A healthy young woman with massive hemorrhagic ascites.

Retrograde menstruation is the backward movement of menstrual fluids. The underlying mechanisms remain unknown. The converse current itself is benign, but the result can be abdominal pain caused by peritoneal irritation and, eventually, endometriosis. The case was of a 25-year-old woman with lower abdominal pain accompanied by significant hemoperitoneum. Physical examination and inspection using abdominal ultrasonography and computed tomography failed to reveal a differential diagnosis. Detailed history taking revealed sexual activities during her menstrual period, which allowed for a diagnosis of retrograde menstruation. These findings emphasize the importance of extensive history taking.

Toward understanding transverse relaxation in human brain through its field dependence.

Apparent transverse-relaxation rate constants (R2⁺ = 1/T2⁺) were measured in various regions of the healthy human brain using a multiecho adiabatic spin-echo sequence at five different magnetic fields, 1.5, 1.9, 3, 4.7, and 7 T. The R2⁺ values showed a clear dependence on magnetic field strength (B(0) ). The regional distribution of the R 2⁺ was well explained by the sum of three components: (1) regional nonhemin iron concentration ([Fe]), (2) regional macromolecular mass fraction (f(M) ), and (3) a region-independent factor. Accordingly, R2⁺ = α[Fe] + ßf(M) + γ, where coefficients α, ß, and γ were experimentally determined at each magnetic field by a least square fitting method using multiple regression analysis. Although the coefficient α linearly increased with B(0) , ß showed a quadratic dependence on top of a field-independent component. The coefficient γ also increased slightly with B(0) on top of a field-independent component. The linear dependence of α on B(0) was consistent with that observed for the transverse-relaxation rate of water protons in ferritin solutions as found previously by others. The quadratic dependence of ß on B(0) was accounted for by isochronous and anisochronous exchange mechanisms using intrinsic-relaxation parameters obtained from the literature.

Magnetic Resonance Imaging as a Novel Method for Elucidating Sediment Burrow Structures and Functions.

Burrow structures produced by various benthic animals in sediments are important components of aquatic ecosystems, allowing the circulation of interstitial water via ingress of fresh bottom water into the burrows upon feeding and intraburrow migration. Although X-ray computed tomography has been used to visualize burrow structures, it could not reveal the structures in the soft mud in Lake Kasumigaura, where evaluation of the water-circulation effect of burrows is an important issue. Here, we describe the first attempt to use magnetic resonance (MR) imaging (MRI) to visualize intact burrow structures in the soft mud sediment cores collected from a eutrophic lake. Our MRI application clarified the dynamic distribution of burrows inhabited by chironomids in the soft mud that previous studies could not visualize. By examining the relationships between the degree of chloride ion depletion in deeper layers and the burrow density calculated from the MR images, we were able to consistently explain the water-circulation effect of burrows, suggesting the higher reliability of burrow density calculated from MR images. In addition, we were able to evaluate the activity of burrows, which is difficult to achieve in sediment core experiments. We observed a smaller water-circulation effect of burrows on ammonium ions than on chloride ions, suggesting the enhancement of ammonium production or release in burrow-rich sediments.

Optimal phase analysis of electrocardiogram-gated computed tomography angiography in patients with Stanford type A acute aortic dissection.

OBJECTIVE: To determine the phase that facilitates flap observation of the ascending aorta in Stanford type A acute aortic dissection with perfused false lumen. METHODS: We reconstructed retrospective Electrocardiogram-gated Computed Tomography Angiography images of the ascending aorta of all 20 patients to 20 phases of curved-multiplanar reconstruction in 5% increment. One radiologist created and randomized 10 cross-sectional images of each phase for every patient and two radiologists scored these images on a 5-point scale depending on the degree of flap stoppage. We calculated the average score for each phase of each case and compared them among the three groups. RESULTS: Image scores were significantly better in the 65 %-100 % R-R interval group than those in the 5%-30 % (p < 2e-16) and 35 %-60 % R-R interval groups(p = 7.2e-10). Similar scores were observed in the Heart Rate > 70 group (p = 0.00039, 2.2e-14). Moreover a similar tendency was observed in the arrhythmia group (p = 0.0035, 0.294). No difference was found in the degree of flap stoppage in the 65 %-100 % R-R interval group between the Heart Rate > 70 and Heart Rate ≤ 70 groups (p = 0.466) and between the arrhythmia and non-arrhythmia groups (p = 0.1240). CONCLUSION: In observing the ascending aorta, We obtained a good image at 65 %-100 % R-R interval and similar tendency was observed in the patients with arrhythmia.

