CT pulmonary angiography: a comparative analysis of the utilization patterns in emergency department and hospitalized patients between 1998 and 2003

Optimizing emergency department imaging utilization for pulmonary emboli: A study on the effects of IV contrast rationing

PURPOSE

To study the impact of a contrast mitigation protocol on imaging utilization for pulmonary embolism (PE) in the emergency department (ED).

MATERIAL AND METHODS

Medical records of ED patients with suspected PE who underwent CT pulmonary angiography (CTPA) or ventilation-perfusion (VQ) scans were analyzed in control (3/15/22-4/15/22) and test (5/15/22-6/15/22) periods. The test period included a contrast mitigation protocol due to a global iodinated contrast shortage (05/2022-06/2022). Out of 610 scans, 28 were excluded for non-PE indications. Patient demographics, time metrics, and imaging reports were recorded.

RESULTS

Among 11,019 ED visits, there were 582 imaging events for suspected PE. The test period exhibited a significantly lower imaging rate of 4.16 % compared to 6.54 % in the control period (p < 0.001). CTPA usage decreased by 47.73 %, while VQ scan usage increased by 775.00 % during the test period. Test period positivity rate was 0.82 %, with CTPA at 0.58 % (1/173) and VQ scan at 1.43 % (1/70). In the control period, the positivity rate was 0.29 %, with CTPA at 0.30 % (1/331) and VQ scan at 0.00 % (0/8). Previous hospitalization history was significantly higher in the test period (70/243 vs. 39/339, p < 0.001). The positivity rates between the two periods showed no significant difference (p = 0.57). There were no significant differences in ED length of stay and image acquisition times.

CONCLUSION

The contrast mitigation protocol reduced CTPA use, increased VQ scans, and maintained positivity rates and image acquisition times. However, concerns persist about unnecessary imaging and low positivity rates, necessitating further research to optimize PE diagnostic algorithms.

A deep learning-based algorithm improves radiology residents' diagnoses of acute pulmonary embolism on CT pulmonary angiograms

PURPOSE

To compare radiology residents' diagnostic performances to detect pulmonary emboli (PEs) on CT pulmonary angiographies (CTPAs) with deep-learning (DL)-based algorithm support and without.

METHODS

Fully anonymized CTPAs (n = 207) of patients suspected of having acute PE served as input for PE detection using a previously trained and validated DL-based algorithm. Three residents in their first three years of training, blinded to the index report and clinical history, read the CTPAs first without, and 2 months later with the help of artificial intelligence (AI) output, to diagnose PE as present, absent or indeterminate. We evaluated concordances and discordances with the consensus-reading results of two experts in chest imaging.

RESULTS

Because the AI algorithm failed to analyze 11 CTPAs, 196 CTPAs were analyzed; 31 (15.8 %) were PE-positive. Good-classification performance was higher for residents with AI-algorithm support than without (AUROCs: 0.958 [95 % CI: 0.921-0.979] vs. 0.894 [95 % CI: 0.850-0.931], p < 0.001, respectively). The main finding was the increased sensitivity of residents' diagnoses using the AI algorithm (92.5 % vs. 81.7 %, respectively). Concordance between residents (kappa: 0.77 [95 % CI: 0.76-0.78]; p < 0.001) improved with AI-algorithm use (kappa: 0.88 [95 % CI: 0.87-0.89]; p < 0.001).

CONCLUSION

The AI algorithm we used improved between-resident agreements to interpret CTPAs for suspected PE and, hence, their diagnostic performances.

MR Angiography of Pulmonary Vasculature

Pulmonary MR angiography (MRA) is a useful alternative to computed tomographic angiography (CTA) for the study of the pulmonary vasculature. For pulmonary hypertension and partial anomalous pulmonary venous return, a cardiac MR imaging and the pulmonary MRA are useful for flow quantification and planning treatment. For the diagnosis of pulmonary embolism (PE), MRA-PE has been shown to have non-inferior outcomes at 6 months when compared with CTA-PE. Over the last 15 years, pulmonary MRA has become a routine and reliable examination for the workup of pulmonary hypertension and the primary diagnosis of PE at the University of Wisconsin.

Deep Learning-Based Algorithm for Automatic Detection of Pulmonary Embolism in Chest CT Angiograms

Purpose: Since the prompt recognition of acute pulmonary embolism (PE) and the immediate initiation of treatment can significantly reduce the risk of death, we developed a deep learning (DL)-based application aimed to automatically detect PEs on chest computed tomography angiograms (CTAs) and alert radiologists for an urgent interpretation. Convolutional neural networks (CNNs) were used to design the application. The associated algorithm used a hybrid 3D/2D UNet topology. The training phase was performed on datasets adequately distributed in terms of vendors, patient age, slice thickness, and kVp. The objective of this study was to validate the performance of the algorithm in detecting suspected PEs on CTAs. Methods: The validation dataset included 387 anonymized real-world chest CTAs from multiple clinical sites (228 U.S. cities). The data were acquired on 41 different scanner models from five different scanner makers. The ground truth (presence or absence of PE on CTA images) was established by three independent U.S. board-certified radiologists. Results: The algorithm correctly identified 170 of 186 exams positive for PE (sensitivity 91.4% [95% CI: 86.4–95.0%]) and 184 of 201 exams negative for PE (specificity 91.5% [95% CI: 86.8–95.0%]), leading to an accuracy of 91.5%. False negative cases were either chronic PEs or PEs at the limit of subsegmental arteries and close to partial volume effect artifacts. Most of the false positive findings were due to contrast agent-related fluid artifacts, pulmonary veins, and lymph nodes. Conclusions: The DL-based algorithm has a high degree of diagnostic accuracy with balanced sensitivity and specificity for the detection of PE on CTAs.

