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OB GYN Scans DMS 100 Video Notes

  • Introduction to OB GYN

    • OB stands for Obstetrics (focuses on pregnancy, childbirth, and postpartum period).

    • GYN stands for Gynecology (focuses on the health of the female reproductive system).

    • Visual examples of ultrasound imaging:

    • Uterus imaged with a transvaginal probe.

    • Uterus imaged transabdominally.

    • Coronal view showing a baby's nose and lips.

    • 3D picture of an infant.

  • Credentials

    • ARDMS (American Registry for Diagnostic Medical Sonography).

    • ARRT (American Registry of Radiologic Technologists).

    • The specific relevant credential for sonographers is RDMS (Registered Diagnostic Medical Sonographer).

  • Who Reads OB GYN Exams?

    • Radiologists:

    • Read some very early first trimester scans.

    • Occasionally read GYN exams.

    • Primary readers of OB exams:

    • Obstetric Gynecologists (OBGYN): General doctors seen annually for routine care.

    • Maternal Fetal Medicine (MFM) Physicians: Specialists who handle non-routine cases, specifically for obstetrics, often involving high-risk pregnancies or anomalies.

  • Gynecology Ultrasound 4.1. Purpose of a Gynecology Exam

    • To evaluate the organs of the pelvis and the uterus, including the ovaries and the adnexa.

    • The adnexa is defined as the area that surrounds the uterus and ovaries and includes the fallopian tubes.

      • Fallopian tubes are not always visible unless there is an issue with them.

    • Uses ultrasound to:

      • Help diagnose masses.

      • Detect free fluid.

      • Identify infections.

    • Monitor different conditions (e.g., follicle development, fibroid growth).
      4.2. Structures

    • Uterus:

      • A pear-shaped muscular organ.

      • Position: Posterior to the bladder but anterior to the rectum, effectively "sandwiched" between them.

      • Size varies depending on:

      • Patient's pregnancy history.

      • Menstrual cycle status.

      • Measurements:

      • Young (pre-menarche): Approximately 3 \text{ cm}.

      • Older (post-menarche): Approximately 4 \text{ inches}.

      • Plays a critical role in:

      • Menstruation.

      • Fertility.

      • Pregnancy.

    • Ovaries:

      • Typically almond-shaped structures, though shapes can vary.

      • Size: Approximately 3 \text{ cm} long in a menstruating female.

      • Position: Usually lie posterior to the uterus, around the level of the cornua (where the fallopian tubes attach), slightly lower than the uterine fundus.

      • Note: Ovaries can be found in various locations, making them sometimes challenging to locate.

      • Play a key role in:

      • Fertility.

      • Follicular development (egg maturation).

      • Hormone production (e.g., estrogen, progesterone).


  • 4.3. Anatomy

    • Uterus:

      • Positioned posterior to the bladder and anterior to the rectum.

      • While generally posterior to the bladder, it can appear superior to the bladder, especially when the bladder is full (transabdominal scanning), causing it to shift slightly.

    • Cervix: The bottom, narrow part of the uterus that extends into the vagina.

    • Vagina/Vaginal Vault: The muscular canal connecting the uterus to the outside of the body.

    • Cornua: The superior-lateral regions of the uterine fundus where the fallopian tubes attach.

    • Fallopian Tubes: Ducts connecting the ovaries to the uterus, often not visible unless enlarged or abnormal.

    • Ovarian Ligament: Connects the ovary to the lateral aspect of the uterus.

    • Endometrium:

      • The inner lining of the uterus.

      • Appears as a hyperechoic (bright) line or area in ultrasound images.
        4.4. Ultrasound Imaging

    • Bladder as an acoustic window:

      • Essential for imaging pelvic organs transabdominally.

      • A full bladder helps with acoustic enhancement, allowing better visualization of the uterus and ovaries.

      • Appears anechoic (black) on ultrasound because it is filled with fluid (urine).

    • Ovaries:

      • Can sometimes resemble a "chocolate chip cookie" due to the presence of follicles within the ovarian stroma.
        4.5. Instrumentation

    • Transabdominal Transducer:

      • Type: Curved linear array transducer.

      • Purpose: Provides deep penetration, necessary for imaging through the bladder and abdominal wall to reach deeper pelvic and abdominal structures.

      • Frequency range: Typically 3 \text{ to } 5 \text{ MHz}, but can be higher depending on the patient's body habitus.

      • Use cases: GYN scans, first trimester OB scans, and third trimester OB scans (especially as the fetus grows, requiring deeper penetration through maternal tissues and the fetus itself).

