Cardiac activation mapping using ultrasound current source density imaging (UCSDI)

We describe the first mapping of biological current in a live heart using ultrasound current source density imaging (UCSDI). Ablation procedures that treat severe heart arrhythmias require detailed maps of the cardiac activation wave. The conventional procedure is time-consuming and limited by its poor spatial resolution (5-10 mm). UCSDI can potentially improve on existing mapping procedures. It is based on a pressure-induced change in resistivity known as the acousto-electric (AE) effect, which is spatially confined to the ultrasound focus. Data from 2 experiments are presented. A 540 kHz ultrasonic transducer (f/# = 1, focal length = 90 mm, pulse repetition frequency = 1600 Hz) was scanned over an isolated rabbit heart perfused with an excitation-contraction decoupler to reduce motion significantly while retaining electric function. Tungsten electrodes inserted in the left ventricle recorded simultaneously the AE signal and the low-frequency electrocardiogram (ECG). UCSDI displayed spatial and temporal patterns consistent with the spreading activation wave. The propagation velocity estimated from UCSDI was 0.25 +/- 0.05 mm/ms, comparable to the values obtained with the ECG signals. The maximum AE signal-to-noise ratio after filtering was 18 dB, with an equivalent detection threshold of 0.1 mA/ cm(2). This study demonstrates that UCSDI is a potentially powerful technique for mapping current flow and biopotentials in the heart.

Experimental determination of proton-induced cross-sections on natural zirconium

We measured cross-sections for the formation of (86g,87m,87g)Y, (88,89g)Zr, and (90,92m)Nb radionuclides for proton-induced reactions on natural zirconium by using a conventional stacked-foil activation technique in the energy range between 1 and 40MeV at the MC-50 cyclotron of the Korea Institute of Radiological and Medical Science. We compared the measured data with the available literature data and the theoretical calculation by the model codes TALYS and ALICE-IPPE. We also deduced the integral yields for thick targets from the measured cross-sections of the produced radionuclides. The optimum production possibility of the medically important (89g)Zr and (86)Y radionuclides were discussed elaborately.

Realization of the quantum Toffoli gate with trapped ions

Gates acting on more than two qubits are appealing as they can substitute complex sequences of two-qubit gates, thus promising faster execution and higher fidelity. One important multiqubit operation is the quantum Toffoli gate that performs a controlled NOT operation on a target qubit depending on the state of two control qubits. Here we present the first experimental realization of the quantum Toffoli gate in an ion trap quantum computer, achieving a mean gate fidelity of 71(3)%. Our implementation is particularly efficient as the relevant logic information is directly encoded in the motion of the ion string.

Absolute frequency measurement of the 40Ca+ 4s(2)S_(1/2)-3d(2)D_(5/2) clock transition

We report on the first absolute transition frequency measurement at the 10;{-15} level with a single, laser-cooled 40Ca+ ion in a linear Paul trap. For this measurement, a frequency comb is referenced to the transportable Cs atomic fountain clock of LNE-SYRTE and is used to measure the 40Ca+ 4s ;{2}S_{1/2}-3d ;{2}D_{5/2} electric-quadrupole transition frequency. After the correction of systematic shifts, the clock transition frequency nu_{Ca;{+}}=411 042 129 776 393.2(1.0) Hz is obtained, which corresponds to a fractional uncertainty within a factor of 3 of the Cs standard. In addition, we determine the Landé g factor of the 3d;{2}D_{5/2} level to be g_{5/2}=1.200 334 0(3).

Evaluation of response to neoadjuvant chemotherapy in primary breast cancer using PET

