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1.
Eur J Radiol ; 154: 110445, 2022 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-35901601

RESUMO

PURPOSE: To assess the clinical effectiveness of temporal subtraction computed tomography (TS CT) using deep learning to improve vertebral bone metastasis detection. METHOD: This retrospective study used TS CT comprising bony landmark detection, bone segmentation with a multi-atlas-based method, and spatial registration of two images by a log-domain diffeomorphic Demons algorithm. Paired current and past CT images of 50 patients without vertebral metastasis, recorded during June 2011-September 2016, were included as training data. A deep learning-based method estimated registration errors and suppressed false positives. Thereafter, paired CT images of 40 cancer patients with newly developed vertebral metastases and 40 control patients without vertebral metastases were evaluated. Six board-certified radiologists and five radiology residents independently interpreted 80 paired CT images with and without TS CT. RESULTS: Records of 40 patients in the metastasis group (median age: 64.5 years; 20 males) and 40 patients in the control group (median age: 64.0 years; 20 males) were evaluated. With TS CT, the overall figure of merit (FOM) of the board-certified radiologist and resident groups improved from 0.848 to 0.876 (p = 0.01) and from 0.752 to 0.799 (p = 0.02), respectively. The sub-analysis focusing on attenuation changes in lesions revealed that the FOM of osteoblastic lesions significantly improved in both the board-certified radiologist and resident groups using TS CT. The sub-analysis focusing on lesion location showed that the FOM of the resident group significantly improved in the vertebral arch (p = 0.04). CONCLUSIONS: TS CT was effective in detecting bone metastasis by both board-certified radiologists and radiology residents.


Assuntos
Neoplasias Ósseas , Aprendizado Profundo , Neoplasias Ósseas/diagnóstico por imagem , Neoplasias Ósseas/secundário , Humanos , Masculino , Pessoa de Meia-Idade , Estudos Retrospectivos , Técnica de Subtração , Tomografia Computadorizada por Raios X/métodos
2.
Neuroimage ; 245: 118708, 2021 12 15.
Artigo em Inglês | MEDLINE | ID: mdl-34743050

RESUMO

INTRODUCTION: Electroencephalography (EEG) is increasingly used to investigate brain responses to transcranial magnetic stimulation (TMS). A relevant issue is that TMS is associated with considerable auditory and somatosensory stimulation, causing peripherally evoked potentials (PEPs) in the EEG, which contaminate the direct cortical responses to TMS (TEPs). All previous attempts to control for PEPs suffer from significant limitations. OBJECTIVE/HYPOTHESIS: To design an optimized sham procedure to control all sensory input generated by subthreshold real TMS targeting the hand area of the primary motor cortex (M1), enabling reliable separation of TEPs from PEPs. METHODS: In 23 healthy (16 female) subjects, we recorded EEG activity evoked by an optimized sham TMS condition which masks and matches auditory and somatosensory co-stimulation during the real TMS condition: auditory control was achieved by noise masking and by using a second TMS coil that was placed on top of the real TMS coil and produced a calibrated sound pressure level. Somatosensory control was obtained by electric stimulation (ES) of the scalp with intensities sufficient to saturate somatosensory input. ES was applied in both the sham and real TMS conditions. Perception of auditory and somatosensory inputs in the sham and real TMS conditions were compared by psychophysical testing. Transcranially evoked EEG signal changes were identified by subtraction of EEG activity in the sham condition from EEG activity in the real TMS condition. RESULTS: Perception of auditory and somatosensory inputs in the sham vs. real TMS conditions was comparable. Both sham and real TMS evoked a series of similar EEG signal deflections and induced broadband power increase in oscillatory activity. Notably, the present procedure revealed EEG potentials and a transient increase in beta band power at the site of stimulation that were only present in the real TMS condition. DISCUSSION: The results validate the effectiveness of our optimized sham approach. Despite the presence of typical responses attributable to sensory input, the procedure provided evidence for direct cortical activation by subthreshold TMS of M1. The findings are relevant for future TMS-EEG experiments that aim at measuring regional brain target engagement controlled by an optimized sham procedure.


