[Sensitivity of MRI in detecting alveolar Infiltrates: Experimental studies].
OBJECTIVE
An experimental study using porcine lung explants and a dedicated chest phantom to evaluate the signal intensity of artificial alveolar infiltrates with T 1 - and T 2 -weighted MRI sequences.


METHODS
10 porcine lung explants were intubated, transferred into the cavity of a MRI-compatible chest phantom and inflated by continuous evacuation of the artificial pleural space. All lungs were examined with MRI at 1.5 T before and after intra-tracheal instillation of either 100 or 200 ml gelatine-stabilised liquid to simulate alveolar infiltrates. MR-examination comprised gradient echo (2D- and 3D-GRE) and fast spin echo sequences (T 2 -TSE and T 2 -HASTE). The signal intensity of lung parenchyma was evaluated at representative cross sections using a standardised scheme. Control studies were acquired with helical CT.


RESULTS
The instilled liquid caused patchy confluent alveolar infiltrates resembling the findings in patients with pneumonia or ARDS. CT revealed typical ground-glass opacities. Before the application of the liquid, only T 2 -HASTE and T 2 -TSE displayed lung parenchyma signals with a signal/noise ratio of 3.62 and 1.39, respectively. After application of the liquid, both T 2 -weighted sequences showed clearly visible infiltrates with an increase in signal intensity of approx. 30 % at 100 ml (p < 0.01) and 60 % at 200 ml (p < 0.01). With 2D- and 3D-GRE the infiltrates were not visible, although the lung parenchyma signal increase was statistically significant. On 2D-GRE the increase in signal intensity reached 0.74 % (p = 0.32) after 100 ml and 5.6 % (p < 0.01) after 200 ml (for 3D-GRE: 2.2 % [p = 0.02] at 100 ml and 4.4 % at 200 ml [p < 0.01]). The CT controls revealed a significant increase of lung density of 17 H.E. at 100 ml (p = 0.02) and 75 H.E. at 200 ml (p < 0.01).


CONCLUSIONS
MRI with T 2 -weighted sequences detects artificial alveolar infiltrates with high signal intensity and may be a highly sensitive tool to detect pneumonia in patients.
Biederer
J
J
Klinik für Diagnostische Radiologie, Universitätsklinikum Kiel, Germany. juergen.biederer@rad.uni-kiel.de
Busse
I
I
Grimm
J
J
Reuter
M
M
Muhle
C
C
Freitag
S
S
Heller
M
M
D000818:Animals; D017352:Echo-Planar Imaging / Q000295:instrumentation; D006801:Humans; D007089:Image Enhancement; D007091:Image Processing, Computer-Assisted; D021621:Imaging, Three-Dimensional; D008175:Lung Neoplasms / Q000175:diagnosis*; D008279:Magnetic Resonance Imaging / Q000295:instrumentation; D019047:Phantoms, Imaging; D011014:Pneumonia / Q000175:diagnosis*; D011650:Pulmonary Alveoli / Q000473:pathology*; D012128:Respiratory Distress Syndrome / Q000175:diagnosis*; D013552:Swine; D014057:Tomography, X-Ray Computed