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Purpose To quantify [ABSTRACT FROM AUTHOR]

ABSTRACT It is a major challenge to guarantee homogeneous acquisition during a prospective multicenter magnetic resonance imaging (MRI) study that makes use of different devices. The goal of the multicenter Grand Ouest Glioblastoma Project (GOGP) was to correlate MRI quantitative parameters with biological markers extracted from image-guided biopsies. Therefore, it was essential to ensure spatial coherence of the parameters as well as the signal intensity and homogeneity. The project included the same MRI protocol implemented on six devices from different manufacturers. The key point was the initial acceptance of the imaging devices and protocol sequences. For this purpose, and to allow comparison of quantitative patient data, we propose a specific method for quality assessment. A common quality control based on 10 parameters was established. Three pulse sequences of the clinical project protocol were applied using three test-objects. A fourth test-object was used to assess T1 accuracy. Although geometry-related parameters, signal-to-noise ratio, uniformity, and T1 measurements varied slightly depending on the different devices, they nevertheless remained within the recommendations and expectations of the multicenter project. This kind of quality control procedure should be undertaken as a prerequisite to any multicenter clinical project involving quantitative MRI and comparison of data acquisitions with quantitative biological image-guided biopsies. [ABSTRACT FROM AUTHOR]

Choroid plexus carcinomas are malignant brain tumors predominantly arising in young children. Because a prognostic role of p53 alterations has been demonstrated, further research into potential underlying mechanisms is essential. Our objective was, therefore, to investigate the role of p53 in the growth-inhibitory potential of a variety of anticancer agents in the rodent choroid plexus epithelial cell line Z310. Furthermore, association of p53 alterations with proliferative activity (Ki67/MIB1) in choroid plexus carcinoma samples ( N = 20) was examined by use of immunohistochemistry. Silencing of TP53 expression did not significantly alter metabolic activity in Z310 cells and p53 protein expression status was not associated with increased proliferative activity in choroid plexus carcinomas. However, the growth-inhibitory activity of vincristine, doxorubicin, carboplatin, etoposide, and temozolomide was significantly impaired by silencing of TP53. In conclusion, these results indicate a potential predictive role of p53 in choroid plexus carcinomas. Alterations of p53 should be taken into account when evaluating the effect of anticancer agents in future clinical trials. [ABSTRACT FROM AUTHOR]

A new dual temporal resolution-based, high spatial resolution, pharmacokinetic parametric mapping method is described - improved coverage and spatial resolution using dual injection dynamic contrast-enhanced (ICE-DICE) MRI. In a dual-bolus dynamic contrast-enhanced-MRI acquisition protocol, a high temporal resolution prebolus is followed by a high spatial resolution main bolus to allow high spatial resolution parametric mapping for cerebral tumors. The measured plasma concentration curves from the dual-bolus data were used to reconstruct a high temporal resolution arterial input function. The new method reduces errors resulting from uncertainty in the temporal alignment of the arterial input function, tissue response function, and sampling grid. The technique provides high spatial resolution 3D pharmacokinetic maps (voxel size 1.0 × 1.0 × 2.0 mm3) with whole brain coverage and greater parameter accuracy than that was possible with the conventional single temporal resolution methods. High spatial resolution imaging of brain lesions is highly desirable for small lesions and to support investigation of heterogeneity within pathological tissue and peripheral invasion at the interface between diseased and normal brain. The new method has the potential to be used to improve dynamic contrast-enhanced-MRI techniques in general. Magn Reson Med, 2012. © 2011 Wiley Periodicals, Inc. [ABSTRACT FROM AUTHOR]

Recurrent diffuse intrinsic pontine gliomas (DIPG) are traditionally treated with palliative care since no effective treatments have been described for these tumors. Recently, clinical studies have been emerging, and individualized treatment is attempted more frequently. However, an informative way to compare the treatment outcomes has not been established, and historical control data are missing for recurrent disease. We conducted a retrospective chart review of patients with recurrent DIPG treated between 1998 and 2010. Response progression-free survival and possible influencing factors were evaluated. Thirty-one patients were identified who were treated in 61 treatment attempts using 26 treatment elements in 31 different regimens. The most frequently used drugs were etoposide (14), bevacizumab (13), irinotecan (13), nimotuzumab (13), and valproic acid (13). Seven patients had repeat radiation therapy to the primary tumor. Response was recorded after 58 treatment attempts and was comprised of 0 treatment attempts with complete responses, 7 with partial responses, 20 with stable diseases, and 31 with progressive diseases The median progression-free survival after treatment start was 0.16 years (2 months) and was found to be correlated to the prior time to progression but not to the number of previous treatment attempts. Repeat radiation resulted in the highest response rates (4/7), and the longest progression-free survival. These data provide a basis to plan future clinical trials for recurrent DIPG. Repeat radiation therapy should be tested in a prospective clinical study. [ABSTRACT FROM AUTHOR]

