Tomographic density imaging using modified DF-DBIM approach.

Ultrasonic computed tomography based on back scattering theory is the most powerful and accurate tool in ultrasound based imaging approaches because it is capable of providing quantitative information about the imaged target and detects very small targets. The duple-frequency distorted Born iterative method (DF-DBIM), which uses density information along with sound contrast for imaging, is a promising approach for imaging targets at the level of biological tissues. With two frequencies f1 (low) and f2 (high) through N f 1 and N f 2 iterations respectively, this method is used to estimate target density along with sound contrast. The implications of duple-frequency fusion for the image reconstruction quality of density information along with sound contrast based ultrasound tomography have been analyzed in this paper. In this paper, we concentrate on the selection of parameters that is supposed to be the best to improve the reconstruction quality of ultrasound tomography. When there are restraints imposed on simulated scenarios to have control of the computational cost, the iteration number N f 1 is determined resulting in giving the best performance. The DF-DBIM is only effective if there are a moderate number of iterations, transmitters and receivers. In case that the number of transducers is either too large or too small, a result of reconstruction which is better than that of the single frequency approach is not produced by the implementation of DF-DBIM. A fixed sum N iter of N f 1 and N f 2 was given, the investigation of simulation results shows that the best value of N f 1 is N iter 2 - 1 . The error, when applying this way of choosing the parameters, will be normalized with the reduction of 56.11%, compared to use single frequency as used in the conventional DBIM method. The target density along with sound contrast is used to image targets in this paper. It is a fact that low-frequency offers fine convergence, and high-frequency offers fine spatial resolution. Wherefore, this technique can effectively expand DBIM's applicability to the problem of biological tissue reconstruction. Thanks to the usage of empirical data, this work will be further developed prior to its application in reality.

Deterministic compressive sampling for high-quality image reconstruction of ultrasound tomography.

BACKGROUND: A well-known diagnostic imaging modality, termed ultrasound tomography, was quickly developed for the detection of very small tumors whose sizes are smaller than the wavelength of the incident pressure wave without ionizing radiation, compared to the current gold-standard X-ray mammography. Based on inverse scattering technique, ultrasound tomography uses some material properties such as sound contrast or attenuation to detect small targets. The Distorted Born Iterative Method (DBIM) based on first-order Born approximation is an efficient diffraction tomography approach. One of the challenges for a high quality reconstruction is to obtain many measurements from the number of transmitters and receivers. Given the fact that biomedical images are often sparse, the compressed sensing (CS) technique could be therefore effectively applied to ultrasound tomography by reducing the number of transmitters and receivers, while maintaining a high quality of image reconstruction. METHODS: There are currently several work on CS that dispose randomly distributed locations for the measurement system. However, this random configuration is relatively difficult to implement in practice. Instead of it, we should adopt a methodology that helps determine the locations of measurement devices in a deterministic way. For this, we develop the novel DCS-DBIM algorithm that is highly applicable in practice. Inspired of the exploitation of the deterministic compressed sensing technique (DCS) introduced by the authors few years ago with the image reconstruction process implemented using l 1 regularization. RESULTS: Simulation results of the proposed approach have demonstrated its high performance, with the normalized error approximately 90% reduced, compared to the conventional approach, this new approach can save half of number of measurements and only uses two iterations. Universal image quality index is also evaluated in order to prove the efficiency of the proposed approach. CONCLUSIONS: Numerical simulation results indicate that CS and DCS techniques offer equivalent image reconstruction quality with simpler practical implementation. It would be a very promising approach in practical applications of modern biomedical imaging technology.

A dual-chamber system for screening cytotoxic effects of hybridoma-produced antibodies.

There are many methods for evaluating the cytotoxic effect of monoclonal antibodies (MAbs) against cancer cells. Most of these methods require either purified MAbs or biological solutions (e.g., cell culture supernatants, ascitic fluids) containing high concentrations of MAbs. This makes the primary screening of antibody-producing hybridomas for specific cytotoxic antibodies a challenging task. Addressing this issue, this work introduces a high throughput screening method, which enables the identification of cytotoxic antibodies using primary hybridoma populations without prior antibody concentration and/or purification. The method is comprised of a dual-chamber system, where antibody-producing hybridomas and target cancer cells are co-cultured but separated by a porous membrane in which the pore size is sufficient for the diffusion of antibody molecules. The MAbs produced in the system continuously diffuse through the membrane between the two chambers and interact with the target cells placed on the other side of a membrane, resulting in death or proliferation arrest of these cells, if MAbs are cytotoxic or cytostatic. The cytotoxic/cytostatic effect can be registered by measuring the viability of target cells. The advantage of this method is that purification or concentration of antibodies secreted by hybridomas is not required. In addition, this method does not require MAb-secreting hybridomas, which are subcloned or have a high level of MAb production. The method may serve as an effective primary high throughput screening for cytotoxic antibodies.

