CT venography: a necessary adjunct to CT pulmonary angiography or a waste of time, money, and radiation?

The History of Diagnosing Venous Thromboembolism

An accurate and prompt diagnosis of deep vein thrombosis and/or pulmonary embolism is important to prevent serious complications and mortality. Because the clinical presentation of venous thromboembolism (VTE) is often nonspecific, objective testing by means of radiological imaging is required to confirm the diagnosis. Historically, a diagnosis of VTE involved invasive imaging techniques like contrast venography or conventional pulmonary angiography. Technological developments toward more accurate and less invasive diagnostics have driven the implementation of a variety of newer technologies over the past decades, as well as the derivation and validation of clinical decision rules (CDRs) that can be used to rule out VTE in combination with D-dimer blood tests. In this narrative review, we provide a historical overview of the most notable developments in the imaging techniques and CDRs for VTE diagnosis.

Deep vein thrombosis in donor or recipient veins encountered during lower extremity reconstruction with a free anterolateral thigh perforator flap: How do we deal with it?

Background

The free anterolateral thigh perforator (ALTP) flap has been successfully adopted to reconstruct traumatic soft tissue defects in the lower extremities. However, the occurrence of deep vein thrombosis (DVT) in donor or recipient veins has been overlooked, and there has been no reliable guideline to manage it. Therefore, in this study, we review our cases where the ALTP flaps were transferred to traumatic lower limbs even though DVT was found in the pedicle or recipient veins. Furthermore, based on our experiences, we suggest an algorithmic approach for dealing with DVT.

Patients and methods

This study included 108 patients who underwent lower extremity reconstruction using a free ALTP flap between January 2014 and January 2021. All medical records were reviewed, including preoperative assessment data, intraoperative findings, and postoperative complications. Notably, when DVT was found in both the donor and recipient veins, we thoroughly assessed operative findings, surgical solutions, and final outcomes.

Results

Sixty-one of 108 (56.4%) patients underwent computed tomographic venography (CTV) preoperatively, revealing DVT in 11 of these 61 (18%) patients. Three of these 11 patients had iliofemoral DVT, and surgery was delayed more than two weeks after detection. The remaining eight patients had calf DVT and underwent free ALTP flap transfer as scheduled. Conversely, 47 of 108 (43.6%) patients did not undergo CTV, and an occult DVT was found in five of these 47 (10.6%) patients. In two of these five patients, free flap surgery was replaced with amputation and local flap coverage. In the remaining three patients and one patient with an occult DVT that was not found on CTV, the free ALTP flap transfer was carried out. In 15 patients with DVT, free ALTP flap transfer was performed using various alternative methods for venorrhaphy. Consequently, all flaps survived, with partial necrosis occurring in two patients.

Conclusion

If DVT-affected veins are appropriately managed, the free ALTP flap can be successfully transferred to the traumatic lower limb even when DVT occurs in donor or recipient veins. The author's algorithm can help surgeons overcome the insufficiency of veins for pedicle anastomosis due to DVT and avoid postoperative thromboembolic complications.

Diagnosis of Deep Venous Thrombosis and Pulmonary Embolism: New Imaging Tools and Modalities

Imaging continues to be the modality of choice for the diagnosis of venous thromboembolic disease, particularly when incorporated into diagnostic algorithms. Improvement in imaging techniques as well as new imaging modalities and processing methods have improved diagnostic accuracy and additionally are being leveraged in prognostication and decision making for choice of intervention. In this article, we review the role of imaging in diagnosis and prognostication of venous thromboembolism. We also discuss emerging imaging approaches that may in the near future find clinical usefulness in improving diagnosis and prognostication as well as differentiating disease phenotypes.

