Benefit of CT venography for the diagnosis of thromboembolic disease

Impact of CT venography added to CT pulmonary angiography for the detection of deep venous thrombosis and relevant incidental CT findings

OBJECTIVES

To assess the additional diagnostic value of CT venography (CTV) simultaneously performed with CT pulmonary angiography (CTPA) in the context of thromboembolic disease for the detection of deep venous thrombosis (DVT) and other relevant incidental CT findings.

MATERIALS AND METHODS

Retrospectively and consecutively, we included all patients referred to our emergency department within the last 24 months for suspected pulmonary embolism (PE) who underwent CTPA combined with CTV. Two radiologists blinded to clinical information and results independently analysed CTV images in the context of DVT of the lower extremities and other, unsuspected abdominal/pelvic findings. These latter were classified as relevant with therapeutic consequences or irrelevant. One radiologist reviewed patient clinical records. Inter-observer agreement for DVT detection was calculated.

RESULTS

Of 696 patients, 119 had PE (17.1%) and 54 had DVT (7.8%), 16 (2.3%) of them without concomitant PE. Inter-observer agreement between the two readers was substantial (kappa = 0.78). CTV examinations led to diagnosis of relevant incidental abdominal/pelvic findings in 40 (5.7%) patients, including 11 with new malignant tumours, and 8 with progressive metastatic disease. The evaluated clinical and biological risk factors were not significantly associated with the presence of relevant incidental findings. CTV changed therapeutic management in 29 patients (4.3%): 15 had DVTs without PE, and 14 had abdominal/pelvic findings with therapeutic consequences.

CONCLUSION

CTV simultaneously performed with CTPA offers limited incremental value for detecting DVT. It may reveal other relevant findings leading to therapeutic changes, but the low rate does not justify screening patients with suspected PE.

Comparison of the image qualities of filtered back-projection, adaptive statistical iterative reconstruction, and model-based iterative reconstruction for CT venography at 80 kVp

PURPOSE

To evaluate the subjective and objective qualities of computed tomography (CT) venography images at 80 kVp using model-based iterative reconstruction (MBIR) and to compare these with those of filtered back projection (FBP) and adaptive statistical iterative reconstruction (ASIR) using the same CT data sets.

MATERIALS AND METHODS

Forty-four patients (mean age: 56.1 ± 18.1) who underwent 80 kVp CT venography (CTV) for the evaluation of deep vein thrombosis (DVT) during 4 months were enrolled in this retrospective study. The same raw data were reconstructed using FBP, ASIR, and MBIR. Objective and subjective image analysis were performed at the inferior vena cava (IVC), femoral vein, and popliteal vein.

RESULTS

The mean CNR of MBIR was significantly greater than those of FBP and ASIR and images reconstructed using MBIR had significantly lower objective image noise (p < .001). Subjective image quality and confidence of detecting DVT by MBIR group were significantly greater than those of FBP and ASIR (p < .005), and MBIR had the lowest score for subjective image noise (p < .001).

CONCLUSION

CTV at 80 kVp with MBIR was superior to FBP and ASIR regarding subjective and objective image qualities.

KEY POINTS

• MBIR provides superior image quality compared with FBP and ASIR • CTV at 80kVp with MBIR improves diagnostic confidence in diagnosing DVT • CTV at 80kVp with MBIR presents better image quality with low radiation.

Diagnosis of DVT: Antithrombotic Therapy and Prevention of Thrombosis, 9th ed: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines

BACKGROUND

Objective testing for DVT is crucial because clinical assessment alone is unreliable and the consequences of misdiagnosis are serious. This guideline focuses on the identification of optimal strategies for the diagnosis of DVT in ambulatory adults.

METHODS

The methods of this guideline follow those described in Methodology for the Development of Antithrombotic Therapy and Prevention of Thrombosis Guidelines: Antithrombotic Therapy and Prevention of Thrombosis, 9th ed: American College of Chest Physicians Evidence-Based Clinical Practice Guidelines.

RESULTS

We suggest that clinical assessment of pretest probability of DVT, rather than performing the same tests in all patients, should guide the diagnostic process for a first lower extremity DVT (Grade 2B). In patients with a low pretest probability of first lower extremity DVT, we recommend initial testing with D-dimer or ultrasound (US) of the proximal veins over no diagnostic testing (Grade 1B), venography (Grade 1B), or whole-leg US (Grade 2B). In patients with moderate pretest probability, we recommend initial testing with a highly sensitive D-dimer, proximal compression US, or whole-leg US rather than no testing (Grade 1B) or venography (Grade 1B). In patients with a high pretest probability, we recommend proximal compression or whole-leg US over no testing (Grade 1B) or venography (Grade 1B).

