X-ray Fluorescence Photons Research Articles

Oblique fluorescence in a MARS scanner with a CdTe-Medipix3RX

The latest version of the MARS small bore scanner makes use of the Medipix3RX ASIC, bonded to a CdTe or CZT semi-conductor layer, to count x-ray photons and create a spectroscopic CT data set. The MARS imaging chain uses the energy-resolved 2D transmission images to construct quantitative 3D spectral and material images. To improve the spectral performance of the imaging system it is important that the energy response of the detector is well calibrated. A common methodology for energy calibration is to use x-ray fluorescence (XRF), due to its effective monochromatic nature. Oblique (off-axis) XRF can be measured in situ in the MARS small bore scanner. A monoatomic foil is placed in front of the x-ray source and off-axis XRF is measured. A key issue is identifying near optimal measurement positions that maximize the XRF signal while minimizing transmitted and scattered x-rays from the primary beam. This work shows the development of a theoretical model that is able to identify where in the detector plane XRF is maximum. We present: (1) a theoretical model that calculates the XRF photon distribution across the detector plane produced from illuminated foils attached to the scanner's filter bar; (2) preliminary experimental measurements of the XRF distribution outside of the main beam taken with a CdTe-Medipix3RX detector; and (3) a comparison between the model and experiment. The main motivation behind creating this model is to identify the region in the detector plane outside of the main beam where XRF is at a maximum. This provides the optimum detector location for measuring a monochromatic XRF source with minimal polychromatic contamination for its use in per-pixel energy calibration of Medipix3RX detectors in MARS scanners.

Feasibility study of Compton cameras for x-ray fluorescence computed tomography with humans

X-ray fluorescence imaging is a promising imaging technique able to depict the spatial distributions of low amounts of molecular agents in vivo. Currently, the translation of the technique to preclinical and clinical applications is hindered by long scanning times as objects are scanned with flux-limited narrow pencil beams. The study presents a novel imaging approach combining x-ray fluorescence imaging with Compton imaging. Compton cameras leverage the imaging performance of XFCT and abolish the need for pencil beam excitation. The study examines the potential of this new imaging approach on the base of Monte-Carlo simulations. In the work, it is first presented that the particular option of slice/fan-beam x-ray excitation has advantages in image reconstruction in regard of processing time and image quality compared to traditional volumetric Compton imaging. In a second experiment, the feasibility of the approach for clinical applications with tracer agents made from gold nano-particles is examined in a simulated lung scan scenario. The high energy of characteristic x-ray photons from gold is advantageous for deep tissue penetration and has lower angular blurring in the Compton camera. It is found that Doppler broadening in the first detector stage of the Compton camera adds the largest contribution on the angular blurring; physically limiting the spatial resolution. Following the analysis of the results from the spatial resolution test, resolutions in the order of one centimeter are achievable with the approach in the center of the lung. The concept of Compton imaging allows one to distinguish to some extent between scattered photons and x-ray fluorescent photons based on their difference in emission position. The results predict that molecular sensitivities down to 240 pM l−1 for 5 mm diameter lesions at 15 mGy for 50 nm diameter gold nano-particles are achievable. A 45-fold speed up time for data acquisition compared to traditional pencil beam XFCT could be achieved for lung imaging at the cost of a small sensitivity decrease.

High pressure XANES and XMCD in the tender X-ray energy range

ABSTRACTWe have developed an experimental setup at the ESRF beamline ID12 dedicated to X-ray absorption and magnetic circular dichroism measurements at high pressure adapted for the tender X-ray energy range and compatible with low temperatures and with high magnetic field. The focused incoming X-ray beam passes through a thin diamond disk attached to a fully perforated diamond anvil and X-ray fluorescence photons from the sample are collected in back-scattering geometry through the same diamond disk. The pressure in the cell is measured using the ruby luminescence through a full diamond anvil. The highest pressure attainable with this diamond anvil cell (DAC) depends on the thickness of the diamond disk and it is above 16 GPa for a 80-μm thick plate and exceeds 4.5 GPa in the case of 30-μm diamond disk. Excellent performances of this setup in the tender X-ray range are illustrated with X-ray absorption near-edge structure studies of the phase transitions in KCl at the potassium and chlorine K-edges (3.61 and 2.82 keV, respectively) as well as in CdS at the sulfur K-edge (2.47 keV). This DAC together with a dedicated total fluorescence yield (TFY) detector could be mounted in the main heat exchanger of a cryostat and inserted in a bore of a superconducting magnet, this makes possible to perform X-ray magnetic circular dichroism (XMCD) experiments at low temperature, high magnetic field and high pressure. Feasibility of this approach is shown with the XMCD results obtained at the U M-edges in ferromagnetic superconductor UGe.

