Badges are a legal record read months after the fact, not a warning. Where the dose actually is, why extremity monitoring matters more than most departments assume, what makes a dosimetry record defensible, and how an investigation level is supposed to work.
A dosimetry badge tells you what a person received during a wear period that ended some weeks ago. It does not tell them anything while they are working, it does not alarm, and it cannot be read in the department. Everything sensible about a dosimetry programme follows from accepting that: the badge is the legal record, and something else has to do the job of protecting people in real time.
The licensing side is covered in radiation safety and regulatory compliance for nuclear medicine in Bangladesh. What follows is what a physicist or radiation safety officer has to run week to week for the records to mean anything.
Passive dosimeters store energy from the radiation they receive and release it when the reading laboratory stimulates them. Thermoluminescent types release light when heated. Optically stimulated luminescence types release it under light. Either way the dose is recovered afterwards, in a reader, by somebody else, and the result comes back as a number for a period that has already passed.
That makes the badge excellent as a record and useless as a warning. The complement is an electronic personal dosimeter, which reads out continuously and alarms on rate or accumulated dose. It is rarely accepted as the formal dose of record, and it does not need to be. Its value is operational: it shows a technologist within a single procedure that standing a metre further from the injection chair during uptake changes their reading, which no quarterly report will ever do convincingly. A department doing therapy work should treat electronic dosimeters as ordinary equipment rather than as an optional extra.
In a nuclear medicine department the whole body dose is usually unremarkable and the hands are where the exposure concentrates. Eluting a generator, drawing a dose from a bulk vial, purging a syringe of air and injecting a patient all put fingers within a few centimetres of unshielded activity, and dose rate at that distance is in a different league to dose rate at the trunk. A department that monitors only whole body dose has no data at all on the quantity most likely to approach a limit.
The control badge deserves its own sentence, because when it is kept in a cupboard in the hot lab, the reading laboratory subtracts a contaminated control from everybody's result and the whole batch comes back wrong in the same direction. If a department's readings are inexplicably uniform, look at where the control badge lives before you look at anybody's practice.
A dosimetry record is a document that has to outlive the physicist who started it. In practice that means it is not a spreadsheet on one laptop, and it is not the pile of monthly reports from the service in a drawer.
The register should carry, for each monitored worker: name, identification, date of birth, the date monitoring began, the wear periods, the dose for each period, the running total for the calendar year, the lifetime cumulative dose, the control reading for each batch, and a reference to any investigation. Retention runs for the period the Bangladesh Atomic Energy Regulatory Authority requires, so confirm the current position rather than working from what a colleague remembers, and hold the record somewhere the hospital owns.
Three procedural points that inspections ask about and departments rarely have written down.
Then there is turnaround, which is the practical Bangladeshi problem. A three month wear period followed by a two month delay in reporting means a change in someone's exposure is discovered five months after it started. For hot lab and therapy staff that is too slow. Shorter wear periods for the people handling activity, and electronic dosimeters read weekly, close the gap without changing the formal record at all.
An investigation level is a dose, set below the regulatory limit, at which the department is required to look into a reading. Its purpose is to make sure that the first time anyone examines a person's working practice is not the occasion on which a limit was passed. Set it as a stated fraction of the annual limit, apportioned to the wear period, and write the number into the local rules so it is not renegotiated each time it is reached.
What the investigation consists of matters more than the threshold. A useful one runs roughly like this.
A raised reading with a completed investigation on file is a department managing its exposures. The same reading with nothing attached to it is the finding an inspector writes up, and it is also the reason the same thing happens again next quarter. Most of the fixes that come out of these investigations are cheap: a vial shield used consistently, a syringe shield that fits the barrels actually in use, a shielded holder that stands a loaded syringe upright on the bench instead of leaving it lying in the open. Those are covered in shielding at the bench.