This study was supported by the Open Source Consortium of Instrumentation (Open-It), Japan, JSPS KAKENHI Grant (Nos. 22244019, 26610055, 15H04769 and 19H04492).

The protocol was conducted following the guidelines of the research ethics committee at the National Cancer Center Hospital East, Japan.
1. Monitoring of sealed radiation source in experiment room at RI facility
<ol>
	<li>Set the Compton camera beside the dose rate monitor as shown in Figure 2a. Set the height of the detectors from the ground to 2.5 m. Build the dose rate monitor, which consists of a parallel plate ionization chamber, into the upper part of the entrance of the experiment room at the RI facility to monitor the air dose rate of the position at intervals of 1 min.</li>
	<li>Turn on the power of the Compton camera and online computer.</li>
	<li>Start the simultaneous measurement with Compton camera and the dose rate monitor.</li>
	<li>Set a 137Cs sealed source (3.85 MBq) at a position labelled &#39;A&#39; in Figure 2a and leave it for 30 min. Set the distance between the detector and the sealed source to 3.6 m.</li>
	<li>Move the sealed source to a position labelled &#39;B&#39; and leave it during 30 min. Set the distance between the detector and the sealed source to 6.7 m.</li>
	<li>Move the sealed source at a position labelled &#39;C&#39; and leave it during 30 min. Set the distance between the detector and the sealed source to 6.7 m.</li>
	<li>Move the sealed source at a position labelled &#39;D&#39; and leave it during 30 min. Set the distance between the detector and the sealed source to 1 m.</li>
	<li>Move the sealed source outside the room. After 30 min, stop all measurement.</li>
</ol>
2. Environmental monitoring in PET facility
<ol>
	<li>Set the Compton camera in front of reception desk in PET facility as shown in Figure 2b. Set the height of the detectors from the ground to 1 m.</li>
	<li>Set the online computer in the staff room.</li>
	<li>Turn on the power of the Compton camera and online computer.</li>
	<li>Start Compton camera measurement early in the morning before patients arrive at facility.</li>
	<li>After all patients leave for the day, stop all measurement.</li>
</ol>
3. Outdoor measurement in Kawamata-machi, Fukushima, Japan
<ol>
	<li>Set the Compton camera near a private house as shown in Figure 2c, where the existence of some radiological Caesium hot spots with surface dose rates of 1 &#181;Sv/h or less are suspected. Set the height of the detectors from the ground to 1.5 m.</li>
	<li>Turn on the power of the Compton camera and online computer.</li>
	<li>Start Compton camera measurement.</li>
	<li>After 30 min, stop all measurement.</li>
</ol>

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The authors have nothing to disclose.

We presented three experimental protocols for visualizing various low-level gamma radiation sources using the omnidirectional Compton camera that we developed. The representative results demonstrated that gamma-ray imaging at low radiation levels permits derivation of novel and useful information on the surrounding environment. In the RI facility, the protocol revealed that our Compton camera system successfully discovers the position of the gamma-ray source, as well as the counting rate at the given position relative to the source. This means that the proposed method can serve as a next-generation technology for environmental radiation monitoring, replacing conventional stationary dose rate monitors already mounted on the walls of almost any RI facility. In this paper, we depicted gamma-ray intensity as a red field mapping the region experiencing intensities in the upper half of observed values (Figure 3, Figure 5, and Figure 6), so as to suit various purposes without bias. An approach that rather gives priority to a peak intensity, rather than to the distribution of gamma-ray sources, would adopt a narrower range of the red field, perhaps the upper quarter of observed values, in order to enable directive findings at shorter timescales. Indeed, in Figure 3c, the peak direction could be identified with a measurement time of 30 s for case (i) as shown in Figure 4, for which the peak position&#39;s intensity was around 20 counts.
As for environmental monitoring in the PET facility, the protocol demonstrated the possibility of visualizing the radioactivity movement through the facility, which in this case is considered to be the movement of a patient injected with 18F-FDG. In Figure 5d,e, the direction of the patient can be identified in less than 10 s by adopting the narrower red field range as mentioned above. In the future, the environmental monitoring of gamma-ray sources by animation would be useful for various situations, not only for the movement of patients as in this study, but also for monitoring the transfer of nuclear fuel materials such as in airports for purposes of terrorism, by taking advantage of the high-sensitivity and low-cost characteristics of the system, although the energy resolution of a system that uses a scintillator is inferior to that of more expensive semiconductor detectors, such as high purity germanium (HPGe) and CdZnTe (CZT).
In the Fukushima field, the protocol successfully visualized the extended gamma radiation source with surface dose rates of much less than 1 &#956;Sv/h, which is an order of magnitude lower than that in a recent report25,26. Our Compton camera system was found to be capable of operating stably and robustly for outdoor measurement. We have already confirmed that the system can be operated by using WiFi and portable battery for more convenient use in various situations, especially for outdoor measurement. The Ministry of Environment in Japan has set the air dose rate minimum at 0.23 &#956;Sv/h to designate areas to be decontaminated. We believe that our system and protocols will be a great help for the decontamination procedure in areas of low-level radioactive contamination in broad areas of eastern Japan where radioactive cesium was released by the Fukushima Daiichi nuclear power plant accident in 2011.
The Compton camera used in this study has high sensitivity for gamma rays with energies between 300 keV and 1400 keV, attributable to the use of 3.5 cm CsI(Tl) scintillator cubes18. Scintillator type and size can be optimized for environmental monitoring of low-level gamma radiation sources below 300 keV, such as 99mTc (141 keV) and 111In (171 keV, 245 keV), which are frequently used in scintigraphy. This work will be presented in another paper in the near future. The detector can be manufactured at a low price. In fact, the cost of the detector materials used in this study was no more than $20,000, and this amount was dominated by the price of the counter consisting of CsI (Tl) and PMT; this configuration is significantly less expensive than the GAGG scintillators and HPGe semiconductor detectors that are used in other Compton cameras. Furthermore, the system used in this study should be made more compact for the sake of versatility and convenience. The size of the system produced in this study was 30 cm x 25 cm x 40 cm, which is larger than the existing portable gamma camera5,27. The main reasons for such large system size are the large size of the PMT attached to CsI (Tl) (&#966;4 cm &#215; 12 cm) and the large electronics handmade by us. In the future, portability will be improved by replacing the PMT with a metal package PMT or Silicon Photomultiplier (SiPM) as well as by repackaging the electronics at small size.

