Sadek K. Hilal

In vivo NMR imaging of sodium-23 in the human head

Surgicale report the first clinical nuclear magnetic resonance (NMR) images of cerebral sodium distribution in normal volunteers and in patients with a variety of pathological lesions. We have used a 1.5 T NMR magnet system. When compared with proton distribution, sodium, shows a greater vriation in its concentration from tissue to tissue and from normal to pathological conditions. Image contrast calculated on the basis of sodium concentration is 7 to 18 times greater than that of proton spin density. Normal images emphasize the extracellular compartments. In the clinical studies, areas of recent or old cerebral infarction and tumors show a pronounced increase of sodium content (300–400%). Actual measurements of image density values indicate that there is probably a further accentuation of the contrast by the increased “NMR visibility” of sodium in infarcted tissue. Sodium imaging may prove to be a more sensitive menas for early detection of some brain disorders than other imaging methods.

Primary Cerebral Arterial Occlusive Disease in Children

Of 87 children with acute acquired hemiplegia, 17 had primary arterial occlusions. These cases are analyzed in detail, and an angiographic classification presented. Each group showed a similarity between morphology and prognosis. Of interest are (1) correlation between the pattern of lenticulostriate artery occlusion and that of muscular weakness in basal occlusion without telangiectasia, (2) transcerebral anastomoses between lenticulostriate vessels and leptomeningeal branches of the middle cerebral artery in basal occlusion with telangiectasia, (3) angiographic findings of periarteritis nodosa. Angiography is particularly indicated if hemiplegia is associated with subarachnoid hemorrhage or with headache.

Cerebral hyperemia, stroke, and transfusion in sickle cell disease

To investigate cerebral hemodynamics in sickle cell disease (SCD), we used the 133Xenon inhalation technique of quantifying cerebral blood flow (CBF) in 67 patients. Clinical examinations and cerebral magnetic resonance imaging also were performed in all patients. Compared with age-matched healthy controls, CBF was elevated by 68% in patients, and inversely related to hematocrit. An experimental index of cerebral blood volume, pr4, was also elevated in the patients in a similar manner. Cerebral blood volume was positively correlated to CBF in SCD patients but not in controls. History of stroke and current neurologic symptoms were associated with lower flow and higher cerebral blood volume. Transfusion therapy reduced the hyperemia, the reduction being greater than expected by hematocrit elevation alone. These findings document a vasodilatory hyperemia in SCD. This dilatation may be a risk factor for ischemic distal-field infarctions, as visualized by MRI, due to a limitation of cerebrovascular reserve capacity.

Computed tomographic measurement of the xenon brain-blood partition coefficient and implications for regional cerebral blood flow: a preliminary report.

The calculation of regional cerebral blood flow requires, in addition to the measurement of the clearance, a knowledge of the regional brain-blood partition coefficient. The usual 133Xe washout techniques do not measure this latter parameter but use published values for normal brain tissue. This may lead to large errors in pathological tissue because the partition coefficient changes significantly in brain tumors. Investigations have begun into the use of CT and stable xenon to produce a cross sectional view of the brain in terms of its brain-blood partition coefficients. Results of experiments using an iodine phantom and xenon inhalation in animals are presented.

Computerized Tomography of the Orbit Using Thin Sections

OMPUTERIZED tomography (CT) has made a great impact on the diagnosis and management of orbital disease.‘~2.7,8.‘0,‘2,14,16-18~20 It has replaced orbitography, orbital venography, and to a great extent arteriography.” The natural radiographic contrast provided by the high fat content in the orbit facilitates detection of a broad spectrum of pathologic conditions, and particularly of small lesions. To maximize the usefulness of CT in the orbit, we have modified our EMI head scanner with a special collimator that thins the x-ray beam from the standard 8 mm down to 4 mm. With this modification, improved anatomic resolution, particularly in the orbital apex, was achieved. Lesions in the apex are difficult to detect and characterize on thick sections, even with machines featuring a finer matrix than the 160 X 160 used in this work. The dose delivered by the technique described here is approximately 2 rads per patient. The dose is usually substantially higher if a total body machine with a finer matrix is used.

