7 T renal MRI: challenges and promises

The progression to 7 Tesla (7 T) magnetic resonance imaging (MRI) yields promises of substantial increase in signal-to-noise (SNR) ratio. This increase can be traded off to increase image spatial resolution or to decrease acquisition time. However, renal 7 T MRI remains challenging due to inhomogeneity of the radiofrequency field and due to specific absorption rate (SAR) constraints. A number of studies has been published in the field of renal 7 T imaging. While the focus initially was on anatomic imaging and renal MR angiography, later studies have explored renal functional imaging. Although anatomic imaging remains somewhat limited by inhomogeneous excitation and SAR constraints, functional imaging results are promising. The increased SNR at 7 T has been particularly advantageous for blood oxygen level-dependent and arterial spin labelling MRI, as well as sodium MR imaging, thanks to changes in field-strength-dependent magnetic properties. Here, we provide an overview of the currently available literature on renal 7 T MRI. In addition, we provide a brief overview of challenges and opportunities in renal 7 T MR imaging

Technical recommendations for clinical translation of renal MRI: a consensus project of the Cooperation in Science and Technology Action PARENCHIMA.

PURPOSE: The potential of renal MRI biomarkers has been increasingly recognised, but clinical translation requires more standardisation. The PARENCHIMA consensus project aims to develop and apply a process for generating technical recommendations on renal MRI. METHODS: A task force was formed in July 2018 focused on five methods. A draft process for attaining consensus was distributed publicly for consultation and finalised at an open meeting (Prague, October 2018). Four expert panels completed surveys between October 2018 and March 2019, discussed results and refined the surveys at a face-to-face meeting (Aarhus, March 2019) and completed a second round (May 2019). RESULTS: A seven-stage process was defined: (1) formation of expert panels; (2) definition of the context of use; (3) literature review; (4) collection and comparison of MRI protocols; (5) consensus generation by an approximate Delphi method; (6) reporting of results in vendor-neutral and vendor-specific terms; (7) ongoing review and updating. Application of the process resulted in 166 consensus statements. CONCLUSION: The process generated meaningful technical recommendations across very different MRI methods, while allowing for improvement and refinement as open issues are resolved. The results are likely to be widely supported by the renal MRI community and thereby promote more harmonisation

Consensus-based technical recommendations for clinical translation of renal T1 and T2 mapping MRI

To develop technical recommendations on the acquisition and post-processing of renal longitudinal (T1) and transverse (T2) relaxation time mapping. A multidisciplinary panel consisting of 18 experts in the field of renal T1 and T2 mapping participated in a consensus project, which was initiated by the European Cooperation in Science and Technology Action PARENCHIMA CA16103. Consensus recommendations were formulated using a two-step modified Delphi method. The first survey consisted of 56 items on T1 mapping, of which 4 reached the pre-defined consensus threshold of 75% or higher. The second survey was expanded to include both T1 and T2 mapping, and consisted of 54 items of which 32 reached consensus. Recommendations based were formulated on hardware, patient preparation, acquisition, analysis and reporting. Consensus-based technical recommendations for renal T1 and T2 mapping were formulated. However, there was considerable lack of consensus for renal T1 and particularly renal T2 mapping, to some extent surprising considering the long history of relaxometry in MRI, highlighting key knowledge gaps that require further work. This paper should be regarded as a first step in a long-term evidence-based iterative process towards ever increasing harmonization of scan protocols across sites, to ultimately facilitate clinical implementation

Technical recommendations for clinical translation of renal MRI: a consensus project of the Cooperation in Science and Technology Action PARENCHIMA

Purpose The potential of renal MRI biomarkers has been increasingly recognised, but clinical translation requires more standardisation. The PARENCHIMA consensus project aims to develop and apply a process for generating technical recommendations on renal MRI. Methods A task force was formed in July 2018 focused on fve methods. A draft process for attaining consensus was distributed publicly for consultation and fnalised at an open meeting (Prague, October 2018). Four expert panels completed surveys between October 2018 and March 2019, discussed results and refned the surveys at a face-to-face meeting (Aarhus, March 2019) and completed a second round (May 2019). Results A seven-stage process was defned: (1) formation of expert panels; (2) defnition of the context of use; (3) literature review; (4) collection and comparison of MRI protocols; (5) consensus generation by an approximate Delphi method; (6) reporting of results in vendor-neutral and vendor-specifc terms; (7) ongoing review and updating. Application of the process resulted in 166 consensus statements. Conclusion The process generated meaningful technical recommendations across very diferent MRI methods, while allowing for improvement and refnement as open issues are resolved. The results are likely to be widely supported by the renal MRI community and thereby promote more harmonisation

