148 results on '"Lawrence E. Crooks"'
Search Results
2. Image Formation Methods
- Author
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Lawrence E. Crooks
- Subjects
Image formation ,Intensity dependence ,business.industry ,Computer science ,Resolution (electron density) ,Spatial localization ,Computer vision ,Artificial intelligence ,Biographical sketch ,business ,Signal ,Image contrast ,Image (mathematics) - Abstract
The sections in this article are 1 Introduction 2 Concepts for Spatial Localization 3 Image Intensity Dependence on Imaging Parameters 4 Image Intensity Dependence on Signal 5 Imaging Techniques 6 Image Contrast 7 Resolution, S/N, and Imaging Time 8 Conclusion 9 Acknowledgements 10 Biographical Sketch Related Articles
- Published
- 2007
3. Crooks, Lawrence E.: Field Strength Selection for MR Imaging
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Lawrence E. Crooks
- Subjects
Engineering ,Engineering drawing ,business.industry ,Electric field ,Magnet ,Electrical engineering ,Field strength ,business ,Biographical sketch ,Mr imaging ,Selection (genetic algorithm) - Abstract
The sections in this article are 1 Introduction 2 Conceptual Limits on Field Strength 3 Magnet Selection 4 Imaging Results 5 Conclusions 6 Biographical Sketch
- Published
- 2007
4. The contrast and signal difference-to-noise of MRI imaging between muscle and mammary adenocarcinoma at different magnetic field strengths — Analysis results
- Author
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Jyh-Horng Chen, Douglas A. Ortendahl, and Lawrence E. Crooks
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Physics ,medicine.medical_specialty ,Mri imaging ,Noise measurement ,Noise (signal processing) ,media_common.quotation_subject ,Mammary adenocarcinoma ,Mr imaging ,Signal ,Magnetic field ,Nuclear magnetic resonance ,medicine ,Contrast (vision) ,Radiology ,media_common - Abstract
Purpose To study the effects of T1, T2 changes due to field difference on imaging contrast C and signal difference-to-noise K between a certain tumor model, mammary adenocarcinoma, and muscle. The results may provide a guide in optimizing the imaging sequences for MR imaging at different magnetic fields.
- Published
- 1992
5. In vivo relaxation times and hydrogen density at 0.063-4.85 T in rats with implanted mammary adenocarcinomas
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H. E. Avram, L Kaufman, Lawrence E. Crooks, Antonio C. Brito, Jyh-Horng Chen, and Mitsuaki Arakawa
- Subjects
medicine.diagnostic_test ,Hydrogen ,business.industry ,Relaxation (NMR) ,chemistry.chemical_element ,Mammary Neoplasms, Experimental ,Magnetic resonance imaging ,Field strength ,Adenocarcinoma ,Magnetic Resonance Imaging ,Rats, Inbred F344 ,Magnetic field ,Rats ,Lesion ,Nuclear magnetic resonance ,chemistry ,In vivo ,medicine ,Relative density ,Animals ,Radiology, Nuclear Medicine and imaging ,Female ,medicine.symptom ,business ,Neoplasm Transplantation - Abstract
Magnetic resonance (MR) imaging at 0.063 T, 0.17 T, 0.35 T, 2.94 T, and 4.85 T was performed in rats with implanted mammary adenocarcinomas (and in control rats) to study hydrogen density and the effects of magnetic field strength on T1 and T2 relaxation times in vivo. T1 increased by an order of magnitude and T2 decreased by a factor of two between the lowest and highest field strengths. Only about half of the increased water content of tumor, compared with that of muscle, was reflected in increased hydrogen density. The sensitivity of relaxation time change was increased at the lower field strengths. These results are of significance in understanding the effects of field strength on lesion detectability, contrast, and signal-to-noise ratio.
- Published
- 1992
6. Direction of MR imaging
- Author
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Alexander R. Margulis, Peter A. Rothschild, and Lawrence E. Crooks
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Materials science ,Nuclear magnetic resonance ,Magnetic Resonance Spectroscopy ,medicine.diagnostic_test ,medicine ,Humans ,Radiology, Nuclear Medicine and imaging ,Magnetic resonance imaging ,General Medicine ,Nuclear magnetic resonance spectroscopy ,Mr imaging ,Magnetic Resonance Imaging - Published
- 1990
7. Magnetic Resonance Imaging for the Visualization of Vasculature and Atherosclerosis
- Author
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Lawrence E. Crooks, James D. Hale, Leon Kaufman, Joseph H. Rapp, Phil Sheldon, and Gary Caputo
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medicine.medical_specialty ,Modality (human–computer interaction) ,medicine.diagnostic_test ,business.industry ,Medicine ,Magnetic resonance imaging ,Radiology ,business ,Phase image ,Visualization - Abstract
Magnetic resonance imaging (MRI) offers a unique and extraordinary window into the body. Since 1983 the growth and acceptance of this modality as a diagnostic tool has been prodigious, and the enthusiasm with which it is received still grows. The original uses were centered on head imaging, and have since expanded to spine and extremities. Some acceptance is now being seen for body imaging, more for central portions of the chest and in the pelvis than in the abdomen. The routine use of MRI for cardiovascular work is generally limited to large centers. Because of the patient demand for MRI, and because of the desire to obtain revenue from the units, MRI has not been fully exploited in areas where the primary payoff is a contribution towards understanding disease processes. For this latter purpose, one of the most important characteristics of MRI is that it is non-invasive, and therefore ideally suited for both cross-sectional and longitudinal studies. There is an obvious match between MRI and the needs of those who aim to understand the evolution of the human atherosclerotic plaque.
- Published
- 1990
8. 5606258 Control interface for an MRI system
- Author
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Lawrence E. Crooks and J Hoenninger
- Subjects
Materials science ,Interface (computing) ,Biomedical Engineering ,Biophysics ,Radiology, Nuclear Medicine and imaging ,Simulation - Published
- 1997
9. 5529068 Synchronized digital signal processor for MRI reception
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J Hoenninger, James W. Jones, and Lawrence E. Crooks
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Digital signal processor ,business.industry ,Computer science ,Biomedical Engineering ,Biophysics ,Radiology, Nuclear Medicine and imaging ,Digital signal ,business ,Digital signal processing ,Computer hardware - Published
- 1997
10. 5172061 Q control for capacitively coupled MRI/MRSI RF coil
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Mitsuaki Arakawa and Lawrence E. Crooks
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Nuclear magnetic resonance ,Materials science ,Biomedical Engineering ,Biophysics ,Radiology, Nuclear Medicine and imaging ,Radiofrequency coil - Published
- 1993
11. 4885542 MRI compensated for spurious NMR frequency/phase shifts caused by spurious changes in magnetic fields during NMR data measurement processes
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James D. Hale, Lawrence E. Crooks, Leon Kaufman, and Ching Yao
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Chemistry ,Biomedical Engineering ,Biophysics ,Phase (waves) ,Magnetostatics ,Signal ,law.invention ,Magnetic field ,NMR spectra database ,Nuclear magnetic resonance ,law ,Eddy current ,Calibration ,Radiology, Nuclear Medicine and imaging ,Spurious relationship - Abstract
At least one extra NMR measurement cycle is performed without any imposed magnetic gradients during readout and recordation of the NMR RF response. Calibration data derived from this extra measurement cycle or cycles can be used for resetting the RF transmitter frequency and/or for phase shifting other conventionally acquired NMR RF response data to compensate for spurious changes in magnetic fields experienced during the NMR data measuring processes. Some such spurious fields may be due to drifting of the nominally static magnetic field. Another source of spurious fields are due to remnant eddy currents induced in surrounding conductive structures by magnetic gradient pulses employed prior to the occurrence of the NMR RF response signal. Special procedures can be employed to permit the compensation data itself to be substantially unaffected by relatively static inhomogeneities in the magnetic field and/or by differences in NMR spectra of fat and water types of nuclei in imaged volumes containing both.