TH-AB-209-01: Making Benchtop X-Ray Fluorescence Computed Tomography (XFCT) Practical for in Vivo Imaging by Integration of a Dedicated High-Performance X-Ray Source in Conjunction with Micro-CT Functionality

Purpose: To make benchtop x-ray fluorescence computed tomography (XFCT) practical for routine preclinical imaging tasks with gold nanoparticles (GNPs) by deploying, integrating, and characterizing a dedicated high-performance x-ray source and addition of simultaneous micro-CT functionality. Methods: Considerable research effort is currently under way to develop a polychromatic benchtop cone-beam XFCT system capable of imaging GNPs by stimulation and detection of gold K-shell x-ray fluorescence (XRF) photons. Recently, an ad hoc high-power x-ray source was incorporated and used to image the biodistribution of GNPs within a mouse, postmortem. In the current work, a dedicated x-ray source system featuring a liquid-cooled tungsten-target x-ray tube (max 160 kVp, ∼3 kW power) was deployed. The source was operated at 125 kVp, 24 mA. The tube's compact dimensions allowed greater flexibility for optimizing both the irradiation and detection geometries. Incident x-rays were shaped by a conical collimator and filtered by 2 mm of tin. A compact “OEM” cadmium-telluride x-ray detector was implemented for detecting XRF/scatter spectra. Additionally, a flat panel detector was installed to allow simultaneous transmission CT imaging. The performance of the system was characterized by determining the detection limit (10-second acquisition time) for inserts filled with water/GNPs at various concentrations (0 and 0.010–1.0 wt%) and embedded in a small-animal-sized phantom. The phantom was loaded with 0.5, 0.3, and 0.1 wt% inserts and imaged using XFCT and simultaneous micro-CT. Results: An unprecedented detection limit of 0.030 wt% was experimentally demonstrated, with a 33% reduction in acquisition time. The reconstructed XFCT image accurately localized the imaging inserts. Micro-CT imaging did not provide enough contrast to distinguish imaging inserts from the phantom under the current conditions. Conclusion: The system is immediately capable of in vivo preclinical XFCT imaging with GNPs. Micro-CT imaging will require optimization of irradiation parameters to improve contrast. Supported by NIH/NCI grant R01CA155446; This investigation was supported by NIH/NCI grant R01CA155446

A novel prepless X-ray imaging capsule for colon cancer screening

The demand for bowel cleansing hampers participation in screening colonoscopy, while poor preparation impairs adenoma detection. A novel prepless X-ray imaging capsule for colon screening is presented; the capsule emits...

TH-AB-204-12: Practical/ultrasensitive Benchtop Gold L-Shell XRF Imaging System with a Kilowatt-Range X-Ray Source and Silicon Drift Detector

Purpose: To improve the sensitivity and throughput of a benchtop x-ray fluorescence (XRF) imaging system capable of locating and quantifying distributions of gold nanoparticles (GNPs) by detecting gold L-shell XRF photons from subcentimeter-sized ex vivo samples or superficial tumors for preclinical small animal studies. Methods: A proof-of-principle L-shell XRF imaging system has been developed previously. Originally, the system was configured with a low-power (∼50 W) x-ray source (62 kVp, 0.8 mA) and a silicon PIN diode detector. The detection limit of the system was approximately 0.02 mg/cm3 (20 ppm) for an acquisition time of 10 min. Currently, the system has been retrofitted with a high-power (∼3 kW) x-ray source. The detector was replaced with a silicon drift detector (SDD) to handle the increased photon flux at the new settings (62 kVp, 45 mA). Calibration was performed using phantoms containing water/GNPs at a wide range of concentrations (0 and 0.0001–10 mg/cm3). The acquisition time was set to 10 s (60 times shorter than that used with the former configuration, to maintain the same overall x-ray fluence and dose). The XRF/scatter spectrum at 90° was acquired from each phantom. The data were processed to extract XRF signal from background, which was then corrected for attenuation using a Compton-scatter-based normalization algorithm. The corrected XRF signals were plotted vs. GNP concentration and analyzed to determine the detection limit. Results: The detection limit with the current configuration was found to be 0.007 mg/cm3 (7 ppm), a three-fold improvement compared to the former configuration for the same dose. Conclusion: By adopting a high-power x-ray source and SDD, the material detection limit has been improved to a level comparable to that of a synchrotron-based system. Concurrently, much shorter acquisition time afforded by the higher photon flux makes the current setup practical for routine preclinical imaging tasks.

