CT-Based Evaluation of the Shape of the Diaphragm Using 3D Slicer.

The diaphragm is the main inspiratory muscle and separates the thorax and the abdomen. In COPD, the evaluation of the diaphragm shape is clinically important, especially in the case of hyperinflation. However, delineating the diaphragm remains a challenge as it cannot be seen entirely on CT scans. Therefore, the lungs, ribs, sternum, and lumbar vertebrae are used as surrogate landmarks to delineate the diaphragm. We herein describe a CT-based method for evaluating the shape of the diaphragm using 3D Slicer-a free software that allows delineation of the diaphragm landmarks-in ten COPD patients. Using the segmentation performed with 3D Slicer, the diaphragm shape was reconstructed with open-source Free Pascal Compiler. From this graduated model, the length of the muscle fibers, the radius of curvature, and the area of the diaphragm-the main determinants of its function-can be measured. Inter- and intra-user variabilities were evaluated with Bland and Altman plots and linear mixed models. Except for the coronal length (p = 0.049), there were not statistically significant inter- or intra-user differences (p values ranging from 0.326 to 0.910) suggesting that this method is reproducible and repeatable. In conclusion, 3D Slicer can be applied to CT scans for determining the shape of the diaphragm in COPD patients.

Fleischner Society: Glossary of Terms for Thoracic Imaging.

Members of the Fleischner Society have compiled a glossary of terms for thoracic imaging that replaces previous glossaries published in 1984, 1996, and 2008, respectively. The impetus to update the previous version arose from multiple considerations. These include an awareness that new terms and concepts have emerged, others have become obsolete, and the usage of some terms has either changed or become inconsistent to a degree that warranted a new definition. This latest glossary is focused on terms of clinical importance and on those whose meaning may be perceived as vague or ambiguous. As with previous versions, the aim of the present glossary is to establish standardization of terminology for thoracic radiology and, thereby, to facilitate communications between radiologists and clinicians. Moreover, the present glossary aims to contribute to a more stringent use of terminology, increasingly required for structured reporting and accurate searches in large databases. Compared with the previous version, the number of images (chest radiography and CT) in the current version has substantially increased. The authors hope that this will enhance its educational and practical value. All definitions and images are hyperlinked throughout the text. Click on each figure callout to view corresponding image. © RSNA, 2024 Supplemental material is available for this article. See also the editorials by Bhalla and Powell in this issue.

Cryobiopsy and dye marking guided by electromagnetic navigation bronchoscopy before resection of pulmonary nodule.

BACKGROUND: Our aims were to explore the feasibility, safety, and efficacy of peroperative transbronchial lung cryobiopsy (TBLC) guided by electromagnetic navigation bronchoscopy (ENB) and ENB-guided methylene blue marking of presumably non-palpable pulmonary nodules, and to assess its impact on video-assisted thoracoscopic surgery (VATS) and postoperative lung function. METHODS: This approach was applied to 16 consecutive patients (Group A, mean age 64 years) who were compared retrospectively to a historical group of 49 patients (Group B, mean age 62 years) with similar nodules resected without guidance. The usefulness of dye marking was graded. The success rates of both ENB-guided TBLC and nodule localization through dye marking were computed. The type of resection, volume of resected parenchyma, duration of procedures, and postoperative lung function were compared between groups. Unpaired t-test, chi-square test, unpaired Wilcoxon test, and exact Fisher test were used when appropriate. RESULTS: Malignancy was pathologically proven in all patients. TBLC revealed malignancy in 9 patients in Group A. The success rate of ENB-guided dye marking was 94%. Lobectomy was less frequently performed in Group A than in Group B (p = 0.022). Forced expiratory volume in 1 s and total lung capacity were significantly less reduced in Group A than in Group B (p = 0.006 and p = 0.019, respectively). Combined procedure was longer than surgery alone (p<0.001), but its surgical part was shorter than VATS without guidance (p < 0.001). CONCLUSION: Peroperative ENB-guided TBLC with methylene blue marking of non-palpable lung nodules is feasible. A sparing lung parenchyma procedure could be achieved thanks to the ENB-guided dye marking before VATS.

Trans-bronchial lung cryobiopsy in patients at high-risk of complications.

