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K A Johansson

Publications and source records attributed to K A Johansson.

At least 19 recordsLinked to original sources
PubMed1991

Quality audit of radiotherapy with EORTC mailed in water TL-dosimetry.

A mailable TL-dosimetry (LiF) system has been designed and tested for the EORTC Radiotherapy Group for periodic monitoring of radiation therapy machines between and prior to on-site visits. Three TL-dosimeters were enclosed in a capsule which was placed in a holder and irradiated in photon beams in a water phantom. The institutes were instructed to irradiate the capsule to an absorbed dose of 2 Gy. After the irradiation, all capsules with dosimeter, the holder and completed data sheets were returned to Gothenburg for evaluation. The heating procedure used for reading the dosimeters was optimised regarding fading and reproducibility (less than 0.5%, 1. S.D.). The fading of the TL-signal was eliminated by adding an external annealing to the heating procedure. Both supralinearity and energy dependence were tested and routinely corrected for. The dosimeters were individually calibrated. During 1987, 1988 and the first part of 1989, dosimeters were mailed to 22 institutes, participating in clinical trials organised by the Radiotherapy Group. Of the 178 beams measured, 89% were within acceptable levels of variation for the absorbed dose states (less than or equal to 4%). The photon results gave a mean of 1.012 and a standard deviation of 0.025.

Absorption↗
PubMed1991

Entrance and exit TL-dosimetry in the conservative treatment of breast cancer: a pilot study for the EORTC-Radiotherapy Cooperative Group.

Mailed dosimetry, using thermoluminescent dosimeters, can play an important role in quality assurance procedures in radiotherapy. In 1989, a pilot study was started with the main aim to show the feasibility of this method for the multicentre EORTC trial 22881 on the conservative management of breast carcinoma. Two anthropomorphic breast phantoms and six patients with breast carcinoma were irradiated according the prescriptions of the protocol. TLD measurements of the entrance and exit dose were performed in 6 MV tangential X-ray beams. It proved to be possible to correlate the dose measured in the entrance and exit points of the beams to the calculated dose closely under the surface. A thickness of at least 5 mm bolus material must be applied over the dosimeters and a distance of at least 3 cm from the lateral and medial field borders must be maintained in order to reach a clinically acceptable accuracy in the measurements.

Breast Neoplasms↗
PubMed1991

Quality assurance in conservative treatment of early breast cancer. Report on a consensus meeting of the EORTC Radiotherapy and Breast Cancer Cooperative Groups and the EUSOMA (European Society of Mastology).

A consensus on a quality assurance programme of the treatment of early breast cancer was reached in a multidisciplinary meeting of surgeons, pathologists, radiotherapists, physicists and radiographers. Guidelines for treatment preparation and execution have been set up, including careful location and excision with marking of the primary tumour. The target volumes for irradiation of the whole breast and boost area have been defined. Radiation dose prescription rules, specification and checking procedures are given, together with measures to achieve a homogeneous dose within the target volume. The rules for a quality assurance programme in each clinic are designed for checking equipment and treatment method.

Axilla↗
PubMed1991

Primary radiotherapy for glottic laryngeal carcinoma stage I and II. A retrospective study with special regard to failure patterns.

A retrospective study has been made of 302 patients with vocal cord carcinoma stage I and II treated between 1963 and 1983, emphasizing treatment failure patterns. The primary treatment modalities were radiotherapy for 266 patients and surgery for 36 patients. The minimum follow-up was 4 years. After primary radiotherapy there were 63 local recurrences and 7 neck lymph node recurrences, all appearing outside the target volume. The actuarial loco-regional recurrence-free rates at 5 years were 78% for T1, 76% for T2a (normal cord mobility) and 60% for T2b (impaired cord mobility) tumors. The actuarial regional lymph node recurrence-free rates at 5 years were 99, 100 and 93% for T1, T2a and T2b tumors respectively. The actuarial corrected survivals at 5 years were 95, 96 and 79% for T1, T2a and T2b tumors with primary radiotherapy and salvage surgery for recurrence. Salvage surgery was less successful in T2b compared to T1 and T2a tumors. In conclusion, after primary radiotherapy with salvage surgery the loco-regional control rate was high and very similar for glottic cancer T1 and T2a but less satisfactory for T2b tumors. Regional lymph node metastases were not a large problem in any of the subgroups. More effective radiotherapy with higher dose levels or an altered fractionation might increase the local control rate for T2 tumors with impaired cord mobility.

