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2.
BMJ ; 368: m134, 2020 01 14.
Artigo em Inglês | MEDLINE | ID: mdl-31937593
3.
Anticancer Res ; 40(1): 271-280, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31892576

RESUMO

BACKGROUND/AIM: To investigate whether a radiomic machine learning (ML) approach employing texture-analysis (TA) features extracted from primary tumor lesions (PTLs) is able to predict tumor grade (TG) and nodal status (NS) in patients with oropharyngeal (OP) and oral cavity (OC) squamous-cell carcinoma (SCC). PATIENTS AND METHODS: Contrast-enhanced CT images of 40 patients with OP and OC SCC were post-processed to extract TA features from PTLs. A feature selection method and different ML algorithms were applied to find the most accurate subset of features to predict TG and NS. RESULTS: For the prediction of TG, the best accuracy (92.9%) was achieved by Naïve Bayes (NB), bagging of NB and K Nearest Neighbor (KNN). For the prediction of NS, J48, NB, bagging of NB and boosting of J48 overcame the accuracy of 90%. CONCLUSION: A radiomic ML approach applied to PTLs is able to predict TG and NS in patients with OC and OP SCC.


Assuntos
Carcinoma de Células Escamosas/diagnóstico por imagem , Carcinoma de Células Escamosas/patologia , Linfonodos/patologia , Neoplasias Bucais/diagnóstico por imagem , Neoplasias Bucais/patologia , Neoplasias Orofaríngeas/diagnóstico por imagem , Neoplasias Orofaríngeas/patologia , Idoso , Algoritmos , Humanos , Aprendizado de Máquina , Gradação de Tumores , Tomografia Computadorizada por Raios X
4.
Medicine (Baltimore) ; 99(1): e18569, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31895800

RESUMO

An adverse drug reactions avoidability tool called the Liverpool ADR avoidability assessment tool (LAAT) was recently developed (for research purposes), and subsequently validated with mixed interrater reliability (IRR). We investigated the comparative IRR of this tool in an inpatient cohort to ascertain its practical application in this setting.The patient population was comprised of 44 ADR drug pairs drawn from an observational prospective cohort of patents with ADR attending a Weill Cornell Medicine-affiliated tertiary medical Centre in Doha Qatar (Hamad General Hospital). Using the LAAT, and modified Hallas tools, 4 independent raters (2 Clinical Pharmacologists, and 2 General Physicians) assessed and scored the 44 ADR-drug pairs. Agreement proportions between the rating pairs were evaluated as well individual/overall kappa statistics and intraclass correlation coefficients. We evaluated the weight of each of the 7 questions on the LAAT tool to ascertain its determinative role.Across 44 ADR-drug pairs, the overall median Fleiss kappa using the LAAT, and modified Hallas tools were 0.67 (interquartile range (IQR) 0.55, 0.76), 0.36 (IQR, 0.23-0.71) respectively. The overall percentage pairwise agreement with the LAAT and modified Hallas tools were 78.5%, and 62.2% respectively. Exact pairwise agreement occurred in 37 out of 44 (range 0.71-1), and 27 of 44 (0.53-0.77) ADR-drug pairs using the LAAT and modified Hallas tools respectively. Using the LAAT tool, the overall intraclass correlation coefficient was 0.68 (CI 0.55, 0.79), and 0.37 (CI 0.22, 0.53) with the modified Hallas tool.We report a higher proportion of "possible" and "definite" avoidability outcomes of adverse drug reactions compared with the modified Hallas, or that reported by developers of the LAAT tool. Although initially developed for research purposes, our report has suggested for the first time a potential applicability of this tool in clinical environment as well.


