Performance of PROPELLER relative to standard FSE T2-weighted imaging in pediatric brain MRI

Background  

T2-weighted fast spin-echo imaging (T2-W FSE) is frequently degraded by motion in pediatric patients. MR imaging with periodically rotated overlapping parallel lines with enhanced reconstruction (PROPELLER) employs alternate sampling of k-space to achieve motion reduction.     

Fast-recovery fast spin-echo T2-weighted MR imaging: a free-breathing alternative to fast spin-echo in the pediatric abdomen

In the mid 1990s, the fast spin-echo (FSE) and turbo spin-echo (TSE) T2-weighted (T2-W) sequences became available and are now widely accepted alternatives to conventional spin-echo sequences since they result in reduced acquisition times while maintaining tissue contrast. Since that time, there has been continued development of new sequences to further decrease acquisition times, minimize artifacts, and preserve lesion detection. The purpose of this pictorial essay is to qualitatively illustrate the newly available fast recovery (FR) FSE T2-W MR images of the abdomen compared with the images acquired using the routine FSE T2-W sequence in non-breath-hold studies in children.     

Optimized T1- and T2-weighted volumetric brain imaging as a diagnostic tool in very preterm neonates

Background  

T1- and T2-W MR sequences used for obtaining diagnostic information and morphometric measurements in the neonatal brain are frequently acquired using different imaging protocols. Optimizing one protocol for obtaining both kinds of information is valuable.     

Isotropic 3-D T2-weighted spin-echo for abdominal and pelvic MRI in children

MRI has a fundamental role in paediatric imaging. The T2-weighted fast/turbo spin-echo sequence is important because it has high signal-to-noise ratio compared to gradient-echo sequences. It is usually acquired as 2-D sections in one or more planes. Volumetric spin-echo has until recently only been possible with very long echo times due to blurring of the soft-tissue contrast with long echo trains. A new 3-D spin-echo sequence uses variable flip angles to overcome this problem. It may reproduce useful soft-tissue contrast, with improved spatial resolution. Its isotropic capability allows subsequent reconstruction in standard, curved or arbitrary planes. It may be particularly useful for visualisation of small lesions, or if large lesions distort the usual anatomical relations. We present clinical examples, describe the technical parameters and discuss some potential artefacts and optimisation of image quality.     

Comparison of turbo inversion recovery magnitude (TIRM) with T2-weighted turbo spin-echo and T1-weighted spin-echo MR imaging in the early diagnosis of acute osteomyelitis in children

Objective. To compare turbo inversion recovery magnitude (TIRM) with standard T1-weighted (T1-W) and T2-weighted (T2-W) MR sequences in the very early detection of acute osteomyelitis in children. Materials and methods. In 15 children with osteomyelitis, 15 sets of T1-W spin-echo (SE) (TR/TE, 400–640/12–17), T2-W turbo spin-echo (TSE) (TR/TE/ETL, 3290–4465/112–120/11), and TIRM (TR/TE/TI, 4000–6120/60/160) images were acquired with a 1.0-T magnet. Contrast-to-noise (C/N) ratios and percentage of signal between lesion and normal bone marrow were analysed with a computer-assisted image analysing system in a region of interest (ROI). Results. In 13 of 15 patients, the absolute signal enhancement in a ROI on the TIRM images was better than on the T1-W SE and T2-W TSE images and in 14 of 15 cases, C/N ratios were also better on the TIRM images than on the other sequences. In the other cases, the TIRM signal was diagnostically equivalent. On the TIRM images, the signal difference between normal and pathological tissue was increased to 43–281 % (mean 124 %). On the T2-W TSE images, this signal difference was 4–79 % (mean 36 %) and on the T1-W SE images 6–77 % (mean 37 %). Conclusion. The TIRM sequence is highly sensitive for detecting bone marrow oedema in the very early stage of acute osteomyelitis in children. MRI utilising the TIRM sequence allowed for an early diagnosis. With scan time of less than 4 minutes, this sequence is superior to T1-W SE and T2-W TSE images for detecting early osteomyelitis-associated bone marrow oedema. Received: 18 August 1997 Accepted: 17 June 1998     

