During a press call outside the Tom Wheldon Building, Professor Alan Rodger, Medical Director of the Beatson Oncology Centre, said: "My colleagues at the Beatson Oncology Centre and I deeply regret the error that has led to Lisa Norris being given an overdose of radiation during her course of treatment.
"We are conscious of the distress that is being caused to Lisa and her family and we are very sorry that this mistake has happened.
"Immediately upon discovering the overdose, we launched an internal investigation.
"This investigation established that no equipment failure was involved but that the overdose was the result of human error.
"Our investigation has also confirmed that no other patient treatments have been compromised. Treatment services for all other patients continue as normal.
"The staff involved with this isolated incident are extremely distraught.
"Our team, including a clinical oncologist, paediatric oncologist and liaison nurse, have held initial meetings with the girl and her family to discuss this error and its possible consequences and will continue to do everything in their power to support both Lisa and her family in the challenges ahead."
"We are also fully co-operating with the Scottish Executive Health Department inquiry, which is now underway. This inquiry is being conducted by the Health Department and the Radiation Protection Division of the UK Health Protection Agency."
Information: NHS Greater Glasgow Communications 0141 201 4429.