Quantitative analysis of technegas SPECT: evaluation of regional severity of emphysema.
The purpose of this study was to quantify the regional severity of emphysema by 3-dimensional fractal analysis of technegas (99mTc-carbon particle radioaerosol) SPECT images.


METHODS
Technegas SPECT was performed on 22 patients with emphysema. The lungs were delineated using 4 cutoff levels (15%, 20%, 25%, and 30% of the maximal pixel radioactivity), and the total number of pixels was measured in the areas surrounded by the contours obtained with each cutoff level. We calculated fractal dimensions from the relationship between the total number of pixels and cutoff levels transformed into logarithms. Fractal dimension for total or regional lung was defined as the severity of emphysema.


RESULTS
Total lung fractal dimension (T-FD), upper lung fractal dimension (U-FD), and lower lung fractal dimension (L-FD) for patients with emphysema were 1.84 +/- 0.46 (mean +/-SD), 2.22 +/- 0.61, and 1.77 +/- 0.49, respectively. U-FD was significantly greater than was L-FD. Patients with the ratio of U-FD to L-FD of <1.16 had a significantly greater percentage forced vital capacity (FVC) than did patients with the ratio of >1.16. Patients with an L-FD of <1.8 had a significantly greater forced expiratory volume in 1 s (FEV1)/FVC than did patients with that of >1.8. No significant difference was found between patient groups stratified by U-FD.


CONCLUSIONS
The regional severity of emphysema was well shown by these fractal dimensions.
Nagao
M
M
Department of Radiology, Ehime University School of Medicine, Onsen-gun, Japan.
Murase
K
K
Ichiki
T
T
Sakai
S
S
Yasuhara
Y
Y
Ikezoe
J
J
D005260:Female; D017709:Fractals; D006108:Graphite; D006801:Humans; D007091:Image Processing, Computer-Assisted; D008168:Lung / Q000000981:diagnostic imaging*; D008297:Male; D008875:Middle Aged; D011656:Pulmonary Emphysema / Q000000981:diagnostic imaging*; D012720:Severity of Illness Index; D013670:Sodium Pertechnetate Tc 99m; D015899:Tomography, Emission-Computed, Single-Photon
C056708:Technegas; D006108:Graphite; D013670:Sodium Pertechnetate Tc 99m