Medical facilities house various low-level gamma radiation sources with a surface and/or air dose rate of just a few &#181;Sv/h. Such sources are also present across broad areas of eastern Japan exhibiting low-level radioactive contamination by radioactive cesium from the Fukushima Daiichi nuclear power plant accident in 2011. These environments sometimes expose workers to the external irradiation exposure limit for the human body for the general population as advised by the International commission on radiological protection (ICRP): 1 mSv/year (e.g., 1 &#956;Sv/h for 4 h per day, 250 days per year)1. If radiation sources are visualized from more than a few meters in advance on short timescales, the amount of radiation exposure can be reduced. One of the best solutions for visualizing these gamma radiation sources is to adopt a gamma-ray imaging Compton camera technique2. In this technique, the energy and cone-direction of incident gamma-rays emitted from the radiation source are measured by the detector for each event, and then the gamma-ray source direction can be reconstructed by back-projection3. Previous studies have developed Compton camera systems aimed at the application of a new diagnostic device in nuclear medicine and/or a new gamma-ray telescope in astrophysics4,5,6,7,8,9,10,11,12,13,14, as well as image reconstruction techniques for Compton cone data by analytical15,16 and statistical17 approaches. More expensive, state-of-the-art devices with complicated electronics are often adopted to obtain high angular resolution within a standard deviation of a few degrees, but this precision makes it difficult to simultaneously achieve high detection efficiency.
Recently, we have proposed and developed a low-cost, high-sensitivity, omnidirectional gamma-ray imaging Compton camera18, based on a two-fold coincidence within a number of independent scintillators that act as either scatterers or absorbers19. The aim of this technique is to easily achieve high detection efficiency with an angular resolution s of ~10 degrees or less, which is adequate for an environmental monitor. This is accomplished through the application of an image-sharpening technique18,20 based on the filtered back-projection algorithm, which applies a convolution filter used in image reconstruction for computed tomography to the Compton reconstruction. Furthermore, the detection efficiency, angular resolution and dynamic range of the detector can be easily optimized when the type, size and arrangement of scintillators are coordinated in accordance with a particular purpose, such as usage in environments emitting elevated radioactivity21,22.
In this study, we present experimental protocols for various trials for visualizing low-level gamma-ray radiation sources using this omnidirectional Compton camera technique in a radioisotope (RI) facility, a positron emission tomography (PET) facility and the Fukushima field. We prepared and utilized the omnidirectional gamma-ray imaging Compton camera previously developed by ourselves18 but with some improvements, in order to achieve higher detection efficiency. Figure 1 shows a schematic view of the arrangement of CsI(Tl) scintillators of eleven elements used in this study. The eleven counters consist of two layers; two counters at the center and nine counters in a half-circle, considering forward and backward scattering configurations. Each CsI(Tl) scintillator cube of 3.5 cm was read out with super-bialkali photo-multiplier tubes (PMT). The signals were fed into a flash ADC board with SiTCP technology23 and the front end was connected to a PC via Ethernet. An online program created using Visual C++ with ROOT library24 was operated on a Windows PC. A gamma-ray image was reconstructed and sharpened18,20 on a spherical surface with accumulating rings with a radius of &#952; that is a scattering angle calculated from Compton kinematics for each two-fold coincidence event. An omnidirectional gamma-ray image can be displayed both online and offline by superimposition on the omnidirectional optical image previously taken by a digital camera. During the measurement, the trigger rate, total energy spectrum (the sum of the energy deposits for each two-fold coincidence event), and the reconstructed images of a preset gamma-ray energy can be displayed on the online PC screen. This information can be updated at a preset time interval (e.g., every 10 s). Here, we set the screen to display two types of reconstructed images: an image that is accumulated at the start of the measurement and an image reaccumulated at every preset time interval (e.g., every 1 min). Furthermore, because the raw data for each event obtained using the measurements are stored, it is possible to reanalyze the data after the measurements and then regenerate a reconstructed image for an arbitrary gamma-ray energy at an arbitrary time interval. Table 1 shows the performance of the Compton camera system used in this study, by comparison with the previous six-counter system18. The comparison revealed that a sub-MeV gamma-ray source was successfully visualized with a detection efficiency twice that of the previous system, while maintaining the angular resolution s of ~11 degrees. We also confirmed that the angular dependence of acceptance was kept to a minimum, showing differences of s ~ 4%. The details on the fundamental techniques of the system are described in Watanabe et al. (2018)18. Here we introduce three experimental protocols for visualizing various low-level gamma-ray radiation sources using the Compton camera described above.

