Cancer Imaging (supplementary) (DONE) Flashcards
Biomarkers
A biological molecule found in blood, other body fluids, or tissues that is a sign of a normal or abnormal process, or of a condition or disease
May be used to see how well the body responds to a treatment
Two main types of biomarker
Invasive- tissue and blood samples
Non-invasive- imaging technologies
(Variety of flavours- predisposition, diagnostic etc. )
MRI
A powerful and widely used scanning technique for imaging solid tumours
Uses powerful magnetic fields and radio waves to generate 3D images of tissue
Highlights differences in water content and blood flow between tissues
Contrast agent often administered to accentuate differences in blood flow
Harmless, high resolution images, high cost, low throughput, low sensitivity
PET
Non-invasive, highly sensitive scanning technique used to measure tissue uptake of radiolabelled tracer (18F)
Rapidly emerging as the imaging technique of choice for in vivo/clinical studies in oncology
How does PET work?
Positron ejected from nucleus
Positron loses energy from scatter in tissue
Two gamma rays are produced 180 degrees apart as the positron loses energy and annihilates with an electron
How do cancer cells make ATP?
Cellular ATP production via glycolysis is a cancer hallmark
Hypoxic cells under a fundamental glycolytic switch
Persistent aerobic glycolysis, the Warburg effect
Why does aerobic glycolysis in cancer cells make FDG the best molecule for PET imaging?
Cancer cells are glucose hungry
FDG taken up selectively by cancer cells, phosphorylated but not further biotransformed, trapped within cancer cells
Once trapped within cancer cells, can image using PET for cancer detection, staging, treatment planning and monitoring of response to therapy
What can 18F be used to detect (biomarkers)?
Uncontrolled proliferation Insensitivity to tumour suppressor signals Evasion of apoptosis Angiogenesis Unlimited replicative potential Invasion/metastasis Aerobic glycolysis Adaptation for survival under hypoxic conditions
Other 18F labelled imaging biomarkers for PET
In principle, any molecule (small or large) can be labelled with a positron-emitting tracer such as 18F
Limited by short radioactive half lives and limited chemical technologies in some cases
Single Photon Emission Computed Tomography
Similar to PET- uses radioactive tracers and a scanner
Similar high sensitivity and resolution compared to PET
Small amount of labelled drug injected into a vein and scanner records areas of cellular uptake, giving information about blood flow and metabolism within the body
Most common radionuclide is 99Tc- medium gamma ray energy suitable for detection and half life compatible with patient studies (6h)
Needs to be bound to a chelating agent
