Acta radiologica. Supplementum最新文献

Purpose: It would be beneficial to design a targetable microbubble ultrasound contrast agent that would selectively bind to the areas of interest in the body and enhance the target organ in the ultrasound examination.

Material and methods: We have studied the feasibility of targeting in a model system. We used avidin and biotin as a model ligand-receptor pair. Avidin was adsorbed on the surface of polystyrene, and biotin derivative was attached to microbubble shells. After removal of unincorporated biotin from the microbubbles, they were allowed to come in contact with avidin-coated or albumin-coated plastic. Unbound bubbles were washed by a stream of water.

Results: Binding of microbubbles to the surface occurred selectively in the areas where avidin layer was deposited. Binding of microbubbles to avidin layer was dependent on the amount of biotin incorporated in the microbubble shell. Presence of free biotin blocked targeting completely. Acoustic studies were performed using a custom-built ultrasound measurement apparatus and an ultrasound medical imaging system. Microbubble-coated areas of the plastic dish were clearly visualized with ultrasound imaging. A strong backscattered signal was obtained for microbubble surface densities as low as 3%.

Conclusion: Microbubbles have been selectively targeted via a ligand-receptor system in vitro. Firm binding of microbubbles to avidin-coated surface has been achieved. Microbubbles deposited on the target were visualized with ultrasound imaging systems.

Some fundamentals of image processing, its applications to MR imaging, and inherent problems are discussed. Processing of contrast-enhanced dynamic imaging studies is introduced and some clinical examples explain the applications in research and clinical routine.

The nuclear spin polarization of noble gases can be strongly enhanced by laser optical pumping followed by electron-nuclear polarization transfer. Direct optical pumping of metastable 3He atoms has been shown to produce enormous polarization in the order of 0.4-0.6. This is about 10(5) times greater than the polarization of water protons at thermal equilibrium used at conventional MR imaging. We demonstrate that hyperpolarized 3He gas can be applied to nuclear MR imaging of human organs with air-filled spaces. In vivo 3He MR experiments were performed in a whole-body MR scanner with a superconducting magnet ramped down to 0.8 T and at 1.5 T using a double resonant Helmholtz coil operating at 63.6 and 48.6 MHz for 1H and 3He, respectively. Anatomical details of the lungs of a volunteer were visualized with the FLASH technique demonstrating the potential of the method for fast imaging of airways in the human body and for pulmonary ventilation studies.

Purpose: The aim of this phase-III clinical trial was prospectively to evaluate the clinical safety and diagnostic efficacy as well as the effects on laboratory and electrocardiographic parameters of new iodinated, nonionic, low-osmolality contrast medium, iobitridol(Xenetix 350) during coronary angiography in adults in comparison to an iodinated, nonionic, low-osmolality reference product, iohexol (Omnipaque).

Materials and methods: This 2-center, comparative, randomized, double-blind trial involved 90 patients, 46 receiving iobitridol and 44 iohexol. Clinical safety was evaluated by recording the adverse events observed during investigation and by the patient's assessments. Electrocardiographic effects on laboratory parameters were evaluated as well as diagnostic efficacy.

Results: The age, sex, presence of risk factors and clinical picture ( unstable angina, postinfarction) were not significantly different between the 2 treatment groups. The incidence of significant coronary lesions (stenosis 50%) was also not significantly different between the 2 treatment groups. Clinical safety was good in both groups. Four patients experienced an adverse event, 2 in each group. In the iobitridol group, one patient had an episode of hypertension, followed by hypertension and prolonged chest pain was observed and one patient had sinus tachycardia. In the iohexel group, chest pain was observed in one patient and nausea in another. ECG safety was good in both groups. Transient excitability disorders were observed in 10 and 6 patients, respectively. Moderate conduction abnormalities were noted in one patient in each group and repolarization abnormalities in 10 and 8 cases, respectively. Safety in laboratory parameters was good with no significant changes in either. Diagnostic efficacy was good to excellent in all patients.