- Published
- 1990
12. Nuclear magnetic resonance imaging of the abnormal live rat and correlations with tissue characteristics
- Author
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Robert J. Herfkens, Leon Kaufman, Peter L. Davis, Alexander R. Margulis, J Hoenninger, Theodore R. Miller, David C. Price, J C Watts, M Arakawa, R McRee, and Lawrence E. Crooks
- Subjects
Male ,Pathology ,medicine.medical_specialty ,Magnetic Resonance Spectroscopy ,Stomach Diseases ,Normal tissue ,Adenocarcinoma ,Skin Diseases ,Diagnosis, Differential ,Liver Neoplasms, Experimental ,Nuclear magnetic resonance ,Animals ,Medicine ,Radiology, Nuclear Medicine and imaging ,Abscess ,Tomography ,medicine.diagnostic_test ,business.industry ,Relaxation (NMR) ,Prostatic Neoplasms ,Resonance ,Rats, Inbred Strains ,Magnetic resonance imaging ,Neoplasms, Experimental ,Nuclear magnetic resonance spectroscopy ,medicine.disease ,Rats, Inbred F344 ,T2 value ,Rats ,Differential diagnosis ,business ,Mathematics - Abstract
Nuclear magnetic resonance (NMR) images of live rats with sterile and pyogenic abscesses, hematomas, and various implanted and spontaneous neoplasms demonstrated good contrast differentiation between pathologic and surrounding normal tissues. This differentiation was maximal when both the T1 and T2 tissue relaxation times were used as criteria. Neoplasms have a broad range of T1 and T2 values and may be confused with abscesses or hematomas. Tissue rate constants (1/T1 and 1/T2) are mainly dependent on total water content, the exception being fat, which has a 1/T2 value much shorter than that expected on the basis of water content alone.
- Published
- 1981
13. Clinical efficiency of nuclear magnetic resonance imaging
- Author
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J C Watts, Peter L. Davis, Alexander R. Margulis, Douglas A. Ortendahl, Lawrence E. Crooks, C.R. Cannon, Michael Brant-Zawadzki, Mitsuaki Arakawa, L Kaufman, and J Hoenninger
- Subjects
Relaxometry ,Physics of magnetic resonance imaging ,Magnetic Resonance Spectroscopy ,Biomedical Engineering ,Biophysics ,Spin–spin relaxation ,Nuclear magnetic resonance ,medicine ,Humans ,Radiology, Nuclear Medicine and imaging ,Image resolution ,Physics ,medicine.diagnostic_test ,Brain Neoplasms ,Magnetic resonance microscopy ,business.industry ,Liver Neoplasms ,Relaxation (NMR) ,Resolution (electron density) ,food and beverages ,Resonance ,Magnetic resonance spectroscopic imaging ,Magnetic resonance imaging ,Cerebral Infarction ,Additional procedure ,Spin echo ,Patient examination ,business ,Nuclear magnetic resonance decoupling - Abstract
Advances in imaging technique have improved the efficiency of clinical nuclear magnetic resonance (NMR) imaging, and will allow total patient examination time that equals or is more favorable than that of x-ray computed tomography (CT). The whole head can be examined with NMR in a 6.5-minute imaging time with a spatial resolution of 1.7 mm. Fifteen sections in the body can be similarly imaged. Quantitative T2 ("spin-spin" relaxation time) information, as well as estimates of T1 ("spin-lattice" relaxation time) can be obtained in this time. Quantitative T1 information requires an additional procedure.
- Published
- 1983
14. Nuclear magnetic resonance contrast enhancement study of the gastrointestinal tract of rats and a human volunteer using nontoxic oral iron solutions
- Author
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George E. Wesbey, Barry L. Engelstad, Lawrence E. Crooks, R C Brasch, Albert A. Moss, and Antonio C. Brito
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Magnetic Resonance Spectroscopy ,Contrast enhancement ,Iron ,Contrast Media ,Ferric Compounds ,Nuclear magnetic resonance ,medicine ,Animals ,Humans ,Radiology, Nuclear Medicine and imaging ,Ferrous Compounds ,Tomography ,Volunteer ,Gastrointestinal tract ,medicine.diagnostic_test ,business.industry ,Ammonium citrate ,Water ,Rats, Inbred Strains ,Magnetic resonance imaging ,Rats ,Ferrous sulfate heptahydrate ,Quaternary Ammonium Compounds ,T2 relaxation ,Ferric ,business ,Digestive System ,medicine.drug - Abstract
Two dilute oral iron solutions, made from commonly available nonprescription dietary supplements, were found to enhance the gastrointestinal tract in nuclear magnetic resonance imaging of live rats and one human volunteer. The paramagnetic and pharmacologic properties of ferric ammonium citrate were more favorable than those of ferrous sulfate heptahydrate. The paramagnetic iron solutions shorten T1 and T2 relaxation times of water protons in the contrast media-filled gastrointestinal tract, producing easily observable change in NMR intensity. Because these iron solutions are available commercially and are known to be well tolerated, the clinical use of iron-containing NMR contrast agents for the gastrointestinal tract is feasible.
- Published
- 1983
15. Echo-planar pediatric imager
- Author
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J C Watts, Lawrence E. Crooks, Mitsuaki Arakawa, Leon Kaufman, H. E. Avram, James D. Hale, Nola M. Hylton, and J Hoenninger
- Subjects
Nuclear magnetic resonance ,medicine.diagnostic_test ,business.industry ,medicine ,Humans ,Radiology, Nuclear Medicine and imaging ,Magnetic resonance imaging ,Child ,business ,Magnetic Resonance Imaging ,Echo planar ,Image resolution - Abstract
Practical constraints make it difficult to build large-aperture echo-planar magnetic resonance (MR) imagers. The implementation of a pediatric imager and its performance are described. Spatial resolution and signal-to-noise levels comparable to those of 1982 state-of-the-art MR imagers have been achieved in imaging times of 0.05-0.15 seconds. T1 and T2 information are obtainable in the echo-planar mode. A major issue is that of chemical-shift displacements.
- Published
- 1988
16. Musculoskeletal applications of nuclear magnetic resonance
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Harry K. Genant, Neil Chafetz, Clyde A. Helms, Leon Kaufman, Lawrence E. Crooks, and Kirk L. Moon
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Adult ,Male ,musculoskeletal diseases ,Relaxometry ,Magnetic Resonance Spectroscopy ,Adolescent ,Biomedical Engineering ,Biophysics ,Bone Neoplasms ,Soft Tissue Neoplasms ,Avascular necrosis ,Femoral head ,Nuclear magnetic resonance ,Lumbar ,Muscular Diseases ,medicine ,Humans ,Radiology, Nuclear Medicine and imaging ,Aged ,medicine.diagnostic_test ,business.industry ,Healthy subjects ,Magnetic resonance imaging ,Nuclear magnetic resonance spectroscopy ,Middle Aged ,musculoskeletal system ,medicine.disease ,Conventional radiography ,Intervertebral disk ,medicine.anatomical_structure ,Female ,Spinal Diseases ,Bone Diseases ,Joint Diseases ,Nuclear medicine ,business ,Nuclear magnetic resonance decoupling - Abstract
Thirty healthy subjects and 15 patients with a variety of musculoskeletal disorders were examined by conventional radiography, computed tomography (CT), and nuclear magnetic resonance (NMR). NMR proved capable of demonstrating important anatomic structures in the region of the lumbosacral spine. Lumbar disk protrusion was demonstrated in three patients with CT evidence of the disease. NMR appeared to differentiate annulus fibrosus from nucleus pulposus in intervertebral disk material. Avascular necrosis of the femoral head was demonstrated in two patients. The cruciate ligaments of the knee were well defined by NMR. Muscles, tendons and ligaments, and blood vessels could be reliably differentiated, and the excellent soft-tissue contrast of NMR proved useful in the evaluation of bony and soft-tissue tumors. NMR holds promise in the evaluation of musculoskeletal disorders.
