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Biomedical subjects

J G Schwade

Publications and source records attributed to J G Schwade.

At least 19 recordsLinked to original sources
PubMed2000

The influence of beam energy on the outcome of postoperative radiotherapy in head and neck cancer patients: secondary analysis of RTOG 85-03.

PURPOSE: To determine whether any difference in toxicity or efficacy occurs when head and neck cancer patients are treated postoperatively with (60)C0, 4 MV, or 6 MV photon beam. METHODS AND MATERIALS: This is a secondary analysis of the Intergroup Study 0034. Three hundred ninety-two patients were evaluable for comparison between treatment with (60)C0, 4 MV, or 6 MV photon beam. All patients had advanced but operable squamous cell carcinoma of the oral cavity, oropharynx, hypopharynx, or larynx. Patients were randomized following surgical resection to receive treatment with either postoperative irradiation alone, or postoperative irradiation plus three cycles of cisplatin and 5-fluorouracil. Patients were categorized as having either "low risk" or "high risk" treatment volumes based on whether the surgical margin was 5 mm or less, presence of extra capsular nodal extension, and/or carcinoma in situ at the surgical margins. Low-risk volumes received 50-54 Gy, and high-risk volumes were given 60 Gy. Patients were compared in regards to acute and late radiotherapy toxicities as well as overall survival and loco-regional control according to the beam energy used. RESULTS: One-hundred fifty-seven, 140, and 95 patients were treated by (60)C0, 4 MV, and 6 MV, respectively. No differences were seen in acute or late toxicity among treatment groups. Locoregional control was achieved in 75%, 79%, and 80% of patients treated with (60)C0, 4 MV, or 6 MV (p = 0.61). Patients treated with 6 MV had a higher incidence of ipsilateral neck failure as first event (13%) than patients treated by (60)C0 and 4 MV (9%). This difference was not statistically significant. CONCLUSION: No differences in outcome, acute, or late toxicity were discernible in patients with advanced head and neck cancer treated with (60)C0, 4 MV, or 6 MV. This result should be interpreted with caution as increased incidence, albeit nonsignificant, of ipsilateral neck recurrence was observed in patients treated with 6 MV and the power of the study to detect a statistically significant difference is small.

Adult↗
PubMed1997

Hyperfractionated radiation therapy and 5-fluorouracil, cisplatin, and mitomycin-C (+/- granulocyte-colony stimulating factor) in the treatment of patients with locally advanced head and neck carcinoma.

BACKGROUND: The authors had previously reported preliminary results of a treatment regimen of concurrent hyperfractionated radiation therapy and chemotherapy in patients with locally advanced head and neck carcinoma that demonstrated both feasibility and high local control. In an attempt to reduce acute mucosal and hematologic toxicity, granulocyte-colony stimulating factor (G-CSF) was added during the second phase of this study. METHODS: Seventy patients (53 with Stage IV and 17 with Stage III disease) were entered between May 1988 and June 1995 into a Phase I/II trial of concurrent radiation therapy (74.4 gray (Gy) total dose; 1.20 Gy twice daily), 5-fluorouracil (1000 mg/m2/24 hours for 72 hours), and cisplatin (50 mg/m2) for 3 cycles with the addition of mitomycin C (8 mg/m2) in Cycle 2. G-CSF was added after the initial entry of 34 patients. RESULTS: At a median follow-up of 41 months (range, 12-80 months), 44 patients were alive with a projected median overall survival of 54 months. Grade 3/4 mucositis, observed in 65% of patients, was equally prevalent and prolonged in both G-CSF-treated (+) and G-CSF-naive (-) patients. Grade 3/4 leukopenia was present in 45% and 36% of G-CSF- and G-CSF+ patients, respectively. The 3-year locoregional control and cause specific survival rates were 68% and 75%, respectively. CONCLUSIONS: This regimen was feasible and effective but caused severe mucositis. No benefit was derived from the addition of G-CSF. This regimen deserves further modification to reduce acute mucositis toxicity yet maintain the high locoregional control rate.

