Acta radiologica. Supplementum最新文献

Purpose: Osteoarthritis (OA) is a multifactorial process affecting cartilage and subchondral bone. Traditionally, plain radiographs and eventually bone scintigraphy are used to establish the diagnosis, whereas MR imaging, as a sensitive instrument for early diagnosis, is less commonly used. Therefore, these methods have been compared in the format of a prospective study of knee OA.

Material and methods: Individuals aged 35-54 years with chronic knee pain have been identified. The prevalence of chronic knee pain was 15% (279/2,000). Within this group, both knees in 61 randomly chosen persons were examined with plain weight-bearing radiographs of the tibiofemoral joint (TFJ), standing axial radiographs of the patellofemoral joint (PFJ), and with bone scintigraphy. One knee (the most painful at inclusion in the study) in each person was examined with MR imaging on a 1.0 T imager.

Results and conclusions: Assessment of the minimal joint space (MJS) width in the p.a. view of the TFJ in weight-bearing examinations should be performed with equal weight on both legs and in semiflexion. The p.a. view of the TFJ and the axial view of the PFJ, as well as the MJS measurements in these views, were reproducible. MJS of 3 mm in the TFJ and MJS of 5 mm in the PFJ are limits in diagnosing joint-space narrowing (JSN) in the TFJ and the PFJ, respectively. There was a high prevalence of meniscal abnormalities within the narrowed compartments of the TFJ when compared with those that were not narrowed. With the presence of marginal osteophytes in the TFJ, there was a high prevalence of MR-detected cartilage defects in the same joints whether JSN (MJS < 3 mm) was present or not. No such relationship, independent of MJS, was found between marginal osteophytes and cartilage defects in the PFJ. The agreement between increased bone uptake and MR-detected subchondral lesion (increased signal in the STIR sequence) was good. The agreement between increased bone uptake and MR-detected osteophytes or cartilage defects was in general poor. Conventional radiography is inexpensive and readily available. With the increased knowledge about interpreting weight-bearing p.a. radiographs of the TFJ and standing axial radiographs of the PFJ, these examinations will, even in the future, be a valuable and competitive technique compared with a more expensive and sophisticated method such as MR imaging, when evaluating knee pain. Further studies have to be performed to evaluate whether MR imaging has the same ability as bone scintigraphy to predict the progression of the OA process in the knee joint.

A series of gadolinium complexes conjugated to bile acids was prepared and investigated as possible hepatospecific MR imaging contrast agents. In the design of such compounds, features such as the nature of the bile acid, the site of conjugation on the bile acid skeleton, and the global charge of the conjugate were taken into account. Relaxivity measurements carried out in human serum indicate interaction of the conjugates with human serum proteins; even small structural variations significantly affect relaxivity in human serum. Pharmacokinetic data (biliary elimination in the range of 18.4-45.6%) show that bile acids can be used as address moieties to transport gadolinium complexes through hepatocytes. For a homogeneous series of compounds, differing only in the bile acid residue conjugated, it was unexpectedly found that cholic acid is twice as efficient an address moiety as cholylglycine or cholyltaurine. Preliminary results show that none of the conjugates is transported through the basolateral membrane of hepatocytes by the Na+/taurocholate carrier.

Synchrotron sources can provide intense, collimated and tunable X-ray beams suitable for medical imaging and research, allowing the use of monochromatic X-rays for human examinations. At the European Synchrotron Radiation Facility (ESRF), a beam line dedicated to medical research is under commissioning. Two imaging programs are being developed, for coronary angiography and cerebral CT. The new monochromatic imaging systems should improve image contrast and provide better image quantification. The properties of synchrotron radiation are described, as well as the instrumentation of the medical beam line and its 2 imaging programs. The new possibilities offered by synchrotron radiation for contrast media research are discussed, the improvement on concentration measurement precision achievable is underlined.

