196 Forensic dentistry
suggest that it is not expected that dental personnel will reach the monitoring
threshold of 1 mSv/year, and hence monitoring is not warranted. However,
the MPD applicable for the fetus of an occupationally exposed pregnant
worker of 0.5 mSv/month indicates that those individuals be monitored once
pregnancy is discovered.
Also, special considerations may be necessary in a disaster morgue setting
where numerous individuals are nearby the x-ray source in the dental section.
This is based on recommendations by the NCRP concerning open-bay dental
units that a patient in the room during a diagnostic exposure of another patient
shall be treated as a member of the public. When portable x-ray machines
are used, all individuals in the environs not directly involved with obtaining
the radiographic image should be deemed as “public” when considering their
MPD levels.
10.7.3 Handheld X-ray Devices
Handheld x-ray-generating devices have come into common use in forensic
dent ist r y, pa r t icu la rly i n mu lt iple fata l it y i ncident morg ues. In fac t , t he A r ibex
Nomad was used to produce all of the radiographic images in the Disaster
Mortuary Operational Response Team’s (DMORT) response to Hurricane
Katrina. During that operation it was assumed that operators using the device
were “safe” based on dose studies conducted by the manufacturer and the
device’s approval by the U.S. Food and Drug Administration. These studies
demonstrated extremely small tube head leakage and backscatter to the oper-
ator. Subsequent research simulating morgue usage in a mass fatality setting
has confirmed the safety of those working within the dental station. A study
simulating doses to those comprising the dental team over a two-week
deployment (5,760 exposures) showed that the team member receiving the
highest dose at that position (60° to the side of the emanating beam) received
an exposure of 0.253 mSv. This dose corresponds to 1/200th of the annual
occupational limit of 50 mSv and approximately 3.5 weeks of the U.S. aver-
age background radiation.^14 Another study that simulated the dose received at
numerous bodily locations revealed a dose of 0.454 mSv after 7,200 exposures,
which equals 0.9% of the annual limit.^15
10.8 Radiographic Equipment in the
Forefront of Forensic Dentistry (CBCT)Dental cone beam computed tomography (CBCT) is an advanced digital x-ray
system that was released in 2001. A tomograph is a radiographic presentation