Sensor-on-Microtips: Design and Development of Hydrothermally Grown ZnO on Micropipette Tips as a Modified Working Electrode for Detection of Glucose.

Miniaturization of electrochemical components has become less common in the last decade, with the focus predominantly being the design and development of state-of-the-art microelectrodes for achieving small volume analysis of samples. However, such microelectrodes involve cumbersome processing procedures to convert the base material for the required application. A potential paradigm shift in such miniaturization could be achieved by using cheaper alternatives such as plastics to build electrochemical components, such as micropipette tips made of polypropylene, which are commercially available at ease. Hence, this work presents the design of an electrochemical working electrode based upon a micropipette tip, involving minimal processing procedures. Furthermore, such a working electrode was realized by sputtering silver onto a bare micropipette tip using a radio-frequency sputtering technique, to obtain electrical contacts on the tip, followed by hydrothermal growth of ZnO, which acted as the active electrode material. The ZnO nanostructures grown on the micropipette tip were characterized for their morphology and surface properties using a scanning electron microscope (SEM), laser microscope, Raman spectrometer, and X-ray photoelectron spectrometer (XPS). The developed micropipette tip-based electrode was then used as the working electrode in a three-electrode system, wherein its electrochemical stability and properties were analyzed using cyclic voltammetry (CV). Furthermore, the above system was used to detect glucose concentrations of 10-200 µM, to evaluate its sensing properties using amperometry. The developed working electrode exhibited a sensitivity of 69.02 µA/µM cm-2 and limit of detection of 67.5 µM, indicating the potential for using such modified micropipette tips as low-cost miniaturized sensors to detect various bio-analytes in sample solutions.

Concurrent intrapericardial-pulmonary hydatidosis: an unusual multisystem echinococcosis.

A 46-year-old male presented with breathlessness for a few months. He had been operated twice for liver hydatid cysts and once for right pulmonary hydatid cysts at other hospitals. Now he was found to have one hydatid cyst in the upper lobe of the left lung and multiple hydatid cysts adjoining left heart border. On computed tomography (CT) scan chest and echocardiography, it was difficult to ascertain whether these cysts were pulmonary or intrapericardial. Left ventricular ejection fraction (LVEF) was 25%. Enzyme-linked immunosorbent assay (ELISA) was positive for hydatid. Left posterolateral thoracotomy revealed dead hydatid cyst in upper lobe of the lung that was removed. Infected mother hydatid cyst was encountered inside pericardial sac. Scores of daughter hydatid cysts, varying in size from 1 to 30 mm, were scooped out intact from the pericardial cavity. There was significant improvement in cardiac activity, once the tamponade effect of hydatid cyst was removed. Pericardium was about 1 cm thick with lot of purulent and necrotic slough. To prevent future constrictive pericarditis, subtotal pericardiectomy was done. Intrapericardial hydatid cyst should be kept in mind whenever it obscures the heart border and patient has features of cardiac tamponade. Early surgical intervention may be required in these cases.

Cleanroom and Template Free Fabrication of Single Polygonal Shaped Microneedle.

For painless skin penetration, microneedles require optimal geometry due to human skin's inherent elastic properties. The fabrication of desired shape microneedle is very critical. To our knowledge, the polygonal geometry microneedle has not been investigated before. To address this issue, in this communication, we propose a novel cleanroom free fabrication of single metal microneedle with square cross section. The microneedle was fabricated using sputtering technique without any mask or template. The morphological analysis with respect to various sputtering parameters via. Argon (Ar) pipe position, rotating speed, working pressure was discussed in detail. The microneedle geometry, its assisted pain was visualized using finite element analysis (FEM). The theoretical evaluations were subsequently compared with experimentally fabricated microneedle. This is the first step towards more rational design of polygonal microneedle geometry.

Fabrication and Analysis of Energy Efficient Low-Cost Wireless Gas Sensor Based on ZnO Thin Films.

