Line scan diffusion tensor MRI of the cervical spinal cord in preterm infants

Line scan diffusion tensor magenetic resonance imaging (DT-MRI) of the cervical spinal cord was demonstrated in vivo for unsedated preterm (gestational age 24-30 weeks at birth), very low birthweight (birthweight 620-1300 g) infants at postmenstrual ages from 29-40 weeks. Scalar invariant measures of diffusion [apparent diffusion coefficient (ADC) and relative anisotropy (RA)] determined from a cervical cord region of interest in each case are reported, characterizing the maturational status of the normal third trimester and newborn spinal cord. Mean ADC of 11 infants was 1.2 +/- 0.1 microm(2)/msec and the mean RA was 24.3 +/- 4.9%. Normal infant cord neural fiber tract morphology was visualized using a mapping of the predominant diffusion tensor eigenvector. Potential clinical applications of line scan DT-MRI of the spinal cord of preterm and term newborns for assessment of spinal cord injury are discussed. J. Magn. Reson. Imaging 2001;13:949-953.

A functional magnetic resonance imaging study of auditory mismatch in schizophrenia

OBJECTIVE

Previous research has noted functional and structural temporal lobe abnormalities in schizophrenia that relate to symptoms such as auditory hallucinations and thought disorder. The goal of the study was to determine whether the functional abnormalities are present in schizophrenia at early stages of auditory processing.

METHOD

Functional magnetic resonance imaging activity was examined during the presentation of the mismatch stimuli, which are deviant tones embedded in a series of standard tones. The mismatch stimuli are used to elicit the mismatch negativity, an early auditory event-related potential. Ten patients with schizophrenia and 10 comparison subjects were presented the mismatch stimuli condition and a control condition in which only one tone was presented repeatedly.

RESULTS

The superior temporal gyrus showed the most prevalent and consistent activation. The superior temporal gyrus showed less activation in the schizophrenic subjects than in the comparison subjects only during the mismatch stimuli condition.

CONCLUSIONS

This result is consistent with those of mismatch negativity event-related potential studies and suggests that early auditory processing is abnormal in chronic schizophrenia.

Normal Brain and Brain Tumor: Multicomponent Apparent Diffusion Coefficient Line Scan Imaging

Magnetic resonance line scan diffusion imaging of the brain, with diffusion weighting between 5 and 5,000 sec/mm(2), was performed in healthy subjects and patients with a 1.5-T machine. For each voxel, biexponential signal decay fits produced two apparent diffusion constants and respective signal amplitudes. Images based on these parameters show potential for use in the differentiation of gray and white matter, edema, and tumor.

Three-dimensional magnetic resonance imaging of fetal brains

We assessed ten prenatal magnetic resonance imaging(MRI) scans for fetal brain anomalies, and identified eight that were suitable for post-processing. Anatomical abnormalities were assessed on three-dimensional (3D) models and compared with two-dimensional (2D) imaging. We calculated the volumes of the intracranial ventricles and of a periventricular haemorrhage. In three cases, additional clinical information was obtained. 3D modelling of the brain in-utero is possible and can be used to plan treatment.

Prefrontal gray matter volume reduction in first episode schizophrenia

Functional measures have consistently shown prefrontal abnormalities in schizophrenia. However, structural magnetic resonance imaging (MRI) findings of prefrontal volume reduction have been less consistent. In this study, we evaluated prefrontal gray matter volume in first episode (first hospitalized) patients diagnosed with schizophrenia, compared with first episode patients diagnosed with affective psychosis and normal comparison subjects, to determine the presence in and specificity of prefrontal abnormalities to schizophrenia. Prefrontal gray and white matter volumes were measured from first episode patients with schizophrenia (n = 17), and from gender and parental socio-economic status-matched subjects with affective (mainly manic) psychosis (n = 17) and normal comparison subjects (n = 17), age-matched within a narrow age range (18--29 years). Total (left and right) prefrontal gray matter volume was significantly reduced in first episode schizophrenia compared with first episode affective psychosis and comparison subjects. Follow-up analyses indicated significant left prefrontal gray matter volume reduction and trend level reduction on the right. Schizophrenia patients showed 9.2% reduction on the left and 7.7% reduction on the right compared with comparison subjects. White matter volumes did not differ among groups. These data suggest that prefrontal cortical gray matter volume reduction is selectively present at first hospitalization in schizophrenia but not affective psychosis.

