Whiffed AKs - standard or spew?

[matrix]

Full Tilt Poker
No Limit Holdem Ring game
Blinds: $0.50/$1
5 players
Converter

Stack sizes:
UTG: $167.35
Matrix: $100.30
Button: $100
SB: $154.25
BB: $123.75

Pre-flop: (5 players) Matrix is CO with K[img]/images/graemlins/club.gif[/img] A[img]/images/graemlins/club.gif[/img]
UTG folds, <font color="#cc0000">Matrix raises to $4</font>, Button folds, SB calls, BB folds.

Flop: 9[img]/images/graemlins/club.gif[/img] 3[img]/images/graemlins/spade.gif[/img] J[img]/images/graemlins/heart.gif[/img] ($9, 2 players)
<font color="#cc0000">SB bets $4</font>, <font color="#cc0000">Matrix raises to $18</font>

Villain is a 30/15 donk and this is the first time this session I've raised the flop rather than calling planning to raise the turn.