-If this quantity is less than or equal to zero, then at least for some
-projections the source is inside the phantom. Perhaps a figure will help at
-this point. Consider first the case where $f_{vR} = f_{lR} =1 $, figure 3. The
-square in the figure bounds the phantom and has sides $l_p$. For this case
-then,
-\latexonly{$$f_l=\sqrt{2}l_p/2 = l_p/\sqrt{2}$$,
-$$f_v = \sqrt{2}l_p$$,
-and
-$$d_{hs} = {l_p}/{2}$$.
-Then
-$$\mathrm{dFocalPastPhm} = ({l_p}/{2}) (\sqrt{2}-1)$$
-}
-\begin{figure}
-\image{5cm;0cm}{ctsimfig3.eps}
-\caption{Equilinear and equiangluar geometry when focal length ratio =
-field of view ratio = 1.}
-\end{figure}
-The angle $\alpha$ is now defined as shown in figure 3, and the detector
-length is adjusted to subtend the angle $2\alpha$ as shown. Note that the
-size of the detector array may have changed and the field of view is not
-used.
-For a circular array of detectors, the detectors are spaced around a
-circle covering an angular distance of $2\alpha$. The dotted circle in
-figure 3 indicates the positions of the detectors in this case. Note that
-detectors at the ends of the range would not be illuminated by the source.
-
-Now, consider increasing the focal length ratio to two leaving the
+Empiric testing with \ctsim\ shows that for very large \emph{fan beam angles},
+greater than approximately
+\latexonly{$120^{\circ}$,}\latexignore{120 degrees,}
+there are significant artifacts. The primary way to manage the
+\emph{fan beam angle} is by varying the \emph{focal length} since the
+\emph{scan diameter} by the size of the phantom.
+
+\subsubsection{Detector Array Size}
+In general, you do not need to be concerned with the detector array
+size. It is automatically calculated by \ctsim. The size of the
+detector array depends upon the \emph{focal length} and the
+\emph{scan diameter}. In general, increasing the \emph{focal length}
+decreases the size of the detector array and increasing the \emph{scan
+diameter} increases the detector array size.
+
+For equiangular geometry, the detectors are spaced around a
+circle covering an angular distance of
+\latexonly{$\alpha$.}\latexignore{\emph{alpha}.}
+The dotted circle in
+figure 2.4 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
+\latexonly{$\alpha$}\latexignore{\emph{alpha}}
+and the \emph{focal length}. It is calculated as
+\latexonly{$$\mathrm{detLengh} = 4\,F_l \tan (\alpha / 2)$$}
+\latexignore{\\$$\emph{detLength} = 4 x Fl x tan(alpha/2)$$\\}
+An example of the this geometry is in figure 2.5.
+
+\subsubsection{Examples of Geometry Settings}
+Consider increasing the focal length ratio to two leaving the