CT pulmonary angiography: optimising acute thoracic imaging by fixed-timing contrast medium delivery with a modified breathing instruction

AIM

To compare the thoracic vascular opacification achieved using the standard bolus-tracking protocol (BTP) with a fixed-timing protocol (FTP) with a modified breathing instruction during computed tomography pulmonary angiography (CTPA) examinations.

MATERIALS AND METHODS

A single-centre review of CTPA examinations performed between July 2018 and January 2019 using the BTP or FTP and weight-based contrast dosing of 20 mg iodine/kg body weight/s for 20 seconds at 100 kV tube potential. Radiodensity (in Hounsfield units) was analysed in the right ventricle, main pulmonary artery (MPA), left atrium, left ventricle, and ascending and descending thoracic aorta (DTA). A p-value of <0.05 was considered significant.

RESULTS

Of 782 examinations, 88 BTP and 90 FTP examinations were included. Mean attenuation of the MPA was similar in the FTP (396 ± 106 HU) and BTP (362 ± 119 HU; p=0.06); however, good-quality (≥250 HU) MPA opacification was achieved in more FTP examinations (87/90, 96.7%) compared to the BTP (73/88, 82.9%; p=0.002). Mean attenuation of the DTA was better in the FTP (325 ± 72 HU) than the BTP (228 ± 75 HU; p <0.0001), with good-quality opacification (≥250 HU) in 76/90 (84.4%) FTP examinations compared with 36/88 (40.9%) BTP examinations (p <0.001).

CONCLUSION

The FTP achieves better opacification of the MPA and DTA compared to the BTP.

Utilization of a Guideline-recommended Imaging Paradigm for Pregnant Patients With Suspicion of Pulmonary Embolism

PURPOSE

A dose reduction imaging paradigm utilizing chest x-ray (CXR) to triage between computed tomography pulmonary angiography (CTPA) and lung scintigraphy (LS) was introduced in 2001 and adopted in 2012 by the American Thoracic Society/Society of Thoracic Radiology (ATS) guideline for the evaluation of pulmonary embolism in pregnancy. We aimed to assess the utilization of this imaging paradigm preadoption and postadoption by the ATS guideline, and identify factors associated with its utilization.

MATERIALS AND METHODS

This retrospective cohort study evaluated consecutive pregnant patients who received CTPA or LS for the evaluation of pulmonary embolism in pregnancy at 2 tertiary hospitals between September 2008 and March 2017, excluding 2012 for guideline release washout. Utilization of the imaging paradigm was defined per patient by the use of CXR before advanced imaging, with CTPA performed following positive CXR and LS performed following negative CXR. Multivariate analyses were performed to assess factors associated with utilization of the imaging paradigm. P <0.05 is considered significant.

RESULTS

Overall, 9.8% (63/643) of studies utilized the dose reduction imaging paradigm, 13.3% (34/256) before the guidelines, and 7.5% (29/387) after. Multivariable analysis showed that the dose reduction imaging paradigm utilization was higher for inpatients (odds ratio [OR]: 4.5) and outpatients (OR: 3.1) relative to the emergency department patients, and lower for second (OR: 0.3) and third (OR: 0.2) trimester patients, without significant differences by study priority, patient age, or patient race.

CONCLUSIONS

Guideline-recommended dose reduction imaging paradigm utilization was low, and decreased after guideline publication. Utilization varied by patient setting and trimester, which are potential targets for interventions to improve guideline compliance.

A deep learning approach for automated diagnosis of pulmonary embolism on computed tomographic pulmonary angiography

BACKGROUND

Computed tomographic pulmonary angiography (CTPA) is the diagnostic standard for confirming pulmonary embolism (PE). Since PE is a life-threatening condition, early diagnosis and treatment are critical to avoid PE-associated morbidity and mortality. However, PE remains subject to misdiagnosis.

METHODS

We retrospectively identified 251 CTPAs performed at a tertiary care hospital between January 2018 to January 2021. The scans were classified as positive (n = 55) and negative (n = 196) for PE based on the annotations made by board-certified radiologists. A fully anonymized CT slice served as input for the detection of PE by the 2D segmentation model comprising U-Net architecture with Xception encoder. The diagnostic performance of the model was calculated at both the scan and the slice levels.

RESULTS

The model correctly identified 44 out of 55 scans as positive for PE and 146 out of 196 scans as negative for PE with a sensitivity of 0.80 [95% CI 0.68, 0.89], a specificity of 0.74 [95% CI 0.68, 0.80], and an accuracy of 0.76 [95% CI 0.70, 0.81]. On slice level, 4817 out of 5183 slices were marked as positive for the presence of emboli with a specificity of 0.89 [95% CI 0.88, 0.89], a sensitivity of 0.93 [95% CI 0.92, 0.94], and an accuracy of 0.89 [95% CI 0.887, 0.890]. The model also achieved an AUROC of 0.85 [0.78, 0.90] and 0.94 [0.936, 0.941] at scan level and slice level, respectively for the detection of PE.

CONCLUSION

The development of an AI model and its use for the identification of pulmonary embolism will support healthcare workers by reducing the rate of missed findings and minimizing the time required to screen the scans.

Applications of artificial intelligence in the thorax: a narrative review focusing on thoracic radiology

OBJECTIVE

This review will focus on how AI-and, specifically, deep learning-can be applied to complement aspects of the current healthcare system. We describe how AI-based tools can augment existing clinical workflows by discussing the applications of AI to worklist prioritization and patient triage, the performance-boosting effects of AI as a second reader, and the use of AI to facilitate complex quantifications. We also introduce prominent examples of recent AI applications, such as tuberculosis screening in resource-constrained environments, the detection of lung cancer with screening CT, and the diagnosis of COVID-19. We also provide examples of prognostic predictions and new discoveries beyond existing clinical practices.

