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.

Use of multicoil arrays for separation of signal from multiple slices simultaneously excited

Increased acquisition efficiency has been achieved by exciting several slices simultaneously. The mixed data were unfolded to produce separate slices using the spatial encoding information inherent in a multicoil receiver system. Each coil yields a linear combination of signals from all excited slices weighted by the sensitivity of each coil. A matrix inversion provides a solution to unfold these images.

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.

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.

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.

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.

Pre-polarized saline: an in vivo feasibility study of a potential contrast agent

The potential for using pre-polarized liquids as contrast agents in vivo is investigated and the feasibility of the method demonstrated. In this study we show the enhancement obtained following intravenous delivery of pre-polarized saline into the antecubital vein of a volunteer. This form of contrast agent provides signal gain on time scales commensurate with its T(1) and allows repeated doses to be administered, thus making alternate acquisitions of data with and without enhancement practicable.

Twisted-pair RF coil suitable for locating the track of a catheter

An RF coil, made by twisting a conventional wire loop, was tuned to form an extended sensor to provide an effective method of showing the track of a catheter. A twisted-pair coil can be made small enough in diameter to pass through needles in common clinical use. The coil has a very small field of view and in transmit/receive operation has minimal effect on the magnetization of the surrounding tissue.

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.

Fecal incontinence in scleroderma: assessment of the anal sphincter with thin-section endoanal MR imaging

PURPOSE

To compare the magnetic resonance (MR) imaging appearance of the anal sphincter in patients with fecal incontinence and scleroderma with that in patients with fecal incontinence alone, scleroderma alone, or neither.

MATERIALS AND METHODS

The study population comprised 14 patients with fecal incontinence and scleroderma, four with scleroderma alone, 13 with incontinence alone, and six with neither. T1- and T2-weighted spin-echo, magnetization transfer contrast-weighted, and dynamic gadolinium-enhanced images were obtained and analyzed for the integrity, thickness, and length of sphincter components. Magnetization transfer contrast ratios and T2 were calculated to assess fibrosis of the internal sphincter. The percentage enhancement above baseline was calculated at 30-second intervals for the internal and the external sphincter.

RESULTS

Eleven patients with incontinence and scleroderma showed descent of rectal air and feces into the anterior anal canal, with forward deviation of the significantly (P < .05) atrophied internal sphincter, which showed a slower gadolinium-enhancement pattern compared with that in other groups. Patients with incontinence alone showed no evidence of internal sphincter deviation or altered vascularity but had a significant reduction (P < .05) in deep external sphincter bulk.

CONCLUSION

In patients with fecal incontinence and scleroderma, endoanal MR imaging helps delineate the anterior sphincter deformity and shows the slower gadolinium-enhancement pattern on dynamic studies of the internal sphincter.

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.

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.

Laser ablation of the endometrium: MR appearance during and after treatment and the relation of MR appearance to clinical outcome

OBJECTIVE

Our objective was to study the appearance of the uterus on MR images obtained during and 3 months after laser ablation of the endometrium and to determine if a correlation exists between the MR imaging findings and the subsequent clinical outcome. The appearance could then be used to guide the application of laser energy during the procedure to optimize the clinical result.

SUBJECTS AND METHODS

Eight women 34-55 years old (mean, 42 years old) with symptoms of heavy, painful menses underwent laser ablation under epidural anesthesia. Imaging was done on a 0.5-T Picker Asset system with a pelvic phased-array receiver coil using conventional T1-weighted spin-echo, T2-weighted spin-echo, and gradient-recalled-echo sequences. Images were obtained preoperatively, after ablation of the anterior surface, after completion of the procedure, and 3 months later. Images were visually assessed for signal intensity changes in the endometrium and myometrium by two observers in conference. Images were quantitatively analyzed by measuring uterine volume and the width of the endometrium, junctional zone (JZ), and outer myometrium (OM) on the T2-weighted images. Preoperative and 3-month postoperative symptom scores including duration, amount of bleeding, and associated pain were recorded.

