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Biomedical subjects

O Mattsson

Publications and source records attributed to O Mattsson.

At least 19 recordsLinked to original sources
PubMed1997

Practical implementation of enhanced dynamic wedge in the CadPlan treatment planning system.

The Varian CadPlan algorithm for computation of relative dose distributions and monitor unit calculations for Enhanced Dynamic Wedge (EDW) fields is based on a combination of open field beam data and Segmented Treatment data Tables. Calculation of dose by the pencil beam convolution model uses scatter kernels and boundary kernels to create the distribution. The principles of the pencil beam convolution model is presented. Comparison of measured and calculated monitor units and relative dose distributions showed good agreement and the deviations are within international accepted tolerans. Test results indicate that the EDW model works satisfactorily for all energies and wedge angles.

Particle Accelerators↗
PubMed1997

Fluence non-uniformity effects in air kerma determination around brachytherapy sources.

In ionization chamber dosimetry close to brachytherapy sources, the non-uniform photon fluence in the vicinity of the air cavity of the ionization chamber must be corrected for. In this paper, experimentally determined relative non-uniformity correction factors are determined for a PTW23331 chamber and a number of Farmer-type chambers. It is concluded that the 'anisotropic' theory of Bielajew agrees better with the experimental results than the 'isotropic' theory of Kondo and Randolph. The experiments show that neither the material choice nor the radius of the central electrode have any significant effect on the non-uniformity correction factors. Experiments on the wall-material dependence in the non-uniformity correction factor, which is predicted by the anisotropic theory, were inconclusive. Parameters for the Farmer-type chambers for calculation of theoretical non-uniformity correction factors are given. Data to derive anisotropic fluence non-uniformity correction factors are given in tabular form. An error in the Kondo and Randolph equations is reported and the corrected equations presented.

Biophysical Phenomena↗
PubMed1996

Structure and organ specificity of an anionic peroxidase from Arabidopsis thaliana cell suspension culture.

The predominant peroxidase (pI 3.5) (E.C. 1.11.1.7) of an Arabidopsis thaliana cell suspension culture was purified and partially sequenced. Oligonucleotides were designed and a specific probe was obtained. A cDNA clone was isolated from an Arabidopsis cell suspension cDNA library and completely sequenced. The cDNA clone comprised 1194 bp and encodes a 30 residue signal peptide and a 305 residue mature protein (Mr 31,966). The sequence of the mature protein is 95% identical to the well-characterized horseradish peroxidase HRP A2 and has therefore been designated ATP A2. Three introns at positions identical to those found in Arabidopsis and horseradish genes encoding cationic peroxidases were identified. RT-PCR analysis revealed root-specific expression.

Amino Acid Sequence↗
PubMed1995

Ionization chamber dosimetry of proton beams using cylindrical and plane parallel chambers. Nw versus Nk ion chamber calibrations.

Determinations of the absorbed dose in a 170 MeV proton beam have been performed using seven ionization chambers of different types: five cylindrical (two FWT IC-18 and three NE-2571, of which one was modified to have the central electrode made of graphite) and two plane parallel (NACP-02 and Roos FK-6). The ionization was converted into absorbed dose in the proton beam according to the generalization of the formalism provided by the IAEA Code of Practice (TRS 277), which enables the use of the same equations for all kinds of beam used in radiotherapy. The absorbed dose obtained with the two IC-18 chambers, a chamber type commonly used as a reference in proton beams, was up to 1.5% lower than that obtained with the Farmer NE-2571 chamber, which was used as the reference in this work when calibration factors in terms of NK were used. To investigate this difference, experimental ND factors for six chambers (the two IC-18 chambers, the NACP-02, the FK-6 and two of the NE-2571 chambers) were determined in a high-energy electron beam. The procedure commonly recommended for plane parallel ion chambers was used for all the chambers, using the same reference chamber, a Farmer NE-2571. In the 170 MeV proton beam all the ND factors yielded consistent absorbed dose determinations within the estimated experimental uncertainties. This finding calls into question the value of the product kattkm for the IC-18 chamber given by the IAEA Code of Practice used in this comparison, and points at possible chamber to chamber variations that theoretical kattkm factors cannot predict. The investigations enabled the determination of the Pwall(60Co) factor of the Roos FK-6 plane parallel chamber, yielding 1.003 +/- 0.5%, and a correction for the effect of the aluminium central electrode of NE-2571 chambers in proton beams, equal to 1.003 +/- 0.4%. Two of the chambers (the plane parallel FK-6 and the modified cylindrical NE-2571) were provided with calibration factors in terms of absorbed dose to water, Nw, at the quality of 60Co by the Primary Standard Dosimetry Laboratory in Germany (PTB). Using the Nw formalism excellent agreement was found with the determination based on the experimental ND, giving support to the implementation of the NW procedure in therapeutic proton beams.

