Calibration of water proton chemical shift with temperature for noninvasive temperature imaging during focused ultrasound surgery

Long-standing ulcerative colitis is considered to be a precancerous condition. Therefore, a practical and reliable method is required for monitoring the progress of the disease. Liberation of the S-phase from karyokinesis occurs in DNA amplification and endoreplication, producing nuclei with more than 4 c DNA. The amount of Feulgen DNA was quantified with an image microphotometer in 8 microns sections for interphase nuclei and in 15 microns sections for chromosome division figures (CDFs). Development of ulcerative colitis was investigated in low grade dysplasia (n = 93 cases; score 3-7) and high grade dysplasia (n = 22; score 8-10). Bacterial colitis (n = 34) and invasive adenocarcinoma (n = 26) provided a basis for data interpretation in dysplasia. Lymphocyte nuclei served as an internal DNA standard. CDFs represent a novel type of aberrant 'mitoses'; they are different from and much more frequent than figures with multipolar spindles. Endoreplication began with low grade dysplasia in interphase nuclei as well as with CDFs; it was fully established in high grade dysplasia and carcinoma. Endoreplicated interphase nuclei and CDFs represent an early morphological mosaic of genomic instability. Both characteristics support a reproducible two-level classification of low and high grade dysplasia in ulcerative colitis.     

Application of focused ultrasound for research on pain

Exteroceptive silent periods (ESPs) of masseter muscle activity evoked by electrical stimulation of the mental nerve were studied over a large range of prepain intensities and at pain threshold in 44 normal subjects. Seven levels of stimulus intensity, based on individual sensory and pain thresholds, were applied and the relationship between ESPs, stimulus intensity and perception, as manifested by the subjective verbal response, was investigated. The analysis revealed that the occurrence of ESPs was not related to the stimulus intensity at the pain threshold. There were individually different patterns of progressive response to increasing current intensities within the pre-pain range in many cases. On the other hand, almost half of all the subjects investigated showed no or only occasional ESPs. In view of this variability the concept of ESPs being a nociceptive behavioural response has to be questioned.     

MR imaging techniques for soft-tissue lesions

MR imaging is the technique of choice for detection, characterization, and staging of soft-tissue neoplasms. MR examinations need to be tailored to each patient based upon the patient's size and anatomic region of interest so that optimal information is obtained. Technique is critical. Proper positioning to allow patient comfort and reduce motion artifacts is essential. Selection of the appropriate coils, image planes, and optimal pulse sequences to identify and determine the extent of lesions is critical for therapy planning.     

Three-dimensional ultrasound imaging of the vasculature

With conventional ultrasonography, the diagnostician must view a series of two-dimensional images in order to form a mental impression of the three-dimensional anatomy, an efficient and time consuming practice prone to operator variability, which may cause variable or even incorrect diagnoses. Also, a conventional two-dimensional ultrasound image represents a thin slice of the patients anatomy at a single location and orientation, which is difficult to reproduce at a later time. These factors make conventional ultrasonography non-optimal for prospective or follow-up studies. Our efforts have focused on overcoming these deficiencies by developing three-dimensional ultrasound imaging techniques that are capable of acquiring B-mode, colour Doppler and power Doppler images of the vasculature, by using a conventional ultrasound system to acquire a series of two-dimensional images and then mathematically reconstructing them into a single three-dimensional image, which may then be viewed interactively on an inexpensive desktop computer. We report here on two approaches: (1) free-hand scanning, in which a magnetic positioning device is attached to the ultrasound transducer to record the position and orientation of each two-dimensional image needed for the three-dimensional image reconstruction; and (2) mechanical scanning, in which a motor-driven assembly is used to translate the transducer linearly across the neck, yielding a set of uniformly-spaced parallel two-dimensional images.     

Histologic effects of high intensity pulsed ultrasound exposure with subharmonic emission in rabbit brain in vivo

In this study, the threshold for subharmonic emission during in vivo sonication of rabbit brain was investigated. In addition, the histologic effects of pulsed sonication above this threshold were studied. Two spherically curved focused ultrasound transducers with a diameter of 80 mm and a radius of curvature of 70 mm were used in the sonications. The operating frequencies of the transducers were 0.936 and 1.72 MHz. The sonication duration was varied between 0.001 and 1 s and the repetition frequency between 0.1 and 5 Hz. The threshold for subharmonic emission at the frequency of 0.936 MHz was found to be approximately 2000 W cm-2 and 3600 W cm-2 for pulse durations of 1 s and 0.001 s, respectively. The threshold was approximately 1.5-fold as high at a frequency of 1.72 MHz. However, there was considerable variation from experiment to experiment. The multiple pulse experiments at a frequency of 1.72 MHz and an intensity of 7000 W cm-2 showed that the histologic effects ranged from no observable damage of the tissue, to blood-brain barrier breakage, to local haemorrhagia, to local destruction of the tissue, to gross hemorrhage resulting in the death of the animal. The severity of the tissue damage increased as the pulse duration, number of pulses and their repetition frequency increased. The results indicate that the end point of the tissue damage may be controlled by selecting the sonication parameters. Such control over tissue effects can have several different applications when brain disorders are treated.     