Post-contrast FLAIR MR imaging of the brain in children: normal and abnormal intracranial enhancement

Objective To describe the normally enhancing intracranial structures on fluid-attenuated inversion recovery (FLAIR) MRI and evaluate the usefulness of postcontrast FLAIR images of the brain in the assessment of enhancing lesions by comparing postcontrast FLAIR imaging with postcontrast T1-weighted (T1-W) imaging in children.Materials and methods In 218 children, 249 pre- and postcontrast FLAIR MRI examinations of the brain were obtained consecutively between August 2001 and April 2002. The normally enhancing intracranial structures on FLAIR imaging were assessed in 77 MRI studies of 74 children who showed normal intracranial imaging findings. In 86 MRI studies in 68 children who showed enhancing intracranial lesions, lesion conspicuity on postcontrast FLAIR imaging was compared with that on postcontrast T1-W imaging for all lesions (n=107), intra-axial lesions (n=40), or extra-axial lesions (n=67).Results The normally enhancing intracranial structures on FLAIR MRI were the choroid plexus (99%, 76/77), pituitary stalk (84%, 65/77), pineal gland (71%, 55/77), dural sinuses (26%, 20/77), and cortical veins (9%, 7/77). Of all the enhancing lesions, lesion conspicuousness on postcontrast FLAIR imaging was better than postcontrast T1-weighted imaging in 42, equal in 28, and worse in 37. Of 40 intra-axial lesions, lesion conspicuousness on postcontrast FLAIR imaging was better in 6, equal in 10, and worse in 24. Of 67 extra-axial lesions, lesion conspicuity on postcontrast FLAIR imaging was better in 36, equal in 18, and worse in 13. Conspicuousness of extra-axial lesions was significantly better than that of intra-axial lesions on postcontrast FLAIR imaging (P<0.001).Conclusions The choroid plexus, pituitary stalk, pineal gland, dural sinuses, and cortical veins show normal enhancement on postcontrast FLAIR MRI in children, and postcontrast FLAIR imaging appears better than postcontrast T1-W imaging in the assessment of extra-axial enhancing lesions in children.Presented at the 46th Annual Meeting of the Society for Pediatric Radiology, San Francisco, California, USA, May 2003     

Role of diffusion-weighted imaging in differentiating benign and malignant pediatric abdominal tumors

Background

Solid malignant tumors are more highly cellular than benign lesions and hence have a restricted diffusion of water molecules.

Objective

To evaluate whether diffusion-weighted MR imaging (DWI) can differentiate between benign and malignant pediatric abdominal tumors.

Materials and methods

We retrospectively analyzed DWI scans of 68 consecutive children with 39 benign and 34 malignant abdominal masses. To calculate the apparent diffusion coefficient (ADC) maps and ADC values, we used 1.5-T sequences at TR/TE/b-value of 5,250–7,500/54–64/b?=?0, 500 and 3-T sequences at 3,500–4,000/66–73/b?=?0, 500, 800. ADC values were compared between benign and malignant and between data derived at 1.5 tesla (T) and at 3 tesla magnetic field strength, using the Mann-Whitney-Wilcoxon test, ANOVA and a receiver operating curve (ROC) analysis.

Results

There was no significant difference in ADC values obtained at 1.5 T and 3 T (P?=?0.962). Mean ADC values (× 10^?3?mm²/s) were 1.07 for solid malignant tumors, 1.6 for solid benign tumors, 2.9 for necrotic portions of malignant tumors and 3.1 for cystic benign lesions. The differences between malignant and benign solid tumors were statistically significant (P?=?0.000025). ROC analysis revealed an optimal cut-off ADC value for differentiating malignant and benign solid tumors as 1.29 with excellent inter-observer reliability (alpha score 0.88).

Conclusion

DWI scans and ADC values can contribute to distinguishing between benign and malignant pediatric abdominal tumors.     

