Placenta Imaging by

Ultrasound and MRI

Mariana L. Meyers, MDAssistant Professor Pediatric Radiology

Director Fetal Imaging

No disclosures

Mariana L. Meyers, MD

Overview

• Brief review of placentation (accreta, increta, percreta) anomalies

• Normal placental appearance in Ultrasound and MRI

• Case base review of imaging evaluation of placentation

• MRI safety

• New advances on placenta imaging

Placentation - Definition

• Abnormal implantation of placenta in the uterine wall

• Depth of implantation:

- Accreta: chorionic villi attach to the myometrium

- Increta: chorionic villi invade into the myometrium

- Percreta: chorionic villi invade through the perimetrium

Incidence

• Has increased > 10 fold in the past 30 years due to increased rate Cesarean section (CS)

• 0.9% of pregnancies have placentation anomalies

• 80% of placentations are associated with previa

• Of those with previa: 9.3% have placentation anomalies

Placenta Accreta: Spectrum of US and MR Imaging Findings Baughman et al. Radiographics November

2008 28, 1905-1916

Risk factors

• Prior CS

• Placenta previa

- Prior CS + previa are the strongest risk factor

• High maternal age

• Intrauterine surgeries

Risk of accreta with prior CS

Silver RM, Landon MB, Rouse DJ, et al. Maternal morbidity associated with multiple repeat cesarean deliveries.

Obstet Gynecol 2006; 107:1226–1232

Pathophysiology

• Primary defect of the trophoblast function

• Abnormal uteroplacental circulation: results in deep trophoblast penetration into the uterus

• A secondary basalis defect due to a failure of normal decidualization

• Abnormal vascularization and tissue oxygenation of the uterine scar: primarily related to surgery or CS

Pathophysiology of Placenta Creta: The Role of Decidua and Extravillous TrophoblastP. Tantbirojn et al. Placenta 29 (2008)

639e645

Benirschke K, Kaufmann P, Baergen RN. Pathology of the human placenta. 5th ed. New York: Springer-Verlag; 2006

Baergen RN. Manual of Benirschke and Kaufmann’s pathology of the human placenta. New York: Springer-Verlag; 2005.

Pathophysiology

• Chantraine et al. studied 13 hysterectomy specimens

with accreta: noted major differences in the vascular

architecture of the placenta-increta bed

• These vessels were larger, and less uniformly

distributed throughout the placental bed

• The hypervascular nature of the placental bed in

abnormally invasive placenta may also explain the risk

of severe bleeding at delivery

Chantraine et. Al. Am. J. Obstet. Gynecol. 207 (3) (2012 Sep)

Millischer et al. Placenta 53 (2017) 40e47 FRANCE

Clinical significance of placentation

• High risk of hemorrhage

• Need for multiple blood transfusions

• Bladder, ureteral, bowel injury

• Need for planed C-S and premature delivery

• Increased risk of materno-fetal death

• High cost: multiple subspecialties involved

Placenta migration

• Starts at the lower uterine segment

• Moves away from the ICO

• Due to progressive increase in uterine volume

• Migration stops around 24 weeks GA

US - Placenta

• Mostly homogeneous

• Few blood vessels seen with

color Doppler

• Placental septae are not usually well seen by

ultrasound

• Fetal surface slightly lobulated

• Normal linear retroplacental lucent space

3 T Pl

19 weeks 30 weeks

33 weeks25 weeks

No septa

US - Placenta

• Grannum classification: weak correlation with adverse perinatal outcome

- Grade 0 < 18 weeks: smooth chorionic plate

- Grade 1 18-29 weeks: Subtle indentation of echogenic lines in chorionic

plate

- Grade 2 > 30 weeks: Marked incomplete indentation from the chorionic

plate to the basal layer and basal echogenic densities

- Grade 3 > 30 weeks: continuous and marked echogenic lines from the

chorionic plate to the basal layer

Normal placental vascularity

Normal retroplacental clear space

Decidua after trophoblast invasion

Imaging

R L

Normal placenta - MRI

23 weeks16 weeks

R R

33 weeks

Normal placenta - MRI

12 weeks. Placental Villi 16 weeks

R L

Early 3rd trimester villi

30 weeks

33 weeks

Worm sign

Abnormal placentation

• Accreta

• Increta

• Percreta

US - Placentation features

• Placenta previa

• Lacunae

• Abnormal color Doppler imaging patterns

• Loss of the retroplacental clear space

• Reduced myometrial thickness

• An irregular bladder wall (placenta percreta)

MRI of Placenta Accreta, Placenta Increta, and Placenta Percreta: Pearls and Pitfalls. Kilcoyne et al. AJR 2017; 208:214–221

