Comb Pattern Research Articles

Performance enhancement of partially shaded PV array using novel shade dispersion effect on magic-square puzzle configuration

Partial shading conditions decrease the power output from PV arrays. In partial shading conditions the PV modules of the array receive the different solar irradiation, so the arrays exhibit multiple peaks in P-V and I-V characteristics hence mismatch loss occurs between the PV modules. This paper investigates the performance improvement in existing solar photovoltaic (PV) array by re-configurations of the array. The MATLAB/Simulink modeling of PV array configurations such as total cross-tied (TCT), proposed hybrid series parallel - total cross-tied (SP-TCT), bridge link- total cross-tied (BL-TCT), bridge link- honey comb (BL-HC), Magic Square (MS) and MS puzzle pattern based reconfiguration like Re-arranged total-cross-tied (RTCT), Re-arranged series parallel- total-cross-tied (RSP-TCT), Re-arranged bridge link- total cross-tied (RBL-TCT) and Re-arranged bridge link- honey comb (RBL-HC) is done. The performance of all these configurations has been investigated using P-V characteristics, power loss due to shading, fill factor and shading dispersion effect on maximum power point (MPP) for various shading patterns namely pattern-1 (vertical shading), 2 (horizontal shading) and 3 (diagonal shading). Extensive analysis is carried out on a 4×4 PV array configurations for these shading patterns. The power at MPP of MS and RTCT configurations is 2279W more, mismatch power loss is 300W less, and fill factor (FF) is 9.91 more than TCT configuration. The performances of proposed configurations are found superior for some cases of shading patterns.

Micromolding of Ni-P with Reduced Ferromagnetic Properties for 3D MEMS

This paper presents the development of nickel phosphorus (Ni-P) micromolding for the manufacturing of a 3D electrostatic energy harvesting microsystem. Ni-P alloy exhibits weak ferromagnetic properties beyond 10–12 wt% phosphorus content. Deposits were prepared at different current densities (−10 to −150 mA/cm²) and concentration of phosphorous acid in the electrolyte (0–20 g/l). It was found that the deposition rate decreases when phosphorus content increases in the deposit. The final process leaded the choice of a H3PO3 concentration of 5 g/l to reach a 0.1 μm/min deposition rate for phosphorus content higher than 13 wt%. Mechanical, electrical and magnetic properties of the Ni-P films were investigated on 1 mm² and 1 cm² square deposit and confirmed the suitability of that material for the target MEMS. Comb patterns of micromolded Ni-P have been realized on a 2-inch wafer, leading to a 10 μm thick deposit containing 13.5 wt% in P, which is, at our knowledge, the first high phosphorus Ni-P micromolding involving electrodeposition growth for 3D MEMS applications.

On the phase noise performance of microwave and millimeter-wave signals generated with versatile Kerr optical frequency combs.

We investigate the phase noise performance of micro- and millimeter-wave signals generated using a ultra-high Q whispering gallery mode disk-resonator with Kerr nonlinearity. Our study focuses on the stability of the optical spectra and on the performances of the corresponding microwave and millimeter-wave beat notes in terms of power and phase noise. The blue slope of an optical mode of the resonator, allowing for the generation of optical frequency combs, is accurately explored in order to identify various comb patterns. Each of these patterns is characterized in the optical and radio-frequency domains. Phase noise levels below -100 dBc/Hz at 10 kHz offset have been achieved for beat notes in the radio-frequency spectrum at 12 GHz, 18 GHz, 24 GHz, 30 GHz, and 36 GHz with the same resonator.

