Effective Field Size Research Articles

Characteristics and performance evaluation of the capacitive Contact Flexible Microstrip Applicator operating at 70 MHz for external hyperthermia

Purpose: To characterise and evaluate the capacitive Contact Flexible Microstrip Applicator operating at 70 MHz, CFMA-70. This applicator is introduced for the treatment of superficial tumours with extension in depth beyond the range of regular superficial applicators.Methods: E-field measurements were performed in an elliptical phantom filled with a saline solution using an E-field vector probe. E-field distributions and SAR patterns are compared to those of the CFMA-434 and of 70 MHz waveguides. The applicator has been used for the treatment of 6 patients with breast cancer with a tumour depth exceeding 4 cm.Results: The effective heating depth of the CFMA-70 is 50% larger than for the CFMA-434. Its effective field size is 26 × 20 cm (aperture 29 × 20 cm), larger than for an equally sized CFMA-434. In contrast to the CFMA-434 the SAR pattern of this applicator is insensitive to the bolus thickness. Comparison to 70 MHz waveguides shows that the E-field component normal to the applicator is 100% larger for the CFMA-70. During clinical applications acceptable temperatures were realised for individual sessions (also at depth), but in many cases treatment limiting hot spots occurred close to superficial bony structures near the applicator edge. Both surface irregularities and the normal field component may be responsible.Conclusions: The CFMA-70 has adequate penetration depth for the treatment of superficial tumours exceeding a depth of 4 cm. However, the relatively large normal E-field component may induce treatment-limiting hot spots at tissue interfaces in the direction normal to the applicator's surface.

SU-GG-T-401: Cell Survival Following X-Ray Activated Auger Electron Radiotherapy

Purpose: To examine enhancement of cell killing as a function of both radiosensitizer (IUdR) concentration and x‐ray beam energy by measuring CHO cell survival following monochromatic x‐ray activated Auger electron radiotherapy.Method and Materials: The dose‐response of CHO cells was measured by irradiating monolayers of log‐phase cells to 1–8 Gy using 30 keV, 35 keV, and 4 MV x‐rays. Estimated maximum radiosensitizer DNA‐incorporation (18% thymidine replacement) was obtained by adding 8 μL IUdR (20 μM in media) 21–39 hours before irradiation. Cell culture tubes were irradiated at 30 and 35 keV by an effective field size of 2.8×2.5‐cm2 on a monochromatic, x‐ray beamline at LSU's CAMD synchrotron. Dose was determined from ionization chamber‐measured dose rates (18–27 cGy⋅min−1 at 100 mA) and verified with GAFCHROMIC® EBT film. Cell culture flasks were also irradiated with 4 MV x‐rays produced using a Varian Clinac 21EX (30×30‐cm2 field, 0.5‐cm depth). Clonogenic assays were performed at the Pennington Biomedical Research Center, where cells were plated, incubated, and allowed to grow for 1 week, then fixed and stained with crystal violet. Colonies of 50 or more cells were scored as survivors. Sensitization enhancement ratio (SER) was calculated as the ratio of doses at 10% surviving fraction. Results: Survival curves for control cells (without IUdR) were identical for the 30 keV, 35 keV, and 4 MV beams. Cells with DNA‐incorporated IUdR showed increased sensitization: SER≈2 with 4 MV, SER≈4 with 30 keV, and SER≈5 with 35 keV x‐ray beams. Conclusion: Our initial results are consistent with those reported previously by others. Future work studying SER as a function of photon energy and percent IUdR replacement of thymidine in DNA is intended to provide sufficient data to develop radiobiological models, which when utilized with the dose distribution, will provide a mechanism for planning x‐ray activated Auger electron therapy.

