The principle of multidimensional arrays.
(57/1232)
Echocardiography is one of the most important diagnostic tools in cardiology today. One-dimensional phased arrays have been used extensively because they have a small footprint and allow beam steering. Their major limitation lies in that these devices can only be used to acquire images of two-dimensional slices in real-time and that the slice thickness cannot be controlled. To allow real-time three-dimensional imaging of the heart and focusing of the ultrasonic beam in two-dimensional, two-dimensional arrays, the design and fabrication of which are enormous engineering challenges, are required. Before reaching this ultimate goal, limited focusing in the elevational plane can be achieved with 1.5-dimensional arrays. Focusing in the elevational plane allows a reduction in slice thickness and thus an improvement in the image quality over a larger depth of view. (+info)
Design of quality assurance for sonographic prostate brachytherapy needle guides.
(58/1232)
OBJECTIVE: Needles are guided to their proper anatomic locations in sonographically guided percutaneous prostate brachytherapy by a mechanical system (template). A quality assurance procedure has been designed to test this template's alignment with the needle position overlay grid displayed in the sonographic image. METHODS: A mechanical arrangement was designed to position the needles properly with respect to the prostate probe's transducer in a liquid-filled test tank. Two liquids were tested: tap water and an ethylene glycol mixture with an acoustic velocity of 1540 m/s. Needle images with the superposed grid were analyzed for needle placement accuracy. RESULTS: The tap water produced misregistration of the needle images. The ethylene glycol mixture yielded images of vertical and horizontal needle positions accurate to 0.3 and 1 mm, respectively. Also, the importance of selecting the lowest possible equipment echo amplitude dynamic range in these tests was shown. CONCLUSIONS: This quality assurance test with the ethylene glycol mixture will permit accurate alignment of the brachytherapy needle position overlay grid for each separate transrectal probe used. (+info)
Time relation between apex cardiogram and left ventricular events using simultaneous high-fidelity tracings in man.
(59/1232)
In 10 patients without left heart valvular disease and having normal function of the left ventricle, the left ventricular apex cardiogram with its first derivative (dA/dt), left ventricular pressure with its first derivative (dP/dt), aortic pressure, electrocardiogram, and phonocardiogram were reocrded simultaneously during cardiac catheterization. The apex cardiographic tracings were obtained by means of a transducer with infinite time constant and very high resonant frequency and the LV and aortic pressures with catheter tip-manometers. The onset of the systolic rise of apex cardiographic and LV pressures were found to occur almost simultaneously with the upstroke of LV pressure, preceding that of the apex cardiogram by only 2 +/- 4 ms (mean +/- 1 SD). The summit of the systolic upstroke of the apex cardiogram (called E-point) occurred 37 +/- 9 ms after opening of the aortic valve and 41 +/- 9 ms after peak dP/dt. The peak of dA/dt preceded peak dP/dt by 10 +/- 4 ms. The protodiastolic nadir of the apex cardiogram (called-O-point) occurred slightly earlier (19 +/- 16 ms) than the nadir of the LV pressure curve, with considerable variation. In conclusion, this study using external and internal transducers with similar characteristics gives a new definition of the time relation between the externally recorded apex cardiogram and the haemodynamic events within the left heart in human subjects with normal left ventricular function. (+info)
In-vitro investigation of a new neuromuscular relaxant, AH8165.
(60/1232)
AH8165 was compared with other neuromuscular relaxants in an in-vitro rat phrenic nerve-diaphragm preparation. Concentrations of 6-10 mug/ml AH8165 produced progressive decreases in strength of concentration. AH8165 was 0.1 times as potent as d-tubocurarine, and its effects were more rapidly reversed by washing. The times to recovery from 90 per cent blockade were the same for succinylcholine and AH8165, but the time to recovery from 50 per cent blockade was shorter for succinylcholine than for AH8165. Neostigmine reversed blockade induced by d-tubocurarine to 80 per cent of control, while it reversed comparable blockade induced by AH8165 to only 40 per cent of control. Doses of 0.5 to 2 mug AH8165 produced contracture and increased the force of contraction of the superfused chick biventer cervicis muscle preparation. Doses of 8 to 32 mug produced decreased contracture followed by diminution of the strength of contraction. The authors conclude that AH8165 in low concentrations has a depolarizing action, which is obscured by nondepolarizing effects in higher concentrations. (Key words: Neuromuscular relaxants: AH8165.) (+info)
Guidance of retrobulbar injection with real-time tomographic reflection.
(61/1232)
OBJECTIVE: Retrobulbar and peribulbar injections are common ophthalmologic procedures used to deliver anesthetics and other medications for ophthalmic therapy and surgery. These injections, typically performed without any type of guidance, can lead to complications that are rare but visually devastating. The needle may penetrate the optic nerve, perforate the globe, or disperse toxic quantities of drugs intraocularly, causing major visual loss. Sonographic guidance may increase the accuracy of the needle placement, thereby decreasing the incidence of complications. However, difficulties arise in coordinating the relative location of the image, the needle, and the patient. Real-time tomographic reflection is a new method for in situ visualization of sonographic images, permitting direct hand-eye coordination to guide invasive instruments beneath the surface of the skin. METHOD: In this preliminary study, real-time tomographic reflection was used to visualize the eye and surrounding anatomic structures in a cadaver during a simulated retrobulbar injection. RESULT: The needle tip was easily followed as it was advanced into the retrobulbar space. CONCLUSIONS: The images presented in this preliminary study show the use of real-time tomographic reflection to visualize insertion of an invasive instrument into the human body. (+info)
FasL deficiency enhances the development of tumors in p53+/- mice.
