Long-term octreotide therapy in growth hormone-secreting pituitary adenomas: evaluation with serial MR.

PURPOSETo compare the changes in tumor volume with length of octreotide treatment in patients with acromegaly, to analyze signal alterations of the pituitary mass during treatment, and to determine an optimal MR imaging protocol.METHODSEighteen patients with growth hormone (GH)-secreting pituitary adenomas were studied with MR imaging before and during octreotide treatment. The length of follow-up was 9 to 70 months. Tumor volume, extension, and signal characteristics were evaluated.RESULTSThe total pituitary volume decreased in 16 patients by a mean of 37%. In 11 patients the tumor could be demarcated from the normal gland, and mean tumor reduction was 51%. Most of the tumor reduction took place within the first year, but an additional effect was noted in four patients during the following 3 years. Tumor reexpansion, hemorrhage, or necrosis did not occur. Serum GH levels were effectively lowered within the first year, with slight additional reductions thereafter.CONCLUSIONIn long-term octreotide treatment of GH-secreting pituitary adenomas, tumor shrinkage occurs primarily during the first year, but effects are noted up to 4 years. The treatment may be considered an alternative to surgery in the select group of patients in whom the peripheral effects of chronic GH elevation, as determined by serum insulinlike growth factor I (IGF-I), are controlled. We suggest MR imaging with T1-weighted coronal and sagittal images at baseline and after 3 and 12 months, with additional MR imaging if GH or IGF-I levels rise during treatment. At baseline, both noncontrast and contrast-enhanced images should be obtained. Unenhanced images may be sufficient during follow-up unless tumor reexpansion occurs or surgery is anticipated.     

Histologic abnormalities associated with gadolinium enhancement on MR in the initial hours of experimental cerebral infarction.

PURPOSETo determine the histologic changes associated with gadopentetate dimeglumine enhancement on MR images in acute focal cerebral ischemia.METHODSIn each of two baboons, a microcatheter was used to occlude partially the middle cerebral artery and reduce cerebral blood flow for approximately 3.5 hours. The catheter was then removed allowing reperfusion for approximately 3.5 hours. In two other baboons, cerebral blood flow was completely and irreversibly interrupted by injecting liquid adhesive into the middle cerebral artery. T2-weighted and serial enhanced T1-weighted MR images were obtained. Brain specimens were studied histopathologically.RESULTSIn the animals with incomplete and reversible reduction of cerebral blood flow, postcontrast T1-weighted images obtained during the initial 3 hours of ischemia showed focal areas of hypointensity. These areas were enhanced on later images. The areas of signal abnormality were subsequently found to be necrotic and were characterized by neuronal cytolysis and vascular "plugging." In the animals with complete and irreversible interruption of cerebral blood flow, no abnormal signal intensity or enhancement was observed. Histologic abnormalities were milder in these animals.CONCLUSIONSContrast enhancement on MR images in the initial hours of cerebral ischemia was associated with histologic evidence of tissue necrosis but was not associated with milder ischemic changes.     

Studies on bromobenzene-induced hepatotoxicity using in vivo MR microscopy with surgically implanted RF coils

Using surgically implanted RF coils at 300 MHz, three-dimensional microscopic MR images of rat liver were obtained in vivo to follow the development of pathology induced by bromobenzene exposure. Formalin fixed specimens of liver from these animals were also imaged using in vitro MR microscopy, followed by conventional optical microscopy. All MR images were acquired using a spin-warp pulse sequence with TR = 950 ms and TE= 23 ms. The in vivo images were reconstructed as 256² × 32 arrays with a voxel size of (50 μm)² × 219 pm, while the in vitro images were reconstructed as 256² × 128 arrays, giving an isotropic resolution at (39 μm)². Based on results from six animals, we have found in all animals exposed to bromobenzene, image intensity decreased in specific hepatic tissue regions. These regions were well correlated to low signal intensity areas observed in in vitro MR images at higher resolution. Conventional optical microscopy indicated that the low signal intensity regions corresponded to areas of necrosis. The decrease in signal intensity is consistent with increased local diffusion coefficients as a result of necrosis. This study demonstrates that MR microscopy with implanted RF coils can be successfully used to follow tissue pathological changes in living tissues.     

Regional dynamic signal changes during controlled hyperventilation assessed with blood oxygen level-dependent functional MR imaging.

