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1.
Eur Radiol ; 2024 May 09.
Artigo em Inglês | MEDLINE | ID: mdl-38724765

RESUMO

OBJECTIVE: Deep learning (DL) MRI reconstruction enables fast scan acquisition with good visual quality, but the diagnostic impact is often not assessed because of large reader study requirements. This study used existing diagnostic DL to assess the diagnostic quality of reconstructed images. MATERIALS AND METHODS: A retrospective multisite study of 1535 patients assessed biparametric prostate MRI between 2016 and 2020. Likely clinically significant prostate cancer (csPCa) lesions (PI-RADS ≥ 4) were delineated by expert radiologists. T2-weighted scans were retrospectively undersampled, simulating accelerated protocols. DL reconstruction (DLRecon) and diagnostic DL detection (DLDetect) were developed. The effect on the partial area under (pAUC), the Free-Response Operating Characteristic (FROC) curve, and the structural similarity (SSIM) were compared as metrics for diagnostic and visual quality, respectively. DLDetect was validated with a reader concordance analysis. Statistical analysis included Wilcoxon, permutation, and Cohen's kappa tests for visual quality, diagnostic performance, and reader concordance. RESULTS: DLRecon improved visual quality at 4- and 8-fold (R4, R8) subsampling rates, with SSIM (range: -1 to 1) improved to 0.78 ± 0.02 (p < 0.001) and 0.67 ± 0.03 (p < 0.001) from 0.68 ± 0.03 and 0.51 ± 0.03, respectively. However, diagnostic performance at R4 showed a pAUC FROC of 1.33 (CI 1.28-1.39) for DL and 1.29 (CI 1.23-1.35) for naive reconstructions, both significantly lower than fully sampled pAUC of 1.58 (DL: p = 0.024, naïve: p = 0.02). Similar trends were noted for R8. CONCLUSION: DL reconstruction produces visually appealing images but may reduce diagnostic accuracy. Incorporating diagnostic AI into the assessment framework offers a clinically relevant metric essential for adopting reconstruction models into clinical practice. CLINICAL RELEVANCE STATEMENT: In clinical settings, caution is warranted when using DL reconstruction for MRI scans. While it recovered visual quality, it failed to match the prostate cancer detection rates observed in scans not subjected to acceleration and DL reconstruction.

2.
Eur Radiol ; 34(4): 2334-2351, 2024 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-37672051

RESUMO

OBJECTIVES: Position- and posture-dependent deformation of the vascular system is a relatively unexplored field. The goal of this scoping review was to create an overview of existing vascular imaging modalities in different body positions and postures and address the subsequent changes in vascular anatomy. METHODS: Scopus, Medline, and Cochrane were searched for literature published between January 1, 2000, and June 30, 2022, incorporating the following categories: image modality, anatomy, orientation, and outcomes. RESULTS: Out of 2446 screened articles, we included 108. The majority of papers used ultrasound (US, n = 74) in different body positions and postures with diameter and cross-sectional area (CSA) as outcome measures. Magnetic resonance imaging (n = 22) and computed tomography (n = 8) were less frequently used but allowed for investigation of other geometrical measures such as vessel curvature and length. The venous system proved more sensitive to postural changes than the arterial system, which was seen as increasing diameters of veins below the level of the heart when going from supine to prone to standing positions, and vice versa. CONCLUSIONS: The influence of body positions and postures on vasculature was predominantly explored with US for vessel diameter and CSA. Posture-induced deformation and additional geometrical features that may be of interest for the (endovascular) treatment of vascular pathologies have been limitedly reported, such as length and curvature of an atherosclerotic popliteal artery during bending of the knee after stent placement. The most important clinical implications of positional changes are found in diagnosis, surgical planning, and follow-up after stent placement. CLINICAL RELEVANCE STATEMENT: This scoping review presents the current state and opportunities of position- and posture-dependent imaging of vascular structures using various imaging modalities that are relevant in the fields of clinical diagnosis, surgical planning, and follow-up after stent placement. KEY POINTS: • The influence of body positions and postures on the vasculature was predominantly investigated with US for vessel diameter and cross-sectional area. • Research into geometrical deformation, such as vessel length and curvature adaptation, that may be of interest for the (endovascular) treatment of vascular pathologies is limited in different positions and postures. • The most important clinical implications of postural changes are found in diagnosis, surgical planning, and follow-up after stent placement.