Conventional contrast-enhanced CT and MRI are now in routine clinical use for the diagnosis, treatment and monitoring of diseases in the brain. The presence of contrast enhancement is a proxy for the pathological changes that occur in the normally highly regulated brain vasculature and blood-brain barrier. With recognition of the limitations of these techniques, and a greater appreciation for the nuanced mechanisms of microvascular change in a variety of pathological processes, novel techniques are under investigation for their utility in further interrogating the microvasculature of the brain. This is particularly important in tumours, where the reliance on angiogenesis (new vessel formation) is crucial for tumour growth, and the resulting microvascular configuration and derangement has profound implications for diagnosis, treatment and monitoring. In addition, novel therapeutic approaches that seek to directly modify the microvasculature require more sensitive and specific biological markers of baseline tumour behaviour and response. The currently used imaging biomarkers of angiogenesis and brain tumour microvascular environment are reviewed. [ABSTRACT FROM AUTHOR]

Purpose: To investigate the accuracy of a method neglecting T2*-relaxation, for the conversion of spoiled gradient echo pulse sequence signal intensity to contrast agent (CA) concentration, in dynamic contrast enhanced MRI studies. In addition a new closed form conversion expression is proposed that accounts for a first order approximation of T2*-relaxation. Materials and Methods: The accuracy of both conversion methods is compared theoretically by means of simulations for four pulse sequences from literature. Both methods are tested in vivo against the numerical conversion method for measuring the arterial input function in mice. Results: Simulations show that the T2*-neglecting method underestimates typical tissue CA concentrations (0 mM to 2 mM) up to 6%, while the errors for arterial concentrations (0 mM to 10 mM) range up to 43%. The results from our first order method are numerically indistinguishable from the simulation input values in tumor tissue, while for arterial concentrations the error is reduced up to a factor 10. In vivo, peak Gd-DOTA concentration is underestimated up to 14% with the T2*-neglecting method and up to 0.9% with our first order method. Conclusion: Our conversion method reduces the underestimation of CA concentration severely in a broad physiological concentration range and is easy to perform in any clinical setting. J. Magn. Reson. Imaging 2011;. © 2011 Wiley-Liss, Inc. [ABSTRACT FROM AUTHOR]

Objectives: T2' values reflect the presence of deoxyhaemoglobin related to high local oxygen extraction. We assessed the feasibility of T2' imaging to display regions with high metabolic activity in brain gliomas.Methods: MRI was performed in 25 patients (12 female; median age 46 years; range 2-69) with brain gliomas with additional T2 and T2* sequences. T2' maps were derived from T2 and T2*. Dynamic susceptibility weighted contrast (DSC) perfusion was performed in 12/25 patients. Images were visually assessed by two readers and five ROIs were evaluated for each patient. Pearson correlation, Mann-Whitney and Kruskal-Wallis tests were applied for statistical analysis.Results: Three patients were not further evaluated because of artefacts. Mean values of high-grade (III-IV) gliomas showed significantly lower T2' values than low-grade (II) gliomas (p < 0.001). An inverse relationship was observed between rCBV and sqr (T2') (r = -0.463, p < 0.001). No correlation was observed between T2' and rCBV for grade II tumours (r = 0.038; p = 0.875).Conclusions: High-grade tumours revealed lower T2' values, presumably because of higher oxygen consumption in proliferating tissue. Our results indicate that T2' imaging can be used as an alternative to DSC perfusion in the detection of subtle deviations in tumour metabolism. [ABSTRACT FROM AUTHOR]

Background: Choroid plexus tumors (CPT) are rare pediatric tumors. A population-based study on choroid plexus carcinoma (CPC) and choroid plexus papilloma (CPP) was carried out to describe the incidence, demographic, and outcome data and to identify potential prognostic factors. Methods: The CPT population from the Canadian databank of CNS tumor in children ≤36 months diagnosed between 1990 and 2005 was reviewed Results: Out of the 579 reported cases of CNS tumors, 37 were CPT. The annual age-adjusted incidence rate was 0.22 + 0.12 (95% CI 0.16-0.28)/100,000 children <3 years. There were 21 (56.7%) CPP and 16 (43.3.5%) CPC. Twenty patients (54%) were males. Median age at diagnosis was 7 months(range 0-30). Ten patients(62.5%) with CPC and one with CPP were metastatic at diagnosis. Twenty patients with CPP (95%) had a complete resection, whereas 6/16 CPC (37.5%) achieved a resection >90%. Fourteen CPC patients received adjuvant chemotherapy. None of the 37 patients received adjuvant radiation. At completion of survey, all CPP and five CPC were alive. Median survival time for CPC patients was 15 months (0-120). One death was related to intraoperative hemorrhage, another to chemotherapy-induced toxicity, and one to secondary AML. Age at diagnosis, degree of resection and metastatic status were not significant prognostic factors for CPC. Conclusion: By contrast to CPC, CPP have an excellent prognosis following surgery alone. Survival of CPC remains poor. However, these data may suggest adjuvant chemotherapy can alter the aggressive natural history of CPC. As with other rare CNS tumors, international collaboration is required to identify optimal therapy. [ABSTRACT FROM AUTHOR]

