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A Dutreix

Publications and source records attributed to A Dutreix.

At least 55 records · Page 3Linked to original sources
PubMed1992

Human errors in data transfer during the preparation and delivery of radiation treatment affecting the final result: "garbage in, garbage out".

Due to the large number of steps and the number of persons involved in the preparation of a radiation treatment, the transfer of information from one step to the next is a very critical point. Errors due to inadequate transfer of information will be reflected in every next step and can seriously affect the final result of the treatment. We studied the frequency and the sources of the transfer errors. A total number of 464 new treatments has been checked over a period of 9 months (January to October 1990). Erroneous data transfer has been detected in 139/24,128 (less than 1%) of the transferred parameters; they affected 26% (119/464) of the checked treatments. Twenty-five of these deviations could have led to large geographical miss or important over- or underdosage (much more than 5%) of the organs in the irradiated volume, thus increasing the complications or decreasing the tumour control probability, if not corrected. Such major deviations, only occurring in 0.1% of the transferred parameters, affected 5% (25/464) of the new treatments. The sources of these large deviations were nearly always human mistakes, whereas a considerable number of the smaller deviations were, in fact, consciously taken decisions to deviate from the intended treatment. Nearly half of the major deviations were introduced during input of the data in the check-and-confirm system, demonstrating that a system aimed to prevent accidental errors, can lead to a considerable number of systematic errors if used as an uncontrolled set-up system. The results of this study show that human mistakes can seriously affect the outcome of patient treatments.(ABSTRACT TRUNCATED AT 250 WORDS)

Humans↗
PubMed1991

Is it necessary to repeat quality control procedures for head and neck patients?

Using serial verification films for detection of localization errors and in vivo measurements of the delivered dose, a comparison was made of the information obtained from a single check on the first treatment session or from repeated checks in subsequent irradiations, leading to an assessment of the predictive value of a single check. A total number of 215 films and 261 entrance dose measurements have been performed on 34 fields for 10 head and neck patients. The patients are immobilized with individual plastic masks fixed on the couch and treated on a 6 MV linac, supplied with an automatic verification system excluding the couch parameters. The global results show Gaussian frequency distributions with standard deviations of 4 mm for port film measurements and 3.4% for the dose measurements. Large errors (greater than 5 mm displacement and greater than 4% deviation from the expected dose) have been detected in 16% in the cranio-caudal direction and 24% in the antero-posterior direction with port films and in 15% of the in vivo measurements. In order to identify the nature of the errors, which can be random or systematic, the first measurement is taken as the reference value and shows that consecutive measurements on the same field were reproducible with standard deviations of respectively 2.5 mm and 1.8%. This means that a large part of the spread of the global results can be explained by systematic errors in the treatment preparation chain. With the first check, 6 out of 10 systematic localization errors and 7 out of 7 systematic errors leading to erroneous dose delivery have been detected. Therefore, most of the systematic errors, which affect the overall quality of the treatment, can be identified with the first check. The four systematic localization errors, missed with the first film, were of rather limited size: only one of them showed a mean displacement larger than 7 mm. Because the first measurement is an acceptable indication of the overall quality of the treatment delivery, the authors propose a code of practice for checking the treatment quality at the patient level.

Dose-Response Relationship, Radiation↗
PubMed1991

In vivo dosimetry for tangential breast irradiation: role of the equipment in the accuracy of dose delivery.

Entrance dose measurements (920) have been performed on both tangential treatment fields for 105 breast cancer patients. About half of them (52) were treated on a modern unit (Mevatron, Siemens), supplied with an automatic verification system, the other half (53) were treated on an old therapy unit (cobalt-60). A team of three radiographers worked on the modern unit, while on the old unit only one radiographer was responsible for the treatment set-up. A small systematic error (+ 1.4%) has been detected on the old unit: a small discrepancy existed in the region of the maximum dose between the measured and the published percentage depth-dose values (Br. J. Radiol., Suppl. 17), the latter being used for dose calculation. A striking difference has been observed for the rate of large deviations (deviations of 5% and more from the mean dose): 2.3% (10/430) for the modern unit versus 15% (75/490) for the old one. This shows clearly that the precision in dose delivery is strongly dependent on the characteristics and staffing of the therapy unit, the modern unit being supplied with a check-and-confirm system and with the beam accessory devices in a fixed position in the beam and a team of radiographers being responsible for the set-up.

