Prospective Evaluation of Artificial Intelligence Triage of Incidental Pulmonary Emboli on Contrast-Enhanced CT Examinations of the Chest or Abdomen

Background: Artificial intelligence (AI) algorithms improved detection of incidental pulmonary embolism (IPE) on contrast-enhanced CT (CECT) examinations in retrospective studies; however, prospective validation studies are lacking. Objective: To assess the effect on radiologists' real-world diagnostic performance and report turnaround times of a radiology department's clinical implementation of an AI triage system for detecting IPE on CECT examinations of the chest or abdomen. Methods: This prospective single-center study included consecutive adult patients who underwent CECT of the chest or abdomen for reasons other than PE detection from May 12, 2021 to June 30, 2021 (phase 1) or from July 1, 2021 to September 29, 2021 (phase 2). Before phase 1, the radiology department installed a commercially available AI triage algorithm for IPE detection that automatically processed CT examinations and notified radiologists of positive results through an interactive floating widget. In phase 1, the widget was inactive, and radiologists interpreted examinations without AI assistance. In phase 2, the widget was activated, and radiologists interpreted examinations with AI assistance. A review process involving a panel of radiologists was implemented to establish the reference standard for the presence of IPE. Diagnostic performance and report turnaround times were compared using Pearson Chi-square test and Wilcoxon rank-sum test, respectively. Results: Phase 1 included 1467 examinations in 1434 patients (mean age, 53.8±18.5 years; 753 male, 681 female); phase 2 included 3182 examinations in 2886 patients (mean age, 55.4±18.2 years; 1520 male, 1366 female). The frequency of IPE was 1.4% (20/1467) in phase 1 and 1.6% (52/3182) in phase 2. Radiologists without AI, in comparison with radiologists with AI, showed significantly lower sensitivity (80.0% vs 96.2%, P=.03), without a significant difference in specificity (99.1% vs 99.9%, P=.58), for detection of IPE. The mean report turnaround time for IPE-positive examinations was not significantly different between radiologists without AI and radiologists with AI (78.3 vs 64.6 min, P=.26). Conclusion: An AI triage system improved radiologists' sensitivity for IPE detection on CECT examinations of the chest or abdomen without significant change in report turnaround times. Clinical Impact: This prospective real-world study supports the use of AI assistance for maximizing IPE detection.

Detection of Incidental Pulmonary Embolism on Conventional Contrast-Enhanced Chest CT: Comparison of an Artificial Intelligence Algorithm and Clinical Reports

BACKGROUND. Artificial intelligence (AI) algorithms have shown strong performance for detection of pulmonary embolism (PE) on CT examinations performed using a dedicated protocol for PE detection. AI performance is less well studied for detecting PE on examinations ordered for reasons other than suspected PE (i.e., incidental PE [iPE]). OBJECTIVE. The purpose of this study was to assess the diagnostic performance of an AI algorithm for detection of iPE on conventional contrast-enhanced chest CT examinations. METHODS. This retrospective study included 2555 patients (mean age, 53.2 ± 14.5 [SD] years; 1340 women, 1215 men) who underwent 3003 conventional contrast-enhanced chest CT examinations (i.e., not using pulmonary CTA protocols) between September 2019 and February 2020. A commercial AI algorithm was applied to the images to detect acute iPE. A vendor-supplied natural language processing (NLP) algorithm was applied to the clinical reports to identify examinations interpreted as positive for iPE. For all examinations that were positive by the AI-based image review or by NLP-based report review, a multireader adjudication process was implemented to establish a reference standard for iPE. Images were also reviewed to identify explanations of AI misclassifications. RESULTS. On the basis of the adjudication process, the frequency of iPE was 1.3% (40/3003). AI detected four iPEs missed by clinical reports, and clinical reports detected seven iPEs missed by AI. AI, compared with clinical reports, exhibited significantly lower PPV (86.8% vs 97.3%, p = .03) and specificity (99.8% vs 100.0%, p = .045). Differences in sensitivity (82.5% vs 90.0%, p = .37) and NPV (99.8% vs 99.9%, p = .36) were not significant. For AI, neither sensitivity nor specificity varied significantly in association with age, sex, patient status, or cancer-related clinical scenario (all p > .05). Explanations of false-positives by AI included metastatic lymph nodes and pulmonary venous filling defect, and explanations of false-negatives by AI included surgically altered anatomy and small-caliber subsegmental vessels. CONCLUSION. AI had high NPV and moderate PPV for iPE detection, detecting some iPEs missed by radiologists. CLINICAL IMPACT. Potential applications of the AI tool include serving as a second reader to help detect additional iPEs or as a worklist triage tool to allow earlier iPE detection and intervention. Various explanations of AI misclassifications may provide targets for model improvement.

