3,249 research outputs found
Depth-resolved full-field measurement of corneal deformation by optical coherence tomography and digital volume correlation
The study of vertebrate eye cornea is an interdisciplinary subject and the research on its mechanical properties has significant importance in ophthalmology. The measurement of depth-resolved 3D full-field deformation behaviour of cornea under changing intraocular pressure is a useful method to study the local corneal mechanical properties. In this work, optical coherence tomography was adopted to reconstruct the internal structure of a porcine cornea inflated from 15 to 18.75 mmHg (close to the physical porcine intraocular pressure) in the form of 3D image sequences. An effective method has been developed to correct the commonly seen refraction induced distortions in the optical coherence tomography reconstructions, based on Fermatโs principle. The 3D deformation field was then determined by performing digital volume correlation on these corrected 3D reconstructions. A simple finite element model of the inflation test was developed and the predicted values were compared against digital volume correlation results, showing good overall agreement
Three-dimensional shape analysis of peripapillary retinal pigment epithelium-basement membrane layer based on OCT radial images
The peripapillary retinal pigment epithelium-basement membrane (ppRPE/BM) layer angle was recently proposed as a potential index for estimating intracranial pressure noninvasively. However, the ppRPE/BM layer angle, measured from the optical coherence tomography (OCT) scans, varied across the radial directions of the optic disc. This made the ppRPE/BM layer angle difficult to be utilized in its full potential. In this study, we developed a mathematical model to quantify the ppRPE/BM layer angles across radial scans in relation to the ppRPE/BM 3D morphology in terms of its 3D angle and scanning tilt angles. Results showed that the variations of the ppRPE/BM layer angle across radial scans were well explained by its 3D angle and scanning tilt angles. The ppRPE/BM layer 3D angle was reversely fitted from the measured ppRPE/BM layer angles across radial directions with application to six eyes from four patients, who underwent medically necessary lumbar puncture. The fitted curve from our