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K Stelzer

Publications and source records attributed to K Stelzer.

At least 19 recordsLinked to original sources
PubMed2004

Evidence for multiphonon giant resonances in electromagnetic fission of 238U.

Differential cross sections for electromagnetic fission of 238U projectiles (500 MeV/u) in C, Sn, and Pb targets are measured and analyzed in terms of single- and multiphonon giant resonance excitations as doorway states to fission. A novel experimental method exploits the linear relationship between neutron multiplicity and the primary 238U excitation energy. Multiphonon states contribute up to 20% of the cross section; a component at high excitation energies is indicated that may arise from three-phonon dipole and two-phonon GDR x GQRiv giant resonance excitations.

Journal Article↗
PubMed2001

Permanent low-activity (125)I seed placement for the treatment of pediatric brain tumors: preliminary experience.

Although external beam radiation therapy is effective in the treatment of many pediatric brain neoplasms its use in this patient population has been associated with the development of significant cognitive and endocrine dysfunction and is severely limited as an option in previously irradiated patients. Therefore, we have adopted a strategy for management of residual microscopic disease by implantation of low-activity (125)I seeds in the tumor bed at the time of surgery. Six patients aged 2-14 years with recurrent tumors including two supratentorial primitive neuroectodermal tumors (n = 2), one medulloblastoma, one malignant ependymoma (n = 1), glioblastoma (n = 1) and one pleomorphic xanthoastrocytoma were implanted at the time of reoperation. A total of 11-126 seeds were implanted resulting in total doses of 16-21.8 Gy (after theoretical infinite time) at a depth of 5 mm from the implanted resection bed. Five patients had prior external beam radiation while the other patient (2 years old at initial diagnosis) progressed after surgery and chemotherapy. Two patients had lasting local tumor control. One patient is alive at 390 weeks of follow-up and another who died of distant failure at 366 weeks had no recurrence on MRI at 333 weeks' follow-up. Only 2 patients had first local failures. These results suggest that the use of permanent low-activity (125)I seeds as an adjunct to surgery can provide good local tumor control and is a suitable treatment option for pediatric patients.

Adolescent↗
PubMed2000

Commissioning an image-guided localization system for radiotherapy.

PURPOSE: To describe the design and commissioning of a system for the treatment of classes of tumors that require highly accurate target localization during a course of fractionated external-beam therapy. This system uses image-guided localization techniques in the linac vault to position patients being treated for cranial tumors using stereotactic radiotherapy, conformal radiotherapy, and intensity-modulated radiation therapy techniques. Design constraints included flexibility in the use of treatment-planning software, accuracy and precision of repeat localization, limits on the time and human resources needed to use the system, and ease of use. METHODS AND MATERIALS: A commercially marketed, stereotactic radiotherapy system, based on a system designed at the University of Florida, Gainesville, was adapted for use at the University of Washington Medical Center. A stereo pair of cameras in the linac vault were used to detect the position and orientation of an array of fiducial markers that are attached to a patient's biteblock. The system was modified to allow the use of either a treatment-planning system designed for stereotactic treatments, or a general, three-dimensional radiation therapy planning program. Measurements of the precision and accuracy of the target localization, dose delivery, and patient positioning were made using a number of different jigs and devices. Procedures were developed for the safe and accurate clinical use of the system. RESULTS: The accuracy of the target localization is comparable to that of other treatment-planning systems. Gantry sag, which cannot be improved, was measured to be 1.7 mm, which had the effect of broadening the dose distribution, as confirmed by a comparison of measurement and calculation. The accuracy of positioning a target point in the radiation field was 1.0 +/- 0.2 mm. The calibration procedure using the room-based lasers had an accuracy of 0.76 mm, and using a floor-based radiosurgery system it was 0.73 mm. Target localization error in a phantom was 0.64 +/- 0.77 mm. Errors in positioning due to couch rotation error were reduced using the system. CONCLUSION: The system described has proven to have acceptable accuracy and precision for the clinical goals for which it was designed. It is robust in detecting errors, and it requires only a nominal increase in setup time and effort. Future work will focus on evaluating its suitability for use in the treatment of head-and-neck cancers not contained within the cranial vault.

Brain Neoplasms↗
PubMed2000

Treatment of locally advanced adenoid cystic carcinoma of the head and neck with neutron radiotherapy.

