MRM Q&A posts
By Jessica McKayMichael Dieckmeyer
This month we talked to Michael Dieckmeyer and Dimitrios (Dimitris) Karampinos about their work to measure apparent diffusion coefficient (ADC) values in bone marrow. Michael has a very diverse education that includes a master’s degree in mathematics, and he is currently completing his final year of medical school. His mentor Dimitris leads a multidisciplinary research team in Munich that focuses on the development of quantitative MRI, targeting musculoskeletal diseases and metabolic diseases like obesity and diabetes. In this paper, they use modeling to overcome some of the challenges of ADC quantification in the presence of fat. By including the proton density fat fraction (PDFF) and the T2 of water, they can reduce the bias in the ADC measurements that is introduced by residual fat.
By Nikola StikovStephen Cauley
The Martinos center in Boston recently brought us wave-CAIPI, an accelerated 3D imaging technique that uses helixes in k-space to encode information and speed up MRI acquisition. However, differences in the calibration of the gradient systems made it difficult to generalize the wave-CAIPI technique and deploy it on any clinical scanner. This is where the Editor’s Pick for September comes in; Stephen Cauley and his colleagues proposed a joint optimization approach to estimate k-space trajectory discrepancies simulataneously with the underlying image. We asked Steve and senior author Larry Wald to tell us the story of autocallibrated wave-CAIPI.
By Blake DeweyBernhard Strasser
This week we gathered across multiple continents (as I feel we always do!) to discuss the ins and outs of spectroscopic imaging with Bernhard Strasser and Wolfgang Bogner, two authors of “(2 + 1)D-CAIPIRINHA accelerated MR spectroscopic imaging of the brain at 7T”, one of the MRM Editor’s Picks for August 2017. In this paper, Bernhard and his colleagues propose a new method of acceleration for magnetic resonance spectroscopic imaging (MRSI) that combines 2D CAIPIRINHA with simultaneous multi-slice (SMS) to accelerate imaging in all three spatial dimensions.
By Mathieu BoudreauXiao-Yong Zhang
The August 2017 Editor’s Pick is from Xiao-Yong Zhang and Zhongliang Zu, researchers at Vanderbilt University in Nashville. Their paper presents a newly discovered Nuclear Overhauser Effect (NOE) signal at -1.6 ppm from water. They measured this signal in normal rat brains at 9.4 T, and found that it changed significantly in a rodent tumor model. Using reconstituted phospholipids and cultured cell experiments, they hypothesize that this signal may originate from membrane choline phospholipids. We recently spoke with Xiao-Yong and Zhongliang Zu about their work.
By Brian ChungPatrick Schuenke
This week we ventured across continents to speak with Drs. Patrick Schünke and Moritz Zaiss, two primary authors of a recent paper from the German Cancer Research Center (DKFZ) in Heidelberg, Germany titled: “Adiabatically Prepared Spin-Lock Approach for T1ρ-Based Dynamic Glucose Enhanced MRI at Ultrahigh Fields.” In this paper, the authors developed an NMR method for imaging glucose using an ultrahigh field MR scanner and a spin-lock approach to gain sensitivity to chemical exchange. At ultrahigh field strengths, distinct artifacts appear predominantly resulting from RF field inhomogeneities. Thus, adiabatic pulses were implemented to enable the application of spin-lock MRI at fields such as 7T. This adiabatic spin-lock approach is explained, its feasibility for application in vivo at 7T is verified, the technique’s sensitivity to glucose is investigated, and a first proof of concept of spin-lock based glucose imaging for the detection of cancer in humans is presented.
By Pinar Ozbay
It is our pleasure to present one of the Editor’s picks for July, Preconditioned Total Field Inversion (TFI) Method for Quantitative Susceptibility Mapping (QSM), from Cornell University. In this work Zhe Liu, Pascal Spincemaille and colleagues proposed an algorithm which allows mapping of tissue magnetic susceptibility in regions with large dynamic susceptibility ranges, such as cavities, bones, and hemorrhages in the head. There are two main steps in QSM algorithm which are removal of background fields to calculate the local field, and solving the local field-to-susceptibility problem. The latter is an ill-posed problem by nature, hence is mainly referred to as the step of inverse problem in the literature of QSM. Their method calculates susceptibility maps via ‘total field inversion’, which generalizes those two steps as one optimization problem, and further employs preconditioning to achieve fast convergence.
By Thijs Dhollander
We sat down across time zones again (Australia in the morning, US east coast late afternoon), this time with Hua Li and Junzhong Xu, first and last author of their recent paper “Impact of transcytolemmal water exchange on estimates of tissue microstructural properties derived from diffusion MRI”. Apart from discussing the paper, we couldn’t resist touching on the topic of social media in research these days, as well as the challenges and peer pressure involved with designing good acronyms for novel methods…
BY Blake DeweyJun Chen
I recently had the pleasure of chatting with Drs. Jun Chen and Jiang Du about their recent MRM manuscript entitled “Measurement of Bound and Pore Water T1 Relaxation Times in Cortical Bone Using Three-Dimensional Ultrashort Echo Time Cones Sequences”. We came together over three distinct time zones, stretching from Peking, China to San Diego, California and finally to me right outside of Washington, D.C, where thanks to a strong internet connection we discussed the ups and downs of ultrashort echo time (UTE) imaging. UTE is a method for direct imaging of tissues that have short transverse relaxation times by shortening the delay between excitation and readout. For example, in this paper, the echo time for UTE imaging was only 8 μs, compared to a traditional gradient echo readout, that would have a minimum of 2-5 ms, depending on the sequence. Jun and Jiang, along with their colleagues in the U.S. and China, have been working to apply UTE sequences to explore the T1 properties of cortical bone and give clinically relevant information on components of the cortical bone structures not easily investigated with conventional radiological techniques.
By Atef Badji and Nikola StikovAlan Wilman (Left) and Kelly McPhee (Right)
Among the Editor’s picks for May comes a paper from the department of Physics at the University of Alberta in Edmonton, Canada. In their work entitled ‘Transverse relaxation and flip angle mapping: Evaluation of simultaneous and independent methods using multiple spin echoes’, Kelly McPhee and Alan Wilman evaluated transverse relaxation (T2) and flip angle maps derived from Bloch simulations and Extended Phase Graphs (EPG). We conducted this interview with Kelly on a beautiful Sunday afternoon at the Honolulu convention center during the annual ISMRM meeting.