Measurements of the neutron dose near a 15 Mv medical linear accelerator.

In this work, simplified recombination methods for routine estimation of dose equivalent in mixed (gamma and neutrons) radiation field outside the irradiation field of linear medical accelerators is considered. The author's earlier reported method of H(10) measurements, involving determination of the recombination index of radiation quality, Q(4) by tissue-equivalent recombination chamber was combined with the new method for determination of the photon to neutron dose ratio D(X)/D(n) from the ratio of ion collection efficiencies measured in the investigated radiation field and in two reference fields of gamma and neutron radiations. The method is suitable when the neutron contribution to the total absorbed dose, D(n)/D, is >3%.

Treatment planning software for afterloading brachytherapy.

The subject of this short communication is to present the main features of an interactive treatment planning software package for brachytherapy. The program was initially developed in the Institute of Oncology in Warsaw and based on a minicomputer configuration by the Siemens treatment planning system. Since it was first introduced into clinical practice it has been constantly developed to meet the repractice it has been constantly developed to meet the requirements of a variety of brachytherapy techniques.

Breast phantom for comparison X-ray and polarimetric optical tomography imaging.

Breast phantom made as combination of paraffin and INTRALIPID™ was tested by use of X-ray classical computed tomography and polarimetric optical tomography. The INTRALIPID™ is a liquid commonly used for simulation breast tissues optical properties but it is useless as X-ray phantom. During our tests we have observed that X-ray tomography allows to recognize a proper placement of INTRALIPID™ inclusions inside paraffin medium but we cannot distinguish density of INTRALIPID™ within each inclusions. On the other hand the polarimetric optical tomography allows to distinguish density of INTRALIPID™ (0%, 10%, 20%) in inclusions but with relatively low accuracy of their placement.

Quality control and patient doses in X-ray computed tomography.

Results of quality control (QC) tests for a period of over a year and patient doses were analysed for several computed tomography units in our centre. The results of the QC tests were generally within limits for all of the examined scanners, proving good and stable performance of the systems. The tests were not helpful in predicting breakdowns of the systems such as tube failure. The doses for the same anatomical areas differed between scanners and in some cases exceeded the diagnostic reference levels (DRLs). DRLs are defined for typical diagnostic examinations performed in general hospitals and are not directly applicable to the examinations performed in the oncological centre.

Comparison of results from quality control of physical parameters and results from clinical evaluation of mammographic images for the mammography screening facilities in Poland.

The material for this study comprised control protocols from 248 mammography screening facilities, prepared by physicists employed at 16 Regional Coordinating Centres and the results from the clinical evaluation of mammographic images in 248 facilities in Poland. All mammograms were evaluated independently by three experts selected from a list approved by the national consultant of radiology and diagnostic imaging. The requirements for proper breast positioning, selection of appropriate parameters for exposure and absence of artefacts were fulfilled only in 38 % of inspected mammography facilities. The requirements of the clinical audit were met only in 15 % of the mammography facilities. The requirements for the physical parameters of mammographic equipment were met only in 28 % of them. The requirements of the quality control (QC) tests and clinical audit were not fulfilled only in 19 % of the mammography facilities. Results from the QC of physical parameters are comparable with results from clinical evaluation of mammographic images in 57 % of the mammography facilities in Poland.

The effect of respiratory activity on brain blood flow during exposure to +Gz acceleration.

The effect of respiratory activity on cardiovascular system during the exposure to +Gz acceleration was studied. For simultaneous, beat to beat evaluation of central and global cerebral blood flow, the system based on modified impedance cardiography method was used. The mechanism of modulation of the central and peripheral (cerebral) venous pressures and blood flow by intrathoracic pressure changes, has been shown. The data obtained from these studies suggest that reconsideration of the respiration technique during Anti-GSM seems indispensable.

Comparison of anti-G trousers equipped with bladder and tightening system.

NASA: Two different anti-G flight suits are compared. The first suit uses a bladder system to compress the lower limbs and abdomen and the second uses a tightening system to produce compression evenly for the lower body. Studies were performed using a centrifuge cabin with exposure to acceleration forces up to 2.5 G. Suits were compared for protection efficiency, comfort, complaints, and put on ease. Results of the study, including heart rate dynamics, ear vascular pulsation amplitude, and peripheral vision loss are presented.^ieng

Fourier analysis of the shape of normal and transformed epithelial cells derived from human transitional epithelium.

The aim of this paper is to show the possibility of objective mathematical description of changes occurring in the shape of cells in the process of transformation. The evaluation of the changes in cell shape of the chosen cell lines differing in transformation grade was performed by the use of Fourier analysis of the shape. Any two-dimensional contour can be described with specific accuracy in a mathematical manner using the closed form Fourier series of cosines. The components forming the analysed shape, called harmonics, are independent and uncorrelated measures of their contribution to the total shape. The shape of each cell can be represented by the spectrum of harmonic amplitudes. To quote the paper by Healy-Williams and Williams (1981): "The observed shape is partitioned into series, where gross shape, as elongation or triangularity, is measured by the harmonic amplitudes of the lower harmonic order and increasingly fine scaled surface sculpture is measured at higher orders". The statistically evaluated results allow the objective comparison of the cell shapes of several compared cell lines differing in transformation grades. Malignant transformation is supposed to be a multistep process. The different grades of transformation could be defined by several parameters as changes in the morphology of the cells, their ability to compete with fibroblasts, their life span, their angiogenic potency, their invasiveness in vitro and their tumorigenicity in nude mice. In this paper several human urothelial cell lines of normal and tumor origin differing in their transformation grade (TGr I-III) were compared by the use of Fourier analysis of their shape. TGr I cultures have finite life span but do not need intermittent collagenase treatment to prevent fibroblast overgrowth. TGr II cultures acquire infinite growth potential, here defined as capacity to survive at least 70 passages. They are neither tumorigenic nor invasive. TGr III cultures show infinite growth transformation, increased angiogenicity and ability to invade normal host tissue in vitro. They produce progressively growing tumors in nude mice. The following human uroepithelial cell lines differing in the degree of transformation were studied and compared by statistical evaluation of the harmonic amplitudes describing mathematically the cell shape: Two cell lines derived from human transitional cell carcinoma (TCC): 1. Hu 1703S classified as TGr I, 2. Hu 1703He classified as TGr III. It was found that these two cell lines differ in all harmonics. Two cell lines derived from morphological normal human bladder epithelium: 3. HCV-29 classified as TGr II.(ABSTRACT TRUNCATED AT 400 WORDS)