OBSTETRIC IMAGING presentation final.pptx

The presentation covers obstetric imaging and is for educational purposes only. Contact your personal doctor or physician for further consultations concerning any obstetric concern or issue.
Thank you; IRAD CRISPUS NYABONGO

1. Obstetric imaging Presentation by: IRAD CRISPUS NYABONGO 09-Oct-24 1

2. OBSTETRIC IMAGING Obstetric imaging refers to imaging of the female reproductive tract and developing fetus during pregnancy . Except in rare cases, obstetric imaging is performed via ultrasound. Ultrasound has the following advantages: No radiation exposure Ability to view real-time images of the moving fetus Relatively low cost and wide availability 09-Oct-24 2

3. Types of probes used in ultrasound imaging. Linear Array Probe: Used for: 2D and 3D imaging High-frequency imaging (10-18 MHz) Superficial structures (e.g., fetal head, limbs ) 2 . Curvilinear Array Probe: Used for: Abdominal imaging Lower frequency imaging (2-5 MHz) Deeper penetration (e.g., fetal abdomen, placenta ) 3 . Phased Array Probe: Used for: Cardiac imaging (fetal heart) High-frequency imaging (5-10 MHz) Sector scanning 09-Oct-24 3

4. 4. Transvaginal Probe (TV Probe): Used for: Early pregnancy scanning Cervical and vaginal imaging Higher frequency imaging (5-10 MHz ) 5 . Transabdominal Probe (TA Probe), used for: Abdominal imaging Fetal imaging (after 12 weeks ) Probe Frequencies : Low Frequency (2-5 MHz): Deeper penetration, used for: - Abdominal imaging - Fetal imaging (later pregnancy ) Medium Frequency (5-10 MHz): Balanced imaging, used for: - General obstetric scanning - Fetal imaging (mid-pregnancy ) High Frequency (10-18 MHz): High-resolution imaging, used for: - Superficial structures (e.g., fetal head, limbs) 09-Oct-24 4

5. Early pregnancy scanning Ultrasound Technologies : 2D Ultrasound: Basic imaging technology 3D/4D Ultrasound: Advanced imaging technology for fetal anatomy and movement Doppler Ultrasound: Measures blood flow and fetal heart rate Power Doppler Ultrasound: Enhanced blood flow imaging 09-Oct-24 5

6. Types of obstetric imaging exams 2 primary types of obstetric imaging exams : Abdominal obstetric ultrasound: for assessing the fetus, placenta, fluid, and uterus starting in the late 1st trimester through delivery Transvaginal ultrasound: Good for assessing the cervix throughout pregnancy Better for evaluating the fetus and uterus in early pregnancy 09-Oct-24 6

7. Specific studies Ultrasound exams and may be either abdominal or transvaginal . Dating scan: for the measurement of either the gestational sac or the fetus itself to establish the gestational age and calculate the estimated date of delivery (EDD) Anatomy survey: to assess the anatomy of both the fetus and the mother Growth scan: Specific measurements are used to calculate the estimated weight of the fetus. Position assessment: to determine the direction in which the fetus is facing within the uterus in preparation for delivery 09-Oct-24 7

8. Continuation of the specific studies. Fluid assessments: measurements to help estimate the amount of amniotic fluid. Biophysical profile: Assessment of fetal well-being Determination of different forms of fetal movements combined with a fluid assessment Doppler studies: Evaluation of the pulse waveforms in specific fetal arteries to assess fetal well-being May demonstrate signs of fetal anemia or utero-placental insufficiency 09-Oct-24 8

9. Indications for Obstetric Imaging Routine prenatal care as part of routine prenatal care, including : 1st trimester: Pregnancy confirmation Pregnancy dating/establishing the EDD Determining the number of fetuses Determining chorionicity of multiple gestations (e.g., monochorionic diamniotic twins) A component of fetal aneuploidy screening Looking for abnormalities of the uterus and/or ovaries 09-Oct-24 9

10. 2nd trimester: Fetal anatomic survey (screening for congenital anomalies) Assessing placentation: Location of the placenta (confirming it is away from the internal cervical os ) Looking for signs of placental invasion into the myometrium (e.g., placenta accreta spectrum (PAS)) Assessing the cervical length 3rd trimester: Estimating fluid volumes Determining fetal position prior to delivery 09-Oct-24 10

