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1.
Medicine (Baltimore) ; 98(42): e17075, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31626080

RESUMO

Motion-induced artifacts have been a major drawback in bladder cancer imaging. This study is to evaluate the clinical utility of periodically rotated overlapping parallel lines with enhanced reconstruction (PROPELLER) acquisition in improving motion-induced artifacts in T2-weighted (T2W) magnetic resonance imaging (MRI) of bladder cancer at 3T.Sixteen patient MRI exams were included. Using a Likert scale, 2 radiologists independently scored T2W data without and with PROPELLER in terms of artifact severity and tumor visualization. Statistical analysis was done to assess the image quality improvement by PROPELLER and inter-observer variability.Without PROPELLER, the median scores of artifact severity and tumor visualization were 1.5 and 1.5 for reviewer 1, and 2.0 and 2.0 for reviewer 2. With PROPELLER, the scores increased to 3 and 3.5 for reviewer 1, and 3.5 and 3.5 for reviewer 2. Despite the inter-observer variability (κ scores < 0.2), both reviewers found significant improvement in artifacts and visualization (all P < .001).PROPELLER acquisition significantly improved the image quality of T2W-MRI. These initial findings indicate that this technique should be utilized in clinical MRI of the bladder.


Assuntos
Artefatos , Carcinoma de Células de Transição/diagnóstico por imagem , Imagem por Ressonância Magnética/métodos , Neoplasias da Bexiga Urinária/diagnóstico por imagem , Humanos , Processamento de Imagem Assistida por Computador/métodos , Movimento (Física) , Variações Dependentes do Observador , Estudos Prospectivos , Melhoria de Qualidade , Neoplasias da Bexiga Urinária/patologia
2.
J Comput Assist Tomogr ; 43(5): 718-720, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31609292

RESUMO

Recently, a novel 3-dimensional visualization methodology for volumetric computed tomography data has become available. This method, known as cinematic rendering, uses an advanced lighting model to create photorealistic images from standard computed tomography acquisition data composed of isotropic voxels. We have observed that cinematic rendering visualizations in which patients have been administered dense, positive oral contrast do not have any substantive visual artifacts and can be used to demonstrate bowel pathology to advantage (ie, "virtual fluoroscopy"). In this technical note, we describe our acquisition and visualization parameters, and we also include demonstrative examples.


Assuntos
Meios de Contraste/administração & dosagem , Enterite/diagnóstico por imagem , Imagem Tridimensional/métodos , Intussuscepção/diagnóstico por imagem , Iohexol/administração & dosagem , Tomografia Computadorizada por Raios X/métodos , Adulto , Idoso , Artefatos , Feminino , Fluoroscopia , Humanos , Interpretação de Imagem Radiográfica Assistida por Computador
3.
J Comput Assist Tomogr ; 43(5): 805-810, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31490890

RESUMO

OBJECTIVE: The objective of this study was to evaluate a prototype, ultrahigh-resolution computed tomography offering higher reconstruction matrix (1024 × 1024) and spatial resolution (0.15 mm) for chest imaging. METHODS: Higher (1024) matrix reconstruction enabled by ultrahigh-resolution computed tomography scanner (128-detector rows; detector width, 0.25 mm; spatial resolution, 0.15 mm) was compared with conventional (512) reconstruction with image quality grading on a Likert scale (1, excellent; 5, nondiagnostic) for image noise, artifacts, contrast, small detail, lesion conspicuity, image sharpness, and diagnostic confidence. Image noise and signal-to-noise ratio were quantified. RESULTS: Diagnostic image quality was achieved for all scans on 101 patients. The 1024 reconstruction demonstrated increased image noise (20.2 ± 4.0 vs 17.2 ± 3.8, P < 0.001) and a worse noise rating (1.98 ± 0.63 vs 1.75 ± 0.61, P < 0.001) but performed significantly better than conventional 512 matrix with fewer artifacts (1.37 ± 0.43 vs 1.50 ± 0.48, P < 0.001), better contrast (1.50 ± 0.56 vs 1.62 ± 0.57, P < 0.001), small detail detection (1.06 ± 0.19 vs 2.02 ± 0.22, P < 0.001), lesion conspicuity (1.08 ± 0.23 vs 2.02 ± 0.24, P < 0.001), sharpness (1.09 ± 0.24 vs 2.02 ± 0.28, P < 0.001), and overall diagnostic confidence (1.09 ± 0.25 vs 1.18 ± 0.34, P < 0.001). CONCLUSIONS: Ultrahigh-resolution computed tomography enabled a higher reconstruction matrix and improved image quality compared with conventional matrix reconstruction, with a minor increase in noise.