Concomitant Deep Vein Thrombosis in Cancer Patients with Unsuspected Pulmonary Embolism

Simple Summary

Cancer patients have a significantly higher risk of developing venous thromboembolism during their disease course when compared with the general population. During routine staging or follow-up imaging studies, incidental venous thromboemboli, including incidental pulmonary embolisms, can be identified. Identifying factors associated with incidental or unsuspected venous thromboembolism is important and can improve the management plan. In the current study, we found that 20.9% of patients with unsuspected pulmonary embolisms had concomitant deep vein thrombosis, and most of these patients were asymptomatic. In addition, we found that concomitant deep vein thrombosis increases the odds of venous thrombosis recurrence in cancer patients presenting with unsuspected pulmonary emboli. Therefore, for patients with isolated incidental subsegmental pulmonary embolism and concomitant deep vein thrombosis, initiating anticoagulants if no contraindications exist is recommended. In addition, the presence of concomitant deep vein thrombosis among cancer patients with unsuspected pulmonary embolisms is associated with poor short- and long-term outcomes in these patients.

Abstract

Incidental venous thromboembolism (VTE) is common in cancer patients and identifying factors associated with these events can improve the management plan. We studied the characteristics of concomitant deep vein thrombosis (C-DVT) in cancer patients presenting with unsuspected pulmonary embolism (PE) and the association of C-DVT with VTE recurrence and survival outcomes. Patients presenting to our emergency department with confirmed unsuspected/incidental PE between 1 January 2006 and 1 January 2016, were identified. Radiologic reports were reviewed to confirm the presence or absence of C-DVT. Logistic regression analyses and cox regression modeling were used to determine the effect of C-DVT on VTE recurrence and survival outcomes. Of 904 eligible patients, 189 (20.9%) had C-DVT. Patients with C-DVT had twice the odds of developing VTE recurrence (odds ratio 2.07, 95% confidence interval 1.21–3.48, p = 0.007). The mortality rates among C-DVT were significantly higher than in patients without. C-DVT was associated with reduced overall survival in patients with unsuspected PE (hazard ratio 1.33, 95% confidence interval 1.09–1.63, p = 0.005). In conclusion, C-DVT in cancer patients who present with unsuspected PE is common and is associated with an increased risk of VTE recurrence and poor short- and long-term survival. Identifying other venous thrombi in cancer patients presenting with unsuspected PE is recommended and can guide the management plan. For patients with isolated incidental subsegmental pulmonary embolism and concomitant deep vein thrombosis, initiating anticoagulants if no contraindications exist is recommended.

Pulmonary Embolism and Sigmoid Sinus Thrombosis After Translabyrinthine Vestibular Schwannoma Resection: A Retrospective Case Series

OBJECTIVE

To describe the presentation and treatment of patients developing pulmonary embolism following translabyrinthine approach for vestibular schwannoma resection.

METHODS

This was a retrospective case series of patients at 2 academic tertiary medical centers who developed symptomatic pulmonary embolism post-operatively following translabyrinthine approach for vestibular schwannoma resection and were found to have evidence of sigmoid sinus thrombosis.

RESULTS

Three patients were identified to have post-operative pulmonary emboli after translabyrinthine approach for vestibular schwannoma resection with sigmoid sinus or internal jugular vein clots in the absence of lower extremity deep vein thrombosis. Caprini scores for these patients were 5 or lower. All patients underwent CT pulmonary angiography and were confirmed to have pulmonary emboli. Two were promptly anticoagulated with heparin drips and transitioned to long-term oral anticoagulation therapy and 1 had delayed anticoagulation. None of these patients suffered from intracranial hemorrhage post-operatively.

CONCLUSIONS

Patients undergoing translabyrinthine approach for vestibular schwannoma can develop pulmonary embolism from sigmoid sinus entry or thrombosis. No clear guidelines exist for the management of this complication in the setting of recent craniotomy and the risk of intracranial hemorrhage must be considered prior to initiating anticoagulation.