Assuntos
Eletroencefalografia , Córtex Somatossensorial/fisiologia , Estimulação Magnética Transcraniana , Adulto , Potenciais Evocados/fisiologia , Feminino , Voluntários Saudáveis , Humanos , Masculino , Técnica de Subtração
3.
Phys Eng Sci Med ; 44(4): 1341-1350, 2021 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-34704221

RESUMO

We aimed to develop a novel method of detecting changes in lung conditions during radiotherapy using temporal subtraction technique. Twenty patients who underwent radiotherapy were retrospectively assessed by calculating optimal direct similarity error (ODSE) between initial and mid-treatment registered images. Patients were grouped according to region in tumor size and atelectasis for lung of < 20 or ≥ 20 cm3, which analyzed two field regions (1024 × 768 pixels, 512 × 512 pixels). Correlations between ODSE and changes in lung conditions were analyzed based on effect of radiation dose; receiver operating characteristic (ROC) analysis was performed to evaluate whether changes can be detected during treatment period. The ODSE of 1024 × 768 pixels was changed to 1.00 (0.28-3.48) for lung lesion size of < 20 cm3 and 1.86 (0.55-6.58) for the ≥ 20 cm3 lung lesion size. ODSE of 512 × 512 pixels was 1.03 (0.40-2.12) for the region in tumor size and atelectasis of < 20 cm3 and 1.90 (0.39-27.8) for the ≥ 20 cm3 lung lesion size. The region under the curve values from ROC analysis were 0.796 (1024 × 768 pixels) and 0.983 (512 × 512 pixels). A novel method can visually and numerically help to detect changes in lung condition at early treatment stages. Using this method, difference between plan and actual positional relationship for target and risk organs that cannot be predicted at the time of planning can be avoided, ensuring high safety and accuracy in lung radiotherapy.


Assuntos
Atelectasia Pulmonar , Técnica de Subtração , Humanos , Pulmão , Planejamento da Radioterapia Assistida por Computador , Estudos Retrospectivos
4.
Front Public Health ; 9: 752509, 2021.
Artigo em Inglês | MEDLINE | ID: mdl-34621723

RESUMO

A process that involves the registration of two brain Magnetic Resonance Imaging (MRI) acquisitions is proposed for the subtraction between previous and current images at two different follow-up (FU) time points. Brain tumours can be non-cancerous (benign) or cancerous (malignant). Treatment choices for these conditions rely on the type of brain tumour as well as its size and location. Brain cancer is a fast-spreading tumour that must be treated in time. MRI is commonly used in the detection of early signs of abnormality in the brain area because it provides clear details. Abnormalities include the presence of cysts, haematomas or tumour cells. A sequence of images can be used to detect the progression of such abnormalities. A previous study on conventional (CONV) visual reading reported low accuracy and speed in the early detection of abnormalities, specifically in brain images. It can affect the proper diagnosis and treatment of the patient. A digital subtraction technique that involves two images acquired at two interval time points and their subtraction for the detection of the progression of abnormalities in the brain image was proposed in this study. MRI datasets of five patients, including a series of brain images, were retrieved retrospectively in this study. All methods were carried out using the MATLAB programming platform. ROI volume and diameter for both regions were recorded to analyse progression details, location, shape variations and size alteration of tumours. This study promotes the use of digital subtraction techniques on brain MRIs to track any abnormality and achieve early diagnosis and accuracy whilst reducing reading time. Thus, improving the diagnostic information for physicians can enhance the treatment plan for patients.


Assuntos
Neoplasias Encefálicas , Técnica de Subtração , Encéfalo/diagnóstico por imagem , Neoplasias Encefálicas/diagnóstico por imagem , Humanos , Imageamento por Ressonância Magnética , Estudos Retrospectivos
5.
Jpn J Radiol ; 39(12): 1168-1173, 2021 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-34173973

RESUMO

PURPOSE: The purpose of this study was to evaluate the usefulness of single-shot dual-energy subtraction (DES) method using a flat-panel detector for lung cancer screening MATERIALS AND METHODS: The subjects were 13,315 residents (5801 males and 7514 females) aged 50 years or older (50-97 years, with an intermediate value of 68 years) who underwent lung cancer screening for a period of 1 year and 6 months from January 2019 to June 2020. We investigated whether the number of lung cancers detected, the detection rate, and the rate of required scrutiny changed, when DES images were added to the judgment based on conventional chest radiography. RESULTS: When DES images were added, the number and percentage of cancer detection increased from 16 (0.12%) to 23 (0.17%) (P < 0.05). Five of the newly detected 7 lung cancers were in the early stages of resectable cancer. The rate of participants requiring scrutiny increased slightly from 1.1 to 1.3%. CONCLUSION: DES method improved the detection of lung cancer in screening. The increase in the percentage of participants requiring scrutiny was negligible.


