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Biomedical subjects

S J Gibbs

Publications and source records attributed to S J Gibbs.

At least 37 records · Page 2Linked to original sources

Radiology: closing a century, opening a millennium.

As we close the file on the first century of radiology, we honor the pioneers and reflect on the progress they started. We also open a new file, not just a new century, but a new millennium of opportunity. The dramatic technologic advances in diagnostic imaging within recent decades have provided the foundation for expanding our activities in Oral and Maxillofacial Radiology. We are no longer just dental radiology; we can no longer rest on the teaching and practice of conventional dental radiography. We can summarize in one word the direction our efforts must take in opening the millennium: research. Only with research at the fundamental as well as clinical level we can continue to expand our service to the public, to our patients, and to our colleagues.

Germany↗

Disk position before and after modified condylotomy in 80 symptomatic temporomandibular joints.

OBJECTIVE: Our primary objective was to determine the frequency of disk reduction after modified condylotomy and whether the type of displacement affected outcome. DESIGN: We classified reducing disk displacements from magnetic resonance images of 80 symptomatic temporomandibular joints before modified condylotomy. Disk position was reassessed after surgery. RESULTS: The disk and condyle typically move in reciprocal directions. The disk was reduced by surgery in 79% of the joints. The rate of reduction varied by the type of displacement, but the differences between the groups were not statistically significant. CONCLUSION: This finding reaffirms that modified condylotomy has a high rate of disk reduction. The unexpected observation that the increase in joint space resulting from the surgery typically permitted a variable degree of spontaneous movement of the disk has implications for the nature of osteoarthrosis and internal derangement and for surgical treatments intended to reduce the risk.

Adolescent↗

Recapture of temporomandibular joint disks using anterior repositioning appliances: an MRI study.

Thirty consecutive patients seeking treatment for painful temporomandibular joint (TMJ) disease were enrolled in a prospective study to assess the relationship between the recapture of displaced disks by anterior repositioning appliances (ARA) and the relief of symptoms. After standard clinical workup including assessment of pain, maxillary and mandibular ARAs were constructed that repositioned condyles to the Gelb 4/7 position. Magnetic resonance imaging (MRI) was performed before and immediately after the insertion of ARAs. Initial MRI findings showed 26 joints with reducing disk displacements in 17 patients, seven partially-reducing joints in four patients, 14 nonreducing joints in 11 patients, and 13 normal joints in eight patients. Postinsertion MRI showed recapture of disks in 25 of 26 reducing displacements (96%), but no recapture in partially-reducing or nonreducing joints. All but one of the normal joints remained unchanged. Pain assessment showed significant relief of symptoms in all three categories. The degree of pain relief was significantly greater in recaptured reducing disks than the other categories (p < 0.05). ARA therapy provides effective pain relief regardless of disk status, although a greater degree of relief may be achieved in recaptured reducing internal derangements.

Facial Pain↗

Brain proton magnetic resonance spectroscopy studies in recently abstinent alcoholics.

Chronic alcohol-dependent patients have reduced brain volumes and concomitant neurobehavioral deficits that may recover during abstinence. In 10 chronic alcoholic patients, using localized proton magnetic resonance spectroscopy, we found reliable increases during the first 3-4 weeks of abstinence in the concentrations within the superior cerebellar vermis of choline (Cho)-containing compounds relative to the neuronal marker, N-acetylaspartate (NAA). Lesser changes were observed following 1 month of abstinence, and in one of the patients studied longitudinally over 3 months, a marked reduction in the Cho/NAA ratio was associated with relapse. After detoxification, the Cho/NAA ratio correlated with a composite clinical impression of brain functions. The lowest Cho/NAA was observed in a patient with persisting alcoholic dementia, in striking contrast to reduced relative concentrations of NAA reported in dementia of the Alzheimer's type. Possible molecular explanations for these brain metabolic changes are discussed.

Adult↗

Pore geometry information via pulsed field gradient NMR.

Studies of echo attenuation at long diffusion times in pulsed field gradient NMR experiments on a variety of rock core samples are interpreted in the light of recent theoretical analysis of the effect of pore geometry and surface relaxation. This study is motivated by the need to test the applicability of that theory to real rock systems.

