Optimal source position for irradiation of coronary bifurcations in endovascular brachytherapy with catheter based beta or iridium-192 sources.
OBJECTIVE
Intracoronary brachytherapy after percutaneous transluminal coronary angioplasty (PTCA) is usually performed with catheter-based treatment techniques in a straight vessel segment. There is a growing interest for treatment of bifurcations, which requires consecutive positioning of the source in main vessel and side branch.


METHODS
In-house developed software (IC-BT doseplan) is used to explore the optimal positioning of the source in modelled bifurcations with different shape for the source types available in our hospital, i.e. (90)Sr/(90)Y, (32)P and (192)Ir. The results were summarised in look-up tables. The usefulness of these look-up tables was tested on various clinical examples.


RESULTS
Tabulated results for the modelled bifurcations yield an estimation of the distance between the sources (gap width) in relation to the geometry and source type: (90)Sr/(90)Y gap range 3-8.5 mm, (32)P gap range 2-7 mm and (192)Ir gap range 3.5-8 mm. The average dose relative to 2 mm from the source axis is: (90)Sr/(90)Y, (mean+/-SD) 120+/-40%; (32)P, 125+/-50% and (192)Ir, 120+/-22%. The look-up tables also provide the coarse location and value of maximum and minimum dose: (90)Sr/(90)Y, 220-60%, (32)P, 230-55% and (192)Ir, 170-85%. It appeared that the look-up tables provide a good approximation of the optimal gap width in the clinical examples.


CONCLUSIONS
Tabulated optimal gap widths are very useful for quick estimation of the required gap width for a given bifurcation and source type, in case the prescribed dose in both vessels is the same. In unfavourable geometries there is a risk of local underdosage. Individual treatment planning using a program such as IC-BT doseplan is then recommended.
Marijnissen
Johannes P A
JP
Department of Radiation Oncology, Erasmus MC/Daniel den Hoed Cancer Center, P.O. Box 5201, 3008 AE Rotterdam, The Netherlands.
Coen
Veronique L M A
VL
van der Giessen
Wim J
WJ
de Pan
Connie
C
Serruys
Patrick W
PW
Levendag
Peter C
PC
D015906:Angioplasty, Balloon, Coronary; D001610:Beta Particles; D001918:Brachytherapy / Q000379:methods*; D023903:Coronary Restenosis / Q000517:prevention & control; D003331:Coronary Vessels / Q000528:radiation effects; D006801:Humans; D007496:Iridium Radioisotopes / Q000627:therapeutic use*; D008954:Models, Biological; D010761:Phosphorus Radioisotopes / Q000627:therapeutic use; D011879:Radiotherapy Dosage; D013326:Strontium Radioisotopes / Q000627:therapeutic use; D015021:Yttrium Radioisotopes / Q000627:therapeutic use
D007496:Iridium Radioisotopes; D010761:Phosphorus Radioisotopes; D013326:Strontium Radioisotopes; D015021:Yttrium Radioisotopes