Spiral computed tomography for pulmonary embolism

Imaging for suspected pulmonary embolism in pregnancy-what about the fetal dose? A comprehensive review of the literature

OBJECTIVE: To give a comprehensive overview of fetal doses reported in the literature when imaging the pregnant woman with suspected pulmonary embolism (PE). METHODS: A comprehensive literature search in the PubMed, MEDLINE and EMBASE databases yielded a total of 1,687 papers that were included in the analysis and have been analysed with regard to fetal dose in suspected PE radiological imaging strategies. RESULTS: Fetal dose in chest computed tomography (CT) ranges between 0.013 and 0.026 mGy in early and 0.06-0.1 mGy in late pregnancy compared with 99mTc-MAA perfusion scintigraphy with a fetal dose of 0.1-0.6 mGy in early and 0.6-0.8 mGy in late pregnancy. (99m)Tc-aerosol ventilation scintigraphy results in 0.1-0.3 mGy. However, there is concern about female breast irradiation in CT, which is higher than in scintigraphy. CT radiation risks for breast tissue remain unclear. CONCLUSION: Knowledge of dosimetry and radiation risks is crucial in the radiological work-up of suspected PE in pregnancy. It is reasonable to reserve scintigraphy for pregnant patients with normal chest radiography findings and no history of asthma or chronic lung disease. Performing CT applying dose reduction instead of scintigraphy will minimise fetal radiation dose and maximise the diagnostic value.

[Mediastinal and abdominal lymphoedema: consequence of massive pulmonary embolism with shock?]

We report a case of severe pulmonary embolism diagnosed using spiral CT-scan in a patient admitted for shock associated with acute abdominal symptoms. Intraluminal clots images were visualized associated with an infiltration of mediastinal fat. Abdominal CT showed infiltration of the hepatobiliary hilum. After thrombolysis, the clinical thoracic and abdominal symptoms improved. A CT-scan at the 48(th) hour showed that the thoracic and abdominal features had disappeared. We emphasize the misleading aspect of the CT-scan images and we speculated that this infiltration could reflect the abdominal and mediastinal lymphoedema.

Comparison of ventilation/perfusion scintigraphy and helical CT for diagnosis of pulmonary embolism; strategy using clinical data and ancillary findings

STUDY OBJECTIVE

To address the question whether ventilation/perfusion scintigraphy (SCINT) or helical computed tomography (CT) should be the first hand method for diagnosis of pulmonary embolism (PE).

SETTING

Departments of radiology, nuclear medicine and internal medicine of a large university hospital.

PATIENTS

During 3 years all 128 patients examined for PE with both methods were analysed. The strategy of interpretation behind original clinical reports, i.e. clinical CT and clinical SCINT, was based upon basic criteria for PE, ancillary findings and information from the referring doctor and from previous examinations. Reviewed SCINT and CT reports were obtained from experts in each field blinded to clinical and laboratory data. The findings with respect to PE were classified as no PE, PE or non-diagnostic. Other pathology than PE was described. A final diagnosis serving as reference was based upon CT, SCINT and other information including clinical follow for 6-24 months.

METHODS

Planar SCINT was made with ventilation always preceding perfusion. CT was made with contrast injection using 3 mm collimation and table feed of 3 mm s-1.

RESULTS

PE was diagnosed in 32 patients. For clinical and reviewed SCINT sensitivity was 91 and 97%, specificity 96 and 100% and rate of non-diagnostic findings 10 and 9%, respectively. For clinical and reviewed CT sensitivity was 81 and 78%, specificity 99 and 100% and non-diagnostic findings was observed in 8 and 1%, respectively. In patients with PE, concordant positive results were obtained with both modalities in 23 of 32 patients (72%).

CONCLUSION

SCINT remains the first hand method because its high sensitivity, general feasibility, low radiation burden and low rate of non-diagnostic findings in our setting. CT is indispensable when SCINT is not available or its result non-diagnostic.