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Radiation safety deviations in healthcare and veterinary medicine

Radiation safety deviations in healthcare and veterinary medicine

An anonymised description of the radiation safety deviations is published on this page, describing the incident, the reasons for the incident, the resolution of the incident and the measures taken to prevent similar incidents. In this way, lessons can be learned from the incident and hopefully avoid similar incidents in the future. The Radiation and Nuclear Safety Authority has recently been notified of the following radiation safety deviations in the use of radiation in healthcare and veterinary medicine:

Case 1

A CT scan of the abdominal area was performed on a patient over 70 years old. The instructions were that the imaging would be performed using only contrast medium, but the radiographer inadvertently selected an imaging protocol for the study that included a series of images without contrast medium. The patient received an excess effective dose of 20.2 mSv from the unnecessary imaging. Staff has been reminded to be careful when performing imaging.

Case 2

The cone beam computed tomography (CBCT) machine had been moved to new premises in the hospital and the installer of the machine was carrying out quality control tests with the door open. Two employees in the control room were working on the equipment next door and did not notice the situation. The incident was noticed when the dose meter of the hospital's maintenance supervisor on site alarmed. The workers' estimated effective dose was 0.3 µSv. The radiation safety deviation happened due to the ignorance of the installer. In the following installations and quality measurements, the appropriate operating procedures at the installation site were reviewed together with the equipment installer.

Case 3

In a hospital's positron emission tomography (PET) imaging unit, a patient's PET-TT examination had to be repeated due to a malfunction of the automated syringe. In addition, when the equipment was dismantled, small amounts of radiopharmaceutical solution spilled on the base of the drip stand, on the floor and on the lead-protected container. The contamination was cleaned up as instructed.

The patient received an additional effective dose of about 18 mSv from the study, of which about 2.5 mSv was caused by the administered radiopharmaceutical and about 15.2 mSv by the CT scan performed during the study. For the two radiographers, the excess effective dose from the event was assessed as very low.

The radiation safety anomaly was due to an unexpected equipment failure. The operation of the automated syringe and the operating instructions were immediately checked. In the future, similar radiation safety deviations will be prevented by checking the condition of the equipment and providing additional training on its use.

Case 4

A radiation safety deviation occurred in an animal hospital during a routine X-ray examination due to human error. The exposed workers were an X-ray nurse and a veterinary nurse who were positioning a cat during an X-ray examination. The workers had positioned themselves close to the X-ray tube to calm the cat, which was in an agitated state, when outside the examination room a third person, acting as a help ready to take the X-ray, negligently triggered the x-ray. The radiation exposure of the workers was estimated to be less than 2 µSv.

Case 5

There was a near-miss at a hospital during a gamma scan of a patient's brain receptors. The activity of the iodine-123 radiopharmaceutical, which had arrived in the morning, was incorrectly displayed as too low in the Nuclear Medicine Management Software. As a result, the dosing of the radiopharmaceutical was exceptionally done using an activity meter in the clean room, which showed the correct activity. However, the patient was injected with less radiopharmaceutical than planned, as the radiopharmaceutical injection was remeasured with a faulty meter, contrary to the instructions. However, it was possible to perform the scan as planned, and no re-scan was necessary.

A malfunctioning activity meter in the injection room could have caused false results, which could have resulted in patients receiving wrong amounts of radiopharmaceutical. Based on the hospital's report, the deviation was due to the faulty activity meter displaying incorrect radiopharmaceutical activity, haste, an error in the Nuclear Medicine Management Software and other human error factors. The event was documented, and it was decided that the old meter would be renewed.

Case 6

A technetium-99m contamination occurred in an ultrasound room of a hospital. The radiologist was injecting the patient with radiopharmaceuticals. During the administration of the radiopharmaceutical, the needle became blocked for some reason and an estimated 35 MBq (approx. 0.3 ml) of activity was splashed between the needle and syringe onto the patient, the radiologist, the X-ray nurse, the ultrasound machine, the bed, on the wall and on the floor. Radiation exposure of the radiologist and X-ray nurse was estimated to be less than 3 µSv. To prevent something similar from happening, in the future the force used to press the syringe will be monitored more closely when injecting, and the connection between the needle and the syringe will be checked before administering the radiopharmaceutical.

Case 7

A child came in for an X-ray with her pregnant mother. Only one X-ray nurse was working at the facility at the time of the incident. The nurse held the child during the imaging and the mother of the patient who was being scanned triggered the X-ray machine. The image showed a failed breathing phase, so the image was repeated later that day at a different location. The patient's exposure due to the extra image was estimated to be less than 1 µSv.

The X-ray nurses working in the unit were briefed on what to do in a similar situation. The one involved in the radiation safety incident was verbally reprimanded for action against instructions and a written report of the incident was prepared. In addition, further guidance was given at organizational level on the correct course of action to take in such a situation.

