Biomedical subjects
Publications and source records attributed to M Kormano.
Four double-breast coils were designed for the low-field resistive magnet MR imaging of female breasts at 0.02, 0.04, and 0.1 T. The signal-to-noise ratio is optimized by shaping the coils, by constructing two different size coils at 0.02 T, and by using special wire for the turns of the solenoidal coils. The approximate linear dependence of the SNR on the Larmor frequency is estimated.
In the Nordic countries there are several reasons why teleradiology has been an interesting topic of research during the last years. The distances in rural areas are long, and radiology expert service is not available in every health centre which is able to provide X-rays. Also, the telecommunication network is on a very advanced level in the Nordic countries. The staff is well educated and they are used to operating with computers. This all means that the infrastructure to develop and use systems like teleradiology exists. This paper describes two separate systems developed in Norway and Finland. Their development has been in many respects the same. The common hardware and software features, as well as the differences and the clinical experiences, are discussed in this paper.
Lumbar intervertebral discs and paraspinal muscles in 74 healthy volunteers ranging in age from 19 to 74 years were evaluated with MRI, and the occurrence of degeneration was correlated to age and body mass. Muscle size and the amount of fat in the muscles was studied from MRI cross sections. When the back muscles were degenerated, they were small and contained fat deposits. By contrast, the psoas muscles never showed gross fat deposits. Degeneration of both the lumbar discs and muscles increased with age. No correlation was found between muscle degeneration and overweight. Muscle degeneration is as common as disc degeneration in the lumbar area. MRI is an excellent method to assess both muscle and disc degeneration.
RATIONALE AND OBJECTIVES: Time-dependent behavior of T1 in brain infarcts and in brain tissue of the contralateral hemisphere was studied in the subacute and early chronic stages of stroke. METHODS: T1 was measured from magnetic resonance images (MRIs) of 29 patients as a function of infarct location and age. Another group of 11 patients was studied with consecutive MRI studies during the first 5 weeks after the onset of infarct, and the distribution of T1 in the infarctions was analyzed from T1 maps using a histographic method. RESULTS: During the first 2 months after a stroke, T1 was longer in the infarcted gray matter than in the infarcted white matter (P = .002), and prolonged linearly in both. The histographic analysis showed a component arising from tissue breakdown products that could be identified for up to 5 weeks. A transient lengthening in T1 of the contralateral hemisphere, reaching a maximum at 3 weeks, also was observed. CONCLUSIONS: These characteristics of recent infarctions differentiate them from older, gliotic lesions. The lengthening of T1 in the contralateral hemisphere may reflect remote flow and metabolic effects of brain infarctions.
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Bovine serum albumin (BSA) and porcine serum fibrinogen (FIB) were multiply labeled with gadolinium3+ by using three different ligands: DTPA dianhydride, isothio-cyanato-benzyl-DTPA (ITCB-DTPA), in which none of the five coordinating carboxylates is employed for macromolecular linkage, and isothiocyanatobenzyl-TRITA, a macrocyclic ligand. The nuclear magnetic resonance dispersion (NMRD) profiles of the protein-(Gd chelate) conjugates were characteristic to each chelate involved, possessing, as expected, greater longitudinal relaxivities than the corresponding Gd chelates alone and exhibiting prominent peaks at the proton Larmor frequency range of 10 to 40 MHz. Particularly favorable relaxation enhancement was measured in the solutions of BSA-(ITCB-DTPA-Gd) at this field range. When the number of chelates conjugated with protein increased, up to 163 Gd chelates per one fibrinogen, a progressive decrease in relaxivity was observed. This study demonstrates the relaxation properties of novel macromolecular contrast agents designed for magnetic resonance imaging.
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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.
MR imaging with a 0.02 T resistive magnet was used to establish the correlation between the histologic grading of patellar cartilage degeneration and fat water separation images or T1- and T2-relaxation times. We examined 23 cadaveric patellae. There was a positive correlation between histologically graded cartilage degeneration and T1-relaxation time. Patellar cartilage was well differentiated from surrounding structures on chemical shift water proton images, and an evaluation of cartilage degeneration was possible. No correlation was found between cartilage damage and T2-relaxation time. Chemical shift imaging at 0.02 T is easy to perform and gives further information of cartilage disorders.
Bovine serum albumin, immunoglobulin G, and fibrinogen were labeled with Gd-DTPA using a bifunctional chelating agent DTPA anhydride. The protein-(Gd-DTPA) conjugates had 1.4- to 2.0-fold greater longitudinal relaxivities at 0.02 and 0.44 T than the relaxivity of plain Gd-DTPA. The increase of longitudinal relaxivity was not directly related to the size of carrier protein. Up to 50 Gd-DTPA chelates per protein, longitudinal relaxivity of the conjugates was proportional to the concentration of Gd and independent of the Gd/protein ratio.
