Search

Calculation, measurement and improvement of two-bounce passive reflectors designed for the external cross-calibration of linearly polarized polarimetric radars are addressed. Derived from the standard right angled dihedral, the reflectors under consideration are designed so that they have broad Co- and X-pol backscattering diagrams. These broad beamwidths are highly required for in situ SAR calibration, where uncertainties on the direction of flight and incidence angle may exist. Several examples are discussed. The first part is concerned with the standard dihedral which is made of two orthogonal conducting plates. Due to the narrow X-pol backscattering beamwidth of this type of dihedral, X-pol channels calibration is harder to achieve, especially outside laboratory. Therefore, dihedrals with elliptical vertex, including the circular case, are studied. The results are compared with the standard dihedral. Subsequently, simulations conducted on this type of target have determined the vertex ellipticity influence on the Co- and X-pol backscattering diagrams. Finally the authors set up a synthesis process to design an optimal shaped dihedral as long as the X-pol backscattering diagram is required to be as flat and as wide as possible. The optimization leads to an helicoidal vertex. Advantages and drawbacks for each kind of structures are also discussed. >

Limits of validity of the Uniform Theory of Diffraction when applied in non standard conditions are investigated through the use of an exact method (FDTD) which has been previously adapted. In this paper both methods are implemented for the calculation of diffraction by a lossy dielectric wedge. First we report a new expression of the diffracted field. Then we outline the adaptation needed to the classic FDTD grid calculation to isolate only one edge diffraction. We present the results obtained through a parametric study concerning the conductivity, the permittivity, the observation distance and the apex angle of the wedge. Agreement is very good in most cases, whatever complex permittivity, and in particular the relevance of the new diffraction coefficient is demonstrated. A very interesting result as well is that the closer the observation point to the apex the better is the agreement between UTD and FDTD.

The authors consider a class of shaped dihedral metallic reflectors whose surface is parameterized in a very general way. They discuss analytical and numerical techniques for calculating the far-field scattering by a combination of geometrical optics and physical optics, whatever the target attitude versus polarization and incidence of the incident wave. They then describe an application of a cross-polarization passive calibrator for airborne synthetic aperture radar (SAR) applications, which is a modified dihedral with a curved vertex. >

A thick perforated plate and an open waveguide array antenna are treated by means of the same formalism. In both cases, the structures are illuminated by an incident plane wave and fields are expanded in Floquet modes in free space and guided modes in waveguides. Matching at the apertures is achieved by the classical moment method. The formalism used includes both the radiation pattern calculation (receiving antenna) and the bistatic and monostatic radar cross section determination. The feeding network is represented by a reflection coefficient, taking into account phase shifters. An experimental check of the computer code is presented. >

During the period from January 1977-August 1979, 18 patients with biopsy-proven pancreas duct or ampullary adenocarcinoma with no distant or liver metastases underwent external beam radiation therapy following laparotomy. With the use of a 25 MEV photon beam and a four field "box" technique, the dose delivered to the target volume identified with radio-opaque clips at laparotomy was 6000 rad in six weeks, while largely sparing the spinal cord, kidney, liver and gut. All patients subjected to low fat, gluten free diet completed treatment as planned without any acute reaction. Three patients developed delayed pancreatic insufficiency. According to actuarial survival analysis and low morbidity such an approach may lead to increase survival in patients with pancreatic cancer.