Estimation of brain iron concentration in vivo using a linear relationship between regional iron and apparent transverse relaxation rate of the tissue water at 4.7T.

Maps of the apparent transverse relaxation time (T(2) were collected on a transaxial plane across the basal ganglia in 54 healthy subjects at 4.7T using a multiecho adiabatic spin-echo (MASE) imaging sequence. We attempted to quantify the nonhemin iron concentration ([Fe]) in various brain regions in vivo based on the linear relationship between the apparent relaxation rate constant (R(2) = 1/T(2) and regional [Fe], as demonstrated previously in 12 subjects. The calculated [Fe] in five gray matter (GM) regions agreed well with the previously reported regional iron distribution as well as reproduced its age-dependent change. In particular, a decrease of iron in the thalamus region in subjects over 30 years of age was demonstrated while an upward trend was shown in other regions. Furthermore, the average R(2) in each GM region in subjects over 30 years of age showed a deviation from the regression line with [Fe] in an identical manner to that obtained in the previous 12 subjects. This strongly suggests that there is a systematic regional factor affecting R(2), in addition to iron. Interregional difference in the macromolecular mass fraction (f(M)) explained this systematic deviation well. When accounting for f(M) in the analysis, the apparent transverse relaxation rate seems to give a significantly better estimation of regional [Fe].

Visualization of seminiferous tubules in rat testes in normal and diseased conditions by high-resolution MRI.

Rat seminiferous tubules were visualized for the first time using high-spatial-resolution MRI and their MRI features were investigated under normal and various kinds of pathological conditions. All testes images were obtained at 4.7 T with a dedicated quadrature surface coil. T2- and T2 *-weighted images with in-plane resolution of 66 x 66 microm(2) demonstrated numerous tubular structures with low-signal-intensity walls and high-signal-intensity lumens tightly packed throughout the entire testicle. The tubular structures were attributed to the seminiferous tubules in the histological specimens. In testicular ischemia, T2*-weighted images demonstrated prominent low-signal-intensity bands along the radiate veins and normal-appearing seminiferous tubules. As the ischemic condition persisted, the contour of the seminiferous tubules became less visible on both T2- and T2*-weighted images, reflecting the disorganization of the seminiferous epithelia and severe interstitial edema. Changes in the images of testes treated with glycerol or diethylstilbestrol, a synthetic estrogen hormone, were also investigated. In the chronic spermatogenic impairment caused by these substances, extensive shrinkage of the seminiferous tubules was demonstrated. High-resolution MRI aids in noninvasive evaluation of seminiferous tubules, and therefore has potential as a diagnostic test for human testes.

Quantitation Error in 1H MRS Caused by B1 Inhomogeneity and Chemical Shift Displacement.

PURPOSE: The quantitation accuracy in proton magnetic resonance spectroscopy (1H MRS) improves at higher B0 field. However, a larger chemical shift displacement (CSD) and stronger B1 inhomogeneity exist. In this work, we evaluate the quantitation accuracy for the spectra of metabolite mixtures in phantom experiments at 4.7T. We demonstrate a position-dependent error in quantitation and propose a correction method by measuring water signals. MATERIALS AND METHODS: All experiments were conducted on a whole-body 4.7T MR system with a quadrature volume coil for transmission and reception. We arranged three bottles filled with metabolite solutions of N-acetyl aspartate (NAA) and creatine (Cr) in a vertical row inside a cylindrical phantom filled with water. Peak areas of three singlets of NAA and Cr were measured on three 1H spectra at three volume of interests (VOIs) inside three bottles. We also measured a series of water spectra with a shifted carrier frequency and measured a reception sensitivity map. RESULTS: The ratios of NAA and Cr at 3.92 ppm to Cr at 3.01 ppm differed amongst the three VOIs in peak area, which leads to a position-dependent error. The nature of slope depicting the relationship between peak areas and the shifted values of frequency was like that between the reception sensitivities and displacement at every VOI. CONCLUSION: CSD and inhomogeneity of reception sensitivity cause amplitude modulation along the direction of chemical shift on the spectra, resulting in a quantitation error. This error may be more significant at higher B0 field where CSD and B1 inhomogeneity are more severe. This error may also occur in reception using a surface coil having inhomogeneous B1. Since this type of error is around a few percent, the data should be analyzed with greater attention while discussing small differences in the studies of 1H MRS.