CONCLUSIONS

Favored strategies for diagnosis of first DVT combine use of pretest probability assessment, D-dimer, and US. There is lower-quality evidence available to guide diagnosis of recurrent DVT, upper extremity DVT, and DVT during pregnancy.

Diagnostic tests and strategies in venous thromboembolism

Venous thromboembolism (VTE) is a term including deep vein thrombosis (DVT) and pulmonary embolism (PE). Timely and accurate diagnosis of both is essential as delayed or missed diagnoses can result in death or longer term complications. Patients with suspected DVT should initially undergo a pretest probability Wells score. Depending on pretest probability Wells score they should then either proceed to two-point ultrasound scanning or D-dimer testing. Likewise, patients suspected of PE should undergo a two-level PE Wells score, and, if scored likely, a computed tomography pulmonary angiogram (CTPA), or, if there is a low pretest probability score, D-dimer testing. If positive, patients should undergo CTPA. Ventilation perfusion scanning (V/Q scan) or V/Q SPECT should be considered in place of CTPA if there is allergy to contrast media or renal impairment.

A retrospective study of the value of indirect CT venography: a British perspective

OBJECTIVE

The aim of this study was to establish the value of indirect CT venography (CTV) in clinical practice within the UK.

METHODS

804 combined CT pulmonary angiogram and CTV studies were retrospectively reviewed. CTV was performed 180 s after the injection of contrast using an incremental technique with a 5-mm collimation and a 5-cm interspace between images extending from the iliac crests to the tibial plateaus.

RESULTS

12.9% of studies had isolated pulmonary emboli (PE), 3.0% had both a PE and deep vein thrombosis (DVT) and 1.1% had an isolated DVT. The proportion of positive cases diagnosed by CTV alone was 6.6%.

CONCLUSION

In a UK-based practice, the incidence and the proportion of isolated DVT diagnosed by CTV are lower than expected from published data. An analysis of possible causes for this is made within the paper.

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.

Negative predictive value of computed tomography pulmonary angiography with indirect computed tomography venography in intensive care unit patients

PURPOSE

The aim of the study was to evaluate the negative predictive value (NPV) of combined computed tomography (CT) pulmonary angiography (CTPA) and indirect CT venography (CTV) in the intensive care unit (ICU) setting.

MATERIALS AND METHODS

We retrospectively reviewed the records of 181 consecutive ICU patients who underwent CTPA/CTV. Radiology reports were examined to determine whether the study was positive for pulmonary embolism (PE), PE and deep venous thrombosis (DVT), or DVT alone; indeterminate; or negative. Results that were reported as negative were further evaluated for evidence of PE or DVT within 30 days by imaging, clinical evaluation, or autopsy data. The outcomes were evaluated for significance by calculating the rate ratio and 95% confidence interval.

RESULTS

A total of 41 patients (22.7%) were diagnosed with venous thromboembolism, 29 (70.7%) with PE, 8 (19.5%) with PE and DVT, and 4 (9.8%) with DVT. Seven studies were considered nondiagnostic. Seventeen deaths occurred within 30 days of CTA/CTV, of which none was felt to be related to PE/DVT. Of the 140 studies read as negative or nondiagnostic, 4 were determined to have venous thromboembolism (3 PEs and 1 DVT) within 30 days of the initial study (NPV = 97.1%). If patients who received prophylactic anticoagulation or inferior vena cava interruption (n = 25) were excluded, NPV decreases to 96.5%

CONCLUSION

A negative CTPA/CTV is reliable for the exclusion of significant venous thromboembolism in ICU patients.

CT Venous Phase Venography With 64-Detector CT Angiography in the Diagnosis of Acute Pulmonary Embolism

The value of computed tomographic (CT) venography in combination with CT pulmonary angiography has been questioned because of the potential dangers of radiation. Accordingly, we retrospectively evaluated the diagnostic yield of 64-detector CT angiography with CT venography. Among patients who routinely underwent CT venography with CT angiography, the CT angiogram showed acute pulmonary embolism (PE) in 206 of 1903 patients (10.8%). A positive CT venogram in a patient with a negative CT angiogram was shown in 25 of 1903 patients (1.3%). Either the CT angiogram or the CT venogram showed venous thromboembolism in 231 of 1903 patients (12.1%). The proportion of patients with venous thromboembolism diagnosed only by a CT venogram was 25 of 231 (10.8%). In conclusion, the proportion of patients with venous thromboembolism diagnosed only by a CT venogram is sufficiently high to merit consideration of its use especially in those at high risk for DVT.

