Single Probe System Research Articles

Microwave ablation of the liver in a live porcine model: the impact of power, time and total energy on ablation zone size and shape

Objective To explore various microwave (MW) time/power combinations to achieve maximum single-probe system performance in a live pig liver model. Methods Fifty-one microwave ablations performed in 12 female pigs using the following time/power combinations: 65 W for 10 min (65W 10MIN), ramped from 20 to 65 W (RAMPED), 95 W pulses with cooling periods (95W PULSED), 40 W for 16 min 15 s (LOW POWER), 1 min 95 W pulse then 8 min 65 W then a second 1 min 95 W pulse (BOOKEND 95W) and 65 W for 15 min (65W 15MIN). Temperatures 1.5 cm from the antenna were measured. Livers were excised, and ablations were measured and compared. Results At fixed overall energy, LOW POWER produced ablation zones with the smallest volume compared to 65W 10MIN, RAMPED and 95W PULSED. At a fixed time of 10-min, BOOKEND 95W protocol achieved wider and larger ablation zones than 65W 10MIN (p = 0.038, p = 0.008) and 95W PULSED (p = 0.049, p = 0.004). The 65W 15MIN combination had significantly larger diameters (p = 0.026), larger lengths (p = 0.014) and larger volumes (p = 0.005) versus 65W 10MIN. Maximum temperatures were highest with BOOKEND 95W (62.9 °C) and 65 W 15 MIN (63.0 °C) and lowest with LOW POWER (45.9 °C), p = 0.009. Conclusions Low power ablations, even if controlled for total energy delivery, create small ablation zones. High peak powers are associated with larger ablation zones and high margin temperatures if cooling pauses are avoided. Ramping and pulsing protocols with interleaved cooling appear to be of no benefit versus continuous 65 W for creating large ablation zones.

Large-area Scanning Probe Nanolithography Facilitated by Automated Alignment and Its Application to Substrate Fabrication for Cell Culture Studies

Scanning probe microscopy has enabled the creation of a variety of methods for the constructive ('additive') top-down fabrication of nanometer-scale features. Historically, a major drawback of scanning probe lithography has been the intrinsically low throughput of single probe systems. This has been tackled by the use of arrays of multiple probes to enable increased nanolithography throughput. In order to implement such parallelized nanolithography, the accurate alignment of probe arrays with the substrate surface is vital, so that all probes make contact with the surface simultaneously when lithographic patterning begins. This protocol describes the utilization of polymer pen lithography to produce nanometer-scale features over centimeter-sized areas, facilitated by the use of an algorithm for the rapid, accurate, and automated alignment of probe arrays. Here, nanolithography of thiols on gold substrates demonstrates the generation of features with high uniformity. These patterns are then functionalized with fibronectin for use in the context of surface-directed cell morphology studies.

Large-area Scanning Probe Nanolithography Facilitated by Automated Alignment and Its Application to Substrate Fabrication for Cell Culture Studies.

Scanning probe microscopy has enabled the creation of a variety of methods for the constructive ('additive') top-down fabrication of nanometer-scale features. Historically, a major drawback of scanning probe lithography has been the intrinsically low throughput of single probe systems. This has been tackled by the use of arrays of multiple probes to enable increased nanolithography throughput. In order to implement such parallelized nanolithography, the accurate alignment of probe arrays with the substrate surface is vital, so that all probes make contact with the surface simultaneously when lithographic patterning begins. This protocol describes the utilization of polymer pen lithography to produce nanometer-scale features over centimeter-sized areas, facilitated by the use of an algorithm for the rapid, accurate, and automated alignment of probe arrays. Here, nanolithography of thiols on gold substrates demonstrates the generation of features with high uniformity. These patterns are then functionalized with fibronectin for use in the context of surface-directed cell morphology studies.

Stereochemistry-Guided DNA Probe for Single Nucleotide Polymorphisms Analysis.

