Evaluating T1-weighted MRI techniques for fetal gastrointestinal diagnostics: A comparative study

PURPOSE

In clinical practice, fetal gastrointestinal magnetic resonance imaging (MRI) encounters significant challenges. T1-weighted images are particularly susceptible to the effects of fetal and maternal movements compared to other weighted images, complicating the acquisition of satisfactory results. This study aimed to compare three fast 3D-T1 weighted gradient echo (GRE) sequences-free-breathing stack-of-stars VIBE (STAR-VIBE), breath-hold VIBE (BH-VIBE), and free-breathing multi-average VIBE (MA-VIBE)-for fetal gastrointestinal MRI in fetuses with both normal and abnormal gastrointestinal tracts between 21 and 36 weeks of gestation.

METHODS

This study enrolled 67 pregnant women who underwent fetal abdominal MRI at our hospital between October 2022 and October 2023, during their gestational period of 21-36 weeks. Among these participants, 22 were suspected of having fetal gastrointestinal anomalies based on ultrasound findings, while the remaining 45 were considered to have normal fetal gastrointestinal development. All subjects underwent True fast imaging with steady-state precession sequence scanning along with three T1-weighted imaging techniques on a Siemens 1.5-T Aera scanner: STAR-VIBE, BH-VIBE, and MA-VIBE. Two radiologists evaluated image quality, intestinal clarity, and lesion conspicuity using a five-point scale where higher scores indicated superior performance for each technique; they were blinded to the acquisition schemes used. Interobserver variability assessments were also conducted.

RESULTS

The free-breathing MA-VIBE sequence demonstrated significantly better performance than both STAR-VIBE and BH-VIBE in terms of fetal gastrointestinal MRI quality (3.81 ± 0.40 vs. 3.35 ± 0.70 vs. 2.90 ± 0.64; p < .05). The STAR-VIBE and BH-VIBE sequences exhibited moderate consistency (kappa = 0.586 and kappa = 0.527 respectively; P < .05), whereas the MA-VIBE sequence showed higher consistency (kappa = 0.712; P < .05).

CONCLUSION

The free-breathing MA-VIBE sequence provided superior visualization for assessing fetal intestinal conditions compared to other methods employed in this study. On a 1.5 T MRI device, T1-weighted images based on the free-breathing MA-VIBE sequence can effectively overcome motion artifacts and compensate for the reduced signal-to-noise ratio caused by the application of acceleration techniques, thus significantly improving the quality of T1-weighted images.

How to Perform Fetal MR Imaging

This article provides the readers with practical guidance on how to perform fetal MR imaging, including technical considerations such as scanner field strength and use of appropriate radiofrequency receive coils, and summarizes the role, strengths, and limitations of the various MR imaging sequences. The authors review the various factors to consider in scan preparation, including study indication, timing, maternal preparation, and the creation of an institutional fetal imaging protocol. Additional factors that go into scan optimization during acquisition including prioritizing maternal comfort and ways to troubleshoot various artifacts that maybe encountered in fetal imaging are discussed.

Fetal MRI at 3 T: Principles to Optimize Success

Fetal MRI has emerged as a cornerstone of prenatal imaging, helping to establish the correct diagnosis in pregnancies affected by congenital anomalies. In the past decade, 3 T imaging was introduced as an alternative to increase the signal-to-noise ratio (SNR) of the pulse sequences and improve anatomic detail. However, imaging at a higher field strength is not without challenges. Many artifacts that are barely appreciable at 1.5 T are amplified at 3 T. A systematic approach to imaging at 3 T that incorporates appropriate patient positioning, a thoughtful protocol design, and sequence optimization minimizes the impact of these artifacts and allows radiologists to reap the benefits of the increased SNR. The sequences used are the same at both field strengths and include single-shot T2-weighted, balanced steady-state free-precession, three-dimensional T1-weighted spoiled gradient-echo, and echo-planar imaging. Synergistic use of these acquisitions to sample various tissue contrasts and in various planes provides valuable information about fetal anatomy and pathologic conditions. In the authors' experience, fetal imaging at 3 T outperforms imaging at 1.5 T for most indications when performed under optimal circumstances. The authors condense the cumulative experience of fetal imaging specialists and MRI technologists who practice at a large referral center into a guideline covering all major aspects of fetal MRI at 3 T, from patient preparation to image interpretation. © RSNA, 2023 Quiz questions for this article are available in the supplemental material.

