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Will radiation therapy (used to treat cancer) cause problems with my pacemaker?

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Todayís technology uses complementary metal oxide semiconductors (CMOS) for their integrated circuits. pacemakers built prior to the early 1970s used transistors that were highly resistant to therapeutic radiation. Low current consumption CMOS circuits are more susceptible to therapeutic doses of radiation. The damage occurs to the silicone and silicone oxide insulators within the transistors. Leads may be irradiated without risk.

Therapeutic radiation therapy is administered in one of the following ways:
  • Radioactive cobalt
  • Linear accelerators
  • Betatrons
The linear accelerators and betatrons produce radiation and a strong electromagnetic field.

pacemaker failures are random. Possible effects include:
  • Loss of sensing
  • Slight or sudden loss of output
  • Runaway rates or increased rates
  • Inhibition
The effects usually are permanent, but may be temporary and resolve within 24 hours. This is more likely to happen if the pacemaker is located in the therapeutic field. The dose of radiation delivered to a pacemaker is cumulative. You must add all doses a pacemaker has received in its lifetime to determine how much radiation it has received.

No exact radiation amount has been determined to cause malfunction. Individual St. Jude Medical pacemakers have been tested to 3,000 rads, without any adverse effects. Note: 2,000 rads is seldom encountered when the pacemaker is located outside of the irradiated field.

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