Missed Incidental Pulmonary Embolism: Harnessing Artificial Intelligence to Assess Prevalence and Improve Quality Improvement Opportunities

PURPOSE

Incidental pulmonary embolism (IPE) can be found on body CT. The aim of this study was to evaluate the feasibility of using artificial intelligence to identify missed IPE on a large number of CT examinations.

METHODS

This retrospective analysis included all single-phase chest, abdominal, and pelvic (CAP) and abdominal and pelvic (AP) CT examinations performed at a single center over 1 year, for indications other than identification of PE. Proprietary visual classification and natural language processing software was used to analyze images and reports from all CT examinations, followed by a two-step human adjudication process to classify cases as true positive, false positive, true negative, or false negative. Descriptive statistics were assessed for prevalence of IPE and features (subsegmental versus central, unifocal versus multifocal, right heart strain or not) of missed IPE. Interrater agreement for radiologist readers was also calculated.

RESULTS

A total of 11,913 CT examinations (6,398 CAP, 5,515 AP) were included. Thirty false-negative examinations were identified on CAP (0.47%; 95% confidence interval [CI], 0.32%-0.67%) and nineteen false-negative studies on AP (0.34%; 95% CI, 0.21%-0.54%) studies. During manual review, readers showed substantial agreement for identification of IPE on CAP (κ = 0.76; 95% CI, 0.66-0.86) and nearly perfect agreement for identification of IPE on AP (κ = 0.86; 95% CI, 0.76-0.97). Forty-nine missed IPEs (0.41%; 95% CI, 0.30%-0.54%) were ultimately identified, compared with seventy-nine IPEs (0.66%; 95% CI, 0.53%-0.83%) identified at initial clinical interpretation.

CONCLUSIONS

Artificial intelligence can efficiently analyze CT examinations to identify potential missed IPE. These results can inform peer-review efforts and quality control and could potentially be implemented in a prospective fashion.

Incidental pulmonary embolism in CT scans of oncological patients with metastatic disease undergoing clinical trials: frequency and linkage with onset of disease progression (PE-PD association)

Objectives:

We aimed to analyze the association between the onsets of PE and of progressive disease (PD) in CT scans of oncological patients undergoing clinical trials.

Methods:

We retrospectively searched our oncological clinical trials database (1/2012 - 6/2017). We retrieved patients who underwent protocol baseline and follow-up CT scans. RECIST 1.1 categories of response were calculated for each scan at interpretation. The entire dataset was searched for reports with incidental PE. For patients with incidental PE, we collected all the scans conducted up to and including the scan with PE. For each scan, we retrieved the recorded RECIST 1.1 category. We excluded patients with PE at baseline. The frequency of incidental PE in oncological clinical trial patients was calculated. For patients with incidental PE, we evaluated the association between PE and PD.

Results:

During the study period, 1,070 patients underwent 3,818 CTs. The total number of follow-up months was 7,292 months. 18 patients developed incidental PE during follow-up. Thus, the frequency of incidental PE in oncological clinical trial patients was 3% per year of follow-up. Patients with incidental PE underwent 60 scans up to development of PE. Of 42 non-baseline scans, 6/6 (100%) PD showed PE, and 5/36 (13.9%) non-PD showed PE, making PE onset associated with PD onset (p < 0.001).

Conclusion:

In oncological clinical trials, the frequency of incidental PE is 3% per year of follow-up. The onset of incidental PE is linked to the onset of PD.

Advances in knowledge:

Incidental PE is associated with the onset of disease progression. Radiologists interpret oncological scans should be aware of the association between PE and PD.

Vena caval filters for the prevention of pulmonary embolism

BACKGROUND

Pulmonary emboli (PE), or blood clots in the lungs,can be potentially fatal. Anticoagulation is the first line therapy to prevent PE. In some instances anticoagulation fails to prevent more emboli, or cannot be given because the person has a high risk of bleeding. Inferior vena caval filters (VCFs) are metal alloy devices that mechanically trap fragmented emboli from the deep leg veins en route to the pulmonary circulation. Retrievable filters are designed to be introduced and removed percutaneously. Although their deployment seems of theoretical benefit, their clinical efficacy and adverse event profile is unclear. This is the third update of a Cochrane Review first published in 2007.

OBJECTIVES

To assess the evidence for the effectiveness and safety of vena caval filters (VCFs) in preventing pulmonary embolism (PE).