BACKGROUND: The surgical lung biopsy (SLB) is the recommended sampling technique when the pathological analysis of the lung is required in the work-up of an interstitial lung disease (ILD) but trans-bronchial lung cryobiopsy (TBLC) is increasingly recognized as an alternative approach. As TBLCs have lower mortality and morbidity risks than SLB, this study aimed to investigate the safety of TBLCs in patients at higher risk of complications and for whom SLB was not considered as an alternative. METHOD: This prospective study was conducted in two hospitals in which TBLCs were performed in patients with body mass index (BMI) > 35, and/or older than 75 years, and/or with severely impaired lung function (FVC < 50% or DLCO < 30%), and/or systolic pulmonary artery pressure > 45 mmHg, and/or a clinically significant cardiac disease. Patients with any of these risk factors constituted the high-risk group. Clinical outcomes were compared with those obtained in patients without these risk factors (low-risk group). RESULTS: Ninety-six patients were included between April 2015 and April 2020, respectively 38 and 58 in the high-risk or the low-risk group. No statistically significant difference was observed between both groups in terms of severity and rate of bleeding, pneumothorax, or duration of hospital stay (p value ranging from 0.419 to 0.914). CONCLUSION: This preliminary study on a limited number of patients suggests that TBLC appears safe in those in whom lung biopsy is at high-risk of complications according to their age, BMI, lung impairment, and cardiac comorbidities.

Are referral guidelines for CT examinations addressing all clinical scenarios? A comparison of EURO-2000 Guidelines and ESR iGuide.

OBJECTIVES: To investigate the proportion of clinical scenarios covered by EURO-2000 Guidelines and ESR iGuide, and assess compliance with both guidelines. METHODS: The clinical indication on archived request forms for head, chest, abdomen-pelvis, and spine CT examinations performed in three hospitals in January 2018 was retrospectively matched with EURO-2000 Guidelines and ESR iGuide. For clinical scenarios addressed in the guidelines, the compliance with the guidelines was assessed. Analysis was performed on pooled data from the three centres and further stratified by centre, body region, and prescriber's specialisation. The differences in categorical data distributions between centres, body regions, and prescribers' specialisations were assessed with paired McNemar's χ2 tests. RESULTS: A total of 6,812 requests for 7,217 CT examinations were analysed. Sixty-five percent of clinical situations that lead to prescribing CT examinations were addressed in EURO-2000 Guidelines compared with 81% for ESR iGuide. Proportions of clinical scenarios covered by the guidelines were statistically different between centres and body regions (p < 0.001) and varied according to prescribers' specialisations (p ranging from < 0.001 to 0.531). Both EURO-2000 Guidelines and ESR iGuide encompassed more clinical scenarios in certain body regions, favouring, e.g. spine and head over abdomen and chest. The proportion of "unjustified examinations" was greater according to EURO-2000 Guidelines (46%) than ESR iGuide (23%) (p < 0.001). CONCLUSIONS: Both EURO-2000 Guidelines and ESR iGuide do not address numerous common clinical scenarios. The proportions of scenarios addressed differ according to the centre, body region, and prescribers' specialisation. Any estimation of compliance with referral guidelines is therefore of relative significance. KEY POINTS: • ESR iGuide performs better than earlier EURO-2000 Guidelines for the coverage of all possible clinical scenarios leading to CT referrals. • Differences in coverage of clinical scenarios by both referral guidelines are observed for different body regions and/or prescribers' subspecialties. • As referral guidelines are incomplete, any estimation of justified or unjustified CT requests is of relative significance.

Eosinopenia in COVID-19 Patients: A Retrospective Analysis.

Objectives: The aim of this study was to assess the diagnostic role of eosinophils count in COVID-19 patients. Methods: Retrospective analysis of patients admitted to our hospital with suspicion of COVID-19. Demographic, clinical and laboratory data were collected on admission. Eosinopenia was defined as eosinophils < 100 cells/mm3. The outcomes of this study were the association between eosinophils count on admission and positive real-time reverse transcription polymerase chain reaction (rRT-PCR) test and with suggestive chest computerized tomography (CT) of COVID-19 pneumonia. Results: A total of 174 patients was studied. Of those, 54% had positive rRT-PCR for SARS-CoV-2. A chest CT-scan was performed in 145 patients; 71% showed suggestive findings of COVID-19. Eosinophils on admission had a high predictive accuracy for positive rRT-PCR and suggestive chest CT-scan (area under the receiver operating characteristic-ROC curve, 0.84 (95% CIs 0.78-0.90) and 0.84 (95% CIs 0.77-0.91), respectively). Eosinopenia and high LDH were independent predictors of positive rRT-PCR, whereas eosinopenia, high body mass index and hypertension were predictors for suggestive CT-scan findings. Conclusions: Eosinopenia on admission could predict positive rRT-PCR test or suggestive chest CT-scan for COVID-19. This laboratory finding could help to identify patients at high-risk of COVID-19 in the setting where gold standard diagnostic methods are not available.