Assuntos
Interpretação de Imagem Radiográfica Assistida por Computador/métodos , Radiografia Torácica/instrumentação , Tomógrafos Computadorizados , Adolescente , Adulto , Idoso , Idoso de 80 Anos ou mais , Artefatos , Meios de Contraste , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Estudos Prospectivos , Razão Sinal-Ruído
4.
Artigo em Japonês | MEDLINE | ID: mdl-31548466

RESUMO

PURPOSE: Computed tomography (CT) attenuation correction of myocardial perfusion in single-photon emission computed tomography (SPECT) /CT systems is possibility of misregistration between emission and transmission scans. This study aimed to evaluate the influence of misregistration using a polar map of 17 segments model. METHODS: Using the fusion software, we assessed the magnitude and direction of misregistration in 200 consecutive myocardial perfusion SPECT images with 99mTechnetium (99mTc) tetrofosmin. After registration, CT data was shifted by ±1, ±2, and ±3 pixels along the cephalad/caudal, dorsal/ventral, and left/right axes, respectively. The registered image was compared with the shifted image. RESULTS: Misregistration between the SPECT and CT images occurred by 1-2 pixels in 127 cases (63.5%) and by 2 or more pixels in four cases (2%); the maximum misregistration was 1.2±0.4 pixels on average. The polar map scoring was most significantly affected by 3 pixel ventral shift. A ventral shift of 1 pixel affected the scores for the anterolateral and inferolateral segments, whereas a caudal shift of 1 pixel affected the scores for the anterior segment. CONCLUSION: Since the 17 segments model can evaluate the position more precisely than the five segments model, it is possible to evaluate up to 1 pixel misregistration.


Assuntos
Artefatos , Tomografia Computadorizada de Emissão de Fóton Único , Tomografia Computadorizada por Raios X , Sensibilidade e Especificidade , Tecnécio , Tomografia Computadorizada de Emissão de Fóton Único/normas , Tomografia Computadorizada por Raios X/normas
5.
Br J Radiol ; 92(1103): 20190384, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31479307

RESUMO

OBJECTIVE: Evaluation of coronary CT image blur using multi segment reconstruction algorithm. METHODS: Cardiac motion was simulated in a Catphan. CT coronary angiography was performed using 320 × 0.5 mm detector array and 275 ms gantry rotation. 1, 2 and 3 segment reconstruction algorithm, three heart rates (60, 80 and 100bpm), two peak displacements (4, 8 mm) and three cardiac phases (55, 35, 75%) were used. Wilcoxon test compared image blur from the different reconstruction algorithms. RESULTS: Image blur for 1, 2 and 3 segments in: 60 bpm, 75% R-R interval and 8 mm peak displacement: 0.714, 0.588, 0.571 mm (1.18, 0.6, 0.4 mm displacement) 80 bpm, 35% R-R interval and 8 mm peak displacement: 0.869, 0.606, 0.606 mm (1.57, 0.79,0.52 mm displacement) 100 bpm, 35% R-R interval and 4 mm peak displacement: 0.645, 0.588, 0.571 mm (0.98, 0.49, 0.33 mm displacement). The median image blur overall for 1 and 2 segments was 0.714 mm and 0.588 mm respectively (p < 0.0001). CONCLUSION: Two-segment reconstruction significantly reduces image blur. ADVANCES IN KNOWLEDGE: Multisegment reconstruction algorithms during CT coronary angiography are a useful method to reduce image blur, improve visualization of the coronary artery wall and help the early detection of the plaque.