- Published
- 1983
17. Technology Needs in Medical Imaging
- Author
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Dale Shosa, Leon Kaufman, John Ewins, and Lawrence E. Crooks
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medicine.medical_specialty ,Chemical technology ,Radiological and Ultrasound Technology ,medicine.diagnostic_test ,business.industry ,media_common.quotation_subject ,Fidelity ,Computed tomography ,Computer Science Applications ,Optical imaging ,Nuclear medicine imaging ,Medical imaging ,Systems engineering ,medicine ,Medical physics ,Instrumentation (computer programming) ,Electrical and Electronic Engineering ,business ,Software ,Digital radiography ,media_common - Abstract
Advances in technology make it possible to extend the range of physical and chemical tissue parameters used for formation of images. This in turn adds to the capabilities to diagnose disease and assess its extent. Quantitative improvements in instrumentation augment the fidelity with which the imaging is performed, and at a certain point provide a quantum jump in diagnostic capability. We discuss recent technological advances in digital radiography, NMR and nuclear medicine imaging that demonstrate these effects.
- Published
- 1982
18. Magnetic Resonance Imaging the Velocity Vector Components of Fluid Flow
- Author
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P E Sheldon, Mitsuaki Arakawa, J Hoenninger, J C Watts, Lawrence E. Crooks, and David A. Feinberg
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Physics ,Magnetic Resonance Spectroscopy ,Fourier Analysis ,Hemodynamics ,Phase (waves) ,Laminar flow ,Magnetic Resonance Imaging ,Computational physics ,symbols.namesake ,Fourier transform ,Classical mechanics ,Flow velocity ,Fourier analysis ,Pulsatile Flow ,symbols ,Precession ,Fluid dynamics ,Humans ,Group velocity ,Radiology, Nuclear Medicine and imaging ,Rheology - Abstract
Encoding the Precession phase angle of proton nuclei for Fourier analysis has produced accurate measurement of fluid velocity vector components by MRI. A Pair of identical gradient pulses separated in time by exactly ½ TE, are used to linearly encode the phase of flow velocity vector components without changing the phase of stationary nuclei, Two-dimensional Fourier transformation of signals gave velocity density images of laminar flow in angled tubes which were in agreement with the laws of vector addition. These Velocity profile images provide a quantitative method for the investigation of fluid dynamics and hemodynamics.© 1985 Academic Press,Inc.
- Published
- 1985
19. Analytical Techniques for Post-Imaging Evaluation of NMR Tissue Contrast
- Author
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Nola M. Hylton, Douglas A. Ortendahl, David A. Feinberg, Lawrence E. Crooks, and Leon Kaufman
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Nuclear and High Energy Physics ,Materials science ,medicine.diagnostic_test ,Pixel ,Pulse (signal processing) ,Image processing ,Magnetic resonance imaging ,Absolute difference ,Signal ,Intensity (physics) ,Nuclear magnetic resonance ,Data acquisition ,Nuclear Energy and Engineering ,medicine ,Electrical and Electronic Engineering ,Biomedical engineering - Abstract
Computational techniques allow the simulation of NMR images as well as the construction of tools for evaluating the impact of changing parameters. Use of these tools assumes the acquisition of a minimal set of patient data from which the tissue properties T1, T2 and hydrogen density H, can be taken. Changes in technique, imaging parameters such as TE, TR or TI, and field can be simulated and examined individually as well as concurrently for their effects on the contrast between a lesion and its surrounding tissue. This evaluation is done by plotting the absolute difference in signal intensities as a function of the imaging parameters of the technique. Retrospective calculations of intensity images at new values of the pulse timing parameters may show improved diagnostic utility.
- Published
- 1985
20. Signal-to-noise ratio and section thickness in two-dimensional versus three-dimensional Fourier transform MR imaging
- Author
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L Kaufman, D M Kramer, Joseph W. Carlson, Douglas A. Ortendahl, and Lawrence E. Crooks
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Fourier Analysis ,medicine.diagnostic_test ,business.industry ,Image quality ,Partial volume ,Magnetic resonance imaging ,k-space ,Magnetic Resonance Imaging ,symbols.namesake ,Quality (physics) ,Nuclear magnetic resonance ,Fourier transform ,Signal-to-noise ratio (imaging) ,Flip angle ,medicine ,symbols ,Radiology, Nuclear Medicine and imaging ,business - Abstract
The efficiency and quality of three-dimensional Fourier transform (3DFT) magnetic resonance imaging were evaluated and compared with those of 2DFT imaging. For a fixed imaging time and number of sections, 3DFT imaging with conventional spin echoes always had a worse signal-to-noise ratio (S/N) than did 2DFT imaging, when both were optimized with respect to choice of repetition time (TR). With partial-flip magnetic resonance (MR) imaging, S/N was nearly equal for 2DFT and 3DFT imaging when both were optimized with respect to TR and flip angle. 3DFT imaging can have cross-section artifacts that exceed those of 2DFT imaging. For very thin sections these artifacts may be lessened, and 3DFT imaging can achieve this with smaller gradient pulses. Over-all, 3DFT imaging was found to be advantageous only for the very-thin-section imaging and in combination with partial-flip MR imaging.
- Published
- 1988
21. Optimal Strategies for Obtaining the Minimal NMR Data Set
- Author
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Douglas A. Ortendahl, Leon Kaufman, Nola M. Hylton, and Lawrence E. Crooks
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Nuclear and High Energy Physics ,Materials science ,medicine.diagnostic_test ,Pixel ,Magnetic resonance microscopy ,Magnetic resonance spectroscopic imaging ,chemistry.chemical_element ,Magnetic resonance imaging ,Nmr data ,Set (abstract data type) ,Nuclear magnetic resonance ,Nuclear Energy and Engineering ,chemistry ,medicine ,Radio frequency ,Electrical and Electronic Engineering ,Tellurium - Published
- 1985
22. Inner volume MR imaging: technical concepts and their application
- Author
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Leon Kaufman, J C Watts, Mitsuaki Arakawa, J Hoenninger, Lawrence E. Crooks, and David A. Feinberg
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Magnetic Resonance Spectroscopy ,medicine.diagnostic_test ,business.industry ,Respiratory motion ,Signal region ,Brain ,Magnetic resonance imaging ,Pulse sequence ,Signal ,Mr imaging ,Nuclear magnetic resonance ,medicine ,Humans ,Radiology, Nuclear Medicine and imaging ,Pulsatile blood flow ,business ,Blood Flow Velocity ,Biomedical engineering ,Volume (compression) - Abstract
Although cross-sectional magnetic resonance examination of the head and body is useful for screening large regions of tissue, subsectional regions of the head and body often need to be examined. Orthogonally directed, selectively irradiated planes with different flip angles produce a spatially limited signal region from which two- or three-dimensional volume images can be reconstructed. Images with limited fields-of-view can be acquired in reduced imaging time. We present a general description of this technique. These subsectional or "inner volume" images eliminate respiratory motion artifacts by excluding moving tissues from the imaged volume. A result of this technique is a high signal from rapid pulsatile blood flow, produced without cardiac gating the pulse sequence.
