Nuclear magnetic resonance imaging with hyperpolarised helium-3

BACKGROUND

Magnetic resonance imaging (MRI) relies on magnetisation of hydrogen nuclei (protons) of water molecules in tissue as source of the signal. This technique has been valuable for studying tissues that contain significant amounts of water, but biological settings with low proton content, notably the lungs, are difficult to image. We report use of spin-polarised helium-3 for lung MRI.

METHODS

A volunteer inhaled hyperpolarised 3He to fill the lungs, which were imaged with a conventional MRI detector assembly. The nuclear spin polarisation of helium, and other noble gases, can be greatly enhanced by laser optical pumping and is about 10(5) times larger than the polarisation of water protons. This enormous gain in polarisation easily overcomes the loss in signal due to the lower density of the gas.

FINDINGS

The in-vivo experiment was done in a whole-body MRI scanner. The 3He image showed clear demarcation of the lung against diaphragm, heart, chest wall, and blood vessels (which gave no signal). The signal intensity within the air spaces was greatest in lung regions that are preferentially ventilated in the supine position; less well ventilated areas, such as the apices, showed a weaker signal.

INTERPRETATION

MRI with hyperpolarised 3He gas could be an alternative to established nuclear medicine methods. The ability to image air spaces offers the possibility of investigating physiological and pathophysiological processes in pulmonary ventilation and differences in its regional distribution.

Nuclear magnetic resonance imaging of airways in humans with use of hyperpolarized 3He

The nuclear spin polarization of noble gases can be enhanced strongly by laser optical pumping followed by electron-nuclear polarization transfer. Direct optical pumping of metastable 3He atoms has been shown to produce enormous polarization on the order of 0.4-0.6. This is about 10(5) times larger than the polarization of water protons at thermal equilibrium used in conventional MRI. We demonstrate that hyperpolarized 3He gas can be applied to nuclear magnetic resonance imaging of organs with air-filled spaces in humans. In vivo 3He MR experiments were performed in a whole-body MR scanner with a superconducting magnet ramped down to 0.8 T. Anatomical details of the upper respiratory tract and 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.

Quantification of regional intrapulmonary oxygen partial pressure evolution during apnea by (3)He MRI

We present a new method to determine in vivo the temporal evolution of intrapulmonary oxygen concentrations by functional lung imaging with hyperpolarized (3)Helium ((3)He-->). Single-breath, single-bolus visualization of (3)He--> administered to the airspaces is used to analyze nuclear spin relaxation caused by the local oxygen partial pressure p(O(2))(t). We model the dynamics of hyperpolarization in the lung by rate equations. Based hereupon, a double acquisition technique is presented to separate depolarization by RF pulses and oxygen induced relaxation. It permits the determination of p(O(2)) with a high accuracy of up to 3% with simultaneous flip angle calibration using no additional input parameters. The time course of p(O(2)) during short periods of breathholding is found to be linear in a pig as well as in a human volunteer. We also measured the wall relaxation time in the lung and deduced a lower limit of 4.3 min.

Analysis of intrapulmonary O(2) concentration by MR imaging of inhaled hyperpolarized helium-3

Inhalation of hyperpolarized (3)He allows magnetic resonance imaging (MRI) of ventilated airspaces. (3)He hyperpolarization decays more rapidly when interacting with paramagnetic O(2). We describe a method for in vivo determination of intrapulmonary O(2) concentrations ([O(2)]) based on MRI analysis of the fate of measured amounts of inhaled hyperpolarized (3)He in imaged regions of the lung. Anesthetized pigs underwent controlled normoventilation in a 1.5-T MRI unit. The inspired O(2) fraction was varied to achieve different end-tidal [O(2)] fractions (FET(O(2))). With the use of a specifically designed applicator, (3)He (100 ml, 35-45% polarized) was administered at a predefined time within single tidal volumes. During subsequent inspiratory apnea, serial two-dimensional images of airways and lungs were acquired. At least once in each animal studied, the radio-frequency excitation used for imaging was doubled at constant FET(O(2)). Signal intensity measurements in regions of interest of the animals' lungs (volume range, 54-294 cm(3)), taken at two different radio-frequency excitations, permitted calculation of [O(2)] in these regions of interest. The [O(2)] fractions in the regions of interest correlated closely with FET(O(2)) (R = 0.879; P < 0.0001). O(2)-sensitive (3)He-MRI may allow noninvasive study of regional distribution of ventilation and alveolar PO(2) in the lung.

