Medical Imaging in ObstetricsMedical Imaging in Obstetrics

Mohamed Kandeel, M.D.Mohamed Kandeel, M.D.

Professor of Obstetrics and GynecologyProfessor of Obstetrics and Gynecology

Menofyia University, EgyptMenofyia University, Egypt

ObjectivesObjectives

At the end of this presentation, you should be:

1-Aware of the different imaging modalities which can be used safely during

pregnancy.

2- Aware of the different uses and risks of the different imaging techniques.

I- I- X - RayX - Ray

X ray is a form of radiant energy, similar to light or radio waves, but they have the ability to

penetrate the body and produce pictures for different organs which can be interpreted on a TV

screen or a computer monitor. Unborn children are particularly sensitive to x-rays because their

cells are rapidly dividing and developing into different types of tissue and organs. Ionizing

radiation (x-ray) are capable of reducing cell division, and damaging genetic DNA and it can be

measured in different units, the gray (Gy) and the rem, or in the older and more commonly

recognized unit, the rad.

The maximal permissible limit of ionizing radiation to which the fetus should be exposed during

pregnancy is a cumulative dose of 5 rad (1). However, the March of Dimes has reported that

studies found no significant relationship between exposure of pregnant women to 5–10 rads of x–

rays and malformations in their children (March of Dimes, September 1997). The National

Council on Radiation Protection (2) stated that the risk of malformations is significantly

increased only at doses above 15 rad.

I- X Ray – X Ray – (Cont.)(Cont.)

Exposure to as little as 1 or 2 rad has been associated with a slight increase in childhood

malignancies, especially leukemia. According to the Nuclear Regulatory Commission (NRC),

children exposed to 2–6 rads of x-rays in utero have an increased chance of developing cancer

(NRC, 1999, Biological Effects of Radiation).

Ionizing radiation is known to create bizarre new mutations. The dosage required to double

the baseline mutation rate, found in general population, is between 50 and 100 rad.

Federal laws have been established to protect the unborn children of women exposed to

radiation in the workplace. In the workplace, the dose of radiation to an unborn child

throughout the entire pregnancy should not exceed 0.5 rem. For x-rays, rem and rad are

equivalent and the limit of exposure for unborn children is therefore 0.5 rads.

I- X Ray X Ray (Cont.)(Cont.)

A radiation physicist can calculate the estimated dose of radiation to the fetus to

assist in patient counseling. No single diagnostic procedure results in a radiation

dose that threatens the well-being of the developing embryo and fetus.

It is essential when you counsel your patient not to promise her a perfect baby to

avoid parenteral disappointments and lawsuits. As part of counseling, you should

inform mother that the actual risk depends on gestational age and that spontaneous

birth anomalies occur in 4 to 6 percent of all deliveries. It is also important to

clarify that x-rays affect only body tissues which come into direct contact with the

beam.

I-I- X Ray X Ray (Cont.) (Cont.)

Uses:

1-Diagnose Intrauterine fetal death, fetal presentation and position

2-Diagnose congenital malformations. e.g. hydrocephalus

3-Pelvimetry

4-Placental localization

5- Exclude vesicular mole: no boney skeleton at 15 weeks or more

I-I- X Ray X Ray (Cont.)(Cont.)

Risks:

1-Congenital fetal malformations. In early pregnancy, A single abdominal

exposure exposes the abdomen for 0.5 r while pelvimetry exposes the

abdomen for 1.1 r. Microcephaly and mental retardation occurs at a dose of

100-200 r.

2-Abortion and Intrauterine fetal death

3-In late pregnancy, cleft palate and cataract

4-Fetal gene mutation and infertility

5-Fetal neoplasms especially leukaemia.

II-II-Iodinated Contrast MediaIodinated Contrast Media

The use of intravascular contrast media is better avoided in pregnancy.

