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Biomedical subjects

B J Wood

Publications and source records attributed to B J Wood.

At least 19 recordsLinked to original sources
PubMed2006

Effect of endocervical-specimen adequacy on detection of Chlamydia trachomatis by the APTIMA COMBO 2 assay.

Six hundred one endocervical specimens were analyzed for Chlamydia trachomatis by the APTIMA Combo 2 assay and evaluated for columnar epithelial cell adequacy by direct fluorescent-antibody staining. With 5.5% positive adequate and 7.8% positive inadequate specimens (P=0.27), the study suggested no difference in positivity rates due to specimen adequacy when this amplified technology was used.

Cervix Uteri↗
PubMed2006

Respiratory motion compensation with tracked internal and external sensors during CT-guided procedures.

This paper investigates the possibility of using the motion of a patient's anterior surface in combination with a motion model to compensate for internal respiratory motion during tracked biopsies. Position data from two electromagnetically tracked sensors, one placed on the patient's sternum, the other incorporated into a biopsy needle, were acquired during a liver biopsy. The data were used to evaluate the correlation between the position measurements of the two sensors and to derive an affine motion model to assess respiratory motion compensation for image-guided interventional procedures. The correlation reached up to 94% for ranges of steady respiration. The residual motion of the internal sensor after compensation is reduced by a factor of approximately four.

Biopsy↗
PubMed2004

Radio frequency ablation of small renal tumors:: intermediate results.

PURPOSE: With evolving radio frequency technology, the clinical application of radio frequency ablation (RFA) has been actively investigated in the treatment for small renal tumors. We present our intermediate patient outcomes after RFA. MATERIALS AND METHODS: Since January 2001, 17 patients with a total of 24 hereditary renal tumors ranging from 1.2 to 2.85 cm were treated with RFA using the 200 W Cool-tip RF System (Radionics, Burlington, Massachusetts) under laparoscopic (9) or percutaneous (8) guidance and had a minimum 1-year followup. A percutaneous approach was considered unsuitable if kidney tumors were contiguous to bowel, ureter or large vessels. Treatment eligibility criteria included an average tumor diameter of less than 3.0 cm, tumor growth during 1 year and solid appearance with contrast enhancement (HU change greater than 20) on computerized tomography (CT). Postoperative followup consisted of CT with and without intravenous contrast, and renal function assessment at regular intervals. RESULTS: Median patient age was 38 years (range 20 to 51). At a median followup of 385 days (range 342 to 691), median tumor or thermal lesion diameter decreased from 2.26 to 1.62 cm (p = 0.0013), and only 1 lesion (4%), which was located centrally near the hilum, exhibited contrast enhancement (HU change greater than 10) on CT at 12 months. Of the 15 renal tumors ablated laparoscopically, 13 were in direct contact with the bowel and 2 were abutting the ureter, necessitating mobilization before RFA. Laparoscopic ultrasound was used to guide radio frequency electrode placement and monitor the ablation process in these cases. Operative time and intraoperative blood loss (mean +/- standard mean of error) were 243 +/- 29 minutes and 67 +/- 9 cc, respectively. In 1 patient whose ureter was adherent to the tumor a ureteropelvic junction obstruction developed after laparoscopic RFA, requiring open repair. CONCLUSIONS: At the minimum 1-year followup 23 of 24 ablated tumors lacked contrast uptake on CT, meeting our radiographic criteria of successful RFA treatment. RFA treatment of small renal tumors using the Radionics system appears to result in superior treatment outcomes compared to those of earlier series with lower radio frequency power generators. A high wattage generator might attain more consistent energy deposition with subsequent cell death in the targeted tissue due to less convective heat loss.

Adult↗
PubMed2003

The 'zero charge' partitioning behaviour of noble gases during mantle melting.