11. Monitoring higher-risk pregnancies Assessing fetal growth (growth scans) Following the development of congenital anomalies Assessing fetal status in higher-risk pregnancies (e.g., biophysical profile or doppler studies in an individual with known preeclampsia) Following fetuses at high risk for developing hydrops fetalis 09-Oct-24 11

12. Emergency care symptoms in pregnancy that warrant ultrasound evaluation : Bleeding and/or pain in early pregnancy: Rule out ectopic and molar pregnancies. Assess fetal viability/evaluate for potential fetal loss (spontaneous abortion). Bleeding in later pregnancy: signs of placental abruption Preterm contractions or pelvic pain: Cervical length measurement to assess for cervical insufficiency or signs of cervical change. Growth scan: important to help the pediatrics team prepare for delivery and provide appropriate counseling to parents (especially in anticipated cases of very premature delivery ) 09-Oct-24 12

13. Loss of fluid: Assess fluid levels. Decreased fetal movement: biophysical profile for the assessment of fetal movement During procedures Ultrasound is often used to assist the physician during procedures such as : Amniocentesis Chorionic villus sampling Cordocentesis External cephalic version 09-Oct-24 13

14. Performing an Obstetric Ultrasound Ultrasound exam technique Positioning of the individual Abdominal scans (supine). Transvaginal scans (in lower lithotomy) Tips for obtaining good images: Maximize contact between the individual’s skin and ultrasound probe. Use plenty and adequate ultrasound gel. Depth and gain to determine the field of view and echogenicity characteristics of the tissue In early pregnancy, the entire gestational sac should be viewed at once. 09-Oct-24 14

15. Preparing for general image interpretation Prior to interpretation of any image, systematic approach should be followed: Confirm name, date, and time on all images. Review the individual’s medical history and physical examination findings. Confirm that the appropriate exams and techniques that can best assess the suspected pathology were ordered/performed. Determine orientation of the image. Have any other previously obtained relevant images available for comparison handy. 09-Oct-24 15

16. Normal Findings on Obstetric Ultrasound Pregnancy confirmation Gestational sac: Earliest sign of intrauterine pregnancy, seen around 4.5‒5 weeks gestational age ( wga ). Should be visible in the uterus if the quantitative serum β- hCG is > 2,000 Anechoic, well-defined round structure Surrounded by an echogenic rim . 09-Oct-24 16

17. Yolk sac: Hyperechoic ring-like structure within the gestational sac 1st seen at approximately 5‒6 wga and disappears at approximately 10 wga Fetal pole: The fetus itself Visible around 5.5‒6 wga A heartbeat is usually visible as soon as the fetal pole is visible. Corpus luteum cyst: An adnexal mass representing the follicle from which the oocyte ovulated, which persists throughout the 1st trimester of pregnancy Produces progesterone, which is vital for survival of the pregnancy Sonographic appearance: Cyst may be simple or complex. Typically surrounded by ↑ vasculature, seen on Doppler studies as a circumferential rim of color known as the “ring of fire 09-Oct-24 17

18. Determining viability Establishing that a pregnancy is viable requires : Intrauterine location: Should be within the main uterine body endometrium At least a gestational sac and yolk sac must be seen in order to establish the pregnancy location (a gestational sac alone is not enough). A detectable fetal heart rate, usually between about 120‒160 per minute (may be slightly higher at certain points in early pregnancy) 09-Oct-24 18

19. Calculation of heart rate by Ultrasound 09-Oct-24 19

20. Pregnancy dating via ultrasound 1st trimester obstetric ultrasound, most accurate to estimate gestational age and calculate the EDD Ultrasound gets less and less accurate as gestation progresses due to normal genetic variations (e.g., height of parents) and due to effects of the intrauterine environment (e.g., smokers have worse placental perfusion). 1st-trimester dating: Measure the crown-rump length. Crown-rump length should be consistent with the expected gestational age based on the last menstrual period (LMP). 09-Oct-24 20

21. 2nd and 3rd trimester dating: Performed using fetal growth scan, which can be used to calculate the estimated fetal weight (EFW) and EDD from specific measurements Measurements include: Biparietal diameter and head circumference Abdominal diameter and circumference Femur length 09-Oct-24 21