Assuntos
Neoplasias Pulmonares , Imagem Radiográfica a Partir de Emissão de Duplo Fóton , Detecção Precoce de Câncer , Feminino , Humanos , Neoplasias Pulmonares/diagnóstico por imagem , Masculino , Radiografia , Radiografia Torácica , Técnica de Subtração
6.
Health Phys ; 121(3): 181-192, 2021 09 01.
Artigo em Inglês | MEDLINE | ID: mdl-34028387

RESUMO

ABSTRACT: Californium-252 (252Cf) is considered essential by the National Institute of Standards and Technology for the calibration of neutron instrumentation and dosimetry. Californium-252 has a relatively short half-life of 2.645 y; consequently, it must be replaced frequently to produce an adequate neutron flux for calibration. The user community is currently looking for a replacement for 252Cf. The patented technology described herein has a high probability of being that replacement. A preferred method to replace 252Cf would use an affordable and easily maintained neutron source that generates neutrons in an energy spectrum as close to that of 252Cf as possible. Deuterium-tritium (D-T) neutron generators are both affordable and easily maintained, which makes them highly attractive for replacing 252Cf. The patented technology discussed in this paper simulates the 252Cf fission spectrum through a D-T neutron generator by using spectral subtraction. The primary spectrum is built using principally (n,xn) and (n,n') reactions in a variety of materials. In conjunction with the primary spectrum, an engineered background spectrum is generated using a second set of materials. This engineered background spectrum corrects for differences between the primary and desired spectra. This subtraction technique generates a spectrum very similar to 252Cf while maintaining a reasonable flux. Further, by choosing different scattering materials, any fission spectrum can be matched, including the thermal and epithermal components. This flexibility expands the potential use of this technology beyond simulating 252Cf to any desired neutron spectrum below 14 MeV.


Assuntos
Califórnio , Nêutrons , Calibragem , Radiometria , Técnica de Subtração , Trítio
7.
J Biomed Opt ; 26(5)2021 05.
Artigo em Inglês | MEDLINE | ID: mdl-33988004

RESUMO

SIGNIFICANCE: Confocal laser scanning enables optical sectioning in fiber bundle endomicroscopy but limits the frame rate. To be able to better explore tissue morphology, it is useful to stitch sequentially acquired frames into a mosaic. However, low frame rates limit the maximum probe translation speed. Line-scanning (LS) confocal endomicroscopy provides higher frame rates, but residual out-of-focus light degrades images. Subtraction-based approaches can suppress this residue at the expense of introducing motion artifacts. AIM: To generate high-frame-rate endomicroscopy images with improved optical sectioning, we develop a high-speed subtraction method that only requires the acquisition of a single camera frame. APPROACH: The rolling shutter of a CMOS camera acts as both the aligned and offset detector slits required for subtraction-based sectioning enhancement. Two images of the bundle are formed on different regions of the camera, allowing both images to be acquired simultaneously. RESULTS: We confirm improved optical sectioning compared to conventional LS, particularly far from focus, and show that motion artifacts are not introduced. We demonstrate high-speed mosaicing at frame rates of up to 240 Hz. CONCLUSION: High-speed acquisition of optically sectioned images using the new subtraction based-approach leads to improved mosaicing at high frame rates.


Assuntos
Artefatos , Técnica de Subtração , Movimento (Física) , Fibras Ópticas , Cintilografia
8.
Magn Reson Med ; 86(1): 320-334, 2021 07.
Artigo em Inglês | MEDLINE | ID: mdl-33645815

RESUMO

PURPOSE: To develop an improved reconstruction method, k-space subtraction with phase and intensity correction (KSPIC), for highly accelerated, subtractive, non-contrast-enhanced MRA. METHODS: The KSPIC method is based on k-space subtraction of complex raw data. It applies a phase-correction procedure to restore the polarity of negative signals caused by subtraction and an intensity-correction procedure to improve background suppression and thereby sparsity. Ten retrospectively undersampled data sets and 10 groups of prospectively undersampled data sets were acquired in 12 healthy volunteers. The performance of KSPIC was compared with another improved reconstruction based on combined magnitude subtraction, as well as with conventional k-space subtraction reconstruction and magnitude subtraction reconstruction, both using quantitative metrics and using subjective quality scoring. RESULTS: In the quantitative evaluation, KSPIC had the best performance in terms of peak SNR, structural similarity index measure, contrast-to-noise ratio of artery-to-background and sharpness, especially at high acceleration factors. The KSPIC method also had the highest subjective scores for all acceleration factors in terms of vessel delineation, image noise and artifact, and background contamination. The acquisition can be accelerated by a factor of 20 without significant decreases of subjective scores. The optimal size of the phase-correction region was found to be 12-20 pixels in this study. CONCLUSION: Compared with combined magnitude subtraction and conventional reconstructions, KSPIC has the best performance in all of the quantitative and qualitative measurements, permitting good image quality to be maintained up to higher accelerations. The KSPIC method has the potential to further reduce the acquisition time of subtractive MRA for clinical examinations.


