Tomonori Isobe PhD, Presenter: Nothing to Disclose

Hiroaki Kumada PhD, Abstract Co-Author: Nothing to Disclose

Takayuki Hashimoto MD, Abstract Co-Author: Nothing to Disclose

Haruko Hashii MD, Abstract Co-Author: Nothing to Disclose

Hideyuki Sakurai MD, PhD, Abstract Co-Author: Nothing to Disclose

Takeji Sakae, Abstract Co-Author: Nothing to Disclose

In recent years, the opportunity to perform radiotherapy to patients bearing pacemaker, is increasing. Although there is a report about the influence on the pacemaker to primary radiation, there is almost no report about the influence of secondary radiation beam. The purpose of this research is to evaluate the relation between the amounts of the secondary neutron generated radiotherapy and the error of Implantable Cardioverter Defibrillators（ICDs）.

We performed experiments for X-ray and proton beam irradiation with a water phantom (external size: 24 x 24 x 24 cm3) with four ICDs in order to know occurrence probability of the soft error efficiently. The ICDs for both experiments were set to the phantom surface locating at the side of distal end which can avoid the influence of a primary beam. The beams used for the irradiations were 10 MV X-ray and 200 MeV proton, respectively. After each radiation fraction, interference by the therapy was checked by ICDs programmer. Moreover, we evaluated the secondary neutron field experimentally and numerically using CR-39 detector and Monte Carlo transport code.

The frequency of the power-on reset, which was the most serious soft error with programmed pacing mode changed to safety back-up mode temporary, was once per approximately 600 Gy in 10 MV X-ray and about 50 Gy in proton beam, respectively. The hardware error (drop dead halt) was not occured in 10 MV X-ray at proton beam, either. The neutron dose caused by thermal neutrons in the proton irradiation at the ICDs position was approximately 22 times the 10 MV X-rays, and fast neutron dose in the proton irradiation was about 520 times the X-rays condition.  

The proton beam had many amounts of secondary neutron, and the error frequency caused by the neutron was also higher than X-rays. We have to take into consideration the influence on ICDs not only by primary beam but secondary neutron.

 To perform radiotherapy to an ICDs wearing person, it needs to be verified enough before irradiation.

Isobe, T, Kumada, H, Hashimoto, T, Hashii, H, Sakurai, H, Sakae, T, Influence of Neutron Generated in 10 MV-X-ray Irradiation and Proton Beam on Implantable Cardioverter Defibrillators (ICDs).  Radiological Society of North America 2010 Scientific Assembly and Annual Meeting, November 28 - December 3, 2010 ,Chicago IL. http://archive.rsna.org/2010/9015070.html