Abdominopelvic CT Examinations Research Articles

Evaluation of radiation dose and establishment of local DRLs for adult during abdominopelvic CT scan imaging for university hospital centers, Morocco

Objective: In this study, we have planned to establish the local Diagnostic Reference Levels (DRLs) for the five University Hospital Centers in Morocco and to propose a national DRL for abdominopelvic CT examinations for adult patients. Materials and methods: Data were collected using a specially designed form, which included patient demographics, exposure parameters and dosimetric indicators such as dose-length product (DLP) and CT volume dose index (CTDIvol). The establishment of local and national DRL in terms of CTDIvol and DLP was carried out in accordance with the methodology described in Report 135 of the International Commission on Radiological Protection (ICRP). The effective dose was assessed using the DLP and the dose conversion factor appropriate for this location. Results: A total of 300 patients undergoing abdominopelvic examinations at the five Moroccan university hospitals were collected for this study. Patients' mean age, weight and BMI were (50.97 ± 15.05) years (67.94 ± 11.41) Kg and (25.71 ± 3.03) Kg/m2 respectively. The local DRL, in terms of DLP were 551.56, 2293.33, 709.02, 843.52 and 1059.62 mGy-cm and in terms of CTDIvol were 11,05, 46,40, 13,14, 12,01, 9,88 mGy respectively for UHC-1, UHC-2, UHC-3, UHC-4 and UHC-5 hospitals. The proposed National DRL, defined as a single value for the 75th percentile on the aggregation of data from the five centers, for abdominopelvic scan CT was 773.20 mGy.cm and 12.05 mGy for DLP and CTDIvol, respectively. Conclusion: The Moroccan DRL was comparable to those of other countries, ranking 10th among 21 countries. However, we are still seeking to reduce and optimize radiation dose while maintaining good image quality for reliable diagnosis, and this can be achieved by enhancing radiographers' and radiologists' knowledge of radiation protection, protocol justification, and optimization through rigorous hospital radiation audits at national level.

Local Diagnostic Reference Levels for Common Adult Computed Tomography Procedures in Addis Ababa.

Computed Tomography has become the major source of population exposure in diagnostic x-rays. This concerned issue will be resolved by stetting Local Diagnostic Reference Levels. The main objective of this study is to assess dose indicators for the establishment of Local Diagnostic Reference Levels. A prospective cross-sectional study design was conducted on 8 public and private hospitals performing CT examinations. A total of 725 adult patients who underwent abdominopelvic, chest, and head CT examinations were evaluated from October 2021 to March 2022. Patients' demography, exposure parameters, and dose descriptors were collected. The minimum, maximum, mean, median, and third quartile values were analyzed using SPSS software version 26. Finally, the third quartile values of collected data were compared with national and international values. The third quartile values obtained from median of volumetric computed tomography dose index (mGy) and dose length product (mGy.cm) which are considered as local DRLs for head, chest, and abdominopelvic CT examination, respectively, were 53mGy, 14mGy and 13mGy; 1307mGy.cm, 575mGy.cm, and 932mGy.cm. The results of this study showed that practices of CT imaging in both public and private hospitals in Addis Ababa were comparable to other national and international values.

Utilization of Chest and Abdominopelvic CT for Traumatic Injury From 2011 to 2018: Evaluation Using a National Commercial Database.

