Download Resonance By Home
Louann Tandy
Standard clinical MRI scanners make use of powerful superconducting magnets that interact strongly with the vast amount of hydrogen nuclei in the human body1. These magnets enable the high SNR and spatial resolution typical for magnetic resonance images. Regrettably, these magnets also require cryogenic refrigeration, they are bulky, heavy, expensive to build, site, operate and maintain, and they ultimately constitute a formidable barrier to the accessibility and democratization of MRI2,3,4. Besides, high-field scanners are subject to patient safety risks, e.g. due to projectile incidents5; they are limited in the imaging pulse sequences that can be played out due to increased specific absorption rates (SAR) of electromagnetic energy in tissues at the corresponding higher excitation radio-frequencies (RF)6; they generate undesirable acoustic noise due to strong magnetic interactions during scans7; and they induce severe image artifacts around metallic implants due to magnetic susceptibility effects8,9,10. Low-field systems (\(
In conclusion, we have demonstrated the viability of a portable, low-cost system for magnetic resonance imaging indoors, outdoors and at home. In this work, we have focused on healthy volunteers and subjects carrying metallic implants. Nevertheless, the acquired images contain sufficient anatomical information to diagnose a large variety of articular diseases, including effusion, synovial engorgement, tendon disruption or bone fractures.
The receive chain consists of an analog stage (RF coil, passive Tx/Rx switch and low-noise amplifier) followed by a digital stage. The digitization is performed at 122.88 Ms/s by an analog-to-digital converter in the Red Pitaya Stemlab board40,41,42. The digital signal is mixed down by complex multiplication with a numerically-controlled oscillator set to the Larmor frequency. The real and imaginary data components pass first a cascaded integrator-comb filter and finally a finite impulse response filter. The resulting data conform the sought in-phase and quadrature components of the magnetic resonance signal. These are sent to the control computer and can be Fourier-transformed for image reconstruction and post-processing.
Mobile medical imaging devices are invaluable for clinical diagnostic purposes both in and outside healthcare institutions. Among the various imaging modalities, only a few are readily portable. Magnetic resonance imaging (MRI), the gold standard for numerous healthcare conditions, does not traditionally belong to this group. Recently, low-field MRI technology companies have demonstrated the first decisive steps towards portability within medical facilities and vehicles. However, these scanners' weight and dimensions are incompatible with more demanding use cases such as in remote and developing regions, sports facilities and events, medical and military camps, or home healthcare. Here we present in vivo images taken with a light, small footprint, low-field extremity MRI scanner outside the controlled environment provided by medical facilities. To demonstrate the true portability of the system and benchmark its performance in various relevant scenarios, we have acquired images of a volunteer's knee in: (i) an MRI physics laboratory; (ii) an office room; (iii) outside a campus building, connected to a nearby power outlet; (iv) in open air, powered from a small fuel-based generator; and (v) at the volunteer's home. All images have been acquired within clinically viable times, and signal-to-noise ratios and tissue contrast suffice for 2D and 3D reconstructions with diagnostic value. Furthermore, the volunteer carries a fixation metallic implant screwed to the femur, which leads to strong artifacts in standard clinical systems but appears sharp in our low-field acquisitions. Altogether, this work opens a path towards highly accessible MRI under circumstances previously unrealistic.
RESEARCH
False lumen rotational flow and aortic stiffness are associated with aortic growth rate in patients with chronic aortic dissection of the descending aorta: a 4D flow cardiovascular magnetic resonance study
Aroa Ruiz-Muñoz, et al.
Published on: 28 March 2022
In August, Scott Flamm was joined by authors Timothy Albert and Lilia Sierra-Galan to discuss their article "Worldwide variation in cardiovascular magnetic resonance practice models". You can view the recording on the SCMR website.
In July, Valentina Puntmann was joined by authors Satoshi Nakamura and Masaki Ishida to discuss their article "Complementary prognostic value of stress perfusion imaging and global coronary flow reserve derived from cardiovascular magnetic resonance: a long-term cohort study". You can view the recording on the SCMR website.
In March, Dr. Ruud van Heeswijk was joined by authors Dr. James Hamilton and Dr. Richard Gilbert to discuss their article "Lipid and smooth muscle architectural pathology in the rabbit atherosclerotic vessel wall using Q-space cardiovascular magnetic resonance." You can view the recording on the SCMR website.
Journal of Cardiovascular Magnetic Resonance (JCMR) publishes high-quality articles on all aspects of basic, translational and clinical research on the design, development, manufacture, and evaluation of cardiovascular magnetic resonance (CMR) methods applied to the cardiovascular system. Topical areas include, but are not limited to:
The LaScala 1 was known for its cabinet resonance. I believe this was addressed by placing a wedge in the bass cabinet to reduce the resonance. The LaScala II and the AL-5 have thicker walls. Is the general assumption that this completely eliminates the resonance? Or is there still some resonance present, and could, for example, a wedge in the bass cabinet still provide improvement?
I have found that some amplifiers can induce a resonance in the upper bass. I had a Sonic Frontiers Power 2 tube amp years ago that did just that. As soon as I got rid of that amp, the problem disappeared entirely.
If you think resonance is a problem , try clamping on a stiffener to the suspected area , like the outside horn edge for example , then compare results , test tones will be helpful . This way you can see for yourself any positive change ,Good luck ?
IIRC, the resonance in the LS is partly to do with the parallel doghouse a cabinet side walls. The Peavey FH-1 doesn't have that issue. Probably something they learned in designing them after the La Scala came out.
For this patch we use a basic mg waveform in oscillator "B" because we know that the Arturia Mini V was used to make the song and this is modeled after the Mini Moog, in oscillator "A" we use a saw wave waveform, both oscillators have 3 voices and their fine-tuning is being modulated by LFO 1.
Now, envelope 2 is modulating the filter cutoff but the most important part is to put the resonance of the filter around 55 - 60 percent.
This preset was the easiest to make, both oscillators are in basic shapes, oscillator "A" is in position 2 and oscillator "B" is in position 4 (which is a square wave), envelope 1 is modulating the cutoff and resonance of the filter and the sound is drenched in reverb, chorus, and ping pong delay.
Information of MRI testing of medical implants, materials, and devices performed by Magnetic Resonance Safety Testing Services. Testing procedures are in accordance with the guidelines from The American Society for Testing and Materials (ASTM) International.
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Meridian Resonance Control for Home Audio uses the dimensions of the room in order to compensate for the primary modal resonances that are especially exacerbated by loudspeakers with downward firing speakers, or by in-wall mounted loudspeakers
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