Field strength dependence of R1 and R2* relaxivities of human whole blood to ProHance, Vasovist, and deoxyhemoglobin.

This study has measured the longitudinal and transverse (T2* relaxivity curves for ProHance (Gadoteridol), Vasovist (Gadofosveset) and deoxyhemoglobin at 1.5, 3.0, and 7.0 Tesla. The plots of R(1) versus both contrast agent and deoxyhemoglobin concentration were linear. The plots of R2* versus deoxyhemoglobin concentration showed a quadratic dependence. R2* versus contrast agent concentration showed a parabolic dependence with a minimum occurring at contrast agent concentrations of approximately 1.5 mM, corresponding to an accessible concentration in vivo. Monte Carlo simulations were performed to support the hypothesis that the minimum results from the susceptibility of the red blood cells being matched to the susceptibility of the plasma. Relaxivity values (s(-1)mM(-1)) for R2* and R1 for all agents and all three field strengths are given.

Cochlear implantation in children with large vestibular aqueduct syndrome and a review of the syndrome.

OBJECTIVE: Children with Large Vestibular Aqueduct Syndrome (LVAS) frequently develop speech and language skills prior to deterioration of their hearing. Operations designed to halt the progression of hearing loss have largely failed so the question of Cochlear Implantation in these children has arisen. It had been suggested that there would be technical difficulties in implanting these patients and, therefore, there had been an initial reluctance to proceed to implantation. The aim of the present paper is to assess surgical and functional outcomes in implanted children with LVAS and review the related literature. MATERIAL AND METHODS: From the 170 children assessed by MRI in the Nottingham Paediatric Cochlear Implant Programme, seven (4%) were identified as having LVAS. Four of these children were implanted and had at least 12 months follow up. Two of the children are on the waiting list for implantation and one child was not implanted because of absence of the cochlear nerve. Operative findings, complications and outcome measures were recorded. The auditory skills of the children were assessed before implantation and 1 year following implantation. A literature search was done to identify other series with experience in implanting children with LVAS. RESULTS: Full insertion of the electrode array was achieved in all our cases. After cochleostomy two patients experienced a mild CSF leak that was easily controlled by the muscle graft. On the first day post-operation two patients were nauseous and one had an episode of vomiting, however, all were discharged within 24 h of surgery. Initial outcome measures at 12 months post-implantation were encouraging showing significant progress in children's auditory skills. CONCLUSIONS: The results of the present study and the review of the literature suggest that LVAS is not a contraindication to implantation as initial concerns about severe perilymph leaks and surgical complications have proved to be unfounded. The post-operative progress of these children in listening skills also suggest that these children are suitable for cochlear implantation

Magnetic resonance angiography in preoperative planning of deep inferior epigastric artery perforator flaps.

Accurate preoperative localisation of deep inferior epigastric artery perforator (DIEaP) provides optimal surgical planning for DIEaP flaps. Cross-sectional imaging by contrast-enhanced magnetic resonance angiography (CE-MRA) has advantages over previously described techniques for perforator imaging including reduced radiation exposure and better muscle to vessel contrast. A retrospective series of 10 unilateral free breast reconstructions following preoperative CE-MRA of the anterior abdominal wall is presented. Mean age of the patients at the time of surgery was 50.3 years (range 44-63 years). An average of 2.8 perforators per study (range 1-5) was identified. Mean perforator luminal diameter was 2.6mm (1.4-4.0mm) with a mean intramuscular course length of 22.3mm (6.4-51.9 mm). Perforator course length was classified as 17% long intramuscular course (>4 cm), 80% short intramuscular course (<4 cm) and 3% paramedian. In all 10 patients, DIEaP flaps were successfully elevated. In all cases the flaps were elevated on vessels identified in preoperative review of the CE-MRA. There was a significant difference in the rates of conversion from DIEaP to transverse rectus abdominis myocutaneous (TRAM) flaps in the group who underwent CE-MRA in comparison to historical controls from the previous year (P=0.025). CE-MRA is an effective tool for DIEaP flap planning.

Postirradiation aortic sarcoma demonstrated by magnetic resonance angiography.

This is the first ever reported case of a radiation-induced aortic sarcoma. This patient had symptoms and signs initially interpreted as a pulmonary embolus. The extent of the disease was demonstrated with magnetic resonance imaging and magnetic resonance angiography, in particular, allowing rapid surgical intervention.

Magnetic resonance imaging of elephantiasis neuromatosa.

