Thromboembolic disease: comparison of combined CT pulmonary angiography and venography with bilateral leg sonography in 70 patients

Role of Combined CT Pulmonary Angiography and Indirect CT Venography in Diagnosing Venous Thromboembolism in COVID-19 Patients - Experience From an Indian Quaternary Centre

OBJECTIVES

To study the role of combined CTPA and indirect CT venogram to diagnose venous thromboembolism (VTE) in patients with COVID-19 pneumonia and to compare the clinical characteristics, laboratory parameters, CT findings and clinical outcomes between the VTE positive and negative groups.

METHODS

In this retrospective study, 131 patients with COVID-19 pneumonia who underwent CTPA and venogram between August 2020 and January 2021 were included. Relevant demographical, clinical and laboratory data and CT images were collected. Two thoracic radiologists independently reviewed the CTPA and venogram images.

RESULTS

VTE was identified in 29 patients (22% of the study population). CT venogram identified DVT in 9 patients. No statistical difference was observed between the two groups with respect to age, gender, BMI and presence of comorbidities. There was a significant difference in the hospital stay duration, which is increased in the VTE positive group. The number of patients who were dependent on oxygen and mortality were also high in the positive group. There was statistically significant difference in the mean D-dimer value and the mean Neutrophil/lymphocyte ratio, which were higher in the VTE positive group.

CONCLUSION

Combined CTPA and venogram can be used as a one-stop investigation for diagnosing PE and DVT of lower limbs in patients with COVID-19 pneumonia. CTPA with venogram should be performed in patients with D-dimer value in the range of 1000 - 1200 μg/L and above to rule out VTE as the hospital stay duration and final outcomes vary between the positive and negative groups.

Low Tube Voltage Computed Tomography Venography for Patients With Deep Vein Thrombosis of the Lower Extremities - A Comparison With Venous Ultrasonography

BACKGROUND

Low tube voltage computed tomography venography (CTV) can be expected to increase imaging contrast and decrease radiation exposure by using iterative reconstruction (IR). This study evaluated the diagnostic ability of low tube voltage CTV with IR for deep vein thrombosis (DVT), compared to ultrasonography (US).Methods and Results:Two experienced radiologists retrospectively reevaluated the CTV data of 55 of 318 consecutive patients suspected of having DVT or pulmonary embolism between December 2015 and April 2017. The 55 patients had undergone both low tube voltage CTV and US (within 1 day before or after CTV). The lower extremity veins were divided into 10 segments. The DVT forms were categorized into 3 types: complete, concentric, and eccentric. We analyzed the 534 overall segments (16 segments excluded in US) measured using both CTV and US. The sensitivity-specificity was overall 73.3-90.0%, for femoropopliteal, it was 90.0-93.2%, and for the calf, it was 71.1-87.2%. The diagnostic accuracy between the 'eccentric only' and 'others' groups focusing on DVT forms was compared, and significant differences were revealed, especially in the muscular vein.

CONCLUSIONS

The DVT diagnostic ability above the knee was comparable between low tube voltage CTV with IR and conventional CTV, and the radiation dose was reduced. It was suggested that eccentric DVT measured by CTV tend to be a false-positive, especially in the calf muscular vein.

[Diagnostic and therapeutic management of venous thromboembolic disease in obese patients]

Despite the high proportion of obese patients this population remains understudied in the field of venous thromboembolic disease (VTE). Obesity is a risk factor for pulmonary embolism and/or deep vein thrombosis, especially when it is associated with other risk factors for VTE. Currently there is no validated diagnostic algorithm for VTE in the population of obese patients. Moreover, imaging examinations can be of poor quality and inconclusive. In the prevention of VTE, data concerning obese patients are mainly based on low-level studies. Apart from the context of bariatric surgery, an adjustment of heparin doses according to the weight of the patient is proposed only on a case-by-case basis. According to the current guidelines, therapeutic fixed dose oral anticoagulants should not be prescribed for patients with weights exceeding 120kg or a body mass index>40kg/m². Heparin doses should be weight adjusted and monitored with anti-Xa activity. Anti vitamin K can be prescribed but require INR monitoring. Therefore, new studies specifically dedicated to obese patients are required in the field of VTE for better diagnostic and therapeutic management.

Coagulation System Disorders and Thrombosis Prophylaxis During Laparoscopic Fundoplications

BACKGROUND

The aim of this study was to assess and recommend the optimal deep vein thrombosis (DVT) prophylaxis regimen during and after laparoscopic fundoplication according to the blood coagulation disorders and the rate of DVT in 2 patient groups, receiving different DVT prophylaxis regimens.

MATERIALS AND METHODS

This was a prospective randomized, single-center clinical study. The study population, 121 patients, were divided into 2 groups: group I received low-molecular-weight heparin 12 hours before the operation; group II received low-molecular-weight heparin only 1 hour before the laparoscopic fundoplication. Both groups received intermittent pneumatic compression during the entire procedure. Bilateral Doppler ultrasound to exclude DVT was performed before the surgery. Venous phase computed tomographic images were acquired from the ankle to the iliac tubercles on the third postoperative day to determine the presence and location of DVT. Hypercoagulation state was assessed by measuring the prothrombin fragment F1+2 (F1+2), the thrombin-antithrombin complex (TAT), and tissue factor microparticles activity (MP-TF) in plasma. The hypocoagulation effect was evaluated by measuring plasma free tissue factor pathway inhibitor (fTFPI).

RESULTS

F1+2, TAT, and MP-TF indexes increased significantly, whereas fTFPI levels decreased significantly during and after laparoscopic fundoplication, when molecular-weight heparin was administered 12 hours before the operation. Computed tomography venography revealed peroneal vein thrombosis in 2 group I patients on the third postoperative day. Total postsurgical DVT frequency was 1.65%: 3.6% in group I, with no DVT in group II.

CONCLUSION

Molecular-weight heparin and intraoperative intermittent pneumatic compression controls the hypercoagulation effect more efficiently when it is administered 1 hour before surgery: it causes significant reduction of F1+2, TAT, and MP-TF indexes and significant increases of fTFPI levels during and after laparoscopic fundoplication.