RESULTS

MR images obtained immediately after treatment showed an increase in the volume of the uterus (mean, 21%). Endometrial thickness increased in five patients, and the JZ:OM ratio increased on the T2-weighted scans in six patients. The increase in the ratio probably represented myometrial edema. Two patients with persistent symptoms were treated with hysterectomy 6 weeks postoperatively. Of the remaining six patients, five showed an improvement in symptom scores after 3 months. The uterus returned to its preoperative size after 3 months in three patients, endometrial thinning was noted in two, and the JZ:OM ratio remained increased in two. The difference between the mean improvement in symptom scores at 3 months was significant in the patients with and without the endometrial swelling seen immediately after treatment. No statistically significant correlation existed between the amount of perioperative uterine swelling or the increase in JZ:OM ratio and the improvement in symptom scores at 3 months.

CONCLUSION

On laser ablation of the endometrium, MR imaging showed significant immediate uterine swelling as well as an increase in the endometrial thickness and JZ:OM ratio. The presence of immediate endometrial swelling and the reduction in the JZ:OM ratio after 3 months correlated with a subsequent improvement in symptom scores. Perioperative endometrial swelling rather than myometrial changes is therefore an indicator of clinical outcome.

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.

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.

Hepatic phosphorus-31 magnetic resonance spectroscopy in primary biliary cirrhosis and its relation to prognostic models

BACKGROUND

In vivo hepatic phosphorus-31 magnetic resonance spectroscopy (31P MRS) provides biochemical information about phosphorus metabolism.

AIM

To assess 31P MRS as a prognostic marker in patients with primary biliary cirrhosis (PBC) in relation to the current clinical prognostic models.

PATIENTS AND METHODS

Twenty three patients with PBC of varying functional severity and 16 matched healthy volunteers were studied using in vivo 31P MRS. Spectra were acquired using a 1.5 T spectroscopy system. Peak area ratios of phosphomonoesters (PME), inorganic phosphate (Pi), and phosphodiesters (PDE) and nucleotide triphosphate (NTP) were calculated. Pugh score, Christensen prognostic index, and R value according to the Mayo model were calculated from the clinical data.

RESULTS

The PME/NTP, Pi/NTP, PME/PDE, and PME/Pi ratios and the PME signal height ratio (SHR) were significantly higher, while the PDE/NTP and PDE/SHR were significantly lower in PBC patients compared with healthy volunteers (p < 0.01). Significant correlations were seen between PME/Pi ratio and the prognostic index according to Christensen (r = 0.63, p < 0.001), R value according to the Mayo model (r = 0.45, p < 0.03), and with the Pugh score (r = 0.55, p < 0.007).

CONCLUSIONS

This study shows that PME/Pi ratio obtained from 31P MRS correlates well with all three of the commonly used models of prognosis in patients with PBC. A longitudinal study with larger number of patients is required to confirm these findings and elucidate the biochemical changes underlying this phenomenon.

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.

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.

MR-guided biopsy of the breast after lumpectomy and radiation therapy using two methods of immobilization in the lateral decubitus position

We describe two methods of breast immobilization using the lateral decubitus position to increase patient comfort and access to the axillary tail for MR-guided biopsy in the postsurgical or irradiated breast. The first method uses a compression device with good immobilization but poor patient tolerance. The second approach uses a thermoplastic mesh material to form a rigid exoskeleton around the breast: immobilization is adequate and patient acceptability is good. The latter method is preferred and requires formal evaluation in larger scale trials.

Endoscopic laser ablation of the prostate: MR appearances during and after treatment and their relation to clinical outcome

OBJECTIVE

Endoscopic laser ablation is a new treatment for benign prostatic hypertrophy. The objectives of this study were to determine the appearances of the prostate on MR images obtained during, 1 week after, and 3 months after this procedure and to determine if a correlation exists between the MR findings and the clinical outcome. Such appearances could then be used to guide the application of laser energy during the procedure in order to optimize the clinical result.

SUBJECTS AND METHODS

Eight consecutive men 58-74 years old with symptoms of bladder outflow obstruction caused by benign prostatic hypertrophy underwent endoscopic laser ablation of the prostate under spinal or epidural anaesthesia. Imaging was done on a 0.5-T Picker Asset system with an endorectal receiver coil and conventional T1-weighted spin-echo, T2-weighted spin-echo, and gradient-recalled-echo sequences. T1-weighted magnetization transfer images were obtained in three patients. Images were obtained preoperatively, after ablation of the left-sided quadrants, immediately after completion of the procedure, and 1 week and 3 months later. Preoperative and 3-month postoperative symptom scores, peak urine flow rates, and bladder residual volumes were studied. Images were visually assessed for signal-intensity changes and the presence of cavitation by three radiologists in conference. The results were quantitatively analyzed by measuring prostatic volumes on the gradient-recalled-echo images and by measuring the width and area of regions of signal-intensity change on the T2-weighted images.

