Single-shot Echo-planar Imaging Technique Research Articles

Somatosensory evoked potentials and their relation to microstructural damage in patients with multiple sclerosis-A whole brain DTI study.

IntroductionSomatosensory evoked potentials (SSEP) play a pivotal role in the diagnosis and disease monitoring of multiple sclerosis (MS). Delayed latencies are a surrogate for demyelination along the sensory afference. This study aimed to evaluate if SSEP latencies are representative of demyelination of the brain overall, by correlating with cerebral microstructural integrity as measured by Magnetic resonance (MR) diffusion tensor imaging (DTI). Analysis was performed in a hypothesis-free whole brain approach using tract-based spatial statistics (TBSS).Material and methodsA total of 46 patients with MS or clinically isolated syndrome were included in the study. Bilateral SSEPs of the median nerve measuring mean N20 latencies (mN20) and Central Conduction Time (CCT), were acquired. MRI scans were performed at 3T. DTI acquisition was done with a single-shot echoplanar imaging technique with 80 diffusion directions. The FSL software package was used to process the DTI datasets and to calculate maps of fractional anisotropy (FA), axial diffusivity (AD), and radial diffusivity (RD). These maps were then further analyzed using the TBSS module. The mean N20 and CCT and the right- and left-sided N20 and CCT were separately correlated to FA, AD, and RD, controlled for age, gender, and EDSS as variables of non-interest.ResultsWidespread negative correlations of SSEP latencies with FA (p = 0.0005) and positive correlations with RD (p = 0.0003) were measured in distinct white matter tracts, especially the optic tracts, corpus callosum, and posterior corona radiata. No correlation with AD was found in any white matter tract.ConclusionHighly significant correlations of FA and RD to SSEPs suggest that their latency is representative of widespread microstructural change, and especially demyelination in patients suffering from MS, reaching beyond the classic somatosensory regions. This points to the usefulness of SSEPs as a non-invasive tool in the evaluation of microstructural damage to the brain.

Diffusion-weighted magnetic resonance imaging in bladder cancer: comparison of readout-segmented and single-shot EPI techniques

BackgroundTo evaluate whether readout-segment echo-planar imaging (RS-EPI) can provide better image quality in assessing bladder cancer than single-shot echo-planar imaging (SS-EPI) and to compare quantitative imaging parameters derived from both techniques.MethodsSeventy patients with bladder lesions were enrolled and underwent diffusion-weighted imaging on a 3 Tesla magnetic resonance scanner using axial RS-EPI and SS-EPI techniques. Two observers independently assessed the susceptibility, detectability, motion artefacts and blurring of the images using qualitative scores. The signal-to-noise ratio (SNR), signal intensity ratio (SIR), contrast-to-noise ratio (CNR) and ADC values of the bladder lesions were measured and compared between the two techniques and between two observers. Qualitative and quantitative comparisons of image quality were performed using the Wilcoxon signed-rank test and paired t-test. In addition, the agreement of the ADC measurements was evaluated using ICC values and Bland-Altman plots.ResultsSixty-eight patients were included in the final analysis. The scores of image susceptibility, detectability and blurring for RS-EPI were significantly higher than those for SS-EPI (all p < 0.05), while the motion artefact was not. There were significant differences between RS-EPI and SS-EPI in the CNR and SIR values (all p < 0.05) but not in the SNR or ADC values (all p > 0.05). The ICC values and Bland-Altman plots also showed excellent agreement between the measured ADC values of the bladder lesions.ConclusionsThe RS-EPI technique provides significantly better image quality in patients with bladder cancer than the SS-EPI technique, without a significant difference in the ADC value.

Multislice T1 -prepared 2D single-shot EPI: analysis of a clinical T1 mapping method unbiased by B0 or B1 inhomogeneity.

