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Biomedical subjects

L Ia Klepper

Publications and source records attributed to L Ia Klepper.

At least 19 recordsLinked to original sources
PubMed1999

[Various aspects of individualized planning of computerized radiotherapy for uterine and ovarian cancer].

The study was concerned with radiotherapy planning using individual data on tissue volume to be treated. The investigation used criteria based on correlations of TDF, actual volume identified by ultrasound, computed and magnetic resonance tomography and dose fractionation regime. As a result, grave complication rates dropped 3 times including cases of locally advanced tumors, non-traditional dose fractionation and advanced regimens of polychemotherapy.

Dose Fractionation, Radiation↗
PubMed1997

[Current issues of mathematical modeling and advancement in radiology].

An analysis of certain issues in mathematical support and optimization of radiological procedures has pointed to many criteria involved in designing effective schedules of radiotherapy of neoplasms. TDF, CRE and ETD may be used for relevant evaluations. The greatest promise is held by such criteria as tumor tissue ablation (TTA) and radiation injury complications (RIC) in normal organs and tissue. This calls for development of suitable methods. Considering the high complexity of the body. It should be expected that body responses to radiation are determined by irradiation parameters and condition of target tissues. The report deals with a procedure for adapting mathematical models to on-line requirements. Newly-developed programming complexes are designed to help the medical radiologist integrate available data with his or her clinical findings.

Models, Theoretical↗
PubMed1990

[Standardization of irradiation planning in radiotherapy of malignant tumors].

The paper is concerned with the discussion of the problem of standardization of designs of cancer radiotherapy which can be regarded as summarized experience in the formation of optimum dose fields in radiation therapy. The author gives his definition of standard and partially standardized irradiation designs and proposes methods for their definition in practice.

Humans↗
PubMed1989

[Optimal conditions for irradiating central cancer of the lung using high-energy photon beams].

The authors describe optimum plans of irradiation of central lung cancer of patients with different stature in a restricted number of radiation directions and without such restrictions. The recommendations obtained are compared with routine methods of irradiation. The description of a single dose field by transformed curves of axial distribution, taking into account the heterogeneity of a medium, are used in computation.

Humans↗
PubMed1989

[Local irradiation planning in prostatic cancer with the use of optimized dosage field variants].

A method of dosimetric planning of multifield local irradiation of prostatic cancer using a file of optimized dose fields was proposed (the fields were computed for concrete patients). Basic charts were used to choose a necessary dose field, then the time of irradiation is computed in present directions for each concrete patient. The method was tested during the treatment of 19 patients who were given a course of radiotherapy in an outpatient setting. A continuous course of radiotherapy at a dose of 70-74 Gy was delivered. Radiation reactions of the rectum were insignificant, and they were eliminated without discontinuation of a course of irradiation.

Humans↗
PubMed1989

[Efficient parameters of grid diaphragms for the radiation therapy of malignant tumors].

In larger size malignant tumors it is necessary to raise a dose of irradiation and to increase field sizes whereas tolerant doses for normal tissues and stroma are reduced with an increase in the volume of irradiation. The adjustment of these two alternative requirements can be achieved with the help of grid diaphragms creating more sparing conditions of the irradiation of normal organs and tissues as a result of inhomogeneous dose distribution. The authors consider some mathematical models for assessment of the quality of an inhomogeneous dose field formed by using grid diaphragms. In this case the sparing of normal organs and tissues results only from a decrease in the volumes of irradiated normal tissues. The proposed mathematical models can be used for a choice of optimum parameters of grid diaphragms.

Humans↗
PubMed1988

[The TDF (time-dose-fractionation) model in brachytherapy].

A method to determine TDF values by standard tables with account of RBE of low-energy x-radiation and a small area of irradiation fields was proposed. Corresponding formulas confirmed by the authors' clinical data, were developed. The authors outlined ways of using these data for assessment and design of courses of brachytherapy to minimize the risk of development of skin radiation damages.

Brachytherapy↗
PubMed1988

[Probability of the occurrence of radiation complications in tissues as a function of the probability of the death of their constituent cells].

