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The Vk gene of MAb with specificity for HBsAg and human Ck gene have been combined to form chimeric light chain (Vk-Ck) by recombinant PCR, which has combined with VH to construct chimeric single-chain antibody(ScFv-Ck) by a linker encoding a flexible peptide[(Gly3 Ser)3]. The ScFv-Ck has been expressed in the heat-induced expression system and secreted expression system of E. coli respectively. Analysis by Western-blot and indirect ELISA shows that the ScFv-Ck product in two systems both have HBsAg-binding ability, and ScFv-Ck has been secreted from E. coli in the direction of secretion peptide.

Total RNAs were extracted from the venom gland of the Agkistrodon halys Pallas snake. The thrombin-like enzyme gene was amplified by RT-PCR, cloned, and its nucleotide sequences have been determined. The enzyme called pallase cDNA encodes 708 nucleotides, namely 236 amino acids. Based on the homology, the catalytic residues and disulfide bridges of pallase were deduced as follows catalytic residues, His(41), Asp(86) and Ser(182) and disulfide bridges, Cys(7)-Cys(139), Cys(26)-Cys(42), Cys(74)-Cys(234), Cys(118)-Cys(188), Cys(150)-Cys(167) and Cys(178)-Cys(203). The pallase expression plasmids under the control of the T7 promoter was constructed and the pallase was expressed in E. coli.

The assessment of regional myocardial perfusion during the first-pass of a contrast agent bolus requires tracking of the signal time course for each myocardial segment so that a detailed perfusion map can be derived. To obtain such a map in practice, however, is not trivial because deformation of the shape of the myocardium and respiratory-induced motion render a major difficulty in this process. This study describes an automated approach for motion and deformation tracking of functional myocardial perfusion images. The effectiveness of the described method has been evaluated using a numerical phantom and results are compared with those from existing techniques which use deformable models. Preliminary results from applying our approach to 20 patients are discussed and compared with those from SPECT studies.

As a step toward understanding the structure and function of phospholipase A2(PLA2), we isolated several novel cDNAs encoding Agkistrodon halys Pallas PLA2 isoenzymes including B-PLA2, Asn49-PLA2, A-PLA2, A'-PLA2 and BA1-PLA2 by polymerase chain reaction with oligonucleotide primers corresponding to the N- and C-terminus of these enzymes. The amino acid sequences of A-PLA2 deduced from cDNA are consistent with that isolated from venom except for four residues. Asn49-PLA2 and B-PLA2 are highly similar (> 95%), but the critical residue Asp49 in the active centre of B-PLA2 is replaced by Asn49 in Asn49-PLA2. The N-terminal residues (1-24) of BA1-PLA2 shows high similarity to that of B-PLA2 which has strong ability to hemolyze erythrocytes, while its C-terminal residues (72-125) are the same as that of A-PLA2 which can inhibit platelet aggregation. The successful cloning of these isoenzymes not only provide excellent native material to study the structure-function relationship of PLA2s, but also to disclose the genesis of structural diversity of PLA2s, namely DNA modification and gene rearrangement. The cloned cDNA for A-PLA2 has been expressed in E. coli. By Q-Sepharose column chromatography, denaturation-renaturation and FPLC, we obtained the active recombinant protein with the initiator Met. This is the first report of the production of an active recombinant PLA2 with the initiator Met.

New optical implementations of the Radon-Wigner display for a one-dimensional signal are proposed based on the fractional Fourier transform. The setups involve only one varifocal lens. Furthermore, the same magnification can be realized simultaneously for all the fractional transform orders, which is quite convenient for practical applications.

Purpose: To describe an automatic method for studying vortical flow features using multidirectional magnetic resonance velocity imaging., Methods: The technique relied on the use of linear differential equations to provide local approximation to the acquired MR velocity data and to identify vortical flow patterns that were characterised by their circular or swirling motion. Two directional MR velocity images were acquired on a 0.5 T system with a TE of 14 ms, slice thickness of 10 mm, and field of view of 30-40 cm., Results: The method was validated using numerical simulation, and the potential of this technique for studying blood flow features was demonstrated in the ascending aorta of a healthy volunteer and that of a patient with Marfan's syndrome. The difference in vortex flow dynamics of the left ventricle between a normal subject and a patient with dilated ventricle was also compared., Conclusion: The approach of detecting critical flow features prior to analysing dynamical indices of the fluid is suited to the topological study of complex flow patterns depicted by MR velocity mapping techniques.

