Intraoperative cerebral blood flow monitoring in neurosurgery: A review of contemporary technologies and emerging perspectives.

Intraoperative monitoring of cerebral blood flow (CBF) has become an invaluable adjunct to vascular and oncological neurosurgery, reducing the risk of postoperative morbidity and mortality. Several technologies have been developed during the last two decades, including laser-based techniques, videomicroscopy, intraoperative MRI, indocyanine green angiography, and thermography. Although these technologies have been thoroughly studied and clinically applied outside the operative room, current practice lacks an optimal technology that perfectly fits the workflow within the neurosurgical operative room. The different available technologies have specific strengths but suffer several drawbacks, mainly including limited spatial and/or temporal resolution. An optimal CBF monitoring technology should meet particular criteria for intraoperative use: excellent spatial and temporal resolution, integration in the operative workflow, real-time quantitative monitoring, ease of use, and non-contact technique. We here review the main contemporary technologies for intraoperative CBF monitoring and their current and potential future applications in neurosurgery.

Advanced multiparametric magnetic resonance imaging of multinodular and vacuolating neuronal tumor.

BACKGROUND AND PURPOSE: Multinodular and vacuolating neuronal tumor (MVNT) of the cerebrum is a rare brain lesion with suggestive imaging features. The aim of our study was to report the largest series of MVNTs so far and to evaluate the utility of advanced multiparametric magnetic resonance (MR) techniques. METHODS: This multicenter retrospective study was approved by our institutional research ethics board. From July 2014 to May 2019, two radiologists read in consensus the MR examinations of patients presenting with a lesion suggestive of an MVNT. They analyzed the lesions' MR characteristics on structural images and advanced multiparametric MR imaging. RESULTS: A total of 64 patients (29 women and 35 men, mean age 44.2 ± 15.1 years) from 25 centers were included. Lesions were all hyperintense on fluid-attenuated inversion recovery and T2-weighted imaging without post-contrast enhancement. The median relative apparent diffusion coefficient on diffusion-weighted imaging was 1.13 [interquartile range (IQR), 0.2]. Perfusion-weighted imaging showed no increase in perfusion, with a relative cerebral blood volume of 1.02 (IQR, 0.05) and a relative cerebral blood flow of 1.01 (IQR, 0.08). MR spectroscopy showed no abnormal peaks. Median follow-up was 2 (IQR, 1.2) years, without any changes in size. CONCLUSIONS: A comprehensive characterization protocol including advanced multiparametric magnetic resonance imaging sequences showed no imaging patterns suggestive of malignancy in MVNTs. It might be useful to better characterize MVNTs.

Multinodular and Vacuolating Posterior Fossa Lesions of Unknown Significance.

Multinodular and vacuolating neuronal tumor of the cerebrum is a rare supratentorial brain tumor described for the first time in 2013. Here, we report 11 cases of infratentorial lesions showing similar striking imaging features consisting of a cluster of low T1-weighted imaging and high T2-FLAIR signal intensity nodules, which we referred to as multinodular and vacuolating posterior fossa lesions of unknown significance. No relationship was found between the location of the lesion and clinical symptoms. A T2-FLAIR hypointense central dot sign was present in images of 9/11 (82%) patients. Cortical involvement was present in 2/11 (18%) of patients. Only 1 nodule of 1 multinodular and vacuolating posterior fossa lesion of unknown significance showed enhancement on postcontrast T1WI. DWI, SWI, MRS, and PWI showed no malignant pattern. Lesions did not change in size or signal during a median follow-up of 3 years, suggesting that multinodular and vacuolating posterior fossa lesions of unknown significance are benign malformative lesions that do not require surgical intervention or removal.

[Diagnosis and treatment of nephrolithiasis and prevention of recurrences]. / Mise au point et traitement des lithiases rénales et prévention des récidives.

