Semantic search

Patient was treated intraoperatively following surgical removal of a metastatic lesion in the sacral region. Treatment involved Ir-192 in a Gammamed HDR (High Dose Rate). In standard cases implant geometry calls for a single-plane treatment, and entry of treatment plan into a commercial planning treatment system to control stopping positions of dwell times of source catheter. Size of treatment volume was such in this case that two treatment planes were required. Decision was made to select a single plane midway between the two treatment planes so that both treated regions would receive required dose. Prescribed dose was 15 Gray at a position 1cm away from the source plane on either side, thus simulating a volume source implant. Treatment plan in this case required manual input of treatment parameters. Physicist incorrectly entered distance between treatment planes as 3 cm, instead of 3 mm. A treatment plan was generated using the larger distance, and corresponding source stopping positions and dwell times for this separation. The result was incorrectly large dwell times and an overdose to the two treatment planes separated in fact by 3 mm. It was calculated that the dose delivered was 22.2 Gray rather than the prescribed 15 Gy, an overdose of 48%. Discovery of Event: Event was discovered during chart rounds when a supervising physicist noticed the difference between prescribed dose and the iCheck results. After discovery of the event, it became evident upon reconstructing the timeline of events that treatment planning sheets in the patient's record had been altered. Effect on Patient: In the opinion of the attending radiation oncologist, it is unlikely that there will be any medical consequences. Root Cause of Event: An analysis concluded that the root cause of the event included:

• Incorrect entry of data;
• Failure to follow specifics of quality assurance procedure;
• Inappropriate chart alterations;
• Perception of some members of the staff that people who make or find a mistake will be punished regardless of the specifics of the event.

Actions Taken to Prevent Recurrence of Event:

• Training to reverse perception of some members of the staff that people who make or find a mistake will necessarily be punished, regardless.
• Retraining in actions to be taken in cases of non-standard geometry.
• Disciplinary actions against physicist and dosimetrist involved.
• Annual documented training of medical physicists, dosimetrists and radiation oncology physicians on appropriate quality assurance procedures.
• Change in cover sheet for brachytherapy radiation treatments to include iCheck calculations including quality assurance verifications.

Inspection Results: An inspector from the Office of Radiological Health conducted an inspection on 9/21/11. The inspector found the circumstances of the event to be as described above. In addition, the inspector found that:

• Upon check of the initial treatment plan by the physicist, the dosimetrist calculated a dose of 22.29 Gray rather than the prescribed 15 Gy.
• The dosimetrist informed the physicist of the discrepancy.
• The physicist told the dosimetrist that the iCheck results may be wrong. The reason was that the ABACUS program used by the physicist knows that there are two treatment planes, and that the iCheck which assumes one plane may be wrong.
• Dosimetrist at this point failed to follow proper QA by stopping treatment and informing the radiation oncology attending.
• After seeing the 15 Gy calculated dose at 1 cm from source plane, the attending oncology physician concluded that isodose distribution was correct.
• The dosimetrist left the OR and treatment proceeded with the incorrect dwell times.

The inspector found licensee to be highly cooperative and believes that actions taken in the wake of this event were satisfactory. No formal violation was issued. A Medical Event may indicate potential problems in a medical facility's use of radioactive materials. It does not necessarily result in harm to the patient.