In Utero Imaging of the Placenta: Importance for Diseases of Pregnancy
ABSTRACT Maurice Panigel demonstrated by X-rays, almost 40 years ago, placental maternal blood jets in non-human primates. Although to researchers the importance of the placenta is evident, in clinical obstetrical imaging, the fetus takes precedence. The placenta is imaged almost as an after thought and mostly to determine its location in the uterus. In animal species, the placenta was imaged with techniques which would be considered too invasive (or too costly for routine use) in humans, many pioneered by Panigel: radioangiography, radioisotopes scintigraphy, thermography, magnetic resonance imaging (MRI) and spectroscopy, positive emission tomography (PET) and single photon emission computed tomography (SPECT). Ultrasound allows for detailed, and, as far as is known, safe analyses of not only placental structure in the human but also its function. Earlier, only 2-dimensional grey-scale was available and more than 20 years ago, placental grading was popular. Later, colour imaging and spectral Doppler analysis of blood velocity both in the umbilical artery and within the placenta as well as the uterus and fetal vessels became essential and, more recently, the use of ultrasound contrast agents has been described, albeit not yet in a clinical setting. Three-dimensional ultrasound permits evaluation of the placenta in several planes, more precise depiction of internal vasculature as well as more accurate volume assessment. Several medical disorders of the pregnant woman or her fetus begin or end in the placenta, and ultrasound is the optimal investigation method. Obvious examples include pre-eclampsia and other forms of hypertension in pregnancy, less than optimal fetal growth (i.e. intrauterine growth restriction), triploidy (and its placental manifestation: partial mole), non-immune hydrops as well as several infectious processes. Ultrasound is also particularly suited to evaluate specific placental conditions, such as abnormal placentation (placenta previa and accrete for instance), gestational trophoblastic disease and placental tumors (e.g. chorioangioma).
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ABSTRACT: The purpose of this study was to evaluate whether currently available fetal Magnetic Resonance Imaging (MRI/MR) techniques are sufficient for the assessment of placental pathologies. We hypothesized that placental pathologies as detected and evaluated by MRI, would correlate with histological findings. In a retrospective study, 45 singleton pregnancies from 19 to 35 gestational weeks, with placental pathologies on MR scans, were included. MRI was performed on a 1.5T unit using T2-, T1-, and diffusion-weighted and echo-planar sequences. Pathologies were categorized into infarction with/without hemorrhagic components, subchorionic/intervillous thrombi/hemorrhages, retroplacental hematoma, massive perivillous fibrin deposition, and chorioamnionitis. Pathohistological examination was performed postnatally within a median of seven days between MR examination and delivery. Pathologically, 26 placentas showed infarctions (96.2% on MR scans), two retroplacental hematomas were detected by MRI and confirmed by pathology, and 9 of 14 subchorionic hematomas were confirmed. Six of eight intervillous hemorrhages were seen on MRI, and three of six cases of severe chorioamnionitis were diagnosed prenatally. Placental hemorrhages (retroplacental hematoma, intervillous thrombi, subchorionic hematoma), and ischemic lesions could be detected with fetal MRI, while chorioamnionitis and even massive perivillous fibrin deposition showed few signal changes, probably reflecting small macroscopic changes in the placenta. Fetal MRI, therefore, seems to be a promising tool for the assessment of placental insufficiency.Placenta 05/2009; 30(6):555-9. DOI:10.1016/j.placenta.2009.03.010 · 3.29 Impact Factor
Conference Paper: Dynamics of multimode semiconductor lasers[Show abstract] [Hide abstract]
ABSTRACT: This work reports on the existence of deterministic nonlinear dynamics in a free-running multimode semiconductor laser. The main dynamical effects found in a set of experiments realized with several edge-emitting lasers are: (i) periodic fluctuations, in the MHz range, of each modal output, (ii) compensation in the total output which remains practically flat, (iii) the modal switching sequence follows the modal optical frequencies sequence from blue to red; when the reddest mode switches off, the sequence restarts from the bluest mode. These effects are robust against a change of the control parameters which mostly affects the number of oscillating modes. Experimentally, the pump current of the lasers was increased and it was verified that the property of regular modal switching with flat total output is independent of the mode number, up to seven oscillating modes. For large number of modes, the fluctuations persist but they can lose regularity in phase and amplitude. The authors have always noticed the almost complete extinction (more than -40 dB) of the modal switching frequency in the total intensity and the switching sequence that progresses from the blue side of the optical spectrum to the red side. The frequency of the modal switching tends to increase with pumping current and with the number of active modes but it remains in the range 5 to 15 MHz. No significant difference between the power spectra of the different modal amplitudes was observed.Quantum Electronics Conference, 2003. EQEC '03. European; 07/2003
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ABSTRACT: c1 Academic Unit of Radiology, Royal Hallamshire Hospital, University of Sheffield, Glossop Road, Sheffield S10 2JF, United Kingdom.Fetal and Maternal Medicine Review 01/2008; 19(01):33 - 60. DOI:10.1017/S096553950800209X