Background: Recent increases in utilization of CT in patients presenting with trauma have raised concern of inappropriate imaging. The evolving utilization of CT for trauma evaluation may be impacted by injury severity. Objective: To explore patterns in utilization of chest and abdominopelvic CT among trauma-related emergency department (ED) visits across the United States. Methods: This retrospective study used national commercial claims information extracted from the IBM MarketScan Commercial Database. Trauma-related ED encounters were identified from the 2011 to 2018 MarketScan files and classified using the Injury Severity Score (minor, intermediate, or major injuries) based on International Classification of Diseases codes. ED encounters were also assessed for chest CT, abdominopelvic CT, and single-encounter thoracoabdominopelvic CT examinations. Utilization per 1000 trauma-related ED encounters was determined. Multivariable Poisson regression models were used to determine incidence rate ratios (IRRs) as a measure of temporal changes in utilization. Results: From 2011 to 2018, 8,369,092 trauma-related ED encounters were identified (5,685,295 for minor, 2,624,944 for intermediate, and 58,853 for major injuries). Utilization of chest CT per 1000 trauma-related ED encounters increased from 4.9 to 13.5 (adjusted IRR, 1.15 per year) [2.2 to 7.7 (1.17) for minor, 8.5 to 21.5 (1.16) for intermediate injuries, and 117.8 to 200.1 (1.08) for major injuries]. Utilization of abdominopelvic CT per 1000 trauma-related ED encounters increased from 7.5 to 16.4 (1.12) [4.8 to 12.2 (1.13) for minor, 10.6 to 21.7 (1.13) for intermediate, and 134.8 to 192.6 (1.07) for major injuries]. Utilization of single-encounter thoracoabdominopelvic CT per 1000 trauma-related ED encounters increased from 3.4 to 8.9 (1.16) [1.1 to 4.6 (1.18) for minor, from 6.4 to 16.4 (1.16) for intermediate, and 99.6 to 179.9 (1.08) for major injuries]. Conclusions: National utilization of chest and abdominopelvic CT for trauma-related ED encounters increased in commercially insured patients from 2011 to 2018, particularly for single-encounter thoracabdominopelvic CT examinations and for minor injuries. Clinical Impact: Given concerns of increased cost and incidental findings detection, further investigation is warranted to explore the potential benefit of single-encounter thoracabdominopelvic CT examinations in patients with minor injuries, as well as strategies to optimize order appropriateness.

Increased vertebral body area, disc and facet joint degeneration throughout the lumbar spine in patients with lumbosacral transitional vertebrae.

Lumbosacral transitional vertebrae (LSTV), developmental spinal canal stenosis, lumbar disc and facet joint degeneration are all common lumbar spine conditions. This study explores the relationship between these entities. Five hundred and five patients (254 females, 251 males), mean age 57 ± 13 years, who underwent abdominopelvic CT examinations were studied. Vertebral body cross-sectional area (CSA), spinal canal CSA, width and depth were measured from L1 to L5. The presence of LSTV was documented and the severity of disc/facet joint degeneration graded. LSTV was present in 155 (31%) of 505 patients, being twice as common in males than in females. After controlling for age, height and weight, vertebral body CSAs from L1 to L5 in male LSTV patients were, on average, 9.8% larger than those in male non-LSTV patients (p < 0.0001 for all) while vertebral body areas at L3 and L4 were 4.5% larger in female LSTV patients than in non-LSTV female patients. Disc degeneration from L2/3 to L5/S1 and facet joint degeneration from L2/3 to L4/5 were more severe in LSTV patients. LSTV Castellvi Type II patients appear to be most prone to disc and facet degeneration. LSTV patients, and particularly male patients, have an increased vertebral body CSA compared to non-LSTV patients throughout the lumbar spine. LSTV patients also have more severe disc and facet joint degeneration. The increase in vertebral body area may be contributing to the increased lumbar and facet joint degeneration seen in LSTV patients. • LSTV patients have increased vertebral body cross-sectional area throughout their lumbar spine compared to non-LSTV patients. This vertebral body area increase was more pronounced in male patients and also apparent in younger patients with LSTV. • LSTV patients have increased disc and facet joint degeneration affecting most of the lumbar spine than non-LSTV patients. • Increased vertebral body area may contribute to the increased lumbar disc and facet joint degeneration seen in LSTV patients.

Technical note: Advancing size-specific dose estimates in CT examinations: Dose estimates at longitudinal positions of scans.