Assuntos
Angiografia por Ressonância Magnética , Técnica de Subtração , Artefatos , Artéria Femoral/diagnóstico por imagem , Humanos , Processamento de Imagem Assistida por Computador , Estudos Retrospectivos
9.
Br J Radiol ; 94(1120): 20201384, 2021 Apr 01.
Artigo em Inglês | MEDLINE | ID: mdl-33733827

RESUMO

X-ray imaging plays a crucial role in the confirmation of COVID-19 pneumonia. Chest X-ray radiography and CT are two major imaging techniques that are currently adopted in the diagnosis of COVID-19 pneumonia. However, dual-energy subtraction radiography is hardly discussed as potential COVID-19 imaging application. More advanced X-ray radiography equipment often supports dual-energy subtraction X-ray radiography. Dual-energy subtraction radiography enables the calculation of pseudo-radiographs, in which bones are removed and only soft-tissues are highlighted. In this commentary, the author would like to draw the attention to the potential use of dual-energy subtraction X-ray radiography (i.e. soft-tissue pseudo-radiography) for the assessment and the longitudinal follow-up of COVID-19 pneumonia.


Assuntos
COVID-19/diagnóstico por imagem , Pneumonia Viral/diagnóstico por imagem , Humanos , Pneumonia Viral/virologia , Interpretação de Imagem Radiográfica Assistida por Computador , Imagem Radiográfica a Partir de Emissão de Duplo Fóton/métodos , SARS-CoV-2 , Técnica de Subtração
10.
J Digit Imaging ; 34(2): 357-361, 2021 04.
Artigo em Inglês | MEDLINE | ID: mdl-33604806

RESUMO

Subtraction ictal single-photon emission computed tomography (SPECT) coregistered to MRI (SISCOM) is a well-established technique for quantitative analysis of ictal vs interictal SPECT images that can contribute to the identification of the seizure onset zone in patients with drug-resistant epilepsy. However, there is presently a lack of user-friendly free and open-source software to compute SISCOM results from raw SPECT and MRI images. We aimed to develop a simple graphical desktop application for computing SISCOM. MNI SISCOM is a new free and open-source software application for computing SISCOM and producing practical MRI/SPECT/SISCOM image panels for review and reporting. The graphical interface allows any user to quickly and easily obtain SISCOM images with minimal user interaction. Additionally, MNI SISCOM provides command line and Python interfaces for users who would like to integrate these features into their own scripts and pipelines. MNI SISCOM is freely available for download from: https://github.com/jeremymoreau/mnisiscom .


Assuntos
Imageamento por Ressonância Magnética , Tomografia Computadorizada de Emissão de Fóton Único , Encéfalo/diagnóstico por imagem , Eletroencefalografia , Humanos , Técnica de Subtração , Tomografia Computadorizada por Raios X
11.
Physiol Meas ; 42(2): 025001, 2021 03 11.
Artigo em Inglês | MEDLINE | ID: mdl-33508808

RESUMO

OBJECTIVE: Evoked tympanic membrane displacement (TMD) measurements show a correlation with intracranial pressure (ICP). Attempts to use these measurements for non-invasive monitoring of ICP in patients have been limited by high measurement variability. Pulsing of the tympanic membrane at the cardiac frequency has been shown to be a significant source of the variability. In this study we describe a post processing method to remove the cardiac pulse waveform and assess the impact of this on the measurement and its repeatability. APPROACH: Three-hundred and sixteen healthy volunteers were recruited for evoked TMD measurements. The measurements were quantified by V m, defined as the mean displacement between the point of maximum inward displacement and the end of the stimulus. A sample of spontaneously pulsing TMDs was measured immediately before the evoked measurements. Simultaneous recording of the ECG allowed a heartbeat template to be extracted from the spontaneous data and subtracted from the evoked data. Intra-subject repeatability of V m was assessed from 20 repeats of the evoked measurement. Results with and without subtraction of the heartbeat template were compared. The difference was tested for significance using the Wilcoxon sign rank test. MAIN RESULTS: In left and right ears, both sitting and supine, application of the pulse correction significantly reduced the intra-subject variability of V m (p value range 4.0 × 10-27 to 2.0 × 10-31). The average improvement was from 98 ± 6 nl to 56 ± 4 nl. SIGNIFICANCE: The pulse subtraction technique substantially improves the repeatability of evoked TMD measurements. This justifies further investigations to assess the use of TMD measurements in clinical applications where non-invasive tracking of changes in ICP would be useful.


