Nuclear Medicine and Isotope Therapy

Questions and Answers

To reduce the background activity from external sources

662-keV gamma ray of 137Cs

The efficiency decreases with the square of the distance

To select the energy range of interest Signup and view all the answers

It allows for more accurate measurements of thyroid uptake Signup and view all the answers

The thyroid probe uses a collimator, while the well counter does not Signup and view all the answers

To detect gamma rays from the thyroid Signup and view all the answers

It decreases the counting rate Signup and view all the answers

To select the energy range of interest Signup and view all the answers

It is more portable than a stationary stand Signup and view all the answers

Study Notes

Examples of radioactive tracers include technetium-99, thallium-201, iodine-131, and sodium-24.
These tracers can be used to target specific organs, such as the heart, liver, and lungs, for diagnostic and therapeutic purposes.

Attached radionuclides can be delivered to a targeted location, allowing for localized therapeutic radiation with minimal impact on surrounding organs.

In nuclear medicine, examinations can be classified into two types: static and dynamic.
Static examinations involve the accumulation of radiotracers in normal tissues, pathologic lesions, or distribution spaces, resulting in a single image or "snapshot" of the radiopharmaceutical distribution.

Examples of static images include lung scans, spot bone scan images, and thyroid images.

Dynamic examinations can produce images of spatial activity and follow the course of certain processes or flow over time, such as renal filtration and myocardial blood flow.
Dynamic examinations can be used to follow urine excretion in the kidney, for instance.

Attenuation of photons in thyroid tissues reduces the overall detection efficiency of the probe.
Scattered photons in the thyroid gland may interact with the detector, but can be excluded by selecting appropriate discriminator settings.

The depth of the source distribution within the patient is often unknown, which can result in a 10% to 40% difference in recorded counting rate.
Measurements are typically made with the SCA window set on the photopeak of the γ-ray emission to be counted, to minimize the contribution from scattered radiation.

Miniature γ-ray probes are designed for surgical use, particularly for detecting sentinel lymph nodes in patients with breast cancer and melanoma.
These probes are compact and have a collimator that limits the field of view, reducing background activity from outside the thyroid.

The NaI(Tl) probe system consists of a collimated detector mounted on a stand, which can be oriented and positioned over an area of interest on the patient.
The detector is connected to electronics, including a single-channel analyzer (SCA) and a digital counter or computer, used for diagnostic tests for thyroid disease.