The amount of diastolic blood flow in the carotid and vertebral axes determines the tolerance capacity of the cerebral circulation to physiological variations. In the elderly subject this "circulatory reserve" is modified by increases in cerebral circulation resistance, but also by various common cardiac or blood pressure disorders. Furthermore, direct visualization of the atheromatous plaques and calcifications in the vessel walls by ultrasonography can reveal lesions that have no clinical expression.

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PubMedDate not supplied

Spheroids in radiobiology and photodynamic therapy.

Spheroids are tridimensional aggregates of tumor cells coming from one or several cell clones. This model, which mimics the micro-tumors structure and some of their properties, shows oxygen, pH and nutrient gradients inducing a necrotic area in the center of the spheroid. Analysis of spheroids, cultured under static or stirred conditions, can be performed on whole spheroids or dissociated spheroids. The spheroids sensitivity to ionizing radiation and photodynamic therapy can be altered by oxygen status, damage repair, intercellular commmunications and apoptosis induction, as in experimental tumor models. In radiobiology, the similarity of radiation response between spheroids and tumor xenograft bearing mice makes the spheroids to be a good alternative model to in vivo irradiation studies. In photodynamic therapy, spheroids lead to a better understanding of the own tumor response without interactions with vascular system. Finally, despite the quality of spheroid model, only the use of new technology for analysis of spheroid populations will help to increase their experimental use, particularly in preclinical oncology.

Animals↗

PubMedDate not supplied

[Comparative dosimetry study of two methods of intensity modulation performed on the same accelerator].

Intensity modulated radiation therapy (IMRT) is an advanced method of conformal radiotherapy. It permits optimal dose distribution to the target volume while preserving surrounding normal tissues. IMRT, with a multileaf collimator, can be realised in two different ways: either the segmented mode, which consists of combining small elementary static field, or the dynamic mode, which consists of moving the leaves while irradiating. The purpose of this work was to study these two methods of modulation on a Varian linear accelerator equipped with a collimator consisting of 40 pairs of one-centimetre-wide leaves. The measurements, obtained by using a diode array, showed that the quality of the irradiation in the dynamic mode does not depend on either the dose rate or the duration of the irradiation. In the segmented mode, weak magnitude segments are preferable, but increase the errors in the delivered dose. Comparisons of various profiles showed that the measured profiles are consistent with those programmed. Both modes seem to be equivalent for step-shaped profiles. In the case of profiles with constant slope, the segmentation generated by the segmented method deteriorates the profile. Even though the choice of technique is strongly dependent on the material available, the dynamic mode presents greater flexibility of use and has been chosen in our institution for IMRT.

Calibration↗

PubMedDate not supplied

[Conformal radiotherapy in cancer of the upper aerodigestive tract].

The outcome of head and neck malignancies is closely related to the achievement of local tumor control. The occurrence of severe late complications is the consequence of the anatomic vicinity between dose-limiting normal tissues and the tumor, thus reducing the curative potential of radiotherapy. Conformal radiotherapy is presently actively investigated as a way to improve the dose distribution in head and neck malignancies (especially when originating from the nasopharynx or the sinuses) while protecting healthy organs. Such an approach requires a chain of sophisticated procedures, including efficient quality assurance programs, in order to achieve the proper degree of safety. The relatively limited clinical studies published to-date have already confirmed the advantage of conformal radiotherapy in terms of dose delivery. The development of beam intensity modulation is likely to further contribute to the improvement of the therapeutic ratio.

Adult↗

PubMedDate not supplied

[Tolerance and role of irradiation in the treatment of epithelial cancer of the ovary].

