X-rays

Question 1

Define radiation:

Answer 1

Transmission of energy through space.

Question 2

What kinds of rays are involved with medical radiation?

Answer 2

X-rays and gamma rays

Question 3

Why is it called “ionizing” radiation?

Answer 3

Has enough energy to knock electrons loose, creating ion atoms or molecules.

Question 4

Which end of the spectrum has shorter wavelength?

Answer 4

Gamma rays, X-rays, and upper region of ultraviolet spectrum.

Question 5

Which rays have higher energy?

Answer 5

Higher frequencies (ultraviolet and up) have more energy.

Question 6

Where does radiation come from in nature?

Answer 6

Cosmic rays, terrestrial radiation from Earth deposits, and radon.

Question 7

Where do we get most of the radiation we get in our lives?

Answer 7

Medical radiation is most of our exposure.

Question 8

What are other sources of man-made radiation?

Answer 8

Nuke power, research, industrial sources, certain consumer items.

Question 9

What are some units of measure for radiation? (7 examples)

Answer 9

Bequerels, curies, roentgens, rads, grays, rems, sieverts

Question 10

How much exposure is maximum?

Answer 10

5,000 mrems annually

Question 11

What kinds of harm can excess exposure cause?

Answer 11

Skin burns, radiation sickness, higher cancer risk, genetic damage

Question 12

What does “ALARA” stand for?

Answer 12

As Low As Reasonably Achievable

Use the mimimum possible/ necessary

Question 13

What are the three factors that control the amount of exposure to radiation?

Answer 13

Time, distance, protection (shielding)

Question 14

What is the inverse square law?

Answer 14

Dosage is reduced with the square of the distance (i.e., big reduction in dosage with modest increase of distance: twice as far away from source means 1/4 the intensity).
This is because the energy from a point source is distributed more widely over a 2-dimensional area at each point of distance…

Question 15

What on earth is a Crookes tube?

Answer 15

Glass container, partial vacuum, cathode and anode, cathode rays (electrons) generated by voltage.

Question 16

Who used one to discover X-rays?

Answer 16

Wilhelm Roentgen

Question 17

Who invented the fluoroscope?

Answer 17

Thomas Edison

Question 18

What on earth is a Snook transformer?

Answer 18

Who knows. Works with Coolidge’s tube to produce X-rays.

Question 19

In the X-ray tube, what component emits the electrons?

Answer 19

Cathode emits electrons.

Question 20

What component is hit by the electrons?

Answer 20

The electrons hit the anode (or target).

Question 21

When the electrons hit the anode, what happens to the energy?

Answer 21

Most energy is lost as heat, but some electrons release energy as photons: X-rays.

Question 22

What is a C-arm?

Answer 22

X-ray unit used in cath lab (and portable version elsewhere sometimes).

Question 23

Why that shape of the C-arm?

Answer 23

X-ray emitter is underneath, sensing device is above patient.
C shape facilitates rotating around patient for different projections.

Question 24

How is an X-ray image produced?

Answer 24

Differences in tissue density hold back or allow to pass the X-ray energy; this is registered on film (not any more) or digital sensing plate.

Question 25

What kind of tissue causes light vs. dark areas on the image?

Answer 25

Dense, calcified structures (bone, etc) hold back X-rays;

Soft tissue allows it to pass.

Question 26

What kind of absorption occurs?

Answer 26

Photoelectric absorption

Question 27

What does “opacification” mean?

Answer 27

Making opaque: holding back the X-rays.

Question 28

How accurate are visual assessments of coronary angiograms?

Answer 28

Only sort of accurate.

Question 29

When estimating stenosis, how much variation is there among interpreters?

Answer 29

20% or more variation in estimates of stenosis among interpreters.

Question 30

What are typical categories (ranges) of coronary artery stenosis?

Answer 30

50% or less. 50-75%. 75-95%. Total occlusion.

Question 31

Stenosis of which coronary artery is especially dicey during angiography?

Answer 31

Left main; any obstruction compromises LV acutely.

Question 32

What quantitative measure is provided by the ventriculogram?

Answer 32

EJ: ejection fraction.

Qualitative assessment: wall motion.

Question 33

What complications can result from LV gram? (5 examples given)

Answer 33

Arrhythmia (including asystole), staining, embolism, reaction to contrast, transient hypo-tension.

Question 34

Why on earth would you want to use a septal occluder?

Answer 34

Septal occluders close septal defects (openings).

Question 35

What are some other man-made objects that might show up on a chest X-ray?

Answer 35

New valves (annular rings), pacemakers and or defibrillators, sternal wires, LVAD (left-ventricular assist device), catheters

Question 36

What are a couple of disorders?

Answer 36

Pneumothorax, calcification (arteries, etc.).

Question 37

What characterizes the appearance on X-ray of a myxoma?

Answer 37

It has a highly vascular appearance (blush).

Question 38

What distinguishes fluoroscopy from standard X-ray imaging?

Answer 38

Fluoroscopy is in real time.

Question 39

How does fluoroscopy image quality compare to acquisition mode image quality?

Answer 39

Fluoroscopy image quality is not as good.

Question 40

How does X-ray dosage with fluoroscopy compare to acquisition mode?

Answer 40

X-ray dosage with fluoroscopy is not as high.

Question 41

What is “acquisition mode”?

Answer 41

Higher-intensity X-rays, reducing noise and obtaining higher resolution.

Question 42

What does the image-intensifier do?

Answer 42

Image intensifier converts X-rays to visible light.

Question 43

What are the components (including the patient) of the fluoroscopy imaging chain?

Answer 43

X-ray generator. X-ray tube. Collimator. Filtration. Table. Patient. Grid. Image intensifier. Optical coupling. Video camera. Monitor.