RF-induced heating for active implantable medical devices in dual parallel leads configurations at 1.5 T MRI.

PURPOSE: The Radiofrequency (RF)-induced heating for an active implantable medical device (AIMD) with dual parallel leads is evaluated in this paper. The coupling effects between dual parallel leads are studied via simulations and experiments methods. The global transfer function technique is used to assess the RF-induced heating for dual-lead AIMDs inside four human body models. METHODS: RF-induced heating for spinal cord stimulator systems with 60 and 90 cm length leads are studied at three parallel dual-lead configurations (closely spaced, 8 mm spaced, and 40 mm spaced) and a single-lead configuration. The global transfer function method is used to develop the AIMD models of different configurations and is used for lead-tip heating assessments inside human body models. RESULTS: In simulation studies, the peak 1g specific absorption rate/temperatrue rises of dual parallel leads systems is lower than those from the single-lead system. In experimental American Society for Testing and Materials phantom studies, the temperature rises for the single-lead AIMD system can be 2.4 times higher than that from dual-lead AIMD systems. For the spinal cord stimulator systems used in the study, the statistical analysis shows the RF-induced heating of dual-lead configurations are also lower than those from the single-lead configuration inside all four human body models. CONCLUSION: For the AIMD system in this study, it shows that the coupling effects between the dual parallel leads of AIMD systems can reduce RF-induced heating. The global transfer function for different spatial distance dual-lead configurations can potentially provide a method for the RF-induced heating evaluation for dual-lead AIMD systems.

Multiparametric MRI prostate PI-RAD scoring in a district general hospital: correlating PI-RADS 3 results with histological findings.

OBJECTIVE: Prostate cancer is the most common male cancer in the UK. In many hospitals, patients are now being referred for a multiparametric (mp) MRI scan of their prostate as part of an evaluation for the presence of prostate cancer, prior to an ultrasound-guided biopsy. Prostate Imaging Reporting and Data System (PI-RADS) score of 3 are defined as "equivocal" for the presence of prostate cancer. Thus, a PI-RADS 3 lesion does not confidently determine whether there is significant prostate disease or not.Our aim is to determine the correlation of PI-RADS 3 prostatic lesions with histology proven, clinically significant cancer. METHODS: We performed a retrospective review on a cohort of 143 consecutive patients. Each patient underwent a mp-MRI scan of their prostate given a PI-RADS score. PI-RADS 3 lesions were analysed further based on histology and categorised into malignant and non-malignant lesions. Prostate-specific antigen (PSA) results and prostatic volume of PI-RADS 3 lesions were also analysed. RESULTS: We identified 45 patients with PI-RADS 3 lesions out of 143 patients. 32 patients subsequently underwent transrectal/transperineal ultrasound-guided biopsy. 43% of patients were found to have had a malignant prostatic adenocarcinoma on histology. The remaining 56% had non-malignant findings. Of those with malignant disease, there was a higher median PSA and lower mean prostatic volume. CONCLUSION: The study confirms that a score of PI-RADS 3 does not accurately differentiate between malignant and non-malignant lesions. Further investigations such as ultrasound-guided prostate biopsy and PSA parameters are required to accurately ascertain the nature of a prostate lesion with PI-RADS score 3. ADVANCES IN KNOWLEDGE: An ultrasound-guided prostate biopsy in patients with PI-RADS 3 remains of paramount importance when distinguishing malignant vs non-malignant lesions. Multicentre data of MRI findings with PI-RADS 3 scores is required to yield a sample size large enough to carry out statistical analysis.

Accessory articulation of cervical vertebral transverse process: a rare case.

There are several anatomical variants of the cervical vertebrae described in literature ranging from benign findings to those with varying clinical implications, including association with congenital diseases. We describe a case of an extremely rare anatomical variant of the cervical spine consisting of an accessory articulation of the cervical vertebrae C4 and C5 right transverse processes. The case is of a 35-year-old female who presented to primary care with 6-week history of intermittent, dull neck pain. An X-ray of the cervical spine was obtained which did not demonstrate radiological evidence of an acute fracture, dislocation, nor vertebral collapse. However, the X-ray revealed subtle multilevel anterior marginal osteophytic lipping. As a minor fragmented fracture or osteophytic growth could not be excluded; the patient proceeded to have a CT of the cervical spine. This revealed an accessory articulation of both the C4 and C5 right transverse processes, an extremely rare anatomical variant. Our comparison of both X-ray and CT imaging modality results highlighted the importance of utilising CT in identification in the accessory articulation anomaly, which aids in directing patient to appropriate care. Although similar cases may have been seen in clinical practice, to our knowledge, there are no previously documented C4-5 accessory articulations in the literature.

Sources, presence and potential effects of contaminants of emerging concern in the marine environments of the Great Barrier Reef and Torres Strait, Australia.