Case 8

Users of an X-ray machine in a hospital noticed an abnormal sound coming from the machine. The discovery was reported to the hospital's own equipment maintenance department, which contacted the equipment supplier. Two service technicians from the equipment supplier inspected the equipment together with the hospital's maintenance staff and the cause of the noise was found to be a malfunctioning collimator. The supplier's maintenance staff found the equipment to be in working order. A dose sampling of the X-ray machine about a month later drew attention to abnormal radiation doses. Quality assurance measurements were carried out on the equipment, which showed that the additional filtering of the equipment was not functioning correctly. However, the device did not report a malfunction of the additional filtering. The device was immediately put out of service.
A total of 600 patients have been imaged between the time the device was serviced and the time the fault was detected. It is impossible to assess with certainty whether the additional filtration was working correctly for an individual patient. The dose to the patient from a conventional X-ray scan varies from patient to patient but is on average small in relation to the potential adverse effects of the radiation. The hospital estimates, based on dose sampling, that patients imaged with defective equipment were exposed to an average dose 140% higher than planned.

The hospital, hospital equipment maintenance and the equipment supplier have addressed the radiation safety deviation and investigated the reasons for the it. The deviation was the result of a malfunction of the radiation equipment, inadequate repair, and failure to ensure that the equipment was in good working order. The root cause was identified as a lack of compliance with the operating instructions and a lack of clarity in the communication and division of responsibilities between the parties involved. As a result of the radiation safety deviation, the operation of the repaired unit will be subject to enhanced monitoring until the original cause of the failure in the operation of the filtration system is identified. As a result of the deviation, the operational guidelines, and the division of responsibilities between operators have also been clarified to prevent similar anomalies from occurring in the future.

Case 9

The iodine-123 injection fluid (37 MBq) ordered for the hospital's department of nuclear medicine was in transit. Early in the morning, a forklift had apparently driven over this shipment of injection fluid. As the assessment of the fire brigade was that no leakage was visible, it was decided to transport the broken shipment, wrapped in a double plastic bag, to the hospital's department of nuclear medicine for ageing. In the department, it was found that the ampoule of injection fluid was intact, although the shipping carton and the protective container were badly damaged. No contamination was found in the package, the protective container or the packaging materials of the shipment. The iodine-123 injection fluid in question was aged in the waste storage facility of the department of nuclear medicine.

This was a near miss. No radioactive substances were released into the environment. Negligence in the handling of the radioactive consignment was assessed as the cause. The transport operator should review the incident and the reasons that led to it internally with their safety advisor. Radioactive sources are usually quite well packed and in this case the packaging protected against contamination. However, looking at the packaging, the ampoule would probably not have survived intact if the forklift had driven completely over the metal container. Such a possibility should already be considered when packing the consignment. Finnish Safety and Chemicals Agency (Tukes) is handling the accident report related to this radiation safety deviation.

Case 10

Due to temporary malfunctions of the positron emission tomography/computed tomography (PET/TT) machine, two patients failed to be imaged. Re-imaging could not be performed immediately because the camera took so long to recover that the activity of the radioactive drug the patient had received had been reduced by half to too low a level. Furthermore, the corrective measures taken after the first malfunction did not allow the assumption that the failure would occur again within the same day. 

Both patients had had time to have a CT scan taken during the study, so the additional radiation exposure consists of the CT scan plus the injected fluorine-18-FDG. This radiation safety deviation resulted in excess radiation exposures of 10.9 mSv and 11.5 mSv for the patients. 

The cause of the radiation safety deviation was a technical malfunction of the equipment, which may have been related to a thunderstorm the previous day. The equipment manufacturer will ensure the condition of the equipment and carry out maintenance. The radiation safety deviation will be discussed in a team meeting and in the quality working group to avoid similar incidents in the future. An incident report has been submitted to Finnish Medicines Agency (Fimea).

Case 11

One nurse had already turned on the radiation therapy unit's computed tomography simulator (CT simulator) for the morning heating, while another nurse went to turn on the DIBH machine (a device to ensure that radiation therapy is given at the phase of breathing). The nurse did mention turning on the heating, but the DIBH machine had not started the first time, so the second nurse inadvertently went to turn it on again. The morning heating of the CT machine started while the nurse was in the side room turning on the DIBH machine - not actually in the imaging room. The door to the control room was also open while the machine was on, so the other nurse in the control room must also have had a small additional radiation exposure. The CT simulator alarmed twice before the nurse noticed the situation and interrupted the radiation.

The nurses have personal dosimeters. The dosimeters were read after the event. The nurse in the side room had a deep dose reading of 1 µSv and the nurse in the control room had a deep dose reading of 3 µSv. Both had a surface dose reading of 0.00 mSv.

The situation was reviewed, and the exposures were assessed with those involved and discussed in a joint unit meeting. The situation was caused by human error and an unexpected situation. In the future, people are reminded to check that the CT is not on when entering the filming room. The instructions will be revised to ensure that when filming or testing on the machine, the operator is at the control machine, so that he or she is able to stop the irradiation as quickly as possible in the event of an unexpected situation.