Industrialization can be greatly appreciated only by limiting the downside of the proposed technology. In this aeon, the recurrent monitoring of industries is statutory in detecting harmful gases and explosions for the global environment safety. Hence, employing specific gas sensors for detecting malicious gases benefits the welfare of the society. Thus, in this present work, we developed an energy efficient toxic gas sensor using ZnO thin film by seed layer assisted hydrothermal technique. The sensing mechanism of ZnO with the CO analyte was explained and the sensing parameters such as sensitivity, selectivity, response and recovery time were studied. Further, the developed energy efficient sensor was embedded with wireless sensor assembly for online monitoring which may be functional in developing portable, compact and cost-effective system for various real time industrial control applications.

Viral Science: Masks, Speed Bumps, and Guard Rails.

The speed of science, especially while solving the recent pandemic puzzles, is causing concerns. We describe some salient issues as well as a framework for making the process of publishing, organizing, and retrieving scientific literature more efficient. Emerging building blocks leveraging AI, including natural language processing tools such as SciSight from the Allen Institute for AI, that permit faceted navigation and research group detection are highlighted.

Vanadium oxide nanostructures for chemiresistive gas and vapour sensing: a review on state of the art.

This review (with 200 references) summarises the state of the art of gas and vapour sensors based on the use of vanadium oxide (VOx; with V occurring in various valencies) nanostructures. Following an introduction that covers the discussion of VOx and their stable forms, the first large section covers experimental techniques employed for preparing VOx nanostructures, with methods such as precipitation, hydrothermal synthesis, electrospinning, polyol techniques, laser deposition, and magnetron sputtering. The next section deals with VOx-based sensors for oxidising gases such as nitrogen dioxide, carbon dioxide, oxygen, and ozone. We then discuss sensors for reducing gases and vapour, such as various alcohols, formaldehyde, hydrogen, methane, various amines, hydrogen sulphide, LPG, and neutral gases and vapours such as helium and humidity. An overview of the wealth of materials, methods, and sensing characteristics such as sensor response, analytical ranges, and operational temperatures is presented in Tables. The final section briefs the VOx-based flexible sensors, followed by a concluding section that summarises the current status and challenges, and gives an outlook on potential future perspectives. Graphical abstract The state of the art of vanadium oxide nanostructures in gas/vapour sensing has been discussed in this work.

Investigation on CH4 sensing characteristics of hierarchical V2O5 nanoflowers operated at relatively low temperature using chemiresistive approach.

Methane (CH4) gas, the second most potent greenhouse gas share a substantial role in contributing to the global warming and it is a necessary pre-requisite to detect the release of CH4 into the environment at its early stage to combat climate change. In that front, this work is focussed to develop an effective CH4 gas sensor using vanadium pentoxide (V2O5) thin films that works at an operating temperature of ∼100 °C. To understand the effect of sputtering power towards the structural characteristics of V2O5 films, X-ray diffraction (XRD) and high-resolution transmission electron microscopy (HR-TEM) analysis were performed from which the orthorhombic polycrystalline structure of V2O5 thin films was confirmed with varied texture co-efficient. Further, the surface elemental studies using X-ray photoelectron spectroscopy (XPS) confirmed the prominence of V+5 oxidation state from the binding energy of V2p3/2 and O1s peak. The effect of sputtering power on the growth of different nanostructures were observed using field-emission scanning electron microscopy (FE-SEM). The critical role of adsorption and desorption kinetics of the deposited nanostructures were explained through first order kinetics based on Elovich model and the phase stability of different nanostructures were evaluated using Raman spectral analysis. This work achieved the sensor response of about ∼8% towards CH4 at an operating temperature of 100 °C towards 50 ppm concentration.

Advanced Artificial Electronic Skin Based pH Sensing System for Heatstroke Detection.

