Talk:Magnetic Resonance Imaging
High resolution post-mortem MRI of non-fixed in situ foetal brain in the second trimester of gestation: Normal foetal brain development
Eur Radiol. 2018 Jan;28(1):363-371. doi: 10.1007/s00330-017-4965-y. Epub 2017 Jul 28.
Scola E1, Conte G2,3, Palumbo G2, Avignone S2, Cinnante CM2, Boito S4, Persico N4, Rizzuti T5, Triulzi F2,6. Author information Abstract PURPOSE: To describe normal foetal brain development with high resolution post-mortem MRI (PMMRI) of non-fixed foetal brains. METHODS: We retrospectively collected PMMRIs of foetuses without intracranial abnormalities and chromosomal aberrations studied after a termination of pregnancy due to extracranial abnormalities or after a spontaneous intrauterine death. PMMRIs were performed on a 3-T scanner without any fixation and without removing the brain from the skull. All PMMRIs were evaluated in consensus by two neuroradiologists. RESULTS: Our analysis included ten PMMRIs (median gestational age (GA): 21 weeks; range: 17-28 weeks). At 19 and 20 weeks of GA, the corticospinal tracts are recognisable in the medulla oblongata, becoming less visible from 21 weeks. Prior to 20 weeks the posterior limb of the internal capsule (PLIC) is more hypointense than surrounding deep grey nuclei; starting from 21 weeks the PLIC becomes isointense, and is hyperintense at 28 weeks. From 19-22 weeks, the cerebral hemispheres show transient layers: marginal zone, cortical plate, subplate, and intermediate, subventricular and germinal zones. CONCLUSION: PMMRI of non-fixed in situ foetal brains preserves the natural tissue contrast and skull integrity. We assessed foetal brain development in a small cohort of foetuses, focusing on 19-22 weeks of gestation. KEY POINTS: • Post-mortem magnetic resonance imaging (PMMRI) of non-fixed head is feasible. • PMMRI of unfixed in situ foetal brains preserves the natural tissue contrast. • PMMRI provide a good depiction of the normal foetal brain development. • PMMRI of unfixed in situ foetal brains preserves the skull integrity. • PMMRI pattern of foetal brain development at early gestational age is described. KEYWORDS: Autopsy; Brain; Foetus; Magnetic resonance imaging; Post-mortem PMID: 28755056 DOI: 10.1007/s00330-017-4965-y
The effect of magnetic resonance imaging on neural tube development in an early chicken embryo model
Childs Nerv Syst. 2018 Feb 1. doi: 10.1007/s00381-018-3734-9. [Epub ahead of print]
Kantarcioglu E1, Kahilogullari G2,3, Zaimoglu M1, Atmis EO4, Peker E5, Yigman Z6, Billur D6, Aydin S6, Erden IM5, Unlü A1.
PURPOSE: We aimed to determine whether varying the magnetic field during magnetic resonance imaging would affect the development of chicken embryos and neural tube defects. METHODS: Following incubation for 24 h, we exposed chicken embryos to varying magnetic fields for 10 min to assess the impact on development. Three magnetic resonance imaging devices were used, and the eggs were divided into four groups: group 1 is exposed to 1 T, group 2 is exposed to 1.5 T, group 3 is exposed to 3 T, and group 4, control group, was not exposed to magnetic field. After MRI exposure, all embryos were again put inside incubator to complete 48 h. "The new technique" was used to open eggs, a stereomicroscope was used for the examination of magnified external morphology, and each embryo was examined according to the Hamburger and Hamilton chicken embryo stages. Embryos who had delayed stages of development are considered growth retarded. Growth retardation criteria do not include small for stage. RESULTS: Compared with embryos not exposed to a magnetic field, there was a statistically significant increase in the incidence of neural tube closure defects and growth retardation in the embryos exposed to magnetic fields (p < 0.05). However, although the incidence of neural tube closure defects was expected to increase as exposure (tesla level) increased, we found a higher rate of defects in the 1.5-T group compared with the 3-T group. By contrast, the highest incidence of growth retardation was in the 3-T group, which was consistent with our expectation that growth retardation would be more likely as tesla level increased. CONCLUSIONS: We therefore conclude that the use of magnetic resonance imaging as a diagnostic tool can result in midline closure defects and growth retardation in chicken embryos. We hypothesize that this may also be true for human embryos exposed to MRI. If a pregnant individual is to take an MRI scan, as for lumbar disc disease or any other any other reason, our results indicate that consideration should be given to an avoidance of MRI during pregnancy. KEYWORDS: Chicken embryo; Growth retardation; Magnetic resonance imaging; Neural tube defects
PMID: 29392421 DOI: 10.1007/s00381-018-3734-9
MR microscopy of the human fetal upper extremity - a proof-of-principle study
BMC Dev Biol. 2016 Jun 18;16(1):21. doi: 10.1186/s12861-016-0123-z.