Characterization of a novel micro-irradiator using Monte Carlo radiation transport simulations

Small animals are highly valuable resources for radiobiology research. While rodents have been widely used for decades, zebrafish embryos have recently become a very popular research model. However, unlike rodents, zebrafish embryos lack appropriate irradiation tools and methodologies. Therefore, the main purpose of this work is to use Monte Carlo radiation transport simulations to characterize dosimetric parameters, determine dosimetric sensitivity and help with the design of a new micro-irradiator capable of delivering irradiation fields as small as 1.0 mm in diameter. The system is based on a miniature x-ray source enclosed in a brass collimator with 3 cm diameter and 3 cm length. A pinhole of 1.0 mm diameter along the central axis of the collimator is used to produce a narrow photon beam. The MCNP5, Monte Carlo code, is used to study the beam energy spectrum, percentage depth dose curves, penumbra and effective field size, dose rate and radiation levels at 50 cm from the source. The results obtained from Monte Carlo simulations show that a beam produced by the miniature x-ray and the collimator system is adequate to totally or partially irradiate zebrafish embryos, cell cultures and other small specimens used in radiobiology research.

Linear attenuation coefficients for compensator based imrt

With rapid technological improvements in computer driven 3-D radiotherapy treatment planning systems (RTPS) the use of compensating filters for intensity modulated radiation therapy (IMRT) will dramatically increase the ease of treatment. The procedure for commissioning .decimal (Sanford, Florida) compensators involved the measurement of the effective linear attenuation coefficients for aluminium and brass. Field sizes to be measured vary from small square field size of 5 cm to the larger square field size of 25 cm with additional measurements at each 5 cm2 increments. The energies commissioned where 6 MV and 18 MV photons. The depth of measurements varied from 5 cm to 10 cm within phantom material and the source surface distance varied from 100 cm to 90 cm. The beam quality was measured by obtaining percentage depth dose (PDD) curves for the various field sizes with and without the compensating material. Results of the series of measurements showed no significant differences in the effective linear attenuation coefficients with respect to chamber depth and source surface distance with constant energy and field size. The main factor that was shown to influence the effective linear attenuation coefficient was field size variation. A correlation was shown between the effective linear attenuation coefficient and field size, up to a field size of 15 cm x 15 cm. Our results showed that for optimal patient treatments using IMRT compensating filters, there is a need for establishing two field size dependent linear attenuation coefficients.

Elliptically bent conformal phased array of modified box‐horns for hyperthermia treatment of tumors

A novel and effective hyperthermia applicator utilizing an elliptically bent conformal phased array of modified box‐horns is analyzed using Fresnel‐Kirchhoff scalar diffraction field theory. This configuration is mainly intended as a specialized and very effective applicator for hyperthermia treatment of tumor within curved portions of human body such as abdomen, chest, neck, etc. It is proposed that the interior of the modified box‐horn as well as feeding device be filled with de‐ionized water to provide a better impedance match to the tissue. The contour distribution of specific absorption rate (SAR) in x‐y plane, SAR distribution in z‐direction, penetration depth, power absorption coefficient and effective field size (EFS) due to the conformal array as well as single modified box‐horn are evaluated and compared at 2450 MHz. The effect of change in phase and amplitude excitation of modified box‐horn of the array on SAR distribution is also investigated. Results demonstrate that conformal phased array of modified box‐horns offers marked improvement in SAR distribution and penetration depth over single modified box‐horn. The results obtained by the present analysis for linear array of four titanium dioxide loaded horns terminated in water are validated against published experimental results available in the literature.

Guided plasmon polariton at 2D metal corners

We investigate the properties of plasmon polaritons guided by 2D monoangular metal corners with a vector finite-element method. Such corner waveguides in general include both V-channel- and Λ-wedge-type waveguides. The influences of both geometric parameters (i.e., corner angle, tip sharpness, etc.) and operating wavelength to the mode properties, such as effective mode index, loss, and mode field size, are inspected. It is noticed that both a smaller corner angle and a sharper corner tip help to better confine the mode field. The confinement of the V-channel waveguide is found to be especially sensitive to its angle, while the confinement of the Λ-wedge waveguide is affected about equally by its angle and tip sharpness. Almost all superior mode field confinement is realized at the expense of higher propagation loss for such waveguides. The chromatic dispersion of such waveguides is found to be adequate for applications in integrated optical circuits. The mode behaviors of realistic corner waveguides with finite sidewalls are also studied.