Higher Intensity Thromboprophylaxis Regimens and Pulmonary Embolism in Critically Ill Coronavirus Disease 2019 Patients.

OBJECTIVES: To assess the role of thromboprophylaxis regimens on the occurrence of pulmonary embolism in coronavirus disease 2019 patients. DESIGN: Retrospective analysis of prospectively collected data on coronavirus disease 2019 patients, included between March 10, and April 30, 2020. SETTING: ICU of an University Hospital in Belgium. PATIENTS AND INTERVENTIONS: Critically ill adult mechanically ventilated coronavirus disease 2019 patients were eligible if they underwent a CT pulmonary angiography, as part of the routine management in case of persistent hypoxemia or respiratory deterioration. The primary endpoint of this study was the occurrence of pulmonary embolism according to the use of standard thromboprophylaxis (i.e. subcutaneous enoxaparin 4,000 international units once daily) or high regimen thromboprophylaxis (i.e. subcutaneous enoxaparin 4,000 international units bid or therapeutic unfractioned heparin). MEASUREMENTS AND MAIN RESULTS: Of 49 mechanically ventilated coronavirus disease 2019, 40 underwent CT pulmonary angiography after a median of 7 days (4-8 d) since ICU admission and 12 days (9-16 d) days since the onset of symptoms. Thirteen patients (33%) were diagnosed of pulmonary embolism, which was bilateral in six patients and localized in the right lung in seven patients. D-dimers on the day of CT pulmonary angiography had a predictive accuracy of 0.90 (95% CIs: 0.78-1.00) for pulmonary embolism. The use of high-regimen thromboprophylaxis was associated with a lower occurrence of pulmonary embolism (2/18; 11%) than standard regimen (11/22, 50%-odds ratio 0.13 [0.02-0.69]; p = 0.02); this difference remained significant even after adjustment for confounders. Six patients with pulmonary embolism (46%) and 14 patients without pulmonary embolism (52%) died at ICU discharge (odds ratio 0.79 [0.24-3.26]; p = 0.99). CONCLUSIONS: In this study, one third of coronavirus disease 2019 mechanically ventilated patients have a pulmonary embolism visible on CT pulmonary angiography. High regimen thromboprophylaxis may decrease the occurrence of such complication.

Pulmonary hypertension due to left heart disease: diagnostic value of pulmonary artery distensibility.

OBJECTIVES: To evaluate how pulmonary artery (PA) distensibility performs in detecting pulmonary hypertension due to left heart disease (PH-LHD) in comparison with parameters from ungated computed tomography (CT) and echocardiography. METHODS: One hundred patients (79 men, mean age = 63 ± 17 years) with either severe heart failure with reduced ejection fraction (HFrEF), aortic stenosis, or primary mitral regurgitation prospectively underwent right heart catheterization, ungated CT, ECG-gated CT, and echocardiography. During the ECG-gated CT, the right PA distensibility was calculated. In ungated CT, dPA, dPA/AA, the ratio of dPA to the diameter of the vertebra, segmental PA diameter, segmental PA-to-bronchus ratio, and the main PA volume were measured; the egg-and-banana sign was recorded. During echocardiography, the tricuspid regurgitation (TR) gradient was measured. The areas under the ROC curves (AUC) of these signs were computed and compared with DeLong test. Correlation between PA distensibility and PA pressure (PAP) was investigated through Pearson's coefficient. RESULTS: PA distensibility was lower in patients with PH than in those without PH (11.4 vs. 21.2%, p < 0.001) and correlated negatively with mean PAP (r = - 0.72, p < 0.001). Age, PA size, and mean PAP were independent predictors of PA distensibility. PA distensibility < 18% detected PH-LHD with 96% sensitivity and 73% specificity; its AUC was 0.92, larger than that of any other sign at ungated CT and TR gradient (AUC ranging from 0.54 to 0.83, DeLong: p ranging from 0.020 to < 0.001). CONCLUSION: PA distensibility on an ECG-gated CT can detect PH-LHD better than the parameters reflecting PA dilatation in ungated CT or TR gradient in the echocardiography of patients with severe HFrEF, aortic stenosis, or mitral regurgitation. KEY POINTS: • In left heart disease, pulmonary artery distensibility is lower in patients with PH than in those without pulmonary hypertension (11.4 vs. 21.2%, p < 0.001). • In left heart disease, pulmonary artery distensibility detects pulmonary hypertension with an area under the receiver operating curve of 0.92. • In left heart disease, the area under the receiver operating curve of pulmonary artery distensibility for detecting pulmonary hypertension is larger than that of all other signs at ungated CT (p from 0.019 to < 0.001) and tricuspid regurgitation gradient at echocardiography (p = 0.020).

