MRI 'magic angle' imaging of finger tendons.

The value of using the technique of magic angle MR imaging to demonstrate finger tendons is explored. Images of fresh frozen cadaveric specimens are presented and the structures that can be visualized in the finger are described. The results suggest that magic angle MR imaging may be a useful non-invasive technique of visualizing the details of the tendons and their surrounds in the hand.

Systemic inflammation affects reperfusion following transient cerebral ischaemia.

Reperfusion after stroke is critical for improved patient survival and recovery and can be achieved clinically through pharmacological (recombinant tissue plasminogen activator) or physical (endovascular intervention) means. Yet these approaches remain confined to a small percentage of stroke patients, often with incomplete reperfusion, and therefore there is an urgent need to learn more about the mechanisms underlying the no-reflow phenomenon that prevents restoration of adequate microvascular perfusion. Recent evidence suggests systemic inflammation as an important contributor to no-reflow and to further investigate this here we inject interleukin 1 (IL-1) i.p. 30 min prior to an ischaemic challenge using a remote filament to occlude the middle cerebral artery (MCA) in mice. Before, during and after the injection of IL-1 and occlusion we use two-dimensional optical imaging spectroscopy to record the spatial and temporal dynamics of oxyhaemoglobin concentration in the cortical areas supplied by the MCA. Our results reveal that systemic inflammation significantly reduces oxyhaemoglobin reperfusion as early as 3h after filament removal compared to vehicle injected animals. CD41 immunohistochemistry shows a significant increase of hyper-coagulated platelets within the microvessels in the stroked cortex of the IL-1 group compared to vehicle. We also observed an increase of pathophysiological biomarkers of ischaemic damage including elevated microglial activation co-localized with interleukin 1α (IL-1α), increased blood brain barrier breakdown as shown by IgG infiltration and increased pyknotic morphological changes of cresyl violet stained neurons. These data confirm systemic inflammation as an underlying cause of no-reflow in the post-ischaemic brain and that appropriate anti-inflammatory approaches could be beneficial in treating ischaemic stroke.

Design and use of internal receiver coils for magnetic resonance imaging.

This review describes coils for MRI that are inserted into the body through natural orifices. It covers the design and implementation of small internal receiver coils for use in the pelvis and gastrointestinal tract. Normal anatomy delineated by the high resolution obtained by using these coils and the appearances in a number of disease states for each clinical application are described.

In vivo evaluation of the effects of continuous exercise on skeletal muscle triglycerides in trained humans.

Magnetic resonance spectroscopy (1H MRS) and imaging (MRI) were used to investigate the effects of a bout of moderate prolonged exercise on intra (IMCL)- and extramyocellular lipid (EMCL) utilization in the soleus, tibialis anterior, and gastrocnemius muscles of five trained human subjects. MRI and 1H MRS measurements were obtained before and after a 90 min run on a calibrated treadmill at a velocity corresponding to 64 +/- 1.5% of each subjects' maximal rate of oxygen consumption. There were significant decreases in IMCL following exercise in the tibialis (pre: 22.37 +/- 4.33 vs. post: 15.16 +/- 3.25 mmol/kg dry wt; P < 0.01) and soleus (pre: 36.93 +/- 1.45 vs. post: 29.85 +/- 2.44 mmol/kg dry wt; P < 0.01) muscles. There was also a decrease in the gastrocnemius muscle, although this did not reach the level of significance (pre: 33.78 +/- 5.35 vs. post: 28.48 +/- 5.44 mmol/kg dry weight; P < 0.10). No significant changes were observed in EMCL or subcutaneous fat. In conclusion, this study showed that IMCL were significantly utilized in the tibialis and soleus muscles of aerobically endurance-trained humans. The absence of significant utilization of IMCL in the gastrocnemius may reflect differences in fiber type and/or intensity of contraction for each muscle group.

Fast and reproducible method for the direct quantitation of adipose tissue in newborn infants.

The role of body fat content and distribution in infants is becoming an area of increasing interest, especially as perception of its function appears to be rapidly evolving. Although a number of methods are available to estimate body fat content in adults, many are of limited use in infants, especially in the context of regional distribution and internal depots. In this study we developed and implemented a whole-body magnetic resonance imaging (MRI)-based protocol that allows fast and reproducible measurements of adipose tissue content in newborn infants, with an intra-observer variability of <2.4% and an inter-observed variability of <7%. The percentage total body fat for this cohort of infants ranged from 13.3-22.6% (mean and standard deviation: 16.6 +/- 2.9%), which agrees closely with published data. Subcutaneous fat accounted for just over 89% of the total body fat, whereas internal fat corresponded to almost 11%, most of which was nonabdominal fat. There were no gender differences in total or regional body fat content. These results show that whole-body MRI can be readily applied to the study of adipose tissue content and distribution in newborn infants. Furthermore, its noninvasive nature makes it an ideal method for longitudinal and interventional studies in newborn infants.

