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1.
Quintessence Int ; 51(3): 238-245, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32020134

RESUMO

OBJECTIVES: Replacing conventional round intraoral collimators with rectangular collimators provides a considerable radiation dose reduction in adult patients. This study aimed to determine the radiation dose reduction via mathematical phantom when converting from round to appropriately sized rectangular collimation in children ages 5 to 15 years. METHOD AND MATERIALS: Virtual full mouth series (FMX) were simulated using a commercially available radiation dose software. This software is designed to calculate patient radiation doses from x-ray exams for various age pediatric and adult mathematical phantoms. For this pediatric study an 18-image FMX was simulated for the 15-year-old and a 12-image FMX was simulated for the 5-year-old and 10-year-old pediatric phantoms. An area of 12.0 to 16.8 cm2 represented rectangular collimation, while a 20.4 to 31.7 cm2 area represented typical round collimation. RESULTS: Effective doses decreased in all ages by nearly 60% when switching from 31.7 cm2 round to 12.0 cm2 rectangular collimation. Reduction in absorbed doses to the thyroid (70% to 73%), salivary glands (62% to 78%), and active bone marrow (60% to 62%) were also noted when switching from the largest to smallest collimation. CONCLUSION: This study suggests the use of rectangular collimators provides clinically relevant dose reduction for pediatric patients, even when altering from smaller round to rectangular collimation with equivalent beam quality, and this information can be utilized in all dental practices.


Assuntos
Software , Glândula Tireoide , Adolescente , Adulto , Criança , Pré-Escolar , Humanos , Imagens de Fantasmas , Doses de Radiação
2.
J Comput Assist Tomogr ; 44(1): 32-36, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-31939879

RESUMO

OBJECTIVE: To evaluate the effect of ultra high-resolution computed tomography (UHRCT) and model-based iterative reconstruction (MBIR) on the detectability of simulated submillimeter artery. METHODS: A small vessel phantom ranging from 0.4 to 2.0 mm in diameter and edge phantoms of low to high attenuation values were scanned by UHRCT (super-high-resolution mode and normal-resolution-mode) and conventional CT, and data were reconstructed by MBIR and filtered back projection (FBP). Vessel detectability was assessed subjectively and the effective size at which 50% of response was achieved (ES50 [mm]) was calculated. Modulation transfer function (MTF) was calculated by an edge spread function method. RESULTS: ES50 of super high-resolution mode (0.36 mm for MBIR and 0.50 mm for FBP) was significantly smaller than those of normal-resolution mode (P < 0.01). In the MTF analysis, the MTF of MBIR improved as the edge phantom attenuation increased, whereas that of FBP was stable. CONCLUSIONS: Both UHRCT and MBIR are effective for the detectability of simulated submillimeter artery.


Assuntos
Angiografia por Tomografia Computadorizada/métodos , Vasos Coronários/diagnóstico por imagem , Algoritmos , Humanos , Imagens de Fantasmas , Doses de Radiação , Interpretação de Imagem Radiográfica Assistida por Computador
3.
J Comput Assist Tomogr ; 44(1): 95-101, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-31939889

RESUMO

PURPOSE: This study aimed to evaluate image quality of ultra-low dose chest computed tomography using 6 iterative reconstruction (IR) algorithms. METHOD: A lung phantom was scanned on 4 computed tomography scanners using fixed tube voltages and the lowest mAs available on each scanner, resulting in dose levels of 0.1 to 0.2 mGy (80 kVp) and 0.3 to 1 mGy (140 kVp) volume CT dose index (CTDIvol). Images were reconstructed with IR available on the scanners. Image noise, signal-to-noise ratios, contrast-to-noise ratios, uniformity, and noise power spectrum (NPS) were assessed for evaluation of image quality. RESULTS: Image quality parameters increased with increasing dose for all algorithms. At constant dose levels, model-based techniques improved the contrast-to-noise ratio of lesions more than the statistical algorithms. All algorithms tested at 0.1 mGy showed lower NPS peak frequencies compared with 0.39 mGy. In contrast to the statistical techniques, model-based algorithms showed lower NPS peak frequencies at the lowest doses, indicating a coarser and blotchier noise texture. CONCLUSION: This study shows the importance of evaluating IR when introduced clinically.