Respiration causes continuous change in cardiac position, which leads to image degradation. Phase-encode reordering methods are often used to reduce these artifacts. An improved method for suppressing motion artifacts by reordering the acquisition of k space has been developed that is less sensitive to change of breathing patterns and bulk movement. We describe the theory behind the new approach and compare its results with those of existing methods by use of a phantom with simulated and actual acquired breathing patterns. The comparison was also made in vivo; cardiac scans were performed in 15 subjects with image planes that are known to be particularly susceptible to respiratory artifact. A significant improvement in image quality was achieved compared with conventional nonreordered and existing reordering methods.

Several pulmonary conditions are characterized by the finding of areas of decreased attenuation relative to adjacent normal lung parenchyma on computed tomography. In particular, the identification of areas of the lung affected by small airways disease is difficult as the reduction in lung density is subtle and the regions are poorly marginated. This paper presents a novel wavelet analysis technique which increases the conspicuity of differences between normal and abnormal lung parenchyma.

Using an adapted two-dimensional spatially selective RF excitation scheme, a novel yet practical three-dimensional (3D) zonal echo-planar imaging technique for MR coronary angiography has been developed. The robustness of the technique compared with the two-dimensional (2D) segmented fast low angle shot (FLASH) method was evaluated using the right coronary artery images of 16 asymptomatic volunteers with a 0.5-T mobile scanner. Each 3D acquisition required multiple breath-holds, and real-time navigator echoes were used to ensure consistent breath-holding. Advantages of the technique include an improved signal-to-noise ratio, clearer depiction of tortuous coronary vessels due to decreased partial volume effects, and reduced motion blurring by the use of a short echo-planar readout.

The design of diffractive phase elements (DPE's) for generating color pseudo-nondiffracting beams (PNDB's) in a multiple-wave illuminating system by the conjugate-gradient method is described. The axial-intensity distributions for dual-color PNDB's generated by the DPE's are shown. The color PNDB's behave as segmented axial-intensity distributions; in each of segments only one color persists. The sequence of wavelength components in the color PNDB's can be arbitrarily preset. Three-dimensional plots of a dual-color PNDB indicate the characteristics of a beam with high transverse resolution.

Pulse sequences based on FID signals and projection reconstruction (PR) were investigated for lung MRI at 0.5 T and evaluated for artifacts caused by: (1) k-space mismapping due to either delay or distortion of the readout gradient waveform, (2) cardiac motion and pulsatile flow, and (3) respiratory motion. Nonstructured artifacts were described, simulated, and experimentally confirmed for the first time. Nonstructured artifacts did not impair the demonstration of structures of high signal-to-noise ratio (SNR) but generated quantitative errors in the image intensity analysis over the lung parenchyma. The use of FID-based PR techniques for lung MRI is not justified at 0.5 T.

A 600 bp DNA fragment was amplified by PCR, from an adult Schistosoma japonicum cDNA library. Sequence analysis revealed that this fragment containedthe S. japonicum Chinese Mainland strain fatty acid binding protein (Sj-14FABPc) gene. This gene was then cloned into the expression vector pGEX-2T, and subsequently expressed in Escherichia coli. The recombinant GST-fusion protein could be purified by glutathione agarose affinity chromatography. Its molecular weight was about 41 kD. The yield of expression was around 25 mg/L E. coli culture. The immunological test suggested that the recombinant protein had good antigenicity, and could be developed into a new vaccine molecule of S. japonicum.

We used degenerate primers to amplify phospholipase A(2)(PLA(2)) gene by RT-PCR from venom total RNA of Agkistrodon halys Pallas, and screened with B-PLA(2) gene as probe. Finally we isolated three cDNAs containing A-PLA(2) and two other genes showing similar characteristic structure--Asn(49)-PLA(2) and BA-PLA(2). Their complete sequence was determined by bidirectional sequencing and their amino acid sequence was deduced. The amino acid sequence of A-PLA(2) deduced from the cDNA agreed with that determined by protein sequencing except for four residues; Asn(49 )-PLA(2) and B-PLA(2) are very alike (up to 95%), but the Asp(49)-PLA(2) of B-PLA(2) involved in the enzyme reaction is replaced by Asn(49) of Asn(49)-PLA(2). Therefore, it possibly affects the enzyme reaction of Asn(49)-PLA(2). The N-terminus sequence of BA-PLA(2) is highly homologous to B-PLA(2), but its C-terminus sequence is almost the same as A-PLA(2). The successful cloning of these isoenzyme genes not only discloses the structure diversity of PLA(2)(namely DNA modification and recombination), but also provides excellent material for the study of structure-function relationship in PLA(2).