Adult↗
PubMed1994

A multivariate analysis of clinicopathologic factors for predicting outcome in uterine sarcomas.

This study involved a comprehensive review of the histologic slides of 62 patients who were diagnosed with uterine sarcoma from 1978 through 1988 at a single institution. In addition, DNA content (ploidy level) could be determined from the H & E slides of these tumors using image analysis. Also, 42 of these cases had retrievable cell blocks on which DNA analysis was performed by means of flow cytometry. A linear regression analysis found a high degree of correlation (r = 0.8) between the measurement of the DNA index of these tumors by these two techniques. All cases were retrospectively restaged using the newly adopted FIGO surgical staging criteria which found the following distribution: 22 (35.5%) Stage I, 10 (16.1%) Stage II, 12 (19.4%) Stage III, and 18 (29%) Stage IV. A multivariate analysis of 60 evaluable patients using the Cox proportional hazard model found that surgical staging was the most significant prognostic factor with respect to the endpoint of overall survival (P = 0.00004). Both patient age at diagnosis and mitotic index were independent from surgical staging in predicting outcome. Furthermore, there was a trend suggesting that DNA index also had prognostic value. Of particular interest was that patients with diploid tumors (DNA index, 0.9-1.1) had a 5-year overall survival of 72% and did not approach median survival; however, hyperdiploid tumors (DNA index > 1.1) and hypodiploid tumors (DNA index < 0.9) were associated with median survivals of 18 and 12 months, respectively. In conclusion, this study supports the use of surgical staging of patients with uterine sarcomas in order to optimally determine their chance for survival. Further biologic investigations which may result in identifying those patients who could benefit from adjunctive treatment are recommended.

Adult↗
PubMed1994

Long-term follow-up of gliomas treated with fractionated stereotactic irradiation.

Eighteen patients have been treated for gliomas with fractionated stereotactic linear accelerator (LINAC) irradiation. A plastic halo ring secured with skull pins allows daily attachment of the patient to the stereotactic frame mounted on the linear accelerator. The patients received 9-31 fractions of 1.8-3 Gy/fraction over periods of 20-49 days. Total doses delivered stereotactically where 16-60 Gy (90% isodose) delivered to 3-7 cm diameter tumors. The six patients with glioblastoma had a median survival of 16 months (range 7-60 months). The two patients with anaplastic astrocytoma survived 7 and 78 months. Most of the patients with high grade tumors also received other adjuant treatments. Of the ten patients with low grade gliomas, one expired 66 months after treatment, and the remainder are alive 22-82 months after treatment. One pediatric patient displayed evidence of focal radiation injury with visual loss. No patient developed initial recurrence of tumor outside the focally irradiated field. Stereotactic localization of irradiation protects surrounding brain tissue; fractionation improves the therapeutic ratio. These extended follow-up data indicate that stereotactic restriction of radiation fields in treatment of gliomas does not result in deterioration of survival results. Further investigation is warranted into the use of higher focal fractionated radiation doses to attempt to improve local control and survival.

Adolescent↗
PubMed1994

The role of steroids in the management of metastatic carcinoma to the brain. A pilot prospective trial.

This prospective study attempted to evaluate the indications for glucocorticoids which are commonly given to patients with brain metastases. Twelve patients with histologically confirmed malignancies and radiographically documented brain metastases were enrolled. Patients were scored for general performance status and neurologic function class. All subjects were given high-dose dexamethasone (HDD) for 48 hours and then randomized to receive either intermediate-dose dexamethasone (IDD) or no steroids with cranial radiotherapy. Of these 12 study patients, 3 achieved a complete response, 1 partial response, and 8 nonresponses to HDD. Seven patients had IDD, while five received no IDD. Although a small sample size prevented any statistical analysis, this study does suggest that the place for using glucocorticoids in treating patients with metastatic carcinoma to the brain remains uncertain and should be evaluated in a cooperative prospective trial.

Adult↗
PubMed1994

Retreatment of intracranial gliomas.

