CT confirms extent of lung involvement in H1N1 pneumonia

Severe H1N1 pneumonia has a distinct imaging signature, according to University of California, Los Angeles researchers, who presented their work at the Society of Critical Care Medicine meeting earlier this month in Houston.

In the largest analysis to date of severe H1N1 pneumonia requiring intensive care, the team found that all 18 patients had abnormal radiographic and CT findings. In addition, 100% of the patients had ground-glass opacities and consolidation on CT on admission to intensive care units (ICUs).

Dr. Nader Kamangar, a pulmonary and critical care specialist at Olive View-UCLA Medical Center; Dr. Cecilia Jude, a thoracic radiologist; and several fellows and residents conducted the retrospective study of patients during the 2009 H1N1 pandemic.

"Compared to prior studies of H1N1 patients requiring intensive care, this study demonstrated a higher rate of ground-glass opacities and greater involvement of middle and lower lung zones," Jude noted.

All 18 individuals were admitted to the ICU with a primary diagnosis of H1N1. Their ages ranged from 23 to 62 years (mean 41). Each had chest x-ray on admission, and five also had a CT scan.

The diagnosis was confirmed in each patient with either a rapid influenza detection test or a real-time reverse transcriptase polymerase chain reaction assay. Twelve (67%) of the patients met the criteria for acute respiratory distress syndrome and required mechanical ventilation. Three (25%) of these individuals died.

On chest x-ray, 16 (89%) of the patients had ground-glass opacities, 16 (89%) had consolidation, and six (33%) had reticular opacities. Seventeen (94%) patients had bilateral radiographic abnormalities.

The abnormalities involved primarily the middle (78%) and lower (100%) lung zones. Sixteen (89%) had extensive chest x-ray abnormalities involving three or more lung zones. The team also found pleural effusions in 16 (89%) patients.

The most common CT findings were consolidation and ground-glass opacities, seen in all patients. All the CT abnormalities were bilateral and extensive, involving three or more lung zones.

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7T MRI protocol shows brain plaques in MS patients

A new study published online February 20 in Archives of Neurology suggests that 7-tesla MRI with a specialized protocol is highly sensitive for detecting plaques in white and gray brain matter in patients with multiple sclerosis (MS).

German researchers used 7-tesla MRI with a T1-weighted magnetization-prepared rapid acquisition and multiple gradient echoes (MPRAGE) technique. They found that the protocol "clearly delineated every cortical lesion" that was visualized by any other MRI sequence at 1.5-tesla or 7-tesla. The lead author of the study was Tim Sinnecker, from the NeuroCure Clinical Research Center at Charité Medical University in Berlin.

T2-weighted MRI is often used to quantify accumulated MS lesions in the brain, while T1-weighted sequences are used to differentiate, among other things, irreversible brain tissue damage commonly called black holes, the authors wrote. Black holes are associated with the progression of MS and cerebral atrophy. On spin-echo T1-weighted images, a proportion of T2 hyperintense lesions (black holes) appears hypointense to the surrounding normal-appearing white matter for a long time, the group added.

The study included 20 patients with relapsing-remitting multiple sclerosis from the outpatient clinics of the NeuroCure Clinical Research Center. There were 11 male and nine female patients with a mean age of 42 years and mean disease duration of 3.1 years (range, 0.5 to 14.4 years).

For comparison purposes, 14 healthy control subjects also were enrolled. All 34 subjects underwent brain scans with a 7-tesla MRI scanner (Magnetom, Siemens Healthcare), using a 24-channel head coil. In addition, a subgroup of 18 patients with MS received brain scans with a 1.5-tesla scanner.

The imaging protocol included 2D T2-weighted fast low-angle shot (FLASH) and turbo inversion recovery magnitude (TIRM) sequences. For 3D T1-weighted imaging, the researchers used the MPRAGE sequence.

A reader blinded to the data independently evaluated each sequence. In a second study, all detected lesions were retrospectively analyzed in a side-by-side comparison of all sequences.

The analysis found that 7-tesla MPRAGE detected a total of 728 lesions, compared with 584 lesions with 7-tesla FLASH and 399 lesions with 1.5-tesla MPRAGE.

In addition, 7-tesla T2-weighted FLASH discovered 604 cerebral lesions in the patients with relapsing-remitting MS, with a mean of 30.2 lesions per patient. No lesions were discovered among the healthy controls.

Cortical pathology was visible in 10 patients, with the detection of six cortical lesions and 37 leukocortical lesions. Within the 7-tesla acquisitions, each lesion detected at T2-weighted sequences was also visible on corresponding MPRAGE sequences in the side-by-side analysis. At 1.5-tesla MRI, the MPRAGE images found only 452 of 561 lesions (80%) in T2-weighted sequences.

7-tesla MPRAGE was also beneficial regarding the 217 T1 hypointense lesions detected in the MS subgroup. The images showed that each lesion persisted without major change in formation or size for at least one year, and could be classified as a black hole.

T1-weighted MPRAGE at 7 tesla is "highly sensitive" in detecting multiple sclerosis plaques within white and gray brain matter, and the technique depicted structural damage in each lesion, Sinnecker and colleagues concluded.

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