A Comprehensive Review of In-Body Biomedical Antennas: Design, Challenges and Applications

In-body biomedical devices (IBBDs) are receiving significant attention in the discovery of solutions to complex medical conditions. Biomedical devices, which can be ingested, injected or implanted in the human body, have made it viable to screen the physiological signs of a patient wirelessly, without regular hospital appointments and routine check-ups, where the antenna is a mandatory element for transferring bio-data from the IBBDs to the external world. However, the design of an in-body antenna is challenging due to the dispersion of the dielectric constant of the tissues and unpredictability of the organ structures of the human body, which can absorb most of the antenna radiation. Therefore, various factors must be considered for an in-body antenna, such as miniaturization, link budget, patient safety, biocompatibility, low power consumption and the ability to work effectively within acceptable medical frequency bands. This paper presents a comprehensive overview of the major facets associated with the design and challenges of in-body antennas. The review comprises surveying the design specifications and implementation methodology, simulation software and testing of in-body biomedical antennas. This work aims to summarize the recent in-body antenna innovations for biomedical applications and indicates the key research challenges.

Switchable edge-line coupler based on parity time-reversal duality symmetry

A compact broadband Edge-Line Coupler (ELC) based on Parity Time-reversal Duality (PTD) symmetry has been conceived, designed, constructed and measured. The coupler connects four PTD bifilar edge lines (BELs), recently introduced by the authors. The PTD-BELs are constituted by a parallel plate waveguide whose walls are formed by a junction between Perfect Electric Conductor (PEC) and Perfect Magnetic Conductor (PMC) boundary conditions. Reversing the axis orthogonal to the plates interchanges the position of PEC and PMC. Such a waveguide supports unimodal transverse electromagnetic (TEM) propagation, extremely confined along the top and bottom junction edges; its propagation is protected against backscattering from any discontinuity that preserves the PTD symmetry. The ELC presented here is constituted by a 4-port junction in which each port is intrinsically matched due to the PTD symmetry, strongly coupled with a second port, strongly decoupled with a third port, and weakly coupled with a fourth port. The ELC is designed by using a mushroom metasurface for the PMC portion of the device; the connection is based on a switch circuit which imposes open and short conditions on the two opposite sides of the structure. Switching simultaneously the open and short circuits reroutes the signal in a different port, while maintaining the same level of coupling with the other ports. A static prototype has been built and its measurements have confirmed the matching performance and the good directionality of the coupler in a broadband frequency range between 24 and 30 GHz.

The Use of Intracranial Vessel Wall Magnetic Resonance Imaging to Detect a Presumptive Syphilitic Brain Aneurysm

ABSTRACT

Syphilitic intracranial aneurysm is a rare presentation of meningovascular syphilis in developed countries. In this case report, we discuss the utilization of the intracranial vessel wall magnetic resonance imaging in the management of a patient with a rare fusiform brain aneurysm, positive syphilis serologies, and inconclusive cerebrospinal fluid findings.

Development and validation of an economical uric acid-Fe3+/Fe2+-ferrozine-based colorimetric assay to estimate uric acid level of pure and biological samples

This work presents the development and validation of a simple, rapid, and cost-effective spectrophotometric method for quantitative analysis of uric acid in biological samples. The method relies upon uric acid-led reduction of Fe(III) to Fe(II) of sample/standard solutions which stoichiometrically engages ferrozine to form a magenta-colored complex. Different parameters including pH, metal and chelator concentrations, temperature, etc., were optimized for the maximum intensity and stability of the complex. The uric acid concentrations of synthetic/plasma solutions were determined by comparing the color intensity of Fe(ferrozine)32+ complex produced by test solution with the standard curve formed by known uric acid concentrations. The method was validated in accordance with ICH guidelines and subjected to human plasma analysis. The results obtained were compared with a reference (enzymatic) method which revealed that there was no significant difference between the two methods at 95% confidence level. The method is highly specific, precise, linear, accurate, and robust.

Recurrent urinary tract infections caused by Raoultella planticola after kidney transplant

Recurrent urinary tract infections are difficult to manage in patients with a history of kidney transplant and may contribute to graft loss. Few cases describe recurrent urinary tract infections due to Raoultella planticola in this population. We describe the management of recurrent urinary tract infections due to R planticola in a kidney transplant recipient and review other case reports of urinary tract infections due to this organism.

1592. Safety of Oral Trimethoprim/Sulfamethoxazole Prophylaxis in Renal Transplant Recipients

Background

Trimethoprim/sulfamethoxazole (TMP/SMX) is the agent of choice for Pneumocystis jirovecii Pneumonia (PJP) prophylaxis in renal transplant (RT) recipients. All other prophylactic agents are considered second-line due to efficacy, drug intolerances, cost, administration requirements, and lack of coverage of Toxoplasma. Anecdotally, alternative agents are commonly used at our institution due to clinician hesitancy and perceived risk of adverse drug reactions (ADRs). Our objective was to assess the safety of TMP/SMX prophylaxis in RT recipients.

Methods

RT recipients transplanted at a tertiary US medical center between May 9, 2015 and November 30, 2017 were retrospectively identified. Patient charts were reviewed for antimicrobial agents used for PJP prophylaxis and ADRs due to TMP/SMX. ADRs were classified using the National Institutes of Health, Division of Microbiology and Infectious Diseases (DMID) criteria and were scored for probability of association with TMP/SMX using the Naranjo ADR probability scale.