Assuntos
Postura , Tomografia Computadorizada por Raios X , Humanos , Imageamento por Ressonância Magnética/métodos , Artéria Poplítea
3.
Int Urogynecol J ; 35(6): 1255-1261, 2024 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-38743071

RESUMO

INTRODUCTION AND HYPOTHESIS: The gold standard for quantifying pelvic organ prolapse is the pelvic organ prolapse quantification (POP-Q) system; however, upright magnetic resonance imaging (MRI) is a promising new method. The objective of this study was to determine the correlation between POP-Q and MRI measurements of the bladder and cervix. METHODS: This prospective study included patients with prolapse in whom POP-Q points Aa or Ba and C were measured as standard care. MRI scans were performed in an upright position, and the distances of the lowest points of the bladder and cervix to the Pelvic Inclination Correction System (PICS) were calculated. Correlations between POP-Q and MRI-PICS measurements were determined using the Pearson correlation coefficient for normally distributed data and the Spearman's rank correlation coefficient for non-normally distributed data. RESULTS: A total of 63 patients were suitable for analysis. There was a moderate positive correlation between the POP-Q and MRI-PICS measurements for bladder (r(61) = 0.480, r < 0.001) and uterus (r(61) = 0.527, p < 0.001). Measurement differences between POP-Q and MRI-PICS of the bladder and uterus vary from -3.2 cm to 7.1 cm, and from -2.1 cm to 8.5 cm respectively. In 71.4% of patients more descent was seen on upright MRI than with POP-Q measurement for both bladder and uterus. For patients with similar POP-Q measurements, a high variation in MRI measurements of the bladder and uterus was found. CONCLUSION: Despite a moderate positive correlation, upright MRI shows a larger POP extent in 71.4% of the patients than POP-Q. A high variation in MRI measurements for patients with the same POP-Q measurement was seen.


Assuntos
Imageamento por Ressonância Magnética , Prolapso de Órgão Pélvico , Bexiga Urinária , Humanos , Feminino , Prolapso de Órgão Pélvico/diagnóstico por imagem , Estudos Prospectivos , Pessoa de Meia-Idade , Idoso , Bexiga Urinária/diagnóstico por imagem , Bexiga Urinária/patologia , Colo do Útero/diagnóstico por imagem , Colo do Útero/patologia , Adulto
4.
J Vasc Res ; 60(1): 1-11, 2023.
Artigo em Inglês | MEDLINE | ID: mdl-36882023

RESUMO

Endovascular revascularization is the preferred treatment for peripheral arterial disease. Restenosis often occurs as a response to procedure-induced arterial damage. Reducing vascular injury during endovascular revascularization may improve its success rate. This study developed and validated an ex vivo flow model using porcine iliac arteries, obtained from a local abattoir. Twenty arteries (of 10 pigs) were equally allocated to two groups: a mock-treated control group and an endovascular intervention group. Arteries of both groups were perfused with porcine blood for 9 min, including 3 min of balloon angioplasty in the intervention group. Vessel injury was assessed by calculating the presence of endothelial cell denudation, vasomotor function, and histopathological analysis. MR imaging displayed balloon positioning and inflation. Endothelial cell staining showed 76% of denudation after ballooning compared to 6% in the control group (p < 0.001). This was confirmed by histopathological analysis, showing a significantly reduced endothelial nuclei count after ballooning compared to the controls (median: 22 vs. 37 nuclei/mm, p = 0.022). In the intervention group, vasoconstriction and endothelium-dependent relaxation were significantly reduced (p < 0.05).We present an ex vivo flow model to test the effects of endovascular therapy on the vessel's wall morphology, endothelial denudation, and endothelial-dependent vasomotor function under physiological conditions. Additionally, it allows the future testing of human arterial tissue.


Assuntos
Angioplastia Coronária com Balão , Angioplastia com Balão , Humanos , Suínos , Animais , Angioplastia Coronária com Balão/métodos , Angioplastia com Balão/efeitos adversos , Imageamento por Ressonância Magnética , Vasoconstrição/fisiologia , Artéria Ilíaca/diagnóstico por imagem , Artéria Ilíaca/cirurgia
5.
J Magn Reson Imaging ; 2023 Nov 19.
Artigo em Inglês | MEDLINE | ID: mdl-37982353

