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PURPOSE: This work proposes the ISMRM Raw Data format as a common MR raw data format, which promotes algorithm and data sharing. METHODS: A file format consisting of a flexible header and tagged frames of k-space data was designed. Application Programming Interfaces were implemented in C/C++, MATLAB, and Python. Converters for Bruker, General Electric, Philips, and Siemens proprietary file formats were implemented in C++. Raw data were collected using magnetic resonance imaging scanners from four vendors, converted to ISMRM Raw Data format, and reconstructed using software implemented in three programming languages (C++, MATLAB, Python). RESULTS: Images were obtained by reconstructing the raw data from all vendors. The source code, raw data, and images comprising this work are shared online, serving as an example of an image reconstruction project following a paradigm of reproducible research. CONCLUSION: The proposed raw data format solves a practical problem for the magnetic resonance imaging community. It may serve as a foundation for reproducible research and collaborations. The ISMRM Raw Data format is a completely open and community-driven format, and the scientific community is invited (including commercial vendors) to participate either as users or developers. Magn Reson Med 77:411-421, 2017. © 2016 Wiley Periodicals, Inc.
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Processamento de Imagem Assistida por Computador/métodos , Imageamento por Ressonância Magnética/métodos , Software , Algoritmos , Bases de Dados Factuais , Imagens de Fantasmas , Razão Sinal-RuídoRESUMO
BACKGROUND: Cone beam computed tomography (CBCT) provides means for respiratory resolved volumetric imaging of the thorax. However, merely sorting the acquired projections into respiratory phases and performing a series of conventional three-dimensional (3D) reconstructions lead to clinically prohibitive reconstruction artifacts. This problem can be mitigated by iterative 4D reconstruction. We present a clinical evaluation of two iterative 4D-CBCT reconstruction algorithms during stereotactic body radiation therapy. MATERIAL AND METHODS: Two types of iterative 4D-CBCT reconstructions were performed utilizing: 1) total variation (TV) minimization; and 2) optical flow (OF) based deformable registration between phases. The reconstructions were initially evaluated on a lung phantom with a moveable target insert. Subsequently, 4D-CBCT reconstructions were performed for 19 patients on 2-3 CBCT projection datasets previously acquired for conventional 3D-CBCT reconstruction (â¼650 half-fan projections per scan in a full one-minute gantry rotation). The 4D reconstructions were imported into a treatment planning system, where the gross tumor volume (GTV) was delineated and used to extract the tumor motion amplitude. RESULTS: For both phantom and patient scans, the iterative 4D-CBCT reconstructions had sufficient quality for GTV delineation when the breathing period was faster than 3.5 seconds (15 of 19 patients), but not for slower breathing periods (4 patients). The 3D tumor motion amplitude for the patients was significantly lower (p = 10(-6), Wilcoxon signed rank test) in the OF reconstructions (mean 4.0 mm) than in the TV reconstructions (mean 5.3 mm). CONCLUSION: TV and OF iterative 4D-CBCT reconstruction of the thorax in a lung phantom and for 19 patients was demonstrated from standard CBCT scans and used to estimate the daily lung tumor motion.
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Algoritmos , Artefatos , Tomografia Computadorizada de Feixe Cônico/métodos , Tomografia Computadorizada Quadridimensional/métodos , Neoplasias Pulmonares/diagnóstico por imagem , Movimento , Respiração , Idoso , Idoso de 80 Anos ou mais , Humanos , Processamento de Imagem Assistida por Computador , Neoplasias Pulmonares/patologia , Pessoa de Meia-Idade , Imagens de Fantasmas , Estudos Retrospectivos , Pesquisa Translacional Biomédica , Carga TumoralRESUMO
BACKGROUND: Methods to accurately accumulate doses in radiotherapy (RT) are important for tumour and normal tissues being influenced by geometric uncertainties. The purpose of this study was to investigate a pre-release deformable image registration (DIR)-based dose accumulation application, in the setting of prostate RT. MATERIAL AND METHODS: Initially accumulated bladder and prostate doses were assessed (based on 8-9 repeat CT scans/patient) for nine prostate cancer patients using an intensity-based DIR and dose accumulation algorithm as provided by the Dynamic Adaptive Radiation Therapy (DART) software. The accumulated bladder and prostate dose-volume histograms (DVHs) were compared on a range of parameters (paired Wilcoxon signed-rank test, 5% significance level) to DVHs derived using an in-house developed dose accumulation method based on biomechanical, contour-driven DIR (SurfaceRegistration). Finally, both these accumulated dose distributions were compared to the 'static' DVH, assessed from the planning CT. RESULTS: Over the population, doses accumulated with DART were overall lower than those from SurfaceRegistration (p < 0.05: D2%, gEUD and NTCP (bladder); Dmin (prostate)). The magnitude of these differences peaked for the bladder gEUD with a population median of 47 Gy for DART versus 57 Gy for SurfaceRegistration. Across the ten bladder dose/volume parameters investigated, the most pronounced individual differences were observed between the 'accumulated' DVHs and the 'static' DVHs, with deviations in mean dose up to 22 Gy. CONCLUSION: Substantial and significant differences were observed in the dose distributions between the two investigated DIR-based dose accumulation applications. The most pronounced individual differences were seen for the bladder and relative to the planned dose distribution, encouraging the use of repeat imaging data in RT planning and evaluation for this organ.