BACKGROUND

Artificial intelligence (AI) has shown promising performance for thoracic diseases, particularly in the field of thoracic radiology. However, it has not yet been established how AI-based image analysis systems can help physicians in clinical practice.

METHODS

This review included peer-reviewed research articles on AI in the thorax published in English between 2015 and 2021.

CONCLUSIONS

With advances in technology and appropriate preparation of physicians, AI could address various clinical problems that have not been solved due to a lack of clinical resources or technological limitations.

KEYWORDS

Artificial intelligence (AI); deep learning (DL); computer aided diagnosis (CAD); thoracic radiology; pulmonary medicine.

PENet-a scalable deep-learning model for automated diagnosis of pulmonary embolism using volumetric CT imaging

Pulmonary embolism (PE) is a life-threatening clinical problem and computed tomography pulmonary angiography (CTPA) is the gold standard for diagnosis. Prompt diagnosis and immediate treatment are critical to avoid high morbidity and mortality rates, yet PE remains among the diagnoses most frequently missed or delayed. In this study, we developed a deep learning model-PENet, to automatically detect PE on volumetric CTPA scans as an end-to-end solution for this purpose. The PENet is a 77-layer 3D convolutional neural network (CNN) pretrained on the Kinetics-600 dataset and fine-tuned on a retrospective CTPA dataset collected from a single academic institution. The PENet model performance was evaluated in detecting PE on data from two different institutions: one as a hold-out dataset from the same institution as the training data and a second collected from an external institution to evaluate model generalizability to an unrelated population dataset. PENet achieved an AUROC of 0.84 [0.82-0.87] on detecting PE on the hold out internal test set and 0.85 [0.81-0.88] on external dataset. PENet also outperformed current state-of-the-art 3D CNN models. The results represent successful application of an end-to-end 3D CNN model for the complex task of PE diagnosis without requiring computationally intensive and time consuming preprocessing and demonstrates sustained performance on data from an external institution. Our model could be applied as a triage tool to automatically identify clinically important PEs allowing for prioritization for diagnostic radiology interpretation and improved care pathways via more efficient diagnosis.

Performance of Computed Tomographic Pulmonary Angiography Compared With Standard Chest Computed Tomography for Identification of Solid Organ, Serosal, and Nodal Findings

PURPOSE

Computed tomographic pulmonary angiography (CTPA) is the test of choice for patients with acute chest pain and suspected pulmonary embolism (PE). This examination is excellent for the diagnosis of PE and can also often identify alternative diagnoses. The early phase of contrast, however, may not allow for optimal evaluation of lymph nodes, serosal surfaces, and solid organs, leading to the nonvisualization of important findings and the potential for missed diagnoses. The purpose of this study was to determine the frequency of relevant findings only identified on standard portal venous phase CT compared with CTPA.

MATERIALS AND METHODS

The reports for all patients in the previous 10 years who underwent both standard CT and CTPA within 7 days, for a total of 675 pairs of scans, were tabulated according to the presence of PE, serosal abnormalities, solid organ abnormalities, and lymphadenopathy. All findings were categorized as present on both scans, standard CT only, or CTPA only. The scans were manually evaluated to exclude findings that were new or resolved on the second study or outside the field of view on one of the studies.

RESULTS

Significantly more PEs were identified only on CTPA examinations. However, significantly more pleural, peritoneal, and solid organ abnormalities, and abnormal mediastinal and abdominal lymph nodes were identified on standard CT only. There was no significant difference in the identification of pericardial abnormalities or abnormal hilar lymph nodes between the two scans.

CONCLUSIONS

Many serosal abnormalities, solid organ abnormalities, and lymphadenopathy were only reported on standard portal venous phase CT compared with CTPA.

Assessment of the current D-dimer cutoff point in pulmonary embolism workup at a single institution: Retrospective study

Background:

The currently used D-dimer (DD) cutoff point is associated with a large number of negative CT-pulmonary angiographies (CTPA). We hypothesized presence of deficiency in the current cutoff and a need to look for a better DD threshold.

Materials and Methods:

We conducted a retrospective medical records analysis of all patients who had a CTPA as part of pulmonary embolism (PE) workup over a 1-year period. All emergency room (ER) patients who had DD assay checked prior to CTPA were included in the analysis. We assessed our institutional cutoff point and tried to test other presumptive DD thresholds retrospectively.

Results:

At our institution 1591 CTPA were performed in 2014, with 1220 scans (77%) performed in the ER. DD test was ordered prior to CTPA imaging in 238 ER patients (19.5%) as part of the PE workup. PE was diagnosed in 14 cases (6%). The sensitivity and specificity of the currently used DD cutoff (0.5 mcg/mL) were found to be 100% and 13%, respectively. Shifting the cutoff value from 0.5 to 0.85 mcg/mL would result in a significant increase in the specificity from 13% to 51% while maintaining the same sensitivity of 100%. This would make theoretically 84 CTPA scans, corresponding to 35% of CTPA imaging, unnecessary because DD would be considered negative based on this presumptive threshold.

Conclusions:

Our results suggest a significant deficiency in the institutional DD cutoff point with the need to find a better threshold through a large multicenter prospective trial to minimize unnecessary CTPA scans and to improve patient safety.

Clinical Probability Tools for Deep Venous Thrombosis, Pulmonary Embolism, and Bleeding

Overdiagnosis of venous thromboembolism is associated with increasing numbers of patient complications and health care burden. Multiple clinical tools exist to estimate the probability of pulmonary embolism and deep venous thrombosis. When used with d-dimer testing, these can further stratify venous thromboembolism risk to help inform the use of additional diagnostic testing. Although there are similar tools to estimate bleeding risk, these are not as well-validated and lack reliability.