The APLA(2) gene from Agkistrodon halys Pallas has been cloned into the expression plasmid pBLMVL2 and expressed in E. coli RR1. The molecular weight of the expressed product is approximately 14 kD as shown by SDS-PAGE, its expression level is about 30% of the total cellular proteins. The protein was produced as insoluble inclusion bodies. After partially purified by washing the inclusion bodies, the product was denatured and refolded into active form. Then, the expressed APLA(2) was purified by FPLC Superose (TM) 12 and was a single band as shown by SDS-PAGE. The purified expressed protein had specific activity as the native enzyme and cross-reacted with antisera prepared against the native enzyme. The successful expression of the APLA(2) gene from Agkistrodon halys Pallas provides a good basis for further structure-function studies.

Triose-phosphate isomerase is an important candidate for schistosoma antigens. An 800 bp DNA fragment was amplified by RT-PCR from adult Schistosoma japonicum mRNA. Sequence analysis revealed that this fragment contained S. japonicum (Chinese strain) triose-phosphate isomerase gene. Then this gene was cloned into the expression vector pGEX-4T and subsequently expressed in E. coli. The recombinant GST-fusion protein was purified by glutathione agarose affinity chromatography. Its molecular weight was determined to be 54 kD. The yield of expression was around 30 mg/L E. coli culture. Western blotting showed that the recombinant protein had good antigenicity which could be helpful for the making of anti-S. japonicum multi-valent recombinant vaccine.

A fractional Gabor transform (FRGT) is proposed. This new transform is a generalization of the conventional Gabor transform (GT) based on the Fourier transform to the windowed fractional Fourier transform (FRFT). The FRGT provides analyses of signals in both the real space and the FRFT frequency domain simultaneously. The space-FRFT frequency pattern can be rotated as the fractional order changes. The FRGT has an additional freedom, compared with the conventional GT, i.e., the transform order. The FRGT may offer a useful tool for guiding optimal filter design in the FRFT domain in signal processing.

Objective: To assess three-dimensional computed tomography 'bronchoscopic' (3-DCTB) reconstruction of routine CT data as a non-invasive method of airway visualization, and compare it with fibreoptic bronchoscopy (FOB)., Methods: Fourteen datasets were acquired from 13 patients undergoing both FOB and CT examination of the chest. Standard continuous volume CT using 6 mm collimation and clinical FOB techniques were employed. Images were obtained from 3-DCTB reconstructions by segmentation and surface recognition algorithms generating surface rendered 'bronchoscopic views'. These were scored for technical quality and anatomical detail. The most distal bronchi seen in left upper and right lower lobes were recorded for FOB and 3-DCTB., Results: On FOB, the subsegmental bronchi were seen in right lower and in left upper lobe in 10/14 cases and 4/14 cases, respectively. Visualization of the subsegmental airways was not achieved with 3-DCTB, as they could not be identified with confidence. 3-DCTB never achieved a more distal view than obtained by FOB. Using 3-DCT, the right, lower lobe segmental bronchi were seen in 10/14 cases, and lobar bronchus in 14/14 cases (two occluded). In the left upper lobe, 3-DCT showed segmental bronchi in 6/14 cases, lobar bronchus in 11/14 cases (one occluded) and the left main bronchus appeared occluded in 3/14 cases. Overall, technical quality and anatomical detail scores of the carina and proximal bronchi ranked significantly higher than views of segmental bronchi., Conclusions: 3-DCTB cannot routinely replace FOB for inspection of major and segmental bronchi. Subsegmental bronchi cannot be adequately demonstrated by 3-DCTB using 6 mm collimation datasets.

Retinoic acid and its analogues play important roles in modulating cell growth, differentiation, immunity and apoptosis. Clinically they are used for cancer chemoprevention and chemotherapy. Based upon the moiety of 3,5-di-t-butyl-4-hydroxy phenyl ring, a series of substituted aromatic amide, ester and chalcones were designed and synthesized, which mimic the molecular shape, size, and spacial disposition of functional groups of retinoic acid. The general structure is as follows: [formula: see text] where R stands for hydrogen atom or methyl group, Y is the linkage -CONH-, -NHCO-, -COO-, -COCH = CH-, or a member of a heterocycle, X represents various substituents at different positions. The SAR indicates that the presence of hydrophobic group(s) at one end of the molecule, and a carboxyl group at the other end, and a conjugative system of molecule are necessary and full prerequisite for exhibiting activity. Loss of any one factor of them will abolish the activity. Being obligatory for anti-oxidative effect, the phenolic hydroxy group does not convey biological activity, because after methylation of the hydroxy group the compound increases the differentiation-inducing activity and loses the anti-oxidative effect, indicating that there is no correlation between the two activities. With a stable conformation of two phenyl rings with cis-conformation N-methylated acyl amide (No. 30) features in bent shape of the molecule, instead of an extended conformer, which is taken by the non-N-methylated partner and all-trans retinoic acid. A bent conformer of No. 30 accounts for the inactivity. In this paper compounds No. 4f, 4g, 5a, 7, 13, 32, 37, and 38 exhibited significant activity among them 4-[3-(3, 5-di-t-4-methoxyphenyl)-3-oxo-1-propenyl] benzoic acid (No. 38) showed high activity comparable to that of retinoic acid. The pharmacological action of No. 38 is under investigation.