mathematical model matched well with the experimental measurements (R2 \u3e 0.9 in most cases). This further validated our mathematical model. The proposed model in this study has elucidated the variations of ppRPE/BM layer angle across 2D radial scans from the perspective of the ppRPE/BM layer 3D morphology. It is expected that the ppRPE/BM layer 3D angle developed in this study could be further exploited as a new biomarker for the optic disc
Multi-Energy Blended CBCT Spectral Imaging Using a Spectral Modulator with Flying Focal Spot (SMFFS)
Cone-beam CT (CBCT) spectral imaging has great potential in medical and
industrial applications, but it is very challenging as scatter and spectral
effects are seriously twisted. In this work, we present the first attempt to
develop a stationary spectral modulator with flying focal spot (SMFFS)
technology as a promising, low-cost approach to accurately solving the X-ray
scattering problem and physically enabling spectral imaging in a unified
framework, and with no significant misalignment in data sampling of spectral
projections. Based on an in-depth analysis of optimal energy separation from
different combinations of modulator materials and thicknesses, we present a
practical design of a mixed two-dimensional spectral modulator that can
generate multi-energy blended CBCT spectral projections. To deal with the
twisted scatter-spectral challenge, we propose a novel scatter-decoupled
material decomposition (SDMD) method by taking advantage of a scatter
similarity in SMFFS. A Monte Carlo simulation is conducted to validate the
strong similarity of X-ray scatter distributions across the flying focal spot
positions. Both numerical simulations using a clinical abdominal CT dataset,
and physics experiments on a tabletop CBCT system using a GAMMEX multi-energy
CT phantom, are carried out to demonstrate the feasibility of our proposed SDMD
method for CBCT spectral imaging with SMFFS. In the physics experiments, the
mean relative errors in selected ROI for virtual monochromatic image (VMI) are
0.9\% for SMFFS, and 5.3\% and 16.9\% for 80/120 kV dual-energy cone-beam scan
with and without scatter correction, respectively. Our preliminary results show
that SMFFS can effectively improve the quantitative imaging performance of
CBCT.Comment: 10 pages, 13 figure