PURPOSETo quantitate the amplitude changes and temporal dynamics of regional functional MR imaging signals during voluntary hyperventilation using blood oxygen level-dependent contrast echo-planar imaging.METHODSSeven male subjects were studied during voluntary hyperventilation (PetCO2 = 20 mm Hg) regulated by capnometry. Measurements were made on multisection echo-planar MR images obtained with parameters of 1000/66 (repetition time/echo time), flip angle of 30 degrees, and voxel size of 3 x 3 x 5 mm3. Sensitivity of the functional MR imaging signal to changes in PetCO2, time delays in relation to PetCO2 changes, and time constants of functional MR imaging signal changes were assessed on a region-by-region basis.RESULTSWithin 20 seconds of starting hyperventilation, rapid and substantial decreases in the functional MR imaging signal (by as much as 10%) were measured in areas of gray matter, which were significantly greater than the modest changes observed in white matter. Regional-specific effects in areas of the frontal, occipital, and parietooccipital cortex were stronger than in subcortical regions or in the cerebellum. Signal decreases measured with functional MR imaging were significantly delayed with respect to the reduction in PetCO2. Apparent differences between regional time constants did not reach statistical significance.CONCLUSIONRegional and gray-white matter differences in functional MR imaging signal changes during controlled hyperventilation may reflect differences in metabolic activity, vascular regulation, and/or capillary density. When measuring brain activation with functional MR imaging, arterial PCO2 differences due to unregulated respiration may confound interpretation of activation-related functional MR imaging signal changes.     

Susceptibility-weighted MR for evaluation of vasodilatory capacity with acetazolamide challenge.

PURPOSETo investigate cerebral vasodilatory capacity by acetazolamide challenge in healthy subjects and in patients with chronic occlusive cerebrovascular disease by using susceptibility-weighted gradient-echo MR imaging.METHODSEight patients with chronic occlusive cerebrovascular disease and four healthy volunteers were studied with susceptibility-weighted MR imaging before and after intravenous administration of 1000 mg of acetazolamide. Signal intensities were measured as a function of time in several regions of interest defined on anatomic images. In all patients with chronic occlusive cerebrovascular disease, acetazolamide challenge and resting regional cerebral blood flow were also evaluated with single-photon emission CT (SPECT).RESULTSIn healthy volunteers, signal intensities began to increase 3 to 4 minutes after acetazolamide administration, with a continuous increase during the subsequent 10 minutes. The effect lasted for approximately 45 minutes after administration. In patients with chronic occlusive cerebrovascular disease, signal changes on susceptibility-weighted MR images of occluded areas with normal vasodilatory capacity on SPECT images did not differ from signal changes of nonocclusive areas. In those patients with changes that reflected diminished vasodilatory capacity, the MR images showed a lower percentage of signal changes after acetazolamide administration than those in normally perfused areas.CONCLUSIONSusceptibility-weighted MR imaging offers an alternative method for estimating vasodilatory capacity.     

Cerebellar MR changes in patients with olivary hypertrophic degeneration.

PURPOSETo describe MR changes in the cerebellar cortex and the dentate nucleus in patients with inferior olivary nucleus hypertrophy.METHODSMR scans of 11 patients with palatal myoclonus were reviewed. Among them, we selected 5 cases that showed lesions in the central tegmental tract and the ipsilateral inferior olivary nucleus. We evaluated MR changes of the cerebellar cortices and dentate nuclei contralateral to the affected inferior olivary nuclei. Evaluation was performed by side-to-side comparison in each case. Six cases were excluded, because comparison of the cerebellar hemispheres or dentate nuclei with those of the opposite sides was not possible.RESULTSThe dentate nuclei opposite affected inferior olivary nuclei showed mild to moderate shrinkage of the normal low-signal areas and increases in signal intensity on T2-weighted images in 4 of 5 patients. The cerebellar cortices on the same sides as the involved dentate nuclei showed atrophic changes in 4 of 5 patients.CONCLUSIONOur MR findings suggest that there is a degenerative process involving the dentate nucleus and the cerebellar cortex associated with the hypertrophic degeneration of the inferior olivary nucleus.     

White matter changes in patients with breast cancer treated with high-dose chemotherapy and autologous bone marrow support.