The concept of organ donation for research purposes has evolved to overcome limited availability of tissue and foster research, in particular in diseases for which surgery is not routinely performed. Diffuse intrinsic pontine glioma (DIPG) is an almost invariably fatal childhood tumour, not amenable to surgery because of its location and infiltrative nature. We report our institutional experience of post mortem brain or tumour donation and its impact on the families. Since July 2002, we have requested permission for post mortem brain examination for research purposes, from parents whose children succumbed to DIPG. Brain donation was discussed with 21 of 27 families of patients diagnosed with DIPG between July 2002 and June 2008 at the Hospital for Sick Children. Ten (47.6%) agreed, and autopsy was performed in 9 cases. Eight of these children died at home, one in the hospital. Autopsy was performed within 48 h from death in all cases except one. Pathological diagnosis was PNET in two and glioblastoma multiforme in seven patients. A disclosure of autopsy results was provided to all parents by the neuro-oncology team. None of the families expressed distress from the autopsy, or regretted the choice made. Autopsy limited to the brain did not interfere with the choices related to palliation. The families derived comfort from the hope that scientific breakthroughs could be made and felt that they were helping to make a difference in the future management of DIPG. [ABSTRACT FROM AUTHOR]

Background:There is no consensus on the indications for stereotactic biopsy for brain stem masses in children. Objectives: We analyzed the results of stereotactic biopsy for brain stem masses in 106 consecutive children to define current indications for this surgery. Methods: We performed a retrospective review of inpatient summaries, stereotactic worksheets and radiological investigations of 106 consecutive patients, under the age of 18 years, who underwent CT-guided stereotactic biopsies for brain stem lesions between 1987 and 2008. Patients were divided into two eras: era I from 1987 to 1997 and era II from 1998 to 2008. Results: 91 children underwent a biopsy in era I, and 15 had the procedure in era II, this difference clearly indicating the impact of the availability of magnetic resonance imaging. There was no difference in the proportion of diffuse lesions biopsied in both eras. Astrocytoma was the most frequently diagnosed pathology in both eras accounting for nearly 90% of biopsies. Inflammatory masses were diagnosed in less than 10% of patients. There was no mortality or permanent morbidity. Mortality, on follow-up, in children with diffuse low- and high-grade astrocytoma was similar. Conclusions:CT-guided stereotactic biopsy for brain stem masses in children is safe and is presently indicated in ruling out an inflammatory pathology of an enhancing mass of the brain stem. Copyright © 2010 S. Karger AG, Basel [ABSTRACT FROM AUTHOR]

Objectives: To examine the feasibility of deriving quantitative microcirculatory parameters and to investigate the relationship between vascular and metabolic characteristics of head and neck tumours in vivo, using dynamic contrast-enhanced (DCE) MRI and fluorodeoxyglucose (FDG) PET imaging.Methods: Twenty-seven patients with primary squamous cell carcinoma (SCCA) underwent DCE-MRI and combined PET/CT imaging. DCE-MRI data were post-processed by using commercially available software. Transfer constant (K (trans)), extravascular extracellular blood volume (v (e)), transfer constant from the extracellular extravascular space to plasma (k (ep)) and iAUC (initial area under the signal intensity-time curve) were calculated. 3D static PET data were acquired and standardised uptake values (SUV) calculated.Results: All microcirculatory parameters in tumours were higher than in normal muscle tissue (P ≤ 0.0019). Significant correlations were shown between k (ep) and K (trans) (ρ = 0.77), v (e) and k (ep) (ρ = -0.7), and iAUC and v (e) (ρ = 0.53). Significant correlations were observed for SUV(mean) and v (e) as well as iAUC (ρ = 0.42 and ρ = 0.66, respectively). SUV(max) was significantly correlated with iAUC (ρ = 0.69).Conclusions: The demonstrated relationships between vascular and metabolic characteristics of primary SCCA imply a complex interaction between vascular delivery characteristics and tumour metabolism. The lack of correlation between SUV and K (trans)/k (ep) suggests that both diagnostic techniques may provide complementary information. [ABSTRACT FROM AUTHOR]

This report describes the perinatal management of a prenatally detected choroid plexus papilloma in an otherwise unaltered singleton pregnancy of a healthy woman. After elective Caesarean section, a successful embolization of the feeding vessel followed by a craniotomy and complete removal of the remaining tumor were performed. Histological examination confirmed the diagnosis. One-, 2-, and 3-year follow-up showed a normal development of the girl with a regular neuropediatric status. A review of literature including related papers listed in PubMed between 1985 and 2009 are included. [ABSTRACT FROM AUTHOR]

The purpose of this study was to determine the impact of water exchange on tracer kinetic parameter estimates derived from T1-weighted dynamic contrast-enhanced (DCE)-MRI data using a direct quantitative comparison with DCE-CT. Data were acquired from 12 patients with bladder cancer who underwent DCE-CT followed by DCE-MRI within a week. A two-compartment tracer kinetic model was fitted to the CT data, and two versions of the same model with modifications to account for the fast exchange and no exchange limits of water exchange were fitted to the MR data. The two-compartment tracer kinetic model provided estimates of the fractional plasma volume ( v p), the extravascular extracellular space fraction ( v e), plasma perfusion (Fp), and the microvascular permeability surface area product. Our findings suggest that DCE-CT is an appropriate reference for DCE-MRI in bladder cancers as the only significant difference found between CT and MR parameter estimates were the no exchange limit estimates of v p ( P = 0.002). These results suggest that although water exchange between the intracellular and extravascular-extracellular space has a negligible effect on DCE-MRI, vascular-extravascular-extracellular space water exchange may be more important. Magn Reson Med, 2010. © 2010 Wiley-Liss, Inc. [ABSTRACT FROM AUTHOR]

