Functional recovery of subepicardial myocardial tissue in transmural myocardial infarction after successful reperfusion: an important contribution to the improvement of regional and global left ventricular function

BACKGROUND

The transmural extent of myocardial necrosis after an acute coronary artery occlusion can vary considerably. The contribution of residual subepicardial viable myocardium to global left ventricular function is largely unknown.

METHODS AND RESULTS

We studied 12 patients with single-vessel disease 1 week after successful reperfusion of a first transmural anterior myocardial infarction (MI). With PET, myocardial blood flow (MBF) and glucose metabolism were measured regionally, and the viability was graded as normal, mismatch, or match with severely (<50% of normal) or intermediately (50% to 80% of normal) impaired MBF. Magnetic resonance tagging was used to regionally quantify fiber strains, wall thickening, and ejection fraction in patients 1 week and 3 months after the MI and in age-matched healthy volunteers. From 1 week to 3 months, subepicardial fiber shortening improved significantly in the match region (MBF <50%, -5.1+/-7.0% to -9.9+/-8. 7%; MBF of 50% to 80%, -7.1+/-7.6% to -14.9+/-7.9%). This was associated with an improvement in regional ejection fraction in the infarcted myocardium (29.6+/-21.8% to 43.5+/-15.5%, P<0.0001) and in normal regions (54.3+/-15.1% to 56.5+/-13.1%, P=0.013), contributing to an increase in global ejection fraction from 44.2+/-22.2% to 49. 3+/-17.9% (P<0.0001).

CONCLUSIONS

Functional recovery of viable subepicardial regions is a mechanism of late improvement in regional and global ejection fraction after a so-called transmural MI.

Functional MRI of the brain: localisation of eloquent cortex in focal brain lesion therapy

The aim of this study was to assess the feasibility of functional MRI (fMRI) in a clinical environment on a large patient group, and to evaluate the pretherapeutic value of localisation of eloquent cortex. Forty patients with focal brain lesions of different origin were studied using fMRI. Functional information was obtained using motor, somatosensory, auditory and phonological stimuli depending on the localisation of the lesions. To obtain information about the spatial accuracy of fMRI, the results were compared with postoperative electrocortical stimulation. Two patients with secondary trigeminal neuralgia were scanned using a motor protocol and were implanted with an extradural plate electrode. Imaging was successful in 40 of 42 patients (including the 2 with trigeminal neuralgia). These patients were analysed for strength of activation, the relation of the lesion to activation sites and the presence of mass effect. The correlation between these data and surgical findings provided significant additional clinical information. Functional MRI can be accurately performed in patients with focal brain lesions using a dedicated approach. Functional MRI offers important clinical information as a contribution to a decrease in posttherapeutic morbidity. The accuracy of the technique can be confirmed by other modalities, including invasive cortical electrostimulation.

Acute obstruction of the renal collecting system: the intrarenal resistive index is a useful yet time-dependent parameter for diagnosis

The aim of this study was to determine whether the intrarenal resistive index (RI) can be used for the diagnosis of acute obstruction in patients with renal colic and to determine whether the index is time-related. Seventy patients referred to the Emergency Department with acute renal colic and without known associated renal disease underwent duplex Doppler ultrasonography to determine the intrarenal RI at the symptomatic and asymptomatic side. The age range of the patients was 18-72 years. An RI greater than 0.68 and/or an interrenal difference in RI greater than 0.06 and/or an increase in RI of more than 11% compared with the normal side proved reliable cut-off values to diagnose acute renal obstruction. In addition, time dependency of the increase in RI was noted. No significant differences were observed within the first 6 h after the onset of symptoms. From 6 to 48 h, however, the mean RI in the affected kidney (0.70 +/- 0.06; mean +/- SD) was significantly different from that in the normal kidney (0.59 +/- 0.04) (P < 0.001). In the same period the mean difference in RI was 0.08-0.13 (P < 0.001). After 48 h the sensitivity of RI dropped substantially. It is concluded that renal duplex Doppler ultrasonography is useful for diagnosing acute renal obstruction between 6 and 48 h after the onset of symptoms.

Attenuation of virulence by disruption of the Mycobacterium tuberculosis erp gene

The virulence of the mycobacteria that cause tuberculosis depends on their ability to multiply in mammalian hosts. Disruption of the bacterial erp gene, which encodes the exported repetitive protein, impaired multiplication of M. tuberculosis and M. bovis Bacille Calmette-Guérin in cultured macrophages and mice. Reintroduction of erp into the mutants restored their ability to multiply. These results indicate that erp contributes to the virulence of M. tuberculosis.

An image-guided planning system for endosseous oral implants

A preoperative planning system for oral implant surgery was developed which takes as input computed tomographies (CT's) of the jaws. Two-dimensional (2-D) reslices of these axial CT slices orthogonal to a curve following the jaw arch are computed and shown together with three-dimensional (3-D) surface rendered models of the bone and computer-aided design (CAD)-like implant models. A technique is developed for scanning and visualizing an eventual existing removable prosthesis together with the bone structures. Evaluation of the planning done with the system shows a difference between 2-D and 3-D planning methods. Validation studies measure the benefits of the 3-D approach by comparing plans made in 2-D mode only with those further adjusted using the full 3-D visualization capabilities of the system. The benefits of a 3-D approach are then evident where a prosthesis is involved in the planning. For the majority of the patients, clinically important adjustments and optimizations to the 2-D plans are made once the 3-D visualization is enabled, effectively resulting in a better plan. The alterations are related to bone quality and quantity (p < 0.05), biomechanics (p < 0.005), and esthetics (p < 0.005), and are so obvious that the 3-D plan stands out clearly (p < 0.005). The improvements often avoid complications such as mandibular nerve damage, sinus perforations, fenestrations, or dehiscences.