Development of Pinhole X-ray Fluorescence Imaging System to Measure in vivo Biodistribution of Gold Nanoparticles
ํ์๋
ผ๋ฌธ(๋ฐ์ฌ)--์์ธ๋ํ๊ต ๋ํ์ :์ตํฉ๊ณผํ๊ธฐ์ ๋ํ์ ์ตํฉ๊ณผํ๋ถ,2019. 8. ์์ฑ์ค.๋ชฉ์ : ๋ณธ ์ฐ๊ตฌ์ ๋ชฉํ๋ ๊ธ๋๋
ธ์
์์ ์ฒด๋ด ๋๋ ๋ถํฌ ์ธก์ ์ ์ํ ํํ ์์ค์ ํ๊ด ์์์์คํ
์ ๊ฐ๋ฐํ๊ณ , ์๊ฐ์ ๋ฐ๋ฅธ ์ฅ์ ์ฒด๋ด ๊ธ๋๋
ธ์
์ ๋ถํฌ ์์์ ํ๋ํ์ฌ ๊ฐ๋ฐ ์์์์คํ
์ด ์ ์์์ํ์ ํ์ฉ ๊ฐ๋ฅํจ์ ์คํ์ ์ผ๋ก ์ฆ๋ช
ํ๋ ๊ฒ์ด๋ค. 2์ฐจ์ cadmium zinc telluride (CZT) ๊ฐ๋ง ์นด๋ฉ๋ผ๋ฅผ ์ฌ์ฉํ์ฌ K-shell ์์ค์ ํ๊ด ์ ํธ๋ฅผ ์ธก์ ํจ์ผ๋ก์จ, ์์ ํ๋ ์๊ฐ๊ณผ ํผํญ ๋ฐฉ์ฌ์ ๋์ ์ค์ผ ์ ์๋ค. ๋ํ, ๋ณธ ์ฐ๊ตฌ๋ ์ํ์ ๋ณต์กํ ์ ์ฒ๋ฆฌ ๊ณผ์ ์์ด ๊ธ๋๋
ธ์
์์ ์ฒด์ธ ๋๋๋ฅผ ์ธก์ ํ ์ ์๋ silicon drift detector (SDD)๋ฅผ ์ฌ์ฉํ L-shell ์์ค์ ํ๊ด ์ธก์ ์์คํ
์ ๊ฐ๋ฐํ๊ณ ์ ํ๋ค.
๋ฐฉ๋ฒ: ๊ธ๋๋
ธ์
์์ ๋๋์ K-shell ์์ค์ ํ๊ด ์ ํธ ์ฌ์ด์ ๊ต์ ๊ณก์ ์ ํ๋ํ๊ธฐ ์ํด 0.0 wt%, 0.125 wt%, 0.25 wt%, 0.5 wt%, 1.0 wt%, 2.0 wt%์ ๊ธ๋๋
ธ์
์ ์ํ์ ๋ฐ์ง๋ฆ 2.5 cm์ธ ์ํฌ๋ฆด ํฌํฐ์ ์ฝ์
ํ์ฌ 140 kVp ์์ค์ ์ 1๋ถ์ฉ ์กฐ์ฌํ์๋ค. K-shell ์์ค์ ํ๊ด ์ ํธ๋ ๊ธ๋๋
ธ์
์๊ฐ ์ฝ์
๋์ด ์๋ ์ํฌ๋ฆด ํฌํฐ์ผ๋ก๋ถํฐ ์ธก์ ํ ์์ค์ ์คํํธ๋ผ์์ ๊ธ๋๋
ธ์
์๊ฐ ์ฝ์
๋์ด ์์ง ์์ ์ํฌ๋ฆด ํฌํฐ์ผ๋ก๋ถํฐ ์ธก์ ํ ์์ค์ ์คํํธ๋ผ์ ์ฐจ์ด๋ฅผ ํตํด ์ถ์ถํ์๋ค. ๊ธ๋๋
ธ์
์ ์ฃผ์
ํ ์ธก์ ๋ฐ์ดํฐ๋ง์ผ๋ก ๊ธ๋๋
ธ์
์์ ์์ค์ ํ๊ด ์์์ ํ๋ํ๊ธฐ ์ํด ์ธ๊ณต์ง๋ฅ convolutional neural network (CNN) ๋ชจ๋ธ์ ๊ฐ๋ฐํ๊ณ ์ ์ฉํ์๋ค. ์คํ์ฉ ์ฅ๋ก๋ถํฐ ์ถ์ถํ ์ฅ๊ธฐ์ ๊ธ๋๋
ธ์
์ ๋๋ ์ธก์ ์ ์ํด L-shell ์์ค์ ํ๊ด ์์คํ
์ธก์ ์ ๊ฐ๋ฐํ์์ผ๋ฉฐ, ์ด ์์คํ
์ SDD ์ธก์ ๊ธฐ์ 40 kVp์ ์ ์์ ์ด์ฉํ์ฌ 2.34 ฮผg โ 300 ฮผg (๊ธ๋๋
ธ์
์)/30 mg (๋ฌผ) (0.0078 wt%-1.0 wt%)์ ๊ธ๋๋
ธ์
์์ L-shell ์์ค์ ํ๊ด ์ ํธ ์ฌ์ด์ ๊ต์ ๊ณก์ ์ ์ป์ด ์ฅ๊ธฐ ๋ด ์ถ์ ๋ ๊ธ๋๋
ธ์
์์ ์ง๋์ ์ธก์ ํ์๋ค.
ํํ ์์ค์ ํ๊ด ์์์์คํ
์ ์ด์ฉํ์ฌ ์คํ์ฉ ์ฅ์ ๊ธ๋๋
ธ์
์๋ฅผ ์ฃผ์
ํ ์๊ฐ์ ๋ฐ๋ฅธ ์ ์ฅ ๋ด ๊ธ๋๋
ธ์
์ ๋๋ ์์์ ํ๋ํ์๋ค. ์๋ฝ์ฌ ํ ์ ์ถํ ์์ชฝ ์ ์ฅ, ๊ฐ, ๋น์ฅ, ํ์ก์ ๊ธ๋๋
ธ์
์ ๋๋๋ฅผ L-shell ์์ค์ ํ๊ด ์ฒด์ธ ์ธก์ ์์คํ
๊ณผ ICP-AES๋ฅผ ์ฌ์ฉํ์ฌ ์ธก์ ํ์๊ณ ์์์์คํ
์ ํตํด ํ๋ํ ๋๋์ ๋น๊ตยท๊ฒ์ฆํ์๋ค. ์์ ํ๋ ์ ์คํ์ฉ ์ฅ์ ์กฐ์ฌ๋๋ ๋ฐฉ์ฌ์ ๋์ TLD๋ฅผ ์คํ์ฉ ์ฅ์ ํผ๋ถ์ ๋ถ์ฌ ์ธก์ ํ์๋ค.
๊ฒฐ๊ณผ: ์์ค์ ํ๊ด ์์ ๋ถ์์ ํตํด ์ธก์ ํ ์คํ์ฉ ์ฅ์ ์ค๋ฅธ์ชฝ ์ ์ฅ ๋ด ๊ธ๋๋
ธ์
์์ ๋๋๋ ์ฃผ์
์งํ 1.58ยฑ0.15 wt%์์ผ๋ฉฐ, 60๋ถ ํ ๊ทธ ๋๋๋ 0.77ยฑ0.29 wt%๋ก ๊ฐ์ํ์๋ค. ๊ฐ๋ฐํ ์ธ๊ณต์ง๋ฅ CNN ๋ชจ๋ธ์ ์ ์ฉํด ๊ธ๋๋
ธ์
์ ์ฃผ์
์ ์์์ ํ๋ ์์ด ๊ธ๋๋
ธ์
์์ ์์ค์ ํ๊ด ์์์ ์์ฑํ ์ ์์๋ค. ์ ์ถํ ์ฅ๊ธฐ์์ ์ธก์ ๋ ๊ธ๋๋
ธ์
์์ ์ ์ฅ ๋ด ๋๋๋ L-shell ์์ค์ ํ๊ด ์ธก์ ๋ฒ์ผ๋ก 0.96ยฑ0.22 wt%, ICP-AES๋ก๋ 1.00ยฑ0.50 wt% ์๋ค. ์์ ํ๋ ์ ์คํ์ฉ ์ฅ์ ํผ๋ถ์ ์ ๋ฌ๋ ๋ฐฉ์ฌ์ ๋์ ๊ธ๋๋
ธ์
์ ์ฃผ์
์ ๊ณผ ํ ์์์ ๋ชจ๋ ํ๋ ์(์ด 2๋ถ) 107ยฑ4 mGy, CNN ๋ชจ๋ธ ์ ์ฉ ์(1๋ถ) 53ยฑ2 mGy๋ก ์ธก์ ๋์๋ค.