Diagnostic value of computerized tomography venography in detecting stenosis and occlusion of subclavian vein and superior vena in chronic renal failure patients

Introduction

Currently, venography is the standard diagnostic method to examine veins before implementing access, which is invasive in nature. Computerized tomography venography (CTV) can simultaneously indicate deep and superficial venous systems in the upper extremity and their relation to the surrounding anatomical structures; however, its diagnostic value in the detection of central venous disease has yet to be defined. The aim of this study was to determine the diagnostic value of CT venography compared to venography in the diagnosis of stenosis and the occlusion of subclavian veins and the superior vena in renal failure patients.

Methods

This cross-sectional study was conducted from January to September 2015 on patients with chronic renal failure undergoing upper extremity venography at the Radiology Department of Imam Reza Hospital in Mashhad, Iran. We excluded patients with catheters in their jugular and subclavian vein routes, venous hypertension with reverse-function fistula, or sensitivity to contrast agents. Several factors, including age, gender, catheterization record in jugular and subclavian veins, and fistula record in the upper extremity, as well as clinical symptoms consisting of edema, dermatitis, and ulcers in these organs, were recorded in the corresponding form. Then, the patients consecutively underwent indirect venography and CT venography and traces of stenosis (more than 50%) or complete occlusion in the subclavian vein and superior vena were recorded. The data were analyzed using SPSS software by the chi-squared test, and sensitivity, specificity, and positive and negative predictive values were calculated by means of MedCalc Online, version 16.2.

Results

The study was conducted on 40 patients (26 males and 14 females) with a mean age of 46.7 ± 10.4 years. In this study, 58 subclavian veins, as well as 32 superior vena cava, were studied. The results showed that the diagnostic value of CTV in the detection of subclavian stenosis had a sensitivity and a specificity of 88.2 and 97.5%, respectively. Moreover, in the superior vena cava, the greatest CTV diagnostic sensitivity and specificity was related to vein stenosis detection (sensitivity = 88.8%; specificity = 100%).

Conclusion

It seems that the CTV, based on its high sensitivity, specificity, and predictive value, can be used as an efficient tool in the study of stenosis in subclavian veins and superior vena in patients undergoing venography

Obesity and lower limb venous disease - The epidemic of phlebesity

Introduction Lower limb venous disease affects up to one half, and obesity up to one quarter, of the adult population. Many people are therefore affected by, and present to health services for the treatment of both conditions. This article reviews the available evidence of pathophysiological and clinical relationship between obesity and varicose veins, chronic venous insufficiency and ulceration and deep vein thrombosis. Methods A literature search of PubMed and Cochrane libraries was performed in accordance with PRISMA statement from 1946 to 2015, with further article identification from following cited references for articles examining the relationship between obesity and venous disease. Search terms included obesity, overweight, thrombosis, varicose veins, CEAP, chronic venous insufficiency, treatment, endovenous, endothermal, sclerotherapy, bariatric surgery and deep vein thrombosis. Results The proportion of the population suffering from lower limb venous disease and obesity is increasing. Obesity is an important risk factor for all types of lower limb venous disease, and obese patients with lower limb venous disease are more likely to be symptomatic as a result of their lower limb venous disease. The clinical diagnosis, investigation, imaging and treatment of lower limb venous disease in obese people present a number of challenges. The evidence base underpinning medical, surgical and endovenous management of lower limb venous disease in obese people is limited and such treatment may be associated with worse outcomes and increased risks when compared to patients with a normal body mass index. Conclusion Lower limb venous disease and obesity are both increasingly common. As such, phlebologists will be treating ever greater numbers of obese patients with lower limb venous disease, and clinicians in many other specialties are going to be treating a wide range of obesity-related health problems in people with or at risk of lower limb venous disease. Unfortunately, obese people have been specifically excluded from many, if not most, of the pivotal studies. As such, many basic questions remain unanswered and there is an urgent need for research in this challenging and increasingly prevalent patient group.

Management of Venous Thromboembolisms: Part I. The Consensus for Deep Vein Thrombosis

Deep vein thrombosis (DVT) is a potentially catastrophic condition because thrombosis, left untreated, can result in detrimental pulmonary embolism. Yet in the absence of thrombosis, anticoagulation increases the risk of bleeding. In the existing literature, knowledge about the epidemiology of DVT is primarily based on investigations among Caucasian populations. There has been little information available about the epidemiology of DVT in Taiwan, and it is generally believed that DVT is less common in Asian patients than in Caucasian patients. However, DVT is a multifactorial disease that represents the interaction between genetic and environmental factors, and the majority of patients with incident DVT have either inherited thrombophilia or acquired risk factors. Furthermore, DVT is often overlooked. Although symptomatic DVT commonly presents with lower extremity pain, swelling and tenderness, diagnosing DVT is a clinical challenge for physicians. Such a diagnosis of DVT requires a timely systematic assessment, including the use of the Wells score and a D-dimer test to exclude low-risk patients, and imaging modalities to confirm DVT. Compression ultrasound with high sensitivity and specificity is the front-line imaging modality in the diagnostic process for patients with suspected DVT in addition to conventional invasive contrast venography. Most patients require anticoagulation therapy, which typically consists of parenteral heparin bridged to a vitamin K antagonist, with variable duration. The development of non-vitamin K oral anticoagulants has revolutionized the landscape of venous thromboembolism treatment, with 4 agents available,including rivaroxaban, dabigatran, apixaban, and edoxaban. Presently, all 4 drugs have finished their large phase III clinical trial programs and come to the clinical uses in North America and Europe. It is encouraging to note that the published data to date regarding Asian patients indicates that such new therapies are safe and efficacious. Ultimately, our efforts to improve outcomes in patients with DVT rely on the awareness in the scientific and medical community regarding the importance of DVT.

KEY WORDS

Combination therapy; Hypertension; α1-blocker.

