The endovenous treatment assembly comprises a wire-like element (1) for delivering treatment doses, such as, for example, an optical fibre, that is flexible and suitable for being inserted longitudinally, over part of the length of same, into a vein (V), and a positioning and guide piece (2A), that is secured to the wire-like element (1) for delivering treatment doses in such a way as to allow the wire-like element (1) for delivering treatment doses to be manipulated by means of this piece (2A)； the piece (2A) comprises at least one first translational guide means for guiding a first portion (110a) of the wire-like element (1) for delivering treatment doses in translation in the length direction of same, the wire-like element (1) for delivering treatment doses being able to slide in the length direction of same relative to said first translational guide means of said piece (2A)； said piece (2A) comprises first mechanical assembly means (202, 203) allowing it to be removably mounted relative to a drive system (4), such that said first portion (110a) of the wire-like element (1) for delivering treatment doses can be positioned and guided by means of this piece (2A) in such a way as to be able to be engaged with drive means of the drive system (4) in order to drive the wire-like element (1) for delivering treatment doses in the length direction of same at least in a first direction (R).L'ensemble de traitement endoveineux comporte un élément filaire (1) de délivrance de doses de traitement, tel que par exemple une fibre optique, qui est souple et apte à être inséré, sur une partie de sa longueur, longitudinalement dans une veine (V), et une pièce (2A) de positionnement et guidage, qui est solidaire de l'élément filaire (1) de délivrance de doses de traitement de manière à permettre la manipulation de l'élément filaire (1) de délivrance de doses de traitement au moyen de cette pièce (2A),； la pièce (2A) comporte au moins un premier moyen de guidage en translation d'une
