scholarly journals Surgical wound monitoring by MRI with a metamaterial-based implanted local coil

2018 ◽  
Vol 5 ◽  
pp. 5 ◽  
Author(s):  
Hanan Kamel ◽  
Richard R.A. Syms ◽  
Evdokia M. Kardoulaki ◽  
Marc Rea
Keyword(s):  
Signal To Noise Ratio ◽  
Electrical Response ◽  
Field Of View ◽  
Ring Resonators ◽  
Resonance Imaging ◽  
Surgical Wound ◽  
Agar Gel ◽  
Surgical Wounds ◽  
Signal Output ◽  
Implantable Sensor

An implantable sensor for monitoring surgical wounds after bowel reconstruction is proposed. The sensor consists of a coupled pair of 8-element magneto-inductive ring resonators, designed for mounting on a biofragmentable anastomosis ring to give a local increase in signal-to-noise ratio near an annular wound during 1H magnetic resonance imaging. Operation on an anti-symmetric spatial mode is used to avoid coupling to the B1 field during excitation, and a single wired connection is used for MRI signal output. The electrical response and field-of-view are estimated theoretically. Prototypes are constructed from flexible elements designed for operation at 1.5 T, electrical responses are characterized and local SNR enhancement is confirmed using agar gel phantoms.

The Clifford Paterson Lecture, 1993, Accurate measurement in in vivo magnetic Resonance: an engineering problem?

1994 ◽  
Vol 349 (1691) ◽  
pp. 357-388
Keyword(s):  
Magnetic Resonance ◽  
Signal To Noise Ratio ◽  
Engineering Problem ◽  
Resonance Imaging ◽  
Significant Extent ◽  
Performance System ◽  
Imaging And Spectroscopy ◽  
Intractable Problem ◽  
Conceptual Difficulties

Measurement in in vivo magnetic resonance — both in imaging and spectroscopy — has proved to be a much more intractable problem than extrapolation from conventional high resolution studies might have suggested. Although this paper concentrates mainly on some of the complications of magnetic resonance imaging, the same conceptual difficulties (compounded by much reduced signal levels) affect in vivo spectroscopy. Tissue is an extremely complex system and many of the difficulties studying it arise from the interactions that are unintentionally engendered when it is observed. Patient motion is a potent source of artifact to the technical challenge of making better measurements, and different forms of motion are likely to be the ultimate limitation on the sensitivity and discrimination of the technique as a whole. In this context it is observed that the traditional criterion of performance — system signal-to-noise ratio — should be replaced by a signal-to-artifact estimate, and that this may affect the design and implementation of detector systems to a significant extent.

scholarly journals Performance of compressed sensing for fluorine‐19 magnetic resonance imaging at low signal‐to‐noise ratio conditions

2019 ◽  
Vol 84 (2) ◽  
pp. 592-608
Author(s):  
Ludger Starke ◽  
Andreas Pohlmann ◽  
Christian Prinz ◽  
Thoralf Niendorf ◽  
Sonia Waiczies
Keyword(s):  
Magnetic Resonance Imaging ◽  
Magnetic Resonance ◽  
Compressed Sensing ◽  
Signal To Noise Ratio ◽  
Resonance Imaging ◽  
Signal To Noise ◽  
Noise Ratio

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

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.

scholarly journals Photoacoustic Imaging with Capacitive Micromachined Ultrasound Transducers: Principles and Developments

Sensors ◽  
2019 ◽  
Vol 19 (16) ◽  
pp. 3617 ◽  
Author(s):  
Jasmine Chan ◽  
Zhou Zheng ◽  
Kevan Bell ◽  
Martin Le ◽  
Parsin Haji Reza ◽  
...  
Keyword(s):  
Photoacoustic Imaging ◽  
Signal To Noise Ratio ◽  
Complementary Metal Oxide Semiconductor ◽  
Photoacoustic Signal ◽  
Motion Artifacts ◽  
Oxide Semiconductor ◽  
Ring Resonators ◽  
Ultrasound Transducers ◽  
Fabrication Technique ◽  
Acoustic Techniques

