Unusual Air Crescents on Chest Radiographs.

The air crescent (AC) is a common radiological sign. Even if its commonest aetiology remains pulmonary aspergillosis, various other causes have been described. In this study, we report four rare causes of ACs seen on chest radiographs that haven't been described in the literature. Teaching point: The differential diagnosis of an air crescent sign on chest radiographs includes oesophageal bezoar, interstitial lung emphysema, central bronchial stenosis and perforated emphysematous cholecystitis.

Reject Analysis in Digital Radiography and Computed Tomography: A Belgian Imaging Department Case Study.

Objective: Reject analysis is usually performed in digital radiography (DR) for quality assurance. Data for computed tomography (CT) rejects remains sparse. The aim of this study is to help provide a straightforward benchmark for reject analysis of both DR and CT. Materials and methods: This retrospective observational study included 107,277 DR and 20,659 CT during 18 months in a tertiary care center. Rejected acquisitions were retrieved by Dose Archiving and Communication System (DACS). The DR and CT reject analysis included reject rates, reasons for rejection and supplementary radiation dose associated with these rejects. Results: 8,904 rejected DR and 514 rejected CT were retrieved. The DR reject rate was 8.3% whereas the CT reject rate was 2.5%. The cumulative effective dose (ED) of DR rejects was 377.3 mSv while the cumulative ED of CT rejects was 1267.4 mSv. The major reason for rejects was positioning for both DR (61%) and CT (44%). Conclusion: This study helps constitute a simple reproducible method to analyze both DR and CT rejects simultaneously. Although CT rejects are less often monitored than DR rejects, the radiation dose associated with CT rejects is much higher, which emphasizes the need to systematically monitor both DR and CT rejects. Investigating the reasons and the most frequently rejected examinations gives an opportunity for improvement of imaging techniques in cooperation with technologists.

Audit on Compliance to Guidelines in CT Scanning for Urolithiasis.

Introduction: According to the ALARA principle, CT-imaging procedures should be implemented to optimize radiation doses. The purpose of this study is to determine whether a quality control process has an impact on compliance with procedures. Materials and methods: This retrospective study was conducted in three hospitals, focusing on the selection of the appropriate acquisition protocol and the reduction of acquisition height in abdominal computed tomography (CT) examinations performed to diagnose or rule out urolithiasis. A first audit was conducted to measure the compliance with the procedure. Next, a reminder of the CT-urolithiasis procedure was given to stakeholders. Three months later, a second audit was conducted to measure the impact of the repeat recall information on compliance, and to compare the outcome with an earlier audit conducted five years earlier. Results: We included 517 'urolithiasis CT examinations'. The compliance ranged from 41.67% to 64.8% for the first audit. After the reminder of the urolithiasis procedure, compliance ranged from 50% to 76.10%. This improvement was statistically significant for hospital A and B (p < 0.001 for hospital A, p = 0.013 for hospital B) but not for hospital C (p = 0.405). Despite prior demonstration that improved compliance persisted at one year from an initial audit, our actual data show that this compliance had decreased at year five, confirming the need to repeat compliance audits more frequently, or to monitor it continuously. Conclusion: Surveying compliance to procedures can improve compliance but only for a limited duration. Monitoring compliance more frequently or even continuously is recommended.

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.

Kommerell Aneurysm.

Teaching Point: Kommerell aneurysm is a rare differential diagnosis of mediastinal enlargement on a chest radiograph that requires CT for accurate diagnosis.

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%.

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.

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.

Short- and long-term effects of clinical audits on compliance with procedures in CT scanning.