Assuntos
Angiografia por Tomografia Computadorizada/normas , Doença da Artéria Coronariana/diagnóstico por imagem , Algoritmos , Análise de Variância , Artefatos , Doença da Artéria Coronariana/fisiopatologia , Frequência Cardíaca/fisiologia , Humanos , Movimento , Imagens de Fantasmas , Projetos Piloto , Estudos Prospectivos , Intensificação de Imagem Radiográfica/métodos
6.
Stud Health Technol Inform ; 264: 253-257, 2019 Aug 21.
Artigo em Inglês | MEDLINE | ID: mdl-31437924

RESUMO

During the acquisition on a low-dose radiation computed tomography (CT) scan, images are usually marked by heavy noise and undesired artifacts, which dramatically reduce its applicability in the image processing workflow. A noise reduction and detail preservation filter based on mathematical morphology is presented in this paper. The filter is geared to allow control of an opening operator followed by a systematic contrast limited adaptive histogram equalization (CLAHE) in conjunction with a reconstruction by dilation in last stage. A quantitative metric built on peak signal-to-noise ratio (PSNR), structural similarity (SSIM), and mean-squared error (MSE) were applied to check noise reduction, detail preservation, and performance. The results obtained by the proposed filter were compared with those obtained in the literature, showing very good results: compared with the best-tested filter, the filter had a gain of 7.91% on PSNR, 7.57% on SSIM and 37.8% on MSE.


Assuntos
Processamento de Imagem Assistida por Computador , Tomografia Computadorizada por Raios X , Algoritmos , Artefatos , Imagens de Fantasmas , Doses de Radiação , Razão Sinal-Ruído
8.
Praxis (Bern 1994) ; 108(10): 679-684, 2019 Aug.
Artigo em Alemão | MEDLINE | ID: mdl-31387491

RESUMO

Vascular Color-Coded Duplex Ultrasound in Practice: Artifacts Abstract. Ultrasound artifacts are technical phenomena which may cause diagnostic mistakes and do not correlate with the real target organ. These optical and acoustic phenomena of color-coded duplex ultrasound are very common in the real world and may lead to misinterpretations and diagnostic errors. The twinkling artifact, for example, imitates high-flow velocities and turbulences, which may lead to the misdiagnosis of a high-grade stenosis or of vascularization. Mirror image artifacts may irritate the sonographer and cause an impression of an additional - really not existing - vessel. The "seagull cry", whose origin is not well understood, is usually found in the region of a high-grade stenosis.


Assuntos
Artefatos , Ultrassonografia Doppler em Cores , Erros de Diagnóstico , Humanos , Ultrassonografia Doppler Dupla
9.
Cancer Radiother ; 23(6-7): 753-760, 2019 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-31427076

RESUMO

Imaging provides the basis for radiotherapy. Multi-modality images are used for target delineation (primary tumor and nodes, boost volume) and organs at risk, treatment guidance, outcome prediction, and treatment assessment. Next to anatomical information, more and more functional imaging is being used. The current paper provides a brief overview of the different applications of imaging techniques used in the radiotherapy process, focusing on uncertainties and QA. The paper mainly focuses on PET and MRI, but also provides a short discussion on DCE-CT. A close collaboration between radiology, nuclear medicine and radiotherapy departments provides the key to improve the quality of radiotherapy. Jointly developed imaging protocols (RT position setup, immobilization tools, lasers, flat table…), and QA programs are mandatory. For PET, suitable windowing in consultation with a Nuclear Medicine Physician is crucial (differentiation benign/malignant lesions, artifacts…). A basic knowledge of MRI sequences is required, in such a way that geometrical distortions are easily recognized by all members the RT and RT physics team. If this is not the case, then the radiologist should be introduced systematically in the delineation process and multidisciplinary meetings need to be organized regularly. For each image modality and each image registration process, the associated uncertainties need to be determined and integrated in the PTV margin. When using functional information for dose painting, response assessment or outcome prediction, collaboration between the different departments is even more important. Limitations of imaging based biomarkers (specificity, sensitivity) should be known.


Assuntos
Imagem por Ressonância Magnética/métodos , Imagem Multimodal/métodos , Neoplasias/diagnóstico por imagem , Neoplasias/radioterapia , Garantia da Qualidade dos Cuidados de Saúde , Planejamento da Radioterapia Assistida por Computador/métodos , Incerteza , Artefatos , Humanos , Imagem por Ressonância Magnética/normas , Imagem Multimodal/normas , Estadiamento de Neoplasias , Neoplasias/patologia , Imagens de Fantasmas , Tomografia por Emissão de Pósitrons/métodos , Tomografia por Emissão de Pósitrons/normas , Tomografia Computadorizada por Raios X/métodos
10.
Br J Radiol ; 92(1103): 20190345, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31453718