Non-invasive imaging of the great vessels of the chest

Several excellent imaging modalities are available for studying the great vessels of the chest noninvasively. Besides computed tomography (CT), magnetic resonance imaging (MRI) and echocardiography (in particular the transesophageal approach) can accurately depict abnormalities of the thoracic vasculature, and are a valuable substitute for contrast angiography in most circumstances. The aim of this paper is to provide a comprehensive review of the current contribution of CT and MRI to the diagnosis of great vessel pathology of the chest.

Arterial bleeding after biliary drainage catheter placement: diagnosis and treatment

A case of hepatic arterial haemorrhage after percutaneous biliary drainage catheter placement is presented. Temporary control of the haemorrhage was obtained by placement of a larger drainage catheter which tamponaded the bleeding artery. Hepatic angiography followed by transcatheter embolotherapy provided a definitive control of bleeding.

Osler-Rendu-Weber with liver involvement

Osler-Rendu-Weber disease, or hereditary hemorrhagic telangiectasia, is a vascular disease with autosomal dominant transmission. The liver is involved in 31% of patients with hereditary hemorrhagic telangiectasia (1). It appears that the lesions uncommonly causes serious disease. We report the imaging findings and the therapy in a case with extensive telangiectasis in the liver.

Computed tomography of laryngeal carcinoma: technique, imaging findings and implications for radiation therapy

Optimal radiological visualisation of laryngeal carcinoma demands for a tailored imaging technique. The technique for computed tomography of the larynx is reviewed, and imaging findings in laryngeal carcinoma are described. The application of CT-findings for selection of patients into the favourable group for radiation therapy is discussed. The use of CT in the follow-up of irradiated laryngeal carcinoma is reviewed.

T2-weighted MR imaging of the uterus: comparison of optimized fast spin-echo and HASTE sequences with conventional fast spin-echo sequences

OBJECTIVE

Our objective was to compare the value of a half-Fourier acquisition single-shot turbo spin-echo (HASTE) sequence with optimized fast spin-echo and conventional fast spin-echo techniques in evaluation of the uterus.

SUBJECTS AND METHODS

Optimized fast spin-echo imaging was compared with fast spin-echo and HASTE imaging, for both image quality and ability to assess the zonal anatomy of the uterus, in 40 volunteers. In optimized fast spin-echo imaging, the imaging time was reduced using partial-Fourier reconstruction, reducing the echo spacing, and increasing the echo train length.

RESULTS

HASTE imaging offered the least motion artifact of all techniques. On optimized fast spin-echo imaging, motion artifacts were moderate to severe in 10% of patients. On fast spin-echo imaging, motion artifacts were moderate to severe in 40% of patients. Optimized fast spin-echo imaging was superior to the other two techniques in terms of anatomic sharpness and overall image quality.

CONCLUSION

Although HASTE imaging offers the unique feature of providing images free of motion artifacts, optimized fast spin-echo imaging appears to be the preferred technique for T2-weighted imaging of the uterus.

Normal Vaterian sphincter complex: evaluation of morphology and contractility with dynamic single-shot MR cholangiopancreatography

OBJECTIVE

The objective of this study was to assess the usefulness of dynamic single-shot MR cholangiopancreatography in the evaluation of the morphology and contractility of the normal Vaterian sphincter complex and to assess whether i.v. injection of glucagon can improve visualization.

SUBJECTS AND METHODS

Sixty patients without signs of Vaterian sphincter complex dysfunction were studied. A fast single-shot MR imaging sequence was used to obtain 20 consecutive images of the Vaterian sphincter complex during successive episodes of breathholding. In patients of group A (n = 30), 10 images were obtained before and 10 after i.v. administration of a sphincter-relaxing agent (glucagon). In the patients of group B (n = 30), no glucagon was administered. The degree of visualization of the Vaterian sphincter complex was assessed.

RESULTS

Overall, the morphology and contractility of the Vaterian sphincter complex was adequately assessed in 57 patients (95%). However, the number of repetitions required to obtain this result varied greatly (mean, seven; range, two to 18). Glucagon had no apparent effect on the visibility of the most distal portion of the common bile duct.

CONCLUSION

Nonvisualization of the most distal portion of the common bile duct on MR cholangiopancreatography studies is a normal variant that can simulate disease. Obtaining serial breath-hold images using a single-shot technique is helpful to avoid diagnostic errors.

Enhanced magnetic resonance imaging for tissue characterization of liver abnormalities with hepatobiliary contrast agents: an overview of preclinical animal experiments

Because of the demand for an extension of the range of diagnostic uses for currently available extracellular magnetic resonance imaging (MRI) contrast agents, a new generation of tissue-specific (i.e., hepatobiliary) contrast agents have been successfully developed to enhance the performance of hepatic MRI. These agents include mangafodipir trisodium (formerly manganese dipyridoxal diphosphate [Mn-DPDP]), gadoxetic acid (formerly gadolinium ethoxybenzyl diethylenetriaminopentaacetic acid [Gd-EOB-DTPA]), and gadolinium butylbenzyl diethylenetriaminepentaacetic acid (MS-264). In a series of experiments in animals, the potential of these agents for noninvasive characterization of liver lesions was evaluated with the use of a comprehensive methodology. The purpose of this report was to summarize the observed imaging behaviors of these agents toward different types of cholestasis and focal liver lesions, compare the similarities or dissimilarities of these agents in their possible mechanisms of action, and discuss the clinical implications of the results of the experiments. In summary, through intravenous administration of these agents, both global and local obstructive cholestases can be identified on the postcontrast image. With certain reliability, liver tumors of different origins and grades of cellular differentiation can be detected and classified according to their contrast enhancement patterns occurring at certain postcontrast phases. The invasiveness or degree of a malignancy of the liver tumor can also be suggested by the presence or absence of a peritumoral rim sign. Such diagnostic information, otherwise only invasively achievable, may prove to be invaluable in clinical decision making.