Three-dimensional modelling of the venous system by direct multislice helical computed tomography venography: technique, indications and results

The aim of multislice helical computed tomography venography (CTV) is to provide a precise, global and three-dimensional (3D) anatomical depiction of the venous network of the lower limbs. A multislice and multidetector spiral CT acquisition of the lower limbs with contrast injection of the dorsal foot produces about 1000 slices in 30 seconds. Dedicated volume-rendering software can compute a realistic and interactive 3D model of the venous system in realtime. This new tool furnishes an accurate 3D representation of the whole venous system of the lower limb with a realistic 3D model of the limbs, providing a road map of the varicose networks complementary to the duplex ultrasound (DUS). CTV allows a complete morphological study of the deep veins, including the detection of anatomical variations and proximal venous obstruction, not easily detectable by DUS. In the case of deep vein thrombosis, it has been shown to be a good diagnostic tool, well correlated with sonography. It also demonstrates, in some cases, haemodynamic patterns which are not available by DUS, particularly for perforator veins and congenital vascular malformations. The use of virtual reality techniques enables a complete anatomical study of both deep and superficial veins including a virtual dissection of the limbs. CTV is also a great educational tool to learn anatomy of the venous system and a powerful research tool to improve our knowledge of venous anatomy.

Comparison of helical and axial mode indirect computed tomographic venography in patients with pulmonary thromboembolism

OBJECTIVE

To compare the helical and axial modes of indirect computed tomographic (CT) venography (CTV) for accuracy for diagnosing deep venous thrombosis (DVT) of the lower extremities as well as for their radiation burden in patients proven to have pulmonary thromboembolism (PTE) on CT pulmonary angiography (CTPA).

SUBJECTS AND METHODS

Of patients evaluated with CTPA for suspected acute PE, 20 of patients who were found to have PTE underwent both indirect CTV of the lower extremities and color Doppler examination. For indirect CTV, patients were randomly assigned to helical and axial modes. The CTV and Doppler findings were interpreted by two experienced radiologists who were blinded to the results of each other.

RESULTS

Out of total of 260 venous segments analyzed (130 venous segments each by helical or axial CTV), thrombi were seen in 43 venous segments (15 and 28 each by helical or axial CTV respectively). On comparison with Doppler, helical CTV had 82.35% sensitivity and 99.11% specificity, whereas axial CTV had 96.6% sensitivity and 100% specificity. The mean radiation dose was significantly higher for helical (1153.57 mgy.cm) as compared to axial mode CTV (806.28 mgy.cm) with P value of <0.0001.

CONCLUSION

Axial CTV results in decreased radiation dose without significant change in the accuracy, as compared to helical CTV in the evaluation of DVT.

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.

Difficulties in diagnosing pulmonary embolism in the obese patient: a literature review

Several of the signs and symptoms of pulmonary embolism, such as dyspnea, tachypnea, and tachycardia, are common in the obese population, so these patients are frequently suspected of having a pulmonary embolism. Establishing an accurate diagnosis in this situation is often difficult. We performed a review of the literature examining the difficulty of diagnosing pulmonary embolism in obese patients. Several factors compromise the ability of clinicians to accurately diagnose pulmonary embolism in obese patients. When patients weigh over 350 lbs (159 kg), thoracic imaging often cannot be performed because of the weight limitations of the scanning equipment. If equipment is available that can scan these patients, image quality is often poor. The literature that is available to guide the clinician in this difficult clinical scenario is sparse. Access to radiology equipment that can image morbidly obese patients is improving, but questions about image quality remain. Further research on both imaging and outcomes is needed.

Multimodality imaging of the peripheral venous system

The purpose of this article is to review the spectrum of image-based diagnostic tools used in the investigation of suspected deep vein thrombosis (DVT). Summary of the experience gained by the author as well as relevant publications, regarding vein imaging modalities taken from a computerized database, was reviewed. The imaging modalities reviewed include phlebography, color Doppler duplex ultrasonography (CDDUS), computerized tomography angiography (CTA) and venography (CTV), magnetic resonance venography (MRV), and radionuclide venography (RNV). CDDUS is recommended as the modality of choice for the diagnosis of DVT. A strategy combining clinical score and D-dimer test refines the selection of patients. Phlebography is reserved for discrepant noninvasive studies.

Peripartum pulmonary embolism

Pregnancy is an example of Virchow's triad predisposing to the development of venous thromboembolism (VTE). Specific risk factors for antepartum and postpartum VTE have been identified. The diagnosis of pulmonary embolism in pregnancy is complicated by the physiologic changes of pregnancy as well as physicians' apprehension about ordering radiologic studies during pregnancy because of concerns with fetal well-being. Therapy for VTE is complicated by pregnancy physiology affecting medication pharmacokinetics and bioavailability, and the unpredictable occurrence of labor during therapeutic anticoagulation.

Venous thromboembolism: additional diagnostic value and radiation dose of pelvic CT venography in patients with suspected pulmonary embolism

PURPOSE

To assess the additional diagnostic value of indirect CT venography (CTV) of the pelvis and upper thighs performed after pulmonary CT angiography (CTA) for the diagnosis of venous thromboembolism (VTE).

MATERIALS AND METHODS

In a retrospective analysis, the radiology information system entries between January 2003 and December 2007 were searched for patients who received pulmonary CTA and additional CTV of the pelvis and upper thighs. Of those patients, the radiology reports were reviewed for the diagnosis of pulmonary embolism (PE) and deep venous thrombosis (DVT) in the pelvic veins and veins of the upper thighs. In cases with an isolated pelvic thrombosis at CTV (i.e. which only had a thrombosis in the pelvic veins but not in the veins of the upper thigh) ultrasound reports were reviewed for the presence of DVT of the legs. The estimated radiation dose was calculated for pulmonary CTA and for CTV of the pelvis.

RESULTS

In the defined period 3670 patients were referred to our institution for exclusion of PE. Of those, 642 patients (353 men, 289 women; mean age, 65±15 years, age range 18-98 years) underwent combined pulmonary CTA and CTV. Among them, PE was found in 227 patients (35.4%). In patients without PE CTV was negative in all cases. In patients with PE, CTV demonstrated pelvic thrombosis in 24 patients (3.7%) and thrombosis of the upper thighs in 43 patients (6.6%). Of those patients 14 (2.1%) had DVT in the pelvis and upper thighs. In 10 patients (1.5%) CTV showed an isolated pelvic thrombosis. Of those patients ultrasound reports were available in 7 patients, which revealed DVT of the leg veins in 5 cases (1%). Thus, the estimated prevalence of isolated pelvic thrombosis detected only by pelvic CTV ranges between 1-5/642 patients (0.1-0.7%). Radiation dose ranges between 4.8 and 9.7 mSv for additional CTV of the pelvis.

