Requirements of emergency control managements on data and information for assessment of the radiological situation in case of a severe accident in a nuclear power plant

In case of a severe accident in one of the nuclear power plants in northern Germany consequences may reach across the borders of counties and Länder and several local and regional authorities will have responsibilities for disaster response measures. Consistent assessment of the situation and coordinated action are essential for protection of the population and task personnel as effective as possible. Disaster response managements have to come to a comprehensive assessment of the developing radiological situation at an early stage to be able to initiate appropriate protective measures. The results of a working group from several local and regional authorities from Schleswig-Holstein, Hamburg, Lower Saxony and Mecklenburg-West Pomerania on this topic will be presented here. The working group has compiled sets of data and information which are relevant in decision making for protective measures and has developed a concept for the efficient distribution of data and information to the disaster response managements and other recipients with responsibilities in emergency control.

Viscosity measurements of liquids under pressure by using the quartz crystal resonators

A quartz crystal viscometer has been developed for measuring viscosity in liquids under pressure. It employs an AT-cut quartz crystal resonator of fundamental frequency 3 MHz inserted in a variable-volume vessel designed for working up to 80 MPa. Viscosity is determined by two methods from resonance frequency and bandwidth measurements along up to eight different overtones. The resonance frequency allows an absolute measurement of the viscosity but leads to an accuracy limited to 5% whereas the bandwidth technique which works in a relative way provides an accuracy of 2%. The techniques were tested by carrying out measurements in two pure compounds: heptane and toluene. Measurement results demonstrate the feasibility of the technique in this viscosity range. The apparatus was also used to determine the viscosity of n-decane with dissolved methane. The results obtained with these mixtures reveal the applicability of the apparatus for reservoir fluids study.

PRACTICAL PARALLEL IMAGING COMPRESSED SENSING MRI: SUMMARY OF TWO YEARS OF EXPERIENCE IN ACCELERATING BODY MRI OF PEDIATRIC PATIENTS

For the last two years, we have been experimenting with applying compressed sensing parallel imaging for body imaging of pediatric patients. It is a joint-effort by teams from UC Berkeley, Stanford University and GE Healthcare. This paper aims to summarize our experience so far. We describe our acquisition approach: 3D spoiled-gradient-echo with poisson-disc random undersampling of the phase encodes. Our re-construction approach: ℓ₁-SPIRiT, an iterative autocalibrating parallel imaging reconstruction that enforces both data consistency and joint-sparsity in the wavelet domain. Our implementation: an on-line parallelized implementation of ℓ₁-SPIRiT on multi-core CPU and General Purpose Graphics Processors (GPGPU) that achieves sub-minute 3D reconstructions with 8-channels. Clinical results showing higher quality reconstruction and better diagnostic confidence than parallel imaging alone at accelerations on the order of number of coils.

Maximum yields might improve public health--if filter vents were banned: a lesson from the history of vented filters

Filter ventilation is the dominant design feature of the modern cigarette that determines yields of tar, nicotine, and carbon monoxide on smoking machine tests. The commercial use of filter ventilation was precipitated by the 1964 United States Surgeon-General's report, further advanced by the adoption of an official Federal Trade Commission test in 1967, and still further advanced by the inclusion of a gas phase (carbon monoxide) measure in 1979. The first vented-filter brand on the market in the United States (Carlton) in 1964 and the second major vented-filter brand (True) in 1966 illustrate this. Ultimately, filter ventilation became a virtually required way to make very low tar cigarettes (less than 10 mg or, even more so, less than 5 mg tar). The key to the lower tar cigarette was not, in effect, the advanced selective filtration design characteristics or sophisticated tobacco selection or processing as envisioned by experts (although these techniques were and are used); the key to the very much lower tar cigarette was simply punching holes in the filter. We propose that the banning of filter vents, coupled with low maximum standard tar, nicotine, and carbon monoxide yields, would contribute to making cigarettes much less palatable and foster smoking cessation or the use of clearly less hazardous nicotine delivery systems. It may be necessary to link low maximum yields with the banning of filter ventilation to achieve public health benefit from such maxima.

