Progression of emphysema in a 12-month hyperpolarized 3He-MRI study: lacunarity analysis provided a more sensitive measure than standard ADC analysis.
OBJECTIVE
Inhaled hyperpolarized (3)He magnetic resonance (MR) imaging has been used to measure alveolar size in patients with emphysema. The aim of this study was to test the hypothesis that (3)He MR images could be used to develop a biomarker of emphysema progression.


METHODS
Twelve healthy controls and 18 patients with emphysema (eight current smokers, 10 ex-smokers) were imaged at baseline and 6 and 12 months. An additional nine subjects with alpha-1 antitrypsin deficiency (four with emphysema, six without symptoms) were also imaged at baseline and at 6 months. Each subject was imaged at two lung volumes: functional residual capacity (FRC) and FRC plus 15% of total lung capacity. Means and standard deviations of apparent diffusion coefficients (ADCs) were calculated from coronal images of the entire lung and correlated with pulmonary function test results. The lacunarity hypothesis was tested and calculated from the data using a range of 2 x 2 x 2 to 6 x 6 x 6 voxels, and the average was calculated.


RESULTS
There was no change in the mean ADC at either lung volume in any subject over the 6- or 12-month period. FRC and residual volume increased over the 12 months, suggesting air trapping. The lacunarity of images collected at FRC increased at 6 and 12 months in smokers only (P = .063 and P = .023, respectively).


CONCLUSIONS
The mean ADC calculated from MR images of the lungs with helium was not sufficiently sensitive to detect changes over a 12-month period. However, lacunarity captured more of the spatial information in the images and detected emphysema progress in the smokers.
Department of Radiology, Malmö University Hospital, S Förstadsgatan 101, Ing 44, SE-205 02 Malmö, Sweden. sandra.diaz@med.lu.se
Sandra
S
Diaz
Ingrid
I
Casselbrant
Eeva
E
Piitulainen
Peter
P
Magnusson
Barry
B
Peterson
Evelyn
E
Pickering
Theresa
T
Tuthill
Olle
O
Ekberg
Per
P
Akeson
D000280:Administration, Inhalation; D000328:Adult; D000368:Aged; D003287:Contrast Media / Q000008:administration & dosage; D004646:Emphysema / Q000175:diagnosis*; D005260:Female; D006371:Helium / Q000008:administration & dosage*; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D007554:Isotopes / Q000008:administration & dosage; D008279:Magnetic Resonance Imaging / Q000379:methods*; D008297:Male; D008875:Middle Aged; D015203:Reproducibility of Results; D012680:Sensitivity and Specificity
D003287:Contrast Media; D007554:Isotopes; D006371:Helium