1340 / 1456
Incident description:
During weekly off-line check of the patient’s CBCT the physicist noticed that the patient
(H&N) lost weight / experienced tumour shrinkage in the treatment area. There is 8-10
mm air under the immobilisation net, on both right and left side. By analysing older
CBCTs, it was discovered, that the loss of tissue already occurred 1-2 weeks earlier, but
without reactions.
Incident consequences:
Uncertain setup, uncertainty in the delivered dose distribution
Assumed cause of incident:
Image guidance was not performed satisfactorily
Suggestion to avoid repeating the incident:
Better/more detailed information to the RTT’s to observe the images for potential weight
loss resulting in air under the immobilisation mask. Better/more detailed information t
the physicists to evaluate the images (during off-line controls) as a whole and not only
focusing on the matching structures. Quicker actions required when observing
anatomical changes.
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Case example