CONCLUSION

CTV of the pelvis performed after pulmonary CTA is of neglectable additional diagnostic value for the detection of VTE, because the additional radiation dose is high and isolated pelvic DVT is very rare. Venous imaging of the legs (preferably by radiation-free ultrasound) is sufficient for the diagnosis of underlying DVT in patients with suspected PE.

Multidetector computed tomography venography: optimum dose of contrast material

PURPOSE

The aim of this study was to determine the optimum dose of contrast material for evaluating veins in the lower limbs.

MATERIALS AND METHODS

A total of 134 patients who underwent multidetector computed tomography (MDCT) due to suspected deep vein thrombosis (DVT) or pulmonary embolism (PE) were included in this study. One hundred milliliters of iopamidol 100 ml, with 370 mg I/ml was administered. The degree of contrast enhancement of veins in the lower limbs was classified on a 4-point scale (grade 1, poor --> 4, excellent). Regions of interest (ROIs) were positioned in the femoral vein and the popliteal vein to measure CT numbers in these veins. Correlations between the CT number in each ROI and body weight were examined.

RESULTS

The mean +/- SD body weights of patients by contrast-enhancement grade were as follows: grade 1, 86.3 +/- 10.2 kg; grade 2, 72.6 +/- 10.7 kg; grade 3, 59.7 +/- 8.7 kg; grade 4, 51.3 +/- 7.9 kg. Negative correlations were found between body weight and CT number for both the femoral vein and the popliteal vein. Grade 3 or better contrast enhancement was obtained in 79 of 81 patients (97.5%) weighing <60 kg.

CONCLUSION

For patients weighing <60 kg, 100 ml of contrast material (370 mg I/ml) is considered sufficient for evaluating veins in the lower limbs.

Utility of balanced steady-state free precession MR venography in the diagnosis of lower extremity deep venous thrombosis

OBJECTIVE

The purpose of this study was to determine the sensitivity and specificity of balanced steady-state free precession MR venography in the diagnosis of lower extremity deep venous thrombosis.

SUBJECTS AND METHODS

After undergoing lower extremity ultrasound because of suspicion of deep venous thrombosis, 64 patients were prospectively recruited to undergo balanced steady-state free precession MR venography with ultrasound as the reference standard. Ultrasound images were independently interpreted by two blinded ultrasound radiologists, and MR venograms were independently interpreted by two blinded MRI radiologists. The sensitivity, specificity, positive predictive value, and negative predictive value of MR venography were calculated for the diagnoses of all deep venous thrombosis, acute thrombi, and thrombosis of the popliteal, femoral, and common femoral veins individually. Proximal extent, thrombus age, ancillary findings, and interobserver agreement calculated with the Cohen kappa test were evaluated for ultrasound and MRI. The McNemar test was used to evaluate for statistical differences in diagnostic accuracy.

RESULTS

MR venography had a sensitivity of 94.7%, specificity of 100%, positive predictive value of 100%, and negative predictive value of 97.7% for the diagnosis of all thrombi. For acute thrombi, the MR venography and ultrasound results were completely concordant. MR venography depicted greater proximal extent in five of 18 cases in which thrombosis was found. The MR venographic findings agreed completely with the ultrasound findings in determination of thrombus age. For both ultrasound and MR venography, interobserver agreement was 100% on a per-patient basis. No statistical difference was identified in the diagnostic performance of the two techniques.

CONCLUSION

Balanced steady-state free precession MR venography is highly accurate in the diagnosis of lower extremity deep venous thrombosis.

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 role of multidetector computed tomography angiography for the diagnosis of pulmonary embolism

From a radiological point of view, computed tomography pulmonary angiography (CTPA) has effectively become the de-facto first-line imaging test for the evaluation of pulmonary embolism (PE), as patients with a high-quality negative CTPA do not require further examination or treatment for suspected PE. We are likely to see further technical developments in CT technology in the near future. These advances will most likely further improve image quality. Several questions or issues remain, including strategies for further imaging when CT is inconclusive or contraindicated, issues regarding radiation exposure, the prevalence of PE in specific populations, best tests and pathways in specific patient groups, including patients with specific comorbidities such as oncology patients or patients with chronic obstructive pulmonary disease. Also, the question whether all PE patients need anticoagulation, the clinical effect of follow-up imaging, and the accuracy of different clinical prediction rules, remains.

Computer tomography for venous thromboembolic disease

Venous thromboembolic disease is composed of two disease entities: pulmonary thromboembolism/pulmonary embolism and deep venous thrombosis. Clinical signs and symptoms of venous thromboembolic disease often are nonspecific and, as a result, the diagnosis may be difficult. If left untreated, pulmonary embolism can lead to a potentially fatal outcome. This article focuses on CT angiography as the diagnostic modality for thromboembolic pulmonary embolism and briefly discusses nonthromboembolic pulmonary embolism.

Contribution of indirect computed tomographic venography to the diagnosis of postpartum venous thromboembolism

BACKGROUND

The diagnostic value of indirect computed tomographic venography (CTV), following thoracic computed tomographic angiography (CTA), has not been specifically evaluated in postpartum patients with suspected pulmonary embolism.

OBJECTIVES

To assess the diagnostic value of CTV in postpartum venous thromboembolism.

METHODS

We reviewed all CTA and CTV procedures performed during the last 7 years in our institution for suspected pulmonary embolism during the postpartum period. We focused on the quality of CTA, the rates of positive CTA and isolated positive CTV findings, and alternative diagnoses provided by CTV.

RESULTS

Fifty-five CTA and 33 CTV procedures were performed for suspected pulmonary embolism in 47 patients referred between 24 h and 2 months after Cesarean (34 patients) or vaginal (13 patients) delivery. Of the 33 patients who had both CTA and CTV, seven had positive CTA findings and four had isolated positive CTV findings. Thus, the absolute increase in the venous thromboembolism detection rate following CTV was 12.1% [95% confidence interval (CI) 4.0-29.1]. Subcapsular hematoma of the liver or spleen was found on CTV in another two patients without venous thromboembolism. Consequently, CTV had a direct impact on clinical management in six of 33 patients (18%).