Heatstroke is a serious illness that can potentially damage many victims every year. Many intelligent physical sensors have been developed to prevent heatstroke fatalities. However, it remains a challenge to fabricate skin-adhesive, small, and low-cost sensors for in situ heatstroke detection to overcome the weaknesses of the physical sensors. As far as we know, this is the first breakthrough for exploiting a PDMS based freestanding nanosheet skin patch consisting of pH sensing elements (antimony/antimony oxide and silver/silver iodate) to achieve high pH sensitivity and repeatability. The sensing elements were investigated for structural and morphological properties. The easy to use and easy to fabricate nanosheet sensor exhibited a linear pH response of -43 mV/pH. Overall, the developed sensor showed high sensitivity, repeatability, and stability. Our initial results indicate that the developed sensor adhered well to a skin surface. It is expected that this proof of concept approach gives reliable fabrication and measurement unlike other physical sensors.

Advanced TiO2-SiO2-Sulfur (Ti-Si-S) Nanohybrid Materials: Potential Adsorbent for the Remediation of Contaminated Wastewater.

In this present work, TiO2-SiO2-sulfur (Ti-Si-S) nanohybrid material was successfully prepared using TiO2 nano powder, TEOS sol-gel precursor, and elemental sulfur as raw material by sol-gel process and hydrothermal method at 120 °C temperature. Raman spectroscopy, XRD, SEM, TEM, and N2 absorption-desorption characterized the synthesized nanohybrid material. The characterization results confirmed the homogeneous distribution of sulfur in the nanohybrid material. The size of the Ti-Si-S nanohybrid material is vary between 20 and 40 nm and the surface areas of the nanohybrid material was measured using N2 absorption-desorption, which showed value of 57.2 m2 g-1. The potential of Ti-Si-S nanohybrid material as an adsorbent was further tested to adsorb methylene blue (MB) from aqueous solution. Adsorption performance of hybrid material was highly influenced by the solution pH and mass of adsorbent. The adsorption of MB using Ti-Si-S nanohybrid material was homogeneous monolayer adsorption, which followed the Langmuir adsorption isotherm with a qe,max value of 804.80 mg g-1 and pseudo-second-order rate equation. The dye diffusion mechanism partially followed both intraparticle and liquid film diffusion mechanisms. Thermodynamics studies predicted the spontaneous and endothermic nature of the whole adsorption process. The Ti-Si-S nanohybrid material was used for six repeated cycles of MB dye adsorption-desorption.

Development of an acetone sensor using nanostructured Co3O4 thin films for exhaled breath analysis.

In recent times, the development of breath sensors for the detection of Diabetic Keto-Acidosis (DKA) has been gaining prominent importance in the field of health care and advanced diagnostics. Acetone is one of the prominent biomarkers in the exhaled breath of persons affected by DKA. In this background, nanostructured cobalt oxide sensing elements were fabricated using a spray pyrolysis technique at different deposition temperatures (473 to 773 K in steps of 100 K) towards the fabrication of an acetone sensor. The influence of deposition temperature on the various properties of the nanostructured cobalt oxide thin films was investigated. Formation of cubic spinel phase cobalt oxide was confirmed from the structural analysis. The shifting of plane orientation from (3 1 1) to (2 2 0) at 773 K deposition temperature revealed the migration of cobalt atoms to the highly favorable energy positions. Further, the downshifted peak absorption wavelength and upshifted PL profile at higher deposition temperature confirmed the migration of cobalt ions. The sensor fabricated at higher deposition temperature (773 K) showed a sensing response of 235 at room temperature towards 50 ppm of acetone. Also, the fabricated sensor showed a lower detection limit (LOD) of 1 ppm with the response-recovery times of 6 and 4 s, respectively. The LOD reported here is lower than the minimum threshold level (1.71 ppm) signifying the presence of DKA.

Preparation and Characterization of Tetrahydrocurcumin-Loaded Cellulose Acetate Phthalate/Polyethylene Glycol Electrospun Nanofibers.

