Anne Sorensen1, Ditte Nymark Hansen2, David Peters3, Marianne Sinding2, and Jens Brøndum Frøkjær4
1Aalborg University Hospital, Denmark, 2Aalborg University Hospital, Aalborg, Denmark, 3Aarhus University Hospitalh, Aarhus, Denmark, 4Aalborg University, Aalborg, Denmark
Synopsis
Placental relaxometry provides quantitative characterization of placental
tissue. Placental dysfunction is associated with placental hypoxia, which can
be depicted by placental relaxometry. Thus, this method provides direct evidence
of placental dysfunction during pregnancy, which has the potential to improve pregnancy outcome
through optimal pregnancy monitoring and timely delivery.
This session will
cover a comparison of placental T1, T2 and T2* in the prediction placental
dysfunction, a correlation between MR images and placental anatomy, and a summary of current pitfalls of placental relaxometry in
terms of acquisition, processing, and interpretation.
Background
Placental
relaxation includes longitudinal relaxation (T1) and transversal relaxation (T2
and T2*). There parameters are related to placental oxygenation and thereby
placental function. Thus, placental relaxometry provides direct evidence of
placental dysfunction during pregnancy. The performance of placental T1, T2 and
T2* in the prediction of placenta related outcomes such as small for
gestational age have been investigated for each parameter separately. However,
a direct comparison of the parameters remains to be performed.Aim
The aim of this
study is to compare the performance of placental T1, T2 and T2* in the
prediction of small for gestational age (SGA) at birth. Method
A total of 99 singleton
pregnancies were retrieved from our placental MRI database. Inclusion criterion
was that placental transversal relaxation (T2 and T2*) and longitudinal
relaxation (T1) was obtained in all cases. Placental MRI was performed in a 1.5T
system at gestational week 32.5 ± 0.5 (mean±SD) using the following protocols;
T1 weighted MRI was
obtained using a single-shot fast
spin-echo sequence; field of view (FOV): 38 × 38 cm; inversion time (TI)(5):
60 - 3000 ms; repetition time (TR): 8000 ms; slice spacing 20 mm and slice
thickness 8 mm.
T2 weighted MRI was
obtained using an echo-planar imaging spin-echo sequence; FOV: 40 × 40 cm; echo
time (TE) (8): 50-440 ms; TR: 4000 ms; slice spacing 20 mm and slice thickness
8 mm.
T2* weighted MRI was
obtained using a gradient recalled echo sequence; FOV: 35 × 35 cm; TE(16): 3.0
- 67.5 ms; TR: 70.9 ms; slice spacing 20mm and slice thickness 8 mm.
Placental ROIs were
drawn manually covering the entire placental, and placental T1, T2 and T2* was calculated
as an average of three placental slices. The predictive performance of placental
relaxation was estimated by logistic regression adjusted for gestational age at
MRI and area under the ROC-curve (AUC).Results
The mean
gestational age at birth was 38.9 ± 0.25 weeks. When defined as birth weight ≤
-2SD, the proportion of SGA at birth was 17% (17/99). The predictive performance
of placental relaxation was the following; AUC(T1)=0.63,
AUC(T2)=0.78, and AUC(T2*)=0.80. Combining the three MRI parameters did not
improve the predictive performance; AUC(combined)=0.80.Conclusion
Placental relaxation can predict small for gestational age at birth. Placental
transversal relaxation (T2 and T2*) is superior to longitudinal relaxation
(T1). Thus, placental transversal relaxation has the potential to improve the antenatal care by optimal
pregnancy monitoring and timely delivery.Acknowledgements
No acknowledgement found.References
No reference found.