American Association of Physicists in Medicine (AAPM) (Report 204) introduced the size-specific dose estimate (SSDE) for the average dose to the center of a fixed-mA scan. International standards establish a method that CT manufacturers and radiation dose index monitoring software may use to calculate SSDE(z) at longitudinal positions of scans with fixed mA or tube current modulation, and its scan range average . We sought to test how accurate SSDE(z) is in tracking the average dose to the transverse slab of an axial image slice (Dslice ), evaluated with Monte Carlo calculation, in the chest and abdominopelvic examinations. We retrospectively identified 65 consecutive adult patients undergoing whole-body CT for transcatheter aortic valve implantation planning. Examination parameters (kV, mA, CTDIvol ) were extracted from the DICOM headers. Patient water equivalent diameter DW (z) was calculated at each image slice, excluding the patient table. A previously validated Monte Carlo simulation (Geant4) program was used to evaluate Dslice from the chest and abdominopelvic examinations. Alternatively, SSDE(z) was calculated at each slice. The results of the two methods were compared with descriptive statistical outcomes (R, version 4.0.2). In chest and abdominopelvic CT examinations, Dslice largely changed with anatomic location and uniformly fell off toward scan range edges. Scan range averages and were consistent within 2.5%-3.1% (median) and 6.3%-10.4% (maximum) in two examinations. On individual image slices, SSDE(z) could be lower or higher than Dslice , with deviation ranging from -18.3% to 85% in two edges (2 × 5cm) of scan range and from -35.2% to 18.7% in the remaining central region of the scan. This study provides critical inputs for quality assurance programs. is useful to track the average dose of all image slices, but further development may be useful for tracking patient dose at the level of individual image slices, especially near a scan range edge.

"Perifollicular rim sign" in an enlarged ovary-an additional non-contrast CT finding in ovarian torsion.

To look for the presence of "perifollicular rim sign" on non-contrast CT in surgically proven cases of ovarian or adnexal torsion. A retrospective analysis of abdominopelvic non-contrast CT examinations in surgically proven cases of ovarian or adnexal torsion was conducted seeking the presence of "perifollicular rim sign" in torsed ovaries. "Perifollicular rim sign" was defined as a complete ring of perifollicular hyperdensity around ovarian follicles with an attenuation value of > 50 HU and thickness > 1-2mm. A positive sign was equated to the presence of perifollicular hemorrhage. Pre-operative non-contrast CT was available in 7 out of the 39 ovarian or adnexal torsions included in our study. "Perifollicular rim sign" was present in 5 out of the 7 ovarian torsions on pre-operative non-contrast CT. MRI correlation was available in one patient. Ovarian enlargement (>4cm) was present in all 7 cases. In an appropriate clinical setting, presence of "perifollicular rim sign" in an enlarged ovary on non-contrast CT examination can be considered a useful additional sign for ovarian torsion.

Establishment of Local Diagnostic Reference Levels of Pediatric Abdominopelvic and Chest CT Examinations Based on the Body Weight and Size in Korea.

ObjectiveThe purposes of this study were to analyze the radiation doses for pediatric abdominopelvic and chest CT examinations from university hospitals in Korea and to establish the local diagnostic reference levels (DRLs) based on the body weight and size.Materials and MethodsAt seven university hospitals in Korea, 2494 CT examinations of patients aged 15 years or younger (1625 abdominopelvic and 869 chest CT examinations) between January and December 2017 were analyzed in this study. CT scans were transferred to commercial automated dose management software for the analysis after being de-identified. DRLs were calculated after grouping the patients according to the body weight and effective diameter. DRLs were set at the 75th percentile of the distribution of each institution's typical values.ResultsFor body weights of 5, 15, 30, 50, and 80 kg, DRLs (volume CT dose index [CTDIvol]) were 1.4, 2.2, 2.7, 4.0, and 4.7 mGy, respectively, for abdominopelvic CT and 1.2, 1.5, 2.3, 3.7, and 5.8 mGy, respectively, for chest CT. For effective diameters of < 13 cm, 14–16 cm, 17–20 cm, 21–24 cm, and > 24 cm, DRLs (size-specific dose estimates [SSDE]) were 4.1, 5.0, 5.7, 7.1, and 7.2 mGy, respectively, for abdominopelvic CT and 2.8, 4.6, 4.3, 5.3, and 7.5 mGy, respectively, for chest CT. SSDE was greater than CTDIvol in all age groups. Overall, the local DRL was lower than DRLs in previously conducted dose surveys and other countries.ConclusionOur study set local DRLs in pediatric abdominopelvic and chest CT examinations for the body weight and size. Further research involving more facilities and CT examinations is required to develop national DRLs and update the current DRLs.

Expanding the Concept of Diagnostic Reference Levels to Noise and Dose Reference Levels in CT.

