Regions Of High Signal Intensity Research Articles

Magnetic resonance imaging of myocardial infarction in kawasaki disease

We performed magnetic resonance imaging in patients with Kawasaki disease following myocardial infarction to assess the usefulness of the technique in detecting myocardial infarction and coronary artery lesions. In six patients (group A), the interval after myocardial infarction was from 7 days to 7 months, and in five patients (group B), it was from 1 to 4 years. Imaging was performed with a superconducting magnet operating at 0.5 T with spin-echo sequence and ECG-gated multiple slices of 5 mm thickness. Myocardial signals were increased in group A, and the region of high signal intensity corresponded to the site of myocardial infarction. The signal intensity within the myocardium was homogeneous in five patients in group B. Coronary arteries were visualized in 20 of 22 instances. Signals within the coronary artery were observed in all 14 instances with poor contrast runoff from the coronary aneurysm, and 11 of these vessels showed high signal intensity. In all six instances in which large aneurysms with severe stenosis were present, signals in the coronary artery were increased. In contrast, high signal intensity in the coronary artery was not observed in five of six instances with good contrast runoff. Signals in the coronary arterial cavity and high signal intensity in the coronary artery persisted in five of six instances with turbulent coronary flow. The findings of increased coronary arterial signals suggested stagnant blood flow in the coronary aneurysm. In conclusion, magnetic resonance imaging was a useful modality for assessment of myocardial infarction and coronary artery lesions in Kawasaki disease.

The Effect of PhenylTert-Butyl Nitrone (Pbn) on Ccl4-Induced Rat Liver Injury Detected by Proton Magnetic Resonance Imaging (Mri)in vivoand Electron Microscopy (Em)

Acute intoxication by CCl4 induces morphological changes in rat liver which are readily detectable by 1H-NMR imaging techniques in situ. Two to four hours after the administration of CCl4, regions of high proton signal intensity are observed in the centrilobular region of the liver. The regions of high signal intensity are attributed to the formation of local edema as a result of CCl4-induced damage. Electron microscopy of the high intensity regions of CCl4 treated liver sections revealed characteristic subcellular changes which include the disapperance of ribosomes from the rough endoplasmic reticulum (RER), the fragmented appearance of the smooth endoplasmic reticulum (SER), formation of vacuoles in the cisternae and swelling of the mitochondria. Pretreatment of rats with alpha-phenyl-tert-butyl nitrone (PBN), a free radical spin trap, prior to halocarbon exposure, was found to reduce the halocarbon-induced edema in the liver. Electron microscopy of the PBN pretreated CCl4 exposed rat liver sections revealed no observable changes in subcellular organization when compared to controls.

右前腕の筋肉内に発生したＳｐｉｎｄｌｅ ｃｅｌｌ ｈｅｍａｎｇｉｏｅｎｄｏｔｈｅｌｉｏｍａの１例

Spindle cell hemangioendothelioma is a new entity defined by Weiss and Enzinger in 1986, as a low-grade malignant vascular tumor. Although the neoplasm has involved in the dermis and subcutaneous fatty tissues, no case has occurred in the muscle. The first case of spindle cell hemangioendothelioma originated from the muscle is reported. A 48-year-old female had a tumor which occurred in the extensor digiti minimi of right forearm.CT scan demonstaratetd multinodules in an isodensity region within the skeltal muscle.MRI showed multinodules in a high signal intensity region on both T1-and T2-weighted images.The patient was treated with wide excision and had no evidence of local recurrence or metastasis 5 months later.

Demarcation of myocardial ischemia: magnetic susceptibility effect of contrast medium in MR imaging.

Dysprosium diethylenetriamine-pentaacetic acid-bis (methylamide) (DTPA-BMA), a new nonionic contrast medium for magnetic resonance (MR) imaging, produces signal loss on T2-weighted images because of induced magnetic field gradients. The potential of this agent to delineate myocardial ischemia was investigated in 10 rats with acute (30 minutes) occlusion of the left coronary artery. T2-weighted MR images were acquired before and for 1 hour after intravenous administration of 1 mmol/kg of Dy-DTPA-BMA. Before administration of the contrast medium, signal intensity (SI) in the ischemic region was significantly greater than that in the normal myocardium; however, the borders of the ischemic region were not consistently distinct. The contrast medium caused marked decrease in SI of normal myocardium (18% +/- 3% of the control value), only slight decrease in the jeopardized region (76% +/- 6% of the control value), and no discernible effects on heart rate or blood pressure. Substantial contrast between normal and ischemic myocardium persisted for 1 hour. Moderate signal loss was observed in skeletal muscle. Dy-DTPA-BMA has the potential to demarcate the myocardial area in jeopardy as a region of high signal intensity because it erases signal preferentially in the normal myocardium.

Proton nuclear magnetic resonance imaging as a predictor of the outcome of photodynamic therapy of tumours.

