Perfusion magnetic resonance imaging in pediatric brain tumors.

PURPOSE: The use of DSC-MR imaging in pediatric neuroradiology is gradually growing. However, the number of studies listed in the literature remains limited. We propose to assess the perfusion and permeability parameters in pediatric brain tumor grading. METHODS: Thirty children with a brain tumor having benefited from a DSC-MR perfusion sequence have been retrospectively explored. Relative CBF and CBV were computed on the ROI with the largest lesion coverage. Assessment of the lesion's permeability was also performed through the semi-quantitative PSR parameter and the K2 model-based parameter on the whole-lesion ROI and a reduced ROI drawn on the permeability maps. A statistical comparison of high- and low-grade groups (HG, LG) as well as a ROC analysis was performed on the histogram-based parameters. RESULTS: Our results showed a statistically significant difference between LG and HG groups for mean rCBV (p < 10-3), rCBF (p < 10-3), and for PSR (p = 0.03) but not for the K2 factor (p = 0.5). However, the ratio K2/PSR was shown to be a strong discriminating factor between the two groups of lesions (p < 10-3). For rCBV and rCBF indicators, high values of ROC AUC were obtained (> 0.9) and mean value thresholds were observed at 1.07 and 1.03, respectively. For K2/PSR in the reduced area, AUC was also superior to 0.9. CONCLUSIONS: The implementation of a dynamic T2* perfusion sequence provided reliable results using an objective whole-lesion ROI. Perfusion parameters as well as a new permeability indicator could efficiently discriminate high-grade from low-grade lesions in the pediatric population.

Percutaneous, computed tomography-guided drainage of deep pelvic abscesses via a transgluteal approach: a report on 30 cases and a review of the literature.

AIM: Percutaneous drainage of abdominal and pelvic abscesses is a first-line alternative to surgery. Anterior and lateral approaches are limited by the presence of obstacles, such as the pelvic bones, bowel, bladder, and iliac vessels. The objective of this study was to assess the feasibility, safety, tolerability, and efficacy of a percutaneous, transgluteal approach by reviewing our clinical experience and the literature. MATERIALS AND METHODS: We reviewed demographic, clinical and morphological data in the medical records of 30 patients having undergone percutaneous, computed tomography (CT)-guided, transgluteal drainage. In particular, we studied the duration of catheter drainage, the types of microorganisms in biological fluid cultures, complications related to procedures and the patient's short-term treatment outcome. RESULTS: From January 2005 to October 2011, 345 patients underwent CT-guided percutaneous drainage of pelvis abscesses in our institution. A transgluteal approach was adopted in 30 cases (10 women and 20 men; mean age: 52.6 [range 14-88]). The fluid collections were related to post-operative complications in 26 patients (86.7 %) and inflammatory or infectious intra-abdominal disease in the remaining 4 patients (acute diverticulitis: n = 2; appendicitis: n = 1; Crohn's disease: n = 1) (13.3 %). The mean duration of drainage was 8.7 days (range 3-33). Laboratory cultures were positive in 27 patients (90 %) and Escherichia coli was the most frequently present microorganism (in 77.8 % of the positive samples). A transpiriformis approach (n = 5) was more frequently associated with immediate procedural pain (n = 3). No major complications were observed, either during or after the transgluteal procedure. Drainage was successful in 29 patients (96.7 %). One patient died from massive, acute cerebral stroke 14 days after drainage. CONCLUSION: When an anterior approach is unfeasible, transgluteal, percutaneous, CT-guided drainage is a safe, well tolerated and effective procedure. Major complications are rare. This type of drainage is an alternative to surgery for the treatment of deep pelvic abscesses (especially for post-surgical collections).

Correlation between tap test and CSF aqueductal stroke volume in idiopathic normal pressure hydrocephalus.