RESUMO

OBJECTIVE: To compare image quality and breast density of two reconstruction methods, the widely-used filtered-back projection (FBP) reconstruction and the iterative heuristic Bayesian inference reconstruction (Bayesian inference reconstruction plus the method of total variation applied, HBI). METHODS: Thirty-two clinical DBT data sets with malignant and benign findings, n = 27 and 17, respectively, were reconstructed using FBP and HBI. Three experienced radiologists evaluated the images independently using a 5-point visual grading scale and classified breast density according to the American College of Radiology Breast Imaging-Reporting And Data System Atlas, fifth edition. Image quality metrics included lesion conspicuity, clarity of lesion borders and spicules, noise level, artifacts surrounding the lesion, visibility of parenchyma and breast density. RESULTS: For masses, the image quality of HBI reconstructions was superior to that of FBP in terms of conspicuity,clarity of lesion borders and spicules (p < 0.01). HBI and FBP were not significantly different in calcification conspicuity. Overall, HBI reduced noise and supressed artifacts surrounding the lesions better (p < 0.01). The visibility of fibroglandular parenchyma increased using the HBI method (p < 0.01). On average, five cases per radiologist were downgraded from BI-RADS breast density category C/D to A/B. CONCLUSION: HBI significantly improves lesion visibility compared to FBP. HBI-visibility of breast parenchyma increased, leading to a lower breast density rating. Applying the HBIR algorithm should improve the diagnostic performance of DBT and decrease the need for additional imaging in patients with dense breasts. ADVANCES IN KNOWLEDGE: Iterative heuristic Bayesian inference (HBI) image reconstruction substantially improves the image quality of breast tomosynthesis leading to a better visibility of breast carcinomas and reduction of the perceived breast density compared to the widely-used filtered-back projection (FPB) reconstruction. Applying HBI should improve the accuracy of breast tomosynthesis and reduce the number of unnecessary breast biopsies. It may also reduce the radiation dose for the patients, which is especially important in the screening context.


Assuntos
Densidade da Mama/fisiologia , Neoplasias da Mama/diagnóstico por imagem , Idoso , Idoso de 80 Anos ou mais , Algoritmos , Artefatos , Teorema de Bayes , Neoplasias da Mama/patologia , Feminino , Humanos , Processamento de Imagem Assistida por Computador/métodos , Processamento de Imagem Assistida por Computador/normas , Mamografia/métodos , Mamografia/normas , Pessoa de Meia-Idade , Estudos Retrospectivos , Carga Tumoral
11.
Cancer Radiother ; 23(5): 395-400, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31331842

RESUMO

PURPOSE: Lung and some digestive tumours move during a respiratory cycle. Four-dimensional scanography (4D-CT) is commonly used in treatment planning to account for respiratory motion. Although many French radiotherapy centres are now equipped, there are no guidelines on this subject to date. We wanted to draw up a description of the use of the 4D-CT for the treatment planning in France. METHODS AND MATERIAL: We conducted a survey in all French radiotherapy centres between March and April 2017. RESULTS: One hundred and seventy-two were contacted. The participation rate was 88.37%. The use of the 4D-CT seems to be common and concerned planning for 15.28% of kidney and adrenal cancers, 19.72% of pancreatic cancers, 27.78% of oesophageal cancers and 73.24% of lung cancers in case of normofractionated treatments. The use of the 4D-CT was also widespread in the case of stereotactic body radiation therapy: with 61.11% in the case of pulmonary irradiation and 34.72% in the case of hepatic irradiation. Many centres declared they carried out several 4D-CT for treatment planning (29, 55% in case of stereotactic body radiation therapy for lung tumours and 20% for liver tumours). Private centres tend to repeat 4D-CT more. CONCLUSION: Although the use of the 4D-CT appears to be developing, it remains very heterogeneous. To date, the repetition of the 4D-CT has been very poorly studied and could be the subject of clinical studies, allowing to define in which indications and for which populations there is a real benefit.


Assuntos
Tomografia Computadorizada Quadridimensional , Planejamento da Radioterapia Assistida por Computador/métodos , Artefatos , Institutos de Câncer/estatística & dados numéricos , França , Pesquisas sobre Serviços de Saúde , Hospitais Privados/estatística & dados numéricos , Hospitais Públicos/estatística & dados numéricos , Hospitais Universitários/estatística & dados numéricos , Humanos , Imagem Tridimensional/estatística & dados numéricos , Movimento (Física) , Neoplasias/diagnóstico por imagem , Neoplasias/radioterapia , Utilização de Procedimentos e Técnicas , Serviço Hospitalar de Radiologia/estatística & dados numéricos , Radiocirurgia/métodos , Planejamento da Radioterapia Assistida por Computador/estatística & dados numéricos , Planejamento da Radioterapia Assistida por Computador/tendências , Respiração
12.
Clin Biochem ; 71: 77-80, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31299318