Imaging techniques used in the diagnostic workup of acute venous thromboembolic disease

Early diagnosis is one of the most important factors affecting the prognosis of pulmonary embolism (PE); however, the clinical presentation of PE is often very unspecific and it can simulate other diseases. For these reasons, imaging tests, especially computed tomography angiography (CTA) of the pulmonary arteries, have become the keystone in the diagnostic workup of PE. The wide availability and high diagnostic performance of pulmonary CTA has led to an increase in the number of examinations done and a consequent increase in the population's exposure to radiation and iodinated contrast material. Thus, other techniques such as scintigraphy and venous ultrasonography of the lower limbs, although less accurate, continue to be used in certain circumstances, and optimized protocols have been developed for CTA to reduce the dose of radiation (by decreasing the kilovoltage) and the dose of contrast agents. We describe the technical characteristics and interpretation of the findings for each imaging technique used to diagnose PE and discuss their advantages and limitations; this knowledge will help the best technique to be chosen for each case. Finally, we comment on some data about the increased use of CTA, its clinical repercussions, its "overuse", and doubts about its cost-effectiveness.

Historical Evolution of Imaging Techniques for the Evaluation of Pulmonary Embolism

As we celebrate the 100th anniversary of the founding of the Radiological Society of North America (RSNA), it seems fitting to look back at the major accomplishments of the radiology community in the diagnosis of pulmonary embolism. Few diseases have so consistently captured the attention of the medical community. Since the first description of pulmonary embolism by Virchow in the 1850s, clinicians have struggled to reach a timely diagnosis of this common condition because of its nonspecific and often confusing clinical picture. As imaging tests started to gain importance in the 1900s, the approach to diagnosing pulmonary embolism also began to change. Rapid improvements in angiography, ventilation-perfusion imaging, and cross-sectional imaging modalities such as computed tomography (CT) and magnetic resonance imaging have constantly forced health care professionals to rethink how they diagnose pulmonary embolism. Needless to say, the way pulmonary embolism is diagnosed today is distinctly different from how it was diagnosed in Virchow's era; and imaging, particularly CT, now forms the cornerstone of diagnostic evaluation. Currently, radiology offers a variety of tests that are fast and accurate and can provide anatomic and functional information, thus allowing early diagnosis and triage of cases. This review provides a historical journey into the evolution of these imaging tests and highlights some of the major breakthroughs achieved by the radiology community and RSNA in this process. Also highlighted are areas of ongoing research and development in this field of imaging as radiologists seek to combat some of the newer challenges faced by modern medicine, such as rising health care costs and radiation dose hazards.

Natural language processing of radiology reports for the detection of thromboembolic diseases and clinically relevant incidental findings

Background

Natural Language Processing (NLP) has been shown effective to analyze the content of radiology reports and identify diagnosis or patient characteristics. We evaluate the combination of NLP and machine learning to detect thromboembolic disease diagnosis and incidental clinically relevant findings from angiography and venography reports written in French. We model thromboembolic diagnosis and incidental findings as a set of concepts, modalities and relations between concepts that can be used as features by a supervised machine learning algorithm. A corpus of 573 radiology reports was de-identified and manually annotated with the support of NLP tools by a physician for relevant concepts, modalities and relations. A machine learning classifier was trained on the dataset interpreted by a physician for diagnosis of deep-vein thrombosis, pulmonary embolism and clinically relevant incidental findings. Decision models accounted for the imbalanced nature of the data and exploited the structure of the reports.

Results

The best model achieved an F measure of 0.98 for pulmonary embolism identification, 1.00 for deep vein thrombosis, and 0.80 for incidental clinically relevant findings. The use of concepts, modalities and relations improved performances in all cases.

Conclusions

This study demonstrates the benefits of developing an automated method to identify medical concepts, modality and relations from radiology reports in French. An end-to-end automatic system for annotation and classification which could be applied to other radiology reports databases would be valuable for epidemiological surveillance, performance monitoring, and accreditation in French hospitals.

Incremental value of CT venography combined with pulmonary CT angiography for the detection of thromboembolic disease: systematic review and meta-analysis

OBJECTIVE

The objective of our study was to assess the incremental role of CT venography (CTV) combined with pulmonary CT angiography (CTA) in detecting venous thromboembolic disease with a systematic review and meta-analysis of the literature.

MATERIALS AND METHODS

MEDLINE, Embase, and Web of Science were searched for relevant original articles published from January 1, 1995, to December 31, 2009. A random-effects model was used to obtain the incremental value of CTV in detecting thromboembolic disease.