Measured peripheral dose in pediatric radiation therapy: A comparison of intensity-modulated and conformal techniques

Background and purpose The interest in IMRT for the treatment of pediatric malignancies has raised concern about possible increased total body dose. This study examines the pediatric peripheral dose resulting from IMRT compared to 3D conformal therapy. Methods and materials Five brain or base of skull pediatric cases were planned with both IMRT and 3D conformal techniques. A pediatric-sized anthropomorphic phantom was created and ion chambers were placed at interest points approximating the position of the thyroid, breast, ovary and testes. Measured peripheral doses at the interest points were compared for both IMRT and 3D conformal techniques for the 5 cases. Results While tumor coverage was similar for both techniques, the IMRT delivery resulted in lower peripheral doses at points near the target (thyroid) presumably due to reduced internal scatter from a smaller effective field size for sliding window dynamic multi-leaf collimation. The IMRT delivery resulted in higher doses to the more distant points, presumably due to the higher monitor units and resulting increased head leakage. Since the magnitude of dose at the distant points was much smaller than that of the thyroid point, the overall absolute peripheral dose was similar for both techniques. Conclusions Peripheral dose is difficult to predict by monitor units alone. In this study, interest points closer to the beam received less dose with IMRT. This difference may result from the competing factors of reduced internal scatter from dynamic multileaf collimation IMRT and reduced head leakage for 3D conformal therapy.

SU-FF-T-57: A Simple Method of Calculating Isocenter Dose From Measured D-Max Dose of IMRT Field

Purpose: To provide a simple method of calculating isocenter dose from the measured d‐max dose of IMRT fields, then compare the result dose with the calculated isocenter dose from the treatment planningcomputer system in the patient geometry. Method and Materials:IMRT plans are developed with Varian Eclipse, and delivered on two Varian 21EX treatment units by using sliding window technique. We use a device with a film holder and a diode holder about 2 cm below the film at central axis of the field. This device is mounted at the block tray level. A Kodar X‐OMAT V film gives fluence map and effective field size. A diode (SunNuclear RF‐IVD) reading gives the d‐max dose. Using the effective field size and the depth from the plan, one can find the effective TMR. The following formula gives the relation between dose at d‐max with 100 SSD and dose at isocenter. Dose_iso = Dose _dmax × TMR ×[ (SAD + dmax)/SAD]2 Results: We have used this method to calculate isocenter dose from diode readings for about 150 IMRT plans. The average differences between QA isocenter dose and plan isocenter dose are: −0.5 % with a standard deviation of 2.3% for 80 prostate plans using 6 MV photon beams; 2.4 % with a standard deviation of 1.5% for 36 prostate plans using 10 MV photon beams; 2.2 % with a standard deviation of 2.3% for 40 IMRT plans treating sites other than prostate using 6 MV photon beams. Conclusion: We have good agreement between the QA isocenter dose and isocenter dose from treatment planning system. Unlike IMRT QA methods using phantom, our method also checks a point dose with patient geometry; Unlike MU calculation programs, our method also checks the delivery of the treatment machine.

Effects of waterbolus size, shape and configuration on the SAR distribution pattern of the Lucite cone applicator

The effects of waterbolus dimensions and configuration on the effective field size (EFS) of the Lucite cone applicator (LCA) for superficial hyperthermia are presented. The goal of the research is to develop guidelines which mark out a sub-set of optimal LCA-waterbolus set-ups. The effects of variations in (i) waterbolus thickness, (ii) waterbolus area, (iii) waterbolus length/width ratio and (iv) eccentric placement of the applicator have been investigated in an FDTD model study. The prominent effects are verified with IR thermography measurements. An optimal EFS value of 80 cm2 is found for waterbolus area of 200–400 cm2. A small (10 × 10 cm2) waterbolus area restricts the EFS to 25% of the optimal value. The sensitivity to sub-optimal waterbolus area and length/width ratio increases with waterbolus height. Eccentric placement of the LCA near the waterbolus edge reduces the EFS to up to 50% of the optimal value. The IR measurements confirm the model findings. Based on the results, the following guidelines for the clinical application of the LCA have been defined: the waterbolus (i) should extend the LCA aperture at least 2.5 cm, especially at the Lucite windows, and (ii) the height should not exceed 2 cm.

