Week 3: Diagnostic Imaging

Question 1

What does diagnostic imaging mean?

Answer 1

Techniques and processes used to create images of the human body for clinical purposes

Question 2

Who devised x-ray technology?

Answer 2

Wilhelm Roentgen discovered the activation of fluorescent paper by x-rays, and the ability of x-rays to move through tissues

Question 3

How are x-rays attenuated by the body? How does this appear in x-ray imaging?

Answer 3

Tissues “slow down” x-rays based on density–more density = slower motion. The denser the tissue, the fewer x-rays pass through, leaving white on activated paper

Question 4

What is the wavelength of an x-ray? How do we remember this?

Answer 4

X = 10, and x-rays have a wavelength of 10^-10m

Question 5

How do we describe subject placement for radiography?

Answer 5

You refer to the side receiving the rays first, then the side closest to the film receiving the rays. You normally want to put the object of study closest to the film.

Ex.: anterior-posterior (AP) vs. posterior-anterior (PA)

Question 6

What is used to differentiate tissues from one another on x-rays?

Answer 6

Contrast agents allow us to highlight specific structures. Contrast agents usually have high attenuation to make the structures in between them and the x-ray stand out more than usual.

Question 7

What is used as a contrast agent for the bowels?

Answer 7

Barium sulfate

Question 8

What is used as a contrast agent for arteries and veins?

Answer 8

Iodine

Question 9

What can iodine be used to assess as far as renal issues?

Answer 9

Perfusion of blood vessels by iodine allows docs to look for kidney stones

Question 10

What is the most commonly used form of imaging worldwide, and how does it work?

Answer 10

Ultrasound, which exposes parts of the body to high frequency soundwaves. These are then reflected back and interpreted by a computer, which displays a real-time picture.

Question 11

Why are ultrasounds so useful? What are the potential side effects?

Answer 11

Inexpensive, portable, and no radiation so LITTLE harm to the patient

Two potential effects:

increases inflammatory response

can heat soft tissue

Question 12

What is “the modern” ultrasound used for?

Answer 12

Assessing fetuses

Assessing eyes, neck, soft tissues, and peripheral musculoskeletal system

Probes into GI system

Endocavity ultrasound to assess genital tract in women

Transrectal ultrasound to image the prostate in men

Question 13

Why is doppler ultrasound useful?

Answer 13

Can assess the speed and direction (velocity) of bloodflow in arteries, can assess obstructions and flow blockage

Question 14

What is a CT scan?

Answer 14

It is a computed tomography scan, and it is really just a multidimensional x-ray. X-ray tube passes around the body and a series of images are obtained. This produces a 3-D image using a compilation of 2-D images.

Question 15

What is the orientation of the image produced by a CT scan, and what does this assume about how the scan is taken?

Answer 15

Anterior is at the top, posterior is at the bottom, pt right is on the left, pt left is on the right–this, put together, means the pt goes headfirst into the tube

Question 16

What are MRIs?

Answer 16

Uses magnets, radio pulse waves, and computers to analyze the free protons in the hydrogen nuclei in molecules of water. A large magnet aligns all of the water molecules, a pulse knocks them off kilter, then energy is released as they realign. This released energy is what is measured by the MRI machine.

Question 17

Compare and contrast MRIs and CT scans?

Answer 17

CTs use ionizing radiation, so they work best for examining tissues of higher density.

MRI works best for analyzing greater contrast between surrounding tissues. This allows for better visualization of tumors and other abnormalities.

MRIs also use non-ionizing radio waves, which are less harmful for patients who will need similar tests in the future.

CTs are less expensive and are more widely available.

Question 18

What is nuclear medicine imaging?

Answer 18

A radiotracer is entered into the body and/or organ of interest.

There, it gives off energy in the form of gamma radiation. The energy is detected and analyzed, and an image is detected.

It is different because it shows physiologic function instead of static anatomy.

Question 19

What is PET? What is used during this process?

Answer 19

Positron emission tomography is an imaging modality that allows us to detect positron-emitting radionuclides via the use of metabolically-active radionuclides.

A positron is an anti-electron, a positively charged form of antimatter. They are emitted from the decay of proton-rich radionuclides.

Fluorodeoxyglucose (FDG) is an example of a PET radionuclide, which is metabolized much like glucose in the body. This allows us to see metabolic and anatomic information.