    • Transvaginal Endocavitary Probe:

      • Type: Endocavitary probe, designed for insertion into the vagina.

      • Frequency range: Higher frequency, typically 5 \text{ to } 8 \text{ MHz} or higher (commonly around 12 \text{ MHz}).

      • Advantages:

      • Allows the transducer to be positioned much closer to the area of interest (uterus, ovaries), providing better resolution.

      • Higher frequency transducers produce better image detail (resolution) but have shallower penetration.

      • Excellent for evaluating the cervix in detail.
        4.6. Transabdominal vs. Transvaginal Ultrasound

    • Transabdominal Anatomy:

      • Advantages:

      • Provides a wider field of view, allowing for a broader overview of the pelvis.

      • Offers deeper penetration, useful for larger patients or when organs are deep within the pelvis.

      • Limitations:

      • Inadequate bladder filling: If the bladder is not sufficiently full, image quality of the uterine adnexa can be severely compromised.

      • Excessive bowel gas: Gas acts as a barrier to sound waves, obstructing visualization of structures behind it.

      • Body habitus: Increased adipose tissue can limit penetration and resolution.

      • Distance from the probe: The further the organ from the transducer, the lower the resolution.

    • Transvaginal Anatomy:

      • Advantages:

      • Offers better resolution and detail due to higher frequency and closer proximity to target organs.

      • Ideal for detailed assessment of the uterine lining, ovaries, and cervix.

      • Orientation:

      • The transducer top (often shaped like a half-circle or moon) is oriented superiorly (towards the patient's head).

      • The display orientation reflects this: inferior structures are seen at the top, superior are on the bottom; anterior structures are depicted to the left of the screen, and posterior structures to the right of the screen.

      • Limitations:

      • Large uterus: If the uterus is too large (e.g., due to large fibroids or advanced pregnancy), the entire structure may not fit within the field of view. (fibroids shadow especially when they get older and become calcified and can obstruct what your seeing)

      • Dense uterine tissue: Conditions like fibroids can cause acoustic shadowing, obscuring areas behind them, especially if calcified.

      • Bowel gas: Can still interfere with imaging, though often less so than with transabdominal approach.

      • Scar tissue: Post-surgical scarring (e.g., C-section) can cause shadowing and obstruct views of parts of the uterus.

      • Patient comfort: Requires internal insertion, which can cause discomfort or be impossible for some patients (e.g., virgins, severe pain conditions, anecdotally experienced as a sonographer).
        4.7. Ultrasound Pictures

    • Longitudinal Uterus (Transabdominal): 16:30

      • Shows the uterus in its long axis, often with the bladder providing an acoustic window.

    • Transverse Uterus (Transabdominal):

      • Shows the uterus in cross-section, often with visible ovaries on either side.

    • Longitudinal Uterus (Transvaginal): 17:07

      • Clearly outlines the uterus and its inner lining, the endometrium, in its long axis.

    • Transverse Uterus (Transvaginal):

      • Shows the uterus in cross-section with a clear view of the oval-shaped endometrium within.

  • 4.8. Indications for Pelvic Ultrasound

    • Abnormal menses (most common reason). 

    • Amenorrhea - abnormal absence of mensuration

    • Dysmenorrhea - painful menses 

    • Metrorrhagia - irregular uterine bleeding including Postmenopausal bleeding

    • Menometrorrhagia - excessive irregular bleeding 

    • Pediatrics:

      • Delayed menses (e.g., suspected imperforate hymen).

      • Precocious puberty (early onset of puberty).

      • Vaginal bleeding in a pre-pubertal child (requires careful evaluation for underlying causes).

  • Screening for malignancies in patients with increased risk for ovarian cancer.

  • Follow-ups for findings from other imaging modalities like CTs and MRIs.

  • Evaluation of congenital anomalies of the reproductive tract.

  • Infertility:

    • To ensure an adequate number of follicles on the ovaries.

    • To confirm the correct shape and structure of the uterus.

  • IUDs (Intrauterine Devices):

    • To check for proper placement; IUDs can migrate to various locations:

    • Into the cervix.

    • Fall out of the uterus.

    • End up outside the uterus (perforation).

    • Poke through different parts of the uterus.

    • Anecdote: A 70-year-old patient had an IUD in for 40 years that had migrated, developed scar tissue and infection, likely leading to surgical removal and possibly a hysterectomy.

  • Post-delivery or post-surgery:

    • Transvaginal scans are sometimes performed for excessive bleeding, pain, or signs of infection.