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24. Determining the number of embryos The uterus should be fully evaluated in all planes to get an accurate fetal count. Multiple gestation: when > 1 fetus is present Twins Higher-order multiples (e.g., triplets, quadruplets, etc.) 09-Oct-24 24

25. Determining chorionicity in multiple gestations Chorionicity describes whether the fetuses share a chorion or amnion: Dichorionic /diamniotic twins (each twin is in their own chorioamnion and has their own placenta): Thick intertwin membrane Lambda sign: a thick, triangular protrusion of tissue leading up to the intertwin membrane 2 separate placentas (however, if they are right next to each other, they may appear as a single placenta) 09-Oct-24 25

26. Monochorionic /diamniotic (twins are in their own amniotic sac, but share a chorion and placenta): Thin intertwin membrane T sign: The intertwin membrane comes straight into the sac wall, without the thick triangular protrusion of tissue that is seen in dichorionic diamniotic twins. Single placenta Monochorionic / monoamniotic (twins share a chorioamnion and placenta) No intertwin membrane Single placenta 09-Oct-24 26

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29. Anatomic survey A complete anatomic survey assesses both the maternal reproductive tract and fetal anomalies. Maternal anatomy: Cervical length: should be > 25 mm until at least 24 wga Presence of any uterine fibroids distorting the cavity, or in the lower uterine segment, which may be in the way of a potential cesarean incision Adnexal masses Placental and umbilical cord assessment: Placenta; not cover the internal cervical os or invade into the underlying myometrium Umbilical cord: Should have 3 visible vessels 09-Oct-24 29

30. Should insert near the middle of the placenta and at the fetal umbilicus Vessels should be surrounded by protective jelly all the way down to the placental insertion. Fetal anatomy: Multiple structures, and all major organs assessed . Brain Face Heart/lungs, including 4-chamber and outflow-tract views of the heart Abdomen Limbs Genitalia 09-Oct-24 30

31. Amniotic fluid assessment Amniotic fluid can be assessed in 2 ways : Single deepest pocket (SDP): Measures the single deepest vertical pocket of fluid The measured pocket must be free of the umbilical cord and fetal parts. Normal range (2nd and 3rd trimesters): 2‒8 cm Amniotic fluid index (AFI): Divide the uterus into 4 quadrants and obtain an SDP for each quadrant; the AFI is the sum of the 4 SDP measurements. Normal range (2nd and 3rd trimesters): 5‒24 cm 09-Oct-24 31

32. Normal findings on obstetric ultrasound Single intrauterine pregnancy Fetal heart rate between 120 and 160 per minute No significant congenital anomalies identified Normal placental attachment, away from the cervical os 3-vessel umbilical cord Normal volume of amniotic fluid Cervical length > 25 mm until at least 24 wga Appropriate fetal weight for gestational age Vertex fetal positioning in the late 3rd trimester (not important earlier) 09-Oct-24 32

33. Abnormal Findings on Obstetric Ultrasound Abnormal/nonviable pregnancies (threatened and missed abortions): Threatened abortion: A pregnancy with clinical signs indicating the possibility of a miscarriage (e.g., bleeding and cramping) Fetal heart rate (FHR) will still be present. Hyper- or hypo-echoic areas may be visible near the placenta or behind the membranes, suggestive of bleeding. Missed abortion: A fetus is present in the uterus, but no longer viable. FHR will be absent. 09-Oct-24 33

34. Ectopic pregnancy, characterized by implantation outside the uterine cavity. Ultrasound findings include : Heterogeneous adnexal mass Tubal ring sign: an echogenic ring separating the ectopic pregnancy from the ovary Pseudogestational sac: Cystic sac within the uterus, with no embryo Decidual reaction present: thickened echogenic endometrium surrounding the intrauterine sac (because pregnancy hormones are still being produced by the ectopic pregnancy) Misleading, because it can appear identical to an early gestational sac before the yolk sac appears 09-Oct-24 34

