Dielectric Coagulometry: A New Approach To Estimate Venous Thrombosis Risk

Pathophysiology of acute graft-versus-host disease from the perspective of hemodynamics determined by dielectric analysis

BACKGROUND

Numerous reports have demonstrated that the pathophysiology of graft-versus-host disease (GVHD) during hematopoietic stem cell transplantation (HSCT) is closely related to vascular endothelial disorders and coagulation abnormalities. We previously presented the discovery of a principle and the development of a novel instrument for measuring whole blood coagulation. This was achieved by assessing the variations in the dielectric properties of whole blood.

AIM

To investigate how GVHD affects the changes of dielectric properties of whole blood in patients with HSCT.

METHODS

We examined the changes of dielectric properties of whole blood and erythrocyte proteins by sodium dodecyl sulfate-polyacrylamide gel electrophoresis sequentially in patients with HSCT and compared it with clinical symptoms and inflammatory parameters of GVHD.

RESULTS

During severe GVHD, the dielectric relaxation strength markedly increased and expression of band3 decreased. The dielectric relaxation strength normalized with the improvement of GVHD. In vitro analysis confirmed that the increase of relaxation strength was associated with severe erythrocyte aggregates, but not with decreased expression of band3.

CONCLUSION

Severe erythrocyte aggregates observed in GVHD may cause coagulation abnor malities and circulatory failure, which, together with the irreversible erythrocyte dysfunction we recently reported, could lead to organ failure.

Influence of Na+ disorder on cytoplasmic conductivity and cellular electromagnetic (EM) energy absorption of human erythrocytes (PONE-D-21-36089)

Cytoplasmic conductivity of human erythrocytes may be significantly disturbed by the composition of the external suspending media. Effects of external NaCl on cytoplasmic conductivity of human erythrocyte (Human Red Blood Cells, HRBC) were investigated in a simple NaCl system. Using thermodynamic theory cytoplasmic conductivities could be calculated from internal [K+], [Na+], [Cl-] and [HCO3-]. Effect of cell volume and cell water changes were introduced and allowed for using the Debye-Hückel-Onsager relation and Walden's rule of viscosity. Cell volume and cell water change of HRBCs were measured in suspending isotonic solutions with conductivities from 0.50 S m-1 up to hypertonic solutions of conductivity of 2.02 S m-1 at selected temperatures of 25°C (standard benchmark temperature) and 37°C (physiological temperature). In isotonic solutions, cytoplasmic conductivity of human erythrocyte decreases with rise in the external media ionic concentration and vice versa for hypertonic solutions. The HRBC is capable of rapidly regulating its volume (and shape) over quite a wide range of osmolality. Specific Absorption Rate (SAR, 900 MHz) values (W kg-1) of electromagnetic radiation are below safe limits at non-physiological 25°C but above legal limits at 37°C [National Council on Radiation Protection and Measurements, NCRP]. However, at 37°C under both hypertonic [Na+] and isotonic but low [Na+], SAR increases further beyond legal limits.

Evaluation of fibrinogen concentration by clot firmness using a dielectric blood coagulation test system

PURPOSE

To determine if fibrinogen concentration can be evaluated by dielectric permittivity changes in dielectric blood coagulation testing (DBCM) during cardiovascular surgery with cardiopulmonary bypass (CPB).

METHODS

We performed a single-center prospective observational study at a university hospital. One hundred patients undergoing cardiovascular surgery with CPB were enrolled. Whole-blood samples were obtained after weaning from CPB, and dielectric clot strength (DCS) was measured by intrinsic pathway testing with or without heparinase in DBCM. The FIBTEM test was performed during rotational thromboelastometry using the same samples, and maximum clot firmness (MCF) was evaluated. Spearman's correlation analysis was performed, and receiver operating characteristics (ROC) curve analyses were used to evaluate the performance of hypofibrinogenemia detection.

RESULTS

DCS showed a strong positive correlation with plasma fibrinogen concentration (Rs = 0.76, P < 0.0001). The area under the ROC curve for evaluating plasma fibrinogen concentration < 200 mg/dL was 0.91 (95% confidence interval (CI) 0.85-0.97) for DCS, compared with 0.88 (95% CI 0.81-0.94) for FIBTEM MCF. The optimal cutoff value of DCS was 17.0 (sensitivity 94%, specificity 80%).

