8.9. MONITORING
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8.9.1. Personnel monitoring
All nuclear medicine staff must be routinely monitored for occupational
radiation exposure. This includes nursing staff but may not need to include
clerical staff, unless they are involved with patients.
The main points to remember with monitoring are:
(a) Either film badges or TLDs (Section 4.5.1) should be used as these are
relatively cheap, passive, rugged and, in the case of TLDs, can be re-used.
(b) Monitors should be worn between waist and chest, and underneath any
protective clothing (lead gowns) which might be used.
(c) The monitor should be changed regularly and, in any case, at intervals of
no longer than 12 weeks.
(d) Each batch of monitors will come with a control monitor (to correct for
natural background radiation and other factors), which must be kept in a
place where there is no chance of radiation exposure from radionuclides
or X rays.
(e) An accurate record must be kept of each person’s radiation exposure
history. Records must be kept for their working lifetime, including the
cumulative (running total) dose. Depending on the local regulatory
requirements, it may be convenient to maintain detailed records only for
the current year, and to keep yearly totals otherwise.
(f) Staff must be required to wear their monitors at all times whilst working.
Under the laws of many countries, the head of nuclear medicine will be
held responsible for this, as well as for staff safety.
Monitoring results must be reviewed regularly by an appropriate person,
such as a physicist or senior technologist. The basic principle of radiation safety
is to aim for the lowest feasible dose, not to allow staff to receive any regulatory
dose limit. The BSS dose limit for workers is 20 mSv/a, but nuclear medicine
staff should generally not receive more than 2–3 mSv/a at the most. A local
dose limit of around 5 mSv should be applied to nuclear medicine staff. Staff
who exceed this limit, on a pro rata basis (dose multipied by monitoring period
in weeks/52), should be checked to ensure that their work practices are safe and
that they have not been accidentally or unnecessarily exposed.
8.9.1.1. Special monitoring
There are some occasions where special or additional monitoring of staff
may be needed, for example: