CT for thromboembolic disease

Chronic CT features in PE patients with co-existing DVT

OBJECTIVE

Clinical features may be different in patients with PE without co-existing DVT compared to those with PE with co-existing DVT. This prospective study aims to investigate the different clinical features between patients with isolated pulmonary embolism (PE) and those with PE associated with deep venous thrombosis.

METHOD

This is a prospective study conducted in 107 consecutive patients diagnosed with acute PE in the emergency department or other departments of Kırıkkale University Hospital. The diagnosis of PE was confirmed by computed tomography pulmonary angiography (CTPA), which was ordered on the basis of symptoms and findings. Bilateral lower extremity compression ultrasound with standard 7.5 MHz linear array probe was applied to all patients. According to compression ultrasound results, the patients were divided into two classes as with and without deep venous thrombosis. Embolism in the main or lobar pulmonary arteries were classified as central, and those found only in segmental or subsegmental arteries were classified as peripheral. Laboratory parameters and Oxygen saturation were assessed on admission.

RESULTS

67 of 107 (62.6%) patients with PE were isolated pulmonary embolism, and 40 (37.4%) were PE + DVT. Patients with PE with co-existing DVT have wider pulmonary artery, higher d-dimer and pro BNP level, and lower saturation than those with isolated pulmonary embolism. Central pulmonary embolism is more common in patients with deep vein thrombus than those without it. (87.5% (35/40) vs 32.8% (22/67),p = 0.001). 38.6% of central pulmonary embolism occur without deep vein thrombosis of the lower extremities. Patients with PE with co-existing DVT have 42.5% mosaic perfusion pattern,70% chronic infarct appearance such as linear band, pleural nodüle, %15.0 thickened, small arteries and, %12.5 shrunken complete artery occlusion, suggesting the chronic background.

CONCLUSION

PE patients with co-existing DVT are clinically more serious than those who do not have a DVT. An acute picture may be present in the chronic background in a significant proportion of patients with PE with co-existing DVT. In the presence of deep vein thrombosis, pulmonary embolism is usually central, but more than one-third of central pulmonary emboli occur without lower extremity deep vein thrombosis.

Cardiothoracic CT angiography: current contrast medium delivery strategies

OBJECTIVE

Over the last decade, rapid technologic evolution in CT has resulted in improved spatial and temporal resolution and acquisition speed, enabling cardiothoracic CT angiography to become a viable and effective noninvasive alternative in the diagnostic algorithm. These new technologic advances have imposed new challenges for the optimization of contrast medium delivery and image acquisition strategies.

CONCLUSION

Thorough understanding of contrast medium dynamics is essential for the design of effective acquisition and injection protocols. This article provides an overview of the fundamentals affecting contrast enhancement, emphasizing the modifications to contrast material delivery protocols required to optimize cardiothoracic CT angiography.

Optimisation of contrast medium volume and injection-related factors in CT pulmonary angiography: 64-slice CT study

OBJECTIVE

To compare the image quality of computed tomography pulmonary angiography (CTPA) obtained with the injection of various low doses of contrast medium (CM) with different injection-related factors.

METHODS

A total of 90 patients (42 females, 48 males; 54.3 +/- 18.6 years) undergoing CTPA were included. Three CM protocols, each containing 30 patients, were created. Protocols 1, 2 and 3 consisted of a CM of 60 ml, 55 ml and 50 ml, and a bolus trigger level of 120 HU, 90 HU and 75 HU, respectively. Injection was uniphasic for protocols 1 and 2 (flow rate 5 ml/s), and biphasic for protocol 3 (flow rates 5 and 4 ml/s); with saline flushing afterwards. Enhancement was measured in three central and six peripheral pulmonary arteries.

RESULTS

The mean attenuation value for pulmonary arteries was over 250 HU for all protocols. There was no difference between the attenuation levels with the protocols (p > 0.05). The percentage of pulmonary arteries exceeding optimal attenuation (> or =250 HU) showed that protocols 2 and 3 were 90-100% successful (p < 0.05).

CONCLUSION

The use of proper injection-related factors during CTPA, such as a low trigger level and a high flow rate with saline injection following a decreased CM volume (55 ml or 50 ml), will enable adequate pulmonary artery contrast enhancement.

Unsuspected pulmonary embolism identified using multidetector computed tomography in hospital outpatients

AIM

To evaluate the incidence of unsuspected pulmonary embolism (PE) in an unselected population of outpatients undergoing contrast-enhanced multidetector computed tomography (MDCT) for indications other than the investigation of PE.

MATERIALS AND METHODS

Outpatients undergoing CT of the chest over a 6-month period were retrospectively identified and images reviewed. Inpatients and patients undergoing unenhanced CT of the chest were excluded. Data, including referring specialty, patient age and sex, reasons for examination, level of embolism, image quality, and section thickness were recorded. Radiology reports were reviewed with respect to whether or not the embolism was noted at the time of initial reporting.

RESULTS

Following exclusions 440 patients were reviewed (195 women and 245 men). PE was identified in 10 of the 440 patients, an incidence of 2.23%. One pulmonary embolus was in the main pulmonary artery, three were in lobar arteries, three in segmental arteries, and three in subsegmental arteries. Patients over the age of 60 years were more likely to have an embolism (9/300, 2.9%) compared with those under 60 years (1/140, 0.7%). Seven of the 10 positive examinations were carried out in patients who were known or later shown to have malignancy. Seven of the 10 emboli were reported at the time of initial reporting.