Printed Circuit Board Surface Finish and Effects of Chloride Contamination, Electric Field, and Humidity on Corrosion Reliability

Corrosion reliability is a serious issue today for electronic devices, components, and printed circuit boards (PCBs) due to factors such as miniaturization, globalized manufacturing practices which can lead to process-related residues, and global usage effects such as bias voltage and unpredictable user environments. The investigation reported in this paper focuses on understanding the synergistic effect of such parameters, namely contamination, humidity, PCB surface finish, pitch distance, and potential bias on leakage current under different humidity levels, and electrochemical migration probability under condensing conditions. Leakage currents were measured on interdigitated comb test patterns with three different types of surface finish typically used in the electronics industry, namely gold, copper, and tin. Susceptibility to electrochemical migration was studied under droplet conditions. The level of base leakage current (BLC) was similar for the different surface finishes and NaCl contamination levels up to relative humidity (RH) of 65%. A significant increase in leakage current was found for comb patterns contaminated with NaCl above 70% to 75% RH, close to the deliquescent RH of NaCl. Droplet tests on Cu comb patterns with varying pitch size showed that the initial BLC before dendrite formation increased with increasing NaCl contamination level, whereas electrochemical migration and the frequency of dendrite formation increased with bias voltage. The effect of different surface finishes on leakage current under humid conditions was not very prominent.

Micro Printing Using Microfluidics for Printed Biodegradable Devices in Trillion Sensing

Printed and biodegradable devices are a promising technology for the up-coming trillion sensor universe, in which over a trillion networked sensors annually will be used for smart solution for global social problems, such as energy, food, manufacturing, and infrastructure [1]. To achieve this universe, a hundred-fold increase in networked sensors must use the same order of resources as current sensors, with at most 1% of cost and environment impact of traditionally fabricated sensors. From this viewpoint, we investigated a fabrication process for printed biodegradable devices and here successfully prepared micro-printed pattern of metal nanoparticles on biodegradable polymer substrate for the first time. Such processes would enable flexible, disposable, and environmentally friendly electronics for the trillion sensors universe. This printed fabrication process uses a template to guide metal nanoparticle ink deposition. A polymer (e.g., poly dimethyl siloxane, poly 4-methyl 2-pentyne) template with nano- or micro- patterned channels was put on the biodegradable polymer substrate. Then, the nanoparticle ink was injected into the channel to form the desired pattern. Further details of this process are described in [2, 3]. To prepare the biodegradable polymer film, a biodegradable polymer (poly lactic acid (PLA), poly caprolactone (PCL), or poly (3-hydroxybutyrate- co- 3-hydroxyvalerate) (PHBV)) in pellet form was dissolved in dichloromethane with various concentrations and cast on a petri dish to prepare various thickness of substrate from 10 through 200 mm. As the result, a micro- printing pattern on PLA film is shown. The thickness of the PLA film was measured as ca. 150 μm. The material and printed metal pattern retain their flexibility. From optical microscopic measurements, we confirm that the interdigitated comb pattern was transferred to the PLA substrate. This shape was consistent with the original micro pattern on the surface of the template. Further, the SEM image demonstrates the interdigitated comb pattern is comprised of closely-packed Ag nanoparticles. In the presentation, we will discuss the micro printing of metal nanoparticles for printed biodegradable devices from the viewpoint of effect of kinds of biodegradable materials, surface roughness and morphology, and the effect of contact angle on printing success and fidelity. We will consider the adaptability of biodegradable polymer for printed electronics and devices. Acknowledgement This research was partially financially supported by the Walter J. Zable Chair in Engineering at UC San Diego and AIST short-term fellowship, and Grant-in-Aid for Scientific Research (B). NT shows gratitude to all members of PRIME in UC San Diego and UC Berkley, for example Mr. Shunichi Arakawa (UCSD), Mr. David Rolfe and Mr. John Herr (UC Berkley). Some measurement such as SEM was supported by NANO3 staff member in UC San Diego. Reference [1] J. Bryzek, Roadmap for the Trillion Sensor Universe [2] M. T. Demko, J. C. Cheng, A. P. Pisano, ACS Nano, 6, 6890 (2012). [3] M. T. Demko, T. M. Blackbill, A. P. Pisano, Langmuir, 28, 9857 (2012). [4] As review, L. S. Naira, C. T. Laurencin, Prog. Polym., Sci. 32, 762 (2007).

