Types Of CT Examinations Research Articles

Age and size dependent diagnostic reference levels and achievable doses for 48 types of CT examinations: a multicenter cross-sectional study of one million CT examinations in China

Age and size dependent diagnostic reference levels and achievable doses for 48 types of CT examinations: a multicenter cross-sectional study of one million CT examinations in China

Establishing paediatric diagnostic reference levels using reference curves - A feasibility study including conventional and CT examinations.

To derive Regional Diagnostic Reference Levels (RDRL) for paediatric conventional and CT examinations using weight-based DRL curves and compare the outcome with DRL derived using the weight groups. Data from 1722 examinations performed at 29 hospitals in four countries were included. DRL was derived for four conventional x-ray (chest, abdomen, pelvis, hips/joints) and two types of CT examinations (thorax, abdomen). DRL curves were derived using an exponential fit to the data using weight as an independent variable and the respective radiation dose indices (PKA, CTDIvol, DLP) as dependent variables. DRL was also derived for weight groups for comparison. The result was compared with national diagnostic reference level (NDRL) curves. The derived curves show similarities with the NDRL curves available and corresponded sufficiently well with DRL for weight groups using the same data set, if sufficient number of data was available. We conclude that weight-based DRL curves are a feasible approach and could be used together with DRL for weight groups. The main advantage of DRL curves is its application in the clinic. When the examination frequency is low, time to collect enough data to establish typical values for one or several weight groups may be unreasonably long. The curve provides the means to compare dose level faster and with fewer data points.

EXPERIMENTAL EXAMINATION OF RADIATION DOSES OF DUAL- AND SINGLE-ENERGY COMPUTED TOMOGRAPHY IN CHEST AND UPPER ABDOMEN IN A PHANTOM STUDY.

The aim of this phantom study is to examine radiation doses of dual- and single-energy computed tomography (DECT and SECT) in the chest and upper abdomen for three different multi-slice CT scanners. A total of 34 CT protocols were examined with the phantom N1 LUNGMAN. Four different CT examination types of different anatomic regions were performed both in single- and dual-energy technique: chest, aorta, pulmonary arteries for suspected pulmonary embolism and liver. Radiation doses were examined for the CT dose index CTDIvol and dose-length product (DLP). Radiation doses of DECT were significantly higher than doses for SECT. In terms of CTDIvol, radiation doses were 1.1-3.2 times higher, and in terms of DLP, these were 1.1-3.8 times higher for DECT compared with SECT. The third-generation dual-source CT applied the lowest dose in 7 of 15 different examination types of different anatomic regions.

Machine Learning and Coronary Artery Calcium Scoring.

To summarize current artificial intelligence (AI)-based applications for coronary artery calcium scoring (CACS) and their potential clinical impact. Recent evolution of AI-based technologies in medical imaging has accelerated progress in CACS performed in diverse types of CT examinations, providing promising results for future clinical application in this field. CACS plays a key role in risk stratification of coronary artery disease (CAD) and patient management. Recent emergence of AI algorithms, particularly deep learning (DL)-based applications, have provided considerable progress in CACS. Many investigations have focused on the clinical role of DL models in CACS and showed excellent agreement between those algorithms and manual scoring, not only in dedicated coronary calcium CT but also in coronary CT angiography (CCTA), low-dose chest CT, and standard chest CT. Therefore, the potential of AI-based CACS may become more influential in the future.

Deep Learning for Automatic Calcium Scoring in CT: Validation Using Multiple Cardiac CT and Chest CT Protocols.