Quantitative MR imaging is as sensitive in detecting lesions as qualitative imaging, but it is potentially more specific in differentiating disease. T1 mapping in particular might help to assess acute ischemic stroke, multiple sclerosis, epilepsy and Alzheimer's disease better. Thus, a rapid and robust clinical technique is vital. In 1990, Ordidge and colleagues developed the multislice T1 -prepared two-dimensional (2D) single-shot echo planar imaging technique. Subsequent studies demonstrated its clinical viability, but none performed an in-depth analysis of the strengths and advantages of this T1 mapping method. Herein, theoretical and experimental evidence shows that the technique accounts for 2D slice profile effects and is unbiased by B0 or B1 inhomogeneity. This is verified explicitly by varying the linear shims, the T1 preparation flip angle and the excitation flip angle. Furthermore, it is shown that the repetition time (and hence scan time) can be reduced without a loss of T1 accuracy. Copyright © 2016 John Wiley & Sons, Ltd.

MRI In rectal cancer: Correlations between MRI features and molecular markers Ki‐67, HIF‐1α, and VEGF

To investigate whether the apparent diffusion coefficient (ADC) values acquired from diffusion-weighted magnetic resonance imaging (DW-MRI) are correlated with molecular markers Ki-67, hypoxia-inducible factor 1α (HIF-1α), and vascular endothelial growth factor (VEGF) in rectal cancer (RC). Ninety-one patients (64 males and 27 females) diagnosed with rectal cancer underwent 3.0T DW-MRI before any anticancer treatment. DW-MRI was performed using the single-shot echo-planar imaging technique (b = 0 and b = 800 s/mm(2) ). The patients underwent surgery within 1 week after MRI. Ki-67, HIF-1α, and VEGF expression were assessed by immunohistochemistry at both the resected margins and the center of the tumor. We noted that ADC values correlated positively with histology differentiations (r = 0.336, P = 0.001) and negatively with carcinoembryonic antigen level (r = -0.217, P = 0.039) in RC. Both the value and the level of Ki-67 expression were correlated inversely with the ADC values (r = -0.475, P < 0.001 and r = -0.555, P < 0.001). There was a weak negative correlation between HIF-1α expression and the ADC values (r = -0.304, P = 0.003). VEGF expression was correlated inversely with the ADC values of the RCs (r = -0.290, P = 0.005). However, no significant correlation was observed between VEGF expression and the ADC values in pT4 RCs (r = -0.166, P = 0.255). Our results suggest that the ADC values on DW-MRI may be used as a measurement of cell proliferation and hypoxia in RC. J. Magn. Reson. Imaging 2016;44:594-600.

Characterization of Soft Tissue Tumors by Diffusion-Weighted Imaging.

Background:Diffusion-weighted imaging (DWI) is a noninvasive method for investigation of tumor histological content. It has been applied for some musculoskeletal tumors and reported to be useful.Objectives:The aim of the present study was to prospectively evaluate the apparent diffusion coefficient (ADC) values of benign and malignant soft tissue tumors and to determine if ADC can help differentiate these tumors.Patients and Methods:DWI was performed on 25 histologically proven soft tissue masses. It was obtained with a single-shot echo-planar imaging technique using a 1.5T magnetic resonance (MR) machine. The mean ADC values were calculated. We grouped soft tissue tumors as benign cystic, benign solid or mixed, malignant cystic and malignant solid or mixed tumors and compared mean ADC values between these groups.Results:There was only one patient with a malignant cystic tumor and was not included in the statistical analysis. The median ADC values of benign and malignant tumors were 2.31 ± 1.29 and 0.90 ± 0.70 (median ± interquartile range), respectively. The mean ADC values were different between benign and malignant tumors (P = 0.031). Benign cystic tumors had significantly higher ADC values than benign solid or mixed tumors and malignant solid or mixed tumors (p values were < 0.001 and 0.003, respectively). Malignant solid or mixed tumors had lower ADC values than benign solid or mixed tumors (P = 0.02).Conclusion:Our preliminary results have shown that although there is some overlap between benign and malignant tumors, adding DWI, MR imaging to routine soft tissue tumor protocols may improve diagnostic accuracy.