Placenta Previa

A P

Abnormal color Doppler in accreta

Lacunae: moth eaten or Swiss cheese appearance

Fetal Imaging. US and MRI. Kline-Fath, Bulas. Wolters Kluwer, Chapter 7

• Lacunae

• Abnormal vascularization

• Increased blood interface

bladder – myometrium

MRI- Placentation features

• Lumpy contour, uterine bulge, previa secondary to tethering of the placenta

• Heterogeneous signal, dark bands

• Very difficult to distinguish accreta from increta

• High false positives by inexperience radiologists: high cost, unnecessary risks to patient and preventable physician’s time

• Previa

• Heterogeneous bands dark

T2

• Areas of disorganized

vessels

• Abnormal bladder wall

Cases

Accreta Cases

Questioned accreta by ultrasound

Uterine fundus – History of removed septum

No placentation seen at

surgery

No accreta by path report

R LLR

OP report: Right retroperitoneal

space abnormal placentation

consistent with patient's imaging

diagnosis of accreta

PATH: Placenta accreta overlying

thinned area of myometrium at the

posterior LUS

LR

A P

PA

Post

Suspected

accreta and

percreta

PALP

• OP report:

• Accreta, no percreta

• PATH:

• Placenta accreta

• The placenta is adherent to the anterior, posterior,

and supracervical myometrial wall, but does not

grossly invade the myometrium

Op and path reports

Case of extensive accreta

Cervix and placenta previa

Hysterotomy incision at top

Percreta Cases

A A A

A A

P P P

PP

• Percreta with invasion into the posterosuperior wall of the

bladder

• Placental adherence to the entire LUS and the entire

cervix. No invasion into vagina

• Intentional cystotomy with repair

• 90 min lysis of adhesions from placenta to bladder and

uterus, blood loss 7000 cc, 9 U PRBC and 9 U of plasma!

Op Report

Path

• Placenta previa

• Protruding placenta through the left superior portion of the LUS

• Placenta percreta in anterior LUS

• Multiple intervillous thrombi

Similar case with area of serosal rupture

Recess sign

LR R L

Sato et. al. Placental recess accompanied by a T2 dark band: a new finding for diagnosing placental invasionAbdomRadiol (2017) 42:2146–2153

A AP P

Left

Ant – Inf

LUS

Op report

• Placenta percreta visually with the placenta protruding

through the serosa of the anterior inferior aspect of the

LUS, as well as on the left lateral aspect

• The placenta invaded the detrusor muscle of the bladder

but not the mucosa

Path report

• Placenta percreta involving a myometrial scar, arising in a background of multifocal placenta accreta

• Anterior LUS bulging placenta with focally disruptedsurface

Anterior Posterior

Hysterotomy site with protruding cord and membranes

Cervical os

Placental

tissue

Cross-section from area of bulging placental tissue, not thin layer of muscle,

peritoneum, and ragged rupture

Cross-section from area of bulging placental tissue, not thin layer of muscle,

peritoneum, and ragged rupture

PA

PA

4.5 x 2 cm

Placenta accreta with villi adjacent to smooth muscle without intervening decidua

Villi adjacent to thin myometrium and large uterine vessels

Villi adjacent to very thin smooth muscle bundles at inked surface

Villi at blue ink – consistent with percreta

A P

L

R

A P

Operative report

• Complete placenta percreta with invasion of the placenta

into the posterior wall of the bladder (cystotomy with

repair)

• No bladder resection due to small area of invasion

thought to eventually die off

• A significant amount of abdominopelvic adhesive disease

of the bladder to the LUS at the junction of the placenta,

LUS, and bladder (120 min)

• Blood loss: 1800 cc

Path

• Placenta percreta in anterior lower uterine segment

• No bladder wall specimen given

• Multiple intervillous thrombi

7:00

4:00

Anterior LUS:

Beard- like

distribution

R L

LR

R

R

L

L

OP report

• Complete placenta previa noted to be invading into

the posterior wall of the bladder, no plane could be

developed between the dome of the bladder and the

anterior uterine segment

• Severe intraoperative hemorrhage requiring 20 units

of packed red blood cells

PATH

• Diffuse placenta accreta with areas of placenta percreta

• Complete placenta previa and unremarkable endocervical glands

• Slightly immature placenta with subchorionic and basal thrombi and chorangiosis

• Predominantly denuded urothelial mucosa and underlying bladder wall without histopathologic abnormality

A

A

P

P

LR

R L

LR

• Adhesions from the bladder to the anterior abdominal

wall, omental adhesions to anterior abdominal wall

• The placenta did not invade through the bladder

mucosa

• Uterine and placental invasion into the right pelvic

sidewall

• Concern for extension into the left pelvic sidewall

OP report

Hospital Course

• Hysterectomy with intraoperative estimated blood loss of 6000 ml

• Jehovah's Witness: refusal of blood products

• Admitted to the SICU: subsequence brisk blood per JP tube, Hemoglobin 1.8!