Background Although several deep learning (DL) calcium scoring methods have achieved excellent performance for specific CT protocols, their performance in a range of CT examination types is unknown. Purpose To evaluate the performance of a DL method for automatic calcium scoring across a wide range of CT examination types and to investigate whether the method can adapt to different types of CT examinations when representative images are added to the existing training data set. Materials and Methods The study included 7240 participants who underwent various types of nonenhanced CT examinations that included the heart: coronary artery calcium (CAC) scoring CT, diagnostic CT of the chest, PET attenuation correction CT, radiation therapy treatment planning CT, CAC screening CT, and low-dose CT of the chest. CAC and thoracic aorta calcification (TAC) were quantified using a convolutional neural network trained with (a) 1181 low-dose chest CT examinations (baseline), (b) a small set of examinations of the respective type supplemented to the baseline (data specific), and (c) a combination of examinations of all available types (combined). Supplemental training sets contained 199-568 CT images depending on the calcium burden of each population. The DL algorithm performance was evaluated with intraclass correlation coefficients (ICCs) between DL and manual (Agatston) CAC and (volume) TAC scoring and with linearly weighted κ values for cardiovascular risk categories (Agatston score; cardiovascular disease risk categories: 0, 1-10, 11-100, 101-400, >400). Results At baseline, the DL algorithm yielded ICCs of 0.79-0.97 for CAC and 0.66-0.98 for TAC across the range of different types of CT examinations. ICCs improved to 0.84-0.99 (CAC) and 0.92-0.99 (TAC) for CT protocol-specific training and to 0.85-0.99 (CAC) and 0.96-0.99 (TAC) for combined training. For assignment of cardiovascular disease risk category, the κ value for all test CT scans was 0.90 (95% confidence interval [CI]: 0.89, 0.91) for the baseline training. It increased to 0.92 (95% CI: 0.91, 0.93) for both data-specific and combined training. Conclusion A deep learning calcium scoring algorithm for quantification of coronary and thoracic calcium was robust, despite substantial differences in CT protocol and variations in subject population. Augmenting the algorithm training with CT protocol-specific images further improved algorithm performance. © RSNA, 2020 See also the editorial by Vannier in this issue.

The impact of contracts on outsourcing computed tomography examinations from a Swedish public university hospital to a private radiology unit

IntroductionAfter years of outsourcing without detailed contracts from one of Sweden's largest university hospitals to external radiology units, the hospital started to use a specific contract for outsourcing computed tomography (CT) examinations. The purpose of this study was to compare the cost-effectiveness of two outsourcing approaches, where examinations were performed either with a detailed, specific contract (with-contract) or without (no-contract), between a hospital radiology department and private external units. MethodsThis retrospective study included a group of electively outsourced CT-examinations (n = 132) and a control group of in-house CT-examinations (n = 132), selected from the three different types of CT-examinations referred from the Departments of Oncology and Hematology.These examinations were randomly selected from four different groups over two time periods of one year each, one being outsourcing without a contract (no-contract, during 2013), one time period with a specific contract (with-contract, during 2014) and two control groups of examinations performed in-house within both these time periods. We compared outsourced examinations (both no-contract and with-contract groups) and in-house examinations. The comparison of these groups include five parameters; management-time, patient waiting-time, the quality of the examinations, - image interpretations and costs. ResultsDuring 2013, management-time for CT-examinations was longer in the outsourced group (no-contract) than in the in-house group, with a statistical significance (P = 0.002). Fewer examinations performed in-house and in the with-contract group needed re-interpretation than in the no-contract group. CT-examinations in the with-contract group were associated with shorter overall management-time, patient waiting time and lower costs compared to the no-contract group. ConclusionUsing a contract with detailed specifications for outsourcing CT-examinations may be an effective way of reducing patient waiting time. Outsourcing based on a well-founded contract can be cost-effective, compared with outsourcing without a detailed plan for the services required.