Serial intraoperative magnetic resonance imaging of brain shift

OBJECTIVE

A major shortcoming of image-guided navigational systems is the use of preoperatively acquired image data, which does not account for intraoperative changes in brain morphology. The occurrence of these surgically induced volumetric deformations ("brain shift") has been well established. Maximal measurements for surface and midline shifts have been reported. There has been no detailed analysis, however, of the changes that occur during surgery. The use of intraoperative magnetic resonance imaging provides a unique opportunity to obtain serial image data and characterize the time course of brain deformations during surgery.

METHODS

The vertically open intraoperative magnetic resonance imaging system (SignaSP, 0.5 T; GE Medical Systems, Milwaukee, WI) permits access to the surgical field and allows multiple intraoperative image updates without the need to move the patient. We developed volumetric display software (the 3D Slicer) that allows quantitative analysis of the degree and direction of brain shift. For 25 patients, four or more intraoperative volumetric image acquisitions were extensively evaluated.

RESULTS

Serial acquisitions allow comprehensive sequential descriptions of the direction and magnitude of intraoperative deformations. Brain shift occurs at various surgical stages and in different regions. Surface shift occurs throughout surgery and is mainly attributable to gravity. Subsurface shift occurs during resection and involves collapse of the resection cavity and intraparenchymal changes that are difficult to model.

CONCLUSION

Brain shift is a continuous dynamic process that evolves differently in distinct brain regions. Therefore, only serial imaging or continuous data acquisition can provide consistently accurate image guidance. Furthermore, only serial intraoperative magnetic resonance imaging provides an accurate basis for the computational analysis of brain deformations, which might lead to an understanding and eventual simulation of brain shift for intraoperative guidance.

MR imaging-guided focused ultrasound surgery of fibroadenomas in the breast: a feasibility study

PURPOSE

To test the feasibility of noninvasive magnetic resonance (MR) imaging-guided focused ultrasound surgery (FUS) of benign fibroadenomas in the breast.

MATERIALS AND METHODS

Eleven fibroadenomas in nine patients under local anesthesia were treated with MR imaging-guided FUS. Based on a T2-weighted definition of target volumes, sequential sonications were delivered to treat the entire target. Temperature-sensitive phase-difference-based MR imaging was performed during each sonication to monitor focus localization and tissue temperature changes. After the procedure, T2-weighted and contrast material-enhanced T1-weighted MR imaging were performed to evaluate immediate and long-term effects.

RESULTS

Thermal imaging sequences were improved over the treatment period, with 82% (279 of 342) of the hot spots visible in the last seven treatments. The MR imager was used to measure temperature elevation (12.8 degrees -49.9 degrees C) from these treatments. Eight of the 11 lesions treated demonstrated complete or partial lack of contrast material uptake on posttherapy T1-weighted images. Three lesions showed no marked decrease of contrast material uptake. This lack of effective treatment was most likely due to a lower acoustic power and/or patient movement that caused misregistration. No adverse effects were detected, except for one case of transient edema in the pectoralis muscle 2 days after therapy.

CONCLUSION

MR imaging-guided FUS can be performed to noninvasively coagulate benign breast fibroadenomas.

Microstructural brain development after perinatal cerebral white matter injury assessed by diffusion tensor magnetic resonance imaging

OBJECTIVE

Brain injury in premature infants is characterized predominantly by perinatally acquired lesions in the cerebral white matter (WM). The impact of such injury on the subsequent development of cerebral WM is not clear. This study uses diffusion tensor magnetic resonance imaging (MRI) to evaluate the effects of cerebral WM injury on subsequent microstructural brain development in different WM areas of the brain.