Breast Neoplasms↗
PubMed1991

Tangential breast irradiation: influence of technique of set-up on transfer errors and reproducibility.

Using conventional portal films, the influence of the technique of set-up on the transfer error from simulator to treatment couch and on the subsequent reproducibility was made for the irradiated volume in the treatment of breast cancer. A total number of 376 portal films have been performed on 14 patients. All the patients were treated on a 6 MV Linac supplied with an automatic verification system excluding, however, the couch parameters. The overall precision of the treatment delivery is evaluated by the global analysis of the discrepancies between the simulator films and the different portal films. For the patient group lying on a inclined plane with (group 2) or without (group 1) fixed arm support, a narrow gaussian distribution is obtained in the anteroposterior (AP) direction with a SD of 4 mm. In the craniocaudal (CC) direction, the frequency of distribution of the patients treated without fixed arm support is much larger than in the other group: the SD is respectively 15.5 mm for the first and 5.5 mm for the second one. The reproducibility of the series of set-ups of the two groups estimated by reference to the mean value are similar in the AP direction. The SD within the series of portal films in the CC direction is 5.8 mm for the first group and 3.7 mm for the second group. Their comparison with the discrepancies of 15.5 mm and 5.5 mm when assessing the deviation between the simulated and portal films shows the importance of systematic errors. The localisation of the irradiation port can be improved by using support systems with fixed arm indicators.

Axilla↗
PubMed1990

Correlation between temperature and dose rate dependence of semiconductor response; influence of accumulated dose.

The temperature and dose per pulse dependence of 20 Therados semiconductor detectors have been investigated. The rise in relative response observed when increasing temperature from 20 degree C to 32 degree C ranges between 1.00 and 1.07, that observed when increasing dose per pulse from 9.8 x 10(-6) to 6.5 x 10(-4) Gy/pulse between 1.01 and 1.11. The diodes with the most pronounced dose per pulse dependence have also the most pronounced temperature dependence. Accumulated dose has been found to increase both temperature and dose per pulse dependence until a level off dose (less than 4 kGy for one of the diodes) is reached. However, no level off has been observed concerning sensitivity decrease with dose: after an accumulated dose of 29 kGy a sensitivity decrease of 65% was still observed when giving another 25 kGy to one of the diodes.

Calibration↗
PubMed1990

Quality assurance in radiotherapy by in vivo dosimetry. 1. Entrance dose measurements, a reliable procedure.

Entrance dose measurements were performed with semiconductor detectors on patients treated for head and neck and brain tumors with a 6 MV X-ray beam. A total number of 554 treatment set-ups were measured. The results showed a gaussian distribution with a mean value of 97.8% and a standard deviation of 2.8%. A systematic error of 2.2% on the mean value was shown to be due to a systematic deficiency in the algorithm used in the planning system and to a systematic error in the application of the dosimetry protocol. Two treatment techniques were identified leading to an erroneous dose delivery. Finally, large deviations (more than 2 S.D.) of the measured dose from the expected dose were detected in 3% of the measured treatment set-ups, the sources of the errors could in all cases be identified and eliminated in the further treatment sessions. This study demonstrated the reliability of the use of semiconductor detectors for in vivo dosimetry and its usefulness as part of a departmental quality assurance program.

Brain Neoplasms↗
PubMed1990

Quality assurance in radiotherapy by in vivo dosimetry. 2. Determination of the target absorbed dose.