PURPOSE: To examine the efficacy of fast neutron radiotherapy for the treatment of locally advanced and/or recurrent adenoid cystic carcinoma of the head and neck and to identify prognostic variables associated with local-regional control and survival. METHODS AND MATERIALS: One hundred fifty-nine patients with nonmetastatic, previously unirradiated, locally advanced, and/or recurrent adenoid cystic carcinoma (ACC) of the head and neck region were treated with fast neutron radiotherapy during the years 1985-1997. One hundred fifty-one patients had either unresectable disease, or gross residual disease (GRD) after an attempted surgical extirpation. Eight patients had microscopic residual disease and were analyzed separately. Sixty-two percent of patients had tumors arising in minor salivary glands, 29% in major salivary glands, and 9% in other sites such as the lacrimal glands, tracheal-bronchial tree, etc. Fifty-five percent of patients were treated for postsurgical recurrent disease and 13% of patients had lymph node involvement at the time of treatment. The median duration of follow-up was 32 months (range 3-142 months). Actuarial curves for survival, cause-specific survival, local-regional control, and the development of distant metastases are presented for times out to 11 years. RESULTS: The 5-year actuarial local-regional tumor control rate for the 151 patients with GRD was 57%; the 5-year actuarial overall survival rate was 72%; and the 5-year actuarial cause-specific survival rate was 77%. Variables associated with decreased local-regional control in the patients with GRD as determined by multivariate analysis included base of skull involvement (p < 0.01) and biopsy only versus an attempted surgical resection prior to treatment (p = 0.03). Patients without these negative factors had an actuarial local-regional control rate of 80% at 5 years. Patients with microscopic residual disease (n = 8) had a 5-year actuarial local-regional control rate of 100%. Base of skull involvement (p < 0.001), lymph node metastases at the time of treatment (p < 0.01), biopsy only prior to neutron radiotherapy (p = 0.03), and recurrent tumors (p = 0.04) were found to be associated with a diminished cause-specific survival as ascertained by multivariate analysis. Patients with base of skull involvement and positive lymph nodes at presentation had an increased rate of the development of distant metastases at 5 years, (p < 0.01 and p < 0.001, respectively). No statistical difference in outcome was observed between major and minor salivary gland sites. CONCLUSIONS: Fast neutron radiotherapy is an effective treatment for locally advanced ACC of the head and neck region with acceptable toxicity. Further improvements in local-regional control are not likely to impact survival until more effective systemic agents are developed to prevent and/or treat distant metastatic disease.

Analysis of Variance↗
PubMed1998

Uterine papillary serous carcinoma: evaluation of long-term survival in surgically staged patients.

OBJECTIVE: Earlier studies have demonstrated that the uterine papillary serous carcinoma (UPSC) variant of endometrial carcinoma has a high recurrence rate, even when disease is apparently confined to the uterus. The current study evaluated survival in patients with surgically staged UPSC. METHODS: Patients with UPSC were identified from surgical pathology files and charts were retrospectively reviewed. Only patients who had undergone a TAH-BSO, lymph node dissection, and peritoneal cytology were included. RESULTS: The FIGO stages of the 36 patients were 12 Stage I (4 IA, 4 IB, 4 IC), 2 Stage IIB, 13 Stage III (5 IIIA, 8 IIIC), and 9 Stage IV. Of the 14 Stage I/II patients, 6 did not receive adjuvant therapy, 5 received whole pelvic radiation (WPXRT), and 3 received whole abdominal radiation therapy (WART); after a median follow-up interval of 50 months only 2 (14%) of these Stage I/II patients have developed a recurrence. Both of the recurrences were in Stage IC patients who received radiation; 1 recurred in the radiation field. Of the 5 Stage IIIA patients, 3 patients declined therapy and 2 were treated with WART; 3 patients, including the 2 who received radiation therapy, are alive without disease. Of the 8 Stage IIIC patients, 2 declined postoperative therapy, 2 received WART, and 4 received WPXRT with an extended field to include paraaortic nodes. Four of the 6 Stage IIIC patients treated with curative intent are without evidence of disease and 1 died of unrelated causes after a median follow-up interval of 48 months. Both of the Stage IIIC patients who declined treatment recurred. Of the 9 patients with Stage IV disease, 8 have died of disease. CONCLUSION: Women with UPSC have a good prognosis when surgical staging confirms that disease is confined to the uterus (Stage I/II). Surgical findings can also be used to tailor adjuvant radiation treatments. Further study is required to define the optimal treatment for women with metastatic UPSC.