We present the case of a 43-year-old man with neurofibromatosis type 1 who developed elephantiasis neuromatosa of his left leg. The gross limb enlargement was extremely disfiguring, and resulted in such severe disability that he was only able to walk a very short distance using crutches. Previous debulking procedures had resulted in massive blood loss, and prior to attempting further surgical intervention MRI studies were requested. Taking advantage of the excellent tissue characterisation and multiplanar imaging capabilities of MRI, we were able to assess the extent of soft tissue and osseous involvement. The use of recently developed MR angiographic sequences enabled us to non-invasively provide detailed images to assess the relationship of the lesions to the major vessels, as well as the vascular supply and angiographic features of the lesions themselves. This article describes our MRI-based findings, which precluded debulking surgery in this unusual manifestation of neurofibromatosis.

Magnetic resonance imaging virtual endoscopy of the labyrinth.

OBJECTIVE: To explore the feasibility of applying virtual endoscopic (VE) techniques to examine the normal anatomy of the labyrinth using magnetic resonance imaging (MRI) data. STUDY DESIGN: Feasibility study using data from a normal subject. MATERIALS AND METHODS: MRI data was acquired in a single normal subject using a three-dimensional (3D) CISS (Constructive Interference in the Steady State) sequence. Perspective volume rendering (PVR) techniques were used to produce virtual endoscopic visualization of the fluid filled structures of the inner ear. RESULTS: The reconstructive algorithms enabled generation of a "fly-through" simulation of the labyrinth. The cochlea, the oval window, the vestibule, the common crus, and the semicircular canals were successfully visualized. CONCLUSIONS: Virtual endoscopic techniques were successfully applied to MRI data enabling a 3D virtual display of the internal anatomy of the normal labyrinth.

Silent meniscal abnormalities in athletes: magnetic resonance imaging of asymptomatic competitive gymnasts.

BACKGROUND: Magnetic resonance imaging (MRI) produces exceptionally detailed images of the intra-articular structures of the knee. Recognising the range of MRI appearances within a normal population is therefore necessary in order to avoid attributing a greater significance to these than is clinically justified. OBJECTIVE: To compare MRI appearances in asymptomatic gymnasts with those in a less active population in order to identify findings that may be seen in the absence of significant pathology and thereby aid the clinical management of this athletic group. METHODS: MR images were obtained from 24 knees of asymptomatic competitive American collegiate gymnasts aged 18-22. The menisci were evaluated according to established grading criteria, and compared with a group of controls matched for age and sex. RESULTS: Grade 3 intrameniscal signal abnormalities are considered to be highly correlated with meniscal tears. When compared with control group, the experimental group of gymnasts had a significantly different distribution (p<0.001) of grade 3 intrameniscal signal changes, preferentially involving the lateral meniscus. The overall incidence of grade 3 changes (13%) in gymnasts was not, however, significantly different from the incidence in the controls. CONCLUSIONS: A knowledge of these MRI appearances is important when evaluating the lateral menisci within this group of athletes to prevent unnecessary treatment or intervention. This is particularly pertinent when the imaging findings do not closely correlate with the site of symptoms.

Endovascular repair of perisplanchnic abdominal aortic aneurysm with visceral vessel transposition.

PURPOSE: To report a combined endoluminal and open surgical approach for a suprarenal abdominal aortic aneurysm (AAA) with coexistent splanchnic vessel stenoses. METHODS AND RESULTS: A 64-year-old man presented with an aneurysm of the proximal abdominal aorta and severe stenoses of the celiac axis and superior mesenteric artery (SMA). An initial 2-stage plan to stent the visceral vessel stenoses and exclude the aneurysm with a fenestrated stent-graft failed when the celiac lesion could not be crossed. The approach was changed to restore visceral perfusion with a bifurcated left iliosplenic and ilio-SMA bypass graft. Exclusion of the aneurysm was achieved with a custom-made suprarenal aortic tube stent-graft (Ivancev-Malmö) system. The patient is free of symptoms at 22 months, and there was no aneurysm visible on the 14-month CT scan. CONCLUSIONS: Hybrid techniques are an alternative treatment for complex perivisceral aortic aneurysms when total endovascular reconstruction is not possible.

Feasibility of using dynamic contrast-enhanced magnetic resonance angiography as the sole imaging modality prior to endovascular repair of abdominal aortic aneurysms.

