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Biomedical subjects

M A Greenfield

Publications and source records attributed to M A Greenfield.

At least 19 recordsLinked to original sources
PubMed1996

Instrumentation of the patellar osteotomy in total knee arthroplasty. The relationship of patellar thickness and lateral retinacular release.

This study investigates the influence of patellar thickness in total knee arthroplasty (TKA) with routine patellar resurfacing on the rate of lateral retinacular release. A study group comprised of 121 TKAs using surgical instrumentation allowing a measured resection of the patella was compared with a control group comprised of 100 TKAs using an "eye-ball" technique for patellar resurfacing without particular attention to patellar thickness. A composite without patellar thickness equal to or slightly less than the original patella was attempted in the study group. The average thickness difference of the patella in the study group was -1.58 mm. Lateral retinacular release for patellar maltracking was performed in 12.4% of knees in the study group compared with 55% of knees in the control group. The variation in patellar thickness in this series often led to a residual bone thickness < 15 mm. No clinical problems have been observed to date.

Aged↗
PubMed1992

Arthroscopic evaluation and treatment of the patellofemoral joint.

Patellofemoral pain is a multifactorial problem. No single successful solution for problems related to the patellofemoral joint has been identified. One needs to consider the interaction of all of the factors affecting the extensor mechanism. Evaluation begins with a careful history, physical examination, and appropriate radiographic studies. Arthroscopy can provide additional information regarding the condition of the articular cartilage, patellar tracking, and the presence of other intra-articular lesions. Conservative treatment is the cornerstone of management and is effective in more than two-thirds of patients, making surgical treatment necessary in only a minority of instances. ALRR, although not an innocuous procedure, has an acceptably low complication rate and provides predictably good results when used in properly selected patients.

Arthroscopy↗
PubMed1986

Trabecular bone mineral density measurement in vivo: use of the ratio of coherent to Compton-scattered photons in the calcaneus.

Trabecular bone mineral density (TBMD) was measured in vivo in the calcaneus by a new method that uses the ratio of coherent to Compton-scattered photons arising from irradiation of a small volume of trabecular bone by a gamma ray source with highly collimated geometry. TBMD values for healthy men (22-77 years) were in the range of 180-357 mg/ml, and values for healthy women (18-73 years) were in the range of 160-321 mg/ml. In contrast, values in a small group of paraplegics were in the range of 90-199 mg/ml.

Adult↗
PubMed1984

Quantitative differences between the thyroid uptake of 123I and 99mTc.

Unlike 123I, sodium pertechnetate Tc99m is known to be trapped by the thyroid gland without being further processed. Whether this property alone explains the total difference between the early thyroid uptake of these two isotopes was studied in a group of goitrous patients. The absolute activities of 99mTc were measured by a conjugate-view counting method and those of 123I by a coincidence counting method. The uptake was continuously registered to give uptake curves which were analyzed according to a three-compartment model of the thyroid. Both isotopes are postulated to bind to some carriers and then to be transported into the thyroid gland before they are further metabolized. Although the differences observed between the two uptakes were somewhat model dependent, the application of compartmental analysis provides a more detailed description of the differences between the two uptakes which occur even before the organification step.

Adolescent↗
PubMed1982

A dose table describing fractions of peripheral volume for 125I volume implants.

A dose table that provides the dose as a function of fractions of peripheral volume for 125I implants is presented. The table is based on seed distributions from 50 actual patient implants. Computer dosimetry was used to determine peripheral doses and dose ranges within implant volumes. The effects of seed distribution were also examined. The patient data and a study of computer-generated randomized seed coordinates within a given volume suggest that matched doses do not depend strongly on the exact position of each seed. The table provides the means for planning an implant to obtain a desired peripheral dose that can be directly compared with the postimplant computer dose calculation.

Brachytherapy↗
PubMed1982

In vivo evaluation in intrathyroidal iodide metabolism.

A new coincidence counting method is used to measure absolute thyroid 125I activity with accurate correction of extrathyroidal neck activity. Data collected are analyzed according to a three-compartment model, giving parameters both dependent and independent of plasma iodide concentration. Iodide is postulated to form a complex with the iodide trap before it is transported and organified. The initial carrier-iodide complex, the intrathyroidal free iodide, and the thyroidal organic iodide pool can be determined as percentages of the injected activity. The trapping rate, the leakage rate, and the organification rate for iodide are determined as fractional turnover rates of the compartments independent of the plasma iodide concentration. The analysis is applied to the study of intrathyroidal iodide metabolism in a group of goitrous patients and a group of treated hyperthyroid patients. In the euthyroid goitrous patients, the trapping rate is slow, ranging from 0.051-0.085 min-1, and the intrathyroidal iodide pool is characteristically small, being 0.017-0.118%. The organification rate is 0.628-1.19 min-1. The leakage of iodide is virtually zero. In the treated hyperthyroid group, organification is not detectable, due to suppressive treatment by thionamides. The trapping rate is elevated (0.199-0.592 min-1), and the leakage rate is estimated to be in the range of 0.057-0.157 min-1. Because of the organification block, the intrathyroidal iodide pool is larger than that of our euthyroid group, being 1.50-7.59%. The compartment sizes and fractional turnover rates are in good agreement with previously reported values.

