Optimized imaging of pulmonary embolism

Contrast Circulation Time to Assess Right Ventricular Dysfunction in Pulmonary Embolism: A Retrospective Pilot Study

Objective

To optimize enhancement of pulmonary arteries and facilitate diagnosis of pulmonary embolism (PE), modern computed tomography angiography (CTA) contains a contrast bolus tracking system. We explored the diagnostic accuracy of the time-intensity curves given by this automated system to identify right ventricular dysfunction (RVD) in acute PE.

Methods

114 CTAs with a diagnosis of PE were reviewed. RVD was defined as right-to-left ventricular diameter ratio of 1 or greater. Four parameters on time-intensity curves were identified. Parameters between CTAs with and those without RVD were compared with the Wilcoxon rank-sum test. The ability of the four parameters to discriminate patients with RVD was explored by compiling the area under the operating curves (AUC).

Results

The time needed by the contrast media to reach the pulmonary artery [8 seconds (IQR: 7–9) versus 7 seconds (IQR: 6–8), p<0.01], the time needed to reach 40 Hounsfield units (HU) [11 seconds (IQR: 8.5–14) versus 9.5 seconds (IQR: 8–10.5), p<0.01], and the contrast intensity reached after 10 seconds [19 HU (IQR: 4–67) versus 53 HU (IQR: 32–80), p<0.05] were all statistically different between CTA with and CTA without RVD. Those three parameters changed gradually across severity categories of RVD (p<0.05 for trend). Their AUC to identify RVD ranged from 0.63 to 0.66. The slope of contrast intensity over time was not informative: [31 HU/s (IQR: 20–57) in CTA with, compared to 36 HU/s (IQR: 22.5–53) in CTA without RVD, p = 0.60].

Conclusion

Several parameters of the time-intensity curve obtained by the bolus tracking system are associated with RVD assessed on CTA images. Of those, the time needed to reach a predefined threshold seems to be the easiest to obtain in any CTA without additional processing time or contrast injection. However, the performance of those parameters is globally low.

Low-contrast agent dose dual-energy CT monochromatic imaging in pulmonary angiography versus routine CT

OBJECTIVE

This study aimed to retrospectively evaluate the feasibility and reliability of low-contrast agent dose dual-energy computed tomography (DECT) monochromatic imaging in pulmonary angiography.

METHODS

Computed tomography pulmonary angiography was performed in 86 patients, 41 in 120-kVp computed tomography (CT) and 45 in DECT with low-contrast agent dose. The images in DECT were reconstructed at optimal kiloelectron-voltage (keV), demonstrating the best contrast-to-noise ratio between pulmonary artery and soft tissue, and at 70 keV. Image quality was compared by quantitative and subjective indexes. The radiation doses were recorded.

RESULTS

Compared with 120-kVp CT, optimal keV showed superior quantitative indexes with inferior subjective image quality, whereas 70 keV demonstrated no statistical difference in quantitative indexes with superior subjective image quality. All suspicious pulmonary embolisms in DECT were diagnosed confidently by combination of 2 kinds of monochromatic imaging. The radiation dose in DECT is almost twice as 120-kVp CT.

CONCLUSIONS

Low-contrast agent dose DECT monochromatic imaging in pulmonary angiography accommodates superior intravascular enhancement and contrast in pulmonary arteries, and improves diagnostic confidence with compatible radiation dose.

The prevalence of pulmonary embolism in chronically paralyzed subjects: a review of available evidence

STUDY DESIGN

Qualitative systematic review.

OBJECTIVES

To examine the validity of the prevailing notion that pulmonary embolism (PE) is rare in the chronic spinal cord injury (SCI) population.

SETTING

USA.

METHODS

Review surveys of adult SCI subjects >2 months after injury in which PE has been looked for and its prevalence estimated.

RESULTS

A total of 16 surveys of chronic SCI subjects published between 1956 and 2009 offered data on PE prevalence. Two autopsy surveys, 178 subjects paralyzed >2 months, revealed no PE. Eleven surveys of the cause of death, 3193 subjects paralyzed 1-25 years, revealed PE in 2.1%. Two surveys of survivors of SCI, 5761 subjects paralyzed 1-25 years, revealed PE in 0.4%. Our survey of 112 subjects paralyzed 1-50 years before death, revealed PE in 21 (18.7%), based on autopsy, imaging, clinical and electrocardiographic evidence. In 7 (33%) of the 21 subjects with PE, pulmonary hypertension by transthoracic echocardiography was detected, indicating recurrent and/or unresolved PE.

CONCLUSION

PE is not infrequent in the chronic SCI subject; but its presentation may be subclinical; and its apparent recurrence may lead to pulmonary hypertension.

[Improvement of pulmonary angiography in the framework of a maintenance of certification]

PURPOSE

This evaluation of clinical practices (pulmonary embolus) was performed to evaluate the quality of CT pulmonary angiograms for suspected acute pulmonary embolus.

MATERIALS AND METHODS

Five validated criteria evaluating both the acquisition technique and the quality of image interpretation were selected: slice thickness, pulmonary arterial enhancement over 250 HU, caudocranial acquisition, visualization of fifth order pulmonary arterial branches, and right-left ventricular ratio in the presence of pulmonary embolus. Forty CT pulmonary angiograms were reviewed before and after implementation of a practice quality improvement program: modification of acquisition protocol, training of medical and paramedical staff, and implementation of a standardized radiology report.

RESULTS

Thin collimation was already implemented. The implementation of two other technical parameters significantly improved the technical quality of the examinations. The detection of findings with adverse clinical outcome was also significantly improved. Only the accuracy of detection of embolus involving fifth order pulmonary arterial branches could not be improved, a criteria allowing formal exclusion of pulmonary embolus.

CONCLUSION

This study resulted in an improvement in the quality of CT pulmonary angiograms and increased awareness of radiologists for the prognostic value of right ventricular dilatation. It has also underscored the need for quality control of a CT pulmonary angiogram prior to interpretation.