Variabilities in X-ray diagnostic reference levels.

OBJECTIVES: To estimate the variability of X-ray diagnostic reference levels (DRLs) depending on the number of X-ray devices and data per device. METHODS: Dose-area products (DAP) were collected by the national nuclear control agency from the 590 devices installed in 345 medical centers in the country. From 2015 to 2017, the number of chest (postero-anterior (PA) view alone, and both postero-anterior and lateral views (PA/LAT)), abdomen, pelvis, and lumbar spine examinations collected in these centers ranged from 23,000 to 77,000. The impact of the number of devices and DAP data per device on DRLs' variabilities (95th confidence intervals divided by medians) is estimated using a bootstrapping method as a function of the number of devices and DAP per device. RESULTS: The DRLs' variabilities ranged from 30 to 200% depending on the number of devices and DAP data per device but stabilized at 30% when the number of devices was higher than 200 for chest PA and abdomen examinations, 300 for lumbar spine and pelvis examinations, and 400 for chest PA/LAT examinations, regardless of the number of DAP data per device. Extrapolations of our results suggest that thousands of devices are necessary to reduce DRLs' variabilities to 10%. CONCLUSION: DAP-related DRL variabilities are high but only moderately influenced by the number of DAP data per device and of devices provided this number is higher than 200 to 400 devices according to the type of examination. Harmonization of methods of data collection between the authorities of the EU states should be recommended. KEY POINTS: • DAP-related DRLs are not fixed values but ranges of values with at least 30% variability. • DAP-related DRLs strongly depend on the number of devices included when lower than 100. • If the number of devices included exceeds 200 to 400, the DRLs' variabilities do not depend on the number of DAP per device and should not exceed 30%.

Prevalence and frequency of subchondral bone marrow edema in the lumbar facet joints of asymptomatic and symptomatic individuals.

OBJECTIVE: To prospectively compare the prevalence and frequency of subchondral bone marrow edema (BME) in the lumbar facet joints of low back pain patients and healthy subjects. MATERIALS AND METHODS: Lumbar magnetic resonance imaging (MRI) examinations were performed on 55 asymptomatic participants (18 men; age range 21-63; mean 36 ± 12 years; body mass index (BMI) range 16-31; mean 22.6 ± 3.2 kg/m2) and 79 low back pain patients (36 men; age range 18-77; mean 47 ± 14 years; BMI range 18-40; mean 27.8 ± 4.4 kg/m2). In both groups, facet joint subchondral BME signal was evaluated using T2-weighted STIR imaging, and facet joint osteoarthritis was characterized as mild, moderate, and severe. RESULTS: The BME signal was found in seven asymptomatic participants (12.7%) and 28 low back pain patients (35.4%) (P = 0.003). A significant portion of the patients (15.2%) presented more than one BME signal (P = 0.011). By pooling the ten facet joints of all subjects in each group, a significant difference in osteoarthritis grade distribution was observed between the two groups (P < 0.001). When adjusted for low back pain status, age, BMI, Modic type 1, disk herniation, and facet joint osteoarthritis maximal grade, only the latter was significantly associated with the facet joint BME signal (P < 0.001). CONCLUSION: Despite the higher prevalence and frequency of the BME signal in facet joints of low back pain patients compared to that in healthy subjects, the signal was found to be associated with the severity of the patients' osteoarthritis and not with their low back pain status.

