Water imaging (hydrography) in the fetus: the value of a heavily T2-weighted sequence

MR Imaging of the Fetal Genitourinary Tract

Fetal MR imaging overcomes many of the technical barriers of ultrasound and is an important diagnostic tool for fetal genitourinary (GU) anomalies. It is suited for evaluation of GU anomalies because of the fluid-sensitive sequences and superior soft tissue contrast. Often GU malformations are part of a multisystem genetic or congenital condition, and imaging the entire fetus with MR adds additional clarity about the extent of disease. It adds confidence to diagnoses of renal agenesis, urinary tract dilation, cystic disease, and tumors. It is particularly useful to delineate anatomy in complex GU malformations. This additional information guides counseling.

Application value of magnetic resonance hydrography of the inner ear in cochlear implantation

OBJECTIVE

This study aims to investigate the application value of magnetic resonance (MR) hydrography of the inner ear in cochlear implantation.

METHODS

146 patients were enrolled. MR hydrography and spiral CT examinations for the intracranial auditory canal were performed before surgery, and all imaging results were statistically analyzed in order to explore the application value of MR hydrography of the inner ear in cochlear implantation.

RESULTS

146 patients (292 ears) were examined. Among these patients, 13 were diagnosed with abnormal vestibular aqueducts (20 ears) by MR hydrography, while five were diagnosed with this disease by CT; 15 patients were diagnosed with inner ear malformation (19 ears) by MR hydrography, while 11 were diagnosed by CT (four were misdiagnosed); five patients were diagnosed with internal acoustic canal stenosis (eight ears) by MR hydrography, while two were diagnosed by CT (three were misdiagnosed); and four patients were diagnosed with cochlear fibrosis (five ears) by MR hydrography, while four were diagnosed by CT (four ears). The correct rate of diagnosis was 77.40% (113/146) based on CT, while the rate was 93.84% (137/146) based on MR hydrography.

CONCLUSIONS

MR hydrography imaging technique can be applied to the preoperative evaluation of cochlear implantation, providing accurate and reliable anatomic information on the inner membranous labyrinth and nerves in the internal acoustic canal and an accurate basis for the diagnosis of cochlear fibrosis and nerve development. This has a guiding significance for the selection of treatment schemes.

Chinese expert consensus on diagnosis and management of split cord malformation

Split cord malformation (SCM) is a neural tube defect that the spinal cord is longitudinally separated into two hemicords with individual functions, which causes severe spinal cord impairment and sensorimotor deficit. As a kind of myelodysplasia and a special type of tethered cord syndrome, SCM is not widely understood, and common issues in the diagnosis and treatment of SCM should be clarified. In this paper, the Chinese Split Cord Malformation Working Group made a consensus for SCM on embryopathogenesis and types, clinical presentations, neuroimaging assessment, indications and principle of the surgery, surgical techniques and nuances, and prognosis and follow up.

Volume growth trend and correlation of atrial diameter with lateral ventricular volume in normal fetus and fetus with ventriculomegaly: A STROBE compliant article

To explore the growth trend of fetal lateral ventricular volume, for understanding the relationship between atrial diameter (AD) and volume in normal fetus and fetus with ventriculomegaly.Overall, 97 sequential fetal head magnetic resonance imaging scans were performed; these pertained to 50 fetuses with normal lateral ventricles [normal group; gestational age (GA): 24-38 weeks] and 47 fetuses with ventriculomegaly (VM) (VM group; GA: 24-37 weeks). The left, right, and total lateral ventricular volume were measured using 3-dimensional magnetic resonance hydrography (MRH). Correlation coefficient (r) was calculated to assess the relationships of measurements. Lineal regression analysis was used to assess correlation of AD and GA with volume. Between-group differences in terms of AD and volume were assessed using t test.Significant linear growth was observed in the total lateral ventricular volume compared with GA in the normal group with a relative growth rate of 2.87% per week (P <.001). Significant linear relationship between AD and volume was observed, and a significant equation was acquired in the normal group and VM groups, respectively, using the simple linear regression model: left volume = 0.438 * normal left diameter (NLD) + 1.359; right volume = 0.493 * normal right diameter (NRD) + 1.012; left volume = 0.959 * left diameter in VM (VLD) - 2.074; right volume = 0.799 * right diameter in VM (VRD) - 0.443. A significant equation was obtained in the normal group and the VM group, using the multiple linear regression model: Total volume (mL) = 0.396 * NLD + 0.410 * NRD + 3.101; and total volume = 0.989 * VLD + 0.834 * VRD - 3.141, respectively. In terms of AD and volume, the left lateral ventricle was significantly larger than the right side in both groups. The volume of lateral ventricle in AD ≥10 mm group was larger than that in the AD <10 mm group. The total volume in the VM group was significantly larger than that in the normal group.The total lateral ventricular volume increased with GA. AD can be used to evaluate the fetal ventricular volume.