Purpose: Choroid plexus tumors (CPT) are rare neoplasms that pose considerable treatment challenges. This study reviews a single institute's experience with 25 patients of CPT and attempts to contribute to the general body of knowledge on CPT. Materials and Methods: A retrospective analysis of the case records of 25 patients operated for CPT since January 1998 and having a minimum of 1 year follow-up. Results: The study group included 12 (48%) cases of choroid plexus papilloma (CPP), 09 (36%) cases of choroid plexus carcinoma (CPC) and 4 cases of atypical CPP. The mean age at presentation was 18.6 years (range, 6 months to 54 years; SD, 18.7) and a male preponderance was noted (17:8). Raised intracranial pressure was the commonest presenting symptom (72%). The tumors were distributed as follows: lateral ventricle (16; 64%), fourth ventricle (5; 20%), fourth ventricle with cerebellopontine angle extension (3; 12%), and third ventricle (1; 4%). A complete surgical excision was achieved in 11 cases of CPP and 8 cases of CPC. Operative complications include pneumocephalus (40%), focal deficits (36%), subdural effusion (32%), and persistent hydrocephalus requiring shunt (24%). All patients with CPP had a good outcome at the end of a mean follow-up of 5.4 years, whereas the median survival for patients with CPCs who underwent a subtotal resection with adjuvant therapy was 36 months. Conclusion: CPTs include a spectra ranging from CPP to CPC. Radiologic and histologic characterization of these tumors is difficult and newer immunohistochemical and genetic studies should be done to differentiate them from each other. Total excision offers a good prognosis and should be attempted for all forms of CPTs. CPPs carry a good prognosis, and adjuvant therapy is not indicated even after partial excision. CPCs and atypical CPCs carry a poor prognosis, and adjuvant therapy improves survival marginally after total excision. Spinal drop metastases are common for CPC and screening of the spine for possible metastasis should be part of the routine preoperative and postoperative investigation protocol. [ABSTRACT FROM AUTHOR]

Neuroimaging is presently utilised in clinical practice for initial diagnosis and mapping of disease extent and distribution, noninvasive, preoperative grading of tumours, biopsy planning, surgery and radiation portal planning for tumors, judging response to therapy and finally, prognostication. Newer advances include magnetic resonance (MR) diffusion and diffusion tensor imaging with tractography, perfusion imaging, MR spectroscopy and functional imaging using the blood oxygen level-dependent contrast technique. Neuroimaging plays a pivotal role in various degenerative and neoplastic diseases, improving diagnostic accuracy, affecting patient care, monitoring dynamic changes within the brain during therapy, and establishing them as the arbiter of novel therapy that may one day prove cure of various brain diseases a reality. [ABSTRACT FROM AUTHOR]

Surgery is an integral component and typically the first line of therapy for children with central nervous system tumors. The outcome with regard to surgical morbidity and disease control can be greatly influenced by the initial care that these children receive. Conventional aims of neurosurgery including tumor removal, management of hydrocephalus, and diagnostic sampling have been radically modified with innovative technologies such as navigational guidance, functional mapping, endoscopic surgery, second-look surgery, and physiologic imaging. The overall role of the pediatric neurosurgeon in caring for children with nervous system tumors is also expanding to include unconventional responsibilities including disease staging, tissue procurement, and drug delivery. It is thus anticipated that the pediatric neurosurgeon will be increasingly relied upon for oncologic therapeutic strategies and should thus remain abreast of forthcoming information and technologies. [ABSTRACT FROM AUTHOR]

A wide range of dynamic-contrast-enhanced (DCE) sequences and protocols, image processing methods, and interpretation criteria have been developed and evaluated over the last 20 years. In particular, attempts have been made to better understand the origin of the contrast observed in breast lesions using physiological models that take into account the vascular and tissue-specific features that influence tracer perfusion. In addition, model-free algorithms to decompose enhancement patterns in order to segment and classify different breast tissue types have been developed. This review includes a description of the mechanism of contrast enhancement by gadolinium-based contrast agents, followed by the current status of the physiological models used to analyze breast DCE-MRI and related critical issues. We further describe more recent unsupervised and supervised methods that use a range of different common algorithms. The model-based and model-free methods strive to achieve scientific accuracy and high clinical performance - both important goals yet to be reached. Copyright © 2008 John Wiley & Sons, Ltd. [ABSTRACT FROM AUTHOR]

Magnetic resonance imaging has shown promise for evaluating tissue oxygenation. In this study differences in the tissue longitudinal relaxation rate ( R 1) and effective transverse relaxation rate ( R [ABSTRACT FROM AUTHOR]