Although intracranial gliomas carry a poor long-term prognosis, retreatment at the time of tumor progression may prolong survival and maintain or improve the quality of life. Thirty-three patients who underwent retreatment with surgery, radiotherapy, and chemotherapy were reviewed retrospectively. Median survival after initiation of retreatment was 8 months for glioblastoma, 13 months for anaplastic astrocytoma, 22 months for astrocytoma, and 47 months for oligodendroglioma/mixed glioma. Survival was significantly better for younger patients and for those with better functional status. One third of patients were neurologically improved by surgery. Surgical morbidity was minimal (2.1%); there was no surgical mortality. Chemotherapy and radiotherapy produced expected adverse reactions. Retreatment of intracranial gliomas carries acceptable risk and is beneficial in selected patients. Decisions regarding retreatment must be carefully individualized with consideration of the quality of life and the wishes of the patient and family.

Adult↗
PubMed1993

Is a surgical resection leaving positive margins of benefit to the patient with locally advanced squamous cell carcinoma of the head and neck: a comparative study using the intergroup study 0034 and the Radiation Therapy Oncology Group head and neck database.

PURPOSE: The purpose of this study was to determine whether or not for patients with squamous cell carcinomas of the head and neck, a surgical resection leaving positive margins followed by postoperative adjuvant therapy improves the outcome compared to a matched group of patients treated with definitive radiotherapy alone. METHODS AND MATERIALS: From January 1985 through January 1990 a consortium of national cooperative groups (Radiation Therapy Oncology Group, Cancer and Leukemia Group B, Eastern Cooperative Oncology Group, Northern California Oncology Group, Southeast Group, and Southwest Oncology Group) conducted a phase III clinical trial testing the efficacy of adjuvant chemotherapy for patients with resectable, squamous cell carcinomas of the head and neck. One hundred and nine patients were excluded from this study due to positive surgical margins. These patients have been followed prospectively with regards to local/regional tumor control, development of distant metastases, and survival. The postoperative treatment of these patients was not specified by the protocol but the majority of patients received postoperative radiotherapy +/- chemotherapy. These patients were compared with a matched group of patients from the Radiation Therapy Oncology Group head and neck database of patients treated with definitive radiotherapy alone using a standard fractionation schema. Matching parameters included primary tumor site, T-stage, N-stage, Karnofsky performance status, and age. RESULTS: Actuarial curves are presented for local/regional control and survival. At 4 years the local/regional control rate is 44% for the positive margin patients compared to 24% for the patients from the data base (p = 0.007). However, there is no significant difference between the survival curves (p = 0.76) with respective median survivals being 18.1 months vs. 17.9 months and 4-year survivals being 29% vs. 25%. CONCLUSION: While an incomplete excision followed by postoperative therapy does not seem to improve survival compared to treatment with radiotherapy alone, it appears to yield significantly better local/regional control. This would argue for its applicability in selected palliative settings. A follow-up, Phase III trial for patients with advanced tumors may be warranted to test traditional resectability criteria.

Actuarial Analysis↗
PubMed1993

In vitro potentiation of radiation cytotoxicity by recombinant interferons in cervical cancer cell lines.

