield unit measured by CT of the brain and effect on gray-to-white matter ratio

Purpose: The density ratio of gray matter (GM) to white matter (WM) on brain computed tomography (CT) (gray-to-white matter ratio, GWR) helps predict the prognosis of comatose patients after cardiac arrest. However, Hounsfield units (HU) are not an absolute value and can change based on imaging parameters and CT scanners. We compared the density of brain GM and WM and the GWR by using images scanned with different types of CT machines.Method: 102 patients with normal readings who were scanned using three types of CT scanners were included in the study. HU were measured at the basal ganglia level by two observers with circular regions of interest.Result: The difference in GM was 0.98–10.30 HU and WM was 1.05–7.55 HU. The mean value of measured HU and GWR were different for each CT group. The ANOVA test showed significant difference all variables. The post hoc test for GWR, which was used to compare the differences between each scanner, was statistically significant. Interclass correlation coefficients of measured GM and WM between the two observers were very high (Cronbach's α=0.995 and 0.990, respectively) and GWR was showed good confidence level (0.798).Conclusion: In this study, the HU values of GM and WM in the normal adult brain differed up to 23% among scanners. Unfortunately, the GWR may not compensate for the HU difference between GM and WM occurring between scanners. Therefore, rather than applying consistent GWR cut-offs, the protocol or manufacturer differences between imaging scanners should be considered.

Radiation dose and image quality of computed tomography of the supra-aortic arteries: A comparison between single-source and dual-source CT Scanners

PurposeThe purpose of this work was to compare the image quality and radiation dose delivered to patients during computed tomography (CT) angiography (CTA) of the supra-aortic arteries using two single-source (SS) and two dual-energy (DE) CT scanners. Material and methodsIn this retrospective study, 120 patients who underwent CTA of supra-aortic arteries were studied using four different types of CT scanners: a sixteen and forty-detector-row SS and two DE CT scanners. Seventy milliters of contrast medium were injected at a flow rate of 4mL/s using a power injector. For each patient the dose-length product (DLP), the volume computed tomography dose index (CDTIvol), the length of the scan and the effective dose (ED) were calculated. Qualitative and quantitative [image noise, signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR)] image quality assessment was performed. ResultsA statistically significant lower value of the DE compared to the SS technology (P<0.0001) for the CDTI, DLP and ED was found, whereas we did not find any statistically significant difference between the four scanners for the measurements of the image noise, SNR and CNR. ConclusionDS CT scanners allow performing CTAs with a reduced dose compared to SS CT scanner with comparable image quality.

Change in Neighborhood Characteristics and Change in Coronary Artery Calcium: A Longitudinal Investigation in the MESA (Multi-Ethnic Study of Atherosclerosis) Cohort.

Although some evidence shows that neighborhood deprivation is associated with greater subclinical atherosclerosis, prior studies have not identified what aspects of deprived neighborhoods were driving the association. We investigated whether social and physical neighborhood characteristics are related to the progression of subclinical atherosclerosis in 5950 adult participants of the MESA (Multi-Ethnic Study of Atherosclerosis) during a 12-year follow-up period. We assessed subclinical disease using coronary artery calcium (CAC). Neighborhood features examined included density of recreational facilities, density of healthy food stores, and survey-based measures of availability of healthy foods, walking environment, and social environment. We used econometric fixed-effects models to investigate how change in a given neighborhood exposure is related to simultaneous change in subclinical atherosclerosis. Increases in density of neighborhood healthy food stores were associated with decreases in CAC (mean changes in CAC Agatston units per 1-SD increase in neighborhood exposures, -19.99; 95% confidence interval, -35.21 to -4.78) after adjustment for time-varying demographic confounders and computed tomography scanner type. This association remained similar in magnitude after additional adjustment for time-varying behavioral risk factors and depression. The addition of time-varying biomedical factors attenuated associations with CAC slightly (mean changes in CAC per 1-SD increase in neighborhood exposures, -17.60; 95% confidence interval, -32.71 to -2.49). Changes across time in other neighborhood measures were not significantly associated with within-person change in CAC. Results from this longitudinal study provide suggestive evidence that greater access to neighborhood healthy food resources may slow the development of coronary atherosclerosis in middle-aged and older adults.

The Impact of Sources of Variability on Parametric Response Mapping of Lung CT Scans.