An in vivo 13C magnetic resonance spectroscopic study of the relationship between diet and adipose tissue composition.

13C magnetic resonance spectroscopy (MRS) is a noninvasive technique used in the study of lipids. We applied 13C MRS to assess the effects of long-term dietary variation on adipose tissue composition in humans. In vivo 13C MRS was used to analyze the fatty acid composition of adipose tissue in 88 healthy volunteers with significantly different diets (38 vegans, 11 vegetarians, and 39 omnivores) assessed by analysis of dietary records. Results were compared with the serum lipid profile. 13C MRS revealed clear differences in the adipose tissue composition of vegans, which contained more unsaturated (P < 0.01) and fewer saturated fatty acids (P < 0.01) compared with omnivores and vegetarians. The vegan subjects had a significantly lower intake of saturated fatty acids and higher intake of polyunsaturated fatty acids than either the omnivore or the vegetarian groups (P < 0.01). These findings were associated with significantly lower levels of serum total cholesterol and low density lipoprotein-cholesterol in the vegan group compared with the omnivores. Our results demonstrate the use of 13C MRS for the noninvasive study of adipose tissue composition and its application to the study of the interaction between long-term dietary and metabolic risk factors in humans.

Tuned fiducial markers to identify body locations with minimal perturbation of tissue magnetization.

A fiducial marker is described in which a small cell containing a short T1 solution is surrounded by single- or quadrature-tuned windings. It is shown how these can be used to enhance small externally applied RF pulses, which do not significantly perturb the magnetization of the tissue, to excite the fiducial sample, and get substantial signals from it. The fiducials can be used to mark locations on the body unambiguously for, for example, frameless stereotaxy, and to identify coils, catheters, or other inserted devices.

Integrated and interactive position tracking and imaging of interventional tools and internal devices using small fiducial receiver coils.

A method is described of tracking the position of a rigid device within an MR scanner and imaging with the image slice position determined by the current position of the device, such that the manipulation of the device can be achieved in a robust, interactive manner. The device can be either external or internal to the patient. The position tracking is performed by means of two or three small MR receiver coils attached to individual receiver channels. Each coil contains a small sample that acts as a fiducial (MR-visible marker point). The imaging is performed by any suitable receiver coil attached to a further receive channel. This method has a large number of applications, both in the field of MR-guided procedures and in MR imaging using endocavitary coils. In particular, two devices are described, the first being a device for MR-guided biopsies and the second being one for dynamic endorectal imaging of the anal sphincter.

A solid reusable endorectal receiver coil for magnetic resonance imaging of the prostate: design, use, and comparison with an inflatable endorectal coil.

We have designed a solid endorectal receiver coil for MRI of the prostate. The coil provided an improved signal-to-noise ratio up to 5 cm from its surface when compared with a standard pelvic phased array. This preliminary report describes 16 patients who were imaged using this coil, seven of whom had been examined previously with a balloon-design endorectal coil. Patient tolerance of these coils was compared. The solid coil was easy to insert and quick to set up because it did not require external tuning and matching. It avoided uncomfortable rectal distension experienced with the balloon coil as well as susceptibility artifacts from air in the balloon. In addition, it could be sterilized and reused.

MRI of fistula-in-ano: a comparison of endoanal coil with external phased array coil techniques.

PURPOSE: The objective of our study was to compare MRI of fistulas-in-ano using an endoanal coil with that using a pelvic phased array coil and to assess the value of a combined approach by correlating the findings with those at surgery. METHOD: Twenty consecutive patients with clinical suspicion of perianal sepsis were studied using an endoanal coil immediately followed by a phased array coil. T1 weighted and STIR images in transverse and coronal planes were made with each coil and analysed by noting the presence and site of a collection and primary track, the position of any internal opening, and subcutaneous or supralevator extension. Operative findings were similarly recorded. RESULTS: Of 20 patients with suspected fistulas, 8 had simple fistulas, 8 had complex fistulas, and 4 had no current evidence of infection. The concordance between MR and surgery for identifying the presence and site of the collection, the primary track, and the internal opening in both simple and complex cases was superior using the endoanal coil as compared with the phased array. Both coils together reflected the findings of the endoanal coil used alone. However, for supralevator/subcutaneous extension, concordance was superior using the phased array compared with the endoanal coil, and a combined approach reflected the values of the phased array coil used alone. CONCLUSION: Endoanal MRI is highly sensitive in the delineation of fistulas-in-ano. In combination with phased array techniques, it provides valuable preoperative assessment in both simple and complex cases.