Contrary to animal studies, in vitro studies have shown iodinated contrast

to be mutagenic to human cells. Also, the iodine content of contrast media

have the potential to produce neonatal hypothyroidism. The evidence for

this potential stems from the occurrence of neonatal hypothyroidism after

direct instillation of ionic contrast into the amniotic cavity. Therefore; it is

essential to screen all infants of mothers who received iodinated contrast

during pregnancy for hypothyroidism. On the other hand, the use of an

intravascular non-ionic contrast media was not found to have any

detrimental effect on neonatal thyroid function.

Management of Irradiated Pregnant womenManagement of Irradiated Pregnant women

1-According to Danish rule of 1959, termination was indicated for a fetal

dose > 10 rads.

2-Wagner et al suggested termination only be considered if a radiation

dose exceeds 5 rad between 2 and 15 weeks of gestation, and is indicated

only for doses over 15 rad.

3-Hall suggests termination for a radiation dose of over 10 rad received

between a gestational age of 10 days and 26 weeks.

III-III-Radionuclide ScansRadionuclide Scans

• Whenever a pregnant woman is scheduled for a Radionuclide exams

(nuclear medicine scan), she should inform her physician/technologist who

will consult with her caring physician for either possible postponement of

the procedure if not urgent, or taking extra precautions to minimize

exposure.

• Another precaution is advised for women who are breast-feeding. Because

some of the pharmaceuticals that are used for the procedure can pass into

the mother's milk, the patient should discontinue breast-feeding for a short

while, pump her breasts in the interim and discard the milk. Breast-feeding

can often resume shortly afterwards.

IV-IV-UltrasoundUltrasound

This is a procedure which uses high-frequency sound waves to view internal

organs. Ultrasound imaging uses the principles of sonar developed for ships at sea,

or radar detection for speedy cars. As sound passes through the body it produces

echoes, which can be used to identify distance between body parts and their size

and shape.

Ultrasound has no known detrimental effects on either mother or fetus.

Methods of UltrasoundMethods of Ultrasound1-1-Vaginal UltrasoundVaginal Ultrasound

Technique:

1-A specially designed transducer is covered with a condom, lubricated, and placed

inside the vagina.

2-The transducer is then moved around the vagina, pressed up on either sides of the

cervix, to allow visualization inside the uterus and pelvis. The procedure might

cause some tolerable pain, which usually does not prevent the examination.

Trans-vaginal ultrasound is most useful in the first trimester and is of great help in

fat women and in those with an RVF uterus.  

2-2-Abdominal UltrasoundAbdominal Ultrasound

Technique:

1-The patient should be advised to drink plenty of fluids before examination so that to have a full

bladder. This allows the uterus to be lifted out of the pelvis during examination for better

image. This advise is valid till 28 weeks gestation.

2-Warmed lubricant is applied over the patient’s abdomen.

3-The transducer is then palced in contact with the patient’s abdomen and moved around over the

patient’s abdomen as needed to visualize the fetus and determine its viability, its organs, the

placenta, and the cervix for length and comptence.  Gestational age is determined using a set

of parameters including crown-rump Length, abdominal circumference, biparietal diameter,

head circumference or femur length.

3-3-3-4 D Ultrasound3-4 D Ultrasound

• Using a specially designed probe for 3 D image, the transducer takes a series of

imagesof the subject and the computer, using special software, processes these

images and presents them as a 3 dimensional image.

• Having a good quality image depends on many factors:

1-The operator skill

2-The amount of amniotic fluid

3- Fetal position

4-Abdominal maternal obesity

• 4-D scanners allows parents to see the details of their baby before birth helping the

establishment of strong psychological and emotional bonds.

IV-IV-UltrasoundUltrasound

Uses in pregnancy:

1-Determine gestational age, growth, viability & presentation of the fetus

2-Identify multiple gestations and zygosity

3-Measurements of the amniotic fluid volume and diagnosis of oligo/polyhydramnios

4-Diagnosis of placenta previa and placental abruption

5-Diagnosis of congenital fetal malformations, IUGR and IUFD

6-As a guide for amniocentesis, cordocentesis and chorionic villus sampling and during

intrauterine blood transfusion in treating RH isoimmunization

7- 3-D ultrasound improves the diagnosis of congenital anomalies such as spina

bifida,cardiac malformations, cleft lips/palate, polydactyly, facial dysmorphism or

clubbing of feet.

