calibration phantom
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Author(s):  
Victor Merza ◽  
Christian HRANITZKY ◽  
Andreas STEURER ◽  
Franz Josef MARINGER

Abstract In this article, the proposal of ICRU/ICRP, that the ISO slab phantom should continue to be used as calibration phantom for the new ICRU Report 95 operational quantity personal dose should be legitimized by simulation and performance of experiments to determine backscatter factors on the ISO slab phantom and, in comparison, on an anthropomorphic Alderson Rando phantom. The scope of this work was restricted to the photon energy range of radiation qualities commonly used in X-ray diagnostics. For this purpose, a shadow-free diagnostic (SFD) ionization chamber was used to measure backscatter factors for X radiation in the energy range of 24 keV to 118 keV. The Monte Carlo code MCNP 6.2 was used to validate measurement results on the ISO slab phantom. Additionally, the influence of varying the SFD position on the Rando phantom on the backscatter factor was determined. Since backscatter factors on the ISO slab phantom differ only up to 5 % from those on the Rando phantom, it could be concluded that it is not necessary to develop a new phantom for calibrations in terms of personal dose. A position variation of the detector by few centimeters on the surface of the Rando phantom causes similarly large deviations and thus alone represents an equally large uncertainty contribution in practical personal dosimetry than that arising from the dissimilarity of the real human body to the ISO slab phantom.


Author(s):  
Ki-Cheol Yoon ◽  
Kwang Gi Kim

Abstract For diagnosis of the secondary lymphedema, amplitude mode (A-mode) examination using a single ultrasound probe has been suggested as one of possible diagnostic modalities due to its relatively low cost, ease of usage, and mobility. However, A-mode ultrasound waves with respect to time have lots of noise and are complicated to analyze and achieve well correlated information related to change in volume of each layer of skin and subcutaneous tissues. Thus, development of adequate ultrasound calibration phantom is needed. For this, fundamental study on proper phantom materials which show acoustic characteristics of skin and subcutaneous tissues are needed. In this research, the fabrication method for ultrasonic phantom using gelatin material is presented in a wide range of acoustic impedance and their acoustic characteristics and usability were discussed.


2021 ◽  
Author(s):  
E Courtney Henry ◽  
Matthew Strugari ◽  
George Mawko ◽  
Kimberly Brewer ◽  
David Liu ◽  
...  

Abstract Purpose To perform precision dosimetry in yttrium-90 radioembolization through CT imaging of radiopaque microspheres in a rabbit liver model, and to compare extracted dose metrics to those produced from conventional PET-based dosimetry. Materials and Methods A CT calibration phantom was designed to contain posts having nominal microsphere concentrations of 0.5 mg/mL, 5.0 mg/mL, and 25.0 mg/mL. The mean Hounsfield unit was extracted from the post volumes to generate a calibration curve to relate Hounsfield units to microsphere concentration. A nominal bolus of 40 mg of microspheres was administered to the livers of 8 rabbits followed by PET/CT imaging. A CT-based activity distribution was calculated through the application of the calibration curve to the CT liver volume. Post-treatment dosimetry was performed through the convolution of yttrium-90 dose-voxel kernels and the PET- and CT-based cumulated activity distributions. The mean dose to the liver in PET- and CT-based dose distributions was compared through linear regression, ANOVA, and Bland-Altman analysis. Results A linear least-squares fit to the average Hounsfield unit and microsphere concentration data in the calibration phantom confirmed a strong correlation (r2 > 0.999) with a slope of 14.13 HU/mg/mL. A poor correlation was found between the mean dose derived from CT and PET (r2 = 0.374) while the ANOVA analysis revealed statistically significant differences (p < 10–12) between the MIRD-derived mean dose and the PET- and CT-derived mean dose. Bland-Altman analysis predicted an offset of 15.0 Gy between the mean dose in CT and PET. The dose within the liver was shown to be more heterogeneous in CT than in PET with an average coefficient of variation equal to 1.99 and 1.02, respectively. Conclusion The benefits of a CT-based approach to post-treatment dosimetry in yttrium-90 radioembolization include improved visualization of the dose distribution, reduced partial volume effects, a better representation of dose heterogeneity, and the mitigation of respiratory motion effects. Post-treatment CT imaging of radiopaque microspheres in yttrium-90 radioembolization provides the means to perform precision dosimetry and extract accurate dose metrics used to refine the understanding of the dose-response relationship, which can permit an individualized approach to treatment planning that translates into improved patient outcomes.