Adolescent↗
PubMed1981

Measurement of the velocity of ultrasound in human cortical bone in vivo. Estimation of its potential value in the diagnosis of osteoporosis and metabolic bone disease.

Using a method combining the velocity of ultrasound and photon absorptiometry in the human radius in vivo, the authors measured the speed of sound in bone (U) and bone mineral content (BMC). From these measurements and a "simple" bone model, they then computed the bone mineral density, compact bone density, and modulus of elasticity. The accuracy of these parameters and of the bone model is assessed, and normal values for each parameter are given and compared with published values. The authors feel that a combination of U and BMC permits better discrimination between normal and abnormal in patients with osteoporosis or metabolic bone disease than either parameter alone.

Adolescent↗
PubMed1981

Simultaneous determination of free thyroxine and capacity of thyroxine-binding globulin.

A simple method is described for the simultaneous determination of capacity thyroxine-binding of globulin (TBG) and free thyroxine concentration (FT4). The ratio of bound to free T4 (B/F) is first determined for two total-T4 concentrations using a Sephadex G-25 competitive-binding technique. TBG capacity and FT4 can both the calculated assuming a known value of affinity constant of TBG. The method is linear over a twenty-fold serum dilution. FT4 calculated is identical to that calculated using the method of Irvine. TBG capacity is shown to be linearly correlated to TBG concentration as determined by radioimmunoassay and is consistent with a molecular weight of 69,000 Daltons and one T4 binding site per molecule. FT4 is found to correlate with the free thyroxine index in a complicated way, depending on the degree of TBG saturation.

Binding, Competitive↗
PubMed1980

Accuracy of bone mineral data.

The reliability of data obtained from the Norland-Cameron Bone Mineral Analyzer has been questioned and the possibility of an inherent calibration error in the machine has been raised. To make an absolute measurement of the instrumental accuracy, bone mineral content measured by the bone mineral analyzer was compared with an absolute value obtained by the ashing method. The instrument bone mineral content values were found to be higher by about 6.5%. The ash content (%), bone mineral density, and compact bone density in these same bone samples were 62.9%, 1.346 g/cm3, and 2.140 g/cm3, respectively, as determined by direct measurement.

Bone and Bones↗
PubMed1978

The in vivo measurement of the total iodine content of the thyroid gland by x-ray fluorescence.

An accurate, in vivo Am-241 excited x-ray fluorescence techniques was investigated for exploring the correlation between thyroid iodine content (TIC) and various thyroid disorders. The correction for fluorescent x-ray absorption by overlying tissues was made by using the x-ray to gamma ray peak ratio from administered I-123 as an index of thyroid gland depth. In a series of phantom studies, TIC was measured with an uncertainty of +/- 11%, and the depth correction added another +/- 26% error. Radiation doses to the patient were estimated with TLD measurements to be about 15 mrem from I-123, and 13 mrem from Am-241.

Gamma Rays↗
PubMed1978

Use of I-123 in early radioiodide uptake and its suppression in children and adolescents with hyperthyroidism.

Absolute activity measurement of I-123 by coincidence counting was used to study the early thyroidal iodide uptake in 20 hyperthyroid children. Patients were pretreated either with methimazole or propylthiouracil before injection of Na123I. The usual method of analysis of the early uptake was modified to account for a rapidly equilibrating compartment, to give thyroidal iodide trapping rate constant (K1) and absolute iodide uptake (AIU). The suppressibility of the early uptake by triiodothyronine (T3) was evaluated in some patients. The upper limit of normal for K1 was 0.03 min-1 and for AIU was 0.04 microgram/min. In the hyperthyroid subjects, K1 and AIU were in the hyperthyroid range before and after T3 suppression. For patients with suppressible uptake, remission from hyperthyroidism was maintained for 6 mo to 2 1/2 yr. Only two patients with nonsuppressible uptake achieved remission from hyperthyroidism, perhaps because of coexistence of thyroiditis.

Adolescent↗
PubMed1976

The energy response of LiF, film and a chemical dosemeter to high energy photons and electrons.

The physical responses of LiF, film and a chemical dosemeter in high energy photon and electron beams has been studied. It is shown that the response for film and the chemical dosemeter does not change significantly up to 42 MeV, while for LiF it decreases by about 10%. Analysis of calculations and measurements showed that this decrease could not be explained by existing theories.

Electrons↗
PubMed1975

The modulus of elasticity of human cortical bone: an in vivo measurement and its clinical implications.

The modulus of elasticity was derived by combining the velocity of ultrasound measurements and photon absorption (Norland-Cameron method) in human cortical bone (proximal radius) in vivo. The results compare favorably with published values of the elasticity modulus obtained in vitro. Values obtained for a heterogeneous group of patients with bone and joint complaints differed from those of normal volunteers.

Adult↗