<table><tbody><tr><td>Compton camera</td><td></td><td></td><td>Custom made</td></tr><tr><td>Dose rate monitor</td><td>Hitachi, Ltd.</td><td>DAM-1102</td><td></td></tr><tr><td>Flash ADC board</td><td>Bee Beans Technologies Co.,Ltd.</td><td>BBT-019</td><td></td></tr><tr><td>PC</td><td>Panasonic Corporation</td><td>CF-SZ6</td><td></td></tr><tr><td>Photo-multiplier tube</td><td>Hamamatsu Photonics K.K.</td><td>H11432-100</td><td></td></tr><tr><td>Survey meter</td><td>Fuji Electric Co., Ltd.</td><td>NHC7</td><td></td></tr></tbody></table>

visualization of low-level gamma radiation sources using a low-cost, high-sensitivity, omnidirectional compton camera

We present experimental protocols for visualizing various low-level gamma radiation sources in the ambient environment. Experiments were conducted by using a low-cost, high-sensitivity, omnidirectional, gamma-ray imaging Compton camera. In the laboratory, the position of a sub-MeV gamma radiation source such as 137Cs can easily be monitored via omnidirectional gamma-ray imaging obtained by the Compton camera. In contrast, a stationary, wall-mounted dose rate monitor cannot always successfully monitor such a source. Furthermore, we successfully demonstrated the possibility of visualizing the radioactivity movement in the environment, for example, the movement of a patient injected with 18F-fluorodeoxyglucose (18F-FDG) in a nuclear medicine facility. In the Fukushima field, we easily obtained omnidirectional gamma-ray images concerned with the distribution on the ground of low-level radioactive contamination by radioactive cesium released by the Fukushima Daiichi nuclear power plant accident in 2011. We demonstrate clear advantages of using our procedure with this camera to visualize gamma-ray sources. Our protocols can further be used to discover low-level gamma radiation sources, in place of stationary dose rate monitors and/or portable survey meters used conventionally.

