Nuclear medicine

What is nuclear medicine

What is nuclear medicine

Uses radioactive tracers to assess the function of organs and to diagnose and treat disease. Photons emitted in all directions in body therefore high degree of collimation needed. Made usually from tungsten or lead to provide high absorption probability

Collimaters

Collimaters are an array of hexagonally shaped holes drilled or cast in tungsten or lead. The purpose of Collimaters are to filter out the extra photons to provide a diagnostic image.

Parallel hole (type of Collimater)

Used for wider/ bigger body parts

Pin hole (type of collimater )

Used for small organs to make them appear bigger

Converging Collimaters

Similar to pin hole but on a wider scale

Diverging Collimaters

Have holes in conical array with the center lines of the holes intersecting at a focal point behind collimator

PET pros and cons

Advantage: higher sensitivity and better spatial resolution

Disadvantage: not readily available and expensive

Nal crystals

It receives / interacts with gamma rays emitted from the patient and converts them to visible light and UV photons

Static - image aquistion

Stationary image aquistion where the machine collects the number of counts. Patient stands in front of the board and the machine counts the number of photons being emitted

Dynamic- image aquistion

Quick set of images taken consecutively overtime.

Whole body

The camera moves over one plane

Gated acquisition

Usually times to the heart rate to observe the wall motion using ECG

spect

Single photon emission computerised tomography

How does Spect work

• Can be fused with other modalities usually ct or mri

• Uses radiotracer and special camera to create 3d image

ALARP

As low as reasonably practicable (radiation protection)

4 principles of radiation protection

Time - spend the least amount of time with patient as much as possible

Distance - maximize the distance from the source of radiation

Shielding - use radiation shielding where practicable. Use PPE and dose monitors

Containment - for unsealed radiotactive materials use containment to minimise risk of containmenation spread and avoid inhalation

Tc-99

Is obtained from technetium generators though a process called elution. Its mixed with cold kits depending on what procedure is being performed

Pros of tc-99

• cheap

• Easy to produce

• Shor half life

• Pure gamma rays

ARSAC

Means administration of radioactive substance advisory commitee

Commitee provides guidance and sets out DRLS (diagnostic radiation levels)

SPECT pros and cons

Advantages; more available and less radiation dose to patient

Disadvantage; longer imaging times due to longer half life

FDG-

Glucose analogue, is useful because increased glucose metabolism occurs in most cancers due to expression of membrane glucose transports

PET

Detectio of the radiation given off radiotracer as collects in different part of body

4 components found in gamma camera

Crystals , light guide, digitiser, Collimaters

Describe how gamma rays are produced in pet scan

Gamma rays used for imaging are produced when a position collides with an electron inside the patients body..