ELLIPTICALLY BENT SLOTTED WAVEGUIDE CONFORMAL FOCUSED ARRAY FOR HYPERTHERMIA TREATMENT OF TUMORS IN CURVED REGION OF HUMAN BODY

In present paper, a novel and effective hyperthermia applicator utilizing an elliptically bent conformal array of longitudinal slots in narrow wall of rectangular waveguide is analyzed by two different approaches, viz., the vector potential method and Fresnel- Kirchhoff scalar diffraction field theory. The agreement between two theories is reasonably very good. This configuration is mainly intended as a specialized and very effective applicator for hyperthermia treatment of tumor within curved portions of human body such as abdomen, neck, chest etc. Each slot of the conformal array is excited by a coaxial line probe. It is proposed that the interior of the waveguide be filled with water to provide a good impedance match with the bio-medium. The contour distribution of specific absorption rate (SAR) in x-z plane, SAR distribution in y-direction and parameters such as penetration depth, power absorption coefficient, effective field size (EFS) due to the conformal array as well as single slot are evaluated and compared at 433 MHz. The results for contour SAR distribution at 433 MHz for elliptically bent conformal array are also compared with those for other array configurations such as circularly bent conformal array and planar array. The effect of change in phase and amplitude excitation of each slot of the array on SAR distribution is also examined. The results demonstrate that slotted waveguide conformal array offers marked improvement in SAR distribution and penetration depth over single slot. It also has better focusing ability as compared with planar array for controlled amplitude and phase excitations of the elements.

Assessment of the performance characteristics of a prototype 12-element capacitive contact flexible microstrip applicator (CFMA-12) for superficial hyperthermia

The electrical performance of the CFMA-12 operating at 433 MHz is assessed under laboratory conditions using a RF network analyser. From measurements of the scattering parameters of the CFMA-12 on both a multi-layered muscle- and fat/muscle-equivalent phantom, the optimal water bolus thickness, at which the transfer of the energy to the phantom configuration is maximal, is determined to be ∼1 cm. The SAR distribution of the CFMA-12 in a multi-layered muscle-equivalent phantom is characterized using Schottky diode sheets and a TVS-600 IR camera. From the SAR measurements using the Schottky diode sheets it is shown that the contribution of the Ex component to the SAR (SARx) is maximal 7% of the contribution of the Eycomponent to the SAR (SARy) at different layers in both phantom configurations. The complete SAR distribution (SARtot) at different depths is measured using the power pulse technique. From these measurements, it can be seen that SARyat a depth of 0 cm in the muscle-equivalent phantom represents up to 80% of SARtot. At 1 and 2 cm depth, SARy is up to 95% of SARtot. Therefore, in homogeneous muscle-equivalent phantoms, Ey is the largest E-field component and measurement of SARy distribution is sufficient to characterize SAR-steering performance of the CFMA-12. SAR steering measurements at 1 cm depth in the muscle-equivalent phantom show that the SAR maximum varies by 40% (1 SD) around the average value of 38.8 W kg−1 (range 10–65 W kg−1) between single antenna elements. The effective fieldsize (E50) varies by 14% (1 SD) around the average value of 19.1 cm2.

Enhanced transient eddy current detection of deep corrosion

Recent developments in the use of transient eddy current methods have demonstrated the advanced ability to detect and characterise corrosion and cracks within complex structures, using a single acquisition scan. In addition, the use of Hall sensors to measure the magnetic field directly enables measurements at greater depths in metals than is achieved using a conventional coil sensor. However, the rapid increase in effective field size with depth in the structure means that there is always a trade-off between defect sensitivity and susceptibility to the presence of nearby edges, fasteners and other sub-structure. The ability to characterise the defect in terms of metal loss, size and depth can also suffer when defect sensitivity is increased. This paper reports an investigation to determine how the sensitivity could be increased for metal-loss defects deeper than 15 mm (0.625) in the case when the proximity of structural changes is not an issue. The essential requirement is to increase the contrast between good and defective structure by either reducing noise levels or increasing the strength of the field reflected from the defect. An increase in the reflected field can be achieved by either increasing the incident field strength, or changing its spatial characteristics. Results have shown that defect sensitivity can be increased using these methods to enable a considerable improvement in detectability of metal loss deep in thick aluminium structure.

