Reduce Noise Levels Research Articles

Understanding Noise Exposure During Cast Removal: The Effect of Cast Saw Type and Casting Material.

Cast removal can be associated with considerable noise exposure, especially impacting the pediatric patient and provider. Although noise generation from cast saws has been deemed safe by the U.S. Occupational Safety and Health Administration and the U.S. Centers for Disease Control and Prevention standards, there are no current studies on the effects of cast material on noise levels generated. A simulated casting model utilizing plaster, fiberglass, and plaster with fiberglass overwrapping was used for experimental testing. Four different casting conditions were tested, with 5 samples in each group. Samples were tested using 2 different cast saws: a standard cast saw and a quiet saw. Each saw was used for 30 seconds of continuous cutting for each sample, measuring peak, mean, and minimum sound levels in decibels with sound level meters. Noise levels were measured at 18, 36, and 72 in (20, 91, and 183 cm) from the saw, comparing saw and cast types against ambient noise and baseline cast-saw noises. Between-group comparisons were performed using univariate analyses. Mean noise generation differed between casting materials, with plaster material demonstrating significantly greater noise levels than fiberglass casts at all distances for each saw type. Increasing fiberglass thickness significantly increased the mean noise levels with standard (18-in distance for 10 and 5 ply: 87.4 and 85.8 dB; p = 0.0004) and quiet cast saws (78.3 and 76.1 dB; p = 0.041. Additionally, the quiet cast saw provided a 5.7 to 10.6 dB reduction in mean and peak noise levels, varying by casting material and distance. Occupational noise exposure can be mitigated with the use of fiberglass casting material that is not >5 ply in thickness, with a quiet cast saw for removal. The use of a quiet cast saw substantially decreased noise exposure to patients and staff members over standard orthopaedic cast saws.

The use of rice husk ash, saw dust and coconut fiber (CASE2SK) in a diesel engine at sawmill industry

The machine has noise with a high-power sound, one of the negative impacts it causes is Noise Induced Hearing Loss (NIHL), for this reason it needs a material that can reduce noise. The result of the measurement of the noise level at this sawmill industry is 96.95 dBA which exceeds the TLV, according to Permenkes No. 70 of 2016 concerning Standards and Health Requirements for the Industrial Work Environment, which is 85 dBA. The purpose of this study was to determine the effect of using a mixture of rice husk ash, sawdust and coconut fiber in a diesel engine to reduce the noise level in the sawmill industry. This type of research is a True Experiment with a pretest – posttest design with a control group, with the object of the research being a diesel engine that will be repeated 16 times at one point for each group, namely the control and experimental groups. The average reduction in bulkhead noise level is 13.08 dBA or 14.03%, with the noise level after treatment is 80.14 dBA. The Wilcoxon test to test the pre data with the control group post and the pre data with the post experimental group, the value of p = 0.000 which means less than 0.05, it can be concluded there is a difference between the noise level. Pretest and posttest in the control and experimental groups, and the independent t test obtained p value = 0.000 it means that there is a significant difference between the control group and the experimental group. However, the percentage of reduction was higher in the experimental group, so it is still advisable to use a mixture of rice husk ash, sawdust and coconut husk.

