Tag Archives: Medical Physics

Tomographic Imaging by a Si/CdTe Compton Camera for In-111 and I-131 Radionuclides [CL]

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http://arxiv.org/abs/2108.10149


Tomographic imaging with radionuclides commonly used in nuclear medicine, such as $^{111}$In (171 and 245 keV) and $^{131}$I (364 keV), is in high demand for medical applications and small animal imaging. The Si/CdTe Compton camera with its high angular and high energy resolutions is an especially promising detector to extend the energy coverage for imaging to the range that covers gamma-ray emitted from these radionuclides. Here, we take the first steps towards short-distance imaging by conducting experiments using three-dimensional phantoms composed of multiple sphere-like solutions of $^{111}$In and $^{131}$I with a diameter of 2.7 mm, placed at a distance of 41 mm. Using simple back-projection methods, the positions of the sources are reproduced with a spatial resolution of 11.5 mm and 9.0 mm (FWHM) for $^{111}$In and $^{131}$I, respectively. We found that a LM-MLEM method gives a better resolution of 4.0 mm and 2.7 mm (FWHM). We resolve source positions of a tetrahedron structure with a source-to-source separation of 28 mm. These findings demonstrate that Compton Cameras have the potential of close-distance imaging of radioisotopes distributions in the energy range below 400 keV.

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G. Yabu, H. Yoneda, T. Orita, et. al.
Tue, 24 Aug 21
21/76

Comments: N/A

Cosmic ray radiography of a human phantom [CL]

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http://arxiv.org/abs/2106.01542


Cosmic ray muons, that reach the earth’s surface, provide a natural source of radiation that is used for radiography. In this paper, we show that radiography using cosmic radiation background provides a method that can be used to monitor bulk aspects of human anatomy. We describe a method that can be used to measure changes in patients as a function of time by radiographing them using cosmic-ray muons. This could provide hourly readouts of parameters such as lung density with sufficient sensitivity to detect time changes in inflammation of the lungs in, e.g., Covid patients.

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C. Morris, J. Perry and F. Merrill
Fri, 4 Jun 21
53/71

Comments: N/A

HEALPix View-order for 3D Radial Self-Navigated Motion-Corrected ZTE MRI [CL]

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http://arxiv.org/abs/1910.10276


Compressed sensing has reinvigorated the field of non-Cartesian sampling in magnetic resonance imaging (MRI). Until now there has been no 3D radial view-order which meets all the desired characteristics for simultaneous dynamic/high-resolution imaging, such as for self-navigated motion-corrected high resolution neuroimaging. In this work, we examine the use of Hierarchical Equal Area iso-Latitude Pixelization (HEALPix) for generation of three-dimensional (3D) radial view-orders for MRI, and compare to a selection of commonly used 3D view-orders. The resulting trajectories were evaluated through simulation of the point spread function and slanted surface object suitable for modulation transfer function, contrast ratio, and SNR measurement. Results from the HEALPix view-order were compared to Generalized Spiral, 2D Golden Means, and Random view-orders. Finally, we show the first use of the HEALPix view-order to acquire in-vivo brain images.

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C. Corum, S. Kruger and V. Magnotta
Thu, 24 Oct 19
4/68

Comments: 4 pages, 6 figures, 2 tables

Comment On the Connection Between Planets, Dark Matter and Cancer, by Hector Socas-Navarro (arXiv:1812.02482 [physics.med-ph]) [CL]

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http://arxiv.org/abs/1812.10332


In arXiv:1812.02482 Socas-Navarro (SN) provided multiple confirmation of the claimed 88 days melanoma periodicity. This greatly strengthens the observation by Zioutas and Valachovic (ZV). Here we comment on the work by SN, because it objects the interpretation of the observation by ZV. Notice that SN objection is based on serious assumptions, which were explicitly excluded by ZV. Further, the conclusion made with a sub-set of data (4 percent) is statistically not significant to dispute ZV. On the contrary, since the same periodicity appears also in other 8 major cancer types, we consider it as a global oscillatory behaviour of cancer. At this stage, such a rather ubiquitous cancer periodicity makes any discussion of a small subset of data at least secondarily. Further, we show here that the 88 days Melanoma periodicity is not related to solar activity. Planetary lensing of streaming low speed invisible massive particles remains the only viable explanation, as it has been introduced previously with a number of physics observations [4]. We also show that planetary lensing of low speed particles cannot be considered in isolation, because of the dominating Sun gravity, at least for the inner planets. Interestingly, gravitational lensing – deflection favours low speed particles.