BACKGROUND: This investigation, which evaluates the combination of radiation and interferon, bridges two clinical treatments of cancer. Radiation therapy (RT) is an integral part of cervical cancer treatment; interferons (IFN), however, are classified as modifiers of biologic response. The authors evaluated the radiation-modulation effects of recombinant alpha-IFN and beta-IFN on two different human cervical cancer cell lines: ME-180 and SiHa. The radiation sensitivity based on the cell growth rate (logarithmic growth phase versus confluence) was also evaluated. METHODS: Control cells and cells pretreated with either alpha-IFN or beta-IFN were exposed to RT at doses of 0, 2, 5, 10, and 15 Gy. The pretreated cells received IFN at doses of 100, 500, 1000 and 5000 IU/ml for 24 hours. The adenosine triphosphate bioluminescence assay was used to measure the surviving fractions after 7 days of incubation. The data were analyzed using the linear-quadratic model and the radiosensitivity index D. The combined effects of IFN and RT on cytotoxicity were evaluated using the synergistic interaction formula for anticancer agents. RESULTS: The ME-180 and SiHa cell lines had the same mean inactivation D values of 13.2 when radiated at confluence. Irradiation of ME-180 and SiHa cells in the logarithmic growth phase resulted in mean inactivation D values of 7.5 and 10.2, respectively. Enhanced radiosensitivity was observed in all IFN-RT combinations. Synergism was observed in the majority of experiments. CONCLUSIONS: Recombinant alpha-IFN and beta-IFN potentiate the radiotoxicity of two cervical cancer cell lines. ME-180 cells were less sensitive to IFN alone than were SiHa cells, but they showed higher a radiosensitizing effect from both IFN. Proliferating cells were more sensitive than confluent cells to RT by itself and to RT-IFN combinations.

Carcinoma, Squamous Cell↗
PubMed1993

Synergistic antitumor activity of cisplatin and interleukin 1 in sensitive and resistant solid tumors.

The antitumor activity of cis-diamminedichloroplatinum(II) (cP) and human recombinant interleukin-1 alpha (IL-1 alpha) was studied in RIF-1 and SC VII solid tumor models and in a cP-resistant subline of RIF-1 designated RIF-R1cP. In RIF-1 tumors, clonogenic cell survival after cP plus IL-1 alpha combinations was highly schedule and IL-1 alpha dose dependent. More than additive clonogenic cell kill was seen when cP was given 6 h before, but not 8 h before or at 2-6 h after IL-1 alpha. Time course studies indicated that maximal clonogenic cell killing was achieved within 4-6 h after the cP plus IL-1 alpha combination, with little or no recovery for up to 24 h. In vivo dose-response studies indicated that cP plus IL-1 alpha combinations induced more clonogenic cell kill than cP alone in all three tumor models, and analysis by the median effect principle indicated highly synergistic antitumor activity. Dexamethasone but not indomethacin inhibited the synergistic interaction. IL-1 alpha had no effect on the cytotoxicity of cP in SCC VII cells in vitro, and neither in vitro hypoxia nor in vivo ischemia, induced by clamping tumor blood supply, significantly affected cP clonogenic cell killing. Increased clonogenic cell killing was seen, however, after removal of the clamp, implicating reperfusion events, such as oxyradical stress, as a potential mechanism for increased cP cytotoxicity in SCC VII solid tumors. The data from our model systems provide a rationale for additional work to define the mechanisms of the synergistic antitumor activity of the cP plus IL-1 alpha combination and indicate that IL-1 alpha might be a useful adjunct to increase the clinical efficacy of cP-containing strategies for both sensitive and cP-resistant cancers.

Animals↗
PubMed1993

Dose rate effect of 125I irradiation on normal rabbit eyes and experimental choroidal melanoma.

The dose rate effect of radiation by 125I plaque on choroidal melanoma and normal intraocular tissue was studied. In the first part of the experiment, high activity plaques (HAP) and low activity plaques (LAP) were implanted on rabbit eyes with experimental Greene choroidal melanoma to deliver a total dose of 10,000 cGy to the tumor apex. The mean dose rate calculated at 0.5 mm from the inner sclera in eight eyes with high activity plaques was 3341.5 cGy hr-1 (1 cGy = 1 rad) while that in ten eyes with low activity plaques was 239.9 cGy hr-1. For tumors less than 1.0 mm in height, both groups showed complete tumor regression at the tumor implantation site after plaque treatment. For tumors more than 1.0 mm in height, two out of two eyes in the low activity plaque group and one of four eyes in the high activity plaque group failed to show complete tumor regression. Both LAP and HAP were effective in eradicating tumors, but logistic regression analysis demonstrates that HAP was more effective than LAP when adjustment was made for initial tumor height (P = 0.032). Nine tumor control eyes without 125I plaque implantation demonstrated marked tumor growth within 3 weeks. In the second part of the experiment, 125I plaques were implanted on the sclera of 12 normal rabbits' eyes. Six received high dose rate plaque treatment, while the other six received low dose rate plaque treatment. Clinical and histologic examinations demonstrated more damaging effects to the normal chorioretinal tissues at the plaque implantation site in the high dose rate plaque group at 24 weeks of follow-up. These results suggest that high dose rate plaques are more effective than low dose rate plaques when tumor height is statistically controlled. However, high dose rate delivery increases the damaging effects on normal intraocular tissue.