Intestinal lesions in pediatric Crohn disease: comparative detectability among pulse sequences at MR enterography

Background

Variable sequences can be used in MR enterography, and no consensus exists for the best protocol in children with Crohn disease.

Objective

To compare the lesion detectability of various MR enterography sequences and to correlate the findings of these sequences with the Pediatric Crohn’s Disease Activity Index (PCDAI) in children with Crohn disease.

Materials and methods

Children with clinically or pathologically confirmed Crohn disease underwent MR enterography, including a single-shot fast spin-echo (SSFSE) sequence, motility imaging (coronal 2-D balanced fast field echo), diffusion-weighted imaging (DWI), and dynamic contrast enhancement imaging (including arterial, portal and delayed phases). The lesion detectability of each sequence was graded 0–2 for each involved bowel segment. The lesion detectability and PCDAI result on different sequences were compared using the weighted least squares method and Student’s t-test, respectively.

Results

Fifteen children (11 boys, 4 girls, mean age 13.7?±?1.4 years) with a total of 41 lesions were included in this study. All lesions detected in more than two sequences were visible on the single-shot fast spin-echo (SSFSE) sequence. The relative lesion detection rate was 78.1% on motility imaging, 90.2% on DWI, and 92.7% on arterial, 95.1% on portal and 95.1% on delayed phase imaging. Compared to the SSFSE sequence, motility imaging (P?<?0.001) and DWI (P?=?0.039) demonstrated lower detectability. The mean PCDAI result in the detected lesions was statistically higher only on dynamic enhancement imaging (P?<?0.001).

Conclusion

All MR enterography sequences were found to have relatively high lesion detectability in children with Crohn disease, while motility imaging showed the lowest lesion detectability. Lesions detected on dynamic enhancement imaging showed a higher PCDAI result, which suggests that this sequence is specific for active inflammation.     

Patent ductus venosus associated with a hyperintense globus pallidum on T1-weighted magnetic resonance imaging and pulmonary hypertension

Abstract We report the case of a 13-year-old Japanese boy with a patent ductus venosus. He experienced mild disorientation and hallucination at age 8 years. Hyperammonaemia was discovered at age 12 years. Brain MRI demonstrated multiple intracranial hyperintense lesions, mainly in the globus pallidum, which suggested portosystemic encephalopathy. Patent ductus venosus was demonstrated by abdominal ultrasonography and angiography. Cardiopulmonary investigation revealed pulmonary hypertension. An intracranial hyperintense lesion observed on T1-weighted MRI may be an initial clue for discovering a patent ductus venosus in asymptomatic patients.Conclusion When patent ductus venosus is disclosed, pulmonary hypertension should be sought, as in cases with other portosystemic shunts.     

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

Background Since the development of fast imaging sequences, MR has proved to be a helpful tool in the evaluation of fetal pathology. Because of the high water content of fetal tissues and pathology, hydrography imaging (MR fetography) can provide additional diagnostic information. Objective To demonstrate the benefit of MR fetography in fetal imaging. Materials and methods From 2004 to 2005, 126 fetal MR examinations were performed for evaluation of an abnormality depicted on an antenatal sonogram. Single-shot fast spin-echo MR imaging and MR fetography were performed through the area of fetal pathology. The two studies were retrospectively compared. Results The primary diagnosis was not changed with the addition of MR fetography. New findings, particularly in the kidneys and spine, were identified in 9% of the patients. When fetal pathology was of high water content (80% patients), the MR fetography imaging increased diagnostic confidence. In 11% of the patients, those with cardiovascular or low water pathology, the MR fetography was not beneficial. Conclusion The mainstay of fetal imaging is currently the HASTE and SSFSE sequences. However, MR fetography is an excellent adjunct that highlights fetal pathology by reinforcing the diagnosis, identifying additional findings, and providing high-contrast high-resolution images that are helpful when counseling clinicians and patients.     

