New developments in the neuroradiological diagnosis of craniocerebral trauma.

Accurate radiographic diagnosis is a cornerstone of the clinical management and outcome prediction of the head-injured patient. New technological advances, such as multi-detector computed tomography (MDCT) scanning and diffusion-weighted magnetic resonance imaging (MRI) have influenced imaging strategy. In this article we review the impact of these developments on the neuroradiological diagnosis of acute head injury. In the acute phase, multi-detector CT has supplanted plain X-ray films of the skull as the initial imaging study of choice. MRI, including fluid-attenuated inversion recovery, gradient echo T2* and diffusion-weighted sequences, is useful in determining the severity of acute brain tissue injury and may help to predict outcome. The role of MRI in showing diffuse axonal injuries is emphasized. We review the different patterns of primary and secondary extra-axial and intra-axial traumatic brain lesions and integrate new insights. Assessment of intracranial hypertension and cerebral herniation are of major clinical importance in patient management. We discuss the issue of pediatric brain trauma and stress the importance of MRI in non-accidental injury. In summary, new developments in imaging technology have advanced our understanding of the pathophysiology of brain trauma and contribute to improving the survival of patients with craniocerebral injuries.

3D time-of-flight MR angiography of the intracranial vessels: optimization of the technique with water excitation, parallel acquisition, eight-channel phased-array head coil and low-dose contrast administration.

The aim of this study is three folds: to compare the eight-channel phased-array and standard circularly polarized (CP) head coils in visualisation of the intracranial vessels, to compare the three-dimensional (3D) time-of-flight (TOF) MR angiography (MRA) techniques, and to define the effects of parallel imaging in 3D TOF MRA. Fifteen healthy volunteers underwent 3D TOF MRA of the intracranial vessels using eight-channel phased-array and CP standard head coils. The following MRA techniques were obtained on each volunteer: (1) conventional 3D TOF MRA with magnetization transfer; (2) 3D TOF MRA with water excitation for background suppression; and (3) low-dose (0.5 ml) gadolinium-enhanced 3D TOF MRA with water excitation. Results are demonstrating that water excitation is a valuable background suppression technique, especially when applied with an eight-channel phased-array head coil. For central and proximal portions of the intracranial arteries, unenhanced TOF MRA with water excitation was the best technique. Low-dose contrast enhanced TOF MRA using an eight-channel phased-array head coil is superior in the evaluation of distal branches over the standard CP head coil. Parallel imaging with an acceleration factor of two allows an important time gain without a significant decrease in vessel evaluation. Water excitation allows better background suppression, especially around the orbits and at the periphery, when compared to conventional acquisitions.

Does the location of a vascular loop in the cerebellopontine angle explain pulsatile and non-pulsatile tinnitus?

The purpose was to investigate patients with unexplained pulsatile and non-pulsatile tinnitus by means of MR imaging of the cerebellopontine angle (CPA) and to correlate the clinical subtype of tinnitus with the location of a blood vessel (in the internal auditory canal or at the cisternal part of the VIIIth cranial nerve). Clinical presentation of tinnitus and perceptive hearing loss were correlated. In 47 patients with unexplained tinnitus, an MR examination of the CPA was performed. Virtual endoscopy reconstructions were obtained using a 3D axial thin-section high-resolution heavily T2-weighted gradient echo constructive interference in steady state (CISS) data-set. High-resolution T2-weighted CISS images showed a significantly higher number of vascular loops in the internal auditory canal in patients with arterial pulsatile tinnitus compared to patients with non-pulsatile tinnitus (P<0.00001). Virtual endoscopy images were used to investigate vascular contacts at the cisternal part of the VIIIth cranial nerve in patients with low pitch and high pitch non-pulsatile tinnitus. A significantly different distribution of the vascular contacts (P=0.0320) was found. Furthermore, a correlation between the clinical presentation of non-pulsatile tinnitus (high pitch and low pitch) and the perceptive hearing loss was found (P=0.0235). High-resolution heavily T2-weighted CISS images and virtual endoscopy of the CPA can be used to evaluate whether a vascular contact is present in the internal auditory canal or at the cisternal part of the VIIIth cranial nerve and whether the location of the vascular contact correlates with the clinical subtype of tinnitus. Our findings suggest that there is a tonotopical structure of the cisternal part of the VIIIth cranial nerve. A correlation between the clinical presentation of tinnitus and hearing loss was found.