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Próstata/efeitos da radiação , Neoplasias da Próstata/radioterapia , Bexiga Urinária/efeitos da radiação , Relação Dose-Resposta à Radiação , Humanos , Masculino , Órgãos em Risco/efeitos da radiação , Próstata/diagnóstico por imagem , Neoplasias da Próstata/diagnóstico por imagem , Dosagem Radioterapêutica , Radioterapia de Intensidade Modulada , Estatísticas não Paramétricas , Tomografia Computadorizada por Raios X/métodos , Bexiga Urinária/diagnóstico por imagemRESUMO
Cardiac function has traditionally been evaluated using breath-hold cine acquisitions. However, there is a great need for free breathing techniques in patients who have difficulty in holding their breath. Real-time cardiac MRI is a valuable alternative to the traditional breath-hold imaging approach, but the real-time images are often inferior in spatial and temporal resolution. This article presents a general method for reconstruction of high spatial and temporal resolution cine images from a real-time acquisition acquired over multiple cardiac cycles. The method combines parallel imaging and motion correction based on nonrigid registration and can be applied to arbitrary k-space trajectories. The method is demonstrated with real-time Cartesian imaging and Golden Angle radial acquisitions, and the motion-corrected acquisitions are compared with raw real-time images and breath-hold cine acquisitions in 10 (N = 10) subjects. Acceptable image quality was obtained in all motion-corrected reconstructions, and the resulting mean image quality score was (a) Cartesian real-time: 2.48, (b) Golden Angle real-time: 1.90 (1.00-2.50), (c) Cartesian motion correction: 3.92, (d) Radial motion correction: 4.58, and (e) Breath-hold cine: 5.00. The proposed method provides a flexible way to obtain high-quality, high-resolution cine images in patients with difficulty holding their breath.
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Artefatos , Técnicas de Imagem de Sincronização Cardíaca/métodos , Coração/anatomia & histologia , Aumento da Imagem/métodos , Imagem Cinética por Ressonância Magnética/métodos , Técnica de Subtração , Algoritmos , Humanos , Interpretação de Imagem Assistida por Computador/métodos , Movimento (Física) , Reconhecimento Automatizado de Padrão/métodos , Reprodutibilidade dos Testes , Sensibilidade e EspecificidadeRESUMO
BACKGROUND AND AIM OF THE STUDY: The assessment of three-dimensional (3-D) mitral valve geometry in patients with chronic functional ischemic mitral valve regurgitation (FIMR) has been hampered by a lack of adequate imaging techniques. The study aim was to use a clinically applicable cardiac magnetic resonance imaging (MRI) technique to assess the 3-D mitral annular, leaflet and papillary muscle geometry in pigs with chronic FIMR. METHODS: Ten pigs with moderate chronic FIMR induced by catheter-based coiling of the circumflex artery, were examined using cardiac MRI. The reconstruction of 3-D data from two-dimensional cardiac MRI scans allowed the mitral annulus and leaflet geometries to be assessed. Using 3-D morphology scans, the spatial position of the posterior papillary muscle (PPM) relative to the anterior papillary muscle (APM), mitral annulus and anterior (A-trig) and posterior (P-trig) trigones was assessed. Using dedicated software for image analysis, data were transferred to a Cartesian coordinate system (x,y,z) for geometric analysis. Ten healthy pigs served as controls. RESULTS: Compared to controls, at end-systole in the chronic FIMR group the PPM was significantly displaced (p <0.05) from the APM (38 +/- 2 versus 23 +/- 1 mm), A-trig (48 +/- 2 versus 36 +/- 1 mm) and P-trig (41 +/-1 versus 33 +/- 1 mm). There was no significant apical PPM displacement (20 +/- 2 versus 20 +/- 1 mm). The annular area (1,240 +/- 90 versus 850 +/- 90 mm2), septolateral distance (36 +/- 2 versus 26 +/- 1 mm), commissure-to-commissure distance (38 +/- 2 versus 33 +/- 1 mm), mean tenting height (8 +/- 1 versus 5 +/- 0 mm), maximum tenting height (10 +/- 1 versus 7 +/- 0 mm), tenting volume (2,600 +/- 400 versus 1,500 +/- 200 mm3), and occlusional leaflet area (1,820 +/- 110 versus 1,120 +/- 70 mm2) were each significantly increased. CONCLUSION: This clinically applicable cardiac MRI modality permitted a detailed geometric insight to be made into the mitral annular, leaflet and PPM geometries that cause FIMR. Such a reliable tool for geometric mitral valve analysis has previously been demonstrated only by using invasive techniques. Hence, this approach holds promise for further clarifying the pathogenesis of chronic FIMR and improving preoperative surgical planning.
