Computed Tomography Pulmonary Angiogram Scan Research Articles

A quality improvement project addressing motion artefact on CTPAs in a district general hospital setting: A complete cycle resulting in changed practice.

Introduction: A still breath hold from the patient is one of the key requirements for a diagnostic computed tomography pulmonary angiogram (CTPA). It is important for the timely identification and treatment of patients with life threatening pulmonary emboli (PEs). Motion artefact on CTPA can cause blurring, double borders, shading and streaking in the lungs, which can either obscure PEs or create artefact that mimics PEs. This risks patient harm from delayed diagnoses, missed PEs, false positives and extra radiation and contrast exposure due to repeat studies. Methods: We devised local standards and methodology for assessing the presence and degree of motion artefact on CTs. The study consisted of initial data collection, implementation of changes to clinical practice, and subsequent repeat data collection 3 months after implementation of interventions. For each data collection round, 100 consecutive inpatient and emergency CTPAs performed in a UK District General Hospital were retrospectively identified and images reviewed to categorise each as having either: ‘no significant’, ‘minor’ or ‘major’ motion artefact. There were no exclusions. Interventions after initial data collection included a multidisciplinary meeting with radiographers, department assistants, and radiologists to devise changes to workflow and practices to build in 'rehearsal' of a breath-hold and explanation of breathing instructions with patients before scanning. A prompting phrase for this was added to our CTPA scanning protocol. Results: Initial results demonstrated that 50% of CTPA showed either minor or major motion artefact, while 50% showed no significant motion artefact. For 2% with minor motion, a clinical reason for why this was unavoidable was provided. Therefore 52% of studies met the proposed local standards. In total, 45% of CTPA were assessed to have minor motion and 5% had major motion artefact (non-diagnostic). 18% of CTPA were positive for PE. Following implementation of changes to practice, repeat data collection demonstrated that 67% of CTPA showed no significant motion artefact. 3% with minor motion provided a clinical reason why this was unavoidable. Therefore 70% of studies met the proposed standard. The increase in compliance with local standards was statistically significant (p=0.00906). Conclusion: Our interventions improved compliance with local standards from 52% to 70%. We recommend rehearsal of breath-holding with patients before CTPA scans as a quick and easy way to improve the diagnostic quality of scans. A prompting phrase within the CTPA scanning protocol has proven effective.

Single-center outcomes of artificial intelligence in management of pulmonary embolism and pulmonary embolism response team activation.

Multidisciplinary pulmonary embolism response teams (PERTs) have shown that timely triage expedites treatment. The use of artificial intelligence (AI) may help improve pulmonary embolism (PE) management with early CT pulmonary angiogram (CTPA) screening and accelerate PERT coordination. This study aimed to test the clinical validity of an FDA-approved PE AI algorithm. CTPA scan data of 200 patients referred due to automated AI detection of suspected PE were retrospectively reviewed. In our institution, all patients suspected of PE received a CTPA. The AI app was then used to analyze CTPA for the presence of PE and calculate the right-ventricle/left-ventricle (RV/LV) ratio. We compared the AI's output with the radiologists' report. Inclusion criteria included segmental PE with and without RV dysfunction and high-risk PE. The primary endpoint was false positive rate. Secondary end points included clinical outcomes according to the therapy selected, including catheter-directed interventions, systemic thrombolytics, and anticoagulation. Fifty-seven of 200 exams (28.5%) were correctly identified as positive for PE by the algorithm. A total of 143 exams (71.5%) were incorrectly reported as positive. In 8% of cases, PERT was consulted. Four patients (7%) received systemic thrombolytics without any complications. There were six patients (10.5%) who developed high-risk PE and underwent thrombectomy, one of whom died. Among 46 patients with acute PE without right heart strain, 44 (95%) survived. The false positive rate of our AI algorithm was 71.5%, higher than what was reported in the AI's prior clinical validity study (91% sensitivity, 100% specificity). A high rate of discordant AI auto-detection of suspected PE raises concerns about its diagnostic accuracy. This can lead to increased workloads for PERT consultants, alarm/notification fatigue, and automation bias. The AI direct notification process to the PERT team did not improve PERT triage efficacy.