INTRODUCTION: The diagnosis and management of idiopathic normal pressure hydrocephalus (INPH) remains unclear despite the development of guidelines. In addition, the role of cerebrospinal fluid (CSF) aqueductal stroke volume (ASV) remains unspecified. OBJECTIVES: The aim of this study was to compare the results of the tap test (TT) and ASV in patients with possible INPH. MATERIALS AND METHODS: Among 21 patients investigated with both TT and phase-contrast (PC) MRI, we identified two groups, with either (1) a positive TT (PTT) or (2) a negative one (NTT), and we compared their ASV as measured by PC-MRI. ASV cutoff value was set at 70 µL/cardiac cycle (mean value +2 standard deviations in age-matched healthy subjects). RESULTS: In the PTT group (n = 9), the mean ASV was 175 ± 71 µL. Among these patients, four were shunted, and improved after surgery. In the NTT group, two patients were finally diagnosed with aqueductal stenosis and excluded. Among the remaining patients (n = 10), the mean ASV was 96 ± 93 µL (p < 0.05). However, three of these patients presented with hyperdynamic ASV, and an associated neurodegenerative disorder was diagnosed. Two patients had ventriculoperitoneal shunting despite their NTT, and improved. DISCUSSION/CONCLUSIONS: In our patient population, the noninvasive measurement of hyperdynamic ASV correlated with PTT, suggesting PC-MRI could be utilized to select those patients who would benefit from shunting. ASV may therefore be an interesting supplemental diagnosis tool.

Phase-contrast MR imaging support for the diagnosis of aqueductal stenosis.

BACKGROUND AND PURPOSE: Patients with aqueductal stenosis (AS) present with various clinical and radiologic features. Conventional MR imaging provides useful information in AS but depends on a subjective evaluation by the neuroradiologist. The purpose of this study was to evaluate the support of the phase-contrast MR imaging (PC-MR imaging) technique (sensitive to CSF flows) for the diagnosis of AS. MATERIALS AND METHODS: We retrospectively considered 17 patients who underwent PC-MR imaging to explore hydrocephalus, with the absence of CSF flow at the aqueductal level. We analyzed their clinical and morphologic MR imaging data. RESULTS: None of the usually reported direct or indirect signs of aqueductal obstruction were seen in 7 patients in whom the clinical suggestion of AS was confirmed by PC-MR imaging results. Seven patients in this population had a third ventriculostomy, and 5 of them were among those in whom conventional MR imaging failed to reveal signs of aqueductal obstruction. All of these 7 patients had a positive postsurgical outcomes. The analysis of CSF and vascular dynamic data in this population was compared with an aged-matched population, and these data were found similar except for the fourth ventricular CSF flush flow latency. CONCLUSIONS: PC-MR imaging supports the diagnosis of CSF flow blockage at the aqueductal level in a reliable, reproducible, and rapid way, which aids in the diagnosis of AS in patients with clinical and/or radiologic suggestion of obstructive hydrocephalus. We, therefore, suggest using this technique in the current evaluation of hydrocephalus.

[Acute CSF changes in the mesencephalon aqueduct after subarachnoid hemorrhage as measured by PC-MRI]. / Caractérisation des perturbations du flux de LCS dans l'aqueduc du mésencéphale par IRM-CP à la phase aiguë de l'hémorragie méningée.

PURPOSE: Determining acute intracranial hydrodynamic changes after subarachnoid hemorrhage through an analysis of the CSF stroke volume (SV) as measured by phase-contrast MRI (PC-MRI) in the mesencephalon aqueduct. METHOD: A prospective study was performed in 33 patients with subarachnoid hemorrhage. A PC-MRI imaging study was performed n the acute phase (< 48 hours). CSF flow was measured in the aqueduct. The appearance of acute hydrocephalus (HCA) was then compared with data on CSF flow, and the location of the intraventricular and perimesencephalic bleeding. RESULTS: CSF analysis was performed on 27 patients, 11 of whom presented with an acute HCA. All 11 patients had an abnormal SV in the aqueduct: patients with a communicating HCA had an increased SV (n=8); and patients with a noncommunicating HCA had a nil SV (n=3). Patients with a normal SV in the aqueduct did not develop an acute HCA. Intraventricular bleeding significantly led to HCA (P=0.02), which was of the communicating type in 70% of cases. CONCLUSION: Subarachnoid hemorrhage leads to intracranial CSF hydrodynamic modifications in the aqueduct in the majority of patients. CSF flow can help us to understand the mechanism of the appearance of acute HCA. Indeed, hydrocephalus occurred - of the communicating type in most cases - even in the presence of intraventricular bleeding.

Neonatal probabilistic models for brain, CSF and skull using T1-MRI data: preliminary results.