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Imageamento Tridimensional/métodos , Imageamento por Ressonância Magnética/métodos , Insuficiência da Valva Mitral/patologia , Valva Mitral/patologia , Isquemia Miocárdica/patologia , Animais , Doença Crônica , Modelos Animais de Doenças , Valva Mitral/fisiopatologia , Insuficiência da Valva Mitral/complicações , Insuficiência da Valva Mitral/fisiopatologia , Contração Miocárdica/fisiologia , Isquemia Miocárdica/complicações , Isquemia Miocárdica/fisiopatologia , Músculos Papilares/patologia , Reprodutibilidade dos Testes , Índice de Gravidade de DoençaRESUMO
OBJECTIVES: To assess the impact of head motion artefacts and an automated artefact-correction system on cone beam CT (CBCT) image quality and interpretability for simulated diagnostic tasks. METHODS: A partially dentate human skull was mounted on a robot simulating four types of head movement (anteroposterior translation, nodding, lateral rotation, and tremor), at three distances (0.75, 1.5, and 3 mm) based on two movement patterns (skull returning/not returning to the initial position). Two diagnostic tasks were simulated: dental implant planning and detection of a periapical lesion. Three CBCT units were used to examine the skull during the movements and no-motion (control): Cranex 3Dx (CRA), Orthophos SL 3D (ORT), and X1 without (X1wo) and with (X1wi) an automated motion artefact-correction system. For each diagnostic task, 88 examinations were performed. Three observers, blinded to unit and movement, scored image quality: presence of stripe artefacts (present/absent), overall unsharpness (present/absent), and image interpretability (interpretable/non-interpretable). κ statistics assessed interobserver agreement, and descriptive statistics summarized the findings. RESULTS: Interobserver agreement for image interpretability was good (average κ = 0.68). Regarding dental implant planning, X1wi images were interpretable by all observers, while for the other units mainly the cases with tremor were non-interpretable. Regarding detection of a periapical lesion, besides tremor, most of the 3 mm movements based on the "not returning" pattern were also non-interpretable for CRA, ORT, and X1wo. For X1wi, two observers scored 1.5 mm tremor and one observer scored 3 mm tremor as non-interpretable. CONCLUSIONS: The automated motion artefact-correction system significantly enhanced CBCT image quality and interpretability.
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Artefatos , Tomografia Computadorizada de Feixe Cônico/métodos , Movimentos da Cabeça , Intensificação de Imagem Radiográfica/métodos , Humanos , Técnicas In Vitro , Modelos AnatômicosRESUMO
OBJECTIVES: To assess the accuracy of detecting robot-simulated head movements using video observation (VO) and 3-dimensional head tracking (HT) in a cone beam computed tomography examination setup. STUDY DESIGN: A mannequin head was mounted on a robot that was programmed to simulate patient head movements. Six types of movement (tremor, nodding, lateral rotation, lifting, swallowing, and anteroposterior translation), 3 distances (0.25, 1, and 5 mm), and 2 speeds (1 and 5 mm/s) were tested in triplicate (108 examinations). An additional 18 videos and HT of no-motion served as controls for a total of 126 examinations. Three blinded observers viewed video recordings of the examinations, scoring whether the head moved and the movement type. HT provided quantitative measures of movement distance. Accuracy, sensitivity, and specificity for movement detection by VO and HT were calculated, related to true type, distance, and speed of movement. Differences between the true and the measured movement distances were assessed for HT. RESULTS: VO movement detection presented accuracy of 0.86, sensitivity of 0.85, and specificity of 0.94. Anteroposterior translation (33.3%) and 0.25 mm movements (41.7%) were often not detected by VO. HT correctly detected all cases (accuracy = 1). HT presented small differences between the true and the measured movement distances (average 20-54 µm). CONCLUSIONS: VO missed 41.7% of the 0.25 mm movements. HT correctly detected all movements and quantified movements with an average error <55 µm.