Automatic detection of pulmonary embolism on computed tomography pulmonary angiogram scan using a three-dimensional convolutional neural network

ObjectiveTo propose a convolutional neural network (EmbNet) for automatic pulmonary embolism detection on computed tomography pulmonary angiogram (CTPA) scans and to assess its diagnostic performance. Methods305 consecutive CTPA scans between January 2019 and December 2021 were enrolled in this study (142 for training, 163 for internal validation), and 250 CTPA scans from a public dataset were used for external validation. The framework comprised a preprocessing step to segment the pulmonary vessels and the EmbNet to detect emboli. Emboli were divided into three location-based subgroups for detailed evaluation: central arteries, lobar branches, and peripheral regions. Ground truth was established by three radiologists. ResultsThe EmbNet’s per-scan level sensitivity, specificity, positive predictive value (PPV), and negative predictive value were 90.9%, 75.4%, 48.4%, and 97.0% (internal validation) and 88.0%, 70.5%, 42.7%, and 95.9% (external validation). At the per-embolus level, the overall sensitivity and PPV of the EmbNet were 86.0% and 61.3% (internal validation), and 83.5% and 57.5% (external validation). The sensitivity and PPV of central emboli were 89.7% and 52.0% (internal validation), and 94.4% and 43.0% (external validation); of lobar emboli were 95.2% and 76.9% (internal validation), and 93.5% and 72.5% (external validation); and of peripheral emboli were 82.6% and 61.7% (internal validation), and 80.2% and 59.4% (external validation). The average false positive rate was 0.45 false emboli per scan (internal validation) and 0.69 false emboli per scan (external validation). ConclusionThe EmbNet provides high sensitivity across embolus locations, suggesting its potential utility for initial screening in clinical practice.

Implementation, Clinical Benefit and Safety of a D-Dimer-Focused Pulmonary Embolism Testing Pathway in the Emergency Department

Computed tomography pulmonary angiogram (CTPA) is overused during pulmonary embolism (PE) testing in the emergency department (ED), whereas prediction rules and D-dimer are underused. We report the adherence, clinical benefit, and safety of a D-dimer-only strategy to guide need for PE imaging in the ED. This was a prospective multicenter implementation study in 2 EDs with historical and external controls. Patients with suspected PE underwent D-dimer testing and imaging (CTPA or ventilation-perfusion scan) when D-dimer levels were 500 ng/mL or more. PE was ruled out if D-dimer was less than 500 ng/mL or with negative imaging. The primary implementation outcome was the proportion of patients tested for PE in adherence with the pathway. The primary clinical benefit outcome was the proportion of patients tested for PE who received pulmonary imaging. The primary safety outcome was diagnosis of PE in the 30 days following negative PE testing postimplementation. Between January 2018 and June 2021, 16,155 patients were tested for PE, including 33.4% postimplementation, 30.7% preimplementation, and 35.9% in an external control site. Adherence with the D-dimer-only pathway was 97.6% (adjusted odds ratio (aOR) post- versus preimplementation 5.26 (95% confidence interval 1.70 to 16.26). There was no effect on the proportion undergoing PE imaging. Imaging yield increased aOR 4.89 (1.17 to 20.53). Two cases of PE (0.04%; 0.01% to 0.16%) were diagnosed within 30 days. In this Canadian ED study, the uptake of a D-dimer-only PE testing strategy was high. Implementation was associated with higher imaging yield and a D-dimer level of less than 500 ng/mL safely excluded PE.

An audit of CTPA and V/Q scan for investigation of pulmonary embolism in pregnancy.

Pulmonary embolism (PE) can be fatal yet difficult to diagnose in pregnancy. Computed tomography pulmonary angiogram (CTPA) or ventilation/perfusion (V/Q) scans are often conducted, potentially leading to low positive scan rates. Retrospective data analysis was conducted for pregnant women and non-pregnant age-matched control who underwent CTPA and/or V/Q scan for investigation of PE. The main outcomes were the positive and non-diagnostic imaging rates. In total, 440 women underwent V/Q or CTPA scans, 86 of whom were pregnant (19.5%). The positive scan rate was 3.5% and 8.8% in the pregnant and non-pregnant groups, respectively (p = 0.1). The non-diagnostic scan rate was similar between pregnant and non-pregnant groups (13.9% vs 9.9%, p = 0.3). Within the pregnant group, there were more non-diagnostic CTPAs than V/Q scans (p = 0.005). Our study confirms a low positive imaging rate and a relatively high non-diagnostic CTPA rate in pregnancy. Newer strategies are needed to reduce the number of negative imaging studies conducted.

Clinical and radiological characteristics of acute pulmonary embolus in relation to 28-day and 6-month mortality.