Strength training: importance of genetic factors

PURPOSE

This study focuses on the quantification of genetic and environmental factors in arm strength after high-resistance strength training.

METHODS

Male monozygotic (MZ, N = 25) and dizygotic (DZ, N = 16) twins (22.4 +/- 3.7 yr) participated in a 10-wk resistance training program for the elbow flexors. The evidence for genotype*training interaction, or association of interindividual differences in training effects with the genotype, was tested by a two-way ANOVA in the MZ twins and using a bivariate model-fitting approach on pre- and post-training phenotypes in MZ and DZ twins. One repetition maximum (1RM), isometric strength, and concentric and eccentric moments in 110 degree arm flexion at velocities of 30 degrees x s(-1), 60 degrees x s(-1), and 12 degrees x s(-1) were evaluated as well as arm muscle cross-sectional area (MCSA).

RESULTS

Results indicated significant positive training effects for all measures except for maximal eccentric moments. Evidence for genotype*training interaction was found for 1RM and isometric strength, with MZ intra-pair correlations of 0.46 and 0.30, respectively. Bivariate model-fitting indicated that about 20% of the variation in post-training 1RM, isometric strength, and concentric moment at 120 degrees x s(-1) was explained by training-specific genetic factors that were independent from genetic factors that explained variation in the pretraining phenotype (30-77%).

CONCLUSIONS

Genetic correlations between measures of pre- and post-training strength were indicative for high pleiotropic gene action and minor activation of training-specific genes during training.

Inheritance of static and dynamic arm strength and some of its determinants

Maximal static, eccentric and concentric torques and arm components estimated by anthropometry and measured by computed tomography were evaluated in 25 male monozygotic twins and 16 dizygotic twins (22.4 +/- 3.7 years). The importance of genetic and environmental factors in the observed variation in these measurements was estimated by genetic model-fitting techniques. In this sample of young adult male twins, genetic factors were significant in most of the strength measurements, arm muscle components and muscle activation variables. The contribution of genetic factors in strength measures depended on the angle, contraction type and to some extent on contraction velocity. For isometric strength, angle-specificity in genetic and environmental variation could be attributed to the degree of variability in muscle activation and performance discomfort at each specific angle, with the highest unique environmental impact at extreme angles. The high genetic contribution at 170 degrees, but not at 50 degrees, possibly expressed different contributions of genetic factors in the muscle-length factor and moment arm in torques at both angles. The importance of genetic factors in eccentric arm flexor strength (62-82%) was larger than for concentric flexion (29-65%), as the pattern of genetic determination followed the torque-velocity curve. Genetic variations in contractile and elastic components, contributing differently to eccentric and concentric torques, together with velocity-dependent actin-myosin binding factors, could account for the observed differences. The broad heritability was very high for all anthropometric and arm cross-sectional area measurements (> 85%) and common environmental factors were only significant for anthropometrically estimated mid-arm muscle tissue are (48%). Heritability estimates of different arm muscularity measurements were comparable.

Lack of direct correlation between CD4 T-lymphocyte counts and induration sizes of the tuberculin skin test in human immunodeficiency virus type 1 seropositive patients

SETTING

The study was conducted in Bobo-Dioulasso, Burkina Faso, where Mycobacterium tuberculosis infection and human immunodeficiency virus type 1 (HIV-1) infection are prevalent.

OBJECTIVE

To identify proportions of representative (test) populations who are reactive to the tuberculin skin test, and to study the relationship between CD4 T-lymphocyte counts and the induration size of the tuberculin skin test in these groups.

DESIGN

A group of 435 healthy students was tuberculin skin tested in order to evaluate the intensity of skin testing in a 'normal' population. The study group consisted of 195 subjects with or without tuberculosis, and with or without HIV-1 infection, who received a tuberculin skin test and a CD4 T lymphocyte count on the same day.

RESULTS

In total, 90% of the control (nontuberculous, HIV negative) subjects, 32% of the HIV-1 seropositive subjects, 76.5% of the tuberculous patients and 57% of the tuberculous HIV-1 seropositive patients were tuberculin positive. There was no direct correlation between the induration size of reactions to the tuberculin skin test and CD4 T-lymphocyte count in these study groups using linear regression analysis.

CONCLUSION

In vivo skin testing using tuberculin yields clinically significant information on the degree of immunodeficiency which is different from that of CD4 T-lymphocyte counts. The tuberculin skin test should therefore be used as an independent marker of the weakened immunological status of HIV-1 seropositive subjects.

Nonalcoholic duct-destructive chronic pancreatitis: imaging findings

OBJECTIVE

Nonalcoholic duct-destructive chronic pancreatitis is a new entity that should be distinguished from alcoholic chronic pancreatitis. The purpose of this study was to assess the imaging features of nonalcoholic duct-destructive chronic pancreatitis.

CONCLUSION

Nonalcoholic duct-destructive chronic pancreatitis has characteristic CT and MR imaging features that include the presence of a focal or more diffuse mass causing either regular or irregular narrowing of the main pancreatic duct, the absence of parenchymal atrophy and significant ductal dilatation proximal to the site of stenosis, and the absence of extrapancreatic spread.

Functional magnetic resonance imaging (fMRI) visualises the brain at work

Functional Magnetic Resonance Imaging (fMRI) is a recent MRI technique capable of visualising neuronal activity in humans in a non-invase way. The technique visualises the physiological changes in oxy- and deoxyhemoglobin concentration changes in small cortical blood vessels upon neuronal activation without the need for radiation or the administration of contrast media or radioactive tracers. The spatial accuracy of the technique is of the order of millimeters and the temporal resolution of the order of one second. The concept has captured the interest of neuroradiologists as well as neuroscientists, who now have a means to visualise their theories in human volunteers. In the clinical environment the non-invasive studies should aid neurosurgeons in adopting a safe course into the brain and assist neurologists in unraveling neurological hypotheses. This report describes the technical principals of fMRI and presents some of our clinical results on the mapping of several cortical functions, such as motor, auditory and language functions, in a large group of patients.