PURPOSETo study MR changes in the white matter of the brain in patients with breast cancer treated with a widely used protocol of high-dose chemotherapy and autologous bone marrow support.METHODSThirteen patients with high-risk stage II or stage IV breast cancer treated with high-dose cyclophosphamide, cisplatin, carmustine, and bone marrow support underwent posttransplant MR examination of the brain. Serial posttransplant MR examinations were performed in 5 of the 13 patients and single MR examinations in 8. The severity of the white matter change was evaluated by two neuroradiologists and rated mild, moderate, or severe.RESULTSIn 9 of the 13 patients, central and peripheral cerebral white matter changes were observed. Four patients had severe changes, extending from the ependyma of the lateral ventricles to the gyri. An additional 4 patients had moderate white matter change at the last observation. One had mild change, and 4 had no white matter change. In all patients, there was sparing of inferior frontal, posterior inferior occipital, and anterior temporal lobes, and of the centrosylvian brain.CONCLUSIONSWhite matter change occurred in patients treated with a high-dose chemotherapy and bone marrow support protocol. Most of the changes, and the more severe ones, occurred 5 or more months after the transplants. There was no apparent relationship between these changes and central nervous system function. Because of the increased longevity with this treatment, it is important to appreciate these white matter changes, recognizing however that their expression may be subclinical.     

Magnetic resonance imaging spectrum of spinal meningioma

PurposeTo evaluate magnetic resonance (MR) imaging findings of spinal meningioma and to determine the radiological subtypes based on the MR imaging findings and their respective clinical features.Material and methodsData for 105 patients with surgically treated and histopathologically diagnosed spinal meningiomas at our hospital between May 1, 2003 and May 1, 2017 were evaluated in this study. Two radiologists reviewed the characteristics of spinal meningiomas on MR images and categorized the spinal meningiomas into subtypes based on MR imaging findings.ResultsMost spinal meningiomas showed higher signal intensity than that of the spinal cord but lower than that of the subcutaneous fat on T2-weighted images (WI). 56 cases (54%) showed adjacent spinal cord signal changes. Meningiomas could be categorized according to MR imaging findings into type A: dural-based tumors with a homogeneous signal intensity and intense contrast enhancement (81 cases, 77%); type B: round or oval-shaped tumors with an internal hypointense portion on T2-weighted images (18 cases, 17%); type C: en plaque tumors (three cases, 3%); and type D: tumors with unusual findings and a heterogeneous appearance (three cases, 3%). All type C patients showed spinal cord signal changes.ConclusionsSpinal meningioma showed slightly high signal intensity rather than high signal intensity on T2-weighted images. Spinal cord signal changes were present in more than half of the cases. Clinical differences were observed among the different MR imaging types.     

Incontinentia pigmenti: MR demonstration of brain changes.

PURPOSETo describe the MR findings in eight girls and women with incontinentia pigmenti, from two families. Four had skin lesions and neurologic disease, and four had only skin lesions.METHODSEight patients had physical examination, family history, electroencephalogram and MR examination of the brain. MR was repeated in the two cases with more severe changes several years after the first study.RESULTSMR revealed brain changes only in the four patients who had neurologic disease associated with the cutaneous lesions of incontinentia pigmenti. Abnormalities were located in the cerebral hemisphere contralateral to the most affected side of the body. In two cases, the MR changes were subjacent to the scalp areas where the most severe cutaneous lesions were located in the neonatal period. Hypoplasia of the corpus callosum, probably secondary to atrophy of one or both cerebral hemispheres, and abnormal signal and atrophy of the lateral regions of one of the cerebellar hemispheres also were found in all four cases. Although the changes were seen in both the T1- and T2-weighted images, they were most evident in the latter. The four patients in the fourth stage who had only cutaneous lesions without neurologic problems did not reveal any MR abnormalities.CONCLUSIONSThis study demonstrates MR signal changes and focal atrophy of the cerebrum, cerebellum, and corpus callosum in patients with incontinentia pigmenti and neurologic disorders. The MR images appear normal in patients with incontinentia pigmenti who have no neurologic abnormalities.     

In vivo MR study of brain maturation in normal fetuses.