INTRODUCTION: despite fluctuations, the prevalence of nephrolithiasis has significantly increased during the last decades in industrialized nations worldwide (1 to 15 %), which has a significant impact on the cost of healthcare. This increased prevalence is mainly explained by diet modifications. Environmental, metabolic and genetic factors may also influence the formation of kidney stones. As a consequence, the medical management of this disease is preferentially multidisciplinary and involves urologists, nephrologists, radiologists, biologists and dietitians. Urological management : may be mandatory during any acute and/or remote phase of an episode of renal colic, in case of residual stones. Several techniques are available: insertion of double J stent, extracorporeal shock wave lithotripsy, ureteroscopy (flexible or rigid), percutaneous nephrolithotomy and more occasionally, open surgery. Nephrological management: is justified in the course of the acute episode and aims to identify the causal factor(s) of kidney stones formation. The diagnostic approach involves a thorough interrogation (personal medical and surgical history, details of the kidney stone disease and family medical history) as well as a metabolic assessment. Moreover, given the high rate of recurrence (about 50 % within 5 to 10 years), individualized secondary prevention measures are necessary. The recommendations should take into account the identified risk factors and any metabolic abnormalities.

INTRODUCTION: la néphrolithiase est une affection dont la prévalence (1 à 15 %) a beaucoup augmenté ces dernières décennies dans les pays industrialisés et a, de ce fait, un impact sur les dépenses en soins de santé. Cette augmentation de prévalence s'explique essentiellement par une modification des habitudes alimentaires. La survenue d'une néphrolithiase peut en outre, être influencée par des facteurs environnementaux, métaboliques voire génétiques. La prise en charge de cette affection est le plus souvent pluridisciplinaire, impliquant urologues, néphrologues, radiologues, biologistes et diététiciens. La prise en charge urologique peut être nécessaire en phase aiguë et/ou à distance de l'épisode de colique néphrétique, pour l'élimination éventuelle de calculs résiduels. Plusieurs techniques sont disponibles : la mise en place de sondes double J, la lithotritie extracorporelle, l'urétéroscopie (souple ou rigide) voire la néphrolithotomie percutanée et plus rarement la chirurgie ouverte. La prise en charge néphrologique est justifiée au décours de l'épisode aigu et vise à identifier la ou les cause(s) ayant conduit à la formation de calculs. La démarche diagnostique comporte un interrogatoire approfondi (antécédents personnels médicaux et chirurgicaux, histoire de la maladie lithiasique et antécédents familiaux) et un bilan métabolique. Par ailleurs, compte-tenu du taux élevé de récidive (environ 50 % dans les 5 à 10 ans), la mise en place de mesures individualisées de prévention secondaire est nécessaire. Ces recommandations doivent tenir compte des facteurs de risque identifiés et des éventuelles anomalies du bilan métabolique.

[Recurrent episodes of brushite nephrolithiasis revealing primary hyperparathyroidism]. / Néphrolithiases récurrentes de brushite révélant une hyperparathyroïdie primaire.

INTRODUCTION: Nephrolithiasis is a frequent disease observed in 1 to 20 % of the general population. This disease predominates in male patients (2:1) and is characterized by a high rate of recurrences (about 50 %). CASE REPORT: We report the case of a 45-year old male patient who experienced during about ten years recurrent bilateral renal colic episodes due to brushite lithiasis. These stones were treated with multiple extracorporeal shock wave lithotripsy sessions. A pyeloureteral junction syndrome predisposing to bulky stones formation has been put in evidence and required a pyeloplasty. After more than ten years of disease activity, a biochemical screening diagnosed primary hyperparathyroidism (PHPT). Radiological assessment identified a parathyroid gland adenoma. Successful surgical removal of this lesion was followed by resolution of the symptomatic kidney stones formation. DISCUSSION: PHPT is associated with kidney stones in about 20 % of the patients. Hypercalciuria is the main risk factor of stones formation but other predisposing factors are also probably involved. Patients carrying a polymorphism located in the coding sequence of the calcium-sensing receptor gene or in the regulatory region of this gene seem to experience an increased occurrence of urinary lithiasis. CONCLUSION: The present case stresses the importance of a metabolic assessment in all patients with recurrent nephrolithiasis, especially in case of bilateral episodes.