Noble-gas geochemistry is an important tool for understanding planetary processes from accretion to mantle dynamics and atmospheric formation. Central to much of the modelling of such processes is the crystal-melt partitioning of noble gases during mantle melting, magma ascent and near-surface degassing. Geochemists have traditionally considered the 'inert' noble gases to be extremely incompatible elements, with almost 100 per cent extraction efficiency from the solid phase during melting processes. Previously published experimental data on partitioning between crystalline silicates and melts has, however, suggested that noble gases approach compatible behaviour, and a significant proportion should therefore remain in the mantle during melt extraction. Here we present experimental data to show that noble gases are more incompatible than previously demonstrated, but not necessarily to the extent assumed or required by geochemical models. Independent atomistic computer simulations indicate that noble gases can be considered as species of 'zero charge' incorporated at crystal lattice sites. Together with the lattice strain model, this provides a theoretical framework with which to model noble-gas geochemistry as a function of residual mantle mineralogy.

Journal Article↗
PubMed2001

The Earth's mantle.

Seismological images of the Earth's mantle reveal three distinct changes in velocity structure, at depths of 410, 660 and 2,700 km. The first two are best explained by mineral phase transformations, whereas the third-the D" layer-probably reflects a change in chemical composition and thermal structure. Tomographic images of cold slabs in the lower mantle, the displacements of the 410-km and 660-km discontinuities around subduction zones, and the occurrence of small-scale heterogeneities in the lower mantle all indicate that subducted material penetrates the deep mantle, implying whole-mantle convection. In contrast, geochemical analyses of the basaltic products of mantle melting are frequently used to infer that mantle convection is layered, with the deeper mantle largely isolated from the upper mantle. We show that geochemical, seismological and heat-flow data are all consistent with whole-mantle convection provided that the observed heterogeneities are remnants of recycled oceanic and continental crust that make up about 16 and 0.3 per cent, respectively, of mantle volume.

Journal Article↗
PubMed2001

The Earth's 'missing' niobium may be in the core.

As the Earth's metallic core segregated from the silicate mantle, some of the moderately siderophile ('iron-loving') elements such as vanadium and chromium are thought to have entered the metal phase, thus causing the observed depletions of these elements in the silicate part of the Earth. In contrast, refractory 'lithophile' elements such as calcium, scandium and the rare-earth elements are known to be present in the same proportions in the silicate portion of the Earth as in the chondritic meteorites-thought to represent primitive planetary material. Hence these lithophile elements apparently did not enter the core. Niobium has always been considered to be lithophile and refractory yet it has been observed to be depleted relative to other elements of the same type in the crust and upper mantle. This observation has been used to infer the existence of hidden niobium-rich reservoirs in the Earth's deep mantle. Here we show, however, that niobium and vanadium partition in virtually identical fashion between liquid metal and liquid silicate at high pressure. Thus, if a significant fraction of the Earth's vanadium entered the core (as is thought), then so has a similar fraction of its niobium, and no hidden reservoir need be sought in the Earth's deep mantle.

Journal Article↗
PubMed2001

Radiofrequency thermal ablation of a splenic metastasis.

Effective local ablation of large tumors with radiofrequency has been made possible by recent advancements. Tumor ablation with radiofrequency has been described mainly in the liver, but also recently in the kidney, adrenal gland, lung, and breast. A rapidly growing splenic metastasis from renal cell carcinoma was effectively treated percutaneously, with US guidance. Focal splenic disease may not be a common indication for ablation; however, further work is necessary to evaluate the safety and efficacy of this procedure in this setting.

Carcinoma, Renal Cell↗
PubMed2001

Radiofrequency liver ablation: experimental comparative study of water-cooled versus expandable systems.