The Noise Level in Residential Areas Bordering Jagorawi Highway

Noise pollution has not become a priority in environmental issues, but the potential negative impact on society based on studies can be in the form of physical and psychological disturbances, the main cause of noise in the urban area is transportation. Identification of noise sources needs should be done to ensure that the sound produced accordance with environmental characteristics. The Jagorawi toll road is the 3rd density toll road in the Jabodetabek area, compared to several other toll roads. Jagorawi toll road is bordered by residential areas. In the Cibubur-Cimanggis sector, this toll road is directly adjacent to residential areas with a distance of < 20 meters and some points do not have barriers to reduce noise. The Cibubur-Cimanggis sector is currently developing with the addition of the LRT, which will operate in 2022 so that current noise measurements can be used as baseline data at the study site. This noise monitoring is intended to conclude whether or not there is an effect of noise felt by the surrounding community from activities on the Jagorawi toll road and to obtain a reduction in noise levels using a single barrier with a height of 0.5, 1, 1.5 and 2 m. Noise monitoring is carried out using SNI 8421:2017 for 24 hours at 2 measurement points in residential areas. Point one and point two each have a noise value (Lsm) of 68.87 and 61.29 dBA with a correlation value of 0.605 (medium). The noise value has exceeded the quality standard for residential designation based on the Minister of Environment Decree No. 48 of 1996 (55 dBA), so a barrier is needed to reduce the noise received by the community. The analysis of the use of the barrier studied is a single barrier with G = 1. As the result of adding a barrier at point 1 with high 2 m, the noise value can be reduced by 16.7 dBA with a p-value of 0.00, so the addition of a barrier has a significant impact on the noise value. This study found the effect of noise from the Jagorawi toll road up to a distance of 114 m at a point that does not use a barrier, so the role of the barrier along the toll road is very important. With the use of a barrier, the distance required to reduce single noise originating from the toll road to < 55 dBA is 20 m.

PENGGUNAAN GERINDA DUDUK MENURUNKAN KADAR KEBISINGAN DAN KELUHAN MUSKULOSKELETAL PADA PANDE BESI DI DESA GUBUG TABANAN

Introduction: Blacksmith is one of the small industries growing in the village of Gubug, Tabanan Regency. These blacksmith craftsmen have been in the job for quite a long time and passed down from generation to generation from their ancestors. They do work as the responsibility of their ancestors. One of the processes in making household tools is small knives, large knives, sickles, and machetes; they are faced with a tool in the form of a grinder. In this process, the worker holding a grinder weighing 1.7 kg vibrates, makes a noise, and sits as is. Working in a noisy environment, being exposed to vibration for a long time is an additional burden that will cause hearing loss complaints and diseases such as Raynaud's Syndrome, Tenosynovitis, and Carpal Tunnel Syndrome. This study aimed to determine the effect of using an ergonomic sitting grinding wheel to reduce noise levels and musculoskeletal complaints in Pande Besi in Gubug Tabanan Village. Methods: This research is an experimental study with treatment by subject design. The population is the small industry workers of Pande Besi in Gubug Village, Tabanan Regency, with as many as 40 people from 10 small industries. The sample is determined based on small industry groups by simple random sampling or simple random sampling with a table of random numbers. The sample size was determined based on the score of musculoskeletal complaints so that the number of small industrial groups was 3.94, rounded up to 4 groups. Each small industry group consists of four people, so the sample size is 16 people. Results: The mean age of the subjects was 49.112±12.15 years, body weight 66.68±6.64 kg, height 162.31±6.78 cm, and body mass index of subjects 25.29±1.71 kg/m2. Statistical analysis showed that there was a significant difference. The average ambient temperature, namely wet temperature, dry temperature, and air humidity, showed no significant difference, noise showed a significant difference, and there was a decrease in the noise of 30.54% before and after using the seat grinder. There was a decrease in complaints of 13.23% after improving the working attitude of the blacksmith. Conclusion: There was a significant decrease between noise levels and musculoskeletal complaints before and after using a seated grinder (p0.05).Keywords: Noise Levels, Musculoskeletal Complaints

Excessive noise in the operating room: Can it be improved?

Introduction: Excessive noise in the operating room has been a topic of interest since the early 70s. It has been recognised that excessive noise can affect cognitive behavior and impair memory function which can be a health and safety issue. Though different approaches have been explored there remains a deficit in research into the application of noise modification programs within the operating room to combat the issue of noise pollution. This project aimed to identify if a discussion about appropriate noise levels and the use of a safe phrase at ‘time out’ would reduce noise levels in the operating room.

