Rapid lung MRI recommended to diagnose pediatric pulmonary infections

By Staff News Brief

A rapid lung MRI protocol is comparable to multidetector CT (MDCT) for detecting thoracic abnormalities in children with clinically suspected pulmonary infections, according to a multidisciplinary team of physicians at the Post Graduate Institute of Medical Education and Research in Chandigarh, India. The results of a study published in the Journal of Magnetic Resonance Imaging suggest that MRI has great potential as the first line cross-sectional imaging modality of choice for pediatric patients.

Although MRI does not expose children to radiation, its higher cost, longer duration, and the combination of low signal intensity from pulmonary tissue and a high predilection for susceptibility artifacts within the lungs, has made CT the preferred secondary imaging choice if a chest X-ray exam is inadequate to make a diagnosis. However, recent MRI technical advancements such as increased gradient strength, 3D imaging, volume interpolation, parallel imaging, and the development of ultrafast sequences have improved its feasibility for lung imaging. Published studies show that MRI can detect fungal infections, empyema, necrosis/abscess, pulmonary consolidation, and community–acquired pneumonia in children.

Kushaljit Singh Sodhi, MD, PhD, of the Department of Radio Diagnosis and Imaging, and colleagues enrolled 75 consecutive pediatric patients who had both CT and MRI scans for suspected thoracic abnormalities. All but two patients had both procedures performed on the same day, with the others having procedures within a 48-hour period. The children ranged in age from 5 to 15 years. They included immunocompromised patients with suspected lung infection, patients with hematological malignancies having neutropenia and fever lasting for more than 72 hours, patients suspected of having a parasitic infection, and patients clinically suspected of having pneumonia.

Dr. Sodhi and colleagues used a new rapid four sequence MRI protocol they had developed. Designed to detect lung parenchymal findings in children with pulmonary infections, the protocol included HASTE-T2, BLADE-T2, TRUFI-T2, and VIBE-T1 sequences. The authors explained that these fast sequences with short acquisition times were chosen, optimized, and standardized to provide the maximum information in the shortest possible time. The total scan time took two minutes, with the time a patient spent in the MRI suite ranging from 14 to 20 minutes. This reduced the need for long sedation or anesthetic support.

Two experienced pediatric thoracic radiology specialists individually interpreted the MDCT and the MRI exams, grading each for diagnostic image quality. MRI findings were defined and recorded in accordance with established CT nomenclature. The radiologists evaluated pulmonary parenchyma for nodules, consolidation, ground glass opacity, hyperinflation, bronchietasis, and cyst/cavitary lesion. The size and number of pulmonary nodules were recorded, and pleural cavities were evaluated for the presence of pleural effusion.

All CT studies were rated as being diagnostically acceptable, as were all of the MRI studies. Eleven of the MRI studies had artifacts, but were rated as having diagnostically acceptable images.

The rapid MRI lung protocol demonstrated sensitivity, specificity, positive predictive value (PPV) and negative predictive value (NPV) of 100%. Thirty three nodules were identified on CT compared to 32 on MRI, and CT identified seven ground glass opacities compared to four on MRI. CT also identified one more case of bronchiectasis (5) compared to four identified by MRI. However, both CT and MRI identified the same number of findings of consolidation, pleural effusion, hyperinflation, cyst/cavity only, and lymph nodes.

The authors said that the TRUFI-T2 sequence was best for detection of lymph nodes. The HASTE-T2 and BLADE-T2 sequences demonstrated the highest sensitivity for detection of bronchiectasis and nodules. However, MRI showed relatively poor sensitivity in the detection of small pulmonary nodules 3 mm in size or smaller.

Based on their findings, Dr. Sodhi and colleagues believe that rapid lung MRI is an excellent diagnostic imaging modality to diagnose children suspected of having pulmonary infections. They recommend that larger prospective studies be performed to validate the feasibility of replacing CT with fast MRI scans instead.

REFERENCE

  1. Sodhi, KS, Khandelwal N, Saxena AK, et al. Rapid Lung MRI in Children with Pulmonary Infections: Time to Change our Diagnostic Algorithms. J Magn Reson Imaging. Published online November 6, 2015.
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Rapid lung MRI recommended to diagnose pediatric pulmonary infections.  Appl Radiol. 

By Staff News Brief| November 19, 2015
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