Caroli's syndrome

We report the case of a two-year-old girl presenting with recurrent episodes of fever and hepatomegaly. High resolution ultrasound (US) and computed tomography (CT) of the liver show dilated intrahepatic bile ducts with bridge formation and intraluminal protrusions. The extrahepatic bile duct is normal. The diagnosis of irregular dilated bile ducts with signs of cholangitis and cholangiolitis is proved by liver biopsy. The histologically associated congenital liver fibrosis in our patient enter into the Caroli's syndrome. We illustrate the high resolution US and the CT findings in this case.

Experimental teleradiology. Novel telematics services using image processing, hypermedia and remote cooperation to improve image-based medical decision making

We illustrate the possible impact of information technology on digital radiology using two pilot projects. The first aimed to improve the transfer of radiological information and the interaction between radiologist and referring physician, using hypermedia documents and hypermedia electronic mail. During a 12-month evaluation period, approximately 100 hypermedia reports were generated and distributed to hepatologists and neurosurgeons. The second project aimed to improve planning of orthopaedic surgery, using an image processing service for three-dimensional visualization and a conferencing system to support active cooperation. Over two months, 12 routine cases were reconstructed in three dimensions and conferencing was carried out between surgeons and radiologists in hospitals 15 km apart. Initial results were encouraging. Telematics may be valuable in reconciling the growing need for multidisciplinary cooperation with the growing geographical and organizational separation of different experts. We conclude that to benefit from information technology, the focus should not be on a direct translation of traditional working methods, but rather on possibilities that were not available in the film-based environment.

[Ataxic hemiparesis with cerebellar dysarthria due to an opercular lesion]

A 63 year-old-man, with an opercular infarct had a motor deficit with ataxic hemiparesis and cerebellar dysarthria. The motor deficit disappeared, but the cerebellar signs remained after three months. A voice instrumental analysis confirmed the cerebellar pattern of the dysarthria. CT and MRI showed the opercular lesion and the normality of the cerebellum and the pons. A volumic MRI analysis precised the localisation and the volume of the lesion. The oxygen consumption (CMRO2) was measured with PET and showed no cerebellar diaschisis. We propose that, in this case, the cerebellar dysarthria is the orofacial ataxic component of the hemiparesis. We suggest that it is related to disruption of the cortico-cerebellar tract, connecting the right orofacial frontal area of the primary motor cortex with the paravermal segment of the left cerebellar hemisphere.

Magnetic resonance imaging-histomorphologic correlation studies on paramagnetic metalloporphyrins in rat models of necrosis

RATIONALE AND OBJECTIVES

The authors intended to confirm previous findings that paramagnetic porphyrins are avid only for intratumoral nonviable tissues, but not for viable tumor cells, and to test the hypothesis that necrosis, regardless of location and origin, can be visualized by metalloporphyrin enhanced magnetic resonance imaging (MRI).

METHODS

Intravenous administrations of gadolinium mesoporphyrin (Gd-MP), manganese tetraphenylporphyrin (Mn-TPP), manganese methylpyrroporphyrin-gadopentetate dimeglumine complex (Mn-MPP-Gd) and manganese tetra(4-sulfonatophenyl)porphyrin (MnTPPS4) at 0.05 mmol/kg were compared with those of gadopentetate dimeglumine (Gd-DTPA) at 0.1 mmol/kg in 38 rats with cholestatic liver necrosis, alcohol- and laser-induced coagulation necrosis in liver, and skeletal muscle, reperfused hepatic infarction, and segmental renal infarction. T1-weighted spin echo MRI (TR/TE = 300/15 mseconds) was acquired before and as long as 48 hours after injection, matched with histologic findings, and correlated with Gd/ Mn tissue content measurements.

RESULTS

Both Gd-DTPA and the four metalloporphyrins initially caused a similar nonspecific negative contrast enhancement in the necrosis. However, a strong and persisting positive enhancement (necrosis-to-normal contrast ratio ranging from 1.5 to 2.0) developed only with metalloporphyrins in all types of necrosis. In liver and kidney, Gd and Mn concentrations at 24 hours were comparable in necrotic and normal tissues. In muscle, the concentrations were more than eight times higher in necrotic than in normal tissue.

CONCLUSIONS

The implied affinity of metalloporphyrins for necrosis with presumably increased relaxivity suggests a possible mode of targetability for MRI contrast media that may elicit novel applications.

Localization and determination of infarct size by Gd-Mesoporphyrin enhanced MRI in dogs

BACKGROUND

Accurate localization and sizing of a myocardial infarction are necessary for clinical decision making and even more in research. Gd-Mesoporphyrin enhanced magnetic resonance imaging (MRI) was recently shown to specifically delineate necrosis in liver tumors, renal and muscle necrosis and myocardial infarction in rats. In this study, we investigated this technique's potential to accurately delineate myocardial infarction in a larger animal species, the dog.

METHODS

Myocardial infarction was induced in 8 dogs by ligation of the left anterior descending coronary artery, 4 of which were reperfused after 3 hr Gd-Mesoporphyrin (0.05 mmol/kg) was injected intravenously 210 min after the onset of ischemia (n = 6) or after 24 hr in 2 dogs with non-reperfused infarctions. MRI was performed 10 hr after administration of Gd-Mesoporphyrin. In vivo MRI consisted of EKG-triggered, respiratory gated T1-weighted spin echo and segmented turboFLASH long and short axis measurements. Post-mortem, a spin echo short axis measurement was repeated. Infarct size was determined planimetrically by TTC staining of left ventricular slices.

RESULTS

In all instances, there was a very close qualitative agreement between the MRI and TTC defined myocardial infarction. Quantitatively, the linear regression from post-mortem MRI to TTC determined infarct size yielded a result very close to the line of identity (regression coefficient: 0.980 +/- 0.026, p < 0.000001, adjusted R2 = 0.964).