MODIFIKASI KNALPOT MESIN DIESEL UNTUK MENGURANGI EMISI GAS BUANG DAN KEBISINGAN DI RUANGAN PABRIK PENGGILINGAN PADI

The placement of the Type R175 diesel engine in the rice mill factory in Kebonpedes caused two problems, namely exhaust gas emissions that filled the factory room and noise levels that exceeded NAB which could cause health hazards to workers, so exhaust modifications were needed to be able to emit exhaust gases into outside the factory and also reduce engine noise that exceeds the NAB. The exhaust modification stage starts from modification design, application of exhaust modification results to diesel engines, and testing of exhaust emissions and noise levels in the factory. The exhaust emission test results before modification were CO 0.07%, CO2 3.13%, O2 14.81%, and HC 22.33 ppm and the maximum noise value before modification was 115 dB. The results of gas emission tests inside the factory after modification are CO 0.00% , CO2 0.00%, O2 20.98% , and HC 0 ppm, while the maximum noise value is 84 dB. This exhaust modification has succeeded in eliminating exhaust emissions in the factory room and reducing noise levels by 31 dB in the rice mill plant.

Experimental and Numerical Study of Cross-flow Fan in Air-conditioner Indoor Unit

The cross-flow fan is an essential component of an air-conditioner indoor unit, and its aerodynamic performance seriously affects the performance and heat exchange efficiency of air-conditioning. The internal flow of the cross-flow fan is studied by PIV measurements combined with the three-dimensional unsteady simulation. It is observed that the internal flow of the cross-flow fan is unevenly distributed along the axial direction, and it presents prominent three-dimensional characteristics. Due to the influence of the end-wall, the eccentric vortex is strong in the middle and weak at both ends. Therefore, a pressure gradient along the axial direction in the eccentric vortex area, resulting in axial fluid transport inside the eccentric vortex. At the exit of the impeller, there is a small recirculation zone near the end-wall, which grows continually as it moves downstream in the diffuser section, thereby blocking the outlet. This paper further proposes a structure optimization, which effectively enhances the eccentric vortex near the end-wall and reduces the recirculation zone in the diffuser section, resulting in a 2.1% increase in the flow rate of air-conditioner indoor unit and a 0.8dB reduction in noise level. It is indicated that the structure optimization strategy based on the understanding of three-dimensional flow is beneficial to the internal flow and effectively improves the aerodynamic performance and the aeroacoustics performance of the whole air-conditioner indoor unit.

Tonal and broadband noise attenuation of an axial flow fan with forward and backward swept blades

A swept blade is one of the efficient ways to control unsteady flow and passively attenuate the noise radiated from an axial flow fan. Herein, an experimental study was conducted to investigate the effect of the blade sweep on the acoustic characteristics of an axial fan system operating under system resistances at an anechoic chamber facility. The noise level and fan performance of the axial fans with forward-swept, backward-swept, and straight blades were systematically measured using an acoustic fan tester, which can simultaneously measure them at various system resistance conditions. The variations in the overall A-weighted sound pressure levels (OASPLs) as a function of the static pressure and air flow rate, and acoustic spectra at the specific operating conditions were examined. The results showed that the forward-swept blade has superior aerodynamic and acoustic performance in a wide range of operating conditions to the other blades, except for the high system resistance corresponding to rotating stall conditions. In conclusion, the use of a forward-swept blade can achieve noise level reductions of 2–4 dBA under system resistance conditions since the amplitude of tonal noise associated with blade passing frequency is decreased.