Langner I1, Stahnke T2, Stachs O2, Lindner T3, Kühn JP4, Kim S1, Wree A5, Langner S6.
Abstract BACKGROUND: Current knowledge of the human fetal and embryonic development relies on early descriptive studies of humans and from experimental studies of laboratory animals and embryos. Taking the upper extremity as an example, this study explores the potential of magnetic resonance microscopy (MRM) for the assessment of the development of the fetal upper extremity and discusses its correlation with histological findings. METHODS: Ex vivo MRM at 7.1 T (Clin Scan, Bruker Biospin, Germany) was performed in 10 human specimens at 8 to 12 weeks of gestational age (GA). In-plane resolution was 20 μm with a slice thickness of 70 μm. MRM was followed by histological work-up of the specimens. MRM images were then correlated with conventional histology with a focus on the presence of chondrification and ossification. RESULTS: Ossification of the upper human extremity is detectable at 8 weeks GA in the humerus and the long bones of the forearm. There is excellent correlation for location and size of ossification between MRM and conventional histology. MRM imaging is in accordance with historical studies. CONCLUSION: Ex vivo MRM for the non-invasive assessment of the embryonic and fetal development of the upper human extremity is feasible. It may provide an accurate complementary tool for the evaluation of embryological development. KEYWORDS: Fetal development; MR microscopy; Ultra high-field MRI; Upper extremity
PMID 27316469 PMCID: PMC4912725 DOI: 10.1186/s12861-016-0123-z
High Resolution MRI Reveals Detailed Layer Structures in Early Human Fetal Stages: In Vitro Study with Histologic Correlation
Front Neuroanat. 2015 Nov 25;9:150. doi: 10.3389/fnana.2015.00150. eCollection 2015.
Wang R1, Dai G2, Takahashi E3.
Abstract An understanding of normal fetal brain development is essential in detecting the early onset of brain disorders. It is challenging to obtain high-quality images that show detailed local anatomy in the early fetal stages because the fetal brain is very small with rapidly-changing complex structures related to brain development, including neurogenesis, neuronal migration, and axonal elongation. Previous magnetic resonance imaging (MRI) studies detected three layers throughout the fetal cerebral wall that showed differences in MR contrasts at 10 gestational weeks (GW), which is one of the earliest ages studied using MRI. Contrary to the MRI studies, histological studies found more layers at this fetal age. The purpose of this work is to study the development of brain structures from an early fetal period to an early second trimester stage using ex vivo MRI and compare it to histology. Special attention was paid to laminar structures in the cerebral wall. T2-weighted imaging was performed on fetal brain specimens ranging from 10 GW to 18 GW on a 4.7 tesla MR scanner. We obtained standard grayscale as well as color-coded images using weighted red-green-blue scales, and compared them with the histological images. Our study confirmed laminar structure in the cerebral wall in all the fetal specimens studied. We found that MRI detected four layers within the cerebral wall as early as 10 GW during the early fetal period (10-13 GW). Early second trimester (15-18 GW) was characterized by the emergence of subplate structures and five layers within the cerebral wall. The color-coded images were more useful than the standard grayscale images in detecting the laminar structures. Scans with appropriate parameters from a high tesla MR scanner showed detailed laminar structures even through a very small and thin cerebral wall at 10 GW ex vivo. A combination of high-resolution structural imaging and color-coding processing with histological analysis may be a potential tool for studying detailed structures of typical developing fetal brains, as well as fetal brains with developmental disorders as references for clinical MRI. KEYWORDS: cerebral wall; histology; human fetal brain; neurogenesis; structural mri
PMID 26834575 PMCID: PMC4714631 DOI: 10.3389/fnana.2015.00150
Magnetic resonance microscopy of chemically fixed human embryos at high spatial resolution
Magn Reson Med Sci. 2015;14(2):153-8. doi: 10.2463/mrms.2014-0034. Epub 2015 Feb 12.