The ability to monitor non-invasively and at early times, the cytotoxic efficacy of a cancer treatment in an individual subject, plainly of great potential clinical value. In a recent publication, Naruse et al (1986) showed proton nuclear magnetic resonance (NMR) images of a rat glioma that had been treated 48 h previously by radiofrequency (RF) hyperthermia. Regions of high signal intensity were readily distinguishable and were equated qualitatively with histological necrosis caused by the heat treatment. These increases in signal intensity almost certainly reflected an increase in water content associated with oedematous changes in the tumour. This might expected after in vivo hyperthermia, where an important contribution to the toxic effect is vascular collapse with subsequent secondary ischaemic necrosis of sheets of tumour cells (reviewed by Reinhold & Endrich, 1986). A similar form of damage occurs after photodynamic therapy (PDT), the combination of non-toxic photosensitizing drugs and non-thermal power densities of visible light (Star al, 1986), and it appeared to us that NMR imaging might be useful in assessing damage in this new form of cancer treatment. We have shown elsewhere that NMR images taken soon after a PDT treatment correspond quantitatively with histologically defined cell killing at the same interval (Dodd etal, 1989) and we present preliminary experimental results in which we relate quantitatively proton NMR images and the overall therapeutic outcome measured by tumour regrowth delay.

In vivo magnetic resonance imaging of the effects of photodynamic therapy.

Nuclear magnetic resonance (NMR) proton imaging and measurements of the parameters T1 and T2, have been carried out in vivo on the murine mammary tumour T50/80. Tumours had been treated 24 h previously by photodynamic therapy (PDT, using haematoporphyrin derivative and 630 nm laser light). Proton images clearly demarcated a high signal-intensity region on the side of the tumour closest to the incident light beam, while the parts of the tumour more remote from the beam resembled the images from untreated controls. Both T1 and T2 values were raised in the high-intensity region. This high-intensity region was shown to correspond to PDT-induced histological necrosis, the low-intensity region to histologically intact tumour. Linear regression analysis of the relationship of depth of necrosis measured histologically and 'depth of necrosis' measured from the NMR images, yielded a slope of 0.93 (r2 = 0.95).

Magnetic resonance imaging of rat brain following kainic acid-induced lesions and fetal striatal tissue transplants

Use of a small diameter (5.1 cm) radiofrequency coil provided relatively high resolution magnetic resonance (MR) images of rat heads at 0.14 Tesla. On T1-weighted images, the rat brain was clearly visible in the rat head as a region of high signal intensity. No structures were distinguished within the normal rat brain. In contrast, in the brains of rats receiving unilateral kainic acid lesions of the striatum, enlarged lateral ventricles, which are characteristics of the lesion, were clearly visible as dark areas of low signal intensity. Extrastriatal damage on the lesioned side of the brain was also evident in some of the images. Fetal striatal tissue transplants growing within the lesioned striata were also identified in the MR images. The transplanted tissue appeared as areas of high intermediate signal intensity, similar to the host brain. MR imaging is a useful technique for monitoring excitotoxin lesions of brain and fetal striatal tissue transplants in vivo.

Massive Hemorrhage within an Acoustic Neurinoma

A 39-year-old male experienced unilateral right hearing loss and tinnitus for 7 years and was hospitalized after he suddenly developed severe headache, vertigo, and right facial paralysis. Computed tomography (CT) showed a round, high-density are in the right cerebellopontine angle. Magnetic resonance (MR) imaging demonstrated a crescent-shaped region of high signal intensity, representing hemorrhage, in the superior aspect of the tumor, surrounded by edema. The right internal auditory canal was enlarged. Four-vessel angiography disclosed neither an aneurysm nor an arteriovenous malformation. A right suboccipital craniectomy revealed an encapsulated mass 3 cm in diameter in the right cerebellopontine angle. The tumor was totally removed. Histological examination revealed a typical neurinoma composed of Antoni type A and B cells. After undergoing anastomosis of the right hypoglossal and facial nerves, the patient was discharged in good condition. In this case MR imaging demonstrated intratumoral hemorrhage (which is rare in cases of acoustic neurinoma) and the surrounding tissue more clearly than did CT scanning.

Posterior pituitary gland: appearance on MR images in normal and pathologic states.

T1-weighted magnetic resonance (MR) images of the pituitary gland and sella turcica routinely demonstrate a region of high signal intensity in the neurohypophysis. High-resolution MR imaging studies of the sella turcica in 200 subjects with a normal or abnormal sella were analyzed. The hyperintensity was found in the images of about 90% of healthy subjects and patients with microadenoma, in only 43% of patients with macroadenoma, and in 12% of patients with empty sellae. The signal was absent in several patients with functional or anatomic abnormalities of the hypothalamic-hypophyseal axis. It is concluded that the high signal intensity in the posterior lobe of the pituitary gland is present in most healthy individuals and that its absence in many patients with large intrasellar masses and empty sellae is due to compression of posterior lobe tissue. Its absence in diabetes insipidus further suggests a relationship between hyperintensity and the functional status of the hypothalamic-hypophyseal axis.