We present a new algorithm for the robust and accurate tracking of the aorta in cardiovascular magnetic resonance (MR) images. First, a rough estimate of the location and diameter of the aorta is obtained by applying a multiscale medial-response function using the available a priori knowledge. Then, this estimate is refined using an energy-minimizing deformable model which we define in a Markov-random-field (MRF) framework. In this context, we propose a global minimization technique based on stochastic relaxation, Simulated annealing (SA), which is shown to be superior to other minimization techniques, for minimizing the energy of the deformable model. We have evaluated the performance and robustness of the algorithm on clinical compliance studies in cardiovascular MR images. The segmentation and tracking has been successfully tested in spin-echo MR images of the aorta. The results show the ability of the algorithm to produce not only accurate, but also very reliable results in clinical routine applications.

The objective was to investigate how the blood flows in the thoracic aorta, with special emphasis on flow reversal and flow into the coronary arteries. Three-directional MR velocity mapping was used to map multidirectional flow velocities in the aorta in 14 normal subjects and 14 patients with coronary artery disease. Dynamic flow vector maps and through-plane velocity maps were used. The flow reversed in all subjects in the upper ascending aorta and usually also in the distal aortic arch. Retrograde flow became antegrade again at various levels in the ascending aorta and in the coronary sinuses. Seven flow characteristics were investigated that, lumped together, were significantly different (P = .0005) in normal subjects compared with patients and in normal subjects 70 years of age and older compared with those younger than 70 years of age.

Magnetic resonance imaging (MRI) with navigating techniques based on consecutive breath-holds demand a level of respiratory control that is often beyond the capability of patients with lung disease. The objectives of this investigation were to develop and evaluate a navigating technique for lung MRI that does not rely on patient cooperation. Navigating techniques were implemented at 0.5 T using conventional imaging techniques of short echo-time and imaging during normal breathing in the diastolic phase of the cardiac cycle. A column of spins, orthogonal to the diaphragm, was excited both immediately before and after the imaging segment. These signals were processed in real time to provide the position of the lung-diaphragm interface. An imaging segment was considered correctly acquired only when the interface position was within the acceptance window both before and after the acquisition of the segment. A distribution of lung-diaphragm interface positions obtained during normal respiration was employed to define the acceptance window. In the case of multislice techniques, the position of the lung-diaphragm interface immediately before the imaging segment was also employed to decide which phase-encoding step to acquire next, therefore reducing the apparent frequency of the respiratory motion. A distribution of interface positions, updated in real time, served as a reference for the allocation of phase-encoding steps according to diaphragm position. The lung images obtained represent a significant advance in image quality, improving further the ability of MR to detect and monitor pulmonary disease. Motion artifacts were reduced, and images reliably demonstrated smaller vessels, which are not normally visible without navigation.

We have constructed a double-recombinant virus BacHL4.2 containing both the chimeric heavy- and light-chain cDNAs from monoclonal antibody of the HBsAg gene. Both murine-human chimeric antibody heavy- and light-chain were expressed in Sf9 cells infected with a double-recombinant virus BacHL4.2 or co-infected with separate heavy- and light-chain recombinant viruses. In both cases, expressed products were correctly assembled into normal H(2)L(2) immunoglobulin monomers. ELISA and functional immunoblot assay showed that the recombinant chimeric antibody exhibited a specificity for HBsAg similar to that of the parental murine monoclonal antibody OH3.

The gene of the 28 kD glutathione S-transferase (GST) from the Chinese strain of Schistosoma japonicum had been expressed in the silkworm (Bombyx mori) cells and larvae by Bombyx mori nuclear polyhedrosis virus (BmNPV) vector which had been modified. The GST gene was inserted into the right position of the BmNPV genome as identified by Southern hybridization. The product was a 28 kD protein, had GST activity and antigenicity. The yield in BmN cells (1x10(6) cells/ml) was 0.77 mg and more than 5 mg in a silkworm larvae. All the results showed that it is possible to develop the GST expressed in the silkworm larvae to a new kind of genetic engineered schistosomiasis vaccine.

Precise prediction of the binding constant of ligand to receptor is an important aspect of structure-based drug design. Almost all methods including de novo design and 3D database search are over concentrated on structure generation rather than quantitative evaluation of the binding properties of the newly produced molecule. Using epididymal retinoic acid binding protein (ERABP) as a model, we simulated the interaction between retinoids and their receptor with DOCK program and obtained an equation for predicting the binding constants. According to the docking conformers of the ligands, CoMFA was also used to deduce a pharmacophoric model of this series of compound.