RESULTS

MR images made immediately after treatment showed an increase in the volume of the prostate (mean, 34%) and a poorly defined, low-signal-intensity region around the urethra on the T2-weighted images in six patients. This probably represented coagulative necrosis. The prostate was smaller on MR images made 1 week after treatment, and after 3 months the prostate returned to its preoperative size. After 1 week, the low-signal-intensity periurethral region on the T2-weighted images was less obvious, and at 3 months it was replaced in four patients by a well-demarcated low-signal-intensity ring on the T2-weighted and gradient-recalled-echo images. No evidence of cavity formation in the prostate was seen on MR images in any patient. Symptom scores and peak urinary flow rates improved after 3 months, with a significant difference between the mean increase in symptom scores in the patients with and without the periurethral changes seen immediately after treatment. However, we found no significant difference between the mean increase in peak urinary flow rates in the patients with and without periurethral changes seen either immediately or at 3 months after treatment. No statistically significant correlation was found between the amount of prostatic swelling and the improvement in symptom scores or peak urine flow rates.

CONCLUSION

In patients who have had laser prostatectomy, MR imaging shows significant immediate glandular swelling, which may account for the delayed improvement in symptoms reported with this technique. The presence of the periurethral changes immediately after treatment was correlated with a subsequent improvement in symptom scores. After 3 months, no cavity could be seen in the prostate. This may account for the poorer long-term clinical outcome reported with endoscopic laser ablation of the prostate compared with transurethral prostatectomy.

Effect of functional grade and etiology on in vivo hepatic phosphorus-31 magnetic resonance spectroscopy in cirrhosis: biochemical basis of spectral appearances

Hepatic phosphorus-31 magnetic resonance spectroscopy (31P MRS) was undertaken in 85 patients with histologically proven cirrhosis of varying etiologies and functional severity. Reference data were acquired from 16 healthy volunteers who had no history or evidence of liver disease or alcohol abuse. In vivo hepatic 31P MR spectra were acquired with pulse angle 45 degrees and repetition times (TR) of 5 and 0.5 seconds. Peak area ratios of phosphomonoesters (PME), inorganic phosphate (Pi), and phosphodiesters (PDE) relative to beta ATP, and of PME relative to PDE were calculated from spectra acquired at TR 5 seconds. Estimates of saturation effects for individual resonances were obtained by dividing the peak height at TR 5 seconds by that at TR 0.5 seconds to yield a T1-related signal height ratio (SHR). When compared with reference values, the patients with liver disease showed a significantly higher PME/ATP (P < .0001), PME/PDE (P < .0001), PME SHR (P < .001), and Pi SHR (P < .02), and a lower PDE/ATP (P < .001) and PDE SHR (P < .001). The magnitude of these changes increased significantly and progressively with increasing functional impairment. In patients with compensated cirrhosis spectral appearances varied with etiology; thus, patients with postviral cirrhosis showed a significantly higher Pi/ATP; those with alcoholic cirrhosis, a significantly lower PDE/ATP; and those with cirrhosis secondary to primary sclerosing cholangitis, a significantly lower Pi/ATP than the healthy volunteers or other etiological groups. However, spectral appearances did not vary with etiology in patients with decompensated disease. In vitro 31P MRS of perchloric extracts of samples of liver tissue obtained from 10 patients with cirrhosis at transplant hepatectomy showed increases in levels of the soluble PME metabolites, phosphorylcholine and phosphorylethanolamine, and reductions in the levels of the soluble PDE metabolites, glycerophosphorylcholine and glycerophosphorylethanolamine. These changes suggest regenerative activity in cirrhotic livers. The increases in soluble phosphomonoesters in the aqueous extracts accounted for the increased PME/ATP ratio seen in the in vivo spectra, and might account for the increase in PME SHR. The reduction in soluble phosphodiesters in the aqueous extracts did not entirely account for the reduction PDE/ATP ratio seen in vivo.(ABSTRACT TRUNCATED AT 400 WORDS)

