poi

Question 1

where are the x ray photons generated from

Answer 1

a complex X-ray tube, which is a type of cathode ray tube

Question 2

why are The X-rays are then collimated

Answer 2

directed through lead-lined shutters to stop them from fanning out) to the appropriate area of the body.

Question 3

what happens when the x ray goes through the body

Answer 3

As the X-rays pass through the body they are attenuated (reduced in energy) by the tissues.

Question 4

what are the relative attenution if air fat water bone

Answer 4

▪ air attenuates X-rays a little;
▪ fat attenuates X-rays more than air but less than water; and
▪ bone attenuates X-rays the most

Question 5

why is bone shown white

Answer 5

bone appears white on the film because this region of the film has been exposed to the least amount of X-rays. Air appears dark on the film because these regions were exposed to the greatest number of X-rays.

Question 6

What is barium sulphate

Answer 6

Contrast agents

Question 7

what is commonly added to barium and how

Answer 7

by either ingesting “fizzy” granules or directly instilling air into the body cavity, as in a barium enema. This is known as a double-contrast (air/barium) study.

Question 8

which contrast agent is intervanoulsy added to teh vien /arteries  
and why (2)

Answer 8

Iodine is chosen because it has a relatively high atomic mass and so markedly attenuates X-rays, but also, importantly, it is naturally excreted via the urinary system

Question 9

Subtraction angiography

Answer 9

subtract structures from the image, thus allowing for an accurate depiction of the blood vessels.

Question 10

Ultrasound

Answer 10

very high frequency sound wave

The sound waves are then interpreted by a powerful computer, and a real-time image is produced on the display panel.

Question 11

what is it generated by

Answer 11

piezoelectric materials

The sound waves are then interpreted by a powerful computer, and a real-time image is produced on the display panel.

Question 12

what does Doppler ultrasound allow

Answer 12

determination of flow, its direction, and its velocity within a vessel

Question 13

how

Answer 13

Sound waves bounce off moving structures and are returned. The degree of frequency shift determines whether the object is moving away from or toward the probe and the speed at which it is traveling

Question 14

Computed tomography

Answer 14

A CT scanner obtains a series of images of the body (slices) in the axial plane. The patient lies on a bed, an X-ray tube passes around the body

Question 15

Magnetic resonance imaging what it do

Answer 15

determine the structure of complex molecules

Question 16

what does it depend on and why is it ideal

Answer 16

free protons in the hydrogen nuclei in molecules of water (H 2 O). Because water is present in almost all biological tissues,

Question 17

how is mri carried out

Answer 17

The patient is placed in a strong magnetic field, which aligns the bar magnets. When a pulse of radio waves is passed through the patient the magnets are deflected, and as they return to their aligned position they emit small radio pulses. The strength and frequency of the emitted pulses and the time it takes for the protons to return to their pre-excited state produce a signal. These signals are analyzed by a powerful computer, and an image is created

Question 18

two types of imaging sequences provide differences

Answer 18

image contrast

Question 19

Most T1-weighted images show

Answer 19

dark fluid and bright fat

Question 20

T2-weighted images demonstrate

Answer 20

a bright signal from fluid and an intermediate signal from fat