Role of mr angiography in the evaluation of renovascular hypertension.

Renovascular hypertension accounts for less than 5% of all cases of hypertension in general population. The prevalence may be as high as 40% in patients referred to hypertension clinics. Timely diagnosis and treatment of the condition are important because it has a worse prognosis when compared to essential hypertension. In most of these patients, the underlying cause of the vascular disease is atherosclerosis. Renal insufficiency due to chronic renal artery disease is not uncommon in this population. The ability of MR angiography (MRA) to provide morphologic and hemodynamic assessment of renal arteries without the need for the use of nephrotoxic iodinated contrast agents, make MRA the first choice in the evaluation of patients with renovascular hypertension.

Spinal tumors.

Spinal tumors are uncommon lesions but may cause significant morbidity in terms of limb dysfunction. In establishing the differential diagnosis for a spinal lesion, location is the most important feature, but the clinical presentation and the patient's age and gender are also important. Magnetic resonance (MR) imaging plays a central role in the imaging of spinal tumors, easily allowing tumors to be classified as extradural, intradural-extramedullary or intramedullary, which is very useful in tumor characterization. In the evaluation of lesions of the osseous spine both computed tomography (CT) and MR are important. We describe the most common spinal tumors in detail. In general, extradural lesions are the most common with metastasis being the most frequent. Intradural tumors are rare, and the majority is extramedullary, with meningiomas and nerve sheath tumors being the most frequent. Intramedullary tumors are uncommon spinal tumors. Astrocytomas and ependymomas comprise the majority of the intramedullary tumors. The most important tumors are documented with appropriate high quality CT or MR images and the characteristics of these tumors are also summarized in a comprehensive table. Finally we illustrate the use of the new World Health Organization (WHO) classification of neoplasms affecting the central nervous system.

CT-guided percutaneous needle biopsy in spine lesions.

Vertebral bone biopsy is an accurate, rapid, and cost-effective method to diagnose benign and malignant spine lesions. The major complications are uncommon. Nondiagnostic or insufficient specimens are encountered in less than ten per cent. The accuracy of the biopsy depends on the location and type of the lesion, needle system, and biopsy route. The major indications are focal lesions with non-specific medical imaging findings, to exclude metastasis in patients with known primary malignancy, lesion without response to treatment, no clinical improvement in children with diskitis after six weeks of therapy to exclude occult tumor and extreme pain due to vertebral collapse. If histology yields only peripheral blood elements in an obviously destructive mass, biopsy can be repeated, by directing at a slightly different area of the lesion. No more than three percutaneous biopsies of the same lesion should be performed.

Pattern recognition of degenerative disorders in the lumbar spine. Guidelines to MR image interpretation.

Interpreting MR images of the lumbar spine remains a formidable diagnostic challenge, especially in patients with degenerative changes. What are the pertinent findings? Which abnormalities are clinically relevant? Which changes should be viewed as normal aging? The purpose of this presentation is to present a standardized 7-step approach towards interpreting MR images of the degenerative lumbar spine.

Cervical spine fractures and soft tissue injuries.

Spinal cord injury is the major cause of quadriplegia and disability. Plain radiographs have a low sensitivity for identifying traumatic cervical spine lesions. Therefore trauma victims with plain films negative for cervical injury but with a high clinical suspicion of injury, or positive for cervical injury should undergo CT or MR for a more definitive evaluation of the cervical spine. Besides the higher sensitivity than plain radiography in detecting fractures, CT is also able to show soft-tissue abnormalities. MR is the definitive modality in assessing cervical soft-tissue injuries, especially in the evaluation of the spinal cord, intervertebral discs, and ligaments. It also allows differentiate spinal cord hemorrhage and edema, which may have a prognostic value. The role of medical imaging in the evaluation of whiplash injuries remains to be determined.

The correlation of preoperative CT, MR imaging, and clinical staging (FIGO) with histopathology findings in primary cervical carcinoma.