Humidity Build-Up in a Typical Electronic Enclosure Exposed to Cycling Conditions and Effect on Corrosion Reliability

The design of electronic device enclosures plays a major role in determining the humidity build-up inside the device as a response to the varying external humidity. Therefore, the corrosion reliability of electronic devices has direct connection to the enclosure design. This paper describes the internal humidity build-up in a typical enclosure prescribed for electronic applications as a function of external humidity conditions and enclosure-related parameters. Investigated parameters include external temperature and humidity conditions, the temperature and time of the internal heating cycle, thermal mass, and port/opening size. The effect of the internal humidity build-up on corrosion reliability has been evaluated by measuring the leakage current (LC) on interdigitated test comb patterns, which are precontaminated with sodium chloride and placed inside the enclosure. The results showed that the exposure to cycling temperature causes significant change of internal water vapor concentration. The maximum value of humidity reached was a function of the opening size and the presence of thermal mass inside the enclosure. A pumping effect was observed due to cycling temperature, and the increase in the level of absolute humidity at each cycle led to condensation, which caused a sudden increase in LC.

Micromolding of Ni-P for the Realization of a 3D Electrostatic Energy Harvesting MEMS

This paper presents the development of nickel phosphorous (Ni-P) micromolding for the manufacturing of a 3D electrostatic energy harvesting microsystem. Ni-P alloy exhibits weak ferromagnetic properties beyond 10-12 wt% P content. Deposits were prepared at different current densities (-10 to -150 mA/cm²) and concentration of phosphorous acid in the electrolyte (0 -20g/l). The rate decreases when phosphorous content increases in the deposit. The final process leaded to choose a H3PO3 concentration of 5 g/l which give a 0.1 µm/min deposition rate for P content higher than 13 wt%. Mechanical, electrical and magnetic properties of the Ni-P films were investigated on 1mm² and 1cm² deposits and confirmed the suitability of that material for the target MEMS. Comb patterns of Ni-P micromolding have been realized on 2 inch wafer, leading to a 10 µm thick deposit containing 13.5 wt% in P, which is, at our knowledge, the first Ni-P micromolding involving electrodeposition growth.

Ultrastructural Analysis of Incinerated Teeth by Scanning Electron Microscope – A Short Study

In forensic context precise knowledge on physical and histological changes of teeth subjected to high temperatures is of great importance. Preserving fragile incinerated teeth for physical, histological and ultra structural examinations is essential in fire investigations involving the origin of fire, its cause as well as the identification of victims which relies on a thorough understanding of the structural changes in dental tissues subjected to heat. The study was conducted to evaluate the physical and ultrastructural changes seen in freshly extracted teeth when subjected to gradual heating at different temperatures using Scanning Electron Microscope (SEM). Freshly extracted teeth collected from subjects of different age groups were subjected to different temperatures using laboratory furnace and findings were correlated to the temperature. The study was conducted on 60 healthy freshly extracted teeth belonging to age group between 20-30 years. Group A comprised of control group which included teeth that were not subjected to heat whereas Group B, C and D comprised of teeth that were subjected to different temperatures i.e., 100(o)C, 300(o)C and 600(o)C respectively for a time of fifteen minutes in laboratory furnace, after which they were processed for SEM examination. Each group included 15 teeth; 5 anteriors, 5 premolars and 5 molars. Examination under SEM revealed definite ultra structural changes which were explicitly seen at particular temperatures (100(o)C, 300(o)C and 600(o)C). The samples showed cracks and charring of the tooth structure with ultra structural findings such as pebbles, granules, dots on enamel surface; and soap bubble pattern, honey comb pattern and snail track pattern on cementum surface. Because of the consistency of morphological changes and the ultra structural patterns at various temperatures, evaluation of incinerated dental remains using SEM can provide additional investigative avenues in victim identification and in the areas of forensic fire investigations.