CONCLUSION

We conclude that Gd-Mesoporphyrin enhanced MRI is a promising tool for the accurate delineation of myocardial infarction.

[Pathophysiology and immunology of tuberculosis]

Only isolated bacilli are capable of reaching the pulmonary alveoli. Draining towards the lymphatic glanglia which corresponds to the infected pulmonary segment or transported by alveolar macrophages after being phagocytosed, these bacteria liberate molecules (antigens) presented to T lymphocytes. After clonal expansion, specific lymphocytes migrate out of the lymph nodes. From the initial area, other areas are infected and these specific lymphocytes lead to a local inflammatory reaction which is very rich in cells, in particular in activated monocytes and macrophages. The inflammatory granuloma or "tubercle" leads to control of the infection in the majority of cases. The inverse of this is that in five or ten per cent of cases a part of this granuloma is necrosed and caseus and leads to (or accompanies) an intense bacterial multiplication. At this stage with the formation of the cavity numerous bacilli may seed other regions of the lung or infect other people. The immune response in which T lymphocytes play a fundamental role thus permit at the same time the control of infection and the establishment of a lesion assuring the perpetuation of the species of Mycobacterium tuberculosis by contaminating new subjects. The respective roles of the different types of T lymphocyte and of liberated lymphokines remains to be determined. Also the principle antigens of the bacillus need to be characterised. The "dominant" antigens are probably liberated by bacteria during their growth phase.

High sensitivity of transgenic mice expressing soluble TNFR1 fusion protein to mycobacterial infections: synergistic action of TNF and IFN-gamma in the differentiation of protective granulomas

To investigate the role of tumor necrosis factor (TNF) in protective immune responses to Mycobacterium tuberculosis and M. bovis Bacillus Calmette Guérin (BCG), we have used transgenic mice unable to use TNF because of the expression of high amounts of a soluble TNF receptor (R) type I (sTNFR1) fusion protein, and studied resistance of these mice to infection by lethality assays, evaluation of bacterial recovery and histologic examination. These mice showed a strongly increased sensitivity to M. tuberculosis and BCG infections, with bacterial overgrowth and marked inhibition of macrophage differentiation within granulomas; after M. tuberculosis infection, this resulted in extensive lesions of caseous necrosis in the lung. To explore the respective roles of TNF and interferon (IFN)-gamma in resistance to BCG and granuloma differentiation, controls and sTNFR1-transgenic mice were compared to IFN-gammaR mutant mice and mice double defective in TNF and IFN-gamma activity (obtained by crossing transgenic and mutant mice). The three groups of deficient mice showed a strongly enhanced susceptibility to BCG infection, with the following decreasing order of sensitivity between groups: TNF + IFN-gamma --> TNF --> IFN-gamma-deficient mice. The hepatic granulomas of IFN-gammaR mutant mice were small and contained eosinophils but few differentiated macrophages; compared to those of sTNFR1-transgenic mice, acid-fast bacilli were less numerous within the macrophages. Granulomas of double-deficient mice were strikingly different by their very large size and cellular content, made up large numbers of polymorphonuclears, eosinophils, and cells undergoing apoptosis, but without detectable differentiated macrophages; acid-fast bacilli were spread in the lesions. These studies show the essential role of both TNF and IFN-gamma in the development, during mycobacterial infections, of protective granulomas containing highly differentiated macrophages capable of destroying ingested bacteria, and emphasize that these two cytokines act synergistically in granuloma formation.

Using WWW and JAVA for image access and interactive viewing in an integrated PACS

We start from the observations that (1) potential benefits from PACS can only be realized if PACS and HIS are integrated into a 'multimedia medical information system', and (2) that this also requires integration at the level of the user interface. The user interface should allow integrated interaction with information from different subsystems, of which PACS is one. However, in the real world, different information systems are constructed using different technologies. Moreover, radiological image viewing is a highly interactive task that puts a particular burden on the graphical user interface. We describe our experiences in applying technology emerging around the 'World Wide Web' (WWW) for interactive access to an integrated PACS/HIS. We illustrate the use of Web browsers to access new medical services, touch technologies for interactive access to HIS-PACS information, and emphasize the potential of JAVA applets. We argue that JAVA may become an important tool for providing highly interactive user interfaces to larger multimedia information systems. We discuss Web technology in the general context of HIS/PACS integration.

FMRI studies of the supplementary motor area and the premotor cortex

Brain activation patterns associated with three motor tasks, differing in the mode of movement selection, were studied in seven right-handed subjects, using functional magnetic resonance imaging (fMRI). The tasks consisted of sequences of finger movements in which the next finger was selected (i) according to a fixed sequence (FIX), (ii) in response to an external sensory cue (RAND), or (iii) on the basis of free, internal selection (SELF). Periods of hand relaxation (REST) alternating with the tasks served as a control. Functional maps resulting from comparison of the motor tasks with REST reveal activation in primary sensorimotor cortex, medial and lateral premotor areas, cingulate cortex, and parietal cortex. The task activation level, defined as the percentage MR signal increase for each task relative to REST, and the differential activation, defined as the percentage MR signal increase for RAND and SELF relative to FIX, were calculated in each area. All areas showed a higher activation level for RAND and SELF than for FIX. A significant difference in activation level or differential activation between SELF and RAND was found in the posterior part of the superior frontal sulcus, in a part of the premotor cortex on the lateral brain surface, in the anterior cingulate motor cortex, and in the posterior part of the superior parietal cortex. The high-resolution and single-subject approach, provided by fMRI, allowed the distinguishing of multiple foci in medial frontal areas, premotor cortex, and parietal cortex, reflecting the functional heterogeneity of these areas suggested by previous studies.