CONCLUSIONS

DCS variables showed a significantly strong correlation with plasma fibrinogen concentration, and the diagnostic performance for hypofibrinogenemia was comparable to that for FIBTEM MCF. This novel methodology has the potential to provide a point-of-care test with sufficient accuracy for the detection of perioperative hypofibrinogenemia during cardiovascular surgery with CPB.

Assessment of fibrinolytic status in whole blood using a dielectric coagulometry microsensor

Rapid assessment of the fibrinolytic status in whole blood at the point-of-care/point-of-injury (POC/POI) is clinically important to guide timely management of uncontrolled bleeding in patients suffering from hyperfibrinolysis after a traumatic injury. In this work, we present a three-dimensional, parallel-plate, capacitive sensor - termed ClotChip - that measures the temporal variation in the real part of blood dielectric permittivity at 1 MHz as the sample undergoes coagulation within a microfluidic channel with <10 μL of total volume. The ClotChip sensor features two distinct readout parameters, namely, lysis time (LT) and maximum lysis rate (MLR) that are shown to be sensitive to the fibrinolytic status in whole blood. Specifically, LT identifies the time that it takes from the onset of coagulation for the fibrin clot to mostly dissolve in the blood sample during fibrinolysis, whereas MLR captures the rate of fibrin clot lysis. Our findings are validated through correlative measurements with a rotational thromboelastometry (ROTEM) assay of clot viscoelasticity, qualitative/quantitative assessments of clot stability, and scanning electron microscope imaging of clot ultrastructural changes, all in a tissue plasminogen activator (tPA)-induced fibrinolytic environment. Moreover, we demonstrate the ClotChip sensor ability to detect the hemostatic rescue that occurs when the tPA-induced upregulated fibrinolysis is inhibited by addition of tranexamic acid (TXA) - a potent antifibrinolytic drug. This work demonstrates the potential of ClotChip as a diagnostic platform for rapid POC/POI assessment of fibrinolysis-related hemostatic abnormalities in whole blood to guide therapy.

Simultaneous multiparameter whole blood hemostasis assessment using a carbon nanotube-paper composite capacitance sensor

Rapid and accurate clinical assessment of hemostasis is essential for managing patients who undergo invasive procedures, experience hemorrhages, or receive antithrombotic therapies. Hemostasis encompasses an ensemble of interactions between the cellular and non-cellular blood components, but current devices assess only partial aspects of this complex process. In this work, we describe the development of a new approach to simultaneously evaluate coagulation function, platelet count or function, and hematocrit using a carbon nanotube-paper composite (CPC) capacitance sensor. CPC capacitance response to blood clotting at 1.3 MHz provided three sensing parameters with distinctive sensitivities towards multiple clotting elements. Whole blood-based hemostasis assessments were conducted to demonstrate the potential utility of the developed sensor for various hemostatic conditions, including pathological conditions, such as hemophilia and thrombocytopenia. Results showed good agreements when compared to a conventional thromboelastography. Overall, the presented CPC capacitance sensor is a promising new biomedical device for convenient non-contact whole-blood based comprehensive hemostasis evaluation.

Connector sensors for permittivity-based thrombus monitoring in extracorporeal life support

Extracorporeal circulation is vital in cardiovascular surgery, but thrombus formation at connector interface is a major threat. Optical coherence tomography (OCT) is presently used to monitor thrombogenesis at connectors, but it is expensive to install and complex to use. This study fabricated and evaluated a connector sensor for real-time permittivity-based thrombus monitoring at tube-connector interface. Computational simulations were initially done to pre-evaluate the applicability of connector sensor. The sensor was fabricated by incorporating two stainless steel electrodes on acrylic tube for measuring permittivity changes at the tube-connector interface. OCT images were also taken from the interface at intervals for comparisons. Results show that the sensor was able to detect thrombus formation at the interface in form of sudden rise in permittivity after time t = 9 min. The permittivity changes were confirmed by OCT images which showed thrombus formation after time t = 14 min implying that permittivity changes were due to regional aggregation of red blood cells. The connector sensor is therefore envisioned as an affordable alternative to OCT for real-time permittivity-based monitoring of thrombogenesis at tube-connector interface.

