Nuc Med - Week 8

What are the scintigraphic functions of a gamma camera?

• Planar/Static Imaging

• Dynamic Imaging

• Whole Body Imaging

• SPECT Imaging

How is pixel size calculated?

Image size of the area of interest (mm)/matrix size

What is a bar phantom?

Bar phantoms are testing tool that is placed on a collimator head of a gamma camera to test its spatial resolution.

What is planar/static imaging?

A 2D image of the radiation distribution in the area of interest at any point in time. This typically takes several minutes and can be sequential imaging, which is several images at timed intervals, or a number of different angles.

What is dynamic imaging?

Sequence of 2D images at timed intervals that depicts physiological functioning by tracking the distribution of the tracer.

How does dynamic imaging change depending on the area of interest?

Rapid bodily processes such as arterial perfusion require a fast frame rate (eg. 3 seconds per frame) compared to slower bodily processes such as hepatobilliary processes where the frame rate can be slower (eg. 1 minute per frame).

What are the 3 phases of dynamic imaging?

Phase 1 - administration of tracer into a vein, that then travels to the heart, lungs and then target organ via systemic circulation

Phase 2 - tracer is taken up by the target organ

Phase 3 - delayed imaging 2-4 hours after administeration

What is a Time Activity Curve (TAC)?

A graph used in dynamic imaging that represents radioactivity within a tissue over time.

What is whole body imaging and what is it typically used for?

Image of the entire body that is typically taken for patients with systemic diseases.

How does whole body imaging work?

There are static dual camera heads from the posterior and anterior and the bed moves in or out of the gantry.

What is SPECT imaging?

3D images of the area of interest that show physiological functioning by tracking metabolic activity.

Why is SPECT typically fused with CT scans?

• SPECT lacks the ability to capture anatomy, therefore CT can provide anatomical data that allows for the precise locating of abnormal activity

• CT also allows for attenuation correction in which tissue density and attenuation coefficients are determined to compensate for attenuation that could possibly cause artifacts within the images.

How does SPECT work?

There are dual camera heads that each rotate180 degrees and take 2D images at varying angles which are then used to create 3D images.

What is Maximum Intensity Projection (MIP)?

A 3D imaging technique that is used to highlight the highest-density point in a structure.

What are the characteristics of an ideal radiopharmaceuitcal?

• Short half-life

• Emits gamma rays only (no beta or alpha particles)

• Is readily available, easy to produce and cost-effective

• High labelling efficiency at favourable conditions

• Emissions are between 100-200 keV

• Specific to the target organ

• Non-toxic and no side effects

What type of radiation is used for theranostics?

Beta emitters as they have a balance of ionisation and penetration for targeting only tumour cells.