Lesions of the ovary with T1-hypersignal.

Pelvic magnetic resonance imaging (MRI) has been used successfully to diagnose ovarian masses that cannot be adequately evaluated using pelvic ultrasound. T1 hyperintensity is a common finding in an ovarian mass and has important diagnostic implications. The aims of this review are to list the substances that may produce high signal intensity on T1-weighted MRI, to explain the physical basis for causes of the high T1 signal intensity, and to describe common and uncommon T1 hyperintense ovarian lesions. The morphological findings, the imaging features of the additional sequences, and clinical variables can help in the differential diagnosis, and in some cases, enable a specific diagnosis, leading to appropriate management of the patient.

[Nosology and etiologies of acute longitudinally extensive transverse myelitis]. / Cadre nosologique et stratégie diagnostique de la myélite aiguë transverse longitudinalement étendue.

Acute transverse myelitis had many names and definitions, based primarily on clinical criteria. The role of MRI in the exploration of myelitis has increased recently after the individualization of neuromyelitis optica (NMO) in 2004. This approach has enabled clarification of the diagnostic and prognostic value of acute longitudinally extensive transverse myelitis (LETM), defined by an extensive T2 lesion affecting three vertebral segments in the sagittal plane. The limitations of this definition, the multiplicity of terms used to characterize it as well as the large number of etiologies associated with it led our group of experts to clarify its etiology and nosology. We conducted a national survey on this subject in order to propose a new definition of LETM. Additional first- and second-intention examinations were determined according to the clinical context. Infectious/para-infectious, inflammatory or paraneoplastic causes can thus be identified. To determine within a short time the cause of LETM is essential, since most of its causes are severe and require urgent treatment.

Management of respiratory motion in extracorporeal high-intensity focused ultrasound treatment in upper abdominal organs: current status and perspectives.

Extracorporeal high-intensity focused ultrasound (HIFU) is a minimally invasive therapy considered with increased interest for the ablation of small tumors in deeply located organs while sparing surrounding critical tissues. A multitude of preclinical and clinical studies have showed the feasibility of the method; however, concurrently they showed several obstacles, among which the management of respiratory motion of abdominal organs is at the forefront. The aim of this review is to describe the different methods that have been proposed for managing respiratory motion and to identify their advantages and weaknesses. First, we specify the characteristics of respiratory motion for the liver, kidneys, and pancreas and the problems it causes during HIFU planning, treatment, and monitoring. Second, we make an inventory of the preclinical and clinical approaches used to overcome the problem of organ motion. Third, we analyze their respective benefits and drawbacks to identify the remaining physical, technological, and clinical challenges. We thereby consider the outlook of motion compensation techniques and those that would be the most suitable for clinical use, particularly under magnetic resonance thermometry monitoring.

[Giant ameloblastoma of the mandible]. / Améloblastome géant mandibulaire.

INTRODUCTION: Giant ameloblastomas are more common in developing countries. They raise a serious problem of management. We present the case of one of the largest ameloblastoma ever reported. CASE REPORT: A 48-year-old Congolese female patient was referred for mandibular swelling having begun 23 years before and now inducing severe functional disorders. A cephalic CT scan revealed a multicystic mass, 30×18×10cm in size, with a typical "soap bubble" presentation, and with thinned and inflated cortical bone. The treatment was sub-total segmental mandibulectomy with immediate reconstruction using a fibular free flap, modeled on the sampling site by four ostectomies. The pathological examination confirmed the diagnosis of a benign follicular and plexiform ameloblastoma. The excess of soft tissue was treated with a right commissuroplasty on the 15th postoperative day. There was no complication. DISCUSSION: Radical treatment followed by immediate reconstruction using a free flap is the treatment of choice for giant mandibular ameloblastomas, when considering immediate functional and esthetic benefits. This is a prime concern for patients with a difficult access to health care and for whom long-term follow-up is not feasible.