Assuntos
Rotas de Resultados Adversos , Efeitos Colaterais e Reações Adversas Relacionados a Medicamentos/prevenção & controle , Adulto , Algoritmos , Feminino , Humanos , Pacientes Internados/estatística & dados numéricos , Masculino , Pessoa de Meia-Idade , Variações Dependentes do Observador , Estudos Prospectivos , Catar , Reprodutibilidade dos Testes
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.
J Comput Assist Tomogr ; 44(1): 13-19, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-31939876

RESUMO

OBJECTIVE: To evaluate image quality and radiation dose exposure of low-kV setting and low-volume contrast medium (CM) computed tomography angiography (CTA) protocol for transcatheter aortic valve implantation (TAVI) planning in comparison with standard CTA protocol. METHODS: Sixty-patients were examined with 256-row MDCT for TAVI planning: 32 patients (study group) were evaluated using 80-kV electrocardiogram-gated protocol with 60 mL of CM and IMR reconstruction; 28 patients underwent a standard electrocardiogram-gated CTA study (100 kV; 80 mL of CM; iDose4 reconstruction). Subjective and objective image quality was evaluated in each patient at different aortic levels. Finally, we collected radiation dose exposure data (CT dose index and dose-length product) of both groups. RESULTS: In study protocol, significant higher mean attenuation values were achieved in all measurements compared with the standard protocol. There were no significant differences in the subjective image quality evaluation in both groups. Mean dose-length product of study group was 56% lower than in the control one (P < 0.0001). CONCLUSION: Low-kV and low-CM volume CTA, combined with IMR, allows to correctly performing TAVI planning with high-quality images and significant radiation dose reduction compared with standard CTA protocol.


Assuntos
Estenose da Valva Aórtica/diagnóstico por imagem , Angiografia por Tomografia Computadorizada/métodos , Meios de Contraste/administração & dosagem , Interpretação de Imagem Radiográfica Assistida por Computador/métodos , Adulto , Idoso , Idoso de 80 Anos ou mais , Algoritmos , Estenose da Valva Aórtica/cirurgia , Feminino , Humanos , Bases de Conhecimento , Masculino , Pessoa de Meia-Idade , Tomografia Computadorizada Multidetectores , Período Pré-Operatório , Doses de Radiação , Substituição da Valva Aórtica Transcateter
7.
J Comput Assist Tomogr ; 44(1): 26-31, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-31939878

RESUMO

Coronary computed tomography angiography is widely used in clinical practice. Although 3-dimensional (D) volume rendering is useful for interpretation of coronary path and territory, 2D output is common for image interpretation. Most picture archiving and communication system is incapable of manipulating 3D due to insufficient graphic specification. Thus, 2D bull's eye map display is frequently used in cardiac imaging. We developed a bull's eye map which emulated the anatomical information of individual coronary path and dominancy.


Assuntos
Vasos Coronários/diagnóstico por imagem , Ventrículos do Coração/diagnóstico por imagem , Interpretação de Imagem Radiográfica Assistida por Computador/métodos , Idoso , Algoritmos , Angiografia por Tomografia Computadorizada , Feminino , Humanos , Imagem Tridimensional , Masculino , Pessoa de Meia-Idade , Estudos Retrospectivos
8.
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
9.
J Comput Assist Tomogr ; 44(1): 83-89, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-31939887

RESUMO

RATIONALE AND OBJECTIVES: This novel study aims to investigate texture parameters in distinguishing malignant and benign breast lesions classified as Breast Imaging Reporting and Data System 4 in dynamic contrast-enhanced magnetic resonance imaging (MRI). MATERIALS AND METHODS: This retrospective study included 203 patients with 136 breast cancer and 67 benign lesions who underwent breast MRI between November 23, 2016, and August 27, 2018. Co-occurrence matrix-based texture features were extracted from each lesion on T1-weighted contrast-enhanced MRI using MatLab software. The association between texture parameters and breast lesions was analyzed, and the diagnostic model for breast cancer was created. Classification performance was evaluated by the area under the receiver operating characteristic curve, sensitivity, and specificity. RESULTS: Significant differences were seen between malignant and benign lesions for a number of textural features, including contrast, correlation, autocorrelation, dissimilarity, cluster shade, and cluster performance (P < 0.05). After the analysis of the multicollinearity, 5 texture features (contrast, correlation, dissimilarity, cluster shade, and cluster performance) were included for the next principal component analysis. The differentiation accuracy of breast cancer based on the diagnostic model was 0.948 (95% confidence interval, 0.908-0.974). CONCLUSIONS: Texture features that measure randomness, heterogeneity, or homogeneity may reflect underlying growth patterns of breast lesions and show great difference in malignant and benign lesions. Therefore, texture analysis may be a valuable assisted tool for diagnostic analysis on breast.


