Fast method for 1D non-cartesian parallel imaging using GRAPPA.

MRI with non-Cartesian sampling schemes can offer inherent advantages. Radial acquisitions are known to be very robust, even in the case of vast undersampling. This is also true for 1D non-Cartesian MRI, in which the center of k-space is oversampled or at least sampled at the Nyquist rate. There are two main reasons for the more relaxed foldover artifact behavior: First, due to the oversampling of the center, high-energy foldover artifacts originating from the center of k-space are avoided. Second, due to the non-equidistant sampling of k-space, the corresponding field of view (FOV) is no longer well defined. As a result, foldover artifacts are blurred over a broad range and appear less severe. The more relaxed foldover artifact behavior and the densely sampled central k-space make trajectories of this type an ideal complement to autocalibrated parallel MRI (pMRI) techniques, such as generalized autocalibrating partially parallel acquisitions (GRAPPA). Although pMRI can benefit from non-Cartesian trajectories, this combination has not yet entered routine clinical use. One of the main reasons for this is the need for long reconstruction times due to the complex calculations necessary for non-Cartesian pMRI. In this work it is shown that one can significantly reduce the complexity of the calculations by exploiting a few specific properties of k-space-based pMRI.     

In Vivo Skin Penetration of Acitretin in Volunteers Using Three Sampling Techniques

Etretinate and acitretin are given orally to treat psoriasis and various keratinization disorders. Acitretin, the main active metabolite of etretinate, has the pharmacokinetic advantage of being rapidly eliminated, but it shares etretinate's toxicologic profile. Thus a topical delivery of acitretin with no or reduced systemic adverse effects is desirable. To characterize the therapeutic potential of topically delivered acitretin, we quantitatively assessed its percutaneous penetration in healthy human volunteers. Additionally, three skin sampling techniques, the punch biopsy, the shave biopsy, and the suction blister technique, were validated to quantitate acitretin in the skin. The results suggest that topical delivery of acitretin renders skin concentrations which exceed those reported after oral administration of etretinate or acitretin. However, because of possible interlaminate drug contamination, drug localization within a particular skin compartment cannot be determined.     

大气细菌粒子浓度的时间分布特征及最佳采样时间的研究

用ＭＦ－４５型和ＨＴＫ－２０１型空气微生物采样器分别在北京、天津和沈阳三地观测了不同季节和一天中大气细菌粒子的浓度及其变化。结果表明：京、津二地春季大气细菌粒子浓度高，分别为２０５３个／ｍ３和２５５６个／ｍ３；夏季低，分别为９９５个／ｍ３和１０６４个／ｍ３。沈阳秋季大气细菌粒子浓度高，为１０１０８个／ｍ３；冬季低，为１２９４个／ｍ３。一天中，大气细菌粒子浓度呈双峰型变化，６：００～７：００和１８：００时大气细菌粒子浓度高，１１：００～１３：００和１：００～２：００时大气细菌粒子浓度低。根据大气细菌粒子浓度的季节变化和一天中大气细菌粒子浓度的时间分布特征，经过京、津、沈三地一天中分别１２次、８次、６次和４次不同采样时间组合的大气细菌粒子浓度的数理统计分析，大气细菌粒子浓度的监测拟集中在一年冬、春、夏、秋四季的中间月份，即１月、４月、７月、１０月进行；一天中采样８次的时间序列可为７：００、１０：００、１３：００、１６：００、１９：００、２２：００、１：００、４：００一天采样４次的时间序列可为５：００、１１：００、１７：００、２３：００。白天采样４次的时间序列可为春、秋季６：００、９：００、１２：００、１５：００?     

Partial k-space reconstruction in single-shot diffusion-weighted echo-planar imaging.

Partial k-space sampling is frequently used in single-shot diffusion-weighted echo-planar imaging (DW-EPI) to reduce the TE and thereby improve the SNR. However, it increases the sensitivity of the technique to bulk rotational motion, which introduces a phase gradient across the tissue that shifts the echo in k-space. If the echo is displaced into the high spatial frequencies, conventional homodyne reconstruction fails, causing intensity oscillations across the image. Zero-padding, on the other hand, compromises the image resolution and may cause truncation artifacts. We present an adaptive version of the homodyne algorithm that detects the location of the echo in k-space and adjusts the center and width of the homodyne filters accordingly. The adaptive algorithm produces artifact-free images when the echo is shifted into the high positive k-space range, and reduces to the standard homodyne algorithm in the absence of bulk motion.     

冲击式二级采样对呼吸粉尘与总粉尘浓度比值的影响

为了验证冲击式二级粉尘采样对呼吸性粉尘与总粉尘浓度比值的影响，作者采用瞬时定点采样方法测定作业场所空气中呼吸性粉尘浓度与总粉尘浓度。结果表明，在采样体积相同的条件下，呼吸性粉尘的比值与总粉尘浓度间具有较好的从属共变关系（ｒ＞０．８），呼吸性粉尘的比值随着总粉尘浓度的升高而相应增大     

Sources of unwanted variability in measurement and description of skin surface topography

Background/aims: Quantitative measurement of skin roughness has proved to be a valuable tool in the efficacy-control of external applications, but it suffers from not yielding easily comparable results. The most important sources of inter-observer variability are high-pass filters used to separate roughness and waviness, and low-pass filters which result from the finite resolution of the instrument or from the finite sampling interval of digital measurement. In the present study, the effects of high-pass filters and sampling intervals on the roughness measured were investigated. Methods: Dynamically focusing optical profilometry was used to measure the surfaces of negative replicas of healthy human skin. High-pass cut-off wavelengths and sampling intervals were varied systematically. Results/conclusions: Virtually unbiased estimates for the roughness parameters K, Sk, R_q, and R_a can be obtained using sampling intervals of 40 or even 80 μm. Regarding these roughness parameters, it is far better to do more scans than to shorten the sampling interval. The roughness parameters R_z, R_p, R_t, R_pm, R_max, P_t, on the other hand are very sensitive to the influence of the sampling interval; to achieve satisfying estimates, the sampling interval should be no longer than 2 to 5 urn; as an important parameter’of the measurement, it is worthy of remark and should always be indicated. The way the mean square roughness R_q depends on the cut-off wavelength is not well described by the Sayles-Thomas-relation R_q～λ_c^0.5. If the power-spectrum |h*(v)|² approximates sufficiently to a power law, |h*(v)|²～v^δ, a better estimate is given by R_q～λ_c^γ with γ=-(δ+1)/2. In many cases, γ=1 or R_q～λ_c will suffice.     

免疫层析法用于HCG快速检测的研究

目的：研制用于尿液HCG快速检验试纸条。方法：采用胶体金免疫层析分析方法。结果：检测灵敏度可达50IU／L，与高含量的LH、FSH、TSH均无交叉反应，检测214例临床样品，准确率为100％。结论：该方法简单、快速、特异性强，是检测尿液HCG较好的免疫学方法。     

Partial hydatidiform mole and hypertension associated with a live fetus--variable presentation in two cases

Partial hydatidiform mole associated with live births is a rarecondition. There are not enough cases in the literature to allowthe assessment of comprehensive risks to be made and upon whichmanagement policies can be based. Several clinical dilemmasarise following diagnosis of a viable pregnancy associated withmolar tissue. We present two cases demonstrating the problemsand suggest management based on outcome and a review of theliterature.