The time course of perisaccadic receptive field shifts in the lateral intraparietal area of the monkey.

Neurons in the lateral intraparietal area of the monkey (LIP) have visual receptive fields in retinotopic coordinates when studied in a fixation task. However, in the period immediately surrounding a saccade these receptive fields often shift, so that a briefly flashed stimulus outside the receptive field will drive the neurons if the eye movement will bring the spatial location of that vanished stimulus into the receptive field. This is equivalent to a transient shift of the retinal receptive field. The process enables the monkey brain to process a stimulus in a spatially accurate manner after a saccade, even though the stimulus appeared only before the saccade. We studied the time course of this receptive field shift by flashing a task-irrelevant stimulus for 100 ms before, during, or after a saccade. The stimulus could appear in receptive field as defined by the fixation before the saccade (the current receptive field) or the receptive field as defined by the fixation after the saccade (the future receptive field). We recorded the activity of 48 visually responsive neurons in LIP of three hemispheres of two rhesus monkeys. We studied 45 neurons in the current receptive field task, in which the saccade removed the stimulus from the receptive field. Of these neurons 29/45 (64%) showed a significant decrement of response when the stimulus appeared 250 ms or less before the saccade, as compared with their activity during fixation. The average response decrement was 38% for those cells showing a significant (P < 0.05 by t-test) decrement. We studied 39 neurons in the future receptive field task, in which the saccade brought the spatial location of a recently vanished stimulus into the receptive field. Of these 32/39 (82%) had a significant response to stimuli flashed for 100 ms in the future receptive field, even 400 ms before the saccade. Neurons never responded to stimuli moved by the saccade from a point outside the receptive field to another point outside the receptive field. Neurons did not necessarily show any saccadic suppression for stimuli moved from one part of the receptive field to another by the saccade. Stimuli flashed <250 ms before the saccade-evoked responses in both the presaccadic and the postsaccadic receptive fields, resulting in an increase in the effective receptive field size, an effect that we suggest is responsible for perisaccadic perceptual inaccuracies.

Contact flexible microstrip applicators (CFMA) in a range from microwaves up to short waves.

Contact flexible microstrip applicator (CFMA) is a new light-weight microstrip applicator type for superficial and deep local hyperthermia. Typical specimens are developed for operation at frequencies of 434, 70, 40, and 27 MHz. The main common features of CFMA, namely, their flexibility and light weight, as well as their aperture dimensions slightly depend on the operating frequency. Two antenna types are used in CFMAs: inductive antennas with a radiating plane electrical dipole at microwaves, and coplanar capacitive antennas, providing depression of the normal component of the electrical field in the very high-frequency (VHF) and high-frequency (HF) range. The flexibility of the applicators enables one to conform them with curved surfaces. In a bent state of the applicators there arises a focusing effect of energy deposition in deeper located tissues due to linear polarization of the irradiated electromagnetic (EM) field, inherent in CFMA. All CFMA are integrated with silicon water boluses which serve as a matching element, so as a skin cooling agent. Due to this and to the predominance of the tangential electrical component in the radiated EM field, no fat overheating effects are noticed, as a rule. The aperture of the developed applicators overlap the range 160-630 cm2 providing effective heating field sizes (EFSs) 64-400 cm2, respectively. The most bulky CFMAs with an aperture of (21 x 29) cm2 operating at the frequency of 434 MHz weigh 0.8 kg and 2.5 kg at 27 MHz. Phenomenological analysis of the radiating systems, as well as experimental evaluation of the applicators are presented. CFMAs operating at frequencies of 434 and 40 MHz are used in clinical practice. CFMA at 70 and 27 MHz are subjected to laboratory clinical investigations.

