KEYWORDS: Data modeling, Magnetic resonance imaging, 3D modeling, Heart, Computed tomography, Sensors, Data acquisition, Transparency, Surgery, 4D CT imaging
Congenital heart defect (CHD) is the most common birth defect and a frequent cause of death for children.
Tetralogy of Fallot (ToF) is the most often occurring CHD which affects in particular the pulmonary valve and
trunk. Emerging interventional methods enable percutaneous pulmonary valve implantation, which constitute
an alternative to open heart surgery. While minimal invasive methods become common practice, imaging and
non-invasive assessment tools become crucial components in the clinical setting. Cardiac computed tomography
(CT) and cardiac magnetic resonance imaging (cMRI) are techniques with complementary properties and ability
to acquire multiple non-invasive and accurate scans required for advance evaluation and therapy planning. In
contrary to CT which covers the full 4D information over the cardiac cycle, cMRI often acquires partial information,
for example only one 3D scan of the whole heart in the end-diastolic phase and two 2D planes (long and
short axes) over the whole cardiac cycle. The data acquired in this way is called sparse cMRI. In this paper, we
propose a regression-based approach for the reconstruction of the full 4D pulmonary trunk model from sparse
MRI. The reconstruction approach is based on learning a distance function between the sparse MRI which needs
to be completed and the 4D CT data with the full information used as the training set. The distance is based
on the intrinsic Random Forest similarity which is learnt for the corresponding regression problem of predicting
coordinates of unseen mesh points. Extensive experiments performed on 80 cardiac CT and MR sequences
demonstrated the average speed of 10 seconds and accuracy of 0.1053mm mean absolute error for the proposed
approach. Using the case retrieval workflow and local nearest neighbour regression with the learnt distance function
appears to be competitive with respect to "black box" regression with immediate prediction of coordinates,
while providing transparency to the predictions made.
Disorders of the heart valves constitute a considerable health problem and often require surgical intervention.
Recently various approaches were published seeking to overcome the shortcomings of current clinical practice,that
still relies on manually performed measurements for performance assessment. Clinical decisions are still based on
generic information from clinical guidelines and publications and personal experience of clinicians. We present a
framework for retrieval and decision support using learning based discriminative distance functions and visualization
of patient similarity with relative neighborhood graphsbased on shape and derived features. We considered
two learning based techniques, namely learning from equivalence constraints and the intrinsic Random Forest
distance. The generic approach enables for learning arbitrary user-defined concepts of similarity depending on
the application. This is demonstrated with the proposed applications, including automated diagnosis and interventional
suitability classification, where classification rates of up to 88.9% and 85.9% could be observed on a
set of valve models from 288 and 102 patients respectively.
Disorders of the aortic valve represent a common cardiovascular disease and an important public-health problem
worldwide. Pathological valves are currently determined from 2D images through elaborate qualitative evalu-
ations and complex measurements, potentially inaccurate and tedious to acquire. This paper presents a novel
diagnostic method, which identies diseased valves based on 3D geometrical models constructed from volumetric
data. A parametric model, which includes relevant anatomic landmarks as well as the aortic root and lea
ets,
represents the morphology of the aortic valve. Recently developed robust segmentation methods are applied
to estimate the patient specic model parameters from end-diastolic cardiac CT volumes. A discriminative
distance function, learned from equivalence constraints in the product space of shape coordinates, determines
the corresponding pathology class based on the shape information encoded by the model. Experiments on a
heterogeneous set of 63 patients aected by various diseases demonstrated the performance of our method with
94% correctly classied valves.
State-of-the-art morphological imaging techniques usually provide high resolution 3D images with a huge number
of slices. In clinical practice, however, 2D slice-based examinations are still the method of choice even for these
large amounts of data. Providing intuitive interaction methods for specific 3D medical visualization applications
is therefore a critical feature for clinical imaging applications. For the domain of catheter navigation and surgery
planning, it is crucial to assist the physician with appropriate visualization techniques, such as 3D segmentation
maps, fly-through cameras or virtual interaction approaches. There has been an ongoing development and
improvement for controllers that help to interact with 3D environments in the domain of computer games.
These controllers are based on both motion and infrared sensors and are typically used to detect 3D position and
orientation. We have investigated how a state-of-the-art wireless motion sensor controller (Wiimote), developed
by Nintendo, can be used for catheter navigation and planning purposes. By default the Wiimote controller
only measure rough acceleration over a range of +/- 3g with 10% sensitivity and orientation. Therefore, a pose
estimation algorithm was developed for computing accurate position and orientation in 3D space regarding 4
Infrared LEDs. Current results show that for the translation it is possible to obtain a mean error of (0.38cm,
0.41cm, 4.94cm) and for the rotation (0.16, 0.28) respectively. Within this paper we introduce a clinical prototype
that allows steering of a virtual fly-through camera attached to the catheter tip by the Wii controller on basis
of a segmented vessel tree.
KEYWORDS: 3D displays, Cameras, 3D image processing, 3D scanning, Coded apertures, Visualization, 3D visualizations, Infrared radiation, 3D imaging standards, Imaging systems
Although the medical scanners are rapidly moving towards a three-dimensional paradigm, the manipulation and
annotation/labeling of the acquired data is still performed in a standard 2D environment. Editing and annotation
of three-dimensional medical structures is currently a complex task and rather time-consuming, as it is carried
out in 2D projections of the original object. A major problem in 2D annotation is the depth ambiguity, which
requires 3D landmarks to be identified and localized in at least two of the cutting planes. Operating directly
in a three-dimensional space enables the implicit consideration of the full 3D local context, which significantly
increases accuracy and speed. A three-dimensional environment is as well more natural optimizing the user's
comfort and acceptance. The 3D annotation environment requires the three-dimensional manipulation device
and display. By means of two novel and advanced technologies, Wii Nintendo Controller and Philips 3D WoWvx
display, we define an appropriate 3D annotation tool and a suitable 3D visualization monitor. We define non-coplanar
setting of four Infrared LEDs with a known and exact position, which are tracked by the Wii and
from which we compute the pose of the device by applying a standard pose estimation algorithm. The novel
3D renderer developed by Philips uses either the Z-value of a 3D volume, or it computes the depth information
out of a 2D image, to provide a real 3D experience without having some special glasses. Within this paper we
present a new framework for manipulation and annotation of medical landmarks directly in three-dimensional
volume.
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