MEDRADSC 2X03 - Lecture 20 - Dose and Risk for Medical Sources of Radiation

how has technology improved radiation safety and effectiveness?

improved dose rates, increased availability and number of exams

collective effective doses estimate:

detriment to patients and health-care workers exposed to radiation

ICRP estimates that ____% per Sv will die from fatal and nonfatal cancer induction.

5.5

ICRP estimates that ___% per Sv will die from severe hereditary effects.

0.2

lifetime attribute risk (LAR)

0.004% of the population exposed to radiation is at risk of detriment

collective effective dose to patients (2006)

899,000 person-Sv

what are some factors to consider when looking at the NCRP report 160 numbers?

increased use of CT in the last two decades can attribute lower numbers in the report, population is skewed in age, as almost 1/2 of diagnostic procedures are performed on patients with terminal illnesses or within 18 months of death

collective effective dose to workers number

410 person-Sv

____ individuals in the US health industry will develop a fatal cancer as a consequence of a year's use of medical radiation

16

what is the limitation with estimating risk detriment in populations exposed to low doses of radiation?

there is no direct evidence that small doses can cause harmful effects, only estimation, extrapolation is required

what type of effect is typically seen in diagnostic radiology?

stochastic effects, not sufficient enough dose to cause deterministic effects

what is the exception to seeing only stochastic effects in diagnostic radiology?

inadvertent in-utero exposure of the embryo or fetus

what is the deterministic assumed threshold for in-utero irradiation to cause detriment?

0.3 Gy

what projections is radiography have the highest ESE/absorbed doses?

Lumbar spine, barium enema series and upper GI series

what specialty has some of the largest diagnostic doses in radiology?

fluoroscopy

what is the dose limit for fluoroscopy per min?

10 R/min

what is the typical entrance exposure in fluoroscopy>

3 R/min

there is no limit for ______ for recorded fluoroscopy.

ESE

what is a dominant result to the patient of prolonged exposure during a fluoroscopy exposure?

skin erythema

which fluoroscopic procedures have some of the highest effective doses?

thoracic angiography, hepatic angiography and TIPS

early effects of prolonged interventional procedures

erythema and epilation

erythema

redness of skin, occurs within hours in skin doses of more than 2 Gy

epilation

hair loss, occurs within weeks with skin doses of more than 3 Gy

late effects of prolonged interventional procedures

telangiectasia, hyperpigmentation and necrosis

telangiectasia

permanent enlargement of blood vessels

hyperpigmentation

darkening of skin

what is the dose that organs can receive in a CT scan?

10-100mGy, usually 15-30mGy for each sequence

how much does organ dose vary between different CT manufacturers?

by a factor of 6

how much does organ dose vary between different departments, but same scanner?

by a factor of 5

what must be done to technical factors for a pediatric CT?

decrease dose considerability

dose rate of CT fluoroscopy

0.2-0.5 Gy after 90 seconds

what is different about dose estimations in radiation therapy compared to radiography?

therapists are not expected to receive much dose, and if they are exposed the dose is very large

exception to limited exposures to radiation therapists

physicians/nurses handling brachytherapy sources