Imaging In Pregnancy Jamal Alkoteesh MD FRCR Consultant &Head of Interventional Radiology Alain Hospital.UAE Imaging and Diagnostics Management Conference Hospital build Middle East 2012 Radiology in Modern Medicine Medical problems during pregnancy Pregnant women are not IMMUNE!! 36Y -33w-Pregnant C/O Headache Talk objectives The purpose of this talk is to discuss the Indications of various forms of radiologic evaluation(XRAY;MRI;CT;US;NM) in pregnant women and their potential adverse effects (if any) on pregnancy. • X-ray Imaging during pregnancy • X-ray exposure involves ionizing radiation, which is something that could adversely affect a pregnancy but is dose dependent. . • However, the stigmata surrounding xray procedures during pregnancy has been somewhat blown out of proportion. Radiation exposure complications • In theory, x-ray exposure in pregnancy can lead to three potential problems, which are • 1- the development of birth defects (teratogenic effect), • 2- an increased risk for developing cancer in the future (carcinogenic risk), • 3- and mutation of germ cells (genetic risk). Genetic risk • • • • • Radiation exposure to germ cells (the egg and the sperm) has been shown to cause damage to chromosomes (genetic material). However, the damage is such that the cells become nonfunctional and therefore could not result in a successful conception or pregnancy. Unfortunately there is no way to know if subtle changes can occur, which could effect the genetics of future generations. In an overview perspective, x-ray imaging has been around for many years, but the incidence of chromosomal abnormalities identified in the general population has not changed. Therefore, in a general sense, x-ray exposure would not appear to substantially increase future genetic problems. Birth defects (Teratogenic risk). • This risk is dose dependent. • Much of the data on radiation exposure during pregnancy comes from the atomic bomb survivors in Japan. • High doses of radiation can cause damage to the central nervous system, especially between 8 and 15 weeks gestation. • It is believed, that significant exposure resulting in cell death or damage prior to 8 weeks gestation (which is the first 6 weeks after conception) produces an all or none effect, meaning that the pregnancy will usually be lost (miscarried). Carcinogenic risk to the fetus • • • • • The carcinogenic risk to the fetus from in utero exposure to radiation is also unclear. Several studies have been performed on the development of childhood leukemia after x-ray exposure, many of which show no increase. However, an equal number of studies have demonstrated an increase in risk, though this risk is at most only doubled. Therefore, if the baseline risk for a child developing leukemia is 1 in 3000, this risk could be 1 in 2000 at the most. It has been suggested that the development of cancer following radiation exposure may be higher in children when compared to adults; however, it is unlikely that this increase is any higher than 1 in 1000. Pregnancy Dating • It is important to discuss the dating of a pregnancy and the significance of the first trimester. • In most instances, the due date of a pregnancy is based upon a woman’s last menstrual period(40W vs 38). • Therefore, when examining the issue of radiation exposure during pregnancy, the first two weeks of gestation are not a concern because the woman is NOT pregnant yet. • Week three is the first week after conception. Pregnancy US Dating • It is also important to know that many pregnancies are actually dated and given a due date by ultrasound. • The gestational age of a pregnancy given by an ultrasound examination adds in the same two-week fudge factor that is seen when using the last menstrual period. • Therefore, if a first trimester ultrasound states that a pregnancy is at 8 weeks gestation, in reality that pregnancy is 6 weeks from conception. Fetus development 4w-12w • • • • • A gestational age of more than 4 weeks (or after the first two weeks of conception) through 12 weeks is when the major body parts and organs of the fetus form. The central nervous system is the first organ system to develop starting at 4 ½ weeks gestation and is basically finished by 10 weeks; The heart also begins at 4 ½ weeks gestation and is also basically finished