Multislice Spin-echo Imaging Research Articles

Changes in T<sub>2</sub>-weighted MRI of supinator muscle, pronator teres muscle, and extensor indicis muscle with manual muscle testing

[Purpose] In order to detect muscle activity with manual muscle testing, T2-weighted magnetic resonance (T2w-MR) images were detected by a 0.2 T compact MRI system. [Subjects and Methods] The subjects were 3 adult males. Transverse T2-weighted multi-slice spin-echo images of the left forearm were measured by a 39 ms echo-time with a 2,000 ms repetition time, a 9.5 mm slice thickness, 1 accumulation and a total image acquisition time of 4 min 16 s. First, T2w-MR images in the resting condition were measured. Then, manipulative isometric contraction exercise (5 sec duration) to the supinator muscle, the pronator teres muscle or the extensor indicis muscle was performed using Borg’s rating of perceived exertion (RPE) scale of 15–17. The T2w-MR images were measured immediately after the exercise. [Results] T2w-MR image intensities increased significantly in the supinator muscle, the pronator teres muscle and the extensor indicis muscle after the exercise. However, the image intensities in the rest of the muscle did not change. [Conclusion] Using T2w-MR images, we could detect muscle activity in a deep muscle, the supinator muscle, and a small muscle, the extensor indicis muscle. These results also support the reliability of the manual muscle testing method.

New phase‐based B1 mapping method using two‐dimensional spin‐echo imaging with hyperbolic secant pulses

To propose a new phase-based B1-mapping method that exploits phase information created by hyperbolic secant (HS) pulses in conventional 2D spin-echo imaging. In this B1-mapping method, HS pulses are used to accomplish π/2 excitation and π refocusing in standard multislice spin-echo imaging. When setting the ratio of pulse lengths of the π/2 and π HS pulses to 2:1, the spin-echo phase is independent of offset frequency and varies as a function of B1 strength. To eliminate undesired phase accumulations induced by unknown factors other than the B1 strength, two spin-echo images are acquired using HS pulses applied with opposite frequency-sweep directions, and the resulting phase images are subtracted from each other. To demonstrate the performance of the proposed method, phantom and in vivo experiments were performed using a surface coil and a volume coil. The B1 maps obtained by using the proposed method were in accordance with the B1 maps obtained using previous methods in both phantom and in vivo experiments. The proposed method is easy to implement without any sequence modification, is insensitive to B0 inhomogeneity and chemical shift, and is robust in a reasonably wide range of B1 field strength.

Characterisation of in vivo ovarian cancer models by quantitative 1H magnetic resonance spectroscopy and diffusion‐weighted imaging

Magnetic resonance imaging (MRI) and spectroscopy (MRS) offer powerful approaches for detecting physiological and metabolic alterations in malignancies and help investigate underlying molecular mechanisms. Research on epithelial ovarian carcinoma (EOC), the gynaecological malignancy with the highest death rate characterised by frequent relapse and onset of drug resistance, could benefit from application of these molecular imaging approaches. In this study, MRI/MRS were used to characterise solid tumour models obtained by subcutaneous (s.c.) or intraperitoneal (i.p.) implantation of human SKOV3.ip cells in severe combined immunodeficiency (SCID) mice. In vivo MRI/MRS, ex vivo magic-angle-spinning (MAS), and in vitro (1)H-NMR measurements were carried out at 4.7 T, 9.4 T, and 9.4/16.5 T, respectively. MRI evaluation was performed by T1-, T2-, and diffusion-weighted (DW) multislice spin-echo imaging. The in vivo (1)H spectra of all tumour models showed a prominent resonance of total choline-containing metabolites (tCho). Quantitative in vivo MRS of both i.p. and s.c. SKOV3.ip xenografts showed that the mean tCho content was in the 2.9-4.5 mM range, with a mean PCho/tCho ratio of 0.99 ± 0.01 [23 examinations, 14-34 days post injection (dpi)], in good agreement with ex vivo and in vitro analyses. Myo-inositol ranged between 11.7 and 17.0 mM, with a trend towards higher values in i.p. xenografts at 14-16 dpi. The average apparent diffusion coefficient (ADC) values of SKOV3.ip xenografts [1.64 ± 0.11 (n = 9, i.p.) and 1.58 ± 0.03 x10(-3) mm(2)/s (n = 7, s.c.)] were in agreement with values reported for tumours from patients with EOC, while the mean vascular signal fraction (VSF) was lower (≤ 4%), probably due to the more rapid growth of preclinical models. Both s.c. and i.p. xenografts are valuable preclinical models for monitoring biochemical and physiopathological changes associated with in vivo EOC tumour growth and response to therapy, which may serve as the basis for further clinical development of noninvasive MR approaches.