Time course of iron metabolism in critically ill patients.

BACKGROUND: Altered iron metabolism plays a central role in the development of anaemia in critically ill patients but the time course of iron status in septic and non-septic critically ill patients has not been well defined. METHODS: Prospective study in a 34-bed medico-surgical ICU. The complete blood count, iron, ferritin, transferrin, and transferrin receptor concentrations, transferrin saturation and C-reactive protein (CRP) concentrations were measured on days 1, 3 and 5 of the ICU stay in 95 consecutive ICU patients (33 with sepsis and 62 without). RESULTS: Despite an identical complete blood count on day 1, septic patients had significantly lower iron concentrations (21 [13-34] vs 50[28-75] microg/dL, p<0.001), transferrin concentrations (169[121-215] vs 214[173-247] mg/dL; p=0.003), and transferrin saturation (11[7-15] vs 19[11-25]%; p= 0.004), and higher ferritin concentrations (432[184-773] vs 204[78-354] ng/mL; p=0.002) than non-septic patients. These alterations were associated with a lower reticulocyte count (42[29-61] vs 58[48-77] x 10(3)/mm3; p=0.028). On day 1, CRP concentrations, which were higher in septic than in non-septic patients (20.0[13.5-27.5] vs 2.3[0.7-5.9] mg/dL; p<0.001), were directly correlated with ferritin concentrations (rho=0.55, p<0.001) and inversely correlated with transferrin concentrations (rho=-0.49, p=0.0001) and transferrin saturation (rho=-0.49, p=0.0001). After 3 days, iron and transferrin concentrations were identical in septic and non-septic patients. Iron metabolism remained altered in both populations until the 5th day. CONCLUSIONS: Iron status is rapidly altered in critically ill patients, especially in septic patients. These alterations persist during the course of the disease and are associated with decreased erythropoiesis.

Therapeutic drug monitoring of posaconazole in patients with acute myeloid leukemia or myelodysplastic syndrome.

Posaconazole is a broad-spectrum triazole antifungal available as an oral suspension. Pharmacokinetic data showed a high variability of plasma posaconazole concentrations (PPCs) in patients, suggesting a potential interest in drug monitoring. The aim of our prospective study was to measure the PPCs in prophylactically treated patients to evaluate the impact of different factors on these concentrations. In 40 patients treated prophylactically with posaconazole for acute myeloid leukemia or myelodysplastic syndrome between February 2009 and August 2010, PPCs were measured at day 7 of treatment and then twice weekly. Demographic data, clinical data (including gastrointestinal disorders, comedications, and treatment compliance), caloric and fat intake, and biological data were collected and evaluated. We obtained 275 measurements of PPCs, with a median of 430 ng/ml. PPCs were significantly lower in patients with mucositis (P < 0.001), nausea (P = 0.03), diarrhea (P = 0.03), or vomiting (P = 0.05). PPCs were higher in patients with a higher caloric intake (P = 0.02), while the proportion of fat intake had no influence on PPCs (P = 0.84). The concomitant use of proton pump inhibitors decreased the PPCs (P = 0.02), while the use of tacrolimus increased the PPC (P = 0.03). In the multivariate analysis, the factors influencing the PPCs independently were the concomitant use of tacrolimus (P < 0.001), the presence of mucositis (P = 0.01), and food intake (P = 0.02). Our study confirmed the high variability of posaconazole bioavailability and showed the significant influence of gastrointestinal disorders, food intake, and concomitant medication on the PPCs. However, the optimal PPCs still remain to be defined and correlated with clinical efficacy.

Hypothalamo-pituitary sarcoidosis: a multicenter study of 24 patients.

