Chest ultrasound can provide the same diagnostic information as chest CT in children with complicated pneumonia and parapneumonic effusion, according to an article to be published in the December issue of the American Journal of Roentgenology.
In a retrospective comparison of chest CT and ultrasound in 19 children, a New York study team found that CT failed to uncover any additional clinical detail not seen on ultrasound. In line with the goal of minimizing radiation exposure, the researchers believe that chest radiography and chest ultrasound should be utilized instead of CT for the imaging workup of complicated pediatric pneumonia.
"Chest CT may be reserved for patients in whom chest ultrasound is technically difficult or discrepant with the clinical finding," wrote a research team led by Dr. Jessica Kurian of Montefiore Medical Center in New York City.
To determine if chest ultrasound could serve as a useful alternative to chest CT in this patient population, the researchers retrospectively compared the results of studies in nine girls and 10 boys admitted with complicated pneumonia and parapneumonic effusion between December 2006 and January 2009. The children ranged in age from eight months to 17 years (AJR, December 2009, Volume 193:6, pp. 1648-1654).
Both the CT and ultrasound images were evaluated for effusion, loculation, fibrin strands, parenchymal consolidation, necrosis, and abscess. The researchers also correlated imaging results with operative findings in a subset of patients who were surgically managed.
The ultrasound studies were performed by two experienced ultrasound staff sonographers on an iU22 ultrasound scanner (Philips Healthcare, Andover, MA), an HDI 5000 scanner (Philips), or an Acuson Sequoia 512 system (Siemens Healthcare, Malvern, PA). Linear, curved linear, and vector transducers were employed.
The chest CT scans were performed on an Mx8000 IDT 16-slice scanner (Philips), a Brilliance 16-slice scanner (Philips), or a LightSpeed VCT 64-slice system (GE Healthcare, Chalfont St. Giles, U.K.). Of the 19 patients, 13 received Visipaque nonionic contrast (GE) with their CT exam. CT data were reconstructed at a slice thickness of either 3 or 5 mm for image review, according to the researchers.
For the purposes of the study, the chest CT and ultrasound images were retrospectively reviewed in consensus by a board-certified pediatric radiologist and a radiology resident, blinded to the results from the other modality. They examined the studies for the presence of pleural effusion and fibrin strands within the effusion, as well as for parenchymal consolidation and the presence of lung necrosis or abscess.
The researchers noted that 15 effusions were loculated on chest CT; 13 were loculated on chest ultrasound. In one patient, loculation visualized on chest CT could not be determined on chest ultrasound due to scan quality limitations, according to the authors.
Chest ultrasound was superior for identifying fibrin strands, according to Kurian and colleagues. "Fibrin strands were identified in all patients with effusion on chest ultrasound except for one patient with only trace fluid; some patients showed few fibrin strands, whereas others showed numerous strands of variable thickness," the authors wrote. "Although presumably present, fibrin strands could not be clearly delineated on any of the chest CT images."
As for parenchymal findings, all 19 chest CT scans and 18 chest ultrasound studies showed parenchymal consolidation. One ultrasound study had technical limitations that precluded evaluation of the lung.
The 13 contrast-enhanced CT studies found six patients with coexisting necrosis and two with coexisting abscess. In comparison, the chest ultrasound exams discovered six patients with coexisting necrosis and one with a coexisting abscess. Both modalities concurred on the presence of necrosis in five patients, and differed in two. In one patient, necrosis was identified on chest CT, but the lack of evaluation with a linear transducer limited the ultrasound study. Also, necrosis was identified on chest ultrasound in one patient who had an unenhanced chest CT.
Of the 14 patients who received video-assisted thoracoscopy, five had surgically proven parenchymal abscess or necrosis. Ultrasound was able to show parenchymal abscess or necrosis in four patients, while chest CT was only able to do so in three patients.
The authors acknowledged study limitations including its small sample size, the lack of real-time evaluation of chest ultrasound images, and the variable technical quality of the chest ultrasound images.
Nonetheless, the authors concluded that chest ultrasound confers a number of benefits over chest CT in this patient group, including portability and avoidance of patient sedation. Chest ultrasound is also superior for detecting fibrin strands within an effusion, a finding that corresponded to the presence of empyema in their study.
By Erik L. Ridley
AuntMinnie.com staff writer
November 20, 2009
Related Reading
Pulmonary CTA finds more than pulmonary embolism in children, August 25, 2009
Chest x-rays questioned: Wheezing in children unlikely to mean pneumonia, August 3, 2009
Color-coded CT protocols help reduce pediatric radiation dose, June 4, 2009
MRI used to diagnose complex lung infections in children, October 16, 2008
CAD offers potential for diagnosing pediatric pneumonia, July 23, 2008
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