The top quark mass is a fundamentally important parameter of the Standard Model. The fact that the top quark is much more massive than the other fermions has led to speculation that it has a special role within the Standard Model, and that its interactions may be sensitive to new physics. A precise measurement of the top quark mass, in conjunction with further improvements in the W mass measurement, will allow us to place stringent constraints on the Standard Model Higgs boson mass and set the stage for a final confrontation of the Standard Model at the Large Hadron Collider. I will present a measurement of the top quark mass with the Matrix Element method in the lepton+jets final state, using data collected with the DZero experiment at the Fermilab Tevatron collider. The Matrix element method makes extensive use of the available statistical information and has been extended for the first time to include b-quark jet tagging using secondary vertex reconstruction to further improve the precision of the measurement.