A simple composite electrospun nanofiber of cellulose acetate phthalate (CAP)-polyethylene glycol (PEG) loaded with tetrahydrocurcumin (THC) was developed in this study, and the in vitro diffusion of THC was evaluated. The nanofibers were characterized by scanning electron microscopy, powder X-ray diffraction (PXRD), Fourier-transform infrared spectroscopy (FT-IR), and differential scanning calorimetry (DSC). The formulated nanofiber (NF) with THC has smooth morphology with diameter of around 300-500 nm. The complete entrapment and dispersion of THC was observed from the results of PXRD and DSC due to the loss of THC crystalline property. Further, FT-IR demonstrated that the vibration bands for the polymers used were dominant over the THC, and the vibrational bands of THC were not observed from the final formulation. The drug entrapment by the final CAP + PEG NF was found to be 95.5% with the high swelling index. From the in vitro release study, it was found that the formulated THC-loaded CAP + PEG NF has followed anomalous mechanism, demonstrating both diffusion and swelling controlled modes. The drug release extended up to 12 h with a final cumulative release of 94.24%.

Radiation-Induced Second Cancer Risk from External Beam Photon Radiotherapy for Head and Neck Cancer: Impact on in-Field and Out-of-Field Organs

The purpose of this paper is to provide data on development of second primary cancers within or adjacent to tissue irradiated in the treatment of primary head and neck cancers using different techniques and modalities. Materials and methods: We selected five patients with HandN tumors located in base of the tongue for risk assessment. In order to examine the impact of choices of various planning techniques, numbers of beams and beam energy used in treatment plans - 7 and 9 field Intensity modulated radiotherapy (IMRT) plans using 6MV and 10 MV beam energies and a 6MV Volumetric modulated arc therapy (VMAT) plans were planned. Out-of-field measurements for secondary photon doses for the treatment plans were measured using diode-dosimeters and solid water slabs. Differential dose-volume histograms (DVH) for all 5 patients and 5 techniques, were exported and used to calculate organ equivalent dose (OAR), excess absolute risk (EAR), and life-time attributable risk (LAR) for in-field organs. Results: For all treatment plans, the DVH showed clinically acceptable values; adequate clinical target coverage and dose constraints were met for all organs at risk. There was a clear advantage for the VMAT plan; it provided superior organ at risk (OAR) sparing and adequate target coverage. VMAT has relatively low monitor units at 0.93±0.034 times 7F6. The average percentage scattered to prescription doses for the five patients at 15, 30, 45, 60 and 75 cm from the isocenter were 0.9212 ± 0.115, 0.2621 ± 0.080, 0.1617 ± 0.057, 0.0936 ± 0.026, 0.0296 ± 0.014, for VMAT. Conclusion: Organ-specific LAR was higher with VMAT compared to 7F6 for skin. 6-MV VMAT is an acceptable alternative to IMRT for HandN cancer and offers advantages in terms of sparing adjacent OAR.

Microneedle pH Sensor: Direct, Label-Free, Real-Time Detection of Cerebrospinal Fluid and Bladder pH.

Acid-base homeostasis (body pH) inside the body is precisely controlled by the kidneys and lungs and buffer systems, such that even a minor pH change could severely affect many organs. Blood and urine pH tests are common in day-to-day clinical trials and require little effort for diagnosis. There is always a great demand for in vivo testing to understand more about body metabolism and to provide effective diagnosis and therapy. In this article, we report the simple fabrication of microneedle-based direct, label-free, and real-time pH sensors. The reference and working electrodes were Ag/AgCl thick films and ZnO thin films on tungsten (W) microneedles, respectively. The morphological and structural characteristics of microneedles were carefully investigated through various analytical methods. The developed sensor exhibited a Nernstian response of -46 mV/pH. Different conditions were used to test the sensor to confirm their accuracy and stability, such as various buffer solutions, with respect to time, and we compared the reading with commercial pH electrodes. Besides that, the fabricated microneedle sensor ability is proven by in vivo testing in mouse cerebrospinal fluid (CSF) and bladders. The pH sensor procedure reported here is totally reversible, and results were reproducible after several rounds of testing.