RESUMO

The increasing incidence of prostate cancer cases worldwide has led to a tremendous demand for multiparametric MRI (mpMRI). In order to relieve the pressure on healthcare, reducing mpMRI scan time is necessary. This review focuses on recent techniques proposed for faster mpMRI acquisition, specifically shortening T2W and DWI sequences while adhering to the PI-RADS (Prostate Imaging Reporting and Data System) guidelines. Speeding up techniques in the reviewed studies rely on more efficient sampling of data, ranging from the acquisition of fewer averages or b-values to adjustment of the pulse sequence. Novel acquisition methods based on undersampling techniques are often followed by suitable reconstruction methods typically incorporating synthetic priori information. These reconstruction methods often use artificial intelligence for various tasks such as denoising, artifact correction, improvement of image quality, and in the case of DWI, for the generation of synthetic high b-value images or apparent diffusion coefficient maps. Reduction of mpMRI scan time is possible, but it is crucial to maintain diagnostic quality, confirmed through radiological evaluation, to integrate the proposed methods into the standard mpMRI protocol. Additionally, before clinical integration, prospective studies are recommended to validate undersampling techniques to avoid potentially inaccurate results demonstrated by retrospective analysis. This review provides an overview of recently proposed techniques, discussing their implementation, advantages, disadvantages, and diagnostic performance according to PI-RADS guidelines compared to conventional methods. LEVEL OF EVIDENCE: 3 TECHNICAL EFFICACY: Stage 3.

6.
Int Urogynecol J ; 34(10): 2407-2414, 2023 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-37145125

RESUMO

INTRODUCTION AND HYPOTHESIS: Symptoms of pelvic organ prolapse (POP) can affect quality of life and are reported to progress during the day, although this was never objectified. The aim of this study is to determine whether the pelvic anatomy changes during the day using upright magnetic resonance imaging (MRI), in POP patients and asymptomatic women. METHODS: In this prospective study 15 POP patients and 45 asymptomatic women were included. Upright MRI scans were obtained three times per day. The distances from the lowest points of the bladder and cervix to a standardized reference (pelvic inclination correction system) line were determined. A principal component analysis was performed on the levator plate (LP) shape. Statistical differences between time points and the groups were determined for the bladder, cervix, and LP shape. RESULTS: For all women a significant decrease in bladder and cervix height of -0.2 cm (p<0.001) was seen between morning/midday and afternoon scans. A significant difference in bladder descent during the day between POP patients and asymptomatic women was found (p=0.004). Individual differences in bladder position in the POP group of up to 2.2 cm between the morning and afternoon scan were reported. There was a significant difference in LP shape (p<0.001) between the groups but there were no significant changes during the day. CONCLUSIONS: This study found no clinically relevant pelvic anatomy changes during the day. Still, on an individual level differences can be large, so repeating clinical examination at the end of the day can be recommended in patients when anamnesis and physical examination do not match.

7.
J Magn Reson Imaging ; 56(5): 1302-1308, 2022 11.
Artigo em Inglês | MEDLINE | ID: mdl-35322920

RESUMO

BACKGROUND: Cerebral venous pathways are subjected to geometrical and patency changes due to body position. The internal jugular veins (IJVs) are the main venous drainage pathway in supine position. Their patency and geometry should be evaluated under different body inclination angles over a three-dimensional (3D) volume in the healthy situation to better understand pathological cases. PURPOSE: To investigate whether positional changes in the body can affect the geometrical properties and patency of the venous system. STUDY TYPE: Prospective. POPULATION: 15 healthy volunteers, of which seven males and median age 22 years in a range of 19-59. FIELD STRENGTH/SEQUENCE: A 0.25-T tiltable MRI system was used to scan volunteers in 90° (sitting position), 69°, 45°, 21°, and 0° (supine position) in the transverse plane with the top at vertebra C2. A gradient echo sequence was used. ASSESSMENT: Three observers assessed IJVs on patency and created automatic centerlines from which diameter and patency were analysed perpendicular to the vessel at every 4 mm starting at the level of C2. STATISTICAL TESTS: A Student's t test was used to find statistical difference (p < 0.05) in average IJV diameters per inclination angle. RESULTS: The amount of fully collapsed IJVs increased from 33% to 93% (left IJV) and 14% to 80% (right IJV) when increasing the inclination angle from 0° to 90°. In both IJVs, the mean diameter (±SD) of the open vessels was significantly higher at 0° than 90° with 6.3 ± 0.5 mm vs. 4.4 ± 0.1 mm (left IJV) and 6.6 ± 0.6 mm vs. 4.3 ± 0.4 mm (right IJV). DATA CONCLUSION: Tiltable low-field MRI can be used to assess IJV geometry and its associated venous pathways in 3D under multiple inclination angles. Next to a higher amount of collapsed vessels, the average diameter of noncollapsed vessels decreases with increasing inclination angles for both left and right IJVs. LEVEL OF EVIDENCE: 2 TECHNICAL EFFICACY STAGE: 1.