2021 ◽  
Author(s):  
Kai Mei ◽  
Michael Geagen ◽  
Leonid Roshkovan ◽  
Harold I. Litt ◽  
Grace J. Gang ◽  
...  

Purpose: Phantoms are a basic tool for assessing and verifying performance in CT research and clinical practice. Patient-based realistic lung phantoms accurately representing textures and densities are essential in developing and evaluating novel CT hardware and software. This study introduces PixelPrint, a 3D printing solution to create patient-based lung phantoms with accurate attenuation profiles and textures. Methods: PixelPrint, a software tool, was developed to convert Patient DICOM images directly into printer instructions (G-code). The density was modeled as the ratio of filament to voxel volume to emulate attenuation profiles for each voxel. A calibration phantom was designed to determine the mapping between filament line width and Hounsfield Units (HU) within the range of human lungs. For evaluation of PixelPrint, a phantom based on a human lung slice was manufactured and scanned with the same CT scanner and protocol used for the patient scan. Density and geometrical accuracy between phantom and patient CT data was evaluated for various anatomical features in the lung. Results: For the calibration phantom, measured mean Hounsfield units show a very high level of linear correlation with respect to the utilized filament line widths, (r > 0.999). Qualitatively, the CT image of the patient-based phantom closely resembles the original CT image both in texture and contrast levels, with clearly visible vascular and parenchymal structures. Regions-of-interest (ROIs) comparing attenuation illustrated differences below 15 HU. Manual size measurements performed by an experienced thoracic radiologist reveal a high degree of geometrical correlation of details between identical patient and phantom features, with differences smaller than the intrinsic spatial resolution of the scans. Conclusion: The present study demonstrates the feasibility of 3D printed patient-based lung phantoms with accurate organ geometry, image texture, and attenuation profiles. PixelPrint will enable applications in the research and development of CT technology, including further development in radiomics.


Animals ◽  
2021 ◽  
Vol 11 (5) ◽  
pp. 1413
Author(s):  
Glynn Woods ◽  
Nicolas Israeliantz Gunz ◽  
Ian Handel ◽  
Tiziana Liuti ◽  
Richard J. Mellanby ◽  
...  

Despite bone mineral density (BMD) being regularly measured in human patients, BMD studies in clinical cohorts of dogs is lacking. In order to facilitate BMD assessment and in turn better identify dogs suffering from metabolic bone disease, rapid, easy and precise computed tomography (qCT) techniques are required. In this study we aimed to assess the utility of quantitative computed tomography (qCT) bone mineral density (BMD) measurement of the canine calvarium using a semiautomated osteodensitometry software and define host factors associated with canine bone mineral density in a skeletally healthy population. Calvarial qCT at the level of the temporomandibular joints was performed on 323 dogs using a dedicated osteodensitometry calibration phantom during a clinically indicated head computed tomography (CT). Calvarial BMD was analyzed using a dedicated semiautomatic osteodensitometry software for contouring of the calvarial lamellar bone margins and BMD calculation. The mean duration of the calvarial qCT scanning was 64.6 s, and the mean duration of BMD analysis was 34 s, with a mean of two manual adjustments required for the bone margin tracing. The median BMD of all dogs in our study was 659 mg Calcium hydroxyapatite/mL. There was a negative linear correlation between BMD and body weight, but no correlation with age, sex or neutered status. Canine BMD assessment using qCT of the calvarium is a practical and fast technique that can be added to a clinical CT examination with minimal extra time requirements. Canine BMD host-dependent factors exhibit different relationships from that of humans; however, further investigation is warranted.