Monitoring of sealed radiation source in experiment room at RI facility 
Figure 3a shows the time variation of trigger rate measured by the Compton camera (black solid line), after applying a time-lag selection of two-hit counters less than 1 &#956;s. The trigger rate changed every 30 min depending on the position of the sealed source (i.e., distance from the position to the camera). This variation was confirmed from the data measured by the stationary dose rate monitor (blue dashed line); the behavior remained constant (i.e., background level) other than between 5750 s and 7800 s. Here, we tentatively set five periods labelled (i), (ii), (iii), (iv) and (v), representing the five positions of the sealed source (Figure 3a). Figure 3b shows the total energy spectra for each such period (30 min for each), the horizontal axis representing the sum of energy deposits for each two-fold coincidence event. We note 662 keV photo-absorption peaks originating from the 137Cs sealed source for (i), (ii), (iii) and (iv), while (v) shows only background levels. Peak heights for (ii) and (iii) are the same, which we attribute to the same 6.7 m distance from the camera to the sealed source. By selecting the event within 662&#177;40 keV for 662 keV, we calculated the scattering angles and reconstructed the omnidirectional gamma-ray image. The results are shown in Figures 3c-f, respectively, for periods (i), (ii), (iii) and (iv). Here gamma-ray images are indicated by the red region, which indicates gamma-ray intensities in the upper half of the observed range. We find that the position of the 137Cs sealed source can be successfully identified from the gamma-ray images. Figure 4 shows the changes in the image with integration time, where the red field instead corresponds to a narrower range (the upper 30%) of the observed range. This narrower range was adopted in order to give priority to a peak intensity. In this case, 137Cs source direction could be identified after 30 s.
Environmental monitoring in PET facility 
Figure 5a shows the overall time variation of the trigger rate during the daytime (5.6 h) as measured by the Compton camera (black line) in front of a reception desk in a PET facility. We observe remarkable enhancement in the trigger rate with various patterns, which could be attributed to the movement of patients injected with 18F-fluorodeoxyglucose (18F-FDG) around the reception desk. As an example of such patterns, we focus on the period from 6200 s to 7000 s. According to the trigger rate in this period shown in Figure 5b, a series of enhancements are apparent, with two plateaus labelled (i) and (ii). Figure 5c shows the total energy spectra for Figure 5b&#39;s periods (i), (ii) and (iii). We observe 511 keV photo-absorption peaks originating from the 18F-FDG. Figure 5d,e show the 511 keV gamma-ray omnidirectional image in periods (i) and (ii), respectively, in which we selected events within 511&#177;40 keV for image reconstruction. The directions of gamma-ray peaks in both figures correspond respectively to the directions of the sofa and the restroom behind the wall. Considering the trigger rates of both (i) and (ii), we interpret the gamma-rays in (i) as leakage penetrating the shield of the wall from the restroom; we presume that a patient entered the restroom and spent two minutes, and after that sat on the sofa a few minutes before the PET scan.
Outdoor measurement in Kawamata-machi, Fukushima, Japan 
Figure 6a shows the time variation of the trigger rate for 30 min of outdoor measurement. The stability of the trigger rate implies that our Compton camera system operates stably even for measurements conducted outdoors over a long period. To demonstrate how the extended gamma-ray source was reconstructed, we set four different integration periods labelled (i) (1 min), (ii) (10 min), (iii) (20 min) and (iv) (30 min), as shown in Figure 6a. Figure 6b shows the total energy spectra for each period, depicting the structures superimposed on the photo-absorption peaks of gamma-rays emitted from radioactive nuclides at 605 keV and 796 keV for 134Cs and 662 keV for 137Cs. To reconstruct the gamma-ray image, we selected events within 565-622 keV for 605 keV, 662&#177;40 keV for 662 keV and 796&#177;40 keV for 796 keV. The gamma-ray omnidirectional images for 605, 662 and 796 keV are shown in Figures 6c-f for integration periods (i), (ii), (iii) and (iv), respectively. In this case, we find that the reconstructed gamma-ray distribution is stable as long as the integration time exceeds 20 min. The slope of a hill in front and the lower part of rain gutter are clearly contaminated, while the area covered with uncontaminated soil in the right part of image is demonstrably not contaminated. The gamma-ray intensity is in good agreement with dose rate values measured by a scintillation-type survey meter, the values of which are shown in yellow in Figure 6f.
<img alt="Figure 1" class="xfigimg" src="/files/ftp_upload/60463/60463fig1.jpg" /> 
Figure 1: Omnidirectional Gamma-ray imaging Compton camera system. (a) Geometrical arrangement of scintillators with eleven elements used in this study. Two scintillators were arranged at the center of a circle, with nine more arranged in a half-circle, staggered vertically. (b) Photograph of the detector without housing. The counters were fixed inside an expanded polystyrene. <a href="https://www.jove.com/files/ftp_upload/60463/60463fig1alarge.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 2" class="xfigimg" src="/files/ftp_upload/60463/60463fig2.jpg" /> 
Figure 2: Experimental setup. (a) Monitoring of a sealed radiation source in the experiment room at the RI facility, where a 137Cs-sealed source was sequentially set at the positions labelled &#39;A&#39;, &#39;B&#39;, &#39;C&#39; and &#39;D&#39;. (b) Environmental monitoring in front of a reception desk in the PET facility. (c) Outdoor measurement in the Fukushima field, Japan. The Compton camera was fixed on a stepladder. <a href="https://www.jove.com/files/ftp_upload/60463/60463fig2alarge.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 3" class="xfigimg" src="/files/ftp_upload/60463/60463fig3.jpg" /> 
Figure 3: Representative results of the monitoring of a 137Cs-sealed source in the experiment room. (a) Time variation of the trigger rate as measured by the Compton camera (black solid line) and of the air dose rate as measured by the stationary dose rate monitor (blue dashed line). (b) Total energy spectra (the sum of energy deposits for each two-fold coincidence event) in Figure 3a&#39;s periods (i) (red line), (ii) (blue line), (iii) (green line), (iv) (pink line) and (v) (black line), with the result of (iv) was scaled by 0.15. (c) 662 keV gamma-ray omnidirectional image superimposed on the optical image in period (i) (30 min). The red field indicates gamma-ray intensities in the upper half of the observed range. (d) Same as (c) but for period (ii) (30 min). (e) Same as (c) but for period (iii) (30 min). (f) Same as (c) but for period (iv) (30 min). <a href="https://www.jove.com/files/ftp_upload/60463/60463fig3large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 4" class="xfigimg" src="/files/ftp_upload/60463/60463fig4.jpg" /> 
Figure 4: Same as Figure 3c, but with various measurement times: 3 s, 5 s, 10 s, 15 s, 30 s, and 60 s. Here gamma-ray images are identified by the red region, which indicates gamma-ray intensities in the upper 30% of the observed range. <a href="https://www.jove.com/files/ftp_upload/60463/60463fig4large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 5" class="xfigimg" src="/files/ftp_upload/60463/60463fig5.jpg" /> 
Figure 5: Representative results of environmental monitoring in front of a reception desk in the PET facility. (a) Time variation of the trigger rate as measured by the Compton camera (black line) during the daytime (5.6 h). (b) Trigger rate detailed for a period between 6200 s and 7000 s in (a). (c) Total energy spectra for Figure 4b&#39;s periods (i) (red line), (ii) (blue line) and (iii) (black line). (d) 511 keV gamma-ray omnidirectional image superimposed on the optical image for period (i) (2 min). (e) Same as (d) but for period (ii) (2 min). <a href="https://www.jove.com/files/ftp_upload/60463/60463fig5large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<img alt="Figure 6" class="xfigimg" src="/files/ftp_upload/60463/60463fig6.jpg" /> 
Figure 6: Representative results of outdoor measurement in Kawamata-machi, Fukushima, Japan. (a) Time variation of the trigger rate as measured by the Compton camera (black solid line). (b) Total energy spectra for Figure 5a&#39;s periods (i) 1 min (blue line), (ii) 10 min (green line), (iii) 20 min (red line) and (iv) 30 min (black line). (c) Omnidirectional image of 605, 662 and 796 keV gamma-rays superimposed on the optical image for period (i) (1 min). (d) Same as (c) but for period (ii) (10 min). (e) Same as (c) but for period (iii) (20 min). (f) Same as (c) but for period (iv) (30 min). The dose rate values measured by a scintillation-type survey meter at a height of 1 cm from the ground are shown in the figures for comparison. <a href="https://www.jove.com/files/ftp_upload/60463/60463fig6large.jpg" target="_blank">Please click here to view a larger version of this figure.</a>
<table border="1" fo:keep-together.within-page="1">
	<tbody>
		<tr>
			<td></td>
			<td>This study</td>
			<td>Previous study18</td>
		</tr>
		<tr>
			<td>Number of counters</td>
			<td>11</td>
			<td>6</td>
		</tr>
		<tr>
			<td>Detection efficiency (cps/(&#956;Sv/h)) for 511 keV gamma-rays</td>
			<td>36</td>
			<td>18</td>
		</tr>
		<tr>
			<td>Angular resolution &#963; (deg)*</td>
			<td>11</td>
			<td>11</td>
		</tr>
	</tbody>
</table>
Table 1: Performances of present and previous Compton camera systems. *The angular resolution was estimated from 511 keV omnidirectional gamma ray images obtained during measurement of a 22Na sealed source (0.8MBq) placed 1 m ahead of the detector.

