Low-field magnetic resonance imaging of the pelvis in patients with anal dynamic graciloplasty: initial experience

The aim of this study was to determine whether low-field magnetic resonance (MR) imaging can safely and accurately depict inflammatory changes in patients with anal dynamic graciloplasty, in whom high-field MR imaging is contraindicated and ultrasonography and computed tomography are inadequate. A 0.2-T field-strength MR examination was performed in six patients with anal dynamic graciloplasty malfunction in whom reoperation was contemplated. The following sequences were applied:T ₂-weighted turbo spinecho with fat saturation,T ₁-weighted conventional spin-echo, and contrastenhancedT ₁-weighted conventional spin-echo with fat saturation. Results indicated that none of the patients experienced relevant discomfort, pacemaker malfunction, or electrode dislocation with low-field MR imaging. Inflammatory pelvic changes were visualized in four patients and atrophy of the transposed gracilis muscle in another. Surgery was thus avoided in the four, who underwent conservative treatment for their pelvic inflammation. It was concluded that these prelininary results demonstrate the feasibility of MR imaging with a low field strength in patients with anal dynamic graciloplasty. In such patients, in whom diagnostic imaging had been problematic, the potential for safe and accurate visualization will be a boon to treatment planning.     

Retrospective analysis for evaluation of the value of contrast-enhanced MRI in patients treated with breast conservative therapy

Purpose The aim of this study was to assess the value of contrast-enhanced (c.-e.) MRI in the follow-up of patients with conservatively treated breast cancer since detection and exclusion of malignancy may interfere significantly with posttherapeutic changes within the treated breast. Material and methods A total of 207 patients with a history of limited surgery and radiation therapy underwent MR imaging, 40 patients were examined 0–12 months and 167 patients were examined later than 12 months after radiotherapy. Suspicious or indeterminate findings were suggested by clinical examination or conventional imaging in 80 studies. In 127 women, MRI was performed within breast tissue that was difficult to assess due to scarring or dense breast tissue. Results Recurrent carcinoma was confirmed in 27 patients by surgical biopsy. All 27 carcinomas, except for one with a slow signal increase, demonstrated early rise of signal intensity on dynamic T1-weighted contrast enhanced images. During the first year after therapy, the diagnostic accuracy could not be improved by additional use of c.-e. MRI. Differentiation between posttherapeutic changes and recurrent carcinoma was frequently not possible because of strong and sometimes early and ill-circumscribed enhancement. Later than 12 months after therapy enhancement decreased significantly, thus the false positive calls could be reduced from 49 (conventional imaging) to 12 (conventional imaging plus MRI). A total of 12 of 26 recurrences and multifocality in 4/5 cases were diagnosed by MR imaging alone at this time interval. Conclusion In the first year after therapy, c.-e. MRI is only indicated in selected cases. The results later than 12 months emphasize that c.-e. MRI may contribute significant additional information. It allows better distinction of posttherapeutic fibrosis from recurrent carcinoma and proved to be able to detect recurrent disease more sensitive and at an earlier stage.     

Breathhold imaging of the upper abdomen using a circular polarized-array coil: comparison with standard body coil imaging

Current studies emphasize the use of array coils to decrease noise and increase the signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR). We applied Tl-weighted and T2-weighted standard nonbreathhold spin echo (SE) sequences and Tl-weighted FLASH, TurboFLASH, T2-weighted spin-echo time (TSE), and heavily T2-weighted half Fourier acquisition single-shot TSE (HASTE) sequences during breathhold for abdominal imaging in 15 normal volunteers. The breathhold scans were performed using both a standard coil and a circular polarized array coil. We analyzed the signal intensity (SI), SNR, and CNR of abdominal organs in all sequences. SNRs increased in all cases by an overall factor of 3 due to an 8% increase in overall Sis and a 50% decrease in noise when applying the array coil. Although the array-coil FLASH sequence performed at least as well as the respective SE sequence, the SNRs of the array-coil TurboFLASH, TSE breathhold, and HASTE sequences were generally lower. We conclude that array-coil imaging significantly improves fast imaging of the abdomen.     

3-Methyl-α-himachalene: Proposed structure for novel homosesquiterpene sex pheromone ofLutzomyia longipalpis (diptera: Psychodidae) from Jacobina,Brazil

The principal behaviorally active volatile component (ca. 90% +) of the sex pheromone glands ofLutzomyia longipalpis from Jacobina. Brazil, has been isolated and characterized as a novel homosesquiterpene with the structure 3-methyl--himachalene (C₁₆H₂₆). A minor component (ca. 10%) of the gland extract has also been identified as the sesquiterpene-himachalene (C₁₅H₂₄). This work confirms that there are at least 3 members of theL. longipalpis species complex.     

