\begin{table}%T1
%\centering
\small
\caption{Values of the rms error in the reconstruction of the ring:
in the case of OSEM and TKR we give the minimum values and, in brackets, the 
corresponding number of iterations; in the case of HDR we give the limiting 
values, which are reached after a number of iterations of the order of 2000. 
The values of the parameters $\eta$ and $\mu$ are those indicated in the text.}\label{t1}
\begin{tabular}{cccc} \hline\hline
              & Ideal        & AO 70\%     & AO 26\%       \\ \hline
OSEM          & 12.3 (1770)  & 20.4 (4150)  & 58.2 (10670)  \\ %\hline
TKR           &  12.3 (886)   & 20.8 (2110)  & 62.6 (5330)  \\ %\hline
HDR           & 6.5    & 9.3        & 28.4           \\ \hline
\end{tabular}
\end{table}