Adult↗
PubMed1987

Quality assurance control in the EORTC cooperative group of radiotherapy. 3. Intercomparison in an anatomical phantom.

Two papers concerning the quality control study organised by the EORTC (European Organisation for Research on Treatment of Cancer) Cooperative Group on Radiotherapy have been published. The medical profile (part 1) and the dosimetric intercomparison (part 2) of the participating institutions were presented. This part (paper 3) presents an integrated clinical and dosimetric investigation in an anatomical phantom. A tonsillar tumour and a homolateral subdigastric node were marked in an anatomical phantom. The institutions were asked to treat the phantom once like an ordinary patient. The phantom was loaded with dosimeters and irradiated. From the results obtained, it can be concluded that we did not find any major dosimetric problem related to absorbed dose calibration or calculation in the phantom. However, several major problems were related to non-optimal planning, treatment technique and dose distribution. The investigation shows the importance of a quality assurance programme for cooperative groups.

Models, Anatomic↗
PubMed1986

Quality assurance control in the EORTC cooperative group of radiotherapy. 2. Dosimetric intercomparison.

The European Organization for Research on Treatment of Cancer (EORTC) has performed site reviews at 17 institutions participating in clinical trials organized by the Cooperative Group of Radiotherapy. In this paper the dosimetric part of the quality assurance control programme is presented. In a previous paper (part 1) the medical profile of the participating centres was presented. In part 3 an integrated clinical and dosimetric investigation in an anatomical phantom will be presented. The deviations between the absorbed dose values, for specific points along the beam axis in a water phantom, determined by us and reported by the hospitals were within an acceptable level of variation (about +/- 3%) for 85, 70 and 71% of the 60Co gamma, X-ray and electron beams, respectively. In some scanning electron beams, too large deviations were found. The flatness and symmetry of the beams were measured. 73% of the X-ray and 60% of the electron beams were within the acceptable levels of variations. Dosimetric recommendations for institutions participating in EORTC clinical trials are presented.

Cobalt Radioisotopes↗
PubMed1986

Quality assurance control in the EORTC cooperative group of radiotherapy. 1. Assessment of radiotherapy staff and equipment. European Organization for Research and Treatment of Cancer.

A quality control study was carried out by the EORTC Cooperative Group of Radiotherapy. From January 1982 to December 1984, 17 institutions were visited by a group of "experts" in radiotherapy and radiation physics. The evaluation included three steps: a comparison of megavoltage units, technical and staff environment, and data present in clinical and radiotherapy charts for each center; radiation physics calibration of photon and electron beams; and radiation physics measurements on a stimulated clinical case using an Alderson Rando anatomical phantom. This paper presents the results of Part 1. The results of Parts 2 and 3 will be analyzed in separate papers. Large variations were observed in the number of patients treated per year, per radiotherapist, per radiation physicist and per technician. On average, 400 patients were treated per year per megavoltage unit, but 8/17 centers treated more than 500 patients per unit per year. The number of simulators was suboptimal in 12/17 centers. These observations were summarized by a workload and staff index, and this index shows that in 5/17 centers major problems are present which make it difficult to comply with all the requirements of EORTC protocols. The quality of work-up regarding tumor extension was considered to be satisfactory in all centers. Dental care in patients irradiated to the head and neck was not well organized in 5/17 centers. Interaction between CT scan and dosimetry treatment planning could be improved in most centers and this should be one of the primary objectives of future quality control.

Brain Neoplasms↗
PubMed1984

The influence of irradiation time per treatment session on acute and late skin reactions: a study on human skin.