Assessment of whole blood coagulation with a microfluidic dielectric sensor

Essentials ClotChip is a novel microsensor for comprehensive assessment of ex vivo hemostasis. Clinical samples show high sensitivity to detecting the entire hemostatic process. ClotChip readout exhibits distinct information on coagulation factor and platelet abnormalities. ClotChip has potential as a point-of-care platform for comprehensive hemostatic analysis.

SUMMARY

Background Rapid point-of-care (POC) assessment of hemostasis is clinically important in patients with a variety of coagulation factor and platelet defects who have bleeding disorders. Objective To evaluate a novel dielectric microsensor, termed ClotChip, which is based on the electrical technique of dielectric spectroscopy for rapid, comprehensive assessment of whole blood coagulation. Methods The ClotChip is a three-dimensional, parallel-plate, capacitive sensor integrated into a single-use microfluidic channel with miniscule sample volume (< 10 μL). The ClotChip readout is defined as the temporal variation in the real part of dielectric permittivity of whole blood at 1 MHz. Results The ClotChip readout exhibits two distinct parameters, namely, the time to reach a permittivity peak (Tpeak ) and the maximum change in permittivity after the peak (Δεr,max ), which are, respectively, sensitive towards detecting non-cellular (i.e. coagulation factor) and cellular (i.e. platelet) abnormalities in the hemostatic process. We evaluated the performance of ClotChip using clinical blood samples from 15 healthy volunteers and 12 patients suffering from coagulation defects. The ClotChip Tpeak parameter exhibited superior sensitivity at distinguishing coagulation disorders as compared with conventional screening coagulation tests. Moreover, the ClotChip Δεr,max parameter detected platelet function inhibition induced by aspirin and exhibited strong positive correlation with light transmission aggregometry. Conclusions This study demonstrates that ClotChip assesses multiple aspects of the hemostatic process in whole blood on a single disposable cartridge, highlighting its potential as a POC platform for rapid, comprehensive hemostatic analysis.

Red blood cells aggregability measurement of coagulating blood in extracorporeal circulation system with multiple-frequency electrical impedance spectroscopy

Red blood cells (RBCs) aggregability A_G of coagulating blood in extracorporeal circulation system has been investigated under the condition of pulsatile flow. Relaxation frequency f_c from the multiple-frequency electrical impedance spectroscopy is utilized to obtain RBCs aggregability A_G. Compared with other methods, the proposed multiple-frequency electrical impedance method is much easier to obtain non-invasive measurement with high speed and good penetrability performance in biology tissues. Experimental results show that, RBCs aggregability A_G in coagulating blood falls down with the thrombus formation while that in non-coagulation blood almost keeps the same value, which has a great agreement with the activated clotting time (ACT) fibrinogen concertation (F_bg) tests. Modified Hanai formula is proposed to quantitatively analyze the influence of RBCs aggregation on multiple-frequency electrical impedance measurement. The reduction of RBCs aggregability A_G is associated with blood coagulation reaction, which indicates the feasibility of the high speed, compact and cheap on-line thrombus measurement biosensors in extracorporeal circulation systems.

Simultaneous assessment of blood coagulation and hematocrit levels in dielectric blood coagulometry

BACKGROUND

In a whole blood coagulation test, the concentration of any in vitro diagnostic agent in plasma is dependent on the hematocrit level but its impact on the test result is unknown.

OBJECTIVE

The aim of this work was to clarify the effects of reagent concentration, particularly Ca2+, and to find a method for hematocrit estimation compatible with the coagulation test.

METHODS

Whole blood coagulation tests by dielectric blood coagulometry (DBCM) and rotational thromboelastometry were performed with various concentrations of Ca2+ or on samples with different hematocrit levels. DBCM data from a previous clinical study of patients who underwent total knee arthroplasty were re-analyzed.

RESULTS

Clear Ca2+ concentration and hematocrit level dependences of the characteristic times of blood coagulation were observed. Rouleau formation made hematocrit estimation difficult in DBCM, but use of permittivity at around 3 MHz made it possible. The re-analyzed clinical data showed a good correlation between permittivity at 3 MHz and hematocrit level (R2=0.83).

CONCLUSIONS

Changes in the hematocrit level may affect whole blood coagulation tests. DBCM has the potential to overcome this effect with some automated correction using results from simultaneous evaluations of the hematocrit level and blood coagulability.

