Optical Density Distribution Research Articles

Quality Assessment of Stereotactic Radiosurgery of a Melanoma Brain Metastases Model Using a Mouselike Phantom and the Small Animal Radiation Research Platform

To establish a novel preclinical model for stereotactic radiosurgery (SRS) with combined mouselike phantom quality assurance in the setting of brain metastases. C57B6 mice underwent intracranial injection of B16-F10 melanoma cells. T1-weighted postcontrast magnetic resonance imaging (MRI) was performed on day 11 after injection. The MRI images were fused with cone beam computed tomography (CBCT) images using the Small Animal Radiation Research Platform (SARRP). The gross tumor volume (GTV) was contoured using the MRI. A single sagittal arc using the 3×3mm2 collimator was used to deliver 18Gy prescribed to the isocenter. MRI was performed 7days after radiation treatment, and the dose delivered to the mice was confirmed using 2 mouselike anthropomorphic phantoms: 1 in the axial orientation and the other in the sagittal orientation. The SARRP output was measured using a PTWFarmer type ionization chamber as per the American Association of Physicists in Medicine Task Group report 61, and the H-D curve was generated up to a maximum dose of 30Gy. Irradiated films were analyzed based on optical density distribution and H-D curve. The tumor volume on day 11, before intervention, was 2.48±1.37mm3 in the no-SRS arm versus 3.75±1.19mm3 in the SRS arm (NS). In the SRS arm, GTV maximum dose (Dmax) and mean dose were 2048±207 and 1785±14cGy. Using the mouselike phantoms, the radiochromic film showed close precision in comparison with projected isodose lines, with a Dmax of 1903.4 and 1972.7cGy, the axial and sagittal phantoms, respectively. Tumor volume 7days after treatment was 7.34±8.24mm3 in the SRS arm and 60.20±40.4mm3 in the no-SRS arm (P=.009). No mice in the control group survived more than 22days after implantation, with a median overall survival (mOS) of 19days; mOS was not reached in the SRS group, with 1 death noted. Single-fraction SRS of 18Gy delivered in a single arc can be delivered accurately with MRI T1-weighted postcontrast-based treatment planning. The mouse like phantom allows for verification of dose delivery and accuracy.

Study of exciton adjusting layer on electroluminescent and ultraviolet detective properties of organic optoelectronic integrated device

Organic optoelectronic integrated device (OID) with ultraviolet (UV) photodetective and electroluminescent (EL) properties was constructed by using four kinds of organic materials with various film thicknesses as exciton adjusting layer (EAL). The effect of EAL on the performance of OID was studied via energy level regulation, simulation of optical density distribution and charge transport analyses. Three orders of magnitude in UV-detectivity from 109 to 1012 Jones, and five folds of luminance from 5000 to 25000 cd/m2, were achieved by optimizing the species and thickness of EAL materials. We found that the energy level and thickness of EAL play important roles on the improvement of EL and UV detective properties. On one hand, the energy difference of highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO) between hole transport layer and active layer has a significant effect on the EL property through adjusting hole injection and passivating leaking current processes. On the other hand, the optimized EAL thickness is beneficial to enhance the distribution of optical density in the active layer, leading to more photocurrent generation for high UV detective property. Meanwhile, the EAL can trap leaking electrons to decrease the dark current for high detective performance. Moreover, both high EL and UV detective properties of OID can be simultaneously achieved by emulating calculation the carrier transport length of EAL.

Spatial Distribution of Macular Pigment in an Elderly French Population: The Montrachet Study.

We describe the spatial distribution and cross-sectional associations with physical and lifestyle attributes. The participants of the Montrachet (Maculopathy Optic Nerve, nuTRition neurovAsCular and HEarT) study underwent an exhaustive ophthalmologic examination, including optical coherence tomography, to measure retinal thickness. The spatial distribution of macular pigment optical density (MPOD) defined as a ring-like, intermediate or no-ring pattern, was assessed by means of the two-wavelength autofluorescence technique. Blood samples were taken to measure plasma lutein and zeaxanthin using high performance liquid chromatography (HPLC). We studied 635 subjects with good-quality MPOD measurements. The mean age was 82.0 ± 3.4 years. A ring-like structure was found in 109 (17.2%) participants. Participants with a ring-like spatial distribution had a thinner macula in the central subfield (P < 0.001). In multivariate analysis, individuals never protecting themselves from sunlight and with dark iris color were less likely to present a ring-like than a no-ring spatial distribution (P = 0.033 and P = 0.013, respectively). Only in males were lutein plasma levels higher in ring-like and intermediate MPOD profiles than in no-ring structures (odds ratio [OR] = 1.59 for 100 additional μg; 95% confidence interval [CI] = 1.16-2.18 and OR = 1.64; 95% CI, 1.17-2.28). In this population-based study, individuals never protecting themselves from sunlight, and with dark iris color and a thinner macula were less prone to displaying a ring-like MPOD spatial distribution.