AIM: To assess clinical features, treatment and outcome of Hypothalamo-pituitary (HP) sarcoidosis and to determine whether HP is associated with a particular clinical phenotype of sarcoidosis. DESIGN: Multicentric retrospective study. METHODS: Retrospective chart review. Each patient was matched with two controls. RESULTS: Twenty-four patients were identified (10 women, 14 men). Their median age at the sarcoidosis diagnosis was 31.5 years (range: 8-69 years). HP involvement occurred in the course of a previously known sarcoidosis in 11 cases (46%), whereas it preceded the diagnosis in 13 patients (54%). All but two patients had anterior pituitary dysfunction, 12 patients presented with diabetes insipidus. The most common hormonal features were gonadotropin deficiency (n=21), TSH deficiency (n=15) and hyperprolactinemia (n=12). Magnetic Resonance Imaging (MRI) revealed infundibulum involvement (n=8), pituitary stalk thickness (n=12) and involvement of the pituitary gland (n=14). All but two patients received prednisone. After a mean follow-up of 4 years, only two patients recovered from hormonal deficiencies. MRI abnormalities improved or disappeared in 12 cases under corticosteroid. There was no correlation between the hormonal dysfunctions and the radiologic outcomes. Patients with HP sarcoidosis had significantly more frequent sinonasal localizations and neurosarcoidosis and required a systemic treatment more frequently than controls. CONCLUSION: Although HP sarcoidosis is unusual, physicians should be aware that such specific localization could be the first manifestation of sarcoidosis. HP involvement is associated with general severity of sarcoidosis. MRI abnormalities can improve or disappear under corticosteroid treatment, but most endocrine defects are irreversible.

[Toxic leucoencephalopathy after use of sniffed heroin, an unrecognized form of beneficial evolution]. / Leucoencéphalopathie toxique après consommation d'héroïne prisée "sniff", une forme méconnue d'évolution favorable.

INTRODUCTION: Serious leukoencephalopathy can be related to heroin injection or inhalation. OBSERVATION: We report the first case of leukoencephalopathy observed three weeks after a 46-year-old man sniffed heroin. The clinical presentation included cognitive and behaviour disorders, pyramidal irritation and slight gait instability. Blood and cerebrospinal fluid analyse were normal. Brain magnetic resonance imaging showed diffuse, symmetrical supratentorial white matter lesions producing high intense signals on FLAIR and b1000-weighted sequences. Proton spectroscopy revealed an increased rate of cholin, in favour of active demyelinated lesions. Brain biopsy showed intramyelinic oedema with reactive gliosis. After two and a half years, moderate attentional fluctuations and difficulties in initiating activities persisted. Repeated MRI showed a reduction of the leukoencephalopathy. CONCLUSION: Heroin could be a cause more common than thought of leukoencephalopathy. The clinical and radiological expression and prognosis could be related to the mode of consummation (inhalation, intravenous injection, sniffing). This parameter may modulate severity and localization of brain lesions. More systematic use of MRI for patients with psychiatric symptoms after heroin intoxications could lead to a better evaluation of heroin-related neurotoxicity and potentially improve prevention.

[Superficial siderosis, an underestimated entity]. / L'hémosidérose superficielle du névraxe, une entité probablement sous-estimée.

OBJECTIVE: To review the clinical and MRI aspects in a series of cases with superficial siderosis of the central nervous system. METHODS: We retrospectively reviewed the patients with imaging evidence of superficial siderosis, investigated in two radiological centers between January 2006 and January 2010. The patients with aneurysms or arterio-venous malformations were excluded from this study. RESULTS: Cortical hemosiderin deposits were present in 25 (0.2%) of the 5904 MRIs with a T2-weighted gradient echo sequence. The classic association bilateral hypoacousia, ataxia and pyramidal signs were rarely found (two cases - 8%). Seven patients (28%) had a bilateral hearing impairment, seven (28%) a cerebellar syndrome and two (8%) a pyramidal syndrome. Sixteen patients (64%) had only supratentorial hemosiderin deposits. A cause of subarachnoid bleeding was identified in 76% of cases: amyloid angiopathy (40%), trauma (16%), cranio-spinal surgery (8%), cavernomas (8%) and brain tumors (4%). CONCLUSION: Superficial siderosis seems to be more frequent than previously thought. The classic clinical triad is rare, although the asymptomatic cases are frequent. A source of subarachnoid bleeding is generally found. Amyloid angiopathy is a frequent etiology of superficial siderosis in elderly patients. In the absence of other causes of subarachnoid bleeding, superficial siderosis may become a magnetic resonance marker for amyloid angiopathy.