Conclusion: Diagnostic efficacy and safety of iobitridol 350 in terms of effects on clinical, laboratory and electrocardiographic parameters were comparable to those of the nonionic reference product.

A better understanding of the biologic behavior of embolic agents in the liver and the blood supply to hepatic tumors is of utmost importance in embolization and chemoembolization. In vivo microscopy, which allows observation of live hepatic circulation, was used in this study along with angiography, vascular cast technique, and light and electron microscopy. Iodized oil injected into the hepatic artery passed through the peribiliary plexus to enter the portal vein, and subsequently traversed the hepatic sinusoids. The time required for clearance of the oil from the liver and recovery of the microcirculation depended largely on the patency of the hepatic artery. Kupffer cells actively captured and phagocytosed iodized oil droplets in hepatic sinusoids. The hepatic tumors were confirmed to have a dual blood supply from the hepatic artery and the portal vein. Embolization of either the hepatic artery or the portal vein alone did not completely stop the blood circulation in the tumors. A reciprocal relationship between the hepatic artery and the portal vein in the blood supply to hepatic tumors was demonstrated dynamically and intrahepatic arterioloportal communications, especially the peribiliary plexus, play an important role in the tumor circulation. The current trans-catheter intraarterial management of hepatic tumors is insufficient in that it deals only with the hepatic arterial blood supply and ignores that from the portal vein. Iodized oil creates the potential for dual embolization of the hepatic tumor through a single hepatic arterial catheterization.

Although the incidence of serious adverse effects is low during clinical coronary arteriography, life-threatening cardiovascular complications occasionally occur. Ventricular fibrillation (VF) is most often seen during contrast media (CM) injection through a wedged catheter. A simulated wedged catheter model in dogs has therefore been developed. Further, patients with heart failure are at greater risk for CM-related side effects during coronary arteriography. Thus, an acute ischemic heart failure model has been used. The present thesis was designed to investigate the cardiac electrophysiologic and hemodynamic effects of CM during selective coronary arteriography in normal and failing hearts, and in particular the role of electrolyte addition to nonionic CM. The risk of spontaneously induced VF and the arrhythmogenic mechanisms were studied when using iso-osmolal and low-osmolal CM having different contents of electrolytes, and after pretreatment with antiarrhythmic drugs. Further, effects of adding electrolytes to nonionic CM during single and fast repeated injections in normal and failing hearts were studied. Also possible effects of oxygenating CM were studied. CM injection in a wedged catheter situation had a high risk for VF. Probably, VF was due to induced regional electrophysiologic changes in ventricular activation and repolarization. Pretreatment with antiarrhythmic drugs did not prevent VF. However, addition of low concentrations of electrolytes to nonionic CM reduced the risk for VF in a wedged catheter situation. The results indicate that side-effects of CM during coronary arteriography are related mainly to the passive washout of cardiac electrolytes. Electrolyte shifts during coronary arteriography may change the myocardial Na/Ca balance and cellular calcium control. The nonionic, iso-osmolal CM iodixanol, with a balanced content of sodium and calcium and the low-osmolal, nonionic CM iohexol, also with a balanced content of electrolytes, had about the same low risk for inducing VF and presented a much lower risk for inducing VF than did iohexol and ioxaglate in a wedged catheter situation. Single injection of iohexol with a balanced eletrolyte addition induced only minimal electro-physiologic changes and was well tolerated hemodynamically. Repeated intracoronary CM injections during ischemic heart failure were associated with similar additive electrophysiologic and hemodynamic changes as when using iohexol without electrolyte supplement. Oxygenated and nonoxygenated CM presented the same risk for inducing VF. Only minor electrophysiologic and hemodynamic differences could be detected during wedged catheter injection. In conclusion, addition of key electrolytes to nonionic CM can reduce the risk of cardiac complications during coronary arteriography. Oxygenation of CM does not seem to significantly further reduce the risk.