Pulmonary hypertension detection by computed tomography pulmonary transit time in heart failure with reduced ejection fraction.

AIMS: To evaluate the relationships between pulmonary transit time (PTT), cardiac function, and pulmonary haemodynamics in patients with heart failure with reduced ejection fraction (HFrEF) and to explore how PTT performs in detecting pulmonary hypertension (PH). METHODS AND RESULTS: In this prospective study, 57 patients with advanced HFrEF [49 men, 51 years ± 8, mean left ventricular (LV) ejection fraction 26% ± 8] underwent echocardiography, right heart catheterization, and cardiac computed tomography (CT). PTT was measured as the time interval between peaks of attenuation in right ventricle (RV) and LV and was compared between patients with or without PH and 15 controls. PTT was significantly longer in HFrEF patients with PH (21 s) than in those without PH (11 s) and controls (8 s) (P < 0.001) but not between patients without PH and controls (P = 0.109). PTT was positively correlated with pulmonary artery wedge pressure (PAWP) (r = 0.74), mean pulmonary artery pressure (r = 0.68), N-terminal pro-B-type natriuretic peptide (r = 0.60), mitral (r = 0.54), and tricuspid (r = 0.37) regurgitation grades, as well as with LV, RV, and left atrial volumes (r from 0.39 to 0.64) (P < 0.01). PTT was negatively correlated with cardiac index (r = -0.63) as well as with LV (r = -0.66) and RV (r = -0.74) ejection fractions. PAWP, cardiac index, mitral regurgitation grade, and RV end-diastolic volume were all independent predictors of PTT. PTT value ≥14 s best-detected PH with 91% sensitivity and 88% specificity (area under the receiver operating characteristic curve: 0.95). CONCLUSION: In patients with HFrEF, PTT correlates with cardiac function and pulmonary haemodynamics, is determined by four independent parameters, and performs well in detecting PH.

Inter-observer agreement in identifying traction bronchiectasis on computed tomography: its improvement with the use of the additional criteria for chronic fibrosing interstitial pneumonia.

PURPOSE: To assess inter-observer variability in identifying traction bronchiectasis on computed tomography (CT) using additional criteria for chronic fibrosing interstitial pneumonia. METHODS: Seven experts categorized CT image set representing 39 patients into three groups on the basis of the presence of traction bronchiectasis, using a three-point scale: 3-definitely/probably yes; 2-possibly yes; and 1-definitely/probably no. This scale served as a reference standard. The image set included cases of chronic fibrosing interstitial pneumonia, non-interstitial lung disease, and difficult-to-determine cases. Forty-eight observers similarly assessed the same image set, first according to the Fleischner Society definition, and second with additional criteria, in which traction bronchiectasis was observed exclusively in chronic fibrosing interstitial pneumonia. The agreement level between the reference standard and each observer's evaluation in each session was calculated using weighted kappa values which were compared between the two sessions using a paired t test. RESULTS: The mean weighted kappa value for all observers was significantly higher in the second reading session (mean 0.75) than in the first reading session (mean 0.62) (p < 0.001). CONCLUSION: Inter-observer agreement in identifying traction bronchiectasis improves when using the additional criteria which specify chronic fibrosing interstitial pneumonia as the underlying disease.

CT diagnostic reference levels: are they appropriately computed?

OBJECTIVES: To estimate the variability of CT diagnostic reference levels (DRLs) according to the methods used for computing collected data. METHODS: Dose-length products (DLP) were collected by our national nuclear control agency from the 250 devices installed in 140 medical centers in the country. In 2015, the number of head, thorax, abdomen, and lumbar spine examinations collected in these centers ranged from approximately 20,000 to 42,000. The impact on DRLs of the number of devices considered, as well as the differences in descriptive statistics (mean vs. median DLP) or methods of pooling DLP data (all devices vs. all patients), was investigated. Variability in DRLs was investigated using a bootstrapping method as a function of the numbers of devices and examinations per device. RESULTS: As expected, DRLs derived from means were higher than those from medians, with substantial differences between device- and patient-related DRLs. Depending on the numbers of devices and DLP data per device, the variability ranged from 10 to 40% but was stabilized at a level of 10-20% if the number of devices was higher than 50 to 60, regardless of the number of DLP data per device. CONCLUSION: Number of devices and of DLP data per device, descriptive statistics, and pooling data influence DRLs. As differences in methods of computing survey data can artificially influence DRLs, harmonization among national authorities should be recommended. KEY POINTS: • Due to CT dose variability, that of DRLs is at least of 10%. • DRLs derived from medians are lower than from means and differ from those obtained by pooling all patient data. • Fifty to 60 devices should be sufficient for estimating national DRLs, regardless of the number of data collected per device.