PURPOSETo illustrate normal maturation of the fetal brain, including the migrational layer, gray matter, early myelination of internal capsules, optic radiations, and corona radiata.METHODSSeventy-seven fetal brains, ranging from 21 to 38 weeks of gestational age, were examined with MR in vivo; 33 were considered normal. MR examinations were performed as T1-weighted sequences in the axial, sagittal, and coronal planes. The neuropathologic examination (four cases) and clinical and/or neuroradiologic examinations confirmed the antenatal data.RESULTSFrom 21 to 25 weeks, the cerebral ventricles are large, corresponding to the relative fetal hydrocephalus. A slight high signal intensity can be observed in the basal ganglia as early as 21 weeks. In the cerebral hemispheres, a multilayered pattern that can be observed from 23 to 28 weeks includes the cortical ribbon, the germinal matrix, and an intermediate layer corresponding to the migrating glial cells. These findings are probably related to areas of increased cellularity. A high signal intensity can be seen within the dorsal part of the brain stem as early as 23 weeks, within the posterior limb of the internal capsules at 31 weeks, and within the central area of the cerebral hemispheres at 35 weeks. Those patterns are probably caused by the evolving process of myelination.CONCLUSIONSMR allows depiction of signal changes corresponding either to an increase in cellularity or to the evolving processes of myelination, depending on the stage of the pregnancy.     

MR Imaging–Based In Vivo Macrophage Imaging to Monitor Immune Response after Radiofrequency Ablation of the Liver

PurposeTo establish molecular magnetic resonance (MR) imaging instruments for in vivo characterization of the immune response to hepatic radiofrequency (RF) ablation using cell-specific immunoprobes.Materials and MethodsSeventy-two C57BL/6 wild-type mice underwent standardized hepatic RF ablation (70 °C for 5 minutes) to generate a coagulation area measuring 6–7 mm in diameter. CD68⁺ macrophage periablational infiltration was characterized with immunohistochemistry 24 hours, 72 hours, 7 days, and 14 days after ablation (n = 24). Twenty-one mice were subjected to a dose-escalation study with either 10, 15, 30, or 60 mg/kg of rhodamine-labeled superparamagnetic iron oxide nanoparticles (SPIONs) or 2.4, 1.2, or 0.6 mg/kg of gadolinium-160 (¹⁶⁰Gd)-labeled CD68 antibody for assessment of the optimal in vivo dose of contrast agent. MR imaging experiments included 9 mice, each receiving 10-mg/kg SPIONs to visualize phagocytes using T2¹-weighted imaging in a horizontal-bore 9.4-T MR imaging scanner, ¹⁶⁰Gd-CD68 for T1-weighted MR imaging of macrophages, or 0.1-mmol/kg intravenous gadoterate (control group). Radiological-pathological correlation included Prussian blue staining, rhodamine immunofluorescence, imaging mass cytometry, and immunohistochemistry.ResultsRF ablation–induced periablational infiltration (206.92 μm ± 12.2) of CD68⁺ macrophages peaked at 7 days after ablation (P < .01) compared with the untreated lobe. T2¹-weighted MR imaging with SPION contrast demonstrated curvilinear T2¹ signal in the transitional zone (TZ) (186 μm ± 16.9), corresponsing to Iron Prussian blue staining. T1-weighted MR imaging with ¹⁶⁰Gd-CD68 antibody showed curvilinear signal in the TZ (164 μm ± 3.6) corresponding to imaging mass cytometry.ConclusionsBoth SPION-enhanced T2¹-weighted and ¹⁶⁰Gd-enhanced T1-weighted MR imaging allow for in vivo monitoring of macrophages after RF ablation, demonstrating the feasibility of this model to investigate local immune responses.     

Fast spin-echo MR in hippocampal sclerosis: correlation with pathology and surgery.

PURPOSETo identify the extent of hippocampal sclerosis in temporal lobe epilepsy with fast spin-echo MR and correlate it with histopathologic findings and surgical outcome.METHODSMR images of 30 patients with temporal lobe epilepsy and pathologically proved hippocampal sclerosis and 30 control subjects were obtained using a fast spin-echo technique with 4000/100/4 (repetition time/echo time/excitations), 16 echo train, 2- to 3-mm section thickness with interleave, 256 x 256 matrix, and 18-cm field of view. Criteria for MR diagnosis of hippocampal sclerosis included hippocampal atrophy diagnosed with MR volumetry and/or T2-weighted signal change. Hippocampal sectional areas were plotted, and T2 signal changes were topographically evaluated to identify the extent of hippocampal sclerosis, which was subsequently correlated with histopathologic findings and surgical outcome.RESULTSHippocampal sclerosis was diffuse, involving both hippocampal head and body, in 96.7% of patients (29 of 30 patients). One patient had normal MR findings. Focal hippocampal sclerosis was not seen. Histopathologic findings of hippocampal sclerosis were present in all 29 patients who had abnormal MR findings. Eighty-six percent of patients (18 of 21 patients), who were followed for at least 1 year after temporal lobectomy, were seizure free (81%, 17 of 21 patients) or significantly improved (5%, 1 of 21 patients).CONCLUSIONFast spin-echo MR enables accurate definition of the extent of hippocampal sclerosis in patients with temporal lobe epilepsy. All cases of hippocampal sclerosis identified in this study involved the hippocampus diffusely. However, leaving the posterior portion of the hippocampus during surgery does not seem to be a major factor influencing surgical outcome.     

