Predefined attenuation coefficientsAbsorptiometryTissueCorrectionCorticalBeamElectronScatterMalignantPeripheralSkeletalDensityOsteoporosisMetastasisPediatricPhantomDoseTissuesFemurComputed tomographyAccurateIntensityConventionalDecreasePelvisClinicalApoptosisLinearConclusionMeasurementDual-energyLossSimilarEnergyPatientsRatesTotalSingleImagesYoungHighTime
Predefined attenuation coefficients1
- MRAC maps were derived by segmenting the MR images into 4 tissue classes and assigning predefined attenuation coefficients. (snmjournals.org)
Absorptiometry4
- Single and dual-energy photon absorptiometry utilized radionuclide sources. (boneandspine.com)
- Bone mineral density in the femoral neck and distal femur was measured using dual energy X-ray absorptiometry before training, immediately after the initial 3 months of training, and at the end of the subsequent 3 months. (tmu.edu.tw)
- Studies using dual-photon or -energy X-ray absorptiometry (DXA) had reported a prevalence of osteoporosis (i.e. (her2-signaling.com)
- Dual-energy X-ray absorptiometry (DXA) was introduced in the mid-1980s as a rapid and safe imaging modality to estimate bone mineral density (BMD) and predict skeletal fracture risk [ 2 ]. (biomedcentral.com)
Tissue9
- For patients with bone or soft-tissue sarcoma, malignant melanoma, or head and neck carcinoma, CT scanning of the chest should be performed as an initial evaluation. (medscape.com)
- A coregistered bone probability map was also included in the unknown tissue class. (snmjournals.org)
- Finally, the GMM prior was constrained over known tissue classes of attenuation maps using unimodal gaussians parameterized over a patient population. (snmjournals.org)
- The results showed that the MLAA-GMM algorithm outperformed the MRAC method by differentiating bones from air gaps and providing more accurate patient-specific attenuation coefficients of soft tissue and lungs. (snmjournals.org)
- In addition, lung tissues and cortical bones, which are 2 important tissue types in attenuation maps, exhibit low signals on images acquired using conventional MR pulse sequences because of their low water content and short transverse relaxation time. (snmjournals.org)
- In these methods, MR images are segmented into 3 or 4 tissue classes-that is, background air, lung, and fat and nonfat soft tissues-and predefined constant attenuation coefficients are assigned to each tissue class ( 6 , 7 ). (snmjournals.org)
- However, inter- and intrapatient heterogeneity of attenuation coefficients in the different tissue classes is ignored by these approaches. (snmjournals.org)
- CONCLUSIONS The challenges of pseudarthrosis, like bone defects and compromised tissue, highlight the need for precise implant selection based on evaluations of bone quality, defects, knee stability, and hyperextension, rather than resorting to overly-constrained implants. (bvsalud.org)
- By Osteoporosis is a skeletal disease, characterized by low bone mass and micro-architectural deterioration of bone tissue, with a consequent increase in bone fragility and susceptibility to fracture. (boneandspine.com)
Correction6
- The joint maximum-likelihood reconstruction of activity and attenuation (MLAA) for emission-based attenuation correction has regained attention since the advent of time-of-flight PET/MR imaging. (snmjournals.org)
- In this study, we compare the performance of our proposed algorithm with standard 4-class MR-based attenuation correction (MRAC) implemented on commercial systems. (snmjournals.org)
- Accurate attenuation correction (AC) of PET data is one of the major challenges of quantitative PET/MR imaging ( 2 ). (snmjournals.org)
- In this review article, we will discuss the mechanisms of these artifacts and suggest solutions to reduce or eliminate them, such as reviewing the non-attenuation-corrected PET images, performing extended-field-of-view reconstruction, not applying scatter correction, and using software to correct beam-hardening, scatter, and truncation artifacts. (snmjournals.org)
- Although not causing significant image artifacts on PET images, beam hardening, if severe, may cause suboptimal attenuation correction (AC), a reduction in the detectability of small lesions, or inaccurate or suboptimal SUVs ( Fig. 1 ). (snmjournals.org)
- Influence of Attenuation Correction by Brain Perfusion SPECT/CT Using a Simulated Abnormal Bone Structure: Comparison Between Chang and CT Methods. (kanazawa-u.ac.jp)
Cortical3
- In recent years, better CT technology and the advantages of CT over DXA in the differentiation of cortical and trabecular bone mineral density and others, the use of quantitative computed tomography in musculoskeletal research studies is increasing. (boneandspine.com)