Hepatic ADC map as an adjunct to conventional abdominal MRI to evaluate hepatic fibrotic and clinical cirrhotic severity in biliary atresia patients.

Hepatic apparent diffusion coefficient (ADC) values and ADC-related indices were correlated with the Mayo risk score for primary biliary cirrhosis (MRSPBC) and METAVIR scores of liver specimens to determine the clinical and pathological significance of diffusion-weighted magnetic resonance imaging (DWMRI). Thirty-two patients with biliary atresia (BA; mean age 461 days, range 11-4616 days) received magnetic resonance examinations from March 2009 to August 2013. A free-breathing DWMRI sequence was performed with the single-shot echo-planar imaging technique with b = 0 and 500 s/mm(2) in all 32 BA patients and 24 controls. We used the ordinal logistic regression test and Spearman rank correlation test to analyse the relationships between the MRSPBC and METAVIR fibrosis scores and right liver-to-psoas ADC ratios (LTPARs). BA patients had significantly lower LTPARs in both hepatic lobes than controls (p < 0.01). Right LTPARs, showing moderate intraobserver agreement (intraclass correlation coefficient = 0.736) and interobserver reliability (intraclass correlation coefficient = 0.659), were negatively correlated with MRSPBC and METAVIR fibrosis scores (R(2) = 0.398, p = 0.024 and R(2) = 0.628, p < 0.001, respectively). Right LTPARs may be used for long-term follow-up of cirrhosis severity in BA patients. • Hepatic ADC values by DWI correlates well with clinical/pathologic fibrosis scores • Periodic, non-invasive, quantitative imaging follow-up of patients with biliary cirrhosis is feasible • Information on cirrhosis severity could help decide on management options in children with BA • ADC values may be useful in this regard.

Clinical Evaluation of Single-Shot and Readout-Segmented Diffusion-Weighted Imaging in Stroke Patients at 3 T

Diffusion-weighted imaging (DWI) magnetic resonance imaging (MRI) is most commonly performed utilizing a single-shot echo-planar imaging technique (ss-EPI). Susceptibility artifact and image blur are severe when this sequence is utilized at 3 T. To evaluate a readout-segmented approach to DWI MR in comparison with single-shot echo planar imaging for brain MRI. Eleven healthy volunteers and 14 patients with acute and early subacute infarctions underwent DWI MR examinations at 1.5 and 3T with ss-EPI and readout-segmented echo-planar (rs-EPI) DWI at equal nominal spatial resolutions. Signal-to-noise ratio (SNR) and contrast-to-noise ratio (CNR) calculations were made, and two blinded readers ranked the scans in terms of high signal intensity bulk susceptibility artifact, spatial distortions, image blur, overall preference, and motion artifact. SNR and CNR were greatest with rs-EPI (8.1 ± 0.2 SNR vs. 6.0 ± 0.2; P <10(-4) at 3T). Spatial distortions were greater with single-shot (0.23 ± 0.03 at 3T; P <0.001) than with rs-EPI (0.12 ± 0.02 at 3T). Combined with blur and artifact reduction, this resulted in a qualitative preference for the readout-segmented scans overall. Substantial image quality improvements are possible with readout-segmented vs. single-shot EPI - the current clinical standard for DWI - regardless of field strength (1.5 or 3 T). This results in improved image quality secondary to greater real spatial resolution and reduced artifacts from susceptibility in MR imaging of the brain.