Long-term outcomes following antenatal exposure to low-dose aspirin: study protocol for the 4-year follow-up of the APRIL randomised controlled trial

Introduction The use of low-dose aspirin by pregnant women to prevent preterm pre-eclampsia is gradually increasing. The administration of aspirin during pregnancy improves perinatal outcome, which could translate into improved child outcome in the long term. However, antenatal exposure to aspirin could have adverse effects on child development that may manifest later in life. The aim of this follow-up study is to assess the long-term effects of antenatal exposure to low-dose aspirin compared with placebo on survival, (neuro)development, behaviour and general health at 4 years corrected age. Methods and analysis This is a follow-up study of the Dutch double-blind randomised controlled APRIL trial which assessed the effectiveness of treatment with aspirin (80 mg daily) compared with placebo for the prevention of preterm birth in women with a previous spontaneous preterm birth. Treatment was initiated before 16 weeks of gestation and continued until 36 weeks or birth. We aim to follow-up all 379 children born to women who participated in the APRIL trial and survived the neonatal period, at the corrected age of 4 years. The main outcomes are (neuro)development as assessed by the Ages and Stages Questionnaire, and behaviour as assessed by the Strength and Difficulties Questionnaire. Additional outcomes include mortality, growth and general health from birth up to 4 years, and a composite outcome including mortality, abnormal (neuro)development and problem behaviour. Analyses will be performed by intention-to-treat using a superiority design. Ethics and dissemination Institutional Review Board approval was obtained from the Medical Research Ethics Committee from Amsterdam Medical Center (no. W20 289#20.325). The results will be published in a peer-reviewed journal and presented at conferences. Trial registration number The APRIL trial (NTR5675, NL5553; EudraCT number 2015-003220-31) and the APRIL follow-up study (NL8950) are registered in the Dutch trial register. The study is funded by the Amsterdam Reproduction & Development research institute

Pessary or progesterone to prevent preterm birth in women with short cervical length.: Protocol of the 4–6 year follow-up of a randomised controlled trial (Quadruple-P)

INTRODUCTION: Vaginal progesterone and a cervical pessary are both interventions that are investigated for the prevention of preterm birth (PTB). Thus far, beneficial or harmful effects of these interventions on long-term child health and development are described, but evidence is not robust enough to draw firm conclusions. With this follow-up study, we intent to investigate if progesterone or a pessary is superior for the prevention of PTB considering the child's health at 4-6 years of corrected age. METHODS AND ANALYSIS: This study is a follow-up study of the Quadruple-P trial; a multicentre, randomised clinical trial (NL42926.018.13, Eudractnumber 2013-002884-24) which randomises women with an asymptomatic midtrimester short cervix to daily progesterone or a pessary for the prevention of PTB. All children born to mothers who participated in the Quadruple-P study (n=628 singletons and n=332 multiples) will be eligible for follow-up at 4-6 years of corrected age. Children will be assessed using parental questionnaires. Main outcomes are child (neuro)development and behaviour. Other outcomes include child mortality, growth and general health. A composite of adverse child outcomes will be compared between the progesterone and pessary groups reporting OR and the corresponding 95% CI. Analyses will be performed separately for singletons and multiples and using the intention-to-treat approach. ETHICS AND DISSEMINATION: The Medical Research Ethics Committee from Amsterdam UMC confirmed that de Medical Research Involving Human Subjects Act (WMO) did not apply to our study (W20_481 #20.531). Results will be published in a peer-reviewed journal and shared with stakeholders and participants. This protocol is published before analysis of the results. TRIAL REGISTRATION NUMBER: Dutch Trial Register (NL9646)

