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Biomedical subjects

M Gitterman

Publications and source records attributed to M Gitterman.

36 records · Page 2Linked to original sources
PubMed1994

A non-Markovian model for calcium kinetics in the body.

We present a new generalized compartmental model for calcium kinetics as measured by tracer concentration in blood plasma. The parameter measuring incorporation of calcium in bone discriminates between different levels of physical development in female teenagers and between teenagers and adults.

Adolescent↗
PubMed1994

Generalized theory of the kinetics of tracers in biological systems.

Most theoretical analyses of tracer kinetics in capillaries contain an implicit assumption that the tissues to which they are connected have homogeneous material properties. The microscopic description of the exchange of tracer molecules and tissues is then modeled in terms of first-order kinetics. We consider a class of more general models allowing us to assess the robustness of simplifying assumptions made above. It is shown that when amorphous properties are important the kinetics of the system may differ considerably from those predicted by standard theories.

Animals↗
PubMed1987

The first heart sound during the isovolumetric contraction.

We make the first attempt to construct a qualitative theory covering the whole process of the major part of the first heart sound from an electrical activation to the phonocardiographic observations at the thorax. We calculate the amplitudes and frequencies of the radiated pressures during the isovolumetric contraction period generated by the muscular wall of the left ventricle and by the valves considered as a spherical shell and two-dimensional membranes, respectively. The analysis shows that both the hemodynamic and the valvular theory are able to explain most of the characteristic features of the first heart sound (linear relation between the amplitudes of the radiated pressure and the slope of the left ventricular pressure-time curve; directional polarity of the amplitudes; equidistant frequency peaks with a decline in amplitudes). However, existing magnitudes of the set of physiological parameters involved seems to favour the hemodynamic theory of the first heart sound. The aortic valve can be neglected as a source of sound. The initial conditions (like valve closure velocity), according to our theory, cannot be important. The predicted time-plot and frequency spectrum of the radiated pressure show a general resemblance with the recorded ones. It is essential to have considerably more quantitative acoustic data both for normal and diseased hearts for subsequent theoretical development.

Heart Auscultation↗
PubMed1984

Shielding hospital rooms for brachytherapy patients: design, regulatory and cost/benefit factors.

The current regulations of the U.S. Nuclear Regulatory Commission (NRC) normally require limitation of radiation exposure in any part of unrestricted occupied areas to 2 mrem in any one hour and to 100 mrem in 7 days. To meet these limits when patients are treated therapeutically with radioactive materials, it is advisable to designate specific rooms in a hospital and often necessary to incorporate substantial costly shielding into one or more walls and the room door. Plans have been formulated for shielding existing hospital rooms housing brachytherapy patients receiving 192Ir and 137Cs therapy in order to meet the above NRC requirements for adjacent corridors and rooms. Typical shielding thicknesses required are 4-6 in. of concrete for certain walls and 1/4 in. of lead in the doors. Shielding costs are approx. $6000 per room for one shielded wall and a shielded door. Applying recent estimates of the cancer risk from low-level gamma radiation, the cost of shielding per cancer fatality averted has been estimated to range from $1.8 million to $10.9 million. Cost/benefit comparisons with many other life-saving activities suggest that these costs and the application of the 2 mrem/hr limit which necessitated them are not justified.

Brachytherapy↗
PubMed1975

Rethinking the necessity of treating all fields at each radiotherapy session.

Examples of multifield and wedged treatment plans are evaluated in terms of the fractionation protocol. Isoeffect distributions derived from time-dose fractionation values are examined, emphasizing alternate treatment schedules of the same plan. The necessity of treating all fields at each session is found to be a function of the detailed nature of the individual treatment plan.

Bone Neoplasms↗