(3)He MRI in healthy volunteers: preliminary correlation with smoking history and lung volumes

MRI with hyperpolarized helium-3 ((3)He) provides high-resolution imaging of ventilated airspaces. The first aim of this (3)He-study was to compare observations of localized signal defects in healthy smokers and non-smokers. A second aim was to describe relationships between parameters of lung function, volume of inspired (3)He and signal-to-noise ratio. With Ethics Committee approval and informed consent, 12 healthy volunteers (seven smokers and five non-smokers) were studied. Imaging was performed in a 1.5 T scanner using a two-dimensional FLASH sequence at 30V transmitter amplitude (TR/TE/alpha = 11 ms/4.2 ms/<10 degrees ). Known amounts of (3)He were inhaled from a microprocessor-controlled delivery device and imaged during single breath-holds. Images were evaluated visually, and scored using a prospectively defined 'defect-index'. Signal-to-noise ratio of the images were correlated with localization, (3)He volumes and static lung volumes. Due to poor image quality studies of two smokers were not eligible for the evaluation. Smokers differed from non-smokers in total number and size of defects: the 'defect-index' of smokers ranged between 0.8 and 6.0 (median = 1.1), that of non-smokers between 0.1 and 0.8 (median = 0.4). Intraindividually, an anteroposterior gradient of signal-to-noise ratio was apparent. Signal-to-noise ratio correlated with the estimated amount of hyperpolarization administered (r = 0. 77), but not with static lung volumes. We conclude that (3)He MRI is a sensitive measure to detect regional abnormalities in the distribution of ventilation in clinically healthy persons with normal pulmonary function tests.

(3)he-MRI-based measurements of intrapulmonary p(O2) and its time course during apnea in healthy volunteers: first results, reproducibility, and technical limitations

We applied a recently developed method of following the time course of the intrapulmonary oxygen partial pressure p(O2)(t) during apnea by (3)He MRI to healthy volunteers. Using two imaging series with different interscan times during two breathholds (double acquisition technique), relaxation of (3)He due to paramagnetic oxygen and depolarization by RF pulses were discriminated. In all four subjects, the temporal evolution of p(O2) was found to be linear, and was described by an initial partial pressure p(0) and a decrease rate R. Also, regional differences of both p(0) and R were observed. A correlation between p(0) and R was apparent. Finally, we discuss limitations of the double acquisition approach.

[Ultrafast MRI of lung ventilation using hyperpolarized helium-3]

OBJECTIVE

Assessment of the temporal and spatial dynamics of hyperpolarized Helium-3 (3He) distribution in the lung with ultrafast gradient-echo magnetic-resonance imaging.

MATERIAL AND METHODS

Coronal images of the lung were acquired using ultrafast gradient-echo pulse sequences with TR/TE = 3.3 ms/1.3 ms (slice thickness, 40 mm) and TR/TE = 2.0 ms/0.7 ms (without slice selection). A series of 80 or 160 projection images was obtained with 210 ms or 130 ms temporal resolution, respectively. Imaging was performed during several respiratory cycles after application of a single bolus of 300 mL hyperpolarized 3He. Measurements were performed in six healthy volunteers (spontaneous breathing).

RESULTS

Different phases of in- and expiration could be visualized. During the course of consecutive respiratory cycles the 3He signal decreased due to dilution of 3He in residual alveolar gas and by inspired air, relaxation due to oxygen and the RF pulses, and due to Helium-3 washout. The signal of a single bolus of 3He was detected in the lung for up to four respiratory cycles. Anatomical structures were better visualized on slice selective images than on images without slice selection.

CONCLUSION

Distribution of inspired 3He within the tracheobronchial tree and alveolar space and its washout can be visualized by ultrafast imaging of a single bolus of hyperpolarized 3He gas. This method may allow for regional analysis of lung function with temporal and spatial resolution superior to conventional methods.

Volumetry of ventilated airspaces by 3He MRI: preliminary results

RATIONALE AND OBJECTIVES

To develop a validated post-processing routine for volumetry of the ventilated airspaces by 3He MRI.

METHODS

3Helium MRI and pulmonary function tests were performed in seven healthy volunteers. After segmentation of ventilated airspaces, their volumes were calculated. Functional residual capacity (FRC) was used as a reference. For comparison of absolute volumes, correction factors were evaluated.

