Radiation Risk Flashcards
First photographic recording of a radiograph in NA at Dartmouth Hitchcock Hospital
(Hanover, NH)
on February 3, 1896 for an injured left wrist from ice skating.
The referring physician, Dr. Gilman Dubois Frost (standing), the physicist and
radiographer, Dr. Edwin Brant Frost (seated), the patient, Eddie McCarthy and his
mother appear in this nine minute exposure.
Maximum Permissible Dose
That amount of radiation which in the light of
present knowledge will not produce any
serious, harmful, or deleterious effects on the
individual receiving it.
Occupational limits
5.0 rem/year (5,000 mrem)
50 mSv
Non-occupational limits
0.5 rem/year (500 mrem)
5 mSv
In May 2007, the American College of
Radiologists published a white paper
cautioning the medical profession that
Americans are being exposed to record
amounts of ionizing radiation.
- Nuclear medicine and CT exams have
risen sharply in this time period.
- Age
Pediatric Patients at risk
* Rate of cellular and organ growth puts tissues
at greatest level of
radiosensitivity
* Greater life expectancy puts children at 2-6
times greater risk of being afflicted with a
radiation induced cancer
Figure 4. Estimated Dependence of Lifetime Radiation-Induced Risk of
Cancer on Age at Exposure for Two of the Most Common Radiogenic
Cancers.
Cancer risks decrease with increasing
age both because children have more
years of life during which a potential
cancer can be expressed (latency
periods for solid tumors are typically
decades) and because growing children
are inherently more radiosensitive,
since they have a larger proportion of
dividing cells.
These risk estimates (2005) are
applicable to a Western population25
and are derived from survivor studies
of atomic bombings. The data have
been averaged according to sex.
(2) cancer have the highest
risk from dental radiographic exposure
Leukemia and thyroid
Artificial/Manmade Radiation Sources
–2%
(5)
- Consumer products
– Televisions, wristwatches, computers - Airport scanners
- Nuclear fuel cycle
- Weapons production
- Fall-out from atomic weapons
Radiation Erythema
* 250 Rads –
* 500 Rads –
* 750 Rads –
Threshold radiation Erythema Dose (TED)
Average radiation Erythema Dose
Maximum radiation Erythema Dose
1959
In 1959, dental radiation dose was
1 Rad/ second with an 8”
focal distance 10 mA, 65 kV (Ennis and Berry)
78
One periapical exposure averaged 2 seconds;
i.e., 120 impulses or 2.00 s; this equates to 20mAs;
1,250/20 = 62 exposures delivers the TED
2021
An 8” focal distances at 7mAs and 0.2 s
(7mA * 0.2s = 1.4 mAs)
1.4 mAs/ exposure
It takes 417 mAs/1.4 mAs = ~298 exposures
1/3 of the TED is delivered with ~298 intraoral
dental exposures at an 8” focal distance
2021
Using properties of the Inverse Square Law,
the dose is decreased ~— % if the focal distance is
doubled to —”
At a 16” focal distance 1/3 of the TED is delivered with
—
37
16
~473 intraoral dental exposures
Risk Estimates for Pregnancy
- Studies show risk for congenital defects is
negligible at 50 mSv or less
Dental Diagnostic Ionizing Radiation
* Radiographs of pregnant patients as part of any new patient or recall exam must be postponed until —
* If urgent care dental treatment is required during pregnancy, radiographs may be necessary as the
post-partum.
standard of care to treat and diagnose a condition that threatens the health of the mother and the unborn child. The clinician must assure that the primary beam is not directed toward the child-bearing area.
