Attenuation Coefficient Of Tissue Research Articles

Characterization of selected additive manufacturing materials for synchrotron monochromatic imaging and broad-beam radiotherapy at the Australian synchrotron-imaging and medical beamline

Objective. This study aims to characterize radiological properties of selected additive manufacturing (AM) materials utilizing both material extrusion and vat photopolymerization technologies. Monochromatic synchrotron x-ray images and synchrotron treatment beam dosimetry were acquired at the hutch 3B and 2B of the Australian Synchrotron-Imaging and Medical Beamline. Approach. Eight energies from 30 keV up to 65 keV were used to acquire the attenuation coefficients of the AM materials. Comparison of theoretical, and experimental attenuation data of AM materials and standard solid water for MV linac was performed. Broad-beam dosimetry experiment through attenuated dose measurement and a Geant4 Monte Carlo simulation were done for the studied materials to investigate its attenuation properties specific for a 4 tesla wiggler field with varying synchrotron radiation beam qualities. Main results. Polylactic acid (PLA) plus matches attenuation coefficients of both soft tissue and brain tissue, while acrylonitrile butadiene styrene, Acrylonitrile styrene acrylate, and Draft resin have close equivalence to adipose tissue. Lastly, PLA, co-polyester plus, thermoplastic polyurethane, and White resins are promising substitute materials for breast tissue. For broad-beam experiment and simulation, many of the studied materials were able to simulate RMI457 Solid Water and bolus within ±10% for the three synchrotron beam qualities. These results are useful in fabricating phantoms for synchrotron and other related medical radiation applications such as orthovoltage treatments. Significance and conclusion. These 3D printing materials were studied as potential substitutes for selected tissues such as breast tissue, adipose tissue, soft-tissue, and brain tissue useful in fabricating 3D printed phantoms for synchrotron imaging, therapy, and orthovoltage applications. Fabricating customizable heterogeneous anthropomorphic phantoms (e.g. breast, head, thorax) and pre-clinical animal phantoms (e.g. rodents, canine) for synchrotron imaging and radiotherapy using AM can be done based on the results of this study.

Review of the Low-Temperature Acoustic Properties of Water, Aqueous Solutions, Lipids, and Soft Biological Tissues.

Existing data on the acoustic properties of low-temperature biological materials is limited and widely dispersed across fields. This makes it difficult to employ this information in the development of ultrasound applications in the medical field, such as cryosurgery and rewarming of cryopreserved tissues. In this review, the low-temperature acoustic properties of biological materials, and the measurement methods used to acquire them were collected from a range of scientific fields. The measurements were reviewed from the acoustic setup to thermal methodologies for samples preparation, temperature monitoring, and system insulation. The collected data contain the longitudinal and shear velocity, and attenuation coefficient of biological soft tissues and biologically relevant substances-water, aqueous solutions, and lipids-in the temperature range down to -50 °C and in the frequency range from 108 kHz to 25 MHz. The multiple reflection method (MRM) was found to be the preferred method for low-temperature samples, with a buffer rod inserted between the transducer and sample to avoid direct contact. Longitudinal velocity changes are observed through the phase transition zone, which is sharp in pure water, and occurs more slowly and at lower temperatures with added solutes. Lipids show longer transition zones with smaller sound velocity changes; with the longitudinal velocity changes observed during phase transition in tissues lying between these two extremes. More general conclusions on the shear velocity and attenuation coefficient at low-temperatures are restricted by the limited data. This review enhance knowledge guiding for further development of ultrasound applications in low-temperature biomedical fields, and may help to increase the precision and standardization of low-temperature acoustic property measurements.

Current Status and Future Prospects of the Linear and Non-Linear Attenuation Coefficients of Cancer Cells, Tissues and Tumors by Synchrotron X-Ray Radiation (SXR) Computed Tomography

Current Status and Future Prospects of the Linear and Non-Linear Attenuation Coefficients of Cancer Cells, Tissues and Tumors by Synchrotron X-Ray Radiation (SXR) Computed Tomography

Two-dimensional multifunctional nanosheets as radiosensitizers for chemodynamic/radio-therapy