PURPOSE: In a retrospective analysis, our aim was to evaluate the immediate tolerance and the early and late complications of abdomino-pelvic radiotherapy in the Centre Alexis-Vautrin (France). PATIENTS AND METHODS: From 1st January 1983 to 31st December 1993, 117 patients were treated at Centre Alexis Vautrin in Nancy for epithelial ovarian cancer by abdominal and/or pelvic irradiation after surgery. They were aged from 24 to 85 with a median of 56 years. There were ten patients with stage I (9%), 28 patients with stage II (24%), 60 patients with stage III (61%) and 19 patients with stage IV (16%) disease. Results of surgery were determined as follows: satisfactory with absence of tumoral residuum in 26% cases (30 patients) and with residuum inferior to 20 mm in 46% cases (52 patients; incomplete in 26% cases (31 patients) either because of residuum superior in 20 mm and/or incomplete surgery; and not evaluable in 3% cases (four patients). Seventy-seven patients were sent to the Centre for postoperative treatment (66% patients of the series), 48 of them (62.4%) after non-satisfactory surgery, 29 after satisfactory surgery (37.6%). Chemotherapy was administered to only 104 patients (89% cases), and contained platinum salts and cyclophosphamid for 87% of these patients. Fourteen patients (12%) received a single irradiation dose after surgery: three in stage I, three with poor evaluation of the disease in the initial stage, three with medical contraindications to chemotherapy treatment, six with contraindications due to advanced age (?? Makes 15 ). Histologically, 46% of patients had a serous adenocarcinoma, 9% a mucinous adenocarcinoma, 11% an endometrioid adenocarcinoma, 2% a clear cell adenocarcinoma, 1% an undifferentiated adenocarcinoma, and 31% an epithelial carcinoma without any other indication. The histological grade which was recently introduced was rarely indicated. Complementary radiotherapeutic treatment consisted of pelvic irradiation for 14 patients (12%), abdomino-pelvic irradiation for 63 patients (54%), and total abdominal irradiation with a pelvic boost for 40 patients (34%). RESULTS: The immediate tolerance to irradiation can be considered as globally satisfactory since 9% of the patients (ten cases) had no problems and 64% of the patients developed a minor intolerance easily controlled by symptomatic treatments. There were also digestive complications: nausea, vomiting and diarrhea for 66% of the patients (50 cases); to a lesser extent, 20% of the cases experienced associated digestive and hematological complications (15 patients); 9% isolated hematological troubles such as anemia (seven patients); 4% digestive complications (three patients) and 1% hematological and urinary digestive troubles (one patients). Late irradiation sequelae were evaluated for 89 patients with a follow-up lasting from 4 months to 11 years. Sixty-six patients had no sequelae, eleven patients had minor tolerability problems--mainly digestive for more than half of them. Five patients presented severe complications, including hematological problems such as chronic thrombopenia in two cases, urinary-problems in two other cases, and one patient presented with a case of histologically proven malabsorption. Two patients presented major problems; one case of radic cystitis and one of radic bowel. Two patients died of iatrogenic causes: one of induced leukemia, the other of treatment-induced digestive and renal complications. The overall survival rate was 30% at 5 years and 22% at 10 years. It was 90% at 5 and 10 years for stage I patients, 60% at 5 years and 30% at 10 years for stage II patients, 22% at 5 years and 8% at 10 years for stage III patients, and finally 10% at 5 years for stage IV patients. CONCLUSION: In this retrospective analysis of 117 epithelial ovarian cancers, treated over 10 years and which all received pelvic and/or abdominal irradiation, we can conclude that this treatment is globally well tolerated and that it yields a

Adenocarcinoma↗

PubMedDate not supplied

Preliminary technical, experimental and clinical results of the use of the HPLR 27 system for the treatment of deep-seated tumours by hyperthermia.

Based on the theoretical deep penetration of radio frequencies, we have developed several 27.12 MHz ridged wave guides, with large apertures, and filled with circulating deionized water. Different low impedance matching networks have been tested and a 0-800 W power generator has been designed for this particular clinical use. This can be driven easily by a microcomputer which is used to regulate the temperature at depth by varying the sequencing time and/or by adjusting the RF power. The complete system, known as HPRL 27, is manufactured by Sairem Ets. Studies of the spatial power density distributions show a relatively homogeneous RF field for an aperture greater than 30 X 14 cm. Preliminary heating patterns studied in phantoms indicate the possibility of treating volumes greater than 2000 cm3 within the 50 per cent isotherm. Maximum heating is observed between 2 and 5 cm deep with passive cooling, and between 3 and 6 cm deep with active cooling, in which case the 50 per cent isotherm is situated between 2 and 10 cm deep. Preliminary phase I clinical results on 20 patients with pelvic or thoracic carcinomas show the possibility of heating deep-seated tumours to above 42 degrees C with a good patient tolerance. Temperature is controlled by implantable catheters or in the case of pelvic heating, by inserting catheters into the vagina, the rectum and the bladder. This new device is well adapted for the treatment of pelvic tumours.

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