PURPOSE: To test the hypothesis that quality clinical audits improve compliance with the procedures in computed tomography (CT) scanning. MATERIALS AND METHODS: This retrospective study was conducted in two hospitals, based on 6950 examinations and four procedures, focusing on the acquisition length in lumbar spine CT, the default tube current applied in abdominal un-enhanced CT, the tube potential selection for portal phase abdominal CT and the use of a specific "paediatric brain CT" procedure. The first clinical audit reported compliance with these procedures. After presenting the results to the stakeholders, a second audit was conducted to measure the impact of this information on compliance and was repeated the next year. Comparisons of proportions were performed using the Chi-square Pearson test. RESULTS: Depending on the procedure, the compliance rate ranged from 27 to 88 % during the first audit. After presentation of the audit results to the stakeholders, the compliance rate ranged from 68 to 93 % and was significantly improved for all procedures (P ranging from <0.001 to 0.031) in both hospitals and remained unchanged during the third audit (P ranging from 0.114 to 0.999). CONCLUSION: Quality improvement through repeated compliance audits with CT procedures durably improves this compliance. KEY POINTS: • Compliance with CT procedures is operator-dependent and not perfect. • Compliance differs between procedures and hospitals, even within a unified department. • Compliance is improved through audits followed by communication to the stakeholders. • This improvement is sustainable over a one-year period.

Chest Computed Tomography Radiation Dose Optimization: Comparison of Automatic Exposure Control Strength Curves.

PURPOSE: The aim of the study was to compare radiation dose and image quality between the "average" and the "very strong" automatic exposure control (AEC) strength curves. MATERIALS AND METHODS: Images reconstructed with filtered back-projection techniques and radiation dose data of unenhanced helical chest computed tomography (CT) examinations obtained at 2 hospitals (hospital A, hospital B) using the same scanner devices and acquisition protocols but different AEC strength curves were evaluated over a 3-month period. The selected AEC strength curve applied to "slim" patients (diameter <32 cm estimated from the attenuation automatically measured on the topogram) was "average" and "very strong" in hospital A and hospital B, respectively. Two radiologists with 13 and 24 years of experience scored the image quality of the lung parenchyma and the mediastinum on a 5-point scale. The patients' effective diameter, the delivered CT dose index volume, and dose-length products were recorded. RESULTS: A total of 410 patients were included. The average body mass index was 24.0 kg/m in hospital A and 24.8 kg/m in hospital B. There was no significant difference between hospitals with respect to age, sex ratio, weight, height, body mass index, effective diameters, and image quality scores for each radiologist (P ranging from 0.050 to 1.000). The mean CT dose index volume for the entire population was 2.0 mGy and was significantly lower in hospital B with the "very strong" AEC curve as compared with hospital A (-11%, P=0.001). The mean dose-length product delivered in this 70 kg-weight population was 68 mGy cm, corresponding to an effective dose of 0.95 mSv. CONCLUSION: Changing the AEC strength curve from "average" to "very strong" for slim patients maintains image quality and reduces the radiation dose to <1 mSv in routine chest CT examinations reconstructed with filtered back-projection techniques.

[Diffuse parenchymal lung diseases: clinical-radiological correlation]. / Pneumopathies interstitielles diffuses: corrélation clinico- radiologique.

Diffuse parenchymal lung diseases can have various clinical and radiological presentations. The high-resolution CT scan has a central role in the diagnostic process of an interstitial disease. As a first step in the analysis of such an exam, one has to look for the major radiological sign and then to describe it to build a differential diagnosis in order to guide the management. The goal of this article is to illustrate this approach with examples of diffuse parenchymal lung diseases.

Multidetector-row computed tomography in suspected pulmonary embolism.

BACKGROUND: Single-detector-row computed tomography (CT) has a low sensitivity for pulmonary embolism and must be combined with venous-compression ultrasonography of the lower limbs. We evaluated whether the use of D-dimer measurement and multidetector-row CT, without lower-limb ultrasonography, might safely rule out pulmonary embolism. METHODS: We included 756 consecutive patients with clinically suspected pulmonary embolism from the emergency departments of three teaching hospitals and managed their cases according to a standardized sequential diagnostic strategy. All patients were followed for three months. RESULTS: Pulmonary embolism was detected in 194 of the 756 patients (26 percent). Among the 82 patients with a high clinical probability of pulmonary embolism, multidetector-row CT showed pulmonary embolism in 78, and 1 patient had proximal deep venous thrombosis and a CT scan that was negative for pulmonary embolism. Of the 674 patients without a high probability of pulmonary embolism, 232 (34 percent) had a negative D-dimer assay and an uneventful follow-up; CT showed pulmonary embolism in 109 patients. CT and ultrasonography were negative in 318 patients, of whom 3 had a definite thromboembolic event and 2 died of possible pulmonary embolism during follow-up (three-month risk of thromboembolism, 1.7 percent; 95 percent confidence interval, 0.7 to 3.9). Two patients had proximal deep venous thrombosis and a negative CT scan (risk, 0.6 percent; 95 percent confidence interval, 0.2 to 2.2). The overall three-month risk of thromboembolism in patients without pulmonary embolism would have been 1.5 percent (95 percent confidence interval, 0.8 to 3.0) if the D-dimer assay and multidetector-row CT had been the only tests used to rule out pulmonary embolism and ultrasonography had not been performed. CONCLUSIONS: Our data indicate the potential clinical use of a diagnostic strategy for ruling out pulmonary embolism on the basis of D-dimer testing and multidetector-row CT without lower-limb ultrasonography. A larger outcome study is needed before this approach can be adopted.