OBJECTIVE: We evaluate the uniformity and reproducibility of thermal lesion ablation and quantify the volume of tissue destruction and hemorrhage induced with two different commercially available radiofrequency ablation devices. MATERIALS AND METHODS: A four-array anchor expandable needle electrode and a triple-cluster cooled-tip needle electrode were used to induce lesions in three explanted calf livers and in vivo in eight swine livers. The sizes of the radiofrequency-induced lesions were macroscopically evaluated by measuring two perpendicular dimensions immediately after the experiment. Bleeding was evaluated by weighing gauze swabs used to dry the hemorrhage caused by electrode insertions. RESULTS: In explanted liver, the mean diameter of the radiofrequency-induced lesion was 5.3 +/- 0.7 cm for the cooled-tip needle and 3.7 +/- 0.4 cm for the expandable needle (p = 0.042), which correspond to approximate volumes of 65.35 +/- 26.22 cm(3) and 26.67 +/- 9.59 cm(3), respectively (p < 0.002). In vivo, the mean diameter was 3.7 +/- 0.4 cm for the cooled-tip needle and 3 +/- 0.4 cm for the expandable needle (p < 0.0001), which correspond to approximate volumes of 24.18 +/- 7.56 cm(3) and 11.16 +/- 3.65 cm(3), respectively (p < 0.0001). Blood loss attained a median value of 3.5 g for the cooled-tip needle and 2.6 g for the expandable needle; this difference was not statistically significant (p = 0.06). CONCLUSION: The cooled-tip needle induced significantly larger lesions than the expandable needle, but the lesions produced by the expandable needle are more reproducible, uniform, and spheric. The larger size of the lesions produced by the cooled-tip needle may be attributed to the higher maximum power used by the generator and the higher energy deposition, which is due to the cooling of the needle electrode.

Animals↗
PubMed2001

Retroperitoneoscopic-guided radiofrequency ablation of renal tumors.

OBJECTIVE: Minimally invasive approaches to the management of renal tumors are being studied intensively in urology. Herein, we describe the use of multiple organ-sparing techniques for the management of tumors in a patient with von Hippel Lindau disease (VHL). MATERIALS AND METHODS: A 42 year-old woman with VHL underwent a right partial adrenalectomy and a left renal radiofrequency ablation (RFA) of two renal tumors. RESULTS: A 2.2 cm solitary right adrenal pheochromocytoma was resected using a transperitoneal approach. A retroperitoneal approach to the left kidney was performed and RFA of the two renal tumors completed using sonographic guidance. On the 5-month follow-up CT scan, there was no evidence of residual adrenal tumors and both renal lesions lacked contrast enhancement. No complications occurred during the post-operative recovery. CONCLUSIONS: Multiple organ-ablative laparoscopic procedures may be performed in a single sitting. Laparoscopic partial adrenalectomy is an effective technique in patients with bilateral tumors or a familial syndrome predisposing to multiple adrenal tumors. Further study of renal RFA is required to assess the long-term durability of the procedure.

Adrenal Gland Neoplasms↗
PubMed2001

Sources of the eutrophication problems associated with toxic algae: an overview.

Blooms of cyanobacteria (toxic blue-green algae) can produce health and environmental hazards in water, including water used for drinking or recreational purposes. How, why, and when these blooms are produced, as well as how to deal with them, are questions whose answers are vital to the safeguarding of public health in regions where the algae occur. The blooms are linked to eutrophication of water, and this paper discusses the eutrophication problems, their nature, and their relevance to the production of cyanobacteria. Nutrient limitations on algal productivity are considered, as is the involvement of the atmosphere, the storage of nutrients in soils, and the influence of anthropogenic activity.

Agriculture↗
PubMed2000

Helical CT and ureteral colic.

The advantages of nonenhanced helical CT for the diagnosis of ureteral calculi include rapid scan time and patient throughput, safety (no contrast, less radiation), cost-effectiveness, high accuracy, minimal invasiveness, and ability to suggest of alternative diagnoses for flank pain--urologic and otherwise. Size measurement and location in the ureter, the two most important determinants of therapy, are precise with CT. It is particularly good for imaging small or radiolucent calculi, and calculi located at the ureterovesical. Secondary signs of obstruction and the soft-tissue rim sign are additional aids to the routine diagnosis of ureteral calculi. CT numbers indicate the fragility and therefore the likelihood of successful treatment of a calculus. Postprocessing options may help guide management decisions and may help plan interventions. The authors' experience after 30 months of using helical CT exclusively in the work-up of ureteral colic has been extremely favorable. Without hesitation, the authors believe that nonenhanced helical CT is the study of choice for the work-up of ureteral calculi.

Clinical Protocols↗
PubMed2000

Pain after uterine artery embolization for leiomyomata: can its severity be predicted and does severity predict outcome?

