T1w/FLAIR ratio standardization as a myelin marker in MS patients.

INTRODUCTION: Calculation of a T1w/T2w ratio was introduced as a proxy for myelin integrity in the brain of multiple sclerosis (MS) patients. Since nowadays 3D FLAIR is commonly used for lesion detection instead of T2w images, we introduce a T1w/FLAIR ratio as an alternative for the T1w/T2w ratio. OBJECTIVES: Bias and intensity variation are widely present between different scanners, between subjects and within subjects over time in T1w, T2w and FLAIR images. We present a standardized method for calculating a histogram calibrated T1w/FLAIR ratio to reduce bias and intensity variation in MR sequences from different scanners and at different time-points. MATERIAL AND METHODS: 207 Relapsing Remitting MS patients were scanned on 4 different 3 T scanners with a protocol including 3D T1w, 2D T2w and 3D FLAIR images. After bias correction, T1w/FLAIR ratio maps and T1w/T2w ratio maps were calculated in 4 different ways: without calibration, with linear histogram calibration as described by Ganzetti et al. (2014), and by using 2 methods of non-linear histogram calibration. The first nonlinear calibration uses a template of extra-cerebral tissue and cerebrospinal fluid (CSF) brought from Montreal Neurological Institute (MNI) space to subject space; for the second nonlinear method we used an extra-cerebral tissue and CSF template of our own subjects. Additionally, we segmented several brain structures such as Normal Appearing White Matter (NAWM), Normal Appearing Grey Matter (NAGM), corpus callosum, thalami and MS lesions using Freesurfer and Samseg. RESULTS: The coefficient of variation of T1w/FLAIR ratio in NAWM for the no calibrated, linear, and 2 nonlinear calibration methods were respectively 24, 19.1, 9.5, 13.8. The nonlinear methods of calibration showed the best results for calculating the T1w/FLAIR ratio with a smaller dispersion of the data and a smaller overlap of T1w/FLAIR ratio in the different segmented brain structures. T1w/T2w and T1w/FLAIR ratios showed a wider range of values compared to MTR values. CONCLUSIONS: Calibration of T1w/T2w and T1w/FLAIR ratio maps is imperative to account for the sources of variation described above. The nonlinear calibration methods showed the best reduction of between-subject and within-subject variability. The T1w/T2w and T1w/FLAIR ratio seem to be more sensitive to smaller changes in tissue integrity than MTR. Future work is needed to determine the exact substrate of T1w/FLAIR ratio and to obtain correlations with clinical outcome.

Demographic changes in brain CT and MR imaging between 1990 and 2010.

STUDY OBJECTIVE: During the last decades, computed tomography and magnetic resonance imaging have revolutionized neuro-imaging. Nowadays these techniques are routinely used, but the extent and variation of use has been investigated poorly. Our purposes were to retrospectively determine the evolution in demographic variables and indications of cranial CT and MRI scanning in 1993, 2000 and 2009, at our hospital. METHODS: We retrospectively studied medical and neurologic in- and outpatients, who underwent CT- or MR imaging of the head for several demographic and patient characteristics. RESULTS: We observed a modest increase in mean age and a marked increase in total number of cranial CT examinations, MR confirmation studies and repeat examinations. Metastatic disease, head injury and headache were indications associated with more rapid growth in CT use than were others. CONCLUSION: Among the 5 patient and hospital factors considered (total number of examinations, age, indication, MR confirmation study and repeat examinations), all had a significant variation during the past 16 years. Strict regulations with compelling guidelines for the rational use of brain CT and MRI are inevitable in order to control expenditure and radiation exposure.

Staging of lung cancer. Do we need a diagnostic CT of the brain after an integrated PET/CT for the detection of brain metastases?

Brain CT has been recommended in staging of patients with lung cancer because of its usefulness in the detection of metastases. Purpose of this study is to examine if a diagnostic brain CT (CT,) can be obviated when an integrated PET/CT (PET/CT) is available. 87 consecutive patients underwent a diagnostic brain CT and a whole-body PET/CT within a period of 3 weeks to stage a known primary tumour. CT examinations were evaluated by two experienced neuroradiologists on the detection of brain lesions (benign and malignant). The results of PET/CT and CT reading were compared and both readings were compared with the clinical results. Statistical analysis was done by measuring sensitivity, specificity, PPV, NPV and accuracy. The relative accuracies were compared by a McNemar (exact) test for correlated proportions. Considering the CT, as standard of reference, sensitivity, specificity, PPV, NPV and accuracy for the brain CT of PET/CT (CT2) and PET/CT were respectively 83%, 96%, 77%, 97%, 94% and 69%, 98%, 90%, 95%, 94%. Considering the clinical diagnosis as standard of reference these figures were for CT1, CT2 and PET/CT respectively 80%, 100%, 100%, 96%, 96% and 66%, 95%, 77%, 93%, 90% and 66%, 97%, 83%, 93%, 91%. There was no statistical difference between CT1 and CT2. The comparison of the additional CT in PET/CT with a diagnostic CT of the brain did not yield a statistical difference in the detection of brain lesions despite the inferior quality of the CT component of PET/CT. A diagnostic brain CT can be obviated when a PET/CT is available.

Angiographic confirmation of brain death after decompressive craniectomy for posttraumatic brain oedema.

In patients who underwent decompressive craniectomy for brain oedema, angiography for the assessment of brain death can show filling of the intracranial supratentorial arteries.This does not exclude brain death, provided circulatory arrest and absence of venous drainage are present.

Epidermoid cyst of the fourth ventricle: diffusion-weighted and flair MR imaging findings.