by 10 weeks; The intestinal tract starts to develop at about 6 to 7 weeks gestation, The small and large intestines actually form outside the body of the baby, they rotate, and then move to the inside of the body by 11 to 12 weeks gestation; Fetus development 4w-12w • The eyes and the ears start to form at around 5 to 6 weeks and are basically finished by 10 weeks; • The arms and legs start to develop at about 6 weeks, they have an upper portion, a lower portion, and • The hands and feet by 9 weeks, and are usually complete with fingers and toes by 10 weeks gestation. • Therefore, the first trimester is the most concerning regarding the issue of birth defects because that is the time period in which most of the fetus is formed. Radiation adverse effect • • • • • • In humans, the most common adverse effects seen from highdose radiation are intrauterine growth restriction, microcephaly, and mental retardation. The risk of mental retardation appears to take at least a dose of 20 rads. This risk is 40% following a dose of 100 rads and increases to 60% with a dose of 150 rads. Microcephaly and fetal growth restriction have been reported at doses between 10 and 20 rads; however, no adverse effects have really been seen below 10 rads. (ACOG) and (ACR) both state that exposures of less than 5 rads do not increase the risk for anomalies This threshold is well above the range for the majority of diagnostic procedures in use today Exposure to Radiation without knowing pregnancy • Likewise, if a woman discovers that she was pregnant after she already underwent X-RAY procedure, she should be advised on the amount of fetal exposure that occurred and the gestational age of exposure should be determined. • In the majority of cases, the potential risk will be negligible. • American College of Obstetricians and Gynecologist have stated that exposure to x-rays during a pregnancy is not an indication for therapeutic abortion Toppenberg KS, et al. Safety of Radiographic Imaging During Pregnancy. Am Fam Physician. 1999 Apr; 59(7):1813-18 Daily Radiation exposure • Remember!!!, we are exposed to small amounts of radiation from the atmosphere on a daily basis and this is increased with altitude (for example, a higher dose during airplane travel or at the top of a mountain when compared to sea level). • Also small amounts of exposure occur when passing through metal detectors at airport terminals and entrances to courthouses, etc. • Mobile phones&labtops • Therefore, radiation exposure is a daily occurrence. • . Ultrasound Imaging during pregnancy • • • • • • • Ultrasound utilizes sound waves to create an image and therefore is not a form a radiation. No studies have ever documented that ultrasound usage in human pregnancy can lead to fetal harm. Therefore, it has become the main modality for imaging during pregnancy. However, in theory and in animal experiments, ultrasound at certain levels can produce certain bioeffects, which include an increase in tissue temperature and the ability to produce cavitation. ACOG and the American Institute of Ultrasound in Medicine (AIUM) initially set the upper limit for energy exposure with obstetrical ultrasound at 100mW/cm2. The FDA lowered this level to 94mW/cm2 in 1996. Therefore, ultrasound machines are now required to have output display screens that predict tissue heating (the thermal index or TI) or the potential for cavitation (the mechanical index or MI). Of note, increasing the “gain” of the ultrasound machine does not increase the energy delivered, whereas increasing the “power” output will. Magnetic Resonance Imaging • • • • Magnetic resonance imaging (MRI) employs the use of magnets that alter the energy state of hydrogen protons and again is not ionizing radiation. The use of MRI in pregnancy has greatly increased in the past 3 to 4 years with multiple publications regarding its usage in diagnosing inutero fetal CNS abnormalities. MRI is indicated in the evaluation of fetal neck masses, fetal chest disorders (differentiating between congenital diaphragmatic hernia, congenital cystic adenomatoid malformation, and pulmonary sequestration) and fetal urinary tract abnormalities. Ultrasound imaging is at its best when a good amount of amniotic fluid is present, but is hampered by oligohydramnios (very low amniotic