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Visualization of Low-Level Gamma Radiation Sources Using a Low-Cost, High-Sensitivity, Omnidirectional Compton Camera

We present experimental protocols for visualizing various low-level gamma radiation sources in the ambient environment using a low-cost, high-sensitivity, omnidirectional, gamma-ray imaging Compton camera.

We present experimental protocols for visualizing various low-level gamma radiation sources in the ambient environment. Experiments were conducted by ...

visualization-low-level-gamma-radiation-sources-using-low-cost-high

Research

JoVE Journal

Environment

12.5K Views.  Kitasato University. Deze eenvoudige methode maakt het mogelijk om snel te visualiseren van laag-niveau gammastraling bronnen met omgevingsoppervlak en, of lucht dosis tarieven over een paar microsievert per uur of minder. De detector is omnidirectioneel, zeer gevoelig, goedkoop en draagbaar, en kan worden gebruikt voor low-level gamma stralingsbronnen binnen RI faciliteiten, en uit de wijk rond Fukushima. De methode kan dienen als een next-generation technologie voor milieustraling monitoring, ter vervanging van...

Video: Visualization of Low-Level Gamma Radiation Sources Using a Low-Cost, High-Sensitivity, Omnidirectional Compton Camera

Measuring Spatially- and Directionally-varying Light Scattering from Biological Material

Light interacts with an organism's integument on a variety of spatial scales. For example in an iridescent bird: nano-scale structures produce color; the milli-scale structure of barbs and barbules largely determines the directional pattern of reflected light; and through the macro-scale spatial structure of overlapping, curved feathers, these directional effects create the visual texture. Milli-scale and macro-scale effects determine where on the organism's body, and from what viewpoints and under what illumination, the iridescent colors are seen. Thus, the highly directional flash of brilliant color from the iridescent throat of a hummingbird is inadequately explained by its nano-scale structure alone and questions remain. From a given observation point, which milli-scale elements of the feather are oriented to reflect strongly? Do some species produce broader "windows" for observation of iridescence than others? These and similar questions may be asked about any organisms that have evolved a particular surface appearance for signaling, camouflage, or other reasons.
In order to study the directional patterns of light scattering from feathers, and their relationship to the bird's milli-scale morphology, we developed a protocol for measuring light scattered from biological materials using many high-resolution photographs taken with varying illumination and viewing directions. Since we measure scattered light as a function of direction, we can observe the characteristic features in the directional distribution of light scattered from that particular feather, and because barbs and barbules are resolved in our images, we can clearly attribute the directional features to these different milli-scale structures. Keeping the specimen intact preserves the gross-scale scattering behavior seen in nature. The method described here presents a generalized protocol for analyzing spatially- and directionally-varying light scattering from complex biological materials at multiple structural scales.

We present a non-destructive method for sampling spatial variation in the direction of light scattered from structurally complex materials. By keeping the material intact, we preserve gross-scale scattering behavior, while concurrently capturing fine-scale directional contributions with high-resolution imaging. Results are visualized in software at biologically-relevant positions and scales.

Light interacts with an organism's integument on a variety of spatial scales. For example in an iridescent bird: nano-scale structures produce color; the ...

Engineering

A Basic Positron Emission Tomography System Constructed to Locate a Radioactive Source in a Bi-dimensional Space

A simple Positron Emission Tomography (PET) prototype has been constructed to fully characterize its basic working principles. The PET prototype was created by coupling plastic scintillator crystals to photomultipliers or PMT&#39;s which are placed at opposing positions to detect two gamma rays emitted from a radioactive source, of which is placed in the geometric center of the PET set-up. The prototype consists of four detectors placed geometrically in a 20 cm diameter circle, and a radioactive source in the center. By moving the radioactive source centimeters from the center the system one is able to detect the displacement by measuring the time of flight difference between any two PMT&#39;s and, with this information, the system can calculate the virtual position in a graphical interface. In this way, the prototype reproduces the main principles of a PET system. It is capable to determine the real position of the source with intervals of 4 cm in 2 lines of detection taking less than 2 min.