Combined entrance and exit dose measurements were performed with semiconductor detectors on patients, treated for neck and oral cavity malignancies. Transmission measurements showed the important influence of contour inaccuracies and tissue inhomogeneities. In 39.6% (21/53) of the checked contours, the discrepancy between the contour diameter used for routine treatment planning and the actual patient diameter was 1 cm or more, and in this group a systematic tendency for patient diameter underestimation due to the procedure was detected. When the X-ray beam passed through important bone structures such as the mandibular bones or the vertebral body, large discrepancies of 10% and more between the measured and the expected transmission were found. The target absorbed dose was determined from the transmission and entrance dose measurement. A systematic underdosage of about 2% at midline level was found to be due to an inaccuracy in the algorithms of the treatment planning system. Underdosages of 5% or more at midline were detected in more than 20% (47/230) of the measurements. In all cases, the reason for erroneous dose delivery was identified. Entrance dose measurements were previously demonstrated to be useful for the assessment of uncertainties related to treatment machine, patient set-up and treatment planning system (part 1). Transmission measurements (the ratio of the exit to the entrance dose measurement) are shown to be very useful to evaluate uncertainties related to patient data such as contour errors and tissue inhomogeneities as well as to the algorithms of the planning system. The influence of these errors on the target absorbed dose can be estimated and corrections can be applied for each individual patient.

Algorithms↗
PubMed1990

Techniques applied for total body irradiation.

In this review, different techniques of total body irradiation are discussed with special attention to their advantages and disadvantages. The results of an EBMT questionnaire, which was sent out to the European TBI centres, are also presented. It turned out that there exists a great variety in techniques, total doses, and fractionation schedules used all over Europe. It was also clear that the documentation concerning dosimetry and the time factor in TBI still has some deficiencies. Therefore, a proposal is now made for reporting the technical and dosimetric aspects used in total body irradiation in an unambiguous manner.

Humans↗
PubMed1990

Dosimetry for total body irradiation.

Basic dosimetry as well as patient dosimetry are considered. The following items concerning the basic beam dosimetry are discussed: dosimetry calibration, phantom material, beam quality and depth dose measurements in TBI conditions. Dose to the patient should be specified to the midplane of the abdomen but dose to the lung should be estimated for each patient. In vivo, dosimetry is strongly recommended for determination of dose homogeneity, as well as to check patient position, reproducibility of treatment and instabilities in dose rate during TBI. Many physical problems are associated with in vivo dosimetry. All influences on the detector response have to be considered and the detectors must be calibrated for TBI conditions.

Absorption↗
PubMed1990

Late effects of total body irradiation in correlation with physical parameters.

Clear and complete documentation of the physical parameters of total body irradiation (TBI) is one of the essential requirements for the evaluation and improvement of the clinical results of TBI. Concerning the dosimetric aspects of TBI, a number of recommendations have been formulated with emphasis on basic dosimetry, patient dosimetry and dose specification. The dosimeters should be calibrated regularly with reference to the absorbed dose in water. Depth dose measurements should be performed in water equivalent phantoms of specified dimensions. It has been strongly suggested to measure the absorbed dose at the surface of the patient at 8 different regions at the entry and exit of the beam under TBI conditions. The reference dose to the patient should be specified as the total dose to mid abdomen at the height of the umbilicus. As an independent parameter, the lung dose should be specified as the mean dose in the central region of the shielded part of both lungs. Recent, more complete, information on the physical and dosimetric aspects of TBI will be incorporated in the registry of the European Bone Marrow Transplant Group (EBMT). A cooperation has been established between the EBMT and the European Late Effects Project Group (EULEP) to study the development of late effects in man caused by ionising radiation.

Calibration↗
PubMed1989

Role of radiotherapy and chemotherapy in the risk of second malignant neoplasms after cancer in childhood.

