A molecular testing company that has gained considerable traction over the past two years for its work in the concussion detection space has nearly doubled its total fundraising amount with a $46 million series D round. Lexington, Mass.-based Quanterix Corp. previously raised $54 million across its series A, B, and C rounds, and the D round brings the company's fundraising total to $100 million. Quanterix also noted that its post-money valuation now exceeds $200 million.