OBJECTIVE. Diagnostic reference levels were developed as guidance for radiation dose in medical imaging and, by inference, diagnostic quality. The objective of this work was to expand the concept of diagnostic reference levels to explicitly include noise of CT examinations to simultaneously target both dose and quality through corresponding reference values. MATERIALS AND METHODS. The study consisted of 2851 adult CT examinations performed with scanners from two manufacturers and two clinical protocols: abdominopelvic CT with IV contrast administration and chest CT without IV contrast administration. An institutional informatics system was used to automatically extract protocol type, patient diameter, volume CT dose index, and noise magnitude from images. The data were divided into five reference patient size ranges. Noise reference level, noise reference range, dose reference level, and dose reference range were defined for each size range. RESULTS. The data exhibited strong dependence between dose and patient size, weak dependence between noise and patient size, and different trends for different manufacturers with differing strategies for tube current modulation. The results suggest size-based reference intervals and levels for noise and dose (e.g., noise reference level and noise reference range of 11.5-12.9 HU and 11.0-14.0 HU for chest CT and 10.1-12.1 HU and 9.4-13.7 HU for abdominopelvic CT examinations) that can be targeted to improve clinical performance consistency. CONCLUSION. New reference levels and ranges, which simultaneously consider image noise and radiation dose information across wide patient populations, were defined and determined for two clinical protocols. The methods of new quantitative constraints may provide unique and useful information about the goal of managing the variability of image quality and dose in clinical CT examinations.

Comparison of Positive Oral Contrast Agents for Abdominopelvic CT.

OBJECTIVE. The objective of our study was to compare the quality of bowel opacification from three different positive oral contrast agents-barium sulfate, diatrizoate, and iohexol-at abdominopelvic CT. MATERIALS AND METHODS. Abdominopelvic CT examinations with three different oral contrast agents (each contrast agent: n = 300 patients) of 900 patients were retrospectively evaluated by two independent readers. For four segments of the gastrointestinal tract (i.e., the stomach, jejunum, ileum, and colon), readers recorded qualitative data (grade of nonuniform lumen opacification, types of inhomogeneous opacifications, presence of artifacts, and distribution of contrast agent) and quantitative data (CT attenuation of lumen [in Hounsfield units]). The results were compared among the three contrast agents using the Mann-Whitney U test and repeated-measures ANOVA with a post hoc Bonferroni correction. RESULTS. Fewer artifacts were detected with iohexol (4.3%) as the oral contrast agent than with diatrizoate (13.0%) and barium sulfate (14.3%) (each, p < 0.05). Barium showed a greater frequency of bowel lumen heterogeneity (388/831 segments, 47%) than iohexol (155/679, 23%) and diatrizoate (185/763, 24% segments) (p < 0.001). Barium showed higher CT attenuation than iohexol and diatrizoate in the stomach but lower CT attenuation in the ileum (each, p < 0.05). CONCLUSION. The frequency of inhomogeneous bowel opacification was lower for iohexol than for diatrizoate or barium sulfate. Barium showed the highest frequency of bowel lumen heterogeneity. The iodinated agents showed greater increases in mean CT attenuation from the proximal bowel segments to the distal bowel segments than barium sulfate.

The effective and collective dose to patients undergoing abdominopelvic and trunk computed tomography examinations: A Belgian multicentre study

ObjectivesThis study aims to evaluate the radiation exposure to patients undergoing an abdominopelvic or a chest and abdominopelvic (trunk) CT examination and to assess compliance to imaging referral guidelines. MethodsTo this end, 357 standard abdominopelvic and trunk CT scans were collected from 8 Belgian institutions in 2011 and 2015. Effective dose (E) and collective dose were calculated using CT dose descriptors (CTDIvol and DLP), which were obtained from dose reports generated by the CT scanner. Subsequently, these CT requests were compared against the national referral guidelines to assess compliance. Population estimates for dose and compliance were obtained using multilevel linear regression and generalized estimating equation models. ResultsBetween 2011 and 2015, a significant decrease of 28% in CTDIvol and DLP was found for abdominopelvic CT. The corresponding E decreased by 27%, and the collective dose by 23%. For trunk CT, a non-significant decrease of 6% was found in CTDIvol and a significant decrease of 14% in both DLP and E. However, the collective dose of trunk examinations increased by 39%. In 2011, 24% of the abdominopelvic examinations were not compliant with the guidelines, whereas this percentage dropped to 17% in 2015. Non-justified examinations accounted for 8% and 12% of all trunk CT scans in 2011 and 2015, respectively. ConclusionBetween 2011 and 2015, there was a decrease in dose for patients undergoing abdominopelvic or trunk CT in Belgium. However, a fraction of the estimated doses are linked to unnecessary CT examinations, which should be avoided.