Magnetic resonance imaging guided breast biopsy using a frameless stereotactic technique.

The high sensitivity but poor specificity of contrast enhanced magnetic resonance (MR) imaging for delineating malignant breast lesions is increasing the demand for MR guide breast biopsy. However, the poor patient access offered by conventional MR systems makes such procedures extremely difficult. We describe a method of performing breast biopsy outside the bore of the magnet using the 3-D MR imaging data. This involves a frameless stereotactic technique using an ultrasonic localizer. The position in space of the tip of a pointer with a handle which incorporates two ultrasound emitters can be tracked using an array of ultrasound detectors. MR visible marker beads (fiducials) placed on the breast and imaged at the same time are identified to the computer in relation to images of the breast. The ultrasonic localizer is used to register the position in space of the fiducials by touching them with the tip of the pointer. The image of the lesion within the breast can then be displayed in relation to the position of the tip of the pointer and the needle approach planned. Nine women with foci of enhancement on their dynamic contrast enhanced MR images underwent frameless stereotactic breast cytology. Needle placement within 2 mm of the lesion was achieved at first pass in eight out of nine (89%) cases: in one case the needle had to be re-positioned prior to sampling. This technique provides a means of targetting MR visible lesions using the MR imaging data whilst performing the procedure outside the magnet bore.

Use of ultralong echo time imaging to assist in measuring the velocity of perfused flow in vivo.

The measurement of the velocity of perfused flow in tissue in vivo is complicated by the presence of stationary as well as moving spins and by a variety of dephasing phenomena which affect signal amplitudes. This paper describes a technique by which, using flow-sensitized spin-echo sequences with a set of very long TE times, the velocity of the moving component can be assessed.

Some considerations concerning susceptibility, longitudinal relaxation time constants and motion artifacts in vivo human spectroscopy.

Artifacts due to localized susceptibility effects, variations in the spin-lattice relaxation time constants of signals and a mixing of signals arising from tissue motions can contaminate otherwise credible results. The sources and magnitude of some of these are discussed and their likely impact assessed, so that the necessity of incorporating additional measurements in an individual study can be demonstrated.

Magnetic resonance imaging of the uterine cervix using an intravaginal coil.

Cylindrical receiver coils designed for intravaginal use were utilized to image the uterine cervix. Good quality images of the cervix, vaginal wall, and parametrium were obtained and patient tolerance of the procedure was good.

Elimination of magnetic field foldover artifacts in MR images.

Foldover artifacts arise when the same imaging frequency occurs both at a desired location within a slice and at another location within the sensitive region of the radiofrequency (RF) coil. Foldover artifacts can be caused by nonlinearity in the gradient system and by inhomogeneity in B(0). This study investigates an approach in which an extra RF receiver coil and a postprocessing method are used to identify and remove foldover artifacts.

Saturation effects in phosphorus-31 magnetic resonance spectra of the human liver.

Phosphorus-31 liver spectra were recorded from 6 controls and 12 patients with liver disease using TR values of 0.5 and 5 s and a pulse angle of 45 degrees. One of the control subjects was also examined at seven TR values ranging from 0.5 to 20 s. Spectra from one additional patient were collected at TRs of 0.5, 1, and 2 s only. There was a significant increase in the mean ratio of peak areas phosphomonoesters (PME)/beta-ATP in 9 of the 13 patients and a decrease in phosphodiesters (PDE)/beta-ATP in 3 of the patients, compared with controls, at the longer TR values. The saturation factors for PME and PDE were greater than those for Pi and beta-ATP, and spectral abnormalities in disease were often more evident as the TR value was increased from 0.5 to 5 s. Acquisition parameters need to be chosen with a knowledge of the impact that saturation effects have on metabolite quantification and spectral contrast.

MR imaging of the anal sphincter in multiparous women using an endoanal coil: correlation with in vitro anatomy and appearances in fecal incontinence.