MR imaging of solitary osteochondromas: report of eight cases.

MR imaging was performed in eight patients with osteochondromas, and the results were compared with the histologic findings in six of these cases. MR imaging effectively showed the essential anatomic features of lesions and was particularly useful in assessing the presence and thickness of the cartilage cap. The cartilage cap was clearly seen as a region of high signal intensity on T2-weighted images. A superficial zone of low signal intensity was seen covering the cartilage cap, corresponding to an intact perichondrium, in all of the five cases in which histologic examination confirmed the presence of an intact perichondrium. The results of MR in these cases suggest that MR is useful in the preoperative planning of cases in which excision of an osteochondroma is necessary. Optimal surgical resection of the lesion requires complete excision of an intact perichondrium to prevent possible recurrence of the tumor.

Anterior and posterior lobes of the pituitary gland: assessment by 1.5 T MR imaging.

Pituitary glands of 60 normal volunteers (30 men 20-36 years old, and 30 women 18-42 years old) were studied by 1.5 T magnetic resonance (MR) imaging. The T1-weighted images (T1WI) [repetition time (TR) = 400 ms; echo time (TE) = 25 ms] were obtained in the coronal, sagittal, and axial planes. Proton density (PD)/T2-weighted images (PDWI/T2WI) (TR = 2,000 ms; TE = 25/100 ms) were obtained in the sagittal plane using 3 mm slice thickness. On T1WIs of all subjects the posterior part (PP) of the pituitary fossa showed the highest signal, which was indistinguishable from fatty tissue. This study reveals that this region of high signal intensity (PP) corresponds to the posterior lobe and not intrasellar fat because its shape, size, and position are compatible with the posterior lobe; its signal intensity differs from that of fatty tissue on PDWI and T2WI; the absence of an intrinsic chemical shift artifact (CSA) characteristic of fat; and due to CSA, a dorsum with fatty marrow is shifted relative to the PP (or may be made to merge with it). Regarding the differentiation of the two lobes of the pituitary gland on MR, the morphology of the anterior and posterior lobes was evaluated and great variation found. Appreciation of normal is particularly important in evaluating coronal images for small pituitary lesions.

Brain radiation lesions: MR imaging.

This retrospective study was performed to assess the capability of magnetic resonance (MR) to depict and characterize diffuse and focal radiation lesions in the brain using the spin-echo technique. The MR images of 55 patients who had undergone radiation therapy were reviewed. Comparative computed tomography (CT) studies were available for all the patients. Normal white matter was chosen as reference tissue for the quantitative comparison of signal intensities. Radiation lesions (identified in eight patients) were seen as regions of high signal intensity on the sequence with a long repetition time (TR) (2.0 sec) and showed no difference in signal compared with white matter when the TR was short (0.5 sec). Nonspecific prolongation of T1 and T2 relaxation times was measured in such lesions. In one patient, subependymal tumor spread, demonstrated by contrast-enhanced CT, was missed on MR images, masked by the adjacent abnormal signal owing to radiation effects. Recurrent or residual brain tumor could not be distinguished from radiation brain necrosis either by CT or by MR imaging. It is concluded that MR can depict radiation lesions with great sensitivity but is not very helpful for discrimination between recurrent or residual brain tumor, radiation necrosis, and other brain lesions.

Imaging and characterization of acute myocardial infarction in vivo by gated nuclear magnetic resonance.

Imaging by nuclear magnetic resonance (NMR) techniques has been shown to provide high-contrast resolution between soft tissues and characterization of normal and pathologic tissues by differences in magnetic relaxation times. The current study was designed to determine whether electrocardiogram (ECG)-gated NMR imaging of the canine heart in vivo could distinguish normal from infarcted myocardium without the use of intravenous paramagnetic contrast agents. Seven dogs were studied by ECG-gated NMR imaging in vivo (spin-echo technique) with a 0.35 Tesla superconducting magnet at 2 to 7 days after ligation of the left anterior descending coronary artery. In six of the seven dogs, signal intensity was increased in the anterior wall compared with the remainder of the left ventricle; this region of high signal intensity corresponded to the area of myocardial infarction demonstrated at postmortem examination. The signal intensity of the infarcted region was 66 +/- 27% greater than that of normal myocardium (p less than .01). The T2 (spin-spin) relaxation time was 69 +/- 3% longer in the infarcted myocardium as compared with normal myocardium (p less than .01). The NMR images from the seventh dog had uniform signal intensity throughout the myocardium of the left ventricle. An infarct was not evident on postmortem examination in this dog. Thus gated NMR imaging in vivo by the spin-echo technique displays acute myocardial infarctions as regions of high signal intensity without the use of contrast media. The infarct is characterized by a prolonged T2 relaxation time.