Radiology in Obstetrics Flashcards
1
Q
x-rays: are they safe?
A
- “All-or-none” phenomenon
- Location of irradiation
- Amount of radiation
- Timing (during pregnancy) of exposure
2
Q
harmful effects of ionizing radiation
A
- Cell death and birth defects (Teratogenesis)
- Carcinogenesis
- Genetic effects
3
Q
HDR and Carcinogenesis: weak data
A
- Unclear risk, probably very small
- At 10-20 mGy, 1/2000 develop childhood leukemia
- Background risk is 1/3000
- Non-irradiated siblings also have higher risk of leukemia
- Termination of pregnancy should not be based on exposure to typical dosing
4
Q
genetic effects of radiation
A
- May increase frequency of natural mutations, not create de novo mutations
- No increased risk of genetic disorders has been noted in any human population at any dose
- “Little or no evidence exists for estimating the frequency or magnitude of genetic effects on future generations”
5
Q
nuclear medicine and pregnancy
A
- “Tagging” a chemical agent with a radioisotope
- Fetal exposure depends on radioisotope’s physical and biochemical properties
-
Tc 99m – used in brain, bone, renal, CV scans
- Exposure < 0.5 rads
- VQ Scans – Tc 99m for perfusion, 127Xe or 133Xe for ventilation
- Exposure ~ 50 mrad (0.05 rads)
-
Tc 99m – used in brain, bone, renal, CV scans
6
Q
MRI contrast agents
A
- Gadolinium and iron oxide based agents are most commonly used
- Gadolinium is associated with nephrogenic systemic fibrosis (NSF), especially in “free” form
- AKA nephrogenic fibrosing dermopathy (NFD)
- Disease of fibrosis of the skin and internal organs
7
Q
safety of ultrasound in pregnancy
A
- Sound waves, not ionizing radiation
- No reports of adverse fetal effects
- FDA arbitrarily limits energy exposure
8
Q
indications for first trimester ultrasound
A
- Confirm fetal viability and dates
- Rule out ectopic pregnancy
- Diagnose multifetal pregnancy
- Guidance for removal of IUD
- Rule out molar pregnancy
- Guidance for chorionic villous sampling
- Nuchal translucency testing
9
Q
pregnancy dating
A
- Error of ultrasound:
- ≤ 8-6/7 weeks: 5 days
- 9 to 15-6/7 weeks: 7 days
- 16 to 21-6/7 weeks: 10 days
- 22 to 27-6/7 weeks: 14 days
- 28 to term: 21 days
- Assessment of fetal growth patterns linked to ultrasound error
10
Q
pregnancy with IUD
A
- Higher risk of ectopic
- 50-60% risk of miscarriage if left inside uterus
- String retraction hampers removal
11
Q
ectopic pregnancy and ultrasound
A
- Most ectopic pregnancies are tubal
- Presentation: 7-8 weeks
- Clinical triad: Pain, bleeding, amenorrhea
- Ultrasound cannot definitively rule OUT an ectopic pregnancy, but can rule IN an intrauterine pregnancy
- Other less common sites: cornual, cervical
12
Q
molar pregnancy and ultrasound
A
- Molar gestation – neoplastic placental growth
- Fetus present (partial) or absent (complete)
- Inheritance: uniparental disomy
- Lab: high levels of HCG
- Symptoms: hyperemesis, hyperthyroidism
- US: “Snowstorm” or “Grape-like” clusters
- High incidence of fetal CNS anomalies
- Uniparental disomy – both chromosomes come from dad or both come from mom
13
Q
CVS and ultrasound
A
- Biopsy of placental tissue at 10-13 weeks
- Diagnoses chromosomal or genetic disorders for which DNA testing is available
- Ultrasound guides needle/catheter into placental tissue
14
Q
fetal nuchal translucency
A
- 11.5 and 14.5 weeks
- Abnormal edema associated with chromosomal and fetal structural abnormalities
- Down syndrome
- Fetal anomalies mostly cardiac
- If pt has test that shows nuchal translucency that is greater than 3, this is BAD
15
Q
1st trimester cystic hygroma
A
- Commonly associated with Downs, trisomy 18, and turner syndrome