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K. Zioutas, E. Valachovic and M. Maroudas
Thu, 3 Jan 19
5/48

Comments: 5 pages, 2 Figures

On the Connection Between Planets, Dark Matter and Cancer [CL]

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http://arxiv.org/abs/1812.02482


In a recent paper, Zioutas and Valachovic (2018) claim that dark matter is responsible for a significant fraction of the melanoma skin cancer. This conclusion is drawn from their observation of a significant correlation between skin melanoma incidence in the US and the inner planets positions (especially those of Mercury and Earth). Here I present a number of objections to their interpretation. Some (but not all) of the counterarguments are based on the analysis of a larger dataset from the same source, considering more cancer types and separating by patient attributes, such as race. One of the counterarguments is that, if the melanoma fluctuations with periods similar to planetary orbits were produced by dark matter density enhancements on Earth, then we would have to conclude that the black population is somehow immune to dark matter, a conclusion that seems incompatible with the current WIMP paradigm. Interestingly, some periodicities are present in the data, including the ones reported by Zioutas and Valachovic, but I argue that they must have a societal rather than astronomical origin.

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H. Socas-Navarro
Fri, 7 Dec 18
19/66

Comments: To appear in Biophysical Reviews and Letters

Nonscanning large-area Raman imaging for ex vivo/in vivo skin cancer discrimination [IMA]

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http://arxiv.org/abs/1810.03363


Imaging Raman spectroscopy can be used to identify cancerous tissue. Traditionally, a step-by-step scanning of the sample is applied to generate a Raman image, which, however, is too slow for routine examination of patients. By transferring the technique of integral field spectroscopy (IFS) from astronomy to Raman imaging, it becomes possible to record entire Raman images quickly within a single exposure, without the need for a tedious scanning procedure. An IFS-based Raman imaging setup is presented, which is capable of measuring skin ex vivo or in vivo. It is demonstrated how Raman images of healthy and cancerous skin biopsies were recorded and analyzed.

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E. Schmälzlin, B. Moralejo, I. Gersonde, et. al.
Tue, 9 Oct 18
17/77

Comments: N/A

Multilevel Bayesian Parameter Estimation in the Presence of Model Inadequacy and Data Uncertainty [CL]

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http://arxiv.org/abs/1711.10599


Model inadequacy and measurement uncertainty are two of the most confounding aspects of inference and prediction in quantitative sciences. The process of scientific inference (the inverse problem) and prediction (the forward problem) involve multiple steps of data analysis, hypothesis formation, model construction, parameter estimation, model validation, and finally, the prediction of the quantity of interest. This article seeks to clarify the concepts of model inadequacy and bias, measurement uncertainty, and the two traditional classes of uncertainty: aleatoric versus epistemic, as well as their relationships with each other in the process of scientific inference. Starting from basic principles of probability, we build and explain a hierarchical Bayesian framework to quantitatively deal with model inadequacy and noise in data. The methodology can be readily applied to many common inference and prediction problems in science, engineering, and statistics.

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A. Shahmoradi
Thu, 30 Nov 17
11/77

Comments: N/A

The Novel ABALONE Photosensor Technology [CL]

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http://arxiv.org/abs/1703.04546


The patented and proven ABALONE Photosensor Technology (Daniel Ferenc, U.S. Patent 9,064,678, 2010) has the capability of opening new horizons in the fields of fundamental physics, functional medical imaging, and nuclear security. This article discusses our new technology and overviews the unprecedented performance of ABALONE Photosensors, produced in the custom designed production line at UC Davis and continuously tested since 2013. In conclusion, the modern ABALONE Technology is far superior to prior art in performance, robustness and the capacity for integration into large area detector shells. It is about two orders of magnitude more cost effective while being mass-producible with a relatively low investment.