A “quality-control-based correction method” for displayed dose indices on CT scanner consoles in patient dose surveys

PurposeA new quality-control-based (QC-based) method is introduced to obtain correction factors to be applied to displayed patient dose indices (CTDIVol and DLP) on CT scanner consoles to verify improvement of dose surveys for diagnostic reference levels (DRLs) determination. MethodAn available data-base of QC documents and reports of 57 CT scanners in Tehran, Iran was used to estimate CTDIVol, DLP and relevant correction factors for three CT examination types including head, chest and abdomen/pelvis. The correction factor is the ratio of QC-based estimated dose to displayed dose. A dose survey was performed by applying on-site “data collection method” and correction factors obtained in order to select CT scanners in three modes for determination of CT DRLs by inclusion of: (a) all CT scanners before displayed dose indices were corrected (57), (b) only CT scanners calibrated by QC experts (41) and (c) all CT scanners after displayed dose indices were corrected (57). ResultsFor the 41 CT scanners, correction factors of three examination types obtained in this study are within the acceptance tolerance of IAEA HHS-19. The correction factors range from 0.45 to 1.7 (average of 3 examinations) which is due to the change in the calibrated value of CTDIVol over extended time. The DRL differences in three modes are within ±1.0% for CTDIVol and ±12.4% for DLP. ConclusionsThe “QC-based correction method” applied to mode (c) has improved the DRLs obtained by other two modes. This method is a strong alternative to “direct dose measurement” with simplicity and cost effectiveness.

Evaluating the impact of dose reduction software on Computed Tomography radiation dosimetry using radiology information systems meta data: An example of the use of novel linkable data.

ABSTRACTObjectivesRecently concerns have been expressed regarding the cancer risk to patients undergoing CT scanning prompting the development of dose-reducing software. Experimental studies using phantoms, have shown the potential to significantly reduce radiation dose without compromising diagnostic accuracy. However since dose reduction requires acceptance of more noise in the image the findings from these studies may not be representative of the impact in routine clinical practice. The aim of this study was to evaluate the effect of introduction of iterative reconstruction software on radiation dosimetry in routine clinical practice over a range of CT examinationsApproachRandom samples of CT scans pertaining to 10 commonly performed CT examination types undertaken at two hospitals in Western Australia (WA), before and after the introduction of iterative reconstruction software were extracted from the WA centralised Picture Archiving Communication System. Technical information about the scanning parameters used and radiation dose metrics were extracted from the Digital Imaging and Communications in Medicine (DICOM) information contained in the meta-data for each examination. Changes in the mean dose length product and effective dose were evaluated along with estimations of associated changes to annual cancer incidence using established radiation dosimetry techniques.ResultsWe observed statistically significant reductions in the effective radiation dose for head CT (22-27%) consistent with those reported in the literature. In contrast the reductions observed for non-contrast chest (37-47%); chest pulmonary embolism study (28%), chest/abdominal/pelvic study (16%) and thoracic spine (39%) CT were lower than expected based on experimental studies. Statistically significant reductions in radiation dose were not identified in angiographic CT. Dose reductions translated to substantial lowering of the lifetime attributable risk, especially for younger females, and estimated numbers of incident cancers. ConclusionsOur study has demonstrated a reduction in radiation dose for some scanning protocols, but not to the extent experimental studies had previously shown or in all protocols expected, raising questions about the extent to which iterative reconstruction achieves dose reduction in real world clinical practice. In addition, our study showcases a practical application of the use of technical meta-data from CT scanning examinations to monitor radiation dose and evaluate the impact of dose reduction initiatives. These readily available data provide the ability to routinely monitor CT radiation dose (within and between providers) and, when linked to other administrative data, the opportunity to conduct large scale whole-of-population epidemiological studies evaluating the effect policies and practice on population radiation dose and cancer risk.