Gated silicon drift detector fabricated from a low-cost silicon wafer.

Inexpensive high-resolution silicon (Si) X-ray detectors are required for on-site surveys of traces of hazardous elements in food and soil by measuring the energies and counts of X-ray fluorescence photons radially emitted from these elements. Gated silicon drift detectors (GSDDs) are much cheaper to fabricate than commercial silicon drift detectors (SDDs). However, previous GSDDs were fabricated from 10-kΩ·cm Si wafers, which are more expensive than 2-kΩ·cm Si wafers used in commercial SDDs. To fabricate cheaper portable X-ray fluorescence instruments, we investigate GSDDs formed from 2-kΩ·cm Si wafers. The thicknesses of commercial SDDs are up to 0.5 mm, which can detect photons with energies up to 27 keV, whereas we describe GSDDs that can detect photons with energies of up to 35 keV. We simulate the electric potential distributions in GSDDs with Si thicknesses of 0.5 and 1 mm at a single high reverse bias. GSDDs with one gate pattern using any resistivity Si wafer can work well for changing the reverse bias that is inversely proportional to the resistivity of the Si wafer.

Quantitative time-averaged gas and liquid distributions using x-ray fluorescence and radiography in atomizing sprays.

A method for quantitative measurements of gas and liquid distributions is demonstrated using simultaneous x-ray fluorescence and radiography of both phases in an atomizing coaxial spray. Synchrotron radiation at 10.1keV from the Advanced Photon Source at Argonne National Laboratory is used for x-ray fluorescence of argon gas and two tracer elements seeded into the liquid stream. Simultaneous time-resolved x-ray radiography combined with time-averaged dual-tracer fluorescence measurements enabled corrections for reabsorption of x-ray fluorescence photons for accurate, line-of-sight averaged measurements of the distribution of the gas and liquid phases originating from the atomizing nozzle.

Simulation of 1.5-mm-thick and 15-cm-diameter gated silicon drift X-ray detector operated with a single high-voltage source

High-resolution silicon X-ray detectors with a large active area are required for effectively detecting traces of hazardous elements in food and soil through the measurement of the energies and counts of X-ray fluorescence photons radially emitted from these elements. The thicknesses and areas of commercial silicon drift detectors (SDDs) are up to 0.5 mm and 1.5 cm2, respectively. We describe 1.5-mm-thick gated SDDs (GSDDs) that can detect photons with energies up to 50 keV. We simulated the electric potential distributions in GSDDs with a Si thickness of 1.5 mm and areas from 0.18 to 168 cm2 at a single high reverse bias. The area of a GSDD could be enlarged simply by increasing all the gate widths by the same multiple, and the capacitance of the GSDD remained small and its X-ray count rate remained high.

Mass Attenuation Coefficients of Binderless and Polylactic Acid Added Oil Palm Trunk Particleboard in the Diagnostic Energy Range

Two types of oil palm trunk particleboards namely binderless and polylactic acid (PLA) added board were manufactured with a target density of 1.0 g/cm 3 . The mass attenuation coefficients of the binderless and PLA added particleboards were determined by using X-ray fluorescence (XRF) photons emanating from high purity metal plates. The energies of the XRF emitted from those metal plates were in the range of 16.59 keV– 25.26 keV. The experimental values of the mass attenuation coefficients of the binderless particleboards and the XCOM calculated values for water are comparable. These results suggest that binderless particleboards have the potential to be a phantom material at diagnostic photon energies.