The interobserver agreement between residents and experienced radiologists for detecting pulmonary embolism and DVT with using CT pulmonary angiography and indirect CT venography

Objective

We wanted to prospectively evaluate the interobserver agreement between radiology residents and expert radiologists for interpreting CT images for making the diagnosis of pulmonary embolism (PE).

Materials and Methods

We assessed 112 consecutive patients, from April 2007 to August 2007, who were referred for combined CT pulmonary angiography and indirect CT venography for clinically suspected acute PE. CT scanning was performed with a 64×0.5 collimation multi-detector CT scanner. The CT studies were initially interpreted by the radiology residents alone and then the CT images were subsequently interpreted by a consensus of the resident plus an experienced general radiologist and an experienced chest radiologist.

Results

Two of the 112 CTs were unable to be interpreted (1.7%). Pulmonary artery clots were seen on 36 of the thoracic CT angiographies (32%). The interobserver agreement between the radiology residents and the consensus interpretation was good (a kappa index of 0.73). All of the disagreements (15 cases) were instances of overcall by the resident on the initial interpretation. Deep venous thrombosis was detected in 72% (26 of 36) of the patients who had PE seen on thoracic CT. The initial and consensus interpretations of the CT venography images disagreed for two cases (kappa statistic: 0.96).

Conclusion

It does not seem adequate to base the final long-term treatment of PE on only the resident's reading, as false positives occurred in 13% of such cases. Timely interpretation of the CT pulmonary angiography and CT venography images should be performed by experienced radiologists for the patients with suspected PE.

64-MDCT pulmonary angiography and CT venography in the diagnosis of thromboembolic disease

OBJECTIVE

The purpose of our study was to investigate whether CT venography (CTV) performed after CT pulmonary angiography (CTPA) using 64-MDCT provides additional findings in the diagnosis of thromboembolic disease.

MATERIALS AND METHODS

Three hundred six consecutive patients in whom pulmonary embolism (PE) was clinically suspected were included in the study. The study group was classified according to the diagnostic quality of the CTPA examinations, the presence or absence of PE and deep venous thrombosis (DVT), and the most proximal localization that the embolus could lodge in the pulmonary artery.

RESULTS

The diagnostic quality of CTPA was insufficient in 5.9%, acceptable in 8.2%, and excellent in 85.9% of the patients. The diagnostic quality of CTV was insufficient in 11.4%, acceptable in 47.4%, and excellent in 41.2%. The percentages of nondiagnostic examinations for CTPA and CTV were 5.2% and 10.8%, respectively. Acute PE and acute DVT were observed in 25.2% and 18.0%, respectively. The percentage of subsegmental emboli among patients with acute PE was 15.6%. The percentage of patients with thromboembolic disease was 29.1%. Of patients who were diagnosed as having thromboembolic disease, 13.5% (12 of 89 patients) had DVT only. Of all patients, 3.9% (12 of 306) had only isolated DVT. The number of patients with subsegmental PE who had DVT was two (0.7% all patients).

CONCLUSION

As in MDCT scanning with a smaller number of slices, the combination of CTV with CTPA in 64-MDCT results in a small but definitive increase in the percentage of patients with a diagnosis of thromboembolic disease.

Imaging of deep vein thrombosis

Background

Deep vein thrombosis of the leg affects 1–2 per cent of the population with an annual incidence of 0·5–1 per 1000. It presents with non-specific symptoms and signs making clinical diagnosis difficult. Techniques to image and diagnose this condition are advancing rapidly.

Methods and results

A literature review from 1980 to 2007 was undertaken using PubMed, The Cochrane Library, Medline and Embase. The most frequently used diagnostic test is duplex ultrasonography which is accurate above the knee and has a low cost, but is limited by inaccuracy when assessing the pelvic and distal veins and in diagnosing a new thrombosis in the post-thrombotic limb. Magnetic resonance imaging (MRI) and sonographic elasticity imaging are more recent techniques that have shown promise in overcoming these limitations. However, their availability is currently restricted because they are expensive. Computed tomography (CT) is sensitive, specific and provides good imaging of the pelvis. It has the advantage that it can be performed at the same time as CT pulmonary angiography.

Conclusion

MRI has some specific advantages over duplex ultrasonography, but requires refinement before it can be used clinically. Venography or CT venography should be considered when duplex scanning is inadequate.