Case study of noise pollution from vehicles and legal mechanisms for road noise control

Among the many environmental problems of the modern world one of the important ones is noise pollution. Currently, noise pollution from vehicles requires special attention in densely populated and industrial cities, as there is a trend towards an increase in the areas of acoustic discomfort in built-up areas. The noise that occurs on the roadway of the highway extends not only to the territory near the highway, but also deep into the housing development. Study' objective was to assess noise pollution from vehicles in the most densely populated area of Poltava (Ukraine), as well as to establish the possibility of influencing the situation through legal mechanisms to have an understanding of further research directions and ways to achieve a comfortable urban environment in Ukraine. The noise levels from traffic flows were measured in accordance with GOST 20444-2014, using the Testo 815. To determine the equivalent noise level from the traffic flows movement, an empirical dependence was applied in accordance with the methodology of the State Agency for Highways of Ukraine. Determined that the daytime threshold values are exceeded by 20–28.9 dB(A), which is not acceptable. The reasons for the increase in noise are the road bumps, a significant number of cars and number of stops and streets junctions, the movement of vehicles at a non-constant speed, lack of roadside landscaping. About 62,550 people live in areas where the noise level exceeds the permissible value for the area near residential buildings. The calculation method used turned out to be more accurate than the measured results and showed a significant effect of traffic intensity on noise pollution. Apparently, the low measurement accuracy is justified by outdated road noise measurement standards, which, in turn, need to be seriously revised. Reducing noise levels by optimizing traffic flows is one of the priority areas in which it is necessary to bring the environmental legislation of Ukraine. Ukrainian legislation still needs to undergo many changes to reach a level where it can be used as a control lever to achieve a safe ecological environment.

Energy Efficiency of IoT Networks for Environmental Parameters of Bulgarian Cities

Building modern Internet of Things (IoT) systems is associated with a number of challenges. One of the most significant among them is the need for wireless technology, which will serve to build connectivity between the individual components of this technology. In the larger cities of Bulgaria, measures to ensure low levels of harmful emissions, reduce noise levels, and ensure comfort in urban environments have been taken. LoRa technology shows more advantages in transmission distance and low energy consumption compared to other technologies. That is why this technology was chosen for the design of wireless sensor networks (WSN) for six cities in Bulgaria. These networks have the potential to be used in IoT configurations. Appropriate modules and devices for building WSN for cities in Bulgaria have been selected. It has been found that the greater number of nodes in the WSN leads to an increase in the average power consumed in the network. On the other hand, depending on the location of these nodes, the energy consumed may decrease. The performance of wireless sensor networks can be optimized by applying appropriate routing protocols, which are proposed in the available literature. The methodology for energy efficiency analysis of WSN can be used in the design of wireless sensor networks to determine the parameters of the environment, with the possibility of application in IoT.

Using supervised learning algorithms as a follow-up method in the search of gravitational waves from core-collapse supernovae

We present a follow-up method based on supervised machine learning (ML) to improve the performance in the search of gravitational wave (GW) burts from core-collapse supernovae (CCSNe) using the coherent WaveBurst (cWB) pipeline. The ML model discriminates noise from signal events using as features a set of reconstruction parameters provided by cWB. Detected noise events are discarded yielding to a reduction of the false alarm rate (FAR) and of the false alarm probability (FAP) thus enhancing of the statistical significance. We tested the proposed method using strain data from the first half of the third observing run of advanced LIGO, and CCSNe GW signals extracted from 3D simulations. The ML model is learned using a dataset of noise and signal events, and then it is used to identify and discard noise events in cWB analyses. Noise and signal reduction levels were examined in single detector networks (L1 and H1) and two detector network (L1H1). The FAR was reduced by a factor of $\sim10$ to $\sim100$, there was an enhancement in the statistical significance of $\sim1$ to $\sim2\sigma$, while there was no impact in detection efficiencies.

Noise Characteristics Analysis of Medical Electric Leg Compression Machine Using Multibody Dynamic Simulation

Conventional medical equipment used for treating patients with ischemic heart disease relies on pneumatic compression to achieve intense and instantaneous compression of the legs. Because the pneumatic operation of a compressor inevitably produces noise, the treatment is given to a patient in a separate room to avoid causing discomfort to other patients. This need for a dedicated treatment room could be another source of increased medical costs. In this study, a new electrical motor-driven system was developed to address the noise problem of existing pneumatic compression devices. Additionally, the new system features a reduced footprint and weight, and can be carried by medical staff. To develop a low-noise leg compression machine, the noise level at the surface of the structure was estimated using multibody dynamics simulation. Based on the initial design of the electric leg compression machine, parameters including assembly tolerance, component material, and shape of the structure were adjusted to prepare variations of the initial design, and their noise characteristics were analyzed. It was found that by applying the design variables, the noise levels were reduced by 7.2–11.7% compared with the initial design. The most significant reduction in noise levels was 11.7% and was achieved by reinforcing the section surrounding the gearbox enclosing a noise source.