Gunshot injury without direct injury to the cord may lead to complete paraplegia.

Paraplegia following gunshot injury without direct injury to the cord is extremely rare. We describe the case of a 31-year-old woman who was admitted to our trauma resuscitation unit for a penetrating gunshot wound to the abdomen with hemorrhagic shock and paraplegia. Computed tomography (CT) scan of the abdomen showed severe hepatic and pulmonary injuries, with the trajectory of the missile away from the spinal canal. Magnetic resonance imaging (MRI) confirmed a spine contusion from T8 to T10. After 24 months, no significant neurologic improvement occurred. Physicians managing severe trauma should be aware of the possibility to observe severe neurologic deficit following gunshot wounds even without violation of the spinal canal. These injuries might be in relation to the kinetic energy emission to the surrounding tissue by the missile.

Sickle cell disease from Africa to Belgium, from neonatal screening to clinical management.

AIM: To describe the severity of sickle cell disease (SCD) in newborns in Belgium and evaluate the impact of neonatal screening (NS) on clinical outcome. METHODS: Universal NS of umbilical cord blood for hemoglobinopathy was progressively deployed in Brussels and Liège starting in 1994. No particular population was targeted. Samples were analyzed initially using the isoelectric focusing technique and since 2008 the capillary electrophoresis technique. If a hemoglobin variant was suspected, further analysis was carried out using high performance liquid chromatography. Children presenting major hemoglobinopathy, especially SCD, were referred to a specialized centre for comprehensive management. Preventive measures included antipneumococcal prophylaxis immunization/antibiotic therapy, parental training to recognize severe anemia and splenic sequestration, and transcranial ultrasound recording for early detection of intracranial stenosis. A database was set up in Belgium to collect clinical and laboratory data including parental phenotype, diagnostic technique (neonatal screening or not), major clinical events (episodes of dactylitis, acute chest syndrome, severe anemia, infection, etc), number and duration of required hospitalizations, and treatment used. RESULTS: Screening of 222352 newborns in maternity units in Brussels led to diagnosis of SCD in 145 patients, Adequate data for analysis of clinical outcome was available for 96 of these children born before 2007. Median age in the study group was 4.2 years and the total duration of follow-up was 510 years. Most cases occurred in families from the Democratic Republic of Congo. (64/96 patients; 66.7%) and involved homozygous hemoglobin S disease (80/96 patients; 83.3%). Twenty-seven percent of patients (26/96) presented no severe clinical events during the study (17 SS, median age 2,1 years (0-13.1 years). Conversely 33% presented an episode of dactylitis and 47.9% (46/96) presented recurrent vasoocclusive crises. Severe anemia was observed in 39.6% (38/96) of cases. Six patients (6.3%) developed septicemia despite prophylactic antibiotic therapy and anti-pneumococcal immunization using heptavalent conjugate vaccine and polysaccharide vaccine, No penicillin-resistant strains were observed. The incidence of stroke was 2.1% (3/96). Two patients presenting homozygous hemoglobin S disease died due to septicemia due to non-compliance with antibiotic therapy in one case and severe anemia in one case. All episodes of septicemia and both deaths occurred at the beginning of the NS program. Hydroxyurea therapy was used in 30 patients (31.2%) including 7 in whom transcranial Doppler depicted blood flow abnormalities and 8 in whom allogeneic bone marrow transplantation was performed. CONCLUSIONS: Sickle cell disease is still associated with high morbidity and mortality but clinical care has improved and no death has occurred in the last 10 years. NS is an effective tool for early detection and management of SCD. Neonates with SCD diagnosed by NS in Belgium presented severe manifestations, but clinical outcomes were improved by comprehensive management.