Calcium Carbonate↗

Partially restricted diffusion in a permeable sandstone: observations by stimulated echo PFG NMR.

We demonstrate a variant, insensitive to eddy current effects, of an alternating pulsed field gradient technique designed to null the effect of background gradients in liquid-saturated porous media, using a 38 mm diameter sample of a natural sandstone. Measurements of the effective diffusivity confirm predictions of a decline as the square root of an effective diffusion time. A value of the ratio S/Vp for the dominant pores is extracted, yielding with T1 a value for the surface relaxivity. We test also a geometry-dependent data collapse recently suggested for a range of diffusion times and wavenumbers. The data agree with a sheet-like pore model for this granular sandstone, and fail to agree with a tube-like model; a pore length scale is also extracted.

Diffusion↗

Dissecting and implementing STEAM spectroscopy.

A rapid, simple method for constructing a site-specific STEAM sequence from a basic Hahn three-pulse sequence is presented. The method assures maximum signal available from the hardware.

Image Enhancement↗

Comparative imaging of the jaws.

Explosive growth in high-technology imaging continues in dentistry as in all health sciences. Some new technology will find its way into general and some specialty dental practices; two examples, digital intraoral radiography and multimodality panoramic machines, are reviewed. New developments in the application of current imaging procedures (both conventional and "high tech") to diagnosis and management of diseases and injuries of the jaws, muscles of mastication, and salivary glands are presented. Recent information suggests that the risk of radiation-induced cancer in exposed populations may be greater than had been recognized. The impact of this data on both occupational and patient radiation exposure in dentistry is reviewed.

Humans↗

Qualitative and quantitative evaluation of charge capture by a radiology information system.

Installation of a radiology information management system (RIS) is usually justified on the basis of improved departmental efficiency and improved charge capture. However, evaluation of the success of these expected improvements is often difficult. The installation and operation of such a system in a medium-sized tertiary care hospital has permitted the effects of the RIS on the operation of the department to be studied and the improvements in charge capture provided by the system to be quantitatively assessed. As a result of a side-by-side comparison with a conventional check-sheet manual billing system, it is apparent that the RIS reduces the errors inherent in manual systems. Subjectively, it is also apparent that personnel prefer the computerized system to the manual charge sheets.

Accounting↗

Dermatomyositis: correlative MR imaging and P-31 MR spectroscopy for quantitative characterization of inflammatory disease.

Magnetic resonance (MR) imaging and phosphorus-31 MR spectroscopy were used to examine four patients with dermatomyositis and five control subjects. T2-weighted images of the thigh muscles of patients showed increased signal intensity, with focal and inhomogeneous involvement predominantly in the vastus lateralis and secondarily in the vastus intermedius and vastus medialis. T1 and T2 values of the vastus lateralis in patients were significantly higher than those of the control subjects. T1 values of the rectus femoris and biceps femoris with more generalized inflammation were moderately elevated but still significantly higher than those of the control subjects. P-31 MR spectra of the quadriceps muscles were obtained during rest, during exercise at two graded levels, and in recovery. Concentrations of adenosine triphosphate and phosphocreatine (PCr) in the diseased muscles were 30% below normal values, and the inorganic phosphate/PCr ratios were increased in the patients' muscles at rest and throughout exercise. The T1 and T2 values as well as the P-31 metabolite data correlated with symptoms and clinical assessment.

Adult↗

Influence of organs in the ICRP's remainder on effective dose equivalent computed for diagnostic radiation exposures.

The ICRP effective dose equivalent has been compared with a weighted dose equivalent, computed by treating the entire remainder instead of the sample of five remainder organs in the ICRP method as uniformly radiosensitive, for dose distributions from three common diagnostic exposures: chest, dental full-mouth and dental panoramic. Complete dose distributions were computed by a Monte Carlo model. In all three cases the effective dose equivalent was greater than the weighted dose equivalent. The difference was only 20% for the chest exam but was more than fivefold for both dental exposures. Dose distributions for the dental exposures were less homogeneous than for the chest examination. Selection of organs to be included in the remainder markedly affects the effective dose equivalent. In the case of highly inhomogeneous dose distributions, the effective dose equivalent probably significantly over-estimates radiation detriment.

Computer Simulation↗