Lateral ventricular volume measurement by 3D MR hydrography in fetal ventriculomegaly and normal lateral ventricles

BACKGROUND

In fetuses with prenatal ventriculomegaly (VM), ventricular volume on MRI has been shown to correlate with poor postnatal outcomes and in utero death. 3D magnetic resonance hydrography (MRH) has been widely used for MR cholangiopancreatography.

PURPOSE

To investigate the reliability of 3D MRH for lateral ventricular volume measurement in fetuses with VM and normal lateral ventricles, using manual multisection planimetry (MSP) as a reference standard.

STUDY TYPE

Prospective study.

POPULATION

Thirty-five fetuses with VM at 24-37 gestational weeks (GA) and 35 fetuses with normal lateral ventricles at 24-38 GA.

FIELD STRENGTH/SEQUENCE

1.5T MRI with 3D MRH and T₂ -weighted single-shot fast-spin echo sequence.

ASSESSMENT

Left, right, and total lateral ventricle volumes in fetuses were acquired from 3D MRH and manual MSP. All image analysis was performed by a radiologist twice and another radiologist once, blindly.

STATISTICAL TESTS

Analysis of linear regression analysis, Pearson's correlation coefficient, Bland-Altman plots, intraclass correlation coefficient (ICC), and independent samples t-test were used for statistical analyses.

RESULTS

There were highly significant relationships between all 3D MRH and manual MSP measurements of lateral ventricular volumes (r_VM  = 0.92-0.98; r_N  = 0.95-0.98; all P < 0.0001; VM: VM group, N: normal group), although left, right, and total lateral ventricular volumes measured by 3D MRH tended to be slightly larger than MSP (bias_VM 0.1 ± 0.95, 0.26 ± 0.63, and 0.3 ± 0.68 mL, respectively; bias_N 0.1 ± 0.95, 0.26 ± 0.63, and 0.3 ± 0.68 mL, respectively). Interrater agreement and intrarater repeatability were also excellent for 3D MRH (ICC_VM  = 0.994-0.99, ICC_N  = 0.989-0.992; ICC_VM  = 0.975-0.987, ICC_N  = 0.958-0.971, respectively). 3D MRH showed significantly reduced measurement time (VM: 3.55 ± 0.42 vs. 11.81 ± 0.13 min; N: 3.08 ± 0.39 vs. 12.12 ± 0.11 min; all P < 0.0001).

DATA CONCLUSION

Lateral ventricular volume measurement by 3D MRH was comparable to manual MSP.

LEVEL OF EVIDENCE

1 Technical Efficacy Stage 1 J. Magn. Reson. Imaging 2017.

Fetal MRI of the central nervous system: State-of-the-art

Prenatal ultrasonographic (US) examination is considered as the first tool in the assessment of fetal abnormalities. However, several large-scale studies point out that some malformations, in particular central nervous system (CNS) anomalies, are not well characterized through US. Therefore, the actual malformation severity is not always related to prenatal ultrasound (US) findings. Over the past 20 years, ultrafast Magnetic Resonance Imaging (MRI) has progressively increased as a prenatal 3rd level diagnostic technique with a good sensitivity, particularly for the study of fetal CNS malformations. In fact, CNS anomalies are the most common clinical indications for fetal MRI, representing about 80% of the total examinations. This review covers the recent literature on fetal brain MRI, with emphasis on techniques, safety and indications.