Assuntos
Veias Jugulares , Imageamento por Ressonância Magnética , Adulto , Voluntários Saudáveis , Humanos , Veias Jugulares/diagnóstico por imagem , Masculino , Pessoa de Meia-Idade , Estudos Prospectivos , Adulto Jovem
8.
Int Urogynecol J ; 33(10): 2801-2807, 2022 10.
Artigo em Inglês | MEDLINE | ID: mdl-35907021

RESUMO

INTRODUCTION AND HYPOTHESIS: Pelvic organ prolapse quantification by means of upright magnetic resonance imaging (MRI) is a promising research field. This study determines the angle for the pelvic inclination correction system (PICS) for upright patient position, which is hypothesized to deviate from the supine PICS angle. The necessity of different PICS angles for various patient positions will also be discussed. METHODS: Magnetic resonance scans of 113 women, acquired in an upright patient position, were used to determine the upright PICS angle, defined as the angle between the sacrococcygeal-inferior pubic point (SCIPP) line and the horizontal line. The difference and correlation between the upright and supine PICS angles were calculated using the paired Student's t-test and the Pearson's correlation coefficient (r) respectively. The effect of the difference between the upright and supine PICS angle on the measured pelvic organ extent was calculated using goniometry. RESULTS: The mean (interquartile range) PICS angles were 29° (26-35°) for the upright and 33° (30-37°) for the supine patient position. They were significantly different (p<0.001) and very strongly correlated (r = 0.914, p<0.001). The 4° difference between the average upright and supine PICS angle results in an average underestimation of the measured cervix height of approximately 0.5 cm for patients scanned in upright position. CONCLUSIONS: The PICS angle for the upright patient position is 29°. The use of a dedicated PICS angle for different patient positions allows for more accurate pelvic organ extent analysis in patients with prolapse.


Assuntos
Prolapso de Órgão Pélvico , Colo do Útero/patologia , Feminino , Humanos , Imageamento por Ressonância Magnética , Prolapso de Órgão Pélvico/diagnóstico por imagem , Prolapso de Órgão Pélvico/patologia , Postura , Posição Ortostática
9.
Magn Reson Med ; 81(5): 3358-3369, 2019 05.
Artigo em Inglês | MEDLINE | ID: mdl-30656738

RESUMO

PURPOSE: The arterial input function (AIF) is a major source of uncertainty in tracer kinetic (TK) analysis of dynamic contrast-enhanced (DCE)-MRI data. The aim of this study was to investigate the repeatability of AIFs extracted from the complex signal and of the resulting TK parameters in prostate cancer patients. METHODS: Twenty-two patients with biopsy-proven prostate cancer underwent a 3T MRI exam twice. DCE-MRI data were acquired with a 3D spoiled gradient echo sequence. AIFs were extracted from the magnitude of the signal (AIFMAGN ), phase (AIFPHASE ), and complex signal (AIFCOMPLEX ). The Tofts model was applied to extract Ktrans , kep and ve . Repeatability of AIF curve characteristics and TK parameters was assessed with the within-subject coefficient of variation (wCV). RESULTS: The wCV for peak height and full width at half maximum for AIFCOMPLEX (7% and 8%) indicated an improved repeatability compared to AIFMAGN (12% and 12%) and AIFPHASE (12% and 7%). This translated in lower wCV values for Ktrans (11%) with AIFCOMPLEX in comparison to AIFMAGN (24%) and AIFPHASE (15%). For kep , the wCV was 16% with AIFMAGN , 13% with AIFPHASE , and 13% with AIFCOMPLEX . CONCLUSION: Repeatability of AIFPHASE and AIFCOMPLEX is higher than for AIFMAGN , resulting in a better repeatability of TK parameters. Thus, use of either AIFPHASE or AIFCOMPLEX improves the robustness of quantitative analysis of DCE-MRI in prostate cancer.


Assuntos
Meios de Contraste/administração & dosagem , Imageamento por Ressonância Magnética , Neoplasias da Próstata/diagnóstico por imagem , Idoso , Algoritmos , Biópsia , Simulação por Computador , Humanos , Interpretação de Imagem Assistida por Computador/métodos , Processamento de Imagem Assistida por Computador , Cinética , Masculino , Pessoa de Meia-Idade , Modelos Estatísticos , Reprodutibilidade dos Testes
10.
J Magn Reson Imaging ; 49(6): 1528-1542, 2019 06.
Artigo em Inglês | MEDLINE | ID: mdl-30637943

RESUMO

Historically, clinical MRI started with main magnetic field strengths in the ∼0.05-0.35T range. In the past 40 years there have been considerable developments in MRI hardware, with one of the primary ones being the trend to higher magnetic fields. While resulting in large improvements in data quality and diagnostic value, such developments have meant that conventional systems at 1.5 and 3T remain relatively expensive pieces of medical imaging equipment, and are out of the financial reach for much of the world. In this review we describe the current state-of-the-art of low-field systems (defined as 0.25-1T), both with respect to its low cost, low foot-print, and subject accessibility. Furthermore, we discuss how low field could potentially benefit from many of the developments that have occurred in higher-field MRI. In the first section, the signal-to-noise ratio (SNR) dependence on the static magnetic field and its impact on the achievable contrast, resolution, and acquisition times are discussed from a theoretical perspective. In the second section, developments in hardware (eg, magnet, gradient, and RF coils) used both in experimental low-field scanners and also those that are currently in the market are reviewed. In the final section the potential roles of new acquisition readouts, motion tracking, and image reconstruction strategies, currently being developed primarily at higher fields, are presented. Level of Evidence: 5 Technical Efficacy Stage: 1 J. Magn. Reson. Imaging 2019.