Animals↗
PubMed1993

Survival comparison of radiosurgery-eligible and -ineligible malignant glioma patients treated with hyperfractionated radiation therapy and carmustine: a report of Radiation Therapy Oncology Group 83-02.

PURPOSE: The purpose is twofold: (1) to identify the malignant glioma patients treated in a trial of hyperfractionated radiotherapy (RT) and carmustine (BCNU) who may have been eligible for a stereotactic radiosurgery (SRS) boost; and (2) to compare survival of such patients with that of those considered SRS-ineligible. PATIENTS AND METHODS: From January 1983 to July 1989, 778 malignant glioma patients were enrolled on Radiation Therapy Oncology Group (RTOG) 83-02, a randomized phase I/II hyperfractionated RT dose-escalation trial with BCNU chemotherapy. The SRS criteria used in a single-institution trial were applied to these patients; they are: Karnofsky performance status (KPS) of greater than 60; well-circumscribed tumor less than 4.0 cm; no subependymal spread; and a location not adjacent to brainstem or optic chiasm. RESULTS: Eighty-nine patients (11.9%) were identified as potentially SRS-eligible. The median survival times (MST) and 18-month survival rates of the 89 eligible and 643 ineligible patients were 14.4 versus 11.7 months and 40% versus 27%, respectively (P = .047). The MST and 18-month survival rate of the 544 SRS-ineligible patients with KPS greater than 60 were 12.1 months and 29%, respectively, and were not statistically inferior to the survival of the SRS-eligible group (P = .21). Multivariate analysis revealed age, KPS, and histopathology to be strongly predictive of survival, and SRS eligibility was also significantly predictive (P = .047). CONCLUSION: SRS-eligible patients enrolled on RTOG 83-02 had survival superior to that of the SRS-ineligible group, and this advantage is mainly due to the selection of a subgroup with a high minimum KPS.

Carmustine↗
PubMed1992

A randomized trial of accelerated hyperfractionated radiation therapy and bis-chloroethyl nitrosourea for malignant glioma. A preliminary report of Radiation Therapy Oncology Group 83-02.

BACKGROUND: The third and final randomization of Radiation Therapy Oncology Group (RTOG) 83-02 was performed to identify the maximal tolerated dose and potential efficacy of accelerated hyperfractionated radiation therapy (AHRT) in 1.6 Gy twice-daily fractions for adult malignant glioma. METHODS: From December 1987 to July 1989, 304 patients with malignant glioma were stratified by age, performance status, and histologic findings and randomized to receive total AHRT doses of 48.0 or 54.4 Gy, with 80 mg/m2 of bis-chloroethyl nitrosourea (BCNU) for 3 days every 8 weeks. Distribution of other prognostic factors, including neurologic function, extent of surgery, tumor size, and sex, was comparable in each treatment arm. RESULTS: One Grade 5 radiation therapy (RT)-related toxic effect was reported (in the 54.4-Gy treatment arm), and the incidence of late Grade 3-5 RT-related toxic effects at 18 months was 1% at 48.0 Gy and 4% at 54.4 Gy. The median survival times (MST) for the 48.0 Gy and 54.4 Gy treatment arms were 11.7 and 10.8 months, respectively, comparable to the MST in prior RTOG trials with a similar proportion of patients with glioblastoma multiforme (79%). For the 123 patients who were 60 years of age or older, the MST for the 48.0 Gy and 54.4 Gy treatment arms were 8.9 and 10.4 months, respectively, and compare favorably with the MST of 6.0 months reported with standard RT and BCNU treatment used for 101 patients who were 60 years of age or older in two prior RTOG malignant glioma trials (74-01 and 79-18). Although these results differ significantly (P = 0.0015), this contrast is not significant when adjusted by performance status. CONCLUSIONS: The maximum tolerated dose of AHRT has yet to be identified, and pursuit of this information may most benefit patients with malignant glioma who are 60 years of age or older.