We present a simple but well-constructed Positron Emission Tomography (PET) system and elucidate its basic working principles. The goal of this protocol is to guide the user in constructing and testing a simple PET system.

A simple Positron Emission Tomography (PET) prototype has been constructed to fully characterize its basic working principles. The PET prototype was ...

Low-energy Cathodoluminescence for (Oxy)Nitride Phosphors

Nitride and oxynitride (Sialon) phosphors are good candidates for the ultraviolet and visible emission applications. High performance, good stability and flexibility of their emission properties can be achieved by controlling their composition and dopants. However, a lot of work is still required to improve their properties and to reduce the production cost. A possible approach is to correlate the luminescence properties of the Sialon particles with their local structural and chemical environment in order to optimize their growth parameters and find novel phosphors. For such a purpose, the low-voltage cathodoluminescence (CL) microscopy is a powerful technique. The use of electron as an excitation source allows detecting most of the luminescence centers, revealing their luminescence distribution spatially and in depth, directly comparing CL results with the other electron-based techniques, and investigating the stability of their luminescence properties under stress. Such advantages for phosphors characterization will be highlighted through examples of investigation on several Sialon phosphors by low-energy CL.

Low-energy Cathodoluminescence for OxyNitride Phosphors

An excellent chemical and luminescence stabilities of (oxy)nitride phosphors present it as an promising alternative to currently used sulfide and oxide phosphors. In this paper, we present the way to investigate its local luminescence properties using low-energy cathodoluminescence (CL).

Nitride and oxynitride (Sialon) phosphors are good candidates for the ultraviolet and visible emission applications. High performance, good stability and ...

Chemistry

Optical Recording of Electrical Activity in Guinea-pig Enteric Networks using Voltage-sensitive Dyes

The enteric nervous system (ENS) is a self-contained network with identified functions, capable of performing complex behaviors in isolation. Its neurons (10 to 25 &mu;m in diameter) are arranged in plexuses that are confined to distinct planes of the gut wall 1; the myenteric plexus can be found between the longitudinal and circular muscle layers, and the submucous plexus between the circular muscle layer and the mucosa. Since the effector systems for these plexuses (transporting epithelium, endocrine cells, immune elements, blood vessels and smooth muscle) are also contained within the gut wall, semi-intact preparations can be dissected that preserve individual components of different reflex pathways. The behavior of the effector systems is controlled by the submucous and myenteric plexuses acting in concert. Therefore, detailed knowledge of synaptic interactions within and between ganglia, and of communication between the plexuses, is essential for understanding normal gastrointestinal function. The ENS, as an intact nervous system, is a unique experimental model in which one can correlate molecular and cellular events with the electrical behavior of the neuronal network and its physiological outputs. Because of the quasi-two-dimensional organization of its plexuses, the ENS is particularly well suited for the study of neural networks using multiple site optical recording techniques that employ voltage-sensitive dyes 2,7,8,9. We will illustrate here the use of a relatively new naphthylstyryl-pyridinium dye (di-4-ANEPPDHQ) 3 that offers multiple advantages over its predecessors, including very low phototoxicity, slow rate of internalization, and remarkable chemical stability. When used in conjunction with a camera that permits sub-millisecond time resolution, this dye allows us to monitor the electrical activity of all the neurons in the field of view with a maximal spatial resolution of ~ 2.5 &mu;m at 100X magnification. At lower magnification (10X or 20X), the sacrifice of single-cell resolution is compensated by a gain in perspective, revealing the intricacies of the inter-ganglionic circuitry.

This protocol illustrates how voltage-sensitive dyes enable optical recording of electrical activity from intact neural networks such as the plexuses of the guinea-pig enteric nervous system, with an adjustable resolution that ranges from single-cells to multi-ganglionic circuitry.

The enteric nervous system (ENS) is a self-contained network with identified functions, capable of performing complex behaviors in isolation. Its neurons ...

Biology

Studying Soft-matter and Biological Systems over a Wide Length-scale from Nanometer and Micrometer Sizes at the Small-angle Neutron Diffractometer KWS-2

The KWS-2 SANS diffractometer is dedicated to the investigation of soft matter and biophysical systems covering a wide length scale, from nm to &#181;m. The instrument is optimized for the exploration of the wide momentum transfer Q range between 1x10-4 and 0.5 &#197;-1 by combining classical pinhole, focusing (with lenses), and time-of-flight (with chopper) methods, while simultaneously providing high-neutron intensities with an adjustable resolution. Because of its ability to adjust the intensity and the resolution within wide limits during the experiment, combined with the possibility to equip specific sample environments and ancillary devices, the KWS-2 shows a high versatility in addressing the broad range of structural and morphological studies in the field. Equilibrium structures can be studied in static measurements, while dynamic and kinetic processes can be investigated over time scales between minutes to tens of milliseconds with time-resolved approaches. Typical systems that are investigated with the KWS-2 cover the range from complex, hierarchical systems that exhibit multiple structural levels (e.g., gels, networks, or macro-aggregates) to small and poorly-scattering systems (e.g., single polymers or proteins in solution). The recent upgrade of the detection system, which enables the detection of count rates in the MHz range, opens new opportunities to study even very small biological morphologies in buffer solution with weak scattering signals close to the buffer scattering level at high Q.
In this paper, we provide a protocol to investigate samples with characteristic size levels spanning a wide length scale and exhibiting ordering in the mesoscale structure using KWS-2. We present in detail how to use the multiple working modes that are offered by the instrument and the level of performance that is achieved.

