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Biomedical subjects

L Crooks

Publications and source records attributed to L Crooks.

31 records · Page 2Linked to original sources
PubMed1983

Nuclear magnetic resonance imaging of the kidney.

The role of nuclear magnetic resonance (NMR) imaging of the kidney was analyzed in 18 persons (6 normal volunteers, 3 patients with pelvocaliectasis, 2 with peripelvic cysts, 1 with renal sinus lipomatosis, 3 with renal failure, 1 with glycogen storage disease, and 2 with polycystic kidney disease). Ultrasound and/or computed tomography (CT) studies were available for comparison in every case. In the normal kidney distinct anatomical structures were clearly differentiated by NMR. The best anatomical detail was obtained with spin echo (SE) imaging, using a pulse sequence interval of 1,000 msec and an echo delay time of 28 msec. However, in the evaluation of normal and pathological conditions, all four intensity images (SE 500/28, SE 500/56, SE 1,000/28, and SE 1,000/56) have to be analyzed. No definite advantage was found in using SE imaging with a pulse sequence interval of 1,500 msec. Inversion recovery imaging enhanced the differences between the cortex and medulla, but it had a low signal-to-noise level and, therefore, a suboptimal overall resolution. The advantages of NMR compared with CT and ultrasound are discussed, and it is concluded that NMR imaging will prove to be a useful modality in the evaluation of renal disease.

Glomerulonephritis↗
PubMed1983

The potential impact of nuclear magnetic resonance imaging on cardiovascular diagnosis.

Nuclear magnetic resonance (NMR) is used to generate cross-sectional images of the human body that show excellent anatomic and functional definition. The NMR imaging process involves interactions between electromagnetic fields and the hydrogen nuclei being imaged. These interactions occur on time scales of milliseconds to seconds. Consequently, the motion of these nuclei, for instance, when carried by blood, produces distinct signatures that are used to assess flow in major vessels. Myocardial dyskinesis also produces visible effects. Because of these effects, NMR imaging may be a safe and effective tool in the diagnosis and assessment of cardiovascular disease.

Blood Flow Velocity↗
PubMed1981

Nuclear magnetic resonance imaging of the abnormal live rat and correlations with tissue characteristics.

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.

Abscess↗
PubMed1981

Potential hazards in NMR imaging: heating effects of changing magnetic fields and RF fields on small metallic implants.

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.

Hot Temperature↗
PubMed1981

Nuclear magnetic resonance imaging.

NMR imaging is based on the ability to induce and monitor resonance of the magnetic moment of nuclei with an odd number of protons and/or neutrons in the presence of magnetic fields. By the use of magnetic fields whose strength varies with position, it is possible to define both the location and concentration of resonant nuclei, and, thereby, to create images that reflect their distribution in tissue. Hydrogen because it is the most sensitive of the stable nuclei to NMR and because it is also the most abundant nucleus in the body, is ideally suited for NMR imaging.

Animals↗
PubMed1980

Tomography of hydrogen with nuclear magnetic resonance.

A nuclear magnetic resonance (NMR) imager with a 6.5-cm aperture is described. Spatial resolution is 0.47 X 2.0 mm with a slice thickness of 8.4 mm. Contrast resolution is 3% for a 4-minute image. Because of the excellent spatial resolution and high contrast between soft tissues, the images provide a great deal of detail and reconstruction artifacts due to motion are avoided. Blood flow can be observed, and selected enhancement of lesions thorough the modification of software-controlled operational parameters is demonstrated.

Animals↗
PubMedDate not supplied

Experimental hypersensitivity pneumonitis: suppressor cell influences.

Experimental hypersensitivity pneumonitis (EHP) can be transferred to strain 2 guinea pigs by lymph node cells (LNC) cultured in vitro with antigen. Using mixtures of cell populations, we sought to determine if functional suppressor cells were present in our system. We also characterized the composition of cell populations that were capable (blast 10 micrograms/mL Micropolyspora faeni from 2-week donor animals) and incapable (blast 0 micrograms/mL M. faeni from 2-week donor animals; blast 10 micrograms/mL from 8-week donor animals) using flow cytometry, anti-Ig and monoclonal antibody 8BE6 (T cell marker) of transferring EHP. Two groups of donors were used: animals sensitized with Freund's adjuvant and M. faeni and challenged with either two or eight weekly intratracheal (IT) injections of M. faeni (2- and 8-week groups). LNC from donor animals were cultured with a soluble extract of M. faeni (10 or 0 micrograms/mL) blasts isolated and transferred IV to syngeneic recipients. Control animals received media IV. Recipients were challenged IT with M. faeni 48 h after the cell transfer and sacrificed 4 days thereafter. All animals were maintained in HEPA filtered air. Randomly selected microscopic fields of the lung (250/animal) were judged to be normal or abnormal without knowledge of treatment. There was a low level of pulmonary response to an IT challenge of M. faeni in media recipients. There was a substantial increase (P less than .01) in pulmonary abnormalities in the animals receiving blasts from the 10-micrograms/mL M. faeni 2-week group. Addition of cells from incompetent cell populations (0 micrograms/mL M. faeni 2-week donors or 10 micrograms/mL M. faeni 8-week donors) did not alter the ability of competent populations to transfer EHP. Cells cultured with antigen had a decreased proportion of T cells and an increased proportion of SIg+ and large cells. Competent and incompetent cell populations did not differ in regard to proportion of large cells, surface Ig+, or T cells. We conclude that the inability of certain cell populations to transfer EHP is not associated with the appearance of functional suppressor cells. Differences of ability to transfer EHP do not correlate with differences of size distribution or T and B cell composition.

Alveolitis, Extrinsic Allergic↗
PubMedDate not supplied

NMR of the normal and pathologic eye and orbit.

Nuclear magnetic resonance (NMR) images of the eye and orbit were reviewed in a series of 100 normals and in four patients with orbital or ocular pathology. A rich retrobulbar fat content rendered the orbit well suited for NMR imaging. The lens, vitreous, optic nerve, and extraocular muscles were well visualized with spin-echo technique. However, NMR spatial resolution was inferior to that of high-resolution computed tomography (CT). NMR was comparable to CT in demonstrating choroidal melanoma and orbital pseudotumor. NMR exhibited a particular sensitivity in displaying tissue contrast for infiltrative orbital fat lesions with a relatively long T1. This initial experience suggests a promising role for NMR in orbital imaging.

Adolescent↗