๊ฒฐ๋ก : 2์ฐจ์ CZT ๊ฐ๋ง ์นด๋ฉ๋ผ์ ํํ ์ฝ๋ฆฌ๋ฉ์ดํฐ๋ฅผ ์ฌ์ฉํ ์์ค์ ํ๊ด ์์์์คํ
์ ์์ ํ๋ ์๊ฐ๊ณผ ํผํญ ๋ฐฉ์ฌ์ ๋์ ํฌ๊ฒ ๊ฐ์์์ผฐ์ผ๋ฉฐ, ์ด์์๋ ์ฅ์ ์๊ฐ์ ๋ฐ๋ฅธ ์ฒด๋ด ๊ธ๋๋
ธ์
์ ๋ถํฌ ๋ณํ๋ฅผ ์์ํ ํ ์ ์์์ ์ฆ๋ช
ํ์๋ค. ๋ํ L-shell ์์ค์ ํ๊ด ์ธก์ ์์คํ
์ ๋ณต์กํ ์ ์ฒ๋ฆฌ ๊ณผ์ ์์ด ์ฒด์ธ ๊ธ๋๋
ธ์
์์ ๋๋๋ฅผ ์ ํํ๊ฒ ์ธก์ ํ ์ ์์๋ค. ๋ณธ ๊ฐ๋ฐ ์์คํ
์ ๊ธ์๋๋
ธ์
์์ ์ฒด๋ด ๋ถํฌ ์ฐ๊ตฌ๋ฅผ ์ํ ์ ์์์ํ์ฉ ๋ถ์์์์ฅ๋น๋ก์ ํ์ฉํ ์ ์์ ๊ฒ์ผ๋ก ๊ธฐ๋ํ๋ค.Purpose: This work aims to show the experimental feasibility for a dynamic in vivo X-ray fluorescence (XRF) imaging of gold in living mice exposed to gold nanoparticles (GNPs) using polychromatic X-rays. By collecting K-shell XRF photons using a 2D cadmium zinc telluride (CZT) gamma camera, the imaging system was expected to have a short image acquisition time and deliver a low radiation dose. This study also investigated the feasibility of using an L-shell XRF detection system with a single-pixel silicon drift detector (SDD) to measure ex vivo GNP concentrations from biological samples.
Methods: Six GNP columns of 0 % by weight (wt%), 0.125 wt%, 0.25 wt%, 0.5 wt%, 1.0 wt% and 2.0 wt% inserted in a 2.5 cm diameter polymethyl methacrylate (PMMA) phantom were used for acquiring a linear regression curve between the concentrations of GNPs and the K-shell XRF photons emitted from GNPs. A fan-beam of 140 kVp X-rays irradiated the phantom for 1 min in each GNP sample. The photon spectra were measured by the CZT gamma camera. The K-shell XRF counts were derived by subtracting the photon counts of the 0 wt% PMMA phantom (i.e., pre-scanning) from the photon counts of the GNP-loaded phantom (i.e., post-scanning). Furthermore, a 2D convolutional neural network (CNN) was applied to generate the K-shell XRF counts from the post-scanned data without the pre-scanning. For a more sensitive detection of the ex vivo concentrations of GNPs in the biological samples, the L-shell XRF detection system using the single-pixel SDD was developed. Six GNP samples of 2.34 ฮผgโ300 ฮผg Au/30 mg water (i.e., 0.0078 wt%โ1.0 wt% GNPs) were used for acquiring a calibration curve to correlate the GNP mass to the L-shell XRF counts.
