Introduction to Medical Imaging Flashcards
Anatomic position
Patient erect, facing you, feet together, arms at sides with palms forward
Right vs left
Your right is the patient’s left, and vice versa. Describe using patient’s orientation
Toward the head
Cranial, cephalad, superior
Toward the feet
Inferior, caudal
Front of body
Anterior, ventral
Rear of body
Posterior, dorsal
Closest to torso
Proximal
Farthest from torso
Distal
Longitudinal planes
Coronal, sagittal
Coronal plane
Slices body top to bottom in a horizontal direction (think “crown”)
Sagittal plane
Slices body top to bottom in a vertical direction
Horizontal plane
Axial/transverse
Axial/transverse plane
Slices across body
Different imaging modalities
Radiography, computed tomography (CT), magnetic resonance imaging (MRI), ultrasound, nuclear medicine
Radiography
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
Computed Tomography
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
CT contrast
Differentiates structures of similar densities, tissues that take it up appear lighter than without
X-ray contrast
Used to make tubular structures lighter
X-rays used for…
Fractures, tumors, arthritis
CT windowing
Images can be displayed different ways to highlight certain structures
CTs used for…
Occult fractures, characterizing known fractures
Magnetic resonance imaging
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
T1 vs T2 weighting
Changing the radiofrequency pulses to bring out different features, T1 bones appear white, T2 bones are black
MRI with contrast
Causes tissues that take up contrast to appear lighter
MRIs used for…
Occult fractures, joints, soft tissues, tumors
Ultrasound
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
Ultrasound used for…
Pregnancy, liver, gallbladder
Nuclear medicine
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
Nuclear medicine used for…
Bone scans, detecting metastases, assess organ function, therapy
Advantages of x-ray
Inexpensive, fast, widely accessible, good for bones, lungs, free air, bowel obstruction
Disadvantages of x-ray
Can’t see “inside” of body very well, only provides limited or no information in many circumstances, low levels of ionizing radiation
Advantages of CT
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
Disadvantages of CT
More ionizing radiation, relatively expensive, limited information in brain and joints
Advantages of MRI
Excellent contrast and anatomic resolution, can image in multiple and complex planes, excellent for tendons, ligaments, brain, and spinal cord, no ionizing radiation
Disadvantages of MRI
Some safety issues with magnet, expensive, less available, must know your anatomy to interpret
Advantages of ultrasound
No ionizing radiation, safe, accessible and relatively inexpensive, great from gallbladder and female pelvic organs
Disadvantages of ultrasound
Only useful for certain body parts, anatomic resolution less than CT or MRI
Advantages of nuclear medicine
Functional and dynamic imaging (physiology or pathophysiology of body/organ), can be combined with CT for better anatomic resolution
Disadvantages of nuclear medicine
High ionizing radiation, relatively expensive, poor anatomic resolution