A Post-processing framework for localized 2D MR spectroscopy in vivo.

PURPOSE: We propose a post-processing framework for localized two-dimensional (2D) magnetic resonance spectroscopy (MRS) in vivo. METHODS: Our framework consists of corrections on eddy current and subject motion along with the framework used in conventional analytical 2D nuclear magnetic resonance (NMR) spectroscopy. In the eddy current correction, the phases of the free induction decays (FIDs) of the metabolite (1)H are corrected along the t2 direction by the phase of the FID of water (1)H. The corrected FIDs are Fourier transformed along the t2 direction, and interferograms of F(t1, ω2) are calculated. In the motion correction, the zero-order phase of the N-acetyl aspartate (NAA) singlet peak for each t1 axis is corrected after correction of frequency drift. We applied this framework in phantom and human brain measurements in a 4.7T whole-body MR system. Two-dimensional data were collected by the localized 2D constant-time correlation spectroscopy (CT-COSY) sequence. We used a phantom containing a brain metabolite mixture of NAA, creatine (Cr), glutamate (Glu), glutamine (Gln) and γ-amino butyric acid (GABA). We demonstrated the eddy current correction procedure in the phantom experiments and the subject motion correction in human measurements. RESULTS: Though asymmetric patterns of the singlets of NAA and Cr were shown around the peak along the F2 direction in the reconstructed phantom spectra without eddy current correction, symmetric patterns arose after the correction. The t1 noise caused by those singlets was found in the human brain spectra without motion correction. The t1 noise was sufficiently suppressed by the motion correction. CONCLUSION: Our proposed post-processing framework for localized 2D MRS can improve the quality of in vivo 2D spectra and may allow improved quantitation and robustness of in vivo 2D spectroscopy.

Highly resolved two-dimensional ¹H spectroscopy of the human brain using ISIS CT-PRESS with resolution enhancement.

In constant time (CT) point-resolved spectroscopy (PRESS), echo centers shift with the fast decay of short T2* on two-dimensional (2D) time domain (TD) data under inhomogeneous B0 field like in vivo conditions. Though ¹H decoupling along the F1 direction is a feature of this method, the tilted and broadened peak pattern on the F1-F2 plane after reconstruction causes the peaks to overlap. To enhance resolution to achieve highly resolved 2D CT-PRESS spectra in the human brain, we propose a 2-part window function that comprises an enhancement part for shifting echoes with fast decay and a conventional part, such as Lorentzian, Gaussian, or sine-bell function. We obtained 2D spectra from human brains at 4.7T. The 3 diagonal peaks of C4H of glutamate (Glu C4H) at 2.35 ppm, C2H of γ-amino butyric acid (GABA C2H) at 2.28 ppm, and C4H of glutamine (Gln C4H) at 2.44 ppm-overlapped on the spectra processed with the conventional window but clearly resolved on the spectra using the proposed enhancement window. The signal-to-noise ratio per unit measurement time of Glu C4H on a CT-PRESS spectrum of the human brain was 1.7 times higher than that on a spectrum obtained by CT-correlation spectroscopic (COSY). In conclusion, 2D CT-PRESS spectra processed with the proposed window function to enhance resolution can resolve peaks of coupled ¹H spins with higher accuracy and sensitivity.