High Reliability No-Clean Solder Paste for Designs where Flux Cannot be Dried

The miniaturization trend is driving industry to adopting low standoff components or components in cavity. The cost reduction pressure is pushing telecommunication industry to combine assembly of components and electromagnetic shield in one single reflow process. As a result, the flux outgassing/drying is getting very difficult for devices due to poor venting channel. This resulted in insufficiently dried/burnt-off flux residue. For a properly formulated flux, the remaining flux activity posed no issue in a dried flux residue for no-clean process. However, when venting channel is blocked, not only solvents remain, but also activators could not be burnt off. The presence of solvents allows mobility of active ingredients and the associated corrosion, thus poses a major threat to the reliability. In this work, a new halogen-free no-clean SnAgCu solder paste, 33-76-1, has been developed. This solder paste exhibited SIR value above the IPC spec 100 MΩ without any dendrite formation, even with a wet flux residue on the comb pattern. The wet flux residue was caused by covering the comb pattern with 10 mm × 10 mm glass slide during reflow and SIR testing in order to mimic the poorly vented low standoff components. Paste 33-76-1 also showed very good SMT assembly performance, including voiding of QFN and HIP resistance. The wetting ability of paste 33-76-1 was very good under nitrogen. For air reflow, 33-76-1 still matched paste C which is widely accepted by industry for air reflow process. The above good performance on both non-corrosion with wet flux residue and robust SMT process can only be accomplished through a breakthrough in flux technology.

Study of Parameters Affecting the Electrostatic Attractions Force

This paper contains 2 main parts. In paper we simulated and studied three types of in various industries for suspension and handling of the semiconductor and glass and we selected evaluating the electrostatic force, which was comb pattern electrode. In the second part we investigated the parameters affecting the amount of electrostatic force such as the gap between surface and electrode (g), the electrode width (w), the gap between electrodes (t), the surface permittivity and electrode length improvement of adhesion force by changing these values Keywords—Electrostatic force, electrostatic adhesion, electrostatic chuck, electrostatic application in industry, Electroadhesive grippers.

Microfabrication of surface acoustic wave device using UV LED photolithography technique

Microfabrication of typical surface acoustic wave (SAW) devices using low cost ultra-violet light emitting diodes (UV LED) lithography technique is demonstrated. UV lithography is one of the prime fabrication steps while manufacturing SAW devices. Recently, UV LED based lithography has created attention for their low cost setup, low power consumption, and submicron manufacturing features. Interdigital transducers (IDTs) and reflectors of a SAW device generally consist of a long chain of electrodes separated by gaps. Minor fabrication anomalies in these kinds of features can lead to failure in fabrication and thus, the lithography technique should ensure high quality of fabrication. In this work, we have employed a commercially available UV LED torch as a UV source and transferred SAW device features (in an optical chrome mask) such as IDT comb patterns onto photoresist coated piezoelectric substrates through contact lithography technique. Typical SAW devices operating in 130 and 148MHz were considered for the fabrication. The minimum electrode width dimension fabricated in the present work was 7μm. The optimized fabrication method adopted to realize the features are presented in the experimental section of this technical note. The optical microscope images and the frequency response of the fabricated devices confirm the successful fabrication using the proposed technique. The fabricated SAW devices features had an accuracy of ±0.5μm. Although the contact lithography technique using UV LED torch is simple and cost-effective to use, the non-uniform irradiance from the torch has caused irregular pattern transfer in the fabrication trials. However these issues were overcome by optimizing the sample placement under the UV source and UV exposure conditions.

Fabrication of Multiple Al Micro-Materials by Electromigration Using a Comb Pattern and a Conductive Passivation Film

Electromigration (EM) is the phenomenon of atomic diffusion in a metallic film with a high-density electron flow. Our group used EM to fabricate Al micro-materials. The EM technique can be used to fabricate micro-materials with a high aspect ratio, pure metal components, an arbitrary form, and a single-crystal structure. Recently, two micro-materials have been simultaneously fabricated using an array pattern consisting of parallel or series connections. However, multiple micro-materials have not been fabricated simultaneously thus far. In this study, a new comb sample pattern was used with a conductive passivation film to produce multiple Al micro-materials.