Here, we present a protocol to investigate soft matter and biophysical systems over a wide mesoscopic length scale, from nm to &#181;m that involves the use of the KWS-2 SANS diffractometer at high intensities and an adjustable resolution.

The KWS-2 SANS diffractometer is dedicated to the investigation of soft matter and biophysical systems covering a wide length scale, from nm to &#181;m. ...

Bioengineering

High Spatial Resolution Chemical Imaging of Implant-Associated Infections with X-ray Excited Luminescence Chemical Imaging Through Tissue

Microbial infections associated with implantable medical devices are a major concern in fracture fixation failure. Early diagnosis of such infection will allow successful eradication with antibiotics without an extra cost for a second surgery. Herein, we describe XELCI as a technique with high X-ray resolution, implant specificity, and chemical sensitivity to noninvasively image chemical concentrations near the surface of implanted medical devices. The devices are coated with chemically reporting surfaces. This chemically responsive surface consists of two layers coated on an implantable medical device; a pH-sensitive layer (bromothymol blue or bromocresol green incorporated hydrogel) which is coated over a red-light emitting scintillator (Gd2O2S: Eu) layer for monitoring. A focused X-ray beam irradiates a spot on the implant, and the red light generated by the scintillator (with 620 nm and 700 nm peaks) is transmitted through the sensing layer which alters the spectral ratio depending on the pH. An image is generated by scanning the X-ray beam across the implant and measuring the spectral ratio of light passing through the tissue point-by-point. We used this imaging technique for monitoring implant-associated infections previously on the bone surface of the femur with a modified implantable plate sensor. Now we are studying pH changes that occur from tibial intramedullary rod infections. Two different types of intramedullary rod designs are used in pre-pilot rabbit studies, and we learned that the XELCI technique could be used to monitor any chemical changes that occur not only on the bone surface but also inside the bone. Thus, this enables noninvasive, high spatial resolution, low background local pH imaging to study implant-associated infection biochemistry.

Here, we present a protocol for high-resolution optical detection of chemical information around implanted medical devices with X-ray excited luminescence chemical imaging (XELCI). This novel imaging technique is developed in our lab which enables studying implant-associated infection biochemistry.

Microbial infections associated with implantable medical devices are a major concern in fracture fixation failure. Early diagnosis of such infection will ...

Ratiometric Calcium Imaging of Individual Neurons in Behaving Caenorhabditis Elegans

It has become increasingly clear that neural circuit activity in behaving animals differs substantially from that seen in anesthetized or immobilized animals. Highly sensitive, genetically encoded fluorescent reporters of Ca2+ have revolutionized the recording of cell and synaptic activity using non-invasive optical approaches in behaving animals. When combined with genetic and optogenetic techniques, the molecular mechanisms that modulate cell and circuit activity during different behavior states can be identified.
Here we describe methods for ratiometric Ca2+ imaging of single neurons in freely behaving Caenorhabditis elegans worms. We demonstrate a simple mounting technique that gently overlays worms growing on a standard Nematode Growth Media (NGM) agar block with a glass coverslip, permitting animals to be recorded at high-resolution during unrestricted movement and behavior. With this technique, we use the sensitive Ca2+ reporter GCaMP5 to record changes in intracellular Ca2+ in the serotonergic Hermaphrodite Specific Neurons (HSNs) as they drive egg-laying behavior. By co-expressing mCherry, a Ca2+-insensitive fluorescent protein, we can track the position of the HSN within ~ 1 &#181;m and correct for fluctuations in fluorescence caused by changes in focus or movement. Simultaneous, infrared brightfield imaging allows for behavior recording and animal tracking using a motorized stage. By integrating these microscopic techniques and data streams, we can record Ca2+ activity in the C. elegans egg-laying circuit as it progresses between inactive and active behavior states over tens of minutes.

Ratiometric Calcium Imaging of Individual Neurons in Behaving Caenorhabditis Elegans

This protocol describes the use of genetically encoded Ca2+ reporters to record changes in neural activity in behaving Caenorhabditis elegans worms. &#8195;

It has become increasingly clear that neural circuit activity in behaving animals differs substantially from that seen in anesthetized or immobilized ...