ZnO-Based Microfluidic pH Sensor: A Versatile Approach for Quick Recognition of Circulating Tumor Cells in Blood.

The present study is concerned about the development of highly sensitive and stable microfluidic pH sensor for possible identification of circulating tumor cells (CTCs) in blood. The precise pH measurements between silver-silver chloride (Ag/AgCl) reference electrode and zinc oxide (ZnO) working electrode have been investigated in the microfluidic device. Since there is a direct link between pH and cancer cells, the developed device is one of the valuable tools to examine circulating tumor cells (CTCs) in blood. The ZnO-based working electrode was deposited by radio frequency (rf) sputtering technique. The potential voltage difference between the working and reference electrodes (Ag/AgCl) is evaluated on the microfluidic device. The ideal Nernstian response of -43.71165 mV/pH was achieved along with high stability and quick response time. Finally, to evaluate the real time capability of the developed microfluidic device, in vitro testing was done with A549, A7r5, and MDCK cells.

Estimating Second Malignancy Risk in Intensity-Modulated Radiotherapy and Volumetric-Modulated Arc Therapy using a Mechanistic Radiobiological Model in Radiotherapy for Carcinoma of Left Breast.

OBJECTIVES: The aim of this study is to estimate second cancer risk (SCR) in intensity-modulated radiotherapy (IMRT) and volumetric-modulated arc therapy (VMAT) using a mechanistic radiobiological model. The model also takes into account patient age at exposure and the gender-specific correction factors of SCR. MATERIALS AND METHODS: Fifty IMRT and VMAT plans were selected for the study. Monte Carlo-based dose calculation engine was used for dose calculation. Appropriate model parameters were taken from the literature for the mechanistic model to calculate excess absolute risk (EAR), lifetime attributable risk, integral dose and relative risk (RR) for lungs, contralateral breast, heart, and spinal cord. RESULTS: The mean monitor unit (MU) in IMRT and VMAT plans were 751.1 ± 133.3 and 1004.8 ± 180, respectively, for IMRT and VMAT. The mean EAR values with age correction were 44.6 ± 11.9, 11.2 ± 6.4, 5.4 ± 4.0, 1.4 ± 0.5, and 0.3 ± 0.2 for left lung, right lung, contralateral breast, heart, and spinal cord, respectively, for the IMRT treatments and 54.6 ± 20.6, 30.2 ± 12.0, 13.8 ± 8.6, 1.6 ± 0.6, and 0.9 ± 0.5 for the VMAT treatments in units of 10,000 PY. The RR of 6.7% and 9.1%, respectively, for IMRT and VMAT found in our study using computational models is in close comparison with the value reported in a large epidemiological breast cancer study. CONCLUSIONS: VMAT plans had a higher risk of developing second malignancy in lung, contralateral breast, heart, and cord compared to IMRT plans. However, the increase in risk was found to be marginal compared to IMRT. Incorporating the age correction factor decreased the risk of contralateral breast SCR. No strong correlation was found between EAR and MU.

Substrate Temperature Effects on Room Temperature Sensing Properties of Nanostructured ZnO Thin Films.

Zinc oxide (ZnO) thin films were deposited on glass substrates using chemical spray pyrolysis technique at different substrate temperatures such as 523, 623 and 723 K. X-ray diffraction (XRD) patterns confirmed the formation of polycrystalline films with hexagonal wurtzite crystal structure and revealed the change in preferential orientation of the crystal planes. Scanning electron micrographs showed the formation of uniformly distributed spherical shaped grains at low deposition temperature and pebbles like structure at the higher temperature. Transmittance of 85% was observed for the film deposited at 723 K. The band gap of the films was found to be increased from 3.15 to 3.23 eV with a rise in deposition temperature. The electrical conductivity of the films was found to be improved with an increase in substrate temperature. Surface of ZnO thin films deposited at 523 K, 623 K and 723 K were found to be hydrophobic with the contact angles of 92°, 105° and 128° respectively. The room temperature gas sensing characteristics of all the films were studied and found that the film deposited at 623 K showed a better response towards ammonia vapour.