METHODS

Twenty premature infants (gestational age: 29.1 +/- 1.9 weeks) were studied by conventional MRI within the first 3 weeks of life and again at term, with the addition at the latter time of diffusion tensor MRI. Ten of the preterm infants had cerebral WM injury identified by the early MRI and were matched with 10 premature infants of similar gestational age and neonatal course but with normal neonatal MRI scans. Diffusion tensor MRI at term was acquired in coronal and axial planes and used to determine the apparent diffusion coefficient, a measure of overall restriction to water diffusion, and the relative anisotropy (RA), a measure of preferred directionality of diffusion, in central WM, anterior frontal WM, occipital WM, temporal WM, and the posterior limb of the internal capsule. Diffusion vector maps were generated from the diffusion tensor analysis to define the microstructural architecture of the cerebral WM regions.

RESULTS

At term, the diffusion tensor MRI revealed no difference in apparent diffusion coefficient among preterm infants with or without perinatal WM lesions. By contrast, RA, the measure of preferred directionality of diffusion and thereby dependent on development of axonal fibers and oligodendroglia, was 25% lower in central WM, the principal site of the original WM injury. However, RA was unaffected in relatively uninjured WM areas, such as temporal, anterior frontal, and occipital regions. Notably, RA values in the internal capsule, which contains fibers that descend from the injured cerebral WM, were 20% lower in the infants with WM injury versus those without. Diffusion vector maps showed striking alterations in the size, orientation, and organization of fiber tracts in central WM and in those descending to the internal capsule.

CONCLUSIONS

Perinatal cerebral WM injury seems to have major deleterious effects on subsequent development of fiber tracts both in the cerebral WM and more distally. The ultimate impact of brain injury in the newborn should be considered as a function not only of tissue destruction, but also of impaired subsequent brain development.

Development of the acetabulum in patients with slipped capital femoral epiphysis: a three-dimensional analysis based on computed tomography

Orientation and shape of the acetabulum were determined by the use of three-dimensional reconstruction of computed tomography (CT) data sets in 22 patients with a total of 30 slipped capital femoral epiphyses. We developed an interactive three-dimensional software program to measure the anteversion and inclination of the acetabulum without projectional and pelvis-tilting errors. Furthermore, we determined the height, width, depth, volume, and surface of the acetabulum as parameters describing the acetabular shape. Comparison of the affected side with the contralateral unaffected hip showed no significant differences for acetabular orientation and shape. The relationship between the degree of the slip and the acetabular orientation was calculated. No correlation was found. Based on the results of this study, we conclude that the slipping of the capital femoral epiphysis has no influence on acetabular development.

Three-dimensional analysis of the proximal femur in patients with slipped capital femoral epiphysis based on computed tomography

A three-dimensional (3D) analysis based on computed tomography was performed to study the 3D geometry of the proximal femur in cases of slipped capital femoral epiphysis (SCFE). For this purpose, new interactive software was developed to analyze hip joint geometry using 3D models without pelvis tilting and projected errors. Twenty-two patients, 8 girls and 14 boys, with a total of 30 slipped capital femoral epiphyses, were reviewed. In the affected hips, we observed a reduced femoral anteversion of 7.0 degrees (vs. 12.7 degrees) and a reduced femoral shaft neck angle of 134.2 degrees (vs. 141.0 degrees). In response to these results, we suggest that an SCFE is associated with reduced femoral anteversion and a reduced femoral shaft neck angle.

Initial experience with intraoperative magnetic resonance imaging in spine surgery

STUDY DESIGN

A case series of 12 patients who underwent spine surgery in an intraoperative magnetic resonance imager (IMRI).

OBJECTIVES

To determine the advantages, limitations, and potential applications to spine surgery of the IMRI.

SUMMARY OF BACKGROUND DATA

Existing stereotactic navigational systems are limited because images are obtained before surgery and are not updated to reflect intraoperative changes. In addition, they necessitate manual registration of fiducial landmarks on the patient's anatomy by the surgeon to the previously obtained image data set, which is a potential source of error. The IMRI eliminates these difficulties by using intraoperative acquisition of MRI images for surgical navigation with the capacity for both image update and image-guided frameless stereotaxy. The IMRI is a novel cryogenless superconducting magnet with an open configuration that allows the surgeon full access to the patient during surgery and intraoperative imaging.

METHODS

T1- and T2-weighted fast spin echo images were obtained for localization, after surgical exposure and after decompression during the course of 12 spine surgeries performed in the IMRI.

