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Abstract Per- and polyfluoroalkyl substances (PFAS) are a group of synthetic chemicals that resist degradation, posing a significant environmental and health risk. Current methods for removing PFAS from water are often complex and costly. Here we report a simple, cost-effective method to synthesize an iron oxide/graphenic carbon (Fe/g-C) hybrid photocatalyst for PFAS degradation. This photocatalyst efficiently degrades perfluorooctanoic acid (PFOA), a common type of PFAS, achieving over 85% removal within 3 hours under ultraviolet light. The catalyst also maintains high degradation rates over extended periods, demonstrating its stability and potential for long-term use. This innovative approach offers a promising solution for addressing PFAS contamination in water, contributing to a cleaner and healthier environment.

The aim of this paper is to investigate the intrinsic spatial resolution limit by coupling a CsI(Tl) micro-pixel scintillation array to position sensitive photomultipliers (PSPMTs) for ultra-high resolution gamma-ray imaging. On this purpose, 1 mm thick array with 0.2 mm pixel side, 0.4 mm pitch has been realized by Spectra Physics (Hilger). The present scintillation arrays technology is suitable to produce larger crystal areas. In this paper we present spatial resolution and positioning results obtained by coupling the micro-pixel scintillation array to Hamamatsu square PSPMTs: 1' R8520-C12, 1' R5900-L16 and 2' H8500 Flat panel PMT. Preliminary measurements demonstrate better performance in term of uniformity response when micro-pixel array is coupled to a H8500 PSPMT model. This setup carries out an intrinsic spatial resolution lower limit of about 0.6 mm FWHM at 50% FWHM energy resolution, defining it as the minimum scintillation array pitch detectable at 122 keV. The results obtained by R5900-L16 with a better sampling of the scintillation light has shown an improvement of the position linearity in spite of a worse spatial resolution due to the poor light output of scintillation array. Index Terms--Biomedical nuclear imaging, photomultipliers, scintillation detectors.

Radiolabeled agents that bind to specific receptors have shown great promise in diagnosing and characterizing tumor cell biology. In vivo imaging of gene transcription and protein expression represents an other area of interest. The radioisotope [.sup.125] I is commercially available as a label for molecular probes and utilized by researchers in small animal studies. We propose an advanced imaging detector based on planar NaI(Tl) integral assembly with a Hamamatsu Flat Panel Photomultiplier (MA-PMT) representing one of the best trade-offs between spatial resolution and detection efficiency. We characterized the imaging performances of this planar detector, in comparison with a gamma camera based on a pixellated scintillator. We also tested the in-vivo image capability by acquiring images of mice as a part of a study of inflammatory bowel disease (IBD). In this study, four 25g mice with an IBD-like phenotype (SAMP1/YitFc) were injected with 375, 125, 60 and 30 [mu]Ci of [.sup.125] I-labelled antibody against mucosal vascular addressin cell adhesion molecule (MAdCAM-1), which is up-regulated in the presence of inflammation. Two mice without bowel inflammation were injected with 150 and 60 [mu]Ci of the labeled anti-MAdCAM-1 antibody as controls. To better evaluate the performances of the integral assembly detector, we also acquired mice images with a dual modality (X and Gamma Ray) camera dedicated for small animal imaging. The results coming from this new detector are considerable: images of SAMP1/YitFc injected with 30 [mu]Ci activity show inflammation throughout the intestinal tract, with the disease very well defined at two hours post-injection. Index Terms--Biomedical nuclear imaging, photomultipliers, scintillation detectors.

The design of detectors for radio-imaging of small animals is challenging because of the high spatial resolution required, possibly coupled with high efficiency to allow dynamic studies. Spatial resolution and sensitivity are difficult to attain at the same time with single photon imaging techniques because collimators define and limit performance. In this paper we first describe a simple desktop gamma imager equipped with a pinhole collimator and based on a pixellated NaI(TI) scintillator array coupled to a Hamamatsu R2486 PSPMT. The limits of such a system as well as the way to overcome them in future systems is shown next. Better light sampling at the anode level would allow better pixel identification for a higher number of pixels, which is one of the parameters defining image quality and improving spatial resolution. The performance of such a design is compared with other designs using other PSPMT types with different light sampling schemes at the anode level. Finally, we show how the substitution of the pinhole collimator with a coded aperture collimator can result in a substantial improvement in system sensitivity while maintaining very good spatial resolution, possibly at a sub-millimeter level. Calculations and simulations of a particular solution show that sensitivity can improve by a factor of nearly 30. Index Terms--Nuclear imaging, scintillation detectors, sensitivity, spatial resolution.

