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Results for “Radiotherapy, Computer-Assisted”

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PubMedDate not supplied

The development of distant pulmonary infiltrates following thoracic irradiation: the role of computed tomography with dosimetric reconstruction in diagnosis.

High doses of external beam radiotherapy are required to obtain local control of many intrathoracic neoplasms. Because spinal cord tolerance limits the radiation dose that can be given through anterior and posterior fields, it is often necessary to increase the dose to the primary tumor site using oblique or lateral fields. When pulmonary infiltrates develop following treatment in these patients, it is frequently difficult to distinguish between infection, recurrent tumor, and radiation pneumonitis. In nine patients in whom acute pulmonary infiltrates occurred following a course of thoracic irradiation, computed tomography (CT) with computed dosimetric reconstruction (CDR) were studied in an attempt to correlate the treatment volumes with the location and configuration of the infiltrates and in this way establish the source for the pulmonary abnormalities. In seven of these patients, the diagnosis was changed, and the resulting post-irradiation clinical therapy was altered as a consequence of this retrospective study.

Adult↗
PubMedDate not supplied

Encoding patient contours using Fourier descriptors for computer treatment planning.

Frequently it is desirable to digitize patient's external and internal contours from computer-assisted tomography (CAT) scan images and to use them for computer treatment planning. After the contours are digitized, each contour could contain over 1000 points. It is a common practice to reduce the number of contour points by interpolation methods in order to use them in a treatment planning program, and in order to save storage space. This paper describes an alternative method for encoding contours. The x-y coordinates of each contour point are represented as a complex number, x + jy. The discrete Fourier transform (DFT) of the array of complex numbers is then computed. Only the 50 lowest frequency components of the DFT are retained. Each contour is then represented by these 50 complex numbers, known as Fourier descriptors. The original contour is restored by performing the inverse Fourier transform. All the frequency components higher than 50 are assumed to be zero during the inverse Fourier transform. The algorithm is described in detail.

Computers↗
PubMedDate not supplied

A study of quality of bremsstrahlung spectra reconstructed from transmission measurements.

A numerical method for the reconstruction of bremsstrahlung spectra has been applied to the analysis of simulated data. The method is found to be reliable in reconstructing x-ray spectra of maximum energy up to 10 MeV. Measurements of aluminum transmission data carried out for five linear accelerators have also been analyzed by this method to determine the fractional energy fluence. The values of the Spencer-Attix water/air stopping power ratio, SS.A. w,air, reported as a function of the ratios TPR20 10, are in good agreement with computed results. Quality index values were correlated to mean incident energies of x-ray beams used in radiotherapy. The experimental setup has also provided information regarding the softening effect on the off-axis beam, which can be used in clinical computer dosimetry to correct conventional zero field size tissue maximum ratio.

Image Processing, Computer-Assisted↗
PubMed1978

A computer-assisted three-dimensional treatment planning system.

The three-dimensional treatment planning system developed at the Rhode Island Hospital visualizes the spatial interrelationships of the radiation beam, the tumor, and the adjacent organs within the patient. It is possible to rotate and vary the scale of the display to better comprehend the extent of these structures. By viewing the display as if from along the radiation beam, one can design shaped treatment fields which best suit the three-dimensional nature of the disease. With this system, it is possible to reduce the volume of normal tissue which would typically be irradiated if two-dimensional treatment planning techniques and assumptions were employed.

Computers↗
PubMed1987

Interstitial brachytherapy of malignant brain tumors using computed tomography-guided stereotaxis and available imaging software: technical report.

The implantation of radioactive sources into malignant intraaxial brain tumors, interstitial brachytherapy, is a theoretically attractive treatment for these nearly uniformly fatal lesions. Optimal application of this treatment modality requires careful preoperative planning, computer-assisted dosimetry, and computed tomography-guided stereotactic implantation of the isotope-bearing catheters. A method is presented by which available computed tomographic imaging software can be used with a standard radiotherapy treatment planning computer and the Brown-Roberts-Wells stereotactic system for preoperative imaging, dosimetry planning, and brachytherapy catheter insertion. Dedicated computer facilities are not required, making this method available to any neurosurgeon with access to a current generation computed tomographic scanner.

Brachytherapy↗
PubMed1975

Backgrounds of computer-assisted treatment planning in radiation therapy.

Interaction of ionising radiation and living materials causes biological damage of tempory or permanent nature. In radiation therapy this phenomenon is used in a controlled fashion in order to stop the proliferation of malignant cells, while at the same time limiting the permanent damage to healthy tissues and organs to at least tolerable levels. Because of the often relatively small differences in response of malignant growths and normal tissues, the margins between tolerable and intolerable are so small that the greatest precision in treatment planning and execution is required. The nature of this treatment agent implies that the radiation therapist has to rely very much on instrumentally obtained and processed information, in all phases of this medical activities around the patient. In this paper a description is given of the backgrounds of computer-assisted methods which have enabled modern individualised and optimised planning for therapy with high enery X - and gamma beams.

Cobalt Radioisotopes↗
PubMed1975

[The effectiveness of treatment for breast cancer patients].

The study of late results of treatment in 1166 patients with breast cancer permitted to find the percentage of a 5-year survival to be equal to 55.58, 37.93% of patients survived for 10 years, 28.25% -- for 15 years. In the first stage a 5-year survival was 87.20%, while in the second and third -- 57.7% and 31.56% of patients survived for 5 years, accordingly. The modern methods of radiotherapy (radiosurgical method, interstitial gamma therapy with Au-198 granules, distance grammatherapy on the machine LUCH) enhanced the efficacy of therapeutic measures in patients with widespread breast cancer. A complex diagnosis -- cytology, non-contrast mammography and mathematical analysis by means of a computer contributes to recognition of early forms of breast cancer.