X-ray examination dose surveys: how accurate are my results?

OBJECTIVES: To determine the variabilities of dose-area-products (DAP) of frequent X-ray examinations collected for comparison with diagnostic reference levels (DRLs). METHODS: DAP values of chest, abdomen, and lumbar spine examinations obtained on devices from two manufacturers were collected in three centers over 1 to 2 years. The variability of the average DAP results defined as the 95% confidence interval in percentage of their median value was calculated for increasing sample sizes, each examination and center. We computed the sample sizes yielding variabilities lower or equal to 25% and 10%. The effect of narrowing patient selection based on body weight was also investigated (ranges of 67-73 Kg, or 60-80 Kg). RESULTS: DAP variabilities ranged from 75 to 170% of the median value when collecting small samples (10 to 20 DAP). To reduce this variability, larger samples are needed, collected over up to 2 years, regardless of the examination and center. A variability ≤ 10% could only be reached for chest X-rays, requiring up to 800 data. For the abdomen and lumbar spine, the lowest achievable variability was 25%, regardless of the body weight selection, requiring up to 400 data. CONCLUSION: Variabilities in DAP collected through small samples of ten data as recommended by authorities are very high, but can be reduced down to 25% (abdomen and lumbar spine) or even 10% (chest) through a substantial increase in sample sizes. Our findings could assist radiologists and regulatory authorities in estimating the reliability of the data obtained when performing X-ray dose surveys. KEY POINTS: • Low but reasonable variabilities cannot be reached with samples sized as recommended by regulatory authorities. Higher numbers of DAP values are required to reduce the variability. • Variabilities of 10% for the chest and 25% for abdomen and lumbar spine examinations are achievable, provided large samples of data are collected over 1 year. • Our results could help radiologists and authorities interpret X-rays dose surveys.

Diagnostic Yield of Combined Pulmonary Cryobiopsies and Electromagnetic Navigation in Small Pulmonary Nodules.

BACKGROUND: An increasing number of pulmonary nodules of unknown nature are detected as a result of screening by CT in high lung cancer risk patients. OBJECTIVES: The purposes of this study were to assess the diagnostic yield of electromagnetic navigation bronchoscopy (ENB) combined with transbronchial lung cryobiopsy (TBLC) and to compare it with standard transbronchial biopsy (TBB) in pulmonary nodules of less than 2 cm in diameter. METHODS: We prospectively included 32 patients (18 men and 14 women, mean age 68 ± 9 years) with nodules of less than 2 cm in diameter and no metastasis at 18FDG PET-CT. The nodule position was determined by ENB, radial endobronchial ultrasonography miniprobe, and fluoroscopy. Eight samples were obtained, six by TBB and two by TBLC. RESULTS: Nodule diameter averaged 16 ± 3 mm. Twenty-five nodules were malignant and 18 were surgically resected. Surgery was avoided in four patients as the biopsies revealed a benign disease. The samples obtained by TBLC were five times larger than those by TBB. The diagnostic yields of TBLC and TBB were 69% and 38%, respectively (p=0.017). Adverse events consisted in 15 mild or moderate bleedings and one pneumothorax. CONCLUSIONS: In the setting of peripheral pulmonary lesions of less than 20 mm in diameter, ENB-combined TBLC is feasible and safe, provides larger samples, and has higher diagnostic yield than TBB.

Variability of CT Airways Measurements in COPD Patients Between Morning and Afternoon: Comparisons to Variability of Spirometric Measurements.