Parametric response mapping (PRM) of inspiration and expiration computed tomography (CT) images improves the radiological phenotyping of chronic obstructive pulmonary disease (COPD). PRM classifies individual voxels of lung parenchyma as normal, emphysematous, or nonemphysematous air trapping. In this study, bias and noise characteristics of the PRM methodology to CT and clinical procedures were evaluated to determine best practices for this quantitative technique. Twenty patients of varying COPD status with paired volumetric inspiration and expiration CT scans of the lungs were identified from the baseline COPDGene cohort. The impact of CT scanner manufacturer and reconstruction kernels were evaluated as potential sources of variability in PRM measurements along with simulations to quantify the impact of inspiration/expiration lung volume levels, misregistration, and image spacing on PRM measurements. Negligible variation in PRM metrics was observed when CT scanner type and reconstruction were consistent and inspiration/expiration lung volume levels were near target volumes. CT scanner Hounsfield unit drift occurred but remained difficult to ameliorate. Increasing levels of image misregistration and CT slice spacing were found to have a minor effect on PRM measurements. PRM-derived values were found to be most sensitive to lung volume levels and mismatched reconstruction kernels. As with other quantitative imaging techniques, reliable PRM measurements are attainable when consistent clinical and CT protocols are implemented.

X線CTの基礎知識と岩盤工学への適用

X-Ray CT (Computed Tomography) was developed as a non-distractive inspection tool, and the system spread firstly in the medical field. Since the advantage as a non-distractive inspection tool is recognized in the engineering field, X-ray CT system has been applied in the various kinds of research field including rock engineering. In the case of rock engineering, rocks inevitably contain a lot of hetelogeneity, such as cracks, pores and different kinds of grains. Therefore, the understanding of these characteristics is the first step to develop the research, and X-ray CT has been expected as one of the most useful and effective tools. In this paper, fundamental knowledge of X-ray CT system, types of X-ray CT scanners and their applicability to the rock engineering were introduced. Here, the subjects were focused on the geomaterials such as rocks, stones and closely related materials, and histories of the X-ray CT applications for each research topic, way of analysis and merit/demerit of X-ray CT applications were introduced. The prospective of X-ray CT and its application were also discussed.

Effect of Different CT Scanner Types and Beam Collimations on Measurements of Three-Dimensional Volume and Hounsfield Units of Artificial Calculus Phantom

The objective of this study was to evaluate the differences and reproducibility of Hounsfield unit (HU) value and volume measurements on different computed tomography (CT) scanner types and different collimations by using a gelatin phantom. The phantom consisting of five synthetic simulated calculus spanning diameters from 3.0 mm to 12.0 mm with 100 HU was scanned using a two-channel multi-detector row CT (MDCT) scanner, a fourchannel MDCT scanner, and two 64-channel MDCT scanners. For all different scanner types, the thinnest possible collimation and the second thinnest collimation was used. The HU values and volumes of the synthetic simulated calculus were independently measured three times with minimum intervals of 2 weeks and by three experienced veterinary radiologists. ANOVA and Scheffe test for the multiple comparison were performed for statistical comparison of the HU values and volumes of the synthetic simulated calculus according to different CT scanner types and different collimations. The reproducibility of the HU value and volume measurements was determined by calculating Cohen’s k. The reproducibility of HU value and volume measurements was very good. HU value varied between different CT scanner types, among different beam collimations. However, there was not statistically significant difference. The percent error (PE) decreased as the collimation thickness decreased, but the decrease was statistically insignificant. In addition, no statistically significant difference in the PEs of the different CT scanner types was found. It can be concluded that the CT scanner type insignificantly affects HU value and the volumetric measurement, but that a thinner collimation tends to be more useful for accurate volumetric measurement.

TU‐A‐12A‐04: Quantitative Texture Features Calculated in Lung Tissue From CT Scans Demonstrate Consistency Between Two Databases From Different Institutions

