imaging Flashcards
What is the biophysics behind ultrasounds?
Ultrasound waves and frequency
* Piezo-Elictric crystals(the ability of the material to develop electric charge in response to the applied mechanical stress)
* Grows and shrinks depending on the voltage run through it
* Running an alternating current through it causes it to vibrate at a high speed and to produce an ultrasound wave
* Sound is then reflected back to the PE crystals converting sound into electrical energy and then to photo energy
how is doppler ultrasound different from regular ultrasound?
-doppler estimates the blood flow through vessels by bouncing high frequency sound waves of circulating blood cells, whereas regular ultrasound uses sound waves to produce image and cant show blood flow
Doppler Waveform
- Christian Johann Doppler
- Doppler effect-the shift between emitted and
observed frequency of sound - Velocity and Angle
- Light moving away—red
- Light moving towards– blue
- Blood cells – scatter—RBC
- Pulsed Doppler pulsed echo system
- defines the rate which data is collected
- Resistance Index – A-B/Mean Difference of the
highest and lowest value divided by the mean in one
cardiac cycle - Pulsatility Index- A/B ratio indicates peripheral
resistance - RI absent or reversal – Increase peripheral
resistance causes diminution and then loss of blood
imaging in normal menstrual cycle
- Endometrial
- Ovarian
- Changes during the menstrual cycle
Endometrial scan pattern
scans done in two part:
1.pre-ovulation (follicular phase)
2.post ovulation (luteal phase)
measure thickness(mm) and endometrial volume
Follicles and corpus luteum - ovary
-follicles are sacs that contain eggs (more follicles = higher reserve)
polcystic ovaries >12 follicles
* Early follicular phase the follicles are small
with less than 8 mm in size and multiple
* Midfollicular phase there is a dominant follicle
ahead of the other follicles
* Periovulatory follicle is about 17-23 mm in size
* Corpus luteum cystic or solid collapsed or full
appearance with irregular edge and shadows
with the the cyst.
* Raised dopplers are classical – roughly day 21.
The endometrium after period
-thin endometrium after periods
Mid follicular phase
-20 follicles /10 on each ovary
- 19 stop growing and one grows and becomes dominant follicle
periovulatory phase - thick white line
almost ovulating - just before day 14
Homegenous Hyperechogenic endometrium, corpus luteum with raised dopplers
after ovulation you see this
homogenous means smooth no
hypergogenic is when the endometrium becomes thicker due to hyperplasia so appears more dense and darker.
Changes in the endometrium during menstruation:
- (A) shortly after menstruation the endometrium appears as a thin white line
- (B) in the mid and late proliferative phase of the menstrual cycle the endometrium becomes thicker and manifests a “triple-layer” appearance
- (C) on the day before ovulation the endometrium still has a “triple-layer” appearance but there is a thick white line surrounding it; this probably reflects some progesterone production from the dominant follicle
- (D) in the luteal phase of the menstrual cycle the endometrium is thick and homogenously hyperechoic (white)
Triple layer
- menstrual phase
- proliferative phase
- secretory phase
normal uterine cavity
junctional zone between endometrium and myometrium suggesting cavity is normal
systolic and diastolic phase in doppler
- heart contracts = systolic = blood is going to organ
-diastolic phase = interchange takes place in organ = low pressure
In fetal department you do…
resistance index (RI)
systolic flow velocity - diastolic velocity/systolic velocity
In the gynaecological department in women we do ..
Pulsitility index (PI)
systolic flow velocity - diastolic velocity / mean velocity
