PubMed Health⌕ Search

Biomedical subjects

M Schlienger

Publications and source records attributed to M Schlienger.

At least 145 records · Page 8Linked to original sources
PubMedDate not supplied

[Implementation of receiver operating characteristics for the quantitative evaluation of stereotactic radiotherapy treatment plans].

The definition of criteria and of a methodology dedicated to the quantitative evaluation of conformal stereotactic treatment plans is presented. We implemented the 'Receiver Operating Characteristics' (ROC) analysis, already used in medical imaging, for the quantitative evaluation of irradiation treatment plans. This implementation is based on data provided by dose-volume histograms (DVH). Three techniques, each one using a different dosimetric criterion, were defined for the choice of a reference isodose for a given treatment plan. We used this ROC analysis for the selection of the most conformal treatment plan and its reference isodose among the treatment plans proposed for one patient. This study revealed the interest of ROC analysis based on dose-volume histograms for the quantitative evaluation of treatment plans.

Humans↗
PubMedDate not supplied

[The point of view of the radiotherapist].

During the last decade, stereotactic radiotherapy has widely improved in France. Thus one should study the present situation and its future trend. QUANTITATIVE NEED: Considering single dose radiotherapy, there are about 900 to 1,000 cases treated per year. However, the trend towards more fractionated treatment will disturb this temporary equilibrium; thus more machine time will be necessary. QUALITATIVE NEED: Stereotactic radiotherapy is practiced by multi-disciplinary teams including physicians, physicists and scientific specialists. Radiotherapists and physicist are responsible for treatment planning and evaluation as well as for clinical and methodological research. Accordingly, they should possess computers, treatment planning systems, etc. Such teams are necessary to carry out complex irradiations. GENERAL EVOLUTION: Fractionation of irradiation nowadays seems mandatory for most intracranial tumors except metastases and small regular arteriovenous malformations. Heterogeneity of lesion dose is related to the geometry and the physics of convergent fixed or mobile beams. It can be improved and the healthy tissue irradiation can be diminished using the multi-isocentric planning for complex lesion or with micro multi leaf collimators. MODALITIES OF STEREOTACTIC RADIOTHERAPY ACCORDING TO LESION TYPE: For neurinomas of the acoustic nerve, fractionated stereotactic radiotherapy yields few of the complications published after single dose stereotactic radiotherapy. The same can be said for meningiomas although some series reported very few complications after single dose stereotactic radiotherapy. Solitary metastases without systemic evolution, not situated on the mid-line, are favorable candidates for palliative single dose stereotactic radiotherapy. The conjunction with total brain irradiation seems to be useful. Small arteriovenous malformations will be treated with single dose stereotactic radiotherapy, whereas voluminous and/or geometrically complex nidus could benefit from protons or photon beams modulated by micro multi leaf collimators and a few fractions. EXTRA-CRANIAL STEREOTACTIC RADIOTHERAPY: Single dose stereotactic radiotherapy and fractionated stereotactic radiotherapy will be used as boost in various situations such as massif facial and in all sorts of tumors in the body specially when lesions are close to critical organs.

Brain Neoplasms↗
PubMedDate not supplied

[Locoregional recurrence of adenocarcinomas of the rectum treated with irradiation combined with or without excision surgery].

PURPOSE: Retrospective study to analyze the results of external beam radiation treatment with or without surgery for loco-regional recurrence of adenocarcinoma of the rectum following previous surgery without pre- or post-operative radiotherapy. PATIENTS AND METHODS: Between March 1973 and November 1991, 211 patients with loco-regional recurrence of rectum cancer were treated with external beam radiation treatment. Radical surgery was the only initial treatment modality. Surgical resection of local recurrence was done in 36 patients and only 17 patients could undergo complete resection. Forty-seven patients underwent radiotherapy (RT) combined with surgery and 164 received external beam radiation treatment alone to a mean total dose of 46 Gy. RESULTS: Among the 151 patients whose recurrence was revealed by pain, 64 (42%) were considered to have a complete symptomatic response after loco-regional treatment with radiosurgery or RT alone. The mean duration of response was 12 months. The 3-year overall survival rate was 16%. Five prognostic factors decreased the overall survival rate in multivariate analysis: high age, sex (male), concomitant distant metastasis, no tumor resection, and low total radiation dose with external beam radiation treatment alone. The 3-year overall survival rate for patients with completely resected recurrences was 39%. CONCLUSION: External beam RT treatment can only be considered a palliative symptomatic treatment. New techniques of early detection of local recurrence and new combined modalities approaches (radiation sensitizers or intra-operative radiotherapy) with surgical resection in some favorable cases should be studied.

Adenocarcinoma↗
PubMedDate not supplied

The influence of arc weights on the dose distribution for single target radiosurgery.

To stereotactically irradiate ellipsoidal inclined arteriovenous malformations (AVMs) with a single isocenter one can use an adjusted inclined irradiation space with a reduced angular range of arcs. If one uses the maximum available irradiation space it is necessary to weight some of the arcs in order to closely encompass the lesion. It has been found that there is a relationship between the lesion inclination angle beta and the weights of arcs. Conversely when the beta angle is known, the weights of the arcs can be determined in advance by means of weighting vectors. The dose volume analysis shows that the isodose volumes remain constant for the different weighting vectors except for the 10% isodose volume which increases slightly as the linear weighting vector's slope alpha increases. Moreover, this procedure permits the optimization of the superimposition between the lesion and the reference isodose. These results enable the construction of an "a priori knowledge" database that can be included in an optimization algorithm procedure.

Biophysical Phenomena↗
PubMedDate not supplied

Gallbladder cancer: role of radiation therapy.

BACKGROUND/AIMS: Gallbladder carcinoma is characterized by late diagnosis, ineffective treatment and poor prognosis. These tumors were usually considered to be radioresistant. So far, the role of radiotherapy has not been adequately evaluated. The aim of this report is to assess the value of radiotherapy in carcinoma of the gallbladder. METHODOLOGY: We reviewed all publications concerning the role of radiation therapy in gallbladder carcinoma. External radiation therapy, intra-operative radiation therapy, and brachytherapy were evaluated in two groups in which the prognosis is quite different; a group operated on, with apparent complete resection of the tumor, and a palliative surgery group. RESULTS: It appears that gallbladder carcinomas are not as radioresistant as was formerly thought. Local control of the tumor and reduction of tumor size was reported in several publications. Collected data showed a slight improvement of survival after adjuvant or palliative radiotherapy, especially in the advanced stage of gallbladder carcinomas. It appears preferable to give a "boost" (15 Gy) to the gross lesion or residual lesion at operation (intra-operative irradiation or brachytherapy), and deliver an additional 45-50 Gy post-operatively. CONCLUSIONS: The results published encourage further trials in well defined populations. Radiotherapy seems to be a safe procedure, morbidity is minimal, and a slight effect on survival is observed after curative or palliative surgical procedures.

Brachytherapy↗