CONCLUSION

Our results suggest that postpartum patients with suspected pulmonary embolism have a significant rate of pelvic vein thrombosis and that the use of CTV leads to a 31% relative increase in the detection rate of venous thromboembolism as compared to CTA alone in these patients.

Evaluation of deep vein thrombosis with multidetector row CT after orthopedic arthroplasty: a prospective study for comparison with Doppler sonography

Objective

This prospective study evaluated the ability of indirect 16-row multidetector CT venography, in comparison with Doppler sonography, to detect deep vein thrombosis after total hip or knee replacement.

Materials and Methods

Sixty-two patients had undergone orthopedic replacement surgery on a total of 30 hip joints and 54 knee joints. The CT venography (scan delay time: 180 seconds; slice thickness/increment: 2/1.5 mm) and Doppler sonography were performed 8 to 40 days after surgery. We measured the z-axis length of the beam hardening artifact that degraded the image quality so that the presence of deep vein thrombosis couldn't be evaluated on the axial CT images. The incidence and location of deep vein thrombosis was analyzed. The diagnostic performance of the CT venograms was evaluated and compared with that of Doppler sonography as a standard of reference.

Results

The z-axis length (mean±standard deviation) of the beam hardening artifact was 4.5 ± 0.8 cm in the arthroplastic knees and 3.9 ± 2.9 cm in the arthroplastic hips. Deep vein thrombosis (DVT) was found in the popliteal or calf veins on Doppler sonography in 30 (48%) of the 62 patients. The CT venography has a sensitivity, specificity, positive predictive value, negative predictive value and accuracy of 90%, 97%, 96%, 91% and 94%, respectively.

Conclusion

The ability of CT venography to detect DVT was comparable to that of Doppler sonography despite of beam hardening artifact. Therefore, CT venography is feasible to use as an alternative modality for evaluating postarthroplasty patients.

[Indirect CT venography in patients with clinical suspicion of pulmonary thromboembolism: our experience and possible indications for the test]

OBJECTIVE

Our objective was to evaluate the sensitivity of indirect computed tomography (CT) venography in the evaluation of deep vein thrombosis and to establish possible general indications for this technique in cases with clinical suspicion of thromboembolic disease.

MATERIAL AND METHODS

We studied 76 patients with clinical suspicion of pulmonary thromboembolism who underwent CT angiography of the pulmonary arteries and indirect CT venography. We correlated the results with those of ultrasound examination of the limbs in 63 cases to determine the sensitivity of the test. We analyzed the cases in which the findings at indirect CT venography changed the management of the patient.

RESULTS

The concordance between indirect CT venography and ultrasound was 92%. Thromboembolic disease was diagnosed in 40% of the cases. In these cases, CT angiography of the pulmonary arteries was positive in 80% and in the remaining 20% only CT venography was positive. In two cases, abdominal pathology that changed the clinical management of the patients was found.

CONCLUSIONS

Indirect CT venography is sensitive in the detection of deep vein thrombosis in patients with clinical suspicion of pulmonary thromboembolism. This technique can shorten the time to diagnosis, increase diagnostic precision, and provide additional clinical data that may be important in the patient's management. However, its generalized use is limited because it involves the use of ionizing radiation.

CT and MRI of acute thoracic cardiovascular emergencies

A wide spectrum of acute cardiovascular disorders is seen in patients who are hospitalized in a critical care setting. Imaging plays a central role in the diagnosis and management of these conditions. The most frequently used imaging remains chest radiography; however, more advanced modalities, including coronary angiography, echocardiography, and radioisotope scintigraphy, have well established roles in the assessment of patients in the critical care setting. More recently, multidetector row CT (MDCT) and MRI are being used increasingly for evaluation of coronary artery disease, cardiac structure and function, coronary artery anomalies, cardiac masses, pericardial disease, valvular disease, postoperative cardiovascular abnormalities, venous thromboembolism and acute aortic syndromes, often with other ancillary findings that can provide important clinical information. The three most common life-threatening cardiovascular processes in which advanced imaging plays a role, particularly CT, are discussed, including pulmonary embolism, aortic dissection, and coronary artery disease.

Routine pelvic and lower extremity CT venography in patients undergoing pulmonary CT angiography

OBJECTIVE

The purpose of our study was to assess the utility of performing routine pelvic and lower extremity CT venography (CTV) along with pulmonary CT angiography (CTA) in all patients evaluated for pulmonary embolism.

MATERIALS AND METHODS

Eight hundred twenty-nine consecutive patients (281 men and 548 women) underwent CTA-CTV for pulmonary embolism. Reports were evaluated as follows: positive or negative for pulmonary embolism with or without deep venous thrombosis (DVT) or with nondiagnostic CTV. Coexisting factors of malignancy, previous venous thromboembolism (VTE), recent surgery, and cardiovascular disease comprised the high-risk group of 446 patients. The remaining 383 patients formed the low-risk group. Statistical analysis included four binary predictors (previous VTE, malignancy, cardiovascular disease, and surgery) and three binary outcome variables (pulmonary embolism, DVT, and VTE). Chi-square test and univariate and multivariate regression analyses were performed.

RESULTS

VTE, pulmonary embolism, and DVT occurred in 152 (18.3%), 124 (15.0%), and 61 (7.3%) of 829 patients, respectively. Between the high-risk and low-risk groups, prevalence of VTE was 114 (25.6%) of 446 and 38 (9.9%) of 383 patients, respectively (p < 0.001); prevalence of pulmonary embolism was 92 (20.6%) of 446 and 32 (8.3%) of 383 patients, respectively (p < 0.001). Isolated DVT was found in 28 (3.4%) of 829 patients. The incremental value of CTV for the entire cohort was 3.4%, 0.72% in the low-risk group (six of 829) and 2.6% (22 of 829) in the high-risk group. For outcome variable VTE, malignancy and previous VTE were statistically significant (p = 0.04 and p < 0.001, respectively); for pulmonary embolism, malignancy and previous VTE were statistically significant (p = 0.03 and p = 0.005, respectively); for DVT, only previous VTE was statistically significant (p < 0.001).

CONCLUSION

CTV should not be performed routinely in all patients evaluated for pulmonary embolism and may only be useful in patients with a high probability of pulmonary embolism, including those with a history of VTE and possible malignancy.

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.