Diagnosis of early myocarditis after respiratory or gastrointestinal tract viral infection: insights from cardiovascular magnetic resonance

BackgroundThe diagnosis of myocarditis continues to be a challenging task in clinical practice. The purpose of our study was to investigate cardiovascular magnetic resonance imaging in the diagnostic workup of ambulatory patients with the suspicion of early myocarditis after respiratory or gastrointestinal tract viral infection. The need for accurate diagnosis of early myocarditis arises from the low diagnostic accuracy of routine clinical tests.MethodsWe examined 67 consecutive patients with symptoms of weakness, palpitations, and fatigue after respiratory or gastrointestinal tract infection. We compared these patients to 31 controls. ECG-triggered, T2-weighted, fast-spin-echo triple inversion recovery sequences and delayed enhancement imaging were obtained in all patients, as well as functional parameters of left ventricular function and dimensions. In addition, in 25 patients and 10 controls, ECG-triggered, T1-weighted, multi-slice spin-echo images were obtained in axial orientation.ResultsWe found a significant difference between patients with suspected myocarditis and controls in T2-global myocardial signal intensity. In addition, the ratio of global myocardial signal intensity/muscle signal intensity was 2.3 ± 0.4 in patients and 1.8 ± 0.3 in controls, which was highly significant (p < 0.001). In 23 patients, a pathological late enhancement pattern was seen, but only in one of the controls. There was no significant difference in T1-signal parameters.ConclusionCardiovascular magnetic resonance technique is able to detect early myocardial involvement after respiratory or gastrointestinal tract infection.

Spin-echo T1-weighted Imaging of the Brain with Interleaved Acquisition and Presaturation Pulse at 3 T: A Feasibility Study Before Clinical Use

Although spin-echo (SE) sequence has some advantages over gradient-echo sequence in brain imaging, gradient-echo sequence is commonly used for T1-weighted imaging (T1WI) at 3 T because contrast on SE T1WI is widely believed to be poor at 3 T. Recently, gray-white matter contrast on single-slice and multi-slice SE imaging with interslice gap was reported as better at 3 T than at 1.5 T. This study examined the feasibility of interleaved SE T1WI of the brain at 3 T. This study also examined whether presaturation pulse (PP) sufficiently suppresses intra-arterial signals because these signals tend to be hyperintense due to longer T1 at 3 T.Subjects consisted of 18 healthy volunteers. Two sets of T1WI were performed using SE sequence. One set consisted of imaging without PP, and the other consisted of imaging with PP. Each set contained three types of gapless imaging as follows; sequential, 100% interleaved, and 200% interleaved imaging. In each subject, contrast-to-noise ratio between gray-matter and white-matter (CNR(GM-WM)) and intra-arterial signals were evaluated.CNR(GM-WM) was significantly higher on interleaved images than on sequential images, regardless of PP (P < .0001). PP sufficiently suppressed intra-arterial signals (P < .0001).CNR(GM-WM) on SE T1WI at 3 T can be improved by interleaved acquisition, and PP sufficiently suppressed intra-arterial signals. Interleaved SE T1WI with PP appears clinically feasible at 3 T.

Transient left ventricular dysfunction in Churg Strauss syndrome: a case report

A 42 year old woman was admitted to our hospital for investigation of eosinophilia. There were no findings from the physical examination of the lungs and heart. The echocardiography showed a segmental hypokinesia of the interventricular septum and the apex causing left ventricular dysfunction with an ejection fraction 45% and mild pericardial effusion. Cardiac magnetic resonance was performed, for detection of lesions associated with the underline disease, using electrocardiogram-triggered T2-weighted and T1-weighted multislice spin-echo images (before and after an intravenous bolus of gadolinium).The analysis of T2-weighted images revealed increased signal on the mid part of interventricular septum, suggesting myocardial oedema. In the delayed-enhanced images, areas of late phase gadolinium enhancement (indicative of fibrosis) were identified in the mid part of interventricular septum. Methylprednisolone therapy was started. The patient had follow-up echocardiographic examination every month and on sixth month improvement of left ventricular dysfunction was shown with an ejection fraction 55%.In conclusion our case is a typical Churg Strauss Syndrome with characteristic myocardial involvement which improved after corticosteroid treatment. The cardiac magnetic resonance has significant role for early and accurate detection and differentiation of myocardial damage even in preserved cardiac wall motion and cavity size.

