CT

Question 1

The basics

Answer 1

The narrow beam of x-rays is aimed at a patient and quickly rotated around the body, producing signals that are processed by the machine’s computer to generate cross-sectional images—or “slices”—of the body. These slices are called tomographic images and contain more detailed information than conventional x-rays. Once several successive slices are collected by the machine’s computer, they can be digitally “stacked”

Question 2

How does it work?

Answer 2

Unlike a conventional x-ray—which uses a fixed x-ray tube—a CT scanner uses a motorized x-ray source that rotates around the circular opening of a doughnut-shaped structure called a gantry.

Question 3

During a CT scan

Answer 3

During a CT scan, the patient lies on a bed that slowly moves through the gantry while the x-ray tube rotates around the patient, shooting narrow beams of x-rays through the body. Instead of film, CT scanners use special digital x-ray detectors, which are located directly opposite the x-ray source.

Question 4

What can you use CT scans for?

Answer 4

CT scans can be used to identify disease or injury within various regions of the body. For example, CT has become a useful screening tool for detecting possible tumors or lesions within the abdomen. A CT scan of the heart may be ordered when various types of heart disease or abnormalities are suspected. CT can also be used to image the head to locate injuries, tumors, clots leading to stroke, hemorrhage, and other conditions. It can image the lungs to reveal the presence of tumors, pulmonary embolisms (blood clots), excess fluid, and other conditions such as emphysema or pneumonia. A CT scan is particularly useful when imaging complex bone fractures, severely eroded joints, or bone tumors since it usually produces more detail than would be possible with a conventional x-ray.

Question 5

Risks

Answer 5

X-rays produce ionizing radiation. Ionizing radiation has the potential to cause biological effects in living tissue. This is a risk that increases with the number of exposures added up over the life of an individual.

Question 6

Factors affecting

Answer 6

Factors affecting image production in CT:

• exposure/intensity.
• Compton scattering.
• SNR.
• efficiency.

Question 7

Advantages

Answer 7

• CT scans can be used to identify disease or injury within various regions of the body.
• screening tool for detecting possible tumors or lesions within the abdomen.
• heart disease or abnormalities are suspected.
• CT head - injuries, tumors, clots leading to stroke, hemorrhage, and other conditions.
• CT thorax - tumors, pulmonary embolisms (blood clots), excess fluid, and other conditions such as emphysema or pneumonia.

Question 8

Disadvantages

Answer 8

Disadvantages:
ionizing things.
contrast – allergy, anaphylaxis – bad, kidney function assessment, reduces kidney function since contrast e.g. gadolinium is excreted exlusively by the kidneys.