Single nucleotide polymorphisms (SNPs) are the most abundant genetic polymorphisms and are responsible for many genetic diseases and cancers. In general, SNPs detection is performed by a single probe system (SPS), in which a single probe specifically hybridizes to one target. However, with the use of this method it is hard to improve the hybridization specificity and single mismatched discrimination factors (DF). In addition, the multiprobe system (MPS) requires complex probe designs and introduces at least one auxiliary probe except for the probe complementary to the target, resulting in a complicated detection system. Faced with these difficulties, we perform the SNP detection using a d/l-tryptophan (Trp) guided DNA probe and regulate the DF of electrochemical DNA (E-DNA) sensors by molecular chirality. We show that the DF of the d-Trp incubated E-DNA sensor (d-sensor) is larger than that of the l-sensor. More importantly, we achieve the high specificity by coupling d-Trp and l-Trp incubated E-DNA sensors, and the median DF is 7.21. Furthermore, the specificity of SNP detection can be further improved by supersandwich assay, and the median DF is enlarged to 37.23, which is comparable to that obtained with a multiprobe detection system.

Spatially resolved monitoring of powder mixing processes via multiple NIR-probes

Abstract The production of pharmaceutical dosage forms relies on efficient blending of granular components. By monitoring in real-time the blending processes via non-invasive techniques, such as near-infrared (NIR) spectroscopy, the blending end-point can be determined and homogeneity can be guaranteed for a given material blend. In this study an experimental setup with multiple NIR probes attached to a lab-scale blending vessel is presented. The probes were connected to a Fourier-transform NIR spectrometer via an optical fiber switch. Thereby, the blending processes could be “quasi-simultaneously” monitored at multiple positions. Differences in blending behavior in the monitored positions inside the vessel were identified, which would be impossible using a single probe system. The interpretation of the NIR-spectra was done using a chemometric model based on partial least squares regression. Premixed samples with varied content of an active pharmaceutical ingredient were used for calibration. To prevent segregation problems during calibration, it was performed on a rotating disk outside the vessel. Using this multiple-probe setup in combination with the developed chemometric model, segregation and blending inside the vessel were analyzed by observing the temporal and spatial concentration changes, without interruptions caused by manual sampling and/or pausing of the process.

Base recognition of gap sites in DNA–DNA and DNA–RNA duplexes by short oligonucleotides

To increase base recognition capability and sensitivity, we propose the separation of a commonly used single-probe system for oligonucleotide analysis into a set of three probes: a fluorophore-labeled probe, a promoter probe, and a short probe. In this study, we found that the probes of only 4nt in length can selectively bind the corresponding gap site on complexes consisting of the target, fluorophore-labeled probe, and promoter probe, exhibiting a more than 14-fold difference in ligation between the matched and mismatched sequences. Moreover, we demonstrated that the immobilized short probes accurately recognized the sequences of the gap sites.

Study on the Distribution Control of Etching Rate and Critical Dimensions in Microwave Electron Cyclotron Resonance Plasmas for the Next Generation 450 mm Wafer Processing

A newly designed microwave electron cyclotron resonance (ECR) plasma etching reactor has been developed for 450 mm wafer processing. The etching rates of polycrystalline silicon (poly-Si) and SiO2 across the wafer were evaluated as a function of ECR position. Two-dimensional (radial and vertical) distributions of the ion flux in the reactor were also investigated using a movable single probe system. A ring-shaped region of high-density plasma along the ECR plane was observed. This reveals the mechanism that the etching-rate distribution could be controlled by the ECR position. As a result, a polycrystalline silicon etching rate uniformity of 1.5% across a wafer was successfully obtained. Furthermore, the uniformity control of critical dimensions (CDs) based on wafer temperature was also investigated, and CD uniformity below 3 nm across the wafer was obtained in the optimum temperature distribution.

A dendrimer-based platform for simultaneous dual fluorescence imaging of hydrogen peroxide and pH gradients produced in living cells

We present a modular dendrimer-based platform for simultaneous dual fluorescence imaging of hydrogen peroxide (H2O2) and pH gradients produced in living cells. Acetyl-capped G5 PAMAM dendrimers functionalized with boronate-caged Peroxyfluor-1 (PF1) fluorophores for H2O2 detection and semi-naphthorhodafluor (SNARF2) dyes for pH sensing provide a single probe system that is capable of sensing multiple analytes at a time by multicolor fluorescence imaging. Spectroscopic measurements of the doubly-labeled dendrimer conjugates establish their ability to simultaneously monitor changes in both H2O2 and pH using different excitation/emission profiles. Moreover, this dual-probe platform allows for selective discrimination between H2O2 and pH changes in live RAW 264.7 macrophage cells when stimulated by an immune insult. Further imaging experiments show that pharmacological inhibition of NADPH oxidase (Nox) proteins triggers a decrease in both oxidative burst and in pH regulation within phagocytic compartments and leads to disruptions of endocytic activity, suggesting that Nox-derived H2O2 signaling is critical to the maintenance of multiple components of the immune response. This work establishes a general molecular platform for simultaneous, real-time imaging of multiple analytes associated with redox biology in living systems and should be applicable to a wide range of chemosensor constructs.

