Disc degeneration in magnetic resonance imaging. A comparative biochemical, histologic, and radiologic study in cadaver spines

Magnetic resonance imaging (MRI) findings of 89 autopsied intervertebral discs from 22 cadaveric lumbar spines were correlated with biochemical composition, conventional radiography, and histologic structure to study the nature of disc intensity changes seen in MRI. Discs with a low signal intensity on T2-weighted MRI were characterized by shortening of relaxation times, dehydration, and decreases in total proteoglycan content and chondroitin-keratan sulfate ratios in the nucleus pulposus. This corresponded well with previously published studies. In histologic structure, no obvious differences between MRI findings were found. In conclusion, a low signal intensity in a lumbar disc on T2-weighted MRI probably reflects a true biochemical disc degeneration, but its relation to structural degenerative changes is uncertain. Therefore, MRI seems to be a sensitive and a specific imaging modality for detecting pathologic biochemical disc changes in the spine of a young adult.     

Correlation of transthoracic Doppler echocardiography and magnetic resonance imaging in measuring left anterior descending artery flow velocity and time-course of dipyridamole-induced coronary flow increase

There is an increasing need for new, functional and more quantitative parameters to assess coronary arterial function, for the purposes of evidence-based medicine. Coronary arterial function has been widely studied using pharmacological stimulation induced by dipyridamole or adenosine. Coronary flow reserve (CFR), defined as the ratio of pharmacologically induced hyperemic flow divided by basal flow, has been found to be an important functional index in both the clinical and subclinical stages of cardiovascular diseases. Ten healthy male volunteers were studied to compare transthoracic Doppler echocardiography (TTE) and MRI for measuring left anterior descending coronary artery (LAD) flow velocity and CFR. Additionally, the time-response curve of dipyridamole infusion was studied in five healthy males using TTE. Assessment of blood flow velocity, measured as MDV, PDV and VTI indicated Pearson's correlation coefficients of 0.88, 0.85 and 0.70, respectively, between flow velocity measurements performed using TTE and MRI. The results indicate that, despite minor differences in LAD diastolic velocities measured by TTE and MRI, the correlation of the LAD diastolic velocities measured using both methods are good and both methods are feasible for measuring CFR. Moreover, TTE has the unique capability of continuous measurement of LAD flow velocity, which allowed assessment of the time-response curve for dipyridamole-induced increase in LAD flow velocity in this study. This study indicates that the TTE method may be used in sequential or on-line monitoring of LAD blood flow velocity and therefore can be applied to evaluate the time- or dose-response effects of infused drugs in the coronary circulation of humans.     

Supplementation of cranial defects by an autologous bone flap stored in the abdominal wall

BACKGROUND AND PURPOSE: The aim of this paper is to present an alternative method of cranioplasty with the use of an autologous cranial bone flap stored between primary and restorative surgery in the subcutaneous pocket in the lateral hypogastric region. MATERIAL AND METHODS: Between January 1999 and April 2002, in the Department of Neurosurgery of Medical University of ?ód? we performed 36 procedures of the bone flap implantation into the abdominal subcutaneous fat tissue. These procedures followed craniectomy, mainly in cases of acute subdural hematomas and ruptured intracranial aneurysms. RESULTS: After storage, the bone flap was reimplanted in 28 patients. The mean time between operations was 14 days (range 8-53 days). In the cranioplasty group we had only one infection of the bone flap. Among patients excluded from the bone flap restoration we observed one inflammatory complication in the abdominal wall and one subcutaneous hematoma requiring evacuation. CONCLUSIONS: In our opinion, the presented method of the cranial defect's supplementation may be competitive to procedures utilizing synthetic prostheses in the population of patients for whom reimplantation of the bone flap will be expected in 2-3 months after the primary operation. Advantages of the procedure are: the autologous bone graft, the excellent cosmetic effect, low costs of the procedure and low rate of inflammatory complications.     

Cerebrospinal fluid flow in patients with dilated ventricles studied with MR imaging

The purpose of this study was to measure the cerebrospinal fluid (CSF) velocity and flow in the aqueduct in patients with wide ventricles with or without signs of normal pressure hydrocephalus (NPH) before and after shunt surgery. We studied 18 patients with wide ventricles with MRI and measured the CSF velocity values in the aqueducts. Twelve patients with the clinical triad of NPH were examined. Six patients were studied only before shunt surgery and 6 patients were studied both before and after shunt surgery. Three patients with wide ventricles without clinical triad of NPH, and 3 patients with hydrocephalus following subarachnoid hemorrhage were also examined. Seven NPH patients with hyperdynamic CSF flow and three NPH patients with normal CSF velocity and flow values showed a positive clinical response to shunt surgery. Two of the three patients with hydrocephalus and hyperdynamic CSF flow values in the aqueduct secondary to subarachnoid bleeding responded to shunt surgery. One patient with same disease and low CSF velocity and flow values did not respond. No change was detected in the CSF flow values of the aqueduct when measurements before and after shunt surgery were compared. Ventriculoperitoneal shunting does not change the CSF dynamics in the aqueduct. Received: 8 March 1999; Revised: 30 November 1999; Accepted: 23 February 2000     

Determination of fat content of burbot (Lota lota) liver with low field MR imaging (0.04 T)

A reconstructed separate fat image was used for studying the fat content of the liver of 12 dead and six living fasting burbots (Lota lota) in a 0.04 T magnetic field with olive oil as a reference. The correlation between the MR intensities and the results of the cytological, histological and chemical fat measurements, as well as chemically measured water, collagen and total protein contents were examined. The MR signal intensity in reconstructed fat images correlated well with the changes in fat content of the liver in living fish (r = 0.69, P = 0.0014). Also the contents of water (r = -0.66, P = 0.003) and total protein (r = -0.91, P = 0.013) correlated significantly with the MR signal intensity. The reconstructed fat image is thus a reliable method for following the changes in tissue fat content. The living burbot is an applicable test animal for studying the hepatic fat content with MR.     

T1ρ of protein solutions at very low fields: Dependence on molecular weight,concentration, and structure

The effect of molecular weight, concentration, and structure on 1/T₁ρ, the rotating frame relaxation rate, was investigated for several proteins using the on-resonance spin-lock technique, for locking fields B₁ < 200 μT. The measured values of 1/T₁ρ, were fitted to a simple theoretical model to obtain the dispersion curves 1/T₁ρ(ω₁) and the relaxation rate at zero B₁ field, 1/T₁ρ,(O). 1/T₁ρ, was highly sensitive to the molecular weight, concentration, and structure of the protein. The amount of intra- and intermolecular hydrogen and disulfide bonds especially contributed to 1/T₁ρ. In all samples, 1/T₁ρ(O) was equal to 1/T₂ρ measured at the main magnetic field B_o = 0.1 T, but at higher locking fields the dispersion curves mono-tonically decreased. The results of this work indicate that a model considering the effective correlation time of molecular motions as the main determinant for 1/T₁ρ relaxation in protein solutions is not valid at very low B₁ fields. The underlying mechanism for the relaxation rate 1/T₁ρ at B₁ fields below 200 μT is discussed.