BackgroundPatients with acute pulmonary embolism (PE) exhibit a wide spectrum of clinical and laboratory features when presenting to hospital and pathophysiologic mechanisms differentiating low-risk and high-risk PE are poorly understood.ObjectivesTo investigate the prognostic value of clinical, laboratory and radiological information that is available within routine tests undertaken for patients with acute PE.MethodsElectronic patient records (EPR) of patients who underwent Computed Tomography Pulmonary Angiogram (CTPA) scan for the investigation of acute PE during 6-month period (01.01.2016–30.06.2016) were examined. Data was gathered from EPR for patients that met inclusion criteria and all CTPA scans were re-evaluated. Biochemical thresholds of low-grade and high-grade inflammation, serum CRP >10mg/L and >150mg/L and serum albumin concentrations <35g/L and <25 g/L, were combined in the Glasgow Prognostic Score (GPS) and peri-operative Glasgow Prognostic Score (poGPS) respectively. Neutrophil Lymphocyte ratio (NLR) was also calculated. Pulmonary Embolus Severity Index score was calculated.ResultsOf the total CTPA reports (n = 2129) examined, 245 patients were eligible for inclusion. Of these, 20 (8%) patients had died at 28-days and 43 (18%) at 6-months. Of the 197 non-cancer related presentations, 28-day and 6-month mortality were 3% and 8% respectively. Of the 48 cancer related presentations, 28-day and 6-month mortality were 29% and 58% respectively. On univariate analysis, age ≥65 years (p<0.01), PESI score ≥100(p = <0.001), NLR ≥3(p<0.001) and Coronary Artery Calcification (CAC) score ≥ 6 (p<0.001) were associated with higher 28-day and 6-month mortality. PESI score ≥100 (OR 5.2, 95% CI: 1.1, 24.2, P <0.05), poGPS ≥1 (OR 2.5, 95% CI: 1.2–5.0, P = 0.01) and NLR ≥3 (OR 3.7, 95% CI: 1.0–3.4, P <0.05) remained independently associated with 28-day mortality. On multivariate binary logistic regression analysis of factors associated with 6-month mortality, PESI score ≥100 (OR 6.2, 95% CI: 2.3–17.0, p<0.001) and coronary artery calcification score ≥6 (OR 2.3, 95% CI: 1.1–4.8, p = 0.030) remained independently associated with death at 6-months. When patients who had an underlying cancer diagnosis were excluded from the analysis only GPS≥1 remained independently associated with 6-month mortality (OR 5.0, 95% CI 1.2–22.0, p<0.05).ConclusionPESI score >100, poGPS≥1, NLR ≥3 and CAC score ≥6 were associated with 28-day and 6-month mortality. PESI score ≥100, poGPS≥1 and NLR ≥3 remained independently associated with 28-day mortality. PESI score ≥100 and CAC score ≥6 remained independently associated with 6-month mortality. When patients with underlying cancer were excluded from the analysis, GPS≥1 remained independently associated with 6-month mortality. The role of the systemic inflammatory response (SIR) in determining treatment and prognosis requires further study. Routine reporting of CAC scores in CTPA scans for acute PE may have a role in aiding clinical decision-making regarding treatment and prognosis.

Histological validation of pulmonary infarction detected with contrast‐enhanced ultrasound in patients with negative computed tomography pulmonary angiogram: A case series

The purpose of this case series is to evaluate the diagnostic potential of contrast-enhanced ultrasound (CEUS) in patients with clinically suspected pulmonary embolism (PE), suspicious pleural lesions, and negative computed tomography pulmonary angiogram (CTPA). Between January 2017 and January 2018, we examined patients with an intermediate or a high-risk Wells score and a negative CTPA with lung B-mode ultrasound (LUS). In a total of six patients, pleural defects were identified and further examined by CEUS. Nonenhancing lesions or those with inhomogeneous enhancement were considered to be suspicious for an embolic event and biopsied for histological validation. The data analysis was retrospective. In LUS, the lesions had an average size of 2.4 cm (range 2-3 cm). Five were hypoechoic and one was complex. The shape was wedge shaped (n = 5) or round (n = 1), and the number was solitary (n = 4) or multiple (n = 2) with dorsobasal localization (n = 6). Three lesions were nonenhancing, and three had an inhomogeneous enhancement with areas with complete absence of enhancement. The histological examination showed pulmonary infarction in all six cases, and in one patient also cells of a lung carcinoma. Our case series demonstrates the diagnostic potential of CEUS for detecting peripheral pulmonary infarction in patients with clinically suspected PE and negative CTPA scan regarding PE. A histological validation or a narrow follow-up might be warranted in some cases.