Mechanical Flotation of Mineral Particles with an Underwater Speaker

ABSTRACT This paper aims to demonstrate a safe, non-chemical approach for improving the efficiency of froth flotation. Laboratory scale flotation tests for quartz particles of different sizes (< 20 µm, 20–38 µm, 38–75 µm, 75–106 µm, 106–150 µm, 150–212 µm) with an ether amine collector at different dosages were conducted in batch mode by using a bottom-driven mechanical flotation cell. An underwater loudspeaker was placed in the flotation pulp phase. The solids concentrations tested were 5% and 20% by weight. The results showed that acoustic sound (at 375 Hz and 77 decibels) increased the flotation recovery by at least 6% over a broad particle size range (i.e. 20–212 micron). The results also suggested applying acoustic sound in a flotation system can improve flotation recovery to a larger extent at a lower reagent dosage. An advantage of having the loudspeaker immersed in the pulp phase rather than in air above the flotation cell was the substantially reduced noise level. The present study provides a potential approach for improving flotation performance and reducing the chemical reagent consumption in flotation cells.

Actions and mathematical modeling that will bring noise levels from a racetrack or raceway to a level the community will accept

Historically, new and existing racetracks and raceways encounter conflict between owners, racecar drivers, and the surrounding community. Racecar drivers enjoy the thrill of a raceway, but neighboring residents often complain about the noise negatively impacting the quiet enjoyment of their homes. This is true even when the homes are near a major highway or road. Raceways and neighboring communities are attempting to find workable solutions without compromise to the safety and enjoyment of the raceway. The presentation discusses objective information used to assist communities or town boards, nearby neighbors, and track owners to engage in productive dialogue of the outcome of the possible solution sets. Multiple solution sets are discussed which are typically acceptable to all parties, including various barriers and other innovative noise mitigation plans. The mathematical modeling and analysis of the topography around the track is presented to show how the local terrain can be used to help to achieve the required level of track noise reduction. The information will be presented through the lenses of three case studies. Two studies demonstrate solutions for specific raceways. The other case study is used to further emphasize the importance of incorporating the local terrain into the solution set.

Feed-Forward Neural Network Denoising Applied to Goldstone Solar System Radar Images

The study of Near-Earth Asteroids (NEA) is crucial for human safety. Small hazardous asteroids with small radar cross sections are not easy to detect, track, and characterize due to the small signal-to-noise ratio (SNR) of the radar echo. This manuscript describes the results obtained for the application of a feed-forward neural network (FFNN) denoising methodology to NEA data obtained from the Goldstone Solar System Radar (GSSR). We demonstrate an increase in the signal level of up to ×4 the original value—in terms of sigma above the mean noise—when applying the FFNN denoising technique to radar Z-score normalized Binary Phase Code (BPC) images. This improvement benefits better radar detection of NEAs in general. Reducing the noise background level for antennas that have lower aperture, e.g., 34 m dishes, enables the use of FFNN denoising to improve visual detections on those noisier conditions. In addition, reducing noise level benefits shorter integration times of the data to obtain adequate signal levels. When talking about detection of small bodies crossing the antenna beam, since the asteroids or debris can move across the beam quite fast, it is relevant to reduce the integration time to allow for an increased number of independent pieces of information crossing the target through the antenna beam. The increased distance between the signal level and the noise level enables a better detection of the small-bodies at shorter integration times and therefore would be very useful for the detection of objects in the cis-lunar space.