Opportunistic Measurement of Skeletal Muscle Size and Muscle Attenuation on Computed Tomography Predicts 1-Year Mortality in Medicare Patients

Opportunistic assessment of sarcopenia on CT examinations is becoming increasingly common. This study aimed to determine relationships between CT-measured skeletal muscle size and attenuation with 1-year risk of mortality in older adults enrolled in a Medicare Shared Savings Program (MSSP). Relationships between skeletal muscle metrics and all-cause mortality were determined in 436 participants (52% women, mean age 75 years) who had abdominopelvic CT examinations. On CT images, skeletal muscles were segmented at the level of L3 using two methods: (a) all muscles with a threshold of -29 to +150 Hounsfield units (HU), using a dedicated segmentation software, (b) left psoas muscle using a free-hand region of interest tool on a clinical workstation. Muscle cross-sectional area (CSA) and muscle attenuation were measured. Cox regression models were fit to determine the associations between muscle metrics and mortality, adjusting for age, sex, race, smoking status, cancer diagnosis, and Charlson comorbidity index. Within 1 year of follow-up, 20.6% (90/436) participants died. In the fully-adjusted model, higher muscle index and muscle attenuation were associated with lower risk of mortality. A one-unit standard deviation (SD) increase was associated with a HR = 0.69 (95% CI = 0.49, 0.96; p = .03) for total muscle index, HR = 0.67 (95% CI = 0.49, 0.90; p < .01) for psoas muscle index, HR = 0.54 (95% CI = 0.40, 0.74; p < .01) for total muscle attenuation, and HR = 0.79 (95% CI = 0.66, 0.95; p = .01) for psoas muscle attenuation. In older adults, higher skeletal muscle index and muscle attenuation on abdominopelvic CT examinations were associated with better survival, after adjusting for multiple risk factors.

Comparing Dose-Length Product-Based and Monte Carlo Simulation Organ-Based Calculations of Effective Dose in 16- and 64-MDCT Examinations Using Automatic Tube Current Modulation.

The purpose of this study is to compare dose-length product (DLP)-based calculation of effective dose (EDDLP) with Monte Carlo simulation organ-based calculation of effective dose (EDMCO) in 16- and 64-MDCT examinations, with the use of clinical examinations with automatic tube current modulation. Dose data were obtained from 50 consecutive unenhanced head CT examinations, unenhanced chest CT examinations, and unenhanced and contrast-enhanced abdominopelvic CT examinations performed using 16- and 64-MDCT scanners, as well as from 50 pulmonary CT angiography (CTA) examinations performed using a 64-MDCT scanner and 31 pulmonary CTA examinations performed using a 16-MDCT scanner. The EDMCO and the mean patient effective diameter were calculated using commercially available software. The EDDLP was also calculated. Both the mean difference and percentage difference between EDDLP and EDMCO were calculated, and they were statistically compared according to patient sex, type of examination performed, and type of scanner used. EDDLP significantly underestimated the EDMCO by 0.3 mSv (19%) for men who underwent unenhanced head CT, 0.5 mSv (29%) for women who underwent unenhanced head CT, 0.9-1.4 mSv (9-13%) for men who underwent chest CT, and 4.7-4.8 mSv (39%) for women who underwent chest CT (p < 0.001). The EDDLP overestimated the EDMCO by 1.9-2.0 mSv (12-14%) for men who underwent abdominopelvic CT (p < 0.001), with no significant difference noted for women who underwent abdominopelvic CT's. No significant difference was noted in the percentage difference in ED between the 16- and 64-MDCT scanners (p ≥ 0.13). EDDLP underestimates EDMCO, the reference standard for dose calculation, by 19-39% in unenhanced head CT examinations and, among women, in chest CT examinations. EDDLP deviates from EDMCO by less than 15% for chest CT examinations of men and for abdominopelvic CT. These differences can be attributed to variable patient body habitus, automatic tube current modulation, and sex-neutral k-coefficients, and they should be considered when calculating ED, particularly in women.

