An evaluation of consumer smartphones for generating bolus and surface mould applicators for radiation oncology.

BACKGROUND: The use of Computed Tomography (CT) imaging data to create 3D printable patient-specific devices for radiation oncology purposes is already well established in the literature and has shown to have superior conformity than conventional methods. Using non-ionizing radiation imaging techniques such as photogrammetry or laser scanners in-lieu of a CT scanner presents many desirable benefits including reduced imaging dose and fabrication of the device can be completed prior to simulation. With recent advancements in smartphone-based technology, photographic and LiDAR-based technologies are more readily available than ever before and to a high level of quality. As a result, these non-ionizing radiation imaging methods are now able to generate patient-specific devices that can be acceptable for clinical use. PURPOSE: In this work, we aim to determine if smartphones can be used by radiation oncologists or other radiation oncology staff to generate bolus or brachytherapy surface moulds instead of conventional CT with equivalent or comparable accuracy. METHODS: This work involved two separate studies: a phantom and participant study. For the phantom study, a RANDO anthropomorphic phantom (limited to the nose region) was used to generate 3D models based on three different imaging techniques: conventional CT, photogrammetry & LiDAR which were both acquired on a smartphone. Virtual boli were designed in Blender and 3D printed from PLA plastic material. The conformity of each printed boli was assessed by measuring the air gap volume and approximate thickness between the phantom & bolus acquired together on a CT. For the participant study, photographs, and a LiDAR scan of four volunteers were captured using an iPhone 13 Pro™ to assess their feasibility for generating human models. Each virtual 3D model was visually assessed to identify any issues in their reconstruction. The LiDAR models were registered to the photogrammetry models where a distance to agreement analysis was performed to assess their level of similarity. Additionally, a 3D virtual bolus was designed and printed using ABS material from all models to assess their conformity onto the participants skin surface using a verbal feedback method. RESULTS: The photogrammetry derived bolus showed comparable conformity to the CT derived bolus while the LiDAR derived bolus showed poorer conformity as shown by their respective air gap volume and thickness measurements. The reconstruction quality of both the photogrammetry and LiDAR models of the volunteers was inadequate in regions of facial hair and occlusion, which may lead to clinically unacceptable patient-specific device that are created from these areas. All participants found the photogrammetry 3D printed bolus to conform to their nose region with minimal room to move while three of the four participants found the LiDAR was acceptable and could be positioned comfortably over their entire nose. CONCLUSIONS: Smartphone-based photogrammetry and LiDAR software show great potential for future use in generating 3D reference models for radiation oncology purposes. Further investigations into whether they can be used to fabricate clinically acceptable patient-specific devices on a larger and more diverse cohort of participants and anatomical locations is required for a thorough validation of their clinical usefulness.

A large-scale field experiment across six rivers illustrates how the effects of resource enrichment are context dependent.

Resource supplementation can increase species richness and change the faunal composition of communities, but experiments have produced variable outcomes. An often overlooked element is that species richness can only increase if new taxa can disperse to resource-rich locations and invade established, local communities. We experimentally increased a basal resource (detritus) in six rivers in south-eastern Australia by driving wooden stakes into the riverbed to increase retention of detritus. Control sites were left untreated. Sites were located in agricultural sections with mostly cleared vegetation, but with intact (uncleared) reference sites upstream to provide sources of prospective colonists. We measured channel retentiveness and sampled benthic detritus and invertebrates before and after manipulation. We tested whether: greater retentiveness increased detritus densities, species richness and abundances and altered faunal composition; manipulation sites reached bio-equivalence with reference sites; new species arose from upstream reference areas; and whether outcomes were consistent across rivers. Only three rivers gained increases in detritus densities. All had low pre-existing amounts of in-stream wood compared with rivers that did not respond to treatment. Two rivers (Hughes Creek, Seven Creeks) gained higher species richness and invertebrate densities within 12 months and reached bio-equivalence with reference sites. In contrast, Turtons Creek showed species turnover through replacement of individuals. Only in Hughes Creek was there evidence of successful dispersal from the upstream reference area. The outcomes show that the effects of resource supplementation vary between rivers and suggest that pre-existing conditions (e.g. channel retentiveness) may cause these differences, providing clear evidence of context dependence.

A dosimetric comparison of CT- and photogrammetry- generated 3D printed HDR brachytherapy surface applicators.