Congenital CNS tumors diagnosed on prenatal MRI

Congenital tumors form a unique group among pediatric neoplasms. They are different from other tumor groups in this population not only due to the onset time but also to their histopathology, anatomic location, biologic behavior and prognosis. The development of fetal MRI allowed early diagnosis of these tumors. Three fetuses with congenital central nervous system (CNS) tumors were diagnosed prenatally and confirmed with histopathology. Prenatal ultrasonography (US) and magnetic resonance imaging (MRI) were performed. After birth MRI or computed tomography (CT) were carried out. In one case a large intra-axial brain tumor was diagnosed with solid, cystic and hemorrhagic elements. After surgery the tumor turned out to be choroid plexus carcinoma. In the second case craniopharyngioma arising from the suprasellar region was diagnosed on the basis of prenatal MRI and confirmed. In the third case extra-axial meningioma-like tumor was visualized on fetal MRI. After surgery it turned out to be desmoplastic infantile astrocytoma. Intracranial teratoma, the most typical CNS congenital tumor, was not diagnosed in our material. Our cases were rarely encountered neoplasms: choroid plexus carcinoma, craniopharyngioma and desmoplastic infantile astrocytoma. The examinations were repeated after birth and did not add significant information. In utero diagnostics is easier and safer than postnatal imaging of the sick baby that may require life-support equipment, and provides information of equal value.

Use of two-dimensional multiple-slice magnetic resonance hydrography for diagnosis of hepatic hemangiomas and cysts

BACKGROUND/PURPOSE

Although hepatic hemangiomas and cysts display very high signal intensities on conventional T2 images, their appearances are quite distinct using magnetic resonance hydrography (MRH). We examined the feasibility of using MRH in distinguishing hepatic cysts from hemangiomas.

METHODS

We recruited 97 patients with hepatic hemangiomas and 65 with hepatic cysts. All patients underwent magnetic resonance imaging (including two-dimensional multiple slice MRH, TR/TE: 8000/800) and the results were reviewed independently by two radiologists. The signal intensities of the lesions were measured. For each lesion, the variation in signal to noise ratio between MRH and the fat-saturated T2-weighted images was calculated, and the results were validated using a receiver operating characteristic curve.

RESULTS

There was a significant difference between the signal to noise ratio of hepatic hemangiomas and cysts using MRH (p < 0.001). This difference could be identified by visual inspection. The receiver operating characteristic curve revealed that the ideal cut-off value for the signal intensity reduction ratio between hepatic cysts and hemangiomas was -0.1. Using this ratio, the derived sensitivity was 95.4%, specificity 99.0%, and accuracy 99.7%.

CONCLUSION

Hepatic hemangiomas and cysts have significantly different signal intensities on non-contrast two-dimensional multiple-slice MRH. This approach uses a non-invasive, reliable, and accurate imaging technique to differentiate the two diagnoses.

Magnetic resonance imaging in the evaluation of the fetal spinal canal contents

Ultrasonography (US) remains the first method in the evaluation of fetal central nervous system (CNS) abnormalities but in case of the spinal canal and cord it is often insufficient since the bony structures may obscure these structures. Prenatal magnetic resonance imaging (MRI) is therefore the final noninvasive tool for the assessment of these malformations allowing for correction of sonographic findings, revealing the full extent of complex lesions and choosing the candidates for in utero treatment. The authors present the most frequent anomalies of spinal canal and spinal cord in the consecutive phases of pregnancy, illustrated with their own MR images, with reference to the literature and own experience. In 58 out of 252 fetuses examined due to suspicion of CNS anomalies (23.0%) the spinal canal and spinal cord abnormalities were found on MRI. The cases of diastematomyelia, myelomeningocele, tethered cord, caudal regression syndrome, anterior meningocele, cystic sacrococcygeal teratoma and syringohydromyelia are demonstrated.