fluid volume) which is not a problem for MRI Imaging MRI in Pregnancy • One problem that sometimes occurs with MRI usage in obstetrics is the difficulty in obtaining clear images when fetal movement occurs. • The majority of studies that have utilized MRI in pregnancy have been performed after the first trimester. • The National Radiological Protection Board (NRPB) has arbitrarily advised that MRI not be performed in the first trimester if at all possible until further studies are performed. • A few recent reports have described Fast MRI imaging, which decreases exposure but still obtains quality images. This approach may show promise for further usage in obstetrics. Nuclear Medicine Studies • The most common nuclear medicine study performed on women of childbearing age is the pulmonary ventilation-perfusion (VQ) scan. • Macro-aggregated albumin that is labeled with technetium Tc 99 is used for the perfusion part of the study and inhaled Xenon gas is used for the ventilation part. • The amount of radiation exposure to the fetus with a typical study is very small, estimated to only be about 50 millirads. • Because pulmonary embolism (PE) is one of the major causes for maternal death during pregnancy, if there is a high clinical suspicion for PE, then a VQ scan is an accepted diagnostic modality according to ACOG. • Hyperthyroidism and Radioactive Iodine treatment • Women have a higher rate of thyroid abnormalities when compared to men. • A common non-surgical treatment for significant hyperthyroidism is the radioactive isotope of iodine (Iodine 131 or I131). • Because iodine readily crosses the placenta, I131 treatment is not recommended during pregnancy. • In reality, the fetal thyroid gland develops at about 8 weeks gestation and does not begin to concentrate iodine until about 11 to 12 weeks. • Therefore, usage prior to 10 weeks would be of no consequence. • Therefore, if a woman undergoes treatment for hyperthyroidism, and later she discovers that she was pregnant, timing the exposure in the first trimester is of utmost importance. • If it occurred prior to 10 weeks gestation, she can be reassured that the fetus was probably unaffected. Contrast Material • Iodinated Contrast: – Category B drugs; that is, animal reproduction studies have not demonstrated a fetal risk, • Gadolinium Contrast – Animal studies show growth retardation and congenital anomalies with doses 2-7x normal human dose Protocol for Radiologic Imaging of Pregnant Patients 1 • • • • • • • 1. Renal colic&Suspicion of obstructing ureteral stone a. <24 weeks gestation – limited IVU consisting of scout film, 10 minute film and the minimal number of additional films required b. >24 weeks gestation – helical CT per renal colic protocol. IVU can be substituted but often requires many films, delivers a higher radiation dose, and is more difficult to interpret. 2. Upper or diffuse abdominal pain with suspicion of cholecystitis, pancreatitis or pyonephrosis a. Ultrasound of the abdomen 3. Lower abdominal pain with suspicion of adnexal mass, including appendicitis a.US& MRI of the abdomen and pelvis, Gd-DTPA is to be used judiciously when required to determine the diagnosis but must be avoided entirely during the first trimester Protocol for Radiologic Imaging of Pregnant Patients 2 • 4. Cancer staging of abdomen and pelvis • • • • • • • • a. MRI, with IV Gd-DTPA, except during the first trimester 5. Screening for active maternal tuberculosis a. PA plain film of the chest 6. Cancer staging of the chest, diagnosis of pulmonary embolism, other serious chest disease a. CT of the chest with intravenous contrast agent and appropriate protocol b. V/Q scan may be used as an alternate to contrast-enhanced CT of the chest for the diagnosis of pulmonary embolism 7. Maternal trauma a. CT with IV contrast as per standard trauma protocol 27y f Egy .32w pregnant with Placenta previa and accrete Uterine Artery ballooning and UAE 30y pregnant lady 25w • Chest pain • Gradual shortness of breath • D-Dimer 350??? PE in Pregnancy • The incidence of PE during pregnancy ranges between 0.3 and 1per 1000 deliveries. • PE is the leading cause of pregnancy-related maternal death in developed countries. • The risk of PE is higher in the post-partum period, particularly after a Caesarean section. • The clinical