CHICAGO - There is more evidence for the use of ultrasound instead of CT, with its dangers of ionizing radiation, for chest disorders in children. For many cases in which plain film is insufficient, ultrasound can be the second modality of choice instead of CT, according to research from the Rambam Medical Center in Israel.
The study involved 96 children, and found that ultrasound can do better than CT for certain chest disorders. In one case, plain film and CT could not differentiate normal thymic tissue from pathological tissue while ultrasound could.
In another instance, the follow-up CT scan of a 6-year-old lymphoma patient treated successfully with chemotherapy revealed a new mass in the upper mediastinum. However, ultrasound confirmed it was a normal thymus with no residual disease.
"US is an important adjunct to plain film and CT in the evaluation of mediastinal masses, and can be used to guide biopsy of tumors," said Dr. Michalle Soudack, one of the study authors who presented the findings at the RSNA meeting on Thursday.
Chest ultrasonography was performed to evaluate mediastinal enlargement in 27 children, determine the cause of pulmonary opacification in 45, differentiate drainable fluid from pleural thickening in 20, and clarify one case of postsurgery problematic chest radiograph.
Ultrasound is especially suited for pleural-based imaging, and is very useful in pleural aspiration and drainage. The lung, which is mostly air, absorbs most of the sound waves and cases multiple reverberations. The ultrasound beam can be transmitted when a portion of the lung is consolidated and it becomes airless.
The different cases investigated with ultrasound when plain film was insufficient included complex pleural effusion, fibrothorax, loculated pleural fluid, thoracocentesis, abnormal thymus, mediastinal lymphadenopathy, and mediastinal vascular anomalies, as well as biopsy of the chest wall.
In the last case presented, the chest x-ray of a 2-year-old girl with fever and cough, and who had undergone several surgical procedures, showed a large opacity involving most of the hemithorax. Ultrasound found it to be because of intrathoracic stomach and delayed emptying of gastric contents.
Overall, chest ultrasound allowed a definitive diagnosis in 96% of cases, according to the study authors. "When confronted with a puzzling chest x-ray, radiologists caring for children should be aware chest ultrasound is an important adjunct and may obviate the need for more expensive imaging modalities. It is mobile, dynamic and does not involve radiation," Soudack said.
In addition, she pointed out, small children could be scanned in their parents' arms, reducing anxiety and improving cooperation, which is necessary for good imaging.
By N. Shivapriya
AuntMinnie.com staff writer
December 3, 2004
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