Several conclusions seem evident from this study : firstly radiation myelopathies exist without any doubt; secondly clinical observation, even very attentive, during irradiation is perfectly blind regarding this subject; lastly, one can only, at this time, attempt to anticipate medullary accidents caused by irradiation. Radiation myelopathies exist incontestably. We report 27 new cases which are added to the more than 500 cases already analysed in the world litterature. The improvement of results of cancerology and in particular of radiotherapy make and will continue to make the number of observations published increase. However, if there is no doubt as to existence of these myelopathies, discussions persist concerning their nature : purely vascular, cytotoxic, probably mixed, perhaps maintained and prolonged by a superimposed immunologic phenomenon. Prevention is the sole method at our disposal to be effective. It must be applied as much to the patient as to the technique of irradiation. With regard to the patient treated in a medullary volume, several factors are probably favorable to the development of myelopathy and must cause one to modify eventually the technique of radiation proposed : the existence of anterior vertebral medullary pathology, whatever its nature; two ages demonstrate increased incidences : the young which have relative immaturity of tissue (we report 4 cases patients less than 25 years old), and the old, whose chances of accumulating associated pathologies are great, especially as systemic hypertension and arteriosclerosis are likely to have played a favorable role; the patients for whom restraint is difficult or who present disrupted regions anatomy are qually much more fragile. With regard to the technical plan, several factors incontestably favor the appearance of radiation myelopathy : large medullary volumes irradiated, especially when they encompass the zones of vascular medullary junction; the overlap of fields involving the spinal cord; the reduction of fields too close to the spinal cord not allowing at least 1 cm margin of relative security; the association of physical agents in the measure to which the global dosimetry is uncertain, i.e. in particular the use of high energy electrons for boost dosage, the intensity of which must be chosen with the greatest prudence; finally and most importantly, it seems desirable to us not to surpass at the level of the spinal cord, treating 5 times per week, a dose of 5 000 rads with fractions of 200 rads of 4 500 rads with fractions of 250 rads, and of 4 000 rads with fractions of 300 rads. Can one reasonable pretend always to foresee all radiation myelopathies? No, for on the one hand there exist authentic cases which have occured after doses which were below the limits of tolerance which we have indicated above, in accordance with others authors, and on the other hand, the necessity of sterilising certain inoperable tumors obliges one sometimes to deliver to region of the spinal cord aggressive doses.

Authors present a critical review of 61 cases of squamous carcinoma of paranasal sinuses. Most of these cases were diagnosed at an advanced stage, allowing only external radiotherapy to be proposed. The mean delivred dose was 6,000 to 6,500 rads, mainly to telecobaltherapy. Survival rates are poor (SVI = 50%, SV3 = 14%, SV5 = 8%) in the same range than values previously published by others. However, it seems possible to point out some practical trends in order to improve the management of the disease:--in all cases, irradiated volumes must be large;--prophylactic irradiation of cervical nodes in also a key point, especially when tumor reaches the oral cavity, the skin or the pterygomaxillary fossa.

Between 1952 and 1973, 138 patients with thyroïd carcinoma have been recorded. From the critical study of these cases, the pathological, etiological and clinical features have been studied. Different therapeutic modalities are evaluated from these cases. Surgery was always used when possible. A hemithyroïdectomy was realised most often. We stress that sterilisation was obtained by 131I treatment in plurifocal metastasis, particularly in pulmonary metastasis, only when the iodine uptake was sufficient. Survival has been evaluated according to the pathology: papillary and vesicular carcinomas have a good prognosis (the papillary and vesicular survival rate at 10 years reaches respectively: 65% and 64%). Anaplastic carcinomas have a bad prognosis (the survival rate at 5 years is 18%, at 10 years, 0%. These results are similar to those published by differents authors. At the opposite, trabecular carcinomas have a very short survival (8% at 5 years, 7% at 10 years) which is very unusual in well differentiated thyroïd carcinomas. It has to be isolated from the others.

The records of 32 patients with trabecular carcinomas of the thyroid gland were critically reviewed from a previously published serie of 138 thyroid cancers referred to the Centre Claudius Regaud, between 1952 and 1973. On the basis of clinico-pathological considerations, it seems possible to divide trabecular carcinomas into two groups. Pure trabecular carcinomas (moderately differenciated follicular carcinomas--WOH) which have a poor prognosis (5 years actuarial survival: 13%) related to high rate of local recurrences, fast metastatic spread to the lung, bad response to suppressive hormonotherapy and lack of 131 iode uptake by malignant tissue. Mixed trabeculo-vesicular carcinomas which have in comparison a fairly good prognosis (5 years actuarial survival: 63%) in keeping with a lower tendency to local recurrences and a useful concentration of radioactive iodine by metastases (most of them located in the skeleton) although dependent on the pourcentage of vesicles in the tumor process. Among differentiated thyroid carcinomas, distinction between pure trabecular and mixed trabeculo-vesicular carcinomas with quantitative determination of vesicules seems of great interest in relation to the therapeutic approach.

