33 Endovascular Brachytherapy

Endovascular Brachytherapy 655

depth. The Active Source Lengths are 40 or 60 mm. Due to the dose-fall off at the edges, the RIL is about 2 mm shorter on each side. The radio-opaque markers on the delivery catheter with distances of 32 or 52 mm respectively, indicate the RIL with an additional safety margin of 2 mm on each side.

Fig 32.13: RIL and maximum Interventional Length for a 40 mm Active Source Length in the Guidant Galileo System with 2 dwell positions of the 20 mm long active wire. A safety margin of 5 mm is added on each side: PTL 36 mm (Kirisits (2)).

8.2.2.3 The Novoste Beta-Cath System The dose rate at 2 mm from the source axis is about 4,8 cGy/sec (288 cGy/min) per 1 GBq total activity of a source train containing 16 active seeds. The dose fall off at the edges is about 2.5 mm each at the proximal and distal edge, resulting in 25, 35 and 55 mm reference isodose lengths for the 30, 40 and 60 mm active source lengths, respectively. Radio-opaque markers on the Beta-Cath delivery catheter indicate the distal and proximal part of the inactive gold seed and so by definition are beyond the Reference Isodose Length. To ensure that the PTL receives the therapeutic dose indicated by the Reference Isodose Length, care must be taken to recognize that the catheter marker and the first point receiving the prescribed dose is separated by the inactive gold seed and one active seed.

Fig 32.14: RIL and maximum Interventional Length for a 40 mm Active Source Length in the Novoste BetaCath System with 16 seeds each of 2.5 mm length. A safety margin of 5 mm is added on each side: PTL 35 mm (Kirisits (2)).