The hypoxia tumor microenvironment and low radiation attenuation coefficient of tumor tissue usually limit the efficiency of radiotherapy. In this study, a two-dimensional multifunctional nano-sensitizer, CuNS@Pt, was prepared to function as a radiosensitizer, enhancing radiotherapy through multiple mechanisms. Numerous active sites were provided for the deposition of X-ray radiation energy by the in-situ chemical reduction of Pt to create functional hybrids on Cu-based nanosheets. CuNS@Pt catalyzed high concentration of endogenous hydrogen peroxide to generate oxygen in tumor microenvironment, alleviating the physiological environment of hypoxic tumors. Additionally, CuNS could reduce the content of intrinsic glutathione (GSH) and catalyze hydrogen peroxide to form hydroxyl radicals (·OH). The generated ·OH could damage mitochondria and destroy redox homeostasis due to the functional inclusion of Cu species, thereby achieving chemodynamic therapy and further improving the radiation effect. Both in vivo and in vitro experiments showed that the nano sensitizer effectively improved the therapeutic efficiency of radiotherapy and had good biological safety. All in all, this study provides a pragmatic and doable platform for maximizing the efficacy of RT in cancer. This study also highlights the future research value of two-dimensional nanomaterials.

Calculation of X-ray attenuation coefficients for normal and cancerous breast tissues

The study was carried out by numerical integration based on the diffraction properties and elemental composition. The elemental compositions of breast tissues in the literature were tested. The photon attenuation coefficients calculated using the recent elemental composition were found within 0.2˗16% for adipose tissue and within 0.04˗17% for glandular tissue with the experimental reference data. The attenuation coefficients of cancerous breast tissue calculated according to the elemental content previously measured in breast cancer patients were found within 0˗17% with experimental data in the literature. The attenuation coefficients are of great interest to medical research. To calculate realistic attenuation coefficients, the characteristic coherent scatter, which is most intense at small angles, must be considered. For this reason, experimentally measured form factor data were reviewed, and the most compatible one with the theoretical form factor data produced in this study was used at low momentum transfer x (0 < x ≤ 8 nm−1). The differential linear coherent scattering distributions were calculated for an energy value of 17.44 keV and compared with their experimental counterparts.

Metal-Organic Framework-Derived Multifunctional Nucleic Acid Nanoprobes for Hypoxia Imaging-Guided Radiosensitization.

The efficacy of radiotherapy (RT) is usually restricted by the hypoxic microenvironment and the poor radiation attenuation coefficient of tumor tissue. Theranostic probes that simultaneously evaluate the hypoxia degree and sensitize cancer cells toward RT are promising for improving the treatment efficacy and avoiding overtreatment. We rationally designed a metal-organic framework (MOF)-derived multifunctional nanoprobe for hypoxia imaging-guided radiosensitization. Hf-MOF was carbonized to obtain a porous carbonous nanostructure containing ultrasmall HfO2 (HfC); then, a fluorophore-labeled HIF-α mRNA antisense sequence was readily adsorbed and quenched by HfC to obtain the nanoprobe (termed HfC-Hy). The antisense sequence could easily hybridize with HIF-α mRNA and recover its fluorescence signal to evaluate the degree of hypoxia, while the HfC nanostructure could deposit more radiation energy in cancer cells for radiosensitization. A series of in vitro and in vivo experiments demonstrated that the nanoprobe could be successfully utilized for imaging the hypoxic degree of cancer cells/tumor tissue and guiding radiosensitization. This work not only developed a highly efficient and safe nanosensitizer but also offered a potential solution for customized clinical RT.

Optimal slice thickness for improved accuracy of quantitative analysis of fluorescent cell and microsphere distribution in cryo-images