The design of a diffractive phase element (DPE) that simultaneously implements wavelength demultiplexing and focusing is carried out on the basis of the general theory of amplitude-phase retrieval. The designed DPE is fabricated with optical contact lithography. Three masks are needed to produce the surface-relief structure of the DPE with eight quantized levels in depths. Experiments demonstrate that the designed DPE can successfully implement both the functions of demultiplexing three different-wavelength beams and focusing each component at a predesignated position simultaneously. Experimental measurements are in good agreement with the results of numerical simulations.

Magnetic resonance phase velocity mapping has unrivalled capacities for acquiring in vivo multi-directional blood flow information. In this study, the authors set out to derive both spatial and temporal components of acceleration, and hence differences of pressure in a flow field using cine magnetic resonance velocity data. An efficient numerical algorithm based on the Navier-Stokes equations for incompressible Newtonian fluid was used. The computational approach was validated with in vitro flow phantoms. This work aims to contribute to a better understanding of cardiovascular dynamics and to serve as a basis for investigating pulsatile pressure/flow relationships associated with normal and impaired cardiovascular function.

A motion-registered spatiotemporal phase-unwrapping method for extending the dynamic range of cine magnetic resonance phase velocity measurements is presented. The interframe cardiac movement is estimated from the magnitude image derived from the velocity encoded raw data, which ensures that the phase signal is unwrapped in the temporal direction with reference to pixels belonging to the same anatomic flow region. An extra step of spatial phase correction is then used to further eliminate any residual errors. The combination of spatial and temporal information for phase unwrapping provides a robust way of extending the dynamic range of cine velocity data in the presence of large phase aliasing errors.

Abnormal diastolic left ventricular function is an early marker for myocardial disease and may be impaired even when global systolic function is normal. Subendocardial function is affected early in ischaemic heart disease and by altering left ventricular long axis motion, may contribute to abnormal transmitral pressure gradients. Regional myocardial long axis velocity in diastole measured by magnetic resonance was compared with left ventricular filling measured by Doppler echocardiography in 25 patients with coronary artery disease. Fifteen patients also underwent magnetic resonance assessment at the time of onset of early diastolic blood flow. The onset of diastolic long axis velocity preceded flow across the mitral valve by a mean of 46 ms. Mean long axis myocardial velocity correlated with peak early filling velocity (E) (r = 0.73, P < 0.001), early deceleration (r = -0.73, P < 0.001), and the early to late filling ratio (E/A) ratio (r = 0.6, P < 0.01). Maximum myocardial long axis velocity also correlated with peak early filling velocity (r = 0.56, P < 0.01), early deceleration rate (r = 0.63, P < 0.001), and the E/A ratio (r = 0.53, P < 0.01). The variability of long axis velocity around the ventricle correlated inversely with peak early filling, (r = -0.7, P < 0.001), early deceleration (r = -0.56, P < 0.01), and the E/A ratio (r = -0.48, P < 0.02). Peak atrial filling velocity did not correlate with any measure of long axis myocardial velocity. We conclude that early diastolic long axis myocardial velocity has a significant effect on left ventricular filling.

A chimeric immunoglobulin light chain gene had been expressed in a baculovirus expression system, which was achieved by infecting the silkworm cells with the recombinant virus r-NPVL2 containing the cDNA of immunoglobulin against a small cell lung cancer. PCR analysis and Southern hybridization proved that the antibody light chain cDNA hand been integrated into the modified BmNPV genome. Expression products of human-mouse chimeric antibody light chain in the silkworm cells were detected by both Western blot and ELISA.

First strand cDNA synthesis was primed with synthetic oligonucleotide from total RNA extracted from the gland of the snake Agkistrodon halys Pallas. The pro-BPLA(2) gene was then amplified by PCR and cloned into the pBS-ks vector. Its nucleotide sequence has been determined by analyzing the DNA sequence of three colonies containing the pro-BPLA(2) gene. The deduced amino acid sequence consists of 138 amino acids and agrees with the partly known amino acid sequence except for seven amino acid residues. The successful cloning of the BPLA(2) gene not only has made the determination of its total amino acid sequence possible, but also provided a good basis for further research work in the protein engineering of functional peptides from snakes.

A new optimization method based on the general theory of amplitude-phase retrieval is proposed for designing the diffractive phase elements (DPE's) that produce focal annular patterns. A set of equations for determining the phase distribution of the DPE is given. The profile of a surface-relief DPE can be designed with an iterative algorithm. Numerical calculations are carried out for several examples. A comparison of the performance of the DPE's designed with the Gerchberg-Saxton algorithm and the new algorithm is presented. The effect of quantization of the phase distribution of the DPE's on the results is also investigated. The results show that the new algorithm can successfully achieve the design of the DPE's that convert the uniform incident beam into the focal annular patterns.