This project was initiated with the introduction of magnetic resonance (MR) in Denmark in order to evaluate the possibilities of this technique as a diagnostic aid in non-focal liver and splenic diseases. The signal intensities in the MR image are sensitive to the longitudinal relaxation (T1), the transverse relaxation (T2), flow and chemical shift. All these parameters may be quantified by developing specific pulse sequences sensitive to the parameter in question. Previous studies had indicated that relaxation time measurements might be of value in the diagnosis of liver cirrhosis and haemochromatosis. Measuring relaxation times in these 2 groups of patients posed different challenges. In patients with liver cirrhosis a method had to be developed for simultaneous T1 and T2 relaxation time measurements, which was robust to the respiratory motion of the liver. A combination of multi-echo pulse sequences with different repetition times was chosen, because motion effects were partly refocused. Multi-acquisition was used to improve the signal-to-noise ratio in the heavily saturated experiments with short repetition times, to further reduce the sensitivity to motion. To test the quality of this pulse sequence, phantom experiments were performed, and sensitivity to motion was tested by measuring with and without respiratory synchronization. Respiratory synchronization gave a marked improvement in focal liver diseases, whereas no difference was found in non-focal diseases. Standard imaging sequences with a minimum echo time of 30 ms could not be used to measure the short T2 relaxation times found in patients with increased liver iron. A volume-selective multi-echo spectroscopic pulse was developed with a minimum echo time of 4 ms. Biexponential signal decay could be shown in patients with increased liver iron by using this sequence. Patients with liver cirrhosis, as a group, had increased T1 relaxation times compared to normal volunteers, but an overlap in T1 values was found. No correlation between the degree of fibrosis and the T1 relaxation time was found. Liver iron concentration could be quantified either by using the fast component of the T2 signal decay or by using the decreased signal in spin-echo and gradient echo images. Patients with leukemias and myeloproliferative disorders had prolonged T1 relaxation times in the spleen, but a considerable overlap was found between this group and a group of patients with benign hyperplasia and patients with splenomegaly secondary to portal hypertension. Volume-selective proton spectroscopy was developed and used to quantify the liver fat concentration. The accuracy of the method was about 3 g/100 g. With the implementation of a second generation scanner system it became possible to develop a pulse sequence, using the phase information in the MR signal, to measure portal vein flow during breath-holding. This method made it possible to estimate the portal vein flow during fasting, and the flow increase

Purpose: To obtain information on the morphology of the proximal portion of the vestibular aqueduct.

Material and methods: One hundred plastic casts of temporal bone were examined with a dissection microscope at high magnifications in order to evaluate the proximal portion of the vestibular aqueduct. The difficulties in reproducing these minute structures were solved by light scanning photography.

Results: There is usually more than one paravestibular canaliculus (PVC) around the proximal portion of the vestibular aqueduct closely related to an intra-and a periaqueductal vascular network. An estimate was made of the number of PVCs and their widths measured. The origins of the PVCs at the wall of the vestibule were identified and their widths were measured. Numerous vascular sulci and impressions of a vascular network on the inside of the bony wall of the vestibule were revealed close to the internal aqueductal aperture. The pattern of the channels and the number of the paravestibular canaliculi were not influenced by the pneumatization of the temporal bone.

Conclusion: The significance of these vascular structures and their influence on the radiographic reproducibility of the proximal portion of the vestibular aqueduct is discussed.

