ULTRASOUND IN OBSTETRICS & GYNECOLOGY Hidayat Wijayanegara Department of Obstetric & Gynecology School Medicine Padjadjaran University / Hasan Sadikin Hospital Bandung

Ultrasound examination : Reveals vital information Fetal anatomy Fetal environment Growth Well being No biological hazard The first obstetrical application of USG imaging : Ian Donald (1958)

Ultrasound Sound waves of frequencies higher than the hearing limit of the human ear are called ultrasonic waves The limit is by convention 20 KHz Medical practice frequencies between 1-10 MHz are commonly used

Technology : Sound waves reflecting back from the fetus or image structure  displayed on the ultrasound screen Alternating current is applied to a transducer made of piezoelectric material  intermittent high frequency sound waves exceeding 20,000 cps are generated

Interface between structures of different tissue densities The transducer emits a pulse of sound waves that passes through the layer of soft tissue  Interface between structures of different tissue densities Some of the energy is reflected back to the transducer A small electrical voltage Display on a screen Bone is dense (echogenic)  white on the screen Fluid (anechoic)  black Soft tissues  varying shade of gray

The diagnostic ultrasound visualization method 1.Operator control 6. Visual information 2.Transducer drive 5. Electric information 3.Ultrasound pulses 4. Acoustic information The diagnostic ultrasound visualization method Operator Instrument Transducer Tissue interaction

Transabdominal Scanning : Performed with 3.5 – 7 MHz Safety : no confirmed biological effects in mammalian tissue have been demonstrated in the frequency range of medical ultrasound (AIUM, 1991)

Choice of equipment : Transabdominal scanning Transvaginal scanning Doppler and color flow imaging 3D 2D

Biophysical mechanism : Are not fully understood The effects of ultrasound on various biological entities may be due to one or a combination of any of the following : 1. Heating effects 2. Cavitational effects 3. Mechanical effects Are associated only with high average intensities and not found in diagnostic equipment

Preparation of the patient Ultrasound beam cannot penetrate gas The interface created by gas  the sound beam totally reflected Water  excellent transmission medium The distension of bladder  displaces intestinal loop  acoustic window to the pelvic structure Patient should be scanned with a full bladder The full bladder technique offer : 1. It displaces the fetal head upwards 2. It allow visualization of the cervix

Coupling agents Scanning technique A gel or an oil  eliminates the air interface between the transducer and the patient’s skin Scanning technique The patient is on your right The machine is on your left Work in dim lighting to help reflection on the screen

Indications for ultrasound examination Gynecology : - Uterus, Ovaries, Adnexa - Abnormal bleeding, pelvic pain & discomfort - IUCD location and complications - Pelvic mass reveals mass or enlargement of pelvic organ - Evaluation of masses palpable - Ovulation induction therapy - Guidance for abscess drainage

Uses of ultrasound in gynecology 1. Determine the size and location of lesions 2. Characteristics of the lesion: cystic, complex or solid 3. Determine if mass is uterine or extrauterine 4. Evaluate the extent of pelvic inflammatory disease or endometriosis and follow-up 5. Follow the course of a simple cyst: regression, etc. 6. Locate the position of an intrauterine device 7. Detection of ascites 8. Radiation therapy planning

Obstetrics : Routine obstetrical ultrasound scan: 18-20 weeks 1st Trimester : Confirm pregnancy, viability, gestational age Rule out : Ectopic pregnancy Gestational trophoblastic disease Foreign bodies Large for dates – fibroid, uterine malformation, multiple gestation Small for dates – missed abortion, blighted ova

Ovaries, rule out adnexal lesions, uterine position, rule out uterine anomalies Undetermined etiology of vaginal bleeding Suspected complications, i.e subchorionic hematome

2nd and 3rd trimester : Confirm viability, gestational age, fetal number Evaluated fetal growth, anatomy, lie, position, follow up anomaly Evaluate placenta, AFV, cord Biophysical profile for fetal well being Vaginal bleeding

Components of basic ultrasound examination according to Trimester pregnancy 1st trimester Gestational sac location Embryo identification Crown rump length (CRL) Fetal heart rate motion Fetal number Uterus & adnexal evaluation 2nd and 3rd trimester Fetal number Presentation Fetal heart motion Placental location Amniotic fluid volume Gestational age Survey of fetal anatomy Evaluation for maternal pelvic mass

Ultrasonic Landmark Occurence (weeks of gestation) Gestational sac 5 – 6 weeks Fetal embryonic pale 6 – 7 weeks Detection of fetal life 7 – 8 weeks Placenta 8 – 10 weeks Loss of gestational sac 11 – 13 weeks Fetal head 11 – 14 weeks (Biparietal diameter)

Evaluation of ultrasound to determine gestational age Crown Rump Length (CRL) Biparietal diameter (BPD) Femur Length (FL) Head Circumference (HC) Abdominal Circumference (AC)

Accuracy of ultrasound measurement for different gestational groups Ultrasound parameter Accuracy Gestational sac diameter + 7 days Crown Rump Length + 3-5 days BPD second trimester + 1 to 1.5 weeks BPD third trimester + 2 to 4 weeks FL second trimester + 1 to 1.5 weeks FL third trimester + 3 to 3.5 weeks Multiple parameter (2nd trimester) + 1.5 weeks Multiple parameter (3rd trimester) + 2.5 weeks

Summary 1. Physics of ultrasound The ultrasound used in clinical practice is limited to frequencies in the range of 1-10 cycles per second (1-10 MHz) In Obstetrics : 3.5 MHz and 5 MHz 2.Ultrasound Is produced when transmitted pulses of sound from the transducer cross body structures and reflect energy back to the transducer from the interfaces of organs

3. Ultrasound in Obstetrics Confirmation of an intrauterine pregnancies Exclusion of an ectopic pregnancies Assessment of an intrauterine pregnancies Determination of gestational age : Are uncertain of the date of conception Resolving discrepancies between gestational age and uterine size : Large for dates Small for dates

Investigation of uterine bleeding Visualization for high risk procedures Amniocentesis Chorionic villous sampling Cordocentesis Evaluation of fetal well-being Distinguish congenital malformation Biophysical profile Doppler flow velocimetry IUGR  60-80% of the time in cases where the umbilical artery waveforms are abnormal due to uteroplacental insufficiency

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