Diagnostic Imaging Techniques

Question 1

X-Rays - how it works

Answer 1

photons are directed at a particular region via lead shunts and the waves pass through structures in the body, attenuating as they pass through to the film

Question 2

Attenuation, low to high

Answer 2

(appears black) air, fat, water, bone (appears white)

Question 3

What do you do if you need to see structures that don’t attenuate x-rays very well?

Answer 3

Use a contrast agent

Question 4

What studies is iodine used for in the context of contrast agents? Why is it used

Answer 4

intra-arterial and intravenous studies to see kidneys, bladder, ureters; used because it has a high molecular weight and is naturally excreted

Question 5

What studies is barium sulfate used for in the context of contrast agents? Why is it used?

Answer 5

visualization of bowel loops; high density, insoluble salt that is removed from system leaving a thin coating on the bowels that is passed with bowel movements

Question 6

What is barium commonly used in combination with?

Answer 6

air - via ingesting fizzy particles or enema

Question 7

What is subtraction angiography?

Answer 7

to visualize structures that may be difficult to see with one image, one x-ray is taken and then a contrast agent is administered before a second image is taken

the first image is inverted to created a negative image, and then a computer combines the images to visualize the contrast only

Question 8

How are X-rays interpreted?

Answer 8

X-ray tube is placed 1 m from film
anterior is closest to tube, posterior is closest to film
right side of image is on the left (anatomical position)

Question 9

Chest Radiograph position

Answer 9

patient is upright, posteroanteriorly (PA) positioned (chest to film)

Question 10

Abdominal Radiograph position

Answer 10

AP supine (laying down, face up)

Question 11

Chest Radiograph features

Answer 11

should show lungs, cardiomediastinal contour, diaphragm, ribs, and peripheral soft tissues

Question 12

Ultrasound

Answer 12

high frequency sound waves emitted by piezoelectric material are sent through the body and they bounce back off of internal organs; the waves coming back are received by the piezoelectric material and a computer at generates an image

Question 13

What position is a patient placed when a small bowel obstruction is expected?

Answer 13

erect AP

Question 14

Doppler Ultrasound

Answer 14

a variation of regular ultrasound used to determine flow, direction, and velocity within a vessel

Question 15

Computed Tomography (CT scan)

Answer 15

series of images taken in the axial plane (horizontal slices), and are combined by a computer to produce a final image

Question 16

CT image interpretation (3)

Answer 16

anatomical position (right side of patient is on the left)
uppermost border of image is anterior
view from bottom to top

Question 17

Magnetic Resonance Imaging (MRI)

Answer 17

protons of H-atoms (of water molecules) are oriented randomly throughout the body and can be thought of a magnets; a strong magnet orients all of the H-atoms the same way before a radio wave is emitted, sending the H-atoms back to their ground states

when the H-atoms emit energy to return to their ground state, the signal is read by a computer to provide an image

Question 18

T1 weighted v T2 weighted MRI

Answer 18

difference b/w pulse sequence and scanning parameters
T1: dark fluid/bright fat
T2: bright fluid/intermediate signal for fat

Question 19

MRI image interpretation (4)

Answer 19

anatomical position
uppermost border of image is anterior
view bottom to top
can use paramagnetic contrast agents (weakly magnetic)

Question 20

Nuclear Medicine Imaging

Answer 20

visualize structures using a radiopharmaceutical and a gamma camera (that produces the image)

Question 21

The radioisotopes used for NMI must: (3)

Answer 21

1) have a reasonable half-life
2) have easily measured gamma rays
3) have as low energy deposition as possible in patient tissues

Question 22

What radiopharmaceutical is used to visualize bone?

Answer 22

Technetium-99m w/ methylene diphosphonate

Question 23

Positron Emission Tomography (PET scan)

Answer 23

detects positron emitting radionuclides that are proton rich; commonly used to detect cancer

Question 24

What is a commonly used radionuclide used in PET scans?

Answer 24

Fluorodeoxyglucose (labelled with F-18) - taken up by tissues actively metabolizing glucose (produces hot spots i.e. cancer)

Question 25

Advantage to CT scan

Answer 25

can compress or extend gray scale to visualize bone, soft tissues, and viscera