Direct Delivery and Submicrometer Patterning of DNA by a Nanofountain Probe

Nanopatterning of biological materials has significant potential in life sciences and medicine because highly miniaturized structures provide routes to high-density combinatorial libraries and ways of manipulating biological structures (proteins, viruses, and cells) at the single particle level. Central to the development of this technology is the nanofabrication of arrays of DNA and proteins. Such arrays have influenced the areas of genomics and proteomics because of their ability to simultaneously detect a large number of molecular species or ‘multiplex’. The miniaturization of bioassays has been eagerly pursued in an effort to achieve enhanced performance such as shorter response times, smaller sample volumes, and higher sensitivities. Dip-pen nanolithography (DPN) was developed to write nanoscale patterns directly on substrates. Among the many applications of this technology is the ability to pattern modified oligonucleotides on gold and silicon oxide surfaces. Here, feature sizes can range from a few micrometers to less than 50 nm. In a typical DNA-patterning experiment with DPN, the surfaces of silicon nitride atomic force microscopy (AFM) cantilevers are chemically modified for increased tip hydrophilicity. This step is used to improve the coating efficiency of the DNA molecules. A more attractive way of delivering inks in DPN mode is through the use of microfluidics that can deliver different inks to specific tips within a cantilever array. This approach, when it has been successfully developed, will provide greater flexibility and increased utility of DPN for the generation of combinatorial bioarrays. Other recent approaches to biomolecular patterning include the use of microfluidic components such as reservoirs, microchannels, and small apertures or slots to control the delivery of chemical solutions. Such tools do not require tip coating because samples are directly delivered onto a surface in a solution. However, the reported resolution of microfluidic tools is about 1 lm at best because of limitations from the geometries of the apertures or slots that control the molecular writing mechanisms in these devices. Herein, we present the patterning of DNA molecules on the submicrometer length scale using a volcano-like tip. This eliminates the need for tip-surface modification by implementing direct delivery of a solution containing DNA molecules to the tip. As a microfluidic AFM probe, the nanofountain probe (NFP) was reported to allow high-resolution writing and have advantages for delivery of molecular inks in solution. A feature size as small as 40 nm was demonstrated with thiol molecules. The NFP was microfabricated to integrate an on-chip reservoir, microchannels, and a volcanolike dispensing tip. Following the development of the first generation NFP, a single-probe system, we made augmentations to produce a linear array of 12 NFP cantilevers with two on-chip reservoirs on each side of the chip, Figure 1. The cantilever lengths on each side were 630 and 520 lm, respectively. Each reservoir fed six adjacent cantilevers to achieve simultaneous patterning with two molecular species. The NFP chip was designed to fit commercially available AFM instruments and utilized the instrument scanner, optical detection, and feedback control to engage surfaces. While one cantilever was selected for the feedback control of the chip, the other cantilevers made passive contact with the surface by adjustment of the tilting angle between the array and the substrate. The multiple-tip, double-ink patterning with this linear-array NFP chip was recently demonstrated. More recently, a third generation of the NFP was fabricated. Modifications for this NFP included the possibility of fabrication on silicon-on-insulator (SOI) wafers, improved channel sealing, deeper channels to allow the delivery of larger particles, and more robust fabrication processes that led to enhanced yield and better control of C O M M U N IC A TI O N