Purpose:To evaluate the consistency of computed tomography (CT) scan texture features, previously identified as stable in a healthy patient cohort, in esophageal cancer patient CT scans.Methods:116 patients receiving radiation therapy (median dose: 50.4Gy) for esophageal cancer were retrospectively identified. For each patient, diagnostic‐quality pre‐therapy (0‐183 days) and post‐therapy (5‐120 days) scans (mean voxel size: 0.8mm×0.8mm×2.5mm) and a treatment planning scan and associated dose map were collected. An average of 501 32×32‐pixel ROIs were placed randomly in the lungs of each pre‐therapy scan. ROI centers were mapped to corresponding locations in post‐therapy and planning scans using the displacement vector field output by demons deformable registration. Only ROIs with mean dose &lt;5Gy were analyzed, as these were expected to contain minimal post‐treatment damage. 140 texture features were calculated in pre‐therapy and post‐therapy scan ROIs and compared using Bland‐Altman analysis. For each feature, the mean feature value change and the distance spanned by the 95% limits of agreement were normalized to the mean feature value, yielding normalized range of agreement (nRoA) and normalized bias (nBias). Using Wilcoxon signed rank tests, nRoA and nBias were compared with values computed previously in 27 healthy patient scans (mean voxel size: 0.67mm×0.67mm×1mm) acquired at a different institution.Results:nRoA was significantly (p&lt;0.001) larger in cancer patients than healthy patients. Differences in nBias were not significant (p=0.23). The 20 features identified previously as having nRoA&lt;20% for healthy patients had the lowest nRoA values in the current database, with an average increase of 5.6%.Conclusion:Despite differences in CT scanner type, scan resolution, and patient health status, the same 20 features remained stable (i.e., low variability and bias) in the absence of disease changes for databases from two institutions. Identification of these features is the first step towards quantifying radiation‐induced changes between preand post‐therapy scans.Supported, in part, by NIH Grant Nos. S10 RR021039, and P30 CA14599, the Virginia and D. K. Ludwig Fund for Cancer Research, Imaging Research Institute, Biological Sciences Division, The University of Chicago, and The Institute for Translational Medicine Pilot Award, The University of Chicago.

Comparison of radiation doses between newborns and 6-y-old children undergoing head, chest and abdominal CT examinations--a phantom study

Radiation doses in paediatric computed tomography (CT) were investigated for various types of recent CT scanners with newborn and 6-y-old phantoms in which silicon-photodiode dosemeters were implanted at various organ positions. In the head, chest and abdominal CT for the newborn phantom, doses for organs within the scan region were 21-40, 3-8 and 3-12 mGy, respectively. The corresponding doses for the child phantom were 20-37, 2-11 and 4-17 mGy, respectively. In the head, chest and abdominal CT, the effective doses were respectively 2.1-3.3, 2.0-6.0 and 2.2-10.0 mSv for the newborn, and 1.0-2.0, 1.2-6.6 and 2.9-11.8 mSv for the child. Radiation doses for the newborn were at the same levels as those for the child, excepting effective doses in head CT for the newborn, which were 1.8 times higher than those for the child.

Fast on‐site Monte Carlo tool for dose calculations in CT applications

Monte Carlo (MC) simulation is an established technique for dose calculation in diagnostic radiology. The major drawback is its high computational demand, which limits the possibility of usage in real-time applications. The aim of this study was to develop fast on-site computed tomography (CT) specific MC dose calculations by using a graphics processing unit (GPU) cluster. GPUs are powerful systems which are especially suited to problems that can be expressed as data-parallel computations. In MC simulations, each photon track is independent of the others; each launched photon can be mapped to one thread on the GPU, thousands of threads are executed in parallel in order to achieve high performance. For further acceleration, the authors considered multiple GPUs. The total computation was divided into different parts which can be calculated in parallel on multiple devices. The GPU cluster is an MC calculation server which is connected to the CT scanner and computes 3D dose distributions on-site immediately after image reconstruction. To estimate the performance gain, the authors benchmarked dose calculation times on a 2.6 GHz Intel Xeon 5430 Quad core workstation equipped with two NVIDIA GeForce GTX 285 cards. The on-site calculation concept was demonstrated for clinical and preclinical datasets on CT scanners (multislice CT, flat-detector CT, and micro-CT) with varying geometry, spectra, and filtration. To validate the GPU-based MC algorithm, the authors measured dose values on a 64-slice CT system using calibrated ionization chambers and thermoluminesence dosimeters (TLDs) which were placed inside standard cylindrical polymethyl methacrylate (PMMA) phantoms. The dose values and profiles obtained by GPU-based MC simulations were in the expected good agreement with computed tomography dose index (CTDI) measurements and reference TLD profiles with differences being less than 5%. For 10(9) photon histories simulated in a 256 × 256 × 12 voxel thorax dataset with voxel size of 1.36 × 1.36 × 3.00 mm(3), calculation times of about 70 and 24 min were necessary with single-core and multiple-core central processing unit (CPU) solutions, respectively. Using GPUs, the same MC calculations were performed in 1.27 min (single card) and 0.65 min (two cards) without a loss in quality. Simulations were thus speeded up by factors up to 55 and 36 compared to single-core and multiple-core CPU, respectively. The performance scaled nearly linearly with the number of GPUs. Tests confirmed that the proposed GPU-based MC tool can be easily adapted to different types of CT scanners and used as service providers for fast on-site dose calculations. The Monte Carlo software package provides fast on-site calculation of 3D dose distributions in the CT suite which makes it a practical tool for any type of CT-specific application.

