Biomedical subjects
Publications and source records attributed to T Väyrynen.
1,2-Epoxy alkanes from C3 to C8 were reacted with DNA, deoxyguanosine and 4-(p-nitrobenzyl) pyridine (NBP). DNA was hydrolyzed at neutral pH to release 7-alkylguanines. The products were analyzed by HPLC. The epoxides reacted largely according to the chain length, shorter epoxides being more reactive. Substitutions through carbon 1 predominated. Reactivity with NBP was almost equal between the epoxides.
Dose distributions calculated by six different treatment planning systems (TPSs), used by the hospitals in Finland or in Russia, were compared with measured dose distributions. Five typical cases of irradiation were selected: regular fields, oblique incidence, irregular field, wedge field and inhomogeneity in a water equivalent phantom. The beam data for each TPS where those pertaining to the beam where the comparative relative measurements were performed. The results indicate that the dose distributions produced by different TPSs can differ from each other as well as from the measured dose distributions up to a level which is not acceptable in terms of the ICRU recommendations. Greatest differences seem to be related to the omission or undue consideration of the scatter components of the beam.
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The impurities present after use in 99Mo- 99mTc-generators produced by four different manufacturers were investigated by means of the energy spectrum and half-life measurements. The generators produced with fission contained only a few impurities, and the half-lives of their nuclides were relatively short. The only generator manufactured using neutron bombardment contained several nuclides whose half-lives were in a range of a few months, but also a 60Co nuclide whose long half-life may give rise to difficulties in destroying the generator.
Different mathematical formulas capable of replacing CRE have been analyzed. The purpose was to develop an expression which would yield a value identical with CRE for regular treatment schedules, but would represent more clearly and more truthfully the radiation damage of tissue. This quantity has been called cumulative radiation damage (CRD). Its unit is adequately called CRD unit. CRD does not require a separate gap correction, as does CRE, it is easy to use, explicit and unambiguous. CRE, CRD and some other formulas have been compared in different types of radiation therapy.
Using two infusion anaesthesiamethods for laryngomicroscopy in 187 non-selected patients we studied the recovery phase with the aid of a special questionnaire filled in by the recovery room nurse. Premedication was with Thalamonal and atropine. Muscle relaxation was achieved by a succinylcholine drip. Induction doses: fentanyl 0.05-0.1 mg and thiopental 3-5 mg/kg bodyweight (Th-group) or diazepam 10-20 mg and ketamine 1 mg/kg bodyweight (K-group). Infusion doses: Thiopental 11.7 mg/min. (Th-group) or diazepam 0.2 mg/min. and ketamine 2 mg/min (K-group). Anaesthesia lasted for 20-30 min. We observed and noted during recovery: Breathing, cough-frequency and -quality, alertness, reaction to speech and stimulation, orientation, motor behaviour and well-being. Anaesthesia was sufficient in both groups. The patients of the K-group woke up earlier and their laryngeal reflexes seemed to stabilize quicker than in the Th-group. Because of the elevation of blood pressure caused by the stimulation of the laryngoscopy both methods are not recommended for patients at risk from high blood pressure.
Owing to contamination by long-lived radio-isotopes, the residual activity of an old 99Mo-99mTc generator may be large enough to prevent its disposal. The long-lived impurities of one generator were determined by energy spectrum and half-life measurements. In this generator 46Sc, 51Cr, 60 Co, 92mNb, 95Nb and 124Sb nuclides were found. Only the half-life of 60Co exceeds 3 months, thus a moderately long storage of the generator reduces the activity, and its disposal is then safe.
The CRE concept is not applicable to the assessment of the effect of combined radiotherapy when external and intracavitary radiations are given alternately and with unequal doses. Because of the numerous recurrences, we had to change our radiation treatment schemes for carcinoma cervix uteri, and we attempted, on a theoretical basis, to acquire the same biological effects as Joslin with his own method. In the comparison of different schemes we used as slightly modified approximate CRE and the "nominal dose" presented by Kellerer. In this paper we have presented the treatment schemes we used and the methods for calculating the biological effect in combined treatments. Moreover, we have examined the applicability and compatibility of the above methods in comparing the effects of different combined radiation treatment schemes.
With 260 children under 12 years of age we tried to cannulate the subclavian vein during 3 years 455 times, and were successful 391 times (85.9%). 43.8% of the patients were younger than 1 year. The success rate correlated to the childrens' bodyweight and was less with lower weight of the patients. - In 68.8% of the cases we found the tip of the cannula in the upper caval vein, 19.9% were in the internal jugular vein, and 6.1% were in the opposite subclavian vein. - In this study participated 7 members of the staff and 8 specializing doctors; catheterizations per participant, mean = 30,2, SD 21,49, minimum 6, maximum 65. - Cannulas functioned for 5 +/- 2, max. 19 days. - The most serious complications were 2 pneumo- and one pneumo-hydrothorax, 2 times suspicion of thrombosis and 1 hemorrhage due to a not known hemophilia. None of the complications caused therapeutical problems.
The MTFs of three different gamma camera systems have been measured using two methods. In one method a step function was used as the object and the calculations were made by means of a pocket calculator. This method has been compared with a conventional line source method, where a computer is needed in performing the calculations. The methods give the same results with a fairly good accuracy. Both of the methods are well suited to a regular control of the condition and functioning of a gamma camera, provided that the camera is connected to a data-processing system so that the profile curves measured can be converted into the digital form.
The accuracy of computerized dose planning depends essentially on the computer program. The quickest and simplest way to assess the accuracy of a commercial program is to compare the results of the computer calculations with measured values. The present report deals with the accuracy of the RADPLAN dose planning program in different situations easy to control. The test methods are also applicable to other corresponding systems.
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