Radioactive Sources Flashcards

1
Q

Low dose rates (LDR) range from

A

40 to 80 cGy/h

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2
Q

High dose rates (HDR) start at

A

20 cGy/min

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3
Q

Sources for permanent implants should have

A

a short half-life to minimized radiation to public.

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4
Q

Sources for permanent implants should have

A

low energy radiation so that radiation does not easily escape patients.

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5
Q

Most sources used for brachytherapy are

A

sealed sources.

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6
Q

Activities for LDR sources range

A

0.1 to 100 mCi.

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7
Q

Activities for HDR afterloaders units can be as high as

A

10 Ci.

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8
Q

Radium-226 is difficult to

A

shield due to its high mean energy.

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9
Q

The disadvantages of using radium are:

A

Hard to shield due to its high mean energy of 0.83 MeV and radon gas leak.

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10
Q

One gram of radium has an activity of

A

1 Ci.

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11
Q

Cesium-137 is a HDR or LDR source?

A

LDR

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12
Q

Cesium-137 is predominantly used for

A

cervical cancer.

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13
Q

Cs-137 advantages over Radium-226 are

A

Uses less shielding and has no radon hazard.

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14
Q

What are Cs-137 Half-life, mean energy, and HVL?

A

30 years, 0.662 MeV, and 5.5 mm

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15
Q

High energy sources have identical dose distribution within 10 cm because

A

absorption and out scattering is compensated by in scattering, which leads to dominating inverse square effect.

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16
Q

What are Ra-226 Half-life, Mean energy, and HVL?

A

1600, 0.83 MeV, and 16 mm.

17
Q

Iodine-125 is used for permanent implants of

A

the brain and prostate.

18
Q

Additionally, I-125 can be used on the eye as

A

temporary eye plaques.

19
Q

What are I-125 Half-life, mean energy, and HVL?

A

60.2 days, 28 keV, 0.025 mm.

20
Q

The dose distribution of I-125 is highly anisotropic due to

A

its low energy of radiation.

21
Q

Iridium-192 is a HDR or LDR source?

A

HDR

22
Q

Ir-192 is commonly used for

A

temporary interstitial transplants.

23
Q

What are Ir-192 Half-life, mean energy, and HVL?

A

73.8 days, 0.38 MeV, and 2.5 mm.

24
Q

Ir-192 specific activity is

A

450 Ci/g

25
Q

Ir-192 is well suited for

A

HDR afterloaders.

26
Q

When patients are treated with Cs-137 brachytherapy sources, the dose deposited at 1 cm in tissue is from

A

Gamma only

27
Q

What are the photon energy for the following sources:

Cs-137

I-125

Ir-192

Co-60

A

0.662 keV

30 keV

  1. 380 keV
  2. 25 MeV
28
Q

The dose distribution in tissue up to 5 cm from an Ir-192 seed can be predicted from inverse square alone because:

A

Absorbed and out scattered photons are compensated by in scattered photons at a given point P

29
Q

I-125 seed are used in brachytherapy for their

A

x-ray and gamma rays.

30
Q

Half-life for radioisotopes:

I-125

Cs-137

Co-60

Palladium-103

A

60 days

30 years

5.26 years

17 days

31
Q

Radionuclide which emits photons of average energy of 21 keV and has a 17 day half-life is:

A

Pd-103