SEARCH METHODS

For this review update, the Cochrane Vascular Information Specialist (CIS) searched the Specialised Register (last searched 10 September 2019) and the Cochrane Register of Controlled Trials (CENTRAL) (2019, Issue 8) via the Cochrane Register of Studies Online. The CIS also searched MEDLINE Ovid, EMBASE Ovid, CINAHL, and AMED (1 January 2017 to 10 September 2019) and trials registries to 10 September 2019.

SELECTION CRITERIA

We included randomised controlled trials (RCTs) and controlled clinical trials (CCTs) that examined the efficacy of VCFs in preventing PE.

DATA COLLECTION AND ANALYSIS

For this update, studies were assessed and data extracted independently. We assessed study quality with Cochrane's 'Risk of bias' tool and used the GRADE approach to assess the overall certainty of the evidence. The outcomes of interest were PE, mortality, lower limb venous thrombosis, filter-related complications and major bleeding.

MAIN RESULTS

We identified four new studies for this update, bringing the total to six included studies involving 1388 participants. The six studies were clinically heterogeneous and we were unable to carry out meta-analysis. Only two studies were considered to be both applicable in current clinical settings and of good methodological quality. One was a randomised open-label trial studying the effect of a retrievable inferior vena caval filter plus anticoagulation versus anticoagulation alone on risk of recurrent pulmonary embolism (PE) in 399 participants over three months. There was no evidence of a difference in the rates of PE, death, lower extremity deep vein thrombosis (DVT), or bleeding at three and six months after the intervention (moderate-certainty evidence). A filter was inserted in 193 people, but could only be successfully retrieved from 153. Minor filter complications were noted at six months. The second clinically relevant study was a randomised open-label trial of 240 participants who had sustained multiple traumatic injuries, allocated to a filter or no filter, three days after injury, in conjunction with anticoagulation and intermittent pneumatic compression. Prophylactic anticoagulation was initiated in both groups when it was thought safe to do so. There was no evidence of a difference in symptomatic PE, death, or lower limb venous thrombosis rates (moderate-certainty evidence). The only major filter complication was that one person required surgical removal of the filter. We are unable to draw any conclusions from the remaining four included studies. One study showed an increased incidence of long-term lower extremity DVT at eight years. Three studies are no longer clinically applicable because they utilised permanent filters which are seldom used now, or they did not use routine prophylactic anticoagulation which is current standard practice. The fourth study compared two filter types and was terminated prematurely as one filter group had a higher rate of thrombosis compared to the other filter type.

AUTHORS' CONCLUSIONS

Two of the six identified studies were relevant for current clinical settings. One showed no evidence of a benefit of retrievable filters in acute PE for the outcomes of PE, death, DVT and bleeding during the initial three months in people who can receive anticoagulation (moderate-certainty evidence). The other study did not show any benefit for prophylactic filter insertion in people who sustained multiple traumatic injuries, with respect to symptomatic PE, mortality, or lower extremity venous thrombosis (moderate-certainty evidence). We can draw no firm conclusions regarding filter efficacy in the prevention of PE from the remaining four RCTs identified in this review. Further trials are needed to assess vena caval filter effectiveness and safety, and clinical differences between various filter types.

Incidental pulmonary embolism in pancreatic ductal adenocarcinoma: Impact of tumor and AJCC stages at initial staging CT

BACKGROUND/OBJECTIVES

To determine the prevalence of incidental pulmonary embolism (PE) detected during initial staging CT among patients with newly diagnosed pancreatic ductal adenocarcinoma (PDAC) and assess their association with underlying tumor burden.

MATERIALS AND METHODS

This retrospective cohort study evaluated staging chest CT scans (2013-2017) to identify PE among patients with treatment naïve, biopsy-proven PDAC. Data included age, sex, T stage, AJCC stage, presence/absence of metastases and their location at diagnosis. The association of PE with tumor (T1-T4) and AJCC stage were assessed using Pearson Chi-square and Fischer's exact test. A threshold p-value of <0.05 indicated statistical significance.

RESULTS

A total of 174 patients (90 female, mean age, 68 years; range: 34-93) were identified, of which 10 patients harbored incidental PE (prevalence, 5.7%). In the PE group, two patients presented with distant metastasis (liver, 20%), while eight patients had T4 tumors (80%). No statistical association was detected between PE and age, sex, and the presence/absence or location of distant metastasis (p = 0.065, p = 0.59, p = 0.687 and p = 0.933, respectively). Patients with T4 tumors and higher AJCC stages (stage III/IV) were significantly more likely to present with PE than those with lower T stage (p = 0.045) and AJCC stage (stage I/II; p = 0.017).