Fourth ventricle epidermoid cysts are rare lesions, arising from epithelial remnants at the time of neural tube closure. They are well-defined CT hypoattenuated masses that resemble CSF on all conventional MR imaging sequences. We present a case of a pathological proven less common fourth ventricle epidermoid cyst with special emphasis on the use of FLAIR and EPI-DW imaging sequences in the diagnosis.

Conventional MRI of epilepsy in children.

The imaging findings in childhood epilepsy are different from the findings in adults. The present article describes the major features of symptomatic epilepsy syndromes and stresses the sometimes typical abnormalities.

Hypertensive brain stem encephalopathy in a patient with chronic renal failure.

Hypertensive brain stem encephalopathy is a rare disorder that can be seen in severe hypertensive encephalopathy. Patients with chronic renal failure are more prone to develop this disorder because a mild elevation of the blood pressure can already induce brain changes. It is important to diagnose this entity as soon as possible because the symptoms and brain stem lesions are reversible following treatment and because it is important to exclude brain stem ischemia in the diagnostic work-up. Brain MRI and particularly diffusion weighted images are crucial for this purpose.

[Radiology versus medical imaging]. / De term "medische beeldvorming" kan niet gebruikt worden in de plaats van "radiologie".

In an increasing number of hospitals in Belgium, the radiologists are changing the names from their department from "radiology" to "medical imaging". The reasons behind this change remain unclear and it is certainly not a good move in a time where turf battles will increase.

Intra-axial brain tumours.

The radiological diagnosis and differential diagnosis of intra-axial tumours no longer relies on CT scan and routine MR sequences alone. Standard multiplanar imaging has to be combined with fMRI to allow the exact anatomic location of the lesion and precise determination of the extension of the tumour. Perfusion and diffusion MR is becoming more and more important in the differential diagnosis of cerebral mass lesions and in the grading and typing of gliomas. More sophisticated techniques such as diffusion tensor imaging and spectroscopy will further enhance the value of the radiological studies.

Sequences and techniques in spinal MR imaging.

The optimal protocol in spinal MR imaging is not evident. Sagittal T2 weighted FSE, sagittal T1 weighted SE and axial T2 weighted FSE sequences are widely accepted for imaging patients with sciatica and/or lumbar pain. Because of the limited amount of CSF compared to the lumbar spine, the choice of sequences is much more complex in the study of the cervical spine. Sagittal T2 FSE, sagittal T1 SE and axial 2D GE images are suggested in routine cervical spine imaging. To assess the bone marrow, a STIR sequence can be added to this protocol on both lumbar and cervical spine examinations. The 2D GE produces an acceptable image quality to differentiate between the disc and bony protrusions. The use of FLAIR for imaging spinal cord lesions remains controversial in the literature.

Diffusion-weighted MR imaging findings in a patient with herpes simplex encephalitis.

INTRODUCTION: Herpes simplex meningoencephalitis is one of the most common viral central nervous system infection in adults. Early diagnosis is essential for treatment. CASE REPORT: We present a case of a 68-year-old female patient with herpes simplex infection. On admission, she was in severe clinical condition. Diffusion-weighted (DW) magnetic resonance imaging detected brain involvement better than conventional sequences. After acyclovir therapy, the patient fully recovered. CONCLUSION: DW magnetic resonance imaging is expected to provide a more sensitive imaging in herpes simplex patients than conventional sequences.

An unusual case of hearing loss and cerebellar pathology.

This paper describes an unusual case of neurofibromatosis type I unidentified clinically and diagnosed with MRI. Both the enhancement features and the localization in the cerebellum and corpus callosum are atypical.

Desmoplastic infantile ganglioglioma: a potentially malignant tumor?

Desmoplastic infantile ganglioglioma is a rare intracranial tumor of early childhood with a usually excellent prognosis despite malignant features both radiologically and histologically. We present the case of a desmoplastic infantile ganglioglioma with histologically highly anaplastic features and both intracerebral and pial metastases. After partial resection the tumor was rapidly progressive and new metastases appeared. A combination of vincristine and carboplatinum was used according to the Low Grade Glioma Protocol of the International Society of Pediatric Oncology, with a temporary good response. When histologically characterized by highly anaplastic features, it seems the biologic behavior of this tumor remains uncertain. The aggressive behavior and the responsiveness to chemotherapy in this case may challenge the belief in the benign nature of these rare tumors.

From X-rays to radiofrequency waves or the changing practice of diagnostic neuroradiology: imaging, health care and economical aspects.

Over the past 25 years, radiology has become an increasingly important diagnostic technique in medicine. The majority of radiological techniques still use x-rays, despite the availability of other techniques that do not use ionising radiation. The diagnostic work-up of patients with neurological disorders underwent significant changes in the past 20 years parallel with the advances in medical technology. In neuroradiology, the imaging of the central nervous system, magnetic resonance (MR) imaging has challenged the x-ray procedures such as computed tomography (CT), myelography and angiography. MR imaging uses radiofrequency waves that do not have noxious biological effects. It is generally accepted that MR imaging yields superior image quality compared with CT. Despite the advantages of MR imaging, CT remains an important investigation and has not been replaced by MR. In this memoir the state of the art imaging procedures in diagnostic neuroradiology are reviewed, with their advantages and disadvantages. The failed substitution of CT by MR imaging seems to be mainly due to the limited availability of MR installations and the still long examination times compared with CT. The impact of the changing practice of neuroradiology on health care and the economical aspects are extremely important knowing that financial resources are limited. MR leads to a decrease in invasive diagnostic and therapeutic procedures and the real cost of MR seems to be less than expected. Health care technology assessment and evidence based medicine are less well known in the radiological community, but will become increasingly important in the years to come.