Henning Neubauer

Diffusion-weighted MRI of bone marrow oedema, soft tissue oedema and synovitis in paediatric patients: feasibility and initial experience

BackgroundMRI has become the mainstay of diagnostic imaging in paediatric rheumatology for lesion detection, differential diagnosis and therapy surveillance. MR imaging of synovitis, in particular, is indispensable for early diagnosis and follow-up in arthritis patients. We used diffusion-weighted MRI (DWI) as a new imaging modality in comparison to standard MRI sequences to study bone marrow oedema, soft-tissue oedema and synovitis in paediatric patients.MethodsA total of 52 patients (mean age 11 ± 5 years) with bone marrow oedema (n = 31), soft-tissue oedema (n = 20) and synovitis (n = 15) were examined with transversal diffusion-weighted single-shot echoplanar imaging in addition to standard MR sequences (T2W TIRM, T1W pre- and post-contrast). Diffusion-weighted images were used for lesion detection and apparent diffusion coefficient (ADC, unit × 10-3 mm2/s) values were measured with ROI technique on ADC maps.ResultsIn 50 of 52 patients, DWI delineated the lesion of interest corresponding to pathological signal increase on standard sequences. Mean ADC was 1.60 ± 0.14 (range 1.38 - 1.99) in osseous lesions, 1.72 ± 0.31 (range 1.43 - 2.56) in soft tissue oedema and 2.82 ± 0.24 (range 2.47 - 3.18) for joint effusion (ANOVA p < 0.001). No significant difference in mean ADC was seen for inflammatory vs. non-inflammatory lesions. Relative signal intensity of oedema was similar for DWI and T2W TIRM. DWI visualised synovial restricted diffusion with a mean ADC of 2.12 ± 0.45 in 12 of 15 patients with synovitis.ConclusionsDiffusion-weighted MRI reliably visualises osseous and soft tissue oedema, as compared to standard sequences. DWI of synovitis is feasible in large joints and presents a novel approach to contrast-free imaging of synovitis. Whole-body DWI for chronic non-bacterial osteomyelitis should be evaluated in future studies.

Diffusion-weighted MRI for detection and differentiation of musculoskeletal tumorous and tumor-like lesions in pediatric patients.

BackgroundMRI is the diagnostic mainstay for detection and differentiation of musculoskeletal tumors. However, a projection regarding the biological dignity of lesions based on standard MRI sequences remains difficult and uncertain. This study was undertaken to analyse whether diffusion-weighted MRI (DWI) can distinguish between benign and malignant musculoskeletal tumorous and tumor-like lesions in pediatric patients.MethodsMR examinations of 44 consecutive pediatric patients (26 girls, mean age 11±6 years) including standard sequences and DWI (b=50/800 s/mm2) at 1.5 or 3 Tesla were retrospectively evaluated. The study group contained 10 patients with non-treated malignant tumors and 34 patients with benign lesions. Size, relative signal intensity and apparent diffusion coefficient (ADC, unit ×10−3 mm2/s) were determined in one lesion per patient.ResultsMean ADC was 0.78±0.45×10−3 mm2/s in patients with malignant tumors and 1.71±0.75 ×10−3 mm2/s in patients with benign lesions (P<0.001). Relative operating characteristics (ROC) analysis showed a sensitivity of 90% and a specificity of 91% for malignancy, based on an ADC cut-off value of ≤1.03. On logistic regression, mean ADC and lesion size accounted for 62% of variability in benign vs. malignant tumors. For malignant tumors, the signal intensity ratio was higher on DWI than on T1w post-contrast images (P<0.002). Two cases of local tumor recurrence were diagnosed by DWI only.ConclusionsDWI shows promising results for determination of biological dignity in musculoskeletal tumors. Mean ADC ≤1.03×10−3 mm2/s is a strong indicator of malignancy at the first diagnosis. The use of DWI for early diagnosis of tumor recurrence in comparison with standard MRI sequences should be evaluated in prospective studies.