Joint Reconstruction of Absorbed Optical Energy Density and Sound Speed Distributions in Photoacoustic Computed Tomography: A Numerical Investigation.

Photoacoustic computed tomography (PACT) is a rapidly emerging bioimaging modality that seeks to reconstruct an estimate of the absorbed optical energy density within an object. Conventional PACT image reconstruction methods assume a constant speed-of-sound (SOS), which can result in image artifacts when acoustic aberrations are significant. It has been demonstrated that incorporating knowledge of an object's SOS distribution into a PACT image reconstruction method can improve image quality. However, in many cases, the SOS distribution cannot be accurately and/or conveniently estimated prior to the PACT experiment. Because variations in the SOS distribution induce aberrations in the measured photoacoustic wavefields, certain information regarding an object's SOS distribution is encoded in the PACT measurement data. Based on this observation, a joint reconstruction (JR) problem has been proposed in which the SOS distribution is concurrently estimated along with the sought-after absorbed optical energy density from the photoacoustic measurement data. A broad understanding of the extent to which the JR problem can be accurately and reliably solved has not been reported. In this work, a series of numerical experiments is described that elucidate some important properties of the JR problem that pertain to its practical feasibility. To accomplish this, an optimization-based formulation of the JR problem is developed that yields a non-linear iterative algorithm that alternatively updates the two image estimates. Heuristic analytic insights into the reconstruction problem are also provided. These results confirm the ill-conditioned nature of the joint reconstruction problem that will present significant challenges for practical applications.

Analysis of the central zone of the retina in patients with diabetic macular edema

Aim. To assess morphological changes of retinal layers and optical density of macular pigment in patients with diabetic macular edema (DME) for the diagnostic criterion of pathological process.Materials and methods. 31 patients were divided in two groups. The first group (A) included 19 patients with DME (20 eyes), the second group (B) – 12 patients (20 eyes) without retinal pathology. Both groups were comparable with regard to age. Parameter estimation was conducted with the use of following methods: optical coherence tomography (OCT) of the macular area of the retina; fundus photography with the measurement of macular pigment optical density (MPOD); microperimetry.Results. OCT analysis showed that the inner nuclear and plexiform layers of retina were the most involved in pathological process and revealed significant differences in increase of mean retinal thickness in comparison with the control group. Analysis of MPOD revealed a significant reduction of all parameters in group A compared with the control group. On the basis of microperimetry of the central area of retina in group A light sensitivity indicators were reduced by an average of 9 dB and equaled 9.85 ± 0.09 dB. The analysis showed gross violations of retinal structure and distribution of optical density of macular pigment in patients with DME. Correlation analysis of retinal thickness, functional light sensitivity and optical density of macular pigment traced a strong connection (r = -0.93; p 0.05) between the indices of retinal thickness and MPOD.Conclusions. Diabetic macular edema showed a sharp decrease in optical density of macular pigment determined by deficiency of lutein and zeaxantin. A correlation between quantitative indicator of optical density of macular pigment and area of edema was established. Light sensitivity was significantly reduced in the central part of the retina.

Theoretical analysis and optimization of 3D laser beam shaping

Abstract We report methodology of three-dimensional laser beam shaping. The analytical and numerical analysis is presented. A strategy for designing optical system involves the controlled application of aberrations which is realized by specific aspheric lens shaping. The goal is to obtain the desired optical power density distribution in space, which is optimal for selected application. The proposed method is discussed with regard to the design of optical transmitter for laser shooting simulator, however the developed methodology can be used for a number of other light shaping applications

Hidden image recovery using a biased photorefractive crystal in the Fourier plane of an optical imaging system.