Inappropriate results may be produced if one uses adult or pediatric atlases for evaluation of neonatal cerebral images for morphological studies. This is mainly due to anatomical particularities typical for this early stage of development. In this paper, we describe the construction of a digital neonatal brain atlas from a set of images of neonates aged between 39 and 42 weeks. It consists of probabilistic models for brain, cerebrospinal fluid (CSF) and skull. In the first step, the selected images are segmented automatically followed by manual correction. In the second step, the images are normalized to a stereotaxic space defined by the neonatal brain atlas template GRAMFC_T(39-42) using a popular normalization algorithm implemented in Statistical Parametric Mapping (SPM). The normalization parameters of individual subjects are then used to resample the corresponding brain, CSF and skull. Finally, to construct the probabilistic models, the average is computed for each voxel location. The atlas might be used for different applications such as source localization or neonatal structural image analysis.

Design of a digital phantom of the neonatal brain.

In this paper, we present the design and implementation of a 3D digital phantom of the neonatal brain. Commonly used digital brain phantoms (e.g. BrainWeb) are based on adults' brains. With the increasing interest in computer aided analysis of neonatal Magnetic Resonance (MR) images, it becomes necessary to create a special digital phantom for neonatal brains. This is because of the pronounced differences not only in size but more important in geometrical proportions of different brain tissues in adults and neonates and the additional need to subdivide the white matter of neonatal brains into two different types. Thus, the here created neonatal brain phantom consists of 6 different tissue types: scalp, skull, gray matter, myelinated and non-myelinated white matter and cerebrospinal fluid. Every voxel has a vector consisting of 6 probabilities of being part of one of these six tissues. The digital brain phantom will be used for simulation of tomographic images of the newborns' head and may serve as well as an evaluation data set for comparison of analysis methods for neonatal MR images, e.g. segmentation/registration algorithms, providing the possibility of controlled degradation of image data.

[Cerebrospinal fluid flow imaging in the meningeal hemorrhage]. / Imagerie de l'hydrodynamique cérébrale dans les hémorragies méningées.

BACKGROUND AND PURPOSES: Cerebrospinal fluid (CSF) flow oscillations are synchronized with cerebral blood flow and are also involved in the control of variations of intracranial pressure during the cardiac cycle. The aim of this study was to investigate the possible alterations of CSF flow dynamics during the acute phase of meningeal hemorrhage (MH). METHODS: Eleven patients with MH confirmed by computed tomography (CT) scan were examined by MR imaging, which comprised morphological sequences and flow dynamic sequences for quantification of CSF oscillations and cerebral blood flow rates. CSF oscillations were recorded at the cerebral aqueduct and C2-C3 subarachnoid space (SAS), where a vascular sequence was also performed to quantify artery blood flow. These results were compared to oscillations of a population of 44 control subjects and a difference of at least two standard deviation was used to define a hyperdynamic or hypodynamic appearance of CSF flow. Dilatation of the ventricular system was determined on radiographs by two neuroradiologists and a neurosurgeon. RESULTS: Only four patients presented normal ventricular CSF flow, one patient presented hypodynamic flow and five patients presented hyperdynamic flow. Five patients had normal cervical CSF flow and five patients presented hyperdynamic flow. The two patients with ventricular dilatation both presented hyperdynamic ventricular CSF flow associated with normal cervical CSF flow. One patient was excluded. CONCLUSION: Abnormal CSF flow dynamics were shown suggesting the hypothesis that bleeding increases intracranial volume and induces a reduction of cerebral compliance and an increase of intracranial pressure. The increased oscillations in the ventricular system would therefore predispose to dilatation.

Value of phase contrast magnetic resonance imaging for investigation of cerebral hydrodynamics.

