Micro-scale removal of Cu from a dielectric substrate has applications in microelectronics, patch antenna fabrication and frequency selective surface (FSS) manufacturing. Pulsed laser-based micro-scribing of Copper (Cu) from a dielectric is a preferred technique to avoid the adverse effects of chemical etching, such as toxicity and corrosive nature of the etchant, difficulty in fabrication of mask etc. However, pulsed laser-assisted removal of Cu from a dielectric in the air will produce recast layer/ redeposit, oxide layer near the ablation zone and thermal damage to the dielectric is another challenge. In this study, a hybrid technique with nanosecond laser-activated electrochemical micro-scribing of Cu is demonstrated. The technique was extended to remove 35 μm Cu from Rogers-RO4003 dielectric with a thickness ≈0.75 mm to fabricate FSS samples in X-band. The Cu-deposited dielectric substrate was immersed in Sodium Chloride (NaCl) solution, the laser beam was directed through a negatively biased tool electrode and the sample was biased positively. In this hybrid technique, along with laser-assisted material removal, laser-activated electrochemical etching also removed Cu selectively. The laser irradiation coupled with the NaCl solution induced preferential micro-etching, resulting in improved surface morphology without re-deposition and recast layer and thermal protection to the dielectric substrate. The FSS sample produced with the laser-hybrid micro-scribing was working at 10.3 GHz.
Paul Stauffer, Paolo Maccarini, Kavitha Arunachalam, Valeria De Luca, Sara Salahi, Alina Boico, Oystein Klemetsen, Yngve Birkelund, Svein Jacobsen, Fernando Bardati, Piero Tognolotti, Brent Snow
Background: Vesicoureteral reflux (VUR) is a serious health problem leading to renal scarring in children. Current
VUR detection involves traumatic x-ray imaging of kidneys following injection of contrast agent into bladder via
invasive Foley catheter. We present an alternative non-invasive approach for detecting VUR by radiometric monitoring
of kidney temperature while gently warming the bladder.
Methods: We report the design and testing of: i) 915MHz square slot antenna array for heating bladder, ii) EMI-shielded
log spiral microstrip receive antenna, iii) high-sensitivity 1.375GHz total power radiometer, iv) power
modulation approach to increase urine temperature relative to overlying perfused tissues, and v) invivo porcine
experiments characterizing bladder heating and radiometric temperature of aaline filled 30mL balloon "kidney"
implanted 3-4cm deep in thorax and varied 2-6°C from core temperature.
Results: SAR distributions are presented for two novel antennas designed to heat bladder and monitor deep kidney
temperatures radiometrically. We demonstrate the ability to heat 180mL saline in in vivo porcine bladder to 40-44°C
while maintaining overlying tissues <38°C using time-modulated square slot antennas coupled to the abdomen with
room temperature water pad. Pathologic evaluations confirmed lack of acute thermal damage in pelvic tissues for up to
three 20min bladder heat exposures. The radiometer clearly recorded 2-6°C changes of 30mL "kidney" targets at depth
in 34°C invivo pig thorax.
Conclusion: A 915MHz antenna array can gently warm in vivo pig bladder without toxicity while a 1.375GHz
radiometer with log spiral receive antenna detects ≥2°C rise in 30mL "urine" located 3-4cm deep in thorax,
demonstrating more than sufficient sensitivity to detect Grade 4-5 reflux of warmed urine for non-invasive detection of
VUR.
P. Stauffer, Oana Craciunescu, P. Maccarini, Cory Wyatt, K. Arunachalam, O. Arabe, V. Stakhursky, B. Soher, J. MacFall, Z. Li, William Joines, S. Rangarao, K. Cheng, S. Das, Carlos Martins, Cecil Charles, Mark Dewhirst, T. Wong, E. Jones, Z. Vujaskovic
A critical need has emerged for volumetric thermometry to visualize 3D temperature distributions in real time during
deep hyperthermia treatments used as an adjuvant to radiation or chemotherapy for cancer. For the current effort,
magnetic resonance thermal imaging (MRTI) is used to measure 2D temperature rise distributions in four cross sections
of large extremity soft tissue sarcomas during hyperthermia treatments. Novel hardware and software techniques are
described which improve the signal to noise ratio of MR images, minimize motion artifact from circulating coupling
fluids, and provide accurate high resolution volumetric thermal dosimetry. For the first 10 extremity sarcoma patients,
the mean difference between MRTI region of interest and adjacent interstitial point measurements during the period of
steady state temperature was 0.85°C. With 1min temporal resolution of measurements in four image planes, this noninvasive
MRTI approach has demonstrated its utility for accurate monitoring and realtime steering of heat into tumors at
depth in the body.
The use of conformal antenna array in the treatment of superficial diseases can significantly increase patient comfort
while enhancing the local control of large treatment area with irregular shapes. Originally a regular square multi-fed slot
antenna (Dual Concentric Conductor - DCC) was proposed as basic unit cell of the array. The square DCC works well
when the outline of the treatment area is rectangular such as in the main chest or back area but is not suitable to outline
diseases spreading along the armpit and neck area. In addition as the area of the patch increases, the overall power
density decreases affecting the efficiency and thus the ability to deliver the necessary thermal dose with medium power
amplifier (<50W). A large number of small efficient antennas is preferable as the disease is more accurately contoured
and the lower power requirement for the amplifiers correlates with system reliability, durability, linearity and overall
reduced cost. For such reason we developed a set of design rules for multi-fed slot antennas with irregular contours and
we implemented a design that reduce the area while increasing the perimeter of the slot, thus increasing the antenna
efficiency and the power density. The simulation performed with several commercial packages (Ansoft HFSS, Imst
Empire, SemcadX and CST Microwave Studio) show that the size reducing method can be applied to several shapes and
for different frequencies. The SAR measurements of several DCCs are performed using an in-house high resolution
scanning system with tumor equivalent liquid phantom both at 915 MHz for superficial hyperthermia systems in US) and
433 MHz (Europe). The experimental results are compared with the expected theoretical predictions and both simulated
and measured patterns of single antennas of various size and shapes are then summed in various combinations using
Matlab to show possible treatment irregular contours of complex diseases. The local control is expected to significantly
improve while maintaining the patient comfort.
This work reports the ongoing development of a combination applicator for simultaneous heating of superficial tissue
disease using a 915 MHz DCC (dual concentric conductor) array and High Dose Rate (HDR) brachytherapy delivered
via an integrated conformal catheter array. The progress includes engineering design changes in the waterbolus, DCC
configurations and fabrication techniques of the conformal multilayer applicator. The dosimetric impact of the thin
copper DCC array is also assessed. Steady state fluid dynamics of the new waterbolus bag indicates nearly uniform flow
with less than 1°C variation across a large (19×32cm) bolus. Thermometry data of the torso phantom acquired with
computer controlled movement of fiberoptic temperature probes inside thermal mapping catheters indicate feasibility of
real time feedback control for the DCC array. MR (magnetic resonance) scans of a torso phantom indicate that the
waterbolus thickness across the treatment area is controlled by the pressure applied by the surrounding inflatable
airbladder and applicator securing straps. The attenuation coefficient of the DCC array was measured as 3± 0.001% and
2.95±0.03 % using an ion chamber and OneDose dosimeters respectively. The performance of the combination
applicator on patient phantoms provides valuable feedback to optimize the applicator prior use in the patient clinic.
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