Neuroscience

Probing Nicotinic Acetylcholine Receptor Function in Mouse Brain Slices via Laser Flash Photolysis of Photoactivatable Nicotine

Acetylcholine (ACh) acts through receptors to modulate a variety of neuronal processes, but it has been challenging to link ACh receptor function with subcellular location within cells where this function is carried out. To study the subcellular location of nicotinic ACh receptors (nAChRs) in native brain tissue, an optical method was developed for precise release of nicotine at discrete locations near neuronal membranes during electrophysiological recordings. Patch-clamped neurons in brain slices are filled with dye to visualize their morphology during 2-photon laser scanning microscopy, and nicotine uncaging is executed with a light flash by focusing a 405 nm laser beam near one or more cellular membranes. Cellular current deflections are measured, and a high-resolution three-dimensional (3D) image of the recorded neuron is made to allow reconciliation of nAChR responses with cellular morphology. This method allows for detailed analysis of nAChR functional distribution in complex tissue preparations, promising to enhance the understanding of cholinergic neurotransmission.

This article presents a method for studying nicotinic acetylcholine receptors (nAChRs) in mouse brain slices by nicotine uncaging. When coupled with simultaneous patch clamp recording and 2-photon laser scanning microscopy, nicotine uncaging connects nicotinic receptor function with cellular morphology, providing a deeper understanding of cholinergic neurobiology.

Acetylcholine (ACh) acts through receptors to modulate a variety of neuronal processes, but it has been challenging to link ACh receptor function with ...

Neutron Radiography and Computed Tomography of Biological Systems at the Oak Ridge National Laboratory's High Flux Isotope Reactor

Neutrons have historically been used for a broad range of biological applications employing techniques such as small-angle neutron scattering, neutron spin echo, diffraction, and inelastic scattering. Unlike neutron scattering techniques that obtain information in reciprocal space, attenuation-based neutron imaging measures a signal in real space that is resolved on the order of tens of micrometers. The principle of neutron imaging follows the Beer-Lambert law and is based on the measurement of the bulk neutron attenuation through a sample. Greater attenuation is exhibited by some light elements (most notably, hydrogen), which are major components of biological samples. Contrast agents such as deuterium, gadolinium, or lithium compounds can be used to enhance contrast in a similar fashion as it is done in medical imaging, including techniques such as optical imaging, magnetic resonance imaging, X-ray, and positron emission tomography. For biological systems, neutron radiography and computed tomography have increasingly been used to investigate the complexity of the underground plant root network, its interaction with soils, and the dynamics of water flux in situ. Moreover, efforts to understand contrast details in animal samples, such as soft tissues and bones, have been explored. This manuscript focuses on the advances in neutron bioimaging such as sample preparation, instrumentation, data acquisition strategy, and data analysis using the High Flux Isotope Reactor CG-1D neutron imaging beamline. The aforementioned capabilities will be illustrated using a selection of examples in plant physiology&#160;(herbaceous plant/root/soil system)&#160;and biomedical applications&#160;(rat femur and mouse lung).

This manuscript describes a protocol for neutron radiography and computed tomography of biological samples using a High Flux Isotope Reactor (HFIR) CG-1D beamline to measure a metal implant in a rat femur, a mouse lung, and an herbaceous plant root/soil system.

Neutrons have historically been used for a broad range of biological applications employing techniques such as small-angle neutron scattering, neutron ...

Retrospective Cardiac Gating with A Prototype Small-Animal X-ray Computed Tomograph

The CrumpCAT is a prototype small-animal X-ray computed tomography (CT) scanner developed at our research institution. The CMOS detector with a maximum frame rate of 29 Hz and similar Tungsten X-ray sources with energies ranging from 50 kVp to 80 kVp are widely used across commercially available preclinical X-ray CT instruments. This makes the described work highly relevant to other institutions, despite the generally perceived wisdom that these detectors are not suitable for gating the high heart rates of mice (~600 beats/min). The scanner features medium- (200 &#181;m) and high- (125 &#181;m) resolution imaging, fluoroscopy, retrospective respiratory gating, and retrospective cardiac gating, with iterative or filtered-back projection image reconstruction. Among these features, cardiac gating is the most useful feature for studying cardiac functions in vivo, as it effectively eliminates image blurring caused by respiratory and cardiac motion. 
Here, we describe our method for preclinical intrinsic retrospective cardiac-gated CT imaging, aimed at advancing research on in vivo cardiac function and structure analysis. The cardiac-gating method acquires a large number of projections at the shortest practical exposure time (~20 ms) and then retrospectively extracts respiratory and cardiac signals from temporal changes in raw projection sequences. These signals are used to reject projections belonging to the high motion rate inspiration phase of the respiratory cycle and to divide the remaining projections into 12 groups, each corresponding to one phase of the cardiac cycle. Each group is reconstructed independently using an iterative method to produce a volumetric image for each cardiac phase, resulting in a four-dimensional (4D) dataset. 
These phase images can be analyzed either collectively or individually, allowing for detailed assessment of cardiac function. We demonstrated the effectiveness of both approaches of the prototype scanner's cardiac-gating feature through representative in vivo imaging results.

We provide a comprehensive description of the intrinsic retrospective cardiac gating method of the CrumpCAT, a prototype small-animal X-ray computed tomography (CT) scanner designed and constructed at our research institution.

The CrumpCAT is a prototype small-animal X-ray computed tomography (CT) scanner developed at our research institution. The CMOS detector with a maximum ...

Visualization of Low-Level Gamma Radiation Sources Using a Low-Cost, High-Sensitivity, Omnidirectional Compton Camera

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