The relies upon radioactive sugar that is injected into the body to form representations of the brain.

Answer is Positron Emission Tomography.

Positron emission tomography (PET) is an imaging test based on nuclear medicine. In PET imaging a small amount of liquid radioactive material such as simple sugar (glucose) called fluorodeoxyglucose (FDG) is injected into the bloodstream. It is accumulated in the body and emit gamma rays which are  detected by PET. Many diseases such as cancers, brain diseases and heart diseases are diagnosed by the PET imaging.

The brain imaging method called positron-emission tomography (PET) relies upon radioactive sugar that is injected into the body to form representations of the brain.

It is functional imaging technique that is used to observe metabolic processes in the brain (or some other part of the body) in order to the diagnose the disease. The system detects pairs of γ- rays emitted indirectly by a positron-emitting radionuclide, which is introduced into the body on a biologically active molecule called a radioactive tracer. Commonly used radioactive tracer is an analogue of glucose -fludeoxyglucose (FDG).

the answer that best describes the relative refractory period in the neuron is the resting membrane potential is restored, but concentrations of sodium and potassium are not restored to their original state.

the refractory period is the time during which another stimulus given to the neuron will not lead to a second potential. thus, because na+ channels are inactivated during this time, additional depolarizing stimuli do not lead to new action potentials.  

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thrombocytopenia, which is a deficiency in blood platelets, can cause bleeding and bruising in the dermis similar to senile purpura. other possible causes include: exposure to ultraviolet rays and aging skin are common causes of senile purpura. senile purpura may also be a sign of collagen loss in the skin and bones.