Calculation of tissue attenuation with a clinical ultrasound unit

RATIONALE AND OBJECTIVES: Five alternative methods for estimating tissue attenuation with a clinical ultrasound unit were evaluated. METHODS: Two homogeneous tissue mimicking phantoms (with known attenuations of 0.25 and 0.54 db/cm/MHz) and 22 human placentas were scanned. Attenuation coefficients were computed by linear regression of 1) L(f), the log spectral difference; 2) Fav (d), the average spectral frequency; 3) log[P(d)], the logarithm of the spectral power; 4) Fav (d) x log[P(d)]; and 5) (Fav(d) + log[P(d)])/2. RESULTS: Each of these five heuristics provided accurate estimates for the relative attenuations of the two phantoms. For placental tissue, method 3 provided better regression fits than methods 1 and 2. Methods 4 and 5 provide the best regression fits (P < .01). CONCLUSIONS: The combination of both frequency and power information in methods 4 and 5 compensates, in part, for nonlinearities introduced by tissue heterogeneity. A parameter that combines both frequency and time domain information is likely to provide more reliable estimates of attenuation than power or frequency measurements alone.     

Differential effects of lesions in three limbic areas on ultrasound production and lordosis by female hamsters.

Examined ultrasound production and lordosis in 98 ovariectomized, hormone-primed (estradiol benzoate [10 μg] and progesterone [500 μg]) female golden hamsters before and after sham operations or bilateral electrolytic lesions. During 2-min exposures to synthetic ultrasounds and 1-min exposures to stimulus males, Ss with corticomedial amygdala lesions exhibited reduced ultrasound rates and lordosis durations. Following lesions in the lateral septum/bed nucleus, Ss showed significant increases in ultrasound rates but no change in lordosis. Ablations of the lateral habenula had no effect on calling but were associated with shorter lordosis durations. Results demonstrate that 2 reproductive behaviors, ultrasound production and lordosis, are differentially affected by lesion placement within the limbic system. These differences demonstrate that the neural mechanisms for 2 elements of a single major class of behavior can be distinct, both in terms of the likelihood that particular brain areas will be involved and in the nature of their involvement. (43 ref) (PsycINFO Database Record (c) 2010 APA, all rights reserved)     

Development of the bi-directional ultrasound system for base of tongue imaging

The use of conventional ultrasound systems to image the upper airway has been limited because ultrasound energy is attenuated by the air column. In an attempt to study upper airway geometry, we developed a computer controlled bi-directional ultrasound system which combines two conventional ultrasound devices with computer image processing to yield images of upper airway structures. Human studies and cadaver studies were performed to evaluate the system. Images acquired by the bi-directional ultrasound system were comparable to images from 3D volume rendered CT scans. This system may provide valuable data in the study of upper airway physiology and pathology.     

Transmission imaging for nonuniform attenuation correction using a three-headed SPECT camera

ACTH (1-24) induces cell shape changes in the immunocytes of the bivalve mollusc, Mytilus galloprovincialis. Using computer-assisted microscopic image analysis, we have found that the G protein antagonist suramin sodium, the adenylate cyclase inhibitor 2',5'-dideoxyadenosine, and the protein kinase inhibitor staurosporine inhibit this effect. The highly specific inhibitors H-89 (for protein kinase A) and calphostin C (for protein kinase C) only inhibited partially the morphological alterations. In contrast, the simultaneous action of H-89 and calphostin C completely blocked these changes. The above findings indicate that ACTH (1-24) induces cell shape changes in molluscan immunocytes via adenylate cyclase/cAMP/protein kinase A pathway, as well as the activation of protein kinase C.     

Grey-scale ultrasound in the diagnosis of abdominal mass lesions

With the introduction of grey-scale imaging, the diagnostic capability of ultrasound has been greatly increased. Previously, ultrasound images were limited to a bistable presentation that did not distinguish between high- and low-level echoes. As a result the images could be interpreted by only a few experienced ultrasonographers. Grey-scale imaging with the use of a television scan converter allows both the strong and the weaker echoes to be displayed, so that both the outline and the internal texture of normal abdominal organs and lesions can be visualized on a single scan. Abnormalities are now more readily identified and their relation to normal organs is more easily appreciated so that the scans can be interpreted not only by the ultrasonographer but also by the clinician. Several cases are presented in which grey-scale ultrasound was used.     