(62/1232)
In the multistep process of tumor development, several events occur to transform cells from normal to malignant. Although p53 is one of the most commonly mutated genes in a wide variety of tumors, how other genes interact with p53 to transform cells is only just beginning to be understood. To study the effects of the interaction of the Fas system with p53 in tumor progression and development, mice with a targeted disruption of the p53 tumor supressor gene and a mutation in Fas ligand were bred. Organ weights, life expectancy, and tumor and tissue histology were assessed. Although spleen weights were drastically increased in FasL -/- p53 -/- mice, the FasL deficiency had no effect on life expectancy or the tumor spectrum of homozygous p53-deficient mice. The FasL deficiency reduced the median time to death from 12.1 months in FasL +/+ p53 +/- mice to 9.6 months in FasL -/- p53 +/- mice, and led to a shift in tumor spectrum from predominantly sarcomas (63%) when FasL was present to a large number of lymphomas (76%) in FasL -/- p53 +/- mice. Given the reduced life span and increased incidence of lymphoma in FasL -/- p53 +/- mice, these mice could be useful in carcinogenicity testing, particularly for understanding mechanisms of compounds that are nongenotoxic. (+info)
OBJECTIVE: To determine whether current-generation endoluminal ultrasonic transducer technology could visualize dysplastic and malignant cervical lesions. METHODS: Inclusion criteria for patients enlisted in the study were abnormal Papanicolaou test results, an abnormality seen at colposcopy, and consent for a cone biopsy. In addition, we included 4 women who were undergoing hysterectomy but had no evidence of cervical abnormalities at the time of surgery, for a total of 28 women. We used a 20-MHz annular array intravascular transducer. We correlated all sonographic and pathologic results with regard to being normal or abnormal using the Pearson product moment correlation coefficient, and we evaluated interobserver variation by having 5 blinded sonologists interpret each examination and calculating kappa statistics. RESULTS: We performed intracervical sonography on 24 women with abnormal Papanicolaou test results and on 4 women without abnormalities. Nineteen of the 24 women with proven disease had abnormal sonographic images. Five women with pathologically proven cervical intraepithelial neoplasia I had normal sonographic images. Lesions ranged in size from 0.3 to 7 mm. Two carcinomas (5 and 7 mm diameter), multiple nabothian cysts, cervicitis, and 2 giant cell foreign body reactions were visible on sonography. The correlation coefficient for abnormal sonographic and pathologic findings was 0.87 (P < .005). We obtained a kappa value of 0.75 for interobserver variation. CONCLUSIONS: Intracervical sonography was able to visualize dysplastic lesions and carcinomas as hypoechoic defects with surrounding echogenic areas of glandular cervical mucosa. Lesions were shown with sufficient resolution and interobserver variation to suggest that the technique may be clinically applicable, particularly for planning surgical therapy. However, design of a transducer that can be easily sterilized between examinations, similar to current endovaginal probes, would be necessary to make intracervical sonography a clinically feasible examination. (+info)
The role of hydration on the mechanism of allosteric regulation: in situ measurements of the oxygen-linked kinetics of water binding to hemoglobin.
(64/1232)
We report here the first direct measurements of changes in protein hydration triggered by a functional binding. This task is achieved by weighing hemoglobin (Hb) and myoglobin films exposed to an atmosphere of 98% relative humidity during oxygenation. The binding of the first oxygen molecules to Hb tetramer triggers a change in protein conformation, which increases binding affinity to the remaining empty sites giving rise to the appearance of cooperative phenomena. Although crystallographic data have evidenced that this structural change increases the protein water-accessible surface area, isobaric osmotic stress experiments in aqueous cosolutions have shown that water binding is linked to Hb oxygenation. Now we show that the differential hydration between fully oxygenated and fully deoxygenated states of these proteins, determined by weighing protein films with a quartz crystal microbalance, agree with the ones determined by osmotic stress in aqueous cosolutions, from the linkage between protein oxygen affinity and water activity. The agreements prove that the changes in water activity brought about by adding osmolytes to the buffer solution shift biochemical equilibrium in proportion to the number of water molecules associated with the reaction. The concomitant kinetics of oxygen and of water binding to Hb have been also determined. The data show that the binding of water molecules to the extra protein surface exposed on the transition from the low-affinity T to the high-affinity R conformations of hemoglobin is the rate-limiting step of Hb cooperative reaction. This evidences that water binding is a crucial step on the allosteric mechanism regulating cooperative interactions, and suggests the possibility that environmental water activity might be engaged in the kinetic control of some important reactions in vivo. (+info)