Assuntos
Neoplasias da Mama/diagnóstico por imagem , Interpretação de Imagem Radiográfica Assistida por Computador/métodos , Adolescente , Adulto , Idoso , Idoso de 80 Anos ou mais , Algoritmos , Área Sob a Curva , Feminino , Humanos , Imagem por Ressonância Magnética , Pessoa de Meia-Idade , Estudos Retrospectivos , Sensibilidade e Especificidade , Adulto Jovem
10.
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
11.
J Comput Assist Tomogr ; 44(1): 138-144, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-31939895

RESUMO

OBJECTIVE: The aim of this study was to determine the influence of virtual monoenergetic images (vMEIs) on renal cortex volumetry (RCV) and estimation of split-renal function. METHODS: Twenty-five patients (mean ± SD, 64.7 ± 9.9 years) underwent a contrast-enhanced dual-layer spectral detector computed tomography. Images were reconstructed with a reference standard (iterative model reconstruction, IMRRef), a newly spectral detector computed tomography algorithm (SPcon) and vMEI at 40, 60, 80, 100, and 120 keV. Two blinded independent readers performed RCV on all data sets with a semiautomated tool. RESULTS: Total kidney volume was up to 15% higher in vMEI at 40/60 keV compared with IMRRef (P < 0.001). Total kidney volume with vMEI at 80/100 keV was similar to IMRRef (P < 0.001). Split-renal function was similar in all reconstructions at approximately 50% ± 3%. Bland-Altman analysis showed no significant differences (P > 0.05), except for 40 keV versus SPcon (P < 0.05). The time required to perform RCV was reasonable, approximately 4 minutes, and showed no significant differences among reconstructions. Interreader agreement was greatest with vMEI at 80 keV (r = 0.68; 95% confidence interval, 0.39-0.85; P < 0.0002) followed by IMRRef images (r = 0.67; 95% confidence interval, 0.37-0.84; P < 0.0003). IMRRef showed the highest mean Hounsfield unit for cortex/medulla of 223.4 ± 73.7/62.5 ± 19.7 and a ratio of 3.7. CONCLUSIONS: Semiautomated RCV performed with vMEI and IMRRef/SPcon is feasible and showed no clinically relevant differences with regard to split-renal function. Low-kiloelectron volt vMEI showed greater tissue contrast and total kidney volume but no benefit for RCV. Moderate-kiloelectron volt vMEI (80 keV) results were similar to IMRRef with a faster postprocessing time.


Assuntos
Córtex Renal/diagnóstico por imagem , Interpretação de Imagem Radiográfica Assistida por Computador/métodos , Imagem Radiográfica a Partir de Emissão de Duplo Fóton/métodos , Tomografia Computadorizada por Raios X/métodos , Idoso , Algoritmos , Feminino , Humanos , Córtex Renal/patologia , Masculino , Pessoa de Meia-Idade , Variações Dependentes do Observador , Estudos Retrospectivos , Sensibilidade e Especificidade , Razão Sinal-Ruído
12.
J Chem Theory Comput ; 16(1): 601-611, 2020 Jan 14.
Artigo em Inglês | MEDLINE | ID: mdl-31841332