Usefulness of standard computed tomography pulmonary angiography performed for acute pulmonary embolism for identification of chronic thromboembolic pulmonary hypertension: results of the InShape III study.

Chronic thromboembolic pulmonary hypertension (CTEPH) is often diagnosed after a long delay, even though signs may already be present on the computed tomography pulmonary angiogram (CTPA) used to diagnose a preceding acute pulmonary embolism (PE). In this setting of suspected acute PE, we evaluated the diagnostic accuracy of dedicated CTPA reading for the diagnosis of already existing CTEPH. Three blinded expert radiologists scored radiologic signs of CTEPH on initial CTPA scans with confirmed acute PE in 50 patients who were subsequently diagnosed with CTEPH during follow-up (cases), and in 50 patients in whom sequential echocardiograms performed >2 years after the acute PE diagnosis did not show any signs of pulmonary hypertension (controls). All 50 control index CTPA scans had signs of right ventricular (RV) overload. Sensitivity and specificity of expert CTPA reading was calculated, and best-predicting radiologic parameters were identified. The overall expert reading yielded a sensitivity of 72% (95% confidence interval [CI] 58%-84%) and a specificity of 94% (95% CI 83%-99%) for CTEPH diagnosis. Multivariate analysis identified 6 radiologic parameters as independent predictors: intravascular webs; pulmonary artery retraction or dilatation; bronchial artery dilatation; right ventricular (RV) hypertrophy; and interventricular septum flattening. The presence of 3 or more these parameters was associated with a sensitivity of 70% (95% CI 55%-82%), a specificity of 96% (95% CI 86%-100%), and a c-statistic of 0.92. Standardized reading of CTPA scans performed for acute PE can be useful for the diagnosis of CTEPH when structured identification of 6 characteristics is employed during interpretation. The use of this strategy may help reduce diagnostic delay of CTEPH.

Case Report: Unprovoked venous thromboembolism in a young adult

A 24-year-old male was presented to us with sudden onset of chest pain and dyspnea for the past one hour. There was no history of calf pain, trauma, surgery, prolonged immobilization, long-haul air travel, bleeding diathesis or any other co-morbidity. The patient denied any addiction history. The Electrocardiogram showed tachycardia with S1Q3T3 pattern. The left arterio-venous Doppler study was suggestive of a thrombus in popliteal vein and sapheno-popliteal junction. The CT-Pulmonary Angiogram scan was suggestive of a massive pulmonary thromboembolism. The patient was thrombolysed with Intravenous Alteplase immediately and was put on tab Rivaroxaban for maintenance. He was later discharged after being stable. Unprovoked venous thromboembolism (VTE) is very rare and has the potential to lead to pulmonary embolism which could be disastrous, especially in young adults. We present such a case where unprovoked VTE was diagnosed and treated. This case suggests that high clinical suspicion is the key for the diagnosis of acute pulmonary embolism, especially in the absence of history suggestive of deep vein thrombosis.

Implications of language barrier on the diagnostic yield of computed tomography in pulmonary embolism

ObjectivesTo determine if a physician-patient language barrier impacts the diagnostic accuracy of pulmonary embolism (PE) evaluation. MethodsA retrospective chart review, conducted between June 2015 and December 2016, of a consecutive sample of diagnostic computed tomography pulmonary angiogram (CTPA) studies performed on adult patients. Positive and negative CTPA scans were further categorized by patient language and the positive diagnostic yield was determined for each language group. A post collection sub-analysis was performed to determine the yield when interpreter services were identified as necessary. ResultsThe yield for English speaking patients was 10.24% (92/898, 95% CI 8.39% to 12.36%), similar to the yield in Spanish speaking patients of 9.40% (25/266, 95% CI 6.31% to 13.37%, P=0.69). This contrasted with the yield in patients who identified as bilingual, which was significantly lower at 1.41% (1/71, 95% CI 0.07% to 6.75%) compared to both English-(P<0.02) and Spanish-only speakers (P<0.03). The yield for non-English speaking patients who requested an interpreter was 7.37% (14/190, 95% CI 4.26% to 11.77%) versus 3.23% (2/62, 95% CI 0.54% to 10.25%, P=0.25) in those who did not. ConclusionsThe diagnostic yield in English- and Spanish-only speaking patients was similar, however, the yield in those that self-identified as bilingual was significantly lower. In patient groups in which a language barrier existed and an interpreter was not utilized, there was a trend toward a lower diagnostic yield. This suggests an increased propensity to order diagnostic imaging when potential communication barriers exist.