A comparison of the radiation effect of altering the treatment time per session in fractionated radiotherapy was performed on human skin with 12 MeV electrons. Four fractions of 7.2 Gy were given within 22 days, once a week. The dose per fraction was administered in 4 min and 32 min, respectively. The dose rate was about 2 Gy/min and the prolonged treatment time was achieved by dividing each dose fraction into three equal subfractions with intervals of 14-15 min. Prolongation of the treatment time resulted in a significant reduction of the skin erythema (p less than 0.001), pigmentation (p less than 0.05) and the degree of telangiectasia at 5 years (p less than 0.001). The relative biological effectiveness (RBE) for the prolonged (32 min), in relation to that of the short (4 min) treatment time, RBE4 min/32 min, was 1.09-1.10 for erythema and 1.07-1.12 for telangiectasia. These findings indicate that prolongation of the treatment time per session has to be adjusted for in clinical radiation oncology.

Breast Neoplasms↗
PubMed1982

Dosimetric intercomparison at the Scandinavian radiation therapy centres. I. Absorbed dose intercomparison.

A dosimetric intercomparison was carried out at all the centres in Denmark, Norway and Sweden. All the beam qualities (except conventional roentgen rays) used in radiation therapy were investigated. The ratio of the absorbed dose measured by us to that stated by the centre was determined. The mean ratio and standard deviation with the reference field-size were for 60Co gamma beams 1.001 +/- 0.014, for roentgen ray beams (4-45 MV) 1.017 +/- 0.023, electron beams with energy E0 less than 10 MeV 0.989 +/- 0.027, and electron beams with energy E0 greater than or equal to 10 MeV 0.996 +/- 0.034. The difference between the highest and lowest ratios was 17.8 per cent. A systematic difference due to the application of different protocols (NACP 1972 and 1980) was found.

Denmark↗
PubMed1982

Ferrous sulphate dosimeter for control of ionization chamber dosimetry of electron and 60Co gamma beams.

A check of the dosimetry using ionization chambers and applying the procedures described in the Nordic dosimetry protocols (NACP 1980, 1981) was carried out using the ferrous sulphate dosimeter as reference. Measurements have been carried out in electron beams in the energy range 2.8 to 27.5 MeV and in 60Co gamma beams. Consistent results were obtained with the two systems within about one per cent. Larger differences were only observed in electron beams containing a large proportion of scattered low energy electrons and contaminating roentgen rays which were not corrected for in the ionization chamber method.

Cobalt Radioisotopes↗
PubMed1982

Liquid ionization chamber for absorbed dose determinations in photon and electron beams.

The use of a liquid ionization chamber for measurements in electron and photon beams with energies above 1 MeV has been investigated. The liquid in the chamber is 2,2,4-trimethylpentane. Fundamental properties such as the reproducibility of the measured charge per absorbed dose, the temperature dependence, and the angular dependence have been experimentally analysed. The general recombination losses in pulsed beams are shown to be dependent on the transport time of the ions in the liquid. For a longer transport time than the time between two consecutive pulses the losses depend on the mean dose rate and for a shorter transport time the losses depend on the absorbed dose per pulse. The Jaffe method is used for determination of the initial recombination losses, and compared with results from other authors. The chamber is particularly useful for absorbed dose determination in electron beams since the relation between measured charge and absorbed dose to water is almost energy independent. In photon beams the relation is somewhat quality dependent particularly at qualities below 10 MV. The change of the free ion yield caused by the small change of mean LET with the quality of the photon beam is probably the reason. Procedures for the calibration of the liquid chamber and the absorbed dose determination in electron and photon beams are described.

Electrons↗
PubMed1981

Calibration and use of plane-parallel ionization chambers for the determination of absorbed dose in electron beams.

The dosimetry procedures to be used at electron energies, E0, below 15 MeV in order to determine absorbed dose to water with an ionization chamber have been investigated. The performance of different types of plane parallel ionization chambers was tested. A chamber suitable for use in accordance with the Nordic dosimetry recommendations was designed. Correction factors to be applied in order to use solid phantom materials instead of water were determined.

Electrons↗