ClotChip: A Microfluidic Dielectric Sensor for Point-of-Care Assessment of Hemostasis

This paper describes the design, fabrication, and testing of a microfluidic sensor for dielectric spectroscopy of human whole blood during coagulation. The sensor, termed ClotChip, employs a three-dimensional, parallel-plate, capacitive sensing structure with a floating electrode integrated into a microfluidic channel. Interfaced with an impedance analyzer, the ClotChip measures the complex relative dielectric permittivity, ϵ_r , of human whole blood in the frequency range of 40 Hz to 100 MHz. The temporal variation in the real part of the blood dielectric permittivity at 1 MHz features a time to reach a permittivity peak, , as well as a maximum change in permittivity after the peak, , as two distinct parameters of ClotChip readout. The ClotChip performance was benchmarked against rotational thromboelastometry (ROTEM) to evaluate the clinical utility of its readout parameters in capturing the clotting dynamics arising from coagulation factors and platelet activity. exhibited a very strong positive correlation ( r = 0.99, p < 0.0001) with the ROTEM clotting time parameter, whereas exhibited a strong positive correlation (r = 0.85,  p < 0.001) with the ROTEM maximum clot firmness parameter. This paper demonstrates the ClotChip potential as a point-of-care platform to assess the complete hemostatic process using <10 μL of human whole blood.

The use of dielectric blood coagulometry in the evaluation of coagulability in patients with peripheral arterial disease

Background

Platelets and coagulation proteins contribute to the development of peripheral arterial disease, especially atherosclerotic disease. Several experimental studies have proven a significant correlation between hypercoagulability and atherosclerosis. We used dielectric blood coagulometry, which was initially designed to evaluate the coagulable status, to examine the coagulability of peripheral arterial disease patients, and investigated the factors that were significantly correlated with the results.

Methods

We performed dielectric blood coagulometry in 49 peripheral arterial disease patients. In addition, we recorded the patients’ demographic information, including the presence of comorbidities, hemodynamic status, and laboratory findings. To investigate coagulability, we calculated the T_max value, which indicates the time from recalcification to maximum normalized permittivity.

Results

The T_max values of diabetes mellitus patients were significantly lower than those of non-diabetic patients (1 MHz, P = 0.010; 10 MHz, 0.011). Furthermore, the T_max value was statistically correlated with the activated partial thromboplastin time (1 MHz, ρ = 0.286, P = 0.048; 10 MHz, ρ = 0.301, P = 0.037).

Conclusions

Dielectric blood coagulometry detected the hypercoagulable status in diabetes mellitus patients, and reflected their level of coagulability, which was also evaluated by the activated partial thromboplastin time.

Effect of circulating tissue factor on hypercoagulability in type 2 diabetes mellitus studied by rheometry and dielectric blood coagulometry

BACKGROUND

Hypercoagulability in type 2 diabetes mellitus (T2DM) patients increases their risk of cardiovascular diseases.

OBJECTIVE

The aim of this work was to investigate the hypercoagulation mechanism in T2DM patients in terms of circulating tissue factor (TF).

METHODS

Whole blood coagulation tests by damped oscillation rheometry and dielectric blood coagulometry (DBCM) were performed.

RESULTS

The average coagulation time was significantly shorter for T2DM patients than for healthy controls. In vitro addition of either anti-TF or anti-activated factor VII (FVIIa) antibody to hypercoagulable blood samples prolonged coagulation times for one group of patients, while coagulation times remained short for another group. The levels of circulating TF were estimated in the former group by measuring the coagulation times for blood samples from healthy subjects with addition of various concentrations of TF and comparing them with the coagulation times for the group. The results indicated that the levels of circulating TF were on the order of subpicomolar at most.

CONCLUSIONS

Circulating TF is at least partially responsible for a hypercoagulable group of T2DM patients, while an abnormality in the intrinsic coagulation pathway probably occurs in the other group.

Monitoring time course of human whole blood coagulation using a microfluidic dielectric sensor with a 3D capacitive structure

This paper reports on the design, fabrication, and testing of a microfluidic sensor for dielectric spectroscopy (DS) of human whole blood during coagulation. The sensor employs a three-dimensional (3D), parallel-plate, capacitive sensing structure with a floating electrode integrated into a microfluidic channel. Using an impedance analyzer and after a 5-point calibration, the sensor is shown to measure the real part of complex relative dielectric permittivity of human whole blood in a frequency range of 10kHz to 100MHz. The temporal variation of dielectric permittivity at 1MHz for human whole blood from three different healthy donors shows a peak in permittivity at ~ 4 to 5 minutes, which also corresponds to the onset of CaCl2-initiated coagulation of the blood sample verified visually.

