Let us assume 18.Qb3. True, White also have the option of 18.Qa5 but I am saving it for later.
Normal moves here would be 18. ... Nd7, rerouting the Knight to c5 or 18. ... Rfd8, guarding d6 and eventually preparing d5. Maybe.
I propose a different angle. Constantly baby sitting d6 is trying, to say the least. Let's look at 18. ... d5!?
If we look at the position after 20. ... f5 (I'm not to sure about the moves after that ... It is just guesses as to how it might develop.), we see that Black has gained a pawn centre e5/f5. Queen and bishop is aiming at the white king's position. Rf8 can join in (Rf8/f6/h6). There is still pressure on c2. Nb6 is maybe a bit off but can be rerouted via d7. The black king might be a bit exposed, so eventually it will go to h8. What are White's plan/s? Be3/a5 to fix the queen side? To get the pawn majority rolling on the queen side? Well, White has a pawn but I believe Black has good play and compensation. Most important of all - the trend of the game has been changed.
The move 19.a5 have been proposed. I have added some moves and comments on that. The a5-line in my opinion leads to an equal game/endgame.
Well, those were the thoughts mostly two days ago. Having looked more into the d5 sac and comparing it with the Nd7 lines, I do belive the knight move is slightly better and not so boring as I thought of first. The main reason being the bad night but rerouting it b6-d7-c5-e6 it does not look so bad anymore.
The position I find slightly equal. The black pieces have found some nice positions. Obviously, the pawn d6 is still tied down and white's a5-pawn is restricting black's queen side. There suddenly are freeing moves like g6/f5 or Rb8 pushing b5. White's dark squared bishop is not aimed at d6, so this is maybe a bad line (for White)or even the queen exchange might be less good. So basically I tend to go for the just now more popular move Nd7.