Long-term deep intracerebral microelectrode recordings in patients with drug-resistant epilepsy: Proposed guidelines based on 10-year experience

PurposeHuman neuronal activity, recorded in vivo from microelectrodes, may offer valuable insights into physiological mechanisms underlying human cognition and pathophysiological mechanisms of brain diseases, in particular epilepsy. Continuous and long-term recordings are necessary to monitor non predictable pathological and physiological activities like seizures or sleep. Because of their high impedance, microelectrodes are more sensitive to noise than macroelectrodes. Low noise levels are crucial to detect action potentials from background noise, and to further isolate single neuron activities. Therefore, long-term recordings of multi-unit activity remains a challenge. We shared here our experience with microelectrode recordings and our efforts to reduce noise levels in order to improve signal quality. We also provided detailed technical guidelines for the connection, recording, imaging and signal analysis of microelectrode recordings. ResultsDuring the last 10 years, we implanted 122 bundles of Behnke-Fried hybrid macro-microelectrodes, in 56 patients with pharmacoresistant focal epilepsy. Microbundles were implanted in the temporal lobe (74%), as well as frontal (15%), parietal (6%) and occipital (5%) lobes. Low noise levels depended on our technical setup. The noise reduction was mainly obtained after electrical insulation of the patient's recording room and the use of a reinforced microelectrode model, reaching median root mean square values of 5.8 µV. Seventy percent of the bundles could record multi-units activities (MUA), on around 3 out of 8 wires per bundle and for an average of 12 days. Seizures were recorded by microelectrodes in 91% of patients, when recorded continuously, and MUA were recorded during seizures for 75 % of the patients after the insulation of the room. Technical guidelines are proposed for (i) electrode tails manipulation and protection during surgical bandage and connection to both clinical and research amplifiers, (ii) electrical insulation of the patient's recording room and shielding, (iii) data acquisition and storage, and (iv) single-units activities analysis. ConclusionsWe progressively improved our recording setup and are now able to record (i) microelectrode signals with low noise level up to 3 weeks duration, and (ii) MUA from an increased number of wires . We built a step by step procedure from electrode trajectory planning to recordings. All these delicate steps are essential for continuous long-term recording of units in order to advance in our understanding of both the pathophysiology of ictogenesis and the neuronal coding of cognitive and physiological functions.

Application of De-noising in Identification of the Order of Viscoelasticity as a Function of Material State

Soft tissue modeling is a challenging issue in tissue engineering. Tissue is a complex environment. It is assumed to represent viscoelastic behavior. Therefore, a complicated process is required to model its stress-strain relationship. In this paper, a non-integer order model is considered for the tissue’s mechanical behavior. The order indicates the amount that the tissue tends to behave as a pure viscous or pure elastic material. The main goal of the paper and the main contribution is to interpret the order as a function of the state of the material. To this aim, an experimental estimated model is used in which the order is considered as a function of time. Stress and strain signals are also available as functions of time. Then, an identification process is used to obtain the direct functionality of the order with respect to the state of the material (i.e. the momentary stress and strain). Data are gathered through an experimental setup. The stress signal calculated using a force sensor is highly noisy. Hence, de-noising is necessary. However, noise elimination may cause losing meaningful data. Also, a slight amount of noise enhances the generalization of the trained network in the identification process. Accordingly, a multi-level noise reduction method is used. The method is based on Empirical Mode Decomposition (EMD). To obtain the optimal noise reduction level, the noise reduction process is performed level by level and the best levels in train and test stages are chosen. Results show that supposing an explicit functionality between the order (as the amount of viscoelasticity) and the state of the tissue is reasonable. Also, it is verified that multi-level de-noising significantly improves the identification process.