Otake Y1, Handa S, Kose K, Shiota K, Yamada S, Uwabe C.
1Institute of Applied Physics, University of Tsukuba. Abstract We acquired magnetic resonance (MR) microscopic images of chemically fixed human embryos of Carnegie stages 16 to 22 with a large image matrix (256 × 256 × 512) using an MR microscope that we developed with a 9.4-tesla vertical wide-bore superconducting magnet and a dual-channel receiver system to extend the dynamic range of the MR signal. The images showed clear anatomical structures at spatial resolutions of (40 µm)(3) to (60 µm)(3). We concluded that the experimental technique we developed will aid construction of the next anatomical database of the collection of chemically fixed human embryos.
Fetal MRI: An approach to practice: A review
J Adv Res. 2014 Sep;5(5):507-23. doi: 10.1016/j.jare.2013.06.001. Epub 2013 Jun 11.
MRI has been increasingly used for detailed visualization of the fetus in utero as well as pregnancy structures. Yet, the familiarity of radiologists and clinicians with fetal MRI is still limited. This article provides a practical approach to fetal MR imaging. Fetal MRI is an interactive scanning of the moving fetus owed to the use of fast sequences. Single-shot fast spin-echo (SSFSE) T2-weighted imaging is a standard sequence. T1-weighted sequences are primarily used to demonstrate fat, calcification and hemorrhage. Balanced steady-state free-precession (SSFP), are beneficial in demonstrating fetal structures as the heart and vessels. Diffusion weighted imaging (DWI), MR spectroscopy (MRS), and diffusion tensor imaging (DTI) have potential applications in fetal imaging. Knowing the developing fetal MR anatomy is essential to detect abnormalities. MR evaluation of the developing fetal brain should include recognition of the multilayered-appearance of the cerebral parenchyma, knowledge of the timing of sulci appearance, myelination and changes in ventricular size. With advanced gestation, fetal organs as lungs and kidneys show significant changes in volume and T2-signal. Through a systematic approach, the normal anatomy of the developing fetus is shown to contrast with a wide spectrum of fetal disorders. The abnormalities displayed are graded in severity from simple common lesions to more complex rare cases. Complete fetal MRI is fulfilled by careful evaluation of the placenta, umbilical cord and amniotic cavity. Accurate interpretation of fetal MRI can provide valuable information that helps prenatal counseling, facilitate management decisions, guide therapy, and support research studies. KEYWORDS: Anomalies; Fetal; MRI; Prenatal PMID 25685519
Image source: The MRI images are reproduced with the permission of Prof Sahar Saleem for educational purposes only and cannot be reproduced electronically or in writing without permission. http://creativecommons.org/licenses/by-nc-nd/3.0/
Magnetic resonance diffusion-weighted imaging: reproducibility of regional apparent diffusion coefficients for the normal fetal brain
Ultrasound Obstet Gynecol. 2013 Feb;41(2):190-7. doi: 10.1002/uog.11219. Epub 2013 Jan 3.
Boyer AC1, Gonçalves LF, Lee W, Shetty A, Holman A, Yeo L, Romero R.