A Spectrum of Ultrasound and MR Imaging of Fetal Gastrointestinal Abnormalities: Part 1 Esophagus to Colon

Ultrasound (US) and magnetic resonance imaging (MRI) are two modalities for diagnosing fetal gastrointestinal (GI) anomalies. Ultrasound (US) is the modality of choice. MRI can be used as a complementary method. Despite its expanding utilization in central nervous system (CNS) fetal malformation, MRI has not yet been established for evaluation of fetal GI abnormalities. Therefore, more attention should be paid to the clinical implications of MRI investigations following screening by US.

Optimization of the image contrast for the developing fetal brain using 3D radial VIBE sequence in 3 T magnetic resonance imaging

BACKGROUND

Faster and motion robust magnetic resonance imaging (MRI) sequences are desirable in fetal brain MRI. T1-weighted images are essential for evaluating fetal brain development. We optimized the radial volumetric interpolated breath-hold examination (VIBE) sequence for qualitative T1-weighted images of the fetal brain with improved image contrast and reduced motion sensitivity.

MATERIALS AND METHODS

This was an institutional review board-approved prospective study. Thirty-five pregnant subjects underwent fetal brain scan at 3 Tesla MRI. T1-weighted images were acquired using a 3D radial VIBE sequence with flip angles of 6º, 9º, 12º, and 15º. T1-weighted images of Cartesian VIBE sequence were acquired in three of the subjects. Qualitative assessments including image quality and motion artifact severity were evaluated. The image contrast ratio between gray and white matter were measured. Interobserver reliability and intraobserver repeatability were assessed using intraclass correlation coefficient (ICC).

RESULTS

Interobserver reliability and intraobserver repeatability universally revealed almost perfect agreement (ICC > 0.800). Significant differences in image quality were detected in basal ganglia (P = 0.023), central sulcus (P = 0.028), myelination (P = 0.007) and gray matter (P = 0.023) among radial VIBE with flip angles 6º, 9º, 12º, 15º. Image quality at the 9º flip angle in radial VIBE was generally better than flip angle of 15º. Radial VIBE sequence with 9º flip angle of gray matter was significantly different by gestational age (GA) before and after 28 weeks (P = 0.036). Quantified image contrast was significantly different among different flip angles, consistent with qualitative analysis of image quality.

CONCLUSIONS

Three-dimensional radial VIBE with 9º flip angle provides optimal, stable T1-weighted images of the fetal brain. Fetal brain structure and development can be evaluated using high-quality images obtained using this angle. However, different scanners will achieve different TRs and so the FA should be re-optimized each time a new protocol is employed.

New sonographic feature (C-sign) to improve the prenatal accuracy of jejunal atresia

OBJECTIVES

To describe a new sonographic feature of the C-sign for prenatal diagnosis of jejunal atresia and evaluate its role in prenatal jejunal atresia, particularly preceding bowel dilatation and polyhydramnios.

METHODS

This was a retrospective study from a tertiary maternal hospital. Patients with prenatal sonographic examination and confirmed small bowel atresia postdelivery were included. All sonographic images were reviewed by two senior sonographers. Comparison of sonographic images between prenatal jejunal and ileal atresia using the C-sign resembles the shape of the entire duodenum and other traditional sonographic features. The control group without bowel atresia was assessed for the presence of the C-sign.