Tracking and Resolving CT Dose Metric Outliers Using Root-Cause Analysis

PurposeThe aim of this study was to examine the frequency and type of outlier dose metrics for three common CT examination types on the basis of a root-cause analysis (RCA) approach. MethodsInstitutional review board approval was obtained for this retrospective observational study. The requirement to obtain informed consent was waived. Between January 2010 and December 2013, radiation dose metric data from 34,615 CT examinations, including 26,878 routine noncontrast CT head, 2,992 CT pulmonary angiographic (CTPA), and 4,745 renal colic examinations, were extracted from a radiation dose index monitoring database and manually cleaned. Dose outliers were identified on the basis of the statistical distribution of volumetric CT dose index and dose-length product for each examination type; values higher than the 99th percentile and less than the 1st percentile were flagged for RCA. ResultsThere were 397 noncontrast CT head, 52 CTPA, and 80 renal colic outliers. Root causes for high-outlier examinations included repeat examinations due to patient motion (n = 122 [31%]), modified protocols mislabeled as “routine” (n = 69 [18%]), higher dose examinations for patients with large body habitus (n = 27 [7%]), repeat examinations due to technical artifacts (n = 20 [5%]), and repeat examinations due to suboptimal contrast timing (CTPA examinations) (n = 18 [5%]). Root causes for low-outlier examinations included low-dose protocols (n = 112 [29%]) and aborted examinations (n = 8 [2%]). On the basis of examination frequency over a 3-month period, the 90th and 10th percentile values were set in the radiation dose index monitoring database as thresholds for sending notifications to staff members responsible for outlier investigations. ConclusionsSystematic RCA of dose outliers identifies sources of variation and dose excess and pinpoints specific protocol and technical shortcomings for corrective action.

A Comprehensive CT Dose Reduction Program Using the ACR Dose Index Registry

PurposeThe purpose of this article is to demonstrate the role of the ACR Dose Index Registry® (DIR) in a dose reduction program at a large academic health care system. MethodsUsing the ACR DIR, radiation doses were collected for four common CT examination types (head without contrast, chest with contrast, chest without contrast, and abdomen and pelvis with contrast). Baseline analysis of 7,255 CT examinations from seven scanners across the institution was performed for the period from December 1, 2011, to March 15, 2012. A comprehensive dose reduction initiative was guided by the identification of targets for dose improvement from the baseline analysis. Data for 14,938 examinations from the same seven scanners were analyzed for the postimplementation period of January 1, 2013, to July 1, 2013. ResultsThe program included protocol changes, iterative reconstruction, optimization of scan acquisition, technologist education, and continuous monitoring with feedback tools. Average decrease in median dose-length product (DLP) across scanners was 30% for chest CT without contrast, 29% for noncontrast head CT, 26% for abdominal and pelvic CT with contrast, and 10% for chest CT with contrast. Compared with average median DLP in the ACR DIR, the median institution-wide CT DLPs after implementation were lower by 33% for chest CT without contrast, 32% for chest CT with contrast, 26% for abdominal and pelvic CT with contrast, and 6% for head CT without contrast. ConclusionsA comprehensive CT dose reduction program using the ACR DIR can lead to substantial dose reduction within a large health care system.

Variability in CT Protocols

CT protocols are a collection of scanner settings and scan parameters that specify how data are acquired, reconstructed, and presented. These settings and parameters are interrelated, and changes in settings can affect CT image quality and dose. Acceptable image quality and radiation dose can be achieved using many different combinations of scan parameters and scanner settings. This leads to variability in protocols among different CT manufacturers and even among different generations of CT scanners from the same manufacturer. According to a study of radiation dose associated with common CT examinations [1], radiation dose varied substantially among the different types of CT studies. Even within study type, radiation dose varied substantially. The mean doses differed by 2-fold across institutions, and for several of the study types, the mean doses across institutions differed by 3-fold or more. This illustrates the point that variations in doses across institution are due to site-specific methods of choosing different scan parameters to answer the same clinical questions. According to the 2013 Current Procedural Terminology code book, there are about 50 codes for CT examinations [2], yet many CT scanners have 100 to 150 protocols. The way a particular CT protocol is developed is somewhat similar to building a recipe using available ingredients. Justas there isnoonerecipe that can satisfy all gastronomes, similarly, one cannot have a fixedCT protocol for all types of CT examinations. Yet there is no reason why there should be 100 to 150 CT protocols on a CT scanner. This in combination with various CT generations and CT manufacturers results in the variability of CT