RESUMO

Extensive benchmarking calculations are presented to assess the accuracy of the standard approximate coupled cluster singles and doubles method (CC2) in studying ππ* excited states properties of model protein chains containing a phenylalanine residue, namely capped peptides, whose ground state conformers adopt the prototypical secondary structural features of proteins. First, the dependence with the basis set of the CC2 excitation energies, CC2 geometry optimizations, and amide A region frequencies of the lowest ππ* excited state in a reference system, the N-acetylphenylalaninylamide, are investigated, and the results are compared with experimental data. Second, at the best level of theory determined, the CC2/aug(N,O,π)-cc-pVDZ//CC2/cc-pVDZ level, a series of capped peptides of increasing size and containing residues of different nature are investigated. Along the series, compared to the experimental values, a mean absolute error of 0.10 eV is achieved for the 0-0 transition energies with a systematic overestimation. In addition, mode-dependent linear scaling functions for the calculated frequencies of the amide A region have been determined from the set of 95 experimental frequencies available; they lead to a quantitative simulation of the observed shifts of the amide A region frequencies upon ππ* excitation (root-mean-square deviation of 5 cm-1). These results confirm the reliability of the CC2 method to characterize the lowest ππ* excited state of such medium-sized systems, emphasizing this class of theoretical approaches as a relevant spectroscopic tool, including for tasks as difficult as conformational assignment.


Assuntos
Peptídeos/química , Fenilalanina/química , Proteínas/química , Algoritmos , Modelos Moleculares , Teoria Quântica , Termodinâmica
13.
J Orofac Orthop ; 81(1): 52-68, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31853586

RESUMO

PURPOSE: The aim of this investigation was to create an automated cephalometric X­ray analysis using a specialized artificial intelligence (AI) algorithm. We compared the accuracy of this analysis to the current gold standard (analyses performed by human experts) to evaluate precision and clinical application of such an approach in orthodontic routine. METHODS: For training of the network, 12 experienced examiners identified 18 landmarks on a total of 1792 cephalometric X­rays. To evaluate quality of the predictions of the AI, both AI and each examiner analyzed 12 commonly used orthodontic parameters on a basis of 50 cephalometric X­rays that were not part of the training data for the AI. Median values of the 12 examiners for each parameter were defined as humans' gold standard and compared to the AI's predictions. RESULTS: There were almost no statistically significant differences between humans' gold standard and the AI's predictions. Differences between the two analyses do not seem to be clinically relevant. CONCLUSIONS: We created an AI algorithm able to analyze unknown cephalometric X­rays at almost the same quality level as experienced human examiners (current gold standard). This study is one of the first to successfully enable implementation of AI into dentistry, in particular orthodontics, satisfying medical requirements.


Assuntos
Ortodontia , Algoritmos , Inteligência Artificial , Cefalometria , Humanos , Radiografia Dentária
14.
Syst Biol ; 69(1): 76-90, 2020 01 01.
Artigo em Inglês | MEDLINE | ID: mdl-31125064

RESUMO

A statistical framework to infer areas of endemism from geographic distributions is proposed. This novel method is based on hidden Markov random fields (HMRFs), a type of undirected graph model commonly used in computer vision. This framework assumes areas of endemism are the states of the hidden layer of the model, whereas taxon distributions are emitted values in the observed layer. Taxon distributions are associated to the observed layer through a clustering procedure based on the extent of overlap. Observations are emitted by the hidden layer according to a Gaussian distribution, whereas the joint distribution of the hidden layer follows a Potts model. State and parameter inference of the maximum a posteriori configuration is performed through a modified version of the expectation-maximization algorithm. The optimal number of areas of endemism in the data set is estimated through the pseudolikelihood information criterion, a model selection procedure that uses an approximation to likelihood. The performance of the new algorithm was assessed on simulated data, and compared with the most popular methods for delimitation of areas of endemism: biotic element analysis, parsimony analysis of endemism, and endemicity analysis. HMRFs efficiently recovered the true pattern across a wide range of uncertainty values. The performance was also examined on empirical data: South African weevils (Sciobius) and Central American ground beetles and funnel-web tarantulas (Carabidae and Dipluridae, respectively). HMRFs uncovered six areas of endemism from the weevil data set, whereas eight were estimated for the Central American arthropods (compared with 3-5 and 3-14 from the other methods, respectively).