35. No identifiable pregnancy when the HCG is > 2,000 Free peritoneal fluid, possibly with low-level internal echos suggests hemorrhage from ruptured ectopic pregnancy. Note on heterotopic pregnancies (twin gestations with 1 fetus in the uterus and 1 ectopic): Possible, but too rare If an intrauterine gestation is identified, the adnexa should still be evaluated for masses; if it is not seen, heterotopic pregnancy can be excluded. 09-Oct-24 35

36. Transvaginal ultrasound showing an empty uterus (left) with endometrial thickening and an echogenic mass (right) representing an ectopic pregnancy adjacent to normal ovarian tissue 09-Oct-24 36

37. Molar pregnancy is a type of gestational trophoblastic disease that occur due to abnormal fertilization . How they occur: Complete mole: An enucleated ovum (i.e., an egg without any DNA) is fertilized by 1 sperm (that duplicates) or 2 sperm (rare). Partial mole: 2 sperm fertilize a haploid ovum. Ultrasound findings: Enlarged uterus Heterogeneous tissue within the uterus with a classic “snowstorm” appearance Cystic spaces: anechoic Placental tissue: hyperechoic Fetus/fetal parts may or may not be present. Large bilateral ovarian cysts may be present. 09-Oct-24 37

38. Transvaginal ultrasonography showing a molar pregnancy: The pattern is described as a "cluster of grapes." 09-Oct-24 38

39. Retained products of conception: After an abortion (either spontaneous or induced), or postpartum after delivery of the placenta, tissue may be retained within the uterus, and can lead to hemorrhage and infection. Ultrasound findings include: Intrauterine, heterogeneous material (typically hyperechoic) Enlarged uterus Increased blood flow to the mass on Doppler mode 09-Oct-24 39

40. A transvaginal ultrasound demonstrates a heterogeneous echogenic mass in the endometrial cavity (black arrow), representing retained products of conception. 09-Oct-24 40

41. Fetal abnormalities Nuchal translucency for aneuploidy screening : An assessment of the nuchal translucency (or thickness of the nuchal fold at the back of the neck) is a part of common aneuploidy screening tests . Measures the hypoechoic region between the skin and soft tissue behind the cervical spine A thickened nuchal fold increases the risk for: Trisomy 21 (most common) Trisomies 13 and 18 Turner syndrome Major congenital heart disease Hydrocephalus > 100 different developmental and genetic syndromes have also been associated with an increased nuchal fold 09-Oct-24 41

42. Nuchal translucency (NT) measurements: Figure (A) shows a normal fetus (looking up). Figure (B) shows a fetus with trisomy 21 (looking down), demonstrating increased NT thickness . 09-Oct-24 42

43. Congenital anomalies : Clinically important anomalies and their associated ultrasound findings include : Cardiac defects (most common, found in approximately 1% of births): A full fetal echo can be performed in utero → full spectrum of lesions can be identified Clinically important defects include: Tetralogy of Fallot Transposition of the great vessels Truncus arteriosus Ventral septal defect, atrioventricular canal defect Valve defects: stenosis, regurgitation, atresia Coarctation of the aorta 09-Oct-24 43

44. Neural tube defects (2nd most common): Anencephaly (most common neural tube defect): absence of the brain Cephalocele : cranial defects through which the brain or meninges herniate outside the skull Spina bifida/ meningocele /myelomeningocele: protrusion of the spinal contents through bony defects in the spine Abdominal wall defects: Omphalocele : Multiple bowel loops (+/- liver) are seen herniating through a membrane-covered midline abdominal defect. Gastroschisis : Bowel loops protrude outside the abdominal cavity without an overlying membrane, through a lateral abdominal wall defect. 09-Oct-24 44

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47. Intrauterine growth restriction (IUGR ): Abnormally low Estimated Fetal Weight (EFW) on a growth scan Typically defined as an EFW < 10th percentile for the estimated gestational age Hydrops fetalis ; refers to abnormal fluid collections in ≥ 2 of the following fetal compartments: Significant skin edema (present in almost all hydropic infants) > 5 mm Ascites, Pleural effusions Pericardial effusions Other potential ultrasound findings: Polyhydramnios, increased nuchal translucency and increased placental thickness. 09-Oct-24 47

48. Ultrasound images of an infant with hydrops fetalis : Axial (A) and oblique sagittal (B) images showing fetal ascites (short white arrow) and floating bowel loops (b); axial image of the fetal head (C) showing significant scalp edema (long white arrow ) 09-Oct-24 48