Results

During the study period, 64 of 95 adult RT recipients (67.4%) received TMP/SMX for PJP prophylaxis. Of the patients who received TMP/SMX, 26 (40.6%) had a clinician-documented ADR attributed to TMP/SMX and 24 (37.5%) had the drug discontinued. The most frequent provider-reported ADRs due to TMP/SMX were hyperkalemia (10 patients, 15.6%), neutropenia (nine patients, 14.1%), and elevated liver function tests (LFTs) (three patients, 4.7%). However, when classified using DMID criteria, nine of the 26 ADRs were less severe than Grade 1. Two ADRs were Grade 3 (severe), including 1 case each of neutropenia and elevated LFTs. No ADRs were Grade 4 (life-threatening). All ADRs received a score ≤4 on the Naranjo ADR probability scale, indicating a possible ADR related to TMP/SMX. Often, ADRs did not resolve or other additional medication adjustments were needed following TMP/SMX discontinuation (19 of 26 patients, 73.1%). No cases of PJP occurred.

Conclusion

TMP/SMX is underutilized in RT recipients at our institution, despite being well-tolerated and efficacious. Clinician hesitancy with TMP/SMX in this population may be unfounded. Internal efforts are underway to increase the use of TMP/SMX in RT recipients.

Disclosures

All authors: No reported disclosures.

1225. High Rate of Linezolid (LZD) Nonsusceptibility (LNS) Among Enteric Vancomycin-Resistant Enterococci (VRE) Recovered From Hospitalized Patients Actively Screened for VRE Rectal Colonization (VREC)

Background

Select hospitalized patients are actively screened for VREC but VRE isolates may not undergo antibiotic susceptibility testing. We sought to identify predictors of daptomycin (DAP) nonsusceptibility (DNS, MIC > 4) and LNS (MIC > 2) among enteric VRE isolates recovered from patients actively screened for VREC for which antibiotic susceptibility testing was not preformed.

Methods

This was a retrospective study of consecutive adults admitted to a surgical intensive care unit (ICU) or associated medical unit between June 1, 2017 and March 1, 2018 who had a VRE isolate from active screening. Only index isolates were included. DAP and LZD MICs were determined by Etest. Patient- and antimicrobial-level data, including ambulatory prescriptions, dating back to January 1, 2016 were collected. Multivariable logistic regression models were used to determine predictors of DNS and LNS VRE.

Results

In total, 64 patients’ VRE rectal isolates were included. Fifty-nine (92.2%) were E. faecium and 50 (78.1%) were from ICU patients. Thirty-seven patients (57.8%) were female and the mean age ± SD was 60 ± 13 years. Five (7.8%) and 20 (31.3%) patients had previous abdominal transplant and VRE infection, respectively. DAP and LZD MIC distributions are shown in the table below. Forty-one (64.1%) VRE isolates were LNS, including five LZD-resistant isolates. Only one (1.6%) isolate was DNS precluding an analysis of DNS predictors; 12 (18.8%) isolates had a DAP MIC > 2 mg/L. Common antimicrobial exposures prior to index VRE isolate included: vancomycin (62.5%), ceftriaxone (64.1%), cefepime (53.1%), metronidazole (50%), and ciprofloxacin (50%). Previous LZD (17.2%) and DAP (15.6%) exposure were less common. In a multivariable model, number of previous cefazolin doses (adjusted odds ratio (aOR) 0.74 95% confidence interval (CI) 0.55–0.95), and previous tobramycin exposure (aOR 0.15, 95% CI 0.02–0.81) were inversely associated with LNS. Previous LZD exposure was not associated with LNS.

Conclusion

LNS was common amongst VRE isolates in this cohort. Previous LZD exposure was infrequent and not associated with LNS. LZD susceptibility testing among VRE isolates recovered from patients actively screened for VREC warrants clinical consideration.

Disclosures

All authors: No reported disclosures.

Phytochemical and in vitro total antioxidant capacity analyses of peel extracts of different cultivars of Cucumis melo and Citrullus lanatus

CONTEXT

Cucumis melo Linn. (Cucurbitaceae) and Citrullus lanatus Thunb. (Cucurbitaceae) are desert vegetables popular for their nutritional value and year round availability. The pulp and seeds of these plants are used for dietary purposes or as medications for certain ailments in the folk medicinal system. Peels of the fruit are either wasted or used as feed of grazing animals.

OBJECTIVE

A detailed investigation regarding the chemical constituents and antioxidative analyses of the peel extract of fully ripened fruits from different cultivars of the two vegetables was carried out here for the first time.

MATERIALS AND METHODS

Chemical constituents of the peel extracts of C. melo and C. lanatus cultivars in methanol, 1-butanol, chloroform and n-hexane were analysed by gas chromatography-mass spectrometry (GC-MS) and the antioxidative properties were evaluated using standard in vitro antioxidative assays.

RESULTS

The results demonstrated large variation in the chemical constituents of the extracts including alkanes, saturated and unsaturated fatty acids and their esters, cyclic ketones, aldehydes, phenolic compounds and anthocyanin derivatives. Total phenolic content ranged from 2.96-0.85 mg/L gallic acid equivalents for different extracts.

DISCUSSION AND CONCLUSION

Employing GC-MS analyses and standard in vitro antioxidative assays, the data presented here clearly demonstrate the potency of C. melo and C. lanatus extracts as antioxidant and radical scavenger plants which may be used as good sources of natural antioxidants. The peels of both the plants can be added to the diet at various stages to compensate food shortage and dietary deficiency problems of living beings.

Posttransplantation lymphoproliferative disorder with skin involvement

Posttransplantation lymphoproliferative disorders (PTLD) are lymphoid proliferations or lymphomas that develop as a result of immunosuppression in recipients of solid organs and bone marrow allografts. The disorder is seen in 1-2% of renal transplant recipients with a variable time period of presentation and is usually seen within the first year following transplantation. We report a case of B-cell lymphoma (PTLD WHO class-3) presenting with skin involvement in a patient of renal transplantation, 8 years after receiving the transplant.