The results obtained in a previous study using 131I fibrinogen in cancerous patients suggested a local intravascular clotting precess. In order to elucidate the mechanism of fibrinogen kinetic abnormalities different drugs, including heparin, prednisone, ticlopidin, aspirin and indomethacin were administered in 68 patients and their effects evaluated by change in the 311I fibrinogen disappearance rate. The results suggest that these drugs may counteract with the early stages of coagulation (kinin-forming system, factor XII) and that abnormal 131I fibrinogen kinetic in cancer would be a non specific phenomenon.

Radiation therapy prescribed as an adjuvant to surgery is an effective treatment of many cancers but has not been universally accepted for treatment of rectal cancer. Since 1969, preoperative radiation therapy of rectal carcinoma has been proposed in a curative intent, both at Centre Paul Lamarque in Montpellier and at Centre Claudius Regaud in Toulouse, France. Megavoltage radiotherapy was used in all patients and doses ranges from 35 to 40 Gy during 2.5 to 3 weeks. Among the 344 patients treated between 1969 and 1981, the ratio of abdominoperineal excision to anterior resection was 239/105, the percentage of pelvic recurrence was 7,8 per cent, and the 5-year survival rate, including postoperative mortality (5.2%) was 78 per cent in the Centre Claudius Regaud series and 64 per cent in the Centre Paul Lamarque series. The 10-year survival rate was 50 per cent. There was no evidence of an increased morbidity following irradiation. Pathologic staging showed no residual tumour in the excised specimen in 5.2 per cent of the cases. The number of Dukes'C cases was smaller than according to the clinical pre-treatment assessment of the tumours (16%). Ultrasonography of the liver and plasmatic CEA determination avoid irradiation of metastatic patients. Further development of this curative approach should include a postoperative boost of 25 Gy for patients who are at high risk for local failure in the pelvis, and an adjuvant chemotherapy for Dukes'C patients.

Twenty-four observations of primary malignant tumors of the renal pelvis and ureter derived from epithelial cells were included in this study. Thirteen patients were treated by radiotherapy and surgery. In eleven patients, surgical excision was the only treatment. Although patients were not randomized there was no significant difference between the two groups concerning the following parameters: age distribution, sex ratio, stage of disease, histological grade, surgical procedure. The morbidity related to external radiotherapy (megavoltage technique, delivering 45 grays in 5 weeks) was low: only one patient developed retroperitoneal fibrosis. No patient was lost to follow-up. Local recurrence occurred in 54.5% of the patients treated by surgery alone, against 15.5% after combined radio-surgical therapy. The overall three-year survival rate was 35% without any significant difference between the two groups. The authors advocate postoperative high-voltage radiotherapy for non-disseminated carcinoma of the renal pelvis and ureter.

The beta subunit of human chorionic gonadotropin (betaHCG) was performed on the serum of 1 850 patients with microscopically documented non trophoblastic carcinomas. 96 patients (5,2%) had elevated betaHCG plasma levels. The incidence of elevated plasma values varied little from one studied malignancy to another; the highest circulating levels were observed in patient's with bladder carcinomas (22,2%), squamous cell carcinomas of the bronchus (14,2%), pancreatic (20%) and colo-rectum (15,7%) adenocarcinomas. BetaHCG determinations did not improved the diagnostic sensibility of CEA values except for the bladder carcinomas. The short mean survival of patients with positive betaHCG values suggests that elevated ectopic betaHCG, sometime during the clinical course of metastatic maligancies worsens the prognosis.

Fifty four cases of stage IVa carcinoma of the cervix and treated with radiotherapy were collected between 1971 and 1977. Overall actuarial survival was 16 per cent at 3 years and almost all the deaths occurred before that time. Amongst the factors studied, the initial size of the pelvis tumour and lumbo-aortic lymphography findings were the determing factors in the prognosis. To a lesser extent, the age of the patient, tumour differentiation and the amount of irradiation modified the prognosis. It was thus possible to define, within the stage IVa category, several prognostic groups, the determination of which has therapeutic consequences.