Relating Noise to Image Quality Indicators in CT Examinations With Tube Current Modulation

Modern CT systems use surrogates of noise-noise index (NI) and quality reference effective tube current-time product (Q)-to infer the quality of images acquired using tube current modulation. This study aimed to determine the relationship between actual noise and these surrogates for two CT scanners from two different manufacturers. Two phantoms (adult and 1-year-old child) were imaged on two CT scanners (64 and 128 MDCT) using a clinical range of NI (6-22) and Q (30-300 mA). Each scan was performed twice, and noise was measured in the mediastinum, lung, and abdomen using an image subtraction technique. The effect on noise from changing other imaging parameters, such as beam collimation, pitch, peak kilovoltage, slice thickness, FOV, reconstruction kernel or algorithm, and patient age category (adult or pediatric), was investigated. On the 64-MDCT scanner, noise increased linearly along with NI, with the slope affected by changing the anatomy of interest, peak kilovoltage, reconstruction algorithm, and convolution kernel. The noise-NI relationship was independent of phantom size, slice thickness, pitch, FOV, and beam width. On the 128-MDCT scanner, noise decreased nonlinearly along with increasing Q, slice thickness, and peak tube voltage. The noise-Q relationship also depended on anatomy of interest, phantom size, age selection, and reconstruction algorithm but was independent of pitch, FOV, and detector configuration. We established how noise changes with changing image quality indicators across a clinically relevant range of imaging parameters. This work can aid in optimizing protocols by targeting specific noise levels for different types of CT examinations.

Falls, Older Adults, and the Trend in Utilization of CT in a Level I Trauma Center

The purpose of this article is to evaluate the trend in the utilization of CT for fall victims older than 55 years admitted to a level I trauma center. We used trauma registry data (1996-2006) of a level I trauma center. By using the International Classification of Disease, Ninth Revision (Clinical Modification) codes, we identified the type and frequency of CT examinations for each patient. We used negative binomial regression to evaluate the association between CT utilization rates and age, year of admission, sex, insurance status, ethnicity, ICU admission status, injury severity score, and final disposition (i.e., deceased vs alive). We used logistic regression to evaluate predictors of repeat (i.e., ≥ 2) CT scans. During the study period, the utilization rate of head, abdomen, thorax, and other body region (including spine and extremities) CT examinations increased, on average, by 7%, 16%, 14%, and 15% per year, respectively. Older age was associated with a higher utilization of head CT. Male sex and ICU admission were associated with higher utilization for all types of CT examinations. Repeat head and abdominal CT scans increased, on average, by 28% (95% CI, 20-36%) and 24% (95% CI, 2-51%) per year, respectively. We quantified the increase in utilization rates of all types of CT scans for fall victims admitted to a level I trauma center. We found a marked increase in CT use over time, both for initial as well as repeat studies, and an association between CT use and variables such as sex. Future studies should focus on the evaluation of CT appropriateness and their influence on patient outcomes.

Adult patient radiation doses from non-cardiac CT examinations: a review of published results.

CT is a valuable tool in diagnostic radiology but it is also associated with higher patient radiation doses compared with planar radiography. The aim of this article is to review patient dose for the most common types of CT examinations reported during the past 19 years. Reported dosimetric quantities were compared with the European diagnostic reference levels (DRLs). Effective doses were assessed with respect to the publication year and scanner technology (i.e. single-slice vs multislice). Considerable variation of reported values among studies was attributed to variations in both examination protocol and scanner design. Median weighted CT dose index (CTDI(w)) and dose length product (DLP) are below the proposed DRLs; however, for individual studies the DRLs are exceeded. Median reported effective doses for the most frequent CT examinations were: head, 1.9 mSv (0.3-8.2 mSv); chest, 7.5 mSv (0.3-26.0 mSv); abdomen, 7.9 mSv (1.4-31.2 mSv); and pelvis, 7.6 mSv (2.5-36.5 mSv). The introduction of mechanisms for dose reduction resulted in significantly lower patient effective doses for CT examinations of the head, chest and abdomen reported by studies published after 1995. Owing to the limited number of studies reporting patient doses for multislice CT examinations the statistical power to detect differences with single-slice scanners is not yet adequate.