Thromboembolism in pregnancy

Venous thromboembolism in pregnancy is a clinical emergency that has been associated with significant risk for maternal and fetal morbidity and mortality. The adaptation of the maternal hemostatic system to pregnancy predisposes women to an increased risk of thromboembolism. A timely diagnosis of deep venous thrombosis is crucial because up to 24% of patients with untreated deep venous thrombosis develop a pulmonary embolism. Recent clinical guidelines identify compression venous ultrasound as the best way to diagnose deep venous thrombosis in pregnancy and CT pulmonary angiography as the best way to diagnose pulmonary embolism in pregnancy. Therapy involves supportive care and anticoagulation with unfractionated or low molecular weight heparin, depending on the clinical scenario.

Diagnostic value of CT for deep vein thrombosis: results of a systematic review and meta-analysis

AIM

To estimate the sensitivity and specificity of computed tomography (CT) for the diagnosis of deep vein thrombosis (DVT) in patients with suspected DVT and pulmonary embolus (PE).

MATERIALS AND METHODS

A search of the medical literature and citation lists was undertaken, and selected studies comparing CT to a reference standard in patients with suspected DVT or PE were retrieved. Data were analysed by random effects meta-analysis.

RESULTS

Thirteen articles were included in the meta-analysis. Most compared CT to ultrasound in patients with clinically suspected PE. The sensitivity ranged from 71-100%, while specificity ranged from 93-100%. The pooled estimate of sensitivity was 95.9% (95% CI 93 to 97.8%) and the pooled estimate of specificity was 95.2% (93.6 to 96.5%). However, pooled estimates should be interpreted with caution as these were subject to significant heterogeneity (p=0.025 and p<0.001, respectively). Most studies only appeared to report proximal DVT. Too few data were available to estimate sensitivity for distal DVT.

CONCLUSIONS

CT has a similar sensitivity and specificity to ultrasound in patients with suspected PE where investigation of suspected DVT is required. There is insufficient research to determine the diagnostic accuracy of CT in patients with suspected DVT alone.

Lung cancer: interobserver agreement on interpretation of pulmonary findings at low-dose CT screening

PURPOSE

To evaluate agreement among radiologists on the interpretation of pulmonary findings at low-dose computed tomographic (CT) screening examinations for lung cancer.

MATERIALS AND METHODS

Institutional review board approval and informed consent were obtained. HIPAA guidelines were followed. Sixteen radiologists from the 10 National Lung Screening Trial screening centers of the National Cancer Institute's Lung Screening Study network reviewed image subsets from 135 baseline low-dose screening CT examinations in 135 trial participants (89 men, 46 women; mean age, 62.7 years +/- 5.4 [standard deviation]). Interpretations were classified into one of four of the following categories: noncalcified nodule 4 mm or larger in greatest transverse dimension (positive screening result); noncalcified nodule smaller than 4 mm in greatest transverse dimension (negative screening result); calcified, benign nodule (negative screening result); or no nodule (negative screening result). A recommendation for follow-up evaluation was obtained for each case. Interobserver agreement was evaluated by using the multirater kappa statistic and by using response frequencies and descriptive statistics.

RESULTS

Multirater kappa values ranged from 0.58 (for agreement among all four classifications; 95% confidence interval: 0.55, 0.61) to 0.64 (for agreement on classification as a positive or negative screening result; 95% confidence interval: 0.62, 0.65). The average percentage of reader pairs in agreement on the screening result per case (percentage agreement) was 82%. There was wide variation in the total number of abnormalities detected and classified as pulmonary nodules, with differences of up to more than twofold among radiologists. For cases classified as positive, multirater kappa for follow-up recommendations was 0.35.

CONCLUSION

Interobserver agreement was moderate to substantial; potential for considerable improvement exists. Clinical trial registration no. NCT00047385.

CT venography vs ultrasound in the diagnosis of thromboembolic disease in patients with clinical suspicion of pulmonary embolism

To assess the reliability of indirect computed tomography venography (CTV) in the detection of deep venous thrombosis (DVT) in patients with clinical suspicion of pulmonary embolism (PE). 235 consecutive patients with suspicion of PE underwent an imaging protocol composed of a CT pulmonary angiography (CTPA), a CTV and an ultrasound study of the deep venous system, which was considered the "gold standard." Sensitivity, specificity, and predictive values were calculated for CTV. ith CTV, 30 (12.8%) cases of DVT were detected, 9 (3.8%) of them without pulmonary embolism in CTPA, increasing the diagnosis of thromboembolic disease in 3.8%. However, six of these nine diagnoses were false positives, and CTV missed six cases of DVT. CTV rendered a sensitivity of 58.8%, specificity of 95.0%, a positive predictive value of 66.7%, and a negative predictive value of 93.2%. In patients with clinical suspicion of pulmonary embolism, ultrasound is preferred to CTV for the detection of DVT.

Chronic-Stage Deep Vein Thrombosis of the Lower Extremities

OBJECTIVE

To describe the computed tomographic (CT) findings of chronic deep vein thrombosis (DVT) and its evolution from acute DVT.

METHODS

Fifty-one consecutive patients with 52 legs confirmed as acute DVT by CT venography underwent follow-up computed tomography more than 2 months later. Follow-up CT findings were assessed retrospectively by consensus between 2 radiologists. The frequencies of CT findings were analyzed for affected venous segments: common iliac, external iliac, femoral, popliteal, and calf veins.

RESULTS

Twelve legs (23%) were completely normalized on follow-up computed tomography, but 40 legs (77%) showed abnormal findings as follows: luminal obliteration (n = 16), decreased caliber (n = 30), residual thrombi (n = 3), fibrotic bands (n = 28), ipsilateral muscle enlargement (n = 28), ipsilateral subcutaneous edema (n = 11), and superficial collateral vein development (n = 23). The external iliac vein (26/40, 65%) was the most commonly affected site followed in decreasing order by femoral (29/50, 58%), common iliac (9/18, 50%), popliteal (22/47, 47%), and calf veins (9/43, 21%). Trends were observed whereby luminal obliteration affected iliac veins and fibrotic bands affected femoropopliteal veins.

CONCLUSIONS

Luminal obliteration, decreased caliber, fibrotic bands, ipsilateral muscle enlargement, and superficial collateral vein development are common CT findings in chronic DVT of the lower extremity.