OBJECTIVE: To evaluate the reproducibility of regional apparent diffusion coefficient (ADC) measurements of the normal fetal brain in the second and third trimesters of pregnancy. METHODS: Fifty normal singleton fetuses from healthy pregnant women between 19 and 37 weeks' gestation were studied without sedation. Single-shot diffusion-weighted images of the fetal brain were obtained using a 1.5-Tesla magnetic resonance scanner and a six-channel body array coil. ADC maps were created using 0 and 1000 b-values along three orthogonal directions. Two examiners independently measured ADC values in the cerebellar hemispheres (CH), pons, thalamus, basal ganglia (BG), centrum semiovale (CSO), and frontal (FWM), parietal (PWM), temporal (TWM) and occipital (OWM) white matter. Correlation between ADC values and menstrual age was assessed by linear regression analysis. The bias and agreement of ADC measurements were determined using Bland-Altman plots. RESULTS: ADC values either remained constant (BG, FWM, PWM, TWM, OWM, CSO) or decreased (CH, pons, thalamus) with advancing menstrual age. Mean intraobserver bias for ADC measurements was not significantly different from zero. Small interobserver differences in mean ADC measurements (i.e. a small mean bias) were detected for CH (1.26 ± 0.20 vs 1.20 ± 0.18 μm(2) /ms, P = 0.006), PWM (1.37 ± 0.29 vs 1.33 ± 0.26 μm(2) /ms, P = 0.02) and CSO (1.36 ± 0.29 vs 1.33 ± 0.28 μm(2) /ms, P < 0.0001). Measurement agreement was acceptable. CONCLUSIONS: ADC measurements in normal unsedated fetuses in the second and third trimesters are reproducible except for small differences for PWM, CH and CSO between examiners. Copyright © 2013 ISUOG. Published by John Wiley & Sons, Ltd.
Human birth observed in real-time open magnetic resonance imaging
Am J Obstet Gynecol. 2012 Jun;206(6):505.e1-6. Epub 2012 Jan 13.
Bamberg C, Rademacher G, Güttler F, Teichgräber U, Cremer M, Bührer C, Spies C, Hinkson L, Henrich W, Kalache KD, Dudenhausen JW. Source Department of Obstetrics, Charité University Hospital Berlin, Berlin, Germany.
OBJECTIVE: Knowledge about the mechanism of labor is based on assumptions and radiographic studies performed decades ago. The goal of this study was to describe the relationship between the fetus and the pelvis as the fetus travels through the birth canal, using an open magnetic resonance imaging (MRI) scanner. STUDY DESIGN: The design of the study used a real-time MRI series during delivery of the fetal head. RESULTS: Delivery occurred by progressive head extension. However, extension was a very late movement that was observed when the occiput was in close contact with the inferior margin of the symphysis pubis, occurring simultaneously with gliding downward of the fetal head. CONCLUSION: This observational study shows, for the first time, that birth can be analyzed with real-time MRI. MRI technology allows assessment of maternal and fetal anatomy during labor and delivery. Copyright © 2012 Mosby, Inc. All rights reserved.
MRI: is there a role in obstetrics?
Clin Obstet Gynecol. 2012 Mar;55(1):352-66.
Hibbeln JF, Shors SM, Byrd SE. Source Department of Diagnostic Radiology and Nuclear Medicine, Rush University Medical Center, Chicago, Illinois 60612, USA. firstname.lastname@example.org
Magnetic resonance imaging has a complementary role in obstetrical imaging to ultrasound (US). Although US has advantages as an initial imaging technique, there are significant numbers of patients who cannot be adequately evaluated for a variety of reasons including calvarial calcification, oligoanhydramnios, or simply obesity. MR can provide additional information that cannot be obtained by US and is invaluable in central nervous system anomaly evaluation, airway management, and planning for postnatal intervention. Newer techniques established in the postnatal population such as spectroscopy, diffusion-weighted imaging, and functional imaging have future applications in the fetus.
Magnetic resonance imaging and gynecological devices
Contraception. 2011 Nov 29. [Epub ahead of print]
Correia L, Ramos AB, Machado AI, Rosa D, Marques C. Source Maternidade Dr. Alfredo da Costa, Lisbon, Portugal.