Cryo-imaging has been effectively used to study the biodistribution of fluorescent cells or microspheres in animal models. Sequential slice-by-slice fluorescent imaging enables detection of fluorescent cells or microspheres for corresponding quantification of their distribution in tissue. However, if slices are too thin, there will be data overload and excessive scan times. If slices are too thick, then cells can be missed. In this study, we developed a model for detection of fluorescent cells or microspheres to aid optimal slice thickness determination. Key factors include: section thickness (X), fluorescent cell intensity (Ifluo), effective tissue attenuation coefficient (μT), and a detection threshold (T). The model suggests an optimal slice thickness value that provides near-ideal sensitivity while minimizing scan time. The model also suggests a correction method to compensate for missed cells in the case that image data were acquired with overly large slice thickness. This approach allows cryo-imaging operators to use larger slice thickness to expedite the scan time without significant loss of cell count. We validated the model using real data from two independent studies: fluorescent microspheres in a pig heart and fluorescently labeled stem cells in a mouse model. Results show that slice thickness and detection sensitivity relationships from simulations and real data were well-matched with 99% correlation and 2% root-mean-square (RMS) error. We also discussed the detection characteristics in situations where key assumptions of the model were not met such as fluorescence intensity variation and spatial distribution. Finally, we show that with proper settings, cryo-imaging can provide accurate quantification of the fluorescent cell biodistribution with remarkably high recovery ratios (number of detections/delivery). As cryo-imaging technology has been used in many biological applications, our optimal slice thickness determination and data correction methods can play a crucial role in further advancing its usability and reliability.

Role of MDCT neck in evaluation of neck masses: Our experience

A mass in the neck in adults is a common entity that we customarily encounter in our clinical practice. Diagnosis of these neck masses can be challenging owing to the intricate anatomy and physiology, with a myriad of presenting complaints. Neck masses can be due to multiple causes classified as congenital (eg cystic hygroma), lymphadenopathy, inflammatory or neoplastic (malignant or benign). Various imaging modalities have been applied for the evaluation such as plain x-rays, contrast studies such as lymphogram, xerography and oesophagogram etc. However, these are neither sensitive nor specific in diagnosing the aetiology of neck masses. CT being non-invasive and non-operator dependent depicts excellent quantification of tissue attenuation coefficients and is exceedingly useful in defining both the osseous and soft-tissue extent of the lesion. With the upcoming of newer generation Multidetector CT Scanners (MDCT) have made tremendous improvements in scanning time, tissue resolution and quality of three dimensional (3D) reconstructions. The aim of this study is to evaluate the role of MDCT in neck masses.

X-ray scattering and attenuation cross-sections and coefficients of bone, brain, lung, fat, and soft tissue for applications in dosimetry, cancer detection, and treatment

The Klein-Nishina electronic and atomic cross-sections and Compton mass attenuation coefficients of the bone, lung, soft tissue, brain, and fat are calculated for X-ray or γ-ray energies of 50 keV, 140 keV, 364 keV, 1.25 MeV, 4.784 MeV, and 6.0 MeV. The Klein-Nishina formula was used in the entire calculation. The results show that the Klein-Nishina electronic cross-section (eσ) decreases with increasing photon energy. Due to the complex variation in the effective charge number Z of the tissues, the Klein-Nishina atomic cross-section (aσ) first increases and then decreases for the investigated tissues. The Compton mass attenuation coefficient (σ/ρ) has even more complexity when the calculated values of σ/ρ are analyzed as a function of increasing Z/A for the investigated tissues. An overall trend of increase in σ/ρ is observed for increasing Z/A for all tissues except the cortical bone. In the case of the cortical bone, the values of σ/ρ decrease since cortical bone is a relatively high Z tissue as compared to other tissues where a rapid increase in the effective mass number A occurs when Z is increased. Overall, the results are very useful in calculating and delivering precise and optimum doses to avoid image quality degradation in radiographic images and to treat a tumor more effectively while keeping the normal tissues safe in radiation treatment planning.

Reprogramming of the tumor microenvironment using a PCN-224@IrNCs/D-Arg nanoplatform for the synergistic PDT, NO, and radiosensitization therapy of breast cancer and improving anti-tumor immunity.

The low X-ray attenuation coefficient of tumor soft tissue and the hypoxic tumor microenvironment (TME) during radiation therapy (RT) of breast cancer result in RT resistance and thus reduced therapeutic efficacy. In addition, immunosuppression induced by the TME severely limits the antitumor immunity of radiation therapy. In this paper, we propose a PCN-224@IrNCs/D-Arg nanoplatform for the synergistic radiosensitization, photodynamic, and NO therapy of breast cancer that also boosts antitumor immunity (PCN = porous coordination network, IrNCs = iridium nanocrystals, D-Arg = D-arginine). The local tumors can be selectively ablated via reprogramming the tumor microenvironment (TME), photodynamic therapy (PDT) and NO therapy, and the presence of the high-Z element Ir that sensitizes radiotherapy. The synergistic execution of these treatment modalities also resulted in adapted antitumor immune response. The intrinsic immunomodulatory effects of the nanoplatform also repolarize macrophages toward the M1 phenotype and induce dendritic cell maturation, activating antitumor T cells to induce immunogenic cell death as demonstrated in vitro and in vivo. The nanocomposite design reported herein represents a new regimen for the treatment of breast cancer through TME reprogramming to exert a synergistic effect for effective cancer therapy and antitumor immunity.