The reproducibility of MR imaging for the measurement of aortic compliance was studied in 47 healthy volunteers. Long and short term reproducibility and intraobserver variability were tested. The method was modified to improve image quality and short term reproducibility and intraobserver variability retested. For comparison, spin echo imaging was compared with cine gradient echo imaging. Initial long term reproducibility showed a mean difference (+/-SE) of 3% (+/- 7%) with 95% confidence interval (CI) for limits of agreement of +/- 69%. Short term reproducibility (7% +/- 6%, 95% CI +/- 46%) and intraobserver variability (1% +/- 2%, 95% CI +/- 31%) were better. After modification of the technique and optimization of image quality, both short term reproducibility and intraobserver variability improved (0% +/- 3%, 95% CI +/- 17% and 5% +/- 2%, 95% CI +/- 16% respectively). Aortic compliance can be measured using spin echo MR imaging with good reproducibility provided care is taken to obtain good quality images with high spatial resolution.

Magnetic resonance imaging with multidirectional cine velocity mapping was used to study relationships between aortic blood flow patterns and the geometry of thoracic aortic aneurysms and grafts. Ten patients with 13 thoracic aortic aneurysms, single or multiple, or grafts (4) participated in the study. The causes of disease were atherosclerosis (4), Marfan's syndrome (2), trauma (1), and unknown (1), and there were two dissections. Spin-echo imaging and cine velocity mapping in 10 mm thick slices with vertical and horizontal velocity encoding were done. Maps of the two velocity components were processed into multiple computer-generated streaks whose orientation and length corresponded to velocity vectors in the chosen plane. The dynamic arrow maps were compared with previously reported aortic arrow maps from normal subjects. The forward flow occupied the entire lumen in the normal aorta in systole and small vortices were only present in the sinuses of Valsalva. Atherosclerotic aneurysms in the ascending aorta were located at the anterior right and had oblique, eccentric jet flows that created a large secondary vortex in the aneurysm. Patients with Marfan's syndrome had a central jet and two large vortices, one on each side. All other aneurysms, dissections, and grafts had irregular flows and vortices not seen in normal subjects. Magnetic resonance imaging with multidirectional velocity mapping is a powerful noninvasive tool to assess morphologic features and disturbed blood flow in aortic aneurysms and grafts. Recognizably altered flow patterns were found to be associated with altered vessel geometry. The significance of this requires further investigation.

Background: Magnetic resonance imaging (MRI) is a versatile technique for examination of the cardiovascular system but only recently has assessment of myocardial ischaemia in coronary artery disease (CAD) become possible, for example by demonstrating abnormalities of regional ventricular contraction during stress. Global ventricular function during stress was assessed by MRI of aortic flow, which has not been previously attempted., Design: Variables measured by MRI reflecting the effect of ischaemia on global ventricular function during dobutamine stress were correlated with thallium-201 myocardial perfusion tomography., Patients: 10 normal controls and 25 patients with CAD., Setting: Tertiary cardiac referral centre., Methods: Novel MRI sequences and analysis systems were used to measure the following variables during staged dobutamine infusion to 20 micrograms/kg/min: stroke volume, cardiac output, cardiac power output, peak flow, peak flow acceleration, aortic back flow, and flow wave velocity. Heart rate, blood pressure, double product, and maximum tolerated dobutamine dose were also measured. Multiple regression analysis was used to compare changes during stress with 201TI tomography., Results: All parameters except for stroke volume and diastolic blood pressure increased in the controls. In the patients with CAD a significant relation was shown between the extent of reversible ischaemia and the change in peak flow acceleration (P < 0.00001), peak flow (P = 0.002), cardiac power output (P = 0.036), maximum dobutamine dose (P = 0.039), and systolic blood pressure (P = 0.04). Peak flow acceleration accounted for 58.4% of the variation in reversible ischaemia, and after allowing for this, only cardiac power output remained independently predictive adding a further 4.2% to the model (adjusted r2 = 0.626). A decrease in peak flow acceleration with an increase in dobutamine infusion indicated moderate or severe ischaemia (chi 2 = 10.2, P = 0.017)., Conclusion: MRI may be used to assess variables of aortic flow during stress, which includes acceleration with high temporal resolution. Peak flow acceleration was the most sensitive indicator of the effect of ischaemia on global ventricular function.