Improving x‐ray fluorescence signal for benchtop polychromatic cone‐beam x‐ray fluorescence computed tomography by incident x‐ray spectrum optimization: A Monte Carlo study

To develop an accurate and comprehensive Monte Carlo (MC) model of an experimental benchtop polychromatic cone-beam x-ray fluorescence computed tomography (XFCT) setup and apply this MC model to optimize incident x-ray spectrum for improving production/detection of x-ray fluorescence photons from gold nanoparticles (GNPs). A detailed MC model, based on an experimental XFCT system, was created using the Monte Carlo N-Particle (MCNP) transport code. The model was validated by comparing MC results including x-ray fluorescence (XRF) and scatter photon spectra with measured data obtained under identical conditions using 105 kVp cone-beam x-rays filtered by either 1 mm of lead (Pb) or 0.9 mm of tin (Sn). After validation, the model was used to investigate the effects of additional filtration of the incident beam with Pb and Sn. Supplementary incident x-ray spectra, representing heavier filtration (Pb: 2 and 3 mm; Sn: 1, 2, and 3 mm) were computationally generated and used with the model to obtain XRF/scatter spectra. Quasimonochromatic incident x-ray spectra (81, 85, 90, 95, and 100 keV with 10 keV full width at half maximum) were also investigated to determine the ideal energy for distinguishing gold XRF signal from the scatter background. Fluorescence signal-to-dose ratio (FSDR) and fluorescence-normalized scan time (FNST) were used as metrics to assess results. Calculated XRF/scatter spectra for 1-mm Pb and 0.9-mm Sn filters matched (r ≥ 0.996) experimental measurements. Calculated spectra representing additional filtration for both filter materials showed that the spectral hardening improved the FSDR at the expense of requiring a much longer FNST. In general, using Sn instead of Pb, at a given filter thickness, allowed an increase of up to 20% in FSDR, more prominent gold XRF peaks, and up to an order of magnitude decrease in FNST. Simulations using quasimonochromatic spectra suggested that increasing source x-ray energy, in the investigated range of 81-100 keV, increased the FSDR up to a factor of 20, compared to 1 mm Pb, and further facilitated separation of gold XRF peaks from the scatter background. A detailed MC model of an experimental benchtop XFCT system has been developed and validated. In exemplary calculations to illustrate the usefulness of this model, it was shown that potential use of quasimonochromatic spectra or judicious choice of filter material/thickness to tailor the spectrum of a polychromatic x-ray source can significantly improve the performance of benchtop XFCT, while considering trade-offs between FSDR and FNST. As demonstrated, the current MC model is a reliable and powerful computational tool that can greatly expedite the further development of a benchtop XFCT system for routine preclinical molecular imaging with GNPs and other metal probes.

Measurement of mass attenuation coefficients of Eremurus–Rhizophora spp. particleboards for X-ray in the 16.63–25.30 keV energy range

The roots of Eremurus spp. were used as a bio-adhesive in the fabrication of Rhizophora spp. particleboards. The mass attenuation coefficients of Eremurus–Rhizophora spp. particleboard of six samples with two different weight percentages of the Eremurus spp. root (6% and 12%) and three various Rhizophora spp. particle sizes (≤149µm, 149–500µm and 500–1000µm) were determined by using X-ray fluorescence (XRF) photons in 16.63keV and 25.30keV of the photon energy range. The results were compared with theoretically calculated mass attenuations using the XCOM computer program for younger-age (breast 1: 75% muscle+25% fat), middle-age (breast 2: 50% muscle+50% fat), and old-age (breast 3: 25% muscle+75% fat) breasts. The results indicated that Eremurus–Rhizophora spp. particleboard is the appropriate suitable phantom in the diagnostic energy region. The mass attenuation coefficient in the low weight percentage of the bio-adhesive and the large Rhizophora spp. particle size were found very close to breast 1. Moreover the mass attenuation coefficient of the sample with high weight percentage of the bio-adhesive and small Rhizophora spp. particle size was found very close to water as a standard material phantom. In addition, the viscosity of dissolved Eremurus spp. root in water could be considerably higher than that of formaldehyde-based adhesives, which affects on some properties such as high strength and high binding.

XRF Technique for the Evaluation of Gum Arabic Bonded Rhizophora spp. Particleboards as Tissue Equivalent Material

 Abstract—For the first time, Gum Arabic (GA) is used as a binder in particleboards preparation and the attenuation properties of the fabricated particleboards were evaluated to check their suitability as tissue equivalent material. Gum Arabic was added into Rhizophora spp. particleboards of four particle sizes at three different GA adhesive levels. The X-ray fluorescence (XRF) technique was used to measure the linear and the mass attenuation coefficients of the fabricated particleboards at effective energy range of 17.4 - 26.7 keV. This was achieved by determining the attenuation of Kα1 X-ray fluorescent (XRF) photons from niobium, molybdenum, palladium, silver and tin targets. The results were compared with theoretical values of water calculated using XCOM computer program. The mass attenuation coefficients of the GA bonded Rhizophora spp. particleboards were found to be close to the values of water calculated in XCOM at the same photon energies. Luckily, fabricated particleboards showed tissue equivalent results which optimistically can open a new window on the consumption of such a natural adhesive in particleboards as phantom material in dosimetric phantoms and quality control applications.