- Published
- 1985
23. Detectability of Hepatomas in Rat Livers by Nuclear Magnetic Resonance Imaging
- Author
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Peter L. Davis, Leon Kaufman, Theodore R. Miller, and Lawrence E. Crooks
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Nuclear magnetic resonance ,Materials science ,business.industry ,Relaxation (NMR) ,Experimental pathology ,Radiology, Nuclear Medicine and imaging ,Radionuclide imaging ,General Medicine ,Nuclear magnetic resonance spectroscopy ,Nuclear medicine ,business ,Liver pathology - Abstract
NMR imaging of rats with implanted hepatomas in the liver demonstrates that under the imaging conditions of this study tumors of over 8 mm2 in area can be detected with high accuracy. Compared to normal liver, approximately 70% of these tumors had a combination of relaxation times (T1-T2) that could be uniquely identified as tumors, while the other 30% demonstrated relaxation time combinations that overlapped those previously found for abscesses, brain, and hematomas.
- Published
- 1981
24. Hydrogen MR imaging of the head at 0.35 T and 0.7 T: effects of magnetic field strength
- Author
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J Hoenninger, L Kaufman, J C Watts, Jonathan P. Posin, David A. Feinberg, Catherine M. Mills, Mitsuaki Arakawa, and Lawrence E. Crooks
- Subjects
Brain Diseases ,Magnetic Resonance Spectroscopy ,Hydrogen ,medicine.diagnostic_test ,Field (physics) ,business.industry ,media_common.quotation_subject ,Resolution (electron density) ,Brain ,chemistry.chemical_element ,Magnetic resonance imaging ,Field strength ,Mr imaging ,Magnetic field ,Magnetics ,Nuclear magnetic resonance ,chemistry ,Humans ,Medicine ,Contrast (vision) ,Radiology, Nuclear Medicine and imaging ,business ,media_common - Abstract
To determine whether hydrogen magnetic resonance imaging at 0.7 T provides added clinical value over imaging at 0.35 T, images of the heads of patients with various intracranial disorders were obtained at these field strengths. Measurements of tissue contrast (C), signal-to-noise (S/N) ratio, and T1 and T2 relaxation times were determined. For a given spin-echo sequence with equal imaging time, resolution, and data sampling window, the product C X S/N was somewhat lower for the lower field strength. Under conditions of imaging with equal chemical shift artifact, C X S/N at 0.35 T was equal to or greater than that measured at 0.7 T. With an increase in field strength, T1 of pathologic areas and surrounding normal tissues increased, resulting in a corresponding loss of absolute signal level and decrease in contrast. Lesions were equally well seen at both 0.35 T and 0.7 T. The increased T1 and decreased C X S/N for higher magnetic fields--when measured with a fixed imaging time, resolution, chemical shift, and sequence--suggest that such field strengths may not improve tissue contrast, diagnostic ability, or clinical throughput when compared with lower field strength systems.
- Published
- 1985
25. Partial flip angle MR imaging
- Author
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Leon Kaufman, Douglas A. Ortendahl, Timothy C. Mills, Joseph W. Carlson, Lawrence E. Crooks, and Nola M. Hylton
- Subjects
Magnetic Resonance Spectroscopy ,medicine.diagnostic_test ,business.industry ,Brain ,Magnetic resonance imaging ,Image Enhancement ,Noise (electronics) ,Signal ,Mr imaging ,Image contrast ,Nuclear magnetic resonance ,Repetition Time ,Flip angle ,Flip ,medicine ,Humans ,Radiology, Nuclear Medicine and imaging ,business - Abstract
Theoretical analysis predicts that performing magnetic resonance (MR) imaging with partial (less than 90 degrees) flip angles can reduce imaging times two- to fourfold when lesions with elevated T1 values are being examined. This time savings occurs because repetition time (TR) is reduced when imaging is performed with partial flips. Partial flip MR imaging can also improve signal-to-noise ratio (S/N) in fast body imaging. For this study, analytical tools were used to predict image contrast and S/N for short TR, partial flip sequences. Experimental implementation of the short TR, partial flip sequences that analytical work had predicted would be optimal supported the analytical predictions and demonstrated their validity. Partial flip MR imaging is applicable to reducing imaging time only when the ratio of signal differences to noise exceeds threshold values in conventional MR images. Partial flip sequences can be used to advantage in MR imaging of both the head and the body, and the observed effects are predictable through theoretical analysis.
- Published
- 1987
26. Nuclear magnetic resonance imaging of mammary adenocarcinomas in the rat
- Author
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P E Sheldon, Mitsuaki Arakawa, Leon Kaufman, Theodore R. Miller, Peter L. Davis, J C Watts, J Hoenninger, Lawrence E. Crooks, and Alexander R. Margulis
- Subjects
Cancer Research ,Pathology ,medicine.medical_specialty ,business.industry ,Spin–lattice relaxation ,Hindlimb ,Malignancy ,medicine.disease ,Highly sensitive ,Text mining ,Nuclear magnetic resonance ,Oncology ,T2 relaxation ,Medicine ,business - Abstract
A study of 24 rats implanted in the hind leg with mammary adenocarcinomas and five sham-implanted rats, followed from the second to the eight week postimplantation, showed nuclear magnetic resonance imaging capable of detecting all the tumors without yielding any false-positives in the control rats. The T1 relaxation time of tumors overlapped that of muscle, and the T2 times overlapped fat, but the combination was unique when comparing tumors to muscle and fat. Necrotic regions of the tumor and the bladder contents tended to have very long T1 and T2 relaxation times. The difference in relaxation time between tumors and muscle could be accounted for in terms of water content, which was approximately 8% higher for the tumors. The study corroborates data from previous studies indicating that NMR imaging is a highly sensitive modality, although T1 and T2 times are not exclusive indicators of malignancy.
- Published
- 1983
27. Nuclear magnetic resonance imaging of a fibrosarcoma tumor implanted in the rat
- Author
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Lawrence E. Crooks, Peter L. Davis, Leon Kaufman, Antonio C. Brito, Kirk L. Moon, Theodore R. Miller, Philip Sheldon, and J C Watts
- Subjects
Pathology ,medicine.medical_specialty ,Magnetic Resonance Spectroscopy ,Fibrosarcoma ,Tumor cells ,Hindlimb ,Nuclear magnetic resonance ,medicine ,Animals ,Radiology, Nuclear Medicine and imaging ,medicine.diagnostic_test ,business.industry ,Muscles ,Spin–lattice relaxation ,Water ,Resonance ,Magnetic resonance imaging ,medicine.disease ,Lipids ,Rats, Inbred F344 ,Rats ,Highly sensitive ,Adipose Tissue ,Regression Analysis ,Sarcoma, Experimental ,business ,Neoplasm Transplantation - Abstract
Fibrosarcoma tumor cells were implanted in the hind legs of 25 rats and studied from the first to the sixth week postimplantation. Nuclear magnetic resonance imaging detected all tumors and did not yield any false-positives in five control rats. The T1 relaxation values of tumors overlapped those of muscle, and the T2 values overlapped those of fat, but the combination of the two values allowed discrimination of each of the three tissues with no overlap. The difference in relaxation time between tumor and muscle could be accounted for on the basis of water content, which was approximately 14% higher in the tumors. This study confirms data from previous studies suggesting that nuclear magnetic resonance imaging is a highly sensitive modality, but that T1 and T2 values are not specific for individual pathologic conditions.