Non-uniformity correction of human brain imaging at high field by RF field mapping of B1+ and B1-.

A new method of non-uniform image correction is proposed. Image non-uniformity is originated from the spatial distribution of RF transmission and reception fields, represented as B(1)(+) and B(1)(-), respectively. In our method, B(1)(+) mapping was performed invivo by a phase method. In B(1)(-) mapping, images with multiple TEs were acquired with a multi-echo adiabatic spin echo (MASE) sequence which enables homogeneous excitation. By T(2) fitting of these images an M(0) map (M(0)(MASE)) was obtained, in which signal intensity was expressed as the product of B(1)(-) and M0(1-e⁻(TR/T¹)) . The ratio of this M(0)(MASE) map to the B(1)(+) map showed a similar spatial pattern in different human brains. These ratios of M(0)(MASE) to B(1)(+) in 24 subjects were averaged and then fitted with a spatially polynomial function to obtain a ratio map of B(1)(-)/B(1)(+)(α). Uniform image was achieved in spin echo (SE), MASE and inversion recovery turboFLASH (IRTF) images using measured B(1)(+) and calculated B(1)(-) by αB(1)(+). Water fractions in gray and white matters obtained from the M(0) images corrected by this method were in good agreement with previously reported values. From these experimental results, the proposed method of non-uniformity correction is validated at 4.7 T imaging.

Apparent transverse relaxation rate in human brain varies linearly with tissue iron concentration at 4.7 T.

Multiple pairs of adiabatic passage pulses were implemented in a spin-echo sequence to achieve accurate measurements of the apparent transverse relaxation time (T(2)(dagger)) in a short scan time. In experiments on agarose gel phantoms with T(2) values ranging from 30 to 105 ms, the measured T(2)(dagger) values were in good agreement with transverse relaxation times measured with a nonselective Carr-Purcell-Meiboom-Gill sequence. In experiments on normal human brain at 4.7 T, T(2) (dagger) values in five different gray matter regions were found to range from 38 +/- 2 ms (globus pallidus) to 64 +/- 2 ms (frontal cortex). The apparent relaxation rate (1/T(2)(dagger)) in these five regions showed strong correlation (r = 0.97) with published levels of iron (Fe) in those regions. The linear coefficient relating 1/T(2)(dagger) and [Fe] at 4.7 T was measured to be 0.551 (s x mg Fe/100 g f.w.)(-1). When compared with the values obtained in a previous report for six different static fields (B(0)) up to 1.5 T, the current measurement confirms the linear dependence of the linear coefficient on B(0) up to 4.7 T (r = 0.99). These results suggest that the T(2)(dagger) value in the human brain is predominantly affected by the nonhemin iron distribution. The strong correlation between the obtained T(2)(dagger) values and the regional iron concentrations suggests a role for this pulse sequence in quantifying in vivo brain iron at high magnetic field.

In vivo localized 1H MR spectroscopy of rat testes: stimulated echo acquisition mode (STEAM) combined with short TI inversion recovery (STIR) improves the detection of metabolite signals.

A noninvasive NMR technique for evaluating testicular function was explored in this study. Localized in vivo 1H NMR spectroscopy was performed on rat testes using a stimulated echo acquisition mode (STEAM) sequence with a short echo time (TE). In the 1H spectra, large lipid signals dominated the chemical shift range of 0.89-2.78 ppm, which prevented the observation of metabolite signals in this region. To suppress these lipid signals, short inversion time (TI) inversion recovery (STIR) was combined with STEAM (STIR-STEAM). The optimal TI was typically 320 ms. STIR-STEAM with a TE of 15 ms allowed successful suppression of the lipid signals and the sensitive detection of several new metabolite signals. In normal testes, choline, creatine, glutamate, and glycine signals were identified. In addition to these metabolites, a lactate signal was observed in ischemic testes. To our knowledge, the signals of glutamate, glycine, and lactate have not been previously assigned in 1H MR spectra of testes in vivo. Lipid suppression by STIR aided in the detection of these metabolites, which would otherwise have been masked by the lipid signals.