Humans↗
PubMed1990

Employment of hydrolytic enzymes in the study of the level of DNA methylation.

A new method for the determination of the level of DNA methylation was established. The method involves enzymatic hydrolysis of DNA by nuclease P1 and bacterial alkaline phosphatase, and separation of the resulting deoxyribonucleosides by HPLC. By this method, DNA was hydrolysed completely to the five deoxyribonucleosides and the complete base composition was determined. Pairing bases were shown to occur in similar amounts, and analysis could be performed on as little as 1 microgram of DNA with a high degree of reproducibility. Among other enzymes hitherto used in order to hydrolyze DNA, micrococcal nuclease, phosphodiesterase II and nuclease P1 have been shown to cause deamination of deoxyadenosine, while deoxyribonuclease I, phosphodiesterase I and bacterial alkaline phosphatase have been shown to be sensitive to contamination by RNA, and to release 5-methyldeoxycytidine at a slower rate than the other four deoxyribonucleosides. Neither of these effects was seen with the new method.

Alkaline Phosphatase↗
PubMed1990

Absorbed dose in water. Comparison of several methods using a liquid ionization chamber.

In the present investigation a liquid ionization chamber has been used as a transfer instrument for the quantity absorbed dose in water in a cobalt-60 gamma-ray beam. The characteristics of the liquid ionization chamber are described. The transferred dosimetric information has been compared with absorbed-dose determination using air-ionization-chamber dosimetry, water calorimetry and ferrous-sulphate dosimetry. The agreement between the different measured absorbed-dose values is very good, i.e. within 0.2%. This is an indication that the consistency in the methods used to determine absorbed dose in water is good. The impact of the new standard for air kerma in air, introduced in 1986 by the BIPM, on the air-ionization-chamber dosimetry is investigated. It is shown that any differences in the dosimetry when using the old or the new set of data cancel out for the cobalt-60 beam. The investigation also shows that the value of epsilon mG for the ferrous-sulphate dosimeter recommended in ICRU 35 for electrons can be used also in cobalt-60 beams.

Calibration↗
PubMed1983

Quality assurance in radiographic imaging included in the film marking procedure.

Quality assurance for the radiographic processing can only be obtained by the aid of a continuous densitometric control. A method is described which uses a densitometric step wedge included in the marker equipment. It gives a constant radiation dose to the marking area. The step wedge is exposed simultaneously with the film marking. Disturbances in the radiographic procedure can thus immediately be detected.

Methods↗
PubMed1982

Scintigraphic spleen volume calculation.

An uncomplicated scintigraphic method for estimation of the spleen volume is described. Two films individually exposed with the gamma camera represent the basis for calculation according to the same principle as used for the heart volume. By the use of Co indicators a distance reference is obtained. No extra arrangements for the patient are necessary and the examination is performed during the conventional liver-spleen scintigraphy with 99Tcm colloid.

Body Surface Area↗
PubMed1978

Effect of somatostatin on intestinal motility.

The effect of somatostatin on intestinal motility has been investigated. The demonstrated inhibition of the motility has proved to be suitable for performing double contrast examinations of the small intestine, particularly as the tolerability to somatostatin is better than to other comparative substances.

Drug Evaluation↗
PubMed1975

Effect of 16,16-dimethylPGE2 on gastric emptying and intestinal transit of a barium-food test meal in man.

The effect of 140 mug of 16,16-dimethyl PGE2 on gastric emptying and intestinal transit of a barium-food mixture has been studied in 8 healthy male volunteers. The propagation of the test meal was followed from the stomach to the colon by fluoroscopy wit repeated photograph ic recording. It was found that this analog significantly enhanced the rate of gastric emptying in most subjects, and the food-contrast medium also appeared sooner in the colon following the prostaglandin analog. In addition, the duodenum and the first part of the jejunum had a flaccid and dilated appearance on several occasions after administration of prostaglandin. The more rapid emptying of the stomach after administration of the prostaglandin analog is probably explained by a decreased duodenal resistance towards the gastric outflow; the earlier appearance of contrast in the colon could partly be due to the more rapid gastric emptying following administration of the prostaglandin analog.

Adult↗