BACKGROUND: Performing magnetic resonance imaging (MRI) on women with gynecological devices is a completely accepted practice. The goal of our review is to assess how safe it is to perform MRI on women using contraceptive implants or devices. STUDY DESIGN: Literature review, searching in PubMed-Medline/Ovid for the following keywords: magnetic resonance imaging, intrauterine devices, Implanon® and Essure ®. RESULTS: Though plastic devices do not represent a contraindication to the use of the technique, those including metallic components have been submitted to several tests, after which they were classified as MR Conditional (devices presenting no risks in MR-specific environments) by the Food and Drug Administration. Thus, the use of MRI can be safely advised to women with this type of device as long as the magnetic resonance equipment is ≤3.0 T. CONCLUSIONS: Presently, there is no scientific evidence that contraindicates performing MRI on women with any kind of gynecological device. Therefore, this procedure is safe as long as it is performed under previously tested conditions. Copyright © 2011 Elsevier Inc. All rights reserved.
Situs anomalies on prenatal MRI
Eur J Radiol. 2011 Jun 27. [Epub ahead of print]
Nemec SF, Brugger PC, Nemec U, Bettelheim D, Kasprian G, Amann G, Rimoin DL, Graham JM Jr, Prayer D. Source Department of Radiology, Division of Neuroradiology and Musculoskeletal Radiology, Medical University Vienna, Waehringer Guertel 18-20, A-1090 Vienna, Austria; Medical Genetics Institute, Cedars Sinai Medical Center, 8700 Beverly Boulevard, PACT Suite 400, Los Angeles, CA 90048, USA.
OBJECTIVE: Situs anomalies refer to an abnormal organ arrangement, which may be associated with severe errors of development. Due regard being given to prenatal magnetic resonance imaging (MRI) as an adjunct to ultrasonography (US), this study sought to demonstrate the in utero visualization of situs anomalies on MRI, compared to US.
MATERIALS AND METHODS: This retrospective study included 12 fetuses with situs anomalies depicted on fetal MRI using prenatal US as a comparison modality. With an MRI standard protocol, the whole fetus was assessed for anomalies, with regard to the position and morphology of the following structures: heart; venous drainage and aorta; stomach and intestines; liver and gallbladder; and the presence and number of spleens.
RESULTS: Situs inversus totalis was found in 3/12 fetuses; situs inversus with levocardia in 1/12 fetuses; situs inversus abdominis in 2/12 fetuses; situs ambiguous with polysplenia in 3/12 fetuses, and with asplenia in 2/12 fetuses; and isolated dextrocardia in 1/12 fetuses. Congenital heart defects (CHDs), vascular anomalies, and intestinal malrotations were the most frequent associated malformations. In 5/12 cases, the US and MRI diagnoses were concordant. Compared to US, in 7/12 cases, additional MRI findings specified the situs anomaly, but CHDs were only partially visualized in six cases.
CONCLUSIONS: Our initial MRI results demonstrate the visualization of situs anomalies and associated malformations in utero, which may provide important information for perinatal management. Using a standard protocol, MRI may identify additional findings, compared to US, which confirm and specify the situs anomaly, but, with limited MRI visualization of fetal CHDs.
Copyright © 2011 Elsevier Ireland Ltd. All rights reserved.
PMID: 21715116 http://www.ncbi.nlm.nih.gov/pubmed/21715116
Abnormalities of the Upper Extremities on Fetal MRI
Ultrasound Obstet Gynecol. 2011 Jan 24. doi: 10.1002/uog.8949. [Epub ahead of print]
Nemec SF, Kasprian G, Brugger PC, Bettelheim D, Amann G, Nemec U, Rotmensch S, Graham JM Jr, Rimoin DL, Lachman RS, Prayer D. Source Department of Radiology, Division of Neuroradiology and Musculoskeletal Radiology, Medical University Vienna, Waehringer Guertel 18-20, A-1090 Vienna, Austria; Medical Genetics Institute, Cedars Sinai Medical Center, 8700 Beverly Boulevard, PACT Suite 400, Los Angeles, California 90048, USA. email@example.com, firstname.lastname@example.org. Abstract OBJECTIVE: In view of the increasing use of fetal magnetic resonance imaging (MRI) as an adjunct to prenatal ultrasonography (US), we sought to demonstrate the visualization of upper extremity abnormalities and associated defects on MRI, with regard to fetal outcomes and compared to US.