Aged↗
PubMed1996

[Hematuria--diagnostic procedure and therapeutic approaches].

Hematuria is a common clinical problem. It may arise from benign diseases posing minimal risk to the patient to potentially life-threatening conditions. Due to its many causes, the evaluation of hematuria often requires various different diagnostic procedures. To prevent unnecessary diagnostic tests, the workup should begin with noninvasive techniques such as history, urinalysis, laboratory data and ultrasonography. This proceeding allows a simple and rapid differentiation in renal and non-renal causes of hematuria in most cases.

Acanthocytes↗
PubMed1994

Neoadjuvant therapy: a novel and effective treatment for stage IIIb non-small cell lung cancer. Southwest Oncology Group.

Neoadjuvant therapy has become an accepted treatment for stage IIIa, but not for stage IIIb, non-small cell lung cancer, which is usually considered incurable and treated nonsurgically. We determined the feasibility of neoadjuvant therapy in the setting of stage IIIb non-small cell lung cancer in a prospective multi-institutional trial. For patients to be eligible for entry into the study, they had to have pathologically documented T1-4 N2-3 disease. Treatment consisted of: (1) cisplatin (50 mg/m2) given on days 1, 8, 29, and 36 plus VP-16 (50 mg/m2) given on days 1 to 5 and 29 to 33, together with concurrent radiotherapy (4,500 cGy; 180 cGy per daily fraction); and (2) surgical resection performed 3 to 5 weeks after induction of medical therapy, if the response was stable, partial, or complete. Of the 126 total eligible patients entered into the study, 51 patients had stage IIIb tumors (24 with T4 tumors and 27 with N3 disease). This consisted of 34 men and 17 women with a median age of 57 years. Thirty-two (63%) patients (18 with T4 tumors and 14 with N3 disease) underwent resection of the primary tumor, with a 5.2% operative mortality. There was no difference in the operative time, blood loss, and length of hospital stay for the T4 versus the N3 patients. For all 51 patients, survival at 2 years was 39%. Sites of relapse in all patients were mainly distant, even though patients with N3 disease did not initially have involved N3 nodes resected.(ABSTRACT TRUNCATED AT 250 WORDS)

Adult↗
PubMed1991

Results of neutron radiosurgery for inoperable arteriovenous malformations of the brain.

Twenty patients with inoperable arteriovenous malformations (AVMs) of the brain were treated with neutron radiosurgery. A 50 MeV cyclotron was used to deliver 9 Gy in a single fraction through 7 to 14 isocentric portals. The size and shape of the portals were customized to each treatment site. Nineteen patients have been followed for a median duration of 24 months following neutron radiosurgery. A radiographically demonstrable partial response was seen in 8 patients (42%). No complete responses were observed. There has been one post-treatment hemorrhage, no fatalities, and no evidence of radiation toxicity. The low response rate and absence of toxicity suggest that the appropriate dose for neutron radiosurgical treatment of AVMs is higher than the dose of 9 Gy at isocenter used in this initial study.

Adult↗
PubMed1984

[Behavior of oxypolygelatine (Gelifundol) in patients with dialysis-dependent kidney failure].

Colloidal solutions are used with increasing frequency as plasma replacement, in addition to thrombosis prophylaxis, for treating disturbances of the microcirculation and hemodilution as well as for cases of decreases in blood pressure during hemodialysis and hemofiltration treatments. The effects of the dextran, hydroxyethyl amylum and gelatine preparations available very greatly, for example with regard to expander effect, half life, elimination etc. Gelatine solutions have a particularly short intravascular retention and therefore appeared to us to be especially suitable for treating decreases in blood pressure and states of shock during hemodialysis and hemofiltration. We examined the behaviour of 5,5% oxypolygelatine (OPG) in 11 patients during dialysis treatment (6 patients with a residual diuresis smaller than 500 ml/24 h, 5 patients with a residual diuresis larger than 500 ml/24 h). Before each of the 12 treatments 250 ml OPG was administered to all patients. 48 hours later 86-93% of the infused OPG had been eliminated. Despite repeated doses no remarkable OPG cumulation was registered.

Adult↗