Renal MRI: from Niche Application to New Tool in Nephrology

Around 10% of the general population suffers from some form of chronic kidney damage. Yet, treatment options for chronic kidney diseases are limited. Current therapies can only slow down progression of chronic kidney disease. Early detection therefore is crucial to initiate treatment in an early stage and to prevent progression to end-stage renal disease. Existing diagnostic tests only detect damage in a later stage and do not provide insight in the underlying structural and functional problems. In this thesis, we show that MRI potentially addresses those problems and can proof to be a valuable diagnostic tool for nephrologists. In chapter 2 a multiparametric MRI protocol designed specifically for renal imaging is tested in terms of repeatability. Nineteen healthy volunteers are scanned twice with an interval of about a week. The results of both examinations are compared. In the multiparametric MRI examination multiple techniques are combined, yielding a comprehensive image of renal microstructure and function. Based on the results of this study, we can conclude that repeatability of most measurements is comparable to clinical tests for renal function like eGFR and inulin clearance. In chapter 3 an important problem in renal imaging is addressed: respiratory motion. In DCE MRI, for several minutes quick images of the kidney are continuously acquired, but due to respiratory motion those images are misaligned. We propose a solution for this problem by using slightly different images, simplifying automated motion correction. Chapter 4 describes remaining contrast agent in the kidneys one week after administration, a chance finding from the repeatability study. The current study once again shows that the mechanism of excretion of MR contrast agents is not fully understood. Further research is therefore indicated. In chapter 5 and 6 BOLD MRI is used to assess renal oxygenation in patients with hypertension. A correlation between activity of the renin-angiotensin-aldosterone system and renal hypoxia is found, but an intervention hypothesized to decrease activity of this system (renal denervation) did not improve renal oxygenation. Chapter 7 describes a case of a patient with end-stage failure of her transplant kidney. Since the transplant kidney was explanted, we were able to compare whole-kidney histology with the results of the multiparametric MRI. The MR measures correlated well with histological findings. Chapter 8 explores the possibilities of renal MRI at ultra-high field. Switching to 7 T creates new possibilities, but imposes additional challenges as well. This review article describes which techniques are expected to profit from 7 T MRI, what the challenges are and where to look for solutions. Finally, chapter 9 places these results in context. How should renal MRI be used in clinical practice to aid patients and doctors in early detection of renal damage and prevention of progression to end-stage renal disease? New technical developments can bridge the gap between research and clinical use. And we will touch upon the question how to employ MRI, a technique associated with both significant environmental as well as financial costs, in a sustainable way

Renal MRI: from Niche Application to New Tool in Nephrology

Around 10% of the general population suffers from some form of chronic kidney damage. Yet, treatment options for chronic kidney diseases are limited. Current therapies can only slow down progression of chronic kidney disease. Early detection therefore is crucial to initiate treatment in an early stage and to prevent progression to end-stage renal disease. Existing diagnostic tests only detect damage in a later stage and do not provide insight in the underlying structural and functional problems. In this thesis, we show that MRI potentially addresses those problems and can proof to be a valuable diagnostic tool for nephrologists. In chapter 2 a multiparametric MRI protocol designed specifically for renal imaging is tested in terms of repeatability. Nineteen healthy volunteers are scanned twice with an interval of about a week. The results of both examinations are compared. In the multiparametric MRI examination multiple techniques are combined, yielding a comprehensive image of renal microstructure and function. Based on the results of this study, we can conclude that repeatability of most measurements is comparable to clinical tests for renal function like eGFR and inulin clearance. In chapter 3 an important problem in renal imaging is addressed: respiratory motion. In DCE MRI, for several minutes quick images of the kidney are continuously acquired, but due to respiratory motion those images are misaligned. We propose a solution for this problem by using slightly different images, simplifying automated motion correction. Chapter 4 describes remaining contrast agent in the kidneys one week after administration, a chance finding from the repeatability study. The current study once again shows that the mechanism of excretion of MR contrast agents is not fully understood. Further research is therefore indicated. In chapter 5 and 6 BOLD MRI is used to assess renal oxygenation in patients with hypertension. A correlation between activity of the renin-angiotensin-aldosterone system and renal hypoxia is found, but an intervention hypothesized to decrease activity of this system (renal denervation) did not improve renal oxygenation. Chapter 7 describes a case of a patient with end-stage failure of her transplant kidney. Since the transplant kidney was explanted, we were able to compare whole-kidney histology with the results of the multiparametric MRI. The MR measures correlated well with histological findings. Chapter 8 explores the possibilities of renal MRI at ultra-high field. Switching to 7 T creates new possibilities, but imposes additional challenges as well. This review article describes which techniques are expected to profit from 7 T MRI, what the challenges are and where to look for solutions. Finally, chapter 9 places these results in context. How should renal MRI be used in clinical practice to aid patients and doctors in early detection of renal damage and prevention of progression to end-stage renal disease? New technical developments can bridge the gap between research and clinical use. And we will touch upon the question how to employ MRI, a technique associated with both significant environmental as well as financial costs, in a sustainable way