The key difference of MRI from CT or PET is that it does not require the use of ionizing radiation. When exposed to magnetic field, hydrogen atom resonance at a certain frequency and emit electromagnetic radiation, this is dependent of the hydrogen in various tissues, so this is how MRI create images.
The correct answers are:
Contrast is achieved in MRI by different magnetic properties water across tissues.
MRI uses a combination of magnetic fields and radio frequency to detect hydrogen atoms in water molecules.
Because MRI use magnetic resonance, it does not need radioactivity or fluorescent properties. Material with strong magnetic properties are often heavy metal and is therefore toxic, we need chelator to make sure it does not harm the subject.
The correct answers are:
MRI probes are composed of heavy metal atoms can be used as tiny magnets
MRI probes are surrounded by a chelator that shields the body from the toxicity of heavy metal and promote their excretion by the kidneys.
There are millions of patients of thrombus, so it is not rare, it is too much blood clot, so it cause problem by blockage, not bleeding. Stroke/Hypoxia are caused because there is no/reduced blood flow, not by bleeding.
Therefore the correct answers are:
A thrombus is a blood clot that forms in arteries or veins of the body.
A thrombus can lead to vessel blockage, causing hypoxia in coronary arteries.
The idea of phage screen is to use in-vitro selection of bacteriophages to find out which gene leads to protein that binds. This is a mouthful of jargons. Here is what it means:
Bacteriophages are viruses that infect bacteria. Some of these bacteriophages binds to fibrinogen, these are unwanted, so we eliminate them, some of these bacteriophages does not bind to fibrin, these are also unwanted, so we eliminate them as well. That is selection. These bacteriophages are cultured again and we repeat this experiment again and again, that allow evolution to pick the best gene that binds to fibrin but not fibrinogen.
We wanted to have as many iterations as possible to give good specificity, the experiment can help us to find which gene can bind to fibrin specifically. The key tricky part is the second and the third options, turn out, none of them are correct - Bacteriophages is neither eukaryotic virus nor siRNA.
The correct answers are:
Repeated cycling of fibrinogen and fibrin binding experiments improve phage sensitivity and specificity to fibrin.
The main advantage of using a phage library is linking the genetic code of a protein to its protein-binding properties.
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