Self-diffraction can be induced using a biased photorefractive crystal in the Fourier plane of an imaging system where the light beam intensity is naturally high due to the concentration effect of an optical lens. The spatial frequency spectrum of the output image is proportional to the optical power density distribution in the Fourier plane. A photorefractive crystal with small size can be used and hence an reduced amount of biased voltage is needed to obtain significant diffraction effect in the image plane. When the input image is an overlay of a signal and a noise pattern, theoretic model reveals that the induced diffraction in the Fourier plane may be preferably applied on the noise pattern. In order to illustrate the effect experimentally, a signal from a weakly illuminated object is coupled with an overwhelming noise pattern and then the hidden signal is successfully recovered using a SBN61 crystal with an applied voltage of 800 V in the Fourier plane. Such technology can be employed in encrypted spatial communication systems for security purposes.

Statistical properties of an anomalous hollow beam with orbital angular momentum

Due to the wide application of the vortex beam, a new theoretical model is introduced to describe the anomalous hollow beam (AHB) with optical angular momentum (OAM). The analytical propagation expression for the AHB with OAM passing through an ABCD optical system is derived. The effect of topological charge (TC) on the propagation properties of the AHB with OAM is studied numerically. The dependence of the normalized intensity distribution, the phase distribution and the optical angular momentum density (OAMD) distribution of the proposed beam on its TC is illustrated numerically. Furthermore, it is found that the intensity distribution, phase distribution, and the OAMD distribution are shaped through varying the TC and propagation distance. Our results will be useful for optical communication and optical trapping.

The Heritability of the Ring-Like Distribution of Macular Pigment Assessed in a Twin Study

It has been suggested that ring-like patterns of macular pigment, as measured with dual wavelength autofluorescence, are observed less frequently in subjects with age-related maculopathy. We explored relative contributions of genetic and environmental factors in macular pigment optical density (MPOD) distributions using a classic twin study. As part of a previous nutritional study, 322 healthy Caucasian female twins, aged 16 to 50 (mean 40) years, underwent measurement of MPOD optical density by two-wavelength fundus autofluorescence. In the present study, the right eye MPOD profile was assessed for the presence of a ring-like pattern by two graders independently, using common criteria, with a third grader arbitrating in cases of disagreement. Concordance was calculated as 2C/(2C + D), where C is the number of twin pairs concordant, and D the number discordant, for the ring-like pattern. Also, heritability was calculated using maximum-likelihood structural equation modeling. Images and zygosity data were available for 314 twins (88 monozygotic [MZ] and 69 dizygotic [DZ] pairs). The overall prevalence of the ring pattern was 25.8%. Respective concordances for MZ and DZ twins were 0.75 and 0.22. Additive genetic factors were estimated to contribute to 84.0% of the total variance (95% confidence intervals, 63.7%-94.6%). Concordance for MZ twins was over three times that for DZ twins, with heritability estimated at 84%, indicating that genetic factors contribute to the development of the ring structure. Studies have suggested that ring-like patterns of macular pigment can affect risk for age-related maculopathy. In a classic twin study, we found that the presence of such a pattern was highly heritable.

Application of radiochromic film for quality assurance in the heavy-ion beam scanning irradiation system at HIMAC

For the quality assurance (QA) of therapeutic scanned carbon-ion beams, QA tool having high spatial resolution is required. The radiochromic film (such as Gafchromic EBT2 film model) is a very useful tool because of its high spatial resolution, self-development, and near tissue equivalence. However, for a complex field in carbon-ion therapy, it is difficult to unambiguously determine the dose from the measured net optical density (OD). As a first approach, we investigated the response of EBT2 to carbon-ion beam at the Heavy Ion Medical Accelerator in Chiba (HIMAC) in Japan. Based on the measured results, we performed QA measurements independently of dose. We verified the QA measurements by EBT2 by comparing the ionization chamber and the fluorescent screen. The results obtained with EBT2 were in good agreement with those obtained with the other detector. In addition, to test the use in a complex field, we verified the OD distributions for moving and static target by means of a gamma index analysis. As a result, we confirmed that EBT2 could be used as a part of QA procedures for therapeutic scanned carbon-ion beams.