Assuntos
Pulmão/diagnóstico por imagem , Interpretação de Imagem Radiográfica Assistida por Computador/métodos , Tomografia Computadorizada por Raios X/instrumentação , Algoritmos , Meios de Contraste , Humanos , Imagens de Fantasmas , Doses de Radiação , Razão Sinal-Ruído
4.
J Comput Assist Tomogr ; 44(1): 145-152, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-31939896

RESUMO

OBJECTIVES: We investigated the computed tomographic characteristics of gastrointestinal air motion artifact (GIAMA), which can be misinterpreted as active gastrointestinal bleeding. METHODS: We simulated GIAMA using 3 types of air-ball phantoms (air-ball in water, air-ball in oil, air-water-ball in oil) and a bovine intestine in oil phantom. We also performed a retrospective clinical review of precontrast abdominal computed tomography images of 76 patients to investigate the frequency, location, shape, and maximum density of hyperdense GIAMA. RESULTS: In phantom studies, air motion artifacts appeared as dark and bright streak artifacts at the borders of a moving air-ball and water or oil. In the clinical study, hyperdense GIAMA was visualized in 60 (79.0%) of 76 patients. The small intestine was most commonly affected (46.4%), and the intramural type had the highest frequency (58.0%). CONCLUSION: Knowing the radiologic features of GIAMA can assists radiologists in identifying active gastrointestinal bleeding sites accurately.


Assuntos
Hemorragia Gastrointestinal/diagnóstico por imagem , Tomografia Computadorizada Multidetectores/métodos , Interpretação de Imagem Radiográfica Assistida por Computador/métodos , Adulto , Idoso , Idoso de 80 Anos ou mais , Animais , Bovinos , Reações Falso-Positivas , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Imagens de Fantasmas , Estudos Retrospectivos , Sensibilidade e Especificidade , Adulto Jovem
5.
Adv Exp Med Biol ; 1232: 307-313, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-31893425

RESUMO

Near infrared optical tomography (NIROT) is a non-invasive imaging technique to provide physiological information e.g. the oxygenation of tissue. For image reconstruction in clinical and preclinical scenarios, models to accurately describe light propagation are needed. This work aims to assess the accuracy and efficiency of different models, which paves the way for an optimal design of model-based image reconstruction algorithms in NIROT for realistic tissue geometries and heterogeneities. Two popular simulators were evaluated: the Monte Carlo (MC) method based MCX and the finite element method (FEM) based Toast++. We compared simulated results with experimental data measured on a homogeneous silicone phantom with well-calibrated parameters. The laser light was focused on the center of the phantom surface and images were captured by a CCD camera in both reflection and transmission modes. For transmittance measurements, the two models showed good agreement. Both achieve a cosine similarity of ~99%. In contrast, for reflectance measurements, FEM results deviated more from the measured values than MC, yielding similarity values of 86% and 94%, respectively. This study recommends the use of MC for NIROT in reflection mode and both MC and FEM yield excellent results for transmission mode.


Assuntos
Análise de Elementos Finitos , Modelos Teóricos , Método de Monte Carlo , Tomografia Óptica , Algoritmos , Simulação por Computador , Análise de Elementos Finitos/normas , Luz , Imagens de Fantasmas
6.
Adv Exp Med Biol ; 1232: 347-354, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-31893430

RESUMO

In preterm infants, there is a risk of long-term cognitive, motor and behavioral impairments due to hemorrhagic and/or ischemic lesions. If detected early, lesions can be prevented. A bedside imaging modality, capable of early detection of both disorders, is necessary. We present the state of development of a tomographic imager (named Pioneer), that will be capable of determining the oxygenation of the preterm-infant brain with high spatial resolution. Pioneer is a time-resolved near-infrared optical tomography (TR NIROT) instrument. It employs multiple wavelength laser light in short pulses on 11 distinct locations and measures the re-emerging light in a contactless fashion by means of a time-correlated single-photon counting (TCSPC) camera (named Piccolo) covering ~4.9 cm2 with 300 detectors. Timing response of the entire system is 116 ps. An in-house designed biocompatible source ring ensures fixed relative positions of sources and detectors and provides a secure interface between the patient and the probe. At the present state, the NIROT Pioneer system successfully detected a 6x6x50 mm3 inclusion 3 cm deep inside a phantom. These results confirm that the Pioneer imager is working as expected and is on a solid path towards full 3D tissue oxygenation imaging.


