Kieran J. Murphy

Adult claustrophobia, anxiety and sedation in MRI

The purpose of this study was to identify the proportion of adult patients at our institution who require sedation to tolerate MR imaging. We also wished to identify whether the type of study and patient age or sex was associated with a variation in the use of sedation. A total of 939 patients, 18 years of age or older, underwent MR imaging at a large university hospital during a randomly selected 7-week period. Age, sex, type of study, number of prior MRIs, and use of sedation were identified in this group. Patients requiring sedation were compared by these criteria to all non-sedated members over 18 years of age in the cohort who acted as a control. Of the 939 patients 134 (14.3%) required oral sedation, i.v. sedation, or general anesthesia to tolerate MRI. This group was 35.8% male, 64.1% female (control group 48.1% male, 51.9% female). Of those requiring sedation, 89 patients (66.4%) were having brain MRI (male n = 29 or 32.6%, female n = 60 or 67.4%). In the control group 461 patients (57.3%) were having brain MRI (male n = 209 or 45.3%, female n = 252 or 54.6%). The mean age of the sedated group was 60.75 (range 19-91). The non-sedated group had a mean age of 67.3 (range 28-93). The sedated group had undergone a mean of 1.56 prior MR studies (range 0-16); the control group had a mean of 0.9 prior studies (range 0-7). Sedation was more commonly utilized in women than men, in patients having brain MRI, and in patients who had undergone prior MRI procedures. The identification of a population having the greatest need for sedation may aid in the development and selection of methods of stress reduction which will result in greater patient comfort, reduction in motion artifact, and fewer prematurely terminated studies.

3D gadolinium-enhanced MR angiography of the carotid arteries

PURPOSEnTo compare gadolinium-enhanced magnetic resonance angiography (MRA) of the carotid bifurcation with 2D time-of-flight (TOF) MR angiography with regard to image quality and duration of examination.nnnMATERIALS AND METHODSnGadolinium contrast was administered intravenously during 3D MR imaging at 1.5 Tesla in 46 patients presenting with suspected carotid occlusive disease. 2D time-of-flight MR angiography of the carotid bifurcation had been performed in each patient prior to gadolinium-enhanced MR angiography.nnnRESULTSnGadolinium MRA eliminated slice misregistration and in-plane saturation artifacts that occasionally degrades 2D TOF MR angiography. Gadolinium MRA required less than 4 min to image from the aortic arch to the skull base compared to 11 min for 2D TOF with comparable signal-to-noise ratio (SNR). Postprocessing was required to eliminate overlapping venous enhancement. Both techniques had susceptibility related artifactual loss of signal at the skull base and both demonstrated a linear artifact paralleling the long axis of arteries.nnnCONCLUSIONnGadolinium-enhanced MR angiography is a promising technique for the evaluation of patients with carotid occlusive disease because it rapidly images the carotid arteries from the aortic arch to the skull base and eliminates some of the artifacts that degrade 2D TOF MR angiography.

Occurrence of adverse reactions to gadolinium-based contrast material and management of patients at increased risk: a survey of the American Society of Neuroradiology Fellowship Directors.

RATIONALE AND OBJECTIVESnThe authors attempted to determine the frequency and severity of adverse reactions to gadolinium-based magnetic resonance (MR) contrast agents and to identify strategies for management of patients at increased risk.nnnMATERIALS AND METHODSnAmerican Society of Neuroradiology program directors were surveyed about adverse reactions at their institutions to gadolinium-based contrast agents, the contrast agents responsible, and the management of patients with allergy-like reactions to iodinated or gadolinium-based agents who required MR contrast agent administration.nnnRESULTSnFifty-three (50.5%) surveys were received from 105 centers. Of 687,255 gadopentetate dimeglumine injections, 314 (0.046%) nonallergic reactions and 107 (0.016%) mild, 28 (0.004%) moderate, and five (0.001%) severe allergy-like reactions occurred. Of 74,275 gadodiamide injections, 11 (0.015%) nonallergic and 12 (0.016%) mild allergy-like reactions occurred. Of 64,005 gadoteridol administrations, 171 (0.267%) nonallergic reactions and 49 (0.077%) mild, 29 (0.047%) moderate, and 11 (0.017%) severe allergy-like reactions occurred. Twenty-six departments took no precautions for patients with previous allergy-like reactions to iodinated contrast material. Nineteen did not premedicate patients who previously had reactions to gadolinium-based agents before repeat administration of MR contrast agents.nnnCONCLUSIONnAlthough MR contrast agents are safe, adverse reactions occur. Many centers have not adopted policies for the OFF