PURPOSE: To determine whether the severity of postprocedure pain associated with uterine artery embolization (UAE) for leiomyomata can be predicted and if its severity can predict outcome. MATERIALS AND METHODS: Eighty-one patients underwent UAE and had postprocedure pain managed with use of patient-controlled analgesia (PCA) in the form of an intravenous morphine pump. Baseline uterine and dominant fibroid volumes were calculated for each patient. Attempted doses, doses given, total morphine dose, and maximum numerical rating scale (NRS) score during postprocedure hospitalization were recorded. At 3 months postprocedure, repeat imaging was used to determine uterine and dominant fibroid volume reduction. Each patient also completed a questionnaire assessing change in menstrual bleeding, pelvic pain and pressure symptoms, and satisfaction with symptomatic outcome. Simple regression analysis was used to determine if baseline volumes predicted postprocedure pain and if the pain-related variables could be used to predict outcome. RESULTS: Neither baseline uterine volume nor dominant fibroid volume predicted the severity of postprocedure pain. Similarly, none of the pain-related variables predicted uterine or fibroid volume reduction, symptomatic improvement, or satisfaction with outcome. CONCLUSIONS: Postprocedural pain cannot be predicted based on baseline uterine or fibroid volume and the severity of pain experienced cannot be used to predict outcome.

Adult↗
PubMed2000

Adhesion of microbes using 3-aminopropyl triethoxy silane and specimen stabilisation techniques for analytical transmission electron microscopy.

A variety of adhesive support-films were tested for their ability to adhere various biological specimens for transmission electron microscopy. Support films primed with 3-amino-propyl triethoxy silane (APTES), poly-L-lysine, carbon and ultraviolet-B (UV-B)-irradiated carbon were tested for their ability to adhere a variety of biological specimens including axenic cultures of Bacillus subtilis and Escherichia coli and wild-type magnetotactic bacteria. The effects of UV-B irradiation on the support film in the presence of air and electrostatic charge on primer deposition were tested and the stability of adhered specimens on various surfaces was also compared. APTES-primed UV-B-irradiated Pioloform was consistently the best adhesive, especially for large cells, and when adhered specimens were UV-B irradiated they became remarkably stable under an electron beam. This assisted the acquisition of in situ phase-contrast lattice images from a variety of biominerals in magnetotactic bacteria, in particular metastable greigite magnetosomes. Washing tests indicated that specimens adhering to APTES-primed UV-B-irradiated Pioloform were covalently coupled. The electron beam stability was hypothesised to be the result of mechanical strengthening of the specimen and support film and the reduced electrical resistance in the specimen and support film due to their polymerization and covalent coupling.

Bacillus subtilis↗
PubMed2000

Radio-frequency ablation of renal cell carcinoma: early clinical experience.

PURPOSE: To report the authors' early experience with radio-frequency (RF) ablation of renal cell carcinoma. MATERIALS AND METHODS: Twenty-four percutaneous RF ablation treatments for nine tumors were performed in eight patients with renal cell carcinoma. Indications included coexistent morbidity, previous surgery, or solitary kidney in patients with a life expectancy shorter than 10 years. Smaller (</=3-cm) peripheral lesions (n = 3) were treated with single electrodes. All but one of the larger (>3 cm) and/or central lesions (n = 6) were treated with cluster or multiple electrodes. Patients returned for a second treatment when follow-up imaging depicted tumor enhancement. Follow-up imaging was performed at 1 and 3 months and then at 6-month intervals, with a mean follow-up of 10.3 months. Seven patients were alive at least 6 months after their initial treatment. RESULTS: All five exophytic tumors were free of enhancement. One of three central tumors was free of enhancement. One tumor had both central and exophytic components and was free of enhancement. Three tumors were 3 cm or smaller and free of enhancement. Of the six tumors larger than 3 cm, four were free of enhancement. CONCLUSION: Percutaneous RF ablation is a promising treatment for select patients with renal cell carcinoma. The ultimate role of this modality will continue to evolve and warrants further study.

Aged↗