The capability of the scintimammography to diagnose subcentimeters sized tumors was increased by the employment of a dedicated gamma camera. The introduction of small field of view camera, based on pixellated scintillation array and position sensitive photomultiplier, allowed to enhance the geometric spatial resolution and contrast of the images due to reduced collimator-tumor distance. The aim of this paper is to investigate the realistic possibility of T1a tumors detection (~5 mm size) by comparing the signal-to-noise ratio (SNR) values obtained by different imagers. To this end, we have utilized a self-designed solid breast phantom with different sized hot spots (tumors). The phantom consists of seven disks with different thickness, molded from resin epoxy activated with [Co.sup.57] isotope. The overlapped disks represent a pendula breast with about 800 cc volume. Hot spots have not wall. One disk has holes to fit the hot spots representing the different sized lesions. The imagers utilized were: a standard Anger Camera and three different cameras based on scintillator array, CsI(TI) or NaI(TI), coupled to position sensitive photomultiplier with different technologies, to make detectors with field of view of 3 and 5 inch. The experimental results are supported by Monte Carlo simulation. It was highlighted how spatial resolution is a predominant element in tumor visibility and how background causes a reduction of the image contrast. All gamma cameras show close results at SNR values less than 10 and a full detectability of 8 mm tumor size. However, the results show the 5 mm tumor size is lower detection limit for all cameras. Index Terms--Biomedical nuclear imaging, photomultipliers, scintilation detectors.

Gamma ray imaging is usually accomplished by the use of a relatively large scintillating crystal coupled to either a number of photomultipliers (PMTs) (Anger Camera) or to a single large Position Sensitive PMT (PSPMT). Recently the development of new diagnostic techniques, such as scintimammography and radio-guided surgery, have highlighted a number of significant limitations of the Anger camera in such imaging procedures. In this paper a dedicated gamma camera is proposed for clinical applications with the aim of improving image quality by utilizing detectors with an appropriate size and shape for the part of the body under examination. This novel scintillation camera is based upon an array of PSPMTs (Hamamatsu R5900-C8). The basic concept of this camera is identical to the Anger Camera with the exception of the substitution of PSPMTs for the PMTs. In this configuration it is possible to use the high resolution of the PSPMTs and still correctly position events lying between PSPMTs. In this work the test configuration is a 2 by 2 array of PSPMTs. Some advantages of this camera are: spatial resolution less than 2 mm FWHM, good linearity, thickness less than 3 cm, light weight, lower cost than equivalent area PSPMT, large detection area when coupled to scintillating arrays, small dead boundary zone (

Prone scintimammography with Tc-99m SestaMIBI has been proposed as a method of detecting breast cancers in women with dense breasts. Clinical reports have shown that this technique lacks sensitivity for cancer smaller than 1 cm. To overcome some limitations offered by Anger camera on breast imaging was realized a new scintigraphic detector dedicated to SPEM (Single Photon Emission Mammography). This novel small FOV device, shows high spatial resolution performances (< 2 mm), but poorer energy resolution values, than Anger camera (17% vs. 10%, respectively). In this paper we examine the spatial distribution of Compton-to-photopeak ratio in planar scintimammographic images in order to elucidate the causes of lack of scintimammography in visualizing deep or posteriorly located cancers introduced by the scatter from the patient's body. Phantom and clinical studies with several instruments including a general purpose gamma camera, a dedicated camera and a non imaging Germanium detector were performed. The results obtained suggest that scatter from extramammary sources plays an important role in breast imaging with radiotracers. By using gentle breast compression in cranio-caudal view the energy resolution attained with the dedicated camera is adequate to differentiate between photopeak and Compton counts; the Compton-to photopeak mean ratio resulted 4.5 and 6.9 for mild portion and posterior breast respectively.

In small animal PET applications YAP:Ce scintillator has given some promising results [1]. Because of its somewhat lower efficiency with respect to other PET crystals at 511 keV the depth of the crystal is a crucial parameter. Past measurements of the light attenuation length for YAP:Ce scintillator have given rather different results with values as low as 3 cm [2]. We have studied the pulse height spectra of full energy absorption events as a function of the interaction distance from the photomultiplier window for five match like 2 x 2 x 30 [mm.sup.3] YAP:Ce crystals. Each crystal was covered on the four long sides and on one of the square section sides with a 5 [[micro]meter] reflective layer. The crystals were the middle row of a bundle of 5 by 5 such crystals. By using a transport model for light within the crystals, for this crystal configuration, we obtained a lower limit of 6.8 [+ or -] 0.3 cm on the average 'bulk' (not including the losses from reflection) light attenuation length. This Dower limit is significantly higher than the attenuation length measured by other authors. From these measurements and calculations we have also determined the average absolute light yield for the five crystals to be 24000 [+ or -] 1400 photons/MeV.

For scintimammography (SMM) to have wide clinical use, physicians must be able to rapidly direct biopsy of small cancers. We therefore undertook a theoretical and experimental study of lesion visibility vs. acquisition time and tumor size. Theoretical considerations as to acquisition time and contrast suggested that compression would significantly improve lesion visibility for small cancers. These predictions were confirmed with phantom studies. Patient studies showed that high confidence images of small primary breast tumors can be produced with the addition of breast compression. We conclude that breast compression would improve SMM detection of small primary breast cancers.