RESUMO

Tetrabromphenol blue dye based methods are used to detect proteinuria using urinalysis dipsticks. Manufacturers have claimed that alkalinity leads to false positive proteinuria, and that high specific gravity leads to false negative protein results. However, published reports describing this phenomenon remain equivocal. This study aimed to determine whether pH and/or specific gravity affect protein detection in patient urine using three different tetrabromophenol blue dye-based dipsticks. Patient urine pools were divided into individual aliquots with varied pH or specific gravity, and measured for protein in triplicate using iChem 10SG, iChem Velocity, and Multistix 8SG dipsticks. The pH experiment involved progressive alkalinization of urine aliquots with either 1M NaOH, Na2CO3, or NaHCO3; pH was recorded by electrode. The specific gravity experiment involved mixing aliquots with NaCl and spiking with human albumin. Urine electrolytes and total CO2 were measured (Roche cobas 8000). Fresh patient urines (N = 35) were analyzed for physiological urine pH and total CO2. Urine protein results were not affected by NaOH alkalinization up to pH 10.9. False positive protein occurred at pH 9.9 and >97 mmol/L total CO2 (Na2CO3 alkalization; P < .05). Moreover, false positive protein occurred at pH 7.6 when total CO2 exceeded 137 mmol/L (NaHCO3 alkalization; P < .05). Fresh patient urines did not exceed pH 8.5 or 86 mmol/L total CO2. NaCl elevated specific gravity and caused false negative protein detection when urine ionic strength was >1100 mmol/L (P < .05). Tetrabromphenol blue dipsticks provide robust detection of proteinuria when human urine is within physiological pH, total CO2 and ionic strength.


Assuntos
Concentração de Íons de Hidrogênio , Proteinúria/metabolismo , Fitas Reagentes , Gravidade Específica , Urina/química , Artefatos
13.
J Comput Assist Tomogr ; 43(5): 713-717, 2019.
Artigo em Inglês | MEDLINE | ID: mdl-31356522

RESUMO

OBJECTIVE: The objective of this study was to investigate the quantitative and qualitative effects of virtual monoenergetic images (VMIs) by spectral detector computed tomography (SDCT) on metal artifacts in routine examinations. METHODS: Fifty-nine patients with metal artifacts (caused by pacemakers, ports, screws, or prosthetic joints) affecting muscular tissue in the chest and/or abdomen were scanned using SDCT. Attenuation values around the metallic device were compared with contralateral unaffected values, for conventional images and 80 to 200 keV VMIs. In addition, general image quality and artifact intensity were rated by 2 readers. RESULTS: The VMIs significantly decreased metal artifact intensity in all patients (P < 0.05). In 39 patients (66.1%), the attenuation values of the artifact and the unaffected area on the optimal keV level were very similar (≤5 Hounsfield unit difference). Qualitative analysis showed that high VMIs significantly improved artifact intensity, with best scores at 140 keV. CONCLUSIONS: High monoenergetic images of SDCT significantly reduce metal artifacts, with optimal assessment at 140 keV.


Assuntos
Artefatos , Corpos Estranhos/diagnóstico por imagem , Metais , Próteses e Implantes , Tomografia Computadorizada por Raios X/métodos , Idoso , Feminino , Humanos , Masculino , Interpretação de Imagem Radiográfica Assistida por Computador/métodos , Radiografia Abdominal , Radiografia Torácica
14.
Genome Biol ; 20(1): 138, 2019 07 12.
Artigo em Inglês | MEDLINE | ID: mdl-31300005

RESUMO

Methylation datasets are affected by innumerable sources of variability, both biological (cell-type composition, genetics) and technical (batch effects). Here, we propose a reference-free method based on sparse canonical correlation analysis to separate the biological from technical sources of variability. We show through simulations and real data that our method, CONFINED, is not only more accurate than the state-of-the-art reference-free methods for capturing known, replicable biological variability, but it is also considerably more robust to dataset-specific technical variability than previous approaches. CONFINED is available as an R package as detailed at https://github.com/cozygene/CONFINED .


