Evdokia M. Kardoulaki

Measured hyperbolic-sine (sinh) CMOS results

This paper presents proof-of-concept measured results from CMOS hyperbolic-sine (sinh) filters fabricated in a commercially available 0.35?m CMOS technology. Results from two chips are reported: a practical sinh integrator and a high order (8th) notch filter dedicated to 50/60Hz noise rejection and synthesized by means of the proposed integrator. Linearity, frequency and noise measurements are reported. The notch frequency of the 8th order filter can be tuned over almost two decades. Its attenuation exceeds 70dB for the target frequency range of 20-60Hz and its dynamic range (for THD<4%) amounts to 89dB while consuming 8?W from a 2V power supply level. For an increased power consumption of 74?W its dynamic range (for THD<4%) exceeds 100dB.

An 8Hz, 0.1µW, 110+ dBs Sinh CMOS Bessel filter for ECG signals

Hyperbolic sine (Sinh) CMOS filters are of inherent class-AB nature and offer high dynamic range at half the total capacitance value when compared against their pseudodifferential class-AB log-domain counterparts. This characteristic renders their theoretical and practical study valuable. Only a very limited number of CMOS Sinh filter topologies have been reported in the literature to date mostly due to the considerably increased mathematical complexity associated with their design. This paper presents the transistorlevel synthesis and investigates in detail the performance of a 3rd-order Sinh CMOS 8Hz low-pass filter of Bessel approximation suitable for ECG processing. The filter is based on recent progress made and has been designed in the commercially available 0.35µm AMS process. Its static power consumption amounts to 0.1µW while its dynamic range exceeds 110dBs. The new filter exhibits a flat group delay of less than 1% error up to 6Hz and good variability performance verified by means of Monte Carlo simulations. The suitability of the filter as part of an ECG front-end is confirmed by the processing of artificially generated ECG signals contaminated by various simulated noise sources and fed as signal inputs into the Cadence Design Framework.

SNR in MI Catheter Receivers for MRI

Internal coils have a signal-to-noise ratio (SNR) advantage during magnetic resonance imaging. However, coils with continuous cables are generally unsafe, due to the risk of RF heating. Segmented cables, such as magneto-inductive waveguides, should introduce inherent safety at the price of increased noise, from both the cable and the body. Here, we derive analytical SNR expressions for both types of noise, develop a model to compare the SNR of different types of receiver, and validate the model with data from imaging experiments at 3T. Experiments and theory confirm that body noise does not prevent an SNR gain compared with an eight-element external coil, even when a long section of waveguide is loaded with tissue.

A simulation study of high-order CMOS hyperbolic-sine filters

This paper advances the field of externally linear-internally nonlinear ELIN filters by introducing a synthesis method that enables the design of high-order class-AB sinh filters by means of complementary metal-oxide semiconductor CMOS weak-inversion sinh integrators comprising only one type of devices in their translinear loops. The proposed transistor-level synthesis approach is demonstrated through the examples of 1 a biquadratic and 2 a fifth-order filter, and their simulated performance is studied. The biquadratic filter achieves a dynamic range of 94dB and has a tunable quality factor Q up to the value of 8, whereas its natural frequency can be tuned for four orders of magnitude. Its static power consumption amounts to 6.2µW for Q=1 and fo=2kHz. The fifth-order Chebyshev sinh CMOS filter with a cut-off frequency of 100Hz, a pass band ripple of 1dB, and a power consumption of ~300nW is compared head-to-head with its pseudo-differential class-AB CMOS log domain counterpart. The sinh filter achieves similar or better signal-to-noise ratio SNR and signal-to-noise-plus-distortion ratio SNDR performances with half the capacitor area but at the expense of higher power consumption from the same power supply level. All three presented filter topologies are novel. Cadence design framework simulations have been performed using the commercially available 0.35µm AMS austriamicrosystems process parameters. Copyright

Optothermal profile of an ablation catheter with integrated microcoil for MR‐thermometry during Nd:YAG laser interstitial thermal therapies of the liver—An in‐vitro experimental and theoretical study

PURPOSE Flexible microcoils integrated with ablation catheters can improve the temperature accuracy during local MR-thermometry in Nd:YAG laser interstitial thermal therapies. Here, the authors are concerned with obtaining a preliminary confirmation of the clinical utility of the modified catheter. They investigate whether the thin-film substrate and copper tracks of the printed coil inductor affect the symmetry of the thermal profile, and hence of the lesion produced. METHODS Transmission spectroscopy in the near infrared was performed to test for the attenuation at 1064 nm through the 25 μm thick Kapton substrate of the microcoil. The radial transmission profile of an infrared high-power, light emitting diode with >80% normalized power at 1064 nm was measured through a cross section of the modified applicator to assess the impact of the copper inductor on the optical profile. The measurements were performed in air, as well as with the applicator surrounded by two types of scattering media; crystals of NaCl and a layer of liver-mimicking gel phantom. A numerical model based on Huygens-Fresnel principle and finite element simulations, using a commercially available package (COMSOL Multiphysics), were employed to compare with the optical measurements. The impact of the modified optical profile on the thermal symmetry was assessed by examining the high resolution microcoil derived thermal maps from a Nd:YAG laser ablation performed on a liver-mimicking gel phantom. RESULTS Less than 30% attenuation through the Kapton film was verified. Shadowing behind the copper tracks was observed in air and the measured radial irradiation correlated well with the diffraction pattern calculated numerically using the Huygens-Fresnel principle. Both optical experiments and simulations, demonstrate that shadowing is mitigated by the scattering properties of a turbid medium. The microcoil derived thermal maps at the end of a Nd:YAG laser ablation performed on a gel phantom in a 3 T scanner confirm that the modified irradiation pattern does not disrupt the thermal symmetry, even though, unlike tissue, the gel is minimally scattering. CONCLUSIONS The results from this initial assessment indicate that microcoils can be safely integrated with ablation catheters and ensure that the complete necrosis of the liver tumor can still be achieved.

Magneto-Inductive Magnetic Resonance Imaging Duodenoscope

A magnetic resonance imaging (MRI) duodenoscope is demonstrated, by combining nonmagnetic endoscope components with a thin-film receiver based on a magneto-inductive waveguide. The waveguide elements consist of figure-of-eight shaped inductors formed on either side of a flexible substrate and parallel plate capacitors that use the substrate as a dielectric. Operation is simulated using equivalent circuit models and by computation of twoand three-dimensional sensitivity patterns. Circuits are fabricated for operation at 127.7 MHz by double-sided patterning of copper-clad Kapton and assembled onto non-magnetic flexible endoscope insertion tubes. Operation is verified by bench testing and by 1H MRI at 3T using phantoms. The receiver can form a segmented coaxial image along the length of the endoscope, even when bent, and shows a signal-to-noise-ratio advantage over a surface array coil up to three times the tube diameter at the tip. Initial immersion imaging experiments have been carried out and confirm an encouraging lack of sensitivity to RF heating.