Comparison of Radiation Dose and Image Quality of Abdominopelvic CT Using Iterative (AIDR 3D) and Conventional Reconstructions

The purpose of this study is to compare radiation dose and image quality of abdominopelvic CT studies reconstructed with iterative and conventional techniques. This retrospective study enrolled 99 patients who underwent abdominopelvic CT examinations with the portal venous phase images reconstructed with both filtered back projection and Adaptive Iterative Dose Reduction 3D (AIDR 3D) at different time points. Subjective assessment of image quality was performed by two radiologists who scored axial images for overall quality, sharpness, noise, and acceptability in a blinded fashion. The SD of the mean attenuation of the liver, aorta, and paraspinal muscle (as a measurement of image noise) and contrast-to-noise and signal-to-noise ratios for liver and aorta were used as objective parameters of image quality. Radiation dose parameters included CT dose index volume (CTDIvol), dose-length product, effective dose (ED), and size-specific dose estimate (SSDE). Results were compared for different body mass index (BMI; weight in kilograms divided by the square of height in meters) categories. Paired t test and McNemar paired tests for noninferiority were used, with p < 0.05 considered statistically significant. We obtained a 62.5% mean reduction in CTDIvol, a 58% mean reduction in ED, and a 63% mean reduction in SSDE when AIDR 3D was used (p < 0.001). Subjective parameters of image quality were considered noninferior for AIDR 3D studies compared with filtered back projection (p < 0.001), except for the sharpness of images of patients with BMI 20-24.9. Variable results were found regarding objective assessment of image quality. AIDR 3D allowed a significant reduction in radiation dose of abdominopelvic CT examinations without a loss of image quality in general.

Unindicated multiphase CT scans in non-traumatic abdominal emergencies for women of reproductive age: a significant source of unnecessary exposure.

To determine the frequency of unindicated CT phases and the resultant excess of absorbed radiation doses to the uterus and ovaries in women of reproductive age who have undergone CT for non-traumatic abdomino-pelvic emergencies. We reviewed all abdomino-pelvic CT examinations in women of reproductive age (40years or less), between 1 June 2012 and 31 January 2015. We evaluated the appropriateness of each CT phase on the basis of clinical indications, according to ACR appropriateness criteria and evidence-based data from the literature. The doses to uterus and ovaries for each phase were calculated with the CTEXPO software, taking into consideration the size-specific dose estimate (SSDE) after measuring the size of every single patient. The final cohort was composed of 76 female patients with an average age of 30 (from 19 to 40 years). In total, 197 CT phases were performed with an average of 2.6 phases per patient. Out of these, 93 (47%) were unindicated with an average of 1.2 inappropriate phases per patient. Unindicated scans were most frequent for appendicitis and unlocalized abdominal pain. The excesses of mean radiation doses to the uterus and ovaries due to unindicated phases were, respectively, of 38 and 33mSv per patient. In our experience, unindicated additional CT phases were numerous with a significant excess radiation dose without an associated clinical benefit. This excess of radiation could have been avoided by widespread adoption of the ACR appropriateness criteria and evidence-based data from the literature.

Radiation risk index for pediatric CT: a patient-derived metric

There is a benefit in characterizing radiation-induced cancer risk in pediatric chest and abdominopelvic CT: a singular metric that represents the whole-body radiation burden while also accounting for age, gender and organ sensitivity. To compute an index of radiation risk for pediatric chest and abdominopelvic CT. Using a protocol approved by our institutional review board, 42 pediatric patients (age: 0-16years, weight: 2-80kg) were modeled into virtual whole-body anatomical models. Organ doses were estimated for clinical chest and abdominopelvic CT examinations of the patients using validated Monte Carlo simulations of two major scanner models. Using age-, size- and gender-specific organ risk coefficients, the values were converted to normalized effective dose (by dose length product) (denoted as the k factor) and a normalized risk index (denoted as the q factor). An analysis was performed to determine how these factors are correlated with patient age and size for both males and females to provide a strategy to better characterize individualized risk. The k factor was found to be exponentially correlated with the average patient diameter. For both genders, the q factor also exhibited an exponential relationship with both the average patient diameter and with patient age. For both factors, the differences between the scanner models were less than 8%. The study defines a whole-body radiation risk index for chest and abdominopelvic CT imaging, that incorporates individual estimated organ dose values, organ radiation sensitivity, patient size, exposure age and patient gender. This indexing metrology enables the assessment and potential improvement of chest and abdominopelvic CT performance through surveillance of practice dose profiles across patients and may afford improved informed communication.