Large hospital variation in the utilization of Post-procedural CT to detect pulmonary embolism/Deep Vein Thrombosis in Patients Undergoing Total Knee or Hip Replacement Surgery: Japanese Nationwide Diagnosis Procedure Combination Database Study

OBJECTIVE

The purpose of the study was to investigate variation in the use of in-hospital CT for venous thromboembolism (VTE) detection after total knee or hip replacement (TKR/THR) among surgical patients, using a nationwide Japanese in-hospital administrative database.

METHODS

This retrospective study using a national administrative database (4/2012-3/2013) extracted patients who underwent TKR/THR surgeries at hospitals meeting the annual case-volume threshold of ≥ 30. Hospitals were categorized into three equally sized groups by frequency of postoperative CT use (low, middle, and high CT use group) to compare baseline patient-level and hospital-level characteristics. To further investigate between-hospital variation in CT usage, we fitted a hierarchical logistic regression model including hospital-specific random intercepts and fixed patient- and hospital-level effects. The intra class correlation coefficient was used to measure the amount of variability in CT use attributable to between-hospital variation.

RESULTS

A total of 39,127 patients discharged from 447 hospitals met the inclusion criteria. The median hospital stay was 25 days (interquartile range, 20 - 32) and 7,599 (19.4%) patients underwent CT for VTE. CT utilization varied greatly among the hospitals; the crude frequency ranged from 0 to 100 % (median, 7.3 %; interquartile range, 1.8 - 18.3 %). After adjustment for known hospital- and patient-level factors related to CT use, 47 % of the variation in CT use remained attributable to the behavior of individual hospitals.

CONCLUSION

We observed large inter hospital variability in the utilization of post-procedure CT for VTE detection in this Japanese TKR/THR cohort, suggesting that CT utilization is not optimized across the nation.

ADVANCES IN KNOWLEDGE

We observed significant variability in the utilization of post-procedure CT for VTE detection among inpatients who underwent TKR/THR surgeries in a large sample of Japanese hospitals. The large variation suggests that CT utilization is not optimized across the nation, and that there may be potential overutilization of the technology in the highest CT use hospitals.

Magnetic resonance angiography imaging of pulmonary embolism using agents with blood pool properties as an alternative to computed tomography to avoid radiation exposure

PURPOSE

To evaluate the feasibility and accuracy of a combined magnetic resonance angiography (MRA) - magnetic resonance venography (MRV) protocol using contrast agents with blood pool properties, gadofosveset trisodium and gadobenate dimeglumine, in the evaluation of pulmonary embolus (PE) and deep venous thrombosis (DVT) as compared to the standard clinical reference imaging modalities; computed tomography pulmonary angiography (CTPA) and color-coded Duplex ultrasound (DUS).

MATERIALS AND METHODS

This prospective clinical study recruited patients presenting to the emergency department with clinical suspicion for PE and scheduled for a clinically indicated CTPA. We performed both MRA of the chest for the evaluation of PE as well as MRV of the pelvis and thighs to evaluate for DVT using a single contrast injection. MRA-MRV data was compared to the clinical reference standard CTPA and DUS, respectively.

RESULTS

A total of 40 patients were recruited. The results on a per-patient basis comparing MRA to CTPA for pulmonary embolus yielded 100% sensitivity and 97% specificity. There was a small subset of patients that underwent clinical DUS to evaluate for DVT, which demonstrated a sensitivity and specificity of 100% for MRV.

CONCLUSIONS

This single-center, preliminary study using contrast agents with blood pool properties to perform a relatively rapid combined MRA-MRV exam to image for PE and above knee DVT shows potential as an alternative imaging choice to CTPA. Further large-scale, multicentre studies are warranted.

Submillisievert standard-pitch CT pulmonary angiography with ultra-low dose contrast media administration: A comparison to standard CT imaging

Objectives

To evaluate the image quality and radiation dose of submillisievert standard-pitch CT pulmonary angiography (CTPA) with ultra-low dose contrast media administration in comparison to standard CTPA.

Materials and methods

Hundred patients (56 females, 44 males, mean age 69.6±15.4 years; median BMI: 26.6, IQR: 5.9) with suspected pulmonary embolism were examined with two different protocols (n = 50 each, group A: 80 kVp, ref. mAs 115, 25 ml of contrast medium; group B: 100 kVp, ref. mAs 150, 60 ml of contrast medium) using a dual-source CT equipped with automated exposure control. Objective and subjective image qualities, radiation exposure as well as the frequency of pulmonary embolism were evaluated.

Results

There was no significant difference in subjective image quality scores between two groups regarding pulmonary arteries (p = 0.776), whereby the interobserver agreement was excellent (group A: k = 0.9; group B k = 1.0). Objective image analysis revealed that signal intensities (SI), signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) of the pulmonary arteries were equal or significantly higher in group B. There was no significant difference in the frequency of pulmonary embolism (p = 0.65). Using the low dose and low contrast media protocol resulted in a radiation dose reduction by 71.8% (2.4 vs. 0.7 mSv; p<0.001).

Conclusions

This 80 kVp standard pitch CTPA protocol with 25 ml contrast agent volume can obtain sufficient image quality to exclude or diagnose pulmonary emboli while reducing radiation dose by approximately 71%.