Adenocarcinoma↗
PubMed1988

Computer graphics in medicine: a survey.

Increased interest is presently given to three-dimensional (3-D) medical applications due to simultaneous emergence of high-resolution imaging systems and computer graphics techniques. This paper intends to present a survey of this field together with discussion and prospective views. The general framework is composed of six parts: data acquisition and preprocessing, polygonal object representation, voxel description, system architecture, medical applications, and prospects. Data base acquisition includes characterization of imaging modalities and medical specificity. Preprocessing schemes are directed to improvements (filtering), windowing, and spatial anisotropy (linear or spline interpolation). The two following sections are devoted to descriptions of the main object representations. Particular emphasis is given to optimal contour approximation, surface triangulation, mathematical surfaces on one hand, and cuberille and voxel representations on the other. Display capabilities--hidden surface removal, surface normal shading, structure enhancement--and data base structuration--hierarchical and nonhierarchical (graph and tree encoding)--are, respectively, described. An overview of 3-D systems is further given (Section V), and features of medical applications are reviewed and gathered in basic functionalities, surgery, and radiotherapy specifications (Section VI). The last section provides some prospective views on reconstruction from a few projections, model-guided labeling, multimodality image overlay, and local image network. Some of these issues are illustrated by examples of 3-D images.

Computer Graphics↗
PubMed1977

[Optimization in planning and application of 60 Co gamma irradiations - analysis of the problem (author's transl)].

As an aspect of the complex problem of optimization in therapeutical transmission of radiation energy to Man, the dose distribution within a cross-sectional area of the body is considered. For the judgement on optimal dose distributions, involving judgement on irradiation technique, boundary conditions are needed which encompass important parameters of a dose distribution (= criterion for optima). For computer-assisted optimization the boundary conditions are to be scheduled by an appropriate algorithm. The parameters describing a dose distribution are indicated. Practical utilization of computer-assisted optimization of dose is represented by means of two optimization schedules.

Cobalt Radioisotopes↗
PubMed1978

[Possibilities, limitations and errors with ultrasound tomography in computer-assisted treatment planning (author's transl)].

Ultrasound tomography provides two-dimensional images, true in scale, of sonographic interfaces within nearly every sectional plane desired; it has become especially important, therefore, in irradiation planning. Complementary to results from a therapy simulator, an improvement in localization of tumor and target volume or of critical organs and of tissue inhomogeneities is possible. The hard-copy of gray-scale sonotomograms furnishes all essential geometric and anatomical input data needed for electronic systems used in irradiation planning. Technical, physical and diagnostic limitations of the method are stated. The possible systematic or technical-instrumental errors in sonographic treatment planning are discussed and the necessary calibration controls specified.

Abdomen↗
PubMed1978

[Computer-assisted estimation of the dose distribution in intracavitary radiation therapy (author's transl)].

A new version of a computer-assisted method for determination of the dose distribution in the pelvis of female patients treated with sealed radioactive radium or caesium sources is outlined. The position of the sources in a coordinate system centered on the symphysis is determined stereoradiographically. The dose values are calculated either for singular body points or for points situated on transversal, frontal and sagittal planes through the symphysis or for planes parallel to these. In consideration of the fact that for each patient the anatomical position of the calculation planes can be reproduced with sufficient precision, it is possible to cumulate on each plane the dose values obtained from treatment performed at different times. Experimental controls show good agreement between calculated and measured dose values. Some clinical examples of dose calculation for sagittal planes and of cumulated dose values for a frontal plane 7.4 cm underneath the symphysis are presented.

Cesium Radioisotopes↗
PubMed1980

[First report of experiences with interstitial radiation therapy of the prostatic carcinoma using 125-I-seeds: indication, practical performance and radioprotection (author's transl)].

The practical and organizing performance of interstitial radiation therapy with 125-I-seeds in prostatic carcinoma is reported. Precautions and measurements for radioprotection are emphasized. First evaluations of these measurements show that this therapeutical technique can be performed in complete accordance with the directive for radioprotection. The computer-assisted isodose-planning and the in-vivo-measurements in the rectum, urethra and bladder confirm the steep decrease of the dose outside the irradiated focal volume. Hence, inflammatory symptoms accompanying the therapy are markedly allayed in comparison with percutaneous radiation therapy, in spite of a higher tumor dose. Because of the extensive operation, attention must be paid to the strict observation of indication criteria.

Brachytherapy↗
PubMed1980

[Computer-assisted irradiation planning by means of computed tomography (author's transl)].

Operation of the computer tomograph combined with a computer for irradiation planning leads to an optimization of radiotherapeutic efforts. By means of a careful carrying-over of computed tomographic data into the computing system the demanded homogeneous dose distribution with a deviation rate of +/- 10% may be accomplished to a large extent for any given target volume. At the same time this method achieves an optimal sparing of the sound or else critical organs. An evaluation unit independent of the diagnostics ought to be available, as this renders possible the adaptation of the CT cross-sections of interest under individual aspects.

Computers↗
PubMed1980

[Quality assurance of brachytherapy by means of interactive computer-assisted planning of the dose distribution using visual optimization (author's transl)].

Not earlier than with present generation of afterloading apparatuses,--efficient, reliable and appropriate for many purposes,--it was possible in brachytherapy to give up the previous impractical application techniques. Brachytherapy thus has found the widespread use it merits because of its good results. Additional utilization of a computer for the planning of dose distributions will guarantee the quality possible now in brachytherapy. To that end, a method of computer-assisted planning is described. It can be used for different application techniques. Further improvement of the results obtained till now is discussed in detail.

Brachytherapy↗