Mass attenuation coefficients of fabricated Rhizophora spp. particleboard for the 15.77 – 25.27 keV range

The Rhizophora spp. wood what is hard and heavy is considered strong in strength and is suitable for structural purposes. Generally, Rhizophora spp. was used in radiation dosimetry research and it is being used in this project too. There are some disadvantages in using the raw (natural) material of Rhizophora spp. in radiation dosimetry research and there is a need to modify this natural wood to be easily used as a phantom in radiation dosimetry. The mass attenuation coefficients (/) of fabricated Rhizophora spp. particleboard were determined for photons in the energy range of 15.77–25.27 keV. This was carried out by studying the attenuation of X-ray fluorescent photons from zirconium, molybdenum, palladium, silver, indium and tin targets. The results were compared with theoretical values for average breast tissues in youngage, middle-age and old-age groups calculated using photon cross section database (XCOM), the well-known code for calculating attenuation coefficients and interaction cross-sections. The measured mass attenuation coefficients were found to be very close to the calculated XCOM values in breasts of old-age group.

Simulation and Fabrication of Gated Silicon Drift X-Ray Detector Operated by Peltier Cooling

A proposed simply structured gated silicon (Si) drift X-ray detector operated using Peltier cooling and only a single high-voltage source is investigated. Because the device structure is much simpler than that of commercial Si drift detectors (SDDs), which require at least two high-voltage sources, the cost of the X-ray detection system can be reduced. The absorption of cadmium X-ray fluorescence photons (energy: 23.1 keV) in 0.3-mm-thick Si is only 19% in commercial SDDs. Toward realizing detectors with thicker Si substrates, we simulate the electric potential distribution in the proposed detector with a Si substrate having thickness of 0.625 mm and resistivity of 10 kΩ·cm, and we perform fundamental experiments on a fabricated prototype. The simulation result is in good agreement with the experimental result that the effective active area of the detector is approximately 18 mm2 by using incident X-rays passed through a 0.1-mm-diameter pinhole. An energy resolution of 145 eV at 5.9 keV is experimentally obtained from an 55Fe source at -38 °C.

Simulation of Thick Gated Silicon Drift X-ray Detector Operated by a Single High-Voltage Source

High-resolution X-ray detectors can be used to detect traces of hazardous or radioactive elements in food, soil, and the human body by measuring the energies and counts of emitted X-ray fluorescence photons. We have simulated the electric potential distributions in gated silicon drift detectors (GSDDs) with an active area of 18 mm2 and a Si thickness between 0.625 and 1.5 mm. A GSDD gate pattern was designed for each Si thickness and for various oxide charge densities in the SiO2 passivating layer near the SiO2/Si interface. The simulated GSDDs required approximately half the reverse bias voltage required by Si pin detectors. Our detector design could improve the absorption of Cd or Cs X-ray fluorescence photons and would reduce the cost of X-ray detection systems.

First Demonstration of Multiplexed X-Ray Fluorescence Computed Tomography (XFCT) Imaging

Simultaneous imaging of multiple probes or biomarkers represents a critical step toward high specificity molecular imaging. In this work, we propose to utilize the element-specific nature of the X-ray fluorescence (XRF) signal for imaging multiple elements simultaneously (multiplexing) using XRF computed tomography (XFCT). A 5-mm-diameter pencil beam produced by a polychromatic X-ray source (150 kV, 20 mA) was used to stimulate emission of XRF photons from 2% (weight/volume) gold (Au), gadolinium (Gd), and barium (Ba) embedded within a water phantom. The phantom was translated and rotated relative to the stationary pencil beam in a first-generation CT geometry. The X-ray energy spectrum was collected for 18 s at each position using a cadmium telluride detector. The spectra were then used to isolate the K shell XRF peak and to generate sinograms for the three elements of interest. The distribution and concentration of the three elements were reconstructed with the iterative maximum likelihood expectation maximization algorithm. The linearity between the XFCT intensity and the concentrations of elements of interest was investigated. We found that measured XRF spectra showed sharp peaks characteristic of Au, Gd, and Ba. The narrow full-width at half-maximum (FWHM) of the peaks strongly supports the potential of XFCT for multiplexed imaging of Au, Gd, and Ba ( FWHM(Au,Kα1) = 0.619 keV, FWHM(Au,Kα2)=1.371 keV , FWHM(Gd,Kα)=1.297 keV, FWHM(Gd,Kβ)=0.974 keV , FWHM(Ba,Kα)=0.852 keV, and FWHM(Ba,Kβ)=0.594 keV ). The distribution of Au, Gd, and Ba in the water phantom was clearly identifiable in the reconstructed XRF images. Our results showed linear relationships between the XRF intensity of each tested element and their concentrations ( R(2)(Au)=0.944 , R(Gd)(2)=0.986, and R(Ba)(2)=0.999), suggesting that XFCT is capable of quantitative imaging. Finally, a transmission CT image was obtained to show the potential of the approach for providing attenuation correction and morphological information. In conclusion, XFCT is a promising modality for multiplexed imaging of high atomic number probes.