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Tomografia Computadorizada de Feixe Cônico/métodos , Movimentos da Cabeça , Robótica , Humanos , Imageamento Tridimensional , Manequins , Observação , Rotação , Sensibilidade e Especificidade , Gravação em VídeoRESUMO
PURPOSE: To compare the dose accumulation for bladder and rectum by deformable image registration (DIR) and direct addition (DA) of dose volume histogram parameters in magnetic resonance image-guided adaptive brachytherapy (IGABT). Two DIR algorithms, contour- and intensity-based, also have been analyzed. METHODS AND MATERIALS: Patients (n = 21) treated with IGABT for carcinoma cervix under the IntErnational study on MRI-guided BRachytherapy in locally Advanced CErvical cancer protocol were analyzed. Each patient underwent two HDR-BT applications, 1-week apart with two fractions of 7 Gy each delivered per application. For each application, magnetic resonance imaging, volume delineation, reconstruction, treatment planning (BT1 and BT2), and dose evaluation were carried out. BT1 and BT2 images were registered using an intensity-based DIR, followed by deformable dose accumulation (DDA), which was then compared with DA. To compare the intensity-based DIR to other DIR approaches, nine patients were further evaluated using an in-house contour-based DIR algorithm for bladder dose accumulation. RESULTS: Mean (±standard deviation; range) percentage variation between DA and DDA was found to be 2.4% (±3.3;-1.8, 11.5) and 5.2% (±5.1;-1.7, 16.5) for the rectum and bladder, respectively. The differences between the DA and DDA were found to be statistically significant for both rectum (p = 0.008) and bladder (p = 0.0003). Intensity-based DIR algorithm resulted in a larger mean deviation between DDA and DA as compared with contour-based DIR, although statistically insignificant (p = 0.32). The difference between DDA and DA was 2.4 ± 2.0% and 1.3 ± 1.2%, for intensity- and contour-based DIR, respectively. CONCLUSIONS: DA of dose volume histogram parameters provides a good estimate to the dose to the organs at risk; DIR based on image intensities may lead to systematic underestimation of dose due to implausible DIR.
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Algoritmos , Braquiterapia , Órgãos em Risco , Doses de Radiação , Radioterapia Guiada por Imagem , Reto , Bexiga Urinária , Neoplasias do Colo do Útero/radioterapia , Adulto , Idoso , Feminino , Humanos , Imageamento por Ressonância Magnética , Masculino , Dosagem Radioterapêutica , IncertezaRESUMO
BACKGROUND: Real-time magnetic resonance imaging (MRI) imaging with real-time reconstruction has been available for some time. The technique acquires and presents the MRI images to the operator the instant they are acquired. However, besides guiding purposes, like catheter tracking and placement of electrodes during neurosurgery, the diagnostic value of this method is relatively unexplored. PURPOSE: To test an interactive slice-positioning system with respect to real-time MRI reconstruction for imaging of moving anatomical structures on two different scanner brands by using inexpensive computer hardware. MATERIALS AND METHODS: The MRI data were sampled using two acquisition schemes: a Cartesian sampling scheme and a radial sampling scheme based on the golden ratio. Four anatomical targets, which exhibit non-periodic movement, were identified and imaged: movement of the gastric ventricle emptying, movement of the small bowels, the articulators of a professional singer and of a 20-week old fetus. RESULTS: Informative anatomical images were obtained in different settings of moving targets. The implemented real-time system acquired, reconstructed and displayed MRI images in real time with a high frame rate using inexpensive computer hardware on two standard 1.5 T clinical MRI scanners. CONCLUSION: Our approach verified that when imaging selected moving anatomical targets, with no a priori knowledge of the movement, interactive slice positioning using real-time reconstruction may be a feasible approach for finding the optimal slice position in cases in which a standard 3D volumetric scan is impeded by movement. Future studies are needed to explore its full potential.