RATIONALE AND OBJECTIVES: Computed tomography (CT) airways measurements can be used as surrogates to spirometric measurements for assessing bronchodilation in a particular patient with chronic obstructive pulmonary disease. Although spirometric measurements show variations within the opening hours of a hospital department, we aimed to compare the variability of CT airways measurements between morning and afternoon in patients with chronic obstructive pulmonary disease to that of spirometric measurements. MATERIALS AND METHODS: Twenty patients had pulmonary function tests and CT around 8 am and 4 pm. Luminal area (LA) and wall thickness (WT) of third and fourth generation airways were measured twice by three readers. The percentage of airway area occupied by the wall (WA%) and the square root of wall area at an internal perimeter of 10 mm (√WAPi10) were calculated. The effects of examination time, reader, and measurement session on CT airways measurements were assessed, and the variability of these measurements was compared to that of spirometric measurements. RESULTS: Variability of LA3rd and LA4th was greater than that of spirometric measurements (P values ranging from <.001 to .033). There was no examination time effect on √WAPi10, WT3rd, LA4th, or WA%4th (P values ranging from .102 to .712). There was a reader effect on all CT airways measurements (P values ranging from <.001 to .028), except in WT3rd (P> .999). There was no effect of measurement session on any CT airway measurement (P values ranging from .535 to >.999). CONCLUSION: As the variability of LA3rd and LA4th is greater than that of spirometric measurements, clinical studies should include cohorts with larger numbers of patients when considering LA than when considering spirometric measurements as end points.

Abdominal Attenuation Values on Virtual and True Unenhanced Images Obtained With Third-Generation Dual-Source Dual-Energy CT.

OBJECTIVE: The purpose of this study is to investigate the magnitude of differences between attenuation values measured on virtual unenhanced images and true unenhanced images obtained using third-generation dual-source dual-energy CT (DECT). SUBJECTS AND METHODS: A total of 83 patients requiring thoracoabdominal CT for cancer workup were included in this prospective study. CT examinations included true unenhanced acquisitions (tube potential, 120 kVp) and arterial and portal phase dual-energy CT (DECT) acquisitions (tube potential, 100 kVp and Sn 150 kVp [where Sn denotes the interposition of a tin filter in the high-energy beam]; tube current-exposure time product, 190 and 95 mAs). Virtual unenhanced images were created using two commercially available DECT postprocessing algorithms, one of which was designed to create liver images (hereafter referred to as VNC1 images) and the other of which was designed to create images of organs containing minor amounts of fat (hereafter referred to as VNC2 images). Attenuation values on the liver, spleen, paraspinal muscles, retroperitoneal fat, renal cortex and medulla, and gallbladder and bladder lumens were measured. RESULTS: The attenuation values of all tissues were significantly different between virtual unenhanced and true unenhanced images (p = < 0.001-0.042), except for the liver and spleen in the portal phase and muscles in both phases. When statistically significant, correlations between these differences and body mass index (weight in kilograms divided by the square of height in meters) depended on the tissue imaged and algorithm used. The percentage of cases in which these differences were 10 HU or greater was 1% for the liver and approximately 5% for the spleen and muscles, regardless of the algorithm and phase, but on VNC1 images it reached approximately 30% for the kidney, 70% for the gallbladder and bladder, and depending on the phase, 40-70% for fat. On VNC2 images, the percentage of cases in which these differences were 20 HU or greater was approximately 90% for fat. CONCLUSION: Abdominal virtual unenhanced images obtained with third-generation dual-source DECT still should not replace true unenhanced images because of substantial differences in attenuation measurements for fluid, fat, and renal tissues.

In Vivo Differentiation of Uric Acid Versus Non-Uric Acid Urinary Calculi With Third-Generation Dual-Source Dual-Energy CT at Reduced Radiation Dose.