RESULTS

The C-sign and combined bowel dilatation with polyhydramnios were more frequent in jejunal atresia than ileal atresia, but the C-sign can be used to detect jejunal atresia earlier. The C-sign can be more likely to diagnose jejunal atresia in persisting bowel dilatation and polyhydramnios. The C-sign was not reported in any of the control fetuses.

CONCLUSION

The C-sign is a new sonographic feature that can be used to improve the prenatal accuracy and early detection of jejunal atresia. However, further prospective validation is needed.

Appearance of fetal intestinal obstruction on fetal MRI

OBJECTIVE

To retrospectively analyze the imaging findings of fetal intestinal obstruction diagnosed by MRI and compare with postnatal surgery findings.

METHODS

MRI data of 3346 pregnant women were retrospectively analyzed; we found 47 cases of suspected fetal small intestinal obstruction. Twenty-nine underwent postnatal surgery.

RESULTS

We identified one case of jejunal obstruction secondary to perforation, five annular pancreas, 10 duodenal stenoses, four jejunal stenoses, five jejunal atresias, two ileal atresias, four intestinal volvulus, and four intestinal malrotations. We further found four cases of duodenal stenosis with intestinal malrotation (two cases also showed volvulus). On fetal MRI, annular pancreas and duodenal obstruction manifested as a "double bubble." Jejunal stenosis appeared as a "triple bubble." Jejunal and ileal atresia mainly manifested as proximal dilatation with high signal on T1WI. Intestinal volvulus showed a sausage-like intestinal distortion and mixed signals on T1WI and DWI sequences. Intestinal malrotations were characterized as abnormal duodenal morphology. We missed two malrotations; one jejunal obstruction was misdiagnosed.

CONCLUSION

Prenatal MRI can accurately determine the degree of intestinal obstruction and help qualitatively diagnose its possible etiology according to changes in MRI signals in multiple sequences, providing guidance for prenatal counseling.

Biometric analysis of the foetal meconium pattern using T1 weighted 2D gradient echo MRI

Objectives:

Foetal MRI is used to assess abnormalities after ultrasonography. Bowel anomalies are a significant cause of neonatal morbidity, however there are little data concerning its normal appearance on antenatal MRI. This study aims to investigate the pattern of meconium accumulation throughout gestation using its hyperintense appearance on T₁ weighted scans and add to the current published data.

Methods:

This was a retrospective cohort study in a tertiary referral clinical MRI centre. Foetal body MRI scans of varying gestational ages were obtained dating between October 2011 and March 2018. The bowel was visualised on T₁ weighted images. The length of the meconium and the width of the meconium at the rectum, sigmoid colon, splenic flexure and hepatic flexure was measured. Presence or absence of meconium in the small bowel was noted. Inter- and intrarater reliability was assessed.

Results:

181 foetal body scans were reviewed. 52 were excluded and 129 analysed. Visualisation of the meconium in the large bowel became increasingly proximal with later gestations, and small bowel visualisation was greater at earlier gestations. There was statistically significant strong (r = 0.6–0.8) or very strong (r = 0.8–1.0) positive correlation of length and width with increasing gestation. Interrater reliability was moderate to excellent (r = 0.4–1.0).

Conclusion:

This study provides new information regarding the pattern of meconium accumulation throughout gestation. With care, the results can be used in clinical practice to aid diagnosis of bowel pathology.

Advances in knowledge:

The findings of this study provide further information concerning the normal accumulation of foetal meconium on MR imaging, an area where current research is limited.

Feasibility of free-breathing T1-weighted 3D radial VIBE for fetal MRI in various anomalies

RATIONALE AND OBJECTIVES

In magnetic resonance (MR) fetal imaging, the image quality acquired by the traditional Cartesian-sampled breath-hold T1-weighted (T1W) sequence may be degraded by motion artifacts arising from both mother and fetus. The radial VIBE sequence is reported to be a viable alternative to conventional Cartesian acquisition for both pediatric and adult MR, yielding better image quality. This study evaluated the role of radial VIBE in fetal MR imaging and compared its image quality and motion artifacts with those of the Cartesian T1W sequence.