The influence of electron multiplication and internal X-ray fluorescence on the performance of a scintillator-based gamma camera

When considering the ‘standard’ gamma-camera, one might picture an array of photo-multiplier tubes or a similar array of small-area detectors. This array of imaging detectors would be attached to a corresponding array of scintillator modules (or a solid layer of scintillator) in order to give a high detection efficiency in the energy region of interest, usually 8–140keV. Over recent years, developments of gamma-cameras capable of achieving much higher spatial resolutions have led to a new range of systems based on Charge-Coupled Devices with some form of signal multiplication between the scintillator and the CCD in order for one to distinguish the light output from the scintillator above the CCD noise. The use of an Electron-Multiplying Charge-Coupled Device (EM-CCD) incorporates the gain process within the CCD through a form of ‘impact ionisation’, however, the gain process introduces an ‘excess noise factor’ due to the probabilistic nature of impact ionisation and this additional noise consequently has an impact on the spatial and spectral resolution of the detector. Internal fluorescence in the scintillator, producing K-shell X-ray fluorescence photons that can be detected alongside the incident gamma-rays, also has a major impact on the imaging capabilities of gamma-cameras. This impact varies dramatically from the low spatial resolution to high spatial resolution camera system. Through a process of simulation and experimental testing focussed on the high spatial resolution (EM-CCD based) variant, the factors affecting the performance of gamma-camera systems are discussed and the results lead to important conclusions to be considered for the development of future systems. This paper presents a study into the influence of the EM-CCD gain process and the internal X-ray fluorescence in the scintillator on the performance of scintillator-based gamma cameras (CCD-based or otherwise), making use of Monte Carlo simulations to demonstrate the aspects involved, their influence on the imaging system and the hypotheses previously discussed in experimental studies.

Measurement of mass attenuation coefficients of Rhizophora spp. binderless particleboards in the 16.59–25.26 keV photon energy range and their density profile using x-ray computed tomography

The mass attenuation coefficients of Rhizophora spp. binderless particleboard with four different particle sizes (samples A, B, C and D) and natural raw Rhizophora spp. wood (sample E) were determined using single-beam photon transmission in the energy range between 16.59 and 25.26keV. This was done by determining the attenuation of Kα1 X-ray fluorescent (XRF) photons from niobium, molybdenum, palladium, silver and tin targets. The results were compared with theoretical values of young-age breast (Breast 1) and water calculated using a XCOM computer program. It was found that the mass attenuation coefficient of Rhizophora spp. binderless particleboards to be close to the calculated XCOM values in water than natural Rhizophora spp. wood. Computed tomography (CT) scans were then used to determine the density profile of the samples. The CT scan results showed that the Rhizophora spp. binderless particleboard has uniform density compared to natural Rhizophora spp. wood. In general, the differences in the variability of the profile density decrease as the particle size of the pellet samples decreases.

Mass attenuation coefficients of natural Rhizophora spp. wood for X-rays in the 15.77-25.27 keV range

The mass attenuation coefficients (mu/rho) of Rhizophora spp. were determined for photons in the energy range of 15.77-25.27 keV. This was carried out by studying the attenuation of X-ray fluorescent photons from zirconium, molybdenum, palladium, silver, indium and tin targets. The results were compared with theoretical values for average breast tissues in young-age, middle-age and old-age groups calculated using photon cross section database (XCOM), the well-known code for calculating attenuation coefficients and interaction cross-sections. The measured mass attenuation coefficients were found to be very close to the calculated XCOM values in breasts of young-age group.