Temperature mapping of frozen tissue using eddy current compensated half excitation RF pulses

Cryosurgery has been shown to be an effective therapy for prostate cancer. Temperature monitoring throughout the cryosurgical iceball could dramatically improve efficacy, since end temperatures of at least -40 degrees C are required. The results of this study indicate that MR thermometry based on tissue R(*)(2) has the potential to provide this information. Frozen tissue appears as a complete signal void on conventional MRI. Ultrashort echo times (TEs), achievable with half pulse excitation and a short spiral readout, allow frozen tissue to be imaged and MR characteristics to be measured. However, half pulse excitation is highly sensitive to eddy current distortions of the slice-select gradient. In this work, the effects of eddy currents on the half pulse technique are characterized and methods to overcome these effects are developed. The methods include: 1) eddy current compensated slice-select gradients, and 2) a correction for the phase shift between the first and second half excitations at the center of the slice. The effectiveness of these methods is demonstrated in R(*)(2) maps calculated within the frozen region during cryoablation.

1999 Gary J. Becker Young Investigator Award. MR-guided transjugular portosystemic shunt placement in a swine model

PURPOSE

To evaluate the performance of portal venous puncture with use of magnetic resonance (MR) guidance, and to place a transjugular intrahepatic portosystemic shunt (TIPS) in a swine model.

MATERIALS AND METHODS

A study of 12 swine was performed to evaluate the ability of interventional MR imaging to guide portal vein puncture and TIPS placement. Six swine had catheters placed in the right hepatic vein under C-arm fluoroscopy. A nitinol guide wire was left in the vein and the animals were then moved into an open configuration MR imaging unit. A TIPS needle set was used to puncture the portal vein using MR fluoroscopy. The animals were transferred to the C-arm, and venography confirmed portal vein puncture. A follow-up study was performed in six additional swine to place a TIPS using only MR imaging guidance. MR tracking was used to advance a catheter from the right atrium into the inferior vena cava. Puncture of the portal vein was performed and a nitinol stent was placed, bridging the hepatic parenchyma. MR venogram confirmed placement.

RESULTS

Successful portal vein puncture was achieved in all animals. The number of punctures required decreased from 12 in the first animal to a single puncture in the last eight swine. A stent was successfully placed across the hepatic tract in all six swine.

CONCLUSIONS

Real-time MR imaging proved to be a feasible method to guide portal vein puncture and TIPS placement in pigs.

Isotropic diffusion-weighted and spiral-navigated interleaved EPI for routine imaging of acute stroke

An interleaved echo-planar imaging (EPI) technique is presented for the rapid acquisition of isotropic diffusion-weighted images of stroke patients. Sixteen isotropic diffusion-weighted images at three b values are acquired in less than 3 min. A spiral navigator echo is used to measure the constant and linear phase shifts across the head in both the x and y directions which result from motion during the isotropic diffusion- sensitizing gradients. The measured k-space errors are corrected during a gridding reconstruction. The gridding kernel has a constant width in kx and a variable width in ky which eliminates variable data-density ghosts. The resulting isotropic diffusion-weighted images have excellent lesion-to-normal brain contrast, very good spatial resolution, and little sensitivity to susceptibility effects in the base of the brain. Examples of diffusion-weighted images and ADC maps from several stroke patients are shown.

Consistent fat suppression with compensated spectral-spatial pulses

Reliable fat suppression is especially important with fast imaging techniques such as echo-planar (EPI), spiral, and fast spin-echo (FSE) T2-weighted imaging. Spectral-spatial excitation has a number of advantages over spectrally selective presaturation techniques, including better resilience to B0 and B1 inhomogeneity. In this paper, a FSE sequence using a spectral-spatial excitation pulse for superior fat suppression is presented. Previous problems maintaining the CPMG condition are solved using simple methods to accurately program radio-frequency (RF) phase. Next an analysis shows how B0 eddy currents can reduce fat suppression effectiveness for spectral-spatial pulses designed for conventional gradient systems. Three methods to compensate for the degradation are provided. Both the causes of the degradation and the compensation techniques apply equally to gradient-recalled applications using these pulses. These problems do not apply to pulses designed for high-speed gradient systems. The spectral-spatial FSE sequence delivers clinically lower fat signal with better uniformity than spectrally selective pre-saturation techniques.