PCR validation testing utilizing a novel dynamic measurement system

When PCR validation is done correctly it provides measurements which can allow for the assessment of accuracy and uniformity of the PCR block. Not only does it provide useful information pertinent to the end product, it is a necessity for accreditation. Most methods employ static temperature collection with a single probe. Generally, single probe systems allow for an average of 90sec to achieve the target temperature. This does not allow for an acquisition of temperature as it would occur during normal cycling parameters. Most single probe systems only allow for collection of data at pre-defined points of 95oC/40oC. Our laboratory set out to find a temperature acquisition system which would provide temperatures in a dynamic environment. System criteria should include multi-probe head, ease of use, reproducibility of data, ability to follow data trends and rapid data collection. The Driftcon® system was utilized for purposes of this study. Data was collected from 18 PE thermocyclers using a standard run protocol which targeted temperatures 30oC/95oC/90oC/50oC/70oC/60oC. Average run time for this protocol was 20 minutes. Reports are automatically generated by the system which include results on accuracy and spread (uniformity). All results are compared with a global market database which allows for more accurate assessment of market specifications. 8/18 demonstrated accuracy problems at one of the achieved target temperatures. 6/18 demonstrated accuracy problems at a target temperature not tested by a single probe system. The conclusion of this study was that the Driftcon® system yielded information which can help determine the efficacy of a thermocycler beyond data which is collected from a single probe system, thus enhancing the performance of the instrumentation.

The vibroscanning method for the measurement of micro-hole profiles

In this paper, we present technologies for measuring inner dimensions of small holes. In the first method with a single probe system, the electrical contact between a vibrating probe and the inner surface of a hole is detected and the duty factor of the contact is measured. Through controlled scanning by a probe with a constant duty factor, data on the ups and downs of the surface profile are obtained. To characterize inside profiles of micro-holes regardless of materials, we developed a new technology with a twin-probe system. With a silicon-based micro-twin probe 3 mm in length, a micro-hole with a diameter of around 125 µm was measured and the estimated imprecision of measurement on this set-up is smaller than 0.5 µm.

Computerized single probe system using a cadmium telluride detector

Using cadmium telluride (CdTe) as a detector, we assembled a computerized single probe system. The size of the CdTe used is 16 mm in diameter and 2 mm in thickness. Two types of the straight bore collimators of 16 mm in diameter were prepared. One is 16 mm in length (long type) and the other is 5 mm in length (short type). The response curves of the long and short type collimators to 57Co in water showed that the points at 10% of maximum counts were 4 cm and 3 cm in depth along the center axis. The data were accumulated by using a commercialized single cardiac probe system (OMNISCOPE) and processed by itself or transferred to the microcomputer (LSI-11/23) for further analysis. Twenty percent count loss occurred at 100 000 cps with an integral discriminator setting. This system was applied for cerebrospinal fluid (CSF) shunt flow evaluation and measurement of left ventricular ejection fraction (LVEF). Measurement of CSF shunt flow has been able to do in any patient's positioning. In 21 patients with various heart diseases, LVEFs obtained by CdTe detector were compared with those obtained by scintillation detector. There was good correlation between the LVEFs obtained by these two detectors: correlation coefficient (r)=0.939.

A Stand Alone Data Collection Station Based on an Autonomous CAMAC Crate

The increasing cost of software and hardware for complex acquisition and control systems has made it desirable to implement small stand alone systems with less complex software and more versatile hardware. This paper discusses two applications of an autonomous CAMAC crate based on an LSI-11 controller. The first application is an EKG gated single probe system for cardiac ejection fraction measurement. The second is the control system for a rectilinear scanner in a low level counting facility.

Application of the computer to rapid dynamic studies

Current trends in nuclear medicine to some degree, at least, reflect the level of sophistication available in the instrumentation. A technologically oriented speciality such as this might be expected to shift emphasis from time to time as stepwise advances are made in instrumentation. In its infancy, nuclear medicine concentrated on studies that could be accomplished with a single-probe system. The introduction of rectilinear scanners made imaging practical and of primary concern. Anger's gamma camera made combined static and dynamic studies possible using a single instrument--a decided advantage over previous methodology. The development of digital acquisition, processing, and display systems has had a profound effect on the recently increased emphasis on rapid dynamic studies. Computers are currently being applied to a broad range of clinical problems. Data preparation routines such as uniformity correction and data bounding often are used preliminary to more rigorous mathematical treatment. The development of reasonably low-cost, TV-type displays has greatly increased the quality of the computer display of the radionuclide imaging process.