Assuntos
Pressão Intracraniana , Membrana Timpânica , Voluntários Saudáveis , Humanos , Postura Sentada , Técnica de Subtração
12.
Eur Radiol ; 31(7): 5160-5171, 2021 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-33439320

RESUMO

OBJECTIVES: To compare image quality and radiation dose between dual-energy subtraction (DES)-based bone suppression images (D-BSIs) and software-based bone suppression images (S-BSIs). METHODS: Chest radiographs (CXRs) of forty adult patients were obtained with the two X-ray devices, one with DES and one with bone suppression software. Three image quality metrics (relative mean absolute error (RMAE), peak signal-to-noise ratio (PSNR), and structural similarity index (SSIM)) between original CXR and BSI for each of D-BSI and S-SBI groups were calculated for each bone and soft tissue areas. Two readers rated the visual image quality for original CXR and BSI for each of D-BSI and S-SBI groups. The dose area product (DAP) values were recorded. Paired t test was used to compare the image quality and DAP values between D-BSI and S-BSI groups. RESULTS: In bone areas, S-BSIs had better SSIM values than D-BSI (94.57 vs. 87.77) but worse RMAE and PSNR values (0.50 vs. 0.20; 20.93 vs. 34.37) (all p < 0.001). In soft tissue areas, S-BSIs had better SSIM values than D-BSI (97.56 vs. 91.42) but similar RMAE and PSNR values (0.29 vs. 0.27; 31.35 vs. 29.87) (all p < 0.001). Both readers gave S-BSIs significantly higher image quality scores than D-BSI (p < 0.001). The mean DAP in software-related images (0.98 dGy·cm2) was significantly lower than that in the DES-related images (1.48 dGy·cm2) (p < 0.001). CONCLUSION: Bone suppression software significantly improved the image quality of bone suppression images with a relatively lower radiation dose, compared with dual-energy subtraction technique. KEY POINTS: • Bone suppression software preserves structure similarity of soft tissues better than dual-energy subtraction technique in bone suppression images. • Bone suppression software achieves superior image quality for lung lesions than dual-energy subtraction technique in bone suppression images. • Bone suppression software can decrease the radiation dose over the hardware-based image processing technique.


Assuntos
Imagem Radiográfica a Partir de Emissão de Duplo Fóton , Radiografia Torácica , Adulto , Humanos , Doses de Radiação , Interpretação de Imagem Radiográfica Assistida por Computador , Software , Técnica de Subtração
13.
J Magn Reson ; 323: 106898, 2021 02.
Artigo em Inglês | MEDLINE | ID: mdl-33429170

RESUMO

Long T2 water contamination is a major challenge with direct in vivo UTE imaging of ultrashort T2 components in the brain since water contributes most of the signal detected from white and gray matter. The Short TR Adiabatic Inversion Recovery prepared Ultrashort TE (STAIR-UTE) sequence can significantly suppress water signals and simultaneously image ultrashort T2 components. However, the TR used may not be sufficiently short to allow the STAIR preparation to completely suppress all the water signals in the brain due to specific absorption rate (SAR) limitations on clinical MR scanners. In this study, we describe a STAIR prepared dual-echo UTE sequence with complex Echo Subtraction (STAIR-dUTE-ES) which improves water suppression for selective ultrashort T2 imaging compared with that achieved with the STAIR-UTE sequence. Numerical simulations showed that the STAIR-dUTE-ES technique can effectively suppress water signals and allow accurate quantification of ultrashort T2 protons. Volunteer and Multiple Sclerosis (MS) patient studies demonstrated the feasibility of the STAIR-dUTE-ES technique for selective imaging and quantification of ultrashort T2 components in vivo. A significantly lower mean UltraShort T2 Proton Fraction (USPF) was found in lesions in MS patients (5.7 ± 0.7%) compared with that in normal white matter of healthy volunteers (8.9 ± 0.6%). The STAIR-dUTE-ES sequence provides robust water suppression for volumetric imaging and quantitation of ultrashort T2 component. The reduced USPF in MS lesions shows the clinical potential of the sequence for diagnosis and monitoring treatment in MS.