Assuntos
Encéfalo , Recém-Nascido Prematuro , Oximetria , Oxigênio , Encéfalo/diagnóstico por imagem , Humanos , Recém-Nascido , Oximetria/instrumentação , Oximetria/métodos , Oximetria/normas , Oxigênio/metabolismo , Imagens de Fantasmas
7.
Adv Exp Med Biol ; 1232: 369-374, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-31893433

RESUMO

Multispectral/hyperspectral imaging is one of the imaging modalities to visualize and quantify blood supply in surface tissues such as skin or mucosa. The results of visualization can be potentially affected by various factors, for instance by elevated methemoglobin (MetHb) content (e.g., methemoglobinemia). The scope of the current study is to develop a robust approach for fabrication and validation of tissue-mimicking phantoms, which can be used to assess and improve tissue oximetry. METHODS: The realistic tissue mimicking gelatin-based phantoms with intralipid (4% v/v) and/or hemoglobins (oxy-, deoxyhemoglobins, and MetHb) were molded between two coverslips separated by 2-mm wires. The hemoglobin solutions were prepared by dissolving the lyophilized human hemoglobin powder (H7379, Sigma-Aldrich) in the deionized water. Sodium dithionite (85% purity, 157,953, Sigma-Aldrich) was used to reduce MetHb solution. The phantoms were imaged using a multispectral imaging device (Oxilight, Canada).To demonstrate the utility, the developed approach is applied to emulate elevated systemic MetHb content. RESULTS: Initial results show that elevated systemic MetHb (2.0-6.7% of total blood) does not impact the accuracy of tissue oximetry imaging. DISCUSSION: A robust method for fabrication and optical validation of biocompatible tissue-mimicking phantoms has been developed.The proposed phantom design allows combining different phantoms into multilayer (sandwich) structures, which can be used to emulate a wide range of topical and systemic conditions.


Assuntos
Gelatina , Oximetria , Imagens de Fantasmas , Canadá , Gelatina/química , Humanos , Metemoglobina/análise , Metemoglobinemia/diagnóstico , Oximetria/métodos , Oximetria/normas , Imagens de Fantasmas/normas
8.
Radiologe ; 60(1): 15-23, 2020 Jan.
Artigo em Alemão | MEDLINE | ID: mdl-31897503

RESUMO

CLINICAL/METHODOLOGICAL PROBLEM: In the reconstruction of three-dimensional image data, artifacts that interfere with the appraisal often occur as a result of trying to minimize the dose or due to missing data. Used iterative reconstruction methods are time-consuming and have disadvantages. STANDARD RADIOLOGICAL METHODS: These problems are known to occur in computed tomography (CT), cone beam CT, interventional imaging, magnetic resonance imaging (MRI) and nuclear medicine imaging (PET and SPECT). METHODOLOGICAL INNOVATIONS: Using techniques based on the use of artificial intelligence (AI) in data analysis and data supplementation, a number of problems can be solved up to a certain extent. PERFORMANCE: The performance of the methods varies greatly. Since the generated image data usually look very good using the AI-based methods presented here while their results depend strongly on the study design, reliable comparable quantitative statements on the performance are not yet available in broad terms. EVALUATION: In principle, the methods of image reconstruction based on AI algorithms offer many possibilities for improving and optimizing three-dimensional image datasets. However, the validity strongly depends on the design of the respective study in the structure of the individual procedure. It is therefore essential to have a suitable test prior to use in clinical practice. PRACTICAL RECOMMENDATIONS: Before the widespread use of AI-based reconstruction methods can be recommended, it is necessary to establish meaningful test procedures that can characterize the actual performance and applicability in terms of information content and a meaningful study design during the learning phase of the algorithms.