The goal of this study was to investigate the relationship between an empirical contrast kinetic parameter, the signal enhancement ratio (SER), for three-timepoint, high spatial resolution contrast-enhanced (CE) MRI, and a commonly analyzed pharmacokinetic parameter, kep, using dynamic high temporal resolution CE-MRI. Computer simulation was performed to investigate: 1) the relationship between the SER and the contrast agent concentration ratio (CACR) of two postcontrast timepoints ( t p1 and t p2); 2) the relationship between the CACR and the redistribution rate constant ( kep) based on a two-compartment pharmacokinetic model; and 3) the sensitivity of the relationship between the SER and kep to native tissue T1 relaxation time, T10, and to errors in an assumed vascular input function. The relationship between SER and kep was verified experimentally using a mouse model of breast cancer. The results showed that a monotonic mathematical relationship between SER and kep could be established if the acquisition parameters and the two postinjection timepoints of SER, t p1, t p2, were appropriately chosen. The in vivo study demonstrated a close correlation between SER and kep on a pixel-by-pixel basis (Spearman rank correlation coefficient = 0.87 ± 0.03). The SER is easy to calculate and may have a unique role in breast tissue characterization. Magn Reson Med, 2007. © 2007 Wiley-Liss, Inc. [ABSTRACT FROM AUTHOR]

Molecular oxygen has been previously shown to shorten longitudinal relaxation time ( T1) in the spleen and renal cortex, but not in the liver or fat. In this study, the magnitude and temporal evolution of this effect were investigated. Medical air, oxygen, and carbogen (95% oxygen/5% CO2) were administered sequentially in 16 healthy volunteers. T1 maps were acquired using spoiled gradient echo sequences (TR = 3.5 ms, TE = 0.9 ms, α = 2°/8°/17°) with six acquisitions on air, 12 on oxygen, 12 on carbogen, and six to 12 back on air. Mean T1 values and change in relaxation rate were compared between each phase of gas inhalation in the liver, spleen, skeletal muscle, renal cortex, and fat by one-way analysis of variance. Oxygen-induced T1-shortening occurred in the liver in fasted subjects ( P < 0.001) but not in non-fasted subjects ( P = 0.244). T1-shortening in spleen and renal cortex (both P < 0.001) were greater than previously reported. Carbogen induced conflicting responses in different organs, suggesting a complex relationship with organ vasculature. Shortening of tissue T1 by oxygen is more pronounced and more complex than previously recognized. The effect may be useful as a biomarker of arterial flow and oxygen delivery to vascular beds. Magn Reson Med 58:490-496, 2007. © 2007 Wiley-Liss, Inc. [ABSTRACT FROM AUTHOR]

Few attempts have been made to detect subtle blood-brain barrier (BBB) leakage in visibly nonenhancing MRI lesions in multiple sclerosis (MS). For 19 patients, longitudinal relaxation time (T1) maps were generated from MRI scans obtained before, and at 20, 40 and 60 minutes after injection of gadolinium (Gd)-DTPA (0.3 mmol/kg). Regions of interest (ROI) were placed around non-enhancing lesions, and in paired contralateral normal appearing brain tissue (NABT). Post-Gd rate of R1 (=1/T1) rise (ΔR1/Δt), was used to quantify leakage. ΔR1/Δt was greater in lesions than paired NABT (P⩽0.001 at all post-Gd timepoints). ΔR1/Δt was greater in T1 hypointense than isointense lesions (P=0.001 and 0.01 for first and second timepoints respectively), and negatively related to lesion cross sectional area (P⩽0.001 at all post-Gd timepoints). Relapsing remitting (RRMS) lesions had a greater initial ΔR1/Δt than secondary progressive (SPMS) lesions (P=0.04), but this was not seen in subsequent timepoints. ΔR1/Δt in visibly enhancing lesions was significantly greater than in visibly non-enhancing lesions, with no overlap in the normal ranges of the two populations. Subtle BBB leakage is a consistent feature in non-enhancing lesions, and is distinct from the overt BBB leakage observed in visibly enhancing lesions. It is detectable using quantitative contrast-enhanced MRI. It is apparent in all clinical and lesion subtypes studied, and greater in T1 hypointense and smaller lesions. Larger initial ΔR1/Δt in RRMS than SPMS lesions may reflect differences in blood volume rather than BBB leakage. [ABSTRACT FROM AUTHOR]

Background: The development of a quantifiable and noninvasive method of monitoring disease activity and response to therapy is vital for arthritis management.Objective: The purpose of this study was to investigate the utility of quantitative dynamic contrast-enhanced MRI (DCE-MRI) based on pharmacokinetic (PK) modeling to evaluate disease activity in the knee and correlate the results with the clinical assessment in children with juvenile idiopathic arthritis (JIA).Materials and Methods: A group of 17 children with JIA underwent longitudinal clinical and laboratory assessment and DCE-MRI of the knee at enrollment, 3 months, and 12 months. A PK model was employed using MRI signal enhancement data to give three parameters, K(trans') (min(-1)), k(ep) (min(-1)), and V(p) (') and to calculate synovial volume.Results: The PK parameters, synovial volumes, and clinical and laboratory assessments in most children were significantly decreased (P < 0.05) at 12 months when compared to the enrollment values. There was excellent correlation between the PK and synovial volume and the clinical and laboratory assessments. Differences in MR and clinical parameter values in individual subjects illustrate persistent synovitis when in clinical remission.Conclusion: A decrease in PK parameter values obtained from DCE-MRI in children with JIA likely reflects diminution of disease activity. This technique may be used as an objective follow-up measure of therapeutic efficacy in patients with JIA. MR imaging can detect persistent synovitis in patients considered to be in clinical remission. [ABSTRACT FROM AUTHOR]