Assuntos
Artefatos , Metilação de DNA , Variação Genética , Software , Conjuntos de Dados como Assunto
15.
Br J Radiol ; 92(1103): 20190465, 2019 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-31356106

RESUMO

Increased collagen, or fibrosis, is an important marker of disease and may improve identification of patients at risk. In addition, fibrosis imaging may play an increasing role in guiding therapy and monitoring its effectiveness. MRI is the most frequently used modality to detect, visualize and quantify fibrosis non-invasively. However, standard MRI techniques used to phenotype cardiac fibrosis such as delayed enhancement and extracellular volume determination by T1 mapping, require the administration of gadolinium-based contrast and are particularly difficult to use in patients with cardiac devices such as pacemakers and automatic defibrillators. Therefore, such methods are limited in the serial evaluation of cardiovascular fibrosis as part of chronic disease monitoring. A method to directly measure collagen amount could be of great clinical benefit. In the current review we will discuss the potential of a novel MR technique, ultrashort echo time (UTE) MR, for fibrosis imaging. Although UTE imaging is successfully applied in other body areas such as musculoskeletal applications, there is very limited experience so far in the heart. We will review the established methods and currently available literature, discuss the technical considerations and challenges, show preliminary in vivo images and provide a future outlook on potential applications of cardiovascular UTE.


Assuntos
Sistema Cardiovascular/patologia , Angiografia por Ressonância Magnética/métodos , Artefatos , Meios de Contraste , Fibrose/patologia , Gadolínio , Humanos , Fatores de Tempo
16.
Radiol Clin North Am ; 57(5): 1051-1062, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31351535

RESUMO

MR imaging is the modality of choice to evaluate musculoskeletal pathologies of the upper limb in most settings. However, due to the complexity in anatomy, MR imaging can give a false pathologic appearance and lead to several errors in the interpretation of MR imaging findings. Also, several artifacts can be confused with pathologic entities. This article reviews the most frequently encountered conditions in shoulder, elbow, and wrist MR imaging that can represent diagnostic pitfalls mimicking true pathology, together with some possible tips and tricks that can be useful to solve these equivocal cases and achieve a correct diagnosis.


Assuntos
Artefatos , Erros de Diagnóstico/prevenção & controle , Imagem por Ressonância Magnética/métodos , Extremidade Superior/diagnóstico por imagem , Extremidade Superior/lesões , Diagnóstico Diferencial , Articulação do Cotovelo/diagnóstico por imagem , Articulação do Cotovelo/lesões , Humanos , Articulação do Ombro/diagnóstico por imagem , Articulação do Ombro/lesões , Traumatismos do Punho/diagnóstico por imagem , Articulação do Punho/diagnóstico por imagem
17.
Eur J Radiol ; 116: 21-26, 2019 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-31153567

RESUMO

PURPOSE: To assess the effect on reducing the out-of-plane artifacts from metal objects in breast tomosynthesis (BT) using a novel artifact-reducing reconstruction algorithm in specimen radiography. METHODS AND MATERIALS: The study was approved by the Regional Ethical Review Board. BT images of 18 partial- and whole mastectomy specimens from women with breast cancer were acquired before and after a needle was inserted close to the lesion. The images were reconstructed using both a standard reconstruction algorithm, and a novel algorithm; the latter uses pre-segmentation to remove highly attenuating artifact-inducing objects from projection images before reconstruction. Images were separately reconstructed with and without segmentation, and combined into an artifact-reduced reconstruction. Standard and artifact-reduced BT-algorithms were compared visually and quantitatively using clinical images of mastectomy specimens and a physical anthropomorphic phantom. Six readers independently assessed the visibility of the lesion with and without artifact-reduction in a side-by-side comparison. A quantitative analysis was performed, comparing the signal-difference to background ratio (SDBR) and artifact spread function (ASF) between the two reconstruction methods. RESULTS: The magnitude of out-of-plane artifacts was clearly reduced with the novel reconstruction compared to BT-images without artifact reduction. Lesion masking by artifacts was largely averted; tumour visibility was comparable to standard BT images without a needle. In 76 ± 8% (standard deviation) of cases overall, readers could confidently state needle location. The same figure was 94 ± 6% for whole mastectomy cases, compared to 62 ± 17% for partial mastectomies. With metal artifact reduction, SDBR increased by 97% in the phantom, and by 69% in the mastectomies. The artifact spread function was substantially narrower. CONCLUSION: Artifact reduction in BT using a novel reconstruction method enables qualitatively and quantitatively improved clinical use of BT when metal artifacts can be a limiting factor such as in tomosynthesis-guided biopsy.