- Anti-resorptive medications (bisphosphonates and denosumab) primarily increase endocortical bone by bolstering mineralization of endosteal resorption pits and thereby increase cortical thickness and reduce cortical porosity. (biomedcentral.com)
- Anabolic medications (teriparatide and abaloparatide) increase the periosteal and endosteal perimeters without large changes in cortical thickness resulting in a larger more structurally sound bone. (biomedcentral.com)
Beam10
- These arise because of the higher linear attenuation of most materials at lower energy which shifts the mean energy of the X-ray spectrum towards higher energies as the beam passes through the object. (wikipedia.org)
- By comparing the ratios of counts in different energy bins with those of the attenuated beam, the amount of beam hardening can be accounted for (either explicitly or implicitly in the reconstruction) using a PCD. (wikipedia.org)
- These artifacts include beam hardening and scatter artifacts between the right and left arm bones, truncation artifacts, photopenic or cold areas (cold artifacts) in the soft tissues and bones in the abdomen and pelvis in obese or large patients, artifacts related to arm motion, artifacts caused by metal objects in the arms, and artifacts from extravasated activity at the injection site. (snmjournals.org)
- Beam-hardening and scatter artifacts can occur between the right and left arm bones on CT images and may result in inadequate correlation of CT data with PET images, mimic pathologic conditions, or result in inaccurate Hounsfield units if the artifacts are severe ( 2 - 4 ). (snmjournals.org)
- Beam-hardening and scatter artifacts are produced by different mechanisms but appear as multiple linear bands or streaks between two high-attenuation objects (bone, metal, or barium) on CT images ( Fig. 1 ) ( 3 ). (snmjournals.org)
- When the x-ray beam passes through the body, low-energy x-ray photons are attenuated more easily than high-energy photons, which is a particular problem with high atomic number objects (bone, iodine, or metal) ( 5 ). (snmjournals.org)
- Research in one group showed that back-scattering from bone-titanium interfaces of mandibular implants can be appreciated to nearly -14% in a 6 MY X-ray beam. (experts.com)
- A significant discovery of -51.5% attenuation was announced for one port in a 9 MeV electron beam. (experts.com)
- It has only recently been suggested that electron beam attenuation through nonmetal ports may be clinically feasible. (experts.com)
- Attenuation coefficient quantifies how much the beam is "attenuated", i.e., weakened by the material it is passing through. (boneandspine.com)
Electron1
- However, in contrast to CT, MR imaging signals are not correlated with electron density and photon-attenuating properties of tissues but rather to proton density and magnetic relaxation properties. (snmjournals.org)
Scatter1
- Researchers have investigated consequences of attenuation and scatter through various metals and involving highdensity prosthetics. (experts.com)
Malignant2
- Bone-modifying agents (BMAs), with bone-resorptive inhibitory effects, such as zoledronic acid and denosumab, are widely used at higher doses for bone-related events caused by bone metastasis of malignant tumors. (bvsalud.org)
- Osteosarcoma (OS), the most common primary malignant bone tumor in adolescents and young adults, is known to be highly aggressive and cause progressive bone destruction ( 1 ). (iiarjournals.org)
Peripheral3
- Note attenuated vessels and peripheral pigmentary changes. (aao.org)
- Older individual (30s) with RDH12 mutations and a macular atrophic lesion, as well as attenuated blood vessels and peripheral pigmentary changes. (aao.org)
- Dedicated peripheral CT scanners to measure BMD and bone morphology in the radius and tibia are smaller, more mobile and less expensive that whole-body CT scanners. (boneandspine.com)
Skeletal3
- Hepatic osteodystrophy in the form of osteoporosis (i.e., low bone mass with microarchitectural disruption and skeletal PD-0332991 supplier fragility) resulting in an increased risk of fracture, particularly at the spine, hip, wrist, humerus, and pelvis, is a well-known complication of primary biliary cirrhosis (PBC). (her2-signaling.com)
- This review retreats to basic principles in order to advance clinical management of fragility fractures by examining how skeletal biomechanics, size, shape, and ultra-structural properties are the ultimate predictors of bone strength. (biomedcentral.com)
- 3 Inflammatory myofibroblastic tumour appears as a hypo or iso-attenuating mass compared with skeletal muscle depending on the amount of myxoid or collagenous stroma, respectively. (sajr.org.za)
Density12