- Published
- 1983
28. A Comparison of the Noise Characteristics of Projection Reconstruction and Two-Dimensional Fourier Transformations in NMR Imaging
- Author
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Leon Kaufman, Douglas A. Ortendahl, and Lawrence E. Crooks
- Subjects
Physics ,Nuclear and High Energy Physics ,Frequency response ,Resolution (electron density) ,Iterative reconstruction ,Computational physics ,Noise ,symbols.namesake ,Nuclear magnetic resonance ,Fourier transform ,Nuclear Energy and Engineering ,symbols ,Spatial frequency ,Electrical and Electronic Engineering ,Optical resolution ,Image resolution - Abstract
Human images of excellent quality have been obtained with Nuclear Magnetic Resonance (NMR), using two different techniques: projection reconstruction (PR) and two-dimensional Fourier transformations (2DFT). It has been shown in CT that the reconstruction algorithms will multiply the noise in the projections and change the noise spectrum. A comparison of the noise of the two techniques is presented under the constraint of equal imaging conditions using both computer simulations and data obtained with the UCSF human imager. The computer simulations show that the two techniques produce approximately equal signal to noise values when S/N ~ 15. Below that value small differences are observed. For both simulations and actual data, the 2DFT shows a uniform spatial frequency response while the PR method shows a roll-off at low spatial frequencies. The 2DFT method is shown to be more resistant to artifact formation.
- Published
- 1983
29. Gated MR imaging of the heart: intracardiac signals in patients and healthy subjects
- Author
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Madeleine R. Fisher, Charles B. Higgins, G. K. von Schulthess, and Lawrence E. Crooks
- Subjects
Adult ,Cardiomyopathy, Dilated ,medicine.medical_specialty ,Magnetic Resonance Spectroscopy ,Myocardial Infarction ,Aorta, Thoracic ,Coronary circulation ,Heart Rate ,Coronary Circulation ,medicine.artery ,Internal medicine ,medicine ,Humans ,Thoracic aorta ,Radiology, Nuclear Medicine and imaging ,Prospective Studies ,Myocardial infarction ,Systole ,Aged ,Heart Failure ,Aorta ,Cardiac cycle ,business.industry ,Heart ,Middle Aged ,medicine.disease ,Myocardial Contraction ,medicine.anatomical_structure ,Heart failure ,Descending aorta ,cardiovascular system ,Cardiology ,Radiology ,business ,Blood Flow Velocity - Abstract
The appearance of intraluminal signal in the cardiac chambers, the descending aorta, and blood vessels was studied in healthy subjects and patients with myocardial disease on first and second spin-echo gated magnetic resonance images. Signal was present in the cardiac chambers and the aorta at various phases of the cardiac cycle when physiological or pathological slow flow conditions are expected in healthy subjects and in patients. Healthy individuals tended to show signal in the ventricles and aorta during end-diastole, and signal was less likely to be present at higher heart rates and in systolic images. In patients with regional or global left ventricular dysfunction, intraventricular signal tended to persist into systole. Surprisingly, intraventricular signal was not present with increased frequency adjacent to infarcted regions of the myocardial wall. Thus, the mere presence of intracavitary signal cannot be used as an indicator of either regional or global cardiac contraction abnormalities. In the left atrium, signal was often present during systole. Physical factors determining the appearance of signal of flowing blood are discussed in an Appendix.
- Published
- 1985
30. Nuclear magnetic resonance imaging in multiple sclerosis
- Author
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Leon Kaufman, David Norman, Catherine M. Mills, Michael J. Aminoff, Lawrence E. Crooks, Steven A. Lukes, and Hillel S. Panitch
- Subjects
Adult ,Male ,Magnetic Resonance Spectroscopy ,Multiple Sclerosis ,Materials science ,Computed tomography ,Inversion recovery ,Signal ,Signal acquisition ,White matter ,Nuclear magnetic resonance ,Sampling (signal processing) ,medicine ,Humans ,False Negative Reactions ,medicine.diagnostic_test ,Pulse (signal processing) ,business.industry ,Multiple sclerosis ,Brain ,medicine.disease ,medicine.anatomical_structure ,Neurology ,Evaluation Studies as Topic ,Female ,Neurology (clinical) ,Tomography, X-Ray Computed ,Nuclear medicine ,business - Abstract
Ten patients with definite multiple sclerosis underwent hydrogen nuclear magnetic resonance imaging with a 3.5 kilogauss superconducting magnet, using the inversion recovery and spin-echo techniques of signal acquisition. Results were compared with high-resolution x-ray computed tomography. Spin-echo images demonstrated abnormal regions as areas of variably increased signal intensity. The contrast between abnormal and normal white matter improved as the intervals between sequential radiofrequency pulses and between pulse administration and signal sampling were increased. Inversion recovery images demonstrated abnormal areas as regions of decreased signal intensity but did not visualize lesions as well as spin-echo imaging. Spin-echo and inversion recovery imaging each demonstrated more extensive abnormalities than did computed tomography.
- Published
- 1983
31. Nuclear magnetic resonance imaging of the infarcted muscle: a rat model
- Author
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Philip Sheldon, Martin J. Lipton, Robert J. Herfkens, Leon Kaufman, Douglas A. Ortendahl, Lawrence E. Crooks, Richard E. Sievers, and Charles B. Higgins
- Subjects
Leg ,Magnetic Resonance Spectroscopy ,Hydrogen compounds ,medicine.diagnostic_test ,business.industry ,Muscles ,Rat model ,Infarction ,Rats, Inbred Strains ,Magnetic resonance imaging ,medicine.disease ,Rats ,Nuclear magnetic resonance ,cardiovascular system ,medicine ,Animals ,Radiology, Nuclear Medicine and imaging ,cardiovascular diseases ,Myocardial infarction ,Nuclear medicine ,business - Abstract
Eleven Sprague-Dawley rats with experimentally produced infarction of the lower extremities were imaged by nuclear magnetic resonance (NMR) immediately after infarction, and 6 and 24 hours later. Contrast between the infarcted and control muscles was noted immediately and continued to increase through 24 hours. These changes corresponded to a significant increase in the water content of the infarcted extremity at 24 hours. These results suggest promise for NMR imaging in the identification of myocardial infarction and should encourage further investigation in this area.
- Published
- 1983
32. Cardiovascular Imaging with Nuclear Magnetic Resonance
- Author
-
Robert J. Herfkens, Elias H. Botvinick, Martin J. Lipton, Peter Lanzer, Charles B. Higgins, Leon Kaufman, and Lawrence E. Crooks
- Subjects
Nuclear magnetic resonance ,business.industry ,Metabolic imaging ,Medicine ,Ischemic injury ,General Medicine ,Gating ,Blood flow ,Cardiology and Cardiovascular Medicine ,business ,Image display - Abstract
This article provides some examples of what the previous article outlined. The sections on Image Display and Myocardial Characterization contain numerous illustrations of gating, cross-sectional images, flow signals, and ischemic injury. The possibility of metabolic imaging with NMR and quantitating blood flow is also considered.
- Published
- 1983
33. An Introduction to Magnetic Resonance Imaging
- Author
-
Lawrence E. Crooks
- Subjects
Larmor precession ,Physics of magnetic resonance imaging ,Materials science ,medicine.diagnostic_test ,Magnetic resonance microscopy ,Biomedical Engineering ,Magnetic resonance force microscopy ,Magnetic resonance imaging ,General Medicine ,Nuclear magnetic resonance ,Computer Science::Computer Vision and Pattern Recognition ,medicine ,Spin echo ,Nuclear magnetic resonance decoupling ,Radiofrequency coil - Abstract
The principles underlying nuclear magnetic resonance (NMR) are explained, and its use in image formation is described. The discussion also covers: multislice imaging; image resolution and contrast; effects of flow on images; hardware for magnetic resonance imaging; magnets; magnetic gradients; RF coil, transmitter, and receiver; computer system; and spectroscopy.