Assuntos
Algoritmos , Artefatos , Neoplasias da Mama/diagnóstico por imagem , Processamento de Imagem Assistida por Computador/métodos , Mamografia/métodos , Biópsia , Mama/diagnóstico por imagem , Mama/patologia , Neoplasias da Mama/patologia , Feminino , Humanos , Mastectomia , Metais
18.
Ultrasonics ; 98: 99-107, 2019 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-31238255

RESUMO

Strain imaging in medical ultrasound is the imaging modality of elastic properties of biological tissue. In general, strain image will suffer from artifacts noise, which degrades lesion detectability and increases the likelihood of misdiagnosis. How to both suppress artifacts effectively and preserve the structure is vital for diagnosis and also for image post-processing. The bilateral filtering can reduce artifact noise and, at the same time, maintain the tissue structure. However, the balance between noise suppression and edge preservation often makes the threshold selection difficult. This paper is to solve the problem of difficult threshold selection in bilateral filtering. The probability distribution function of amplitude modulation noise in this paper is derived from the statistics of uncompressed speckle. The statistical model of artifact formation is useful for designing an adaptive fast bilateral filter for artifact reduction in ultrasound strain imaging. Both simulation and phantom testing show that the proposed method can improve the quality of ultrasonic strain imaging. Furthermore, the elastographic signal-to-noise ratio was increased by 129.91% and 52.36% for simulated and phantom strain images. The elastographic contrast-to-noise ratio was increased by 521.42% and 218.07% for simulated and phantom strain images, respectively. As indicated by the profiles, the proposed method produces a better result for the purpose of visualization.


Assuntos
Artefatos , Processamento de Imagem Assistida por Computador/métodos , Ultrassonografia/métodos , Algoritmos , Imagens de Fantasmas , Razão Sinal-Ruído
19.
Food Chem ; 293: 278-284, 2019 Sep 30.
Artigo em Inglês | MEDLINE | ID: mdl-31151612

RESUMO

A headspace sampling-gas chromatography/mass spectrometry (HS-GC/MS) method using mild HS conditions (40 °C, 30 min) was established, validated in terms of specificity, linearity (1.75-87.65 ng mL-1), precision (0.3-9.1% RSD), and accuracy (81.1-117.7%); and applied for the monitoring of 900 commercial beverage samples of six different types. These mild (low-temperature) conditions were compared with 1) optimized (high-temperature) conditions and 2) a liquid-phase microextraction method involving no heat treatment. This method was desirable because a high equilibrium temperature induced artefactual benzene formation from benzoate and ascorbic acid. In a 2IV8-3 fractional factorial design, eight variables-ascorbic acid, benzoate, benzaldehyde, Cu2+, Fe2+, riboflavin, pyridoxine, and heat treatment-were tested as potential factors affecting benzene formation. All variables except Fe2+ and pyridoxine significantly affected benzene formation, both individually and interactively. The present study suggests an accurate and reliable method for benzene analysis and provides strategies to prevent unintentional benzene formation in beverages.


Assuntos
Benzeno/síntese química , Bebidas/análise , Cromatografia Gasosa-Espectrometria de Massas/métodos , Artefatos , Ácido Ascórbico/análise , Benzaldeídos/análise , Benzoatos/análise , Ácido Benzoico/análise , Cobre/análise , Compostos Ferrosos/análise , Temperatura Alta , Piridoxina/análise , Reprodutibilidade dos Testes , Riboflavina/análise , Microextração em Fase Sólida
20.
Sheng Wu Yi Xue Gong Cheng Xue Za Zhi ; 36(3): 486-492, 2019 Jun 25.
Artigo em Chinês | MEDLINE | ID: mdl-31232553

RESUMO

Acoustic properties of biological tissues usually vary inhomogeneously in space. Tissues with different chemical composition often have different acoustic properties. The assumption of acoustic homogeneity may lead to blurred details, misalignment of targets and artifacts in the reconstructed photoacoustic tomography (PAT) images. This paper summarizes the main solutions to PAT imaging of acoustically heterogeneous tissues, including the variable sound speed and acoustic attenuation. The advantages and limits of the methods are discussed and the possible future development is prospected.


Assuntos
Acústica , Processamento de Imagem Assistida por Computador , Tomografia , Artefatos , Humanos , Imagens de Fantasmas
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