IP网络质量的主客观评价融合模型

针对IP网络质量评价问题,利用BP神经网络构建一种主客观特征融合的评价模型。主客观2个评价网络分别进行自适应学习,在学习输出稳定后,2个BP神经网络通过相互共振学习使主客观评价数据融合,由此获得一致的评价结果。结合用户感知的主观评价和多种客观性能评价指标对该模型进行仿真,实验结果表明,模型具有较强的抗噪性能,可以较好地满足IP网络质量的综合评价要求。     

The fractional Fourier transform and quadratic field magnetic resonance imaging

The fractional Fourier transform (FrFT) is revisited in the framework of strongly continuous periodic semigroups to restate known results and to explore new properties of the FrFT. We then show how the FrFT can be used to reconstruct Magnetic Resonance (MR) images acquired under the presence of quadratic field inhomogeneity. Particularly, we prove that the order of the FrFT is a measure of the distortion in the reconstructed signal. Moreover, we give a dynamic interpretation to the order as time evolution of a function. We also introduce the notion of ρ-α space as an extension of the Fourier or k-space in MR, and we use it to study the distortions introduced in two common MR acquisition strategies. We formulate the reconstruction problem in the context of the FrFT and show how the semigroup theory allows us to find new reconstruction formulas for discrete sampled signals. Finally, the results are supplemented with numerical examples that show how it performs in a standard 1D MR signal reconstruction.     

Enhanced surface plasmon resonance detection of DNA hybridization based on ZnO nanorod arrays

We demonstrated an enhanced surface plasmon resonance detection incorporating ZnO nanorod arrays (NRAs) built on a thin gold film. ZnO NRAs were fabricated by wet chemical growth method and used for the detection of DNA hybridization. Experimental results exhibited that ZnO NRAs provided a notable sensitivity improvement by more than 3 times, which is attributed to an increase in the surface reaction area. The measured sensitivity enhancement matched well with the numerical analyses based on the effective medium theory. Our approach is intended to show the feasibility and extend the applicability of the ZnO-based SPR biosensor to diverse biomolecular binding events.     

Sensitivity of guided mode resonance filter-based biosensor in visible and near infrared ranges

The sensitivity of guided mode resonance filter (GMRF) biosensors was analyzed when the initial peak wavelength (IPW) changed from 400 to 1600 nm. The sensitivity of the GMRF to the sample refractive index and thickness was analyzed using rigorous coupled wave analysis method. Results indicate that for a certain IPW, the sensitivity of the GMRF did not change when the sample refractive index varied, but drastically decreased and achieved constant sensitivity with increased sample thickness. When the IPW increased, the sensitivity improved in relation to both sample refractive index and sample thickness. Furthermore, the capability of sample thickness improved with longer IPW. These results are helpful in obtaining an optimal GMRF biosensor.     

A multichannel surface plasmon resonance sensor using a new spectral readout system without moving optics

Surface plasmon resonance (SPR) sensors with spectral interrogation provide a high refractive index resolution, a large dynamic range and a fixed optical detection module. In this work, we propose a new multichannel spectral detection unit that uses only one spectrometer to measure the reflection spectrum from multiple sensing spots serially without any mechanical movement. This spectral detection unit is designed based on a spatial light modulator (SLM) configured as a programmable optical aperture for the spectrometer. To demonstrate this concept, a five-channel laboratory SPR prototype was built based on the proposed multichannel detection unit, and we evaluated the device's sensitivity and resolution using a refractive index test. Refractive index resolution of 1.4 × 10⁻⁶ refractive index units (RIU) can be reached using the five-channel prototype. This sensor is suitable for low-cost multichannel biosensing applications that do not contain fast kinetics.     

Study on design and application of fully automatic miniature surface plasmon resonance concentration analyzer

A fully automatic miniature surface plasmon resonance (SPR) concentration analyzer having high performance and low cost and developed using a Spreeta™ sensor was designed for field applications and concentration analysis. As in the case of Biacore™ instruments, the automatic sampling system of this device can introduce air segments between the sample/regeneration solution and buffer solution in the pipeline, which effectively prevents mixing of the solutions. A temperature sensor (AD 590) and temperature compensation method are used, which make the device insensitive to temperature fluctuations. A real-time data-smoothing algorithm for the SPR detection data is adopted; this can reduce the noise level to 5 × 10⁻⁷ RIU (refractive index units). The noise level of the sensorgram is 3.5% of the original level. Two types of self-prepared sensing chips—SMX-BSA (bovine serum albumin coated with sulfamethoxazole) and SMX-CM5 (carboxymethyl dextran coated with sulfamethoxazole)—are used to analyze the concentrations of sulfamethoxazole (SMX) standard solutions. Each chip's SMX calibration curve is established within the measurement range of 0-2000 ng/ml, and both limits of detection (LOD) are 2 ng/ml. One cycle of assay time is less than 15 min.