Variability of radiation exposure with in‐office sinus computed tomography examinations

An increasing number of patients seeking care by an otolaryngologist are undergoing computed tomography (CT) examinations via in-office CT scanners. Many otolaryngologists and patients are not fully aware of the radiation dosages and the associated risks. A recent study of common CT examinations demonstrated significant variability in radiation dosages for similar studies. Despite the relatively low doses associated with sinus scans, widely publicized studies and events have generated a renewal of physician, public, and regulatory agency awareness and concern regarding medical radiation exposure. Phantom measurements and/or radiation dosage reports from CT scanners utilized by a large otolaryngology group in California were reviewed and compared. Different types of CT scanners from multiple manufacturers were included. There was nearly a 10-fold difference (0.15-1.45 mSv) in radiation between scans obtained from in-office, hospital-based, and outpatient imaging facility CT scanners. Significant relative variability can exist in radiation dosages associated with routine sinus CT scans obtained in different locations. There is a need for increased awareness and understanding among otolaryngologists and their patients regarding medical radiation exposure. All otolaryngologists should constantly consider the principle of "as low as reasonably achievable" (ALARA). Shielding, pediatric protocols, and other dosage reduction measures should be utilized whenever possible.

Socioeconomic Status is Positively Associated with Percent Emphysema on CT Scan: The MESA Lung Study

Higher socioeconomic status (SES) has been associated with lower respiratory mortality and better lung function, but whether a similar gradient exists for computed tomography (CT) measures of subclinical emphysema is unknown. The Multi-Ethnic Study of Atherosclerosis (MESA) recruited African-American, Chinese, Hispanic, and white participants, ages 45 to 84 years, without clinical cardiovascular disease, from six US sites between 2000 and 2002. The MESA Lung Study assessed percent emphysema, defined based on the proportion of pixels below an attenuation threshold of 910 HU from lung windows of cardiac CT scans. Generalized linear models were adjusted for demographic characteristics, height, body mass index, history of respiratory illness, occupational and residential exposures, tobacco use, and CT scanner type. Among 3706 participants with a mean age of 61 (±10), the median value for percent emphysema was 18 (interquartile range = 20). Compared with those who did not complete high school, participants with a graduate degree had a higher percent emphysema (difference of 4; P < .001). Income and wealth were also positively associated with percent emphysema. In contrast, higher SES was associated with better lung function. Descriptive and subgroup analyses were used to explore potential explanations for divergent results, including the possibility that suboptimal inspiration during CT scanning would decrease percent emphysema, making the lungs appear healthier when effort is relatively poor. Although SES indicators were positively associated with subclinical emphysema detectable on CT scan, this unexpected association may highlight potential bias because of effort dependence of both CT measures and spirometry.

Tomographic plaque imaging with CT: technical considerations and capabilities

X-ray computed tomography (CT) is widely available in the world and has the ability to provide high-definition, thin-section imaging of any body part. In particular, CT over the past decade has been shown in numerous publications to allow for quantitation of coronary calcification, a proven surrogate for coronary artery atheromatous plaque. Electron beam tomography (EBT) and multidetector CT (MDCT) have been studied for these purposes. However, there are methodological differences between types of CT scanners and precision of calcium scoring is a function of their individual technical capabilities and limitations. These technical aspects are detailed here. Although MDCT has shown considerable improvements in recent years, EBT remains the clinical reference standard for noninvasive definition of atherosclerotic plaque.

Computed Tomography Dose Assessment - A Practical Approach

A survey of the pattern and frequency of computed tomography (CT) examinations in Sweden has been conducted covering 89 of the 90 existing CT scanners (in 1991). The radiation output and the absorbed doses in phantoms have been measured for all types of CT scanners. For the assessment of the effective dose to the patient a new, practical approach has been developed. The average absorbed doses measured in cylindrical PMMA phantoms were assumed to be valid also for patients, those in the 320 mm diameter phantom for the trunk region and those in the 160 mm diameter phantom for the neck and head. With guidance from the ICRP 60 concept of tissue weighting factors, average weighting factors were adopted for the trunk, the neck, and the head region. Effective patient doses were calculated using three factors for doses measured in phantoms with the settings of exposure parameters as recorded in the survey. The results were compared with dose evaluations based on Monte Carlo calculations. The agreement was found to be satisfactory. It is suggested that this new practical approach should be adopted as a standard method for the assessment of effective dose in CT practices thus enabling direct access to dose evaluations in daily clinical practice - a prerequisite for the implementation of radiation protection concepts into the radiological society.