Clinical characteristics, interdisciplinary treatment and follow-up of 14 children with Takayasu arteritis

BackgroundPediatric patients with Takayasu arteritis were studied by analyzing clinical presentation, diagnostic images, response to multimodal therapy, and long-term outcome.MethodsFourteen consecutive children and adolescents (mean age: 10 years) were diagnosed with Takayasu arteritis at our institution between 1995 and 2007. They were subjected to clinical and diagnostic studies including color ultrasonography, MRI and angiography, and received interdisciplinary treatment.ResultsThe median time lag between the first onset of symptoms and diagnosis was 7.7 weeks. The majority of patients presented with acute severe clinical symptoms and extensive vascular lesions. Hypertension was the most common finding on first presentation (93%), followed by headache (64%), nausea (64%) and palpitation (50%). Ten patients (71%) had reduced or absent carotid, brachial or femoral pulses in one or more locations. C-reactive protein was elevated in 79% of the patients and erythrocyte sedimentation rate in 64%. Cardiovascular imaging showed extensive vasculitis of both sides of the diaphragm in 86%. Complications included renal artery stenosis (n=7), aortic dissection, thoracic aortic aneurysm and infrarenal aneurysm (all n=1). Conservative drug treatment was effective in 50%. Interventional dilatation of stenosis and surgical therapy, including aortic bypass, resection of aneurysms and nephrectomy, were necessary in the remaining patients. Follow-up for 25 months to 12 years showed that all children are well without disease-related mortality.ConclusionsTakayasu arteritis is a rare and potentially life-threatening disease in children, likely with a prolonged subclinical course. Rapid diagnosis and interdisciplinary management help to prevent lifethreatening complications.

Diffusion-weighted MRI of abscess formations in children and young adults

BackgroundDiffusion-weighted MRI (DWI) is helpful for detection of brain abscess and pelvic abscess in adults. In the present study, we evaluated the diagnostic performance of DWI in children and young adults with abdominal and soft tissue abscess formations.MethodsSeventeen patients (11 females, aged 13 ± 6 years) with suspected abdominal or soft-tissue abscess underwent routine MRI including free-breathing DWI and contrast-enhanced T1w imaging. Seventeen random age-matched patients with non-purulent abdominal fluid collections served as controls. Mean apparent diffusion coefficent (ADC) was measured for abscess, muscle, liver, spleen and kidney tissue as well as for cerebrospinal fluid, urine and free abdominal fluid.ResultsAll fluid collections were identified on diffusion-weighted images. Thirteen of 14 confirmed abscess formations showed an ADC < 1.0 × 10−3 mm2/s with a mean value of 0.80 ± 0.38 mm2/s. One tuberculous softtissue abscess had a higher ADC of 1.85 × 10−3 mm2/s. Ring enhancement on T1w imaging was seen in three nonpurulent fluid collections. There were no false-positive findings in the control group.ConclusionsDiffusion-weighted MRI is highly sensitive for abscess and may add specificity to contrast-enhanced T1w imaging of ring-enhancing fluid collections. DWI with free-breathing rapid image acquisition and without the need of intravenous contrast application constitutes a particularly useful choice in pediatric imaging.

Popliteal Cysts in Paediatric Patients: Clinical Characteristics and Imaging Features on Ultrasound and MRI

Popliteal cysts, or Baker cysts, are considered rare in children and may exhibit particular features, as compared with adults. We studied data from 80 paediatric patients with 55 Baker cysts, examined over a period of 7 years, and correlated clinical presentation with findings on ultrasonography and MRI. Prevalence of popliteal cysts was 57% in arthritic knees, 58% with hypermobility syndrome, and 28% without risk factors. Only one patient had a trauma history and showed an ipsilateral cyst. Mean cyst volume was 3.4 mL; cysts were larger in boys. Patients with arthritis had echogenic cysts in 53%. Cyst communication with the joint space was seen in 64% on ultrasonography and 86% on MRI. In conclusion, Baker cysts are a common finding in a clinically preselected paediatric population. Children with Baker cysts should be assessed for underlying arthritis and inherited joint hypermobility, while sporadic Baker cysts appear to be common, as well.