Evaluation of a proper cutoff value on quantitative dual-energy perfusion CT for the assessment of acute pulmonary thromboembolism

Background The cutoff value for assessing the severity of acute pulmonary thromboembolism (PTE) using relative volumetric evaluations of dual-energy perfusion computed tomography (DEpCT) is unclear. Purpose To determine the proper cutoff value for determining the severity of PTE using DEpCT volumetry. Material and Methods A total of 185 patients with venous thromboembolism were included in this study, of whom 61 were diagnosed with acute PTE. DEpCT images were three-dimensionally reconstructed at the following attenuation ranges: 1-2 HU (V2), 1-10 HU (V10), and 1-120 HU (V120). The ratios of low perfusion areas associated with each threshold range per V120 were also calculated, and the relative ratios were expressed as %V2 to %V10. These values were compared with factors indicating the severity of PTE, including the pulmonary arterial pressure, heart rate, CT angiographic obstruction index (CTOI), and right/left ventricular diameter ratio (RV/LV). Results The area under the curve (AUC) of %V2 was highest (0.783) among these values (95% confidence interval, 0.710-0.856) based on the presence of IPCs. The %V2 showed moderate correlations with CTOI (r = 0.36, P = 0.005) and RV/LV (r = 0.36, P = 0.004) in the patients with acute PTE. Conclusion Volumetric evaluations of DEpCT images using the lowest attenuation threshold range (1-2 HU) exhibit the best correlation with factors suggesting the severity of acute PTE.

Clinical and echocardiographic findings of patients with suspected acute pulmonary thromboembolism who underwent computed tomography pulmonary angiography

Background:

The aim of the study was to determine the correlation between clinical and echocardiographic findings and risk factors of patients with suspected acute pulmonary thromboembolism (PTE) who underwent computed tomography pulmonary angiography (CTPA).

Materials and Methods:

In this cross-sectional study, 310 hospitalized patients aged >18 years with high clinical suspicion of PTE referred to imaging center of our hospital from different wards for CTPA were enrolled. The frequency of different clinical presentations, risk factors, items of Wells’ criteria, and echocardiographic findings was compared in patients with and without PTE, which have been diagnosed according to the CTPA results.

Results:

PTE was diagnosed in 53 (17.1%) of patients with suspected PTE. From clinical manifestations, tachypnea, pleuritic chest pain, and edema of lower extremities were significantly more frequent among patients with PTE (P < 0.05). Major surgery was the risk factor which was significantly more prevalent among patients with PTE (P < 0.05). Frequency of all criteria of Wells’ criteria, except hemoptysis, was significantly higher in patients with PTE (P < 0.05). The frequency of all studied echocardiographic variables was significantly higher in patients with PTE (P < 0.05).

Conclusion:

It is suggested that we could use the results of this study for utilizing the diagnostic process of PTE in patients with highly clinical suspicion of PTE and providing more validated decision. Using the results of this study, we could identify high-risk patients and made appropriate risk assessment for better management of patients with suspected PTE as well as reduce the rate of unnecessary CTPA and its related adverse consequences.

The role of computed tomography in the diagnosis of acute and chronic pulmonary embolism

Pulmonary embolism (PE) is a potentially life threatening condition requiring adequate diagnosis and treatment. Computed tomography pulmonary angiography (CTPA) is excellent for including and excluding PE, therefore CT is the first-choice diagnostic imaging technique in patients suspected of having acute PE. Due to its wide availability and low invasiveness, CTPA tends to be overused. Correct implementation of clinical decision rules in diagnostic workup for PE improves adequate use of CT. Also, CT adds prognostic value by evaluating right ventricular (RV) function. CT-assessed RV dysfunction and to lesser extent central emboli location predicts PE-related mortality in normotensive and hypotensive patients, while PE embolic obstruction index has limited prognostic value. Simple RV/left ventricular (LV) diameter ratio measures >1.0 already predict risk for adverse outcome, whereas ratios <1.0 can safely exclude adverse outcome. Consequently, assessing the RV/LV diameter ratio may help identify patients who are potential candidates for treatment at home instead of treatment in the hospital. A minority of patients develop chronic thromboembolic pulmonary hypertension (CTEPH) following acute PE, which is a life-threatening condition that can be diagnosed by CT. In proximal CTEPH, involving the more central pulmonary arteries, thrombectomy usually results in good outcome in terms of both functional status and long-term survival rate. CT is becoming the imaging method of choice for diagnosing CTEPH as it can identify patients who may benefit from thrombectomy. New CT developments such as distensibility measurements and dual-energy or subtraction techniques may further refine diagnosis and prognosis for improved patient care.

Suboptimal implementation of diagnostic algorithms and overuse of computed tomography-pulmonary angiography in patients with suspected pulmonary embolism

BACKGROUND

Majority of our computed tomography-pulmonary angiography (CTPA) scans report negative findings. We hypothesized that suboptimal reliance on diagnostic algorithms contributes to apparent overuse of this test.

METHODS

A retrospective review was performed on 2031 CTPA cases in a large hospital system. Investigators retrospectively calculated pretest probability (PTP). Use of CTPA was considered as inappropriate when it was ordered for patients with low PTP without checking D-dimer (DD) or following negative DD.

RESULTS

Among the 2031 cases, pulmonary embolism (PE) was found in 7.4% (151 cases). About 1784 patients (88%) were considered "PE unlikely" based on Wells score. Out of those patients, 1084 cases (61%) did not have DD test prior to CTPA. In addition, 78 patients with negative DD underwent unnecessary CTPA; none of them had PE.

CONCLUSIONS

The suboptimal implementation of PTP assessment tools can result in the overuse of CTPA, contributing to ineffective utilization of hospital resources, increased cost, and potential harm to patients.

