Fox won all four of its half-hours in key demos Tuesday behind “American Idol” and “24,” according to preliminary nationals from Nielsen.

In Tuesday’s opening hour, “American Idol” averaged a projected 9.4 rating/28 share in adults 18-49 and 22.8 million viewers overall, while lead-out drama “24” notched roughly a 5.1/13 in adults 18-49 and 12 million viewers overall, one of its best scores of the season.

Over at CBS, 9 o’clock spec “The Dick Van Dyke Show Revisited” (3.3/9 in adults 18-49, 14.4 million viewers overall) gave the net its best 18-49 score in the hour since December and its largest overall aud there since November 2002. Show led its hour in total viewers and helped lead-out drama “Judging Amy” to some of its best ratings in a while (3.4/9 in adults 18-49, 12.2 million viewers overall).

NBC was paced by a slot-leading “Law & Order: SVU” at 10 (5.1/13 in adults 18-49, 12.5 million viewers overall), ABC by the season finale of “NYPD Blue” in the same hour (3.5/9 in adults 18-49, 9.1 million viewers overall).

Preliminary 18-49 averages for the night: Fox, 7.3/20; NBC, 3.5/9; ABC, 3.0/8, tied with CBS, 3.0/8; WB, 2.0/5; UPN, 1.5/4.

In total viewers: Fox, 17.5 million; CBS, 12.5 million; NBC, 9.4 million; ABC, 7.5 million; WB, 4.5 million; UPN, 3.4 million.