RESULTS

The authors performed a series of 12 procedures in the IMRI that included three lumbar discectomies, three anterior cervical discectomies with allograft fusion, three cervical vertebrectomies with allograft fusion, two cervical foraminotomies, and one decompressive cervical laminectomy. The system provided rapid and accurate localization in all cases. The adequacy of decompression by MRI during surgery was confirmed in 10 of 12 cases.

CONCLUSIONS

The IMRI provided accurate and rapid localization in all cases and confirmed the adequacy of decompression in the majority of cases. Future applications of the IMRI to spine surgery may include intraoperative guidance for resection of spine and spinal cord tumors and trajectory planning for spinal endoscopy or screw fixation.

Automated segmentation of MR images of brain tumors

An automated brain tumor segmentation method was developed and validated against manual segmentation with three-dimensional magnetic resonance images in 20 patients with meningiomas and low-grade gliomas. The automated method (operator time, 5-10 minutes) allowed rapid identification of brain and tumor tissue with an accuracy and reproducibility comparable to those of manual segmentation (operator time, 3-5 hours), making automated segmentation practical for low-grade gliomas and meningiomas.

Impaired cerebral cortical gray matter growth after treatment with dexamethasone for neonatal chronic lung disease

OBJECTIVE

The specific aim of this study was to quantify at term the influence of postnatal systemic dexamethasone treatment for neonatal chronic lung disease on subsequent brain growth and development in premature infants without evidence of severe intraventricular hemorrhage or white matter injury.

METHODS

Eighteen premature (23 to 31 weeks) infants, 7 treated with dexamethasone and 11 not treated, were studied at term, ie, 38 to 41 postconceptional weeks, by an advanced quantitative volumetric 3-dimensional magnetic resonance imaging (MRI) technique to quantify cerebral tissue volumes. Fourteen healthy term infants also were studied for comparison. A sequence of image processing algorithms was used to segment each of the MRI slices into the following separate tissue classes: cerebral cortical gray matter, basal ganglia/thalami, unmyelinated white matter, myelinated white matter, and cerebrospinal fluid, all classified based on magnetic resonance signal intensity and anatomic location. A final summing of voxels for each tissue class was performed to compute absolute volumes in milliliters.

RESULTS

Cerebral cortical gray matter volume in premature infants treated with dexamethasone was reduced 35% when compared with gray matter volume in premature infants not treated with dexamethasone (mean +/- standard deviation, 130.3 +/- 54.0 vs 200.6 +/- 35.1 mL, respectively). Subcortical gray matter volumes (basal ganglia and thalami) and myelinated and unmyelinated white matter volumes were not significantly different among the treated and untreated groups. However, premature infants treated with dexamethasone exhibited a reduction (30%) in total cerebral tissue volume compared with total cerebral tissue volume in both the premature infants not treated with dexamethasone and the control term infants (312.7 +/- 43.7 vs 448.2 +/- 50.2 and 471.6 +/- 36.4 mL respectively). This latter finding relates primarily to the decrease in cerebral cortical gray matter volume.

CONCLUSIONS

The data suggest an impairment in brain growth, principally affecting cerebral cortical gray matter, secondary to systemic dexamethasone therapy. Although the premature infants who received dexamethasone were smaller with more severe respiratory disease, these findings are consistent with growing evidence of a potential deleterious effect of dexamethasone on neonatal brain and subsequent neurodevelopmental outcome. This apparent deleterious effect should be taken into consideration by clinicians when weighing the potential risks and benefits of this therapy for low birth weight infants with neonatal chronic lung disease.

Intra-operative MR guidance during trans-sphenoidal pituitary resection: preliminary results

The use of intra-operative MR image guidance has the potential to improve the precision, extent, and safety of trans-sphenoidal pituitary resections. The trans-sphenoidal approach to pituitary surgery has been performed for some time (1--3). Until now these surgeries have relied on direct visualization without the aid of image guidance. An open-bore configuration 0.5T SIGNA SP MR system (GE Medical Systems, Milwaukee, Wisconsin) has been used to provide image guidance for seventeen trans-sphenoidal pituitary adenoma resections (4). The intra-operative MRI system allowed the radiologist to successfully direct the surgeon toward the sella turcica while avoiding the cavernous sinus, optic chiasm and other critical structures. Imaging performed during the surgery monitored the extent of resection and allowed for removal of tumor beyond the surgeon's view in seven cases. Dynamic MR imaging was used to distinguish residual tumor from normal gland and postoperative changes, permitting more precise tumor localization. A heme-sensitive long TE gradient echo sequence was used to find the presence of hemorrhagic debris. All patients tolerated the procedure well without significant complications. J. Magn. Reson. Imaging 2001;13:136-141.