In Vivo Measurements of the Bulk Ultrasonic Attenuation Coefficient of Breast Tissue Using a Novel Phase-Insensitive Receiver.

This study describes the first in vivo acoustic attenuation measurements of breast tissue undertaken using a novel phase-insensitive detection technique employing a differential pyroelectric sensor. The operation of the sensor is thermal in nature, with its output signal being dictated by the acoustic power integrated over its surface. The particularly novel feature of the sensor lies in its differential principle of operation, which significantly enhances its immunity to background acoustic and vibration noise. A large area variant of the sensor was used to detect ultrasonic energy generated by an array of 14 discrete 3.2-MHz plane piston transducers, transmitted through pendent breasts in water. The transduction and reception capability represent key parts of a prototype Quantitative Ultrasound Computed Tomography Test Facility developed at the National Physical Laboratory to study the efficacy of phase-insensitive ultrasound computed tomography of breast phantoms containing a range of appropriate inclusions, in particular, the measurement uncertainties associated with quantitative reconstructions of the acoustic attenuation coefficient. For this study, attenuation coefficient measurements were made using 1-D projections on 12 nominally healthy study volunteers, whose age ranged from 19 to 65 years. Averaged or bulk attenuation coefficient values were generated in the range 1.7-4.6 dBcm ^-1 at 3.2 MHz and have been compared with existing literature, derived from in vivo and ex vivo studies. Results are encouraging and indicate that the relatively simple technique could be applied as a robust method for assessing the properties of breast tissue, particularly the balance of fatty (adipose) and fibroglandular components.

Attenuation coefficient for layer-by-layer assessment of the intestinal wall in acute ischemia according to optical coherence tomography

Small laboratory animals (rats) are suitable objects for modelling acute mesenteric ischemia (AMI) and monitoring changes in the structural tissue and intramural blood flow using optical coherence tomography (OCT) and OCT angiography methods. Combined with evaluation of blood circulation the prevalence of a necrotic tissue is a key factor in assessing intestine viability during surgery and determining the resection margins. While the assessment of the blood vessels network is commonly performed visually by surgeons, the assessment of the necrosis within individual layers is quite challenging due to small thickness of each intestine layer in small objects. The study demonstrates that the construction of colour-coded maps of the tissue attenuation coefficient estimated from the OCT data, allows quick layer-by-layer evaluation of the intestine wall. Such maps in the AMI model make it possible to track changes separately in the serous-muscular, submucosa and mucosa layers of the intestine wall in vivo and to carry out a differential diagnosis between the inflammation and necrosis in these layers. Colour-coded mapping may be useful in other medical applications where layer-by-layer assessment of structural tissue changes is required in a small range of depths.

Study on Mass and Linear Attenuation Coefficients of PMMA as Human Tissue-Equivalent Material

Abstract To research the improvements of clinical imaging of human tissues, tissue-equivalent materials are one of the reasonable strategies for evaluating the impact of radiation dosages on human tissues. Hence, considering mass and linear attenuation coefficients is a promising method to foresee the appropriate tissue-identical material. In this examination, we utilise the built-up estimations of elemental compositions (mass portion of every component) of PMMA material by numerous analyses in literature. XCOM program was utilised to figure estimations of mass attenuation coefficients of PMMA for various photon energies (0.015–2.0) MeV. The outcomes reveal that the estimations of mass and linear attenuation coefficients are high as the energies begin to decrease and diminish gradually with an expansion in photon energies. Making a sensible coordinating between mass and linear attenuation coefficients of PMMA as human tissue-equivalent material with mass and linear attenuation coefficients of lung, brain, muscle and blood human tissues has demonstrated a phenomenal match.

Initial evaluation of a new maximum-likelihood attenuation correction factor-based attenuation correction for time-of-flight brain PET.