It has been suggested that nephrotoxic effects of X-ray contrast media (CM) are exerted via renal medullary hypoperfusion and hypoxia. This study was therefore undertaken to investigate the effects of CM injection on renal medullary microcirculation and oxygen tension. Red blood cell velocity (VRBC) in the renal medullary vessels was measured by a cross-correlation technique and was found to be decreased by mannitol and by all CM tested except ioxaglate. The incidence of red blood cell aggregation and cessation of blood flow in the renal medullary vessels was estimated with use of a score based on visual observations. All tested CM and mannitol induced aggregation in the renal medullary vessels. The ionic CM ioxaglate was found to induce the least aggregation. Modified Clark PO2 microelectrodes with a guard cathode were constructed and adapted for tissue PO2 measurements. PO2 was measured simultaneously in the renal cortex and outer renal medulla. The PO2 in rats with blood pressure (BP) above 80 mm Hg was found to be lower in the medulla than in the cortex. In rats with BP below 80 mm Hg the PO2 was paradoxically higher in the outer medulla than in the cortex, probably due to a decrease in the glomerular filtration rate and hence in sodium uptake from the tubules. After injection of all tested CM, PO2 in the renal cortex remained unchanged, while in the outer medulla it decreased. There was no difference in the decrease in PO2 between the tested CM. The decrease in outer medullary PO2 was prevented by injection of furosemide but not by injection of mannitol. A decrease in VRBC and PO2 in the renal medulla may be an underlying cause of CM-induced acute renal failure.

CT is an important technique in liver imaging. To improve the detection of focal liver lesions the use of non-specific, water-soluble contrast media (CM) is mandatory. However, even with use of these CM the sensitivity in tumour detection is low. In the development of liver-specific CM, the majority of the agents have been targeted to the reticuloendothelial system (RES). The clinical use of RES-specific contrast agents has been hampered by frequent adverse reactions, and a new concept whereby the CM is taken up by the hepatocytes has been developed as an alternative. Such a CM is taken up by normal liver parenchyma but not by tumour cells, enhancing the difference between normal and pathological tissue, and therefore improving the diagnostic sensitivity. In the present investigation, FP 736-03 and FP 736-04, two hepatocyte-specific lipid emulsions, have been studied using animal models. In normal liver parenchyma dose-dependent enhancement was found, whereas in tumour tissue of experimental liver metastases and hepatocellular carcinoma, no enhancement was noted. The virtually unchanged attenuation in tumour tissue meant that the liver-to-lesion contrast increased steadily during the observation period. In an attempt to establish the relationship between enhancement and tumour detection, the accumulated doses of FP 736-04 were used. Increasing accuracy in the diagnosis of liver metastases was found up to an enhancement level of 30 HU. A further increase yielded similar detection rates, but a higher proportion of false-positive results. Comparison with iohexol was rendered difficult by the occurrence of image artefacts when this CM was used. However, FP 736-03 proved superior to both native and iohexol-enhanced CT for detection of hepatic metastases. The efficacy of FP 736-04 was also studied in diseased hepatic parenchyma. In cases of fatty liver infiltration, enhancement by FP 736-04 was significantly reduced as compared with normal controls. The degree of enhancement observed in cirrhotic livers did not differ significantly from that in the controls. These preclinical investigations have shown that the hepatocyte-specific lipid emulsions FP 736-03 and FP 736-04 improve the diagnostic accuracy of focal liver lesions as compared to native and water-soluble CM-enhanced CT. FP 736-04 is taken up by diseased liver parenchyma. However, the detection of malignancy in steatotic and cirrhotic livers has not yet been studied with use of this CM.