RESULTS

Mean lung volume (+/- standard deviation) calculated from 3He MRI was 4,082 +/- 908 mL and mean FRC was 3,696 +/- 1166 mL, with a mean difference of 386 mL (r = 0.88). After correction for the relative pulmonary air content (factor 0.82), posture (0.72), and the individual tidal volume, 3He MRI volume was 3,348 +/- 744 mL and mean FRC was 3,422 +/- 817 mL, with the mean difference down to -74 mL (r = 0.9). Comparison on an individual basis confirmed an improvement in the estimation of absolute lung volume.

CONCLUSIONS

Volumetry of ventilated lung from 3He MRI shows high correlation and good agreement with the results of pulmonary function tests.

Preeclamptic nephropathy -- an endothelial lesion. A morphological study with a review of the literature

OBJECTIVE

We investigated wether an endothelial lesion, postulated in pathogenesis of preeclampsia (PE) in general, is also pathogenetically relevant in the characteristic renal lesions of PE, presenting as special glomerular alterations, designated as "preeclamptic nephropathy".

STUDY DESIGN

Renal biopsies of 90 women with PE were analyzed by light microscopy (LM), immunohistology (IH) and electron microscopy (EM). Corresponding with clinical data clinicomorphological correlations were performed.

RESULTS

In IH and EM the altered glomeruli demonstrate an endothelial lesion. Consecutive morphological reactions could be revealed by EM, allowing a subdivision in different stages of disease. The late stage indicates the reversibility of these renal lesions. Close correlations were found between clinical and morphological data. Focal glomerulosclerosis presents a hyperperfusion lesion, developing only facultatively in PE as a result of hyperfiltration.

CONCLUSION

In preeclamptic nephropathy the first morphological substrate of renal changes with the key to pathogenesis presents itself as an endothelial lesion. This results in a disturbance of glomerular basement membrane permeability and in an imbalance of different mediator systems, with dominance of vasoconstrictive reactions but also coagulative-, reparation-, and proliferation-processes, leading to the characteristic glomerular alterations of preeclamptic nephropathy.

Verapamil limits shockwave-induced renal tubular damage in vivo

Previous investigations on Madin Darby Canine Kidney (MDCK) cells demonstrated the protective effect of verapamil against shockwave-induced tubular dysfunction. In the present study, we investigated whether verapamil is also protective against shockwave-induced damage in vivo. Male rates were randomly assigned to three groups: verapamil (N = 18) (Group I), control (N = 18) (Group II), or sham treatment (N = 4) (Group III). Groups I and II were treated with 500 shockwaves to each kidney with the Dornier MFL 5000 at 18 kV. Animals assigned to Group III received only anesthesics. Verapamil was given to the animals in Group I for 5 days starting 1 day before shockwave exposure. Urine was collected for 8 hours the day before and immediately, 1.7, and 28 days after shockwave exposure (SWE) for measurement of volume, osmolality, hemoglobin, protein, N-acetyl-beta-glucosaminidase (NAG), beta 2-microglobulin (beta 2M), sodium, and creatinine. Kidneys were perfused and removed for histologic study 1, 7, and 28 days after SWE in six animals of Groups I and II. Blood was taken in these rats (Day 1 after SWE) for the determination of creatinine and sodium and the calculation of the creatinine clearance (CCr) and the fractional excretion of sodium (FENa). After SWE, there was strong diuresis and significantly increased excretion of NAG and beta 2M in the controls, while urine osmolality decreased. These changes were significantly less pronounced in the verapamil-treated rats. The CCr was higher and FENa lower than in the latter group.(ABSTRACT TRUNCATED AT 250 WORDS)

[The helium-3 MRT of pulmonary ventilation: the initial clinical applications]

PURPOSE

of the study is the visualisation of normal pulmonary ventilation in healthy volunteers and the evaluation of abnormalities in patients with different lung diseases using 3He magnetic resonance imaging (3He-MRI).

MATERIAL AND METHODS

Hyperpolarized 3He gas (V = 300 ml, p = 3 x 10(5) Pa, polarised to 35-45% by optical pumping, provided in special glass cells) was inhaled by eight healthy volunteers and ten patients with different lung diseases. A 3D FLASH sequence (TR = 11.8 ms; TE = 5 ms; matrix 144 x 256, FOV 350 mm, section thickness 7-10 mm, coronal orientation) was performed in a single breath-hold (22-42 s). Clinical and radiological examinations were available for correlation.