Assuntos
Inteligência Artificial , Imagens de Fantasmas , Algoritmos , Artefatos , Humanos
9.
Artigo em Japonês | MEDLINE | ID: mdl-31956186

RESUMO

In the tissue characterization of plaques using magnetic resonance imaging (MRI), T1-weighted imaging is important. However, T1-weighted imaging are obtained by various imaging methods, and show different contrasts depending on parameters such as repetition time, echo time, and inversion time. To evaluate the tissue characterization of plaques using MRI, the characteristics are estimated and evaluated using the strength of the plaque-to-muscle signal intensity ratio (PMR), which is the value obtained by dividing the signal intensity of the plaque by that of the sternocleidomastoid muscle or myocardium. In the present research, we aim to obtain the PMR by phantom experiment and grasp the image characteristics for T1 and T2 values of different T1-weighted imaging methods. In addition, since the PMR of the conventional spin echo (SE) method of T1-weighted imaging (two-dimensional (2D) T1WI SE) is reported to have high discrimination ability in plaque tissue characterization, the experimental results were compared with those of 2D T1WI SE. Among the protocols examined, 3D sampling perfection with application optimized contrasts using different flip angle evolutions, T1-variable, motion-sensitized driven equilibrium (1-axis 300 ms2*mT/m) + had the same tissue characterization ability as 2D T1 WI SE, and was the most suitable imaging method. Moreover, in the gradient echo method, the effect of T2 values was smaller than that of 2D T1 WI SE, and it was suggested that the PMR of the plaque may be lowered when there is a change in the tissue properties that the T2 value and T1 value are prolonged due to liquefaction. The results of this phantom experiment are expected help in selecting the imaging method aimed at optimization and the image characteristics of different T1-weighted imaging method can be grasped.


Assuntos
Imagem Tridimensional , Imagem por Ressonância Magnética , Placa Aterosclerótica , Meios de Contraste , Humanos , Imagens de Fantasmas , Placa Aterosclerótica/diagnóstico por imagem
10.
Medicine (Baltimore) ; 99(1): e18617, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31895818

RESUMO

Development of patient-specific CT imaging phantoms with randomly incorporated lesions of various shapes and sizes for calibrating image intensity and validating quantitative measurement software is very challenging. In this investigation, a physical phantom that accurately represents a patient's specific anatomy and the intensity of lung CT images at the voxel level will be fabricated using fused deposition modeling (FDM) 3D printing. Segmentation and modeling of a patient's CT data were performed by an expert and the results were confirmed by a thoracic radiologist with more than 20 years of experience. This facilitated the extraction of the details of the patient's anatomy; various kinds of nodules with different shapes and sizes were randomly added to the modeled lung for evaluating the size-accuracy of the quantification software. To achieve these Hounsfield Units (HU) ranges for the corresponding voxels in acquired CT scans, the infill ratios of FDM 3D printing were controlled. Based on CT scans of the 3D printed phantoms, the measured HU for normal pulmonary parenchyma, ground glass opacity (GGO), and solid nodules were determined to be within target HU ranges. The accuracy of the mean absolute difference and the mean relative difference of nodules were less than 0.55 ±â€Š0.30 mm and 3.72 ±â€Š1.64% (mean difference ±â€Š95 CI), respectively. Patient-specific CT imaging phantoms were designed and manufactured using an FDM printer, which could be applied for the precise calibration of CT intensity and the validation of image quantification software.


Assuntos
Pulmão/diagnóstico por imagem , Imagens de Fantasmas , Impressão Tridimensional , Tomografia Computadorizada por Raios X/instrumentação , Humanos
11.
Ultrasonics ; 101: 106001, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31505328

RESUMO

Ultrasound is the first-line tool for screening hepatic steatosis. Statistical distributions can be used to model the backscattered signals for liver characterization. The Nakagami distribution is the most frequently adopted model; however, the homodyned K (HK) distribution has received attention due to its link to physical meaning and improved parameter estimation through X- and U-statistics (termed "XU"). To assess hepatic steatosis, we proposed HK parametric imaging based on the α parameter (a measure of the number of scatterers per resolution cell) calculated using the XU estimator. Using a commercial system equipped with a 7-MHz linear array transducer, phantom experiments were performed to suggest an appropriate window size for α imaging using the sliding window technique, which was further applied to measuring the livers of rats (n = 66) with hepatic steatosis induced by feeding the rats a methionine- and choline-deficient diet. The relationships between the α parameter, the stage of hepatic steatosis, and histological features were verified by the correlation coefficient r, one-way analysis of variance, and regression analysis. The phantom results showed that the window side length corresponding to five times the pulse length supported a reliable α imaging. The α parameter showed a promising performance for grading hepatic steatosis (p < 0.05; r2 = 0.68). Compared with conventional Nakagami imaging, α parametric imaging provided significant information associated with fat droplet size (p < 0.05; r2 = 0.53), enabling further analysis and evaluation of severe hepatic steatosis.