The authors report the results of the exploration by 57Co Bleomycin scinitigraphy in 97 thoracic tumors. The Bleo-57Co scintigraphy detects primary and secondary malignant tumors underevaluated by classical tests. In the thorax, the radioactive focus are easily detected on account of the light physiological fixation of the Bleo-57Co. It is particularly interesting in the mediastinal tumors where the picture is not covered by cardiovascular interference. Mediastinal, pleural and costal tumors have been explored. Pulmonary tumors give the best results, they fixe in 93% of the case. All the mediastinal tumors have capted the bleomycin but the authors insist on the fact that the fixation was very light even when the tumor was a large one. The exploration of pleural and costal tumors was less interesting. In conclusion, the Bleo-57Co scintigraphy, gives indications about the volume of the tumor and its spread in the organism. By this method, we can diagnose malignancy in tumor. It can be used to survey cancer patients which have been treated. Nevertheless the long half-life (270 days) and the lack of specificity of the Bleo-57Co for the malignant tumors, justify discussion about indications and the results of such an exploration.

Sixty nine patients suffering from malignant tumours at different stages of their development underwent a kinetic study of fibrinogen 131I with external counting over the tumour and a study of haemostasis including P.D.F. The 1/2 T of fibrinogen 131I is shortened: 2.52 +/- 0.09 days (normal: 3.89 +/- 0.11 days.) The abnormality is proportional to serum P.D.F. levels (r=0.99). External counting demonstrated the uptake of labelled fibrinogen in the tumour. Heparine (15000 U/24h) restores the 1/2 T of fibrinogen to normal in 95 p. cent of cases. The results suggest the existence of a localised compensated intravascular coagulation process inside the tumour. Possible consequences of that phenomenon are discussed.

The authors present a homogeneous series of 133 patients with squamous carcinomas of the base of the tongue, treated mostly by external radiotherapy. The survival rate at the end of three years is 17%, and at five years 13%. Studying the local spread or stage of the tumour and survival, it is seen that only T1, T2, N0 and N1a patients (with a three-year survival of 28%) can, in fact, benefit from a curative course of radiotherapy, in which external radiation and curietherapy are associated. In the other cases, radiosensitization, unusual wavelengths of irradiation, or heavy particle irradiation seem to be the only possible ways of improving the prognosis.

Thirteen cases of primary ovarian seminoma have been referred to the Claudius Regaud Cancer Center during the last 2 decades, patients' ages ranging form 10 to 41 years with a peak in the 20's. Two patients were treated by surgery as definitive therapy, the others underwent combined radiation therapy (dose range 25 to 45 Gy) following surgical excision. The 2 patients treated by surgery alone had pelvic recurrences, whereas only 2 local failures appeared in the group treated by surgery and radiotherapy. Ten patients are asymptomatic and clinically free of disease after a mean follow-up of 3.5 years, the mean survival time of the series being 6 years. Because of the generally improved prognosis, surgical oophoropexy is recommended before radiotherapy.

Ninety-five females with squamous cell carcinoma of the head and neck are reported. Tobacco and alcohol habits were present in only 18% of patients; in these cases tumoral behavior and prognosis are quite similar to those of male patients. When no particular epidemiology was found, female patients present special tumoral localizations as gum, cheek or palate. In addition these patients are elderly, mean age above 75 years. Radiotherapeutic management of female patients allow the same results than in treating males; consequently, since female patients are more elderly than males, these therapeutic results advocate aggressive therapy even in female patients above 80 years old.

1. The hypoxic cell-radiosensitizing drug misonidazole or 2 nitro imidazole was administered by intraperitoneal way at a dose of 25 mg/100 g to Wistar rats bearing a chimio-induced sarcoma. Drug plasma and tissues concentrations were determined by HPLC analysis. The diffusion of the drug in different tissues and tumor was very short: plasmatic and tissular peak levels were obtained 10 to 30 min. after injection. 2. Misonidazole concentrations in muscle, brain, tumor, liver and kidney were 50%, 47%, 36%, 9% and 13% of plasma level. No significative difference of the drug concentration were observed between the center and the outside zone of the tumor. 3. However, half-life of misonidazole in the center of tumor was much shorter than in the outside of the tumor, demonstrating its radiosensitizing properties.

