ratios rather than absolute values.
\subsubsection{Phantom Diameter}\index{Phantom!Diameter}
-\begin{figure}
-$$\image{5cm;0cm}{scangeometry.eps}$$
-\caption{\label{phantomgeomfig} Phantom Geometry}
-\end{figure}
The phantom diameter is automatically calculated by \ctsim\ from
the phantom definition. The maximum of the phantom length and
height is used to define the square that completely surrounds the
\latexonly{\begin{equation}p_d = p_l \sqrt{2}\end{equation}}
CT scanners collect projections around a
circle rather than a square. The diameter of this circle is
-the diameter of the boundary square \latexonly{$p_d$. These
-relationships are diagrammed in figure~\ref{phantomgeomfig}.}
-\latexignore{emph{Pd}.}
+the diameter of the boundary square \latexonly{$p_d$.}
+\latexignore{\emph{Pd}.}
+\latexonly{These relationships are diagrammed in figure~\ref{phantomgeomfig}.}
+\begin{figure}
+\centerline{\image{5cm;0cm}{scangeometry.eps}}
+\latexonly{\caption{\label{phantomgeomfig} Phantom Geometry}}
+\end{figure}
\subsubsection{View Diameter}\index{View diameter}
The \emph{view diameter} is the area that is being processed
the detectors occupy an arc of a circle, then the geometry is equiangular.
\latexonly{These configurations are shown in figure~\ref{divergentfig}.}
\begin{figure}
-\image{10cm;0cm}{divergent.eps}
-\caption{\label{divergentfig} Equilinear and equiangular geometries.}
+\centerline{\image{10cm;0cm}{divergent.eps}}
+\latexonly{\caption{\label{divergentfig} Equilinear and equiangular geometries.}}
\end{figure}
\latexignore{\centerline{\emph{alpha = 2 x asin (
(Sd / 2) / f)}}}
\latexonly{\begin{equation}\label{alphacalc}\alpha = 2 \sin^{-1}
-((s_d / 2) / f)\end{equation}
- This is illustrated in figure~\ref{alphacalcfig}.}
+((s_d / 2) / f)\end{equation}}
+\latexonly{This is illustrated in figure~\ref{alphacalcfig}.}
\begin{figure}
-\image{10cm;0cm}{alphacalc.eps}
-\caption{\label{alphacalcfig} Calculation of $\alpha$}
+\centerline{\image{10cm;0cm}{alphacalc.eps}}
+\latexonly{\caption{\label{alphacalcfig} Calculation of $\alpha$}}
\end{figure}
For equiangular geometry, the detectors are spaced around a circle
covering an angular distance of
-\latexonly{$2\,\alpha$.}\latexignore{\emph{2 \alpha}.} The dotted
-circle in
+\latexonly{$2\,\alpha$.}\latexignore{\emph{2 \alpha}.}
+The dotted circle
+\latexonly{in figure~\ref{equiangularfig}}
+indicates the positions of the detectors in this case.
+
\begin{figure}
-\image{10cm;0cm}{equiangular.eps}
-\caption{\label{equiangularfig}Equiangular geometry}
+\centerline{\image{10cm;0cm}{equiangular.eps}}
+\latexonly{\caption{\label{equiangularfig}Equiangular geometry}}
\end{figure}
-figure~\ref{equiangularfig} indicates the positions of the detectors in this case.
For equilinear geometry, the detectors are space along a straight
line. The length of the line depends upon
length}. It is calculated as
\latexonly{\begin{equation}4\,f \tan (\alpha / 2)\end{equation}}
\latexignore{\\\centerline{\emph{4 x F x tan(\alpha/2)}}}
+\latexonly{This geometry is shown in figure~\ref{equilinearfig}.}
\begin{figure}\label{equilinearfig}
-\image{10cm;0cm}{equilinear.eps}
-\caption{\label{equilinearfig} Equilinear geometry}
+\centerline{\image{10cm;0cm}{equilinear.eps}}
+\latexonly{\caption{\label{equilinearfig} Equilinear geometry}}
\end{figure}
-\latexonly{This geometry is shown in figure~\ref{equilinearfig}.}
\section{Reconstruction}\label{conceptreconstruction}\index{Reconstruction Overview}%