Quantitative in vivo diffusion imaging of cartilage using double echo steady‐state free precession

Single-shot echo-planar imaging techniques are commonly used for diffusion-weighted imaging (DWI) but offer rather poor spatial resolution and field-of-view coverage for species with short T(2) . In contrast, steady-state free precession (SSFP) has shown promising results for DWI of the musculoskeletal system, but quantification is generally hampered by its prominent sensitivity on relaxation times. In this work, a new and truly diffusion-weighted (that is relaxation time independent) SSFP DWI technique is introduced using a double-echo steady-state approach. Within this framework (and this is in contrast to common SSFP DWI techniques using SSFP-Echo) both primary echo paths of nonbalanced SSFP are acquired, namely the FID and the Echo. Simulations and in vitro measurements reveal that the ratio of the Echo/FID signal ratios of two double-echo steady-state scans acquired with and without diffusion sensitizing dephasing moments provides a highly relaxation independent quantity for diffusion quantification. As a result, relaxation-independent high-resolution (0.4 × 0.4 - 0.6 × 0.6 mm(2) in-plane resolution) quantitative in vivo SSFP DWI is demonstrated for human articular cartilage using diffusion-weighted double-echo steady-state scans in the knee and ankle joint at 3.0 T. The derived diffusion coefficients for cartilage (D ∼ 1.0-1.5 μm(2) /ms) and synovial fluid (D ∼ 2.6 μm(2) /ms) are in agreement with previous work.

Fast bound pool fraction mapping using stimulated echoes.

Magnetization transfer imaging advanced to an indispensible tool for investigating white matter changes. Quantitative magnetization transfer imaging methods allow the determination of the bound pool fraction (BPF), which is thought to be directly linked to myelin integrity. Long acquisition times and high specific absorption rates are still inhibiting broad in vivo utilization of currently available BPF mapping techniques. Herewith, a stimulated echoes amplitude modulation-based, single-shot echo planar imaging technique for BPF and T1 quantification is presented at 3T. It allows whole brain mapping in 10–15 min and is low in specific absorption rates. The method was validated with different concentrations of bovine serum albumin (BSA) phantoms. Intra- and inter-subject variability was assessed in vivo. Phantom measurements verified linearity between bovine serum albumin concentrations and measured BPF, which was independent of T1 variations. T1 values in the phantoms correlated well with values provided by standard T1 mapping methods. Intrasubject variability was minimal and mean regional BPFs of 10 volunteers (e.g., left frontal white matter = 0.135 ± 0.003, right frontal white matter = 0.129 ± 0.006) were in line with previously published data. Assessment of interhemispheric BPF differences revealed significantly higher BPF for the left brain hemisphere. To sum up, these results suggest the proposed method useful for cross-sectional and longitudinal studies of white matter changes in the human brain. Magn Reson Med, 2011. © 2011 Wiley-Liss, Inc.

Preliminary application of diffusion-weighted imaging with 3.0 T magnetic resonance scanner for nasopharyngeal carcinoma

To evaluate the clinical value of diffusion-weighted imaging (DWI) with 3.0 T magnetic resonance scanner for nasopharyngeal carcinoma (NPC) and to explore the appropriate b value during this procedure. Totally 50 patients with histopathologically confirmed NPC and 20 volunteers underwent DWI using single-shot echo-planar imaging technique were enrolled in this study. Four groups of b value (600, 800, 1000 and 1200) were applied. The apparent diffusion coefficients (ADC) between the primary tumor of NPC and the metastatic lymph nodes were compared in each group. ADC between the metastatic lymph nodes and benign nodes were also compared. Although the mean ADC were not significantly different between NPC and those of metastatic cervical lymph nodes in each group, the mean ADC of the metastatic lymph nodes were significantly lower than those of benign nodes (P<0.05). When b value was 800, both satisfying images and accurate measurements were acquired. DWI is helpful in the diagnosis of primary lesions and their lymph node metastases of NPC.

