Investigation and modeling of magnetization transfer effects in two‐dimensional multislice turbo spin echo sequences with low constant or variable flip angles at 3 T

Magnetization transfer effects represent a major source of contrast in multislice turbo spin echo sequences (TSE)/fast spin echo sequences. Generally, low refocusing flip angles have become common in such MRI sequences, especially to mitigate specific absorption rate problems. Since the strength of magnetization transfer effects is related to the radiofrequency power and therefore specific absorption rate applied, magnetization transfer induced signal attenuations are investigated for a variety of TSE sequences with low constant and variable flip angles. Noticeable differences between the sequences have been observed. In particular, fewer signal attenuations are observed for TSE with low flip angles such as hyperecho‐TSE and smooth transitions between pseudo steady states–TSE, leading to contrast that is less dependent on the number of slices. It is shown that the strength of the magnetization transfer‐induced signal attenuations can be understood and described by a physical framework, which is based on the mean square flip angle of a given TSE sequence. Magn Reson Med, 2009. © 2009 Wiley‐Liss, Inc.     

Autoimmune mediated regulation of ovarian tumor growth

Objectives

An immune response sufficient to induce organ failure may provide protection and therapy against tumors derived from the targeted organ particularly when removal or ablation of the organ is part of the standard therapy and does not threaten survival. We have previously shown that a targeted immune response directed against the ovarian-specific protein, inhibin-α, causes ovarian failure. Here we determined whether inhibin-α autoimmunity is effective in both prevention and treatment of ovarian tumors.

Methods

A transgene consisting of the SV40 large tumor transformation antigen under the regulation of an anti-Mullerian hormone promoter (AMH-SV40Tag) was transferred by backcrossing for 12 generations to SJL/J mice producing SJL.AMH-SV40Tag (H-2^s) females that develop a high incidence of autochthonous granulosa cell tumors. We determined whether immunization of SJL.AMH-SV40Tag female mice with the IA^s-restricted p215-234 peptide of mouse inhibin-α was capable of preventing and treating these ovarian tumors.

Results

The growth of autochthonous ovarian granulosa cell tumors in SJL.AMH-SV40Tag transgenic mice was significantly inhibited in mice immunized with Inα 215-234. In addition, significant inhibition of tumor growth occurred when mice with established ovarian granulosa cell tumors were therapeutically vaccinated with Inα 215-234.

Conclusions

Our results indicate that induction of ovarian-specific autoimmunity may serve as an effective way to prevent the emergence of autochthonous ovarian tumors and control the growth of established ovarian malignancies.     

Intuitive design guidelines for fast spin echo imaging with variable flip angle echo trains.

We present a simple and intuitive means for determining the flip angles (FAs) required for smooth transitions between static pseudo steady states (SPSSs) in fast spin echo (FSE) imaging with variable FA (VFA) echo trains. We demonstrate the effectiveness of single and multiple transition pulses to successfully vary refocusing FAs while retaining high signal levels. The graphical interpretation presented here is consistent with previous analytical techniques and permits accurate signal-intensity predictions along the echo train.     

Selective parity RARE imaging.

This work describes a novel method for rapid acquisition with relaxation enhancement (RARE)/fast spin-echo (FSE) imaging that removes the constraint of compliance with the Carr-Purcell-Meiboom-Gill (CPMG) condition. In a multiecho sequence, echoes with either odd or even parities are acquired. The refocusing angles are chosen using a recursive algorithm, so that the signal amplitude satisfies a predetermined modulation function. In the examples given in this article an exponential decay to a plateau is used. At each echo the echo parity that gives the desired signal amplitude for the minimum refocusing angle is selected. It is further shown that in the presence of an initial magnetization having an arbitrary phase distribution, the complex conjugate of the signal of one echo parity has to be taken and its k-space coordinates reversed. T(2) (*)-weighted images are presented and initial applications to diffusion-weighted imaging (DWI) and functional imaging shown.     

维甲类X受体与维甲酸反应元件β2RARE结合的研究

目的 确定人真皮成纤维细胞中维甲类Ｘ受体（ＲＸＲ）与维甲酸反应元件（β２ＲＡＲＥ）的结合。方法 培养成纤维细胞,反应维甲酸（Ａｔ－ＲＡ）刺激细胞不同时段,抽提核蛋白,＾３２Ｐ标记β２ＲＡＲＥ作为探针,并加入ＲＸＲα和β抗体,进行凝胶阻滞分析。结果 对照组细胞核蛋白与β２ＲＡＲＥ形成复合体Ｉ;Ａｔ－ＲＡ刺激细胞后,迅速诱导产生明显 合体Ⅱ。选择两组核蛋白（对照组和Ａｔ－ＲＡ刺激４ｈ组）,分别加入ＲＸ     

Parallel and nonparallel simultaneous multislice black-blood double inversion recovery techniques for vessel wall imaging

PURPOSE: To reduce long examination times of black-blood vessel wall imaging by acquiring multiple slices simultaneously and by using parallel acquisition techniques. MATERIALS AND METHODS: DIR-rapid acquisition with relaxation enhancement (RARE) techniques imaging up to 10 simultaneous slices per acquisition with single and multiple 180 degrees -reinversion pulses were developed. A slab-selective reinversion multislice DIR-RARE sequence incorporating generalized autocalibrating partially parallel acquisitions (GRAPPA) imaging was implemented. Four-channel and eight-channel carotid coils were built to test these sequences. A total of 11 subjects were studied. Contrast-to-noise ratio (CNR) and signal-to-noise ratio (SNR) efficiency factor (SEF, SNR/unit time/slice) were measured from aortic images of three healthy subjects to determine optimal MR parameters. The DIR-RARE-GRAPPA sequence was run on aortas and carotid arteries of the five remaining healthy subjects and three atherosclerotic patients with optimal parameters (acquisition times 12-21 seconds). RESULTS: SEFs of slab-selective protocols were significantly higher than those of slice-selective protocols, and SEFs of DIR-RARE-GRAPPA protocols were significantly higher than corresponding non-GRAPPA protocols (P < 0.05). CNR was not significantly different for all imaging protocols. The DIR-RARE-GRAPPA multislice sequence showed 8.35-fold time improvement vs. single-slice DIR-2RARE sequence. CONCLUSION: Future MRI atherosclerotic plaque studies can be performed in substantially shorter times using these methods.