Limited Hospital Variation in the Use and Yield of CT for Pulmonary Embolism in Patients Undergoing Total Hip or Total Knee Replacement Surgery

Purpose To evaluate the variation among U.S. hospitals in overall use and yield of in-hospital computed tomographic (CT) pulmonary angiography (PA) in patients undergoing total hip replacement (THR) or total knee replacement (TKR) surgery. Materials and Methods Patients in the Premier Research Database who underwent elective TKR or THR between 2007 and 2011 were enrolled in this HIPAA-compliant, institutional review board-approved retrospective observational study. The informed consent requirement was waived. Hospitals were categorized into low, medium, and high tertiles of CT PA use to compare baseline patient- and hospital-level characteristics and pulmonary embolism (PE) positivity rates. To further investigate between-hospital variation in CT PA use, a hierarchical logistic regression model that included hospital-specific random effects and fixed patient- and hospital-level effects was used. The intraclass correlation coefficient (ICC) was used to measure the amount of variability in CT PA use attributable to between-hospital variation. Results The cohort included 205 198 patients discharged from 178 hospitals (median of 734.5 patients discharged per hospital; interquartile range, 316-1461 patients) with 3647 CT PA studies (1.8%). The crude frequency of CT PA scans among the hospitals ranged from 0% to 6.2% (median, 1.6%); more than 90% of the hospitals performed CT PA in less than 3% of their patients. The mean hospital-level PE positivity rate was 12.3% (median, 9.1%); there was no significant difference in PE positivity rate across low through high CT PA use tertiles (11.3%, 11.9%, 12.9%, P = .37). After adjustment for hospital- and patient-level factors, the remaining amount of interhospital variation was relatively low (ICC, 9.0%). Conclusion Limited interhospital variation in use and yield of in-hospital CT PA was observed among patients undergoing TKR or THR in the United States. ^© RSNA, 2016 Online supplemental material is available for this article.

Incidental findings on computed tomography angiography in patients evaluated for pulmonary embolism

RATIONALE

To investigate how often computed tomography (CT) pulmonary angiography contributes to establishing a diagnosis in patients presenting to the emergency department and how it performs compared to chest radiograph.

OBJECTIVES

The objective of this study was to measure the ability to identify a diagnosis and to investigate the prevalence and significance of incidental findings in patients evaluated with computed tomography pulmonary angiography in the emergency department.

METHODS

All adult patients evaluated with CT angiography over a 2-year period (January 1, 2011 to December 31, 2012) were included in the analysis. A total of 641 records were identified. Chest radiographs and CT angiography reports were reviewed to determine whether they could provide a diagnosis in patients without pulmonary embolism (PE). Studies negative for PE were stratified into three categories according to significance: type I prompted immediate action, type II required follow up, and type III had findings of limited significance.

MEASUREMENTS AND MAIN RESULTS

CT angiography identified a diagnosis in 22.46% of the patient population and in 14.31% of patients without PE. In patients who had CT angiography with chest radiograph, diagnoses were provided in 14.01 and 9.86% of patients, respectively. When analysis was isolated to patients with low probability for PE, CT angiography provided a diagnosis in 20% and chest radiography in 10.23% of patients. The majority of missed cases represented infiltrates too small to be detected by radiography and were believed to represent lung infections by the interpreting radiologist. Among studies negative for PE, 15% were type I, 17.07% were type II, 48.1% were type III, and the rest were normal.

CONCLUSIONS

CT angiography is superior to chest radiography at providing a diagnosis in patients investigated for PE, even when no PE is present. However, in patients at low risk for PE, the clinical benefit of the additional diagnoses is questionable.

Increase in Utilization of Afterhours Medical Imaging: A Study of Three Canadian Academic Centers

Objectives

The objectives of our study were to assess trends in afterhours medical imaging utilization for emergency department (ED) and inpatient (IP) patient populations from 2006-2013, including analysis by modality and specialty and with adjustment for patient volume.

Methods

For this retrospective study, we reviewed the number of CT, MRI, and ultrasound studies performed for the ED and IP patients during the afterhours time period (5pm - 8am on weekdays and 24 hours on weekends and statutory holidays) from 2006-2013 at three different Canadian academic hospitals. We used the Jonckheere-Terpstra (JT) test to determine statistical significance of imaging and patient volume trends. A regression model was used to examine whether there was an increasing trend over time in the volume of imaging tests per 1000 patients.

Results

For all three sites from 2006-2013 during the afterhours time period: There was a statistically significant increasing trend in total medical imaging volume, which also held true when the volumes were assessed by modality and by specialty. There was a statistically significant increasing trend in ED and IP patient volume. When medical imaging volumes were adjusted for patient volumes, there was a statistically significant increasing trend in imaging being performed per patient.

Conclusion

Afterhours medical imaging volumes demonstrated a statistically significant increasing trend at all three sites from 2006-2013 when assessed by total volume, modality, and specialty. During the same time period and at all three sites, the ED and IP patient volumes also demonstrated a statistically significant increasing trend with more medical imaging, however, being performed per patient.

Improving appropriate use of pulmonary computed tomography angiography by increasing the serum D-dimer threshold and assessing clinical probability

OBJECTIVE

To determine whether the implementation of an increased D-dimer threshold value and clinical probability assessment increases the prevalence of pulmonary embolism (PE) in patients undergoing pulmonary computed tomography angiography (PCTA) in an Emergency Department setting.

METHODS

A retrospective review of all patients undergoing PCTA during 2 separate 12-month intervals, 1 before the implementation of an increased D-dimer threshold and recommendation for formal clinical probability assessment and the other after regional implementation. The primary outcome measure was the prevalence of acute PE in each of the samples.

RESULTS

After the implementation of the increased D-dimer threshold and recommendation for formal clinical probability assessment, the prevalence of PE detected by PCTA increased from 4.7% to 11.7% (p < 0.001). Among all PCTAs performed after the new guidelines were promulgated, 8.6% were still performed on patients who had serum D-dimer values lower than the threshold of 1.0 µg/mL. Despite the recommendation for formal clinical probability assessment before ordering a PCTA, only 4% of patients had a formal clinical probability assessment recorded in their electronic medical record.