CONCLUSION

The prevalence of incidental PE among PDAC patients undergoing initial CT staging is 5.7%. Patients with T4 and AJCC stages III/IV are at higher risk of PE. Caution should be exercised during radiographic interpretation of initial staging chest CTs, as incidental PE may be lurking and require treatment.

Pulmonary embolism: update on diagnosis and management

Pulmonary embolism (PE) is a potentially life-threatening condition, mandating urgent diagnosis and treatment. The symptoms of PE may be non-specific; diagnosis therefore relies on a clinical assessment and objective diagnostic testing. A clinical decision rule can determine the pre-test probability of PE. If PE is "unlikely", refer for a D-dimer test. If the D-dimer result is normal, PE can be excluded. If D-dimer levels are increased, refer for chest imaging. If PE is "likely", refer for chest imaging. Imaging with computed tomography pulmonary angiogram is accurate and preferred for diagnosing PE, but may detect asymptomatic PE of uncertain clinical significance. Imaging with ventilation-perfusion (VQ) scan is associated with lower radiation exposure than computed tomography pulmonary angiogram, and may be preferred in younger patients and pregnancy. A low probability or high probability VQ scan is helpful for ruling out or confirming PE, respectively; however, an intermediate probability VQ scan requires further investigation. The direct oral anticoagulants have expanded the anticoagulation options for PE. These are the preferred anticoagulant for most patients with PE because they are associated with a lower risk of bleeding, and have the practical advantages of fixed dosage, no need for routine monitoring, and fewer drug interactions compared with vitamin K antagonists. Initial parenteral treatment is required before dabigatran and edoxaban.

Cardiovascular findings on cross-sectional imaging: spectrum of incidental and critical findings and clinical relevance for the abdominal radiologist

Although not the primary focus of the exams, cardiovascular structures are included to some extent on all abdominal or whole-body cross-sectional studies. Cardiovascular findings often present incidentally and may range from chronic to acute and emergent pathologies. Among the most common cardiovascular findings are the presence of cardiac calcifications, most commonly coronary, which correlate with the presence of coronary artery and valvular disease. Signs of myocardial ischemia, both acute and chronic, and its complications may also be visualized. Cardiac filling defects most commonly represent thrombus and are associated with systemic arterial embolic complications. Pericardial findings often manifest as effusion or thickening, which may lead to hemodynamic consequences visible at imaging. Incidental pulmonary emboli and systemic venous thrombi may be incidentally detected, particularly in hospitalized and oncologic patients, and warrant immediate attention. This review will highlight the appearance of common and important incidental cardiovascular findings and related pitfalls and discuss reporting and follow-up recommendations relevant to the abdominal radiologist.

Diagnostic Yield and False-Referral Rate of Staging Chest CT in Patients with Colon Cancer

Purpose To measure the diagnostic yield and false-referral rate (FRR) of staging contrast material-enhanced chest CT based on the clinical stage from contrast-enhanced abdominal CT in patients with colon cancer. Materials and Methods This retrospective study included 1743 patients (mean age, 63.4 years; range, 18-96 years) with a diagnosis of colon cancer. The primary outcomes were diagnostic yield and FRR of contrast-enhanced chest CT in the detection of thoracic metastasis. The proportions of patients with occult thoracic metastasis and those undergoing pulmonary metastasectomy for true-positive metastases were key secondary outcomes. The outcomes were stratified according to clinical stage at contrast-enhanced abdominal CT. Results The diagnostic yields in clinical stage 0/I, cII, cIII, and cIV were 0% (95% confidence interval [CI]: 0%, 0.8%), 1.3% (95% CI: 0.4%, 3.3%), 4.4% (95% CI: 3.0%, 6.1%), and 43.3% (95% CI: 36.8%, 49.9%), respectively. The corresponding FRRs were 5.7% (95% CI: 3.8%, 8.2%), 2.9% (95% CI: 1.3%, 5.5%), 6.7% (95% CI: 5.0%, 8.8%), and 6.1% (95% CI: 3.4%, 10.0%), respectively. The proportions of patients with occult metastasis were 0% (95% CI: 0%, 0.8%), 3.3% (95% CI: 1.6%, 5.9%), 1.5% (95% CI: 0.8%, 2.7%), and 6.1% (95% CI: 3.4%, 10.0%), respectively. The proportion of patients who underwent pulmonary metastasectomy was 0% (none of 474; 95% CI: 0%, 0.8%) for clinical stage 0/I tumors. Conclusion In clinical stages 0 and I, the diagnostic yield of staging contrast-enhanced chest CT in detecting thoracic metastasis was zero. For clinical stages II, III, and IV, contrast-enhanced chest CT as a baseline examination was helpful for the detection of thoracic metastasis and allowed for the possibility of a curative metastasectomy. There was no significant association between clinical stage and false-referral rate. © RSNA, 2018 Online supplemental material is available for this article.

