33 Endovascular Brachytherapy

642 Endovascular Brachytherapy

Independently of the dose prescription procedure chosen, the following procedure is recommended (ESTRO recommendations 2001 for recording and reporting a reference depth in an unambiguous and reproducible way (5)). The distance of the reference depth dose point (RDDP) to the source centre should be calculated by indicating a certain radial reference depth (RD) from the vessel lumen into the vessel wall perpendicular to the vessel axis. Usually, in typical anatomical situations, this is given as 1 mm for a coronary and 2 mm for a femoropopliteal artery. In order to arrive at a reference depth dose point, the respective half reference lumen diameter (RLD/2) as defined after angioplasty must be added to this distance. Distance to the RDDP = RLDi/2 + RD The target length should always be significantly longer than the length of the lesion. The target length is first based on the interventional length (IL), which is defined as the angioplasty length of PTA or PTCA. This interventional length must include all positions in the vessel of the device, by which the angioplasty intervention was performed leading to vessel injury. This will be a balloon, a stent, mechanical debulking instrument, or any other method used to clear the vessel lumen.

Fig 32.4: Schematic diagram for the definition of lengths in endovascular brachytherapy. LL: Lesion Length; IL: Intervention Length; CTL: Clinical Target Length; PTL: Planning Target Length; ASL: Active Source Length; RIL: Reference Isodose Length