Benefit of CT venography for the diagnosis of thromboembolic disease

OBJECTIVE

The aim of this study was to determine the benefit of lower extremity CT venography (CTV) with pulmonary CT angiography (CTA) for diagnosing thromboembolic (TE) disease.

SUBJECTS AND METHODS

Reports of all CTAs and CTVs over a 3-year interval (Group I) and CTAs, CTVs, and lower extremity Doppler ultrasounds (US) over a 1 1/2-year subset (Group II) were reviewed. Patient population was inpatients and emergency department patients who were assessed for pulmonary embolism (PE) and deep venous thrombosis (DVT) at a tertiary care hospital. Reported results for CTA or CTV were categorized as positive (CTA(P), CTV(P)), negative (CTA(N), CTV(N)), or indeterminate for PE or DVT. When CTV and US results were discrepant, medical records were reviewed for clinical management. Additional benefit of CTV was assessed by chi-square analysis.

RESULTS

In Group I, 737 (81.1%) of 909 CTAs from combined CTA/CTV studies were negative. The diagnosis rate of TE disease increased from 13.0% to 17.3% with the addition of CTV(P)s (P=.01). Of the 119 cases in Group II undergoing combined CTA, CTV, and US, CTV and US were both positive in eight and both negative in 88. Of the seven discordant CTVs and USs with clinical follow-up, five CTVs were positive while USs were negative, three of which were treated clinically for TE disease, while two were considered falsely positive. As CTA also proved positive in one of the three, CTV therefore affected management in two of these five cases and increased the rate of thromboembolism diagnosis from 21.0% to 22.6%; however, this was not significant (P>.05). Two CTV(N)s were managed as false negatives.

CONCLUSIONS

The combined use of CTA and CTV significantly increases the rate of TE disease over CTA alone. In cases in which ultrasound is performed, however, there is no significant advantage to performing combined CTA/CTV studies.

Can multislice CT alone rule out reliably pulmonary embolism? A prospective study

PURPOSE

To evaluate the safety of withholding anticoagulation in patients with suspected acute pulmonary embolism after negative multislice computed tomography (MSCT) pulmonary angiography and lower-limb venography.

MATERIALS AND METHODS

A total of 383 consecutive patients with suspected acute pulmonary embolism were prospectively studied. Patients underwent MSCT pulmonary angiography and lower-limb venography, as well as pulmonary scintigraphy and lower-limb ultrasound examination. Patients with negative MSCT results for both pulmonary embolism and venous thrombosis were not administered anticoagulants and were followed up for 6 months to rule out thromboembolism.

RESULTS

At MSCT, 156 patients were positive for pulmonary embolism, venous thrombosis, or both; 224 were negative; and findings were inconclusive in three. False-negatives were five patients with high probability scintigram and two with venous thrombosis detected at US. A total of 184 patients with negative MSCT and without anticoagulation were followed up for 6 months. During this period of time just one recurrence of pulmonary embolism was detected. The negative predictive value of MSCT pulmonary angiography plus lower-limb venography was 95.8% (183/191).

CONCLUSION

MSCT is efficacious in diagnosing pulmonary embolism, with negative predictive values reported in the literature ranging from 94% to 100%. This enables omission of anticoagulation in patients with suspected pulmonary embolism after negative MSCT findings without the need for other diagnostic tests.

Evidence-based Practice in Radiology: Steps 3 and 4—Appraise and Apply Diagnostic Radiology Literature

Several paradigms for evidence-based practice (EBP) exist. One model proposes that specialist academic centers should primarily construct valid guidelines for various topics in medicine (top-down model). An alternative model integrates "the best research evidence with clinical expertise and patient values" (bottom-up model). Whereas the former model inherently implies a central specialized process, the latter implies that practitioners working in nonspecialist centers can learn and implement a standardized set of tools with which to ask a question, search and appraise the literature, and then apply best current evidence in a local setting. This article focuses on appraising the literature and applying retrieved results and is part of a series on EBP in radiology. This article describes a clinical scenario in which a new respirologist at a hospital requests indirect computed tomographic (CT) venography as part of a work-up of a patient with a high pretest probability for pulmonary embolism and a positive d-dimer test result. Many controversies surround the technique of indirect CT venography, and difficult topics such as this are ideally suited to the tools of EBP. This article will describe how to approach such a scenario.

Does Multi–Detector Row CT Pulmonary Angiography Reduce the Incremental Value of Indirect CT Venography Compared with Single–Detector Row CT Pulmonary Angiography?

PURPOSE

To compare retrospectively the incremental value of indirect computed tomographic (CT) venography performed after multi-detector row CT pulmonary angiography and single-detector row CT pulmonary angiography for the diagnosis of venous thromboembolism (VTE).

MATERIALS AND METHODS

The institutional ethics committee approved this study; informed consent was not required. The authors retrospectively reviewed results of 1100 combined single-detector row CT pulmonary angiographic and indirect CT venographic examinations (542 men, 558 women; mean age, 61 years +/- 17 [standard deviation]) (group 1) and 308 combined multi-detector row CT pulmonary angiographic and indirect CT venographic examinations (150 men, 158 women; mean age, 62 years +/- 18) (group 2), performed in 1408 patients suspected of having pulmonary embolism (PE). Frequency of deep venous thrombosis (DVT), PE, and VTE, and the incremental value of indirect CT venography were recorded in both groups. Data were compared by means of the Student t test for continuous data and z statistics for independent proportions.

RESULTS

VTE, PE, and DVT were found in 23.3% (n = 256), 19.9% (n = 219), and 18.3% (n = 201) of the 1100 patients in group 1, respectively, and in 23.7% (n = 73), 17.2% (n = 53), and 18.8% (n = 58) of the 308 patients in group 2, respectively (P values ranging from .273 to .876). The incremental value of indirect CT venography was 14.4% (37 of 256 patients) in group 1 and 27.4% (20 of 73 patients) in group 2.

CONCLUSION

Despite potential improved accuracy of multi-detector row CT pulmonary angiography for the diagnosis of PE, the addition of indirect CT venography increased the diagnosis of VTE in 27.4% of patients.