Impact of NaCl Contamination and Climatic Conditions on the Reliability of Printed Circuit Board Assemblies

The effect of climatic conditions and ionic contamination on the reliability of printed circuit board assembly has been investigated in terms of leakage current (LC) and electrochemical migration susceptibility. The change in LC as a function of relative humidity (RH) and temperature was measured using single components (size 0805) and surface insulation resistance comb patterns precontaminated with sodium chloride at levels adjacent to levels used in the IPC J-STD-001 standard. The potential bias of 5-10 V was applied during experiments, and the climatic conditions were in the range 60%-98% RH and 15 °C-65 °C. The variation of RH at the surface of the test specimens was imposed by 1) increasing the RH of the surrounding air and 2) reducing the temperature of the printed circuit boards using a cooling stage, while maintaining a constant climatic condition in the chamber. A considerable increase in LC was observed at sodium chloride concentrations above 1.56 μg·cm-2, as the RH on the surface was close to the critical RH for sodium chloride. Prolonged exposure to conditions close to condensation resulted in the formation of tin whiskers and hillocks growing from the component electrodes due to corrosion of the electrodes freeing the whisker growth.

OS1501 エレクトロマイグレーションによる微細材料大量創製へ向けたサンプル構造改良に関する研究

Micro-materials attract attention with their remarkable properties, including mechanical, thermal, electrical attribute. Various techniques have been developed for fabricating micro-materials. The fabrication technique by utilizing electromigration (EM), which is the physical phenomenon of atomic diffusion in a metallic line with a high-density electron flow, is one of the fabrication methods for generating micro-materials. EM technique can generate micro-materials with a high-aspect ratio, pure Al components, an arbitrary form, and a single-crystal structure. Whereas EM has significantly advantages, multiple micro-materials are difficult to fabricate simultaneously. The technique using conductive passivation and comb pattern has been recently developed for fabricating multiple micro-materials by the authors. The present study demonstrates the multiple fabrication more than previous research, and provides the approach for improving fabrication of multiple micro-materials by EM.

Karakteristik Genetik Eksternal Ayam Kampung di Kecamatan Sungai Pagu Kabupaten Solok Selatan

The purpose of this research is to determine external genetic characteristic that contents cualitatif and cuantitatif traits native chicken at Sungai Pagu Solok Selatan region. This reseachs using 150 native chicken which is 50 male and 100 female in mature period. Reseachs method by survey and sampling method using multi stage random sampling. Data analized by statistic descriptive. Results of this research showed that feather color of male is wild feather type 38%, gold 22%, black 14%, white 10%, bar 10%, and columbian 6%. Single comb pattern 44%, rose 32%, pea 16%, and walnut 4%. Legs color skin(shank) yellow/white 74% and black 26%. Feather color at female is black 50%, bar 17%, gold 12%, white 10%, wild feather type 5%, columbian 4% and white silver(S) 2%. Pea comb pattern 48%, walnut 25%, single 21%, rose 6%. Legs color skin yellow/white 66% and black 34%. The male length of tarsometatarsus was 103.60 mm, tibia 144.48 mm, femur 109.24 mm, comb height 23.15 mm, body weight 1.90 kg, wing length 218.41 mm, length of third legs toe 73.20 mm. While, on the female has length of tarsometatarsus 81.07 mm, tibia 125.34 mm, femur 95.39 mm, comb height 9.89 mm, body weight 1.36 kg, measures of os pubic 30.06 mm, wing length 188.65 mm, and length of third legs toe were 63.52 mm.