The author considers some theoretical aspects of the problem of development of mathematical models to describe probabilities of the absence of radiation complications in tissues as function of the probability of a cell to survive. Since the number of tissue cells in great, a mathematical model based on an assumption of the existence of the maximum number of cells associated with development of radiation complication, leads to a sharp change in dependence of probability of radiation complications in tissues as dose function, which becomes steadier and more adequate to actual functions if one assumes the existence of reparable and irreparable spacious structures which form cells survived after irradiation and characterize cell tissue organization.

Cell Survival↗
PubMed1988

[Population analog of the Blair-Davidson-Korogdin model].

The author compares different models of fractionated irradiation (Blair-Davidson-Korogodin, F. Ellis and L. Cohen). It has been established that if F. Ellis' and L. Cohen's models well reflect the correlation of a skin tolerance dose and time intervals between irradiation sessions, the beta-parameter in the Blair-Davidson-Korogodin model is a function of time intervals and the of parameter remains constant. The population analog of the Blair-Davidson-Korogodin model was proposed for the first time. The use of the analog can facilitate its analysis and comparison with other models of fractionated irradiation.

Humans↗
PubMed1988

[A mathematical model for describing radiation complications].

The paper is devoted to the development of a mathematical model for describing probabilities of occurrence of radiation complications on the skin (as well as in other normal organs and tissues) during its irradiation with homogeneous and inhomogeneous dose fields as a function of an irradiated skin area. The model naturally necessitates the isolation of an equivalent dose (an equidosimetric value) introduced by I. B. Keirim-Marcus which can be effectively used for comparison of homogeneous and inhomogeneous dose fields in normal organs and tissues. The development of mathematical models describing probabilities of occurrence of radiation complications in normal organs and tissues opens up new opportunities for improvement of methods of cancer radiotherapy design.

Humans↗
PubMed1988

[Formation of dose fields in local irradiation of cancer of the prostate].

The authors compare dose distributions in local irradiation of prostatic cancer using moving methods on distant gamma-units while taking and not taking into account individual structure of body section and bone structures. They propose problems of choice of optimum conditions of gamma-beam therapy in localized prostatic cancer and their solution. Optimum irradiation designs have been found preferable. When individual dose field calculations are impossible to implement, rotational 360 degree irradiation with correction for 8% and absorption in the table of a gamma-therapeutic unit is recommended.

Gamma Rays↗
PubMed1987

[Dosimetric planning of combined radiation therapy (tele- and interstitial gamma-therapy) of tumors originating in the mouth mucosa].

The authors proposed a new model of dosimetric design of combined gamma-therapy of patients with oral mucosa tumors on the basis of F. Ellis' modified model with account of a therapeutic volume of tissues to be irradiated, and Henschke's model describing a focal dose optimum value in interstitial gamma-therapy as a function of its volume. The proposed model is based on the concept of relative (partial) tolerance which is equal to a ratio of values of a dose delivered to a therapeutic volume to a tolerance dose and differs from the formula of partial tolerance described by Orton and Ellis.

Brachytherapy↗
PubMed1986

[Application of the DMF model taking into account volume and area of irradiated tissue to the prognosis of radiation complications].

Coefficients Kv and Ks for determination of the influence of a volume and area of irradiated tissues in the assessment of DMF factors were presented. The above coefficients were derived on the basis of calculations and a retrospective analysis of the authors' clinical data on radiation complications in the subcutaneous fatty tissue in teleradiotherapy of malignant tumors. The use of the coefficients will make it possible to predict with greater reliability the probability of radiation complications in designing radiation therapy.

Humans↗
PubMed1983

[Stability of the optimal solution to the problem of determining optimal physicotechnical irradiation conditions].

The problem of determination of optimum physical and technical plans of irradiation often amounts to the problems of linear programming. To solve such a problem, it is necessary to calculate a matrix of conditions (dose rate in the system of distributed control points in the body during irradiation in different present directions). The purpose was to study the influence of errors of the calculation of dose rates upon the optimum irradiation plans. It has been established that though the task of determining optimum plans is a correct one, convergence of the solution of a disturbed problem to an initial one occurs extremely slowly. The optimum values of the functionals of a disturbed problem converge more rapidly to the functional of an initial problem. The comparison of optimum irradiation plans or optimum and traditional irradiation plans seems difficult. To compare different irradiation plans, it is more convenient to use the values of a specific function (optimum criteria).

Humans↗