Diastematomyelia in children. Radiographic study of 34 cases.

The radioanatomic features of diastematomyelia were studied in 34 children. Characteristics of the septum, intermedullary space, the split cord, the low conus, and prominent filum terminale are analyzed, The diastematomyelic septum is calcified from an ossification center different from that of the vertebrae or laminae. The combination of intersegmental laminar fusion and spina bifida at or adjacent to the level of the fusion suggests diastematomyelia. The incidence of scoliosis increases in older children with diastematomyelia when the condition remains untreated.

Sodium nuclear magnetic resonance imaging of myocardial tissue of dogs after coronary artery occlusion and reperfusion

Nuclear magnetic resonance (NMR) imaging techniques have been applied to the observation of tissue sodium-23 in normal and ischemic canine myocardium. To produce a region of ischemia and infarction in the myocardium, in six dogs a coronary artery was subjected to 1 hour of surgical occlusion followed by 1 hour of reperfusion. The dogs were then killed and sodium-23 NMR images of the excised hearts were obtained using a high field NMR imaging system. These images were compared with tissue sodium contents measured by flame photometry. The regions of ischemic damage were clearly visible as areas of increased sodium NMR signal on the three-dimensional images. A good correspondence was found between the relative intensity of the sodium signals and the sodium contents of normal myocardium and myocardium subjected to coronary artery occlusion and reperfusion. The data suggest the feasibility of NMR sodium imaging to detect the location and extent of myocardial damage in patients with coronary artery disease.

Transcranial Doppler ultrasonographic changes after treatment for arteriovenous malformations.

We performed transcranial Doppler ultrasonography on 15 patients with arteriovenous malformations before and after embolization or surgical resection to compare quantitatively the hemodynamic effects of these two treatments. Changes in mean blood velocity and pulsatility index were analyzed in 19 treated feeding arteries. Blood velocity decreased by a mean of 38.1% or 46.5 cm/sec (p less than 0.0001, two-tailed paired t test); decreases were greater for surgically resected arteries (46.2% or 55.9 cm/sec, p less than 0.003) than for embolized arteries (30.8% or 38.0 cm/sec, p less than 0.0003). Pulsatility index increased by a mean of 54.7% or 0.25 (p = 0.0001); increases were greater for surgically resected arteries (65.8% or 0.29, p = 0.0045) than for embolized arteries (44.8% or 0.20, p less than 0.001). The differences in the changes in blood velocity and pulsatility index between treatment groups were not significant. These data demonstrate that embolization results in hemodynamic changes that are qualitatively similar to those occurring after surgical resection of arteriovenous malformations. Transcranial Doppler ultrasonography is a reliable and convenient noninvasive method for monitoring hemodynamic effects of treatments for arteriovenous malformations.

Scintigraphic Detection of Osteoid Osteoma

Bone scanning with 99mTc-diphosphonate disclosed a solitary focus of intense activity in a cervical vertebra of a 17-year-old youth with persistent unexplained neck pain. Surgery subsequently demonstrated a well-circumscribed osteoid osteoma. This experience is further evidence of the efficacy of radionuclide skeletal scintigraphy in the evaluation of benign bone disease.

Development and Evaluation of a New Water-Soluble lodinated Myelographic Contrast Medium with Markedly Reduced Convulsive Effects1

A new water-soluble myelographic contrast agent with more hydrophilic properties than metrizamide was developed and tested in the primate (Macaca mulatto) and the cat. A new animal model that allows study of the convulsive effects of intrathecally administered contrast agents in the awake monkey was designed. With this sensitive model the new contrast agent was shown to have a remarkably reduced convulsive effect when compared with metrizamide and other media. Intrathecal hypertonic solutions in the cat depress the evoked cortico-spinal responses whereas the neurotoxic effects of the iodinated water-soluble contrast media increase them. The net effect is a combination of the two actions.