RAD BIO 7

34問 • 1年前

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• No threshold • Probability of the effect increases with increasing dose • Latency

Stochastic Effect

The stochastic dose-response relationship is what?

Linear

Studies of large numbers of people exposed to a toxic substance require considerable statistical analyses.

Epidemiologic Studies

Epidemiologic studies of people exposed to radiation are difficult because? DF

- dose is not known but is presumed to be low - frequency of response is low.

Irradiation of blood-forming organs can produce ___________ as a deterministic response or ___________ as a stochastic response.

- Hematologic Depression - Leukemia

Chromosome damage in the circulating lymphocytes can be produced as both what response?

deterministic and a stochastic response

Individuals accidentally exposed with high radiation doses continue to show chromosome abnormalities for __ years after the exposure

20 years

1932: ______ used to accelerate charged particle to very high energies

Cyclotron

By ____ nearly every university physics department had one and was engaged in high energy experiments. By ____ - first cataract reported By ____'s - several hundred cases were reported

- 1940 - 1949 - 1960

occur in the posterior pole of the lens

Radiation induced cataracts

Radiosensitivity of the eyes is ___ dependent.

Age

• High LET radiation have high ___ for the production of cataracts.

RBE

Threshold after an acute x-ray exposure for eyes is approximately _ Gyt

After __ Gyt , cataracts develop in nearly 100% of those who are irradiated.

The eye threshold after fractionated exposure is probably in excess of in excess of __ Gyt

_____ exposure to the lens of the eye are too low to require protective lens shields for radiologic technologists.

Occupational

In computed tomography, the lens dose can be __ mGyt

50 mGyt

At worst, humans can expect a reduced life span of approximately __ days for every 10 mGyt. Whereas the average life shortening caused by occupational accidents amounts to 74 days, for radiation workers, life is shortened by only __days

- 10 days - 12 days

Nearly 100,000 died from the blast and early effects. Another 100,000 received a high dose but survived. The remainder received less than __ rad. (ABCC) - received high doses

- 10 rad - Atomic Bomb Casualty Commission

follows a linear, nonthreshold dose-response relationship.

Radiation induced leukemia

Radiation-induced leukemia is considered to have a latent period of _____ years and an at-risk period of approximately __ years.

- 4-7 years - 20 years

- Before, Most radiologist received doses ___ rad/year without radiation protection

- 100 rad/year

1940's-1950's in Great Britain, patients with __________ were treated with radiation to cure the disease.

Ankylosing spondylitis

-20 years until patient cured from ankylosing spondylitis started dying from leukemia. - spinal bone marrow had received _______ rad. - relative risk from the study was ____

- 100-4000 rad - 10:1

Radiation-induced leukemia also can be reported for?

Radiation induced cancer

follows a threshold dose-response relationship.

Radiation-induced skin cancer

has been shown to develop in three groups of patients whose thyroid glands were irradiated in childhood. 1. Ann Arbor series and the Rochester series -They treated shortly after birth for enlarged thymus with up to 500 rad. 2. 21 children natives of Rongelap Atoll in 1954. These children received radiation doses about 12 Gyt (1200 rad)

Thyroid Cancer

Two population groups have contributed an enormous quantity of data showing that radiation can cause this 1. radium watch-dial painters. -72 cases of this in about 800 workers have been observed in 50 years. 2. Patients treated with radium for arthritis and tuberculosis. Relative risk was 122:1

Bone Cancer

Additional studies have produced results suggesting that this developed in patients treated with x-rays for acute postpartum mastitis. -The dose to patients ranged from 0.75 to 10 Gyt (75 to 1000 rad). -The relative risk factor in this population was approximately 3:1.)

Breast Cancer (Radiation induced breast cancer)

was for many years treated by isolation in a sanitarium. During the patient's stay, one mode of therapy was to induce a pneumothorax in the affected lung; this was done under non-image-intensified fluoroscopy. Many patients received multiple treatments and up to several hundred fluoroscopic examinations

Tuberculosis

Early in the 20th century, it was observed that approximately 50% of workers in the Bohemian pitchblende mines of Germany died of this -American uranium miners active in the Colorado plateau in the 1950s and 1960s -Early 1960s, when approximately 5000 miners were active in nearly 500 underground mines and 150 open-pit mines. -4000 uranium miners have been observed and they have received estimated doses to lung tissue as high as 30 Gyt (3000 rad) - The relative risk was approximately 8:1.

Lung Cancer

Under liver cancer, Thorium dioxide (ThO2) in a colloidal suspension known as? -Radiation that was emitted produced a dose in the ratio of approximately 100:10:1 of alpha, gamma radiation, respectively.

Thorotrast

usually begins with the development of radiodermatitis. -Significant data is available on patients treated with orthovoltage (200-300 kVp), and superficial x-rays (50-150 kVp) - Latent period is about 5-10 years. - The relative risk for exposure range of 500 to 2000 rad, the relative risk was 4:1 - For exposure of 4000 rad to 6000 rad the relative risk is 14:1

Skin Cancer

-Approximately 2,000,000 people resided within an 80-km (50-mile) radius. -approximately 330,000 cancer deaths in these persons. During the total period of the radiation incident, the average dose to persons living within a 160-km (100-mile) radius was 15 uGyt (1.5 mrad); to those within the 80-km (50-mile) radius, it was 80 Gyt (8 mrad).

Three Mile Incident in 1979

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