Prediction of Venous Thromboembolism after Total Knee Arthroplasty Using Dielectric Blood Coagulometry

BACKGROUND

Venous thromboembolism (VTE) including deep vein thrombosis (DVT) and pulmonary embolism (PE) frequently occurs in patients undergoing total knee arthroplasty (TKA). This study aimed to evaluate the efficacy of dielectric blood coagulometry (DBCM) as a new technique for predicting postoperative VTE.

METHODS

Thirty patients undergoing TKA were enrolled. DVT was diagnosed by ultrasonography preoperatively and on the fourth or fifth postoperative day. Enhanced computed tomography was performed to detect PE on the fourth postoperative day. The day after surgery, a blood sample was measured by DBCM. All patients received fondaparinux or low-molecular-weight heparin for postoperative thromboprophylaxis.

RESULTS

Eighteen of the 30 patients had DVT postoperatively, and 10 had asymptomatic PE. Seven patients had both DVT and PE. The patterns of permittivity as a function of time and frequency from the DBCM measurement were different between patients with and without VTE. The sensitivity and specificity of the parameter constructed from a set of permittivities at the frequencies of 2.5 kHz, 1 MHz, and 10 MHz were 90% and 78%, respectively.

CONCLUSIONS

DBCM was effective and efficient for predicting VTE after TKA.

Dielectric permittivity change detects the process of blood coagulation: Comparative study of dielectric coagulometry with rotational thromboelastometry

BACKGROUND

Intravascular thrombus formation causes various cardiovascular diseases. To monitor coagulation is important for screening native status, prevention from bleeding and maintaining it within its therapeutic range. The prothrombin time and the activated partial thromboplastin time are widely used for assessment and recognized as the conventional methods. Prothrombin time methods employ enhancement of coagulation with thromboplastin. Since the laboratory data depend on the production lot and/or the manufacturer, the accurate methods are required for evaluation. Rotational thromboelastometry (ROTEM) is a method based on detection of the change in resistance to rotational movement during blood clotting, while dielectric blood coagulometry (DBCM) is a novel method for assessment of clotting by measuring the change of electrical permittivity. These methods are thus based on the technology for observation of different physical phenomena. The aim of this study was to compare parameters such as the clotting time obtained by ROTEM and DBCM to evaluate their clinical usefulness.

METHODS AND RESULTS

ROTEM and DBCM parameters were measured in 128 patients. The ROTEM clotting time showed a significant positive correlation with the DBCM coagulation time (R=0.707, p<0.001). Comparison of the DBCM coagulation time between patients with and without anticoagulant therapy (including novel oral anticoagulants) revealed a significant difference (43.8±11.9min in the anticoagulant group vs 29.4±8.3min in the control group, p<0.001). Evaluation of coagulation was equivalent with DBCM and ROTEM.

CONCLUSIONS

The present study suggested that DBCM, a novel method for measuring blood clotting, could provide the detail assessment for the status of anticoagulant therapy.

A 9 MHz-2.4 GHz Fully Integrated Transceiver IC for a Microfluidic-CMOS Platform Dedicated to Miniaturized Dielectric Spectroscopy

This paper presents a fully integrated transceiver IC as part of a self-sustained, microfluidic-CMOS platform for miniaturized dielectric spectroscopy (DS) from MHz to GHz. Fabricated in AMS 0.35 μm 2P/4M RF CMOS, the transmitter (TX) part of the IC generates a single-tone sinusoidal signal with frequency tunability in the range of ~ 9 MHz-2.4 GHz to excite a three-dimensional (3D), parallel-plate, capacitive sensor with a floating electrode and 9 μL microfluidic channel for sample delivery. With a material-under-test (MUT) loaded into the sensor, the receiver (RX) part of the IC employs broadband frequency response analysis (bFRA) methodology to measure the amplitude and phase of the RF excitation signal after transmission through the sensor. A one-time, 6-point sensor calibration algorithm then extracts both the real and imaginary parts of the MUT complex permittivity, ϵr, from IC measurements of the sensor transmission characteristics in the voltage domain. The "sensor + IC" is fully capable of differentiating among de-ionized (DI) water, phosphate-buffered saline (PBS), and alcoholic beverages in tests conducted at four excitation frequencies of ∼ 50 MHz , 500 MHz, 1.5 GHz, and 2.4 GHz generated by the TX. Moreover, permittivity readings of PBS by the sensor interfaced with the IC at six excitation frequencies in the range of ~ 50 MHz-2.4 GHz are in excellent agreement (rms error of 1.7% (real) and 7.2% (imaginary)) with those from bulk-solution reference measurements by commercial benchtop equipment. The total power consumption of the IC is with 1.5 V (analog) and 3.3 V (digital) supplies.

