PET Imaging in Patients at Risk for Acute Lung Injury

Despite decades of research, the mortality in acute lung injury remains very high and
treatment options are very limited. Given these facts, the best treatment modality may be in
prevention of this lethal syndrome.

Historically, imaging has played a crucial role in understanding ALI. The appearance of
chest radiography is one of the consensus criteria in defining ALI, and commuted tomography
(CT) scans further advanced the understanding of the pathoanatomy of ALI. While valuable,
these imaging modalities are nonspecific and do not incorporate functional cellular
physiology.

PET imaging measures concentrations of radioisotopes in the body. By embedding in, but not
altering molecules, the natural fate of these tracers can be studied with PET imaging.
Advances in the understanding of ALI include blood flow distribution, as well as the
response to alveolar recruitment maneuvers and prone positioning. Not all patients who are
receiving mechanical ventilation develop ALI. Inflammation in the lungs is known to play a
key early role in the development and progression of ALI. Secondary to inflammation, the
lungs develop edema and do not exchange oxygen as well. This early inflammation is in part
driven by a specific type of immune cell called the neutrophil. These cells seem to travel
and become sequestered in the lung- they are "recruited" to the lung during this
inflammatory stage. When there, these neutrophils release inflammatory substances which are
integral in the development of ALI. Neutrophils use primarily glucose as a fuel source. The
radio isotope [18F]Fluorodeoxyglucose (FDG)is a glucose analog and therefore taken
up/ingested by the neutrophils as a part of their normal metabolism. Because of this fact,
positron emission tomography (PET) using the radio isotope [18F]FDG is a highly sensitive
marker to look at the recruitment of neutrophils to the lung, therefore quantifying the
degree of pulmonary inflammation prior to the development of ALI.

The investigators seek to examine the relationship of pulmonary inflammation in patients at
risk for ALI, but without clinical evidence of the syndrome. The investigators seek to
enroll ten patients in a pilot trial.