The kidney slices of three Balb/C mice were scanned at various periods after the injection of GNPs in order to acquire the quantitative information of GNPs. The concentrations of GNPs measured by the CZT gamma camera and the SDD were cross-compared and then validated by inductively coupled plasma atomic emission spectroscopy (ICP-AES). The radiation dose was assessed by the measurement of TLDs attached to the skin of the mice.
Results: The K-shell XRF images showed that the concentration of GNPs in the right kidneys from the mice was 1.58ยฑ0.15 wt% at T = 0 min after the injection. At T = 60 min after the injection, the concentration of GNPs in the right kidneys was reduced to 0.77ยฑ0.29 wt%. The K-shell XRF images generated by the 2D CNN were similar to those derived by the direct subtraction method. The measured ex vivo concentration of GNPs was 0.96ยฑ0.22 wt% by the L-shell XRF detection system while it was 1.00ยฑ0.50 wt% by ICP-AES. The radiation dose delivered to the skin of the mice was 107ยฑ4 mGy for acquiring one slice image by using the direct subtraction method while it was 53ยฑ2 mGy by using the 2D CNN.
Conclusions: A pinhole K-shell XRF imaging system with a 2D CZT gamma camera showed a dramatically reduced scan time and delivered a low radiation dose. Hence, a dynamic in vivo XRF imaging of gold in living mice exposed to GNPs was technically feasible in a benchtop configuration. In addition, an L-shell XRF detection system can be used to measure ex vivo concentrations of GNPs in biological samples. This imaging system could provide a potential in vivo molecular imaging for metal nanoparticles to emerge as a radiosensitizer and a drug-delivery agent in preclinical studies.CHAPTER I. INTRODUCTION 1
I.1 Applications of Metal Nanoparticles in Medicine 1
I.2 Molecular Imaging of Metal Nanoparticles 3
I.3 X-ray Fluorescence Imaging 5
I.3.1 Principle of X-ray Fluorescence Imaging 5
I.3.2 History of X-ray Fluorescence Imaging 8
I.3.3 Specific Aims 12
CHAPTER II. MATERIAL AND METHODS 15
II.1 Monte Carlo Model 15
II.1.1 Geometry of Monte Carlo Simulations 15
II.1.2 Image Processing 21
II.1.3 Radiation Dose 27
II.2 Development of Pinhole K-shell XRF Imaging System 28
II.2.1 System Configuration and Operation Scheme 28
II.2.2 Pinhole K-shell XRF Imaging System 31
II.2.2.1 Experimental Setup 31
II.2.2.2 Measurement of K-shell XRF Signal 36
II.2.2.3 Signal Processing: Correction Factors 39
II.2.2.4 Application of Convolutional Neural Network 42
II.2.3 K-shell XRF Detection System 45
II.2.3.1 Experimental Setup 45
II.2.3.2 Signal Processing 47
II.2.4 L-shell XRF Detection System 49
II.2.4.1 Experimental Setup 49
II.2.4.2 Signal Processing 51
II.3 In vivo Study in Mice 53
II.3.1 Experimental Setup 53
II.3.2 Dose Measurement 56
CHAPTER III. RESULTS 57
III.1 Monte Carlo Model 57
III.1.1 Geometric Efficiency, System and Energy Resolution 57
III.1.2 K-shell XRF Image by Monte Carlo Simulations 59
III.1.3 Radiation Dose 69
III.2. Development of Pinhole XRF Imaging System 70
III.2.1 Pinhole K-shell XRF Imaging System 70
III.2.1.1 Energy Calibration and Measurement of Field Size 70
III.2.1.2 Raw K-shell XRF Signal 73
III.2.1.3 Correction Factors 78
III.2.1.4 K-shell XRF Image 81
III.2.2 K-shell XRF Detection System 85
III.2.3 L-shell XRF Detection System 89
III.3 In vivo Study in Mice 92
III.3.1 In vivo K-shell XRF Image 92
III.3.2 Quantification of GNPs in Living Mice 96
III.3.3 Dose Measurement 101
CHAPTER IV. DISCUSSION 102
IV.1 Monte Carlo Model 102
IV.2 Development of Pinhole K-shell XRF Imaging System 104
IV.2.1 Quantification of GNPs 105
IV.2.2 Comparison between MC and Experimental Results 107
IV.2.3 Limitations 108
IV.2.3.1 Concentration 108
IV.2.3.2 System Resolution 110
IV.2.3.3 Radiation Dose 111
IV.2.4 Application of CNN 112
IV.2.5 Future Work 114