Quasi-independent monitor unit calculation for intensity modulated sequential tomotherapy

The number of linac monitor units (MU) from intensity modulated sequential tomotherapy (IMST) is substantially larger than the MU delivered in conventional radiation therapy, and the relation between MU and dose is obscure due to complicated variation of the beam intensities. The purpose of this work was to develop a practical method of verifying the MU and dose from IMST so that the MU of each arced beam could be double-checked for accuracy. MU calculations for 41 arced beams from 14 IMST patients were performed using the variables of vane open fraction time, field size, target depth output factor, TMR, and derived intensity distribution. Discrepancy between planned and checked MU was quantified as percent. All 41 discrepancies were clustered between to , illustrated in a Gaussian-shaped histogram centered at standard deviation indicating the present MU calculations are in agreement with the planned expectations. To confirm the correctness of the present calculated MUs of the IMST plans, eight of the calculated IMST plans are performed dose verifications using their hybrid plans, which are created by transporting patient's IMST plan beams onto a spherical polystyrene Phantom for dose distribution within the Phantom. The dose was measured with a 0.07 cc ionization chamber inserted in the spherical Phantom during the hybrid plan irradiation. Average discrepancy between planned and measured doses was found to be with single standard deviation uncertainty. The spread of the discrepancies of present calculated MUs relative to their planned ones are attributed to uncertainties of effective field size, effective planned dose corresponding to each arc, and inaccuracy of quantification of scattered dose from adjacent arced beams. Overall, the present calculation of MUs is consistent with what derived from treatment plans. Since the MUs are verified by actual dose measurements, therefore the present MU calculation technique is considered adequate for double-checking planned IMST MUs. PACS number(s): 87.53.–j, 87.66.–a

Quasi-independent monitor unit calculation for intensity modulated sequential tomotherapy.

The number of linac monitor units (MU) from intensity modulated sequential tomotherapy (IMST) is substantially larger than the MU delivered in conventional radiation therapy, and the relation between MU and dose is obscure due to complicated variation of the beam intensities. The purpose of this work was to develop a practical method of verifying the MU and dose from IMST so that the MU of each arced beam could be double‐checked for accuracy. MU calculations for 41 arced beams from 14 IMST patients were performed using the variables of vane open fraction time, field size, target depth output factor, TMR, and derived intensity distribution. Discrepancy between planned and checked MU was quantified as 100(MUcal−MUplan)/MUplan percent. All 41 discrepancies were clustered between −5% to +5%, illustrated in a Gaussian‐shaped histogram centered at −1.0±3.5% standard deviation indicating the present MU calculations are in agreement with the planned expectations. To confirm the correctness of the present calculated MUs of the IMST plans, eight of the calculated IMST plans are performed dose verifications using their hybrid plans, which are created by transporting patient's IMST plan beams onto a spherical polystyrene Phantom for dose distribution within the Phantom. The dose was measured with a 0.07 cc ionization chamber inserted in the spherical Phantom during the hybrid plan irradiation. Average discrepancy between planned and measured doses was found to be 0.6±3.4% with single standard deviation uncertainty. The spread of the discrepancies of present calculated MUs relative to their planned ones are attributed to uncertainties of effective field size, effective planned dose corresponding to each arc, and inaccuracy of quantification of scattered dose from adjacent arced beams. Overall, the present calculation of MUs is consistent with what derived from treatment plans. Since the MUs are verified by actual dose measurements, therefore the present MU calculation technique is considered adequate for double‐checking planned IMST MUs.PACS number(s): 87.53.–j, 87.66.–a

Individual Differences in Working Memory during Reading with and without Parafoveal Information: A Moving-Window Study

We examined individual differences in working memory appearing in the effective visual field size while reading Japanese text. Working memory capacity was measured by a Japanese reading span test, and the subjects were divided into high- and low-score groups. Reading performance was measured by reading time, comprehension, and eye movements using a variable moving window through which the subject could read areas of the Japanese text. As the window size decreased, the reading time increased significantly. High-span subjects showed better performance in reading time, comprehension, and fixation duration than low-span subjects even in small visual fields. Interestingly, high-span subjects appear to show better information integration during reading, whereas low-span subjects showed less integration without parafoveal vision. These findings suggest that reading performance was better for subjects with larger working memory resources in a parafoveal restriction condition.