Intraoperative diffusion imaging on a 0.5 Tesla interventional scanner

Intraoperative line scan diffusion imaging (LSDI) on a 0.5 Tesla interventional MRI was performed during neurosurgery in three patients. Diffusion trace images were obtained in acute ischemic cases. Scan time per slice was 46 seconds and 94 seconds, respectively, for diffusion tensor images. Diagnosis of acutely developed vascular occlusion was confirmed with follow-up scans. White matter tracts were displayed with the principal eigenvectors and provided guidance for the tumor surgery. In all cases, the diagnostic utility of LSDI was established. J. Magn. Reson. Imaging 2001;13:115-119.

Motion robust imaging for continuous intraoperative MRI

The sensitivity of MR imaging to motion and susceptibility normally requires that the physician using intraoperative MRI cease surgical activity while image data sets are acquired. We demonstrate that line scan imaging allows the physician to continue operating without the delays caused by imaging. Consequently, patient anesthesia, surgery, and operating room time can be reduced. J. Magn. Reson. Imaging 2001;13:158-161.

Regional magnetic resonance imaging lesion burden and cognitive function in multiple sclerosis: a longitudinal study

OBJECTIVE

To investigate the relationship between magnetic resonance imaging regional lesion burden and cognitive performance in multiple sclerosis (MS) over a 4-year follow-up period.

DESIGN

Twenty-eight patients with MS underwent magnetic resonance imaging and took the Brief, Repeatable Battery of Neuropsychological Tests in Multiple Sclerosis at baseline, 1-year, and 4-year follow-up. An automated 3-dimensional lesion detection method was used to identify MS lesions within anatomical regions on proton density T2-weighted images. The relationship between magnetic resonance imaging regional lesion volumes and the Brief, Repeatable Battery of Neuropsychological Tests in Multiple Sclerosis results was examined using regression analyses.

RESULTS

At all time points, frontal lesion volume represented the greatest proportion of total lesion volume, and the percentage of white matter classified as lesion was also highest in frontal and parietal regions. On neuropsychological testing, when compared with age- and educational level-matched control subjects, patients with MS showed significant impairment on tests of sustained attention, processing speed, and verbal memory (P<.001). Performance on these measures was negatively correlated with MS lesion volume in frontal and parietal regions at baseline, 1-year, and 4-year follow-up (R = -0.55 to -0.73, P<.001).

CONCLUSIONS

Multiple sclerosis lesions show a propensity for frontal and parietal white matter. Lesion burden in these areas was strongly associated with performance on tasks requiring sustained complex attention and working verbal memory. This relationship was consistent over a 4-year period, suggesting that disruption of frontoparietal subcortical networks may underlie the pattern of neuropsychological impairment seen in many patients with MS.

Integration of interventional MRI with computer-assisted surgery

Interventional MRI (IMRI) has entered into a new stage in which computer-based techniques play an increasing role in planning, monitoring, and controlling the procedures. The use of interactive imaging, navigational image guidance techniques, and image processing methods is demonstrated in various applications. The integration of intraoperative MRI guidance and computer-assisted surgery will greatly accelerate the clinical utility of image-guided therapy in general and interventional MRI in particular. J. Magn. Reson. Imaging 2001;13:69-77.

MR imaging-guided percutaneous cryotherapy of liver tumors: initial experience

PURPOSE

To describe the cryoablation of liver tumors by using a percutaneous approach and intraprocedural magnetic resonance (MR) imaging monitoring and to assess the feasibility and safety of the procedure.