Assuntos
Fígado Gorduroso/diagnóstico por imagem , Ultrassonografia/métodos , Animais , Modelos Animais de Doenças , Aumento da Imagem/métodos , Processamento de Imagem Assistida por Computador/métodos , Masculino , Imagens de Fantasmas , Ratos , Ratos Wistar
12.
Br J Radiol ; 93(1105): 20190069, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31642702

RESUMO

OBJECTIVE: To evaluate the impact of different metal artifact reduction (MAR) algorithms on Hounsfield unit (HU) and standardized uptake values (SUV) in a phantom setting and verify these results in patients with metallic implants undergoing oncological PET/CT examinations. METHODS AND MATERIALS: In this prospective study, PET-CT examinations of 28 oncological patients (14 female, 14 male, mean age 69.5 ± 15.2y) with 38 different metal implants were included. CT datasets were reconstructed using standard weighted filtered back projection (WFBP) without MAR, MAR in image space (MARIS) and iterative MAR (iMAR, hip algorithm). The three datasets were used for PET attenuation correction. SUV and HU measurements were performed at the site of the most prominent bright and dark band artifacts. Differences between HU and SUV values across the different reconstructions were compared using paired t-tests. Bonferroni correction was used to prevent alpha-error accumulation (p < 0.017). RESULTS: For bright band artifacts, MARIS led to a non-significant mean decrease of 12.0% (345 ± 315 HU) in comparison with WFBP (391 ± 293 HU), whereas iMAR led to a significant decrease of 68.3% (125 ± 185 HU, p < 0.017). For SUVmean, MARIS showed no significant effect in comparison with WFBP (WFBP: 0.99 ± 0.40, MARIS: 0.96 ± 0.39), while iMAR led to a significant decrease of 11.1% (0.88 ± 0.35, p < 0.017). Similar results were observed for dark band artifacts. CONCLUSION: iMAR significantly reduces artifacts caused by metal implants in CT and thus leads to a significant change of SUV measurements in bright and dark band artifacts compared with WFBP and MARIS, thus probably improving PET quantification. ADVANCES IN KNOWLEDGE: The present work indicates that MAR algorithms such as iMAR algorithm in integrated PET/CT scanners are useful to improve CT image quality as well as PET quantification in the evaluation of tracer uptake adjacent to large metal implants. A detailed analysis of oncological patients with various large metal implants using different MAR algorithms in PET/CT has not been conducted yet.


Assuntos
Artefatos , Metais , Tomografia Computadorizada com Tomografia por Emissão de Pósitrons/métodos , Próteses e Implantes , Interpretação de Imagem Radiográfica Assistida por Computador/métodos , Idoso , Algoritmos , Feminino , Fluordesoxiglucose F18 , Humanos , Masculino , Imagens de Fantasmas , Estudos Prospectivos , Compostos Radiofarmacêuticos
13.
Br J Radiol ; 93(1105): 20181019, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31724436

RESUMO

OBJECTIVE: The aim of this phantom study was to investigate the effect of scan parameters and noise suppression techniques on the minimum radiation dose for acceptable image quality for CT emphysema densitometry. METHODS: The COPDGene phantom was scanned on a third generation dual-source CT system with 16 scan setups (CTDIvol 0.035-10.680 mGy). Images were reconstructed at 1.0/0.7 mm slice thickness/increment, with three kernels (one soft, two hard), filtered backprojection and three grades of third-generation iterative reconstruction (IR). Additionally, deep learning-based noise suppression software was applied. Main outcomes: overlap in area of the normalized histograms of CT density for the emphysema insert and lung material, and the radiation dose required for a maximum of 4.3% overlap (defined as acceptable image quality). RESULTS: In total, 384 scan reconstructions were analyzed. Decreasing radiation dose resulted in an exponential increase of the overlap in normalized histograms of CT density. The overlap was 11-91% for the lowest dose setting (CTDIvol 0.035mGy). The soft kernel reconstruction showed less histogram overlap than hard filter kernels. IR and noise suppression also reduced overlap. Using intermediate grade IR plus noise suppression software allowed for 85% radiation dose reduction while maintaining acceptable image quality. CONCLUSION: CT density histogram overlap can quantify the degree of discernibility of emphysema and healthy lung tissue. Noise suppression software, IR, and soft reconstruction kernels substantially decrease the dose required for acceptable image quality. ADVANCES IN KNOWLEDGE: Noise suppression software, IR, and soft reconstruction kernels allow radiation dose reduction by 85% while still allowing differentiation between emphysema and normal lung tissue.