CT lower extremity venography in suspected pulmonary embolism in the ED

The purpose of this study was to evaluate the added benefit of computed tomography lower extremity venography (CTLV)--performed following CT pulmonary angiography (CTPA)--in the emergency department (ED) patient suspected of pulmonary embolism (PE). A retrospective review of 427 consecutive patients having both CTPA and CTLV performed to evaluate patients suspected of PE at two community hospitals was conducted. Three-month follow-up was performed on all patients to ensure that no case of PE or deep venous thrombosis (DVT) was missed. Forty patients were positive for PE, and 11 were positive for DVT. There were 6 CTPA studies read as indeterminate for PE and 11 CTLV studies indeterminate for DVT. Only 1 patient was positive for DVT, who did not have a concurrent PE identified by CTPA. The estimated charges for detecting the single case of isolated DVT was 206,400 US dollars. In our ED setting, the additional benefit of adding CTLV to the standard ED work-up of PE was minimal.

Acute Pulmonary Embolism: Imaging in the Emergency Department

Acute pulmonary embolism (PE) is a life-threatening condition that requires accurate diagnostic imaging. Morbidity and mortality that result from PE can be reduced significantly if appropriate treatment is initiated early; this makes timely diagnosis imperative. Historically, the gold standard for the imaging of PE has been pulmonary angiography. Rapid advances in radiology and nuclear medicine have led to this modality largely being replaced by noninvasive techniques, most frequently multidetector helical CT pulmonary angiography (CTPA). In cases in which CTPA is contraindicated, other modalities for diagnosis of PE include nuclear ventilation perfusion scanning, magnetic resonance pulmonary angiography, duplex Doppler ultrasonography for deep venous thrombosis, and echocardiography. This article reviews the literature on the role of these imaging modalities in the diagnosis of PE.

Diagnosis of suspected venous thromboembolic disease in pregnancy

Venous thromboembolic disease is a leading cause of maternal mortality during pregnancy. Early and accurate radiological diagnosis is essential as anticoagulation is not without risk and clinical diagnosis is unreliable. Although the disorder is potentially treatable, unnecessary treatment should be avoided. Most of the diagnostic imaging techniques involve ionizing radiation which exposes both the mother and fetus to finite radiation risks. There is a relative lack of evidence in the literature to guide clinicians and radiologists on the most appropriate method of assessing this group of patients. This article will review the role of imaging of suspected venous thromboembolic disease in pregnant patients, highlight contentious issues such as radiation risk, intravenous contrast use in pregnancy and discuss the published guidelines, as well as suggesting an appropriate imaging algorithm based on the available evidence.

Intravascular hematocrit layering in equilibrium phase contrast-enhanced MR angiography of the peripheral vasculature

PURPOSE

To evaluate intravenous hematocrit (HCT) layering detected in patent calf veins that potentially simulate filling defects seen in deep venous thrombosis (DVT).

MATERIALS AND METHODS

Flow characteristics, vessel size, and enhancement patterns of veins with HCT layering were examined and compared with those of normal veins in vivo. Ex vivo studies were conducted with conventional and blood pool contrast agents to study the effects of MRI parameters and intrinsic variables on detecting HCT layering.

RESULTS

HCT layering was detected in high resolution equilibrium phase images in one of six healthy subjects, and five of five patients with peripheral vascular occlusive disease (PVOD). Layering occurred only in deep veins that had significantly slower flow and larger diameter (P < 0.001) compared to normal veins. Enhancement patterns observed in vivo were similar to those found in the ex vivo study.

CONCLUSION

The HCT layering effect in MR venography has not been previously reported, likely because delayed equilibrium phase venous imaging is not frequently performed. The use of blood pool contrast agents and high resolution equilibrium phase imaging allows intravascular HCT layering to be observed within a 30-60-minute time frame. Several imaging characteristics that distinguish HCT layering from DVT are discussed.

Optimized image reconstruction for detection of deep venous thrombosis at multidetector-row CT venography

The aims of this study were to optimize image quality for indirect CT venography (sequential versus spiral), and to evaluate different image reconstruction parameters for patients with suspected deep venous thrombosis (DVT). Fifty-one patients (26/25 with/without DVT) were prospectively evaluated for pulmonary embolism (PE) with standard multidetector-row computed tomography (MDCT) protocols. Retrospective image reconstruction was done with different slice thicknesses and reconstruction increments in sequential and spiral modes. All reconstructions were read for depiction of DVT and to evaluate best reconstruction parameters in comparison with the thinnest reconstruction ("gold standard"). Image noise and venous enhancement were measured as objective criteria for image quality. Subjective image quality was rated on a four-point scale. Effective dose was estimated for all reconstructions. In sequential 10/50 reconstruction DVT was completely detected in 13/26 cases, partially in 10/26 cases and was not detected at all in 3/26 cases, and 15/26, 9/26 and 2/26 cases for the 10/20 reconstruction, respectively. DVT was completely detected in all spiral reconstructions. Image noise ranged between 14.8-29.1 HU. Median image quality was 2. Estimated effective dose ranged between 2.3 mSv and 11.8 mSv. Gaps in sequential protocols may lead to false negative results. Therefore, spiral scanning protocols for complete depiction of DVT are mandatory.

Prospective Comparison of Indirect CT Venography Versus Venous Sonography in ICU Patients

OBJECTIVE

The purpose of our study was to prospectively compare indirect CT venography (CTV) and duplex venous sonography in the evaluation of acute deep venous thrombosis (DVT) in ICU patients with suspected pulmonary embolism.

SUBJECTS AND METHODS

All ICU patients undergoing CT pulmonary angiography in the evaluation of acute pulmonary embolism during a 10-month period were included in the study group. Indirect CTV was performed 3 min after initiation of the contrast bolus and was compared with duplex venous sonography of the lower extremities. Both techniques were compared with a clinical standard when DVT was considered present if a positive result was obtained on sonography or on CTV in the setting of pulmonary embolism.

RESULTS

The study group comprised 61 ICU patients. Using the clinical standard, DVT was detected in 10 of 61 patients. The sensitivity and specificity for CTV were 70% and 96%, respectively, and for sonography were 70% and 100%.

CONCLUSION

The performance characteristics of CTV and deep venous sonography were similar when compared with a clinical standard. The results support the use of indirect CTV after CT pulmonary angiography as an alternative to sonography in the ICU population.