Variability of T1-weighted signal intensity of pericallosal lipomas in the fetus

Background

Pericallosal lipomas are often associated with corpus callosum dysgenesis. The diagnosis of lipoma, suggested on ultrasonography, relies on the classic T1 hyperintensity on magnetic resonance imaging (MRI). However, this feature may be absent prenatally.

Objective

Our objective was to study the changes of T1 intensity in fetal lipomas with comparison to postnatal/postmortem data and to assess the factors influencing the signal variations of pericallosal lipomas on prenatal MRI.

Materials and methods

Patients with callosum dysgenesis and interhemispheric hyperechogenicity suggestive of a pericallosal lipoma with available postnatal or postmortem data were included. Gestational age, lipoma size and pattern, corpus callosum size and changes in fetal fat T1 intensity were recorded. Comparison with postmortem neuropathology was available for one fetus.

Results

Eleven patients with callosum dysgenesis and pericallosal lipomas (seven curvilinear and four tubulonodular) were included. All MRI scans were performed in the third trimester. Curvilinear lipomas were thinner and six cases were associated with prenatal T1 iso-intensity. Typical T1 hyperintensity appeared on postnatal MRI only. All tubulonodular lipomas were much larger and showed prenatal T1 hyperintensity. In two patients, the lipoma increased in size on postnatal MRI.

Conclusion

The type and size of a lipoma influence T1 prenatal intensity. Absence of T1 intensity was observed in curvilinear lipomas only. Curvilinear lipomas are much thinner. Changes in T1 intensity may also be related to fat maturation within the lipoma and, subsequently, to gestational age. In the case of callosum dysgenesis, absence of prenatal T1 pericallosal hyperintensity should not exclude the diagnosis of pericallosal lipoma.

     

Liver, meconium, haemorrhage: the value of T1-weighted images in fetal MRI

Background Ultrafast T2-weighted (T2-W) MRI sequences are currently considered a routine technique for fetal MR imaging. Limited experience exists with fetal T1-weighted (T1-W) imaging techniques.Objective To determine MRI patterns of some fetal abdominal or haemorrhagic disorders with particular respect to the diagnostic value of T1-W images.Materials and methods In addition to standard T2-W single-shot sequences, T1-W single-shot and/or multislice sequences were employed in 25 MR examinations performed in 23 fetuses between 20 and 36 weeks of gestation for more detailed assessment of liver, meconium-filled digestive tract, haemorrhage, or further characterization of a fetal abdominal mass. Diagnostic value and presence of motion artefacts on T1-W images was recorded in each case.Results T1-W images enabled superior delineation of fetal liver and large intestine. They provided additional diagnostic information in 9 (39%) of 23 fetuses. One false-positive and one false-negative MRI diagnosis of malrotation anomaly were encountered. Use of single-shot T1-W sequences reduced the occurrence of motion artefacts in 64%.Conclusion Our results suggest that the specific signal properties of methaemoglobin, meconium and liver are sufficiently important for T1-W sequences to become a routine part of fetal MRI protocols when dealing with digestive tract anomalies, diaphragmatic and abdominal wall defects, intraabdominal masses, and fetal haemorrhage.     

High-resolution 3-D T2-weighted imaging in the diagnosis of labyrinthitis ossificans: emphasis on subtle cochlear involvement

Background

Meningitis is the most common cause of acquired sensorineural hearing loss (SNHL) in children. Labyrinthitis ossificans develops in a significant number of patients with meningitis-related SNHL. Reduced T2 signal on MRI within the membranous labyrinth is often noted in the fibrous and ossifying stages of labyrinthitis ossificans.

Objective

The purpose of this study is to demonstrate the distribution and extent of involvement of the cochlea in children being evaluated for labyrinthitis ossificans; using high-resolution 3-D T2-weighted imaging, and to evaluate for subtle involvement of the scala tympani within the basal turn of the cochlea.

