33 Endovascular Brachytherapy

Endovascular Brachytherapy 641

coronary or in the femoropopliteal artery and taking into account in addition the vessel lumen diameter. Such a procedure is usually mainly based on angiograms. It may also follow individualised dose prescription, looking case by case into the topography and pathology of the vessel segment to be treated by radiotherapy (9). This procedure is usually based on IVUS. It may also take into consideration whether a centring or non centring device is used for radiotherapy.

Fig 32.3: Radial dimensions in endovascular brachytherapy: definition of the reference depth dose point and reference lumen dose point (based on angiography) (Pötter et al. (5)):

A: Schematic diagram of a vessel along the longitudinal dimension based on angiography: Reference Depth Dose (Point) (RDD(RDDP)) and Reference Lumen Dose (Point) (RLDo (RLDP)) as a function of the Radius (R) defined at the Reference Lumen Diameter (RLDi) plus the Reference Depth (RD) in the central plane of the Planning Target Length (PTL). The distance between the source position and the RDDP (SRD = R + RD) is taken for calculation of the RDD. The RD is 1 mm in coronary arteries and 2 mm in peripheral arteries. In non-centred systems the RDD is calculated in the same way assuming a centred position of the source as R(RLDi) + RD in the central plane. In addition, the maximum and minimum dose levels have to be added for the position of the source close to the vessel wall, both related to the RLDP and the RDDP.

B: Schematic diagram of a vessel cross- section based on IVUS with angiographic parameters superimposed. Reference Depth Dose Point (RDDP c ) for coronary arteries based on the Reference Lumen Diameter (RLD) plus 1 mm, given in the central plane. In addition, the dose at the surface of the RLD is indicated in the same plane, which is the Reference Lumen Dose Point (RLDP c ).