• Cardiorespiratory arrest: patient died within 24 hours of surgery

Path

• Placenta previa percreta

• Multiple placental parenchymal infarcts

• The placenta grossly invades through the myometrium and

overlies the serosa anteriorly. In the posterior inferior uterus,

the placenta approaches to within 1 cm of the serosa

• Membranes are tan-pink, translucent, with scattered fibrin

deposits

Imaging diagnosis summary

• Placenta lacunae is the most sensitive US finding for

accreta

• Loss of interface between placenta and myometrium,

lacunae and bulging vessels into the myometrium can

detect 80% of women with accreta

• MRI aids by demonstrating: increased intra-placental

vascularity, fibrin bands of dark T2-bright T1 signal, uterine

bulging, and direct placental invasion of adjacent structures

MRI placenta

• All adherent placenta cases (12 percreta, 9

increta/accreta) had dark intra-placental bands on T2WI

• The three most common findings of placentation were

heterogeneous signal of the placenta (100 %), dark

placental band on T2WI (100 %), and abnormal uterine

bulging (81 %) (didn’t specify if findings were for all

placentation)

MRI of placenta percreta: differentiation from other entities of placental adhesive disorder Thiravit et. al. Radiol

med (2017) 122:61–68

US vs MRI?

• US: Meta-analysis of US diagnostic performance reported

a sensitivity of 91% and specificity of 97%

• MRI: Meta-analysis of 18 studies and 1010 pregnancies

total compared US vs MRI in diagnosing accreta and

found no statistically significant difference in either the

sensitivity or the specificity

D’Antonio F, at el. Prenatal identification of invasive placentation using magnetic resonance imaging: systematic

review and metaanalysis. Ultrasound Obstet Gynecol 2014; 44:8–16

D’Antonio F, et al. Prenatal identification of invasive placentation using ultrasound: systematic review and meta-

analysis. Ultrasound Obstet Gynecol 2013; 42:509–517

MRI ST and SP

Kilcoyne et al MRI of Placenta Accreta, Placenta Increta, and Placenta Percreta: Pearls and Pitfalls.. AJR 2017;

208:214–221

MRI Contrast

MRI - Contrast

• Not routinely used in the US

• Arguments:

- No reports of deleterious effects in human fetuses

- Gadolinium based contrast agents are used commonly in

neonates and children

• American College of Radiology recommends that

gadolinium-based MR contrast agents be given to

pregnant women only after “a documented, in-depth

analysis of the potential risks”

Warshak et al Obstetrics and gynechology vol 108, 3, part 1. September 2006

Kanal et al. American College of Radiology White Paper on MR Safety. AJR Am J Roentgenol 2004;182:1111–4.

MRI - Contrast

• IV of GAD associated with dose-dependent deposition in

neuronal tissue (dentate nucleus) that is unrelated to

renal function, age or interval between exposure and

death

• Known renal damage (glomerular fibrosis) in children and

adults with low GFR: feared renal damage in fetuses

• Re-circulation of contrast in the amniotic fluid: not just one

pass through the kidneys

McDonald et al. Intracranial Gadolinium Deposition after Contrast-enhanced MR Imaging radiology.rsna.org.

Radiology: Volume 275: Number 3—June 2015

Warshak et al Accuracy in the US and MRI Diagnosis of Placenta Accreta Obstetrics and gynechology vol 108, 3, part 1.

September 2006 SAN DIEGO and MIAMI

• GAD more clearly delineates the outer placental surface

relative to the myometrium

• Sensitivity of 88% and specificity of 100% in detecting

placenta accreta with gadolinium-enhanced MRI (90s% ST

– 80s% SP without gad)

MRI Contrast

• “We believe that the use of gadolinium-based contrast

enhancement adds to the specificity of MRI in the diagnosis

of placenta accreta because it more clearly delineates the

outer placental surface relative to the myometrium and

eliminates the confusion between heterogeneous signals

thought to be within the placenta from those caused by

maternal blood vessels”

• Sensitivity of 88% and specificity of 100% in detecting

placenta accreta with gadolinium-enhanced MRI (90s% ST

– 80s% SP without gad)

Warshak et al Obstetrics and gynechology Vol. 108, No. 3, part 1, September 2006

A- Placenta Accreta: enhancement curves differ between suspected accreta

area and control area

B- Placenta non Accreta: enhancement curves are similar between

Suspected Accreta Area and Control Area

Millischer et al. Dynamic contrast enhanced MRI of the placenta: A tool for prenatal diagnosis of placenta accreta?