Assuntos
Encéfalo/diagnóstico por imagem , Aumento da Imagem/métodos , Imageamento por Ressonância Magnética/métodos , Esclerose Múltipla/diagnóstico por imagem , Adulto , Idoso , Simulação por Computador , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Técnica de Subtração , Água , Substância Branca/diagnóstico por imagem
14.
Eur J Radiol ; 134: 109443, 2021 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-33310553

RESUMO

OBJECTIVE: To compare nodule enhancement on subtraction CT iodine maps to that on dual-energy CT iodine maps using CT datasets acquired simultaneously. METHODS: A previously-acquired set of lung subtraction and dual-energy CT maps consisting of thirty patients with 95 solid pulmonary nodules (≥4 mm diameter) was used. Nodules were annotated and segmented on CT angiography, and mean nodule enhancement in the iodine maps calculated. Three radiologists scored nodule visibility with both techniques on a 4-point scale. RESULTS: Mean nodule enhancement was higher (p < 0.001) at subtraction CT (34.9 ±â€¯12.9 HU) than at dual-energy CT (25.4 ±â€¯21.0 HU). Nodule enhancement at subtraction CT was judged more often to be "highly visible" for each observers (p < 0.001) with an area under the curve of 0.81. CONCLUSIONS: Subtraction CT is able to depict iodine enhancement in pulmonary nodules better than dual-energy CT.


Assuntos
Iodo , Neoplasias Pulmonares , Nódulos Pulmonares Múltiplos , Imagem Radiográfica a Partir de Emissão de Duplo Fóton , Nódulo Pulmonar Solitário , Humanos , Neoplasias Pulmonares/diagnóstico por imagem , Nódulo Pulmonar Solitário/diagnóstico por imagem , Técnica de Subtração
15.
Magn Reson Med ; 85(2): 694-708, 2021 02.
Artigo em Inglês | MEDLINE | ID: mdl-32754954

RESUMO

PURPOSE: To correct the intensity difference of static background signal between bright blood images and dark blood images in subtractive non-contrast-enhanced MR angiography using robust regression, thereby improving static background signal suppression on subtracted angiograms. METHODS: Robust regression (RR), using iteratively reweighted least squares, is used to calculate the regression coefficient of background tissues from a scatter plot showing the voxel intensity of bright blood images versus dark blood images. The weighting function is based on either the Euclidean distance from the estimated regression line or the deviation angle. Results from RR using the deviation angle (RRDA), conventional RR using the Euclidean distance, and ordinary leastsquares regression were compared with reference values determined manually by two observers. Performance was evaluated over studies using different sequences, including 36 thoracic flow-sensitive dephasing data sets, 13 iliac flow-sensitive dephasing data sets, and 26 femoral fresh blood imaging data sets. RESULTS: RR deviation angle achieved robust and accurate performance in all types of images, with small bias, small mean absolute error, and high-correlation coefficients with reference values. Background tissues, such as muscle, veins, and bladder, were suppressed while the vascular signal was preserved. Euclidean distance gave good performance for thoracic and iliac flow-sensitive dephasing, but could not suppress background tissues in femoral fresh blood imaging. Ordinary least squares regression was sensitive to outliers and overestimated regression coefficients in thoracic flow-sensitive dephasing. CONCLUSION: Weighted subtraction using RR was able to acquire the regression coefficients of background signal and improve background suppression of subtractive non-contrast-enhanced MR angiography techniques. RR deviation angle has the most robust and accurate overall performance among three regression methods.


Assuntos
Meios de Contraste , Angiografia por Ressonância Magnética , Artéria Femoral , Sensibilidade e Especificidade , Técnica de Subtração
16.
Pacing Clin Electrophysiol ; 44(1): 135-144, 2021 01.
Artigo em Inglês | MEDLINE | ID: mdl-33283875

RESUMO

INTRODUCTION: Causes of non-response to cardiac resynchronization therapy (CRT) include mechanical dyssynchrony, myocardial scar, and suboptimal left ventricular (LV) lead location. We aimed to assess the utility of Late Iodine Enhancement Computed Tomography (LIE-CT) with image subtraction in characterizing CRT non-response. METHODS: CRT response was defined as a decrease in LV end-systolic volume > 15% at 6 months. LIE-CT was performed after 6 months, and analyzed global and segmental dyssynchrony, myocardial scar, coronary venous anatomy, and position of LV lead relative to scar and segment of latest mechanical contraction. RESULTS: We evaluated 29 patients (age 71 ± 12 years; 72% men) including 18 (62%) responders. All metrics evaluating residual dyssynchrony such as wall motion index and wall thickness index were worse in non-responders. There was no difference in presence and extent of scar between responders and non-responders. However, in non-responders, the LV lead was more often over an akinetic/dyskinetic area (72% vs. 22%, p = .007), a fibrotic area (64% vs. 8%, p = .0007), an area with myocardial thickness < 6 mm (82% vs. 22%, p = .002), and less often concordant with the region of maximal wall thickness (9% vs. 72%, p = .001). Among the 11 non-responders, eight had at least another coronary venous branch visualized by CT, including three (27%) coursing over a potentially interesting myocardial area (free of scar, with normal wall motion, and with a myocardial thickness ≥6 mm). CONCLUSION: LIE-CT with image subtraction allows a comprehensive characterization of patients after CRT and may provide clues for management of non-responders.


