"Ultrasound is the screening modality of choice for
fetal imaging … however, there are cases when the sonographic diagnosis is
limited," wrote Dr. Riccardo Manfredi's group in their poster. Manfredi
and co-authors are from the Policlinico Agostino Gemelli at the Università
Cattolica del Sacro in Rome.
The study included 47 pregnant women with 49 fetuses. The
mean gestational age was 29 weeks. Inclusion criteria included diagnosed or
suspected fetal malformation on ultrasound. The indications for MR included
ventriculomegaly in the majority of fetuses (16 of 49), as well as cranial bone
abnormalities and Dandy-Walker variant.
MRI was performed on a 1.5-tesla scanner using a
phased-array coil. The protocol included a half Fourier RARE sequence along the
three orthogonal planes according to the mother's long axis and three
orthogonal planes according to the fetal body segment. Postnatal diagnostic
imaging, postnatal follow-up, surgery, or autopsy was used to confirm all
According to the results, MRI confirmed ventriculomegaly in
eight of 16 cases. It also detected additional problems, such as partial or
complete callosal agenesis (4/16), intracranial hemorrhages (2/16), and
cerebellar abnormality (1/16). In craniopagus fetuses, the fusion of the
temporal lobe and sagittal sinus was well-defined, the authors said. Outside of
the brain, MRI confirmed two cases of adenomatoid cystic malformations in the
lungs, six cases of renal disease, and one hepatic cyst. MRI failed to turn up
one case of Dandy-Walker variant.
The group described one case of cystic lymphangioma of the
upper chest in which the ultrasound scan showed a hypoechoic, complex cystic
mass lateral to the chest. MR imaging was better able to depict the structure
of the lesion and its relationship with the fetal chest because of its larger
field-of-view. This information was vital for surgical planning, the
During a discussion of the poster, Manfredi said that the MR
exams took between 15-20 minutes, depending on how active the fetus was.
Manfredi said he'd successfully calmed down a moving fetus by encouraging the
mother to relax.
Fetal MR results can go a long way to aid in treatment
planning and reassure parents. However, the exam is covered by Italy's national
healthcare system, unlike in the U.S., where patients experience pushback from
insurance carriers for such expensive tests.
In a second poster presentation, Dr. João Kazan-Tannús,
Ph.D., and colleagues shared the results of their prospective study comparing
fetal MRI to ultrasound for assessing the face, trunk, and fetal limbs. The
group is from the University of São Paolo.
For this research, 66 fetuses were selected based on
morphologic ultrasound. MRI was performed on a 1.5-tesla scanner (Signa Horizon
Healthcare, Waukesha, WI) using FSE, a TR > 30,000 msec, TE = 60-70
msec, and a 5-mm slice thickness. The whole fetus was imagined in three planes.
Measurements of the head circumference, biparietal diameter of the skull, and
the abdominal circumference were also done. Ultrasound was performed with a 3.5
MHz transducer (HDI 5000, Philips
Medical Systems, Bothell, WA).
"For comparison purposes, MRI and ultrasound were
performed on all fetuses in sagittal, coronal, and axial planes of the whole
body," the group wrote.
The images were evaluated and scored based on the
feasibility of axial, coronal, and sagittal images of the skull, thorax,
abdomen, and pelvis (1 = feasible). A quantitative score for 25 anatomic
details and organs (0 = not seen and 3 = detailed exam) was also assigned to
the MR images.
The authors reported superior results with fetal MR,
particularly for evaluating the posterior fossa, the eyes, the lateral
ventricles, the gyri, and the kidneys. The modality also proved better for
looking at white and gray matter differentiation, in the liver, the nose,
mouth, hands, and ears. In one case, ultrasound showed polyhydramnios, while MR
revealed the same as well as a liver cyst. In another instance, MR showed a
giant exophytic lymphangioma in addition to the thoracic mass extending
throughout the neck seen on ultrasound.
Ultrasound turned in better results in the heart, choroid
plexus, and intestines, as well as in the analysis of the corpus callosum, the
authors reported. In one instance, the MR exam yielded a diagnosis of a
multicystic right kidney, oligohydramnios, and a clubfoot. Ultrasound added
left kidney rotation and multicystic kidney dysplasia on the right.
MR and ultrasound offered similar information in cases of
diaphragmatic hernia and polycystic kidneys. "The concomitance of
pathologies reduced the diagnostic accuracy, especially in ultrasound,"
They concluded that MR's capability to produce multiplanar
studies gave it the edge over ultrasound. In addition, MRI correlated well with
biometry and ultrasound, even adding new data for specific organs. The group
said that they have developed a single optimized MR protocol that can be used
between 17-30 weeks gestational age.
During the discussion of the poster, Kazan-Tannús said that
fetal brain MR exams took about 15 minutes, while whole-body exams took 20-30
minutes. He cautioned that the exam might not progress that quickly if
real-time imaging is required to compensate for excessive fetal movement.
Both of these studies build on previous research, making a
solid case for fetal MR from head to toe. In a paper at the 2004 American
Academy of Pediatrics meeting in October in San Francisco, Dr. Orit Glenn
praised MR for allowing "direct visualization of the developing brain
parenchyma." She also pointed out that prenatal MR is not susceptible to
the same limitations as ultrasound, and has a higher contrast resolution,
resulting in better differentiation between normal and abnormal tissue. Glenn
is from the University of California, San Francisco.
More recently, Dr. Susan Connolly and colleagues from
Massachusetts General Hospital in Boston used MR to assess the imaging features
of the femur in fetal pigs. They found that during fetal development, "the
cartilaginous epiphysis of the distal femur transformed from an oval to a
Other musculoskeletal features that were readily apparent on
MR as the fetus grew included perichondrial structures, marrow cavitation, and
bone bark. These results may be transferred to human imaging in the near
future, making it possible for physicians to make a prenatal diagnose of
skeletal abnormalities, such as skeletal dysplasia, clubfeet, or deficiencies,
they concluded (Radiology, November 2004, Vol. 233:2, pp. 505-514).
"Improvements in MR imaging -- the most important
being fast and very fast sequences with gradient-echo techniques --
have allowed the increased use of this modality for fetal imaging,
and have obviated the use of sedation to decrease fetal
motion," wrote Dr. Kimberly Applegate in an accompanying editorial.
"Future use of fetal MR imaging will likely include refinement
of current techniques to allow better investigation of normal and
abnormal fetal musculoskeletal MR imaging characteristics" (Radiology, November 2004, Vol. 233:2,
By Shalmali Pal
AuntMinnie.com staff writer
November 29, 2004
alters management of infants with genitourinary disorders, October 14, 2004
cleft lip and palate seen better with MRI than sonography, July 29, 2004
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