Assuntos
Imagens de Fantasmas , Enfisema Pulmonar/diagnóstico por imagem , Doses de Radiação , Tomografia Computadorizada por Raios X/métodos , Humanos , Interpretação de Imagem Radiográfica Assistida por Computador/métodos
14.
Int J Radiat Oncol Biol Phys ; 106(1): 194-205, 2020 01 01.
Artigo em Inglês | MEDLINE | ID: mdl-31610250

RESUMO

PURPOSE: To develop and validate combined ion-beam with constant relative biological effectiveness (RBE) (CICR) particle therapy in single field arrangements for improved treatment efficacy, robustness, and normal tissue sparing. METHODS AND MATERIALS: The PRECISE (PaRticle thErapy using single and Combined Ion optimization StratEgies) treatment planning system was developed to investigate clinical viability of CICR treatments. Single-field uniform dose (SFUD) with a single ion (proton [p], helium [He], or carbon [C]) and CICR (C-p and C-He) treatments were generated for 3 patient cases with a clinically prescribed dose of 3 Gy (RBE) per fraction. Spread-out Bragg peak plans were irradiated in homogenous and clinical-like settings using an anthropomorphic head phantom. A dosimetric and biological verification of CICRC-p treatments using a murine glioma cell line (GL261) was performed. RESULTS: CICR treatment plans for the 3 patients presented highly uniform physical dose while reducing high dose-averaged linear energy transfer gradients compared with carbon ions alone. When considering uncertainty in tissue parameter (α/ß)x assignment and RBE modeling, the CICRC-p treatment exhibited enhanced biophysical stability within the target volume, similar to protons alone. CICR treatments reduced dose to normal tissue surrounding the target, exhibiting similar or improved dosimetric features compared with SFUDHe. For both CICRC-p and SFUD treatments, measurements verified the planned dose in the target within ∼3%. Planned versus measured target RBE values were 1.38 ± 0.02 and 1.39 ± 0.07 (<1% deviation), respectively, for the CICRC-p treatment in heterogenous settings. CONCLUSIONS: Here, we demonstrate that by combining 2 (or more) ions in a single field arrangement, more robust biological and more conformal dose distributions can be delivered compared with conventional particle therapy treatment planning. This work constitutes the first dosimetric and biological verification of multi-ion particle therapy in homogeneous as well as heterogenous settings.


Assuntos
Neoplasias Encefálicas/radioterapia , Carcinoma Adenoide Cístico/radioterapia , Cordoma/radioterapia , Glioma/radioterapia , Radioterapia com Íons Pesados/métodos , Tratamentos com Preservação do Órgão/métodos , Neoplasias da Coluna Vertebral/radioterapia , Animais , Neoplasias Encefálicas/diagnóstico por imagem , Carbono/uso terapêutico , Carcinoma Adenoide Cístico/diagnóstico por imagem , Linhagem Celular Tumoral , Cordoma/diagnóstico por imagem , Terapia Combinada/métodos , Fracionamento da Dose de Radiação , Glioma/diagnóstico por imagem , Hélio/uso terapêutico , Humanos , Transferência Linear de Energia , Camundongos , Órgãos em Risco , Imagens de Fantasmas , Terapia com Prótons/métodos , Lesões por Radiação/prevenção & controle , Planejamento da Radioterapia Assistida por Computador , Eficiência Biológica Relativa , Sacro , Neoplasias da Coluna Vertebral/diagnóstico por imagem
15.
Niger J Clin Pract ; 22(12): 1644-1653, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31793469