Cell Electrofusion in Centrifuged Erythrocyte Pellets Assessed by Dielectric Spectroscopy

We have characterized cell electrofusion in cell pellets by dielectric spectroscopy. Cell pellets were formed from horse erythrocyte suspensions by centrifugation and were subjected to intense AC pulses. The dielectric spectra of the pellets were measured over a frequency range of 10 Hz to 10 MHz. The application of AC pulses caused low-frequency (LF) dielectric relaxation below about 100 kHz. The LF dielectric relaxation was markedly affected not only by pretreatment of cells at 50 °C, which disrupts the spectrin network of erythrocytes, but also by the parameters of the AC pulses (frequency of the sine wave and repeat count of the pulses). The occurrence of the LF dielectric relaxation was qualitatively accounted for by modeling fusion products in the pellet by prolate spheroidal cells whose long axes run parallel to the applied electric field.

The simultaneous occurrence of both hypercoagulability and hypofibrinolysis in blood and serum during systemic inflammation, and the roles of iron and fibrin(ogen)

Although the two phenomena are usually studied separately, we summarise a considerable body of literature to the effect that a great many diseases involve (or are accompanied by) both an increased tendency for blood to clot (hypercoagulability) and the resistance of the clots so formed (hypofibrinolysis) to the typical, 'healthy' or physiological lysis. We concentrate here on the terminal stages of fibrin formation from fibrinogen, as catalysed by thrombin. Hypercoagulability goes hand in hand with inflammation, and is strongly influenced by the fibrinogen concentration (and vice versa); this can be mediated via interleukin-6. Poorly liganded iron is a significant feature of inflammatory diseases, and hypofibrinolysis may change as a result of changes in the structure and morphology of the clot, which may be mimicked in vitro, and may be caused in vivo, by the presence of unliganded iron interacting with fibrin(ogen) during clot formation. Many of these phenomena are probably caused by electrostatic changes in the iron-fibrinogen system, though hydroxyl radical (OH˙) formation can also contribute under both acute and (more especially) chronic conditions. Many substances are known to affect the nature of fibrin polymerised from fibrinogen, such that this might be seen as a kind of bellwether for human or plasma health. Overall, our analysis demonstrates the commonalities underpinning a variety of pathologies as seen in both hypercoagulability and hypofibrinolysis, and offers opportunities for both diagnostics and therapies.

Radio aneurysm coils for noninvasive detection of cerebral embolization failures: a preliminary study

The rupture of a cerebral aneurysm is the most common cause of subarachnoid hemorrhage. Endovascular embolization of the aneurysms by implantation of Guglielmi detachable coils (GDC) has become a major treatment approach in the prevention of a rupture. Implantation of the coils induces formation of tissues over the coils, embolizing the aneurysm. However, blood entry into the coiled aneurysm often occurs due to failures in the embolization process. Current diagnostic methods used for aneurysms, such as X-ray angiography and computer tomography, are ineffective for continuous monitoring of the disease and require extremely expensive equipment. Here we present a novel technique for wireless monitoring of cerebral aneurysms using implanted embolization coils as radiofrequency resonant sensors that detect the blood entry. The experiments show that commonly used embolization coils could be utilized as electrical inductors or antennas. As the blood flows into a coil-implanted aneurysm, parasitic capacitance of the coil is modified because of the difference in permittivity between the blood and the tissues grown around the coil, resulting in a change in the coil's resonant frequency. The resonances of platinum GDC-like coils embedded in aneurysm models are detected to show average responses of 224-819 MHz/ml to saline injected into the models. This preliminary demonstration indicates a new possibility in the use of implanted GDC as a wireless sensor for embolization failures, the first step toward realizing long-term, noninvasive, and cost-effective remote monitoring of cerebral aneurysms treated with coil embolization.