Systematic radiation dose optimization of abdominal dual-energy CT on a second-generation dual-source CT scanner: assessment of the accuracy of iodine uptake measurement and image quality in an in vitro and in vivo investigations

To assess the accuracy of iodine quantification in a phantom study at different radiation dose levels with dual-energy dual-source CT and to evaluate image quality and radiation doses in patients undergoing a single-energy and two dual-energy abdominal CT protocols. In a phantom study, the accuracy of iodine quantification (4.5-23.5mgI/mL) was evaluated using the manufacturer-recommended and three dose-optimized dual-energy protocols. In a patient study, 75 abdomino-pelvic CT examinations were acquired as follows: 25 CT scans with the manufacturer-recommended dual-energy protocol (protocol A); 25 CT scans with a dose-optimized dual-energy protocol (protocol B); and 25 CT scans with a single-energy CT protocol (protocol C). CTDIvol and objective noise were measured. Five readers scored each scan according to six subjective image quality parameters (noise, contrast, artifacts, visibility of small structures, sharpness, overall diagnostic confidence). In the phantom study, differences between the real and measured iodine concentrations ranged from -8.8% to 17.0% for the manufacturer-recommended protocol and from -1.6% to 20.5% for three dose-optimized protocols. In the patient study, the CTDIvol of protocol A, B, and C were 12.5±1.9, 7.5±1.2, and 6.5±1.7mGycm, respectively (p<0.001), and the average image noise values were 6.6±1.2, 7.8±1.4, and 9.6±2.2HU, respectively (p<0.001). No significant differences in the six subjective image quality parameters were observed between the dose-optimized dual-energy and the single-energy protocol. A dose reduction of 41% is feasible for the manufacturer-recommended, abdominal dual-energy CT protocol, as it maintained the accuracy of iodine measurements and subjective image quality compared to a single-energy protocol.

“Concordance” Revisited: A Multispecialty Appraisal of “Concordant” Preliminary Abdominopelvic CT Reports

PurposeTo determine whether resident abdominopelvic CT reports considered prospectively concordant with the final interpretation are also considered concordant by other blinded specialists and abdominal radiologists. MethodsIn this institutional review board–approved retrospective cohort study, 119 randomly selected urgent abdominopelvic CT examinations with a resident preliminary report deemed prospectively “concordant” by the signing faculty were identified. Nine blinded specialists from Emergency Medicine, Internal Medicine, and Abdominal Radiology reviewed the preliminary and final reports and scored the preliminary report with respect to urgent findings as follows: 1.) concordant; 2.) discordant with minor differences; 3.) discordant with major differences that do not alter patient management; or 4.) discordant with major differences that do alter patient management. Predicted management resulting from scores of 4 was recorded. Consensus was defined as majority agreement within a specialty. Consensus major discrepancy rates (ie, scores 3 or 4) were compared to the original major discrepancy rate of 0% (0/119) using the McNemar test. ResultsConsensus scores of 4 were assigned in 18% (21/119, P < .001, Emergency Medicine), 5% (6/119, P = .03, Internal Medicine), and 13% (16/119, P < .001, Abdominal Radiology) of examinations. Consensus scores of 3 or 4 were assigned in 31% (37/119, P < .001, Emergency Medicine), 14% (17/119, P < .001, Internal Medicine), and 18% (22/119, P < .001, Abdominal Radiology). Predicted management alterations included hospital status (0-4%), medical therapy (1%-4%), imaging (1%-10%), subspecialty consultation (3%-13%), nonsurgical procedure (3%), operation (1%-3%), and other (0-3%). ConclusionsThe historical low major discrepancy rate for urgent findings between resident and faculty radiologists is likely underreported.

The role of Size-Specific Dose Estimate (SSDE) in patient-specific organ dose and cancer risk estimation in paediatric chest and abdominopelvic CT examinations.