Summary  Cerebrospinal metastases of benign choroid plexus papillomas (CPPs) are extremely rare. We report a case of 32-year-old woman who presented with a 6-month history of vertigo and intermittent headache. Plain CT scan of the cranium revealed a partly calcified tumor filling the fourth ventricle and its right recess. Cranial MRI showed an inhomogeneously contrast-enhancing tumor and leptomeningeal enhancement encasing the brain stem. Complete resection of the tumor was carried out, and seedings to the floor of the fourth ventricle and cervico-medullary junction were found during the operation. While intraoperative frozen section suggested pathology of papillary ependymoma or CPP, to our surprise, final histological examination revealed a benign choroid plexus papilloma. One month after the first operation, a metastatic nodule was found in the spinal subarachnoidal space at the level of T8-9. Two months after the first operation, on follow-up MRI of the cranium, the leptomeningeal enhancement encasing the brain stem had resolved spontaneously. This special case helps increase our understanding of benign CPPs and expands our differential diagnostic consideration of lesions with similar manifestations. [ABSTRACT FROM AUTHOR]

Purpose: To evaluate if two gadolinium perfusion studies can be performed during the same table occupancy without degradation of the derived data in the second study.Material and Methods: Magnetic resonance (MR) perfusion studies of the whole brain were performed on 12 patients during the administration of two gadolinium boluses separated by 8 min. In six patients, gadolinium was given as two 20‐ml administrations of standard 0.5 M chelate (Magnevist), whilst the other six patients received two 10‐ml administrations of 1.0 M chelate (Gadovist).Results: There were no significant differences in subjective quality between the time–intensity curves of the first and second perfusion studies using either the 0.5 M or 1.0 M gadolinium chelate. The objective measurements in quality of the time–intensity curves (maximum signal change and full width at half maximum) changed by less than 5% of the original values on the second perfusion study. The first‐moment mean transit times did not change significantly on the sequential studies. The regional cerebral blood volume tended to increase on the second study (by 15% on average), but this did not reach statistical significance.Conclusion: The results from two sequential dynamic gadolinium‐based perfusion studies can be compared in a meaningful manner using the technique described. [ABSTRACT FROM AUTHOR]

Recent advances in molecular biology have enhanced our understanding of the pathogenesis of brain tumors, particularly in children. The use of molecular diagnostic tools is quickly becoming a standard component in the diagnosis and classification of brain tumors in children, in addition to providing insight leading to treatment stratification and improved outcome prediction. All new protocols involving treatments for brain tumors in children include studies of biomarkers and biologic correlates as a means to identify new targets for therapeutics and possible intervention strategies. [ABSTRACT FROM AUTHOR]

Dynamic contrast-enhanced MRI is used to estimate microvascular parameters by tracer kinetics analysis. The time for the contrast agent to travel from the artery to the tissue of interest (bolus arrival time (BAT)) is an important parameter that must be measured in such studies because inaccurate estimates or neglect of BAT contribute to inaccuracy in model fitting. Furthermore, although the precision with which these parameters are estimated is very important, it is rarely reported. To address these issues, two investigations were undertaken. First, simulated data were used to validate an independent method for estimation of BAT. Second, the adiabatic approximation to the tissue homogeneity model was fitted to experimental data acquired in prostate and muscle tissue of 22 patients with prostate cancer. A bootstrap error analysis was performed to estimate the precision of parameter estimates. The independent method of estimating BAT was found to be more accurate and precise than a model-fitting approach. Estimated precisions for parameters measured in the prostate gland were 14% for extraction fraction (median coefficient of variation), 19% for blood flow, 28% for permeability-surface area product, 35% for volume of the extravascular-extracellular space, and 36% for blood volume. Techniques to further reduce uncertainty are discussed. Magn Reson Med, 2006. © 2006 Wiley-Liss, Inc. [ABSTRACT FROM AUTHOR]

Accurate sampling of the arterial input function (AIF) in low-temporal-resolution quantitative dynamic contrast-enhanced MRI (DCE-MRI) studies is crucial for accurate and reproducible parameter estimation. However, when conventional AIFs are sampled at low temporal resolution, they introduce an unpredictable degree of error. An alternative double contrast agent (CA) bolus injection protocol designed to compensate for temporal mis-sampling of the AIF and tissue uptake curve was simulated in addition to a commonly used single CA bolus injection protocol. A range of tissue uptake curves for each AIF form were generated using a distributed parameter model, and Monte Carlo simulation studies were performed over a range of offset times (to mimic temporal mis-sampling), temporal resolutions and SNR in order to compare the performance of both AIF forms in compartmental modeling. Insufficient data sampling of the single bolus AIF at temporal resolutions in excess of 9 s leads to large errors, which can be reduced by employing an additional, appropriately administered, second CA bolus injection. Magn Reson Med, 2006. © 2006 Wiley-Liss, Inc. [ABSTRACT FROM AUTHOR]