English

BACKGROUND: In practical and numerical terms, the solitary nodule is the most important target of thyroid FNAC. Since FNAC can provide an unequivocal benign diagnosis in 60% of patients with benign nodules, its potential to reduce the number of unnecessary operations is significant. Of all the thyroid glands that on surgical resection prove to contain solitary nodules, 70- 80% are benign adenomas and about 10-30% is malignant growth. Over the past two decades, fine needle aspiration cytology (FNAC) has become an essential step in the evaluation of thyroid nodules, due to its superior diagnostic reliability and cost effectiveness. AIMS & OBJECTIVES: The present study aims to explore the role of FNAC in the diagnosis of various thyroid lesions presenting as solitary thyroid nodules (excluding multiple nodular lesion). MATERIAL & METHODS: 140 patients of more than or equal to 15 years of age presenting with solitary thyroid nodule were the subjects of the current study. Subjects were referred for fine needle aspiration by the treating clinicians. OBSERVATIONS: Male: Female ratio was (18/122) 1:6.8 and age of the patients ranged from 15 years to 62 years. Maximum number of cases was in 3 rd and 4 th decades. 4 patients were in 7 th decade. Cytodiagnostic break up of all 122 cases included colloid goitre 31 cases (25.5%), hyperplastic nodule 3 cases (2.5%), lymphocytic thyroiditis 2 cases (1.6%), Hashimoto's thyroiditis 7 cases (5.7%) and subacute thyroiditis 5 cases (4.0%), from non-neoplastic category. Amongst the neoplastic category, follicular neoplasm (45 cases, 36.9 %) was the most common lesion and remaining included 15 cases of papillary carcinoma (12.3%), 4 cases of Hurthle cell neoplasm (3.3%), 3 cases of medullary carcinoma (2.5%), 2 cases of anaplastic carcinoma (1.6%) and a solitary case of squamous cell carcinoma (0.8%). Colloid was observed in all cases and was abundant in 18 cases (58%) and moderate in 11 cases (35.5%). Dominant cellular pattern observed in all cases and uniform follicular cells were arranged in monolayered sheets (honey comb pattern), nuclear pleomorphism was an uncommon finding, being seen in only 4 cases (13%). Foamy histiocytes or hemosiderin laden histiocytes were a fairly common finding, being observed in 23 cases (74.1%). A cytodiagnosis of follicular neoplasm accounted for 36.9% (45 out of 122) of all diagnosis rendered on adequate aspirates and 64.3% of all diagnosed neoplasms. (45 out of 70 cases), thus reflecting that this entity comprised not only the highest number of cases amongst the neoplastic group but also the most common lesion when both non-neoplastic and neoplastic lesions were considered together. Aspirates from follicular neoplasms were either moderately cellular or highly cellular. Thus good cellularity was the outstanding characteristic feature observed in all cases. Blood in the background was a consistent finding observed in almost all the cases. Scant to moderate colloid was observed in 31 cases (68.8%). The dominant pattern was one of repetitive microfollicles or acini being observed in all 45 cases (100%). Most of the cases also had cellular aggregates with nuclear overlapping. Histopathological correlation was available in 20 cases. 19 cases were consistent with cytodiagnosis although 1 case showed discrepancy. CONCLUSION: It was concluded that FNAC of

Silicon vertical microstructure fabrication by catalytic etching

This study presents an effective, simple and inexpensive process for forming micro-scale vertical structures on a (1 0 0) silicon wafer. Several modified etchants and micro-patterns including rectangular, snake-like, circular and comb patterns were employed to determine the optimum etching process. We found that an etchant solution consisting of 4.6 M hydrofluoric acid, 0.44 M hydrogen peroxide and isopropyl alcohol produces microstructures at an etching rate of 0.47 µm min−1 and surface roughness of 17.4 nm. All the patterns were transferred faithfully to the silicon substrate.