From the study of this series of 50 patients suffering from cancer of the penis, and in particular from the comparison of two successive groups, several facts stand out which determine our present attitude: -subjects suffering from cancer of the penis, at least in our area, are aged, fragile people, whose cause of death, in more than half of the cases, was not the penile cancer. Proposable therapeutic methods must take this specific background into account; -tumoral and glandular indications must be looked at separately, as there does not seem to be any strict correlation between the size of the tumor and glandular invasion; -inguinal glandular invasion must as far as possible, be proved histologically, whatever the appearance of adenopathy on palpation; -No and N-patients should not be treated in the inguinal folds, but carefully followed-up; in this connection, very strict follow-up, at least for the first three years, seems to be indispensable; -N+ patients must evidently undergo bilateral removal and subsequent irradiation. This therapeutic attitude, leads to bilateral edema of the lower limbs in a high percentage of cases, against which no therapy is at present active; -tumors of the penis, classified T1, T2, or T3 are best benefitted by the technique of interstitial curietherapy using irridium 192, the only conservative technique offering a high level of local sterilization, without major after-effects; it permits possible reparatory surgery; -on the other hand, T4 tumors cannot be marked, the target-volume being too large, and they justify radical surgery.

Authors present clinical records of 127 patients bearing metastatic cervical lymph nodes of unknown origin and referred to the Cl. Regaud Cancer Center between 1959 and 1973. According the prognosis, it is possible to distinguish patients into three groups. In group I, patients (10%) have a lower neck involvement by an adenocarcinoma. The survival is dramatically bad. Group II includes also 10% of patients who have a fairly better prognosis, they are younger people bearing poorly differenciated squamous metastatic lymphonode(s) in the upper neck. Group III. The remaining eighty per cent of patients are heavy drinkers and smokers. Their upper neck is hurt by lymphatic metastases from a well or moderately differenciated squamous cell carcinoma. They have much about the same prognosis than people bearing a known primary carcinoma of the upper aerodigestive tract. After having excluded the first group of patients who is at high risk of having a widely disseminated illness, we can remark that about one half of relapses occurred in the cervical area. A well planned combination of neck dissection and whole cervical lymphatic areas irradiation may further reduce such recurrences and so may enhance the present results: 23% survival 3 years after completion of treatment.

The clinical features of pelvic recurrence in a series of 52 patients who underwent abdomino-perineal excision for carcinoma of the rectum are described. About 80% of these recurrences occurred within 2 years after surgical treatment. Low level of tumor in the rectum, local spreading into peri-rectal fat or serosa, lymph node involvement are factors related to high incidence of local recurrence. The bad prognosis of this pattern of failure leads to suggest that radiotherapy be given a trail as an adjuvant method of treatment to conventional surgical approach.

The authors present the results of a non randomized study of 33 patients suffering from small cell carcinoma of the lung. After a similar course of monthly chemo-therapy (Endoxan Oncovin, Natulan, CCNU) and mediastinal irradiation in a dose of 30 grays in 10 fractions over two weeks, 14 patients were given adjuvant cerebral irradiation, the 19 others made up the control group (30 grays to the brain overall in 10 fractions over two weeks). With a minimum follow up for 12 months, 42% of the control group had evidence of cerebral secondaries, as opposed to none in the irradiated group with any neurological signs whatsoever. The indisputable efficacy of adjuvant cerebral irradiation contrasts with the absence of any significant improvement in survival time : 2 patients are alive and in complete remission, 1 in each group, while the mean survival was 12.3 and 11.7 months respectively. This is explained by the continued occurrence of extra-cerebral metastatic deposits such as the liver or mediastinum where the efficacy of systemic therapy remains uncertain. The therapeutic approach is currently orientated in two directions : - to raise the dose delivered to the mediastinum even if it appears radiologically normal. - to continue research into new chemo-therapeutic combinations more specifically active at the hepatic level.

During the period from January 1977-August 1979, 18 patients with biopsy-proven pancreas duct or ampullary adenocarcinoma with no distant or liver metastases underwent external beam radiation therapy following laparotomy. With the use of a 25 MEV photon beam and a four field "box" technique, the dose delivered to the target volume identified with radio-opaque clips at laparotomy was 6000 rad in six weeks, while largely sparing the spinal cord, kidney, liver and gut. All patients subjected to low fat, gluten free diet completed treatment as planned without any acute reaction. Three patients developed delayed pancreatic insufficiency. According to actuarial survival analysis and low morbidity such an approach may lead to increase survival in patients with pancreatic cancer.