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Biomedical subjects

L Souhami

Publications and source records attributed to L Souhami.

68 records · Page 4Linked to original sources
PubMed1990

Radiosurgery with photon beams: physical aspects and adequacy of linear accelerators.

The question of the adequacy of isocentric linear accelerators (linacs) for use in radiosurgery is addressed. The general physical requirements for radiosurgery, mainly a high spatial and numerical accuracy of dose delivery, reasonable treatment time, and low skin and leakage dose as well as cost considerations are examined. Various linac-based procedures are analyzed in view of their ability to meet these requirements and are contrasted with the clinically proven system of the Gamma unit. It is shown that the linac-based multiple converging arcs techniques and the dynamic rotation meet the stringent physical requirements on dose delivery and are thus viable alternatives to radiosurgery with the commercially available and dedicated Gamma unit.

Costs and Cost Analysis↗
PubMed1990

Radiosurgery of cerebral arteriovenous malformations with the dynamic stereotactic irradiation.

From December 1986 through December 1988, 33 patients with inoperable arteriovenous malformation (AVM) were treated in our center with the dynamic stereotactic radiosurgery, which uses a standard 10 MV isocentric linear accelerator. There were 18 females and 15 males with a median age of 26 years (range: 9-69) and a median follow-up time of 16 months (range: 7-32). The arteriovenous malformation volumes treated ranged from 0.2 to 42 cm3. The prescribed doses at the isocenter varied from 50 to 55 Gy and were given as a single fraction in the majority of the patients (31/33). Late complications consisting of intracranial bleeding and/or hemiparesis were observed in three patients. To date, 21 patients underwent repeat angiographic studies at 1 year post-treatment. A complete obliteration of the lesion was achieved in 38% of these patients. For the patients whose arteriovenous malformation nidus was covered by a minimum dose of 25 Gy, the total obliteration rate was 61.5% (8/13), whereas none of the patients who had received less than 25 Gy at the edge of the nidus obtained a total obliteration. Our preliminary analysis at 1 year post-radiosurgery reveals results comparable to those previously reported for other radiosurgical techniques for the same follow-up period.

Adolescent↗
PubMed1990

Increased pulmonary toxicity with bleomycin and cisplatin chemotherapy combinations.

Combination chemotherapy that included bleomycin and cisplatin was administered to 45 evaluable patients (30 with cervix carcinoma and 15 with germ cell tumors). Bleomycin was given, following cisplatin infusion, either by intravenous continuous infusion over 72 h (germ cell tumor patients) or intramuscularly every 12 h for 4 days (cervix carcinoma patients). Total bleomycin doses ranged from 156 to 360 U. Nine patients with normal renal function and no previous pulmonary disease prior to chemotherapy developed serious pulmonary toxicity. Six patients died from irreversible respiratory failure. Postmortem lung studies were performed in all six patients and revealed findings compatible with bleomycin-induced lung toxicity. Renal tubular damage was found in four kidneys available for examination. Five (71.5%) of the seven patients whose serum creatinine increased after chemotherapy was initiated developed lung injury, whereas 10.5% of those without change in the serum creatinine level presented this complication (p = 0.001). Renal damage, following cisplatin administration, with subsequent accumulation of bleomycin was the likely cause of the high lung toxicity. Extreme caution is recommended in the administration of combined bleomycin-cisplatin chemotherapy. Whenever possible, bleomycin should precede cisplatin infusion to minimize the risk of lung toxicity.

Adult↗
PubMed1989

Radiosurgery with high energy photon beams: a comparison among techniques.

The presently known radiosurgical techniques with high energy photon beams are based either on the commercially available Gamma unit utilizing 201 stationary cobalt beams or on isocentric linear accelerators. The techniques using linear accelerators are divided into the single plane rotation, the multiple non-coplanar arcs, and the dynamic rotation. A brief description of these techniques is given, and their physical characteristics, such as precision of dose delivery, dose fall-off outside the target volume, and isodose distributions are discussed. It is shown that the multiple non-coplanar arcs technique and the dynamic rotation give dose distributions similar to those of the Gamma unit, which makes these two linear accelerator based techniques attractive alternatives to radiosurgery with the Gamma unit.