The common strategy of combining clinical information, lung scintigraphy and pulmonary angiography in the diagnosis of acute pulmonary embolism (PE), has many limitations in clinical use. The major causes are that pulmonary angiography and lung scintigraphy are not universally available, and that pulmonary angiography is very expensive. The purpose of this thesis was to analyse different aspects of validity in regard to lung scintigraphy, pulmonary angiography, spiral CT, and ultrasound of the legs, with the subsequent intention of discussing new diagnostic strategies. Observer variations in lung scintigraphy interpretation when applying the PIOPED criteria were tested in 2 studies with 2 and 3 observers respectively and expressed as kappa values. The ability to improve agreement in lung scintigraphy interpretation was tested by training 2 observers from different hospitals. The impact of 3 observers' variations in lung scintigraphy interpretation when compared to pulmonary angiography, was tested by comparing the ROC areas of the observers. The value of combining subjectively derived numerical probabilities and the PIOPED categorical probabilities in lung scintigraphy reporting was compared to using the PIOPED categorization only, and this was tested by comparing ROC areas. The sensitivity and specificity of detecting an embolic source in the deep veins of the legs by ultrasound as a sign of PE when lung scintigraphy is inconclusive, was tested by comparison with pulmonary angiography. The sensitivity and specificity of spiral CT, compared to pulmonary angiography, was tested by comparison to pulmonary angiography. The inter- and intra-observer kappa values were in the range of moderate and fair. It was not possible to achieve better kappa values after training. Although observer variations were substantial, the accuracy did not differ significantly between the 3 observers. Incoorporating subjectively derived probabilities into lung scan reporting could not reduce the number of inconclusive investigations. Sensitivity and specificity of ultrasound in detecting PE was 0.70 and 0.97, respectively. However, 2 patients (of 9) had deep venous thrombosis and no pulmonary emboli at angiography. The sensitivity and specificity of spiral CT was 0.90 and 0.96, respectively. The observer variations at lung scintigraphy are substantial and may be difficult to improve between hospitals, even though the accuracy of observers in general is good. Although subjectively derived interpretation criteria did not show to be useful when added to categorical interpretation criteria, they may be useful when substituting established criteria. Despite recent progress in refining interpretation criteria, a substantial fraction of the patients still need pulmonary angiography to be performed. However, in many patients pulmonary angiography is not performed as prescribed. Spiral CT and ultrasound of the legs is a new favourable diagnostic strategy with a high validity

The longitudinal electronic state lifetime of the paramagnetic Gd metal within a macrocyclic ligand core can be increased by designing ligand frames that alter the vibronic interactions between the ligating atoms and the metal. We conducted the first pulsed EPR studies that demonstrated the increase in the longitudinal state lifetimes of the electronic subsystem at cryogenic temperatures. We also designed a simple sucrose/ water model that significantly increases the rotational correlation time in solution of the Gd chelate. This model system enables relaxivity studies at ambient temperatures that more readily interrogate exchange and electronic contributions to the inner-sphere relaxivity by effectively removing the rotational correlation time contribution. These results combined with water residence (Q) measurements suggest that rigidification of the macrocyclic core or that of the pendant arms increases the longitudinal electronic state lifetime of the paramagnetic Gd metal. This increased lifetime possibly contributes to the improved relaxivity for the rigid Gd chelates observed in the sucrose/ water model studies.

Lymphography is the radiological visualization of the lymph vessels and lymph nodes with contrast material. History and different modes of visualization are compared.

The evaluation of myocardial perfusion is of clinical relevance in ischemic heart disease. New noninvasive and nonionizing imaging techniques for the evaluation of myocardial perfusion are progressing. The present status and the future development of echo-contrast and dynamic-contrast MR imaging are discussed for myocardial perfusion studies.

Novel superparamagnetic particles coated with a phospholipid and a surfactant were characterized and evaluated in vivo. These particles (SBPA) were shown to exhibit r2 relaxivities in the range of 350-450 mM-1.s-1, r1 values of 8-12 mM-1.s-1 and sizes of 50-80 nm. Preliminary results of pharmacokinetics were obtained in rats following the administration of 59Fe-labelled preparations. The particles were shown to remain for hours in the blood stream before being cleared mainly by the liver. Most of 59Fe was eliminated from the body and recovered in the feces within a week. These biodistribution and elimination properties deserve more detailed studies and suggest the potential use of this product as a blood pool contrast agent.