Comparative evaluation of organ and effective doses for paediatric patients with those for adults in chest and abdominal CT examinations

Patient doses in paediatric and adult CT examinations were investigated for modern multislice CT scanners by using specially constructed in-phantom dose measuring systems. The systems were composed of 32 photodiode dosemeters embedded in various tissue and organ sites within anthropomorphic phantoms representing the bodies of 6-year-old children and adults. Organ and the effective doses were evaluated from dose values measured at these sites. In chest CT examinations, organ doses for organs within the scanning area were 2-21 mGy for children and 7-26 mGy for adults. Thyroid doses for children were frequently the highest with a maximum of 21 mGy. In abdominal CT examinations, organ doses for organs within the scanning area were 3-16 mGy for children and 10-34 mGy for adults. Effective doses evaluated for children and adults were found to be proportional to the effective mAs of CT scanners, where linear coefficients were specific to the types of CT examinations and to the manufacturers of CT scanners. Effective doses in paediatric chest CT and abdominal CT examinations were lower than those in adult examinations by a factor of two or greater on average for the same CT scanners because of the lower effective mAs adopted in paediatric examinations.

Errata

HomeRadiologyVol. 187, No. 3 Previous ArticlesErrataPublished Online:Jun 1 1993https://doi.org/10.1148/radiology.187.3.880MoreSectionsPDF ToolsImage ViewerAdd to favoritesCiteTrack CitationsPermissionsReprints ShareShare onFacebookTwitterLinked In Abstract"Disk-caused Nerve Compression in Patients with Acute Low-Back Pain: Diagnosis with MR, CT Myelography, and Plain CT." Radiology 1993; 186:731-738.Page 731, in the abstract, the words "...a panel of two expert radiologists" should be replaced with "an expert panel." The panel comprised a neurologist and a neurologic surgeon. Page 733, column 2, the correct initials of the methods expert are not "P.G.F." but "D.G.F." (Dennis G. Fryback, coauthor), and "poshpsible" is a typographical error for "possible." Page 733, column 3, "Oblique, 45°, and 60° anteroposterior and lateral images...." should be "Oblique (45° and 60°), anteroposterior, and lateral images...." Page 734, Table 2, n = 63 for CT myelogram and MR pained images instead of n = 64. Page 737, column 1, "myograms" should be "myelogram images." Page 735, Figures 1-3 should have appeared as below.[See Figure in the PDF File]Figures 1-3. (1) ROC curves for the 32 cases evaluated with plain CT and MR. The data used to construct the curves were (a) the blinded reading diagnostic certainty ratings for HNPNC for the disk space with the highest rating and (b) the reference-standard panel forced-choice diagnoses with all outcome information other than imaging. Thus, each patient is one observation for this analysis. (2) ROC curves for 63 patients evaluated with CT myelography and MR. (3) ROC curves comparing CT and MR for all 95 patients in the study. CT refers generically to the CT procedure—either plain CT or CT myelography—used for each patient. The two types of CT examinations are not distinguished for this analysis. Parametric ROC curves were computed to display for all figures by means of the methods of England (21). Solid line = MR, dotted line = CT.Article HistoryPublished in print: June 1993 FiguresReferencesRelatedDetailsCited ByClinical Endocrinology, Vol. 80, No. 1Pain Research and Treatment, Vol. 2011Insulinoma localization using hepatic venous sampling with selective arterial calcium stimulation: should a fixed calcium dose be used?Clinical Endocrinology, Vol. 63, No. 4Recommended Articles RSNA Education Exhibits RSNA Case Collection Vol. 187, No. 3 Metrics Downloaded 1 times Altmetric Score PDF download