Cardiac Magnetic Resonance Imaging Detects Long-Term Fibrotic Changes in Patients with Primary Eosinophilic Disorders: A Cross-Sectional Study

Myocardial involvement is a major cause of morbidity and mortality in the setting of primary eosinophilia. We sought to compare conventional diagnostic modalities, such as clinical examination, electrocardiography and echocardiography to cardiac magnetic resonance imaging (CMR) for the evaluation of cardiac involvement in patients with primary eosinophilia.Consecutive patients with primary eosinophilia and end-organ involvement were considered eligible. Secondary causes of eosinophilia were excluded using a standardized diagnostic protocol. Clonality was assessed by a combination of diagnostic methods including bone marrow smear, biopsy examination, immunophenotyping (using an extensive panel of T-cell markers), cytogenetic and molecular analysis, including RT-PCR for the detection of eosinophilia related fusion genes [M-BCR-ABL, t(9;22); m-BCR-ABL, t(9;22); μ-BCR-ABL, t(9;22); BCR-FGFR1, t(8;22); ZNF198-FGFR1, t(8;13); FOP-FGFR1, t(6;8); CEP110-FGFR1, t(6;8); BCR-PDGFR, t(4;22); FIP1L1-PDGFRA, del(4)(q12); ETV6-PDGFRB, t(5;12); H4-PDGFRB, t(5;10)], as well as ARMS PCR for the detection of JAK2 V617F. Echocardiography and electrocardiography were performed using standard methods. CMR scans were performed and interpreted by an assessor blinded to the clonality status of patients, using a 1.5 T Philips Intera CV MR scanner (Philips Medical Systems, Best, The Netherlands). Patients were evaluated for the presence of myocardial inflamation using T2-weighted, T1-weighted before and after contrast media injection and late enhanced images. ECG-triggered, T2-weighted (T2-W), multi-slice spin-echo sequence was performed in axial orientation. ECG-triggered, T1-weighted (T1-W) multi-slice spin-echo images were obtained in axial orientation with identical parameters before and after an intravenous bolus of 0.1mmol/kg Gd-DTPA. Measurements after Gd-DTPA were started within 1 minute of injection. Immediately after the second set of T1-W images, 0.1mmol/kg Gd-DTPA was given again and delayed-enhanced images were taken 15 min later, using an inversion recovery sequence. The patients' results were compared with those of 20 healthy volunteers.A total of 15 patients (2 male/13 female) were enrolled in this study. Five patients had been diagnosed with chronic eosinophilic leukemia (CEL; 3 being positive for JAK2 V617F and 2 carrying clonal cytogenetic abnormalities) and 10 with hypereosinophilic syndrome (HES). All patients were receiving treatment to control eosinophilia. 13 were in complete hematologic response (less than 5% eosinophils and less than 10.000 white blood cells/mm3) and 2 displayed mildly elevated eosinophil counts. Five patients had evidence of myocardial involvement by conventional diagnostic modalities. Despite being in hematological and clinical remission, 6 patients, 5 of whom were diagnosed with CEL, had abnormalities detected by CMR, including endomyocardial fibrosis in 5 (all with CEL) and active myocardial inflammation in one HES patient. Overall, cardiac involvement and CMR-detected endomyocardial fibrosis were more common among patients with CEL compared to patients with HES (Fisher's exact test p-value= 0.0088, and 0.0037, respectively). None of the healthy volunteers had evidence of inflamation of fibrosis.Our study demonstrates that CMR detects endomyocardial fibrosis in a substantial proportion of patients with primary eosinophilia, despite adequate disease control. Myocardial involvement and endomyocardial fibrosis in particular, are associated with clonal primary eosinophilia.

MRI Assessment of Pituitary Iron and Volume in Thalassemia, and Relation to Hypothalamic-Pituitary-Gonadal Axis Function (HPG): A Feasibility Study.