The aim of this study was to evaluate an image reconstruction algorithm, including a new maximum-likelihood attenuation correction factor (ML-ACF) for time of flight (TOF) brain positron emission tomography (PET). The implemented algorithm combines an ML-ACF method that simultaneously estimates both the emission image and attenuation sinogram from TOF emission data, and a scaling method based on anatomical features. To evaluate the algorithm's quantitative accuracy, three-dimensional brain phantom images were acquired and soft-tissue attenuation coefficients and emission values were analyzed. The heterogeneous distributions of attenuation coefficients in soft tissue, skull, and nasal cavity were sufficiently visualized. The attenuation coefficient of soft tissue remained within 5% of theoretical value. Attenuation-corrected emission showed no lateral differences, and significant differences among soft tissue were within the error range. The ML-ACF-based attenuation correction implemented for TOF brain PET worked well and obtained practical levels of accuracy.

A Monte Carlo investigation of some important radiation parameters and tissue equivalency for photons below 1 keV in human tissues

The attenuation coefficients are important input values in estimating not only the dose and exposure in radiotherapy and medical imaging, but also in the proper design of photon shields. While studies are widely available above 1 keV, the attenuation coefficients of human tissues for photon energies less than 1 keV have not been studied yet. In this study, the attenuation coefficients of water and some human tissues were estimated for low energy photons using the MCNP6.1 code in the energy region 0.1 keV–1 keV. Mass attenuation coefficients were estimated at photon energies of 100, 150, 200, 250, 300, 350, 400, 450, 500, 550, 600, 650, 700, 750, 800, 850, 900, 950 and 1000 eV for water and ten human tissues (Soft, Breast, Lung, Bone, Brain, Eye lens, Ovary, Skin, Thyroid and Prostate). Results were compared with those available in literature and a fairly good agreement has been obtained. These data were then used to calculate the mean free path, half value layer, tenth value layer, effective atomic number and specific gamma-ray constant (useful for calculation of dose rate) as well. Moreover, for comparison the effective atomic number of the water has been obtained using the results of this work and using the data available in NIST database from 0.1 to 1 keV. In addition, the human tissues were compared with some tissue equivalent materials in terms of effective atomic number and specific gamma-ray constant to study the tissue equivalency from the results, the muscle-equivalent liquid with sucrose has been found to be the best tissue equivalent material for soft tissue, eye lens and brain with relative difference below 4.1%.

Robust Single-Probe Quantitative Ultrasonic Imaging System With a Target-Aware Deep Neural Network.

The speed of sound (SoS) has great potential as a quantitative imaging biomarker since it is sensitive to pathological changes in tissues. In this paper, a target-aware deep neural (TAD) network reconstructing an SoS image quantitatively from pulse-echo phase-shift maps gathered from a single conventional ultrasound probe is presented. In the proposed TAD network, the reconstruction process is guided by feature maps created from segmented target images for accuracy and contrast. In addition, the feature extraction process utilizes phase difference information instead of direct pulse-echo radio frequency (RF) data for robust image reconstruction against noise in the pulse-echo data. The TAD network outperforms the fully convolutional network in root mean square error (RMSE), contrast-to-noise ratio (CNR), and structural similarity index (SSIM) in the presence of nearby reflectors. The measured RMSE and CNR are 5.4 m/s and 22 dB, respectively with the tissue attenuation coefficient of 2 dB/cm/MHz, which are 72% and 13 dB improvement over the state of the art design in RMSE and CNR, respectively. In the in-vivo test, the proposed method classifies the tissues in the neck area using SoS with a p-value below 0.025. The proposed TAD network is the most accurate and robust single-probe SoS image reconstruction method reported to date. The accuracy and robustness demonstrated by the proposed SoS imaging method open up the possibilities of wide-spread clinical application of the single-probe SoS imaging system.