Photoacoustic imaging (PAI) is an emerging imaging technique that bridges the gap between pure optical and acoustic techniques to provide images with optical contrast at the acoustic penetration depth. The two key components that have allowed PAI to attain high-resolution images at deeper penetration depths are the photoacoustic signal generator, which is typically implemented as a pulsed laser and the detector to receive the generated acoustic signals. Many types of acoustic sensors have been explored as a detector for the PAI including Fabry–Perot interferometers (FPIs), micro ring resonators (MRRs), piezoelectric transducers, and capacitive micromachined ultrasound transducers (CMUTs). The fabrication technique of CMUTs has given it an edge over the other detectors. First, CMUTs can be easily fabricated into given shapes and sizes to fit the design specifications. Moreover, they can be made into an array to increase the imaging speed and reduce motion artifacts. With a fabrication technique that is similar to complementary metal-oxide-semiconductor (CMOS), CMUTs can be integrated with electronics to reduce the parasitic capacitance and improve the signal to noise ratio. The numerous benefits of CMUTs have enticed researchers to develop it for various PAI purposes such as photoacoustic computed tomography (PACT) and photoacoustic endoscopy applications. For PACT applications, the main areas of research are in designing two-dimensional array, transparent, and multi-frequency CMUTs. Moving from the table top approach to endoscopes, some of the different configurations that are being investigated are phased and ring arrays. In this paper, an overview of the development of CMUTs for PAI is presented.

RFID-Based Real-Time Navigation for Interventional Magnetic Resonance Imaging: Development and Evaluation of a Novel Tracking System

2017 ◽  
Vol 11 (3) ◽  
Author(s):  
Felix Güttler ◽  
Andreas Heinrich ◽  
Peter Krauß ◽  
Jonathan Guntermann ◽  
Maximilian de Bucourt ◽  
...  
Keyword(s):  
Magnetic Resonance Imaging ◽  
Magnetic Resonance ◽  
Spatial Resolution ◽  
Radio Frequency Identification ◽  
Signal To Noise Ratio ◽  
Tracking System ◽  
Single Shot ◽  
Resonance Imaging ◽  
Magnetic Resonance Imaging Mri ◽  
Steady State Precession

The purpose of this study was to evaluate the suitability of a novel radio-frequency identification (RFID)-based tracking system for intraoperative magnetic resonance imaging (MRI). A RFID tracking system was modified to fulfill MRI-compatibility and tested according to ASTM and NEMA. The influence of the RFID tracking system on MRI was analyzed in a phantom study using a half-Fourier acquisition single-shot turbospin echo (HASTE) and true fast imaging with steady-state precession sequence (TrueFISP) sequence. The RFID antenna was gradually moved closer to the isocenter of the MR scanner from 90 to 210 cm to investigate the influence of the distance. Furthermore, the RF was gradually changed between 865 and 869 MHz for a distance of 90 cm, 150 cm, and 210 cm to the isocenter of the magnet to investigate the influence of the frequency. The specific spatial resolution was measured with and without a permanent line of sight (LOS). After the modification of the reader, no significant change of the signal-to-noise ratio (SNR) could be observed with increasing distance of the RFID tracking system to the isocenter of the MR scanner. Also, different radio frequencies of the RFID tracking system did not influence the SNR of the MR-images significantly. The specific spatial resolution deviated on average by 8.97 ± 7.33 mm with LOS and 11.23 ± 12.03 mm without LOS from the reference system. The RFID tracking system had no relevant influence on the MR-image quality. RFID tracking solved the LOS problem. However, the spatial accuracy of the RFID tracking system has to be improved for medical usage.

