Imaging in Inflammatory Disorders and Infection

Question 1

Positron Emission Tomography

Answer 1

Molecular imaging that uses radionuclides that decay by positron (proton plus neutron) emission to image biologically interesting processes and for absolute quantitation but requires arterial sampling. Tracers are custom made and can detect brain, cancer, heart disease and Alzheimers. Most common tracer is 18F-fluorodeoxyglucose which is radiolabelled sugar (glucose) molecule. It’s used to determine sites of abnormal glucose metabolism and can be used to characterise and localise many types of tumour.

Question 2

Characters of the ideal isotope for labelling

Answer 2

1. Half-life similar to length of examination
2. Gamma emitter
3. 50-300 KeV; energy of gamma rays
4. Radionucleide should be readily available at hospital site.
5. Easily bound to pharmaceutical component
6. Radiopharmaceutical should be simple to prepare and should be eliminated in half-life similar to examination time.

Question 3

Gamma camera

Answer 3

Nuclear energy inside the radioactive nucleus emits gamma electromagnetic energy from the patient. This produces light electromagnetic energy as the image crystal produces flashes of light each time a gamma photon hits it, This produces electrical energy and displays the image. The image produced is known as scintography. The radionuclide used is 99m Technecium; bone - hydroxy-diphosphonate, kidney - dimercapto-succinic acid, brain - hexamethyl-propine amine oxime, lung - macroaggregated albumin.

Question 4

SPECT

Answer 4

Single photon emission computed tomography. A CT version of nuclear medicine in which gamma cameras rotate around an area. Routinely used for brain and cardiac studies.

Question 5

Common dose “currency”

Answer 5

Radiation dose for all nuclear medicine and molecular imaging procedures should be optimised so that the patient receives the smallest possible amount to provide diagnostic information.

Question 6

Role of diagnostic imaging in the diagnosis, monitoring and treatment of inflammatory/infectious conditions

Answer 6

Nuclear medicine imaging techniques detect biological and biochemical changes in the earliest phases of disease thereby allowing the clinician to promptly identify the ailment and to establish the best therapeutic approach. E.g lung - PE, bone - osteomyelitis, cancer - diagnosis, staging, follow ups, Chrohn’s disease - baseline and follow ups, kidney function, Alzheimer/posterior cortical atrophy, Parkinsons’, myocardial perfusion. Fluorodeoxyglucose (FDG) can be used for brain, myocardium, stomach, liver, spleen, colon, urinary tract. Inflammatory disorders include rheumatoid arthritis, aortitis and ulcerative colitis.