Quantitative analysis of emphysema in 3D using MDCT: influence of different reconstruction algorithms.
OBJECTIVE
The aim of the study was to compare the influence of different reconstruction algorithms on quantitative emphysema analysis in patients with severe emphysema.


METHODS
Twenty-five patients suffering from severe emphysema were included in the study. All patients underwent inspiratory MDCT (Aquilion-16, slice thickness 1/0.8mm). The raw data were reconstructed using six different algorithms: bone kernel with beam hardening correction (BHC), soft tissue kernel with BHC; standard soft tissue kernel, smooth soft tissue kernel (internal reference standard), standard lung kernel, and high-convolution kernel. The only difference between image data sets was the algorithm employed to reconstruct the raw data, no additional radiation was required. CT data were analysed using self-written emphysema detection and quantification software providing lung volume, emphysema volume (EV), emphysema index (EI) and mean lung density (MLD).


RESULTS
The use of kernels with BHC led to a significant decrease in MLD (5%) and EI (61-79%) in comparison with kernels without BHC. The absolute difference (from smooth soft tissue kernel) in MLD ranged from -0.6 to -6.1 HU and were significant different for all kernels. The EV showed absolute differences between -0.05 and -0.4 L and was significantly different for all kernels. The EI showed absolute differences between -0.8 and -5.1 and was significantly different for all kernels.


CONCLUSIONS
The use of kernels with BHC led to a significant decrease in MLD and EI. The absolute differences between different kernels without BHC were small but they were larger than the known interscan variation in patients. Thus, for follow-up examinations the same reconstruction algorithm has to be used and use of BHC has to be avoided.
Ley-Zaporozhan
Julia
J
Department of Radiology, Johannes Gutenberg University Hospital, Langenbeckstr. 1, 55131 Mainz, Germany. juliazapo@web.de
Ley
Sebastian
S
Weinheimer
Oliver
O
Iliyushenko
Svitlana
S
Erdugan
Serap
S
Eberhardt
Ralf
R
Fuxa
Adelheid
A
Mews
Jürgen
J
Kauczor
Hans-Ulrich
HU
D000328:Adult; D000368:Aged; D000465:Algorithms; D005260:Female; D006801:Humans; D021621:Imaging, Three-Dimensional; D008297:Male; D008875:Middle Aged; D019047:Phantoms, Imaging; D011656:Pulmonary Emphysema / Q000000981:diagnostic imaging*; D011857:Radiographic Image Interpretation, Computer-Assisted; D012129:Respiratory Function Tests; D012984:Software; D018709:Statistics, Nonparametric; D014057:Tomography, X-Ray Computed / Q000379:methods*