The kinetic occipital (KO) region in man: an fMRI study

We used functional magnetic resonance imaging to explore, in individual subjects, the properties of the kinetic occipital (KO) region, which previous position emission tomography studies have shown to be involved in the processing of kinetic boundaries. The KO region was significantly activated in 23/25 subjects tested in the subtraction of uniform motion from kinetic gratings. The KO region is genuinely specialized for processing kinetic boundaries since it is significantly more activated by kinetic gratings than by luminance-defined gratings, uniform motion or transparent motion. This leaves only the kinetic boundaries, created by discontinuities in motion direction, as the specific stimulus aspect, activating the KO region. The KO region is anatomically and functionally distinct from areas MT/V5, V3 and V3A. It also has minimal overlap with the lateral occipital (LO) region. The selective activation of the KO region is robust and relatively immune to changes in stimulus size, spatial frequency and type of kinetic boundary. These results strongly argue for the view that the KO region is a new, separate, functional region in human occipital cortex.

Transient global amnesia: implicit/explicit memory dissociation and PET assessment of brain perfusion and oxygen metabolism in the acute stage

OBJECTIVES

To assess explicit memory and two components of implicit memory--that is, perceptual-verbal skill learning and lexical-semantic priming effects--as well as resting cerebral blood flow (CBF) and oxygen metabolism (CMRO2) during the acute phase of transient global amnesia.

METHODS

In a 59 year old woman, whose amnestic episode fulfilled all current criteria for transient global amnesia, a neuropsychological protocol was administered, including word learning, story recall, categorical fluency, mirror reading, and word stem completion tasks. PET was performed using the (15)O steady state inhalation method, while the patient still exhibited severe anterograde amnesia and was interleaved with the cognitive tests.

RESULTS

There was a clear cut dissociation between impaired long term episodic memory and preserved implicit memory for its two components. Categorical fluency was significantly altered, suggesting word retrieval strategy--rather than semantic memory--impairment. The PET study disclosed a reduced CMRO2 with relatively or fully preserved CBF in the left prefrontotemporal cortex and lentiform nucleus, and the reverse pattern over the left occipital cortex.

CONCLUSIONS

The PET alterations with patchy CBF-CMRO2 uncoupling would be compatible with a migraine-like phenomenon and indicate that the isolated assessment of perfusion in transient global amnesia may be misleading. The pattern of metabolic depression, with sparing of the hippocampal area, is one among the distinct patterns of brain dysfunction that underlie the (apparently) uniform clinical presentation of transient global amnesia. The finding of a left prefrontal hypometabolism in the face of impaired episodic memory and altered verbal fluency would fit present day concepts from PET activation studies about the role of this area in episodic and semantic memory encoding/retrieval. Likewise, the changes affecting the lenticular nucleus but sparing the caudate would be consistent with the normal performance in perceptual-verbal skill learning. Finally, unaltered lexical-semantic priming effects, despite left temporal cortex hypometabolism, suggest that these processes are subserved by a more distributed neocortical network.

Ex vivo experiment on radiofrequency liver ablation with saline infusion through a screw-tip cannulated electrode

PURPOSE

To investigate whether radiofrequency (RF) therapy with hypertonic saline infusion through a hollow screw-tip electrode can cause a lesion size suitable for liver tumor ablation.

MATERIALS AND METHODS

RF tissue ablation of 180 sites was performed by using a hollow screw-tip electrode in 40 freshly excised swine livers. Under both power and temperature control modes, the ablation effects with and without various regimes of 5% hypertonic saline (1 ml/min) prior to and/or during the procedure were compared by measuring the size of lesions at dissection and confirmed by T1 and T2 weighted magnetic resonance (MR) imaging.

RESULTS

The maximal lesion diameter of 5.5 cm was reached at 30 W with saline infusion 1 min prior to and during 12 min of ablation. The smaller sizes (P < 0.01) between 0.3 and 2.5 cm in diameter were met with noninfusion or preinfusion-only groups. The RF ablation lesions appeared as hyper- and hypointense areas on T1 and T2 MR images, respectively.

CONCLUSIONS

RF ablation in combination with present hollow screw-tip electrode and saline infusion allows for necrotic development of suitable size for liver tumor ablation. Such ablated lesions can be visualized with MR imaging.

Immunoblot analysis for serodiagnosis of tuberculosis using a 45/47-kilodalton antigen complex of Mycobacterium tuberculosis

We evaluated the immunoglobulin G (IgG) antibody response to the 45/47-kDa secreted protein of Mycobacterium tuberculosis by immunoblot assay, to assess its potential value for serological diagnosis. Control subjects consisted of healthy volunteers with negative or positive tuberculin skin tests. Most (>98%) scored negative in an immunoblot test when the sera were analyzed at a 1:400 dilution. Approximately 40% of sera (diluted 1 in 400) from tuberculous patients (positive smears) recognized the antigen complex. The sensitivity of the test for patients suffering from extrapulmonary tuberculosis was similar to that for patients suffering from pulmonary tuberculosis but who had negative smears. The frequency of positive reactions among the patients suffering from other pulmonary diseases was similar to that among the control subjects. In tuberculous patients infected with human immunodeficiency virus, the sensitivity of the immunoblot test was significantly lower. Thus, this test based on an antigen complex used in an immunoblot assay to detect the presence of IgG antibody has a specificity of 98% and a sensitivity of 40%. The simultaneous use of different purified antigens, selected at the same high specificity level, may improve the sensitivity of such an assay.

Dual-phase helical CT of the liver: value of an early-phase acquisition in the differential diagnosis of noncystic focal lesions

OBJECTIVE

Contrast-enhanced helical CT images of the liver are usually obtained during the portal vein phase (PVP), during which the parenchyma achieves peak enhancement. The purpose of this study was to determine whether the addition of arterial-phase (AP) scans would lead to improved characterization of focal lesions.

