Panama's Cobalt-60 — When the Blocks Were Entered Wrong

In 2000–2001 at Panama's National Oncology Institute, a radiotherapy treatment-planning system miscalculated beam-on times for cobalt-60 teletherapy. Staff entered the protective shielding blocks in a way the software did not support — as a single combined shape rather than one block at a time — and the planning system responded by computing treatment times that delivered roughly double the prescribed dose. The console gave no warning that the entry method was invalid.

The IAEA investigated and documented this as a landmark radiotherapy accident driven by a data-entry method the software silently mis-handled. It belongs to the 'the display lies' family: the planning computer confidently produced a plan that was catastrophically wrong. (IAEA, 'Investigation of an Accidental Exposure of Radiotherapy Patients in Panama,' 2001.)

1. Clinicians need to shield healthy tissue and enter the blocking-block geometry into the planning system.
2. The blocks are digitized as one combined shape — a method the software did not support.
3. The system computes beam-on times from the invalid geometry and returns roughly double the intended dose.
4. No alert flags the unsupported entry; the plan looks like any other.
5. Patients are treated to the miscalculated times over successive sessions before the pattern is recognized.

A landmark cluster, not a rate: 28 patients over-exposed at one institute, 2000–2001. (IAEA)

Roughly twice the prescribed dose over successive sessions. Shown through the cobalt-60 unit, the planning console, and the empty treatment room — never the patient.