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Movimento Fetal , Esvaziamento Gástrico , Interpretação de Imagem Assistida por Computador , Intestino Delgado/fisiologia , Imageamento por Ressonância Magnética , Movimento , Faringe/fisiologia , Diagnóstico Pré-Natal/métodos , Fenômenos Biomecânicos , Estudos de Viabilidade , Feminino , Idade Gestacional , Humanos , Fonação , Valor Preditivo dos Testes , Gravidez , Fatores de Tempo , VozRESUMO
OBJECTIVE: Papillary muscle displacement relative to mitral annulus is pivotal in chronic functional ischemic mitral regurgitation. Analysis of 3-dimensional papillary muscle displacement has relied on invasive measurement. In this study, we used noninvasive clinically applicable 3-dimensional morphology cardiac magnetic resonance imaging to define papillary muscle position in a 3-dimensional matrix. METHODS: Fifty pigs (approximately 50 kg) were subjected to posterolateral myocardial infarction and tachycardiac stress. Fourteen animals survived 6 weeks: 10 acquired chronic functional ischemic mitral regurgitation at least grade II and 4 did not. Animals were examined by 3-dimensional morphology cardiac magnetic resonance imaging, and dedicated software enabled assessment of anterior and posterior papillary muscle positions relative to anterior and posterior trigones and posterior mitral annulus. Animals with functional ischemic mitral regurgitation were compared with those without and with 10 healthy controls. RESULTS: Relative to controls, animals with functional ischemic mitral regurgitation at end systole had significantly higher displacements of the posterior papillary muscle from anterior and posterior trigones in lateral and posterior directions, and of anterior papillary muscle from anterior and posterior trigones in apical direction. Relative to animals without functional ischemic mitral regurgitation, there was significantly higher posterior papillary muscle displacement from posterior trigone in lateral direction. Interpapillary muscle distance was the strongest predictor of regurgitant volume (r(2) = 0.85, P < .001). CONCLUSIONS: Three-dimensional morphology cardiac magnetic resonance imaging enabled detailed analysis of local left ventricular remodeling effects causing functional ischemic mitral regurgitation.
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Imageamento Tridimensional , Imageamento por Ressonância Magnética/métodos , Insuficiência da Valva Mitral/fisiopatologia , Músculos Papilares/fisiopatologia , Animais , Angiografia Coronária , Modelos Animais de Doenças , Ecocardiografia , Feminino , Hemodinâmica , Modelos Lineares , SuínosRESUMO
This study demonstrates that modern commodity graphics cards (GPUs) can be used to perform fast Cartesian SENSE and k-t SENSE reconstruction. Specifically, the SENSE inversion is accelerated by up to two orders of magnitude and is no longer the time-limiting step. The achieved reconstruction times are now well below the acquisition times, thus enabling real-time, interactive SENSE imaging, even with a large number of receive coils. The fast GPU reconstruction is also beneficial for datasets that are not acquired in real time. We demonstrate that it can be used for interactive adjustment of regularization parameters for k-t SENSE in the same way that one would adjust window and level settings. This enables a new way of performing imaging reconstruction, where the user chooses the setting of tunable reconstruction parameters, in real time, depending on the context in which the images are interpreted.
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Algoritmos , Gráficos por Computador , Processamento de Imagem Assistida por Computador , Imageamento por Ressonância Magnética , HumanosRESUMO
PURPOSE: First, to measure renal cortical volume (Vc) using different MRI methods combined with a semiautomatic segmentation method. Second, to compare MRI measurements of Vc using the semiautomatic segmentation method with a manual segmentation method. Third, to evaluate the reproducibility of Vc measurements. MATERIALS AND METHODS: A total of 22 pigs, 13 with healthy kidneys and nine with diseased kidneys, underwent MRI with two non-contrast-agent methods (MRI 100 x 900 and MRI 300 x 1100) and one contrast-agent method (MRI Gd). For each of these methods, Vc was estimated using semiautomatic (Vc(100 x 900), Vc(300 x 1100), and Vc(Gd)), as well as manual (Vc MANUAL) segmentation. Reference volumes were estimated by stereological means (Vc STEREOLOGY). MRI-derived volumes were compared with reference volumes using a two-tailed paired t-test, and variances between methods were visualized with Bland Altman plots. Reproducibilities were analyzed using covariance analysis. RESULTS: Neither measurements of Vc 100 x 900, Vc 300 x 1100, nor Vc Gd differed markedly from Vc STEREOLOGY using semiautomatic segmentation. Vc was comparable when semiautomatic and manual segmentations were performed at the same scan. Reproducibility of MRI estimated Vc values offered intra- and interindividual differences <5%. CONCLUSION: Vc can in both healthy and diseased kidneys be measured accurately with MRI using both semiautomatic and manual segmentation, and measurements can be obtained with a high reproducibility. Measurements of Vc 100 x 900 may in the future become suitable in patients with chronic renal failure.