OBJECTIVE: The objective of our study was to evaluate in vivo urinary calculus characterization with third-generation dual-source dual-energy CT (DECT) at reduced versus standard radiation dose. SUBJECTS AND METHODS: One hundred fifty-three patients requiring unenhanced CT for suspected or known urolithiasis were prospectively included in our study. They underwent two acquisitions at reduced-dose CT (90 kV and 50 mAsref; Sn150 kV and 31 mAsref, where Sn denotes the interposition of a tin filter in the high-energy beam) and standard-dose CT (90 kV and 50 mAsref; Sn150 kV and 94 mAsref). One radiologist interpreted the reduced-dose examinations before the standard-dose examinations during the same session. Among 103 patients (23 women, 80 men; mean age ± SD, 50 ± 15 years; age range, 18-82 years) with urolithiasis, dedicated DECT software measured the maximal diameter and CT numbers, calculated the DECT number ratio, and labeled with a color code each calculus visualized by the radiologist as uric acid (UA) or non-UA. Volume CT dose index (CTDIvol) and dose-length product (DLP) were recorded. RESULTS: The radiologist visualized 279 calculi on standard-dose CT and 262 on reduced-dose CT; 17 calculi were missed on reduced-dose CT, all of which were ≤ 3 mm. Among the 262 calculi visualized at both doses, the CT number ratio was obtained with the software for 227 calculi and was not different between the doses (p = 0.093). Among these 262 calculi, 197 were labeled at both doses; 194 of the 197 labeled calculi were labeled with the same color code. Among the 65 remaining calculi, 48 and 61 (all ≤ 5 mm) were not labeled at standard-dose and reduced-dose CT (p = 0.005), respectively. At reduced-dose CT, the mean CTDIvol was 2.67 mGy and the mean DLP was 102.2 mGy × cm. CONCLUSION: With third-generation dual-source DECT, a larger proportion of calculi ≤ 5 mm are not characterized as UA or non-UA at a reduced dose.

Radiation protection: Factors influencing compliance to referral guidelines in minor chest trauma.

OBJECTIVES: To test the hypothesis that referral guidelines are not sufficiently known by prescribers and that medico-legal concerns could influence the prescription of radiographs in minor chest trauma. METHODS: We submitted a questionnaire including a typical clinical history and questions on reasons for prescribing radiographs of the ribs in minor chest trauma to 112 prescriptors (33 residents, 18 surgeons, 7 internists, 24 general practitioners and 30 ER physicians). All accepted to participate. Comparisons were performed by Fisher's exact test followed by a post-hoc analysis and by a McNemar test. RESULTS: Fifty-eight percent of prescriptors proposed rib radiographs, most (89%) being unaware of the guidelines. Only 11% of them changed their intention to order radiographs after information on referral guidelines and radiation dose (P=0.057). The mean dose delivered by rib radiographs was 38 times higher than that of a chest X-ray. Legal and medico-legal concerns (requirements from insurance policies and avoidance of lawsuits) were the main reasons for requesting radiographs. CONCLUSION: Unsharpness of guidelines in addition to social and medico-legal issues, rather than medical reasons or the lack of knowledge of the guidelines, strongly influence the prescription of radiographs of the ribs in minor chest trauma. KEY POINTS: • Most prescriptors order radiographs of the ribs in minor chest trauma. • Only few prescriptors are aware of referral guidelines. • Information on guidelines does not change their need for radiographs. • Motivations for ordering radiographs are rather legal than medical, but poor compliance to guidelines could also be explained by their unsharpness. • Radiation dose of rib radiographs was 38 times that of a PA chest radiograph.

CT dose survey in adults: what sample size for what precision?

OBJECTIVES: To determine variability of volume computed tomographic dose index (CTDIvol) and dose-length product (DLP) data, and propose a minimum sample size to achieve an expected precision. METHODS: CTDIvol and DLP values of 19,875 consecutive CT acquisitions of abdomen (7268), thorax (3805), lumbar spine (3161), cervical spine (1515) and head (4106) were collected in two centers. Their variabilities were investigated according to sample size (10 to 1000 acquisitions) and patient body weight categories (no weight selection, 67-73 kg and 60-80 kg). The 95 % confidence interval in percentage of their median (CI95/med) value was calculated for increasing sample sizes. We deduced the sample size that set a 95 % CI lower than 10 % of the median (CI95/med ≤ 10 %). RESULTS: Sample size ensuring CI95/med ≤ 10 %, ranged from 15 to 900 depending on the body region and the dose descriptor considered. In sample sizes recommended by regulatory authorities (i.e., from 10-20 patients), mean CTDIvol and DLP of one sample ranged from 0.50 to 2.00 times its actual value extracted from 2000 samples. CONCLUSIONS: The sampling error in CTDIvol and DLP means is high in dose surveys based on small samples of patients. Sample size should be increased at least tenfold to decrease this variability. KEY POINTS: • Variability of dose descriptors is high regardless of the body region. • Variability of dose descriptors depends on weight selection and the region scanned. • Larger samples would reduce sampling errors of radiation dose data in surveys. • Totally or partially disabling AEC reduces dose variability and increases patient dose. • Median values of dose descriptors depend on the body weight selection.