Current policy and management for marine water quality in the Great Barrier Reef (GBR) in north-eastern Australia primarily focusses on sediment, nutrients and pesticides derived from diffuse source pollution related to agricultural land uses. In addition, contaminants of emerging concern (CECs) are known to be present in the marine environments of the GBR and the adjacent Torres Strait (TS). Current and projected agricultural, urban and industrial developments are likely to increase the sources and diversity of CECs being released into these marine ecosystems. In this review, we evaluate the sources, presence and potential effects of six different categories of CECs known to be present, or likely to be present, in the GBR and TS marine ecosystems. Specifically, we summarize available monitoring, source and effect information for antifouling paints; coal dust and particles; heavy/trace metals and metalloids; marine debris and microplastics; pharmaceuticals and personal care products (PPCPs); and petroleum hydrocarbons. Our study highlights the lack of (available) monitoring data for most of these CECs, and recommends: (i) the inclusion of all relevant environmental data into integrated databases for building marine baselines for the GBR and TS regions, and (ii) the implementation of local, targeted monitoring programs informed by predictive methods for risk prioritization. Further, our spatial representation of the known and likely sources of these CECs will contribute to future ecological risk assessments of CECs to the GBR and TS marine environments, including risks relative to those identified for sediment, nutrients and pesticides.

The use of FDG-PET/CT in extranodal Rosai-Dorfman disease of bone.

We report the case of a 41-year-old man with extranodal Rosai-Dorfman disease (RDD), presenting with clinically detectable bone involvement only. The use of FDG-PET/CT in the diagnosis of RDD is discussed.

Formation of Zn- and Fe-sulfides near hydrothermal vents at the Eastern Lau Spreading Center: implications for sulfide bioavailability to chemoautotrophs.

BACKGROUND: The speciation of dissolved sulfide in the water immediately surrounding deep-ocean hydrothermal vents is critical to chemoautotrophic organisms that are the primary producers of these ecosystems. The objective of this research was to identify the role of Zn and Fe for controlling the speciation of sulfide in the hydrothermal vent fields at the Eastern Lau Spreading Center (ELSC) in the southern Pacific Ocean. Compared to other well-studied hydrothermal systems in the Pacific, the ELSC is notable for unique ridge characteristics and gradients over short distances along the north-south ridge axis. RESULTS: In June 2005, diffuse-flow (< 50 degrees C) and high-temperature (> 250 degrees C) vent fluids were collected from four field sites along the ELSC ridge axis. Total and filtered Zn and Fe concentrations were quantified in the vent fluid samples using voltammetric and spectrometric analyses. The results indicated north-to-south variability in vent fluid composition. In the high temperature vent fluids, the ratio of total Fe to total Zn varied from 39 at Kilo Moana, the most northern site, to less than 7 at the other three sites. The concentrations of total Zn, Fe, and acid-volatile sulfide indicated that oversaturation and precipitation of sphalerite (ZnS(s)) and pyrite (FeS2(s)) were possible during cooling of the vent fluids as they mixed with the surrounding seawater. In contrast, most samples were undersaturated with respect to mackinawite (FeS(s)). The reactivity of Zn(II) in the filtered samples was tested by adding Cu(II) to the samples to induce metal-exchange reactions. In a portion of the samples, the concentration of labile Zn2+ increased after the addition of Cu(II), indicating the presence of strongly-bound Zn(II) species such as ZnS clusters and nanoparticles. CONCLUSION: Results of this study suggest that Zn is important to sulfide speciation at ELSC vent habitats, particularly at the southern sites where Zn concentrations increase relative to Fe. As the hydrothermal fluids mix with the ambient seawater, Zn-sulfide clusters and nanoparticles are likely preventing sulfide oxidation by O2 and reducing bioavailability of S(-II) to organisms.

Pseudopolarographic determination of Cd2+ complexation in freshwater.

Pseudopolarography was used to detect Cd2+ complexes in samples collected at several locations along the Potomac River in June and September, 2004. Irrespective of site and sampling time, no weak inorganic Cd2+ species were present. However, up to two stable Cd(2+)-organic complexes were detected at each site. These unknown Cd2+ complexes were characterized by their half-wave potential (E1/2). The E1/2 values indicated certain Cd2+ complexes were common at different sites during each sampling but different complexes were observed in June and September. A Cd2+ chelate scale, generated from model ligands, was used to estimate the thermodynamic stability constants (K(THERM)) of the unknown complexes, which ranged from log K(THERM) = 21.5-32.0. Pseudopolarography did not recover all Cd2+ in the samples. This was partly attributed to highly stable Cd-sulfide species; owing to the presence of acid volatile sulfide at concentrations greater than total dissolved Cd2+. These electrochemically inert species may be multinuclear Cd-sulfide clusters and/ or nanoparticles with K(THERM) values that exceed the detection window of pseudopolarography (log K(THERM) > 34.4).