RESUMO

Objectives: To assess the validity of using the calibration ruler for correcting magnification of linear measurements and to explore and compare the vertical and horizontal magnification of four digital cephalometric units. Methods: An acrylic box was imaged at seven sagittal positions using four digital cephalometric units: Orthopantomograph OC100, Orthopantomograph OC200, Sirona Orthophos CD, and Sirona Orthophos DS. The true linear lengths of the phantom, corrected, and uncorrected linear lengths on the images were measured and compared. The validity of measurements using the calibration ruler was assessed. The magnification values and distortion indices were calculated and compared among the four cephalometric units. Results: For linear measurements on the mid-sagittal plane and averaged linear measurements on bilateral symmetric sagittal planes, the bias 1.96 STD of the calibration ruler ranged from 1% to 2% for the four cephalometric testing units. For linear measurements on the single lateral sagittal plane, the bias 1.96 STD ranged from 3% to 6%. The vertical scanning charge-coupled device cephalometric unit produced the greatest distortion, ranging from 1.029 to 0.964. Conclusion: The metal millimeter calibration ruler is an accurate reference for linear measurement magnification correction. Because of unpredictability and machine specificity, the magnification and distortion of a cephalometric unit should be calibrated for the estimation of cephalometric measurement error.


Assuntos
Calibragem/normas , Cefalometria/métodos , Radiografia Dentária Digital/instrumentação , Algoritmos , Cefalometria/normas , Humanos , Ortodontia/instrumentação , Imagens de Fantasmas , Ampliação Radiográfica , Radiografia Dentária Digital/métodos , Radiografia Panorâmica , Ecrans Intensificadores para Raios X
16.
Nan Fang Yi Ke Da Xue Xue Bao ; 39(10): 1213-1220, 2019 Oct 30.
Artigo em Chinês | MEDLINE | ID: mdl-31801709

RESUMO

OBJECTIVE: We propose a sparse-view helical CT iterative reconstruction algorithm based on projection of convex set tensor total generalized variation minimization (TTGV-POCS) to reduce the X-ray dose of helical CT scanning. METHODS: The three-dimensional volume data of helical CT reconstruction was viewed as the third-order tensor. The tensor generalized total variation (TTGV) was used to describe the structural sparsity of the three-dimensional image. The POCS iterative reconstruction framework was adopted to achieve a robust result of sparse-view helical CT reconstruction. The TTGV-POCS algorithm fully used the structural sparsity of first-order and second-order derivation and the correlation between the slices of helical CT image data to effectively suppress artifacts and noise in the image of sparse-view reconstruction and better preserve image edge information. RESULTS: The experimental results of XCAT phantom and patient scan data showed that the TTGVPOCS algorithm had better performance in reducing noise, removing artifacts and maintaining edges than the existing reconstruction algorithms. Comparison of the sparse-view reconstruction results of XCAT phantom data with 144 exposure views showed that the TTGV-POCS algorithm proposed herein increased the PSNR quantitative index by 9.17%-15.24% compared with the experimental comparison algorithm; the FSIM quantitative index was increased by 1.27%-9.30%. CONCLUSIONS: The TTGV-POCS algorithm can effectively improve the image quality of helical CT sparse-view reconstruction and reduce the radiation dose of helical CT examination to improve the clinical imaging diagnosis.


Assuntos
Processamento de Imagem Assistida por Computador , Doses de Radiação , Tomografia Computadorizada Espiral , Algoritmos , Humanos , Imagens de Fantasmas
17.
Anticancer Res ; 39(12): 6931-6938, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31810964

RESUMO

BACKGROUND/AIM: Many patients with head-and-neck cancers receive radiotherapy. Treatment planning can be very complex in case of dental fillings or implants that cause metal artefacts. Verification of dose distributions may be performed using specific phantoms. This study aimed to develop a 3D-printed phantom that can be produced easily and cost-effectively. PATIENTS AND METHODS: The phantom was designed to allow fast adaption to a patient's individual situation with a particular focus on metal artefacts due to dental fillings. Bone and soft-tissue shells were 3D-printed and filled with tissue-equivalent materials. RESULTS: Attenuation properties of the tissue-equivalent structures in the phantom corresponded well to the structures of real human anatomy. In magnetic resonance (MR)-imaging, useful signals of the materials in the phantom were obtained. CONCLUSION: The phantom met the requirements including equivalence with human tissues and can be useful for highly individual treatment planning in precision-radiotherapy of head-and-neck cancers. It can be also used for scientific issues related to MR-imaging.


