possible tuning for query

 My oracle version is 10.2.0.3 on solaris 10.

I have the following query:

select *  from triton.ttdpur045100 t
where t$spur = 3
and   t$suno ='852906'
and   t$srnb = 0
and   (
         (t$bqua <> 0
          and not exists (select b.*
                           from  triton.ttdpur045100 b
                           where b.t$orno = t.t$orno
                           and b.t$pono = t.t$pono
                           and b.t$srnb > 0
                           and b.t$dqua = 0
                           and b.t$bqua = 0)
         )
        or not exists (select a.t$srnb
                           from triton.ttdpur045100 a
                           where a.t$orno = t.t$orno
                           and a.t$pono = t.t$pono
                           and a.t$srnb > 0)
      );

The explain plan for the query shows the following: