Detailed anatomical drawings of the human body first became available in the fifteenth and sixteenth centuries; however, it was not until the end of the nineteenth century, and the discovery of X-rays, that anatomists and physicians discovered non-surgical methods to look inside a living body. Since then, many other techniques, including CT scans, MRI scans, PET scans, and ultrasonography, have been developed, providing more accurate and detailed views of the form and function of the human body.
computed tomography (CT)
medical imaging technique in which a computer-enhanced cross-sectional X-ray image is obtained
magnetic resonance imaging (MRI)
medical imaging technique in which a device generates a magnetic field to obtain detailed sectional images of the internal structures of the body
positron emission tomography (PET)
medical imaging technique in which radiopharmaceuticals are traced to reveal metabolic and physiological functions in tissues
ultrasonography
application of ultrasonic waves to visualize subcutaneous body structures such as tendons and organs
X-ray
form of high energy electromagnetic radiation with a short wavelength capable of penetrating solids and ionizing gases; used in medicine as a diagnostic aid to visualize body structures such as bones
A CT or CAT scan relies on a circling scanner that revolves around the patient’s body. Watch this video to learn more about CT and CAT scans. What type of radiation does a CT scanner use?
X-rays.
A patient undergoing an MRI is surrounded by a tube-shaped scanner. Watch this video to learn more about MRIs. What is the function of magnets in an MRI?
The magnets induce tissue to emit radio signals that can show differences between different types of tissue.
PET relies on radioactive substances administered several minutes before the scan. Watch this video to learn more about PET. How is PET used in chemotherapy?
PET scans can indicate how patients are responding to chemotherapy.
1. In 1901, Wilhelm Röntgen was the first person to win the Nobel Prize for physics. For what discovery did he win?
A) nuclear physics
B) radiopharmaceuticals
C) the link between radiation and cancer
D) X-rays
D
2. Which of the following imaging techniques would be best to use to study the uptake of nutrients by rapidly multiplying cancer cells?
A) CT
B) MRI
C) PET
D) ultrasonography
C
3. Which of the following imaging studies can be used most safely during pregnancy?
A) CT scans
B) PET scans
C) ultrasounds
D) X-rays
C
4. What are two major disadvantages of MRI scans?
A) release of radiation and poor quality images
B) high cost and the need for shielding from the magnetic signals
C) can only view metabolically active tissues and inadequate availability of equipment
D) release of radiation and the need for a patient to be confined to metal tube for up to 30 minutes
B
1. Which medical imaging technique is most dangerous to use repeatedly, and why?
CT scanning subjects patients to much higher levels of radiation than X-rays, and should not be performed repeatedly.
2. Explain why ultrasound imaging is the technique of choice for studying fetal growth and development.
Ultrasonography does not expose a mother or fetus to radiation, to radiopharmaceuticals, or to magnetic fields. At this time, there are no known medical risks of ultrasonography.