RESULTS

The studies were successfully carried out in 8/8 volunteers and in 8/10 patients. The central airways were constantly visualised with intermediate to high signal intensity. The lung parenchyma of volunteers with normal ventilatory function showed rather homogeneous intermediate to high signal, whereas patients with chronic obstructive lung disease and/or pneumonia presented severe signal inhomogeneities. Space-occupying lesions and pleural effusion caused large areas with little or no signal. The represented the lesion and adjacent ventilatory disturbances whose extent had not been presumed from chest x-ray or CT. The spatial resolution was higher than in ventilation scintigraphy.

CONCLUSION

3He MRI is a promising new modality for the assessment of pulmonary ventilation and its anomalies.

An ELISA method for the detection of autoantibodies to adrenal cortex

An enzyme-linked immunosorbent assay (ELISA) is described for autoantibodies to adrenal cortex. Microsomes were prepared from fresh human adrenal glands, and microtitre ELISA plates were incubated at 4 degrees C overnight with 25 micrograms antigen/ml, the optimal concentration for the system. Optimal dilution of patient's serum was 1/500. Peroxidase-labelled anti-human IgG and IgM sera were used in separate tests and o-phenylenediamine and H2O2 served as substrate. Intra-assay variance of optical density units was 4.5%, and inter-assay variance was negligible when antigen preparations from 2 different adrenal glands were compared. All sera positive or negative at first test gave the same qualitative result in a second. Non-organ-specific binding of sera containing mitochondrial or ribosomal antibodies was eliminated by a blocking ELISA system where the antigen-coated plates were incubated with test sera, and in a second step, peroxidase-labelled IgG from an adrenal antibody-positive control serum was added. In this test, optimal antigen concentration for coating of plates was 6.25 micrograms/ml and optimal serum dilution 1/50. The ELISA proved more sensitive and reproducible than indirect immunofluorescence. Adrenal antibodies detected by ELISA were usually of IgG class alone and only 1 of the 30 positives also contained IgM specificity. 30 out of 38 sera (79%) from patients with 'idiopathic' Addison's disease were positive whereas immunofluorescence revealed only 23 (61%) at first testing and another 4 positives when sera were tested on different adrenal glands. The ELISA described is useful for both scientific work and clinical diagnosis of autoimmune adrenalitis.

[Acute renal failure--clinical aspects and morphology]

This study reports the pathological-anatomical diagnoses in 180 cases in which a diagnosis of acute renal failure (ARF) had been made on clinical grounds. The clinical and pathological diagnoses were in agreement in 43.3% of the cases. In 56.7%, the pathological-anatomical diagnosis differed from the clinical diagnosis. Glomerulonephritis (GN) was particularly often concealed behind ARF, in particular rapidly progressive GN, but also acute interstitial nephritis or hemolyticuremic syndrome. In addition, the clinical diagnoses in cases with a pathological-anatomical diagnosis of ARF are presented. Finally, the clinical diagnoses made in cases with a pathological-anatomical diagnosis of GN with ARF are reported. It is thus shown that the pathologist is in a position to distinguish GN with true compensated retention from GN with transient ARF simulating compensated retention.

Magnetized boxes for housing polarized spins in homogeneous fields

We present novel types of permanently magnetized as well as current powered boxes built from soft-ferromagnetic materials. They provide shielded magnetic fields which are homogeneous within a large fraction of the enclosed volume, thus minimizing size, weight, and costs. For the permanently magnetized solutions, homogenization is achieved either by an optimized distribution of the permanent field sources or by jacketing the field with a soft-ferromagnetic cylindrical shell which is magnetized in parallel to the enclosed field. The latter principle may be applied up to fields of about 0.1T. With fields of about 1mT, such boxes are being used for shipping spin-polarized (3)He worldwide for MRI purposes. For current powered boxes, we present concepts and realizations of uniaxial and tri-axial shielded magnetic fields which are homogeneous on the level of 10(-4) within the entire shielded volume. This is achieved by inserting tightly fitting solenoids into a box from soft-magnetic material. The flexible tri-axial solution suits in particular laboratory applications, e.g. for establishing a spin quantization axis.