Performance of Low-Height Railway Noise Barriers with Porous Materials

Rail transport is the most sustainable transportation mode, with the lowest energy consumption and carbon footprint. However, the noise induced by railway traffic in urban regions is a significant drawback and several reports point out the risks and the amount of people suffering from direct exposure to railway noise. One of the most used mitigation measures for railway noise is the implementation of noise barriers. Although they offer a significant reduction in noise levels, their height makes people feel enclosed. Therefore, in the case of railway infrastructure, the solution to the problem may lie in the use of barriers with a lower height placed close to the railway track. As the noise-forming mechanisms are mainly located at the track level, placing the barrier in a position close to the track allows mitigating rail noise without causing the problems identified above for the population in the vicinity. The purpose of this paper is to illustrate the development of a barrier solution to be used in a railway context through numerical modelling with the Boundary Element Method (BEM). The solutions developed were placed close to the track and have a low height. The geometry was defined so as to direct the energy back to the track to take advantage of the acoustic properties of the ballast. The addition of a porous granular material on the inner face of the barrier allows the control of reflections between the vehicle body and the barrier, increasing its acoustic efficiency. Finally, considering the most efficient solution, the insertion loss in a network of receivers located 10 m away from the track is analysed in order to study the noise reduction levels in a place where human receivers are usually located.

Spatio-Temporal Analysis of Noise in Selected Areas of Oyo Township

Noise is an important environmental problem in major cities of tropical African countries with Nigeria not exempted. The study adopted a quantitative measurement of noise at selected sites having heterogeneous spatial characteristics. The data collected were analyzed using totals, means, t-test and a two-way ANOVA. The study showed that noise is a feedback mechanism stemming from myriads of urbanization and industrialization processes, poor urban planning, social functions, vehicular activities (hooting), household activities, hawking and other commercial activities of the recent times. The study also showed that noise level is functionally related to temporal and spatial characteristics of places. All these have resulted in vulnerability and exposure of the cities dwellers to noise related health impairment despite the presence of some health care centres. The immediate responses known to have followed excessive noise in these areas are hearing loss, sleeping disorder, annoyance, communication impairment, health related problems like cardiovascular diseases, temporary or permanent deafness and the likes. It is hereby recommended that adequate and timely environmental education be organized for people to have a change of attitude towards noise level reduction in particular and environmental pollution in general.

Implementation of a Spatially-Variant and Tissue-Dependent Positron Range Correction for PET/CT Imaging.

AimTo develop and evaluate a new approach for spatially variant and tissue-dependent positron range (PR) correction (PRC) during the iterative PET image reconstruction.Materials and MethodsThe PR distributions of three radionuclides (18F, 68Ga, and 124I) were simulated using the GATE (GEANT4) framework in different material compositions (lung, water, and bone). For every radionuclide, the uniform PR kernel was created by mapping the simulated 3D PR point cloud to a 3D matrix with its size defined by the maximum PR in lung (18F) or water (68Ga and 124I) and the PET voxel size. The spatially variant kernels were composed from the uniform PR kernels by analyzing the material composition of the surrounding medium for each voxel before implementation as tissue-dependent, point-spread functions into the iterative image reconstruction. The proposed PRC method was evaluated using the NEMA image quality phantom (18F, 68Ga, and 124I); two unique PR phantoms were scanned and evaluated following OSEM reconstruction with and without PRC using different metrics, such as contrast recovery, contrast-to-noise ratio, image noise and the resolution evaluated in terms of full width at half maximum (FWHM).ResultsThe effect of PRC on 18F-imaging was negligible. In contrast, PRC improved image contrast for the 10-mm sphere of the NEMA image quality phantom filled with 68Ga and 124I by 33 and 24%, respectively. While the effect of PRC was less noticeable for the larger spheres, contrast recovery still improved by 5%. The spatial resolution was improved by 26% for 124I (FWHM of 4.9 vs. 3.7 mm).ConclusionFor high energy positron-emitting radionuclides, the proposed PRC method helped recover image contrast with reduced noise levels and with improved spatial resolution. As such, the PRC approach proposed here can help improve the quality of PET data in clinical practice and research.