The role of diffusion and perfusion magnetic resonance imaging in differentiation of haemangioblastomas and pilocytic astrocytomas.

PURPOSE: Haemangioblastomas (HABLs) and pilocytic astrocytomas (PAs) are brain tumours presenting similar appearance and location in conventional magnetic resonance (MR) imaging. The purpose of our study was to determine whether a detailed analysis of diffusion (DWI) and perfusion (PWI) characteristics can be useful in preoperative differentiation of these tumours. MATERIAL AND METHODS: The study group consisted of biopsy proven six HABLs and six PAs, which underwent preoperative standard MR examinations including PWI and DWI. In PWI relative cerebral blood volume (rCBV) and the shape of perfusion curves (parameters of peak height - rPH and percentage of signal recovery - rPSR) were analysed. All perfusion parameters were measured for the entire tumour core (mean rCBV, mean rPH, mean rPSR) and in regions with maximal values (max rCBV, max rPH, max rPSR). In DWI parameters of apparent diffusion coefficient (ADC) from the entire tumour core (mean ADC) and in regions with minimal values (min ADC) were evaluated. RESULTS: Compared to PAs, HABLs presented significantly higher rCBV and rPH values and lower mean rPSR value. PAs showed significantly lower rCBV and rPH values and higher mean rPSR value. Mean rCBV showed no overlap in the values between HABLs and PAs, and thus it provided the highest accuracy in differentiating between them. Max rPSR, mean ADC, and min ADC did not show any significant differences. CONCLUSIONS: High rCBV values and deep perfusion curves with only partial return to the baseline are characteristic features of HABLs differentiating them from PAs, which show lower rCBV values and perfusion curves overshooting the baseline. Diffusion parameters are not useful in differentiation of these tumours.

Central nervous system lymphoma in a 3-year-old male suffering from a severe juvenile xanthogranuloma - the usefulness of perfusion weighted imaging and diffusion weighted imaging in the diagnostics of pediatric brain tumors.

BACKGROUND: Primary Central Nervous System Lymphomas (PCNSLs) are rare, malignant brain tumors derived from lymphocytes B. Juvenile xanthogranuloma (JXG) is a non-Langerhans histiocytic cell disorder in children which mostly affects the skin. Rare fatalities have been reported in extracutaneous manifestation. Brain magnetic resonance imaging (MRI) is a method of choice in the diagnostics of all neoplastic CNS lesions. Perfusion weighted imaging (PWI) and diffusion weighted imaging (DWI) allow for more detailed analysis of brain tumors including the rate of neoangiogenesis and cellularity. We presented a pediatric patient suffering from JXG with CNS involvement and the role of brain MRI including DWI and PWI in the evaluation of brain focal lesions. CASE REPORT: A 3-year-old male with severe JXG underwent two stem cell transplantations with a development of neurological complications. The patient underwent emergency CT and MRI which revealed a non-specific enhancing focal brain lesion. In DWI it showed restricted diffusion while PWI revealed low values of rCBV and the signal intensity curve returning above the baseline level. Advanced MRI techniques such as DWI and PWI suggested PCNSL. Stereotactic biopsy confirmed PCNSL due to Ebstein-Barr virus reactivation. CONCLUSIONS: The use of advanced MRI sequences is important to differentiate brain lesions in pediatric patients. The use of PWI and DWI facilitated the diagnosis of PCNSL. It is important to remember that PCNSLs show a very typical pattern of changes visualized with MRI such as: usually strong homogenous enhancement, restricted diffusion and low perfusion.

Intracranial Lesions with Low Signal Intensity on T2-weighted MR Images - Review of Pathologies.

In this article we presented intracranial pathological substances and lesions with low signal intensity on T2-weighted images. Eight groups of substances were discussed i.e. 1. Gadolinium-based contrast materials, 2. hemoglobin degradation products 3. melanin, 4. mucous- or protein-containing lesions, 5. highly cellular lesions, 6. lesions containing mineral substances such as: calcium, copper and iron, 7. turbulent and rapid blood or CSF flow 8. air-containing spaces. Appropriate interpretation of signal intensity as well as analysis of lesion location and clinical symptoms enable a correct choice of a further diagnostic algorithm or, in many cases, final diagnosis based exclusively on an MRI examination.

Intracranial lesions with high signal intensity on T1-weighted MR images - review of pathologies.

