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Biomedical subjects

M Tatcher

Publications and source records attributed to M Tatcher.

At least 19 recordsLinked to original sources
PubMed1991

Total-skin electron irradiation for cutaneous T-cell lymphoma: the Northern Israel Oncology Center experience.

Total-skin electron irradiation (TSEI) is effective and frequently used in the treatment of cutaneous T-cell lymphoma. A treatment technique has been developed at our center, using the Philips SL 75/10 linear accelerator. In our method, the patient is irradiated in a recumbent position by five pairs of uncollimated electron beams at a source to skin distance of 150 cm. This method provides a practical solution to clinical requirements with respect to uniformity of electron dose and low X-ray contamination. Its implementation does not require special equipment or modification of the linear accelerator, 19 of 23 patients (83%) with mycosis fungoides, treated by this method, achieved complete regression of their cutaneous lesions.

Adult↗
PubMed1990

Radiation qualities of x-ray beams in cooperative clinical trials.

X-ray beams are usually described by "MV" numbers which represent accelerating potentials (AP) and approximations to the maximum energies in the photon spectra. However, these numbers do not uniquely specify the properties of the beams. Current high energy photon dosimetry protocols specify radiation quality in terms of a measured ionization ratio which is equivalent to the ratio of the tissue-maximum ratios at depths 10 cm and 20 cm, for field size 10 cm X 10 cm [TMR)20(10]. For convenience, the American Association of Physicists in Medicine introduced a new parameter, known as the Nominal Accelerating Potential (NAP), which was derived from (TMR)20(10) and features values in MV units that are similar to those of the conventional accelerating potentials. (TMR)20(10) and Nominal Accelerating Potential may be considered to be expressions of the penetrating powers of x-ray beams. We determined (TMR)20(10) and Nominal Accelerating Potential for 460 treatment machines with stated accelerating potentials from 4 MV to 25 MV in the Quality Assurance Review Center's files of machine data from institutions that participate in cooperative clinical trials. The results demonstrate appreciable variability of the two parameters at each stated accelerating potential, with overlapping of adjacent groups of machines. It is concluded that the manufacturers' MV numbers do not reliably identify x-ray beams in terms of their depth dose properties. To promote standardization and consistency of energy specification in clinical trials as well as in general practice, we propose that x-ray beams be designated by their Nominal Accelerating Potential values as an adjunct to the use of (TMR)20(10) in radiation therapy.

Humans↗
PubMed1989

Experience in the treatment of localized carcinoma of the prostate by definitive external irradiation.

One hundred and sixteen patients with stages A2, B, and C histologically proven adenocarcinoma of the prostate were treated by definitive radiation. They received first whole pelvic irradiation, 46 Gy in 23 treatments, followed by a prostatic "boost" of 20 Gy in 10 fractions. Five-year survival rates varied between 39 and 84%. Prophylactic hormonal manipulation and transurethral resection of the prostate (TURP) did not influence survival figures. Complications of radiotherapy were in an acceptable range. It is concluded that external beam irradiation is an effective, simple, and usually well-tolerated treatment modality for localized carcinoma of the prostate. Stage and degree of differentiation and response of the primary tumour to radiation are predictors of patient outcome. There is no advantage in prophylactic hormonal manipulation, and TURP does not influence survival according to our experience.

Adenocarcinoma↗
PubMed1989

Field matching considerations in craniospinal irradiation.

Radiotherapy of the craniospinal axis in leukemia and medulloblastoma patients usually involves parallel-opposed lateral cranial fields adjacent and orthogonal to a posterior spinal field. Most current treatment protocols require rotation of the cranial fields to compensate for the divergence of the spinal field such that the adjacent field edges abut along the match line in the mid-saggital plane. Some departments introduce gaps up to 1-2 cm wide between the matched fields out of concern for overdosing the spinal cord. The behavior of the dose distribution was studied in the junction region of divergence-compensated fields as the separation of their edges varied from 0.5 cm overlap to a gap 1 cm wide. Composite dose profiles and isodose maps were calculated for 60Co and 4 MV photon beams using static and moving junction (feathering) techniques. When the fields are appropriately matched there is no gap between them in the mid-saggital plane and the dose varies smoothly across the junction. Gapping of divergence-compensated fields is detrimental to dose uniformity, producing underdosage in a volume that extends to all depths in the body. With proper localization, there is no way that the commonly accepted critical dose for myelopathy can be exceeded in typical treatments of leukemia patients. It can occur in the treatment of medulloblastoma patients only in the unlikely situation where there is gross overlapping of the adjacent fields. Feathering may be considered as a safety margin against spinal cord damage in medulloblastoma but it is superfluous in leukemia. The importance of treatment machine quality assurance and verification of patient set up geometry are emphasized.

Humans↗
PubMed1988

The Clatterbridge high-energy neutron facility: dosimetry intercomparisons.

Dosimetry intercomparisons have been performed between the Clatterbridge high-energy neutron facility and the following institutions, all employing beams with similar neutron energies: Université Catholique de Louvain, Belgium; University of Washington, Seattle, USA; MD Anderson Hospital, Houston, USA; and Fermi National Accelerator Laboratory, Batavia, USA. The purpose of the intercomparison was to provide a basis for the exchange of dose-response data and to facilitate the involvement of Clatterbridge in collaborative clinical trials. Tissue-equivalent ionization chambers were used by the participants in each intercomparison to compare measurements of total (neutron plus gamma) absorbed dose in the host institution's neutron beam, following calibration of the chambers in a reference photon beam. The effects of differences in exposure standards, chamber responses in the neutron beams and protocol-dependent dosimetry factors were all investigated. It was concluded that the overall difference in the measurement of absorbed dose relative to that determined by the Clatterbridge group was less than 2%.

