Ch. 19 - US: Understanding the Principles and Recognizing Normal and Abnormal Findings Flashcards
A tissue that reflects many echoes is said to be:
Echogenic (Hyperechoic) –> Usually depicted as bright or white on the sonogram.
A tissue that has few or no echoes is said to be:
Sonolucent (hypoechoic or anechoic) and is usually depicted as being dark or black.
Gallstones:
Characteristically echogenic and produce acoustical shadowing because they reflect most of the signal.
Biliary sludge:
Can be found in the lumen of the gallbladder and is often associated with biliary stasis.
–> May be echogenic - sludge does NOT produce acoustical shadowing like gallstones.
The typical appearance of … is a dilated calyceal system.
Obstructive nephropathy.
In medical renal disease:
Renal parenchyma becomes more echogenic (brighter) that the liver and spleen, the reverse of the normal echo pattern.
US is the screening study of choice when:
An asymptomatic, pulsatile abdominal mass is palpated.
MC MASS in the ovary:
A functional cyst.
Generally, uterine masses are more …, and ovarian masses are more … .
Uterine –> Solid.
Ovarian –> Cystic.
Follicular cysts and corpus luteum cysts are … of the ovary:
Functional cysts.
Functional cysts are characteristically:
- Well-defined.
- Thin-walled.
- Anechoic structures with homogenous internal fluid density.
- They may contain echogenic material if hemorrhage occurs into the cyst.
Non functional cysts of the ovary include:
- Dermoid cysts.
- Endometriomas.
- Polycystic ovaries.
Tumors of the ovaries:
- Most often arise from the surface covering and are either serous or mucinous.
- Most serous tumors + overwhelming number of mucinous tumors are benign.
Acute appendicitis:
Appendix may be blind-ending, aperistaltic tube with a diameter of 6mm or more.
Appendicitis - A fecalith is present in about … of cases:
1/3.
Most ectopic pregnancies are:
Tubal in location and occur near the fimbriated (ovarian) end.
An ectopic pregnancy can be effectively excluded:
If an intrauterine pregnancy is present.
An ectopic pregnancy can be effectively included:
If an extrauterine pregnancy is seen.
Most often, an ectopic pregnancy is diagnosed by a combination of:
Absence of an identifiable intrauterine pregnancy while the β-HCG rises above a certain level.
A molar pregnancy:
Is suggested by a uterine size that is disproportionately large for the dates of gestation and β-HCG levels in excess of 100.000 mIU/mL. (NORMAL –> 60.000mUI/mL).
Carotid stenosis begins to cause changes in the velocity of flow when there is greater than … narrowing of the lumen.
50%.
Sonographic evaluation for DVT of the leg is mainly based on the principle that:
Normal venous structures will be easily compressed and collapsed by the transducer, whereas veins harboring thrombi will NOT compress.
–> Also seeks to visualize the echogenic thrombus itself.
Uses of US during pregnancy:
- Fetal presence and gestational age.
- Fetal abnormalities and viability.
- Presence of multiple pregnancies.
- Placental localization.
- Amniotic fluid volume.
- Intrauterine growth retardation.
- Helping guide invasive studies like:
a. Amniocentesis.
b. Chorionic villus sampling.
c. Intrauterine transfusions.
Advantages of ultrasonography:
- No ionizing radiation.
- No known long-term side effects.
- “Real-time” images.
- Produces little or no patient discomfort.
- Small, portable, inexpensive, ubiquitous.
Disadvantages of US:
- Difficulty penetrating through bone.
- Gas-filled structures reduce its utility.
- Obese patients may be difficult to penetrate.
- Dependent on the skills of the operator scanning.
Types of US - A mode:
- Simplest.
- Spikes along a line represent the signal amplitude at a certain depth.
- Used mainly in ophthalmology.
Types of US - B mode:
- Mode most often used in diagnostic imaging.
- Each echo is depicted as a dot and the sonogram is made up of thousands of these dots.
- Can depict real-time motion.
Types of US - M-Mode:
Used to show moving structures such as blood flow or motion of the heart valves.
Types of US - Doppler:
- Uses the Doppler effect to assess blood flow –> Used for vascular US.
- Pulsed Doppler devices emit short-bursts of energy that allow for an accurate localization of the echo source and has replaces continuous wave Doppler.
Types of US - Duplex US:
Utilized in vascular studies - Refers to the simultaneous use of both gray-scale or color Doppler to visualize the structure of and flow within a vessel and spectral waveform Doppler to quantitate flow.
Creation of a sonographic image (sonogram) depends on 3 major components:
- Production of high-frequency sound wave.
- Reception of a reflected wave or echo.
- Conversion of that echo into the actual image.
By convention sonographic images are viewed …?
With the patient’s HEAD to your LEFT and the patient’s FEET towards your RIGHT; anterior is UP - posterior is DOWN.
Doppler US - By convention, red indicates flow … the transducer, and blue indicates flow … from the transducer.
RED –> TOWARDS.
BLUE –> AWAY.
US is usually the study of 1st choice in imaging …?
- The female pelvis.
- Pediatric patients.
- In differentiating cystic versus solid lesions in ALL patients.
- In non invasive vascular imaging.
- Imaging of the fetus and placenta during pregnancy.
- Real-time, image-guided fluid aspiration biopsies.
Other common uses of US:
- Evaluation of cystic vs solid BREAST masses.
- Thyroid nodules.
- Tendons.
- Assessing the brain, hip, spine in NEWBORNS.
In the fasting patient, the gallbladder is about …?
4x10cm in size and the wall is normally no thicker than 3mm.
What do gallstones produce?
They are echogenic and produce –> Acoustical shadowing –> They reflect most of the signal.
What is the biliary sludge?
An aggregation that may contain CH crystals, bilirubin, and glycoproteins –> Associated with BILIARY STASIS.
While it may be echogenic, sludge …?
DOES NOT produce acoustical shadowing like gallstones.