MATERIALS AND METHODS

We included 246 pregnant women with 50 lesions on 1.5-T MR imaging. Image quality and lesion conspicuity were evaluated by two radiologists, blinded to the acquisition schemes used, using a five-point scale, where a higher score indicated a better trajectory method. Mixed-model analysis of variance and interobserver variability assessment were performed.

RESULTS

The radial VIBE sequence showed a significantly better performance than conventional T1W imaging in the head and neck, fetal body, and placenta region: 3.92 ± 0.88 vs 3 ± 0.74, p < 0.001, 3.8 ± 0.94 vs 3.15 ± 0.87, p < 0.001, and 4.17 ± 0.63 vs 3.12 ± 0.72, p < 0.001, respectively. Additionally, fewer motion artifacts were observed in all regions with the radial VIBE sequence (p < 0.01). Of 50 lesions, 49 presented better lesion conspicuity on radial VIBE images than on T1W images (4.34 ± 0.91 vs 3.48 ± 1.46, p < 0.001).

CONCLUSION

For fetal imaging, the radial VIBE sequences yielded better image quality and lesion conspicuity, with fewer motion artifacts, than conventional breath-hold Cartesian-sampled T1W sequences.

Pediatric whole body MRI detects causative ovarian teratoma in opsoclonus myoclonus syndrome

Opsoclonus Myoclonus Syndrome (OMS, or Opsoclonus Myoclonus Ataxia) is a rare condition that presents with saccadic movements of the eyes, cerebellar ataxia, and choreiform movements of the limbs. While previous reports have described the use of ultrasound, CT, FDG-PET and traditional focused MRI for localization of OMS-associated masses, whole body MRI has not previously been reported for this purpose. Here we describe a 16-year-old patient who exhibited OMS and underwent whole body MRI to rule out the more commonly associated neuroblastoma. An ovarian mass was discovered, resected, and pathology confirmed benign teratoma - there was subsequent resolution of symptoms after complete surgical resection. Whole body MRI should be considered in pediatric cases of OMS due to the paraneoplastic nature of the disease with associated tumor, high sensitivity of disease detection, lack of ionizing radiation, excellent tissue resolution and demonstrated effectiveness in pediatric imaging.

Vermiform Appendix During the Repackaging Process from Umbilical Herniation to Fixation onto the Right Posterior Abdomen: A Study of Human Fetal Horizontal Sections

The anatomical position of the vermiform appendix varies among adults, and these variations are responsible for differences in the symptoms of appendicitis. However, to date no study has examined how and when these variations occur during fetal development. The present study examined horizontal sections of 27 midterm fetuses (crown rump length [CRL] 38-97 mm, gestational age approximately 8-15 weeks). There were 10 fetuses (CRL 56 mm or more) in which the cecum and appendix were in a posterosuperior site near the right kidney (postmigration phase), and 12 fetuses (CRL 39-72 mm) in which the ileocecal junction and appendix remained on the visceral surface of the liver in the anterior or anterolateral abdominal cavity (migration phase, after physiological umbilical herniation). Analysis of the 12 fetuses in the migration phase indicated that the appendix extended inferiorly in eight fetuses and superiorly in four fetuses. Likewise, a "preileal" appendix (a morphology in which the distal part of the appendix was in front of the terminal ileum) was present in eight of these fetuses. Extension of the appendix superiorly or inferiorly during the migration phase seems unrelated to the topographical relationship of the appendix with the terminal ileum at the postmigration phase in fetuses and in adults. Conversely, it seems likely that a retroileal appendix leads to a coiled appendix behind the ileocecal junction. "Guidance" by the liver surface seemed to be important for posterior migration, which ended with the ascent of the liver. Clin. Anat., 33:667-677, 2020. © 2019 Wiley Periodicals, Inc.