features of PE are no different in pregnancy compared with the non-pregnant state. • However, pregnant women often present with breathlessness, and this symptom should be interpreted with caution, especially when isolated and neither severe nor of acute onset. Diagnostic Tests for PE • Imaging Studies – CXR – CD US Legs – V/Q Scans – MDCT PE – MRI PE – Pulmonary Angiography • Laboratory Analysis – CBC, ESR, Hgb/Hct, – D-Dimer – ABG’s – Echocardiography • Ancillary Testing – EKG – Pulse Oximetry 34 Diagnosis of pulmonary embolism in pregnancy • Exposure of the fetus to ionizing radiation is a concern when investigating suspected PE during pregnancy. • However, this concern is largely overcome by the hazards of missing a potentially fatal diagnosis. • Moreover, erroneously assigning a diagnosis of PE to a pregnant woman is also fraught with risk since it unnecessarily exposes the fetus and mother to the risk of anticoagulant treatment. • Therefore, investigations should aim for diagnostic certainty The Reality: Most chest x-rays in patients with PE are nonspecific and insensitive Hampton’s Hump Atelectasis Prominent PA Westermark’s Sign Compression ultrasonography venography • • • • • • In 90% of patients, PE originates from DVT in a lower limb. In a classic study using venography, DVT was found in 70% of patients with proven PE. Up to 40% of patients with DVT without PE symptoms will HAVE a PE by angiography CUS has a sensitivity over 90% for proximal DVT and a specificity of about 95%. CUS shows a DVT in 30–50% of patients with PE, and finding a proximal DVT in patients suspected of PE is sufficient to warrant anticoagulant treatment without further testing. Helpful to rule out DVT in patient with non-diagnostic V/Q scan or when PE imaging is not available or contraindicated. Perrier A, Bounameaux et al. Ann Intern Med 1998;128:243–245. V/Q Scan • Advantages – Excellent negative predictive value (97%) – Can be used in patients with contraindication to contrast medium • Limitations • About 60% of V/Q scans will be indeterminate (intermediate + low probability) and non-diagnostic scan necessitating further investigation Sostman HD et al. Radiology. 2008;246:941-6. Ventilation-Perfusion (V/Q) Scans V/Q with Large Defect V/Q Radiation dose • The radiation exposure from a lung scan with 100 MBq of Tc-99 m macroaggregated albumin particles is 1.1 mSv for an average sized adult according to the International Commission on Radiological Protection (ICRP), and thus significantly lower than that of a spiral CT (2–6 mSv). • Female Breast dose is much lower than MC-CT • In comparison, a plain chest X-ray delivers a dose of approximately 0.05 mSv. Radiation dose to patients from radiopharmaceuticals. Ann ICRP 1998;28:69. Multidetector-CT Technique • Parameters vary by scanner equipment • Contrast material bolus – Duration of injection should approximate duration of scan – Desired flow rate 3-5ml/s – Usually 50-100ml • Best results achieved if: – Thin sections – High and homogenous enhancement of pulmonary vessels – Data acquisition in single breath hold Schaefer-Prokop et al. Eur. Radiol. Suppl. 2005;15(4):d37-d41. Methods of Reducing the Radiation Dose to the Maternal Breast and Fetus at CT Pulmonary Angiography • • • • • • • • • • • Thin-layer bismuth breast shield Lead shielding on the abdomen and pelvis Reduction in tube current Reduction in tube voltage Increase in pitch Increase in detector collimation thickness Reduction of z-axis Oral barium preparation Elimination of lateral scout image Fixed injection timing rather than test run Elimination of any additional CT sequences As low as reasonably achievable”ALARA Comparison of Standard and Reduced-Dose CT Pulmonary Angiography Protocols In Pregnancy • • • • • • • Parameter Standard Protocol Reduced-Dose Protocol Kilovolt peak 120 100 Milliamperage 200 100 Scanning range Entire thorax Aortic arch to diaphragmatic domes Bolus timing Automatic trigger Standard 15-sec delay Injection rate (mL/sec) 4 4 Effective dose (mSv)* 10.2 2.7 Methods of Reducing Fetal Radiation Dose at Lung Scintigraphy V/Q Scan • Reduce dose of perfusion agent • Reduce dose of ventilation agent • Eliminate ventilation portion of scan • Either encourage patient to void frequently or insert Foley catheter to reduce fetal exposure