[The CT-stereotaxic neutron brachytherapy of brain tumors with californium sources on the ANET-B apparatus]. / KT-stereotaksicheskaia neitronnaia brakhiterapiia opukholei golovnogo mozga kalifornievymi istochnikami na apparate "ANET-B".

A method for stereotaxic intratissue radiotherapy of brain tumors based on the findings of computed tomography is described. Radiosurgical implantation of sources with increased 252Cf content emitting mixed neutron + gamma-radiation was accomplished by means of an ANET-B apparatus by the afterloading method. Neutron irradiation is particularly effective in patients with malignant tumors possessing a large fraction of cells in a state of deep anoxia. Dosimetric planning was conducted by means of an original computer system. Devices and radiation-technical equipment for adaptation of the ANET-B apparatus for irradiation of neurosurgical patients are described. The indications for the use of this method and its place among the complex of measures for the treatment of patients with new growths of the brain are discussed. The first experience in using CT-stereotaxic neutron brachytherapy with californium sources on the ANET-B apparatus for the treatment of 6 patients with malignant glial tumors of the brain is dwelt on.

[Computerized system of dosimetric planning of interstitial multiposition stereotaxic irradiation in neutron therapy of brain tumors]. / Kompiuternaia sistema dozimetricheskogo planirovaniia vnutritkanevogo mnogopozitsionnogo stereotaksicheskogo oblucheniia pri neitronnoi terapii opukholei golovnogo mozga.

A computerized system PLUT-B intended for a dosimetric design of stereotaxic neutron brachytherapy of brain tumors, was developed. It is capable of simulating dose distribution in various parameters of irradiation, manipulating them, retaining the surgical aspects within the field of vision, and arriving at an acceptable dosimetric plan. The system permits visualization of a target with an applied dose field in the multiwindow mode, layer-by-layer vision in any direction, displaying a scheme of implantation, and drawing up of maps of isodose distributions. It is intended to be used by a physician, convenient in operation, the time at the design stage is 35-40 minutes.

[The ANET-B apparatus with 252Cf sources for intracavitary radiotherapy of cancer patients]. / Apparat ANET-B s istochnikami 252Cf dlia provedeniia vnutripolostnoi luchevoi terapii onkologicheskikh bol'nykh.

The authors give a brief description and the basic physico-technical characteristics of the AHET-B radiation therapeutic unit with 252Cf sources (the total radionuclide quantity is 2100 micrograms) for intracavitary radiation of malignant neoplasms of the uterine neck, uterine body and rectum. The results of the physical and technical testing and of the main dosimetric and maintenance study are given. Measures for the radiation safety of the unit users are described. The above experiments made it possible to begin clinical testing of the unit. 46 uterine neck cancer, 65 uterine body cancer and 10 rectum cancer patients were treated from February 1983 to February 1987. The preliminary results of the clinical testing are positive.

[Biological action of the radiation from high-activity 252Cf sources]. / Biologicheskoe deistvie izlucheniia istochnikov 252Cf vysokoi aktivnosti.

The radiobiological properties of mixed gamma-neutron radiation from 252Cf sources of high activity have been studied on chinese sand hamster cell culture. The source used has contained 1500 micrograms of radionuclide. In the study of radioprotective effect of hypoxia on the cells it is proposed to use anoxic attenuation factor (AAF) instead of the widely used oxygen enhancement ratio (OER). The comparison of radiation doses leading to a 90% decrease in initial cell viability provided the value of relative biological effectiveness (RBE) of 1.8 +/- 0.2 for mixed radiation and 2.2 +/- 0.2 for the neutron component at the dose of 10 Gy/h. AAF of mixed radiation was estimated as a ratio of radiation doses resulting in the above decrease of the cells viability, defined for the cells irradiation under anoxic or normoxic conditions. Simultaneously, AAF has been defined for gamma-radiation of 60Co. AAF has been shown to be 1.7 +/- 0.2 for 252Cf at dose rate of mixed radiation 10 Gy/h and 3.3 for 60Co. The index of "play back" is proposed as a more objective criterion of any modifier capability to overcome the radioprotective effect of hypoxia on tumour cells. The use of 252Cf sources of high activity instead of 60Co for intracavitary radiotherapy will increase the damage to hypoxic cells of malignant tumours.

[Topometric preparation of patients with cervix cancer for intracavitary irradiation on the ANET-B apparatus]. / Topometricheskaia podgotovka bol'nykh rakom sheiki matki k vnutripolostnomu oblucheniiu na apparate ANET-B.

The authors worked out methods of topometric investigation of cervical cancer patients during preparation for intracavitary irradiation using 252Cf fast neutron sources. The use of balloon catheters made it possible to determine a coefficient of projection enlargement in the point of interest, to determine accurately the distance between endostats, sources and contrasted organs of interest: the bladder and rectum. The results of the studies were used for individual design of intracavitary treatment as well as for the determination of radiation exposure of the pelvic organs in 38 patients. The patients received a total of 138 investigations.