Non-invasive temperature profile estimation in a lossy medium based on multi-band radiometric signals sensed by a microwave dual-purpose body-contacting antenna

Microwave radiometry has during the past two decades been investigated as a non-invasive scheme for measurement of subcutaneous tissue temperatures, basically for monitoring and control in hyperthermic treatment of cancer. In this effort, we test a contact-type, dual-purpose antenna with integral water bolus. To overcome conflicting optimization criteria in the integration of this thermometry technique with heat applicators exhibiting a large effective field size during superficial hyperthermia, a stacked configuration design is proposed, where the radiometer receive antenna (Archimedean spiral) is located on the front (skin) surface of the water bolus and the heating antenna (Dual-Concentric Conductor aperture) is placed on the bolus back surface. The motivation is to achieve homogeneous tissue heating simultaneously with non-invasive thermography of the target tissue under the applicator. This paper addresses the feasibility of predicting one-dimensional depth temperature profiles from multi-band brightness temperatures. The performance is investigated statistically by a Monte Carlo technique on both simulated and real heated-phantom data using up to six radiometric bands. Analysis of measured data shows that during the transient heating period in a solid lossy phantom, the inversion technique exhibits a precision (2 † T ) and skewness (bias) of estimated compared to actual temperature profiles of better than - 0.38°C and - 0.55°C, respectively.

Present Status of Exposure Tool Development for Low Energy Electron-beam Proximity Projection Lithography.

A s-tool for Low Energy Electron-beam Proximity Projection Lithography (LEEPL)1-2 has been developed for proof of lithography (POL) of mass production tool, which is applied to required performance in 100-nm and 70-nm technology node. Major features of system design are an acceleration voltage of 1-5kV, a beam current of 3-20μA, a maximum field size of 40mm x 40mm (effective field size of 25mm x 25mm), a die-by-die alignment system and automatic loader systems for masks and wafers. The throughput is estimated over 20 wafers of 300mmφ per hour. As examples of initial evaluation results, resolution of 45-nm L/S patterns and 48-nmφ hole patterns in resist image were obtained. Alignment experiments are on going now, and overlay accuracy around 20-nm (3σ) over effective area of 8-in. wafer is being expected.

Role of Inhibition in Cortical Reorganization of the Adult Raccoon Revealed by Microiontophoretic Blockade of GABAAReceptors

Cortical reorganization was induced by amputation of the 4th digit in 11 adult raccoons. Animals were studied at various intervals, ranging from 2 to 37 wk, after amputation. Recordings were made from a total of 129 neurons in the deafferented cortical region using multibarrel micropipettes. Several types of receptive fields were described in reorganized cortex: restricted fields were similar in size to the normal receptive fields in nonamputated animals; multi-regional fields included sensitive regions on both adjacent digits and/or the underlying palm and were either continuous over the entire field or consisted of split fields. The proportion of neurons with restricted fields increased with time after amputation and was greater than previously found in subcortical regions. A GABA(A) receptor antagonist (bicuculline methiodide), glutamate, and GABA were administered iontophoretically to these neurons while determining their receptive fields and thresholds. Bicuculline administration resulted in expansion of the receptive field in 60% of the 93 neurons with cutaneous fields. In most cases (33 neurons) this consisted of a simple expansion around the borders of the predrug receptive field, and the average expansion (426%) was not different from that seen in nonamputated animals. In some neurons (n = 4), bicuculline produced an expansion from one digit onto the adjacent palm or another digit, an effect never seen in control animals. Bicuculline also changed the split fields of seven neurons into continuous fields by exposing a responsive region between the split fields. Finally, bicuculline changed the internal receptive field organization of 10 neurons by revealing subfields with reduced thresholds. In contrast to the situation in nonamputated animals, iontophoretic administration of glutamate also produced receptive field expansion in some neurons (n = 6), but the size and/or shape of the change was different from that produced by bicuculline, indicating that the effects of bicuculline were not due to an overall facilitation of neuronal activity. These results are consistent with the hypotheses that an important component of long-term cortical reorganization is the gradual reduction in effective receptive field size and that intracortical inhibitory networks are partially responsible for these changes.