Effect of degeneration of the intervertebral disk on the process of diffusion.

PURPOSETo test the hypothesis that diffusion of contrast medium into the intervertebral disk is affected by the integrity of the nucleus pulposus and annulus fibrosus.METHODSIn canine intervertebral disks, defects were made in the annulus fibrosus and nuclear material was removed from the disk with a nucleotome. MR imaging was performed with intravenous contrast medium at 15, 30, 60, and 90 days after the procedure. The diffusion of contrast medium in the intervertebral disk was studied by visual inspection and by measuring changes in signal intensity. The intervertebral disk were classified at each MR study as normal or abnormal on the basis of the signal intensity on T2-weighted images.RESULTSIn untreated disks after intravenous injection of contrast medium, a band of increased signal intensity was observed near the endplates that became wider with time and approached the center of the disk. In six of the 12 treated disks, the band of increased signal intensity was visibly diminished or less discrete compared with that in the control disks. Weeks later, these treated disks showed diminished signal intensity on T2-weighted images and bulging of the annulus fibrosus.CONCLUSIONSIntervertebral disks with defects in the annulus fibrosus and reduced cartilage content were characterized by abnormal diffusion of contrast medium into the disk, and changes characteristic of early disk degeneration were detected subsequently.     

Lysolecithin-induced demyelination in primates: preliminary in vivo study with MR and magnetization transfer.

PURPOSETo study bystander demyelination in multiple sclerosis with an experimental in vivo model of toxic demyelination.METHODSToxic demyelinating lesions were created in two monkeys by injection of lysophosphatidylcholine in the centrum semiovale. Follow-up was done clinically and with serial MR studies, including T2-weighted and gadolinium-enhanced T1-weighted images and measurement of magnetization transfer ratio, until the animals were killed at days 14 and 34, respectively. Light and electron microscopy analysis was compared with MR data.RESULTSInterval measurement of magnetization transfer ratio during the course of the experiment revealed a maximum decrease at day 7 to day 8, associated with the greatest clinical manifestations. The lowest values of magnetization transfer ratio correlated with histopathologic findings of myelin and axon destruction. Magnetization transfer ratio measurements appear to be sensitive to macromolecular destruction and specifically to membrane disorganization. At no time was gadolinium enhancement observed in this model of toxic demyelination.CONCLUSIONPreliminary results of this study indicated that magnetization transfer is a good technique to follow in vivo matrix destruction in brain parenchyma lesions. The results suggest also that phases of toxic demyelination in multiple sclerosis might not show gadolinium enhancement. Differentiation between demyelinating activity and associated inflammation in multiple sclerosis lesions should be considered in further in vivo work.     

Evaluation of particulate embolic materials with MR imaging,scanning electron microscopy,and phase-contrast microscopy.