Assessment of antral grinding of a model solid meal with echo-planar imaging

2001 ◽  
Vol 280 (5) ◽  
pp. G844-G849 ◽  
Author(s):  
Luca Marciani ◽  
Penny A. Gowland ◽  
Annette Fillery-Travis ◽  
Pretima Manoj ◽  
Jeff Wright ◽  
...  
Keyword(s):  
Mathematical Modeling ◽  
Gastric Volume ◽  
Physical Factors ◽  
Resonance Imaging ◽  
Planar Imaging ◽  
Agar Gel ◽  
Solid Meal ◽  
Gel Beads ◽  
Gastric Contents ◽  
Echo Planar

Mathematical modeling of how physical factors alter gastric emptying is limited by lack of precise measures of the forces exerted on gastric contents. We have produced agar gel beads (diameter 1.27 cm) with a range of fracture strengths (0.15–0.90 N) and assessed their breakdown by measuring their half-residence time (RT1/2) using magnetic resonance imaging. Beads were ingested either with a high (HV)- or low (LV)-viscosity liquid nutrient meal. With the LV meal, RT1/2was similar for bead strengths ranging from 0.15 to 0.65 N but increased from 22 ± 2 min (bead strength <0.65 N) to 65 ± 12 min for bead strengths >0.65 N. With the HV meal, emptying of the harder beads was accelerated. The sense of fullness after ingesting the LV meal correlated linearly (correlation coefficient = 0.99) with gastric volume and was independently increased by the harder beads, which were associated with an increased antral diameter. We conclude that the maximum force exerted by the gastric antrum is close to 0.65 N and that gastric sieving is impaired by HV meals.

Three-tesla magnetic resonance imaging of the meniscus of the knee: What about equivocal errors?

2010 ◽  
Vol 51 (3) ◽  
pp. 296-301 ◽  
Author(s):  
Pieter Van Dyck ◽  
Filip M. Vanhoenacker ◽  
Jan L. Gielen ◽  
Lieven Dossche ◽  
Joost Weyler ◽  
...  
Keyword(s):  
Magnetic Resonance ◽  
Medical Records ◽  
Medial Meniscus ◽  
Signal To Noise Ratio ◽  
Meniscal Tear ◽  
Lateral Meniscus ◽  
Meniscal Tears ◽  
Resonance Imaging ◽  
Mr Images ◽  
Knee Meniscus

Background: The significance of borderline magnetic resonance (MR) findings that are equivocal for a tear of the knee meniscus remains uncertain. Given their higher signal-to-noise ratio (SNR) and greater spatial resolution, these equivocal meniscal tears could be expected to be less frequent using a 3.0T MR system. Purpose: To investigate the prevalence of equivocal meniscal tears using 3.0T MR, and to study their impact on MR accuracy compared with arthroscopy in the detection of meniscal tears. Material and Methods: The medical records of 100 patients who underwent 3.0T MR imaging and subsequent arthroscopy of the knee were retrospectively reviewed. Two observers interpreted MR images in consensus, and menisci were diagnosed as torn (abnormality on two or more images), equivocal for a tear (abnormality on one image), or intact, using arthroscopy as the standard of reference. The prevalence of equivocal meniscal tears was assessed, and MR accuracy was calculated as follows: first, considering both torn menisci and equivocal diagnoses as positive for a tear; and second, considering only torn menisci as positive for a tear. Results: Evidence of meniscal tears on MR images was equivocal in 12 medial (12%) and three lateral (3%) menisci. Of these equivocal MR diagnoses, tears were found at arthroscopy in eight medial and one lateral meniscus. In our study, the specificity and positive predictive value increased for both the medial and lateral meniscus when only menisci with two or more abnormal images were considered to be torn: from 80% and 89% to 91% and 94% for the medial meniscus, and from 91% and 73% to 93% and 78% for the lateral meniscus, respectively. Conclusion: Subtle findings that are equivocal for a tear of the knee meniscus still make MR diagnosis difficult, even at 3.0T. We recommend that radiologists should rather be descriptive in reporting subtle or equivocal MR findings, alerting the clinician of possible meniscal tear.

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