Whole-Brain Perfusion CT Performed with a Prototype 256–Detector Row CT System: Initial Experience

PURPOSEnTo preliminarily evaluate the feasibility and potential diagnostic utility of whole-brain perfusion computed tomography (CT) performed with a prototype 256-detector row CT system over an extended range covering the entire brain to assess ischemic cerebrovascular disease.nnnMATERIALS AND METHODSnInstitutional review board approval and informed consent were obtained. Eleven cases in 10 subjects (six men, four women; mean age, 64.3 years) with intra- or extracranial stenosis were retrospectively evaluated with whole-brain perfusion CT. Three readers independently evaluated perfusion CT data. The diagnostic performance of perfusion CT was visually evaluated with a three-point scale used to assess three factors. Differences between four axial perfusion CT images obtained at the basal ganglia level (hereafter, four-section images) and whole-brain perfusion CT images were assessed with the paired t test. In four subjects, the interval between perfusion CT and single photon emission computed tomography (SPECT) was 1-17 days (mean, 10.3 days). Correlation between perfusion CT findings and SPECT findings was assessed with the Spearman correlation coefficient.nnnRESULTSnThree-dimensional perfusion CT images and axial, coronal, and sagittal whole-brain perfusion CT images were displayed, and the extent of ischemia was assessed. Mean visual evaluation scores were significantly higher for whole-brain images than for four-section images (4.27 +/- 0.76 [standard deviation] vs 2.55 +/- 0.87). The cerebral blood flow ratios of the ischemic lesions relative to normal regions scanned with perfusion CT (x) and SPECT (y) showed a significant positive correlation (R(2) = 0.76, y = 0.44 x + 0.37, P < .001).nnnCONCLUSIONnPerfusion CT performed with a 256-detector row CT system can be used to assess the entire brain with administration of one contrast medium bolus. Thus, ischemic regions can be identified with one examination, which has the potential to improve diagnostic utility.

Power Doppler: It's a good thing

Power Doppler is a new method of ultrasound flow imaging the utility of which is currently under investigation. This technique creates a flow map based on the integrated power of the Doppler spectrum, rather than mean Doppler frequency. Power Doppler imaging is inherently more sensitive in terms of flow detection than standard color Doppler imaging; therefore, power Doppler can display flow for situations in which color Doppler is ineffective and can even display tissue perfusion in highly vascular organs such as the kidneys. Furthermore, power Doppler is not effected by aliasing, nor is it effected by blooming in the same way as color Doppler, which has deleterious effects on color Doppler flow images. The control of blooming with power Doppler may be of great importance in the clinical application of echo-enhancing agents. This review article discusses in detail the technological advantages and disadvantages of power Doppler flow imaging. In addition, it provides a synopsis of the preliminary research studies that have been conducted to date with respect to the clinical applications of power Doppler.

FDG PET imaging of paragangliomas of the neck: comparison with MIBG SPET

Two patients with cervical paragangliomas underwent positron emission tomography (PET) with 2-[18F]-fluoro-2-deoxy-D-glucose (FDG). There was marked tumor uptake and retention of FDG. Adjacent salivary gland accumulation of FDG was minimal, though quite prominent withmeta-iodobenzylguanidine. FDG PET offers another potentially useful approach to functional imaging of these uncommon tumors, independent of the presence of specific amine uptake mechanisms or cell surface receptors required by other scintigraphic techniques.

Miliary tuberculosis involving the central nervous system

Figure 1. A 28-year-old woman with a 10-year history of systemic lupus erythematosus presented with fever, back pain, and bilateral paresthesias and weakness of the legs of 10 days duration. She had been taking prednisone for the preceding nine months for the management of flares. On examination her neck was supple. She had decreased power and sensation in her legs, with diminished knee and ankle reflexes, an extensor right-plantar response, and an equivocal left-plantar response. T1-weighted magnetic resonance imaging after the administration of contrast medium revealed an enhancing lesion within the spinal cord at the T11 level (Panel .xa0.xa0.