Diagnosing pulmonary embolism in outpatients with clinical assessment, D-dimer measurement, venous ultrasound, and helical computed tomography: a multicenter management study.

PURPOSE: To evaluate a diagnostic strategy for pulmonary embolism that combined clinical assessment, plasma D-dimer measurement, lower limb venous ultrasonography, and helical computed tomography (CT). METHODS: A cohort of 965 consecutive patients presenting to the emergency departments of three general and teaching hospitals with clinically suspected pulmonary embolism underwent sequential noninvasive testing. Clinical probability was assessed by a prediction rule combined with implicit judgment. All patients were followed for 3 months. RESULTS: A normal D-dimer level (<500 microg/L by a rapid enzyme-linked immunosorbent assay) ruled out venous thromboembolism in 280 patients (29%), and finding a deep vein thrombosis by ultrasonography established the diagnosis in 92 patients (9.5%). Helical CT was required in only 593 patients (61%) and showed pulmonary embolism in 124 patients (12.8%). Pulmonary embolism was considered ruled out in the 450 patients (46.6%) with a negative ultrasound and CT scan and a low-to-intermediate clinical probability. The 8 patients with a negative ultrasound and CT scan despite a high clinical probability proceeded to pulmonary angiography (positive: 2; negative: 6). Helical CT was inconclusive in 11 patients (pulmonary embolism: 4; no pulmonary embolism: 7). The overall prevalence of pulmonary embolism was 23%. Patients classified as not having pulmonary embolism were not anticoagulated during follow-up and had a 3-month thromboembolic risk of 1.0% (95% confidence interval: 0.5% to 2.1%). CONCLUSION: A noninvasive diagnostic strategy combining clinical assessment, D-dimer measurement, ultrasonography, and helical CT yielded a diagnosis in 99% of outpatients suspected of pulmonary embolism, and appeared to be safe, provided that CT was combined with ultrasonography to rule out the disease.

Cost-effectiveness analysis of diagnostic strategies for suspected pulmonary embolism including helical computed tomography.

We performed a formal decision analysis to evaluate the cost-effectiveness of various strategies for pulmonary embolism, including helical computed tomography (CT), and determined the most cost-effective schemes for each clinical probability of pulmonary embolism. Other tests included D-dimer (DD), lower limb venous ultrasound (US), ventilation-perfusion (V/Q) scan, and angiography. Outcome measures were 3-month survival and costs per patient managed. Baseline sensitivity of CT was 70%, corresponding to the performance of single-detector CT, and that figure was raised in sensitivity analysis to account for the expected higher sensitivity of newer multidetector CT scanners. All strategies were compared with a reference strategy, namely the V/Q scan in all patients followed when nondiagnostic by an angiogram. For low clinical probability patients, the most cost-effective strategy was DD, US, and V/Q scan, patients with a nondiagnostic V/Q scan being left untreated. Replacing V/Q scan by CT was also cost-effective. For intermediate and high clinical probability patients, a fourth test must be added, either CT or angiography in patients with nondiagnostic V/Q scan, or angiography in patients with a negative helical CT. When using sensitivity figures above 85% (in the multidetector range), DD, US, and CT became the most cost-effective strategy for all clinical probability categories. Helical CT as a single test was not cost-effective. In summary, including helical CT in diagnostic strategies for pulmonary embolism is cost-effective provided that it is combined with DD and US. In contrast, helical CT as a single test is not cost-effective.