Assuntos
Distribuição Animal , Modelos Estatísticos , Algoritmos , Animais , Simulação por Computador , Cadeias de Markov
15.
Syst Biol ; 69(1): 155-183, 2020 01 01.
Artigo em Inglês | MEDLINE | ID: mdl-31173141

RESUMO

We describe an "embarrassingly parallel" method for Bayesian phylogenetic inference, annealed Sequential Monte Carlo (SMC), based on recent advances in the SMC literature such as adaptive determination of annealing parameters. The algorithm provides an approximate posterior distribution over trees and evolutionary parameters as well as an unbiased estimator for the marginal likelihood. This unbiasedness property can be used for the purpose of testing the correctness of posterior simulation software. We evaluate the performance of phylogenetic annealed SMC by reviewing and comparing with other computational Bayesian phylogenetic methods, in particular, different marginal likelihood estimation methods. Unlike previous SMC methods in phylogenetics, our annealed method can utilize standard Markov chain Monte Carlo (MCMC) tree moves and hence benefit from the large inventory of such moves available in the literature. Consequently, the annealed SMC method should be relatively easy to incorporate into existing phylogenetic software packages based on MCMC algorithms. We illustrate our method using simulation studies and real data analysis.


Assuntos
Algoritmos , Classificação/métodos , Filogenia , Teorema de Bayes , Método de Monte Carlo , Software
16.
Br J Radiol ; 93(1105): 20190289, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31617732

RESUMO

OBJECTIVE: This study investigated the occurrence of cardiotoxicity-related left-ventricular (LV) contractile dysfunction in breast cancer patients following treatment with antineoplastic chemotherapy agents. METHODS: A validated and automated MRI-based LV contractility analysis tool consisting of quantization-based boundary detection, unwrapping of image phases and the meshfree Radial Point Interpolation Method was used toward measuring LV chamber quantifications (LVCQ), three-dimensional strains and torsions in patients and healthy subjects. Data were acquired with the Displacement Encoding with Stimulated Echoes (DENSE) sequence on 21 female patients and 21 age-matched healthy females. Estimates of patient LVCQs from DENSE acquisitions were validated in comparison to similar steady-state free precession measurements and their strain results validated via Bland-Altman interobserver agreements. The occurrence of LV abnormalities was investigated via significant differences in contractility measurements (LVCQs, strains and torsions) between patients and healthy subjects. RESULTS: Repeated measures analysis showed similarities between LVCQ measurements from DENSE and steady-state free precession, including cardiac output (4.7 ± 0.4 L, 4.6 ± 0.4 L, p = 0.8), and LV ejection fractions (59±6%, 58±5%, p = 0.2). Differences found between patients and healthy subjects included enlarged basal diameter (5.0 ± 0.5 cm vs 4.4 ± 0.5 cm, p < 0.01), apical torsion (6.0 ± 1.1° vs 9.7 ± 1.4°, p < 0.001) and global longitudinal strain (-0.15 ± 0.02 vs. -0.21 ± 0.04, p < 0.001), but not LV ejection fraction (59±6% vs. 63±6%, p = 0.1). CONCLUSION: The results from the statistical analysis reveal the possibility of LV abnormalities in the post-chemotherapy patients via enlarged basal diameter and reduced longitudinal strain and torsion, in comparison to healthy subjects. ADVANCES IN KNOWLEDGE: This study shows that subclinical LV abnormalities in post-chemotherapy breast cancer patients can be detected with an automated technique for the comprehensive analysis of contractile parameters.