A survey of pediatric diagnostic radiologists in North America: current practices in fetal magnetic resonance imaging

BACKGROUND

Fetal magnetic resonance imaging (MRI) is an imaging examination in evolution. Rapid developments over recent decades have led to better image quality, an increased number of examinations and greater impact on patient care.

OBJECTIVE

To gather data regarding current practices among established programs in North America and provide information to radiologists interested in implementing or growing a fetal MRI service.

MATERIALS AND METHODS

An electronic survey containing 15 questions relevant to the use of fetal MRI was submitted to pediatric radiologists and neuroradiologists. Items regarded scheduling and reporting logistics, magnet strength, patient positioning and patient preparation. Answers and comments were collected, and descriptive statistics were summarized.

RESULTS

One hundred and six survey responses were evaluated. Of the survey responses, 62/106 (58.5%) allow fetal MR scheduling any time during the day and 72/105 (68.6%) exclusively use 1.5-T strength platforms for fetal MRI, while only 7/105 (6.7%) use exclusively 3 T. Patient positioning is variable: supine, 40/106 (37.8%); left lateral decubitus, 22/106 (20.8%), and, patient's choice, 43/106 (40.6%). Of the centers responding, 51/104 (49.0%) require no particular fasting instructions, while 20/104 (19.2%) request the patient avoid caffeine before the scanning.

CONCLUSION

Logistical trends in performing fetal MRI may supplement the American College of Radiology's published technical standards and offer guidance to radiologists new to the field.

Fetal MRI in management of complicated meconium ileus: Prenatal and surgical imaging

OBJECTIVE

To review fetal MRI cases surgically proven to have meconium ileus (MI) and obstruction, describe the common fetal MRI findings that distinguish cases of complicated MI, and to compare these findings with surgical images and perinatal outcomes.

METHOD

We performed a retrospective review of all fetal MRI examinations and the corresponding medical record from our tertiary care children's hospital over an 18-month period. Postnatal management and outcomes were reviewed for these patients, and those patients with surgical or postmortem diagnosis of complicated MI were included in the study.

RESULTS

Our analysis revealed 7 cases. In this cohort, 3 imaging features of the fetal bowel were repeatedly seen: gradient appearance of intraluminal bowel contents, abnormally localized meconium signal, and collapsed appearance of the colon on MRI. Surgical diagnoses confirmed MI. All live-born infants underwent surgical repair.

CONCLUSION

Fetal MRI should be included in the diagnostic algorithm of any pregnancy where fetal bowel obstruction is suspected to better risk stratify patients.

Prenatal diagnosis and outcome of fetal gastrointestinal obstruction

INTRODUCTION

The purpose of this study was to evaluate the accuracy of prenatal diagnosis for fetuses with gastrointestinal (GI) obstruction with correlation to postnatal outcomes.

METHODS

Fetuses diagnosed with GI obstruction (excluding esophageal and duodenal) were reviewed for those evaluated between 2006 and 2016. Prenatal diagnosis and imaging studies were compared to postnatal findings. Outcomes evaluated included diagnostic accuracy, rate of other anomalies, neonatal length of stay, incidence of short bowel syndrome, and discharge with TPN or gastrostomy.

RESULTS

Forty-eight patients were diagnosed prenatally with obstruction. Six patients were excluded owing to incomplete records and follow-up. Twelve fetuses were diagnosed with ultrasound alone, and thirty-four with ultrasound and MRI. A diagnosis of obstruction was accurate in 88.1% (n=37/42) with a positive predictive value of 91.3%, while US with MRI had an accuracy of 84.4%. Associated anomalies were highest among fetuses with anorectal obstruction (90.1%), compared to large (50%) or small bowel obstruction (28%). Survival rate was lowest for anorectal obstruction (54.5%), compared to large or small bowel obstruction (100% for both).