Improved solvent suppression and increased spatial excitation bandwidths for three-dimensional PRESS CSI using phase-compensating spectral/spatial spin-echo pulses

Dual phase-compensating spectral/spatial echo-planar (EP) spin-echo (SE) pulses were incorporated into the point resolved spectroscopy (PRESS) excitation sequence to improve water and lipid suppression for 1H chemical shift imaging (CSI) and to decrease the dependence of the PRESS box location upon chemical shift. The asymmetric EPSE pulses (either minimum or maximum phase in the chemical shift domain) were substituted for the two PRESS SE pulses to yield zero phase spectra. Three different pulses were designed and tested at 1.5 T. Pulse 1, targeted for brain CSI (TE > 85 msec), passed choline to lipid resonances, suppressed water, and rephased the methyl lactate doublet independently of TE. Pulse 2, targeted for general purpose shorter TE PRESS, possessed both high chemical shift and spatial domain bandwidths. Pulse 3, designed for prostate CSI, passed choline to citrate resonances while suppressing lipids and water. The three pulses possessed spatial bandwidths ranging between 3.3 and 5.0 kHz, more than three times higher than that offered by one-dimensional SE pulses of equivalent maximum B1 amplitude. Phantom and in vivo experimental results demonstrated that, for EPSE pulses 1 and 2, suppression factors higher than 10(4) were achieved. The increased spatial bandwidths resulted in less contamination by signals from outside the designated PRESS excited region and a significant improvement in the uniformity of metabolite intensities for voxels located near edges of the PRESS box.

Background suppression with multiple inversion recovery nulling: applications to projective angiography

We have developed a technique to accurately null the longitudinal magnetization (Mz) of background material. This suppression involves first saturating the longitudinal magnetization (Mz) of a region, and then applying several nonselective inversions. The inversions are timed relative to the saturation such that Mz is nulled across a broad range of T1 at a predetermined time after the initial saturation. B1 and B0 inhomogeneity, which could lead to inaccurate suppression, are dealt with by the combination of a multiple tip saturation sequence and four adiabatic inversion pulses. The suppression sequence can be used to form projective angiograms by selectively tagging the imaging region with the saturation pulse. After the inversions are played out, a projection taken through the tag region when Mz is nulled will only contain signal from blood that has flown into the region after the saturation. Since only two dimensions are acquired, the technique can acquire gated projection angiograms in reasonable scan times. Representative inflow MIR angiograms of the carotid arteries and renal arteries show excellent background suppression.

RARE spiral T2-weighted imaging

Spiral imaging has a number of advantages for fast imaging, including an efficient use of gradient hardware. However, inhomogeneity -induced blurring is proportional to the data acquisition duration. In this paper, we combine spiral data acquisition with a RARE echo train. This allows a long data acquisition interval per excitation, while limiting the effects of inhomogeneity. Long spiral k-space trajectories are partitioned into smaller, annular ring trajectories. Each of these annular rings is acquired during echoes of a RARE echo train. The RARE refocusing RF pulses periodically refocus off-resonant spins while building a long data acquisition. We describe both T2-weighted single excitation and interleaved RARE spiral sequences. A typical sequence acquires a complete data set in three excitations (32 cm FOV, 192 x 192 matrix). At a TR = 2000 ms, we can average two acquisitions in an easy breath-hold interval. A multifrequency reconstruction algorithm minimizes the effects of any off-resonant spins. Though this algorithm needs a field map, we demonstrate how signal averaging can provide the necessary phase data while increasing SNR. The field map creation causes no scan time penalty and essentially no loss in SNR efficiency. Multiple slice, 14-s breath-hold scans acquired on a conventional gradient system demonstrate the performance.