Influence of different sized nanoparticles combined with ultrasound on the optical properties of in vitro knee joint and knee osteoarthritis cartilage tissue was studied by OCT and diffuse reflectance spectroscopy

The penetration and accumulation of zinc oxide nanoparticles (ZnO NPs) with different sizes in human normal knee joint (NKJ) tissue and knee osteoarthritis (OA) tissue were studied by continuous optical coherence tomography and diffuse reflectance (DR) spectroscopy in this paper, and the effects of ZnO NPs of two sizes (30 nm and 90 nm) and ultrasound (US) on the optical properties of human NKJ and OA tissue were evaluated. The results show that the average attenuation coefficients of NKJ tissue decrease by 14.90%, 26.91%, 33.52% and 37.01%, and the DR spectra increases by 8.444%, 12.901%, 18.219% and 26.125%, respectively, after being treated with 90 nm ZnO NPs, 90 nm ZnO NPs/US, 30 nm ZnO NPs and 30 nm ZnO NPs/US. The average attenuation coefficients of OA tissue are reduced by 32.14%, 49.51%, 57.85% and 72.30%, and the DR spectra increase by 17.426%, 23.116%, 25.218% and 29.326%, respectively, after being treated with 90 nm ZnO NPs, 90 nm ZnO NPs/US, 30 nm ZnO NPs and 30 nm ZnO NPs/US. It is concluded that the optical properties of NKJ and OA tissues are greatly influenced by ZnO NPs and US. Nanoparticles have a greater impact on OA tissue than on NKJ tissue.

The effects of electrical pulses-mediated gold and silver nanoparticles on the optical properties of ex vivo human femoral head tissue with optical coherence tomography

This study aims to monitor and assess the penetration and accumulation of gold nanoparticles (Au NPs) or silver nanoparticles (Ag NPs) (average particle size 40 nm) and the penetration of the Au NPs or Ag NPs assisted by electrical impulses (EP) in human normal femoral head (NFH) and pathological femoral head (PFH) tissues. The results show that optical coherence tomography images can easily distinguish NFH from PFH tissues. The control group show that the average attenuation coefficient of NFH tissue is 4.895 mm−1, and the average attenuation coefficient of PFH tissue is 8.094 mm−1. It shows that the average attenuation coefficient of PFH tissue is significantly greater than that of NFH tissue. High frequency EPS can promote the penetration of nanoparticles into tissues more than low frequency EPS, and the attenuation coefficients of tissues are reduced by 27.31% and 40.35%, respectively. The average attenuation coefficient of PHF tissue changes from 7.75 ± 0.26 mm−1 to 7.60 ± 0.13 mm−1 and 7.93 ± 0.20 mm−1 to 6.94 ± 0.18 mm−1 at 150 min for Ag NPs and Ag NPs/EP treatment, respectively. The attenuation coefficient is reduced by 2.00% and 12.48% respectively. The results suggest that the optical properties of PFH tissues are greatly influenced by Ag NPs and their combination with EP.

Optical coherence microangiography of the mouse kidney for diagnosis of circulatory disorders

Optical coherence tomography (OCT) has become widespread in clinical applications in which precise three-dimensional functional imaging of living organs is required. Nevertheless, the kidney is inaccessible for the high resolution OCT imaging due to a high light attenuation coefficient of skin and soft tissues that significantly limits the penetration depth of the probing laser beam. Here, we introduce a surgical protocol and fixation scheme that enables functional visualization of kidney's peritubular capillaries via OCT microangiography. The model of reversible/irreversible glomerulus embolization using drug microcarriers confirms the ability of OCT to detect circulatory disorders. This approach can be used for choosing optimal carriers, their dosages and diagnosis of other blood flow pathologies.

Fast linear least-squares method for ultrasound attenuation and backscatter estimation

The ultrasonic attenuation and backscatter coefficients of tissues are relevant acoustic parameters due to their wide range of clinical applications. In this paper, a linear least-squares method for the estimation of these coefficients in a homogeneous region of interest based on pulse-echo measurements is proposed. The method efficiently fits an ultrasound backscattered signal model to the measurements in both the frequency and depth dimension simultaneously at a low computational cost. It is demonstrated that the inclusion of depth information has a positive effect particularly on the accuracy of the estimated attenuation. The sensitivity of the attenuation and backscatter coefficients’ estimates to several predefined parameters such as the window length, window overlap and usable bandwidth of the spectrum is also studied. Comparison of the proposed method with a benchmark approach based on dynamic programming highlights better performance of our method in estimating these coefficients, both in terms of accuracy and computation time. Further analysis of the computation time as a function of the predefined parameters indicates our method’s potential to be used in real-time clinical settings.