Differentiation and Migration of Bone Marrow Mesenchymal Stem Cells Transplanted through the Spleen in Rats with Portal Hypertension

AimsThe goals of this paper were to evaluate the differentiation of bone marrow mesenchymal stem cells (BMSCs) into hepatocyte-like cells in vitro, and to determine whether stem cells can migrate and plant into the liver with portal hypertension accompanied by the end-stage of liver disease. MethodsBMSCs were isolated from rats and amplified with hepatocyte growth factor (HGF) and fibroblast growth factor-4 (FGF-4). The expression of alpha-fetoprotein (AFP), cytokeratin 18 (CK-18), and albumin (ALB) was detected by immunofluorescence in induced cells. Rats were randomly divided into experimental (with common bile duct ligation) and control groups. After injection of fluorescence labeled cells, cell distribution was observed under a fluorescence microscope. The integrated optical density (IOD) and cell distribution scores were evaluated using Image-Pro Plus 6.0 software. The portal pressure was measured before the rats were killed. ResultsAfter being induced with HGF and FGF-4, the Golgi apparatus, endoplasmic reticulum, ribosomes, and mitochondria all significantly increased in the fifth generation cells. Immunofluorescent analysis showed that the induced cells expressed AFP, CK-18, and ALB. BMSCs were stained by CM-Dil, and the labeling rate was as high as 95.5%. The portal pressure in experimental group was much higher than that of the control group (18.04±2.35 vs. 9.75±1.40cm H2O p<0.01). The IOD of transplanted cells in the experimental group was also significantly higher than that of the control group (11.30±2.09×105 vs. 2.93±0.88×105, p<0.01). In addition, the cell distribution score in the experimental group was lower than that of the control group (1.99±0.36 vs. 2.36±0.27, P<0.05). ConclusionsThe combination of HGF and FGF-4 induces the differentiation of BMSCs into hepatocyte-like cells, which express AFP, CK-18, and ALB. In addition, the recruitment of BMSCs (after transplantation in the spleen) was improved in rats with portal hypertension.

Dose evaluation of an NIPAM polymer gel dosimeter using gamma index

An N-isopropylacrylamide (NIPAM) polymer gel dosimeter has great potential in clinical applications. However, its three-dimensional dose distribution must be assessed. In this work, a quantitative evaluation of dose distributions was performed to evaluate the NIPAM polymer gel dosimeter using gamma analysis.A cylindrical acrylic phantom filled with NIPAM gel measuring 10cm (diameter) by 10cm (height) by 3mm (thickness) was irradiated by a 4×4cm2 square light field. The irradiated gel phantom was scanned using an optical computed tomography (optical CT) scanner (OCTOPUS™, MGS Research, Inc., Madison, CT, USA) at 1mm resolution. The projection data were transferred to an image reconstruction program, which was written using MATLAB (The MathWorks, Natick, MA, USA). The program reconstructed the image of the optical density distribution using the algorithm of a filter back-projection.Three batches of replicated gel phantoms were independently measured. The average uncertainty of the measurements was less than 1%. The gel was found to have a high degree of spatial uniformity throughout the dosimeter and good temporal stability. A comparison of the line profiles of the treatment planning system and of the data measured by optical CT showed that the dose was overestimated in the penumbra region because of two factors. The first is light scattering due to changes in the refractive index at the edge of the irradiated field. The second is the edge enhancement caused by free radical diffusion. However, the effect of edge enhancement on the NIPAM gel dosimeter is not as significant as that on the BANG gel dosimeter. Moreover, the dose uncertainty is affected by the inaccuracy of the gel container positioning process. To reduce the uncertainty of 3D dose distribution, improvements in the gel container holder must be developed.

Performance of an improved first generation optical CT scanner for 3D dosimetry

Performance analysis of a modified 3D dosimetry optical scanner based on the first generation optical CT scanner OCTOPUS is presented. The system consists of PRESAGE™ dosimeters, the modified 3D scanner, and a new developed in-house user control panel written in Labview program which provides more flexibility to optimize mechanical control and data acquisition technique. The total scanning time has been significantly reduced from initial 8 h to ∼2 h by using the modified scanner. The functional performance of the modified scanner has been evaluated in terms of the mechanical integrity uncertainty of the data acquisition process. Optical density distribution comparison between the modified scanner, OCTOPUS and the treatment plan system has been studied. It has been demonstrated that the agreement between the modified scanner and treatment plans is comparable with that between the OCTOPUS and treatment plans.