A scheme for the design of diffractive phase elements (DPE's) that integrates several optical functions is presented in a consistent sense based on the general theory of amplitude-phase retrieval and the Yang-Gu algorithm [Appl. Opt. 33, 209 (1994)]. We extend the original Yang-Gu algorithm to treat a system illuminated by a beam of incident light whose components are at different wavelengths, and a set of equations for determining the phase distribution of the DPE is derived. The profile of a surface-relief DPE can be designed with an iterative algorithm. Numerical simulations are carried out for the design of one-dimensional DPE's capable of both demultiplexing different wavelength components and focusing each partial wave at predetermined positions. The influence of the extension of sampling points in the DPE's from ideal geometric points to physical spots on design results is also investigated. The numerical simulation results show that the new algorithm can be used successfully to design the desired DPE's. It is therefore expected to be useful in the design of DPE's for micro-optical systems.

A design method based on the Yang-Gu algorithm [Appl. Opt. 33, 209 (1994)] is proposed for computing the phase distributions of an optical system composed of diffractive phase elements that achieve beam shaping with a high transfer efficiency in energy. Simulation computations are detailed for rotationally symmetric beam shaping in which a laser beam with a radially symmetric Gaussian intensity distribution is converted into a uniform beam with a circular region of support. To present a comparison of the efficiency and the performance of the designed diffractive phase elements by use of the geometrical transformation technique, the Gerchberg-Saxton algorithm and the Yang-Gu algorithm for beam shaping, we carry out in detail simulation calculations for a specific one-dimensional beam-shaping example.

Diastolic function is an important element of overall left ventricular function. The pattern of flow across the mitral valve is commonly used as a measure of diastolic ventricular function. Magnetic resonance (MR) velocity mapping of blood flow across the mitral valve was compared with Doppler echocardiography. Nineteen patients with known coronary artery disease (mean age, 62 years; 11 with previous myocardial infarction) were studied. The mean value of peak early filling velocity (+/- standard deviation) was 60.1 cm/sec +/- 14.3 with the MR method and 59.4 cm/sec +/- 13.7 with echocardiography (P = .732). The mean difference between the two measurements (95% confidence interval) was -0.8 cm/sec (-5.2 cm/sec, +2.2 cm/sec). The mean value of early deceleration was 4.3 m/sec2 +/- 1.5 with the MR method and 4.0 m/sec2 +/- 1.5 with echocardiography (P = .073). The mean difference was -0.4 cm/sec2 (-0.92 cm/sec2, +0.05 cm/sec2). The mean value of peak atriosystolic velocity was 51 cm/sec +/- 14.6 with the MR method and 62 cm/sec +/- 17.2 with echocardiography (P = .002). The mean difference was -11 cm/sec (-18.1 cm/sec, -3.45 cm/sec). Peak atrial filling was consistently lower with the MR method than with echocardiography. Time-averaged measurements of ventricular filling with MR velocity mapping are an accurate measure of early diastolic filling but underestimate the velocity of atriosystolic filling.

Objective: To assess the pattern of global and regional left ventricular long axis motion during early diastole in patients with ischaemic heart disease with and without myocardial infarction using magnetic resonance velocity mapping., Design: Prospective study of 26 patients with a history of myocardial infarction (age 29-78, mean 55 years) and 21 patients with coronary artery disease without infarction (age range 39-71, mean 58 years). Values were compared with a control group (19 controls, age 35-76, mean 52 years) with a low likelihood of cardiovascular disease., Results: Regional long axis velocity varied with time and position around the ventricle. All measurements were taken at the time of maximum early diastolic long axis velocity. Patients with coronary artery disease without infarction had lower values for maximum (mean (SD)) (99 (30) v 125 (33) mm/s, P < 0.05) and mean peak early diastolic wall motion (63 (13) v 82 (22) mm/s, P < 0.05) than controls. The coefficient of variation showed greater inhomogeneity of relaxation in patients than in controls (38 (18)% v 27 (10)%). All values were lower in patients with previous infarction than in patients with coronary artery disease without infarction and normal subjects. In patients with previous myocardial infarction the maximum (mean (SD)) early diastolic velocity was 80 (22) mm/s (P < 0.01 compared with controls and P < 0.05 compared with patients without infarction) and the mean (SD) velocity was 47 (18) mm/s (P < 0.01 compared with controls). The coefficient of variation was greater (52 (33)%) than for controls (P < 0.05) and patients with coronary artery disease without infarction. 18 of 26 patients with previous myocardial infarction and 13 of 21 patients with coronary artery disease without infarction had regional abnormalities corresponding to areas of fixed or reversible ischaemia on exercise electrocardiography or thallium myocardial perfusion tomography., Conclusions: Magnetic resonance velocity mapping can be used to assess regional long axis myocardial velocity. Ischaemic heart disease causes alterations in the patterns of left ventricular long axis velocity during early diastole.