Placenta 53 (2017) 40e47 FRANCE

Accreta NormalROIs: in area of

concern and in

normal area

Blue: suspected

accreta

Red: controls

Gadolinium

33 weeks MRA of the

placental chorionic plate

vessels.

Primary and secondary

branches of the chorionic

plate vessels (arrow

heads) are visualized

Neelavalli et al. Magnetic resonance angiography of fetal vasculature at 3.0 T. Eur Radiol (2016) 26:4570–4576

TTTS

• Serious complication of MC/DA twin pregnancies

- Result of unbalanced placental A-V, A-A, V-V anastomoses

• If untreated, high risk of mortality (80-100%)

• Markedly limited imaging evaluation pre-laser

Placental vessels

Fetoscope

Field of View

~ 3 mm

Selective Fetoscopic Laser Photocoagulation

TTTS – Placental Edema

• Usually accompanies fetal hydrops

• Thicker placenta on the donor side

• Causes for fetal hydrops:

- Erythroblastosis fetalis

- Fetal anemia

- Fetal cardiac disease

- Congenital anomalies

- Congenital infections

- Others

Placenta

hydrops/edema?

P

LR

A

Placental lesions (floor infarction)

• 10-15% women with complicated pregnancies have cystic lesions surrounded by peripheral echogenicity in the placenta

• Incidence: 0.09% and associated with fetal death IUGR, preterm, and recurrent spontaneous abortion

Intraplacental cystic areas surrounded by increased echo

associated with massive perivillous fibrin deposition

MRI Safety

Fetal 1.5 T and 3T MRI risks

• Most studies suggest effects of acoustic, heat, and RF field during pregnancy are safe

• Avoid MRI during the 1st trimester due to lack of information about fetal risks

• 3T: Society of Pediatric Radiology:

- There is no sig increased risk to mother and fetus in

performing fetal MRI in 3T as long as the scanner is

operated in normal mode and the heat index is kept low

Radiology 2004; 232:635–652 . MR Procedures: Biologic Effects, Safety, and Patient Care. Shellock FG et al

Imaging Advances

• MRI:

- New sequences

• US:

- Volume

- Color Doppler

Imaging Advances

MRI Advances

• Many different sequences and technique have been tried:

- Susceptibility weighted imaging-based blood oximetry (BOLD)

- MR Spectroscopy (MRS)

- Diffusion weighted sequences

- TENSE sequences

- Phase contrast MRI

Kilcoyne AJR 2017; 208:214–221

Warshak CR. Obstet Gynecol 2010; 115:65–69

Bour Eur Radiol 2014; 24:3150–3160

Riteau PLoS One 2014; 9:e94866

Dwyer J Ultrasound Med 2008; 27:1275–1281

D’Antonio. Ultrasound Obstet Gynecol 2014; 44:8–16

MRI - BOLD sequence

• BOLD imaging detects different levels of tissue oxygenation

• Placentas with abnormal perfusion will show heterogeneous

distribution of O2 compared to the normal placentas

• Correlated with avascular villi and chorangiosis

• Vascular proliferation and chorangiosis are inefficient at

compensating for poor placental perfusion

Luo et al. In Vivo Quantification of Placental Insufficiency by BOLD MRI: A Human Study. Scientific reports. June 16 2017

MR spectroscopy (MRS)

Cho

Lipid

Lipid

Cho

NAANAA

ADC, NAA/lipid, choline/lipid ratios could serve as

markers for placenta insufficiency of IUGR

Song et. al. Assessment of the placenta in IUGR by DWI and MRS: a pilot study. Reproductive Sciences 2017, Vol.

24(4) 575-581

Ultrasound advances

• US placental volume

• US Color Doppler 3D

• Placental volume by 3D US using VOCAL software

• Increased or decreased size: seen with IUGR, infections,

chromosomal abnormalities

• Meaning?

Fetal Imaging. US and MRI. Kline-Fath, Bulas. Wolters Kluwer, Chapter 7

• Placental blood perfusion using 3D power Doppler

• Calculation of vascular, flow and vascular/flow indices

• Potential use in IUGR and TTTS

Fetal Imaging. US and MRI. Kline-Fath, Bulas. Wolters Kluwer, Chapter 7

Conclusion

• MRI and US are complimentary in the evaluation of placentation anomalies

• Need for imaging- pathology correlation and new imaging techniques to allow further evaluation of placental flow

• Need for collaborative research between surgery, radiology and pathology

Thank You