\setheader{{\it CHAPTER \thechapter}}{}{}{\ctsimheadtitle}{}{{\it CHAPTER \thechapter}}%
\ctsimfooter%
-\section{Overview}\label{conceptoverview}\index{Concepts,Overview}%
+\section{Overview}\label{conceptoverview}\index{Conceptual Overview}%
The operation of \ctsim\ begins with the phantom object. A
phantom object consists of geometric elements. A scanner is
specified and the collection of x-ray data, or projections, is
object, but the two objects we need to be concerned with are the
\emph{phantom} and the \emph{scanner}.
-\section{Phantoms}\label{conceptphantom}\index{Concepts,Phantoms}%
-\subsection{Overview}\label{phantomoverview}\index{Concepts,Phantoms,Overview}%
+\section{Phantoms}\label{conceptphantom}
+\subsection{Overview}\label{phantomoverview}\index{Phantom Overview}%
\ctsim\ uses geometrical objects to describe the object being
scanned. A phantom is composed a one or more phantom elements.
The types of phantom elements and their definitions are taken with
permission from G.T. Herman's 1980 book\cite{HERMAN80}.
-\subsection{Phantom File}\label{phantomfile}\index{Concepts,Phantoms,File}
+\subsection{Phantom File}\label{phantomfile}\index{Phantom file syntax}
Each line in the text file describes an element of the
phantom. Each line contains seven entries, in the following form:
\begin{verbatim}
of the overlapped objects are summed.
-\subsection{Phantom Elements}\label{phantomelements}\index{Concepts,Phantoms,Elements}
+\subsection{Phantom Elements}\label{phantomelements}\index{Phantom elements}
\subsubsection{ellipse}
Ellipses use \texttt{dx} and \texttt{dy} to define the semi-major and
below the x-axis. The sector is then rotated and translated the same
as a segment.
-\subsection{Phantom Size}
+\subsection{Phantom Size}\index{Phantom size}
The overall dimensions of the phantom are increased by 1\% above the
specified sizes to avoid clipping due to round-off errors from
sampling the polygons of the phantom elements. So, if the phantom is
defined as a rectangle of size 0.1 by 0.1, the actual phantom has
extent 0.101 in each direction.
-\section{Scanner}\label{conceptscanner}\index{Concepts,Scanner}%
+\section{Scanner}\label{conceptscanner}\index{Scanner concepts}%
\subsection{Dimensions}
Understanding the scanning geometry is the most complicated aspect of
using \ctsim. For real-world CT simulators, this is actually quite
length}. These variables are all input into \ctsim\ in terms of
ratios rather than absolute values.
-\subsubsection{Phantom Diameter}
+\subsubsection{Phantom Diameter}\index{Phantom diameter}
\begin{figure}
$$\image{5cm;0cm}{scangeometry.eps}$$
\caption{\label{phantomgeomfig} Phantom Geometry}
relationships are diagrammed in figure~\ref{phantomgeomfig}.}
\latexignore{emph{Pd}.}
-\subsubsection{View Diameter}
+\subsubsection{View Diameter}\index{View diameter}
The \emph{view diameter} is the area that is being processed
during scanning of phantoms as well as during rasterization of
phantoms. By default, the \emph{view diameter} \rtfsp is set equal
be impossible and is analagous to inserting an object into the CT
scanner that is larger than the scanner itself!
-\subsubsection{Scan Diameter}
+\subsubsection{Scan Diameter}\index{Scan diameter}
By default, the entire \emph{view diameter} is scanned. For
experimental purposes, it may be desirable to scan an area either
larger or smaller than the \emph{view diameter}. Thus, the concept
If the \emph{scan ratio} is less than \texttt{1}, you can expect
significant artifacts.
-\subsubsection{Focal Length}
+\subsubsection{Focal Length}\index{Focal length}
The \emph{focal length},
\latexonly{$f$,}\latexignore{\emph{F},}
is the distance of the X-ray source to the center of
source inside of the \emph{view diameter}.
-\subsection{Parallel Geometry}\label{geometryparallel}\index{Concepts,Scanner,Geometries,Parallel}
+\subsection{Parallel Geometry}\label{geometryparallel}\index{Parallel Geometry}
As mentioned above, the focal length is not used in this simple
geometry. The detector array is set to be the same size as the
significant distortions will occur.
-\subsection{Divergent Geometries}\label{geometrydivergent}\index{Concepts,Scanner,Geometries,Divergent}
+\subsection{Divergent Geometries}\label{geometrydivergent}\index{Divergent geometry}
\subsubsection{Overview}
Next consider the case of equilinear (second generation) and equiangular
(third, fourth, and fifth generation) geometries. In these cases,
\subsubsection{Examples of Geometry Settings}
-\section{Reconstruction}\label{conceptreconstruction}\index{Concepts,Reconstruction}%
+\section{Reconstruction}\label{conceptreconstruction}\index{Reconstruction Overview}%
\subsection{Overview}
\subsection{Direct Inverse Fourier}
This method is not currently implemented in \ctsim, however it is
because interpolation occurs in the frequency domain rather than the
spatial domain.
-\subsection{Filtered Backprojection}
+\subsection{Filtered Backprojection}\index{Filtered backprojection}
The technique is comprised of two sequential steps:
filtering projections and then backprojecting the filtered projections. Though
these two steps are sequential, each view position can be processed individually.
projections over the reconstructing image. Various levels of
interpolation can be specified.
-\section{Image Comparison}
+\section{Image Comparison}\index{Image comparison}
Images can be compared statistically. Three measurements can be calculated
by \ctsim. They are taken from the standard measurements used by
Herman\cite{HERMAN80}.
projects / ctsim.git / blobdiff