Chapters 4 & 17

• What are the highest to lowest scanning intensity scanning modes ?

  Spectral, colour, m mode, b mode
• How many degrees increase is bad and can cause thermal effects ?

  2.5 C
• What should the TI be to prevent thermal effects ?

  less than 1
• What should the MI be kept at to prevent mechanical effects ?

  below 1
• What is cavitation ?

  Formation of bubbles in a liquid due to rapid changes in pressure; bubbles happen in rarefaction and collapse during compression
• Cavitation does / does not have any harmful effects with fetuses ?

  Does not
• it is considered an embryo until what week ?

  week 10
• An embryo becomes a fetus at week 11 until end of pregnancy
• What weeks are the first trimester ?

  Weeks 1-12
• What weeks are the second trimester ?

  Weeks 13 to 26
• What weeks are the third trimester ?

  Weeks 27 to 40
• LMP adds two weeks to dating of gestation
• Naegele's rule:

  EDD = LMP - 3 months + 7 days
• hCg generation doubles every 30-48 hours
• hCG peaks at 8 - 10 weeks
• hCg declines then steadies by week 18
• What is high hCg indicative of ?

  molar pregnancy or multiple gestations
• What is low hCg indicative of ?

  ectopic pregnancy, miscarriage, blighted ovum
• What does the number after G mean ?

  number of pregnancies
• What does the first number after P mean ?

  full term pregnancies
• What does the second number after P mean ?

  Premature deliveries
• What does the third number after P mean ?

  early pregnancy losses
• What does the 4th number after P mean ?

  living children
• A zygote is how many cells ?

  2 - 8 cells
• How many cells are in a morulla ?

  16 cells
• How many cells are in a blastocyst ?

  32 cells
• A blastocyst enters the uterus at day 4 - 5 after fertilization and implants on day 5 - 7
• How is the yolk sac measured ?

  from inner wall to inner wall
• What does the yolk sac do ?

  transfer nutrients, make blood and vessels, form GI tract
• What weeks is the yolk sac seen ?

  Weeks 5 - 12
• How does the yolk sac look sonographically ?

  round, sonolucent structure
• What is the double bleb sign ?

  amniotic sac and yolk sac complex
• What is the basalis connected to in the decidual sign ?

  uterus (maternal placenta)
• What does the capsularis surround in the decidual sign ?

  Gestational sac
• Where is the parietalis/vera in the decidual sign ?

  opposite wall of endo
• What does amnion contain ?

  fluid and embryo
• What is the chorion ?

  Fetal placenta aka gestational sac
• What is the placenta made of ?

  decidual basalis (mother) and chorion (fetus)
• What is the crown rump length ?

  longest measurement of fetus from head to toe
• Mean sac diameter is taken when:

  no fetus present