Introduction to Medical Imaging

Question 1

Anatomic position

Answer 1

Patient erect, facing you, feet together, arms at sides with palms forward

Question 2

Right vs left

Answer 2

Your right is the patient’s left, and vice versa. Describe using patient’s orientation

Question 3

Toward the head

Answer 3

Cranial, cephalad, superior

Question 4

Toward the feet

Answer 4

Inferior, caudal

Question 5

Front of body

Answer 5

Anterior, ventral

Question 6

Rear of body

Answer 6

Posterior, dorsal

Question 7

Closest to torso

Answer 7

Proximal

Question 8

Farthest from torso

Answer 8

Distal

Question 9

Longitudinal planes

Answer 9

Coronal, sagittal

Question 10

Coronal plane

Answer 10

Slices body top to bottom in a horizontal direction (think “crown”)

Question 11

Sagittal plane

Answer 11

Slices body top to bottom in a vertical direction

Question 12

Horizontal plane

Answer 12

Axial/transverse

Question 13

Axial/transverse plane

Answer 13

Slices across body

Question 14

Different imaging modalities

Answer 14

Radiography, computed tomography (CT), magnetic resonance imaging (MRI), ultrasound, nuclear medicine

Question 15

Radiography

Answer 15

AKA X-rays, plain films, image made from broad beam of x-rays and resulting image is related to the subject’s density (the denser, the brighter), so air is black, fat is dark gray/black, soft tissues and organs are gray, and metal, calcium and bone are white

Question 16

Computed Tomography

Answer 16

AKA CT, image made from using rotating thin beams of x-rays that make image “slices” that are reconstructed by computation, the image formed is related to subject’s density (the denser, the brighter), so bone is white, air is black, and soft tissue structures are various shades of gray

Question 17

CT contrast

Answer 17

Differentiates structures of similar densities, tissues that take it up appear lighter than without

Question 18

X-ray contrast

Answer 18

Used to make tubular structures lighter

Question 19

X-rays used for…

Answer 19

Fractures, tumors, arthritis

Question 20

CT windowing

Answer 20

Images can be displayed different ways to highlight certain structures

Question 21

CTs used for…

Answer 21

Occult fractures, characterizing known fractures

Question 22

Magnetic resonance imaging

Answer 22

AKA MRI, image made by transmitting and receiving radio waves inside a high magnetic field, forms image “slices” that are reconstructed by computation, and the formed image is related to tissue composition (hydrogen density, hydrogen chemical/physical environment), so tissues with a lot of protons (water, fat) appear white and tissues with little protons (cortical bone, air) appear black

Question 23

T1 vs T2 weighting

Answer 23

Changing the radiofrequency pulses to bring out different features, T1 bones appear white, T2 bones are black

Question 24

MRI with contrast

Answer 24

Causes tissues that take up contrast to appear lighter

Question 25

MRIs used for…

Answer 25

Occult fractures, joints, soft tissues, tumors

Question 26

Ultrasound

Answer 26

AKA sonogram, uses high frequency sound waves to create images, sound waves give information about depth, tissue type, and tissue interfaces and converts into an image, so strong reflections from tendons, bone, and air appear white, weaker reflections from most solid organs, walls of fluid containing organs, and thick fluid appear gray, and no reflections from fluid appear black

Question 27

Ultrasound used for…

Answer 27

Pregnancy, liver, gallbladder

Question 28

Nuclear medicine

Answer 28

Image organs using radiopharmaceuticals that target specific organs or diseases, then a PET or gamma camera is used to detect and display the distribution of the radiopharmaceuticals

Question 29

Nuclear medicine used for…

Answer 29

Bone scans, detecting metastases, assess organ function, therapy

Question 30

Advantages of x-ray

Answer 30

Inexpensive, fast, widely accessible, good for bones, lungs, free air, bowel obstruction

Question 31

Disadvantages of x-ray

Answer 31

Can’t see “inside” of body very well, only provides limited or no information in many circumstances, low levels of ionizing radiation

Question 32

Advantages of CT

Answer 32

Provides cross-sectional imaging of the body, excellent anatomic resolution, good for detecting acute blood in brain, widely used for chest, abdomen and pelvis, good for detailed evaluation of bones

Question 33

Disadvantages of CT

Answer 33

More ionizing radiation, relatively expensive, limited information in brain and joints

Question 34

Advantages of MRI

Answer 34

Excellent contrast and anatomic resolution, can image in multiple and complex planes, excellent for tendons, ligaments, brain, and spinal cord, no ionizing radiation

Question 35

Disadvantages of MRI

Answer 35

Some safety issues with magnet, expensive, less available, must know your anatomy to interpret

Question 36

Advantages of ultrasound

Answer 36

No ionizing radiation, safe, accessible and relatively inexpensive, great from gallbladder and female pelvic organs

Question 37

Disadvantages of ultrasound

Answer 37

Only useful for certain body parts, anatomic resolution less than CT or MRI

Question 38

Advantages of nuclear medicine

Answer 38

Functional and dynamic imaging (physiology or pathophysiology of body/organ), can be combined with CT for better anatomic resolution

Question 39

Disadvantages of nuclear medicine

Answer 39

High ionizing radiation, relatively expensive, poor anatomic resolution