CONCLUSION

Fetal MRI is an accurate modality in the diagnosis of fetal GI obstruction and can complement findings characterized by ultrasound. Fetuses with anorectal obstruction have a higher rate of associated anomalies and the lowest survival.

LEVEL OF EVIDENCE

IIb.

Fetal MR Imaging of Gastrointestinal Abnormalities

Fetal magnetic resonance (MR) imaging plays an increasing and valuable role in antenatal diagnosis and perinatal management of fetal gastrointestinal (GI) abnormalities. Advances in MR imaging data acquisition and use of motion-insensitive techniques have established MR imaging as an important adjunct to obstetric ultrasonography (US) for fetal diagnosis. In this regard, MR imaging provides high diagnostic accuracy for antenatal diagnosis of common and uncommon GI pathologic conditions. In the setting of fetal GI disease, T1-weighted images demonstrate the amount and distribution of meconium, which is crucial to the diagnostic capability of fetal MR imaging. Specifically, knowledge of the T1 signal intensity characteristics of fetal meconium, the normal pattern of meconium with advancing gestational age, and the expected caliber of small and large bowel in the fetus is key to diagnosis of abnormalities of the GI tract. Use of ultrafast T2-weighted sequences for evaluation of the expected location and morphology of fluid-containing structures, including the stomach and small bowel, in the fetal abdomen further aids in diagnostic confidence. Uncommonly encountered fetal GI pathologic conditions, especially cloacal dysmorphology, may demonstrate characteristic MR imaging patterns, which may add additional information to that from fetal US, allowing improved fetal and neonatal management. This article discusses common indications for fetal MR imaging of the GI tract, imaging protocols for fetal GI MR imaging, the normal appearance of the fetal GI tract with advancing gestational age, and the imaging appearances of common fetal GI abnormalities, as well as uncommon fetal GI conditions with characteristic appearances. (©)RSNA, 2016.

Evaluation of Fetal Thyroid with 3D Gradient Echo T1-weighted MR Imaging

Purpose:

The characteristics of fetal thyroid on magnetic resonance (MR) imaging, including normal thyroid and disorders other than goiter have not been fully evaluated. Our aim was to assess fetal thyroid using three dimensional (3D) gradient echo (GRE) T₁-weighted MR imaging and to examine the usefulness of this modality.

Materials and Methods:

The study included 27 3D GRE T₁-weighted images from 26 fetuses. The largest possible region of interest (ROI) within the thyroid at the slice level depicting the thyroid was manually defined and three circular ROIs on neck muscle were manually defined on the image slices showing the highest signal intensity (SI) of the thyroid. Maximum and mean thyroid-to-muscle SI ratios (SIRs) were then calculated as SIR = maximum or mean thyroid SI/muscle SI.

Results:

The thyroid could not be identified in two cases. Fetal thyroid function was normal in 17 cases, and there were 7 cases of hypothyroidism (6 transient and 1 thyroid dysgenesis). There was no linear relationship between mean and maximum SIR and gestational age. The mean and maximum SIR in the cases of normal fetal thyroid were 1.85 ± 0.20 and 2.61 ± 0.39, and the mean and maximum SIR in fetal hypothyroidism were 1.58 ± 0.20 and 2.13 ± 0.37. Mean (P = 0.0088) and maximum (P = 0.0221) SIR values were significantly different between euthyroid and hypothyroid fetuses.

Conclusion:

Thyroid SIR measurement provided useful information regarding fetal thyroid function.