  1. Obstetrics Ultrasound 5.1. Purpose of Obstetric Exams

    • To monitor a pregnancy and the unborn baby throughout gestation.

    • Allows for checking the health and developmental progress of the fetus.

    • Facilitates the possible detection of many congenital abnormalities and genetic conditions.
      5.2. Structures Examined

    • Uterus, ovaries, and adnexa: Always assessed, even during an OB scan, to ensure the overall health of the female reproductive system.

    • Fetus/Embryo: The primary focus of OB scans.

    • Dependent on gestational age: Different structures are evaluated at various stages to determine the baby's health and well-being.
      5.3. Anatomy (First Trimester Scans) 21:40

    • Early signs:

      • Yolk sac (first visible structure within the gestational sac, indicates viable pregnancy).

      • Small embryo, often described as an "itty bitty bean."

      • Progressive growth of the embryo into a larger fetus.

    • Twins:

      • Identified by the presence of two yolk sacs and two separate embryos within the uterus.
        5.4. Anatomy (Later Trimester Scans - Limited Overview)

    • Fetal Face:

      • Nose and lips: Detailed visualization.

      • Nasal bone: Used as a marker to help detect trisomy 21 (Down syndrome) and other congenital/genetic anomalies.

      • Sagittal and coronal views provide comprehensive assessment.

    • Fetal Heart:

      • Four-chamber heart view: Evaluates all four chambers to ensure appropriate structure and function.

    • Placenta:

      • Appears as a cloudy area within the uterus.

      • Assessed for health, position (e.g., relation to cervix), and any abnormalities.

    • Umbilical Cord:

      • Provides nutrients and oxygen to the baby.

      • Velocities (blood flow) are checked, especially if anomalies are suspected.
        5.5. Types of OB Exams

    • First Trimester:

      • Viability scan: Confirms pregnancy, location (intrauterine/ectopic), presence of fetal heartbeat, and provides early gestational age.

    • Second and Third Trimester:

      • Anatomy scan: Typically performed around 20 weeks (range 18-22 weeks) to assess all fetal anatomy for abnormalities.

      • Growth scan: Performed if the anatomy scan was incomplete, if growth appears off, or for monitoring conditions like IUGR.

      • Other specialized scans (examples):

      • AFI scans (Amniotic Fluid Index) to measure amniotic fluid volume.

      • Cervical scans to assess cervical length and competence.

      • BPP (Biophysical Profile) to assess fetal well-being using multiple parameters.
        5.6. Baby Development Milestones (Ultrasound Views)

    • 6 weeks: Small fetal pole within the gestational sac, tiny developing embryo, and a yolk sac.

    • 9 weeks: Embryo is larger, arm buds are beginning to grow, often showing a discernible profile.

    • 22 weeks: The fetus is considerably larger, with more developed features.

    • 28 weeks: Further significant growth.

    • 32 weeks: The fetus is well-developed; fat accumulation typically starts around 27 weeks, making the baby look chubbier.

    • 3D imaging: Provides detailed, life-like surface images of the baby.
      5.7. Indications for OB Exams

    • Confirm pregnancy.

    • Evaluate pelvic pain.

    • Investigate vaginal bleeding.

    • Confirm the presence of a fetal heartbeat.

    • Estimation of gestational age (when last menstrual period is unknown or uncertain).

    • Suspected anomalies: If an initial scan suggests an issue, the patient is often sent to an MFM specialist for a detailed ultrasound.

    • Evaluation of multiple pregnancies (e.g., twins, triplets) to assess chorionicity and amnionicity.

    • Maternal complications: Certain maternal conditions (e.g., diabetes) automatically trigger specific obstetric scans and monitoring protocols.
      5.8. Complications or Abnormalities in Pregnancy

    • First Trimester:

      • No heartbeats: Unfortunately, a common finding indicating a missed miscarriage.

      • Ectopic pregnancies: Pregnancy implanted outside the uterus (e.g., in fallopian tube), a life-threatening situation requiring termination of the pregnancy.

      • Multiple gestations: While not inherently sad, it is considered a complication because it increases the risks and makes the pregnancy more challenging.

    • Second Trimester:

      • Structural anomalies: Detection of various birth defects, such as cleft lip and palate, severe brain abnormalities, congenital diaphragmatic hernia (CDH), or neural tube defects.

      • Intrauterine Growth Restriction (IUGR): Fetus is significantly smaller than expected for gestational age, increasing the risk of preterm delivery or in utero demise.