MR Imaging of Ventral Thalamic Nuclei

The Vim and VPL are important target regions of the thalamus for DBS. Our aim was to clarify the anatomic locations of the ventral thalamic nuclei, including the Vim and VPL, on MR imaging. Ten healthy adult volunteers underwent MR imaging by using a 1.5T whole-body scanner. The subjects included 5 men and 5 women, ranging in age from 23 to 38 years, with a mean age of 28 years. The subjects were imaged with STIR sequences (TR/TE/TI = 3200 ms/15 ms/120 ms) and DTI with a single-shot echo-planar imaging technique (TR/TE = 6000 ms/88 ms, b-value = 2000 s/mm(2)). Tractography of the CTC and spinothalamic pathway was used to identify the thalamic nuclei. Tractography of the PT was used as a reference, and the results were superimposed on the STIR image, FA map, and color-coded vector map. The Vim, VPL, and PT were all in close contact at the level through the ventral thalamus. The Vim was bounded laterally by the PT and medially by the IML. The VPL was bounded anteriorly by the Vim, laterally by the internal capsule, and medially by the IML. The posterior boundary of the VPL was defined by a band of low FA that divided the VPL from the pulvinar. The ventral thalamic nuclei can be identified on MR imaging by using reference structures such as the PT and the IML.

SSH-EPI diffusion-weighted MR imaging of the spine with low b values: is it useful in differentiating malignant metastatic tumor infiltration from benign fracture edema?

Conventional MR sequences are sometimes not helpful in differentiating benign from pathologic fractures. Our aim was to evaluate the usefulness of single-shot echo-planar imaging sequences (diffusion-weighted imaging (DWI)/SSH-EPI) with low b value in differentiating malignant metastatic tumor infiltration of vertebral bone marrow from benign vertebral fracture edema. A total of 47 patients, 20 with benign fractures and 27 with tumor infiltration, were included in this prospective study. Diffusion-weighted MR images were obtained by single-shot echo-planar imaging technique with diffusion gradient (b = 300 s/mm2; TR/TE, 1,400/100), using a 1.5 T MR scanner. T1- and T2-weighted images and short inversion time inversion-recovery images were available for all 64 lesions. The lesions on DWI/SSH-EPI were categorized as having hypo-, iso-, or hyperintense signal intensity relative to normal vertebrae by two experienced radiologists. We evaluated signal intensity patterns on DWI/SSH-EPI in 64 lesions, which showed low signal intensity on T1-weighted images in both benign fractures and metastasis. With the exception of sclerotic metastases in two patients, malignant metastatic tumor infiltration was hyperintense with respect to normal bone marrow on diffusion-weighted images; all but four benign vertebral fractures were isointense with respect to normal bone marrow. Single-shot echo-planar imaging sequences (DWI/SSH-EPI) with low b value provided excellent distinction between metastatic tumor infiltration and benign vertebral fracture edema. Hyperintense signal intensity on DWI/SSH-EPI was highly specific for the diagnosis of metastatic tumor infiltration of the spine.

Diffusion Anisotropy Measurement of Brain White Matter Is Affected by Voxel Size: Underestimation Occurs in Areas with Crossing Fibers

Voxel size/shape of diffusion tensor imaging (DTI) may directly affect the measurement of fractional anisotropy (FA) in regions where there are crossing fibers. The purpose of this article was to investigate the effect of voxel size/shape on measured FA by using isotropic and nonisotropic voxels. Ten healthy adult volunteers had MR imaging by using a 1.5 T clinical imager. DTI was performed with 2 different voxel sizes: a 2-mm-section isotropic voxel (2 x 2 x 2 mm(3)) and a 6-mm-section nonisotropic voxel (2 x 2 x 6 mm(3)). Images were obtained by using a single-shot echo-planar imaging technique with motion-probing gradients in 15 orientations and a b-value of 1000 s/mm(2). FA and the apparent diffusion coefficient (ADC) were measured at different sites of the brain. When smaller isotropic voxels were used, the FA was greater in areas with crossing fibers, including the superior longitudinal fasciculus, the thalamus, and the red nucleus; the FA was not significantly different in areas without crossing fibers, such as the corpus callosum, the posterior limb of the internal capsule, and the corticospinal tract at the level of the centrum semiovale (P>.05). The ADC values were not affected by voxel size/shape at any of the areas of the brain that were measured. FA values that are measured in regions containing crossing fibers are underestimated when using nonisotropic DTI.