CONCLUSION

The outpatient population has a significant incidence of unsuspected PE. PE should be actively sought when reporting examinations performed for alternative indications, particularly where cancer is a known or suspected diagnosis.

64-Multidetector-row spiral CT in pulmonary embolism with emphasis on incidental findings

AIM

In this retrospective study, we assess the current role and future potential of computed tomography (CT) in the diagnostic algorithm of acute pulmonary embolism (PE).

MATERIALS AND METHODS

Two hundred patients underwent 64-multidetector-row spiral CT of the chest, pelvis, and thigh for suspected PE. CT scans were reviewed, and the degree of contrast enhancement and the presence of PE and/or (deep) venous thrombosis were recorded. In the case of PE, the level of thrombus was noted as central, main, or lobar. If the scan yielded a positive result for thrombosis, intravenous localization was also determined. Patient age, length of admission, clinical course, clinical indication, and incidental findings were registered as well.

RESULTS

PE was detected in 60 of the 200 patients with a high clinical probability of having PE (30%). Thirty-four patients had a positive CT scan result for venous thrombosis (17%). Twenty-four of the 60 patients had proximal deep venous thrombosis (40%), and 2 patients had arm venous thrombosis (3%). Thirty-four of the 60 patients had PE without venous thrombosis (57%). Eight of the 200 patients had deep venous thrombosis without suspicion of PE (4%). The distribution of the proximal thrombi showed 15 in a central artery (25%), 13 in a main pulmonary artery (22%), and 32 in a lobar segmental artery (53%). There was diffuse allocation of the thrombus in all lobes. Furthermore, CT scan noted a total of 120 incidental findings.

CONCLUSION

Our study indicates the potential clinical use of a diagnostic strategy for ruling out PE based on D-dimer testing and multidetector-row CT. A larger outcome study is needed before this approach can be adopted.

Effect of patient weight and scanning duration on contrast enhancement during pulmonary multidetector CT angiography

PURPOSE

To retrospectively evaluate the amount of contrast medium required with 16- and 64-section computed tomography (CT) for a given patient weight to achieve desirable contrast enhancement during pulmonary CT angiography.

MATERIALS AND METHODS

Institutional review board approval was obtained, and informed consent was not required for this HIPAA-compliant study. Eighty-five patients (35 men, 50 women; range, 22-87 years) who had undergone 16-section (n = 48) or 64-section (n = 37) CT for the detection of pulmonary embolism were retrospectively evaluated. Contrast medium containing 350 mg of iodine per milliliter was injected at a rate of 4 mL/sec. The injected volume corresponded to the injection rate multiplied by the sum of the scanning delay plus the scanning duration, up to 125 mL. The scanning delay was determined with bolus tracking. Contrast enhancement was measured in the main pulmonary artery and the aorta. For each patient, the injected contrast medium volume per body weight index was calculated. Linear regression analysis was performed, and the Wilcoxon signed rank test was used to assess differences between 16- and 64-section CT.

RESULTS

A range of patient weights (45.3-153.0 kg) and contrast medium volumes (76-125 mL) were noted. The regression formula indicated that 1.2 mL per kilogram body weight of contrast medium was required to achieve 250 HU. The median scanning duration was shorter for 64-section CT than for 16-section CT (5.7 seconds vs 9.5 seconds, P < .001). Consequently, 64-section CT required 17.6% less contrast medium than did 16-section CT (85.4 mL vs 103.6 mL, P < .001). Median contrast enhancement in the pulmonary artery was 8.9% lower with 64-section CT than with 16-section CT (257.7 HU vs 282.9 HU, P = .11).

CONCLUSION

To achieve consistent contrast enhancement during pulmonary CT angiography, the amount of contrast medium can be adjusted to the patient's body weight.

Prospective evaluation of unsuspected pulmonary embolism on contrast enhanced multidetector CT (MDCT) scanning

AIM

To quantify the incidence of unsuspected pulmonary emboli (PE) in an unselected inpatient population undergoing contrast enhanced multidetector CT (MDCT) scanning of the thorax and to assess aetiological factors in their development.

METHODS

All inpatients undergoing MDCT scanning of the thorax over a 10 month period were prospectively identified. Patients with previous or suspected current PE were excluded. CT scans were reviewed and the degree of contrast enhancement and presence of PE recorded. Where PE was found, the level of the most proximal thrombus was identified. Patient age, length of admission, slice scan thickness and clinical indication were noted.

RESULTS

547 inpatients who had undergone MDCT scanning were identified. Following exclusions 487 remained, 28 of whom (5.7%) had PE. Unsuspected PE was more common with increasing age, occurring in 9.2% (20/218) of all patients over 70 years and 16.7% (11/66) of those over 80 years (p<0.001). Eighteen of the 28 positive scans (64.3%) were at the segmental or subsegmental level. No other aetiological factor was identified which significantly increased the incidence of unsuspected PE. No significant difference was noted between 4-slice and 16-slice MDCT. Nine of the cases of incidental PE (32.1%) were not identified by the original reporting radiologists.

CONCLUSION

PE is an unsuspected finding on contrast enhanced MDCT scanning of the thorax in 5.7% of all inpatients. The incidence is higher in older patients. Most are peripheral and >30% are missed on initial review. PE should be routinely sought in all contrast enhanced MDCT scans of the chest, irrespective of the indication for the CT scan.