MATERIALS AND METHODS

Fifteen hepatic tumors (mean diameter, 2.9 cm) in 12 patients were treated (18 total cryoablations). Fourteen were metastases and one was a hemangioma; all were proved at biopsy. By using a 0.5-T open MR imaging system, cryoneedles were placed and lesions ablated by using real-time monitoring. Clinical signs and symptoms were assessed and laboratory tests performed. Intraprocedural depictions of iceballs were compared with contrast material-enhanced MR imaging-based estimates of cryonecrosis that were obtained 24 hours after cryoablation.

RESULTS

MR imaging-guided percutaneous cryotherapy resulted in no serious complications and no clinically important changes in serum liver enzymes or creatinine or myoglobin levels. Intraprocedural MR imaging demonstrated iceballs as sharply marginated regions of signal loss that expanded and engulfed tumors. The maximal iceball size was 4.9 x 2.2 x 2.2 cm with the use of one cryoneedle and 6.0 x 5.6 x 4.9 cm with three cryoneedles. Intraprocedural iceball depictions correlated well with postprocedural cryonecrosis estimates.

CONCLUSION

MR imaging-guided percutaneous cryotherapy of liver tumors is feasible and safe. MR imaging can be used to estimate cryotherapy effects and guide therapy intraprocedurally.

Hyperpolarized (129)Xe T (1) in oxygenated and deoxygenated blood

The viability of the new technique of hyperpolarized (129)Xe MRI (HypX-MRI) for imaging organs other than the lungs depends on whether the spin-lattice relaxation time, T(1), of (129)Xe is sufficiently long in the blood. In previous experiments by the authors, the T(1) was found to be strongly dependent upon the oxygenation of the blood, with T(1) increasing from about 3 s in deoxygenated samples to about 10 s in oxygenated samples. Contrarily, Tseng et al. (J. Magn. Reson. 1997; 126: 79-86) reported extremely long T(1) values deduced from an indirect experiment in which hyperpolarized (129)Xe was used to create a 'blood-foam'. They found that oxygenation decreased T(1). Pivotal to their experiment is the continual and rapid exchange of hyperpolarized (129)Xe between the gas phase (within blood-foam bubbles) and the dissolved phase (in the skin of the bubbles); this necessitated a complicated analysis to extract the T(1) of (129)Xe in blood. In the present study, the experimental design minimizes gas exchange after the initial bolus of hyperpolarized (129)Xe has been bubbled through the sample. This study confirms that oxygenation increases the T(1) of (129)Xe in blood, from about 4 s in freshly drawn venous blood, to about 13 s in blood oxygenated to arterial levels, and also shifts the red blood cell resonance to higher frequency.

Frameless stereotactic neurosurgery using intraoperative magnetic resonance imaging: stereotactic brain biopsy

OBJECTIVE

To assess the application accuracy of intraoperative magnetic resonance imaging for frameless stereotactic surgery, and to evaluate the performance of intraoperative magnetic resonance imaging for the brain biopsy, a standard stereotactic procedure.

METHODS

A series of spatial coordinate and phantom experiments were performed to analyze the application accuracy of the system. A prospective analysis of 68 consecutive patients undergoing stereotactic brain biopsy was then performed.

RESULTS

The spatial coordinate experiments revealed a mean overall error in acquisition of 0.2 mm. The phantom experiments demonstrated a 1:1 correlation between the magnetic resonance image of a stereotactically guided probe and its relationship to a target and the actual relationship of the probe and target. Sixty-eight brain biopsies were successfully performed in all intracranial compartments except the sella. The radiographic abnormality was localized successfully in all patients (100%). Sixty-six (97.1%) of the biopsies yielded diagnostic tissue. Two biopsies (2.9%) were complicated by intraparenchymal hemorrhage. One expanding temporal lobe hemorrhage was evacuated by immediate craniotomy in the magnet with no postoperative sequelae. A deep hemorrhage from a lymphoma was managed conservatively with interval resolution of symptoms. There were no infections. There was no perioperative mortality.

CONCLUSION

Intraoperative magnetic resonance imaging allows excellent target localization, provides true real-time imaging to account for anatomic changes during surgery, and permits intraoperative confirmation that the biopsy needle has reached the targeted lesion. Immediate postoperative imaging in the operating room allows assessment of adverse events and the potential for immediate management of hemorrhagic complications.