Objective: We describe a noninvasive method for visualization of flow and demonstrate its application in a flow phantom and in the great vessels of healthy volunteers and patients with aortic and pulmonary arterial disease. The technique uses multidirectional MR velocity mapping acquired in selected planes. Maps of orthogonal velocity components were then processed into a graphic form immediately recognizable as flow., Materials and Methods: Cine MR velocity maps of orthogonal velocity components in selected planes were acquired in a flow phantom, 10 healthy volunteers, and 13 patients with dilated great vessels. Velocities were presented by multiple computer-generated streaks whose orientation, length, and movement corresponded to velocity vectors in the chosen plane., Results: The velocity vector maps allowed visualization of complex patterns of primary and secondary flow in the thoracic aorta and pulmonary arteries. The technique revealed coherent, helical forward blood movements in the normal thoracic aorta during midsystole and a reverse flow during early diastole. Abnormal flow patterns with secondary vortices were seen in patients with dilated arteries., Conclusion: The potential of MR velocity vector mapping for in vitro and in vivo visualization of flow patterns is demonstrated. Although this study was limited to two-directional flow in a single anatomical plane, the method provides information that might advance our understanding of the human vascular system in health and disease. Further developments to reduce the acquisition time and the handling and presenting of three-directional velocity data are required to enhance the capability of this method.

The pattern of left ventricular long-axis motion during early diastole was assessed with magnetic resonance (MR) velocity mapping in 31 healthy volunteers. Regional long-axis velocity varied with time and position around the ventricle. During systole, the base descended toward the apex. The greatest magnitude of long-axis velocity occurred during early diastole. The lateral wall had the highest velocity (140 mm/sec +/- 40 [mean +/- standard deviation]); the anterior and inferior walls had lower velocities (96 mm/sec +/- 27 and 92 mm/sec +/- 34, respectively). The inferoseptal area consistently had the lowest velocities (87 mm/sec +/- 40). Absolute values of peak early-diastolic velocity declined with age (r = -.64, P < .001). Peak early-diastolic velocity was not dependent on heart rate (r = .014, P = .94). Regional variations in left ventricular wall motion were seen. MR velocity mapping is a useful technique for assessing regional left ventricular long-axis heart function.

A detailed comparison of the original Gerchberg-Saxton and the Yang-Gu algorithms for the reconstruction of model images from two intensity measurements in a nonunitary transform system is presented. The Yang-Gu algorithm is a generalization of the Gerchberg-Saxton algorithm and is effective in solving the general amplitude-phase-retrieval problem in any linear unitary or nonunitary transform system. For a unitary transform system the Yang-Gu algorithm is identical to the Gerchberg-Saxton algorithm. The reconstruction of images from data corrupted with random noise is also investigated. The simulation results show that the Yang-Gu algorithm is relatively insensitive to the presence of noise in data. In all cases studied the Yang-Gu algorithm always resulted in a highly accurate recovered phase.

The objective was to validate the measurement of myocardial perfusion in humans by ultrafast computed tomography (CT), by comparing measurements with those from single photon emission computed tomography (SPECT). Measurement of myocardial perfusion with high spatial resolution (including the differentiation of subendocardial and subepicardial perfusion) may be possible by ultrafast CT in humans. Although there are encouraging data from experiments with dogs, the technique has not been validated in humans. In 11 patients, ultrafast CT measurement of regional perfusion in a single short-axis slice was compared with that obtained by SPECT, and in 14, reproducibility of ultrafast CT was evaluated. The ultrafast CT scanner was set to acquire 20 images, gated to end-diastole. The images were divided into 32 equal segments, and the time course and extent of opacification of the left ventricular cavity and myocardium were analyzed to calculate absolute perfusion. The thallium tomograms were also divided into 32 segments for comparison. The pattern of relative perfusion by segment was represented as a curve. In 18 of 22 paired scans, the mean difference of the position of the minimum and maximum points of the curves was less than 4, indicating close agreement between the two techniques. When scoring segmental perfusion as normal or abnormal, there was agreement between the methods in 129 of 176 segments ([symbol: see text] 0.41). Reproducibility (mean difference +/- 1 SD) of basal scans was 0.005 +/- 0.2 mL/min/mL, and during adenosine vasodilation was 0.05 +/- 0.32 mL/min/mL. Absolute perfusion (mean +/- 1 SD) at rest was 0.52 +/- 0.21 mL/min/mL. During adenosine infusion, perfusion increased to a mean of 0.84 +/- 0.42 mL/min/mL. Ultrafast CT and intravenous contrast can be used to assess relative myocardial perfusion in humans, at rest and during adenosine vasodilatation, although it may underestimate absolute perfusion, particularly at high flow.