1: Basics of Nuclear Medicine Flash Facts

Public exposure: 100 mrem/year = 0.1 rem/year = 1 mSv/year = 0.001 Sv/year.
Occupational exposure: 5,000 mrem/year = 5 rem/year = 50 mSv/year = 0.05 Sv/year.
Pregnancy exposure: 0.5 rem = 500 mrem = 5 mSv from date of conception until end of pregnancy (10 CFR Part 35.1208).
Radiation area exposure: > 5 mrem/h at 30 cm.
High radiation area: > 0.1 rem/h at 30 cm. Door sign: Yellow color for high radiation area, which requires RWP (radiation work permit) for entry. Example of a door sign: “Dose rate at this point is (x) mrem/h, posted on (Date) by (radiation personnel).”
Public area radiation level limits (unrestricted area): 100 mrem in 1 year and 2 mrem in any 1 h.
Patient release after I-131 treatment:
- <7 mrem/h at 1 m from the chest or <33 mCi I-131 NaI (NRC Regulations).
- <5 mrem/h at 1 m from the chest or <30 mCi I-131 NaI (some Agreement State Regulations).
Body exposure:
- Eye limit dose (lens): 15 rem = 0.15 Sv = 150 mSv = 0.15 Sv/year.
- Whole body (same as occupational exposure): 5 rem = 0.05 Sv = 50 mSv.
- Extremity dose: 50 rem = 0.5 Sv = 500 mSv.
Household contact exposure: < 0.5 rem (5 mSv); child < 0.1 rem (1 mSv).
Yellow radiation sign: Caution radiation area; personnel dosimetry required.

Written Directive required for

30 µCi I-131 or 1.11MBq.

Disposal of Radioactive Material

1.

Monitor surface of each container.
2.

Survey surface with Geiger counter, < 0.05 mrem/h.
3.

Remove shields to measure properly.
4.

Remove labeling.
5.

Record day collected and disposal data.

Minor Spill (Major Spill Is Above These Values)

Tl-201, Tc-99m <100 mCi.
I-131 < 1 mCi.
I-123, In-111, Ga-67 < 10 mCi.

Procedure for Minor Spills

1.

Stop work, and evacuate all personals.
2.

Use gloves.
3.

Absorbent paper and label with “Caution Radiation Material.”
4.

Transfer to radiation waste.
5.

Survey (continue to clean until no counts are detected using Geiger counter).
6.

Survey body (clothing, shoes, gloves etc.).
7.

Report to radiation safety officer (RSO).

Major Spills

Call RSO.

Medical Event

(NRC 10 CFR Part 35.3045)

Definition: An event takes place upon administration of wrong dose (not within ±20 % of prescribed dose; some states or institutions require ±10 % with therapeutic agents); wrong radiotracer, wrong route of administration, wrong patient, wrong treatment, and leaking seal source.
Reportable event: Administration resulting in whole-body exposure of >0.05 Sv (5 rem) effective dose equivalent or 0.5 Sv (50 rem) to an organ or tissue and skin. Must be reported by telephone call within 24 h and notified in writing within 15 days.
Recordable event: Administration resulting in whole-body exposure of <0.05 Sv (5 rem) effective dose equivalent and 0.5 Sv (50 rem) to an organ or tissue and skin.

Package Safety and Unpacking

1.

Must unpack radioactive shipments within 3 h of receipt.
2.

Survey surface with Geiger–Muller counter.
3.

Wipe test 100 cm² of box surface.
4.

Remove vial containing the radiopharmaceutical.

Radioactive Labels

White I <0.5 mrem/h at 1 m.
Yellow II < 50 mrem/h at surface.
<1 mrem/h at 1 m.
Yellow III < 200 mrem/h at surface.
<10 mrem/h at 1 m.

Breast-Feeding Guidelines*

I-131 and Ga-67 – For I-131, complete cessation of breast-feeding for this child.
Avoid Ga-67 scan on a breast-feeding patient due to high breast radiation dose.
I-123 (cyclotron produced therefore not contaminated with I-124): Pump and dump for 48 h.
Tl-201: Pump and dump for 96 h.
Tc-99m: Pump and dump for 12 h (Tc-99m pertechnetate, 4 h only).

2 Radionuclide Decay

Radionuclide decay graph

Radionuclide decay scheme. EC electron capture, IT isomeric transition (originated from the nucleus)

Radionuclide decay table

Tracer	Half-life	Production	Decay	g-ray E (Kev)
Co-57	270.9 days	Cyclotron	EC	122 (85.6 %)
F-18	109.8 min	Cyclotron	β+	511
Ga-67	78.3 h	Cyclotron	EC	91 (3.6 %) 185 (23.5 %) 300 (4.4 %) 394 (4.4 %)
In-111	2.8 days	Cyclotron	EC	172 (89.6 %) 247 (94 %)
I-123	13.2 h	Cyclotron	EC	159 (83.0 %)
I-125	60 days	Nuclear reactor	EC	35 (7 %)
I-131	8 days	Nuclear reactor	β−	364 (81.8 %)
Mo-99	66 h	Nuclear reactor	β−	740 (13.6 %) 778 (4.7 %)
N-13	10 min	Cyclotron	β+	511
0–15	2 s	Cyclotron	β+	511
P-32	14.3 days	Nuclear reactor	β−	None
Rb-82	76 s	⁸²Sr. generator	β+ EC	511 776 (15 %) – prompt gamma
Sm-153	47 h	Nuclear reactor	β−, γ	103 (28 %)
Sr-89	50.5 days	Nuclear reactor	β−	None
Tc-99m	6 h	⁹⁹Mo generator	IT	140
Tl-201	73.5 h	Cyclotron	EC	Mercury X-ray 69–80
Xenon-131	5.2 days	Nuclear reactor	β−	81 (36.6 %)
Y-90	64.5 h	Nuclear reactor	β-	Bremsstrahlung (X-rays)
Ra-223	11.4 days	Decay of uranium-235	α	None

3 Flash Facts: Radiation Biology

Units

R = roentgen = gamma- or X-ray radiation in air (not tissue).
REM = Roentgen equivalent man = normalized radiation dose in a tissue to account for biological effects.
1 g-ray = 1 J/kg tissue (absorbed) = 100 rad.
Q = radiation type weighting factors; photons, electrons, betas, and positrons, Q = 1; protons > 2 MeV, Q = 5; neutrons, Q = 5–10; alpha particles, Q = 20.
W = organ tissue weighting factors summed over all exposed organs to compute an REM or effective dose in sievert

Cell Cycle Sensitivity

S < G1 < G2 < M.

Oxygen-Enhancing Ratio (OER)

Enhancing of radiation damage by adding O₂ to the matrix.

LD 50/30

Lethal dose required to kill 50 % of population in 30 day. Humans’ lethal dose is measured in 60 days. LD 50/60 = 3–5 Gy for human.

Stochastic Effect

Probability that radiation will cause damage = dose dependent

Nonstochastic (Deterministic)

Describe cause and effect relationships between radiation and damage. Have a threshold below which has no side effect. Once threshold is crossed, diseases will develop (2 Gy to eye = cataract).

Basic Science Formulas

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