Assuntos
Dispositivos de Terapia de Ressincronização Cardíaca , Tomografia Computadorizada por Raios X , Falha de Tratamento , Idoso , Terapia de Ressincronização Cardíaca , Meios de Contraste , Angiografia Coronária , Ecocardiografia , Feminino , Humanos , Masculino , Pessoa de Meia-Idade , Interpretação de Imagem Radiográfica Assistida por Computador , Técnica de Subtração
17.
Med Phys ; 48(3): 1039-1053, 2021 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-33283889

RESUMO

OBJECTIVE: Dual energy radiography (DER) makes it possible to obtain separate images for soft-tissue and bony structures (tissue maps) based on the acquisition of two radiographs at different source peak-kilovoltage values. Current DER studies are based on the weighted subtraction method, which requires either manual tuning or the use of precomputed tables, or on decomposition methods, which make use of a calibration to model soft-tissue and bone components. In this study, we examined in depth the optimum method to perform this calibration. METHODS: We used simulations to optimize the calibration protocol and evaluated the effect of the material and size of a calibration phantom composed of two wedges and its positioning in the system. Evaluated materials were water, PMMA and A-150 as soft-tissue equivalent, and Teflon, B-100 and aluminum as bone equivalent, with sizes from 5 to 30 cm. Each material combination was compared with an ideal phantom composed of soft tissue and bone. Our simulation results enabled us to propose four designs that were tested with the NOVA FA X-ray system with a realistic thorax phantom. RESULTS: Calibration based on a very simple and inexpensive phantom with no strict requirements in its placement results in appropriate separation of the spine (a common focus in densitometry studies) and the identification of nodules as small as 6 mm, which have been reported to have a low rate of detection in radiography. CONCLUSION: The proposed method is completely automatic, avoiding the need for a radiology technician with expert knowledge of the protocol, as is the case in densitometry exams. The method provides real mass thickness values, enabling quantitative planar studies instead of relative comparisons.


Assuntos
Osso e Ossos , Radiografia , Técnica de Subtração , Osso e Ossos/diagnóstico por imagem , Calibragem , Simulação por Computador , Humanos , Imagens de Fantasmas
18.
Orthopedics ; 44(1): e31-e35, 2021 Jan 01.
Artigo em Inglês | MEDLINE | ID: mdl-33284983

RESUMO

Interpretation of thoracic spine radiographs is difficult because they cannot clearly depict the vertebrae due to overlap with soft tissues. This study aimed to evaluate whether thoracic spine radiographs obtained using the energy subtraction method could improve the accuracy of a diagnosis of thoracic osteolytic lesions. The authors analyzed 300 thoracic vertebrae from 25 patients with multiple myeloma who underwent thoracic spine radiography. All patients underwent thoracic spine radiography with 2 views. Two sets of images were prepared: computed radiography images (CR images) acquired using conventional processing parameters; and processed images for specifically visualizing bone, using the energy subtraction method (ES images). The CR images (CR group) and paired CR and ES images (CR+ES group) were interpreted in parallel by 5 orthopedic surgeons. The presence of osteolytic lesions was evaluated for each of the 12 thoracic vertebrae, and the sensitivity and specificity of the method were compared with computed tomography (CT), which is considered the gold standard. Subgroup analysis was also performed based on location. Osteolytic lesions were found on CT in 28 (9.3%) vertebrae of 12 patients. The overall sensitivities and specificities of the CR and CR+ES groups were 17.2% and 54.3%, respectively, and 95.6% and 98.0%, respectively, with statistically significant differences. Subgroup analysis showed particular improvement in the sensitivity for the CR+ES group in the middle thoracic spine compared with that at other locations. Thoracic spine radiographs generated using this method may improve the accuracy of diagnosis of thoracic osteolytic lesions. [Orthopedics. 2021;44(1):e31-e35.].