- Published
- 1985
34. Tomographic Imaging with Nuclear Magnetic Resonance
- Author
-
Leon Kaufman, Jerome R. Singer, Thomas P. Grover, and Lawrence E. Crooks
- Subjects
Magnetic Resonance Spectroscopy ,Materials science ,Tomographic reconstruction ,Magnetic resonance microscopy ,Physics::Medical Physics ,Resonance ,Magnetic resonance force microscopy ,General Medicine ,equipment and supplies ,Models, Biological ,Imaging phantom ,Rats ,Nuclear magnetic resonance ,Magnetic particle imaging ,Spin echo ,Animals ,Radiology, Nuclear Medicine and imaging ,Tomography ,Radionuclide Imaging ,human activities ,Elementary Particles ,Hydrogen - Abstract
A technique is described for obtaining tomographic images of hydrogen distribution in animals using nuclear magnetic resonance (NMR). Resonant frequency is proportional to magnetic field strength, so that spatial resolution is achieved by frequency selection and magnetic field shaping. The results of scanning a phantom and two rats are presented.
- Published
- 1978
35. Urinary bladder MR imaging. Part I. Normal and benign conditions
- Author
-
Madeleine R. Fisher, Hedvig Hricak, and Lawrence E. Crooks
- Subjects
Adult ,Male ,medicine.medical_specialty ,Magnetic Resonance Spectroscopy ,Urinary Bladder ,Urine ,urologic and male genital diseases ,Muscle hypertrophy ,Humans ,Medicine ,Radiology, Nuclear Medicine and imaging ,Aged ,Retrospective Studies ,Urinary bladder ,BLADDER DISTENTION ,medicine.diagnostic_test ,business.industry ,Urinary Bladder Diseases ,Healthy subjects ,Magnetic resonance imaging ,Hypertrophy ,Middle Aged ,Mr imaging ,female genital diseases and pregnancy complications ,Urinary Bladder Neck Obstruction ,medicine.anatomical_structure ,Female ,Radiology ,Mr images ,business ,Nuclear medicine - Abstract
The normal urinary bladder and several benign entities of the bladder were examined in 50 patients by magnetic resonance (MR) imaging. Specific features assessed included appearance of the bladder wall, optimal repetition (TR) and echo delay (TE) parameters for bladder-wall demonstration, and differentiation among various benign abnormalities, including bladder-wall hypertrophy, inflammation, and mucosal congestion, on MR images. The bladder wall in the 30 healthy subjects was best displayed using a TR = 2 sec, TE = 56 msec image, which gave 60% contrast between the bladder wall and urine and 48% contrast between the bladder wall and fat. Demonstration of bladder-wall hypertrophy required similar imaging; bladder distention was necessary to demonstrate the thickness of the bladder wall. Congestion and inflammation were best demonstrated on TR = 2 sec, TE = 56 msec images, which gave 45% contrast. Normal and/or hypertrophic bladder wall were distinguished from inflammation and congestion on the basis of signal intensity variations and/or T1 and T2 relaxation parameters.
- Published
- 1985
36. Magnetic resonance imaging of the heart: a review of the experience in 172 subjects
- Author
-
Leon Kaufman, Elias H. Botvinick, M T McNamara, Benjamin F. Byrd, Lawrence E. Crooks, Martin J. Lipton, Peter Lanzer, Nelson B. Schiller, and Charles B. Higgins
- Subjects
Adult ,Heart Defects, Congenital ,Male ,medicine.medical_specialty ,Magnetic Resonance Spectroscopy ,Adolescent ,Heart Diseases ,Wall thinning ,Heart disease ,Hypertension, Pulmonary ,Myocardial Infarction ,Cardiomegaly ,Heart Neoplasms ,Internal medicine ,Healthy volunteers ,medicine ,Humans ,Pericarditis ,Radiology, Nuclear Medicine and imaging ,Child ,Aged ,medicine.diagnostic_test ,business.industry ,Infant ,Heart ,Thrombosis ,Magnetic resonance imaging ,Middle Aged ,medicine.disease ,Pulmonary hypertension ,medicine.anatomical_structure ,Great vessels ,Ventricle ,Child, Preschool ,Angiography ,Cardiology ,Female ,Radiology ,Cardiomyopathies ,business - Abstract
Gated magnetic resonance (MR) imaging was used to evaluate central cardiovascular anatomy in 172 subjects, 31 of whom were healthy volunteers. Using the spin-echo technique, images of diagnostic quality were obtained in 93% of cases with TE = 28 msec and in 65% of cases with TE = 56 msec. Transverse multisection sequences encompassing most of the left ventricle required approximately 6-8 minutes. Corroborative studies were available in 134 of 141 patients who had cardiovascular disease; two dimensional echocardiograms and angiography in 133 and 100 patients, respectively. Gated MR demonstrated the wall thinning and complications caused by prior myocardial infarctions and high signal intensity of the myocardium at the site of acute myocardial infarctions. MR accurately demonstrated anatomic abnormalities owing to hypertrophic and congestive cardiomyopathies, congenital abnormalities of the heart and great vessels, rheumatic heart disease, pulmonary hypertension, and cardiac and paracardiac masses. Depiction of cardiovascular anatomy and pathoanatomy was attained without the use of any contrast media. Consequently, gated MR is an effective technique for cardiac diagnosis. The short time required for tomographic examination of the entire heart using the multisection technique renders this a practical cardiac imaging modality.
- Published
- 1985
37. New Imaging Technologies
- Author
-
Robert F. Wagner, Gary T. Barnes, Leon Kaufman, Samuel J. Dwyer, Roger H. Schneider, Lawrence E. Crooks, Victor M. Spitzer, and William R. Hendee
- Subjects
Computer science ,Radiology, Nuclear Medicine and imaging ,General Medicine - Published
- 1984
38. A New Electromechanical Viscometer Designed for Biological Fluids
- Author
-
Francis W. Chow, Stanley A. Berger, Lawrence E. Crooks, Gaston Convidassamy, and Jerome R. Singer
- Subjects
Engineering ,Viscosity ,business.industry ,Biomedical Engineering ,Viscometer ,Mechanical engineering ,Programming profession ,Body Fluids ,Vibration ,Control theory ,Methods ,Biological fluids ,Animals ,Humans ,business ,Mathematics - Abstract
A new type of electronically driven viscometer with digital readout is described. The advantages of this instrument are that only small samples are required for analysis, fluid perturbations are minimal, cyclical measurements can be carried out rapidly and the system is small and moderate in cost.
- Published
- 1978
39. Magnetic resonance imaging of the lymph nodes: comparison with CT
- Author
-
Lawrence E. Crooks, Hedvig Hricak, Charles B. Higgins, and G C Dooms
- Subjects
Adult ,Male ,medicine.medical_specialty ,Magnetic Resonance Spectroscopy ,Adolescent ,Diaphragmatic breathing ,Humans ,Medicine ,Radiology, Nuclear Medicine and imaging ,Child ,Lymphatic Diseases ,Pelvis ,Aged ,medicine.diagnostic_test ,business.industry ,Electron Spin Resonance Spectroscopy ,Infant ,Magnetic resonance imaging ,Middle Aged ,medicine.disease ,Primary tumor ,Lymphatic system ,medicine.anatomical_structure ,Child, Preschool ,Abdomen ,Female ,Lymph Nodes ,Radiology ,Tomography ,Lymph ,Tomography, X-Ray Computed ,business - Abstract
This retrospective study of 144 patients was made to (a) assess the potential of magnetic resonance (MR) for demonstrating lymph nodes using spin-echo technique, (b) compare the MR results with those of CT, and (c) determine the optimal pulse-sequence interval (TR) and echo-delay time (TE) for imaging lymph nodes. The reported CT findings on normal lymph nodes were compared with MR findings in 60 patients who underwent MR imaging of the neck (20 patients), chest (20 patients), abdomen (10 patients), and pelvis (10 patients) for conditions other than lymph node disease. The results showed that CT is presently better than MR for imaging neck and abdominal lymph nodes less than 13 mm in diameter. The ability of MR to demonstrate normal-size (less than 10 mm) lymph nodes in the chest was comparable to that of CT. In addition, MR scans of 84 patients with proven abnormal lymph nodes (8 neck, 49 chest, and 27 abdomen and pelvis) were assessed: in 72 patients, these nodes had also been imaged by CT. MR and CT gave similar results with abnormal lymph nodes (greater than 13 or 15 mm), but MR displayed these nodes better because of its excellent soft-tissue contrast resolution. MR can clearly differentiate abnormal lymph nodes from normal fat, muscle, vessels, adult thymus, thyroid, and diaphragmatic crura, as well as from primary tumor and lymphoceles. Optimal demonstration of lymph nodes with MR required two sequences: one with a short TR and one with a long TR and long TE. Preliminary results indicate that MR holds great promise for the demonstration of lymph nodes in every part of the body.