Somatotopic Organization of Thalamocortical Projection Fibers as Assessed with MR Tractography

To prospectively evaluate the course of sensory fibers through the supratentorial brain with diffusion-tensor-based tractography. This study was approved by the institutional review board. Informed consent was obtained. Seven healthy volunteers (five men, two women; age range, 20-55 years) underwent 1.5-T magnetic resonance imaging. Diffusion-tensor images with isotropic voxels (2 x 2 x 2 mm) were obtained by using a single-shot echo-planar imaging technique, with a motion-probing gradient in 15 orientations, a b value of 1000 sec/mm(2), and nine signals acquired. The total imaging time was approximately 30 minutes. Fiber tracking of the sensorimotor pathways was performed with the fiber assignment by continuous tracking method. All the pyramidal tracts rotated anteriorly as they traveled through the centrum semiovale. On the other hand, the sensory tracts rotated posteriorly as they coursed through the centrum semiovale toward the cortex. When the sensorimotor tracts were viewed as a unit, the tracts of the lower extremity formed the axis of rotation around which the other parts of the pyramidal and sensory homunculus rotated. Sensorimotor fibers of the lower extremity form an axis of rotation, around which the pyramidal fibers rotate anteriorly and the sensory fibers rotate posteriorly.

Assessment of environmental disturbances to the static magnetic field in magnetic resonance installations

The static magnetic field of MRI scanners can be affected by environmental factors. Magnetic resonance spectroscopy and functional imaging with single-shot echo-planar imaging (EPI) are particularly vulnerable to the movement of lifts, vehicles, trains and other large metallic masses in the vicinity. This work investigates the sensitivity of two different imaging techniques to assess disturbances of the static magnetic field: (i) phase changes in gradient-echo images of a uniform test object; and (ii) image displacement along the phase encoding direction in single-shot EPI images. For the latter a hexane sample was used, and the separation between CH2 and CH3 signals was taken as a reference. Both techniques were evaluated in a site known to be free of any significant environmental disturbances and validated by inducing a magnetic field disturbance. Both techniques provide valuable information in acceptance tests, allowing MRI users to evaluate and manage the environmental conditions surrounding a scanner. The single-shot EPI technique was found to be highly sensitive, being expected to detect magnetic field fluctuations down to 0.005 parts per million (ppm). The phase images method was found to be less sensitive (0.02 ppm) but is more easily available. The single-shot EPI technique was used in acceptance tests and environmental disturbances to the magnetic field of the order of 0.04 ppm were measured at the isocentre on two separate occasions.

Single-Shot Interleaved Z-Shim EPI with Optimized Compensation for Signal Losses due to Susceptibility-Induced Field Inhomogeneity at 3 T

A new single-shot echo-planar imaging (EPI) sequence with interleaved z-shim and optimized compensation for susceptibility-induced signal loss is proposed in this paper. Experiments on human brain demonstrated that the new method is able to regain signal dropout in brain areas with severe susceptibility-induced local gradients, while its image acquisition speed is comparable to that of conventional single-shot EPI techniques. Significant signal-to-noise ratio improvements were demonstrated in the ventral prefrontal and lateral temporal lobes with the new technique compared to a conventional EPI. Brain activation experiments with a bilateral finger-tapping task were performed with intentionally introduced local gradients near the left sensorimotor cortex, by a small gadolinium (Gd)-doped bottle placed on the left side of the head. The results of the functional experiments showed that the interleaved z-shim EPI sequence effectively recovered the signal loss caused by the Gd-doped bottle and reliably detected activation signals in bilateral sensorimotor regions, while the activation signals on the left side diminished considerably in a conventional EPI technique. The new technique, with the capability of reducing susceptibility artifacts and rapid scanning speed, may be particularly useful for event-related functional MRI experiments in the base of the brain, which are of great importance in neuropsychiatric studies.