Fetal MRI: A Technical Update with Educational Aspirations

Fetal magnetic resonance imaging (MRI) examinations have become well-established procedures at many institutions and can serve as useful adjuncts to ultrasound (US) exams when diagnostic doubts remain after US. Due to fetal motion, however, fetal MRI exams are challenging and require the MR scanner to be used in a somewhat different mode than that employed for more routine clinical studies. Herein we review the techniques most commonly used, and those that are available, for fetal MRI with an emphasis on the physics of the techniques and how to deploy them to improve success rates for fetal MRI exams. By far the most common technique employed is single-shot T2-weighted imaging due to its excellent tissue contrast and relative immunity to fetal motion. Despite the significant challenges involved, however, many of the other techniques commonly employed in conventional neuro- and body MRI such as T1 and T2*-weighted imaging, diffusion and perfusion weighted imaging, as well as spectroscopic methods remain of interest for fetal MR applications. An effort to understand the strengths and limitations of these basic methods within the context of fetal MRI is made in order to optimize their use and facilitate implementation of technical improvements for the further development of fetal MR imaging, both in acquisition and post-processing strategies.

Role of magnetic resonance imaging in the prenatal diagnosis of gastrointestinal fetal anomalies

PURPOSE

This study was done to evaluate the role of fetal magnetic resonance imaging (MRI) in the study of gastrointestinal malformations in comparison to prenatal ultrasound (US).

MATERIALS AND METHODS

A prospective (2010-2012) study of 38 fetal MRI scans was performed on 38 fetuses between 24 and 38 weeks of gestation. All the fetuses had a US diagnosis of gastrointestinal anomalies. T2-weighted HASTE, T1-weighted fast gradient echo, TrueFISP and diffusion-weighted images of the fetal abdomen were obtained on a 1.5-Tesla magnet. All fetal MRI diagnoses were compared with postnatal US findings, autopsy or surgical reports.

RESULTS

Fetal MRI was able to confirm the sonographic findings in nine of 38 fetuses (23.7%), to provide additional information in 23 of 38 fetuses (60.6%), to exclude the US diagnosis in five cases (5.2%) and to change it in two cases (5.2%). It was not able to characterize a case of gastric duplication and a case of abdominal cystic lymphangioma (5.2%).

CONCLUSIONS

Fetal MRI can be used as a complementary imaging modality to US in prenatal evaluation of gastrointestinal anomalies and can be considered a valuable tool not only for confirming or excluding but also for providing additional information to fetal ultrasonographic findings.

Comparison of three-dimensional isotropic and conventional MR arthrography with respect to the diagnosis of rotator cuff and labral lesions: focus on isotropic fat-suppressed proton density and VIBE sequences

AIM

To compare the diagnostic accuracies of three-dimensional (3D) isotropic magnetic resonance arthrography (MRA) using fat-suppressed proton density (PD) or volume interpolated breath-hold examination (VIBE) sequences with that of conventional MRA for the diagnosis of rotator cuff and labral lesions.

MATERIALS AND METHODS

Eighty-six patients who underwent arthroscopic surgery were included. 3D isotropic sequences were performed in the axial plane using fat-suppressed PD (group A) in 53 patients and using VIBE (group B) in 33 patients. Reformatted images were obtained corresponding to conventional images, and evaluated for the presence of labral and rotator cuff lesions using conventional and 3D isotropic sequences. The diagnostic performances of each sequence were determined using arthroscopic findings as the standard.

RESULTS

Good to excellent interobserver agreements were obtained for both 3D isotropic sequences for the evaluation of rotator cuff and labral lesions. Excellent agreement was found between two-dimensional (2D) and 3D isotropic MRA, except for supraspinatus tendon (SST) tears by both readers and for subscapularis tendon (SCT) tears by reader 2 in group B. 2D MRA and 3D isotropic sequences had high diagnostic performances for rotator and labral tears, and the difference between the two imaging methods was insignificant.

CONCLUSIONS

The diagnostic performances of 3D isotropic VIBE and PD sequences were similar to those of 2D MRA.

The value of 3D T1-weighted gradient-echo MR imaging for evaluation of the appendix during pregnancy: preliminary results

BACKGROUND

The use of oral contrast has been essential for the identification of a normal appendix on MR imaging during pregnancy. However, stool could be used as a positive oral contrast as it is characterized by a relatively high signal on T1-weighted imaging, and 3D T1-weighted gradient-echo (T1W-GRE) MR imaging has been used to evaluate 3 mm diameter intestines in fetuses.