[Target volume contouring for radiotherapy planning: application of multimodalities imaging]. / La délimitation des volumes cibles en radiothérapie: application des techniques d'imagerie.

The development of three-dimensional conformal radiotherapy (3DCRT) and intensity modulated therapy (IMRT) has enabled high dose radiation to be directed to tumors, this however subject to a perfect demarcation of the tumoral volume and the anatomical structures to be saved. At the same time, imaging modalities have improved their ability to demonstrate the location and the extension of tumors. The precise location of the target volume and the prediction of the dose absorbed by the tumor thus become an essential stage of the planning of the treatment. This planning is mostly determined on CT pictures. The technique usually used is a non enhanced CT allowing a location of the tumor by its mass effect mass or by its spontaneous difference of density from the adjacent structures. However, the clear visualization of the tumoral volume remains sometimes difficult for small-sized tumors or those with limited contrast with regard to surrounding tissues. This lack of contrast represents a source of variability for the demarcation of the target volume which has been highlighted in numerous papers. Tumors must be then localized by correlation with pictures made at the diagnosis time by other imaging modalities, essentially the MRI and the PET. This approach answers the concept of multimodality diagnosis which resumes the principle of complementarity of the various techniques. Every technique indeed brings, according to its physical principle, one or several specific information. It is advisable from then to clarify the contribution of every used imaging modality, this according to the pathologies and their localizations.

[Supervision of low-grade gliomas with multiparametric MR imaging: research of radiologic indicators of malignancy transformation]. / Intérêt de l'IRM, avec séquences de diffusion, de perfusion et de la spectrométrie dans le diagnostic et la surveillance de gliomes d'aspect initial de grade 2 : recherche de marqueurs radiologiques orientant vers une aggravation tumorale de grade.

We assessed the contribution of diffusion, perfusion and spectroscopy imaging for the diagnosis and follow-up of intraaxial tumors, suspected to be grade II gliomas. Twenty-four patients were included from April 2005 to July 2006, 17 initially and seven during their follow-up. The diagnosis was reconsidered in a first group of six patients: a high-grade tumor was suspected and confirmed in five. These patients presented a lipid peak; the perfusion results and the CHO/Cr and CHO/NAA ratios were not pathological. The second group included patients with grade II gliomas: these 18 patients had a radiographic work-up, initially, then at three months and every six months. For this group, no evidence of a change of grade were observed. Abnormal findings were noted in seven patients: among these patients, one developed radiographic progression, one other had radiographic progression associated with a spectroscopy lipid peak; only spectroscopy changes were noted in the third patient; the last patient had radiographic progression with perfusion and spectroscopy abnormalities; these four patients were treated. These observations suggest that diffusion, perfusion and spectroscopy can provide supplementary information for diagnosis and follow-up of glial tumors. The presence of a lipid peak is of particular value. The limitations of this work must also be taken into consideration: the follow-up was too short for slow-growing gliomas; the population was small and patients may have undergone surgery during the study, leading to structural modifications which may have compromised comparisons. This work should be continued with new examinations every six months and inclusion of new patients.

Evolution of brain tumor and stability of geometric invariants.

This paper presents a method to reconstruct and to calculate geometric invariants on brain tumors. The geometric invariants considered in the paper are the volume, the area, the discrete Gauss curvature, and the discrete mean curvature. The volume of a tumor is an important aspect that helps doctors to make a medical diagnosis. And as doctors seek a stable calculation, we propose to prove the stability of some invariants. Finally, we study the evolution of brain tumor as a function of time in two or three years depending on patients with MR images every three or six months.