Of a cohort of 634 children treated from 1942 to 1969 at the Gustave Roussy Institute for a first cancer and alive 5 years after treatment, 32 later developed second malignant neoplasms (SMN). A case-control study was performed to determine the relationship between the dose of radiotherapy received on a given anatomical site for the treatment of a first cancer, and the risk of SMN development at the same anatomical site. Another aim of the study was to analyse the effects of the association of radiotherapy with chemotherapy on the risk of SMN. The 32 cases of second malignant neoplasms were individually matched with one to nine patients of the cohort (a total of 162) who did not develop a SMN after a first cancer, matching on age, sex, type of first cancer and follow-up duration. The doses of radiotherapy delivered for the treatment of the first cancer were retrospectively estimated at the 26 anatomical sites of SMN. When the SMN was a leukaemia, the mean active bone-marrow dose was estimated as a weighted mean of the doses received by 20 bone sites. As compared to anatomical sites in children who had not received radiotherapy, the sites which had received 50 Gy or more had a relative risk of SMN of 5.8 (P less than 0.05). When taking into account the dose received at the site of the SMN, neither the number of fractions nor the type of radiations were related to the risk of SMN. Children who had received chemotherapy had a relative risk of SMN of 2.7 (95% CI: 1.2-6.4), adjusted for the dose of radiotherapy, as compared to those who had not. The relative risk of SMN did not vary with the dose nor the duration of the chemotherapy. Dactinomycin was found to increase the relative risk of second soft tissue and bone sarcomas. Cyclophosphamide was found to be less carcinogenic than the other alkylants. The relative risk of SMN was equal to 2.0 (n.s.) after radiotherapy of more than 25 Gy, to 4.4 (n.s.) after chemotherapy, and to 21.4 (P less than 0.01) after the combination of these two treatments modalities, as compared to patients treated by surgery alone. This study suggests that the oncogenic effect of radiations might be increased by chemotherapy, and that the combination of the two treatment modalities might be one of the major factors responsible for overall risk of SMN.

Adolescent↗
PubMed1989

Long-term risk of second malignant neoplasm after a cancer in childhood.

The risk of subsequent second malignant neoplasm was studied in a cohort of 634 patients, treated for a childhood cancer at the Gustave Roussy Institute between 1942 and 1969, and in complete remission five years after diagnosis. The most frequent types of first primary cancers (FPC) were Wilms' tumours (28% of the children), neuroblastomas (16%), lymphomas (12%) and soft tissue sarcomas (11%). Median follow-up duration after FPC was 19 years. Thirty-two patients (obs = 32) developed a total of 35 second cancers. Bone, thyroid, connective tissues and skin were the most frequent types of second cancer, with six patients for each type. The average annual incidence of second cancer was 0.36%. The average annual incidence for the periods 5-9, 10-14, 15-19, 20-24 and 25+ years after FPC was respectively 0.16%, 0.34%, 0.36%, 0.71% and 1.18%. The cumulative incidence of second cancer for the periods 5-20, 5-25 and 5-30 years after FPC was, respectively, 4.3% (95% CI: 2.8-6.6%), 7.8% (95% CI: 5.1-11.8%) and 13.0% (95% CI: 8.2-20.0%). The expected number of cancers in the cohort, computed from Danish cancer incidence data, was exp = 2.2. When compared to this expected number, the average annual excess incidence of second cancer, defined as obs-exp divided by the number of person years of observation, was 0.33%. This rose from 0.15% for the period 5-9 years after FPC to 1.09% for the period beginning 25 years after FPC. The standardised incidence ratio of second cancer (i.e. obs/exp) was 15 (95% CI: 10-21), and was fairly constant in the period extending from 15 to 20 years after FPC diagnosis. Obs/exp was equal to 25 for the patients who had had chemotherapy and equal to 9 for those who had not. Cyclophosphamide seemed less carcinogenic than the other alkylating agents. Obs/exp was similar for the patients who had received radiotherapy and for those who had not. The risk of cancer increased with age in the reference population and increased faster in the cohort, because the standardised incidence ratio is constant over a long period.

Adolescent↗
PubMed1988

An approach to the interpretation of clinical data on the tumour control probability-dose relationship.