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D. Ferenc, A. Chang and M. Ferenc
Thu, 16 Mar 17
44/92

Comments: 16 pages, 7 figures, Submitted for publication to Nuclear Instruments And Methods In Physics Research A on March 12, 2017 (Ms. Ref. No.: NIMA-D-17-00243)

Non-Invertibility of spectral x-ray photon counting data with pileup [CL]

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http://arxiv.org/abs/1702.04993


-In the Alvarez-Macovski method [R.E. Alvarez and A. Macovski, Phys. Med. Biol., 1976, 733-744], the attenuation coefficient is approximated as a linear combination of functions of energy multiplied by coefficients that depend on the material composition at points within the object. The method then computes the line integrals of the basis set coefficient from measurements with different x-ray spectra. This paper shows that the transformation from photon counting detector data with pileup to the line integrals can become ill-conditioned under some circumstances leading to highly increased noise. Methods: An idealized model that includes pileup and quantum noise is used. The noise variance of the line integral estimates is computed using the Cram{\`e}r-Rao lower bound (CRLB). The CRLB is computed as a function of object thickness for photon counting detector data with three and four bin pulse height analysis (PHA) and low and high pileup. Results: With four bin PHA data the transformation is well conditioned with either high or low pileup. With three bin PHA and high pileup, the transformation becomes ill-conditioned for specific values of object attenuation. At these values the CRLB variance increases by approximately 10 5 compared with the four bin PHA or low pileup results. The condition number of the forward transformation matrix also shows a spike at those attenuation values. Conclusion: Designers of systems using counting detectors should study the stability of the line integral estimator output with their data.

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R. Alvarez
Fri, 17 Feb 17
42/43

Comments: arXiv admin note: text overlap with arXiv:1702.01006

Localisation of gamma-ray interaction points in thick monolithic CeBr3 and LaBr3:Ce scintillators [IMA]

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http://arxiv.org/abs/1701.05548


Localisation of gamma-ray interaction points in monolithic scintillator crystals can simplify the design and improve the performance of a future Compton telescope for gamma-ray astronomy. In this paper we compare the position resolution of three monolithic scintillators: a 28x28x20 mm3 (length x breadth x thickness) LaBr3:Ce crystal, a 25x25x20 mm3 CeBr3 crystal and a 25x25x10 mm3 CeBr3 crystal. Each crystal was encapsulated and coupled to an array of 4×4 silicon photomultipliers through an optical window. The measurements were conducted using 81 keV and 356 keV gamma-rays from a collimated 133Ba source. The 3D position reconstruction of interaction points was performed using artificial neural networks trained with experimental data. Although the position resolution was significantly better for the thinner crystal, the 20 mm thick CeBr3 crystal showed an acceptable resolution of about 5.4 mm FWHM for the x and y coordinates, and 7.8 mm FWHM for the z-coordinate (crystal depth) at 356 keV. These values were obtained from the full position scans of the crystal sides. The position resolution of the LaBr3:Ce crystal was found to be considerably worse, presumably due to the highly diffusive optical in- terface between the crystal and the optical window of the enclosure. The energy resolution (FWHM) measured for 662 keV gamma-rays was 4.0% for LaBr3:Ce and 5.5% for CeBr3. The same crystals equipped with a PMT (Hamamatsu R6322-100) gave an energy resolution of 3.0% and 4.7%, respectively.

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A. Ulyanov, O. Morris, O. Roberts, et. al.
Fri, 20 Jan 17
41/51

Comments: N/A

Electromagnetic 3D subsurface imaging with source sparsity for a synthetic object [IMA]

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http://arxiv.org/abs/1608.06795


This paper concerns electromagnetic 3D subsurface imaging in connection with sparsity of signal sources. We explored an imaging approach that can be implemented in situations that allow obtaining a large amount of data over a surface or a set of orbits but at the same time require sparsity of the signal sources. Characteristic to such a tomography scenario is that it necessitates the inversion technique to be genuinely three-dimensional: For example, slicing is not possible due to the low number of sources. Here, we primarily focused on astrophysical subsurface exploration purposes. As an example target of our numerical experiments we used a synthetic small planetary object containing three inclusions, e.g. voids, of the size of the wavelength. A tetrahedral arrangement of source positions was used, it being the simplest symmetric point configuration in 3D. Our results suggest that somewhat reliable inversion results can be produced within the present a priori assumptions, if the data can be recorded at a specific resolution. This is valuable early-stage knowledge especially for design of future planetary missions in which the payload needs to be minimized, and potentially also for the development of other lightweight subsurface inspection systems.