MATERIALS AND METHODS

We reviewed the CT appearance of 102 focal lesions with a proven diagnosis. In the first part of the study, we assessed whether the addition of AP scans influenced the diagnostic performance of the three observers. In the second part of the study, we analyzed the morphologic appearance revealed on CT scans of the different types of lesions in the AP and PVP.

RESULTS

The addition of AP scans led to a significant increase in the number of correct diagnoses: 71 lesions (70%) were correctly diagnosed with CT scans in both the AP and the PVP, compared with 54 lesions (53%) correctly diagnosed with CT scans in the PVP alone (p < .01). The largest difference was observed in the diagnosis of focal nodular hyperplasia (FNH) and adenoma (16/24 correct diagnoses instead of 6/24) (p < .005). Conversely, AP images did not significantly contribute to the diagnosis of hemangiomas and metastases. The following morphologic features were seen much more often on AP scans than on PVP scans and had a high positive predictive value (PPV): spoke-wheel pattern (FNH; PPV, 100%), central feeding vessel (FNH; PPV, 100%), and heterogeneous appearance with hyperdense components (hepatocellular carcinoma; PPV, 75%).

CONCLUSION

Our data show that the radiologists' evaluation of CT scans in both the AP and the PVP improves the differentiation of hepatocellular carcinoma and FNH from other types of hepatic neoplasms.

Multimodality image registration by maximization of mutual information

A new approach to the problem of multimodality medical image registration is proposed, using a basic concept from information theory, mutual information (MI), or relative entropy, as a new matching criterion. The method presented in this paper applies MI to measure the statistical dependence or information redundancy between the image intensities of corresponding voxels in both images, which is assumed to be maximal if the images are geometrically aligned. Maximization of MI is a very general and powerful criterion, because no assumptions are made regarding the nature of this dependence and no limiting constraints are imposed on the image content of the modalities involved. The accuracy of the MI criterion is validated for rigid body registration of computed tomography (CT), magnetic resonance (MR), and photon emission tomography (PET) images by comparison with the stereotactic registration solution, while robustness is evaluated with respect to implementation issues, such as interpolation and optimization, and image content, including partial overlap and image degradation. Our results demonstrate that subvoxel accuracy with respect to the stereotactic reference solution can be achieved completely automatically and without any prior segmentation, feature extraction, or other preprocessing steps which makes this method very well suited for clinical applications.

The kinetic occipital region in human visual cortex

In the present study we showed that the kinetic occipital (KO) region, located laterally in occipital cortex approximately 20 mm behind human MT/V5, can be strongly and bilaterally activated under passive viewing conditions. We used continuous, randomly changing visual stimulation to compare kinetic gratings to uniform motion and kinetic gratings to luminance defined gratings. The KO activations under these passive conditions are stronger than those observed when the two types of gratings are compared under active conditions, i.e. while subjects perform a task (counting gratings of a given orientation). Region KO was shown to process both shape and motion information, the conjunction of which is typically present in kinetic contours. Area MT/V5 also processes these two aspects of visual stimulation but favors motion signals. Clear segregation of shape and motion processing was observed only in occipitotemporal and parietal regions respectively. Although neurons with properties similar to those derived from the conditions activating the KO region have been documented in the macaque monkey, their location seems inappropriate for them to correspond to the KO activation observed in humans.

Preliminary experience with a new double-echo half-Fourier single-shot turbo spin echo acquisition in the characterization of liver lesions

A new double-echo half-Fourier single-shot turbo spin echo technique has been implemented in which two images are obtained per excitation pulse, one with an echo time (TE) of 60 ms and another with a TE of 438 ms. The acquisition window per image is 380 ms and is determined by the echo spacing of 4.3 ms and the echo train length of 88 for images with resolution of 160 x 256. No breath holding was performed. The aim of the study was to test whether the additional information of the late TE image improves the characterization of liver lesions. Twenty-eight patients with 39 focal liver lesions (9 cysts, 11 hemangiomas, and 19 solid lesions) were imaged with the new technique, and signal intensity (SI) ratios of lesion and liver were obtained. A t-test analysis showed that in the TE 60 ms image, SI ratios of cysts and hemangiomas were not significantly different, whereas in the TE 438 ms images the two types of lesions can be classified. Signal intensity ratios of solid lesions were in both images clearly lower than those of cysts and hemangiomas. The technique, therefore, seems a promising and straightforward new tool for the characterization of liver lesions.

Multivariate genetic analysis of maximal isometric muscle force at different elbow angles

The maximal isometric moment at five different elbow joint angles was measured in 25 monozygotic and 16 dizygotic male adult twin pairs (22.4 +/- 3.7 yr). Genetic model fitting was used to quantify the genetic and environmental contributions to individual differences in isometric strength. Additive genetic factors explained 66-78% of the variance in maximal torque at 170-140-110 and 80 degrees flexion (extension = 180 degrees). At 50 degrees flexion, common and subject-specific environmental factors contributed equally to the variation. The contribution of unique environmental factors concurs with the level of variability in muscle activation and (dis)-comfort of torque production in the specific angle. The relative contribution of lever arm and force-length relationship in torque varies according to the angle. Because these factors might be genetic, this variability is reflected in the genetic contribution at the extreme angles of 170 and 50 degrees. Multivariate analyses suggested a general set of genes that control muscle area and isometric strength, together with a more specific strength factor. Genetic correlations were high (0.82-0.99). Genes responsible for arm-segment lengths did not contribute to muscle area nor to isometric strength.

Size quantification of liver metastases in patients undergoing cancer treatment: reproducibility of one-, two-, and three-dimensional measurements determined with spiral CT

PURPOSE

To assess the reproducibility of one-, two-, and three-dimensional measurements of the size of liver metastases.

MATERIALS AND METHODS

The sizes of 10 liver metastases were determined 200 times: Ten observers measured each lesion by using images obtained at two different CT studies and with five different measurement techniques (maximum diameter, product of diameters, area, volume, and product of three diameters). They repeated each measurement in a separate session. The influence of measurement technique and lesion type (size and morphologic appearance) on measurement reproducibility was assessed.