PURPOSETo analyze the properties and embolic effect of microfibrillar collagen (MFC), Gelfoam powder, and polyvinyl alcohol (PVA) materials that are used in embolization procedures in the head and neck.METHODSThe shape and surface of these embolic agents were examined with scanning electron microscopy and phase-contrast microscopy. The mean number of areas of T2-weighted high signal intensity was measured on MR images in a rat embolization model to estimate the embolic effect.RESULTSBy scanning electron microscopy and phase-contrast microscopy, MFC appears fibriform and has various sizes and an irregular surface. Gelfoam is of uniform size and has a smooth surface. PVA materials are granulated and have a rough surface. MFC is somewhat suspendable and its shape changes moderately after suspension. Gelfoam is very suspendable and its shape changes rapidly. PVA showed only mild swelling. The embolic effect of MFC was the lowest of the materials examined. Large PVA particles (250 to 500 microns) showed a lesser embolic effect than Gelfoam or small PVA particles (50 to 150 microns) or medium-sized PVA particles (150 to 250 microns). No significant differences were observed among the embolic effects of Gelfoam, small PVA particles (50 to 150 microns), and medium PVA particles (150 to 250 microns).CONCLUSIONSMFC and large PVA particles (250 to 500 microns) should be used for embolization of vascular anatomy involving potentially dangerous anastomoses. Gelfoam, PVA particles of 150- to 250-micron diameter, and PVA particles of 50- to 150-micron diameter are adequate for embolization involving homogeneous and peripheral anatomy.     

Typical MR imaging findings of perianal infections in patients with hematologic malignancies

ObjectiveWe aimed to investigate the MR imaging findings of patients with hematologic malignancies who have symptoms suggesting perianal infection and to demonstrate the importance of imaging.Subjects and methodsThe study included 36 patients with hematologic malignancies who underwent anorectal MR imaging in our department between September 2011–May 2016. Two radiologists experienced in abdominal radiology viewed the MR images in consensus. Abscesses, fistulous or sinus tracts, signal alterations and contrast enhancement in keeping with an inflammation and edema in the perianal region were recorded.ResultsPerianal abscess was found in 16 of the 36 patients. In 10 of these 16 patients there was also extensive inflammatory signal alterations in perianal and/or perineal soft tissues.In six of the 36 patients perianal fistula was detected. A sinus tract was seen at the level of subcutaneous external anal sphincter in one patient. Inflammatory signal alterations in the surrounding soft tissues were present in three of these seven patients.There were abscesses in labium majus in two patients and in one patient there were perineal abscesses with accompanying inflammatory signal alterations.In six of the 36 patients no abscess or fistula/sinus tract was seen. There were only inflammatory signal alterations with contrast enhancement in perianal or subcutaneous tissues.In two patients presenting with perianal pain and hemorrhoids, minimal inflammatory changes were detected on MR images.There were two patients with normal MR imaging findings.ConclusionAs digital examination of the anorectum and rectoscopy are avoided in neutropenic patients, MR imaging, which clearly demonstrates the perianal pathology should be preferential.     

Early MR detection of experimentally induced cerebral ischemia using magnetic susceptibility contrast agents: comparison between gadopentetate dimeglumine and iron oxide particles.

PURPOSETo evaluate early patterns of MR changes in a rat model of cerebral ischemia using the first pass of two magnetic susceptibility contrast agents.METHODSOne hours after endovascular middle cerebral artery occlusion, all animals were examined in an experimental MR unit. After bolus application of gadopentetate dimeglumine and, 10 minutes later, of iron oxide particles, the MR changes of the first pass of these contrast agents were followed using a T2*-weighted fast low-angle shot sequence. Time-density curves of both contrast agents were analyzed and compared.RESULTSAfter bolus injection of either (paramagnetic) gadopentetate dimeglumine or superparamagnetic particles, nonischemic brain parenchyma decreased markedly in signal, whereas the ischemic brain area remained relatively hyperintense (and thus became clearly delineated). Only after application of gadopentetate dimeglumine did a mild reduction in signal occur in the ischemic hemisphere, although the main artery was occluded. An explantation for this phenomenon might be residual capillary perfusion (plasma flow), which is detectable only when the smaller (paramagnetic) contrast molecules are being used.CONCLUSIONSCerebral perfusion deficits can be detected 1 hour after vascular occlusion with T2*-weighted fast low-angle shot sequences and bolus injection of paramagnetic or superparamagnetic MR contrast agents. Gadopentetate dimeglumine may be used as a marker of microcirculatory plasma flow.     