Assuntos
Imageamento por Ressonância Magnética/instrumentação , Imageamento por Ressonância Magnética/métodos , Encéfalo/diagnóstico por imagem , Meios de Contraste , Desenho de Equipamento , História do Século XX , História do Século XXI , Humanos , Aumento da Imagem/métodos , Processamento de Imagem Assistida por Computador/métodos , Campos Magnéticos , Imageamento por Ressonância Magnética/economia , Imageamento por Ressonância Magnética/história , Modelos Estatísticos , Movimento (Física) , Física , Ondas de Rádio , Razão Sinal-Ruído
11.
Int Urogynecol J ; 30(11): 1939-1944, 2019 11.
Artigo em Inglês | MEDLINE | ID: mdl-30656361

RESUMO

OBJECTIVE: Pelvic organ prolapse (POP) is clinically diagnosed in the supine position, where the effect of gravity is simulated by having the patients put strain on their pelvic floor. The objective of this study was to determine the degree of POP underestimation in the supine position based on magnetic resonance imaging (MRI) findings. METHODS: This prospective study was conducted with symptomatic POP grade ≥ 2 patients. Fifteen female patients were examined with an MRI system that allows supine and upright imaging. The differences between supine and upright in distances of the bladder neck, cervix, and pouch of Douglas from the pubococcygeal line (PCL) were estimated, together with changes in the genital hiatal area. Patients were scanned at rest and during straining. All distances were compared using the Wilcoxon ranking test. RESULTS: All mean distances from the PCL increased from the supine-strain to the upright-rest and from the supine-strain to the upright-strain position. These distances were found in the supine and upright positions: the bladder descended 1.3 cm to 1.4 cm, the cervix 1.1 cm to 2.2 cm, and the pouch of Douglas 0.8 cm to 1.5 cm respectively (all p values <0.05). The hiatal area was larger in the upright-strain position (mean 42.0 cm2; SD ±14.8) than during the supine-strain position (mean 33.5 cm2; SD ±14.5), with a p value of 0.02. CONCLUSION: Upright MRI scanning of patients with POP grade ≥ 2 both at rest and during straining shows a significantly larger extent of the prolapse than that observed during supine straining.


Assuntos
Imageamento por Ressonância Magnética , Posicionamento do Paciente/métodos , Prolapso de Órgão Pélvico/diagnóstico por imagem , Idoso , Feminino , Humanos , Pessoa de Meia-Idade , Prolapso de Órgão Pélvico/diagnóstico , Estudos Prospectivos , Decúbito Dorsal
12.
Magn Reson Med ; 76(4): 1236-45, 2016 10.
Artigo em Inglês | MEDLINE | ID: mdl-26525012

RESUMO

PURPOSE: Dynamic contrast enhanced (DCE) imaging is a widely used technique in oncologic imaging. An essential prerequisite for obtaining quantitative values from DCE-MRI is the determination of the arterial input function (AIF). However, it is very challenging to accurately estimate the AIF using MR. A comprehensive model, which uses complex data instead of either magnitude or phase, was developed to improve AIF estimation. THEORY AND METHODS: The model was first applied to simulated data. Subsequently, the accuracy of the estimated contrast agent concentration was validated in a phantom. Finally the method was applied to existing DCE scans of 13 prostate cancer patients. RESULTS: The complex signal method combines the complementary strengths of the magnitude and phase method, increasing the precision and accuracy of concentration estimation in simulated and phantom data. The in vivo AIFs show a good agreement between arterial voxels (standard deviation in the peak and tail equal 0.4 mM and 0.12 mM, respectively). Furthermore, the dynamic behavior closely followed the AIF obtained with DCE-CT in the same patients (mean correlation coefficient: 0.92). CONCLUSION: By using the complex signal, the AIF estimation becomes more accurate and precise. This might enable patient specific AIFs, thereby improving the quantitative values obtained from DCE-MRI. Magn Reson Med 76:1236-1245, 2016. © 2015 Wiley Periodicals, Inc.


