Full Text Indexing and Syntax

Hi folks, I am having some trouble with this query that should be using
FTI. There are 2 tables, one with a list of keywords and the other
containing a body of articles.

I am trying to get a query to return the IDs of each keyword with the
ID of each article that contains that keyword.

So the 2 tables are:

test1:
->id
->keyword

test2:
->id
->article

Unfortunately I can not seem to get my query to use PG's full text
indexing, it keeps doing a seq scan:

EXPLAIN
SELECT t1.id, t2.id
FROM test1 t1, test2 t2
WHERE lower( t1.keyword ) ~ ( lower ( '^' || t2.article ));
---------------------------------------------------------------------------------
Nested Loop (cost=20.00..30040.00 rows=5001 width=8)
Join Filter: (lower("outer".keyword) ~ lower(('^'::text ||
"inner".article)))
-> Seq Scan on test1 t1 (cost=0.00..20.00 rows=1000 width=36)
-> Materialize (cost=20.00..30.00 rows=1000 width=36)
-> Seq Scan on test2 t2 (cost=0.00..20.00 rows=1000
width=36)

Could someone explain how I can restructure this SQL to use the index,
or perhaps suggest a workaround?

I am using PG 7.4.7 on Debian 3.1.