Brain Diseases↗
PubMed1988

Combined treatment in carcinoma of the nasopharynx.

From October 1982 to August 1984, 30 previously untreated patients with biopsy-proven carcinoma of the nasopharynx, stage III (26.5%) and stage IV (73.5%), received combined radiotherapy (6,000 to 7,000 cGy over a period of 7 to 7.5 weeks) and chemotherapy (mitomycin-C 10 mg/M2, IV; 5-fluorouracil 750 mg/M2, IV; and methotrexate 30 mg/M2, IV) concomitantly. There were 20 males and 10 females, with a median age of 40 years. Minimal follow-up duration was 24 months. Actuarial overall survival rate at 48 months was 49%. Complete local response was achieved in 75% of the patients, with 31% of the cases failing distantly. The complication rate was high and included severe mucositis, xerostomia, and septicemia (fatal in two cases). Despite high local disease control, survival rate did not increase. A randomized trial is urgently needed to establish whether or not combined treatment is of value in advanced carcinoma of the nasopharynx.

Actuarial Analysis↗
PubMed1987

The treatment of stage III carcinoma of the uterine cervix with telecobalt irradiation.

This is a retrospective analysis of 148 patients with histologically proven carcinoma of the cervix, stage III, treated with irradiation. All patients received external irradiation with cobalt 60 followed by intracavitary radium application. The median age was 55 years. Squamous cell carcinoma was found in 96.5% of the cases. The 8-year actuarial survival rate was 41%. Bilateral parametrial invasion proved to be a strong prognostic factor. Patients with unilateral disease had a survival rate of 43% whereas in those with bilateral involvement it was only 15% (P less than 0.005). The total pelvic failure rate was 29.5%. The overall incidence of distant metastasis was 11%. The complication rate (minor and major complications) was high, with vaginal stenosis (22.5%), proctitis (21.5%), cystitis (13.5%), and fistulae (4%) occurring in 33, 32, 20, and 6 patients, respectively. New treatment modalities are urgently needed for advanced carcinoma of the cervix. Bilateral parametrial involvement is an unfavorable prognostic factor and this should be kept in mind when designing new protocols.

Adult↗
PubMed1984

Quality assurance in radiation therapy: clinical aspects.

A survey was conducted in Latin America to evaluate the clinical aspects of quality assurance in radiotherapy. A questionnaire was prepared and sent to 46 institutions. Twenty-seven centers (58.5%), from nine countries, answered the questionnaire. The study was divided into three topics: a) patient-related statistics; b) staffing and education; and c) equipment and facilities. Fifty-two percent of the radiotherapists and 44% of the physicists work on a part-time basis. One third of the institutions are understaffed. Radiotherapy training programs are available in only 37% of the centers studied. A large number of megavoltage units are old, operating at a shorter than optimum distance with sources of very low activity. The number of high energy linear accelerators is unsatisfactory. Problems in treatment planning facilities were also identified. Regionalization of radiation therapy services is recommended as a possible way to improve quality at a reasonable cost.

Cancer Care Facilities↗
PubMed1979

Micrococcus luteus pneumonia: a case report and review of the literature.

The clinical course of a 69-year-old male with acute myelogenous leukemia is described who, while extremely leukopenic (less than 100 neutrophils/microliter) from chemotherapy, developed a cavitating pneumonia due to a gram-positive coccus, Micrococcus luteus. Aggressive antibiotic management and attainment of complete remission of his leukemia resulted in a successful outcome. A review of the literature regarding the pathogenicity of this organism and, in particular, its occurrence as a cause of pneumonia is presented.