Assuntos
Antineoplásicos/efeitos adversos , Neoplasias da Mama/tratamento farmacológico , Cardiotoxicidade/diagnóstico por imagem , Interpretação de Imagem Assistida por Computador/métodos , Imagem por Ressonância Magnética/métodos , Disfunção Ventricular Esquerda/induzido quimicamente , Disfunção Ventricular Esquerda/diagnóstico por imagem , Algoritmos , Feminino , Humanos , Pessoa de Meia-Idade , Contração Miocárdica
17.
Br J Radiol ; 93(1105): 20190596, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31625759

RESUMO

OBJECTIVE: This study aimed to compare the plan quality of non-coplanar partial arc (NPA) volumetric modulated arc therapy (VMAT) to that of coplanar partial arc (CPA) VMAT for stereotactic ablative radiotherapy (SABR) for lung cancer. METHODS: A total of 20 patients treated for lung cancer with the SABR VMAT technique and whose lung tumors were close to the heart were retrospectively selected for this study. For the CPA VMAT, three coplanar half arcs were used while two coplanar half arcs and one noncoplanar arc rotating 315°-45° with couch rotations of 315° ± 5° were used for the NPA VMAT. For each patient, identical CT image sets and identical structures were used for both the CPA and NPA VMAT plans. Dose-volumetric parameters of each plan were analyzed. RESULTS: For the planning target volume and both lungs, no statistically significant differences between the CPA and NPA VMAT plans were observed in general. For the heart, average values of D0.1cc of the CPA and NPA VMAT plans were 29.42 ± 13.37 and 21.71 ± 9.20 Gy, respectively (p < 0.001). For whole body, the mean dose and the gradient index of the CPA VMAT plans were 1.2 ± 0.5 Gy and 4.356 ± 0.608 while those of the NPA VMAT plans were 1.1 ± 0.5 Gy and 4.111 ± 0.480, respectively (both with p < 0.001). CONCLUSION: The NPA VMAT proposed in this study showed more favorable plan quality than the CPA VMAT plans for lung SABR with tumors located close to the heart. ADVANCES IN KNOWLEDGE: For lung SABR, NPA VMAT can reduce doses to the heart as well as whole-body irradiation.


Assuntos
Coração/efeitos da radiação , Neoplasias Pulmonares/radioterapia , Radiocirurgia/métodos , Planejamento da Radioterapia Assistida por Computador/métodos , Radioterapia de Intensidade Modulada/métodos , Algoritmos , Anisotropia , Fracionamento da Dose de Radiação , Humanos , Órgãos em Risco/efeitos da radiação , Dosagem Radioterapêutica , Estudos Retrospectivos , Tomografia Computadorizada por Raios X
18.
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
19.
Br J Radiol ; 93(1105): 20190655, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31670569

RESUMO

OBJECTIVE: MRI provides clear visualization of spinal cord, tumor, and bone for patient positioning and verification during MRI-guided radiotherapy (MRI-RT). Therefore, we wished to evaluate spine stereotactic ablative radiotherapy (SABR) feasibility with MRI-RT. Given dosimetric limitations of first generation Co-60 MRI-RT, we then evaluated improvements by newer linear accelerator (linac) MRI-RT. METHODS: Nine spinal metastases were treated with Co-60 MRI-RT. Seven received a single 16 Gy fraction, and two received three fractions totaling 24 or 30 Gy. After replanning with linac MRI-RT software, comparisons of organ at risk and dose spillage objectives between Co-60 and linac plans were performed. RESULTS: Spinal cord and cauda equina dose constraints were met in all Co-60 cases. Treatments were delivered successfully with real-time imaging during treatment and no treatment-related toxicities. While limits for dose spillage into surrounding soft tissues were not achieved due to the limitations of the Co-60 system, this could be corrected with linac MRI-RT delivery. CONCLUSIONS: MRI-RT SABR of spinal metastases is feasible with Co-60 MRI-RT. Dose delivery is improved by linac MRI-RT. ADVANCES IN KNOWLEDGE: This is the first report of MRI-RT for SABR of spinal metastases. The enhanced visualization of anatomy by MRI may facilitate RT dose escalation for spine SABR.