Measurement of the ultrasonic attenuation of fat at high frequency

RATIONALE AND OBJECTIVES: High-frequency ultrasound devices are often limited by a decreased depth of acoustic imaging caused by the increased attenuation of tissue at high frequencies. We investigated the role of adipose tissue in this phenomenon. METHODS: A substitution technique was used to calculate the ultrasonic attenuation (decibels per centimeter) of fresh samples of sheep rumen, omental fat, and back fat and swine back fat and various concentrations of bovine milk fat at 22 degrees C and 37 degrees C for frequencies of 15 and 20 MHz. RESULTS: The attenuation was significantly higher for sheep adipose tissue than for the intestinal wall, in descending order, omental fat, back fat, and rumen wall (P < 0.01). A correlation was found between bovine milk fat concentrations and attenuation at both frequencies (R2 > 0.9). The attenuation of adipose tissues decreased significantly with an increase in temperature (P < 0.01), whereas the attenuation of sheep rumen showed no significant change (P > 0.1). CONCLUSIONS: The ultrasonic attenuation of fat may contribute to limitations on the use of high-frequency ultrasound in clinical situations in which adipose tissue is present.     

In vivo target-specific delivery of macromolecular agents with MR-guided focused ultrasound

Pelvic cartilage of chick embryo was used to demonstrate that presence of boron in culture medium decreases synthesis of proteoglycans, collagen and total proteins but on the other hand increases the release of these macromolecules. However, when glucose concentration in culture medium is brought to 22mM, the synthesis decrease is no longer observed, whereas release increase persists. Proteins released into the culture medium included heat shock proteins (70 hsp) and tumor necrosis factor alpha (TNF alpha). The amount of phosphorylated proteins was enhanced in presence of boron while endoprotease activity in cartilage and in culture medium was significantly augmented. The in vitro effects of boric acid may explain its in vivo effect on wound healing.     

Differential diagnosis of hepatocellular nodular lesions

While certain neuroactive volatile organic compounds (VOCs) have been reported to have an uneven distribution in various anatomically distinctive brain regions, this has not yet been reported for the short-chain aliphatic halogenated hydrocarbons. Therefore, the uptake and regional brain distribution of 1, 1, 1-trichloroethane (TRI) in mice and rats following inhalation exposure were examined. Male Sprague-Dawley rats and CD-1 mice were exposed to TRI at either 3500 or 5000 ppm for 10, 30, 60, or 120 min. Seven brain regions from rats and three from mice were sampled, and TRI concentrations in the blood and brain tissues were determined by headspace gas chromatography. In both species, the medulla oblongata was found to have the highest TRI concentrations, while cortex (in both species) and hippocampus (only sampled in rats) contained the lowest TRI concentrations. Substantial differences were also observed between the two species, as the mice exhibited higher capacity to accumulate TRI in the blood as well as in the brain regions. It appears that lipid content is a main factor influencing the differential disposition of TRI among the brains regions. Physiological differences in the respiratory systems of the two species and the physiochemical properties of the chemical favoring diffusion toward lipid-rich compartments could also have been expected to account for the patterns of regional distribution and species differences.     

The sonarographic diagnosis of prostatic and periprostatic cysts on high resolution transrectal ultrasound imaging]

OBJECTIVE: To review the different aspects of epididymal tumors, with special reference to adenomatoid tumor of the epididymis (mesothelial neoplasm). Two such cases are reported herein. METHODS: Two cases of adenomatoid tumor of the epididymis are described. The clinical features, diagnosis and treatment are discussed, within the context of the algorithm recently presented by Pellicé and co-workers. RESULTS/CONCLUSION: Most of the epididymal tumors are benign and treatment using a scrotal approach will suffice. However, inguinotomy should be performed when the benign nature of the tumor cannot be established unequivocally.     

Multicoil array for high resolution imaging of the breast

An RF multicoil array for high resolution imaging of the breast is presented. The RF multicoil is incorporated into a dedicated breast imaging apparatus that holds either breast in gentle compression during imaging. Simulations and imaging experiments demonstrate the high sensitivity and RF homogeneity of the multicoil array. Direct comparisons are made between the multicoil and a surface coil. In vivo images are presented to demonstrate the homogeneity of the RF field of the multicoil over the entire breast. An in vivo image of both high temporal and spatial resolution is shown, which demonstrates the sensitivity of the RF multicoil array that may be achieved in a practical imaging experiment.