CONCLUSION

The implementation of an increased D-dimer threshold value increased the prevalence of PE in patients undergoing PCTA in an Emergency Department setting, but more consistent application of clinical probability assessment remains an elusive target.

Triage for suspected acute Pulmonary Embolism: Think before opening Pandora's Box

This is a review of the current strengths and weaknesses of the various imaging modalities available for the diagnosis of suspected non-massive Pulmonary Embolism (PE). Without careful consideration for the clinical presentation, and the timely application of clinical decision support (CDS) methodology, the current overutilization of imaging resources for this disease will continue. For a patient with a low clinical risk profile and a negative D-dimer there is no reason to consider further workup with imaging; as the negative predictive value in this scenario is the same as imaging. While the current efficacy and effectiveness data support the continued use of Computed Tomographic angiography (CTA) as the imaging golden standard for the diagnosis of PE; this test does have the unintended consequences of radiation exposure, possible overdiagnosis and overuse. There is a persistent lack of appreciation on the part of ordering physicians for the effectiveness of the alternatives to CTA (ventilation-perfusion imaging and contrast enhanced magnetic resonance angiography) in these patients. Careful use of standardized protocols for patient triage and the application of CDS will allow for a better use of imaging resources.

Effect of Evidence-based Clinical Decision Support on the Use and Yield of CT Pulmonary Angiographic Imaging in Hospitalized Patients

PURPOSE

To determine the effect of clinical decision support (CDS) on the use and yield of inpatient computed tomographic (CT) pulmonary angiography for acute pulmonary embolism (PE).

MATERIALS AND METHODS

This HIPAA-compliant, institutional review board-approved study with waiver of informed consent included all adults admitted to a 793-bed teaching hospital from April 1, 2007, to June 30, 2012. The CDS intervention, implemented after a baseline observation period, informed providers who placed an order for CT pulmonary angiographic imaging about the pretest probability of the study based on a validated decision rule. Use of CT pulmonary angiographic and admission data from administrative databases was obtained for this study. By using a validated natural language processing algorithm on radiology reports, each CT pulmonary angiographic examination was classified as positive or negative for acute PE. Primary outcome measure was monthly use of CT pulmonary angiography per 1000 admissions. Secondary outcome was CT pulmonary angiography yield (percentage of CT pulmonary angiographic examinations that were positive for acute PE). Linear trend analysis was used to assess for effect and trend differences in use and yield of CT pulmonary angiographic imaging before and after CDS.

RESULTS

In 272 374 admissions over the study period, 5287 patients underwent 5892 CT pulmonary angiographic examinations. A 12.3% decrease in monthly use of CT pulmonary angiography (26.0 to 22.8 CT pulmonary angiographic examinations per 1000 admissions before and after CDS, respectively; P = .008) observed 1 month after CDS implementation was sustained over the ensuing 32-month period. There was a nonsignificant 16.3% increase in monthly yield of CT pulmonary angiography or percentage of CT pulmonary angiographic examinations positive for acute PE after CDS (P = .65).

CONCLUSION

Implementation of evidence-based CDS for inpatients was associated with a 12.3% immediate and sustained decrease in use of CT pulmonary angiographic examinations in the evaluation of inpatients for acute PE. for this article.

Impact of iterative reconstruction on the diagnosis of acute pulmonary embolism (PE) on reduced-dose chest CT angiograms

PURPOSE

To evaluate the impact of iterative reconstruction on the detectability of clots.

METHODS AND MATERIALS

Fifty-three patients were enrolled in a study comparing reduced-dose and full-dose images, available from the same dual-source data set. From each acquisition, three series of images were generated: (1) full-dose images (from both tubes), reconstructed with filtered back projection (FBP) (group 1; standard of reference), (2) reduced-dose images (from tube A only; 60 % dose reduction) reconstructed with FBP (group 2) and iterative reconstruction (SAFIRE) (group 3).

RESULTS

In group 1 (mean DLP: 264.6 mGy.cm), (1) PE was diagnosed in 8 patients (15 %) with 82 clots in the central (n = 5), segmental (n = 39) and subsegmental (n = 38) arteries and (2) mean level of noise was 30.56 ± 5.07. In group 2 (mean DLP: 105.8 mGy.cm), a significant increase in noise (44.56 ± 6.24; p < 0.0001) (1) hampered detection of PE in one patient and (2) altered detection of peripheral clots (12 false-negative and 2 false-positive results). In group 3, image noise was not significantly different from that in group 1 (p = 0.1525; effect size: 0.2683), with a similar detection of PE compared to group 1 (p = 1).

CONCLUSION

Reconstruction of reduced-dose images (60 % dose reduction) with SAFIRE provided image quality and diagnostic value comparable to those of full-dose FBP images.

KEY POINTS

• Iterative reconstruction does not alter the detection of endoluminal clots. • Iterative reconstruction allows dose reduction in the context of acute PE. • Iterative reconstruction allows radiologists to approach the prospects of submilliSievert CT.

Could the number of CT angiograms be reduced in emergency department patients suspected of pulmonary embolism?

BACKGROUND

This study was undertaken to identify the prevalence of pulmonary embolism (PE) in the emergency department (ED) of an urban teaching hospital and also to test a Bayesian model in estimating the number of CT pulmonary angiography (CTA) expected to be performed in an emergency department.

METHODS

The data for this study was obtained through a retrospective review of electronic medical records for all ED patients suspected of PE who underwent chest CTA or ventilation perfusion scanning (V/Q) between 2009 and 2010. The data is presented as means and standard deviation for continuous variables and percentages with 95% confidence intervals (95%CI) for proportions. The prevalence of PE was used as pre-test probability in the Bayesian model. Post-test probability was obtained using a Fagan nomogram and likelihood ratios for CTA.