- Quantitative computed tomography is a procedure which uses CT scan for quantitative assessment of the bones or bone mineral density. (boneandspine.com)
- There are various methods to estimate bone mineral density in osteoporosis. (boneandspine.com)
- Quantitative computed tomography is used to quantify bone mineral density in the spine, proximal femur, forearm, and tibia. (boneandspine.com)
- Quantification of bone mineral density with QCT is independent of bone size, which is not the case for DXA. (boneandspine.com)
- In spine, quantitative computed tomography gauges mineral density is gauged from analyzing the vertebral bones. (boneandspine.com)
- Objective: To determine whether bone mineral density loss after spinal cord injury can be attenuated by an early intervention with functional electrical stimulation cycling exercises (FESCE) and to ascertain whether the effect persists after FESCE is discontinued. (tmu.edu.tw)
- Results: The bone mineral density decrease rate in the distal femur in the FESCE group was significantly less than that in the control group during the initial 3 months. (tmu.edu.tw)
- Conclusion: FESCE in the early stages of spinal cord injury can partly attenuate bone mineral density loss in the distal femur. (tmu.edu.tw)
- However, bone mineral density loss in the distal femur cannot be ameliorated completely by FESCE. (tmu.edu.tw)
- DXA scanners generate 2 dimensional images of complex 3 dimensional structures, and report bone density as the quotient of the bone mineral content divided by the bone area. (biomedcentral.com)
- An obvious pitfall of this method is that a larger bone will convey superior strength, but may in fact have the same bone density as a smaller bone. (biomedcentral.com)
- Current osteoporosis medications increase bone density and reduce fracture risk but the mechanisms of these actions vary. (biomedcentral.com)
Osteoporosis1
- Bone histomorphometry in hypogonadal and eugonadal men with spinal osteoporosis. (jamanetwork.com)
Metastasis1
- To investigate the clinical features including bone union time of AFFs in patients administered BMA for bone metastasis, we conducted a retrospective multicenter study. (bvsalud.org)
Pediatric1
- Reducing the small-heart effect in pediatric gated myocardial perfusion single-photon emission computed tomography. (kanazawa-u.ac.jp)
Phantom1
- To transform HU into bone mineral equivalents an appropriate bone mineral phantom is included in the scan field. (boneandspine.com)
Dose2
- Some early research has found the dose reduction potential of photon-counting CT for breast imaging to be very promising. (wikipedia.org)
- For locations beyond the device, the maximum change in dose was found to be as much as -16.8% in attenuation for 6 MV photons and -7.2% for 18 MY photons. (experts.com)
Tissues1
- It was found that the MRAC and MLAA-GMM methods resulted in average standardized uptake value errors of -5.4% and -3.5% in the lungs, -7.4% and -5.0% in soft tissues/lesions, and -18.4% and -10.2% in bones, respectively. (snmjournals.org)
Femur1
- In addition, the effect on the attenuation of bone loss in the distal femur faded once FESCE was discontinued. (tmu.edu.tw)
Computed tomography1
- Photon-counting computed tomography (PCCT) is a form of X-ray computed tomography (CT) in which X-rays are detected using a photon-counting detector (PCD) which registers the interactions of individual photons. (wikipedia.org)
Accurate1
- The proposed MLAA algorithm is promising for accurate derivation of attenuation maps on time-of-flight PET/MR systems. (snmjournals.org)
Intensity3
- These EIDs thus register only photon intensity, comparable to black-and-white photography, whereas PCDs register also spectral information, similar to color photography. (wikipedia.org)
- The increase in ipsilateral signal intensity was attenuated by hypothermia. (biomedcentral.com)
- Hypothermia attenuated both the optical increase in intensity after MMPSense750 and the increase in MMP-9 protein expression supporting the proof of concept that NIRF imaging using MMPSense can be used to assess potential therapeutic strategies for stroke treatment. (biomedcentral.com)
Conventional2
- In contrast, more conventional CT scanners use energy-integrating detectors (EIDs), where the total energy (generally from a large number of photons as well as electronic noise) deposited in a pixel during a fixed period of time is registered. (wikipedia.org)
- First, it makes it possible to quantitatively determine the material composition of each pixel in the reconstructed CT image, as opposed to the estimated average linear attenuation coefficient obtained in a conventional CT scan. (wikipedia.org)
Decrease1