OBJECTIVES: to establish the feasibility of using magnetic resonance imaging (MRI) with dynamic contrast-enhanced (DCE) MRA as the sole imaging modality in the assessment of patients prior to endovascular repair of abdominal aortic aneurysms (AAAs). DESIGN: DCE MRA with MRI and helical computed tomography (CT) examinations were performed in patients being assessed for suitability for an endovascular approach to repair of their AAA. Management outcomes determined by the two techniques were compared. MATERIALS: sixteen patients with AAA. METHODS: all subjects underwent DCE MRA/MRI and helical CTA. Criteria for suitability for endovascular repair were established. The management outcomes determined by the MRI findings were compared with those obtained by CTA. RESULTS: high-quality MRA/MRI and CT images were obtained in 16 patients. Six patients were considered suitable for an endovascular approach, one was considered borderline and nine were judged unsuitable. In all cases, the overall management determined by the two methods concurred. CONCLUSIONS: comparison of the two imaging modalities resulted in agreement as to suitability for an endovascular approach. We therefore conclude that in our group the use of MRI and DCE-MRA proved effective as a sole imaging modality for the assessment of these patients.

Force of voluntary exercise does not affect sensorimotor cortex activation as detected by functional MRI at 1.5 T.

Echo-planar brain images (1.5 T, 1-shot GRE, TR/TE = 3000/45) were acquired during 30-60 s cycles of repetitive (1.3-1.7 Hz) finger flexion exercise against light (0.24) vs heavy (1.40 kg) weights. In protocols during which exercise was alternated with periods of rest, active voxels were identified in the contralateral motor and somatosensory areas by cross-correlation against an on-off waveform. However, there was no significant difference between the responses to light vs heavy weights. In a continuous repetitive exercise protocol, in which only the weights were cycled, no force-correlated voxels were identified. Inasmuch as force-correlated neurons are known to be present in the primate cortex, the results illustrate a potential limitation of functional MRI studies based on the BOLD effect.

Lip-reading ability and patterns of cortical activation studied using fMRI.

Lip-reading is a complex cognitive skill with large individual differences in performance. The basis of these individual differences remains poorly understood. Functional magnetic resonance imaging (fMRI) techniques allows brain activation accompanying complex cognitive activities to be studied noninvasively. In the present paper, fMRI was used to study the patterns of cortical activation that occur during the silent lip-reading of connected speech and to investigate whether there are detectable differences in activation between subjects with widely differing lip-reading abilities. From a cohort of 26 volunteers, nine subjects who fell into three distinct lip-reading ability groups were selected. Brain activation was measured in two conditions: an experimental condition where subjects attempted to lip-read sentences; and a baseline condition where subjects passively viewed a static image of a talker's face. Relative to the baseline condition, lip-reading induced activation in several cortical areas, including the auditory cortices, despite the lack of an auditory component to the task. In comparison to the better two groups of lip-readers, subjects in the poorest group displayed significantly less activation in superior and middle temporal gyrus, but not inferior temporal gyrus. These preliminary results justify more extensive investigations of the cortical basis of individual differences in lip-reading.

Safety and effectiveness of single- versus triple-dose gadodiamide injection- enhanced MR angiography of the abdomen: a phase III double-blind multicenter study.

PURPOSE: To evaluate the safety and effectiveness of gadodiamide-enhanced magnetic resonance (MR) angiography with single and triple doses in the assessment of abdominal arterial stenoses. MATERIALS AND METHODS: One hundred five patients were included in the randomized, double-blind, phase III multicenter trial. Results of MR angiography with 0.1 mmol/kg and 0.3 mmol/kg doses of gadodiamide were compared with those of digital subtraction angiography (DSA) and according to dose. RESULTS: No serious adverse events were observed. The mean contrast index at the region proximal to the primary stenosis was significantly higher in the triple-dose group (P =.03). Mean 95% CI values for the difference in depicted degree of stenosis between DSA and postcontrast MR angiography improved from -3.4% +/- 4.7 (SD) in the single-dose group to -1.2% +/- 4.7 in the triple-dose group. Mean values for overall image quality on the visual analogue scale improved with the triple dose (P =.02). Confidence in diagnosis was high at postcontrast MR angiography in 88% and 96% of cases in the single- and triple-dose groups, respectively. CONCLUSION: Gadodiamide-enhanced MR angiography performed with single and triple doses is safe and effective for assessing major abdominal arterial stenoses. Although high agreement between MR angiography and DSA was achieved with both doses, triple-dose MR angiography was superior in the evaluations of image quality, degree of arterial stenoses, and confidence in diagnosis.