Assuntos
Aumento da Imagem/métodos , Imageamento por Ressonância Magnética/métodos , Modelos Biológicos , Compostos Organometálicos/farmacocinética , Neoplasias da Próstata/diagnóstico por imagem , Neoplasias da Próstata/metabolismo , Algoritmos , Simulação por Computador , Meios de Contraste/farmacocinética , Humanos , Interpretação de Imagem Assistida por Computador/métodos , Masculino , Reprodutibilidade dos Testes , Sensibilidade e Especificidade
13.
Magn Reson Med ; 75(4): 1743-51, 2016 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-25977138

RESUMO

PURPOSE: One of the main safety concerns in MR is heating of the subject due to radiofrequency (RF) exposure. Recently was shown that local peak temperatures can reach dangerous values and the most prominent parameter for accurate temperature estimations is thermoregulation. Therefore, the goal of this research is testing the feasibility of measuring thermoregulation in vivo using MR methods. THEORY AND METHODS: The calves of 13 volunteers were scanned at 3 tesla. A Proton Resonance Frequency Shift method was used for temperature measurement. Arterial Spin Labeling and phase contrast scans were used for perfusion and flow measurements respectively. The calves were monitored during extreme RF exposure (20 W/kg, 16 min) and after physical exercise. RESULTS: Temperature increases due to RF absorption (range of the 90th percentile of all volunteers: 1.1-2.5°C) matched with the reference skin temperature changes. Increases in perfusion and flow were defined on the whole leg and normalized to baseline. Perfusion showed a significant increase due to RF heating (ratio compared with baseline: 1.28 ± 0.37; P < 0.05), the influence of exercise was much greater, however (2.97 ± 2.45, P < 0.01). CONCLUSION: This study represents a first exploration of measuring thermoregulation, which will become essential when new safety guidelines are based on thermal dose.


Assuntos
Regulação da Temperatura Corporal/fisiologia , Perna (Membro)/diagnóstico por imagem , Imageamento por Ressonância Magnética/métodos , Músculo Esquelético/diagnóstico por imagem , Termografia/métodos , Estudos de Viabilidade , Feminino , Humanos , Perna (Membro)/fisiologia , Masculino , Músculo Esquelético/fisiologia , Imagens de Fantasmas , Temperatura Cutânea
14.
Magn Reson Med ; 73(3): 1184-9, 2015 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-24664621

RESUMO

PURPOSE: MR thermometry (MRT) is a noninvasive method for measuring temperature that can potentially be used for radio frequency (RF) safety monitoring. This application requires measuring absolute temperature. In this study, a multigradient-echo (mGE) MRT sequence was used for that purpose. A drawback of this sequence, however, is that its accuracy is affected by background gradients. In this article, we present a method to minimize this effect and to improve absolute temperature measurements using MRI. THEORY: By determining background gradients using a B0 map or by combining data acquired with two opposing readout directions, the error can be removed in a homogenous phantom, thus improving temperature maps. METHODS: All scans were performed on a 3T system using ethylene glycol-filled phantoms. Background gradients were varied, and one phantom was uniformly heated to validate both compensation approaches. Independent temperature recordings were made with optical probes. RESULTS: Errors correlated closely to the background gradients in all experiments. Temperature distributions showed a much smaller standard deviation when the corrections were applied (0.21°C vs. 0.45°C) and correlated well with thermo-optical probes. CONCLUSION: The corrections offer the possibility to measure RF heating in phantoms more precisely. This allows mGE MRT to become a valuable tool in RF safety assessment.


Assuntos
Algoritmos , Artefatos , Imagem Ecoplanar/métodos , Interpretação de Imagem Assistida por Computador/métodos , Termografia/métodos , Imagem Ecoplanar/instrumentação , Humanos , Aumento da Imagem/métodos , Campos Magnéticos , Dinâmica não Linear , Imagens de Fantasmas , Reprodutibilidade dos Testes , Sensibilidade e Especificidade , Processamento de Sinais Assistido por Computador
16.
Magn Reson Med ; 72(2): 409-17, 2014 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-24186703

RESUMO

PURPOSE: A high-quality, reproducible, multi-slice T2-mapping protocol for the mouse heart is presented. METHODS: A T2-prepared sequence with composite 90° and 180° radiofrequency pulses in a segmented MLEV phase cycling scheme was developed. The T2-mapping protocol was optimized using simulations and evaluated with phantoms. RESULTS: Repeatability for determination of myocardial T2 values was assessed in vivo in n = 5 healthy mice on 2 different days. The average baseline T2 of the left ventricular myocardium was 22.5 ± 1.7 ms. The repeatability coefficient for R2 = 1/T2 for measurements at different days was ΔR2 = 6.3 s(−1). Subsequently, T2 mapping was applied in comparison to late-gadolinium-enhancement (LGE) imaging, to assess 1-day-old ischemia/reperfusion (IR) myocardial injury in n = 8 mice. T2 in the infarcts was significantly higher than in remote tissue, whereas remote tissue was not significantly different from baseline. Infarct sizes based on T2 versus LGE showed strong correlation. To assess the time-course of T2 changes in the infarcts, T2 mapping was performed at day 1, 3, and 7 after IR injury in a separate group of mice (n = 16). T2 was highest at day 3, in agreement with the expected time course of edema formation and resolution after myocardial infarction. CONCLUSION: T2 prepared imaging provides high quality reproducible T2 maps of healthy and diseased mouse myocardium.