Comb-Push Ultrasound Shear Elastography (CUSE): A Novel Method for Two-Dimensional Shear Elasticity Imaging of Soft Tissues

Fast and accurate tissue elasticity imaging is essential in studying dynamic tissue mechanical properties. Various ultrasound shear elasticity imaging techniques have been developed in the last two decades. However, to reconstruct a full field-of-view 2-D shear elasticity map, multiple data acquisitions are typically required. In this paper, a novel shear elasticity imaging technique, comb-push ultrasound shear elastography (CUSE), is introduced in which only one rapid data acquisition (less than 35 ms) is needed to reconstruct a full field-of-view 2-D shear wave speed map (40 × 38 mm). Multiple unfocused ultrasound beams arranged in a comb pattern (comb-push) are used to generate shear waves. A directional filter is then applied upon the shear wave field to extract the left-to-right (LR) and right-to-left (RL) propagating shear waves. Local shear wave speed is recovered using a time-of-flight method based on both LR and RL waves. Finally, a 2-D shear wave speed map is reconstructed by combining the LR and RL speed maps. Smooth and accurate shear wave speed maps are reconstructed using the proposed CUSE method in two calibrated homogeneous phantoms with different moduli. Inclusion phantom experiments demonstrate that CUSE is capable of providing good contrast (contrast-to-noise ratio ≥ 25 dB) between the inclusion and background without artifacts and is insensitive to inclusion positions. Safety measurements demonstrate that all regulated parameters of the ultrasound output level used in CUSE sequence are well below the FDA limits for diagnostic ultrasound.

Dual-etalon frequency-comb cavity ringdown spectrometer

We have demonstrated a spectroscopic technique for simultaneously obtaining broad spectral bandwidth and high frequency resolution absorption measurements, with 5 μs temporal resolution, continuously for tens of microseconds in an apparatus with no active stabilization. The technique utilizes two passive air-gap etalons to imprint two frequency comb patterns onto a single pulsed light source. The air-gap etalons also serve as cavity ringdown cells increasing the sensitivity of the absorption spectroscopy by increasing the interrogation path length. Here, we demonstrate the operation of the spectrometer utilizing a ~0.15 cm(-1) bandwidth pulsed dye laser and two nearly identical 300 MHz free-spectral range confocal air-gap etalons each with a finesse of ~1 × 10(5), to investigate the (1,1,3) overtone of water and the R(7) transition of the O(2) b(1)Σ(g)(+)←X(3)Σ(g)(-) (2,0) band with high spectral resolution.

Reference dosimetry during diagnostic CT examination using XR‐QA radiochromic film model

The authors applied 2D reference dosimetry protocol for dose measurements using XR-QA radiochromic film model during diagnostic computed tomography (CT) examinations carried out on patients and humanoid Rando phantom. Response of XR-QA model GAFCHROMIC™ film reference dosimetry system was calibrated in terms of Air-Kerma in air. Four most commonly used CT protocols were selected on their CT scanner (GE Lightspeed VCT 64), covering three anatomical sites (head, chest, and abdomen). For each protocol, 25 patients ongoing planned diagnostic CT examination were recruited. Surface dose was measured using four or eight film strips taped on patients' skin and on Rando phantom. Film pieces were scanned prior to and after irradiation using Epson Expression™ 10000XL document scanner. Optical reflectance of the unexposed film piece was subtracted from exposed one to obtain final net reflectance change, which is subsequently converted to dose using previously established calibration curves. The authors' measurements show that body skin dose variation has a sinusoidal pattern along the scanning axis due to the helical movement of the x-ray tube, and a comb pattern for head dose measurements due to its axial movement. Results show that the mean skin dose at anterior position for patients is (51 ± 6) mGy, (29 ± 11) mGy, (45 ± 13) mGy and (38 ± 20) mGy for head, abdomen, angio Abdomen, and chest and abdomen protocol (UP position), respectively. The obtained experimental dose length products (DLP) show higher values than CT based DLP taken from the scanner console for body protocols, but lower values for the head protocol. Internal dose measurements inside the phantom's head indicate nonuniformity of dose distribution within scanned volume. In this work, the authors applied an Air-Kerma in air based radiochromic film reference dosimetry protocol for in vivo skin dose measurements. In this work, they employed green channel extracted from the scanned RGB image for dose measurements in the range from 0 to 200 mGy. Measured skin doses and corresponding DLPs were higher than DLPs provided by the CT scanner manufacturer as they were measured on patients' skin.