Biomedical Engineering Reference
In-Depth Information
1.6.1 Scatterer Radial Distribution
The radial scatterer distribution is an important factor for a good image simula-
tion. The scatterers under consideration in this simulation are: the transducer
sheath, blood, intima, media, and adventitia. We can obtain the arterial structure
configuration from an emulated form and from a real validated IVUS image. For
the study of the synthetic images, we have used two procedures:
1. Standard data . Typical geometric arterial parameters and their interfaces
such as lumen/intima, intima/media, and media/adventitia are obtained
from standard literature.
2. Validated data . Geometrical parameters are obtained from manually seg-
mented IVUS images.
In order to investigate the image dependencies of IVUS parameters (frequency,
attenuation coefficient, original beam number, secondary beam, and smoothing
procedures), we have used a standard data procedure, using a concentric scat-
terer distribution for this modality. To compare simulated images to real data,
we use manually segmented real images, which correspond to the validated data
procedure. In manually delineated structures of IVUS images, we extract the po-
sition radius R k of lumen, intima, media adventitia, and transducer sheath. Fig-
ure 1.25 shows typical 2D spatial scatterer distributions obtained from standard
procedure for the most important arterial structures and the scatterer artifact
caused by the transducer sheath.
The radial scatterer distributions play a crucial role in the definition of the
IVUS images because they define the ultrasound attenuation in the axial direc-
tion. Medical doctors have special interest in gray-level transition in the interface
of two media. For instance, the lumen/intima transition defines the frontiers of
the lumen. These transitions can only be found through a good radial scatterer
distribution.
The radial scatterers distribution of the typical arterial structures and the
transducer sheath are shown in Fig. 1.26.
1.6.2 DBC Distribution
The k -layers DBC k values for a typical simulated arterial structure are shown
in Figs. 1.27 and 1.28 where the count of scatterers of each tissue is shown as
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