In the radiological process it is necessary to develop tools so as to explore how X-rays can be used in the most effective way. Evaluation of models to derive measures of image quality and risk-related parameters is one possibility of getting such a tool. Modelling the image receptor, an important part of the imaging chain, is then required. The aim of this work was to find convenient and accurate ways of describing the blackening of direct dental films by X-rays. Since the beginning of the 20th century, the relation between optical density and photon interactions in the silver bromide in X-ray films has been investigated by many authors. The first attempts used simple quantum theories with no consideration of underlying physical interaction processes. The theories were gradually made more realistic by the introduction of dosimetric concepts and cavity theory. A review of cavity theories for calculating the mean absorbed dose in the AgBr grains of the film emulsion is given in this work. The cavity theories of GREENING (15) and SPIERS-CHARLTON (37) were selected for calculating the mean absorbed dose in the AgBr grains relative to the air collision kerma (Kc,air) of the incident photons of Ultra-speed and Ektaspeed (intraoral) films using up-to-date values of interaction coefficients. GREENING'S theory is a multi-grain theory and the results depend on the relative amounts of silver bromide and gelatine in the emulsion layer. In the single grain theory of SPIERS-CHARLTON, the shape and size of the silver bromide grain are important. Calculations of absorbed dose in the silver bromide were compared with measurements of optical densities in Ultra-speed and Ektaspeed films for a broad range (25-145 kV) of X-ray energy. The calculated absorbed dose values were appropriately averaged over the complete photon energy spectrum, which was determined experimentally using a Compton spectrometer. For the whole range of tube potentials used, the measured optical densities of the films were found to be proportional to the mean absorbed dose in the AgBr grains calculated according to GREENING'S theory. They were also found to be proportional to the collision kerma in silver bromide (Kc,AgBr) indicating proportionality between Kc,AgBr and the mean absorbed dose in silver bromide. While GREENING'S theory shows that the quotient of the mean absorbed dose in silver bromide and Kc,AgBr varies with photon energy, this is not apparent when averaged over the broad (diagnostic) X-ray energy spectra used here. Alternatively, proportionality between Kc,AgBr and the mean absorbed dose in silver bromide can be interpreted as resulting from a combination of the SPIERS-CHARLTON theory, valid at low photon energies ( < 30 keV) and GREENING'S theory, which is strictly valid at energies above 50 keV. This study shows that the blackening of non-screen films can be related directly to the energy absorbed in the AgBr grains of the emulsion layer and that, for the purpose of mo

To assess lateral subluxation of the femoral head, the acetabulum-head index (AHI) was determined on 37 bilateral radiographs and arthrograms from children with unilateral Legg-Clavé-Perthes disease (LCPD). To establish reliable normal limits for the AHI, the non-affected hip was regarded as normal material. On radiographs, the lower normal rate was 80.7. On arthrograms, if the bony acetabular edge was used as the lateral margin of the acetabulum, the lower normal rate was 68.4 and if the labrum was used as landmark, the corresponding rate was 86. To establish normal medial joint space (MJS) and migration percentage (MP) values, 166 hip radiographs from 83 healthy children aged between 3 and 12 years were evaluated. The MJS values varied according to age and sex, the mean upper normal value being 11.2 mm; MP values were dependent on age only, the mean upper normal value being 20.8. Specific upper normal MJS and MP values were established for each age and sex group. To determine the corresponding values on arthrograms, the arthrograms and radiographs of the contralateral hips of 37 children with unilateral LCPD were used, the upper normal MJS and MP values being 5.7 and 31, respectively, which were unrelated to either age or sex. By using these normal values on the radiographs and arthrograms of the 37 affected hips, we found MP to be the best method for detecting whether or not a Perthes hip was contained within the acetabulum. The role of conventional radiography and bone scintigraphy was investigated in predicting the radiological outcome of LCPD in 75 children (86 hips). Bone scintigraphy provided more accurate information concerning the extent of the necrotic process than did the initial radiographs. Moreover it could reveal revascularization and consequently the stage of the disease. Revascularization may occur as early as one month after the onset of symptoms. However, the method was unable to predict the outcome of the disease in some of the cases, especially when it was performed late after the onset of symptoms. Conventional radiography provides important information about other parameters, such as "head-at-risk" signs, which facilitate treatment selection. Of these signs, not only lateral subluxation but also metaphyseal changes strongly predispose to severe deformity of the hip joint. In a prospective study of 22 patients (24 hips) with LCPD, the early conventional radiographs, arthrograms, bone scans and MR images were evaluated. MR imaging gave earlier and more reliable information about the real extent of necrosis of the femoral head, compared with radiography and scintigraphy. Furthermore, revascularization could be more clearly demonstrated on MR images than on scintigrams. MR imaging and arthrography were alike, however, as regards to reveal lateral subluxation, while radiography was less sensitive. The value of MR imaging for assessing the configuration and structure of the femoral head was investigated in comparison with