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S. Pursiainen and M. Kaasalainen
Thu, 25 Aug 16
13/43

Comments: 17 pages, 5 figures. This is an author-created, un-copyedited version of an article accepted for publication/published in Inverse Problems. IOP Publishing Ltd is not responsible for any errors or omissions in this version of the manuscript or any version derived from it. The Version of Record is available online at this http URL

Silicon photomultiplier-based Compton Telescope for Safety and Security (SCoTSS) [CL]

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http://arxiv.org/abs/1601.01979


A Compton gamma imager has been developed for use in consequence management operations and in security investigations. The imager uses solid inorganic scintillator, known for robust performance in field survey conditions. The design was constrained in overall size by the requirement that it be person transportable and operable from a variety of platforms. In order to introduce minimal dead material in the path of the incoming and scattered gamma rays, custom silicon photomultipliers (SiPMs), with a thin glass substrate, were used to collect the scintillation light from the scatter layers. To move them out of the path of the gamma rays, preamplification electronics for the silicon photomultipliers were located a distance from the imager. This imager, the Silicon photomultiplier Compton Telescope for Safety and Security (SCoTSS) is able to provide a one-degree image resolution in a plus-minus 45 degree field of view for a 10 mCi point source 40 m distant, within about one minute, for gamma-ray energies ranging from 344 keV to 1274 keV. Here, we present a comprehensive performance study of the SCoTSS imager.

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L. Sinclair, P. Saull, D. Hanna, et. al.
Mon, 11 Jan 16
7/57

Comments: 9 pages, 8 figures, presented at IEEE NSSMIC 2013 and published in IEEE Trans. Nucl. Sci

A possible role for stochastic radiation events in the systematic disparity between molecular and fossil dates [CL]

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http://arxiv.org/abs/1505.08125


Major discrepancies have been noted for some time between fossil ages and molecular divergence dates for a variety of taxa. Recently, systematic trends within avian clades have been uncovered. The trends show that the disparity is much larger for mitochondrial DNA than for nuclear DNA; also that it is larger for crown fossil dates than stem fossil dates. It was argued that this pattern is largely inconsistent with incompleteness of the fossil record as the principal driver of the disparity. A case is presented that given the expected mutations from a fluctuating background of astrophysical radiation from such sources as supernovae, the rate of molecular clocks is variable and should increase into the past. This is a possible explanation for the disparity. One test of this hypothesis is to look for an acceleration of molecular clocks 2 to 2.5 Ma due to a probable moderately nearby supernova at that time. Another is to look for reduced disparity in benthic organisms of the deep ocean.

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A. Melott
Mon, 1 Jun 15
32/62

Comments: Accepted for Earth and Life II

On the noise-resolution duality, Heisenberg uncertainty and Shannon's information [CL]

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http://arxiv.org/abs/1503.04367


Several variations of the Heisenberg uncertainty inequality are derived on the basis of “noise-resolution duality” recently proposed by the authors. The same approach leads to a related inequality that provides an upper limit for the information capacity of imaging systems in terms of the number of imaging quanta (particles) used in the experiment. These results can be useful in the context of biomedical imaging constrained by the radiation dose delivered to the sample, or in imaging (e.g. astronomical) problems under “low light” conditions.

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T. Gureyev, F. Hoog, Y. Nesterets, et. al.
Tue, 17 Mar 15
18/79

Comments: N/A

A link between solar events and congenital malformations: Is ionizing radiation enough to explain it? [CL]

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http://arxiv.org/abs/1503.02576


Cosmic rays are known to cause biological effects directly and through ionizing radiation produced by their secondaries. These effects have been detected in airline crews and other specific cases where members of the population are exposed to above average secondary fluxes. Recent work has found a correlation between solar particle events and congenital malformations. In this work we use the results of computational simulations to approximate the ionizing radiation from such events as well as longer term increases in cosmic ray flux. We find that the amounts of ionizing radiation produced by these events are insufficient to produce congenital malformations under the current paradigm regarding muon ionizing radiation. We believe that further work is needed to determine the correct ionizing radiation contribution of cosmogenic muons. We suggest that more extensive measurements of muon radiation effects may show a larger contribution to ionizing radiation dose than currently assumed.

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A. Overholt, A. Melott and D. Atri
Tue, 10 Mar 15
27/77

Comments: Journal of Geophysical Research: Space Physics, in press