RESULTS

A total of 778 patients (560 females) with mean age of 50 years (range 18-98 years) were enrolled (98.3% underwent chest CTA and 1.7% underwent V/Q scan). A total of 69 patients had PE, rendering an overall prevalence of 8.9% (95%CI, 7.1% to 11.1%) for PE. We calculated that 132 CTA's per year could be avoided in our institution, without compromising safe exclusions of PE (keeping post-test probability of PE below 2%).

CONCLUSIONS

Despite differences in our patient populations and /or study designs, the prevalence of PE in our institution is about average compared to other institutions. Our proposed model for calculating redundant chest CTA is simple and can be used by institutions to identify overuse of CTA.

U.S. trends in computed tomography use and diagnoses in emergency department visits by patients with symptoms suggestive of pulmonary embolism, 2001-2009

OBJECTIVES

Using computed tomography (CT) to evaluate patients with chest symptoms is common in emergency departments (EDs). This article describes recent trends of CT use in U.S. EDs for patients presenting with symptoms common to acute pulmonary embolism (PE).

METHODS

The 2001-2009 National Hospital Ambulatory Medical Care Survey (NHAMCS), a nationally representative survey of U.S. ED encounters, was used for data collection. Patients with at least one of three complaints (chest pain, dyspnea, or hemoptysis) were categorized into the chest symptom study (CSS) group. The yearly increases in CT use for the complaints were tabulated first, then linear regression analysis was used to calculate average rates of increases in CT use between 2001 and 2007, the years where CT use increased, for the overall population and among specific subgroups. The ratios of the number of visits when CT was ordered and there was a target diagnosis relative to the total number of visits with CT in the CSS group (diagnosis/CT ratio) were calculated for PE and pneumonia.

RESULTS

Annual CT rates for the CSS group increased from 2.6% in 2001 to 13.2% in 2007, subsequently leveling off at approximately 12.5% in 2008 and 2009. The average growth rate of CT use for the CSS group was 28.1% (95% confidence interval [CI] = 20.9% to 35.7%) per year between 2001 and 2007. Testing rates for all subgroups increased. The lowest growth rate was among Hispanic patients, whose CT rates grew 14.2% (95% CI = 5.7% to 23.5%) per year. The highest growth rate was in nonurban hospitals, at 43.1% (95% CI = 15.2% to 77.8%) per year. Patients triaged as nonurgent received the fewest CTs, compared to those who should be seen in 2 hours or less. With regard to sources of payment, the self-pay subgroup experienced the highest rate of increase at 35.1% (95% CI = 18.6% to 53.9%). The PE diagnosis/CT ratio from 2002 to 2009 was 2.7% for the CSS group. The pneumonia diagnosis/CT ratio grew from 5.8% in 2002 to 2005 to 7.8% in 2006 to 2009.

CONCLUSIONS

Computed tomography use in ED visits by patients with chest symptoms increased dramatically from 2001 to 2007 and seems to have leveled off in subsequent years. The low PE diagnosis-to-CT ratio suggests that EDs may need to promote evidence-based use of CT.

CT pulmonary angiography: increasingly diagnosing less severe pulmonary emboli

Background

It is unknown whether the observed increase in computed tomography pulmonary angiography (CTPA) utilization has resulted in increased detection of pulmonary emboli (PEs) with a less severe disease spectrum.

Methods

Trends in utilization, diagnostic yield, and disease severity were evaluated for 4,048 consecutive initial CTPAs performed in adult patients in the emergency department of a large urban academic medical center between 1/1/2004 and 10/31/2009. Transthoracic echocardiography (TTE) findings and peak serum troponin levels were evaluated to assess for the presence of PE-associated right ventricular (RV) abnormalities (dysfunction or dilatation) and myocardial injury, respectively. Statistical analyses were performed using multivariate logistic regression.

Results

268 CTPAs (6.6%) were positive for acute PE, and 3,780 (93.4%) demonstrated either no PE or chronic PE. There was a significant increase in the likelihood of undergoing CTPA per year during the study period (odds ratio [OR] 1.05, 95% confidence interval [CI] 1.04–1.07, P<0.01). There was no significant change in the likelihood of having a CTPA diagnostic of an acute PE per year (OR 1.03, 95% CI 0.95–1.11, P = 0.49). The likelihood of diagnosing a less severe PE on CTPA with no associated RV abnormalities or myocardial injury increased per year during the study period (OR 1.39, 95% CI 1.10–1.75, P = 0.01).

Conclusions

CTPA utilization has risen with no corresponding change in diagnostic yield, resulting in an increase in PE detection. There is a concurrent rise in the likelihood of diagnosing a less clinically severe spectrum of PEs.

Dual-energy perfusion CT of non-diseased lung segments using dual-source CT: correlation with perfusion SPECT

PURPOSE

To determine the utility of dual-energy perfusion CT (DEpCT) of non-diseased lung segments, using dual-source CT, in comparison with perfusion single-photon emission computed tomography (SPECT).

MATERIALS AND METHODS

28 patients (18 male and 10 female; mean age 63 years; age range 18-86 years) underwent DEpCT and SPECT within a 3-day interval. The presence and location of perfusion defects in each segment of the lungs were evaluated.

RESULTS

Perfusion defects were noted in 7 of 361 segments (1.9%) by DEpCT and in 19 of 361 segments (5.3%) by perfusion SPECT. DEpCT was in good agreement with perfusion SPECT for 338 of 361 segments (93.6%). Intraobserver agreement was also good, ranging from 93.4 to 93.6% (κ = 0.64-0.75, p < 0.01).

CONCLUSION

For non-diseased lung segments, DEpCT correlated well with SPECT.