- Published
- 1984
40. Physics of thin-section MR imaging at low field strength
- Author
-
D M Kramer, L Kaufman, R.J. Guzman, Joseph W. Carlson, and Lawrence E. Crooks
- Subjects
Physics ,Field (physics) ,medicine.diagnostic_test ,business.industry ,Relaxation (NMR) ,Magnetic resonance imaging ,Field strength ,Magnetic field gradient ,Magnetic Resonance Imaging ,Mr imaging ,Physical Phenomena ,symbols.namesake ,Fourier transform ,Nuclear magnetic resonance ,Optics ,Diagnostic quality ,symbols ,medicine ,Humans ,Radiology, Nuclear Medicine and imaging ,business - Abstract
Thin-section magnetic resonance imaging at low field strengths requires analysis of the relative merits of data collection techniques for direct three-dimensional versus multisection two-dimensional imaging. This analysis was done with specific emphasis on shortened relaxation times and the use of reduced magnetic field gradients. Three-dimensional Fourier transform techniques can provide thin-section images of good diagnostic quality when combined with partial flip-angle gradient-reversal techniques.
- Published
- 1989
41. Temperature distribution measurements in two-dimensional NMR imaging
- Author
-
Philip Sheldon, Dennis L. Parker, Lauren Fussell, Lawrence E. Crooks, and Vernon Smith
- Subjects
Distribution (mathematics) ,Nuclear magnetic resonance ,Materials science ,Proton resonance frequency ,Mr thermometry ,Medical imaging ,Range (statistics) ,General Medicine ,Nuclear magnetic resonance spectroscopy ,Temperature measurement - Abstract
This paper represents a preliminary study of the effects of regional temperature distribution in two-dimensional nuclear magnetic resonance (NMR) T1 imaging. It is found, as expected, that variations in local temperature appear as variations in the corresponding T1 image. The potential use of NMR T1 imaging in temperature measurements is evaluated in the case of water and blood samples. Using containers where the temperature could be either known or directly controlled with reasonable accuracy, images are obtained with samples having at least two regions at different temperatures. As expected, T1 is found to vary linearly with 1/T over the range of 0 degrees C to about 40 degrees C for blood. The potential use of T1 imaging in hyperthermia applications is also discussed.
- Published
- 1983
42. Potential hazards in NMR imaging: heating effects of changing magnetic fields and RF fields on small metallic implants
- Author
-
Alexander R. Margulis, R McRee, Leon Kaufman, M Arakawa, Lawrence E. Crooks, and Peter L. Davis
- Subjects
Hot Temperature ,Magnetic Resonance Spectroscopy ,Radio Waves ,education ,Copper wire ,Surgical Equipment ,Metal ,Magnetics ,Nuclear magnetic resonance ,Surgical equipment ,Humans ,Medicine ,Radiology, Nuclear Medicine and imaging ,cardiovascular diseases ,Tomography ,business.industry ,Tissue heating ,Prostheses and Implants ,General Medicine ,equipment and supplies ,Magnetic field ,surgical procedures, operative ,Metals ,visual_art ,visual_art.visual_art_medium ,business ,human activities ,Surgical Clips ,Biomedical engineering - Abstract
To test if changing magnetic fields and radiofrequency fields used in nuclear magnetic resonance imagers could induce electrical currents capable of causing localized tissue heating in metal surgical clips and prostheses, steel surgical clips, copper wire clips, and hip prostheses were exposed to fields greater than those used in the nuclear magnetic resonance imager. Observations indicated that no significant heating should be expected from implanted surgical clips during exposure. The heating of larger metallic implants should be further investigated.
- Published
- 1981
43. Quantification of Obstructions in Vessels by Nuclear Magnetic Resonance (NMR)
- Author
-
Leon Kaufman, Theodore R. Miller, Lawrence E. Crooks, Phil Sheldon, and William Rowan
- Subjects
Nuclear and High Energy Physics ,Physics of magnetic resonance imaging ,Materials science ,medicine.diagnostic_test ,Magnetic resonance microscopy ,Magnetic resonance force microscopy ,Magnetic resonance imaging ,Ferromagnetic resonance ,Magnetic field ,Free induction decay ,Nuclear magnetic resonance ,Nuclear Energy and Engineering ,medicine ,Spin echo ,sense organs ,Electrical and Electronic Engineering ,skin and connective tissue diseases - Abstract
The sequence of radiofrequency and magnetic field gradients used to form an NMR image produces changes in the signals emitted by moving blood when compared to the signals from stationary blood. These changes can be used to measure the open area of vessels. In addition, specific relaxation time signatures of lesions may help in identifying the nature of the obstructions.
- Published
- 1982
44. Medical applications of nuclear magnetic resonance imaging
- Author
-
Alexander R. Margulis, Hedvig Hricak, and Lawrence E. Crooks
- Subjects
Male ,Enthusiastic Acceptance ,medicine.medical_specialty ,Modality (human–computer interaction) ,medicine.diagnostic_test ,business.industry ,Interventional magnetic resonance imaging ,Respiratory motion ,Biophysics ,Magnetic resonance imaging ,Computed tomography ,Magnetic Resonance Imaging ,Western europe ,Humans ,Medicine ,Female ,Radiology ,business ,Upper abdomen - Abstract
In the very short time since magnetic resonance imaging (MRI) was born it has gained surprisingly rapid and enthusiastic acceptance and has speedily proliferated, particularly in the United States and Western Europe. Magnetic resonance imaging (MRI) has successfully challenged computed tomography (CT) in all areas of the body where respiratory motion does not degrade the image (Steinberg, 1986). Newer techniques using a multiplicity of approaches are starting to close the gap between CT and MRI, even in the upper abdomen where the effects of respiratory motion are most pronounced. Although MR is already widely clinically applied and is an accepted everyday diagnostic modality in most large medical centres in the United States, it is not a mature modality. It is rapidly evolving, with whole new areas opening to investigation which will vastly broaden its applications.
- Published
- 1987
45. Tissue Characterization Using Intrinsic NMR Parameters and a Hierarchical Processing Algorithm
- Author
-
Leon Kaufman, Lawrence E. Crooks, Nola M. Hylton, and Douglas A. Ortendahl
- Subjects
Data set ,Nuclear and High Energy Physics ,Operator (computer programming) ,Nuclear Energy and Engineering ,Basis (linear algebra) ,Computer science ,Segmentation ,Image processing ,Image segmentation ,Electrical and Electronic Engineering ,Image resolution ,Algorithm ,Color code - Abstract
The multiparametric nature of NMR imaging allows the same section to be displayed in many different ways by either adjusting acquisition parameters or calculating additional images, creating a possibly overwhelming data set. The need for this many images may be reduced by creating tissue type maps where each tissue is identified according to its characteristic NMR parameters and painted using a color code. Although T1 and T2 values for normal tissue are reproducible, variability among patients, the wide range of T1,T2 and N(H) values for abnormal tissue and partial volume averaging make the determination of tissue signatures difficult without significant operator intervention. A hierarchical processing algorithm, pyramidal segmentation, allowing simultaneous analysis at multiple levels of spatial resolution provides the basis for a tissue mapping algorithm with significantly reduced operator supervision.
