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T Zusag

Publications and source records attributed to T Zusag.

5 recordsLinked to original sources
PubMed1999

Dose enhancement by a thin foil of high-Z material: a Monte Carlo study.

The purpose of this work is to study the dose enhancement by a thin foil (thickness of 0.2-4 mm) of high-Z material in a water phantom, irradiated by high-energy photon beams. EGS4 Monte Carlo technique was used. Perturbations on the beam spectra due to the presence of the foils, and dose enhancement dependence of photon-beam quality, beam incident angle, atomic number (Z), the thickness and size of the foil, and the depth of the foil situated in the phantom were studied. Analysis of photon and secondary-electron spectra indicates that the dose enhancement near an inhomogeneity interface is primarily due to secondary electrons. A calculation for 1-mm-thick planar lead foil in a water phantom shows that the dose enhancements at 0.25, 1, 2 and 3 mm away from the foil in the backward region were 58%, 37%, 24% and 17%, respectively, for a 15 MV beam. Calculations for a variety of planar foils and photon beams show that dose enhancement: (a) increases with Z; (b) decreases with decreasing foil thickness when the foils are thinner than a certain value (1 mm for lead foil for 15 MV); (c) decreases with decreasing incident photon-beam energies; (d) changes slightly for beam incident angles less than 45 degrees and more prominently for larger angles; (e) increases with size of foil; and (f) is almost independent of the depth at which the foil is situated when the foil is placed beyond the range of secondary electrons. The dose enhancement calculation is also performed for a cylindrically shaped lead foil irradiated by a four-field-box. The dose enhancement of 34%/13% was obtained at 0.25/2 mm away from the cylindrical outer interface for a 15 MV four-field-box.

Algorithms↗
PubMed1980

Late effects of para-aortic irradiation in carcinoma of the uterine cervix and endometrium.

Twenty-one patients with cervical or endometrial carcinoma and metastases to the para-aortic lymph nodes were treated with extended-field para-aortic irradiation. The late effects of this treatment were evaluated in 16 patients who had a minimum follow-up of six months. All of the patients with massive pelvic tumours died of active disease in the pelvis with or without metastases. Three patients had small-bowel complications; none of the patients who underwent exploratory laparotomy for lymph node biospy had bowel complications. The results indicate that patients with central lesions and minimal para-aortic disease benefit most from para-aortic irradiation. It is concluded that metastases to the para-aortic lymoh nodes do not necessarily indicate more distant spread, and can be cured with irradiation. The late complication rate can be minimized by reducing the dosage to the small bowel with a combination of anterior-posterior fields and 360 degree rotation or opposing lateral 120 degree arc fields, and by using the extraperitoneal approach for lymph node biopsy.

Abdomen↗
PubMedDate not supplied

Whole-abdominal radiation in endometrial carcinoma: an analysis of toxicity, patterns of recurrence, and survival.

PURPOSE: The purpose of this study was to determine the toxicity, patterns of recurrence, and survival in high-risk endometrial cancer patients treated with whole-abdominal radiation. MATERIALS AND METHODS: All patients with endometrial cancer treated at Northwestern University since 1994 and at Rush University since 1993 were retrospectively reviewed. Patients believed to be at high risk for intra-abdominal recurrence and who received whole-abdominal radiation were reviewed for this study. RESULTS: A total of 30 patients completed whole-abdominal radiation (WAR) and were available for study. The mean and median follow-up was 2.3 and 2.1 years, respectively, with a range of 0.13 to 6.1 years. Seventy-eight percent of the cohort received surgical staging with bilateral salpingo-oophorectomy/total abdominal hysterectomy/lymph node sampling. Forty-seven percent of the patients were found to have serous histology as a component of their tumor. Surgical staging results included 19% stage 1B, 4% stage IC, 8% stage IIB, 37% stage IIIA, 26% stage IIIC, and 7% stage IVB. Two patients had gross residual disease at the completion of surgery. Megestrol acetate (Megace) was used as an adjuvant treatment in 37% of patients, and no cases received initial chemotherapy. All patients received WAR with a mean total dose and dose per fraction of 2620 and 143 cGy, respectively. Twenty-two percent of patients received a para-aortic boost. The mean total pelvic dose was 4956 cGy. Seventy percent of patients received a vaginal cuff boost. Eight percent of patients had grade 3 acute gastrointestinal morbidity, and 4% had grade 4 acute gastrointestinal morbidity. No other grade 3 or greater acute or long-term morbidity was noted. At last follow-up, seven (23%) patients had experienced recurrence. The pattern of first recurrence was 0% in the vaginal cuff, 3% other vaginal, 7% pelvic, 7% upper abdominal, 3% lung, 7% bone, and 7% para-aortic lymph nodes. Ultimate recurrences were similar. At last follow-up, 77% patients had no evidence of disease, 13% were alive with disease, and 10% had died of disease. CONCLUSIONS: Utilizing a conservatrive total whole-abdominal radiation dose and limited para-aortic nodal boost resulted in very tolerable treatments. The patterns of recurrence and survival in this early report are encouraging.

Abdominal Neoplasms↗