Aged↗
PubMed1978

Urticaria following intravenous doxorubicin administration.

Urticaria developed above the site of injection with doxorubicin hydrochloride in 11 patients with malignant neoplasms. Generalized urticaria without anaphylaxis developed in one patient, while only local reactions developed in the other ten. A reaction developed in two patients on their first exposure to doxorubicin. Two of the seven patients who received subsequent doxorubicin therapy had further reactions. Urticaria does not seem to be a contraindication to further treatment with doxorubicin if the patient is closely observed. The value of prophylactic antihistamines of corticosteroids is not clear.

Adult↗
PubMedDate not supplied

Primary malignant mesodermal ovarian sarcomas.

Primary malignant mesodermal ovarian sarcomas are rare tumors and have a poor prognosis. The disease is usually diagnosed at a late stage and 5-year survivals are uncommon. Most patients are treated with debulking surgery followed by adjuvant chemotherapy. We report ten patients treated at a single institution. All patients underwent surgery and 90% received adjuvant chemotherapy. The median survival was 20 months, and only one patient survived beyond 5 years. Newer treatment strategies are urgently needed in the management of this disease.

Adult↗
PubMedDate not supplied

Erythropoietin receptor expression in biopsy specimens from patients with uterine cervix squamous cell carcinoma.

Hypoxia, an important mechanism of radioresistance, is a strong stimulus for erythropoietin (EPO) production. The stimulatory effects of EPO are mediated through the activation of its receptors, EPO receptors (EPORs). The objective of this study is to determine whether EPORs are expressed in biopsy specimens of patients with squamous cell carcinoma of the cervix. Eighteen biopsy specimens were studied after obtaining Institutional Review Board-approved consent. Standard immunohistochemistry techniques were utilized. Expression of EPORs was present in 16 out of 18 (88.9%) specimens. The intensity (qualitative) and the frequency (semiquantitative) of EPORs expression showed a statistically significant correlation (P= 0.00379). Statistical analysis was performed to determine whether EPORs expression is related to other parameters such as age, FIGO stage, histologic grade, and hemoglobin levels. Only age showed a statistically significant correlation with EPORs frequency of expression (P= 0.00878). Currently, work is in progress in our laboratory to study the radiobiologic effects of EPO on the radiation response of cultured cancer cell lines in vitro.

Adult↗
PubMedDate not supplied

Dose distributions in radiosurgery.

A PC-based, three-dimensional treatment planning system, which may be used for planning of radiosurgical treatments with the Gamma unit or with any of the radiosurgical techniques based on isocentric linear accelerators (linacs), is described and used to calculate isodose distributions for various linac-based radiosurgical techniques ranging from the single plane rotation to a 4-pi geometry. The latter gives an isotropic dose falloff outside the target volume but cannot be used for practical radiosurgery, while the single plane rotation is simple to use but gives unacceptably shallow dose falloffs in the transverse plane. Dose falloffs for several other techniques of varying degrees of complexity are shown and discussed. Also discussed is the effect of beam energy and beam profiles on radiosurgical dose distributions.

Humans↗
PubMedDate not supplied

Cylindrical dose distributions in pseudodynamic rotation radiosurgery: an experimental study.

A linac-based radiosurgical technique is reported which produces cylindrical isodose distributions covering cylindrical targets of arbitrary orientations within the patient's head. The technique uses rectangular collimators and 4 degrees of freedom: gantry and couch rotation, as defined by a previously known dynamic rotation technique, collimator rotation, and collimator length adjustment. The relationship between the four parameters is derived and because of its complexity, the cylindrical dynamic rotation technique is introduced as a pseudodynamic technique. For cylindrical targets, the cylindrical pseudodynamic technique is comparison to the standard spherical technique produces considerable dose savings to healthy tissue surrounding the target and gives a similar or better dose fall-off outside the target.

Biophysical Phenomena↗