Diffusion Weighted MR Image of Intracranial Hemorrhage

Purpose: To determine changes in the signal intensity of intracerebral hemorrhagic lesions according to the time interval, between the onset of symptoms and MR imaging in the T1-weighted (T1W1), T2-weighted (T2W1) and diffusion-weighted modes. Materials and Methods: Thirty-four patients with hemorrhagic stroke who underwent DWI and conventional MRI were involved in this study. Hemorrhagic phase was determined according to the time interval between the onset of symptoms and MR scanning, and was as follows: acute (3 days or less): eight patients); early subacute (7 days or less): ten patients; late subacute (4 weeks or less): seven patients; early chronic (3 months or less) : four patients); and late chronic (more than 3 months): five patients. Using a 1.5T MR imager and the single-shot echo-planar imaging technique, T1-weighted, fast spin-echo T2-weighted, and diffusion-weighted were obtained. In all cases qualitative signal intensity (SI) at the center of a lesion was recorded, and the ratio between this and normal brain parenchyma was calculated. Results: SI at the center of a lesion was found to be iso or high/high/high (T1WI/T2WI/DWI) in five of eight acute-phase cases (interval of 24 hours or less) and low/low/low in the remaining three (interval of 72 hours or less). Other signal intensities were as follows: early subacute phase: high/low/low (all ten cases); late subacute phase: high/high/high (all seven cases); early chronic phase: high/high/high (all four cases); late chronic phase: low/high/low (all five cases). Mean SIRs were as follows: in the five acute-phase cases in which SI was iso or high: 1.420.78 / 2.580.84 / 1.350.08 (T1WI / T2WI / DWI); in the remaining three acute-phase cases: 0.94 0.18 / 0.630.16 / 0.270.10; in the early subacute phase, 1.350.01 / 0.970.21 / 0.860.22 in early subacute phase, 1.580.04 / 1.540.09 / 1.440.14; in the early chronic phase: 1.260.11 / 1.060.14 / 0.970.12; and in the late chronic phase: 0.652.23 / 1.510.12 / 0.230.18. Conclusion: The DWI findings of intracerebral hemorrhage reflect the findings of T2WI. When interpreting the DWI findings in patients with intracerebral hemorrhage, an understanding of the temporal evolution of this is very helpful . The no-show rate, patient distribution, chief complaint, type and number of additional radiologic examinations, patient compliance rate, biopsy result, rate of cancer detection, and staging of cancers were determined. The merits and demerits of the clinic were also assessed. Results: A total of 671 patients attended, with a no-show rate of 13.2%. Referrals from the Health Promation Centre accounted for 90.4% of patient visits. The most frequent complaint was a suspicious nodule at mammography. One additional radiologic examination was performed in 429 patients, two examinations in 70, and three or more examations in five. The most frequent type of examination was ultrasonography, followed by magnification compression view, mammography, and ultrasound-guided aspiration biopsy. An additional radiologic examination was recommended in 81.2% of patients and compliance rate was 96.7%. Primary breast cancer was diagnosed in 16 patients (2.1%), and was found to be stage 0 and 1 in 64.3% of these. No significant demerits were apparent. Conclusion: Radiologic examinations play a very important role in the detection of early-stage breast cancer, and the establishment of an early detection clinic lead by a radiologist is a very effective and recommendable approach to screening.',PY = '2002-00-00',RF = '5',BN = '

Diffusion tensor trace mapping in normal adult brain using single-shot EPI technique. . A methodological study of the aging brain