Materials and methods

A retrospective review from 2002 to 2012 was performed using a cochlear implant database and PACS search function. Twenty-four patients were found to have MR findings consistent with labyrinthitis ossificans, 13 previously reported. Axial 3-D T2-weighted sequences were obtained in all patients. The presence of abnormal decreased T2 signal within the scala tympani and vestibuli of the cochlea was noted and graded according to the extent. The electronic medical record was reviewed for audiometry and risk factors as well as correlative operative findings.

Results

The average age at imaging was 4.2 years. M:F ratio?=?5:1. Eighty-eight percent (21/24) of patients had bilateral SNHL. The most common risk factor for labyrinthitis ossificans was meningitis (19/24 or 79%). Eighteen (75%) patients had a history of bacterial meningitis. The mean age for the onset of labyrinthitis was 1.2 years with an average of 2.2-year interval to imaging. Nineteen patients (79%) underwent placement of a cochlear implant. Cochlear obstruction was documented in 83% (40/48) of the ears. Lower grade (1) cochlear obstruction was present in 14 ears and limited to the scala tympani. Statistical analysis was performed correlating MRI imaging and surgical findings.

Conclusion

Subtle, isolated involvement of the scala tympani within the proximal basal turn is a common finding in labyrinthitis ossificans and history typical for meningitis is not uniformly present. The extent of cochlear obstruction is important and has surgical implications.     

以腹痛为突出表现的危重病例临床分析

目的 探讨以腹痛为突出表现的危重病例的临床特点.方法 分析11例以腹痛为主要症状并伴有呕吐、面色苍白、口唇发绀等休克和多脏器功能损害表现的危重患儿的临床特征.结果 8例为暴发性心肌炎,以病情进展迅速、病死率高、心电图表现多样、心源性休克、心跳骤停多发为其特点.2例链球菌中毒休克综合征(STSS)早期无特异表现.STSS患儿病程中出现腹痛、少尿时应警惕早期休克的发生.皮疹、咳嗽、发热、白细胞进行性下降和C反应蛋白升高是STSS的临床特点.1例为大网膜囊肿,掌握手术时机是治疗本病的关键所在.结论 应提高对危重疾病引起的腹痛的认识,治疗的关键是原发病的早期发现与及时纠正休克.     

Diagnostic equivalency of fast T2 and FLAIR sequences for pediatric brain MRI: a pilot study

Background

Faster and motion robust magnetic resonance imaging (MRI) sequences are desirable in pediatric brain MRI as they can help reduce the need for monitored anesthesia care, which is a costly and limited resource that carries medical risks.

Objective

To evaluate the diagnostic equivalency of commercially available accelerated motion robust MR sequences relative to standard sequences.

Materials and methods

This was an institutional review board-approved prospective study. Subjects underwent a clinical brain MRI using conventional multiplanar images at 3 Tesla followed by fast axial T2 and FLAIR (fluid-attenuated inversion recovery) sequences optimized for an approximately 50% reduction in acquisition time. Conventional and fast images from each subject were reviewed by two blinded pediatric neuroradiologists. The readers evaluated the presence of 12 findings. Intra-observer agreement was estimated for fast versus conventional sequences. For each set of sequences, interobserver agreement calculations and chi-square tests were used to evaluate differences between fast and conventional acquisitions. An independent third reader reviewed the intra-observer discrepancies and adjudicated them as being more conspicuous on fast sequence, conventional sequence or the equivalent. The readers also were asked to rate motion artifacts with a previously validated score.

Results

Images from 77 children (mean age: 11.3 years) were analyzed. Intra-observer agreement (fast versus conventional) ranged between 89.2% and 92.3%. Interobserver agreement ranged between 86.1% and 88.4%. Interobserver agreement was significantly higher for conventional FLAIR relative to fast FLAIR for small (<5 mm) foci of T2 in the white matter. Otherwise, interobserver agreement was not different between the fast and conventional sequences. For awake subjects, fast sequences had significantly fewer artifacts (P<0.05).

Conclusion

Conventional T2 and FLAIR sequences can be optimized to shorten acquisition while maintaining diagnostic equivalency. These faster sequences were also less susceptible to motion artifacts.