Improvements in transfusion and chelation treatment have led to increased survival of patients with thalassemia (THAL), however, HPG axis dysfunction continues as the most prevalent complication of iron-overload in THAL. The critical target organ for HPG axis dysfunction in thalassemia is the anterior pituitary gland. In a pilot study on iron-induced endocrinopathies in chronically transfused thalassemia and sickle cell disease (SCD) patients, we developed MRI methods to quantitatively assess pituitary iron by measuring the transversal relaxation rate (R2), the anterior and posterior volume, and anterior pituitary height. We examined the hypothesis that iron will be elevated in the pituitary of heavily transfused thalassemia patients, but gland volume and height will correlate more closely with function. We scanned 13 subjects (controls 8, HbE-thalassemia and thalassemia major 4, iron-overloaded SCD 1) with a total of 17 measurements in a 1.5 Tesla imager of Children's Hospital Oakland (Philips Gyroscan®) using a quadrature head coil. Two of 4 thalassemia patients were on hormone replacement treatment. The relaxation rate R2 of the anterior pituitary gland was determined from 2 or 3 sagittal slices (3 mm slice thickness, 0.3 mm gap, manually traced ROI covering more than 60% of the gland within each slice) by a turbo-spin echo sequence acquiring 8 evenly spaced echoes (TE = 15, 30,..., 120 ms, TR = 2500 ms). Anterior and posterior pituitary volumes were analyzed from sagittal slices by manual tracing (3D FFE, 1 mm3 isotropic voxel, TE = 4.6 ms, TR = 9.8 ms, a = 15°). Anterior pituitary height was obtained from routine T1 weighted sagittal multi-slice spin echo images (slice thickness 3 mm, gap 0.3 mm). Liver iron concentration (LIC) by SQUID biosusceptometry was used for total body iron estimation. A reproducibility of 2.6 % (COV) was determined in a normal subject for a mean R2 = 11.8 s−1. The relaxation rates for the control group R2 = 10.8 ± 0.8 s−1 and the thalassemia group R2 = 14.3 ± 1.4 s−1 were significantly different (p (U-test) < 0.001) with no overlap. A weak Spearman rank correlation was found with LIC (RS = 0.71, p < 0.04), but not with plasma ferritin. Anterior pituitary height H and volume V were related by V [mm3] = 95 · H [mm] - 187 (R2 = 0.80). For the anterior pituitary, a significant correlation was found between R2 and volume (RS = −0.59, p < 0.04). Although volumes and heights did not significantly differentiate between the patients and controls, the two THAL patients with abnormal pituitary function had lower anterior pituitary volume and height compared with the two others with normal function. The one iron-overloaded SCD patient had normal R2 and pituitary function; volume and height were in the same range as controls. In summary, the higher transverse relaxation rates indicate elevated iron concentrations in the anterior pituitary gland in all of our thalassemia patients. Pituitary volumes or heights alone may reflect pituitary function, but abnormal volume/height was only seen in patients with high R2. Additional studies in patients with thalassemia and SCD are required to confirm these preliminary observations.

Melatonin suppresses cerebral edema caused by middle cerebral artery occlusion/reperfusion in rats assessed by magnetic resonance imaging.

Melatonin, a pineal secretory product synthesized from tryptophan, has been found to be effective against neurotoxicity. The present study was aimed at demonstrating the effectiveness of melatonin in vivo in reducing ischemia-induced cerebral edema using magnetic resonance imaging (MRI). Rats were subjected to middle cerebral artery (MCA) occlusion/reperfusion surgery. Melatonin was administered twice (6.0 mg/kg, p.o.) just prior to 1 hr of MCA occlusion and 1 day after the surgery. T2-weighted multislice spin-echo images were acquired 1 day after the surgery. In the saline-treated control rats, increases in T2-weighted signals (water content) were clearly observed in the striatum and in the cerebral cortex. In the melatonin-treated group, total volume of edema was reduced by 51.6% compared with control group (P < 0.01). The protective effect of melatonin against edema was more clearly observed in the cerebral cortex (reduced by 59.8%, P < 0.01) than in the striatum (reduced by 34.2%, P < 0.05). Edema volume in a coronal slice was the greatest at the level of the bregma. Suppression of cerebral edema by melatonin was more effective posterior than anterior to the bregma. Melatonin appeared to reduce the volume of the edematous sites rather than to shift the signal intensity distribution. The present MRI study clearly demonstrates the effectiveness of melatonin against cerebral edema formation in ischemic animals in vivo, especially in the cerebral cortex. Melatonin may be highly useful in preventing cortical dysfunctions such as motor, sensory, memory, and psychological impairments associated with ischemic stroke.