In this study, we investigate whether an acceptable dosimetric plan can be obtained for a brachytherapy surface applicator designed using photogrammetry and compare the plan quality to a CT-derived applicator. The nose region of a RANDO anthropomorphic phantom was selected as the treatment site due to its high curvature. Photographs were captured using a Nikon D5600 DSLR camera and reconstructed using Agisoft Metashape while CT data was obtained using a Canon Aquillion scanner. Virtual surface applicators were designed in Blender and printed with PLA plastic. Treatment plans with a prescription dose of 3.85 Gy × 10 fractions with 100% dose to PTV on the bridge of the nose at 2 mm depth were generated separately using AcurosBV in the Varian BrachyVision TPS. PTV D98%, D90% and V100%, and OAR D0.1cc, D2cc and V50% dose metrics and dwell times were evaluated, with the applicator fit assessed by air-gap volume measurements. Both types of surface applicators were printed with minimal defects and visually fitted well to the target area. The measured air-gap volume between the photogrammetry applicator and phantom surface was 44% larger than the CT-designed applicator, with a mean air gap thickness of 3.24 and 2.88 mm, respectively. The largest difference in the dose metric observed for the PTV and OAR was the PTV V100% of - 1.27% and skin D0.1cc of - 0.28%. PTV D98% and D90% and OAR D2cc and V50% for the photogrammetry based plan were all within 0.5% of the CT based plan. Total dwell times were also within 5%. A 3D printed surface applicator for the nose was successfully constructed using photogrammetry techniques. Although it produced a larger air gap between the surface applicator and phantom surface, a clinically acceptable dose plan was created with similar PTV and OAR dose metrics to the CT-designed applicator. Additional future work is required to comprehensively evaluate its suitability in a clinically environment.

Evaluation of camera settings for photogrammetric reconstruction of humanoid phantoms for EBRT bolus and HDR surface brachytherapy applications.

The fabrication of brachytherapy surface moulds is considered laborious and time consuming that often result in repeated attempts due to incorrect catheter positioning or the presence of air gaps. 3-dimensional printing using low-cost and reliable materials has allowed the rapid creation of patient-specific surface mould applicators to be achieved using patient imaging data obtained via CT scan. In this study we investigate whether an alternative approach using photogrammetry techniques can improve this process and how camera settings and object texture affect the reconstructions. Two humanoid phantoms, an anthropomorphic RANDO phantom and a Laerdal Little Anne CPR training manikin were used in this study. Both were imaged using a Nikon D5600 DSLR and Nokia 3.1 smartphone camera and reconstructed using Agisoft Metashape software. CT scans of both phantoms were taken as references for comparing the photogrammetry reconstructions. Models were reconstructed from different photo sets and assessed by distance to agreement with the CT models. Both phantoms were effectively reconstructed for most experiments. Increasing the number of photos used produced the better reconstructions while in general, reconstructions using video data were poor. The two phantoms were reconstructed at a similar quality. Background light that caused undesirable reflections significantly reduced reconstruction quality. Applying a non-reflective tape to the affected regions provided a suitable method for reducing their effects. Photogrammetry techniques were effectively able to reconstruct 3-dimensional models of both phantom. The camera settings and lighting did have a profound effect on the reconstruction quality and should be chosen appropriately depending on the scene.

Catchment land use predicts benthic vegetation in small estuaries.

Many estuaries are becoming increasingly eutrophic from human activities within their catchments. Nutrient loads often are used to assess risk of eutrophication to estuaries, but such data are expensive and time consuming to obtain. We compared the percent of fertilized land within a catchment, dissolved inorganic nitrogen loads, catchment to estuary area ratio and flushing time as predictors of the proportion of macroalgae to total vegetation within 14 estuaries in south-eastern Australia. The percent of fertilized land within the catchment was the best predictor of the proportion of macroalgae within the estuaries studied. There was a transition to a dominance of macroalgae once the proportion of fertilized land in the catchment exceeded 24%, highlighting the sensitivity of estuaries to catchment land use.

Make the Most of the Data You've Got: Bayesian Models and a Surrogate Species Approach to Assessing Benefits of Upstream Migration Flows for the Endangered Australian Grayling.