Lipid droplets characterization in adipocyte differentiated 3T3-L1 cells: size and optical density distribution

The 3T3-L1 cell line, derived from 3T3 cells, is widely used in biological research on adipose tissue. 3T3-L1 cells have a fibroblast-like morphology, but, under appropriate conditions, they differentiate into an adipocyte-like phenotype. During the differentiation process, 3T3-L1 cells increase the synthesis of triglycerides and acquire the behavior of adipose cells. In particular, triglycerides accumulate in lipid droplets (LDs) embedded in the cytoplasm. The number and the size distribution of the LDs is often correlated with obesity and many other pathologies linked with fat accumulation. The integrated optical density (IOD) of the LDs is related with the amount of triglycerides in the droplets. The aim of this study is the attempt to characterize the size distribution and the IOD of the LDs in 3T3-L1 differentiated cells. The cells were differentiated into adipocytes for 5 days with a standard procedure, stained with Oil Red O and observed with an optical microscope. The diameter, area, optical density of the LDs were measured. We found an asymmetry of the kernel density distribution of the maximum Feret’s diameter of the LDs with a tail due to very large LDs. More information regarding the birth of the LDs could help in finding the best mathematical model in order to analyze fat accumulation in adipocytes.

Analysis of Optical properties of nanocrystalline titanium dioxide films

The optical properties of materials can be characterized in terms of the complex refractive index. We developed a simple and efficient method for determining the complex refractive index of nanomaterials that uses the relationship between this parameter and the light spectrum measured for a specimen. The optical properties of nanoparticle and nanotube TiO2 films were investigated. The results show that the morphology of nano-TiO2 affects the complex refractive index spectrum and therefore influences light dispersion and absorption of the film. We also simulated the optical energy density distribution within equivalent plane films using complex refractive index data.

Experimental investigation of natural convection inside a upper part of vertical converging air channel using the Schlieren technique

The article concerns the selected application problem of gradient optical technique for the analysis of development of the thermal boundary layer. The recording of thermal boundary layer development was carried out using the modified Schlieren system. The modifications introduced to the optical measuring systems allowed the extension of the information carrier measuring range along with a reduction in the susceptibility of the systems to misalignment. As the information carrier, a collimated 25-mW He–Ne laser beam was used. The recording of the distribution of optical density of information carrier around the experimental model under analysis was carried out using a CCD matrix with the image acquisition card. The experimental model under consideration was a converging air channel in the form of a space enclosed by two inclined heating surfaces. The measurements of convective heat transfer were carried out for different angles of inclination (18°, 30° and 45°) and thermal conditions (320K, 370K and 490K) of the heating surfaces. The obtained results of experimental analysis were approximated with the power relationship Nux=C(Rax)a.

Upgrade and benchmarking of a 4D treatment planning system for scanned ion beam therapy

Upgrade and benchmarking of a research 4D treatment planning system (4DTPS) suitable for realistic patient treatment planning and treatment simulations taking into account specific requirements for scanned ion beam therapy, i.e., modeling of dose heterogeneities due to interplay effects and range changes caused by patient motion and dynamic beam delivery. The 4DTPS integrates data interfaces to 4D computed tomography (4DCT), deformable image registration and clinically used motion monitoring devices. The authors implemented a novel data model for 4D image segmentation using Boolean mask volume datasets and developed an algorithm propagating a manually contoured reference contour dataset to all 4DCT phases. They further included detailed treatment simulation and dose reconstruction functionality, based on the irregular patient motion and the temporal structure of the beam delivery. The treatment simulation functionality was validated against experimental data from irradiation of moving radiographic films in air, 3D moving ionization chambers in a water phantom, and moving cells in a biological phantom with a scanned carbon ion beam. The performance of the program was compared to results obtained with predecessor programs. The measured optical density distributions of the radiographic films were reproduced by the simulations to (-2 ± 12)%. Compared to earlier versions of the 4DTPS, the mean agreement improved by 2%, standard deviations were reduced by 7%. The simulated dose to the moving ionization chambers in water showed an agreement with the measured dose of (-1 ± 4)% for the typical beam configuration. The mean deviation of the simulated from the measured biologically effective dose determined via cell survival was (617 ± 538) mGy relative biological effectiveness corresponding to (10 ± 9)%. The authors developed a research 4DTPS suitable for realistic treatment planning on patient data and capable of simulating dose delivery to a moving patient geometry for scanned ion beams. The accuracy and reliability of treatment simulations improved considerably with respect to earlier versions of the 4DTPS.