- Published
- 1985
46. Nuclear magnetic resonance imaging of the cardiovascular system: normal and pathologic findings
- Author
-
Bruce H. Brundage, Hedvig Hricak, Leon Kaufman, Elias H. Botvinick, Robert J. Herfkens, Peter Lanzer, Lawrence E. Crooks, Charles B. Higgins, Philip Sheldon, and Martin J. Lipton
- Subjects
medicine.medical_specialty ,Magnetic Resonance Spectroscopy ,Dissection (medical) ,Cardiovascular System ,Cardiovascular Physiological Phenomena ,Nuclear magnetic resonance ,medicine.artery ,medicine ,Humans ,Radiology, Nuclear Medicine and imaging ,Coronary Artery Bypass ,Aorta ,medicine.diagnostic_test ,business.industry ,Magnetic resonance imaging ,Laminar flow ,Blood flow ,medicine.disease ,Blood Vessel Prosthesis ,medicine.anatomical_structure ,Cardiovascular Diseases ,Ventricle ,Cardiac chamber ,cardiovascular system ,Spin echo ,Radiology ,business ,Blood Flow Velocity - Abstract
Whole body nuclear magnetic resonance (NMR) imaging of the cardiovascular system was carried out in early clinical trials in 244 volunteers and patients using a 3.5 KGauss (0.35 T) unit. The spin echo technique with multiple imaging parameters was used. Blood vessels were clearly discriminated from solid organs and lesions because little or no intraluminal signal is seen with laminar blood flow at normal velocities, whereas a more intense image is generated by solid organs. Characteristic flow signals were observed in normal patients and were accentuated by varying the imaging parameters. Cardiac chambers were well delineated in some patients on nongated images. In one case, internal topography of the ventricles was exquisitely displayed on a gated image. Intraluminal pathology, such as dissection of the aorta, aneurysms of the aorta and left ventricle, and aortic atheroma, was clearly demonstrated. Patency of coronary arterial bypass grafts was shown. Abnormal flow patterns due to slow or turbulent flow were accentuated on images using the second spin echo. This preliminary experience indicates the considerable potential of NMR imaging in the evaluation of cardiovascular diseases.
- Published
- 1983
47. Nuclear magnetic resonance imaging of the cardiovascular system
- Author
-
Charles B. Higgins, Elias H. Botvinick, Peter Lanzer, Martin J. Lipton, Nelson B. Schiller, Leon Kaufman, Lawrence E. Crooks, and David D. Stark
- Subjects
Aortic dissection ,medicine.medical_specialty ,business.industry ,Internal medicine ,medicine ,Cardiology ,Radiology, Nuclear Medicine and imaging ,Myocardial infarction ,Radiology ,medicine.disease ,business ,Cardiac imaging ,Pericardial disease - Published
- 1984
48. Magnetic Resonance Imaging of Aortic Aneurysms with 3-D Image Reconstruction
- Author
-
James D. Hale, Leon Kaufman, Lawrence E. Crooks, Charles B. Higgins, and Peter E. Valk
- Subjects
Contrast angiography ,medicine.medical_specialty ,Magnetic Resonance Spectroscopy ,False lumen ,Aorta, Thoracic ,Iterative reconstruction ,medicine.artery ,Image Processing, Computer-Assisted ,medicine ,Humans ,Radiology, Nuclear Medicine and imaging ,Aorta, Abdominal ,Aortic dissection ,Aorta ,medicine.diagnostic_test ,business.industry ,Magnetic resonance imaging ,medicine.disease ,Abdominal aortic aneurysm ,Aortic Aneurysm ,Aortic Dissection ,Angiography ,cardiovascular system ,Radiology ,business ,Software - Abstract
A programme was written to detect flow in a sequence of MR images and to construct 3-D vessel maps from the detected flow regions. Reduction in first echo intensity and prolongation of calculated T2 value were used as flow-detection criteria. The programme was used to image the aorta in 6 patients with abdominal aortic aneurysm and 5 patients with aortic dissection. Results were compared with contrast angiography in 9 cases and X-ray CT in 2. The images obtained by the two techniques were comparable in 9 cases. In 2 cases of aortic dissection, where flow in the false lumen was slow, the false lumen could not be demonstrated by angiography, but was clearly seen in the reconstructed MR images.
- Published
- 1987
49. Cerebral abnormalities: use of calculated T1 and T2 magnetic resonance images for diagnosis
- Author
-
Catherine M. Mills, Michael Brant-Zawadzki, Lawrence E. Crooks, and L Kaufman
- Subjects
Brain Diseases ,Magnetic Resonance Spectroscopy ,Multiple Sclerosis ,medicine.diagnostic_test ,Brain Neoplasms ,business.industry ,Cerebral infarction ,Multiple sclerosis ,Relaxation (NMR) ,Magnetic resonance imaging ,Absolute value ,Cerebral Infarction ,Models, Theoretical ,medicine.disease ,Intensity (physics) ,Hepatolenticular Degeneration ,Region of interest ,medicine ,Spin echo ,Humans ,Radiology, Nuclear Medicine and imaging ,Nuclear medicine ,business - Abstract
The potential clinical importance of T1 and T2 relaxation times in distinguishing normal and pathologic tissue with magnetic resonance (MR) is discussed and clinical examples of cerebral abnormalities are given. T1 and T2 values may be used in three ways: (a) Relative values, obtained by an analysis of intensity images with varying dependence on T1 and T2, may be used if absolute values for T1 and T2 are not required for diagnosis. (b) If an absolute value is desired, the numerical values for the relaxation times may be generated using a region of interest on the intensity images. (c) In cases in which both T1 and T2 change may require a calculated image to indicate the contribution of each to the signal intensity, the numerical value may be used to generate analogue images of T1 or T2 calculations. Five patients with cerebral infarction, 15 with multiple sclerosis, two with Wilson disease, and four with tumors were imaged. Hemorrhagic and ischemic cerebrovascular accidents were distinguished using the spin echo technique. In the patients with multiple sclerosis, lesions had prolonged T1 and T2 times, but the definition of plaque was limited by spatial resolution. No abnormalities in signal intensity were seen in the patient with Wilson disease who was no longer severely disabled; abnormal increased signal intensity in the basal ganglia was found in the second patient with Wilson disease. Four tumors produced abnormal T1 and T2 relaxation times but these values alone were not sufficient for tumor characterization.
- Published
- 1984
50. Recent Developments in Nuclear Magnetic Resonance Imaging and Flow Measurements
- Author
-
Lawrence E. Crooks
- Subjects
Physics ,Nuclear and High Energy Physics ,medicine.diagnostic_test ,Pixel ,Resonance ,Image processing ,Magnetic resonance imaging ,Iterative reconstruction ,Magnetic field ,Nuclear magnetic resonance ,Nuclear Energy and Engineering ,Computer Science::Computer Vision and Pattern Recognition ,medicine ,Radio frequency ,Electrical and Electronic Engineering ,Image resolution - Abstract
All instruments used to produce nuclear magnetic resonance (NMR) images have a number of common features. A strong, uniform, and stable magnetic field has to be imposed through the subject. This field has to be varied in space and time to define the location of pixels in the image. A radio frequency magnetic field is applied to excite the nuclei. The radiofrequency signal from the nuclei is detected and its strength determines the intensities of the pixels in the image. The imaging process, data acquisition, and display are all controlled by computers. Within this general structure many options exist for collecting the data necessary for image reconstruction. Areas of recent improvement include increased numbers of slices in a given time, finer spatial resolution and sensitivity to blood flow.
- Published
- 1984
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