Anatomy And Diagnostics - Principles of Imaging

Question 1

Intro

Answer 1

• 1895, Wilhelm Conrad Roentgen, wife hand, X (unknown) rays blocked by intervening material (more = darker image), 1901 Nobel
• Now more dense = whiter (cortical bone > soft tissue/fluid > fat > air) + structures superimposed (flat, so might need 2 views)
• Air below diaphragm = bowel perforation
• Barium -> GI tract (contrast media to enhance images)

Question 2

Antonio Egas Moniz

Answer 2

Portuguese physician, suggested using x-rays with injected dye; 1927 - first cerebral angiogram using intravenous Na iodide; 1r9 Nobel for lobotomy

Question 3

CT intro

Answer 3

1972, British engineer Sir Godfrey Hounsfield and American Dr Allan Cormack, Nobel 1979, always acquired axially

Question 4

Non contrast hemorrhage and post intravenous iodinated contrast abscess

Answer 4

White area, white ring

Question 5

Ionizing radiation

Answer 5

X-ray, CT scan, nuclear medicine imaging investigations (bone scan, PET/CT, PET/MR), may cause radiation-induced cancer decades later, always try to avoid ionizing radiation where possible, use lowest radiation dose possible

Question 6

Ultrasound

Answer 6

Discovery of echolocation in bats - 1794, work on piezoelectric effect in 1870s (solid materials generate electricity in response to mechanical stress), Titanic sinking led to development of sonar to detect icebergs at night and then submarines in WWI, 1942 medical ultrasound (sonograms) for medical diagnosis (Karl Dussik, Vienna), 1958 Brown and Donald introduced US machine for abdominal diagnosis (start of obs and gynae)

Question 7

Magnetic resonance imaging (MRI)

Answer 7

Phenomenon described independently by Bloch and Purcell 1946, joint Nobel 1952, developed for chemical and molecular analysis, early 1970s Lauterbur and Mansfield developed techniques to generate images from MRI, 1977 Mansfield first image of human anatomy, Nobel 2003 Lauterbur and Sir Peter Mansfield

Question 8

MRI Weighting

Answer 8

T1 images – 1 tissue type is bright – FAT

T2 images – 2 tissue types are bright – FAT and WATER (with fat saturation only water, malignant ovarian mass dark)

Question 9

Hybrid imaging

Answer 9

PET scanners detect radiation given off by radiotracer (injected in arm) as it collects in different parts of body, most use fluorodeoxyglucose (FDG) (similar to naturally occurring glucose), concentration of FDG in the body’s tissues can help identify cancerous cells because cancer cells use glucose at a much faster rate than normal cells
FDG-PET/CT: imaging glucose uptake, FDG-PET/MRI (lower radiation dose)

Question 10

Plain radiography

Answer 10

X rays generated by cathode ray tube tube collimated (directed through lead lined shutters to stop them fanning out) to appropriate body area, attenuated as they pass thru by tissues, cathode + focusing cup w/tungsten filament inside + tungsten target (emits x rays) on anode inside glass x ray tube, difference in attenuation = difference in level of film exposure (whiet = least), continuous output collected on input screen for real-time moving anatomical structures (barium studies, angiography, fluoroscopy)

Question 11

Contrast agents

Answer 11

Fill structures like bowel loops and arteries, barium sulfate (insoluble salt, non toxic, relatively high density, suspension (with air via “fizzy” granules/barium enema = double contrast (air/barium) study)), iodine for arteries/veins, naturally excreted via urinary system (intravenous urography)

Question 12

Subtraction angiography

Answer 12

To appreciate contrast agent in vessels through overlying bone structures, 1/2 images obtained before contrast injections injection and inverted, after injection series of images to show flow, negative precontrast image + positive postcontrast = bones and soft tissues subtracted

Question 13

Ultrasound (in depth)

Answer 13

Very high frequency sound wave generated by piezoelectric materials (that also receive bounce back), abdomen+foetus+eyes+neck+soft tissues+endoscopy (esophagus,stomach, duodenum)+endocavity (assess women genital tract, trans-vaginal/rectal route)+transrectal (prostate hypertrophy/malignancy)+doppler (flow, direction and velocity with degree of frequency shift, blockage of blood vessels)

Question 14

Computed tomography

Answer 14

Series of images of body (slices) in axial plane

Question 15

MRI (in depth)

Answer 15

Dependent on free protons in H nuclei of H2O molecules (aligned by strong magnetic field, deflected when pulse of radio waves passed and emit radio waves back), altering sequences of pulses = different weighting (T1 -> dark fluid, bright fat; T2 -> bright fluid, intermediate fat), assess vessel flow, produce complex angiograms of peripheral and cerebral circulation