OBJECTIVE: Phase Contrast Magnetic Resonance Imaging (PCMRI) is a noninvasive technique that can be used to quantify variations of flow during the cardiac cycle. PCMRI allows investigations of blood flow dynamics in the main arteries and veins of the brain but also the dynamics of cerebrospinal fluid. These cerebral flow investigations provide a description of the regulation mechanisms of intracranial pressure during the cardiac cycle. The objective of this paper is to describe the contribution of this technique in diseases related to disorders of cerebral hydrodynamics in the light of 5 clinical cases. METHOD: Flow measurements were performed using PCMRI sequences on a 1.5 Tesla MR imager in 4 patients with symptomatic ventricular dilation and 1 patient with a syringomyelic cavity. RESULTS: Flow quantification in these 5 patients, representative of the diseases mainly concerned by cerebral hydrodynamics, is useful to guide the indication for ventricular shunting in patients with hydrocephalus, to demonstrate obstruction of the cerebral aqueduct, to demonstrate recirculation of ventricular CSF after ventriculostomy and to characterize the dynamic features of CSF inside a spinal cavity. CONCLUSION: PCMRI, now available to neurosurgeons, is complementary to morphological MR and provides quantitative information on cerebral hydrodynamics. This information is mainly used to confirm alteration of CSF flow in the cerebral and spinal compartments. PCMRI is also a functional tool to better understand the pathophysiology of hydrocephalus and syringomyelia.

Medullary gnathostomiasis in a white patient: use of immunodiagnosis and magnetic resonance imaging.

A 48-year-old French diplomat presented with a sensory-motor paraparesis of rapid onset, leading to paraplegia. Successive magnetic resonance image scans showed lesions of the thoracic spinal cord that were at different levels from one examination to the next. Specific anti-gnathostome antibodies were detected by means of enzyme-linked immunosorbent assay and Western blot test in both plasma and cerebrospinal fluid. Albendazole treatment prevented disease progression, but only partial regression of the neurologic symptoms was obtained.

[MR diffusion and perfusion imaging in clinical practice]. / Imagerie par resonance magnetique de diffusion et de perfusion en pratique clinique.

MR functional imaging, due to the improvement in ultra-speed imaging technology such as echo-planar imaging, has become a very powerful technique since the beginning of the nineties. This imaging technique is divided into diffusion imaging, perfusion imaging and cerebral activation. Diffusion imaging probes the mobility of water molecules characterized by a diffusion coefficient called the apparent diffusion coefficient (ADC) for biological tissues. Perfusion imaging gives hemodynamic information due to the regional cerebral blood volume by the use of contrast agents such as chelates of gadolinium carrying strong magnetic susceptibility. Both imaging techniques can provide information in a wide nosological range : cerebral ischemia, in the acute phase and in case of intracranial tumors, contributing to tumoral grading, localizing the site of biopsy, and assessing response to therapy (after radiotherapy for example). Nevertheless, a wide range of domains remains incompletely studied, for example cerebral white matter diseases and neurodegenerative diseases. For clinical applications, a precise knowledge of the potentials of both techniques and their limitations is needed. Limitations result from the large number of often patient-related parameters, imaging technique (perfusion) and data analysis. Powerful software has been developed in the workstation environment. Thus this imaging technique requires up-to-date equipment and close collaboration between clinical and research teams for optimal efficiency.

[Value of imaging in early diagnosis of peripheral vein tumors]. / Apport de l'imagerie dans le diagnostic précoce des tumeurs veineuses périphériques.

Peripheral venous tumors are uncommon and their delayed clinical expression leads to poor prognosis. We report a series of 7 cases including 6 leiomyosacromas and 1 hemangioendothelioma. Duplex Doppler and MR imaging appeared to be best suited for diagnosis, allowing an evaluation of extension and an analysis of associated endoluminal thrombi. These imaging techniques help guide surgery and improve prognosis.

[Spontaneous contained perforation of a hiatal hernia. A new equivalent of Boerhaave's syndrome]. / Perforation "spontanée" cloisonnée d'une hernie hiatale. Un nouvel équivalent du syndrome de Boerhaave.

The authors report the case of an alcoholic 49-year-old man hospitalized because of epigastric pain and hematemesis. Upper endoscopy showed a tear in a hiatus hernia (interpreted as a Mallory-Weiss lesion) and a bleeding duodenal ulcer. Upper barium examination performed 16 days later revealed a mediastinal collection communicating with the hiatus hernia. Retrospective evaluation of chest roentgenograms obtained at admission showed a limited mediastinal gas collection. With medical management, the collection progressively disappeared. From a theoretical point of view, this case illustrates Watts' theory on the effect of hiatus hernia on the site of postemetic injury. From a practical point of view, it confirms that conservative management is indicated in contained spontaneous perforations.