Nuclear Medicine Imaging Doses

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Questions and Answers

What is the typical effective dose for a bone scan using Technetium-99m diphosphonates?

15 mSv

5 mSv (correct)

10 mSv

0.5 mSv

What is the purpose of checking the accuracy of the dose calibrator?

To verify the half-life of the radionuclide

To ensure the correct effective dose calculation

To ensure the correct activity of the radionuclide (correct)

To detect any contamination of the radionuclide

Which radionuclide is used for tumour imaging and delivers a higher effective dose?

Gallium-67 citrate (correct)

Technetium-99m diphosphonates

Iodine-123 MIBG

Indium-111 leucocytes

What is the typical activity of Technetium-99m MIBI for heart imaging?

400 MBq Signup and view all the answers

Why is it necessary to check and record the activity before administration?

To ensure the correct administration of the radionuclide Signup and view all the answers

What is recommended for patients to minimize their radiation dose?

Drink a good deal of water and empty the bladder frequently Signup and view all the answers

What is the general guideline for female patients who undergo diagnostic examinations with long-lived radionuclides?

Avoid conception for an appropriate period following administration Signup and view all the answers

Why is it important to handle radionuclides with care?

To minimize the risk of internal radiation from accidental ingestion or inhalation Signup and view all the answers

What is a consideration for breastfeeding mothers who undergo diagnostic examinations with radionuclides?

They should seek advice on interrupting breastfeeding Signup and view all the answers

What should be avoided when handling radionuclides?

Contamination of the environment Signup and view all the answers

What is the primary risk associated with radionuclides in a nuclear medicine facility?

Contamination Signup and view all the answers

What is the purpose of separating patients in the waiting area?

To minimize the effect of background radiation Signup and view all the answers

How can departmental layout reduce the effect of background radiation?

By making use of the inverse square law Signup and view all the answers

What is the primary principle of personal protection when handling radionuclides?

Use of distance, shielding, and time Signup and view all the answers

Why should staff only enter areas with radioactivity when necessary?

To minimize exposure to external radiation Signup and view all the answers

Why are syringes protected by heavy metal, tungsten, or lead glass sleeves?

To prevent radiation exposure to the hands Signup and view all the answers

What should be done with syringes before injection?

Vent them into swabs or closed containers Signup and view all the answers

Why are waterproof surgical gloves worn when handling radionuclides?

To prevent accidental ingestion of the radionuclide Signup and view all the answers

What is done to the work surfaces and hands after handling radionuclides?

They are monitored for radioactive contamination Signup and view all the answers

What is done to the air in radiopharmacies?

It is monitored for radioactive contamination Signup and view all the answers

What is the purpose of tissue-weighting factors in calculating the effective dose?

To account for differing organ sensitivities to irradiation Signup and view all the answers

What is the unit of the effective dose?

Sievert (Sv) Signup and view all the answers

What is the typical effective dose range for most nuclear medicine investigations?

Less than 5mSv Signup and view all the answers

What is the process of calculating the effective dose?

Weighting each organ absorbed dose and summing to give the effective dose Signup and view all the answers

What is the purpose of calculating the effective dose?

To determine the risk associated with radiation exposure Signup and view all the answers

What determines the absorbed dose delivered to an organ by the activity within it?

The effective half-life of the activity in the organ and the energy of beta and gamma radiation Signup and view all the answers

What happens to the energy of beta rays in an organ?

Almost all the energy is deposited inside the organ, and very little escapes Signup and view all the answers

What is a key difference between dose delivery in radionuclide examinations and X-ray imaging?

The dose delivered by a radionuclide examination is unaffected by the number of images taken Signup and view all the answers

What happens to the energy of gamma rays in an organ?

Some energy is deposited in the organ, and some leaves it Signup and view all the answers

Why do source organs act as sources of irradiation for other tissues in the body?

Because they act as a source of radiation for other tissues Signup and view all the answers

What is the primary purpose of a SPECT/CT machine?

To perform daily nuclear medicine procedures Signup and view all the answers

What is the most common positron emitter used in PET?

18F Signup and view all the answers

What happens when 18F emits a positron?

It travels 2 mm through the patient Signup and view all the answers

What is the energy of the photons emitted after positron annihilation?

511 keV Signup and view all the answers

What type of detectors are often used in PET cameras?

Scintillation detectors Signup and view all the answers

What material is often used to make PET detectors?

All of the above Signup and view all the answers

What is a desirable property of an ideal PET detector material?

High detection efficiency Signup and view all the answers

What is the purpose of a PET camera?

To image the body using positron-emitting radionuclides Signup and view all the answers

What is a key feature of PET detectors?

They are composed of a very large number of solid scintillation detectors Signup and view all the answers

What is the function of the ring or polygon in a PET camera?

To surround the patient and detect photons Signup and view all the answers

Study Notes

Patient Preparation and Fetal Dose

Patients should drink plenty of water and empty their bladders frequently to minimize radiation dose to the gonads and pelvic bone marrow.
Female patients should avoid conception for a certain period after receiving long-lived diagnostic radionuclides.
Male patients do not need special advice regarding diagnostic examinations.

Handling Radionuclides

Radionuclides pose external and internal radiation hazards, and contamination of the environment, workplace, and persons must be avoided.
Accidental ingestion or inhalation of radionuclides or entry through wounds can occur.
Controlling the spread of radioactive materials is crucial.

Typical Radionuclide Administrations and Doses

Bone: Technetium-99m diphosphonates (600 MBq, 5 mSv)
Lung Ventilation: Technetium-99m DTPA aerosol and Krypton-81m gas (80 and 6000 MBq, 0.5 and 0.1 mSv)
Kidney: Technetium-99m DTPA gluconate and Technetium-99m MAG3 (300 and 100 MBq, 2 and 0.7 mSv)
Infection: Gallium-67 citrate and Indium-111 leucocytes (150 and 20 MBq, 15 and 7 mSv)
Tumor: Iodine-123 MIBG (400 MBq, 5 mSv)
Thyroid: Iodine-123 iodide (20 MBq, 4 mSv)
Heart: Technetium-99m MIBI and Thallium-201 chloride (400 and 80 MBq, 3 and 18 mSv)
Brain: Fluorine-18 FDG (400 MBq, 8 mSv)

Dose to the Patient

The activity administered, fraction taken up by the organ, effective half-life, and energy of beta and gamma radiation affect the absorbed dose.
The dose to an organ also depends on how much energy escapes from the organ and irradiates other tissues.

Effective Dose to the Body

The effective dose (E) has the unit sievert (Sv) and is calculated using the differing sensitivities of organs and tissues to irradiation.
The effective dose is a measure of risk and is unaffected by the number of images taken.

Precautions in Handling Radionuclides

A nuclear medicine facility should have separate areas for radionuclide preparation and storage, patient injection, waiting, imaging, and temporary waste storage.
Patients containing radioactivity should be spaced apart in the waiting area.
Staff should use distance, shielding, and time to minimize radiation exposure.
Radionuclides are contained in shielded generators or lead pots, and long-handled forceps are used for handling.

Personal Protection

Lead barriers, heavy metal or lead glass sleeves, and waterproof surgical gloves are used for personal protection.
Hands and work surfaces are monitored for radioactive contamination, and the air in radiopharmacies is also monitored.
Staff may be monitored for internal contamination, and swabs are taken from the radiopharmacy workstation to monitor for radioactive and bacterial contamination.

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Description

This quiz covers typical radionuclide administrations for adults, including bone, lung ventilation, and lung perfusion imaging, and their corresponding effective doses. It highlights the use of imaging modalities like Technetium-99m and Krypton-81m.