Interactive Transcript
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This is an MRI of the abdomen and pelvis
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in a patient who presented at 28 weeks
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gestation after having an abnormal ultrasound
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in the maternal-fetal medicine clinic.
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There was suspicion raised for placenta
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accreta spectrum on the ultrasound,
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and the MRI was ordered for further
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clarification of the placental anatomy.
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We have axial T2-weighted images of the pelvis.
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These are steady-state free precession,
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and these are turbospin echo images.
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As we scroll inferiorly, we begin to
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see the gravid uterus and we can clearly
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see the heterogeneous myometrium, which
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is indicative of the uterine wall.
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Notice the difference in the appearance of
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the myometrium between these two sequences.
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On the turbospin echo, the myometrium
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will look much brighter on the T2
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weighted sequences than it does on the
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steady-state free precession images.
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As we scroll inferiorly, we
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begin to see the placenta.
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And, if you recall the normal pregnancy
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MRI case that we looked at earlier,
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some of the features that are present in
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that case of a normal placenta include
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homogeneous signal, relatively uniform
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thickness, and intact overlying myometrium.
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As we evaluate this placenta, one
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of the first things that I notice
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about it is that it's low-lying.
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We're down here near the level
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of the bladder and the cervix.
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And we can see that we are encountering
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a lot of placental tissue in this region.
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So this is all placenta here.
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This is all placenta in these images as well.
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Another feature that I'd like
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to point out about this placenta is
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the relative heterogeneity of it.
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You can see some increased placental
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heterogeneity, particularly in the
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third trimester of pregnancy, but
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it should not be to this degree.
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A feature that's present here is this
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wedge-shaped area of T2 hypointensity,
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which we can identify on both sequences.
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This is what's known as a placental band.
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These are thought to be areas of fibrous
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change within the placenta at sites of infarct
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or hemorrhage, and they're a reflection of
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the abnormal microvascular environment in
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patients with placenta accreta spectrum.
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Another feature of this placenta
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is that it has rounded contours
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and it's not uniform in thickness.
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It has sort of a lumpy, bumpy appearance
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to it which we can really appreciate on
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the steady-state free precession images.
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Next, let's look at the sagittal images
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of the placenta for this patient.
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Again, the steady-state free precession
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images are on this side, and the
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turbospin echo images are over here.
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We can see that the placenta
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is low-lying for this patient.
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The patient has a marginal placenta previa,
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meaning that the placenta abuts but does not
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entirely cover the internal cervical os.
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Again, this placenta is lumpy,
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bumpy; it's heterogeneous.
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We see a nice example of a placental
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band here, and there's really a bulging
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appearance of the placenta in this patient.
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In patients with suspected placenta accreta
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spectrum, it is important to trace the
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myometrium all the way around the uterus
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to determine if there is still myometrium
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covering the placenta, which would exclude
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a diagnosis of placenta percreta.
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And so knowing that the myometrium has a
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T2 heterogeneous appearance, we can trace
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it all the way around in this patient.
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And although it gets very thin, we can
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still see a very thin T2 heterogeneous
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myometrial layer in this patient.
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On the steady-state free precession images,
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again, this is T2 heterogeneous myometrium.
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And although the myometrium
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is thin, it is still intact.
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Lastly, these are coronal T2-weighted
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images of the placenta in this patient.
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In this plane, we again see features of placenta
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accreta spectrum, including an irregular
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placental contour, placental heterogeneity
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with multiple placental bands present, and a
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thin but still present intervening layer of
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T2 heterogeneous myometrium for this patient.
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This patient was taken for cesarean hysterectomy
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at 32 weeks gestation, and this was a
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pathology-proven case of placenta accreta.
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