A conventional statistical model allows predicting the sterilisation rate as a function of dose. However, the computation requires data on biological parameters (proportion of clonogenic cells, survival per fraction, multiplication rate) which are inaccessible for human tumours. The curative dose 50% (TCD50) can be used as a synthesis of these parameters and its significance for the response-dose relationship of a population of tumours of uniform radiosensitivity is discussed. The slope of the dose-control curve provides vital information regarding the variation in radiocurability of the various individual tumours. The model allows the analysis of the clinical data and the separation of tumour subsets with different radiation responsiveness. It provides an evaluation of the benefit which could be obtained from the identification of the subsets and a guidance for the clinical, pathological and biological studies which relate to this identification. The change in the response-dose relationships with the tumour size cannot (usually) be explained by the cell number increase alone. Other possible factors of reduced radiocurability are discussed.

Cell Survival↗
PubMed1988

Can we compare systems for interstitial therapy?

Three main dosimetry systems are used for interstitial brachytherapy: Manchester, Quimby and Paris Systems. A comparison is made of the rules of source distributions recommended by the three systems stating the advantages and disadvantages of each system. The comparison shows up the differences in the size of the treated volumes for similar implanted volumes. The next sections emphasize the differences in dose specification which make very difficult any comparison of clinical results obtained with different systems. Furthermore, the recent development of computers has lead some radiotherapists to specify the dose individually for each patient without reference to any published system. Very large variations in the dose delivered to a patient for a given implant and for the same prescribed dose, may results from this subjective procedure. In the last section one considers the various quality criteria proposed in the literature.

Brachytherapy↗
PubMed1987

Prescription, precision, and decision in treatment planning.

The goal of radiotherapy is to eradicate a tumor without causing severe damage to healthy tissues. Various published experiences have lead to the conclusion that an overall precision of +/- 5% on the absorbed doses, at any point in the patient, is required to meet this goal. Clear definitions of the method for specifying the absorbed dose and dose homogeneity throughout the target volume are essential, to facilitate communication, to improve the knowledge of dose-effect relations and to establish the necessary criteria for the optimization of treatment plans. Determination of the optimal energy is one of the most controversial problems in treatment plan optimization. It is clearly related to the criteria selected. A brief review of some criteria is proposed according to the tumor site. Computers may provide three-dimensional dose calculations for treatment conditions for which manual calculations are not feasible. Because the random errors are very small, computer calculations are often considered as exact although large risks of error are associated with each step of the calculation. The reduction of the overall uncertainty to the stated level of +/- 5% requires a constant effort from both radiotherapists and physicists at each step of treatment planning from basic definitions to dose distribution calculations.

Humans↗
PubMed1986

On the use of a quality index to specify high energy photon beams.

It is important to specify the beam quality in a simple and nonambiguous way in order on one hand to make comparisons easier between treatments performed in various hospitals, or at different times in the same hospital and on the other hand to facilitate the choice of numerical values for factors like restricted mass-collision stopping-power ratios and perturbation correction factors used in the conversion of ionization measurements into absorbed dose. We have adopted for high-energy photon beam specification a quality index (I) defined by the ratio (I20/I10) of ionizations measured with a constant source-detector distance for a reference field size 10 X 10 cm2. We have found that this quality index is independent of the source detector distance. On the other hand, the apparent linear attenuation coefficient measured on the exponential part of the tissue-maximum ratio curve can be calculated for any field size from the value of I for most high energy photon beams. In order to check the validity of the quality index for other linacs from other manufacturers, we have compared our results to published data related to various photon beams in a wide energy range: 2.5 to 45 MV.

Humans↗
PubMed1986

A comparison of build-up and depth dose characteristics of different photon beams for the treatment of Hodgkin's disease.

Measurements have been performed of build-up and depth-dose characteristics of photon beams under Hodgkin's disease treatment conditions as applied in two hospitals (AVL, Amsterdam and IGR, Villejuif). Although different types of accelerators, photon energies, field sizes and SSD are employed, similar dose distributions along the beam axis have been obtained in both centers. In order to explain this unexpected good agreement, the influence of the geometrical conditions of irradiation on the build-up and depth-dose distribution has been studied in detail for five photon beams (8 MV-25 MV) of three types of accelerators.

Evaluation Studies as Topic↗