Association of age and macular pigment optical density using dual-wavelength autofluorescence imaging

BackgroundSeveral lines of evidence suggest that macular pigment may play a protective role against age-related macular degeneration, but the influence of age on macular pigment density levels remains unclear. This study was designed to investigate the relationship between age and the normal distribution of macular pigment optical density (MPOD) values surrounding the fovea.MethodsConsecutive healthy subjects with no evidence of ocular disease were enrolled in this study. After inclusion, MPOD values were measured at specific eccentricities (0.5, 1, and 2 degrees) from the foveal center using a dual-wavelength autofluorescence method employing a modified confocal scanning laser ophthalmoscope. Whenever both eyes were eligible, one was randomly selected for analysis. The correlation between age and MPOD values was investigated using regression analysis.ResultsThirty subjects (30 eyes) were included (mean age 48.6 ± 16.4 [range 23–77] years). Significant differences were found between MPOD values measured at 0.5, 1, and 2 degrees from the center of the fovea (0.49 ± 0.12 density units, 0.37 ± 0.11 density units, and 0.13 ± 0.05 density units, respectively, P < 0.05). Significant correlations between age and MPOD values at 0.5 and 1 degree were found (P ≤ 0.02). Values measured at 2 degrees did not correlate significantly with age (P = 0.06).ConclusionIn healthy subjects, MPOD values were highest near the foveal center. These values appeared to increase during adulthood (peak at 45–50 years), followed by a gradual reduction after 60 years of age.

Scanning angle Raman spectroscopy measurements of thin polymer films for thickness and composition analyses

Scanning angle (SA) Raman spectroscopy was used to measure the thickness and composition of polystyrene films. A sapphire prism was optically coupled to a sapphire substrate on which 6–12% (w/v) polystyrene in toluene was spin coated. Raman spectra were collected as the incident angle of the p-polarized, 785-nm excitation laser was varied from 56 to 70°. These angles span above and below the critical angle for a sapphire/polystyrene interface. The thickness of the polystyrene film was determined using a calibration curve constructed by calculating the integrated optical energy density distribution as a function of incident angle, distance from the prism interface and polymer thickness. The calculations were used to determine the incident angle where waveguide modes are excited within the polymer film, which is the angle with the highest integrated optical energy density. The film thicknesses measured by SA Raman spectroscopy ranged from less than 400nm to 1.8μm. The average percent uncertainty in the SA Raman determinations for all films was 4%, and the measurements agreed with those obtained from optical interferometery within the experimental uncertainty for all but two films. For the 1270-nm and 580-nm polystyrene films, the SA Raman measurements overestimated the film thickness by 5 and 18%, respectively. The dependence of the calibration curve on excitation polarization and composition of the polymer and bulk layers was evaluated. This preliminary investigation demonstrates that scanning angle Raman spectroscopy is a versatile method applicable whenever the chemical composition and thickness of interfacial polymer layers needs to be measured.

Observing the localization of light in space and time by ultrafast second-harmonic microscopy

Multiple coherent scattering and the constructive interference of certain scattering paths form the common scheme of several remarkable localization phenomena of classical and quantum waves in randomly disordered media1. Prominent examples are electron transport in disordered conductors2,3, the localization of excitons in semiconductor nanostructures4,5, surface plasmon polaritons at rough metallic films6,7 or light in disordered dielectrics8,9,10,11 and amplifying media1,12,13,14. However, direct observation of the fundamental spatiotemporal dynamics of the localization process remains challenging15. This holds true, in particular, for the localization of light occurring on exceedingly short femtosecond timescales and nanometre length scales. Here, we combine second harmonic microscopy with few-cycle time resolution to probe the spatiotemporal localization of light waves in a random dielectric medium. We find lifetimes of the photon modes of several femtoseconds and a broad distribution of the local optical density of states, revealing central hallmarks of the localization of light. By combining high-resolution nonlinear optical microscopy with few-cycle time resolution, scientists show that they are able to probe the spatiotemporal localization of light waves in random dielectric nanostructures. The findings will aid the study of light localization dynamics in a variety of passive and active random media.