SUMMARY:The current standard of care for newly diagnosed cases of high-grade glioma is surgical resection followed by RT with concurrent chemotherapy. The most widely used criteria for assessing treatment response are based on a 2D measurement of the enhancing area on MR imaging known as the Macdonald Criteria. Recently, nontumoral increases (pseudoprogression) and decreases (pseudoresponse) in enhancement have been found, and these can confuse outcome evaluation. Here we review pseudoprogression and pseudoresponse and describe how better understanding of these phenomena can aid interpretation.ABBREVIATIONS: ADC ϭ apparent diffusion coefficient; BBB ϭ blood-brain barrier; Cho ϭ choline; DSC ϭ dynamic susceptibility-weighted contrast-enhanced perfusion MR imaging; DTI ϭ diffusion tensor imaging; DWI ϭ diffusion-weighted imaging; FDG ϭ fluorodeoxyglucose; FLAIR ϭ fluidattenuated inversion recovery; GBM ϭ glioblastoma multiforme; MGMT ϭ methyltransferase; NAA ϭ N-acetylaspartate; PET ϭ positron-emission tomography; PSR ϭ percentage of signalintensity recovery; RANO ϭ Response Assessment in Neuro-Oncology; rCBV ϭ relative cerebral blood volume; RECIST ϭ Response Evaluation Criteria in Solid Tumors; ROC ϭ receiver operating characteristic analysis; RT ϭ radiation therapy; TMZ ϭ temozolomide; VEGF ϭ vascular endothelial growth factor G BM is the most common primary malignant type of brain neoplasm in adults and is associated with a dismal prognosis. The current standard of care is surgical resection followed by RT and concomitant and adjuvant TMZ chemotherapy. This is a relatively recent standard, with pivotal data published in 2005, and it represents a milestone, because this approach has been shown to prolong the overall survival of these patients.1 With the standardization of treatment around surgery/RT/TMZ, certain patterns are beginning to emerge that were not previously noticed. In addition, in May 2009, the US Food and Drug Administration approved bevacizumab for recurrent glioblastoma. This anti-VEGF agent also can have a marked pattern of change on MR imaging. In addition to impacting individual patient care, these changes have also had an impact on clinical trials of new therapies. Macdonald CriteriaThe Macdonald Criteria 2 are currently the most widely used guideline for assessing response to therapy in patients with highgrade gliomas. These are based on 2D tumor measurements made in MR imaging scans, in conjunction with clinical assessment and corticosteroid dose. According to the Macdonald Criteria, tumor progression is considered to have occurred when an increase of Ͼ25% in the size of the contrast-enhancing lesion is observed. There are important limitations to these criteria, which only address the contrast-enhancing component of the tumor, and various updated guidelines for RANO have been published.3,4 As radiologists learn early in their training, contrast enhancement in posttreatment brain tumors is nonspecific and may not always be considered a true surrogate of tumor response.The limitations of th...

Astrocytes, members of the glial family, interact through the exchange of soluble factors or by directly contacting neurons and other brain cells, such as microglia and endothelial cells. Astrocytic projections interact with vessels and act as additional elements of the Blood Brain Barrier (BBB). By mechanisms not fully understood, astrocytes can undergo oncogenic transformation and give rise to gliomas. The tumors take advantage of the BBB to ensure survival and continuous growth. A glioma can develop into a very aggressive tumor, the glioblastoma (GBM), characterized by a highly heterogeneous cell population (including tumor stem cells), extensive proliferation and migration. Nevertheless, gliomas can also give rise to slow growing tumors and in both cases, the afflux of blood, via BBB is crucial. Glioma cells migrate to different regions of the brain guided by the extension of blood vessels, colonizing the healthy adjacent tissue. In the clinical context, GBM can lead to tumor-derived seizures, which represent a challenge to patients and clinicians, since drugs used for its treatment must be able to cross the BBB. Uncontrolled and fast growth also leads to the disruption of the chimeric and fragile vessels in the tumor mass resulting in peritumoral edema. Although hormonal therapy is currently used to control the edema, it is not always efficient. In this review we comment the points cited above, considering the importance of the BBB and the concerns that arise when this barrier is affected.

Diffusion-weighted imaging is a potential resource as a coadjutant of MRI in the differentiation between benign and malignant lesions. Such imaging can be performed without a significant increase in examination time, especially because it can be done with lower b values.

The diffusion tensor imaging findings in children with autistic disorder suggest impairment of white matter microstructure, possibly associated with reduced connectivity in corpus callosum, internal capsule, and superior and middle cerebellar peduncles.

The reversed halo sign is seen in approximately 10% of patients with paracoccidioidomycosis. In these patients, this sign reflects the presence of a central area of predominantly interstitial inflammation surrounded by predominantly air-space infiltration.

Pulmonary alveolar microlithiasis (PAM) is an uncommon chronic disease characterized by calcifications within the alveoli and a paucity of symptoms in contrast to the imaging findings. We present a 59-year-old woman with a 4-year history of shortness of breath on exertion. Lung auscultation revealed random wheezes and fine and coarse crackles. Pulmonary function tests showed a restrictive pattern. The chest radiograph demonstrated a bilateral symmetric micronodular pattern. High resolution CT scan revealed diffuse ground-glass attenuation with superimposed septal thickening ("crazy-paving" pattern). The patient underwent a lung biopsy, which confirmed the diagnosis of PAM. Our case demonstrates that PAM needs to be considerate in the differential diagnosis of lung lesions that present with crazy-paving pattern on the high resolution CT.

BACKGROUND AND PURPOSE:The T2-weighted gradient-echo (GRE) imaging is currently the gold standard MR imaging sequence for the evaluation of patients with cerebral cavernous malformation (CCM) lesions. We aimed to compare the sensitivity of susceptibility-weighted imaging (SWI) with T2-weighted fast spin-echo (FSE) and GRE imaging in assigning the number of CCM lesions in patients with the familial form of the disease.

BMMNC labeling with technetium-99m allowed imaging for up to 24 h after intra-arterial or intravenous injection in stroke patients.