Calibration↗
PubMed1986

Correlations of dose and time-dose-fractionation factors (TDF) with treatment results and side effects in cancer of the uterine cervix.

Treatment results and side effects were analyzed for 57 patients with stage IB-IIIA cancer of the uterine cervix who received external beam radiotherapy combined with intracavitary insertion of cesium-137 sources. The total dosage and time-dose-fractionation (TDF) factors were calculated at point A and at points of maximum exposure in the rectum and bladder. The overall 5-year survival was 62%, and 78% of the complete responders were free of disease at 5 years. A total of 12 patients (21%) developed rectal complications. Two patients (4%) had rectal fibrosis and proctitis; seven cases of rectal bleeding occurred (12%), and 3 patients (5%) developed rectovaginal fistulas. There was no correlation between dose and TDF at point A and treatment failure or appearance of rectal complications. However, the occurrence of radiation damage in the rectum was consistently associated with high values of TDF when they were calculated in the region of maximal exposure in the rectum. The results suggest that TDF may be a useful parameter for predicting radiation damage in combined external beam and intracavitary treatment of cervical cancer.

Female↗
PubMed1986

A comparison of commercial treatment planning systems when calculating dose under shielding blocks.

Several commercial computerized treatment planning systems were compared when calculating dose under shielding blocks in soft tissue and lung tissue. A test case was studied in which a water-equivalent phantom containing a removable cork insert was exposed to 60Co radiation with and without a lead block in the beam. For simplicity, all cross sections were square and only central axis doses were considered. Manufacturers of treatment planning systems were asked to calculate doses for the test case for comparison with corresponding experimental values determined from ionization chamber measurements. When the initial replies seemed to indicate the existence of errors or misinterpretations, the manufacturers were informed and asked to submit revised values. The results for eight systems exhibit wide variations in the doses under the block, with differences of up to 88% between measurements and calculations. Most of the systems did not take into account heterogeneity and shielding simultaneously. While in comparison with the maximum dose the dose differences under the block are not large and their clinical significance may be debated, better accuracy and more of a consensus would be expected when elaborate computer systems dedicated to radiation therapy deal with a relatively simple problem. The results emphasize the need for caution when users implement the options offered by their treatment planning computers.

Humans↗
PubMed1984

Perturbation of cobalt 60 radiation doses by metal objects implanted during oral and maxillofacial surgery.

The influence on cobalt 60 dose distributions of typical metal parts used in oral and maxillofacial surgery was studied. Relative doses were determined by exposing x-ray films in a polystyrene phantom set-up containing samples of Vitallium, titanium, and stainless steel. Optical densities were converted to doses with the aid of sensitometric curves. The results show that for normal incidence there is a 25% to 40% increase in dose at the entrance side of the metal and a 20% to 25% decrease in dose at the exit side. The enhancement effect falls off rapidly and becomes negligible at about 1 mm from the interface. The reduction effect decreases more gradually and is still evident at distances of a few centimeters. These dose perturbations should be taken into account in the planning of radiation therapy for patients in whom metal objects have been implanted.

Absorptiometry, Photon↗
PubMed1980

Sperm semi-autoanalysis by a combination of multiple exposure photography (MEP) and computer techniques.

A semiautomatic method for sperm analysis is described. The method combines a previously developed multiple exposure photography system with a digitizer connected to a computer. An undiluted specimen is inserted into a 10-mic chamber and the sperms are microscopically photographed for 1 second while illuminated by six short light pulses. On the developed film nonmotile sperms appear very bright, while motile sperms are seen as six-ringed chains. In addition, high magnification photographs of immobilized preheated sperms are taken for morphology analysis. The photographed images are projected onto sheets of paper where the traces of the nonmotile and motile sperms as well as the normal and abnormal forms are marked by a pen. For motility determination, sheets containing the sperm tracks are placed on the digitizer tablet. By means of a sonic pen the coordinates of the ends of the tracks are automatically recorded and the number of motile and nonmotile sperms are counted. Then the percent of abnormal forms are entered at the keyboard. Within a few seconds the computer supplies a printout of the results, including sperm concentration, percent of motile sperms, average velocity and frequency distribution of velocities of moving sperms, percent of abnormal forms, and total number of analyzed sperms.

Autoanalysis↗
PubMed1978

Computer-assisted method for intracavitary radiotherapy of cancer of the uterine cervix.

This paper describes a simple computer system for calculating the radiation dose rate to selected points in the pelvis of a patient treated by gynaecological insertion of applicators loaded with radioactive sources. The calculations are performed on the basis of radiographs made before the sources are placed in the applicators. The system consists of a minicomputer, a teletype and a digitizer. The method allows an optimum loading distribution to be determined within a few minutes once the radiographic images are available.

Computers↗
PubMed1978

Time-dose effects in the matching of adjacent radiotherapy fields.

When adjacent radiotherapy fields are treated in different times, the dose fraction at the junction of the fields is different from that within the portals. When the width of the gab between the fields is adjusted to produce equality of dose at the junction, it will not give equality with respect to radiobiological effect. The authors have used Ellis's NSD equation to take into account time-dose relationships in the matching of adjacent fields. Distribution of physical dose and biologically effective dose in the region near the junction of opposed pairs of parallel 60Co fields are given.

Radiotherapy↗