Owing to the
rapid development of scanner technology, thoracic computed tomography (CT)
offers new possibilities but also faces enormous challenges with respect to the
quality of computer-assisted diagnosis and therapy planning. In the framework
of the Virtual Institute for Computer
Assistance in Clinical Radiology (VICORA) cooperative research project, a
prototypical software application was developed at MeVis Research to assist the radiologist in
functional analysis of thoracic CT data. By identifying the anatomic
compartments of the lungs, the software enables assessment of established
functional CT parameters for each individual lung, pulmonary lobe, and pulmonary
segment. Such region-based assessment allows a more localized diagnosis of lung
diseases such as emphysema and more accurate estimation of regional lung
function from CT data.
Motivation
Recent multidetector CT devices allow improved and
more detailed imaging of lung tissue. Examinations of the lung parenchyma are
frequently performed with a section thickness of 1 mm and approximately
isotropic voxels, resulting in a large number of images. Imaging of patients
with lung emphysema typically produces data sets with 300 or more sections.
Visual examination or comparison with previous examinations is a tedious and
time-consuming task. To perform the necessary analyses in the clinical routine,
computer assistance is desirable.
Today, diseases of the lung parenchyma are
diagnosed mostly descriptively. In order to perform follow-up examinations or
clinical trials up to current standards, a reproducible, objective, and
quantitative evaluation of lung parenchyma diseases is required.
In addition to a global assessment of a parenchymal disease, its spatial
distribution can be of clinical importance. For instance, lung volume reduction
surgery (LVRS) has been shown to be significantly more effective in cases of
heterogeneously distributed emphysema than in patients with a homogeneous
distribution. The degree of deterioration can vary significantly between the
left and right lung or between different lobes and segments. A
compartment-specific assessment of emphysema is especially desirable in
conjunction with recent approaches concerning bronchoscopic LVRS, where air
flow to emphysematous segments is blocked by using one-way bronchial valves.
A method for reproducible 3D identification of lungs,
lobes, and segments provides the means to assess regional quantitative
parameters for treatment planning and monitoring. Although experienced
radiologists might be able to identify lobar boundaries on CT scans, manual
delineation on over 300 CT images is unthinkable in the clinical routine. In
addition to pure assistance in quantification, computers have to provide
support for the radiologist in identifying the lung regions quickly and
conveniently. The methods have to work robustly even in cases of severe
disease. By using the region information, functional parameters such as volume,
mean lung density, pixel index, bulla index, and emphysema type can be
extracted for each compartment. This increases the significance of a CT-based
prediction of postoperative lung function in cases of resection of a lung or a
lobe, which is standard therapy for patients with primary non–small cell lung
cancer. Currently, perfusion scintigraphy is performed in order to obtain a
functional prognosis. Since scintigraphy does not allow 3D image analysis, it
is difficult to acquire accurate estimates for lobar function, not to mention
segmental function. Furthermore, the examination is conducted in addition to CT
and lung function tests. By correlating quantitative analysis results with
patient-individual 3D lung segment morphology obtained directly from CT data
acquired previously for diagnostic reasons, additional scintigraphic
examinations might become dispensable sometime.
MeVisPULMO3D
The application prototype MeVisPULMO3D [1]
allows CT-based functional diagnosis with respect to the anatomic compartments
of the lung. It includes methods for the automated segmentation of airways,
lungs, and lung lobes [4-6]. By providing the means for convenient interactive
refinements of the lobar regions, robustness in patients with severe pathologic
alterations is achieved. The analyses allow a convenient, regional
assessment of CT parameters of the lung, such as total volume, mean density, or
pixel (emphysema) index.
On top of providing quantitative diagnostical information
on parenchymal diseases separately for the major anatomical regions [2], a potential
clinical application is the estimation of post-operative lung function in case
of an oncological lung or lobe resection in the context of pre-operative risk
analysis [3].
MeVisPULMO was implemented using the rapid prototyping
platform MeVisLab and runs standalone on
Linux or Microsoft Windows workstations with at least 1 (but preferably 2) GB
of random-access memory (RAM).
MeVisPULMO3D
Screenshots (click to enlarge):
Related Publications
[1] Kuhnigk JM, Dicken V., Zidowitz S, Bornemann L, Kuemmerlen B, Krass S,
Peitgen HO, Yuval S, Jend H, Rau WS, Achenbach T
"New Tools for Computer Assistance in
Thoracic CT - Part I: Functional analysis of lungs, lung lobes, and
bronchopulmonary segments"
RadioGraphics 25(2): 525-536, 2005 March
[2] Cohen J, Douma WR, van Ooijen PMA, Willems TP, Dicken
V, Kuhnigk JM, ten Hacken NHT, Postma DS, Oudkerk M
"Localization
and Quantification of Regional and Segmental Air Trapping in Asthma"
J Comput Assist Tomogr 32(4):
562-569, 2008 Jul/Aug
[3] Wormanns D, Beyer F, Hoffknecht P, Dicken V., Kuhnigk JM, Lange T,
Thomas M, Heindel WL
"Clinical value of CT-based
preoperative software assisted lung lobe volumetry for predicting postoperative
pulmonary function after lung surgery"
Proceedings of SPIE Vol. 5746, Medical Imaging 2005: Physics
of Medical Imaging: 78-83, SPIE,
[4] Zidowitz S, Schmidt A, Kriete A, Krass S, Peitgen HO
"Steps towards a patient individual
geometric model of the bronchial tree used for functional simulations"
Proceedings of SPIE Vol. 5369 Medical
Imaging 2004: Physiology Function and Structure from Medical Images:
125-131, SPIE, Bellingham, 2004 Feb
[5] Kuhnigk JM, Hahn HK, Hindennach M, Dicken V, Krass S, Peitgen HO
"Lung Lobe Segmentation by
Anatomy-Guided 3D Watershed Transform"
Proceedings of SPIE Vol. 5032 Medical
Imaging 2003: Image Processing: 1482-1490, SPIE, Bellingham, 2003 Feb
[6] Kuhnigk JM, Hahn HK,
Hindennach M, Dicken V, Krass S, Peitgen HO
"Lungenlappen-Segmentierung
durch Kombination von Region Growing, Distanz- und
Wasserscheiden-Transformation"
Proc. BVM: 146-150, Springer, Berlin,
2003 Mar