to radiotracer in the bladder 38-year-old woman at 24 weeks gestation who presented with shortness of breath and occasional hemoptysis PE Imaging • It is important to note that even a combination of CXR;V/Q Scan,MSCT and DSA exposes the fetus to around 1.5 mGy of radiation, which is well below the accepted limit of 50 mGy for the induction of deterministic effects in the fetus and similar to background radiation exposure to the fetus of 1.1–2.5 mGy Appendicitis • Most common non-obstetric surgical condition, also the most delayed due to overlap of symptoms with normal pregnancy. • Most reliable symptom is right lower quadrant pain. • Leukocytosis may be physiologic since the normal range in a gravid patient may range from 6,000 to 16,000. • Delay may cause increased fetal and maternal mortality therefore early diagnosis is essential. Dilated appendix with hypointense appendicolith representing acute appendicitis. Axial FSE T2w image Cholecystitis • Second most common surgical condition during pregnancy. • 1/6000 to 1/10,000 pregnancies. • Cause is usually due to cholelithiasis in >90%. • LFTs elevated. • US is 1st Modality • Gad enhanced T1 weighted images with fat suppression show high sensitivity in diagnosing cholecystitis. Large Leiomyoma(Fibroid) • 25-50% of women of child bearing age. • Composed of smooth muscle and variable amount of fibrous tissue, surrounded by a psuedocapsule of areolar tissue . • Hormonal stimulation due to pregnancy can cause rapid growth. • MRI findings: T2W images demonstrate a well circumscribed mass with predominantly low signal intensity . • T1 weighted images show intermediate signal, often indistinguishable from surrounding uterine tissue. • Degenerative changes appear as high signal on T2 weighted images. • Foci of calcifications appear as low intensity on all sequences . Benign Mucinous Cystadenoma • Multilocular cystic lesions with broad spectrum of signal intensities, filled with water like or mucinous contents. • Multiple cysts of different signal intensities are typical. • T1W images show intermediate signal and high/medium signal on T2W images. • If complicated by hemorrhage, Low intensity signal is present on T1W images Blunt Trauma in the Pregnant Woman • Trauma occurs in 6-7% of pregnancies in US and is a Leading non-obstetric cause of maternal death • Nearly 20% of pregnant woman surveyed never or rarely used seat belts; and 22% used them incorrectly • Pregnant woman can lose 30% (2L) of blood volume before vital signs change • At 30 wks GA the uterus is large enough to compress the great vessels causing – up to a 30mm Hg drop in systolic BP – 30% drop in stroke volume ACOG educational bulletin. Obstetric aspects of trauma management. Number 251, September 1998 (replaced Number 151, January 1991, and Number 161, November 1991). Int J Gynecol Obstet 1999;64:87-94 Uterine Rupture • 0.6% of all injuries during pregnancy • Various degrees ranging from serosal hemorrhage to complete avulsion • 75% of cases involve the fundus • Fetal mortality approaches 100% • Maternal mortality 10% – Usually due to other injuries – Prompt diagnosis is essential. Weintraub AY, Leron E, Mazor M. The Pathophysiology of Trauma in Pregnancy: A Review. J Mat-Fet and Neo Med 2006;19(10):601-5. 29Y Pregnant-29w C/O Back Pain Guidelines for Diagnostic Imaging during Pregnancy-Take home message 1.Fetus:Woman should be counseled that X-ray exposure from a single diagnostic procedure dose not result in harmful fetal effects. Specifically, exposure to less than 5rad has not been associated with an increase in fetal anomalies or pregnancy loss. 2. Mother:Concern about possible effects of high-dose ionizing radiation exposure should not prevent medically indicated diagnostic X-ray procedure from being performed on the mother. 3.US&MRI:During pregnancy, ultrasonography and magneetic resonance imaging, should be considered instead of X-rays when possible Counseling the Pregnant Patient about Imaging Procedures • Decrease the anxiety • Use terms that can be understood by the patient • Risk of congenital anomalies, miscarriage, birth defects, or mental retardation is negligible • Risk of development of childhood cancer and leukemia is real, it is small • Consequences of delaying or refusing imaging must also be explained Questions