Intraarterial reteplase and intravenous abciximab for treatment of acute ischemic stroke

We performed a preliminary feasibility and safety study using intravenous (IV) administration of a platelet glycoprotein IIb/IIIa inhibitor (abciximab) in conjunction with intraarterial (IA) administration of a thrombolytic agent (reteplase) in a primate model of intracranial thrombosis. We introduced thrombus through superselective catheterization of the intracranial segment of the internal carotid artery in 16 primates. The animals were randomly assigned to receive IA reteplase and IV abciximab ( n =4), IA reteplase and IV placebo ( n =4), IA placebo and IV abciximab ( n =4) or IA and IV placebo ( n =4). Recanalization was assessed by serial angiography during the 6-h period after initiation of treatment. Postmortem magnetic resonance (MR) imaging was performed to determine the presence of cerebral infarction or intracranial hemorrhage. Partial or complete recanalization at 6 h after initiation of treatment (decrease of two or more points in pre-treatment angiographic occlusion grade) was observed in two animals treated with IA reteplase and IV abciximab, three animals treated with IA reteplase alone and one animal treated with IV abciximab alone. No improvement in perfusion was observed in animals that received IV and IA placebo. Cerebral infarction was demonstrated on postmortem MR imaging in three animals that received IA and IV placebo and in one animal each from the groups that received IA reteplase and IV abciximab or IV abciximab alone. One animal that received IV abciximab alone had a small intracerebral hemorrhage on MR imaging. IA reteplase with or without abciximab appeared to be the most effective regimen for achieving recanalization in our model of intracranial thrombosis. Further studies are required in experimental models to determine the optimal dose, method of administration and efficacy of these medications in acute ischemic stroke.     

MR of omental myelosynangiosis.

PURPOSETo describe MR findings in patients who have undergone omental transposition (omental myelosynangiosis) for spinal cord revascularization.METHODSSpin-echo MR images, without and with intravenous gadolinium, were obtained before and after surgery in three patients using a quadrature spine coil. Three-dimensional time-of-flight spinal MR angiography was also performed.RESULTSOn routine MR, the transposed omentum is an irregular, lobulated fat-equivalent mass, containing serpiginous areas of flow void, which extends through the laminectomy site to lie directly adjacent to the cord surface. MR angiography demonstrated small omental vessels, some coursing to the omentum-cord interface; however, no definite extension into the cord was detected. In all patients, there was alteration in cord size and contour after transposition, but no change in cord signal. Clinical improvement was observed in one of the three patients. The signal characteristics of the transposed omentum changed, showing less homogeneity and a gradual loss of the signal over a period of 4 months.CONCLUSIONSMR delineates transposed omentum and associated postoperative changes in omental myelosynangiosis. MR angiography is useful as an adjunct to demonstrate the small vessels near the omentum-cord interface, but lacks sufficient resolution to demonstrate neoangiogenesis within the cord.     

Cell tracking with gadophrin-2: a bifunctional contrast agent for MR imaging,optical imaging,and fluorescence microscopy

The purpose of this study was to assess the feasibility of use of gadophrin-2 to trace intravenously injected human hematopoietic cells in athymic mice, employing magnetic resonance (MR) imaging, optical imaging (OI), and fluorescence microscopy. Mononuclear peripheral blood cells from GCSF-primed patients were labeled with gadophrin-2 (Schering AG, Berlin, Germany), a paramagnetic and fluorescent metalloporphyrin, using established transfection techniques with cationic liposomes. The labeled cells were evaluated in vitro with electron microscopy and inductively coupled plasma atomic emission spectrometry. Then, 1×10⁶–3×10⁸ labeled cells were injected into 14 nude Balb/c mice and the in vivo cell distribution was evaluated with MR imaging and OI before and 4, 24, and 48 h after intravenous injection (p.i.). Five additional mice served as controls: three mice were untreated controls and two mice were investigated after injection of unlabeled cells. The contrast agent effect was determined quantitatively for MR imaging by calculating signal-to-noise-ratio (SNR) data. After completion of in vivo imaging studies, fluorescence microscopy of excised organs was performed. Intracellular cytoplasmatic uptake of gadophrin-2 was confirmed by electron microscopy. Spectrometry determined an uptake of 31.56 nmol Gd per 10⁶ cells. After intravenous injection, the distribution of gadophrin-2 labeled cells in nude mice could be visualized by MR, OI, and fluorescence microscopy. At 4 h p.i., the transplanted cells mainly distributed to lung, liver, and spleen, and 24 h p.i. they also distributed to the bone marrow. Fluorescence microscopy confirmed the distribution of gadophrin-2 labeled cells to these target organs. Gadophrin-2 is suited as a bifunctional contrast agent for MR imaging, OI, and fluorescence microscopy and may be used to combine the advantages of each individual imaging modality for in vivo tracking of intravenously injected hematopoietic cells.