Percentage depth dose calculation accuracy of model based algorithms in high energy photon small fields through heterogeneous media and comparison with plastic scintillator dosimetry.

Small fields smaller than 4 × 4 cm2 are used in stereotactic and conformal treatments where heterogeneity is normally present. Since dose calculation accuracy in both small fields and heterogeneity often involves more discrepancy, algorithms used by treatment planning systems (TPS) should be evaluated for achieving better treatment results. This report aims at evaluating accuracy of four model-based algorithms, X-ray Voxel Monte Carlo (XVMC) from Monaco, Superposition (SP) from CMS-Xio, AcurosXB (AXB) and analytical anisotropic algorithm (AAA) from Eclipse are tested against the measurement. Measurements are done using Exradin W1 plastic scintillator in Solid Water phantom with heterogeneities like air, lung, bone, and aluminum, irradiated with 6 and 15 MV photons of square field size ranging from 1 to 4 cm2. Each heterogeneity is introduced individually at two different depths from depth-of-dose maximum (Dmax), one setup being nearer and another farther from the Dmax. The central axis percentage depth-dose (CADD) curve for each setup is measured separately and compared with the TPS algorithm calculated for the same setup. The percentage normalized root mean squared deviation (%NRMSD) is calculated, which represents the whole CADD curve's deviation against the measured. It is found that for air and lung heterogeneity, for both 6 and 15 MV, all algorithms show maximum deviation for field size 1 × 1 cm2 and gradually reduce when field size increases, except for AAA. For aluminum and bone, all algorithms' deviations are less for 15 MV irrespective of setup. In all heterogeneity setups, 1 × 1 cm2 field showed maximum deviation, except in 6MV bone setup. All algorithms in the study, irrespective of energy and field size, when any heterogeneity is nearer to Dmax, the dose deviation is higher compared to the same heterogeneity far from the Dmax. Also, all algorithms show maximum deviation in lower-density materials compared to high-density materials.

Chitosan-HPMC-blended microspheres as a vaccine carrier for the delivery of tetanus toxoid.

The purpose of this research was to develop a suitable and alternate adjuvant for the tetanus toxoid (TT) vaccine that induces long term immunity after a single-dose immunization. In our study, the preformulation studies were carried out by using different ratios (7/3, 8/2, and 9/1) of chitosan-hydroxypropyl methylcellulose (HPMC)-blended empty microspheres. Moreover, TT was stabilized with heparin (at heparin concentrations of 1%, 2%, 3%, and 4% w/v) and encapsulated in ideal chitosan - HPMC (CHBMS) microspheres, by the water-in-oil-in-water (W/O/W) multiple emulsion method. The vaccine entrapment and the in vitro release efficiency of the CHBMS was evaluated for a period of 90 days. The release of antigens from the microspheres was determined by ELISA. Antigen integrity was investigated by SDS-PAGE. From the optimization studies, it was found that a chitosan/HPMC ratio of 8/2 produced a good yield, with microspheres that were spherical, regular and uniformly-sized. In the CHBMS, a heparin concentration of 3% w/v resulted in well-sustained antigen delivery for a period of 90 days. It was found that the characteristics of initial release could be observed in 2 days, followed by a constant release, and an almost 100% complete release in 90 days. From the in vitro release characteristics, the ideal batch of CHBMS (3% w/v heparin) was evaluated for in vivo studies by the antibody induction method. The antibody levels were measured for different combinations for the period of 9 months, and finally, with a second booster dose after 1 year. In conclusion, it was observed that CHBMS (combination-1) resulted in the antibody level of 4.5 IU/mL of guinea pig serum, and the level was 3.5 IU/mL for the Central Research Institute's alum-adsorbed tetanus toxoid (CRITT) (combination 2), after 1 year, with a second booster dose. This novel approach of using CHBMS may have potential advantages for single-step immunization with vaccines.