[Analysis of the reproducibility of conditions of intracavitary irradiation of patients with cervix cancer]. / Analiz vosproizvodimosti uslovii vnutripolostnogo oblucheniia bol'nykh rakom sheiki matki.

The paper is concerned with the results of an analysis of reproducibility of conditions for intracavitary irradiation of 20 cervical cancer patients using metracolpostat, a combined therapeutic endostat consisting of 3 tubes: the central one to introduce radiation sources into the cervical canal and cavity of the uterus and 2 lateral ones with ovoids to deliver the sources to the vaults of the vagina. Topometric investigations for each patient were performed 4 times: before the first session of fractionated intracavitary irradiation with high activity 252Cf sources using the ANET-B unit and after each session of irradiation. It was shown that discordances between distances from the central endostat to the right and left lateral ovoids determined during roentgenotopometric preparation of each patient and taken as a basis of dosimetric design, and discordances between these distances determined as a result of roentgenotopometric control after each laying, are a random value distributed according to the normal law.

[Morphology of cancer of the cervix uteri and surrounding tissues after preoperative intracavity therapy with high-energy 252Cf radiation sources and 60Co]. / Morfologiia raka sheiki matki i okruzhaiushchikh tkanei posle predoperatsionnoi vnutripolostnoi terapii istochnikami izlucheniia 252Cf vysokoi moshchnosti i 60Co.

Comparative morphological study of uterine cervix carcinoma in 21 patients after a intracavity radiotherapy by 252Cf and in 18 patients treated with 60Co is performed. Total focal dose in a point A in both cases was 30 Gy. Morphometric study with the calculation of a volume correlation between stroma and tumour parenchyma in the two main groups and a control (untreated) group with a subsequent determination of a damage index has been done for the assessment of therapy. Both sources of radiation had an approximately similar efficiency in the treatment of superficial exophytic forms of tumour growth. 252Cf was biologically more efficient in the treatment of the deeply invasive forms of growth. The index of damage in 252Cf and 60Co was 96.5 and 84, respectively. Likewise the alterations in the surrounding normal uterine tissues after the intracavity irradiation with fast neutrons were more pronounced than those provoked by 60Co.

[Computer tomography in determining lung density for irradiation planning]. / Komp'iuternaia tomografiia v opredelenii plotnosti legkikh pri planirovanii oblucheniia.

The paper is concerned with the problems of the determination of lung density in the irradiation planning for thoracic tumors using CT. The mean value of density that was equal to 0.252 +/- 0.118 g/cm3 was obtained proceeding from a study of 118 CT sections of the lungs during quiet breathing. The respective value gets equal to 0.162 +/- 0.022 g/cm3 in deep breathing and 0.282 + 0.050 g/cm3 in full expiration. The values of lung density can vary in different persons. The range of measured values is equal to 0.119 = 0.441 g/cm3 in quiet breathing. The values of lung density vary within the limits of one section from the minimum value in its front part to the maximum one in the rear part. To determine lung densities that are representative for radiation therapy, CT should be performed with a patient breathing quietly in an uninterrupted manner. In significant deviations of density values from those accepted for isodose value calculation, individual consideration of lung density for each person is found appropriate.

[Experience in using echotomography in planning the irradiation of cervical cancer patients]. / Opyt ispol'zovaniia ékhotomografii v planirovanii oblucheniia bol'nykh rakom sheiki matki.

A possibility to use echotomography (ET) in the topometric preparation of patients with cervical cancer for radiation therapy is shown. In addition to ET computerized tomography (CT) was performed to 15 patients at the level of classic points A and B. Proceeding from the results of both studies topometric maps were prepared. Using the maps distances between points of interest were compared. It was shown that the mean value of the distance from the middle of the uterine cervix to the bladder posterior wall was 24 and 23 mm in ET and CT, respectively. Some methodological problems of ET for irradiation planning are discussed. It should be noted that ET provides ample information on the small pelvic anatomical structures that are of interest in gamma-beam and intracavitary radiation therapy of cervical cancer. ET positive features are its safety for a patient, insignificant costs and an opportunity to get information for a 3-dimensional irradiation planning.

[Use of computed tomography for planning intracavitary radiotherapy of cervical cancer]. / Primenenie komp'iuternoi tomografii dlia planirovaniia vnutripolostnoi luchevoi terapii bol'nykh rakom sheiki matki.

CT potentialities for irradiation planning have been demonstrated as a result of a study of 20 cervical cancer patients, Stages I-II, using a computerized tomograph for topometric preparation for intracavitary therapy with afterloading units, and subsequent gamma-beam therapy. Complete information on sections that are necessary for clinicodosimetric irradiation planning, has been obtained with the help of digital radiography, transversal tomography and mathematical reconstruction of secondary sections. The study was performed by inserting a centering mount and metrocolpostat after a preliminary determination of A point on the simulator. An effect of the degree of the bladder filling on the organs located in a given section has been shown. It has been established that the degree of the bladder filling at the level of A and B points does not influence a distance from its posterior wall to the metrostat. It is assumed that intestinal radiation injuries can be prevented by controlling the degree of the bladder filling.