Melatonin reduces cerebral edema formation caused by transient forebrain ischemia in rats

Reduction of cerebral edema, an early symptom of ischemia, is one of the most important remedies for reducing subsequent chronic neural damage in stroke. Melatonin, a metabolite of tryptophan released from the pineal gland, has been found to be effective against neurotoxicity in vitro. The present study was aimed to demonstrate the effectiveness of melatonin in vivo in reducing ischemia-induced edema using magnetic resonance imaging (MRI). Rats were subjected to middle cerebral artery (MCA) occlusion/reperfusion surgery. Melatonin was administered twice (6.0 mg/kg, p.o.): just prior to 1 h MCA occlusion and 1 day after the surgery. T 2-weighted multislice spin-echo images were acquired 1 day after the surgery. Increases in T 2-weighted signals in ischemic sites of the brain were clearly observed after MCA occlusion. The signal increase was found mainly in the striatum and in the cerebral cortex in saline-treated control rats. In the melatonin-treated group, the total volume of cerebral edema was reduced by 45.3% compared to control group ( P < 0.01). The protective effect of melatonin against cerebral edema was more clearly observed in the cerebral cortex (reduced by 56.1%, P < 0.01), while the reduction of edema volume in the striatum was weak (reduced by 23.0%). The present MRI study clearly demonstrated that melatonin is effective in reducing edema formation in ischemic animals in vivo, especially in the cerebral cortex. Melatonin may be highly useful in preventing cortical dysfunctions such as motor, sensory, memory, and psychological impairments.

Double-chambered right ventricle or sub-infundibular stenosis assessed by cardiovascular magnetic resonance.

This paper presents magnetic resonance findings in four adults with double-chambered right ventricle or sub-infundibular stenosis, a condition that is treatable by surgery, but which can be difficult to assess echocardiographically. Four patients referred for cardiovascular magnetic resonance in the last 2 years were identified from CMR findings, although not necessarily from previous echocardiography, as having sub-infundibular stenosis. We used multislice spin echo imaging, cine imaging in oblique sagittal planes, and phase velocity mapping. We performed spin echo imaging of a post-mortem heart without known structural abnormality to illustrate right ventricular myocardial morphology. Results in patients showed evidence of sub-infundibular muscular obstruction separating the hypertrophied inlet and apical portions of the right ventricle from a thin-walled, unobstructed infundibular region in each case, with a systolic jet originating at least 15 mm beneath the unstenosed pulmonary valve. In addition to previously described structural components contributing to stenosis--enlargement and/or displacement of the septomarginal trabeculation, septoparietal trabeculations or the moderator band--CMR suggested additional components: a right ventricular papillary muscle in one, an anteriorly bulging aortic sinus in one, and hypertrophied muscular ridges of the parietal wall of the right ventricle. Even in this small group of patients, the causes of sub-infundibular stenosis appeared to be varied and multi-factorial. The abilities of magnetic resonance to give unrestricted, multi-planar views of right ventricular anatomy, movement and flow make it well suited for diagnosis and characterization of sub-infundibular stenosis, especially in adults.

Nuclear Magnetic Resonance Imaging Detects Internal Defects in Potatoes

Potatoes with hollow heart or brown center are considered to be of poor quality for both fresh and processing markets. A reliable nondestructive method, which can distinguish affected and normal potatoes, is described here. A Varian 4.7 Tesla, 33-cm horizontal-bore spectroscopy/imaging system was used to obtain nuclear magnetic resonance (NMR) images of potatoes. A two-dimensional multi-slice spin-echo imaging technique was used to acquire the cross-sectional images along the longitudinal direction. The echo time was 35 msec and the repetition time was 1.2 sec. A total of 13 slice images were taken for each potato. A one-dimensional projection technique was also performed to evaluate the possibility of using fast-scan method. The brown center showed high intensity in long echo scans due to its longer TL relaxation time. A suberin-like layer resembling the periderm developed on the cavity wall of hollow heart causing a tan or dark brown coloration. This cavity wall also appeared in high intensity on the image. The affected potatoes can easily be sorted out using this nondestructive NMR imaging technique.