Effect of functional grade and etiology on in vivo hepatic phosphorus-31 magnetic resonance spectroscopy in cirrhosis: biochemical basis of spectral appearances

Hepatic phosphorus-31 magnetic resonance spectroscopy (31P MRS) was undertaken in 85 patients with histologically proven cirrhosis of varying etiologies and functional severity. Reference data were acquired from 16 healthy volunteers who had no history or evidence of liver disease or alcohol abuse. In vivo hepatic 31P MR spectra were acquired with pulse angle 45 degrees and repetition times (TR) of 5 and 0.5 seconds. Peak area ratios of phosphomonoesters (PME), inorganic phosphate (Pi), and phosphodiesters (PDE) relative to beta ATP, and of PME relative to PDE were calculated from spectra acquired at TR 5 seconds. Estimates of saturation effects for individual resonances were obtained by dividing the peak height at TR 5 seconds by that at TR 0.5 seconds to yield a T1-related signal height ratio (SHR). When compared with reference values, the patients with liver disease showed a significantly higher PME/ATP (P < .0001), PME/PDE (P < .0001), PME SHR (P < .001), and Pi SHR (P < .02), and a lower PDE/ATP (P < .001) and PDE SHR (P < .001). The magnitude of these changes increased significantly and progressively with increasing functional impairment. In patients with compensated cirrhosis spectral appearances varied with etiology; thus, patients with postviral cirrhosis showed a significantly higher Pi/ATP; those with alcoholic cirrhosis, a significantly lower PDE/ATP; and those with cirrhosis secondary to primary sclerosing cholangitis, a significantly lower Pi/ATP than the healthy volunteers or other etiological groups. However, spectral appearances did not vary with etiology in patients with decompensated disease. In vitro 31P MRS of perchloric extracts of samples of liver tissue obtained from 10 patients with cirrhosis at transplant hepatectomy showed increases in levels of the soluble PME metabolites, phosphorylcholine and phosphorylethanolamine, and reductions in the levels of the soluble PDE metabolites, glycerophosphorylcholine and glycerophosphorylethanolamine. These changes suggest regenerative activity in cirrhotic livers. The increases in soluble phosphomonoesters in the aqueous extracts accounted for the increased PME/ATP ratio seen in the in vivo spectra, and might account for the increase in PME SHR. The reduction in soluble phosphodiesters in the aqueous extracts did not entirely account for the reduction PDE/ATP ratio seen in vivo.(ABSTRACT TRUNCATED AT 400 WORDS)

Detection of propan-1,2-diol in neonatal brain by in vivo proton magnetic resonance spectroscopy

Cerebral in vivo proton magnetic resonance spectroscopy of 13 newborn infants displaying seizures and receiving phenobarbitone, in one case supplemented by phenytoin, showed signals from propan-1,2-diol (the injection vehicle for both these anticonvulsants). Subsequent in vitro spectroscopy of cerebro spinal fluid (CSF) from one of these infants also showed signals from this substance. The estimated in vivo propan-1,2-diol concentration (approximately 3 mM) was less than that measured in the CSF sample (14.4 mM). These observations suggest that propan-1,2-diol may accumulate in cerebral tissue and misidentification of its signals in both in vivo and in vitro proton spectra may confuse diagnoses of metabolic or other disorders.

Cerebral phosphorus-31 magnetic resonance spectroscopy in patients with chronic hepatic encephalopathy

