Low-Field MR Imaging of the Spine

Purpose: To evaluate a new steady-state sequence in the delineation of the various structures in the spine at low-field MR imaging with a very high homogeneity of the main field. Methods: 49 patients underwent 53 examinations with both a traditional T1-weighted gradient-echo (PS) sequence and a new completely balanced steady-state 3-D (CBASS3D) sequence; 20 examinations included the cervical spine, 8 the thoracic spine and 25 the lumbar spine. All 106 examinations were reviewed twice regarding visibility of selected structures in the spinal region and diagnostic usefulness. Results: The CBASS3D sequence delineated the medulla, nerve roots, CSF, the intervertebral discs and the posterior longitudinal ligament significantly better than the PS sequence. Disc hernia was also better visualised (p<0.01). There were significantly more artefacts on images obtained with the CBASS3D sequence, but they were usually outside the region of interest and occurred less frequently over time due to increased experience of the staff. Both reviewers found the diagnostic usefulness of CBASS3D to be superior compared to that of PS and excellent for diagnostic purposes. Conclusion: The CBASS3D sequence is a considerable improvement in the visualisation of degenerative changes of the spine at low-field MR imaging.

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Low Field Magnetic Resonance Imaging of Focal Hepatic Masses at 0.02 T

Acta Radiologica ◽

10.1177/028418518903000605 ◽

1989 ◽

Vol 30 (6) ◽

pp. 591-595

Author(s):

L. Ekelund ◽

L. Athlin

Keyword(s):

Magnetic Resonance ◽

Mr Imaging ◽

Malignant Tumors ◽

Signal To Noise Ratio ◽

Malignant Neoplasms ◽

Hepatic Hemangioma ◽

Resonance Imaging ◽

Benign Lesions ◽

Low Field ◽

Better Than

The diagnostic utility of extremely low field magnetic resonance (MR) imaging was evaluated in 25 patients with focal hepatic masses, including 17 with primary (n=7) or secondary (n= 10) malignant neoplasms and 8 with benign lesions (6 hemangiomas). The findings were compared with the results of computed tomography (CT). Out of 16 patients with malignant tumors demonstrated by both modalities, the diagnostic information from MR imaging was equal to or better than that from CT in 6 patients and inferior to CT in 10. Shortcomings of MR were mainly due to low signal-to-noise ratio and poor spatial resolution, resulting in an image quality inferior to that obtained at higher field strengths. Considering these facts, together with the long imaging times required, low field MR cannot be recommended for general use in the evaluation of hepatic masses. On the other hand, our results indicate that this technique may be useful in establishing the diagnosis of hepatic hemangioma.

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Low-Field MR Imaging (0.1 T) in Patients with Clinically Suspected Acute Spinal Block

Acta Radiologica ◽

10.1177/028418519503600103 ◽

1995 ◽

Vol 36 (1) ◽

pp. 15-18 ◽

Cited By ~ 1

Author(s):

U. Heldmann ◽

H. S. Thomsen ◽

T. Mygind

Keyword(s):

Surgical Treatment ◽

Mr Imaging ◽

Clinical Findings ◽

Clinical Impact ◽

Clinical Suspicion ◽

Spinal Block ◽

True Positive ◽

Therapeutic Consequence ◽

Low Field ◽

Diagnostic Usefulness

The diagnostic usefulness of a 0.1 T MR unit in patients with clinical suspicion of acute spinal block was studied in 59 patients who were referred to acute MR investigation. The records were reviewed retrospectively 1 month after the MR for assessing the clinical impact of the examination. Ninety-eight per cent had a true-positive examination confirmed by surgery (21%) or observation (77%). In 60% of the patients the MR imaging had a therapeutic consequence. In only one patient did the level of visualised pathology at the MR examination not correlate with the clinical findings; the patient subsequently refused surgical treatment. We conclude that a low-field MR unit is excellent for acute examination of patients clinically suspected of acute spinal block.