      • Placental abnormalities:

      • Placenta previa: Placenta implants too close to or covers the cervix; often necessitates a C-section for safe delivery.

      • Placental abruption: Premature separation of the placenta from the uterine wall, leading to severe maternal bleeding and putting both mother and baby at significant risk (oftentimes requiring emergency C-section, anecdotally experienced by sonographer resulting in OR within 10 minutes).

      • Maternal coexisting problems:

      • Fibroids or other uterine masses that can impact pregnancy.

      • Maternal illness (e.g., preeclampsia, uncontrolled diabetes).

      • Cervical issues:

      • Incompetent cervix: The cervix opens prematurely and painlessly, leading to preterm birth or pregnancy loss.

      • Membrane rupture:

      • PPROM/PROM (Preterm Premature Rupture of Membranes): Water breaks before it's supposed to. Outcomes vary widely; some babies survive even with early rupture (e.g., 18 weeks), while others do not (e.g., at 27 weeks).
        5.9. Bioeffects in OB Scanning

    • Importance: Critically important in OB scanning to minimize unnecessary energy exposure to the developing fetus.

    • M-mode: Uses significantly less energy than pulsed-wave Doppler for assessing fetal heart rate.

    • ALARA principle (As Low As Reasonably Achievable): Sonographers should always prioritize using M-mode for fetal heart rate assessment if possible, before utilizing pulsed-wave Doppler, to reduce thermal and mechanical indices.
      5.10. Procedures Assisted by OB/GYN Sonographers

    • OBGYN sonographers assist with a range of procedures, from office-based interventions to complex operating room (OR) surgeries.

    • Examples:

      • Office procedure: Assisting with the insertion of an IUD (Intrauterine Device).

      • Sonohystergram (also known as Saline Infusion Sonohysterography - SIS):

      • Involves inserting fluid into the uterus to distend the cavity.

      • Used to visualize polyps, fibroids, or other uterine pathologies that might be missed on standard ultrasound.

      • Amniocentesis:

      • Involves taking a sample of amniotic fluid.

      • Sent for genetic testing to detect chromosomal abnormalities or genetic disorders.

      • Chorionic Villus Sampling (CVS):

      • Involves taking a small sample of the early placenta (chorionic villi).

      • Also sent for genetic testing, usually performed earlier in pregnancy than amniocentesis.

      • Percutaneous Umbilical Blood Sampling (PUBS):

      • A procedure where a needle is inserted into the umbilical cord to draw fetal blood.

      • Performed in the OR for rapid fetal blood testing, e.g., for anemia, infection, or chromosomal analysis (described as "so cool").

    • Fetal Care Center (Cincinnati, Ohio example):

      • Specializes in high-risk obstetrics and advanced fetal surgeries.

      • Procedures include:

      • In utero repair of spina bifida before birth.

      • Saline infusion around the baby when amniotic fluid production is low (oligohydramnios) to prolong gestation.

      • Development of new fetal surgeries.

      • Handles many complex cases, including multiples.

  2.  Patient Positioning

    • Transabdominal:

    • Normally supine (lying on the back).

    • If the baby compresses the Inferior Vena Cava (IVC), causing maternal nausea, lightheadedness, or discomfort, the patient can be positioned on their left side (left lateral decubitus position).

    • Transvaginal:

    • Most commonly in lithotomy position (patient in stirrups).

    • If stirrups are unavailable, the patient's bottom is elevated, feet together, and asked to spread their legs as far as possible.

  3. Patient Prep

    • Transabdominal Exam:

    • Requires a full bladder to serve as an acoustic window.

    • Patients are typically instructed to drink 32 \text{ to } 40 \text{ ounces} of water 1 \text{ to } 2 \text{ hours} prior to the exam.

    • Transvaginal Exam:

    • Typically, there is no specific prep required.

    • Depending on the exam and sonographer's preference, the patient might be asked to keep their bladder full or empty it; usually, an empty bladder is more comfortable for the patient.

  4. Controls Used in Ultrasound (Instrumentation)

    • Compression and Dynamic Range:

    • Used to optimize the grayscale image, ensuring appropriate contrast and detail for tissue visualization.

    • Gain:

    • Adjusts the overall brightness of the image.

    • Improper gain settings (overgaining or undergaining) can cause parts of the anatomy to disappear or be obscured.

    • TCG Profiles (Time Gain Compensation):

    • Adjusts the gain at different depths to compensate for attenuation of sound waves.

    • Without proper TCGs, the bottom of the screen can appear excessively dark, obscuring deeper structures. Proper use ensures uniform brightness throughout the image.