OBJECTIVE: The aim of this study was to correlate the components of the normal female anal sphincter seen on high-resolution MR images with the in vitro anatomy and to describe the change in appearances of these components in multiparous women with fecal incontinence. SUBJECTS AND METHODS: Ten asymptomatic female volunteers (32-72 years old; mean, 54 years old) and 22 women with fecal incontinence were studied. In six patients (26-68 years old; mean, 49 years old) fecal incontinence began immediately after childbirth; in the remaining 16 patients (45-77 years old; mean, 58 years old) fecal incontinence developed 15- 30 years after childbirth. In the latter group of patients, terminal motor latencies of the pudendal nerve were measured. Imaging was done on a 0.5-T Picker Asset unit and on a 1.0-T Picker HPQ unit. A saddle geometry endoanal receiver coil was used for all imaging. T1-weighted spin-echo (720-820/20 [range of TR/TE]), T2-weighted spin-echo (2500/80 [TR/TE]), fast spin-echo (4500/96 [TR/ effective TE]), and short inversion time inversion recovery (2500/80 [TR/TE]; inversion time, 107 msec) MR images were obtained in transverse, coronal oblique, and sagittal planes. Images were assessed for integrity of the sphincter components. A nonpaired separate-variance t test was used to compare thickness of individual muscle components between patients with delayed-onset fecal incontinence and asymptomatic age-matched volunteers. Degree of muscle atrophy was correlated with degree of delay in the terminal motor latency of the pudendal nerve. RESULTS: The high resolution obtained with an endoanal coil allowed differentiation of the various muscle components of the anal sphincter complex. The internal sphincter was seen as a ring of homogeneously high signal intensity with a low-signal-intensity rim that was rich in collagen and contained neurovascular bundles. The external anal sphincter, which had low signal intensity on T1- and T2-weighted images, was shown as three components: subcutaneous, superficial, and deep. In six patients who had fecal incontinence that began immediately after childbirth, endoanal MR imaging revealed the site and extent of a tear. All tears were confirmed at surgery. In the 16 patients who had fecal incontinence that began several years after childbirth, atrophy of the external sphincter was revealed in all cases in the superficial and deep components. The internal sphincter remained normal. However, we found that the degree of atrophy of individual components of the external sphincter did not correlate with the degree of delay in pudendal nerve conduction. CONCLUSION: MR imaging with an endoanal coil reveals the integrity and bulk of individual muscle components of the anal sphincter in multiparous women with fecal incontinence.

Intracellular pH measurements of the whole head and the basal ganglia in chronic liver disease: a phosphorus-31 MR spectroscopy study.

The purpose of this study was to determine the intracellular pH of the whole head and in voxels localized to the basal ganglia in patients with chronic liver disease using phosphorus-31 magnetic resonance spectroscopy (31P MRS). The study group compromised 82 patients with biopsy-proven cirrhosis (43 Child's grade A, 25 Child's grade B and 14 Child's grade C). Eleven subjects showed no evidence of neuropsychiatric impairment on clinical, psychometric and electrophysiological testing, 37 showed evidence of minimal hepatic encephalopathy and 34 had overt hepatic encephalopathy. Unlocalized 31P MRS of the whole head was performed in 48 patients and 10 healthy volunteers. Localized 31P MRS of the basal ganglia was performed in the 34 patients and in 20 healthy volunteers. The intracellular pH values were calculated from the chemical shift difference between the inorganic phosphate (P) and phosphocreatine (PCr) resonances. The percentage inorganic phosphate (%Pi), phosphocreatine (%PCr) and betaNTP signals, relative to the total 31P signal, and peak area ratios of inorganic phosphate and phosphocreatine, relative to betaNTP were also measured. There were no differences between patients and volunteers in intracellular pH in 31P MR spectra measured from the whole head or the basal ganglia. There was no correlation between the severity of encephalopathy (West Haven criteria) or liver dysfunction (Child score) and intracellular pH values. There was also no significant change in the inorganic phosphate, phosphocreatine or betaNTP resonances in spectra acquired from the whole head. However, in spectra localized to the basal ganglia, there was a significant increase in mean P/NTP (p=0.02) and PCr/NTP (p=0.009). The mean %Pi and mean %PCr were also increased (p=0.06; p=0.05, respectively), but there was no significant change in mean %betaNTP. When the patient population was classified according to the severity of encephalopathy, those with overt disease had a higher mean P/NTP and %Pi (p=0.03; p=0.01), compared to the reference population. Our results suggest that there are detectable bioenergetic abnormalities in patients with minimal hepatic encephalopathy or stable, overt chronic hepatic encephalopathy, but any associated intracellular pH change is probably a secondary, rather than a primary phenomenon.