Bayesian estimation of cerebral perfusion using reduced-contrast-dose dynamic susceptibility contrast perfusion at 3T.

BACKGROUND AND PURPOSE: DSC perfusion has been increasingly used in conjunction with other contrast-enhanced MR applications and therefore there is need for contrast-dose reduction when feasible. The purpose of this study was to establish the feasibility of reduced-contrast-dose brain DSC perfusion by using a probabilistic Bayesian method and to compare the results with the commonly used singular value decomposition technique. MATERIALS AND METHODS: Half-dose (0.05-mmol/kg) and full-dose (0.1-mmol/kg) DSC perfusion studies were prospectively performed in 20 patients (12 men; 34-70 years of age) by using a 3T MR imaging scanner and a gradient-EPI sequence (TR/TE, 1450/22 ms; flip angle, 90°). All DSC scans were processed with block circulant singular value decomposition and Bayesian probabilistic methods. SNR analysis was performed in both half-dose and full-dose groups. The CBF, CBV, and MTT maps from both full-dose and half-dose scans were evaluated qualitatively and quantitatively in both WM and GM on coregistered perfusion maps. Statistical analysis was performed by using a t test, regression, and Bland-Altman analysis. RESULTS: The SNR was significantly (P < .0001) lower in the half-dose group with 32% and 40% reduction in GM and WM, respectively. In the half-dose group, the image-quality scores were significantly higher in Bayesian-derived CBV (P = .02) and MTT (P = .004) maps in comparison with block circulant singular value decomposition. Quantitative values of CBF, CBV, and MTT in Bayesian-processed data were comparable and without a statistically significant difference between the half-dose and full-dose groups. The block circulant singular value decomposition-derived half-dose perfusion values were significantly different from those of the full-dose group both in GM (CBF, P < .001; CBV, P = .02; MTT, P = .02) and WM (CBF, P < .001; CBV, P = .003; MTT, P = .01). CONCLUSIONS: Reduced-contrast-dose (0.05-mmol/kg) DSC perfusion of the brain is feasible at 3T by using the Bayesian probabilistic method with quantitative results comparable with those of the full-dose protocol.

Sinonasal imaging: malignant disease.

The clinical presentation of sinonasal malignancy overlaps that of more common benign inflammatory disease. For this reason, unsuspected malignant lesions are often first recognized on the screening CT exam. We will focus on the initial CT appearance of various malignancies and discuss the goals of imaging including the use of MR.

Rehabilitation outcome of individuals with nontraumatic myelopathy resulting from spinal stenosis.

A study was undertaken of 46 patients (19 cervical and 27 lumbar) admitted to an inpatient rehabilitation unit following surgical decompression for myelopathy or cauda equina syndrome resulting from spinal stenosis (SS). Individuals with SS represented 16 percent of all spinal cord injury (SCI) admissions. When compared to patients with traumatic SCI, patients with SS were significantly (t-test, p < .01) older (mean age 68 versus 39 years), more frequently retired/unemployed (89 percent versus 43 percent), more often married (57 percent versus 36 percent) and less often male (54 percent versus 82 percent) but with similar ethnicity. Significant (p < .01) Functional Independence Measurement (FIM) changes for the SS patients were noted after rehabilitation in the categories of self-care, sphincter control and mobility/locomotion. Additionally, outcome comparisons with a group of traumatic SCI patients who had similar motor function revealed similar lengths of stay, discharge FIM scores and discharge-to-community rates. This study suggests that individuals with weakness secondary to SS represent a significant proportion of individuals with SCI, make significant functional gains following inpatient rehabilitation and can achieve functional outcomes similar to those of traumatic SCI individuals.

Sinonasal anatomy.

Recent advances in paranasal sinus imaging have been driven by the development of functional endoscopic sinus surgery. The goal of most sinus imaging is to provide a surgical road map delineating the anatomy, defining the obstructing lesions, and noting anatomic variations that may predispose to operative complications. We review the embryology and development of the nose and paranasal sinuses; review the radiographic anatomy of the adult sinuses and their drainage pathways; and point out variations in the normal anatomic pattern, concentrating on those variations that are significant for the functional endoscopic sinus surgeon.

Cortical and subcortical T2 shortening in multiple sclerosis.

Low signal intensity on long-repetition-time MR sequences has been observed in deep gray matter structures in patients with multiple sclerosis. This T2 shortening most likely represents a nonspecific degenerative process. We recently observed T2 shortening in the pericentral cortical gray matter and subcortical white matter in a patient with severe multiple sclerosis and we postulate that this represents an additional manifestation of neural degeneration.

Hyperactive pectoralis reflex as an indicator of upper cervical spinal cord compression. Report of 15 cases.

