Radiation In Waiting Room

[dookie]

Should I be worred about having been in a radiation oncology waiting room for about an hour? They not only have like 5 different type of radiation machines, but also have 2 CT scanners in their department. Considering that they didn't take all the safety precauctions, how bad could it be?

I have particularly searched online for a question (but haven't been able to find an answer): what distance must you be from a (direct) radiation beam, for the radiation strength to drop to effectively zero? I realize it is unlikely that the radiation beam was pointed directly at me, but as a theoretic question, what distance does it take? What about CT scanners, how far away from a CT scanners (given there are no walls) would drop the radiation to 0?

@DrJ
@Fiver
@Ras
@haidut

 

[Ras]

Should I be worred about having been in a radiation oncology waiting room for about an hour? They not only have like 5 different type of radiation machines, but also have 2 CT scanners in their department.

I don't know the laws of your location, but in the Colonies, rules govern the construction of environments near sources of radiation. Walls surrounding equipment and sources must be shielded to a certain degree, ensuring that leaks are less than or near background levels. I have been present when physicists were performing such tests in the control room of our then-operating 320-slice Toshiba CT, and his equipment showed more than adequate shielding by the leaded glass, walls, and door. We techs also wear radiation monitoring badges, and even the nuclear medicine techs - who are face-to-face with human radiators for many hours - don't approach minimum allowable levels.

Considering that they didn't take all the safety precauctions, how bad could it be?

What precautions did they not take?

I have particularly searched online for a question (but haven't been able to find an answer): what distance must you be from a (direct) radiation beam, for the radiation strength to drop to effectively zero? I realize it is unlikely that the radiation beam was pointed directly at me, but as a theoretic question, what distance does it take? What about CT scanners, how far away from a CT scanners (given there are no walls) would drop the radiation to 0?

Theoretically, rad strength never reaches zero - it divides in half an infinite number of times as it passes through each half-value-layer of lead shielding. That said, even the lead rubber aprons that our techs wear for IR and cath lab procedures won't let enough radiation through to create noise on our DR photodetectors.

Ionizing radiation, like all other light, will issue radially from any point of contact of sufficient atomic density to create scatter. Said scatter will be weakened by the many attenuating substances it will encounter. Radiation that has passed through scanning filters, a patient's body tissues, and environmental structures will be extremely weakened, if present at all, on final approach. And the Inverse Square Law says that the strength of radiation "changes in inverse proportion to the square of the distance from the source," even without dense attentuators in the midst.

 

[DrJ]

No. The CT scanners have their own shielding and the radiation that scatters out of the bore is relatively minimal compared to the primary beam and will already be pretty near background levels by the time it reaches the walls of a reasonably sized room. The rooms they are put in usually have more shielding in the walls (like 1/16" of lead if memory serves). Outside of that room, you would not even be able to tell a CT scanner was in there from the ionizing radiation readings. Radiation levels are monitored frequently in most larger hospitals I've been to, and they will also put wall-mounted radiation sensors around the radiology and radiation oncology areas to monitor radiation and even sound an alarm if a certain level is detected.

 

[dookie]

I asked an assistant working there, if the walls are protected with lead, and she didn't seem to know anything about it, neither did she know about them using "dosimeters" and detectors

@DrJ
@Ras

 

[Ras]

I asked an assistant working there, if the walls are protected with lead, and she didn't seem to know anything about it, neither did she know about them using "dosimeters" and detectors

@DrJ
@Ras

Is this place in the US?