Purpose: To investigate the use of blood volume maps in the non-invasive separation of glioma grades. Material and Methods: T1-weighted quantitative dynamic contrast-enhanced magnetic resonance imaging was used to quantify the fractional intratumoral blood volume of 41 gliomas (World Health Organization (WHO) grades II–IV). Two methods, mean fractional intratumoral blood volume determination and a system based on thresholds for extracting the tumor pixels with the highest vascularization from the blood volume maps, were investigated by means of receiver operating characteristic (ROC) analysis. The thresholds were adjusted using the ROC curve area calculated using the trapezoid method. Results: The ability to separate grade II (WHO) gliomas from grades III–IV was nearly the same for both methods (ROC curve area 0.941 (threshold) versus 0.932 (mean value)) and significantly greater than the ability to separate grade IV (WHO) gliomas from grades II–III (ROC curve area 0.792 (threshold) versus 0.787 (mean value)). The best correspondence with WHO glioma grading was achieved using thresholds corresponding to only the 5.2% of tumor voxels with the largest blood volume for separating grade II gliomas and 4% for separating grade IV gliomas. Conclusion: Use of the optimized threshold resulted in matching with the WHO grading system in 74% of cases. [ABSTRACT FROM AUTHOR]

Purpose To investigate the heterogeneity in the angiogenic response of a human breast cancer xenograft to a novel vascular endothelial growth factor (VEGF)-receptor tyrosine kinase inhibitor, AG-013736, using dynamic contrast-enhanced MR imaging (DCE-MRI). Materials and Methods Changes in pharmacokinetic parameters in a seven-day interval were compared between AG-treated and control groups, using Gd-DTPA and albumin-(Gd-DTPA)30. A voxel-by-voxel analysis was performed to produce parametric spatial pharmacokinetic parametric maps and histograms. Histogram segmentation was used to quantify the heterogeneity in tumor response to therapy, and compared with conventional descriptive measures of distribution in terms of their capacity to separate control from AG-treated tumors. Results The albumin-(Gd-DTPA)30 endothelial transfer constant, K ps, showed changes with AG-013736 treatment and tumor growth. The changes were highly heterogeneous for individual segments of the histogram with different K ps values, and the overall patterns in which the frequency distribution changed differed significantly between the two groups. A change in the number of voxels with K ps rangingfrom 0.03 to 0.14 mL/min/(100 mL tissue) was the most sensitive variable for separating control from AG-treated tumors ( P = 0.0008). Parametric maps of the kinetic parameters also showed spatial heterogeneity in tumor response to treatment. The K ps maps depicted rapid development of central necrosis as a result of AG-013736 treatment. Maps of v p demonstrated a marked increase at peripheral regions of necrotic areas. Similar trends were noted in the Gd-DTPA rate constant Ktrans distribution. Conclusion This study demonstrates the value of histogram analysis of maps of pharmacokinetic parameters for assessing heterogeneity in tumor response to antiangiogenic therapy. Changes in the number of voxels within certain segments of the K ps histogram were the most sensitive variable for separating control from AG-treated tumors. J. Magn. Reson. Imaging 2005. © 2005 Wiley-Liss, Inc. [ABSTRACT FROM AUTHOR]

Contrast-enhanced (CE) MRI provides in vivo physiological information that cannot be obtained by conventional imaging methods. This information is generally extracted by using models to represent the circulation of contrast agent in the body. However, the results depend on the quality of the fit obtained with the chosen model. Therefore, one must check the fit quality to avoid working on physiologically irrelevant parameters. In this study two dimensionless criteria-the fraction of modeling information (FMI) and the fraction of residual information (FRI)-are proposed to identify errors caused by poor fit. These are compared with more conventional criteria, namely the quadratic error and the correlation coefficient, both theoretically and with the use of simulated and real CE-MRI data. The results indicate the superiority of the new criteria. It is also shown that these new criteria can be used to detect oversimplified models. Magn Reson Med, 2005. © 2005 Wiley-Liss, Inc. [ABSTRACT FROM AUTHOR]

Presents the scientific sessions of the European Society of Neuroradiology during its 30th Congresses and 14th Advanced Course in Barcelona, Spain. Schedule of the event; Topics discussed; Lists of lecturers.

Quantification of dynamic contrast-enhanced (DCE) MRI based on pharmacokinetic modeling requires specification of the arterial input function (AIF). A full representation of the plasma concentration data, including the initial rise and decay parts, considering the delay and dispersion of the bolus contrast is important. This work deals with modeling of DCE-MRI data from the knees of children with a history of juvenile rheumatoid arthritis (JRA) by using an AIF extracted from the signal enhancement data from the nearby popliteal artery. Three models for the AIFs were considered: a triexponential (AIF1), a gamma-variate plus a biexponential (AIF2), and a biexponential (AIF3). The pharmacokinetic parameters obtained from the model were Ktrans′, kep, and V [ABSTRACT FROM AUTHOR]

