Did Jesus need to die, or would mere shedding of blood have been sufficient?

Originally: St. Thomas Aquinas on salvation by a drop of Christ's Blood I heard on Relevant Radio a year or so ago something perplexing, I think it was a priest saying it, but it may have been a layman, regardless, he seemed very smart, and seemed to know a lot about the theology of St. Thomas Aquinas. Somewhere, I know not where, St. Thomas said that the Crucifixion was not necessary for salvation and that only a drop of Jesus' blood needed to be spilled. Where and why did he write/say this and what is the reason for this. Is it accepted Catholic Doctrine and how much more does the Crucifixion do for us than a single drop of Christ's Precious Blood?