[St. Ottilia, Patron saint of suffers from eye diseases. an unusual representation with a crab's pincer at the Mercy-Seat Altar in Bad Aussee (author's transl)]

On an altar-piece of the Gothic mercy-seat altar in the hospital church of Bad Aussee, made in 1449, Saint Ottilia, the patron saint of eye sufferers, is depicted with a crab's pincer, an attribute hitherto unknown. In the Middle Ages it was customary to put crab-eyes, which are calcium formations in the stomach of the crab, into the eyes of individuals to remove foreign bodies. As these crab-eyes are too small to be seen at any distance, the author takes the view that another typical and well-known part of the crab's body, more suitable for the representation, was used.

[Guidelines: treatment of distal radius fracture]

The treatment aim is restoration of adequate length of the radius, adjustment of the distal radioulnar joint, alignment of the distal radius joint surface, and prevention of reflex dystrophy syndrome. Stable fractures are treated by close reduction and a cast for 3-4 weeks, depending on bone stock quality. Instable extra-articular fractures are treated by K-wiring using various methods. In case of a comminuted dorsal or palmar area, K-wiring is unstable, so additional fixation is necessary (autogeneous bone graft + external fixator + plate or cast). The external fixator alone or in combination with K-wires is the appropriate fixation method all intra- or extra-articular comminuted fractures. Palmar or dorsal plate osteosynthesis is highly recommended in palmar or dorsal rim fractures (B 3, B 2 type), whereas in C 2 to C 3 fractures additional autogeneous graft and/or K-wires or screws are necessary should be used in combination with autogeneous graft, according to the fracture pattern. Ligament injuries or luxation in the carpal row must be looked for precisely and treated according to the injury pattern.

Demonstration of mercury in the human brain and other organs 17 years after metallic mercury exposure

A male subject became exposed to metallic mercury vapor at work in 1973. He excreted 1,850 mg Hg/l urine initially. Controls of urine mercury excretion after D-penicillamine administration led to the assumption of a total body clearance of mercury latest since 1976. Subsequently he developed an organic psychosyndrome without detectable signs of classical mercurialism. He never returned to work again and died of lung cancer in 1990. In different organs (brain, kidney, and lung) which were sampled at autopsy elevated levels of mercury were documented by atomic absorption analysis. Histological examination of the tissue by the Danscher and Schroder method, which is specific for mercury, showed a highly positive staining in the majority of nerve cells and cells of other organs. Ultrastructurally mercury could be demonstrated by elemental x-ray analysis within lipofuscin deposits. The lipofuscin content was increased in the mercury positive nerve cells as demonstrated by a strong positive autofluorescence.

Flashlamp exited pulsed dye laser and electrohydraulic lithotripsy: in vitro study on tissue effects

Intracorporal lithotripsy has gathered momentum in the management of gallstone disease due to the increasing sophistication of technical equipment for the percutaneous, as well as the retrograde-endoscopic route. Laser-induced shock wave lithotripsy (LISL) and electrohydraulic lithotripsy (EHL) have proved feasible by allowing reliable fragmentation of biliary calculi. Evaluation of therapeutic risks, e.g., effects of accidental irradiation of the gallbladder wall, has been performed in small sample sizes only. We investigated the effects of LISL and EHL on multiple sets of human and porcine gallbladders under in vitro conditions. Gallbladders were freshly harvested, mounted, and immersed in different mediums (normal saline, blood, bile). They were swiftly exposed to LISL (Pulsolith¿) and EHL (Lithotron EL 23¿) under differing experimental conditions (energy setting, pulse mode, exposition time, medium, probe pressure) and subjected to standard procedures for morphometric evaluation (Bioquant¿). Tissue effects were described by the depth (d) and width (w) of the cratered lesions, as well as the extension of the damage in the surrounding tissue(s). Serial cuts of the exposed areas yielded 894 section for morphometric analysis. Multivariate analysis of variance (MANOVA) revealed a significant effect of laser energy (p[d] less than 0.002, p[w] < 0.05, p[s] < 0.05), medium (p[d] less than 0.03, p[w] < 0.001, p[s] < 0.04, and exposition time (p[d] less than 0.001, p[s] < 0.001) on the degree of tissue lesion.(ABSTRACT TRUNCATED AT 250 WORDS)