In the article we present pathological intracranial substances and lesions, which produce high signal intensity on T1-weighted MR images. Six groups of substances are discussed: 1. Gadolinium - based contrast agents, 2.hemoglobin degradation products (intra- and extra-cellular methemoglobin), 3. lipid-containing lesions (lipoma, dermoid cyst, implanted fatty materials, laminar cortical necrosis), 4. substances with high concentration of proteins (colloid cyst, craniopharyngioma, Rathke's cleft cyst, ectopic posterior pituitary gland), 5. melanin (metastatic melanoma), 6. lesions containing mineral substances such as: calcium (calcifications, Fahr's disease), copper (Wilson's disease) and manganese (hepatic encephalopathy, manganese intoxication in intravenous drug abusers). Appropriate interpretation of signal intensity as well as analysis of location of lesions and clinical symptoms enables planning of further diagnostics and, in many cases, establishing the final diagnosis based on MR examination.

Diffusion and perfusion MR patterns of central nervous system lymphomas.

BACKGROUND: Central nervous system lymphomas (CNSLs) are rare tumors which may show variable appearance in standard magnetic resonance imaging (MRI) depending on their origin (primary or secondary) or patients' immunological status. OBJECTIVES: The aim of the study was to analyze imaging patterns of different CNSLs, using diffusion-weighted imaging (DWI) and perfusion-weighted imaging (PWI). MATERIAL AND METHODS: Our material consisted of 16 CNSLs (14 primary, 2 secondary, 13 immunocompetent, 3 immunodeficient) which underwent magnetic resonance (MR) examinations including DWI and T2* dynamic susceptibility contrast (DSC) perfusion (without a preload in 13 cases, with a preload in 3 subjects). In DWI, apparent diffusion coefficient (ADC), and in PWI, parameters of relative cerebral blood volume (rCBV), relative peak height (rPH) and relative percentage of signal recovery (rPSR) were analyzed within the entire tumor (mean values) and in regions with minimal diffusion (ADCmin) and maximal perfusion values (rCBVmax, rPHmax, rPSRmax). RESULTS: All CNSLs showed low values of ADCmean (0.70 × 10-3), ADCmin (0.54 × 10-3), rCBVmean (0.80), rCBVmax (1.27), rPHmean (1.05), rPHmax (1.59), as well as high values of rPSRmean (1.99) and rPSRmax (2.41). There were no significant differences in rCBVmax, as well as in all ADC, rPH and rPSR values between primary and secondary CNSLs or between tumors in immunocompetent and immunodeficient patients. Dynamic susceptibility contrast PWI with a preload resulted in significantly higher rCBV, rPH and lower rPSR values. CONCLUSIONS: Despite various MR appearances, both primary and secondary CNSLs in immunocompetent and immunodeficient patients show very typical patterns of restricted diffusion and hypoperfusion with signal intensity curves returning above the baseline. Dynamic susceptibility contrast perfusion without a preload is recommended.

Differentiation of glioblastoma multiforme, metastases and primary central nervous system lymphomas using multiparametric perfusion and diffusion MR imaging of a tumor core and a peritumoral zone-Searching for a practical approach.

INTRODUCTION: In conventional MR examinations glioblastomas multiforme (GBMs), metastases and primary CNS lymphomas (PCNSLs) may show very similar appearance. The aim of the study was to evaluate usefulness of multiparametric T2*DSC perfusion and diffusion MR imaging in the preoperative differentiation of these tumors. MATERIAL AND METHODS: Seventy four solitary enhancing tumors (27 GBMs, 30 metastases, 17 PCNSLs) were enrolled in the study. Parameters of cerebral blood volume (rCBV), peak height (rPH), percentage of signal recovery (rPSR) and apparent diffusion coefficient (ADC) were assessed from the tumor core and the peritumoral non-enhancing T2-hyperintense zone. RESULTS: Within the tumor core there were no differences in perfusion and diffusion parameters between GBMs and metastases. Compared to GBMs and metastases, PCNSLs showed significantly lower rCBV and rPH, ADC as well as higher rPSR values. Max rCBV with a cut-off value of 2.18 demonstrated the highest accuracy of 0.98 in differentiating PCNSLs from other tumors. To distinguish GBMs from metastases analysis of the peritumoral zone was performed showing significantly higher rCBV, rPH and lower ADC values in GBMs with the highest accuracy of 0.94 found for max rCBV at a cut-off value of 0.98. CONCLUSIONS: Max rCBV seems to be the most important parameter to differentiate GBMs, metastases and PCNSLs. Analysis of max rCBV within the tumor core enables to distinguish hypoperfused PCNSLs from hyperperfused GBMs and metastases while evaluation of max rCBV within the peritumoral zone is helpful to distinguish GBMs showing peritumoral infiltration from metastases surrounded by pure edema.