Cerebral phosphorus-31 magnetic resonance spectroscopy was undertaken in 33 patients with biopsy-proven cirrhosis: 6 had no evidence of neuropsychiatric impairment on standard clinical, psychometric and electrophysiological testing; 8 had evidence of subclinical hepatic encephalopathy; and 19 were classified as having overt hepatic encephalopathy. The reference population comprised 15 healthy volunteers. Unlocalized spectra were acquired from the entire head with a 45-degree pulse angle and repetition times of 1 and 5 sec. Spectra localized to the basal ganglia were acquired with a 45-degree pulse angle and a repetition time of 1 sec. Peak area ratios of phosphomonoesters, inorganic phosphate, phosphodiesters and phosphocreatine relative to beta-ATP were measured in the spectra acquired. We noted no consistent change in the ratios of inorganic phosphate to ATP and phosphocreatine to ATP. Mean values of the ratios of phosphomonoesters to ATP and phosphodiesters to ATP were significantly lower in the total patient population than in the reference population, and they correlated with the patients' neuropsychiatric status. Thus we found no significant reductions in the mean ratios of phosphomonoesters to ATP and phosphodiesters to ATP in patients who were neuropsychiatrically unimpaired, but significant reductions were observed in the mean ratios of phosphomonoesters to ATP and phosphodiesters to ATP in patients with both subclinical and overt hepatic encephalopathy. The most marked reductions in these metabolite ratios were observed in patients with overt encephalopathy.

In vivo fluorine-19 magnetic resonance spectroscopy of cerebral halothane in postoperative patients: preliminary results

This study reports the use of 19F MRS to study halothane in the brain of eight patients recovering from halothane anesthesia of short duration. Resonances attributable to halothane were observed up to 90 min after withdrawal of the anesthetic agent. The signal-to-noise ratio for an unlocalized spectrum acquired using a 6 cm surface coil was typically 20 with data collection times of 2 min. In seven patients a single resonance was seen with a mean (+/- SD) chemical shift of +43.3 (+/- 1.8) ppm, referenced to NaF at 0 ppm. This resonance exhibited a T1 value of between 0.5 and 1 s, and a T2* (estimated from the linewidth of the resonance) between 3.5 and 10 ms. In one patient two resonances were observed with chemical shifts of +38 and +41 ppm. Because we cannot exclude the possibility that this was due to field inhomogeneity, the significance of the last finding is uncertain. However, phantom studies show that the chemical shift of halothane in different environments (such as water, olive oil, methanol, and lecithin) can vary to an extent that accounts for the two resonances seen in our patient. These results demonstrate the feasibility of in vivo 19F MRS studies of fluorinated volatile agents in humans. The potential for clinical 19F MRS of fluorinated anesthetics is discussed.

Effects of fish oil on phospholipid metabolism in human and rat liver studied by 31P NMR spectroscopy in vivo and in vitro

The effect of omega 3 fatty acids on the metabolism of the normal liver was studied using 31P NMR spectroscopy. Human subjects were examined before and after 1, 3 and 7 days of supplementation with 50 mL fish oil per day (12 g omega 3 fatty acids). 31P NMR spectra (1.6 T) revealed a significant increase in phosphodiester (PDE) to ATP ratios after 1 and 3 days of fish oil. After 7 days, [PDE]/[ATP] ratios at a TR of 1 s had returned to baseline levels, but [PDE]/[ATP] at a TR of 5 s appeared to remain high. Rats were fed diets containing 50% of the energy from fish oil or normal rat chow (controls) for 14 days. 31P NMR liver spectra in vivo (4.7 T) confirmed increased [PDE]/[ATP] in rats fed fish oil compared to controls, although the difference was only statistically significant at a TR of 1.5 s but not at a TR of 8 s. 31P NMR spectra of rat liver extracts (8.7 T) suggested that increased concentrations of glycerophosphocholine and possibly glycerophosphoethanolamine were responsible for rising PDE levels in vivo. Phosphocholine (PC) concentrations were markedly reduced in rat liver after fish oil. The combined rise in glycerophosphocholine and reduction in PC would be consistent with a shift from the phospholipase C to the phospholipase A1/A2 pathway of phosphatidylcholine breakdown after fish oil consumption.

Effect of L-alanine infusion on 31P nuclear magnetic resonance spectra of normal human liver: towards biochemical pathology in vivo