Asbestos-related pericardial thickening detected by magnetic resonance imaging

Magnetic resonance imaging was performed in four male asbestos workers in whom the chest radiograph revealed plural but not pulmonary or pericardial disease. Patients underwent thoracic multislice spin echo imaging, with measurement of left and right ventricular volumes at end-diastole and end-systole, and a study of the flow in the superior vena cava as an indirect measure to the filling of the right ventricle. Patients also underwent respiratory function tests and high-resolution computed tomography (HRCT). Magnetic resonance, but not HRCT, showed pericardial thickening in two patients. Magnetic resonance demonstrated reduced diastolic flow in the superior vena cava in one patient, reflecting impaired right ventricular filling. All other magnetic resonance measurements of cardiac function were normal. HRCT demonstrated mild asbestosis in three patients in which neither the chest radiograph nor magnetic resonance showed signs of parenchymal disease, and pericardiac calcification without thickening in one patient. It is concluded that magnetic resonance is superior to HRCT in identifying pericardial thickening, but that HRCT is superior to magnetic resonance in identifying asbestos-related pleural and pulmonary disease.

Measurement of Cardiac Chamber Volumes by Cine Magnetic Resonance Imaging

Cardiac chamber volumes (both atria and ventricles) in 19 healthy volunteers were measured noninvasively by cine magnetic resonance imaging (MRI). First, cardiac localization was determined from the coronal image by 0.5-T superconducting magnetic imager. Then, transaxial ECG gated multislice spin echo images were obtained from the bottom to the top of the heart. In the last step, cine MRI was performed at each level of all these transaxial spin echo MR images involving the heart. Each cardiac chamber volume at the same phase was calculated by adding chamber areas in each anatomic section multiplied by slice thickness. Left ventricular (LV) end-diastolic volume (EDV) 132.0 +/- 26.9 mL) and LV end-systolic volume (ESV) (47.8 +/- 13.9 mL) were smaller than right ventricular (RV) EDV (141.1 +/- 24.8 mL) and RVESV (57.0 +/- 12.6 mL), respectively (p < 0.01). LV stroke volume (84.3 +/- 17.9 mL) was equivalent to RV stroke volume (84.2 +/- 17.6 mL) (r = 0.91, p < 0.01). Left atrial (LA) and right atrial (RA) maximal volumes were 75.8 +/- 15.4 mL and 84.4 +/- 18.7 mL, respectively. LA minimal volume (37.5 +/- 10.7 mL) was smaller than RA minimal volume (47.8 +/- 12.2 mL). These values measured by cine MRI are satisfactory and cine MRI will be a useful method of determining cardiac chamber volumes, especially atrial volumes.

Correction of translational motion artifacts in multi-slice spin-echo imaging using self-calibration.

In this paper, we describe a method for detecting and correcting in-plane bulk translational motion in multislice spin-echo imaging using self-calibration and postprocessing. A constant phase encoding offset between slices is used to evenly spread out the low spatial frequency echoes to allow accurate motion detection by self-calibration. Motion detection in both x and y directions is achieved by interchanging the readout and phase encoding directions for the alternate slices. Displacements are determined by cross correlating the modulus of each 1D transformed echo with a reference box car function whose width equals that of the imaged object. In addition, phase errors induced by the velocity in the readout direction are estimated and corrected using the displacement data. The results obtained from knee studies at 0.5 T and 1.5 T show that the artifacts due to translational motions are significantly suppressed upon correction. The method does not require any additional pulses or time, and the data processing can be easily implemented.