Assuntos
Algoritmos , Aumento da Imagem/métodos , Interpretação de Imagem Assistida por Computador/métodos , Imageamento por Ressonância Magnética/métodos , Infarto do Miocárdio/patologia , Miocárdio/patologia , Animais , Camundongos , Reprodutibilidade dos Testes , Sensibilidade e Especificidade , Processamento de Sinais Assistido por Computador
17.
Eur J Radiol ; 175: 111470, 2024 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-38640822

RESUMO

PURPOSE: To explore diagnostic deep learning for optimizing the prostate MRI protocol by assessing the diagnostic efficacy of MRI sequences. METHOD: This retrospective study included 840 patients with a biparametric prostate MRI scan. The MRI protocol included a T2-weighted image, three DWI sequences (b50, b400, and b800 s/mm2), a calculated ADC map, and a calculated b1400 sequence. Two accelerated MRI protocols were simulated, using only two acquired b-values to calculate the ADC and b1400. Deep learning models were trained to detect prostate cancer lesions on accelerated and full protocols. The diagnostic performances of the protocols were compared on the patient-level with the area under the receiver operating characteristic (AUROC), using DeLong's test, and on the lesion-level with the partial area under the free response operating characteristic (pAUFROC), using a permutation test. Validation of the results was performed among expert radiologists. RESULTS: No significant differences in diagnostic performance were found between the accelerated protocols and the full bpMRI baseline. Omitting b800 reduced 53% DWI scan time, with a performance difference of + 0.01 AUROC (p = 0.20) and -0.03 pAUFROC (p = 0.45). Omitting b400 reduced 32% DWI scan time, with a performance difference of -0.01 AUROC (p = 0.65) and + 0.01 pAUFROC (p = 0.73). Multiple expert radiologists underlined the findings. CONCLUSIONS: This study shows that deep learning can assess the diagnostic efficacy of MRI sequences by comparing prostate MRI protocols on diagnostic accuracy. Omitting either the b400 or the b800 DWI sequence can optimize the prostate MRI protocol by reducing scan time without compromising diagnostic quality.


Assuntos
Aprendizado Profundo , Imageamento por Ressonância Magnética , Neoplasias da Próstata , Humanos , Masculino , Neoplasias da Próstata/diagnóstico por imagem , Estudos Retrospectivos , Imageamento por Ressonância Magnética/métodos , Pessoa de Meia-Idade , Idoso , Interpretação de Imagem Assistida por Computador/métodos , Reprodutibilidade dos Testes , Sensibilidade e Especificidade
18.
Eur Radiol Exp ; 7(1): 82, 2023 12 21.
Artigo em Inglês | MEDLINE | ID: mdl-38123829

RESUMO

BACKGROUND: Abdominal aortic endoleaks after endovascular aneurysm repair might be position-dependent, therefore undetectable using supine imaging. We aimed to determine the feasibility and benefit of using a low-field tiltable magnetic resonance imaging (MRI) scanner allowing to study patients who can be imaged in both supine and upright positions of endoleaks. METHODS: Ten EVAR patients suspected of endoleak based on ultrasound examination were prospectively included. MRI in upright and supine positions was compared with routine supine computed tomography angiography (CTA). Analysis was performed through (1) subjective image quality assessment by three observers, (2) landmark registration between MRI and CTA scans, (3) Euclidean distances between renal and endograft landmarks, and (4) evaluation of endoleak detection on MRI by a consensus panel. Statistical analysis was performed by one-way repeated measures analysis of variance. RESULTS: The image quality of upright/supine MRI was inferior compared to CTA. Median differences in both renal and endograft landmarks were approximately 6-7 mm between upright and supine MRI and 5-6 mm between supine MRI and CTA. In the proximal sealing zone of the endograft, no differences were found among all three scan types (p = 0.264). Endoleak detection showed agreement between MRI and CTA in 50% of the cases, with potential added value in only one patient. CONCLUSIONS: The benefit of low-field upright MRI for endoleak detection was limited. While MRI assessment was non-inferior to standard CTA in detecting endoleaks in selected cases, improved hardware and sequences are needed to explore the potential of upright MRI in patients with endoleaks. RELEVANCE STATEMENT: Upright low-field MRI has limited clinical value in detecting position-dependent endoleaks; improvements are required to fulfil its potential as a complementary modality in this clinical setting. KEY POINTS: • Upright MRI shows potential for imaging endoleaks in aortic aneurysm patients in different positions. • The image quality of upright MRI is inferior to current techniques. • Upright MRI complements CTA, but lacks accurate deformation measurements for clinical use. • Advancements in hardware and imaging sequences are needed to fully utilise upright MRI capabilities.