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Ultra Low Field MR Imaging of Cervical Spine Involvement in Rheumatoid Arthritis

Acta Radiologica ◽

10.1177/028418519203300201 ◽

1992 ◽

Vol 33 (2) ◽

pp. 89-92 ◽

Cited By ~ 3

Author(s):

M. Fagerlund ◽

J. Björnebrink ◽

L. Ekelund ◽

G. Toolanen

Keyword(s):

Rheumatoid Arthritis ◽

Mr Imaging ◽

Clinical Symptoms ◽

Treatment Strategies ◽

Cord Compression ◽

Craniocervical Junction ◽

Plain Radiography ◽

Pannus Formation ◽

Low Field ◽

Diagnostic Usefulness

In a study of 30 patients with longstanding rheumatoid arthritis the diagnostic usefulness of ultra low field MR equipment was analyzed in assessing lesions of the craniocervical junction. It was found that at 0.04 T all the examinations were diagnostic and that in combination with plain radiography the diagnostic information obtained was valuable in further planning of the treatment strategies. The neurologic findings were related to the degree and severity of atlantoaxial luxation, either horizontal or vertical, and to the periodontoid pannus formation. The correlation between the degree of cord compression shown with MR imaging and the clinical symptoms, especially long tract symptoms, was poor. The only correlating factor was the duration of the disease.

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ROUND PERMALLOY 80

Alloy Digest ◽

10.31399/asm.ad.ni0223 ◽

1976 ◽

Vol 25 (1) ◽

Keyword(s):

Corrosion Resistance ◽

Physical Properties ◽

Tensile Properties ◽

Heat Treating ◽

Magnetic Core ◽

Molybdenum Alloy ◽

Nickel Iron ◽

Low Field ◽

Core Losses ◽

Very High

Abstract Round Permalloy 80 is an 80% nickel-iron-molybdenum alloy that provides very high initial and maximum magnetic permeabilities and minimal core losses at low field strengths. This vacuum-melted product also offers the advantages of small size and weight in magnetic core and shielding materials for numerous applications. This datasheet provides information on composition, physical properties, hardness, and tensile properties. It also includes information on corrosion resistance as well as forming, heat treating, machining, and joining. Filing Code: Ni-223. Producer or source: Spang Industries Inc..

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An Accurate Accelerated Steady-State Model For Modular Multilevel Converters With Very High Voltage Levels

2020 IEEE Industry Applications Society Annual Meeting ◽

10.1109/ias44978.2020.9334761 ◽

2020 ◽

Author(s):

Ramadhani Kurniawan Subroto ◽

Yi Chun Chen ◽

Kuo Lung Lian ◽

Chia Chi Chu

Keyword(s):

Steady State ◽

High Voltage ◽

State Model ◽

Multilevel Converters ◽

Steady State Model ◽

Modular Multilevel Converters ◽

Very High

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Modelling the atmosphere of lava planet K2-141b: implications for low- and high-resolution spectroscopy

Monthly Notices of the Royal Astronomical Society ◽

10.1093/mnras/staa2487 ◽

2020 ◽

Vol 499 (4) ◽

pp. 4605-4612

Author(s):

T Giang Nguyen ◽

Nicolas B Cowan ◽

Agnibha Banerjee ◽

John E Moores

Keyword(s):

Steady State ◽

Ocean Circulation ◽

Scale Height ◽

High Resolution Spectroscopy ◽

Return Flow ◽

High Dispersion ◽

Magma Ocean ◽

Steady State Flow ◽

Wide Range ◽

Very High

ABSTRACT Transit searches have uncovered Earth-size planets orbiting so close to their host star that their surface should be molten, so-called lava planets. We present idealized simulations of the atmosphere of lava planet K2-141b and calculate the return flow of material via circulation in the magma ocean. We then compare how pure Na, SiO, or SiO2 atmospheres would impact future observations. The more volatile Na atmosphere is thickest followed by SiO and SiO2, as expected. Despite its low vapour pressure, we find that a SiO2 atmosphere is easier to observe via transit spectroscopy due to its greater scale height near the day–night terminator and the planetary radial velocity and acceleration are very high, facilitating high dispersion spectroscopy. The special geometry that arises from very small orbits allows for a wide range of limb observations for K2-141b. After determining the magma ocean depth, we infer that the ocean circulation required for SiO steady-state flow is only 10−4 m s−1, while the equivalent return flow for Na is several orders of magnitude greater. This suggests that a steady-state Na atmosphere cannot be sustained and that the surface will evolve over time.

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