Environmental water managers must make best use of allocations, and adaptive management is one means of improving effectiveness of environmental water delivery. Adaptive management relies on generation of new knowledge from monitoring and evaluation, but it is often difficult to make clear inferences from available monitoring data. Alternative approaches to assessment of flow benefits may offer an improved pathway to adaptive management. We developed Bayesian statistical models to inform adaptive management of the threatened Australian grayling (Prototroctes maraena) in the coastal Thomson River, South-East Victoria Australia. The models assessed the importance of flows in spring and early summer (migration flows) for upstream dispersal and colonization of juveniles of this diadromous species. However, Australian grayling young-of-year were recorded in low numbers, and models provided no indication of the benefit of migration flows. To overcome this limitation, we applied the same models to young-of-year of a surrogate species (tupong-Pseudaphritis urvilli)-a more common diadromous species expected to respond to flow similarly to Australian grayling-and found strong positive responses to migration flows. Our results suggest two complementary approaches to supporting adaptive management of Australian grayling. First, refine monitoring approaches to allow direct measurement of effects of migration flows, a process currently under way. Second, while waiting for improved data, further investigate the use of tupong as a surrogate species. More generally, alternative approaches to assessment can improve knowledge to inform adaptive management, and this can occur while monitoring is being revised to directly target environmental responses of interest.

Verification of dose delivery for a prostate sIMRT treatment using a SLIC-EPID.

The current work focuses on the verification of transmitted dose maps, measured using a scanning liquid ionization chamber-electronic portal imaging device (SLIC-EPID) for a typical step-and-shoot prostate IMRT treatment using an anthropomorphic phantom at anterior-posterior (A-P), and several non-zero gantry angles. The dose distributions measured using the SLIC-EPID were then compared with those calculated in the modelled EPID for each segment/subfield and also for the corresponding total fields using a gamma function algorithm with a distance to agreement and dose difference criteria of 2.54mm and 3%, respectively.

The use of extended dose range film for dosimetric calibration of a scanning liquid-filled ionization chamber electronic portal imaging device.

A scanning liquid-filled ionization chamber electronic portal imaging device (SLIC-EPID) and extended dose range (EDR2) films were used to evaluate transmitted dose profiles for homogeneous and inhomogeneous phantoms. Calibrated ionization chamber measurements were used to convert the pixel values acquired from the electronic portal images to dose. Because SLIC-EPID was developed to have a uniform response for all liquid ionization chambers, the off-axis dose values were reconstructed using a correction factor matrix, defined as the ratio of the relative EDR2 film and the corresponding EPID dose values measured in air. The transmitted dose distributions in the EPID detector layer were also modeled using a Pinnacle3 treatment planning system (TPS: Philips Radiation Oncology Systems, Milpitas, CA). The gamma function algorithm was then used to assess agreement between transmitted dose distributions measured using a SLIC-EPID and EDR2 film, and those calculated using the TPS. For homogenous and inhomogeneous phantoms, more than 90% agreement was achieved using gamma criteria of 2% and 3 mm and 3% and 2.5 mm respectively. Our results indicate that the calibration procedure proposed in the present study should be performed if SLIC-EPID is to be used as a reliable two-dimensional transmitted dosimeter for clinical purposes.

Experimental evidence for physical cues involved in oviposition site selection of lotic hydrobiosid caddis flies.

Cues involved in determining the distribution of invertebrate propagules within a stream landscape contribute greatly to our knowledge of the supply and arrangement of new recruits and thus an improved understanding of factors that might ultimately affect population parameters. Previous observations indicated that both current velocity and rock size were important determinants of the egg mass distribution of certain hydrobiosid caddis flies that lay their eggs in single masses beneath emergent rocks. These observations were tested experimentally in a temperate, upland Australian stream. Manipulations of current speed confirmed that females of Ulmerochorema sp. and the Taschorema complex deposited more eggs on rocks in elevated current speeds (>0.40 ms(-1)) whereas Apsilochorema sp. deposited more eggs on rocks in slow currents (<0.30 ms(-1)). This latter result did not coincide with previous observational data. The anomaly between observational and experimental data, however, was reconciled by the outcome of a further experiment that tested the influence of the emergent or 'landing pad' size of rocks as the abundance of Apsilochorema egg masses increased with landing pad size independent of the prevailing flow conditions. Landing pad size did not influence the abundance of egg masses of Taschorema or Ulmerochorema. Patterns of female visits to rocks indicated that taxa might distinguish between favoured egg-laying sites prior to landing on rocks. Large aggregations of adult male and female Ulmerochorema collected from rocks favoured for oviposition provide indirect evidence for mating induced swarming behaviour associated with oviposition site selection. This study provides a framework for more sophisticated questions relating to the influence of oviposition site selection on structuring populations of lotic macroinvertebrates.

Ten steps to a successful disease management program.

This primer article suggests the 10 basic steps a health plan must take to successfully create and implement an internal disease management program. Covering everything from patient identification to staffing to educational materials, the author focuses on congestive heart disease and diabetes examples.