49. Placental abnormalities Abnormal placentation, refers to abnormal implantation of the placenta. Ultrasound findings may show an abnormal placental location: Placenta previa : Placenta covers the internal cervical os . Low-lying placenta: Placenta is within 2 cm of the internal cervical os . Placenta accreta (approximately 65%): Placenta attaches directly to the myometrium due to the partial or total absence of the decidua basalis. Placenta increta (15%): Placental villi invade into the myometrium. Placenta percreta (approximately 20%): Placental villi penetrate through the entire myometrium and may invade other surrounding structures . 09-Oct-24 49

50. Types of abnormal placentation 09-Oct-24 50

51. Placental abruption. R efers to the premature separation of the placenta, leading to maternal-fetal hemorrhage. Ultrasound findings are usually only seen in large abruptions and may include: Hyper- or iso -echoic retroplacental hematoma Heterogeneity within the placenta Separation of placental edges from the uterus Placental thickening 09-Oct-24 51

52. Acute placental abruption: Note the bulky heterogeneous placenta (arrows) in this hypertensive, 29-week gestational age pregnant individual. 09-Oct-24 52

53. Fluid abnormalities Fluid assessment ; at least with amniotic fluid index or the single deepest vertical pocket (SDP) technique for estimating the amniotic fluid volume, should be part of every obstetric ultrasound. Fluid abnormalities include : Polyhydramnios: too much fluid (SDP ≥ 8 cm or AFI ≥ 24 cm) Oligohydramnios: too little fluid (SDP < 2 cm or AFI ≤ 5 cm) Anhydramnios : no fluid (no measurable pockets of fluid) 09-Oct-24 53

54. Single deepest vertical pocket of fluid is measured using ultrasound to assess amniotic fluid volume. Polyhydramnios is present in this case ( SDP; 8 cm). 09-Oct-24 54

55. Nonsonographic obstetric imaging Obstetric imaging outside of ultrasound is of limited utility and confined to very specific indications . MRI may be used for: Evaluation of specific fetal congenital abnormalities noted on ultrasound Characterization of maternal pelvic anatomy in cases with unusual or complex abnormalities CT is almost never indicated for evaluation of the fetus or maternal pelvic anatomy for obstetric indications. 09-Oct-24 55

56. Neural tube defect with tonsillar herniation ” 09-Oct-24 56

57. Image: “Neural tube defect with tonsillar herniation” Magnetic resonance imaging findings in a fetus at 23 wga , suggestive of a fetal Chiari II malformation: a: T2-weighted sagittal image demonstrating a lumbosacral neural tube defect (encircled) with cerebellar tonsillar herniation (arrow) b: T2-weighted sagittal image demonstrating a myelomeningocele (encircled) from L2 to the end of the sacrum c: T2-weighted axial image showing the myelomeningocele (encircled) d: T2-weighted axial image demonstrating hydrocephalus 09-Oct-24 57

58. Nonobstetric imaging during pregnancy Ultrasound and MRI are the preferred modalities due to the lack of radiation exposure. Example: Abdominal ultrasound is the preferred initial test for appendicitis over CT. Chest X-ray, abdomen should be shielded and only done when absolutely necessary (e.g., clinical deterioration with concern for pneumonia). Indicated in cases of choriocarcinoma to evaluate for lung metastases If CT is the modality required to make an important diagnosis (e.g., an individual presenting with stroke symptoms): A single CT scan in pregnancy is considered relatively safe. Risks/benefits should be carefully weighed and discussed with the individual. 09-Oct-24 58

59. Round, left midlung airspace opacity in an individual reported to have gestational trophoblastic disease(lung metastasis) 09-Oct-24 59

60. Refferences Shipp, T.D. (2021). Overview of ultrasound examination in obstetric and gynecology. In Barss , V.A. (Ed.), UpToDate . Retrieved July 30, 2021, from https://www.uptodate.com/contents/overview-of-ultrasound-examination-in-obstetrics-and-gynecology https:// www.uptodate.com/contents/assessment-of-amniotic-fluid-volume www.mediscape.com 09-Oct-24 60

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