Placenta Imaging by Ultrasound and MRI
Transcript of Placenta Imaging by Ultrasound and MRI
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