Short TE phosphorus spectroscopy using a spin-echo pulse

In vivo phosphorus spectroscopy requires very short acquisition delays in order to capture the signal from components with short transverse relaxation times (T2). The echo time typical of standard slice selective spin-echo pulses are too long for this application, so hard pulse, free induction decay (FID) acquisitions have frequently been used instead. With FID, however, there is an interval between the time of coherence and data acquisition (acquisition delay), with resulting baseline distortions. In this paper we describe the design of a new short TE, slice-selective, composite spin-echo pulse with echo times as short as 2.5 ms. With a long TR, fully relaxed, multislice spectra can be collected. This technique will be useful for assessing in vivo, changes in brain phospholipid activity associated with psychiatric and neurological diseases.

Echo-planar spin-echo and inversion pulses

The echo-planar k-space trajectory can be used as the basis for any two-dimensional selective pulse. The main application is spectral-spatial pulses, which must be based on the echo-planar trajectory. In this paper we show how echo-planar spin-echo (EPSE) pulses may be designed.

Two-dimensional selective adiabatic pulses

Using the technique of separable k-space excitation, we have designed a two-dimensional selective adiabatic pulse that inverts magnetization from a square region in the xy plane with insensitivity to RF variations. We also have designed a two-dimensional adiabatic pulse that inverts selectively in frequency and in one spatial dimension. The pulses should be useful for both MR imaging and spectroscopy. We present experimental results to demonstrate that the two-dimensional adiabatic pulses are feasible on commercial MR imaging systems.

Two-dimensional selective adiabatic pulses

Using the technique of separable k-space excitation, we have designed a two-dimensional selective adiabatic pulse that inverts magnetization from a square region in the xy plane with insensitivity to RF variations. We also have designed a two-dimensional adiabatic pulse that inverts selectively in frequency and in one spatial dimension. The pulses should be useful for both MR imaging and spectroscopy. We present experimental results to demonstrate that the two-dimensional adiabatic pulses are feasible on commercial MR imaging systems.

Effects of RF amplifier distortion on selective excitation and their correction by prewarping

In a magnetic resonance imaging system, an RF power amplifier is employed to boost an RF pulse to sufficient strength to excite the nuclear spins in a subject. The nonideal behavior of this amplifier distorts a selective-excitation pulse, and this distortion in turn degrades the slice profile. We have found two types of nonideal behavior particularly troublesome: nonlinearity and incidental phase modulation. One of their effects is the introduction of an unwanted "skirt" in the out-of-slice region of a slice profile. We present an effective method of correction in which a selective-excitation pulse is prewarped to compensate for the distortion.

Spectroscopic imaging with multidimensional pulses for excitation: SIMPLE

Proton spectroscopy and spectroscopic imaging in the human brain require the elimination of both water and lipid signals. Strong lipid signals from subcutaneous fat are usually eliminated by confining the excited volume to lie wholly within the skull. Water suppression, however, can be difficult due to both B0 and RF inhomogeneities, which are particularly troublesome in imaging experiments where a relatively large region-of-interest (ROI) is typical. In this paper, we discuss the use of multidimensional selective-excitation pulses (e.g., pulses that are simultaneously selective along two axes) to both define the ROI and provide the necessary water suppression. Pulse sequences providing three-dimensional localization along with water suppression that is insensitive to a range of B0 and RF inhomogeneities are described. Spectra and spectroscopic images (voxel volume = 3.4 cc. acquisition time = 38 min) of various 1H metabolites from a patient with an astrocytoma show clear differences between normal and cancerous tissues and demonstrate the ability of these techniques to be used in vivo.

Parameter relations for the Shinnar-Le Roux selective excitation pulse design algorithm [NMR imaging]

An overview of the Shinnar-Le Roux (SLR) algorithm is presented. It is shown how the performance of SLR pulses can be very accurately specified analytically. This reveals how to design a pulse that produces a specified slice profile and allows the pulse designer to trade off analytically the parameters describing the pulse performance. Several examples are presented to illustrate the more important tradeoffs. These include linear-phase and minimum- and maximum-phase pulses. Linear-phase pulses can be refocused with a gradient reversal and can be used as spin-echo pulses. Minimum- and maximum-phase pulses have better slice profiles, but cannot be completely refocused.