METHODS: This retrospective study included 29 fetuses with upper extremity abnormalities that were positively depicted with fetal MRI and confirmed by postnatal assessment or autopsy. On a 1.5 Tesla unit, dedicated sequences were applied to image the extremities. CNS and extra-CNS anomalies were assessed to define extremity abnormalities as isolated or complex with associated defects. Fetal outcome was identified from medical records. The MRI and US findings were compared.
RESULTS: Isolated upper extremity abnormalities were found in 3/29 (10.3%) fetuses. Complex abnormalities were demonstrated in 26/29 (89.7%) fetuses, including postural extremity disorders (21/26) and structural extremity abnormalities (15/26). Associated defects involved: face (15/26); musculoskeletal system (14/26); thorax and cardio/pulmonary system (12/26); lower extremities (12/26); brain and skull (10/26); and abdomen (8/26). Of 29 cases, 18 (62.1%) pregnancies were delivered and 11 (37.9%) were terminated. MRI and US were compared in 27/29 cases: the diagnosis was concordant in 14/27 (51.9%) cases, and additional MRI findings were made in 13/27 (48.1%) cases.
CONCLUSIONS: Our results demonstrate that the visualization of upper extremity abnormalities on fetal MRI enables the differentiation between isolated and complex defects, which may be related to poor fetal prognosis. MRI mostly confirms the US diagnosis, but may provide additional findings in certain cases. Copyright © 2011 ISUOG. Published by John Wiley & Sons, Ltd.
Copyright © 2011 ISUOG. Published by John Wiley & Sons, Ltd.
PMID: 21308835 http://www.ncbi.nlm.nih.gov/pubmed/21308835
Relationship between fetal head station established using an open magnetic resonance imaging scanner and the "angle of progression" determined by transperineal ultrasound
Ultrasound Obstet Gynecol. 2011 Jan 24. doi: 10.1002/uog.8944. [Epub ahead of print]
Bamberg C, Scheuermann S, Slowinski T, Dückelmann A, Vogt M, Nguyen-Dobinsky T, Streitparth F, Teichgräber U, Henrich W, Dudenhausen J, Kalache K. Department of Obstetrics -Charité University Hospital - Campus Mitte, Berlin Germany.
OBJECTIVES: We investigated the correlation between the angle of progression measured by transperineal ultrasound and fetal head station measured by open magnetic resonance imaging (MRI), the gold standard, in pregnant women at full term.
METHODS: Thirty-one pregnant women at full term with a fetus in the occipitoanterior position were enrolled. First, the distance between the leading part of the skull and the interspinal plane was obtained with an open MRI system with the patients in supine position. Then, immediately after the MRI, the angle of progression was obtained by transperineal ultrasound without changing the women's posture.
RESULTS: There was a significant correlation between the angle of progression determined by transperineal sonography and the distance between the presenting fetal part and the level of the maternal ischial spines (y = -0·51x + 60·8, r(2) = 0·38, p<0·001).
CONCLUSIONS: The present study demonstrated a predictable relationship between the angle of progression obtained by transperineal ultrasound and the traditional scale to quantify fetal head descent. Based on our results, station 0 would correspond to a 120° angle of progression. However, this correlation is based on statistical assumption only and has to be proven in future studies. Copyright © 2011 ISUOG. Published by John Wiley & Sons, Ltd.
PMID: 21308830 http://www.ncbi.nlm.nih.gov/pubmed/21308830
Temperature elevation in the fetus from electromagnetic exposure during magnetic resonance imaging
Phys Med Biol. 2010 Apr 21;55(8):2411-26. Epub 2010 Apr 1.
Kikuchi S, Saito K, Takahashi M, Ito K.
Graduate School of Engineering, Chiba University, 1-33 Yayoi-cho, Inage-ku, Chiba 263-8522, Japan. email@example.com Abstract This study computationally assessed the temperature elevations due to electromagnetic wave energy deposition during magnetic resonance imaging in non-pregnant and pregnant woman models. We used a thermal model with thermoregulatory response of the human body for our calculations. We also considered the effect of blood temperature variation on body core temperature. In a thermal equilibrium state, the temperature elevations in the intrinsic tissues of the woman and fetal tissues were 0.85 and 0.61 degrees C, respectively, at a whole-body averaged specific absorption rate of 2.0 W kg(-1), which is the restriction value of the International Electrotechnical Commission for the normal operating mode. As predicted, these values are below the temperature elevation of 1.5 degrees C that is expected to be teratogenic. However, these values exceeded the recommended temperature elevation limit of 0.5 degrees C by the International Commission on Non-Ionizing Radiation Protection. We also assessed the irradiation time required for a temperature elevation of 0.5 degrees C at the aforementioned specific absorption rate. As a result, the calculated irradiation time was 40 min.