RESULTS

Three-dimensional measurements proved to be as reproducible as one- and two-dimensional measurements. Measurement reproducibility was influenced mainly by the size (P < .0001) and morphologic appearance (P < .01) of the lesions.

CONCLUSION

Three-dimensional size measurements obtained with spiral CT are reproducible and could therefore replace the two-dimensional measurements of tumor size currently obtained with follow-up CT studies.

Factors influencing the accuracy of volume measurements in spiral CT: a phantom study

PURPOSE

The purpose of this study was to investigate the influence of different parameters (object size, shape, orientation, contrast, observer, and window setting) on the accuracy of volume measurements in spiral CT.

METHOD

The phantom study consisted of two parts. First, well-circumscribed ellipsoid objects were scanned with conventional and spiral CT. Volumes were determined by two observers using manual contour delineation and summation-of-areas. The influence of object size, CT technique, and observer was assessed. Second, irregularly shaped gingerroots were scanned and the effect of observer, contrast, and orientation was investigated. Also assessed in both parts of the study was the effect of window setting.

RESULTS

Spiral CT offered higher accuracy and reproducibility than conventional CT did. The accuracy of volume measurements was mainly determined by the window setting used for image display. Using an "optimized" window center value halfway between object density and background density resulted in overestimation of true object volumes if the number of slices through the object (number of samples) was low. Other factors (contrast, observer-related errors in contour delineation) were less important.

CONCLUSIONS

Volume measurements of small objects, obtained with spiral CT and using manual contour delineation, may be grossly erroneous. Major causes of inaccuracy are an inappropriate window center selection and undersampling.

Evaluation of hepatic perfusion disorders with double-phase spiral CT

Double-phase (dual-phase) spiral computed tomography (CT) represents a technologic advance that allows two evaluations of hepatic blood flow during a single 19-29-second breath hold: once during the hepatic arterial phase (HAP) and again during the portal venous phase (PVP). Perfusion disorders of the hepatic parenchyma are more readily observed at double-phase spiral CT. The various hepatic perfusion disorders are related to (a) portal venous inflow obstruction, (b) hepatic venous outflow obstruction (e.g., Budd-Chiari syndrome, cardiac failure, mediastinal fibrosis), (c) mediastinal or thoracic venous inlet obstruction, (d) focal liver lesions, (e) inflammatory processes, (f) normal anatomic variants in the hepatic blood supply, (g) altered hemodynamics after the placement of a transjugular intrahepatic portosystemic shunt, and (h) uncertain causes. In general, the area of involvement appears hyperattenuating on HAP images and of normal or near-normal attenuation on PVP images. Familiarity with the spiral CT appearances of different types of perfusion disorders allows the radiologist to separate clinically insignificant flow phenomena from perfusion disorders caused by underlying parenchymal or vascular disease.

Imaging of gallbladder and biliary tract before laparoscopic cholecystectomy: comparison of intravenous cholangiography and the combined use of HASTE and single-shot RARE MR imaging

To compare intravenous cholangiography (i.v.c.) and magnetic resonance imaging (MRI) as preoperative imaging techniques in patients scheduled for laparoscopic cholecystectomy. Twenty patients underwent i.v.c. and MRI, 40 axial 'localizer' images were first obtained with a half-Fourier single-shot turbo spin echo (HASTE) sequence. Next, an extremely high T2-weighted rapid acquisition relaxation enhancement (RARE) acquisition (TE = 1100 msec) was used for MR cholangiography. All images obtained with i.v.c. and MRI were independently analyzed by two observers. The relative visibility of the (normal or abnormal) gallbladder (GB), cystic duct (CD), and bile ducts (BD) on both types of images was scored as follows: 1 = MRI better than i.v.c.; 2 = no difference; 3 = i.v.c. better than MRI. We observed 3 anatomic variants: 1 of the cystic duct and 2 of the intrahepatic bile ducts; 15 patients had gallstones; one had cholecystitis. Magnetic resonance images were considered more informative than i.v.c.-images for visualization of GB in 11 patients (55%), for CD in 9 patients (45%), and in 8 patients (40%) for visualization of the CBD. Intravenous cholangiography outperformed MRI in the evaluation of the CBD and CD in one patient (5%). The combined use of half-Fourier single-shot RARE and high T2-weighted RARE MR imaging is a valuable alternative to i.v.c. in the preoperative evaluation of gallbladder and biliary tract.

Gastroepiploic artery coronary bypass graft: non-invasive patency evaluation using color and duplex Doppler ultrasonography

OBJECTIVE

Color and duplex Doppler ultrasound and digital subtraction angiography were compared for the evaluation of graft patency of the gastroepiploic artery (GEA).

METHODS

In 77 observations, ultrasound and digital subtraction angiography were compared. The coronary resistance index (cRI) was defined as the maximal systolic flow velocity minus the maximal diastolic flow velocity, divided by the maximal systolic flow velocity. On digital subtraction angiography, the graft was considered patent, occluded, or patent but non-functional. Grafts were defined as non-functional when they had a diameter of less than 5F with the absence of opacification of the native coronary artery.

RESULTS

Of the 77 observations, 64 GEAs were patent angiographically, three were occluded and ten grafts were considered as patent but non-functional. Using color and duplex ultrasound, the GEA was identified in 65 out of 77 observations. There were no cases of false positive visualization of the GEA. All sonographically detected non-functional grafts (n = 7) had a cRI of greater than 0.60. When the non-visualized grafts are considered either non-functional or occluded, a cut-off value for a cRI of 0.60 results in a sensitivity and specificity of 100 and 75%, respectively.

CONCLUSION

We propose ultrasound as a primary screening tool for evaluating graft patency. While color Doppler is a suitable technique for graft visualization, spectral analysis with the calculation of a cRI is required for functional evaluation.