To quantify age-related changes of the average diffusion coefficient value in normal adult brain using orientation-independent diffusion tensor trace mapping and to address the methodological influences on diffusion quantification. Fifty-four normal subjects (aged 20-79 years) were studied on a 1.5-T whole-body MR medical unit using a diffusion-weighted single-shot echo-planar imaging technique. Orientation-independent diffusion tensor trace maps were constructed for each subject using diffusion-weighted MR measurements in four different directions using a tetrahedral gradient combination pattern. The global average (including cerebral spinal fluid) and the tissue average of diffusion coefficients in adult brains were determined by analyzing the diffusion coefficient distribution histogram for the entire brain. Methodological influences on the measured diffusion coefficient were also investigated by comparing the results obtained using different experimental settings. Both global and tissue averages of the diffusion coefficient are significantly correlated with age (p<0.03). The global average of the diffusion coefficient increases 3% per decade after the age of 40, whereas the increase in the tissue average of diffusion coefficient is about 1% per decade. Experimental settings for self-diffusion measurements, such as data acquisition methods and number of b-values, can slightly influence the statistical distribution histogram of the diffusion tensor trace and its average value. Increased average diffusion coefficient in adult brains with aging are consistent with findings regarding structural changes in the brain that have been associated with aging. The study also demonstrates that it is desirable to use the same experimental parameters for diffusion coefficient quantification when comparing between different subjects and groups of interest.

Diffusion tensor trace mapping in normal adult brain using single-shot EPI technique. A methodological study of the aging brain.

To quantify age-related changes of the average diffusion coefficient value in normal adult brain using orientation-independent diffusion tensor trace mapping and to address the methodological influences on diffusion quantification. Fifty-four normal subjects (aged 20-79 years) were studied on a 1.5-T whole-body MR medical unit using a diffusion-weighted single-shot echo-planar imaging technique. Orientation-independent diffusion tensor trace maps were constructed for each subject using diffusion-weighted MR measurements in four different directions using a tetrahedral gradient combination pattern. The global average (including cerebral spinal fluid) and the tissue average of diffusion coefficients in adult brains were determined by analyzing the diffusion coefficient distribution histogram for the entire brain. Methodological influences on the measured diffusion coefficient were also investigated by comparing the results obtained using different experimental settings. Both global and tissue averages of the diffusion coefficient are significantly correlated with age (p<0.03). The global average of the diffusion coefficient increases 3% per decade after the age of 40, whereas the increase in the tissue average of diffusion coefficient is about 1% per decade. Experimental settings for self-diffusion measurements, such as data acquisition methods and number of b-values, can slightly influence the statistical distribution histogram of the diffusion tensor trace and its average value. Increased average diffusion coefficient in adult brains with aging are consistent with findings regarding structural changes in the brain that have been associated with aging. The study also demonstrates that it is desirable to use the same experimental parameters for diffusion coefficient quantification when comparing between different subjects and groups of interest.

Functional magnetic resonance imaging of primary visual processing using a 1.0 Tesla scanner.

Recent advances in functional magnetic resonance imaging (fMRI) at > or = 1.5 T magnetic field strength and with high speed single-shot echo planar imaging techniques have made it possible to monitor local changes in cerebral blood volume, cerebral blood flow, and blood oxygenation level in response to sensory stimulation, simple motor activity, and possibly also to more complex cognitive processing. However, fMRI has also been accomplished on conventional MR scanners of medium field strength (approximately 1.0 T) using special pulse sequences and appropriate methods for image analysis. We present results from six subjects on photic stimulation using a standard 1.0 T MR scanner together with special software for off-line image analysis. Continuous serial T2-weighted imaging were performed for 6 minutes in the plane of the calcarine fissure. There were 3 repetitions of 1 minute resting state of darkness (OFF) and 1 minute activated state (ON) with 8 Hz flicker stimulation. To directly map these functional images to the underlying anatomy we also acquired a high resolution T1-weighted image from the same axial slice. The results demonstrated that stimulus-related signals can be obtained from primary visual cortex with a conventional 1.0 T MR scanner. Further methodological improvements are discussed and related to present and future possibilities for the use of fMRI within psychophysiology.