CHAPTER 35 - HEALTH PHYSICS

Clarence Dally

The first American fatality that resulted from radiation exposure was Thomas Edison’s assistant, ___________.

1931

In ________, the first dose-limiting recommendations were made.

health physics

The term_________ was coined during the early days of the Manhattan Project, the secret wartime effort to develop the atomic bomb.

first health physicists.

The group of physicists and physicians responsible for the radiation safety of persons involved in the production of atomic bombs were the __________

20 greatest scientific

At the turn of the millennium, the year 2000, the National Academy of Sciences identified the ___________ and technical accomplishments of the 20th century.

Health physics

___________ is concerned with providing occupational radiation protection and minimizing radiation dose to the public.

stochastic effects

We practice ALARA in response to our acceptance of the linear nonthreshold (LNT) radiation dose response relationship as most representative for __________ —cancer, leukemia, and genetic effects.

• time

• shielding

• distance

Three cardinal principles of radiation protection developed for nuclear activities— ______, ______ and ________ —find equally useful application in diagnostic imaging.

motion blur

During radiography, the time of exposure is kept to a minimum to reduce _________.

patient and personnel

During fluoroscopy, the time of exposure also should be kept to a minimum to reduce _______ and ________ exposure.

Fluoroscopy

This is an area of radiation protection that is not directly controlled by the radiologic technologist

pulse-progressive fluoroscopy

The use of ____________ can reduce patient dose considerably.

5-minute reset timer

The _________ on all fluoroscopes reminds the radiologist that a considerable amount of fluoroscopic time has elapsed.

5 minutes.

Most fluoroscopic examinations take less than _______

decreases

As the distance between the source of radiation and the person increases, radiation exposure _______ rapidly

point source

If the distance from the source exceeds five times the source diameter, it can be treated as a _________.

five times

If the distance from the source exceeds ________ the source diameter, it can be treated as a point source.

point sources

Most radiation sources are _________.

xray tube target

The __________, for example, is a point source of radiation.

extended area source.

The scattered radiation generated in a patient appears, however, to come not from a point source but rather from an __________

isoexposure lines

The lines on the plot plan, called _________, represent positions of equal radiation exposure in the fluoroscopy room.

3 mGya/hr (300 mR/hr)

At the normal position for a radiologist or a radiologic technologist, the exposure rate is approximately _____________

radiologic technologist

During fluoroscopy, the ____________ should remain as far from the patient as practicable.

50 μGya/hr (5 mR/hr).

Two steps back, the exposure rate is only approximately _________

radiation source and exposed persons

Positioning shielding between the _______ and __________ greatly reduces the level of radiation exposure.

half-value layer (HVL) or the tenth-value layer (TVL)

The amount that a protective barrier reduces radiation intensity can be estimated if the_________ or _____________ of the barrier material is known.

One TVL

______ is the thickness of absorber that reduces the radiation intensity to one-tenth its original value.

protective apparel

Another example of the application of shielding in radiology is the use of ____________.

0.5 mm Pb.

Protective aprons usually contain ___________.

25%

Protective aprons usually contain 0.5 mm Pb. This is approximately equivalent to 2 HVLs, which should reduce occupational exposure to _____

2 HVLs

Protective aprons usually contain 0.5 mm Pb. This is approximately equivalent to______, which should reduce occupational exposure to 25%.

3.3 HVL

1 TVL =______

10%

Actual measurements show that such protective aprons reduce exposure to approximately _____ because scattered x-rays are incident on the apron at an oblique angle.

Effective Dose

It is relatively easy to measure patient radiation exposure and dose during medical x-ray imaging.

effective dose (E).

When only part of the body is exposed, as in medical x-ray imaging, the risk of a stochastic radiation response is not proportional to the tissue dose but rather to the _________

whole-body dose.

Effective dose is the equivalent _________

equivalent whole-body dose

The ___________ is the weighted average of the radiation dose to various organs and tissues.

fluoroscopy

We receive essentially all of our occupational radiation exposure during _________

protective barrier

During radiography and mammography, the radiographer is positioned behind a __________, resulting in zero occupational radiation exposure.

zero

During radiography and mammography, the radiographer is positioned behind a protective barrier, resulting in ______ occupational radiation exposure.

collar

During fluoroscopy, we position our occupational radiation monitor at the _______, to estimate dose to the tissues of the head and neck.

1 mSv.

So the estimation of effective occupational dose for an occupation monitor response of _______

100 μSv.

The result of this exercise is an occupational effective dose of_______

10%

We assume the occupational effective dose to be _____ of the monitor dose.

Emergency responders

__________ are those individuals who must make the first decisions and take the first steps in the early stages of such an event

Rescue and medical emergencies

________ and _______ should be attended to before radiologic concerns are addressed.

• a radiation exposure device (RED)

• a radiologic dispersal device (RDD),

• improvised nuclear device (IND)

The malevolent use of radiologic material by terrorists can be described as one of three devices: (3)

radioactive

Being exposed to radiation does not make an individual _________.

radiation exposure device (RED)

An ______ is a sealed source of radioactive material that directly exposes people.

radiologic dispersal device (RDD)

An ______ can be a bomb or a nonexplosive device which disperses radioactive contamination over a wide area.

improvised nuclear device (IND)

An ______ contains nuclear material that can produce a nuclear explosion.

improvised nuclear device (IND)

An ______ is indeed a nuclear weapon; therefore, it is unlikely to be the form of attack used by a terrorist.

500 mGya/hr(50 R/hr).

Radiation detection apparatus should be capable of measuring radiation exposure levels to_________