PURPOSE

To evaluate the added value of 3D T1W-GRE MR imaging in combination with T2-weighted imaging (T2WI) compared to T2WI alone for evaluating the appendix during pregnancy.

MATERIAL AND METHODS

Eighteen consecutive pregnant patients who were clinically suspected of having acute appendicitis underwent appendix MR imaging which included T2WI with or without spectral presaturation attenuated inversion-recovery (SPAIR) fat suppression, and 3D T1W-GRE with SPAIR fat suppression. Two radiologists reviewed the two image sets (the T2WI set and the combined set of T2WI and 3D T1W-GRE images). Pathologic and clinical results served as the reference standard. The differences in the degree of visibility of the appendix and confidence scale for diagnosing acute appendicitis between two image sets were compared by using the paired Wilcoxon signed rank test.

RESULTS

For both reviewers, the degree of visibility of the appendix using the combined T2WI and 3D T1W-GRE images was significantly higher than using T2WI alone (P < 0.01), and the confidence levels for acute appendicitis using combined T2WI and 3D T1W-GRE images were significantly different from those using T2WI alone (P < 0.01). In the 13 patients with a normal appendix, both reviewers showed improved confidence levels for appendicitis using combined T2WI and 3D T1W-GRE images than T2WI alone.

CONCLUSION

Adding 3D T1W-GRE images to T2WI is helpful for identification of the appendix, as compared to T2WI alone in pregnant women without ingestion of oral contrast material. This may improve diagnostic confidence for acute appendicitis in pregnant patients.

Development of gastroschisis as seen by magnetic resonance imaging

OBJECTIVES

To describe the magnetic resonance imaging (MRI) morphology and fetal development of gastroschisis.

METHODS

Twenty-seven fetal MRI studies of 24 fetuses (mean gestational age 30 (range, 21-38) weeks), with gastroschisis were retrospectively analyzed. The extra- and intra-abdominal positions of the abdominal organs were assessed on T1- and T2-weighted and steady-state free-precession sequences with emphasis on the intra-abdominal findings.

RESULTS

Third-trimester fetuses (n = 16) showed a uniform morphology: the extracorporeal bowel included jejunum, ileum and colon except for parts of the sigmoid and the rectum. Intra-abdominally the stomach was in contact with the left-sided urinary bladder in 15 of these. Second-trimester fetuses (n = 8) differed with respect to the amount of intra-abdominal bowel and had longer sections of the colon and jejunum intra-abdominally. Intrauterine follow-up (n = 3) demonstrated exteriorization of these bowel segments. Three third-trimester fetuses with gastroschisis complicated by small bowel obstruction, in addition to the dilated small bowel loops, had variable lengths of intra-abdominal colon.

CONCLUSIONS

Fetal development of gastroschisis is a dynamic process lasting until birth. The typical morphology of gastroschisis changes from the second to the third trimester, since intra-abdominal bowel becomes eventrated by the end of the second trimester. This process of eventration is stopped in cases of intestinal stenosis/atresia caused by narrowing of the abdominal wall defect, resulting in different lengths of intra-abdominal bowel. The time when this occurs may correlate with the amount of viable bowel in cases of intestinal atresia. The concept presented here explains the findings in closing gastroschisis.

In utero diagnosis of congenital pyloric atresia in a single twin using MRI and ultrasound

Congenital pyloric atresia (CPA) is a rare disorder that has traditionally been diagnosed in the postnatal period. With improvements in ultrasound technology and increasing use of MRI, CPA is now diagnosed with increasing accuracy in utero. This also allows for identification of concomitant anomalies, which greatly affects infant survival. In addition, antenatal diagnosis of CPA and associated anomalies allow for family counseling and planning of treatment for the perinatal period including early referral to a center with pediatric surgical services. Here, we present a case of CPA with preoperative diagnosis using ultrasound and MRI.