Assuntos
Neoplasias de Cabeça e Pescoço/radioterapia , Cabeça/anatomia & histologia , Restauração Dentária Permanente , Restauração Dentária Temporária , Humanos , Imagens de Fantasmas , Impressão Tridimensional , Planejamento da Radioterapia Assistida por Computador/métodos
18.
Zhongguo Yi Liao Qi Xie Za Zhi ; 43(6): 391-396, 2019 Nov 30.
Artigo em Chinês | MEDLINE | ID: mdl-31854520

RESUMO

Fluorescent Diffuse Optical Tomography (FDOT), as a new imaging technology, can achieve three-dimensional quantitative functional imaging of probe in biological tissues, and has wide application value in biomedicine. Forward model which describes the photon propagation within a biological tissue is a prerequisite for implementing FDOT and determines the performance of FDOT. To further improve the efficiency of FDOT, this paper proposes a new forward model based on the Lattice Boltzmann (LB) method derived from the discretization of radiation transfer equation and applies it to FDOT. The experimental results of numerical simulation and physical phantom show that the LB-based forward model proposed in this paper can increase the imaging speed of FDOT by about 5 times compared with the traditional diffusion equation method, without reducing its imaging quality.


Assuntos
Tomografia Óptica , Difusão , Imagens de Fantasmas , Fótons
19.
Sheng Wu Yi Xue Gong Cheng Xue Za Zhi ; 36(6): 930-937, 2019 Dec 25.
Artigo em Chinês | MEDLINE | ID: mdl-31875366

RESUMO

To assess the background field removal method usually used in quantitative susceptibility mapping (QSM), and to analyze the cause of serious artifacts generated in the truncated k-space division (TKD) method, this paper discusses a variety of background field removal methods and proposes an improved method to suppress the artifacts of susceptibility inversion. Firstly, we scanned phase images with the gradient echo sequence and then compared the quality and the speed of reconstructed images of sophisticated harmonic artifact reduction for phase data (SHARP), regularization enable of SHARP (RESHARP) and laplacian boundary value (LBV) methods. Secondly, we analyzed the reasons for reconstruction artifacts caused by the multiple truncations and discontinuity of the TKD method, and an improved TKD method was proposed by increasing threshold truncation range and improving data continuity. Finally, the result of susceptibility inversion from the improved and original TKD method was compared. The results show that the reconstruction of SHARP and RESHARP are very fast, but SHARP reconstruction artifacts are serious and the reconstruction precision is not high and implementation of RESHARP is complicated. The reconstruction speed of LBV method is slow, but the detail of the reconstructed image is prominent and the precision is high. In the QSM inversion methods, the reconstruction artifact of the original TKD method is serious, while the improved method obtains good artifact suppression image and good inversion result of artifact regions.


Assuntos
Algoritmos , Processamento de Imagem Assistida por Computador , Artefatos , Encéfalo , Imagem por Ressonância Magnética , Imagens de Fantasmas
20.
Nihon Hoshasen Gijutsu Gakkai Zasshi ; 75(12): 1403-1410, 2019.
Artigo em Japonês | MEDLINE | ID: mdl-31866638

RESUMO

This research measured the radiation exposure of the computed tomography(CT) localizer radiograph of the trunk of the body. The entrance surface dose for CT localizer radiograph was measured using radiophotoluminescent glass dosimeter(RPLD) on four points of measurement, including the center of the phantom, on the surface of a phantom placed in the center of a CT bed, assuming that the subject has a thickness of 20 cm. The entrance surface dose of the localizer radiograph under the chest CT protocol manufacturer's initial setting conditions of 120 kV 35 mA was 0.80 mGy at the center and 0.53 for the 4-location average for the upper X-ray tube (excluding the CT bed), and 0.74 mGy at the center and 0.48 mGy for the 4-location average for the lower X-ray tube (including the CT bed). Compared to the Japan DRLs 2015 chest X-ray (P→A), the entrance surface dose was 2.67 times at the center and 1.77 times for the 4-location average for the upper X-ray tube and 2.47 times at the center and 1.60 times for the 4-location average for the lower X-ray tube. The CT radiation dose also cannot be ignored for the localizer radiograph entrance surface dose.


Assuntos
Exposição à Radiação , Japão , Imagens de Fantasmas , Doses de Radiação , Tomografia Computadorizada por Raios X
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