Focused, eight-element transceive phased array coil for parallel magnetic resonance imaging of the chest--theoretical considerations.

A new transceive system for chest imaging for MRI applications is presented. A focused, eight-element transceive torso phased array coil is designed to investigate transmitting a focused radiofrequency field deep within the torso and to enhance signal homogeneity in the heart region. The system is used in conjunction with the SENSE reconstruction technique to enable focused parallel imaging. A hybrid finite-difference-time-domain/method-of-moments method is used to accurately predict the radiofrequency behavior inside the human torso. The simulation results reported herein demonstrate the feasibility of the design concept, which shows that radiofrequency field focusing with SENSE reconstruction is theoretically achievable.     

胰岛素与胰岛素样生长因子在肝脏副交感神经反射中的作用

目的 :为了检验一个新的学说 :是胰岛素而不是胰岛素样生长因子 (IGF-1 )激活肝脏副交感神经反射。方法 :应用快速胰岛素敏感试验 (RIST)方法。其指标是 :在胰岛素或胰岛素样生长因子 (IGF- )推注后为了维持大白鼠实验期间的正常血糖水平而灌注的葡萄糖量。我们比较了胰岛素 5 0 mu/kg及 IGF- 2 0 0μg/kg输入实验的大白鼠体内后的血糖贮存量。结果 :IGF- 2 0 0 μg/kg与胰岛素 5 0 mu/kg有相似的低血糖作用。通过输入阿托品 (1 .0 mg/kg)阻断肝脏副交感神经反射导致胰岛素抵抗 ,而对 IGF- 无影响。结论 :是胰岛素而不是IGF- 激活肝脏副交感神经反射释放出一种激素刺激血糖在骨骼肌的摄取     

Acetabular fractures: optimal imaging

In 19 cases of acetabular fracture, computed tomography (CT) with volumetric three-dimensional (3D) reconstructions displayed as video loops about horizontal and vertical axes of rotation replaced the traditional imaging combination of CT and multiple plain radiographs, while offering significant advantages. Overlying bowel content or foreign matter obscured detail in 36 of 45 plain radiographic views, and positioning or radiographic technique was suboptimal in 21. Three-dimensional reconstructions completely eliminated these problems. These 3D reconstructions accurately simulated oblique, inlet, and tangential views in all cases. In ten of 19 cases a nonconventional oblique view, and in 13 of 19 cases a cephalocaudal angulation other than the inlet, tangential, or anteroposterior view, best demonstrated the fracture. Elimination of five plain radiographs resulted in a skin radiation dose savings of 5 rad (50 mGy). No difficult or painful patient positioning was required beyond that necessary for the standard CT examination.     

Intracerebral malignant melanoma: high-field-strength MR imaging

Thirteen patients with intracerebral malignant melanoma underwent high-field-strength (1.5-T) magnetic resonance (MR) imaging. The images were correlated with computed tomography (CT) scans (n = 7) and surgical specimens (n = 7). Most commonly, these lesions were hyperintense to normal white matter on T1-weighted images and hypointense to normal white matter on T2-weighted images. Hemorrhage in the lesion may have a greater influence on this unique appearance than does melanin. The increased tissue sensitivity of MR imaging allowed for 22% greater lesion detection than did CT.     

Effects of bladder volume on transabdominal ultrasound measurements of intravesical prostatic protrusion and volume

BACKGROUND: A filled bladder acts as an acoustic window for transabdominal ultrasound measurements of intravesical prostatic protrusion and volume. The aim of this study is to evaluate the effects of bladder volume on transabdominal ultrasound measurements of these parameters. METHODS: Twenty-two patients undergoing transurethral resection of the prostate (TURP) were studied. Under general anesthesia just before TURP, a transrectal ultrasound measurement of prostate volume was obtained. The bladder was then filled in a stepwise manner with 100, 200, 300, 400 and 500 mL. At each volume, the intravesical prostatic protrusion and prostatic volume were measured transabdominally using ultrasound. RESULTS: There was an obvious trend of decreasing mean transabdominal intravesical prostatic protrusions with increasing bladder volume. The mean transabdominal intravesical prostatic protrusion at bladder volumes 100, 200, 300, 400 and 500 mL was 9.1, 8.8, 7.4, 5.8 and 4.6 mm, respectively. The bladder volume at which maximum prostatic protrusion occurred was between 100 and 200 mL. The mean transabdominal prostate volume at the five increasing bladder volumes was 50.6, 48.7, 49.2, 47.9 and 41.4 mL, and these were correlated to transrectal prostate volume, particularly when the bladder volume was less than 400 mL. CONCLUSIONS: Transabdominal ultrasound measurement of prostatic protrusion is dependent on bladder volume. Transabdominal ultrasound measurement of prostatic volume correlates well with the transrectal measurement of the same parameter when the bladder volume is less than 400 mL.     

Multisection fat-water imaging with chemical shift selective presaturation

Proton chemical shift imaging yielding separate water and lipid images was performed in a multisection mode on a clinical 1.5-T whole-body magnetic resonance imaging unit. Imaging was performed with a minor modification of the standard multisection spin-warp technique: that is, the addition of a sinc pulse or a soft square pulse and a homospoil gradient at the beginning of the pulse sequence. Phantom and human anatomic images are presented.