1. 31P n.m.r. spectroscopy in vivo was used to study the effect of L-alanine infusion on the concentrations of gluconeogenic intermediates in normal human liver. Studies were performed in six healthy male subjects (34-44 years, fasted overnight) using a chemical shift imaging pulse sequence on a whole-body n.m.r. system operating at 1.6T. Hepatic 31P n.m.r. spectra were obtained from 10 min before to 70 min after intravenous administration of 0.70 (n = 2), 1.40 (n = 3) or 2.80 (n = 5) nmol of L-alanine/kg body weight over 4.5 min. Concentrations of phosphomonoesters, Pi and phosphodiesters relative to ATP were calculated from peak areas in the n.m.r. spectra, using the beta-ATP peak as a reference. 2. Dose-dependent spectral changes were observed for [phosphomonoesters]/[ATP] and [Pi]/[ATP]. At the highest dose given, maximal changes in [phosphomonoesters]/[ATP] (mean +/- SEM: 98 +/- 12%, P < 0.005) and [Pi]/[ATP] (-33 +/- 3%, P < 0.001) were observed approximately 45 min after the L-alanine infusion. [Phosphodiesters]/[ATP] showed a maximal increase of 24 +/- 6% (P < 0.05), which was independent of the L-alanine dose. Hepatic ATP levels and pH did not change. 3. To identify the metabolites responsible for the changes observed in vivo, male Wistar rats were infused with 11.2 mmol of L-alanine/kg body weight. After 15 min, livers were freeze-clamped and were extracted according to standard procedures. In vitro, 31P n.m.r. spectra obtained at 8.4 or 11.7 T revealed sharp increases in the concentrations of 3-phosphoglycerate and phosphoenolpyruvate after L-alanine infusion.(ABSTRACT TRUNCATED AT 250 WORDS)

Proton MR spectroscopy of the brain in AIDS dementia complex

Proton MR spectroscopy of the brain has been undertaken in 8 healthy volunteers and in 11 patients with human immunodeficiency virus infection and varying stages of AIDS dementia complex (ADC). Spectral appearances in patients with no ADC or early ADC were not significantly different from normal volunteers. Spectra from patients with moderate to severe ADC exhibited significant reductions in levels of N-acetyl aspartate (NAA) relative to creatine (Cr) and also showed elevations in choline containing compounds (relative to Cr). Because NAA is though to be a metabolic marker for normally functioning neurons, these findings suggest the presence of neuronal injury or loss in moderate to severe ADC. The significance of these findings is discussed.

Phosphorus-31 magnetic resonance spectroscopy of the human liver using chemical shift imaging techniques

Phosphorus-31 magnetic resonance spectroscopy of the human liver was undertaken in 28 healthy adult individuals and in 49 patients with liver disease of varying aetiology. Data localised to the liver were obtained using chemical shift imaging techniques. The mean (+/- 1 S.D.) of the peak area ratio phosphomonoesters (PME)/phosphodiesters (PDE) in healthy adult individuals, from spectra obtained with pulse angle 45 degrees and repetition time 1 s, was 0.24 +/- 0.07. The intra-examination variability of this ratio was 20%, the intra-subject variability 27% and the inter-subject variability 32%. An increase in the PME/PDE was observed in the 31P hepatic MR spectrum from primary or secondary tumours in all 17 patients studied, which invariably represented an increase in PME/ATP and, in some cases, a reduction in PDE/ATP. The spectra did not show aetiological characteristics. A non-specific elevation in PME/PDE was also observed in the 31P hepatic MR spectra of 10 (40%) of 25 patients studied who had diffuse liver diseases, such as cirrhosis and infiltrating malignancies. The spectral pattern did not distinguish between diseases of varying aetiologies, but there was a linear correlation between increasing PME/PDE and a reduction in plasma albumin concentrations (p = 0.03). In three patients with hepatic malignancy and abnormal hepatic 31P-MRS, marked spectral changes were observed after successful treatment to debulk the tumour. Only minor changes were observed in the abnormal spectrum of a fourth patient in whom treatment was unsuccessful. Hepatic 31P-MR spectroscopy may prove useful for monitoring disease processes and treatment effects in well characterised patient populations.

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.

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.

Proton MR spectroscopy in herpes simplex encephalitis: assessment of neuronal loss

We present here the case of an 11-year-old boy with herpes simplex encephalitis diagnosed on the basis of clinical features, serology, and response to acyclovir, who relapsed after 3 weeks of therapy. In vivo proton magnetic resonance spectroscopy (1H MRS) of the brain, at 8 and 16 weeks after the onset of symptoms, showed abnormalities, most prominently a reduction in the N-acetylaspartate/choline ratio. The role of 1H MRS in assessing disease activity is discussed.

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.