Abstract #4019

Purpose
 To estimate the usefulness of PET scan to assess the response of neoadjuvant chemotherapy, PET scan results were compared with conventional imaging modalities(US and MRI).
 Patients and Methods
 Fourty-one patients undergoing neoadjuvant chemotherapy between December 2004 and March 2008 were included. PET scan was performed before and after chemotherapy. Pathologic results were classified into two groups; pathological complete response(pCR) and non-pCR. Clinical responses were assessed with the results of imaging modalities such as post-chemotherapy size or pSUV(postTx), size difference between treatment(delta) and reduction rate(RR) of size or pSUV, and they are compared with postoperative pathologic results.
 Results
 7 out of 41 patients (17.1%) had pCR. The results of US shows that postTx size (1.7±1.5cm) of pCR was not dfferent from those of non-pCR (3.6±3.0cm), and the delta (3.1±1.9cm) and RR (67.7±29.1%) of pCR were higher than those of non-pCR (1.3±1.3cm, 31.0±25.4%), respectively. As a result of MRI, postTx size, delta, RR of pCR was differ from those of non-pCR (1.0±1.7cm vs 2.8±1.7cm p<0.05; 4.5±1.0cm vs 2.3±1.8cm, p<0.05; 88.0±20.8% vs 44.6±24.7%, p<0.01). In PET scan, only postTx pSUV of pCR was differ from that of non-pCR (1.4±1.3 vs 5.3±8.3cm, p<0.05). As a result of receiver operating characteristic curve analyses for the prediction of pathological response of breast cancer, area under curve values (95% confidence interval) of US, MRI, PET for delta were 0.83(0.69∼0.98), 0.91(0.80∼1.01), 0.62(0.38∼0.86), and those of RR were 0.80(0.60∼0.99), 0.90(0.77∼1.02), 0.72(0.47∼0.96), respectively
 Conclusions
 We suggest that MRI is useful method to evaluate the response of neoadjuvant chemotherapy. Although PET scan shows less effective for evaluating the response of chemotherapy than MRI, PET scan with the ability to detect the distant metastatic lesions may be helpful to decide the proper management plans for advanced breast cancer.

Citation Information: Cancer Res 2009;69(2 Suppl):Abstract nr 4019.

Anisotropic cooperative structural rearrangements in sheared supercooled liquids

A supercooled liquid generally exhibits marked shear-thinning behavior, but its detailed mechanism remains elusive. Here we study the dynamics of structural rearrangements in supercooled liquids under shear, using two-dimensional (2D) molecular dynamics simulation. To elucidate the relationship between heterogeneous dynamics and the rheological behavior, we extend the four-point correlation function, which has been used for analyzing "dynamic heterogenity" in a quiescent condition, to a system under steady shear. In the Newtonian regime, the rearrangement dynamics is strongly heterogeneous in space, but remains isotropic. Contrary to this, in the non-Newtonian regime, where marked shear-thinning behavior appears, we find a novel dynamic effect: The mobile region tends to form anisotropic "fluidized bands." This finding suggests a link between nonlinear rheology and inhomogeneization of flow.

A novel laboratory cultivation method to examine antibiotic-resistance-related microbial risks in urban water environments

Although microbial risk due to antibiotic-resistant microbes in water has been a serious public health concern, the current culture-dependent detecting methods using nutrient-rich conditions may not be suitable for evaluating microbial risk. In the present study, a novel cultivation method was developed to detect antibiotic-resistant microbes at various nutrient levels. A nutrient-rich medium Luria-Bertani broth (LB) was diluted at a wide range of dilution factors (10(0)-10(4)) and amended with either tetracycline or vancomycin. A standard environmental cultivation medium, R2A, was also used by amending with antibiotics. The diluted LB with antibiotics was able to detect previously known oligotrophic and antibiotic-resistant bacteria in drinking water and swine manure samples, respectively. These results validate the capability of the new method to detect antibiotic-resistant microbes in various environmental water samples. Using the developed method in assessing microbial risk due to antibiotic-resistant microbes in river and municipal wastewater plants, we found that the viable counts and antibiotic resistance fraction were significantly influenced by the type and concentration level of antibiotic exposure and the cultivation medium conditions. This suggests a further need to standardize cultivation method procedures, to assess microbial risk in water samples.

High-resolution ultrasound speckle tracking may detect vascular mechanical wall changes in peripheral artery bypass vein grafts

We report the use of high-resolution, phase-sensitive ultrasound speckle tracking to measure the local vessel-wall strain in two subjects with artery-vein bypass grafts. In addition, we combined this technique with a free-hand pressure equalization procedure to elucidate the nonlinear effects of blood pressure on vessel wall compliance. While conventional ultrasound imaging can be used to elucidate the mechanical properties of tissues within the body, it is constrained by comparatively lower resolution and inferential, rather than direct, measurements of strain and by the small strain normally produced under physiological pressure in highly nonlinear structures such as arteries. One of our subjects was examined both before and after developing stenosis 3 months postsurgery. The strain values for this individual were found to be significantly lower, indicating a stiffer vessel wall at the stenotic region than at a nonstenotic region under both physiological and equalized pressure. These results suggest the possibility of noninvasive detection of neointimal hyperplasia preceding anastomotic stenosis.