Magnetic Resonance Imaging of the Fetal Central Nervous System in Singapore

The dual energy CT (DECT) technology has been recently employed in the form of two X-ray sources of different energies to enhance the contrast between adjacent structures. Its use in the cardiac arena has been widely highlighted due to the higher temporal resolution. However, it may also be used in the craniocervical and peripheral vasculature for better differentiation between contrast-enhanced vascular lumina and calcified plaques, in the characterisation of ureteric stones, and in the evaluation of hepatic lesions. The objective of this paper is to revisit DECT physics, review the literature and discuss its use in CT neuroangiography with case illustrations from our institution, and impact on dose savings. Key words: Craniocervical CT angiography, Intracranial aneurysms, Radiation dosage, Vascular stenosis

Fetal central nervous system malformations on MR images

Sonography is the method of choice for prenatal malformation screening but it does not always provide sufficient information for correct diagnosis or adequate abnormality evaluation. Fetal magnetic resonance imaging (MRI) is considered as a valuable second line imaging tool for confirmation, completion and correction of sonographic findings. Fetal MRI has proven its value in the evaluation of central nervous system pathologies, especially of midline and posterior fossa malformations. The role of MRI is not only to confirm or exclude possible lesions but also to define their full extent, aiding in their characterization, and to demonstrate associated abnormalities. The authors describe the most common anomalies of CNS revealed by fetal MRI in a chronological way related to the age of pregnancy, with a review of own MR images and with reference to the literature and own experience.

MR fetography using heavily T2-weighted sequences: comparison of thin- and thick-slab acquisitions

PURPOSE

To evaluate the use of MR-fetography sequences in identifying the major fetal structures and to compare thick- and thin-slab acquisitions for their diagnostic value.

MATERIALS AND METHODS

Twenty-one consecutive, pregnant women with suspected fetal pathology underwent fetal magnetic resonance imaging (MRI) using a 1.5 T MRI unit. Heavily T2-weighted, single-shot fast spin-echo (SSFSE) sequences with a long echo train (MR-fetography) were acquired in a thick- and thin-slab modus. Thick- and thin-slab acquisitions were reviewed by two experienced radiologists with regard to the overall image quality and landmark anatomical structures (spinal canal, spinal cord, posterior fossa, cerebellum, brainstem, basal cisterns, stomach, urinary bladder and umbilical cord according to a three-scale grading system (good, moderate and poor). Visibility scores were calculated and compared between both sequences.

RESULTS

Overall image quality was graded good in 76.2%, moderate in 19.0% and poor in 4.8% for thick-slab images and good in 81%, moderate in 14.3% and poor in 4.8% for thin-slab images. The visibility scores of the thick/thin-slab images for evaluation of the main fetal structures were as follows: for the spinal canal 2.8+/-0.4/2.9+/-0.54 (p>0.05), spinal cord 2.4+/-0.75/2.7+/-0.66 (p>0.05), posterior fossa components (cerebellum, brainstem and basal cisterns) 2.4+/-0.68/2.8+/-0.54; 2.4+/-0.67/2.7+/-0.66; 2.5+/-0.51/2.7+/-0.56 (p<0.05), stomach 2.8+/-0.44/2.9+/-0.48 (p>0.05), urinary bladder 2.8+/-0.51/2.8+/-0.54 (p>0.05) and umbilical cord 2.9+/-0.30/2.6+/-0.60 (p<0.05).

CONCLUSION

Heavily T2-weighted MR-fetography renders a quick overview of fetal contours, fetal position, amount of amniotic fluid and integrity and presence of several major fluid containing structures. Thick- and thin-slab acquisitions render complementary information. Thick-slab images display the entire fetus in one projection while thin-slab images provide more detailed anatomical information. The short imaging time usually allows measuring both thick- and thin-slab images. MR-fetography is as a helpful addition to conventional fetal MRI. MR-fetography should not be viewed as a single, stand alone sequence but as a supporting fast MR sequence in a well-designed multisequence fetal MRI protocol. Future studies evaluating larger patient groups are mandatory.

Fetal Magnetic Resonance Imaging as a Complement to Fetal Ultrasonography

Ultrasonography is the screening method of choice for the evaluation of the fetus. It is safe, inexpensive, and easily performed. However, it is operator dependent, and evaluation may be limited because of fetal position, maternal obesity, overlying bone, and/or oligohydramnios. Magnetic resonance imaging is an alternative modality that uses no ionizing radiation, has excellent tissue contrast and a large field of view, is not limited by obesity or overlying bone, and can image the fetus in multiple planes, no matter the fetal lie. Faster scanning techniques allow studies to be performed without sedation in the second and third trimester with minimal motion artifact.