Studies of cultured human T lymphocytes. II. Initiation of paired T- and B-cell lines from healthy donors

We report the sustained cultivation of both B- and T-lymphoblastoid cell lines from randomly selected healthy donors, and the results of studies defining the frequency with which these cell lines can be established. B-cell lines were initiated using the Epstein-Barr virus. Of 52 attempts, 40 B-cell lines (77% success) were obtained from 24 different donors. T-cell lines were started and propagated in long-term (greater than 100 days) cultures using the T-cell growth factor interleukin-2 (IL-2). Of 55 attempts, 54 (98%) were successful in initiating IL-2-dependent T-cell lines, and these were derived from 28 healthy adults. Likewise, of 45 attempts, 32 (71%) were successful in producing paired lines in which both the B-cell line and T-cell line were cultivated from a single blood collection (N = 22 donors). Phenotypic profiles of these lines were defined using multiple marker assays, including rosette formation, surface immunoglobulins, cytochemistry, karyotype, as well as xenoantisera and monoclonal antibodies defining different membrane antigens. This work demonstrates the feasibility of propagating paired human B and T lymphoblastoid lines suitable for many comparative immunobiological studies.

Time-varying effects in mice and rats of several synthetic ACTH preparations

Circadian stage-dependent effects characterize synthetic ACTH 1-17 preparation (HOE 433 = Synchrodyn 1-17), tested in mice and rats, with reference notably to corticosterone and aldosterone production in vitro and to the behavior of rhythms in these two corticoids as an aspect of the adrenal cortical pacemaker of the circadian system. The possibility to advance or delay the rhythm in serum corticosterone by ACTH 1-17 also is demonstrated, as is a differential behavior of the circadian rhythm in serum aldosterone. Differences in timing of circadian corticosterone and aldosterone responses also are described and await further scrutiny for ultradian and infradian (notably circannual) modulation.

Adenosine-aminohydrolase activity in the erythrocytes, lymphocytes, and plasma of healthy subjects and kidney transplant recipients

Adenosine-aminohydrolase activity in the red blood cells and lymphocytes of transplant patients were assayed by continuous flow analysis. This enzyme, which has been implicated in the ability of lymphocytes to mount an immune response, was evaluated in renal allografted patients immunosuppressed by azothiprine and methylprednisone. Red cell adenosine-aminohydrolase activity was depressed in all patients when compared to nontreated health controls. Adenosine aminohydrolase activity was raised in the lymphocytes of the renal allografted patients. Renal transplant patients' in vitro lymphocyte reactivity to antigens, mitogens, or skin testing to specific antigens, confirmed the depressive effects of immunosuppression observed in vivo. We conclude from these studies that red cell adenosine-aminohydrolase activity may be a more sensitive index of the state of immunoresponsiveness than the corresponding enzyme activity in the lymphocyte.

Synergism of stimulating capacity of pooled lymphocytes in the mixed lymphocyte reaction

One-way mixed lymphocyte reactions in cultures of responding cells from a single subject and a pool of stimulating cells from two or more donors exhibited a synergistic response. Increased activity of the responding cells showed a positive correlation with the pool size. Treatment of the responding cells, stimulating cells or both with neuraminidase significantly increased the response.

Simplified whole blood method for evaluating in vitro lymphocyte reactivity of laboratory animals

A whole blood culture technique has been employed to quantitatively evaluate lymphocyte reactivity of small laboratory animals including mice, rats, guinea-pigs and rabbits. This simplified method has been used to study the blastogenic response to phytohaemagglutinin, concanavalin A, pokeweed mitogen and staphy-lococcal filtrate. Tuberculin-induced lymphocyte transformation responses have been studied in serial experiments using sensitized animals. The results of this preliminary study demonstrate that the whole blood method has numerous advantages over the conventional techniques employing leucocyte concentrates. In almost all instances the degree of lymphocyte reactivity as measured by ³H-thymidine incorporation closely approximated or exceeded previously reported results using the standard culture method.