The diagnostic yield of CTPA: pulmonary embolism, alternative diagnoses and incidental findings

Aims: In this retrospective study we assess the diagnostic yield of computed tomography pulmonary angiogram (CTPA) and the incidence of alterative and incidental diagnoses. Methods: The results of all CTPA scans performed in our trust over a period of 18 months were reviewed and all diagnoses noted. Data collected was descriptively analysed. Results: A total of 1138 scans were performed (56.5% men, mean age 59 years). A diagnosis of pulmonary embolism (PE) was made in 20.2%, an alternative aetiology for presenting symptoms in 26.4% and incidental findings in 19.5%. The commonest alternative diagnosis was pneumonia (9.5%). Conclusions: Significant numbers of CTPA yield unexpected findings, which may provide an explanation for the clinical presentation. Furthermore substantial numbers of incidental pathologies are also diagnosed which may lead to inappropriate resource utilization and increased patient anxiety.

Optimization of scan protocol in pulmonary angiography of second generation dual source computed tomography

To explore the scan protocol of second generation dual source computed tomography (CT) for CT pulmonary angiogram (CTPA) in patients with suspected pulmonary embolism and determine the proper volume of contrast medium. A total of 120 patients undergoing CTPA were recruited. All examinations were performed on a second generation dual source CT. The scan delay was determined with the test bolus technique. Four contrast volume protocols were designed, namely groups A, B, C and D respectively (n = 30 each). For CTPA scan of groups A, B, C and D, 35, 40, 45 and 50 ml contrast medium were injected at an injection rate of 4 ml/s, followed by a saline chaser of 55, 50, 45 and 40 ml respectively. Attenuation profiles of different vascular segments (subclavian vein, vena cava, left atrium, pulmonary trunk, S1 artery, S10 artery) were measured to evaluate the timing techniques. The image quality and artifact of iodine map were analyzed by two radiologists for comparisons. The percentage of pulmonary arteries exceeding optimal attenuation (> 200 HU) showed that groups of B, C and D were higher than group A (93% - 100% vs 80% - 90%). The image quality of group A was lower than the others (P < 0.05) while the other groups showed no significant difference. The artifacts of iodine map of group A were much fewer than the others (P < 0.05) and group D was much more than the other groups (P < 0.05). Groups B and C had a score of 4.13 and 3.67 respectively without significant difference (P = 0.091). With the aids of test bolus technique and proper injection protocol (40 ml contrast medium followed by 50 ml saline), the high quality image and low volume of iodine can be realized with second generation dual source CT for CTPA.

Adherence to Prophylaxis Guidelines for Symptomatic Venous Thromboembolism at a Darwin Hospital

ABSTRACTAimTo investigate adherence to venous thromboembolism (VTE) prophylaxis guidelines in patients who developed VTE within 90 days of hospital discharge.MethodInpatients diagnosed with VTE (January 2007 to December 2009) were identified retrospectively from the medical records coding department. Patients were ineligible if they were outpatients, admitted to another hospital in the 3 months prior to the diagnosis of VTE, or if the diagnosis was not confirmed via a Doppler ultrasound or computed tomography pulmonary angiogram scan. A single cycle audit measured adherence to the guidelines by comparing prophylaxis delivered to eligible patients prior to the diagnosis of VTE to the prophylaxis recommended by the hospital guidelines.Results59 medical and surgical patients were eligible (median age 62 years; interquartile range 23 to 84) and 59% (n = 35) were male. Adherence to VTE prophylaxis guidelines was investigated for 59 patients who developed VTE associated with their current indexed admission (n = 32) or within 90 days of discharge (n = 27). Adherence to VTE prophylaxis for high‐risk patients who developed VTE was: 50% for pharmacological prophylaxis and 57% for mechanical prophylaxis in surgical patients, and 63% for pharmacological prophylaxis and 26% for mechanical prophylaxis in medical patients.ConclusionNearly half of the patients had not received appropriate VTE prophylaxis prior to developing VTE.

S20 Time-resolved CT pulmonary angiography contrast transit time in patients with pulmonary embolism: a novel functional CT metric of right heart strain?

Introduction and ObjectivesAcute right ventricular (RV) failure is known to cause death in patients with pulmonary embolus due to circulatory collapse. CT pulmonary angiogram (CTPA) is now considered the gold...