In vivo magnetic resonance imaging of fetal cat neural tissue transplants in the adult cat spinal cord

Magnetic resonance (MR) imaging was evaluated for its possible diagnostic application in determining the survival of fetal central nervous system tissue grafts in the injured spinal cord. Hemisection cavities were made at the T11-L1 level of eight adult female cats. Immediately thereafter, several pieces of tissue, either obtained from the fetal cat brain stem on embryonic Day 37 (E-37), from the fetal neocortex on E-37, or from the fetal spinal cord on E-23, were implanted into the cavities made in seven cats. The eighth cat served as a control for the effect of the lesion only. In another group of four animals, a static-load compression injury was made at the L-2 level. Seven weeks later, the lesion was resected in three cases and fragments of either fetal brain-stem or spinal cord tissue were introduced. A small cyst was observed in a fourth cat in the compression injury group and a suspension of dissociated E-23 brain-stem cells was injected into this region of cavitation without disturbing the surrounding leptomeninges. Five months to 2 years posttransplantation, MR imaging was performed with a 2.0-tesla VIS imaging spectrometer by acquiring multislice spin-echo images (TR 1000 msec, TE 30 msec) in both the transverse and sagittal planes. Collectively, these intermediate-weighted images revealed homogeneous, slightly hyperintense signals at the graft site relative to the neighboring host tissue in seven of the 11 graft recipients. Two of the remaining four cats exhibited signals from the graft site that were approximately isointense with the adjacent host spinal cord, and the final two cats and the lesion-only control presented with very hypointense transplant/resection regions. The hyperintense and isointense images were tentatively interpreted as representing viable graft tissue, whereas the hypointense transplant/resection sites were considered to be indicative of a lack of transplant survival or the absence of tissue in the lesion-only control animal. Postmortem gross inspection of fixed specimens and light microscopy verified the MR findings in the control animal in 10 of the 11 graft recipients by showing either transplants and/or cysts corresponding to the MR images obtained. In one cat in the hemisection group, histological analysis revealed a very small piece of graft tissue that was not detected on the MR images. Therefore, it is suggested that within certain spatial- and contrast-resolution limits, MR imaging can reliably detect the presence of transplanted neural tissue in both the hemisected and compression-injured spinal cord of living animals.(ABSTRACT TRUNCATED AT 400 WORDS)

Distinguishing viable from infarcted myocardium after experimental ischemia and reperfusion by using nuclear magnetic resonance imaging

Early reperfusion has the potential for salvaging ischemic myocardium at risk for infarction. To test the ability of nuclear magnetic resonance (NMR) imaging to differentiate between stunned and infarcted myocardium early after reperfusion, 16 mongrel dogs underwent transient occlusion of the left anterior descending artery or a diagonal branch for 30, 60 or 180 min followed by reperfusion. To identify the area at risk for infarction and to assess the extent of hypoperfusion and reperfusion, two-dimensional and contrast echocardiography were performed at baseline study, during coronary occlusion and at three separate times during reperfusion (before NMR imaging, immediately after NMR imaging and 12 to 14 h later). Wall thickening in the control and ischemic zones and the circumferential extent of abnormal wall motion were analyzed at each time point using short-axis echocardiograms. Nuclear magnetic resonance imaging at 1.5 tesla was performed 2 to 3.5 h (mean 2.7 +/- 0.5) after reperfusion. Short-axis, multislice spin-echo images (TE 26 and TE 60) were obtained. Signal intensity was measured in the control and ischemic areas and expressed as a percent difference compared with normal myocardium. All dogs demonstrated a significant decrease in wall thickening and abnormal wall motion before and after NMR imaging. Seven of the eight dogs with infarction had an area of increased signal intensity on TE 60 images. The mean percent difference in signal intensity compared with adjacent normal myocardium was 127 +/- 68% (p = 0.002). None of the eight dogs without infarction had a visually apparent change in signal intensity on TE 60 images (mean percent difference versus control area 13 +/- 11%), despite regional systolic dysfunction documented by echocardiography at the time of imaging. The area of increased signal intensity correlated with infarct size (r = 0.69), although overestimation by NMR imaging occurred. The area of increased signal intensity did not correlate with the extent of echocardiographic contrast defect during coronary occlusion (risk area). This study demonstrates that NMR imaging can be applied early after coronary reperfusion to assess the potential for recovery of dysfunctional myocardium. In addition, by using a TE 60 multislice spin-echo imaging sequence at 1.5 tesla, quantification of the extent of infarction also may be possible.

SIMA

We present a method of multislice magnetic resonance imaging that utilizes simultaneous binary-encoded excitation. Signals are acquired from all slices at once, and the images are separated in the reconstruction process. This simultaneous multislice acquisition method has been implemented for multislice spin-echo imaging, and the results are compared with those for a standard interleaved multislice method. Advantages include improved signal-to-noise ratios and flexible slice placement. Phantom and volunteer studies are presented and evaluated in comparison with competing methods.