2021 ◽  
Vol 53 (1) ◽  
pp. 15
Author(s):  
Tihomir P Georgiev ◽  
Iliyan Kolev ◽  
Nikolay Dukov ◽  
Stanislava Mavrodinova ◽  
Mariana Yordanova ◽  
...  

2020 ◽  
Author(s):  
Cristóbal Martinez ◽  
Claudia de Molina ◽  
Manuel Desco ◽  
Mónica Abella
Keyword(s):  

2020 ◽  
Vol 10 (1) ◽  
Author(s):  
Koichi Okuda ◽  
Kenichi Nakajima ◽  
Chiemi Kitamura ◽  
Yumiko Kirihara ◽  
Mitsumasa Hashimoto ◽  
...  

AbstractThe 123I-labeled meta-iodobenzylguanidine (MIBG) is an analogue of noradrenaline that can evaluate cardiac sympathetic activity in scintigraphy. Quantitative analysis of 123I-MIBG images has been verified in patients with heart failure and neurodegenerative diseases. However, quantitative results differ due to variations in scintigraphic imaging procedures. Here, we created and assessed the clinical feasibility of a calibration method for 123I-MIBG imaging. The characteristics of scintigraphic imaging systems were determined using an acrylic calibration phantom to generate a multicenter phantom imaging database. Calibration factors corresponding to the scintigraphic imaging procedures were calculated from the database and applied to a clinical study. The results of this study showed that the calibrated analysis eliminated inter-institutional differences among normal individuals. In summary, our standardization methodology for 123I-MIBG scintigraphy could provide the basis for improved diagnostic precision and better outcomes for patients.


2020 ◽  
Author(s):  
Антон Yu. Silin ◽  
Ivan S. Gruzdev ◽  
Sergey P. Morozov

Background: One of the ways to reduce the radiation dose in CT is to improve image reconstruction algorithms. The latest offer from scanner manufacturers is Model Iterative Reconstruction (MIR). Aims: To compare the quality of visualization of the structures of the organs of the chest and to prove the effectiveness of the low-dose protocol with iterative model reconstruction. Materials and methods: A calibration phantom with a spatial resolution module and an anthropomorphic phantom of the upper body of an adult with nodules in the lungs was scanned on two CT scanners of different manufacturers using the standard dose protocol (SDCT) with algorithms of hybrid iterative reconstruction (HIR) of images and MIR and low-dose protocol (LDCT) and MIR algorithm. The quality of the obtained images was evaluated by the parameters: noise (SD), the contrast-to-noise ratio (CNR), spatial resolution and visualization of pulmonary nodules. The radiation dose was calculated according to the scanner data, the data of individual dosimeters placed on the anthropomorphic phantom, and using a dosimetric phantom. Results: The average SD was 11.5; 24.4 and 21.6; CNR 85.47; 40.6 and 45.6; spatial resolution 2 mm; 2 mm and 3 mm for SDCT with MIR, SDCT with HIR and LDCT with MIR, respectively. Visualization of pulmonary lesions remained excellent in all cases. The radiation dose in case of SDCT was 2.7, and in case of LDCT - 0.67 mSv. The dose reduction was confirmed by dosimeter data. Similar results were obtained by repeating the experiment on a second scanner. Conclusions: The average SD was 11.5; 24.4 and 21.6; CNR 85.47; 40.6 and 45.6; spatial resolution 2 mm; 2 mm and 3 mm for SDCT with MIR, SDCT with HIR and LDCT with MIR, respectively. Visualization of pulmonary lesions remained excellent in all cases. The radiation dose in case of SDCT was 2.7, and in case of LDCT - 0.67 mSv. The dose reduction was confirmed by dosimeter data. Similar results were obtained by repeating the experiment on a second scanner.


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