- For photons only, attenuation was found to be -17.5% for 6 MV and -10% for IS MY.6 For each of these efforts, attenuation was found to decrease with increasing energy. (experts.com)
Pelvis1
- Although it occurs most frequently in the metaphyses of long bones, tumor localization in the pelvis, spine or skull may be challenging due to adjacent neurovascular structures. (iiarjournals.org)
Clinical2
- As of January 2021 photon-counting CT is in use at five clinical sites. (wikipedia.org)
- On September 29, 2021 the FDA cleared the first photon-counting CT (developed by Siemens Healthineers) for clinical use. (wikipedia.org)
Apoptosis1
- Background/Aim: Cold atmospheric plasma (CAP) attenuates tumor cell proliferation and induces apoptosis in various cell lines. (iiarjournals.org)
Linear1
- The scale is obtained from a linear transformation of the measured attenuation coefficients. (boneandspine.com)
Conclusion1
- Conclusion: CAP treatment attenuates cell proliferation of OS cancer cells and fibroblasts in a treatment time-dependent manner, whereby U2-OS cells appeared more sensitive to CAP treatment as 3T3 fibroblasts after 10 sec of treatment. (iiarjournals.org)
Measurement1
- The goal is the measurement of bone strength, to predict fractures, and to differentially assess the effects of aging and treatment. (boneandspine.com)
Dual-energy1
- I completed my PhD in Electrical Engineering at Stanford under the supervision of Dr. Norbert Pelc, developing strategies for maximizing the information content of dual energy CT and photon counting detectors. (stanford.edu)
Loss2
- The above-listed measures should be adopted universally in all patients with PBC, not only in postmenopausal women, to reduce bone loss. (her2-signaling.com)
- Because of the differences in the mechanisms of the various drugs, there are likely benefits of selecting a treatment based on a patient's unique bone structure and pattern of bone loss. (biomedcentral.com)
Similar1
- Similar risk attenuation was not evident in time-windows-based models. (cdc.gov)
Energy4
- When a photon interacts in a PCD, the amplitude of the resulting electrical pulse is roughly proportional to the photon energy. (wikipedia.org)
- By comparing each pulse produced in a pixel with a suitable low-energy threshold, contributions from low-energy events (resulting from both photon interactions and electronic noise) can be filtered out. (wikipedia.org)
- This effectively eliminates contributions from electronic noise at the expense of discarding photons with energy comparable to the noise level (which are of little use since they are indistinguishable from noise counts). (wikipedia.org)
- Each registered photon is thus assigned to a specific bin depending on its energy, such that each pixel measures a histogram of the incident X-ray spectrum. (wikipedia.org)
Patients1
- T-score ≤−2.5, i.e., a value for bone mineral densitometry [BMD] 2.5 or more standard deviations below the check details young adult reference mean) in patients with PBC varying from 14% to 52%, with an additional 30%-50% suffering from osteopenia (i.e. (her2-signaling.com)
Rates2
- Due to the large volumes and rates of data required (up to several hundred million photon interactions per mm2 and second) the use of PCDs in CT scanners has become feasible only with recent improvements in detector technology. (wikipedia.org)
- Attenuation rates varied between cell lines, plasma sources and application times. (iiarjournals.org)
Total1
- The "total" reflection is indeed total if the external medium is lossless (perfectly transparent), continuous, and of infinite extent, but can be conspicuously less than total if the evanescent wave is absorbed by a lossy external medium (" attenuated total reflectance "), or diverted by the outer boundary of the external medium or by objects embedded in that medium ("frustrated" TIR). (wikipedia.org)
Single1
- We present single photon sensitive 2D camera chips containing 88x88 avalanche photo diodes which can be read out in full frame mode with up to 400.000 frames per second. (infn.it)
Images1
- In these systems, attenuation maps at 511 keV should ideally be derived from the acquired MR images. (snmjournals.org)
Young1
- Myopic-looking fundus with slight attenuation of the vasculature in this young child with RPE65 mutations. (aao.org)
High1
- Bone, absorb more X-rays, have a high HU number and appear white on the image. (boneandspine.com)
Time2
- Ultrashort-echo-time (UTE) and zero-echo-time (ZTE) MR pulse sequences have been investigated for the detection and visualization of bones as well as lung parenchyma ( 3 - 5 ). (snmjournals.org)
- For heavy samples (i.e., more attenuating) like rocks, soil, cement, etc., the scanning time with the 2x objective is ~90 min and with the 5x objective is ~30 min. (cnpem.br)