To develop a clinically applicable method to estimate patient-specific organ and blood doses and lifetime attributable risks (LAR) from paediatric torso CT examinations. Individualized voxel models were created from full-body CT data of 10 paediatric patients (2-18 years). Patient-specific dose distributions of chest and abdominopelvic CT scans were simulated using Monte Carlo methods. Blood dose was calculated as a weighted sum of simulated organ doses. LAR of cancer incidence and mortality were estimated, according to BEIR-VII. A second simulation and blood dose calculation was performed using only the thoracic and abdominopelvic region of the original voxel models. For each simulation, the size-specific dose estimate (SSDE) was calculated. SSDE showed a significant strong linear correlation with organ dose (r > 0.8) and blood dose (r > 0.9) and LAR (r > 0.9). No significant differences were found between blood dose calculations with the full-body voxel models and the thoracic or abdominopelvic models. Even though clinical CT images mostly do not cover the whole body of the patient, they can be used as a voxel model for blood dose calculation. In addition, SSDE can estimate patient-specific organ and blood doses and LAR in paediatric torso CT examinations. • Blood dose can be simulated using the patient's clinical CT images. • SSDE estimates patient-specific organ/blood dose and LAR in paediatric CAP CT-examinations. • SSDE makes on-the-spot dose and LAR estimations possible in routine clinical practice.

Radiation Dose Reduction in Pediatric Body CT Using Iterative Reconstruction and a Novel Image-Based Denoising Method.

The objective of this study was to evaluate the radiation dose reduction potential of a novel image-based denoising technique in pediatric abdominopelvic and chest CT examinations and compare it with a commercial iterative reconstruction method. Data were retrospectively collected from 50 (25 abdominopelvic and 25 chest) clinically indicated pediatric CT examinations. For each examination, a validated noise-insertion tool was used to simulate half-dose data, which were reconstructed using filtered back-projection (FBP) and sinogram-affirmed iterative reconstruction (SAFIRE) methods. A newly developed denoising technique, adaptive nonlocal means (aNLM), was also applied. For each of the 50 patients, three pediatric radiologists evaluated four datasets: full dose plus FBP, half dose plus FBP, half dose plus SAFIRE, and half dose plus aNLM. For each examination, the order of preference for the four datasets was ranked. The organ-specific diagnosis and diagnostic confidence for five primary organs were recorded. The mean (± SD) volume CT dose index for the full-dose scan was 5.3 ± 2.1 mGy for abdominopelvic examinations and 2.4 ± 1.1 mGy for chest examinations. For abdominopelvic examinations, there was no statistically significant difference between the half dose plus aNLM dataset and the full dose plus FBP dataset (3.6 ± 1.0 vs 3.6 ± 0.9, respectively; p = 0.52), and aNLM performed better than SAFIRE. For chest examinations, there was no statistically significant difference between the half dose plus SAFIRE and the full dose plus FBP (4.1 ± 0.6 vs 4.2 ± 0.6, respectively; p = 0.67), and SAFIRE performed better than aNLM. For all organs, there was more than 85% agreement in organ-specific diagnosis among the three half-dose configurations and the full dose plus FBP configuration. Although a novel image-based denoising technique performed better than a commercial iterative reconstruction method in pediatric abdominopelvic CT examinations, it performed worse in pediatric chest CT examinations. A 50% dose reduction can be achieved while maintaining diagnostic quality.

Automated Technique to Measure Noise in Clinical CT Examinations.

The purpose of this study was to develop and validate an automated method to measure noise in clinical CT examinations. An automated algorithm was developed to measure noise in CT images. To assess its validity, the global noise level was compared with image noise measured using an image subtraction technique in an anthropomorphic phantom. The global noise level was further compared with image noise values from clinical patient CT images obtained by an observer study. Finally, the clinical utility of the global noise level was shown by assessing variability of image noise across scanner models for abdominopelvic CT examinations performed in 2358 patients. The global noise level agreed well with the phantom-based and clinical image-based noise measurements, with an average difference of 3.4% and 4.7% from each of these measures, respectively. No significant difference was detected between the global noise level and the validation dataset in either case. It further indicated differences across scanners, with the median global noise level varying significantly between different scanner models (15-35%). The global noise level provides an accurate, robust, and automated method to measure CT noise in clinical examinations for quality assurance programs. The significant difference in noise across scanner models indicates the unexploited potential to efficiently assess and subsequently improve protocol consistency. Combined with other automated characterization of imaging performance (e.g., dose monitoring), the global noise level may offer a promising platform for the standardization and optimization of CT protocols.