MR-based analysis of regional cardiac function in relation to cellular integrity in Fabry disease☆

BACKGROUND Fabry cardiomyopathy is characterized by left ventricular (LV) hypertrophy and regional fibrosis. Recent high-end echocardiography studies of selected LV sections suggest an interrelation between regional fibrosis, impaired function, and hypertrophy possibly changing under specific enzyme replacement therapy (ERT). METHODS Magnetic resonance imaging (MRI) was used for a region dependent study of cardiac function, morphology and late enhancement (LE) in 25 Fabry patients before and after 12 months of ERT in comparison to 43 healthy volunteers. RESULTS Fabry patients presented with LV increased wall thickness (EDWT) and reduced wall thickening (WT) with a focus on basal and midventricular regions corresponding to areas of LE. The degree of hypertrophy and hypokinesia were the highest if LE was detectable. A significant decrease of the EDWT under ERT was observed in LE negative patients accompanied by a decline of hypokinesia with regional differences. CONCLUSIONS Regional differences of LV hypertrophy and wall motion were detected corresponding to the distribution of myocardial fibrosis (LE). Functional impairment was closely restricted to fibrotic regions while morphologic changes slightly exceeded the areas of fibrosis. ERT resulted in regional improvements whereby absence of fibrosis was connected to a better outcome.

An intravoxel oriented flow model for diffusion-weighted imaging of the kidney.

By combining intravoxel incoherent motion (IVIM) and diffusion tensor imaging (DTI) we introduce a new diffusion model called intravoxel oriented flow (IVOF) that accounts for anisotropy of diffusion and the flow‐related signal. An IVOF model using a simplified apparent flow fraction tensor (IVOFf) is applied to diffusion‐weighted imaging of human kidneys.

Fast MR Imaging of the Paediatric Abdomen with CAIPIRINHA-Accelerated T1w 3D FLASH and with High-Resolution T2w HASTE: A Study on Image Quality

The aim of this study was to explore the applicability of fast MR techniques to routine paediatric abdominopelvic MRI at 1.5 Tesla. “Controlled Aliasing in Parallel Imaging Results in Higher Acceleration-” (CAIPIRINHA-) accelerated contrast-enhanced-T1w 3D FLASH imaging was compared to standard T1w 2D FLASH imaging with breath-holding in 40 paediatric patients and to respiratory-triggered T1w TSE imaging in 10 sedated young children. In 20 nonsedated patients, we compared T2w TIRM to fat-saturated T2w HASTE imaging. Two observers performed an independent and blinded assessment of overall image quality. Acquisition time was reduced by the factor of 15 with CAIPIRINHA-accelerated T1w FLASH and by 7 with T2w HASTE. With CAIPIRINHA and with HASTE, there were significantly less motion artefacts in nonsedated patients. In sedated patients, respiratory-triggered T1w imaging in general showed better image quality. However, satisfactory image quality was achieved with CAIPIRINHA in two sedated patients where respiratory triggering failed. In summary, fast scanning with CAIPIRINHA and HASTE presents a reliable high quality alternative to standard sequences in paediatric abdominal MRI. Paediatric patients, in particular, benefit greatly from fast image acquisition with less breath-hold cycles or shorter sedation.

Hit the mark with diffusion-weighted imaging: metastases of rhabdomyosarcoma to the extraocular eye muscles

BackgroundRhabdomyosarcoma is the most frequent malignant intraorbital tumour in paediatric patients. Differentiation of tumour recurrence or metastases from post-therapeutic signal alteration can be challenging, using standard MR imaging techniques. Diffusion-weighted MRI (DWI) is increasingly considered a helpful supplementary imaging tool for differentiation of orbital masses.Case presentationWe report on a 15-year-old female adolescent of Caucasian ethnicity who developed isolated bilateral thickening of extraocular eye muscles about two years after successful multimodal treatment of orbital alveolar rhabdomyosarcoma. Intramuscular restricted diffusion was the first diagnostic indicator suggestive of metastatic disease to the eye muscles. DWI subsequently showed signal changes consistent with tumour progression, complete remission under chemoradiotherapy and tumour recurrence.ConclusionsRestricted diffusivity is a strong early indicator of malignancy in orbital tumours. DWI can be the key to correct diagnosis in unusual tumour manifestations and can provide additional diagnostic information beyond standard MRI and PET/CT. Diffusion-weighted MRI is useful for monitoring therapy response and for detecting tumour recurrence.

Multifrequency reconstruction for frequency-modulated bSSFP

Banding artifacts in images acquired by balanced steady‐state free precession (bSSFP) remain a challenge in MRI as they considerably reduce image quality, and diagnostic value deteriorates accordingly. As the steady‐state tolerates small shifts in frequency, it is possible to acquire frequency‐modulated bSSFP. Unfortunately, standard reconstructions of such measurements suffer from signal loss. Our study proposes a multifrequency reconstruction and demonstrates its capability of suppressing banding artifacts while retaining the high signal level of standard bSSFP.