Purpose To identify radiation-induced changes in the cerebral vasculature of healthy tissue in the first four months following radiotherapy through the analysis of dynamic-susceptibility contrast perfusion imaging. Materials and Methods Dynamic gradient-echo imaging was performed on 22 patients during injection of a bolus of Gd-DTPA contrast. The relative cerebral blood volume (rCBV), maximum ΔR2* of the first passage of the bolus, and a recirculation parameter were derived from gamma-variate fits of the dynamic data. The white matter (WM) rCBV and peak heights were estimated through correlation with segmented T1-weighted images. A percent recovery to baseline was also computed to further describe the recirculation phase. Results A significant elevation of the recirculation phase was observed at doses > 15 Gy at two months following radiotherapy. This was reflected in an increased recirculation parameter in the fitted curves in the 15-30, 30-45, and >45 Gy dose groups to 2.8%, 3.8%, and 2.4% above the <15 Gy voxels, as well as in a decline in percent recovery to baseline. A trend toward lower rCBV and peak heights was observed at that same time point. Conclusion The observed results suggest a dose-dependent decline in vessel density and increase in vascular permeability and/or tortuosity in irradiated normal-appearing brain tissue at two months following radiotherapy. J. Magn. Reson. Imaging 2005;21:683-693. © 2005 Wiley-Liss, Inc. [ABSTRACT FROM AUTHOR]

Vascular and angiogenic processes provide an important target for novel cancer therapeutics. Dynamic contrast-enhanced magnetic resonance imaging is being used increasingly to noninvasively monitor the action of these therapeutics in early-stage clinical trials. This publication reports the outcome of a workshop that considered the methodology and design of magnetic resonance studies, recommending how this new tool might best be used.British Journal of Cancer (2005) 92, 1599-1610. doi:10.1038/sj.bjc.6602550 www.bjcancer.com [ABSTRACT FROM AUTHOR]

The article presents information on the proceedings of the 145th Meeting of the Society of British Neurological Surgeons. This meeting was held at Manchester, England on September 22-24, 2004. The research paper "Hearing Changes in Non-Enlarging Conservatively Managed Vestibular Schwannomas," presented at the meeting challenges the assumption that hearing will remain static in non-enlarging vestibular schwannomas, and therefore justify managing them expectantly as a means to preserve hearing. 1308 vestibular schwannomas referred to the senior author since 1977 were analysed to identify tumours treated conservatively.

Purpose To characterize human gliomas using T1-weighted dynamic contrast-enhanced MRI (DCE-MRI), and directly compare three pharmacokinetic analysis techniques: a conventional established technique and two novel techniques that aim to reduce erroneous overestimation of the volume transfer constant between plasma and the extravascular extracellular space (EES) ( K trans) in areas of high blood volume. Materials and Methods Eighteen patients with high-grade gliomas underwent DCE-MRI. Three kinetic models were applied to estimate K trans and fractional blood plasma volume ( v p). We applied the Tofts and Kermode (TK) model without arterial input function (AIF) estimation, the TK model modified to include v p and AIF estimation (mTK), and a 'first pass' variant of the TK model (FP). Results K TK values were considerably higher than K mTK and K FP values ( P < 0.001). K mTK and K FP were more comparable and closely correlated (ρ = 0.744), with K mTK generally higher than K FP ( P < 0.001). Estimates of v p( mTK) and v p( FP) also showed a significant difference ( P < 0.001); however, these values were very closely correlated (ρ = 0.901). K TK parameter maps showed 'pseudopermeability' effects displaying numerous vessels. These were not visualized on K mTK and K FP maps but appeared on the corresponding v p maps, indicating a failure of the TK model in commonly occurring vascular regions. Conclusion Both of the methods that incorporate a measured AIF and an estimate of v p provide similar pathophysiological information and avoid erroneous overestimation of K trans in areas of significant vessel density, and thus allow a more accurate estimation of endothelial permeability. J. Magn. Reson. Imaging 2004;20:748-757. © 2004 Wiley-Liss, Inc. [ABSTRACT FROM AUTHOR]

The hypothesis was tested that the intravoxel distribution of water diffusion rates, as measured with a stretched-exponential model of diffusion-weighted imaging (DWI), is a marker of brain tumor invasion. Eight rats underwent intracerebral inoculation of C6 glioma cells. In three rats, cells were labeled with a fluorescent dye for microscopy. One rat was inoculated with a saline solution, and five more rats were imaged without inoculation as controls. Five healthy uninoculated rats were also imaged. DWI was performed 14-15 days after inoculation, with diffusion-weighting factor b = 500 to 6500 sec/mm2, and the resulting signal attenuation was fitted with the stretched-exponential model. The heterogeneity index values were significantly lower ( P < 0.05) in the peritumor ROI than in normal gray matter and significantly higher than in normal white matter. The distributed diffusion coefficient values were significantly lower than in normal white matter or normal gray matter. Fluorescence microscopy confirmed the presence of tumors in the peritumor region that could be histologically distinguished from the main tumor mass. There was no change in proton density or T2-weighted images in the peritumor region, making vasogenic edema unlikely as a source of contrast. It is therefore thought that the heterogeneity parameter α is a marker of brain tumor invasion. Magn Reson Med 52:994-1004, 2004. © 2004 Wiley-Liss, Inc. [ABSTRACT FROM AUTHOR]