PMID: 20360633 http://www.ncbi.nlm.nih.gov/pubmed/20360633
Numerical study of RF exposure and the resulting temperature rise in the foetus during a magnetic resonance procedure
Phys Med Biol. 2010 Feb 21;55(4):913-30. Epub 2010 Jan 20.
Hand JW, Li Y, Hajnal JV.
Imaging Sciences Department, Imperial College London, London W12 0NN, UK. firstname.lastname@example.org Abstract Numerical simulations of specific absorption rate (SAR) and temperature changes in a 26-week pregnant woman model within typical birdcage body coils as used in 1.5 T and 3 T MRI scanners are described. Spatial distributions of SAR and the resulting spatial and temporal changes in temperature are determined using a finite difference time domain method and a finite difference bio-heat transfer solver that accounts for discrete vessels. Heat transfer from foetus to placenta via the umbilical vein and arteries as well as that across the foetal skin/amniotic fluid/uterine wall boundaries is modelled. Results suggest that for procedures compliant with IEC normal mode conditions (maternal whole-body averaged SAR(MWB) < or = 2 W kg(-1) (continuous or time-averaged over 6 min)), whole foetal SAR, local foetal SAR(10 g) and average foetal temperature are within international safety limits. For continuous RF exposure at SAR(MWB) = 2 W kg(-1) over periods of 7.5 min or longer, a maximum local foetal temperature >38 degrees C may occur. However, assessment of the risk posed by such maximum temperatures predicted in a static model is difficult because of frequent foetal movement. Results also confirm that when SAR(MWB) = 2 W kg(-1), some local SAR(10g) values in the mother's trunk and extremities exceed recommended limits.
PMID: 20090188 http://www.ncbi.nlm.nih.gov/pubmed/20090188
JBR-BTR. 2009 Nov-Dec;92(6):271-9.
Buls N, Covens P, Nieboer K, Van Schuerbeek P, Devacht P, Eloot L, de Mey J.
Dienst Radiologie and Dienst Fysische controle, UZ Brussel, Brussels, Belgium. Abstract The participation of pregnant women in radiology can be an emotional experience. The word "radiation" understandably invokes fear and uncertainty. Irradiation of a foetus should be avoided whenever possible. However, radiological examinations of pregnant women are often justified and unintended exposures do occur. Also pregnant radiology staff may remain working in the department. Lack of knowledge about the effects of both ionising (X-rays) and non-ionising (MRI) radiation is responsible for anxiety of patients and workers. If foetal exposures occur, they must be quantitatively evaluated and the risk put into perspective. This paper is intended to inform radiology managers, radiologists, technologists and referring clinicians in their management with pregnant patients and co-workers. The paper describes conceptus doses for both patient and worker that are associated with radiology practice, reviews the risks and effects of in utero irradiation, and discusses current national policies, international guidelines and practical aspects.
PMID: 20166494 http://www.ncbi.nlm.nih.gov/pubmed/20166494
World-first at Charité: Birth in "open" MRI
Developmental atlas of the early first trimester human embryo
MR imaging of fetal abnormalities
Tamsel S, Ozbek SS, Sener RN, Oztekin O, Demirpolat G. Comput Med Imaging Graph. 2004 Apr;28(3):141-9. PMID: 15081497
Ultrafast MR imaging of the fetus
Kubik-Huch RA, Huisman TA, Wisser J, Gottstein-Aalame N, Debatin JF, Seifert B, Ladd ME, Stallmach T, Marincek B. AJR Am J Roentgenol. 2000 Jun;174(6):1599-606. PMID: 10845491
Mouse Brain Atlas MRI Database
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Registered 14 December 2010 see email for login information.