Assuntos
Aneurisma da Aorta Abdominal , Implante de Prótese Vascular , Procedimentos Endovasculares , Humanos , Endoleak/diagnóstico por imagem , Aneurisma da Aorta Abdominal/diagnóstico por imagem , Aneurisma da Aorta Abdominal/cirurgia , Estudos de Viabilidade , Correção Endovascular de Aneurisma , Aortografia/métodos , Procedimentos Endovasculares/métodos , Resultado do Tratamento , Imageamento por Ressonância Magnética
19.
Curr Oncol ; 29(2): 777-784, 2022 02 01.
Artigo em Inglês | MEDLINE | ID: mdl-35200565

RESUMO

Nephron-sparing surgery (NSS) in Wilms tumor (WT) patients is a surgically challenging procedure used in highly selective cases only. Virtual resections can be used for preoperative planning of NSS to estimate the remnant renal volume (RRV) and to virtually mimic radical tumor resection. In this single-center evaluation study, virtual resection for NSS planning and the user experience were evaluated. Virtual resection was performed in nine WT patient cases by two pediatric surgeons and one pediatric urologist. Pre- and postoperative MRI scans were used for 3D visualization. The virtual RRV was acquired after performing virtual resection and a questionnaire was used to assess the ease of use. The actual RRV was derived from the postoperative 3D visualization and compared with the derived virtual RRV. Virtual resection resulted in virtual RRVs that matched nearly perfectly with the actual RRVs. According to the questionnaire, virtual resection appeared to be straightforward and was not considered to be difficult. This study demonstrated the potential of virtual resection as a new planning tool to estimate the RRV after NSS in WT patients. Future research should further evaluate the clinical relevance of virtual resection by relating it to surgical outcome.


Assuntos
Neoplasias Renais , Cirurgiões , Tumor de Wilms , Criança , Humanos , Neoplasias Renais/patologia , Neoplasias Renais/cirurgia , Nefrectomia/métodos , Néfrons/patologia , Néfrons/cirurgia , Tumor de Wilms/patologia , Tumor de Wilms/cirurgia
20.
Eur Radiol Exp ; 6(1): 3, 2022 01 27.
Artigo em Inglês | MEDLINE | ID: mdl-35083595

RESUMO

BACKGROUND: A procedure for sentinel lymph node biopsy (SLNB) using superparamagnetic iron-oxide (SPIO) nanoparticles and intraoperative sentinel lymph node (SLN) detection was developed to overcome drawbacks associated with the current standard-of-care SLNB. However, residual SPIO nanoparticles can result in void artefacts at follow-up magnetic resonance imaging (MRI) scans. We present a grading protocol to quantitatively assess the severity of these artefacts and offer an option to minimise the impact of SPIO nanoparticles on diagnostic imaging. METHODS: Follow-up mammography and MRI of two patient groups after a magnetic SLNB were included in the study. They received a 2-mL subareolar dose of SPIO (high-dose, HD) or a 0.1-mL intratumoural dose of SPIO (low-dose, LD). Follow-up mammography and MRI after magnetic SLNB were acquired within 4 years after breast conserving surgery (BCS). Two radiologists with over 10-year experience in breast imaging assessed the images and analysed the void artefacts and their impact on diagnostic follow-up. RESULTS: A total of 19 patients were included (HD, n = 13; LD, n = 6). In the HD group, 9/13 patients displayed an artefact on T1-weighted images up to 3.6 years after the procedure, while no impact of the SPIO remnants was observed in the LD group. CONCLUSIONS: SLNB using a 2-mL subareolar dose of magnetic tracer in patients undergoing BCS resulted in residual artefacts in the breast in the majority of patients, which may hamper follow-up MRI. This can be avoided by using a 0.1-mL intratumoural dose.


Assuntos
Linfonodo Sentinela , Mama , Humanos , Imageamento por Ressonância Magnética , Mastectomia Segmentar , Linfonodo Sentinela/diagnóstico por imagem , Linfonodo Sentinela/cirurgia , Biópsia de Linfonodo Sentinela
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