Incidental pulmonary embolism in oncology patients with current macroscopic malignancy: incidence in different tumour type and impact of delayed treatment on survival outcome

OBJECTIVES

To evaluate the incidence and outcome of incidental pulmonary embolism (iPE) in patients with current macroscopic malignancy and delayed anticoagulation due to late reporting of CT scan.

METHODS

Reports of CT thorax with i.v. contrast done on oncology patients between 1 January 2015 and 31 December 2015 in two district general hospitals in UK were reviewed. Electronic patient records of iPE patients were reviewed for demographic and treatment information.

RESULTS

26 iPEs were reported in 1,604 scans (731 patients), incidence 1.6%; female = 15; median age = 66 (range 32-90); main artery = 10; lobar artery = 8; segmental = 7; subsegmental = 1; median time (range) from scan to reporting = 1 day (0-60); scan to anticoagulation = 5 days (0-61) (three had no treatment); scan to death = 7 months (1-22+) with nine still alive and two lost to follow up. All had metastatic disease. There was no sudden death. None of the patients whose anticoagulation started more than 5 days after the iPE CT scan died within 3 months. iPE was absent in all repeat staging CT scans (done average 3.4 months after the anticoagulation) in 16 patients, without any anticoagulation in one patient with segmental iPE.

CONCLUSION

Incidence of iPE in patients with current macroscopic malignancy is low-1.6%-mostly seen in lung, breast and colorectal cancer probably due to frequency of imaging. A few days' delay in anticoagulation does not appear to have an impact on the risk of sudden cardiac death. Advances in knowledge: This study tells us that iPE is infrequent, that it can be treated appropriately with anticoagulation, but this does not necessarily need to begin on the same day of diagnosis.

Improved Opacification of a Suboptimally Enhanced Pulmonary Artery in Chest CT: Experience Using a Dual-Layer Detector Spectral CT

OBJECTIVE

The objective of our study was to evaluate the quality of virtual monoenergetic imaging (VMI) from dual-layer detector spectral CT and the effect of virtual monoenergetic images obtained at low energies on the detection of pulmonary embolism (PE) in patients with a suboptimally enhanced pulmonary artery on chest CT.

MATERIALS AND METHODS

Of 1552 consecutive chest CT examinations performed with dual-layer detector spectral CT using a routine protocol with a tube voltage of 120 kVp, 79 examinations with suboptimal enhancement of the pulmonary artery (i.e., mean attenuation of pulmonary artery ≤ 180 HU) were included. The mean attenuation of the pulmonary artery, noise, contrast-to-noise ratio (CNR), and signal-to-noise ratio (SNR) of virtual monoenergetic images obtained at 40-200 keV were compared with those of the conventional 120-kVp images. The virtual monoenergetic images with the best CNR were compared with the 120-kVp images with regard to subjective image quality and diagnostic accuracy for detecting PE.

RESULTS

Sufficient attenuation of the pulmonary artery (> 180 HU) was obtained using VMI for 78 of the 79 examinations. The noise levels of the virtual monoenergetic images were gradually increased with decreasing energy level (i.e., kiloelectron volt setting). The CNR and SNR of virtual monoenergetic images at 40-65 keV were significantly higher (both, p < 0.001) than the CNR and SNR of the 120-kVp images. The CNR was the highest at 40 keV for all cases. Diagnostic accuracy for detecting PE was significantly higher for 40-keV images (reader 1: AUC = 0.992, p = 0.033; reader 2: AUC = 0.986, p = 0.043) than for 120-kVp images (reader 1, AUC = 0.911; reader 2, AUC = 0.933). The subjective quality was not different between these two images.

CONCLUSION

In chest CT examinations in which the pulmonary artery is suboptimally enhanced, obtaining virtual monoenergetic images at a low energy setting using dual-layer detector spectral CT allows sufficient attenuation of the pulmonary artery to be achieved while preserving image quality and increasing diagnostic performance for detecting PE.