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Preoperatively and postoperatively, patellar motion in 11 knees with chondromalacia was analyzed by MRI at 0 degrees, 10 degrees, 20 degrees, and 30 degrees of knee flexion. The preoperative patellar position clearly deviated from normal at 0 degrees-10 degrees of knee flexion. The lateral release operation corrected this deviation.
Negative gastrointestinal contrast enhancement can be achieved by oral administration of superparamagnetic particles. Their feasibility for the MR imaging of the female pelvis and lower abdomen was evaluated in studies on 32 follow-up patients with treated gynaecologic cancer. All the applied doses (0.2-1.0 mg particles/ml given in a volume of 600-800 ml) of contrast medium decreased the intraluminal signal. However, there was unpredictable individual variation in segmental distribution, and in some cases only a limited contrast effect was obtained. Image distortion was detected when the applied particle concentration exceeded 0.5 mg/ml, especially of the sagittal sections.
Intramuscular hemorrhage was induced by injecting autologous blood into the paraspinal muscle of 8 rabbits. In order to evaluate the time-dependent changes of hemorrhage observed on MRI, the animals were imaged at different stages of blood resolution at 0.02 tesla (T), and control examined with ultrasound using a 7.5 MHz linear transducer. Six inversion recovery sequences (TR = 1,000 ms. TE = 30 ms, and TI = 18, 48, 148, 201, 302, and 398 ms) were used for the in vivo calculation of T1 relaxation times. IR 1,000 (398)/30 imaging was performed before and after the Gd-DOTA administration. The hemorrhage was evident on MR images throughout the study, especially on the T2 weighted (SE 1,000/100) images. MRI showed the healing lesion longer than ultrasound. The T1 relaxation time increased during the time of resolution. Lesions on days 4 to 7 enhanced in intensity after the injection of Gd-DOTA.
Blood echogenicity was measured in four patient groups with circulatory disturbances (myocardial infarction, stroke, claudication, and deep venous thrombosis) at hospital admission and one week later. The recording was done by an A-mode ultrasonic method at three shear rates down to 4.1 s-1. The rheological effects of adding an anti-aggregatory drug, naftidrofuryl, was tested in vitro at concentrations ranging from 10(-8)-10(-6) M. Echogenicity was lowest in blood from healthy volunteers and significantly greater in blood from patients with claudication. The in vitro addition of naftidrofuryl significantly lowered the echogenicity of blood samples taken from patients with venous thrombosis in the lower extremities. The authors suggest that increased blood echogenicity, which can be pharmacologically manipulated, may be a nonspecific indicator of disease.
We investigated the effect of radiographic contrast media (RCM) on red blood cell (RBC) aggregation by analyzing echogenicity of flowing blood before and after the addition of 2%, 20%, 50% or 95% volume of undiluted meglumine diatrizoate, iohexol, sodium meglumine ioxaglate, or iopamidol and equiosmolar volume concentration of saline. This was done both by stepwise increasing the concentration with minimal mixing and by stepwise decreasing the concentrations with more efficient mixing. All contrast media caused a drop in blood echogenicity after a proper mixing when compared with saline addition. After minimal stirring, both meglumine diatrozoate and iohexol caused a significant increase in blood echogenicity at volume concentrations over 50%. The paper demonstrates that earlier findings of both increased and decreased RBC aggregation following exposure to RCM can be reproduced and that the result depends on experimental setup. In diatrizoate and iohexol RBC aggregates disappear after mixing (increasing the shear rate) or when the RCM/blood mixture is diluted. After dispersement, the abnormal RBC aggregates will not reform.
The correlation of roentgenographic findings, clinical history, and incipient disc degeneration (DD), diagnosed with magnetic resonance imaging, was analyzed in young patients with low-back pain (LBP). One or more lumbar discs were abnormal in 57% of the 20-year-old LBP patients (n = 75) and in 35% of the asymptomatic controls (n = 34) in MRI. Narrowed disc spaces and alterations attributed to lumbar Scheuermann's disease, shown on the radiographs, were always associated with DD in MRI. Such a strong relationship was not observed with transitional vertebrae, spondylolisthesis, spina bifida, or postural abnormalities. However, an increased weight, a positive straight leg raising test, and a reduced lumbar mobility was consistent with an increase in frequency of DD. Magnetic resonance imaging is a safe and sensitive method for studying the presence and etiologic factors of DD.