Preparation and characterization of gatifloxacin-loaded alginate/poly (vinyl alcohol) electrospun nanofibers.

The aim of this study was to develop novel biomedicated electrospun nanofibers for controlled release. Pre-formulation studies were carried out for nanofibers of sodium alginate (SA) (2 wt %)/polyvinyl alcohol (PVA) (10 wt %) composites (2/8, 3/7 and 4/6), by an electrospinning technique. The morphology and average diameter of the nanofibers were investigated by scanning electron microscopy (SEM). The optimum ratio (3/7) was used to load gatifloxacin hydrochloride (GH) (1wt %), found to form smooth fibers with uniform structures. The drug entrapment in the composite nanofibers was confirmed by SEM, X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), thermo gravimetric analysis (TGA), differential scanning calorimetry (DSC), and swelling behavior. The drug release behavior was investigated using phosphate-buffered saline (PBS) (pH 7.4) at 37°C for 24 h. The XRD and FTIR data demonstrate that there are good interactions between PVA and SA, possibly caused by hydrogen bonds. As much as 90% of the GH was released from the electrospun fibers within 6 h of incubation. Beyond this, the release was sustained for 24 h. The thickness of nanofibers greatly influenced the initial release and rate of drug release. Moreover, GH-loaded sodium alginate/PVA composite nanofibers exhibited a useful and convenient method for electrospinning in order to control the rate and period of drug release in wound-healing applications.

Analysis of direct clinical consequences of MLC positional errors in volumetric-modulated arc therapy using 3D dosimetry system.

In advanced, intensity-modulated external radiotherapy facility, the multileaf collimator has a decisive role in the beam modulation by creating multiple segments or dynamically varying field shapes to deliver a uniform dose distribution to the target with maximum sparing of normal tissues. The position of each MLC leaf has become more critical for intensity-modulated delivery (step-and-shoot IMRT, dynamic IMRT, and VMAT) compared to 3D CRT, where it defines only field boundaries. We analyzed the impact of the MLC positional errors on the dose distribution for volumetric-modulated arc therapy, using a 3D dosimetry system. A total of 15 VMAT cases, five each for brain, head and neck, and prostate cases, were retrospectively selected for the study. All the plans were generated in Monaco 3.0.0v TPS (Elekta Corporation, Atlanta, GA) and delivered using Elekta Synergy linear accelerator. Systematic errors of +1, +0.5, +0.3, 0, -1, -0.5, -0.3 mm were introduced in the MLC bank of the linear accelerator and the impact on the dose distribution of VMAT delivery was measured using the COMPASS 3D dosim-etry system. All the plans were created using single modulated arcs and the dose calculation was performed using a Monte Carlo algorithm in a grid size of 3 mm. The clinical endpoints D95%, D50%, D2%, and Dmax,D20%, D50% were taken for the evaluation of the target and critical organs doses, respectively. A significant dosimetric effect was found for many cases even with 0.5 mm of MLC positional errors. The average change of dose D 95% to PTV for ± 1 mm, ± 0.5 mm, and ±0.3mm was 5.15%, 2.58%, and 0.96% for brain cases; 7.19%, 3.67%, and 1.56% for head and neck cases; and 8.39%, 4.5%, and 1.86% for prostate cases, respectively. The average deviation of dose Dmax was 5.4%, 2.8%, and 0.83% for brainstem in brain cases; 8.2%, 4.4%, and 1.9% for spinal cord in H&N; and 10.8%, 6.2%, and 2.1% for rectum in prostate cases, respectively. The average changes in dose followed a linear relationship with the amount of MLC positional error, as can be expected. MLC positional errors beyond ± 0.3 mm showed a significant influence on the intensity-modulated dose distributions. It is, therefore, recommended to have a cautious MLC calibration procedure to sufficiently meet the accuracy in dose delivery.