The aim of this study was to compare the preoperative findings of abdominal/pelvic CT and MRI with the preoperative clinical International Federation of Obstetrics and Gynecology (FIGO) staging and postoperative pathology report in patients with primary cancer of the cervix. Thirty-six patients with surgical-pathological proven primary cancer of the cervix were retrospectively studied for preoperative staging by clinical examination, CT, and MR imaging. Studied parameters for preoperative staging were the presence of tumor, tumor extension into the parametrial tissue, pelvic wall, adjacent organs, and lymph nodes. The CT was performed in 32 patients and MRI (T1- and T2-weighted images) in 29 patients. The CT and MR staging were based on the FIGO staging system. Results were compared with histological findings. The group is consisted of stage 0 (in situ):1, Ia:1, Ib:8, IIa:2, IIb:12, IIIa:4, IVa:6, and IVb:2 patients. The overall accuracy of staging for clinical examination, CT, and MRI was 47, 53, and 86%, respectively. The MRI incorrectly staged 2 patients and did not visualize only two tumors; one was an in situ (stage-0) and one stage-Ia (microscopic) disease. The MRI is more accurate than CT and they are both superior to clinical examination in evaluating the locoregional extension and preoperative staging of primary cancer of the cervix.

Contrast enhancement in Lhermitte-Duclos disease of the cerebellum: correlation of imaging with neuropathology in two cases.

Lhermitte-Duclos disease (LDD), also known as dysplastic gangliocytoma, is a rare cerebellar lesion. It has long been regarded as avascular. We report two patients with surgically proven LDD in whom contrast enhancement was observed on MRI. Neuropathological examination revealed proliferation of veins. We suggest that peripheral enhancement of LDD probably reflects vascular proliferation of the cerebellar venous draining system, and should be considered part of the imaging features of LDD.

CT angiography: basic principles and post-processing applications.

The introduction of spiral and more specifically multidetector CT scanners has provided unique opportunities in the field of CT angiography. It has also stressed the need of a basic knowledge of post-processing 3D imaging techniques to obtain maximum information of the CT data set. Aim of this article is to give a basic review of technical issues concerning CT angiography, with special attention to 3D imaging techniques such as surface shaded display (SSD), maximum intensity projection (MIP) and volume rendering (VR).

Phase-contrast magnetic resonance angiography.

Time of flight (TOF) and phase contrast (PC) magnetic resonance angiography (MRA) are two established magnetic resonance (MR) techniques that were described and developed in the 1980s. Both of these techniques usually do not involve the use of intravascular contrast, but rather exploit the intrinsic contrast provided by flowing blood to produce vascular signal. Bolus infused (gadolinium-enhanced) MR angiography was only introduced in 1993. PC-MRA uses the phase shifts introduced to nuclei with motion in the presence of a magnetic field gradient. A bipolar magnetic field gradient will induce a phase shift to nuclei moving along the gradient dependent on the velocity, as well as acceleration and higher order motion terms. More complex gradient waveforms enable sensitivity to specific motion terms such as velocity or acceleration. By constructing an image in which the intensity is proportional to the phase shift of the nuclei, it is possible to create an angiographic image related to the flow properties of blood (or other liquids such as cerebrospinal fluid). The PC-MRA is a powerful technique and allows for encoding of flow in one or many directions in such a way that the velocity sensitivity can be chosen depending on the vessel of interest. This technique also allows for quantification of flow velocity and flow rate, which is not generally available with other angiographic techniques.

MR angiography in steno-occlusive disease of the intracranial vessels.

Technical advances in MR angiography (MRA) have improved the sensitivity and the accuracy of this technique in the evaluation of vascular stenoocclusive disease of the brain. In many centers, due to its non-invasive and non-ionizing character, MR angiography has already replaced conventional angiography for the screening of intracranial vascular disease. Several MRA techniques have been developed for imaging the intracranial vascular system, such as time-of-flight MRA (TOF-MRA), phased-contrast MRA (PC-MRA), and more recently contrast-enhanced MRA (CE-MRA).

Hereditary neuromuscular diseases.

This article presents the actual classification of neuromuscular diseases based on present expansion of our knowledge and understanding due to genetic developments. It summarizes the genetic and clinical presentations of each disorder together with CT findings, which we studied in a large group of patients with neuromuscular diseases. The muscular dystrophies as the largest and most common group of hereditary muscle diseases will be highlighted by giving detailed information about the role of CT and MRI in the differential diagnosis. The radiological features of neuromuscular diseases are atrophy, hypertrophy, pseudohypertrophy and fatty infiltration of muscles on a selective basis. Although the patterns and distribution of involvement are characteristic in some of the diseases, the definition of the type of disease based on CT scan only is not always possible.