CHAPTER V. CONCLUSIONS 115
REFERENCES 116
ABSTRACT (in Korean) 123Docto
Relevance of accurate Monte Carlo modeling in nuclear medical imaging
Monte Carlo techniques have become popular in different areas of medical physics with advantage of powerful computing systems. In particular, they have been extensively applied to simulate processes involving random behavior and to quantify physical parameters that are difficult or even impossible to calculate by experimental measurements. Recent nuclear medical imaging innovations such as single-photon emission computed tomography (SPECT), positron emission tomography (PET), and multiple emission tomography (MET) are ideal for Monte Carlo modeling techniques because of the stochastic nature of radiation emission, transport and detection processes. Factors which have contributed to the wider use include improved models of radiation transport processes, the practicality of application with the development of acceleration schemes and the improved speed of computers. This paper presents derivation and methodological basis for this approach and critically reviews their areas of application in nuclear imaging. An overview of existing simulation programs is provided and illustrated with examples of some useful features of such sophisticated tools in connection with common computing facilities and more powerful multiple-processor parallel processing systems. Current and future trends in the field are also discussed
Propiedades รณpticas y estructurales del cristalino: acomodaciรณn y envejecimiento
Tesis inรฉdita de la Universidad Complutense de Madrid, Facultad de Ciencias Fรญsicas, Departamento de รptica, leรญda el 12-01-2015Depto. de รpticaFac. de Ciencias FรญsicasTRUEunpu
Flexible Attenuation Fields: Tomographic Reconstruction From Heterogeneous Datasets
Traditional reconstruction methods for X-ray computed tomography (CT) are highly constrained in the variety of input datasets they admit. Many of the imaging settings -- the incident energy, field-of-view, effective resolution -- remain fixed across projection images, and the only real variance is in the detector\u27s position and orientation with respect to the scene. In contrast, methods for 3D reconstruction of natural scenes are extremely flexible to the geometric and photometric properties of the input datasets, readily accepting and benefiting from images captured under varying lighting conditions, with different cameras, and at disparate points in time and space. Extending CT to support similar degrees of flexibility would significantly enhance what can be learned from tomographic datasets. We propose that traditionally complicated or time-consuming tomographic tasks, such as multi-resolution and multi-energy analysis, can be more readily achieved with a reconstruction framework which explicitly accepts datasets with varied imaging settings. This work presents a CT reconstruction framework specifically designed for datasets with heterogeneous capture properties which we call Flexible Attenuation Fields (FlexAF). Built on differentiable ray tracing and continuous neural volumes, FlexAF accepts X-ray images captured from any position and orientation in the world coordinate frame, including images which differ in size, resolution, field-of-view, and photometric settings. This method produces reconstructions for regular CT scans which are comparable to those produced by filtered backprojection, demonstrating that additional flexibility does not fundamentally hinder the ability to reconstruct high-quality volumes. Our experiments test the expanded capabilities of FlexAF for addressing challenging reconstruction tasks, including automatic camera calibration and reconstruction of multi-resolution and multi-energy volumes
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