\chapter{Concepts}\index{Concepts}%
\setheader{{\it CHAPTER \thechapter}}{}{}{}{}{{\it CHAPTER \thechapter}}%
-\setfooter{\thepage}{}{}{}{\small Version 0.2}{\thepage}%
+\ctsimfooter%
\section{Overview}\label{conceptoverview}\index{Concepts,Overview}%
The operation of \ctsim\ begins with the phantom object. A
element-type cx cy dx dy r a
\end{verbatim}
The first entry defines the type of the element, either
-\rtfsp\texttt{rectangle}, \texttt{}, \texttt{triangle},
+\rtfsp\texttt{rectangle}, \texttt{ellipse}, \texttt{triangle},
\rtfsp\texttt{sector}, or \texttt{segment}. \texttt{cx},
\rtfsp\texttt{cy}, \texttt{dx} and \texttt{dy} have different
meanings depending on the element type.
\emph{phantom diameter}. Remember, as mentioned above, the
phantom dimensions are also padded by 1\%.
-The other important geometry variables for scanning objects are the
-\emph{view ratio}, \emph{scan ratio}, and \emph{focal length ratio}.
-These variables are all input into \ctsim\ in terms of ratios rather
-than absolute values.
+The other important geometry variables for scanning phantoms are
+the \emph{view diameter}, \emph{scan diameter}, and \emph{focal
+length}. These variables are all input into \ctsim\ in terms of
+ratios rather than absolute values.
\subsubsection{Phantom Diameter}
\begin{figure}
experimental purposes, it may be desirable to scan an area either
larger or smaller than the \emph{view diameter}. Thus, the concept
of \emph{scan ratio}, \latexonly{$s_r$,}\latexignore{\emph{SR},}
-is born. The scan diameter
+is arises. The scan diameter
\latexonly{$s_d$}\latexignore{\emph{Sd}} is the diameter over
which x-rays are collected and is defined as \latexonly{$$s_d =
v_d s_r$$}\latexignore{\\$$\emph{Sd = Vd x SR}$$\\} By default and
For parallel geometry scanning, the focal length doesn't matter.
However, divergent geometry scanning (equilinear and equiangular),
the \emph{focal length ratio} should be set at \texttt{2} or more
-to avoid artifacts. Moreover, a value of less than \texttt{1},
-though it can be given to \ctsim, is physically impossible and it
-analagous to have having the x-ray source with the \emph{view
-diameter}.
+to avoid artifacts. Moreover, a value of less than \texttt{1} is
+physically impossible and it analagous to have having the x-ray
+source inside of the \emph{view diameter}.
\subsection{Parallel Geometry}\label{geometryparallel}\index{Concepts,Scanner,Geometries,Parallel}
\subsubsection{Detector Array Size}
In general, you do not need to be concerned with the detector
-array size. It is automatically calculated by \ctsim. For those
-interested, this section explains how the detector array size is
-calculated.
+array size. It is automatically calculated by \ctsim. For the
+particularly interested, this section explains how the detector
+array size is calculated.
For parallel geometry, the detector length is equal to the scan
diameter.
covering an angular distance of
\latexonly{$2\,\alpha$.}\latexignore{\emph{2 \alpha}.} The dotted
circle in
-\begin{figure}
-\image{10cm;0cm}{equiangular.eps}
-\caption{Equiangluar geometry}
+\begin{figure}\label{equiangularfig}
+\image{10cm;0cm}{equiangular.eps} \caption{Equiangular geometry}
\end{figure}
figure 2.4 indicates the positions of the detectors in this case.
\latexonly{$\alpha$}\latexignore{\emph{alpha}} and the \emph{focal
length}. It is calculated as \latexonly{$4\,f \tan (\alpha / 2)$}
\latexignore{\emph{4 x F x tan(\alpha/2)}}
-\begin{figure}
+\begin{figure}\label{equilinearfig}
\image{10cm;0cm}{equilinear.eps}
\caption{Equilinear geometry}
\end{figure}
-An example of the this geometry is in figure 2.5.
+This geometry is shown in figure~2.5.
\subsubsection{Examples of Geometry Settings}
projects / ctsim.git / blobdiff