Polymorphism of the Plasmodium falciparum multidrug resistance and chloroquine resistance transporter genes and in vitro susceptibility to aminoquinolines in isolates from the Peruvian Amazon.

In vitro drug sensitivity to chloroquine (CQ), mefloquine (MQ) and quinine was investigated in 60 culture-adapted Plasmodium falciparum isolates from malaria patients in Padrecocha, a village in the Amazonian Department of Loreto, Peru. All isolates showed resistance to CQ, decreased susceptibility to quinine, and sensitivity to MQ. These isolates were examined for mutations in the P. falciparum multidrug resistance 1 (pfmdr1) and chloroquine resistance transporter (pfcrt) genes previously linked to CQ resistance. The mutations N86Y and D1246Y, two of the five mutations commonly observed in the pfmdr1 gene of CQ-resistant clones, were not found. The pfcrt mutation K76T, associated with CQ resistance, was identified in all the isolates tested. Sequence analysis of codons 72-76 in the pfcrt gene showed the haplotypes SVMNT and CVMNT.

Influence of CD4+CD25+ T cells on Plasmodium berghei NK65 infection in BALB/c mice.

CD4(+) T cells co-expressing CD25 (CD4(+)CD25(+) T cells) have been identified as immunoregulatory suppressors modulating autoimmune response. Beside that, autoimmune response was supposed to be associated with malaria infection. Based on these data, we hypothesised that CD4(+)CD25(+) T cells may influence protective immunity to malaria parasites, while suppressing autoimmune response arising throughout the course of malarial infection. To test this possibility, we evaluated the kinetics of CD4(+)CD25(+) T cells during malaria infection and investigated the influence of CD25 depletion by anti-mouse CD25 monoclonal antibody (PC61) on the infection, using a mouse model of premunition to Plasmodium berghei NK65 malaria. The results showed that, during exacerbation of P. berghei NK65 infection, the proportion of CD4(+)CD25(+) T cells among CD4(+) T cells decreased, although that of CD4(+) T cells increased. CD25 depletion clearly delayed the growth of parasitaemia during parasite challenge, particularly in immunised mice. These findings demonstrated that CD4(+)CD25(+) T cells are able to influence protective immunity underlying premunition to P. berghei NK65 parasites.

Glucose and lactate turnover in adults with falciparum malaria: effect of complications and antimalarial therapy.

Hypoglycaemia and lactic acidosis are potentially life-threatening, poorly understood sequelae of Plasmodium falciparum infections. We investigated relationships between clinical status, treatment, and glucose and lactate kinetics during management of falciparum malaria in 14 Vietnamese adults. Nine had severe malaria, of whom 4 were administered quinine (Group 1a) and 5 artesunate (Group 1b). Five uncomplicated cases received artesunate (Group 2). Glucose and lactate turnover were studied on 3 occasions: (i) immediately after initial antimalarial treatment, (ii) at parasite clearance a median of 3 days later, and (iii) at discharge from hospital a median of 9 days post-admission. Steady-state glucose and lactate kinetics were derived from plasma isotopic enrichment during a primed-continuous infusion of D-[6,6-D2]glucose and a parallel infusion of L-[1-13C]lactate. Group 1a patients had the lowest plasma glucose concentrations in the admission study (median [range] 3.9 [3.6-5.1] vs 6.3 [4.9-7.1] and 4.5 [4.3-5.5] mmol/L in Groups 1b and 2 respectively; P < 0.05 vs Group 1b), but glucose production rates and serum insulin concentrations that were similar to those in the other groups (P > 0.17). This was also the case at parasite clearance and suggested an inappropriate beta cell response. Group 1a patients had the highest admission lactate production (60 [36-77] vs 26 [21-47] and 22 [4-31] mumol/kg.min in Group 1b and 2 respectively; P < 0.05 vs Group 2). Amongst the 9 severe cases, there was an inverse association between plasma glucose and lactate production at admission and parasite clearance (P < 0.05), but no correlation between admission lactate production and serum bicarbonate (P = 0.73). The present data confirm previous studies showing that quinine depresses plasma glucose through stimulation of insulin secretion. It is hypothesized that the low plasma glucose activates Na+,K(+)-ATPase through increased plasma catecholamine concentrations, leading to accelerated glycolysis and increased lactate production in well-oxygenated tissues. In some severely ill patients with falciparum malaria, a raised plasma lactate on its own may, therefore, be an unreliable index of a developing acidosis.

Influence of antimalarial treatment on acquisition of immunity in Plasmodium berghei NK65 malaria.

Antimalarial treatments during primary Plasmodium berghei NK65 infection in BALB/c mice influenced the acquisition of protective immunity against reinfection. Among subcurative treatments, lower doses better enable mice to acquire protective immunity than do higher doses. Eradication of parasites from the start of infection did not promote protective immunity.