Myelopathy from cervical spondylosis is often accompanied by hyperreflexia of the upper-extremity deep tendon reflexes (DTRs). Reflexes such as the pectoralis jerk and the deltoid jerk may only be apparent in the context of hyperreflexia. Although the nerve roots involved in the reflex arcs are well described, levels of cervical spinal cord compression that lead to the hyperreflexia are not as clear. This is of particular significance for patients with multilevel cervical spondylosis in determining the levels responsible for their symptoms. The authors examined 15 consecutive patients who presented for treatment of cervical myelopathy. The clinical examination was then correlated with levels of cervical spinal cord compression by cervical magnetic resonance imaging or computerized tomography with intrathecal contrast enhancement. The presence of a prominent pectoralis jerk was seen only in patients with spinal cord compression at the C2-3 and/or C3-4 levels (nine patients). No patient with compression at or below the C4-5 disc space without coexisting compression at a higher level had hyperactive pectoralis reflexes. This association between the C3-4 level and a hyperactive pectoralis reflex was significant (p < 0.004, Fisher's exact test). The deltoid reflex was tested in the last nine consecutive patients. It was present in patients with compression of the upper spinal cord at levels C3-4 and C4-5 (four of five patients) but appeared in only one of four patients with compression below C4-5. This association did not attain statistical significance. The presence of a hyperactive pectoralis reflex is specific for lesions of the upper cervical spinal cord. Examination of upper-extremity DTRs may be helpful in planning the appropriate levels for surgical decompression in patients with multilevel spondylosis and myelopathy.

The pathological globe: clinical and imaging analysis.

Categorizing globe lesions based on clinical presentation can suggest a short list of diagnostic possibilities. Imaging of the globe with ultrasound, CT and MRI is presented with a focus on key differential points. The radiologist can then efficiently tailor the examination in order to differentiate among the diagnostic possibilities.

Intrasellar presentation of a cystic optic chiasm fibrillary astrocytoma.

The unusual radiologic presentation of an optic chiasm fibrillary astrocytoma extending through and expanding the diaphragma sellae in an 8-year-old male is described. The child presented with decreased vision in the right eye. Magnetic resonance imaging demonstrated a cystic intra- and suprasellar mass, isointense on T1WI and hyperintense on T2WI, that enhanced with contrast. There was no radiographic involvement of the pituitary or hypothalamus. The optic chiasm could not be seen. The tumor mass was believed to be a craniopharyngioma and was partially removed by a transsphenoidal approach. Frozen section was not consistent with craniopharyngioma. Histochemical stains were positive for glial fibrillary acidic protein and S100 protein and nonreactive for EMA or actin. Electron microscopy showed abundant cellular processes and cytoplasmic filaments within the cells. A diagnosis of intrasellar fibrillary astrocytoma, probably arising from the optic chiasm, was made.

Neuro-Behçet's disease.

We are reporting a case of Behçet's disease without vasculitis, but with acute neutrophilic inflammation which involved the brain and other organs. The patient exhibited waxing and waning neurological deficits which were unresponsive to treatment. The neuroradiologic findings simulated those of multiple sclerosis. The neuropathological examination revealed an acute, focal, though disseminated encephalitis involving the frontal lobe, internal capsule, basal ganglia, cerebellum, and brain stem. The acute inflammation consisted of a neutrophilic and eosinophilic infiltration of the perivascular spaces and parenchyma without evidence of vasculitis, fibrinoid necrosis, or thrombosis. Cultures and special stains for microbial organisms were negative. Ultrastructural examination revealed no viral structures or other microorganisms. In situ hybridization for Epstein-Barr virus (EBV), herpes simplex virus type I (HSVI), and cytomegalovirus (CMV) was negative. In this case, the lack of inflammation in the vessel walls points out that the necrotizing lesions in neuro-Behçet's disease need not be the result of vasculitis and superimposed thrombosis, but may occur as a result of primary, acute neutrophilic inflammation.

Extrapontine myelinolysis of the basal ganglia without central pontine myelinolysis.

Since the first descriptions of central pontine myelinolysis (CPM) were put forth it has become evident that myelinolysis may not be exclusively restricted to the pons. In many cases myelinolysis may share other brain regions, while in still others the pons may not be affected at all, as in the present case of pure basal ganglia myelinolysis. Regardless of geographic location, too rapid correction of hyponatremia has been invoked as the triggering mechanism which leads to both CPM and extrapontine myelinolysis (EPM). This case of EPM is that of a 61-year-old male who suffered spinal cord compression and quadriplegia due to the breakdown of a double cervical fusion at C4-5/C5-6 for herniated discs. One month later, following vomiting and poor food intake, a low serum Na+ of 101 mmol/l developed and was corrected to 128 mmol/l in 37 h (and from 104 mmol/l to 121 mmol/l in 15 h). Altered mental status ensued and a T2 weighted MRI showed symmetrical, bilateral high intensity foci in the basal ganglia 3 weeks before death. Histologically there were bilateral, circumscribed, spheroidal areas of demyelination involving the striatal fibers which course through the putamina. The pons was spared. This case illustrates that extrapontine, basal ganglia myelinolysis may occur in the absence of CPM or alternate areas of myelinolysis. We discuss other cases of EPM, with and without CPM, to define the brain regions involved. MRI is uncovering many new cases of EPM and CPM. This permits one to follow the evolution of the myelinolytic lesions and to correlate their progression or regression with treatment modalities and the neurological findings.

Updated management strategy for patients with cervical osteophytic dysphagia.

