PURPOSE: To compare a T1-weighted, three-dimensional (3D), gradient-echo (GRE) sequence for magnetic resonance (MR) imaging of the body (volumetric interpolated breath-hold examination, or VIBE) with a two-dimensional (2D) GRE breath-hold equivalent. MATERIALS AND METHODS: Twenty consecutive patients underwent 1.5-T MR imaging. The examinations included pre- and postcontrast (20 mL gadopentetate dimeglumine) fat-saturated 2D GRE breath-hold imaging and fat-saturated volumetric interpolated breath-hold imaging before, during (arterial phase), and after injection, with thin (2-mm source images) and thick (8-mm reconstruction images) sections. The three images were compared qualitatively and quantitatively (signal-to-noise ratio [SNR] and contrast-to-noise ratio [CNR]). RESULTS: Qualitatively, the 2-mm source images had poorer pancreatic edge definition on precontrast images compared with the other two data sets (P < .05). On gadolinium-enhanced images, scores for clarity of pancreatic edge, number of vessel...

Abdominal MR Imaging with a Volumetric Interpolated Breath-hold Examination

For liver surgical planning, the structure and morphology of the hepatic vessels and their relationship to tumors are of major interest. To achieve a fast and robust assistance with optimal quantitative and visual information, we present methods for a geometrical and structural analysis of vessel systems. Starting from the raw image data a sequence of image processing steps has to be carried out until a three-dimensional representation of the relevant anatomic and pathologic structures is generated. Based on computed tomography (CT) scans, the following steps are performed. 1) The volume data is preprocessed and the vessels are segmented. 2) The skeleton of the vessels is determined and transformed into a graph enabling a geometrical and structural shape analysis. Using this information the different intrahepatic vessel systems are identified automatically. 3) Based on the structural analysis of the branches of the portal vein, their vascular territories are approximated with different methods. These methods are compared and validated anatomically by means of corrosion casts of human livers. 4) Vessels are visualized with graphics primitives fitted to the skeleton to provide smooth visualizations without aliasing artifacts. The image analysis techniques have been evaluated in the clinical environment and have been used in more than 170 cases so far to plan interventions and transplantations.

Analysis of vasculature for liver surgical planning

Objective: To improve the planning of hepatic surgery, we have developed a fully automatic anatomical, pathological, and functional segmentation of the liver derived from a spiral CT scan.Materials and Methods: From a 2 mm-thick enhanced spiral CT scan, the first stage automatically delineates skin, bones, lungs, kidneys, and spleen by combining the use of thresholding, mathematical morphology, and distance maps. Next, a reference 3D model is immersed in the image and automatically deformed to the liver contours. Then an automatic Gaussian fitting on the imaging histogram estimates the intensities of parenchyma, vessels, and lesions. This first result is next improved through an original topological and geometrical analysis, providing an automatic delineation of lesions and veins. Finally, a topological and geometrical analysis based on medical knowledge provides hepatic functional information that is invisible in medical imaging: portal vein labeling and hepatic anatomical segmentation according to the C...

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Fully automatic anatomical, pathological, and functional segmentation from CT scans for hepatic surgery

A survey on skeletonization algorithms and their applications

We describe a pipeline of image processing steps for deriving symbolic models of vascular structures from radiological data which reflect the branching pattern and diameter of vessels. For the visualization of these symbolic models, concatenated truncated cones are smoothly blended at branching points. We put emphasis on the quality of the visualizations which is achieved by anti-aliasing operations in different stages of the visualization. The methods presented are referred to as HQVV (high quality vessel visualization). Scalable techniques are provided to explore vascular structures of different orders of magnitude. The hierarchy as well as the diameter of the branches of vascular systems are used to restrict visualizations to relevant subtrees and to emphasize parts of vascular systems. Our research is inspired by clear visualizations in textbooks and is targeted toward medical education and therapy planning. We describe the application of vessel visualization techniques for liver surgery planning. For this application it is crucial to recognize the morphology and branching pattern of vascular systems as well as the basic spatial relations between vessels and other anatomic structures.

Visualization and interaction techniques for the exploration of vascular structures

PURPOSE: To evaluate qualitatively and quantitatively the current procedures for radiologic delineation of the segmental and subsegmental anatomy of the liver. MATERIALS AND METHODS: Vascular casts of 10 livers were examined with helical computed tomography (CT). Liver segmental and subsegmental anatomy were determined on the CT scans according to customary radiologic practice guidelines. CT anatomic findings were compared with authentic anatomic territories seen at anatomic examination. The differences were assessed quantitatively in five of the 10 livers. RESULTS: For the marginal (cranial and caudal) portions of the liver, an average (+/- 1 standard deviation) of 17.3% +/- 6.5 of the hepatic area visualized on axial CT scans was attributed to an incorrect subsegment. For the central zones (those adjacent to the right and left branches of the portal vein), this error amounted to 51.6% +/- 19.9. Expressed in absolute numbers, the error amounted to 40 mm on axial CT scans. CONCLUSION: The radiologic deter...

Segmental anatomy of the liver: poor correlation with CT.

The aim of this study was to evaluate a software tool for non-invasive preoperative volumetric assessment of potential donors in living donated liver transplantation (LDLT). Biphasic helical CT was performed in 56 potential donors. Data sets were post-processed using a non-commercial software tool for segmentation, volumetric analysis and visualisation of liver segments. Semi-automatic definition of liver margins allowed the segmentation of parenchyma. Hepatic vessels were delineated using a region-growing algorithm with automatically determined thresholds. Volumes and shapes of liver segments were calculated automatically based on individual portal-venous branches. Results were visualised three-dimensionally and statistically compared with conventional volumetry and the intraoperative findings in 27 transplanted cases. Image processing was easy to perform within 23 min. Of the 56 potential donors, 27 were excluded from LDLT because of inappropriate liver parenchyma or vascular architecture. Two recipients were not transplanted due to poor clinical conditions. In the 27 transplanted cases, preoperatively visualised vessels were confirmed, and only one undetected accessory hepatic vein was revealed. Calculated graft volumes were 1110 +/- 180 ml for right lobes, 820 ml for the left lobe and 270 +/- 30 ml for segments II+III. The calculated volumes and intraoperatively measured graft volumes correlated significantly. No significant differences between the presented automatic volumetry and the conventional volumetry were observed. A novel image processing technique was evaluated which allows a semi-automatic volume calculation and 3D visualisation of the different liver segments.

3D CT modeling of hepatic vessel architecture and volume calculation in living donated liver transplantation.

We describe the generation and visualization of resection proposals for oncologic liver surgery which are based on vascular territories of the portal and hepatic vein. Resection proposals are interactively controlled by one parameter: the desired security margin around a tumor. Resection proposals consider vascular structures inside this margin, dependent vascular structures in the periphery as well as the territories supplied by them. The methods have been applied to artificial data from corrosion casts as well as to 5 datasets obtained in the clinical routine from 3 hospitals.

Dirk Selle

Papers

Analysis of vasculature for liver surgical planning

Visualization and interaction techniques for the exploration of vascular structures

Segmental anatomy of the liver: poor correlation with CT.

3D CT modeling of hepatic vessel architecture and volume calculation in living donated liver transplantation.

Resection proposals for oncologic liver surgery based on vascular territories