RESULTS

Twenty-four studies, which included 17,373 patients, met our inclusion criteria. A meta-analysis showed that CTV increased detection rates of venous thromboembolic disease by identifying an additional 3% of cases (95% CI, 2-4%) of isolated deep venous thrombosis (DVT). A subgroup analysis of a high-risk group did not show any difference in the detection of isolated DVT.

CONCLUSION

The addition of CTV results in the increased detection of thromboembolic disease. CTV combined with pulmonary CTA has a promising role as a quick and efficient test for venous thromboembolism.

Magnetic resonance imaging and computed tomography developments in imaging of venous thromboembolism

Venous thromboembolism (VTE) is a disease that causes high morbidity and mortality in the population. At present the first-line imaging test for a suspected pulmonary embolism (PE) is computed tomography (CT) pulmonary angiography, and ultrasonography is widely used for the diagnosis of deep-vein thrombosis (DVT). Although these modalities are proven to be safe and accurate, unresolved issues remain, such as whether CT scanning in patients with a suspected PE should be extended to the legs. Another issue is the diagnosis of recurrent DVT. Magnetic resonance imaging (MRI) offers a number of advantages in the imaging of VTE. Recent developments of scanning protocols with shorter acquisition times, sometimes complemented by navigator gating or making use of endogenous contrast, offer new perspectives for the use of MRI. This review provides an overview of state of the art MRI techniques for the diagnosis of PE and DVT. Furthermore, the use of new contrast agents such as fibrin labeling to detect thrombi are addressed.

Pulmonary embolism: optimizing the diagnostic imaging approach

Venous thromboembolism is a common medical problem that can affect a wide range of patients. The clinical presentation ranges from minor, nonspecific signs and symptoms to severe clinical scenarios. The combination of objective pretest clinical probability, D-dimer testing, and imaging studies plays a critical role in its diagnosis. There are multiple imaging modalities to confirm or exclude the presence of pulmonary embolism and deep vein thrombosis, but, at present, computed tomography angiography is the most frequently used. Other imaging, however, is required for several subpopulations.

Comprehensive evaluation of CT pulmonary angiography for patients suspected of having pulmonary embolism

Recently, CT pulmonary angiography (CTPA), especially performed with multi-detector row CT, has become a key imaging modality for pulmonary embolism. However, CTPA that was performed under clinical suspicion of pulmonary embolism has been shown to lead to high prevalence of alternative diagnosis, up to 25.4%. A comprehensive evaluation of pulmonary and extrapulmonary abnormalities including cardiovascular lesions is critical in proper diagnosis and patient care. Radiologists should be familiar with the comprehensive interpretation of CTPA to facilitate differential diagnosis and further treatment decision.

Diagnosis of pulmonary embolism in the coronary care unit

The clinical diagnosis of pulmonary embolism (PE) is difficult in coronary care units (CCUs) because many findings of PE are similar to those of acute coronary syndromes and heart failure. Immobilization of only 1 or 2 days may predispose to PE. Heart failure and acute myocardial infarction add to the risk. Dyspnea may be absent or occur only with exertion. The onset of dyspnea may occur over seconds to days. Orthopnea occurs with PE as well as heart failure. When the clinical probability and results of objective testing are discordant, the posttest probability of PE may be neither sufficiently high nor sufficiently low to permit therapeutic decisions. Objective scoring systems for clinical assessment have not been developed for patients in a CCU. d-dimer is likely to be of little value for the exclusion of PE in CCUs, because elevations occur with heart failure, unstable angina, and myocardial infarction. Computed tomographic pulmonary angiography with venous phase imaging of the low pelvic and proximal leg veins (computed tomographic venography) is recommended for imaging. Scintigraphy in women aged <50 years with normal or nearly normal results on chest x-ray may be the preferred imaging test to reduce the risk for radiation. Echocardiography with leg ultrasonography is a rapidly obtainable combination of bedside tests that may be useful for young patients and patients in extremis. In conclusion, the choice of diagnostic test depends on the clinical probability of PE, the condition of the patient, the availability of diagnostic tests, the risks of iodinated contrast material, radiation exposure, and cost.