Assuntos
Imagem por Ressonância Magnética , Radiocirurgia/métodos , Planejamento da Radioterapia Assistida por Computador/métodos , Radioterapia Guiada por Imagem/métodos , Neoplasias da Coluna Vertebral/diagnóstico por imagem , Neoplasias da Coluna Vertebral/radioterapia , Algoritmos , Radioisótopos de Cobalto , Fracionamento da Dose de Radiação , Humanos , Órgãos em Risco , Posicionamento do Paciente , Dosagem Radioterapêutica , Neoplasias da Coluna Vertebral/secundário
20.
Br J Radiol ; 93(1105): 20190743, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31670581

RESUMO

OBJECTIVES: Anatomic changes may occur during chemoradiation treatment for lung cancers, requiring adaptive replanning. Here we characterize these cases. METHODS: We retrospectively studied lung cancer cases that underwent resimulation and adaptive replanning during 1/2016-3/2019. We compared first and second CT-simulation regarding tumor location, timing of change, tumor volume, anatomical alteration and change in simulation technique. We also compared dosimetric parameters between the plans, recorded local control, and overall survival outcomes. RESULTS: Out of 281 patients, 58 underwent replanning (20.6%). Histology included small cell (22.4%) and non-small cell (77.6%). Stage III was in 91.4%. Mean radiation dose of 59.4 Gray (Gy) (range 50-66Gy).Tumor location was peribronchial in 53.5%. Timing of replanning was in the first, second and final third of the treatment course in 26%, 43% and 31% respectively. Changes in gross tumor volume were observed in 74%; mean gross tumor volume was 276.7cc vs 192.7 cc (first vs second simulation, p = 0.001). Anatomical changes were identified in 35.4% including pleural fluid accumulation, atelectasis or pneumothorax alteration. Change in simulation technique was performed in 25.9%, including breath-hold or continuous positive airway pressure.Changes in dosimetric parameters when the same technique was used: lung V20Gy 26% (standard deviation, SD 7.6) vs 25.3% (SD 6.6) (p = 0.36), mean lung dose 15.1 Gy (SD 3.7) vs 14.7Gy (SD 3.3) (p = 0.23), heart V40Gy 10.2% (SD13) vs 7.2% (SD 9.8) (p = 0.037). When simulation technique changed: lung V20Gy 30.8% (SD 8.2) vs 27.3% (SD 8) (p = 0.012), mean lung dose 17.3 Gy (SD 4.4) vs 15.3 Gy (SD 3.8) (p = 0.007), heart V40Gy 11.1% (SD 14.7) vs 6.5% (SD 6.7) (p = 0.014).2 year local control was 60.7% (95% confidence interval, 34.5-79.2%), and median overall survival was 19.7 months. CONCLUSION: Adaptive replanning of radiation was performed in a fifth of locally advanced lung cancer patients. In most cases tumor volume decreased, or atelectasis resolved, causing mediastinal shifts, which, if unidentified and left uncorrected, may have led to local failure and increased toxicity. The heart V40Gy was reduced significantly in all cases, but significant reduction in lung doses was evident only if simulation technique was altered. ADVANCES IN KNOWLEDGE: In locally advanced lung cancer image-guidance with cone beam CT can detect significant mediastinal shifts and gross tumor volume changes that raise the need for adaptive replanning. Image guidance-triggered adaptive replanning should be added to the armament of advanced radiation treatment planning in locally advanced lung cancer.


Assuntos
Neoplasias Pulmonares/diagnóstico por imagem , Neoplasias Pulmonares/radioterapia , Planejamento da Radioterapia Assistida por Computador/métodos , Radioterapia Guiada por Imagem/métodos , Tomografia Computadorizada por Raios X/métodos , Adulto , Idoso , Idoso de 80 Anos ou mais , Algoritmos , Quimiorradioterapia , Feminino , Humanos , Neoplasias Pulmonares/patologia , Masculino , Pessoa de Meia-Idade , Estadiamento de Neoplasias , Dosagem Radioterapêutica , Taxa de Sobrevida
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