V-V-Computed TomographyComputed Tomography

Computed tomography (CT) scans allow for cross-sectional views of

body organs and tissues. The procedure utilizes ionizing radiation and

therefore; pregnant women or those intending to become pregnant

should have a CT scan only if the diagnostic benefits outweigh the risks.

They should avoid full body or abdominal scans. It is important not to

repeat the film should any error occur during scanning.

The amount of exposure depends on maternal and fetal sizes, fetal

position and distance from the radiation. Pregnant patients receiving CT

or any x-ray exam away from the abdominal area should be protected by

a lead apron.

V-V-Computed TomographyComputed Tomography (Cont.)(Cont.)

Uses:

1-Cranial CT: detect acute hemorrhage in eclamptic women

2-CT pelvimetry

3-Abdominal CT: done only if the fetus is dead

4-Evaluate brain, lung, liver & pelvic metastases in GTD

5-Diagnoses of DVT

6-Diagnosis of acute neurological catastrophy during pregnancy

VI-VI-Magnetic Resonance Imaging (MRI)Magnetic Resonance Imaging (MRI)

MRI is a form of low-energy non-ionizing radio waves and it gives different and more

detailed information compared with X-ray, ultrasound, or computed tomography scan. During

examination, the part of the body being scanned is placed inside a special machine that

contains a strong magnet. Digital pictures from an MRI scan are then taken and stored on a

computer for more study either on the spot or remote as in a clinic or an operating room.

An informed consent must be signed by the patient. Before the procedure.

VI-VI-MRI-Safety during pregnancyMRI-Safety during pregnancy

MRI avoids the use of ionizing radiation and therefore, is considered safe. During

pregnancy, it should only be performed for maternal rather than fetal reasons. It

should be reserved for pregnant patients with suspected serious problems.

MRI is better avoided during the first trimester and more specifically during the

period of organogenesis. Hazards that may affect the fetus include heating, noise

(which theoretically may cause acoustic damage) and the use of the contrast agents;

gadolinium compounds, which cross the placenta and enter the fetal bloodstream,

and their use during pregnancy should be avoided. Evidence for teratogenic effects

was shown in animal studies.

VIVIMRI-Safety during pregnancyMRI-Safety during pregnancy (Cont.) (Cont.)

A reduction in crown-rump length was seen in mice exposed to MRI in

mid-gestation. Exposure to the electromagnetic fields caused eye

malformations in a mouse strain and several hours of exposure of chick

embryos in the first 48 hours of life to a strong static magnetic field

resulted in an excess number of dead or abnormal chick embryos when

examined at day 5.

If you are going to scan a breast feeding mother receiving a contrast agent,

advise patient to pump breast milk before the study, to be used until

injected contrast material has cleared from the body, which typically takes

about 24 hours.

VIVIMagnetic Resonance Imaging (MRI)Magnetic Resonance Imaging (MRI) (Cont.) (Cont.)

Uses of MRI:

1-Role out associated medical emergencies during pregnancy. e.g. appendicitis

during pregnancy: Typically, ultrasound is the preferred method for imaging the

appendix in pregnant women, but the enlarged uterus and other physiologic

changes--particularly during the third trimester--may prevent proper visualization

of the appendix, rendering the exam inconclusive.

2-Diagnoses of congenital fetal malformations and fetal tumors

3-Facilitating open fetal surgery and other fetal interventions

4-Planning for procedures (such as the EXIT procedure = ex utero intrapartum

treatment procedure) to safely deliver and treat babies whose defects would

otherwise be fatal.

RferencesRferences

1-American College of Obstetricians and Gynecologists, Committee on

Obstetric Practice. Guidelines for diagnostic imaging during pregnancy.

ACOG Committee opinion no. 158. Washington, D.C.: ACOG, 1995.

2-Hall EJ. Scientific view of low-level radiation risks. Radiographics

1991;11:509-18.

Thank You