Anterior cervical osteophytes impinging upon the pharynx or esophagus constitute a rare cause of dysphagia. In severe cases, surgical removal of these osteophytes can provide symptomatic relief. We describe a patient of this type who failed to improve postoperatively, only to be found subsequently to have a carcinoma of the base of the tongue. To assist other clinicians in evaluating similar patients, and also to emphasize the great utility of modern radiologic techniques in these cases, we propose a diagnostic algorithm that incorporates magnetic resonance or computerized tomographic imaging.

Gadolinium-enhanced magnetic resonance imaging of the facial nerve in herpes zoster oticus and Bell's palsy: clinical implications.

Gadolinium-enhanced magnetic resonance imaging was used in the evaluation of the facial nerve in four patients with idiopathic facial paralysis and six with herpes zoster oticus (HZO). Enhancement of the facial nerve was seen in all patients with Bell's palsy, and 50 percent of patients with HZO. The most consistent area of enhancement in both disorders involved the premeatal and labyrinthine segments. Although the images showed changes consistent with the type of viral process that is known to occur in these disorders, we found no significant correlation between the intensity or pattern of facial nerve enhancement on the images, the severity or duration of the disease, or the patient's prognosis for recovery. Nevertheless, gadolinium-enhanced MRI does have a place in the evaluation and decisions for management of select cases of facial paralysis.

Magnetic resonance imaging: improved patient tolerance utilizing medical hypnosis.

Magnetic Resonance Imaging (MRI) is a medical diagnostic procedure which requires a patient to be placed supine into the cylindrical bore of a powerful magnet for approximately one hour. The patient's arms are usually against the sides of the magnet bore with a 3" to 10" space between the patient's face and the top of the magnet bore. This enclosure induces panic and claustrophobic responses in 1% to 10% of the patients undergoing the MRI procedure. There have been many failed diagnostic studies due to patient intolerance, and there are reports of procedure-induced claustrophobia. We describe the hypnotic procedure utilized to reduce anxiety and panic for successful completion of MRI scans. Medical hypnosis has been an effective intervention in ten patients, permitting completion of their diagnostic procedure.

Slowly progressive facial paralysis due to vascular malformation of the brain stem.

Slowly progressive facial paralysis is suggestive of a diagnosis other than Bell's palsy. A case of slowly progressive facial paralysis caused by a cavernous angioma of the brain stem is presented. The classification of vascular malformations of the central nervous system is described with emphasis on the MRI appearance of these lesions.

Extracalvarial soft tissues in cranial computed tomography. Normal anatomy and pathology.

Computed tomography has emerged as the modality of choice for imaging soft tissues of the face and neck. However, the extracalvarial soft tissue anatomy has not been delineated. The CT appearance of normal anatomy and variants, including the cutaneous and subcutaneous tissues, muscle layers, and subgaleal space is described. A pathologic spectrum that includes congenital, inflammatory, traumatic, and neoplastic lesions is presented. When appropriate CT windows for viewing the extracalvarial soft tissues are utilized, significant clinical information may be provided.

Tomosynthesis applied to digital subtraction angiography.

This extension of our previous work on tomographic digital subtraction angiography (DSA) describes the theory of tomosynthetic DSA image reconstruction techniques. In addition to developing the resolution limits resulting from x-ray exposure length and image intensifier field curvature, we describe one method of image formation and show tomosynthetic DSA images of animal and human anatomy. Methods for improving the present technique are discussed.

Work in progress: hybrid temporal-energy subtraction in digital fluoroscopy.

Initial clinical results using a digital fluoroscopic implementation of the combined time-energy ("hybrid") subtraction technique are described, with emphasis on carotid and renal imaging. Where patient motion artifacts are due to soft-tissue motion alone, hybrid subtraction can remove them. Due to the need for a finite separation time between high- and low-energy pairs, however, the present implementation of the hybrid technique is not completely immune to soft-tissue motion. The intrinsic signal-to-noise ratio of hybrid imaging is less than that of conventional temporal subtraction. However, since the low-energy temporal subtraction images are included in the hybrid data set, the diagnostic quality of the examination is not compromised.

The utility of digital subtraction arteriography in peripheral vascular disease.

Digital subtraction angiography (DSA), whether used in conjunction with intravenous or intraarterial injection techniques, has an established role in evaluation of peripheral vascular disease. Use of DSA can reduce the time, cost, and patient discomfort of the standard arteriographic study. While it is limited by field size and patient cooperation in some instances, the utility of noninvasive imaging using intravenous DSA and the added anatomic detail of intraarterial DSA for roadmapping and delineation of small distal vessels provide the basis for future integration of standard arteriographic and DSA methods in assessment of peripheral vascular disease.

Computerized fluoroscopy techniques for intravenous study of cardiac chamber dynamics.

A computerized fluoroscopy system which was recently developed in our laboratories permits image contrast increases of 8-16 relative to conventional image intensifer fluoroscopy and permits study of canine and human ventricular wall motion using peripheral intravenous injections. Two time-dependent image subtraction algorithms are illustrated in connection with observation of artificially infarcted dog hearts. The first algorithm produces a display analogous to direct ventriculography using catheterization. The second displays regions of dyskinetic motion as anomalous image grey shades.