Assuntos
Mieloma Múltiplo/diagnóstico por imagem , Vértebras Torácicas/diagnóstico por imagem , Tomografia Computadorizada por Raios X/métodos , Idoso , Feminino , Humanos , Processamento de Imagem Assistida por Computador , Masculino , Pessoa de Meia-Idade , Estudos Prospectivos , Radiografia Torácica/métodos , Sensibilidade e Especificidade , Técnica de Subtração , Parede Torácica/diagnóstico por imagem
19.
NMR Biomed ; 34(2): e4423, 2021 02.
Artigo em Inglês | MEDLINE | ID: mdl-33029872

RESUMO

Noninvasive measurements of liver perfusion and fibrosis in cirrhotic small animals can help develop treatments for haemodynamic complications of liver disease. Here, we measure liver perfusion in cirrhotic rodents using flow-sensitive alternating inversion recovery arterial spin labelling (FAIR ASL), evaluating agreement with previously validated caval subtraction phase-contrast magnetic resonance imaging (PCMRI) total liver blood flow (TLBF). Baseline differences in cirrhotic rodents and the haemodynamic effects of acute inflammation were investigated using FAIR ASL and tissue T1. Sprague-Dawley rats (nine bile duct ligated [BDL] and ten sham surgery controls) underwent baseline hepatic FAIR ASL with T1 measurement and caval subtraction PCMRI (with two-dimensional infra-/supra-hepatic inferior vena caval studies), induction of inflammation with intravenous lipopolysaccharide (LPS) and repeat liver FAIR ASL with T1 measurement after ~90 minutes. The mean difference between FAIR ASL hepatic perfusion and caval subtraction PCMRI TLBF was -51 ± 30 ml/min/100 g (Bland-Altman 95% limits-of-agreement ±258 ml/min/100 g). The FAIR ASL coefficient of variation was smaller than for caval subtraction PCMRI (29.3% vs 50.1%; P = .03). At baseline, FAIR ASL liver perfusion was lower in BDL rats (199 ± 32 ml/min/100 g vs sham 316 ± 24 ml/min/100 g; P = .01) but liver T1 was higher (BDL 1533 ± 50 vs sham 1256 ± 18 ms; P = .0004). Post-LPS FAIR ASL liver perfusion response differences were observed between sham/BDL rats (P = .02), approaching significance in sham (+78 ± 33 ml/min/100 g; P = .06) but not BDL rats (-49 ± 40 ml/min/100 g; P = .47). Post-LPS differences in liver tissue T1 were nonsignificant (P = .35). FAIR ASL hepatic perfusion and caval subtraction PCMRI TLBF agreement was modest, with significant baseline FAIR ASL liver perfusion and tissue T1 differences in rodents with advanced cirrhosis compared with controls. Following inflammatory stress, differences in hepatic perfusion response were detected between cirrhotic/control animals, but liver T1 was unaffected. Findings underline the potential of FAIR ASL in the assessment of vasoactive treatments for patients with chronic liver disease and inflammation.


Assuntos
Cirrose Hepática Experimental/metabolismo , Angiografia por Ressonância Magnética/métodos , Animais , Área Sob a Curva , Ductos Biliares , Doença Hepática Induzida por Substâncias e Drogas/metabolismo , Doença Hepática Induzida por Substâncias e Drogas/patologia , Modelos Animais de Doenças , Inflamação , Ligadura , Lipopolissacarídeos/toxicidade , Circulação Hepática , Cirrose Hepática Experimental/patologia , Masculino , Ratos , Ratos Sprague-Dawley , Marcadores de Spin , Técnica de Subtração , Veia Cava Inferior/fisiopatologia
20.
Neuroradiol J ; 34(2): 128-130, 2021 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-33263460

RESUMO

Assessing and reporting clinical images constitutes the mainstay of clinical neuroradiology. Continually increasing numbers of neuroradiology referrals and follow-up examinations call for reproducible, accurate, and rapid workflows. Readily available and easy to use, advanced workstation tools such as co-registration of volume series can be used to overlay volume series from two different time points as semi-transparent images, with an inverse color scale. By overlaying semi-transparent inverse color maps, stationary findings will be shaded out in grey, whereas progressing or regressing lesions will be highlighted as white or black in the resulting pseudo-subtraction map. Pseudosubtraction in longitudinal neuroradiology imaging might enhance workflow and imaging assessment.


Assuntos
Interpretação de Imagem Assistida por Computador/métodos , Imageamento por Ressonância Magnética/métodos , Neuroimagem/métodos , Software , Tomografia Computadorizada por Raios X/métodos , Estudos de Viabilidade , Humanos , Técnica de Subtração
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