Heterogeneity of Particle Deposition by Pixel Analysis of 2D Gamma Scintigraphy Images.
BACKGROUND
Heterogeneity of inhaled particle deposition in airways disease may be a sensitive indicator of physiologic changes in the lungs. Using planar gamma scintigraphy, we developed new methods to locate and quantify regions of high (hot) and low (cold) particle deposition in the lungs.


METHODS
Initial deposition and 24 hour retention images were obtained from healthy (n=31) adult subjects and patients with mild cystic fibrosis lung disease (CF) (n=14) following inhalation of radiolabeled particles (Tc99m-sulfur colloid, 5.4 μm MMAD) under controlled breathing conditions. The initial deposition image of the right lung was normalized to (i.e., same median pixel value), and then divided by, a transmission (Tc99m) image in the same individual to obtain a pixel-by-pixel ratio image. Hot spots were defined where pixel values in the deposition image were greater than 2X those of the transmission, and cold spots as pixels where the deposition image was less than 0.5X of the transmission. The number ratio (NR) of the hot and cold pixels to total lung pixels, and the sum ratio (SR) of total counts in hot pixels to total lung counts were compared between healthy and CF subjects. Other traditional measures of regional particle deposition, nC/P and skew of the pixel count histogram distribution, were also compared.


RESULTS
The NR of cold spots was greater in mild CF, 0.221±0.047(CF) vs. 0.186±0.038 (healthy) (p<0.005) and was significantly correlated with FEV1 %pred in the patients (R=-0.70). nC/P (central to peripheral count ratio), skew of the count histogram, and hot NR or SR were not different between the healthy and mild CF patients.


CONCLUSIONS
These methods may provide more sensitive measures of airway function and localization of deposition that might be useful for assessing treatment efficacy in these patients.
1Center for Environmental Medicine, Asthma, and Lung Biology, University of North Carolina, Chapel Hill, North Carolina.|2Pulmonary Medicine, University of North Carolina, Chapel Hill, North Carolina.
William D
WD
Bennett
3Department of Statistics and Operations Research, University of North Carolina, Chapel Hill, North Carolina.
Miao
M
Xie
1Center for Environmental Medicine, Asthma, and Lung Biology, University of North Carolina, Chapel Hill, North Carolina.
Kirby
K
Zeman
3Department of Statistics and Operations Research, University of North Carolina, Chapel Hill, North Carolina.
Harry
H
Hurd
2Pulmonary Medicine, University of North Carolina, Chapel Hill, North Carolina.
Scott
S
Donaldson
D000280:Administration, Inhalation; D000328:Adult; D016022:Case-Control Studies; D003550:Cystic Fibrosis / Q000000981:diagnostic imaging* / Q000503:physiopathology; D005260:Female; D005541:Forced Expiratory Volume; D006801:Humans; D007090:Image Interpretation, Computer-Assisted / Q000379:methods*; D008168:Lung / Q000000981:diagnostic imaging* / Q000503:physiopathology; D008297:Male; D010316:Particle Size; D011237:Predictive Value of Tests; D011877:Radionuclide Imaging / Q000379:methods*; D019275:Radiopharmaceuticals / Q000008:administration & dosage*; D015656:Respiratory Mechanics; D012720:Severity of Illness Index; D013671:Technetium Tc 99m Sulfur Colloid / Q000008:administration & dosage*
D019275:Radiopharmaceuticals; D013671:Technetium Tc 99m Sulfur Colloid
gamma scintigraphy; inhaled particles; regional deposition