Final answer:
A computer assembles many 2D x-rays to form a 3D image of the brain using a technique known as a Computerized Tomography (CT) scan. This method captures multiple x-ray images at various angles and uses computer processing to create a detailed 3D representation of brain structures, helpful for identifying tumors or atrophy. The correct option is D.
Step-by-step explanation:
When a computer assembles many 2D x-rays to form a 3D image of the brain, the process is known as Computerized Tomography (CT) scan. This technique involves taking multiple x-ray images of a section of the body or brain from different angles.
The x-rays pass through body tissues at varying rates based on tissue density, allowing a computer to generate a 3D image of the scanned area. CT scans are highly valuable in medical diagnostics because they can reveal the presence of tumors, brain atrophy, and other structural anomalies in the brain.
Other imaging techniques mentioned, such as Positron Emission Tomography (PET) scans and functional Magnetic Resonance Imaging (fMRI), use different methodologies.
PET scans involve the use of a radioactive tracer to map brain activity, whereas fMRIs utilize magnetic fields and radio waves to measure changes in blood flow and oxygen levels, indicating brain activity. However, the direct answer to the student's question is the CT scan, as it is the technique that assembles 2D x-rays into a 3D image.