Optimized single-slab three-dimensional spin-echo MR imaging of the brain

The development and optimization of spin-echo-based, single-slab, three-dimensional techniques for magnetic resonance imaging of the whole brain are described. T1-weighted and T2-weighted image sets with a volume resolution of 1 mm(3) and fluid-attenuated inversion-recovery image sets with a volume resolution of 3 mm(3) were obtained in acquisition times of less than 10 minutes per image set.

Sensitivity profiles from an array of coils for encoding and reconstruction in parallel (SPACE RIP)

A new parallel imaging technique was implemented which can result in reduced image acquisition times in MRI. MR data is acquired in parallel using an array of receiver coils and then reconstructed simultaneously with multiple processors. The method requires the initial estimation of the 2D sensitivity profile of each coil used in the receiver array. These sensitivity profiles are then used to partially encode the images of interest. A fraction of the total number of k-space lines is consequently acquired and used in a parallel reconstruction scheme, allowing for a substantial reduction in scanning and display times. This technique is in the family of parallel acquisition schemes such as simultaneous acquisition of spatial harmonics (SMASH) and sensitivity encoding (SENSE). It extends the use of the SMASH method to allow the placement of the receiver coil array around the object of interest, enabling imaging of any plane within the volume of interest. In addition, this technique permits the arbitrary choice of the set of k-space lines used in the reconstruction and lends itself to parallel reconstruction, hence allowing for real-time rendering. Simulated results with a 16-fold increase in temporal resolution are shown, as are experimental results with a 4-fold increase in temporal resolution. Magn Reson Med 44:301-308, 2000.

MR-based temperature monitoring for hot saline injection therapy

We applied magnetic resonance (MR) phase mapping methods to monitor the thermal frequency shift of water in order to study temperature changes from percutaneous hot saline injection therapy (PSIT) using in vitro swine livers and in vivo rabbit livers. The thermal coefficients calculated from the shifts of the water frequency with thermocouple based temperature measurements were -0.0085 +/- 0.0019 ppm/ degrees C for the in vitro studies and -0.0089 ppm/ degrees C for the in vivo studies. The error range was estimated to be +/- 3 degrees C and +/- 4.5 degrees C, respectively. Color-coded temperature maps were compared with macroscopic lesion sizes of the specimen. Regions defined using a 20 degrees C elevation in the initial images following hot saline injection (around 55 degrees C in absolute temperature) closely correlated with visible coagulation in size. We conclude that MR temperature monitoring of PSIT is quite feasible and may be helpful in expanding the clinical use of this thermal therapeutic tool for liver tumors.

Changes in activated T cells in the blood correlate with disease activity in multiple sclerosis

OBJECTIVE

To determine whether changes in activation markers on peripheral blood T cells correlate with disease activity in patients with multiple sclerosis.

DESIGN

In a prospective longitudinal study during 1 year, we analyzed the change in percentage of activated T lymphocytes in the peripheral blood of 40 patients with multiple sclerosis in relation to clinical findings and changes on brain magnetic resonance imaging (MRI) scans. The patients underwent repeated imaging of the brain (mean number of MRIs for each patient, 22) at the time blood samples were obtained as well as at monthly neurological examinations, and at the time of scoring on the Kurtzke Expanded Disability Status Scale (EDSS) and ambulation index scale.

RESULTS

A change in the percentage of cells expressing the activation markers interleukin 2 receptor (CD25), class II major histocompatibility complex (MHC) (I3) or surface dipeptidyl peptidase (CD26) correlated significantly with a change in lesion volume or a change in number of gadolinium-enhancing lesions as detected on MRI. Changes in CD25( +) cells and in CD4(+) cells expressing class II MHC also correlated with changes in disability as measured by EDSS in patients with relapsing-remitting disease, and changes in CD4(+)CD25(+) cells correlated with the occurrence of attacks in patients with relapsing-remitting disease. These correlations are dependent on measurement of changes between time points sampled at 1- or 2-week intervals.

CONCLUSION

There is a linkage between peripheral T-lymphocyte activation as measured by cell surface markers and disease activity in patients with multiple sclerosis. Arch Neurol. 2000;57:1183-1189