Carmustine↗
PubMed1992

The prognostic significance of surgical staging for carcinoma of the endometrium.

This study is based on a retrospective review of 156 patients with endometrial carcinoma from 1978 through 1984 who underwent primary surgical evaluation. All cases were retrospectively restaged using the newly adopted FIGO surgical staging. The preoperative FIGO clinical stage distribution for this study was as follows: 121 (77.6%) Stage I, 22 (14.1%) Stage II, 5 (3.2%) Stage III, 2 (1.3%) Stage IV, and 6 (3.8%) unstaged patients. Most patients had TAH-BSO with a collection of peritoneal washings and retroperitoneal lymph node sampling. Surgical staging revealed 122 (78.2%) Stage I, 9 (5.8%) Stage II, 12 (7.7%) Stage III, and 13 (8.3%) Stage IV patients. Surgery upstaged 12.4% of clinical Stage I. In clinical stage II, 59.0% were downstaged while 27.3% were upstaged. For clinical Stage III, 60.6% were upstaged, but no downstaging occurred. No change in stage occurred for clinical Stage IV patients. Ninety-seven surgically staged patients received no adjuvant therapy. The remaining 59 patients had adjunctive treatment which consisted of radiotherapy (59.3%), hormonal therapy (25.4%), chemotherapy (5.1%), or combined modality treatment (10.2%). All patients were followed until death or a minimum of 5 years (60-139 months; median, 82 months) with the exception of 13 patients who were lost to follow-up (2-58 months; median, 34 months). Five-year survival by clinical staging was as follows: 86.2% for Stage I, 85.9% for Stage II, and 0% for Stage III and IV. Five-year survival by surgical staging was 90.6% for Stage I, 85.7% for Stage II, 58.3% for Stage III, and 0% for Stage IV. The 13 patients who were lost to follow-up were censored in all survival analyses at the time of last contact. Stepwise regression analysis using a parametric proportional hazards model identified surgical stage as the most significant prognostic factor (P = 0.02). Univariate analysis showed that patients with surgical Stage IC had significantly worse prognosis (75.0%, 5 years) than those in surgical Stage IA (93.8% 5 YS) or IB (95.4% 5 years). In summary, this study demonstrates that surgical staging as recommended by FIGO is indicated to accurately determine the initial extent of disease in endometrial carcinoma. In addition, surgical staging is the strongest predictor of survival. Deep myometrial invasion appears to be a significant independent prognostic factor within surgical Stage I. The role of adjunctive radiotherapy in Stage I disease awaits the results from an ongoing multi-institutional, prospectively randomized trial.

Adenocarcinoma↗
PubMed1992

Adjuvant chemotherapy for resectable squamous cell carcinomas of the head and neck: report on Intergroup Study 0034.

To test the efficacy of sequential chemotherapy as an adjuvant to surgery and postoperative radiotherapy for patients with locally-advanced but operable squamous cell cancers of the head and neck region, a randomized clinical trial was conducted under the auspices of the Head and Neck Intergroup (Radiation Therapy Oncology Group, Southwest Oncology Group, Eastern Oncology Group, Cancer and Leukemia Group B, Northern California Oncology Group, and Southeast Group). Eligible patients had completely resected tumors of the oral cavity, oropharynx, hypopharynx, or larynx. They were then randomized to receive either three cycles of cis-platinum and 5-FU chemotherapy followed by postoperative radiotherapy (CT/RT) or postoperative radiotherapy alone (RT). Patients were categorized as having either "low-risk" or "high-risk" treatment volumes depending on whether the surgical margin was greater than or equal to 5 mm, there was extracapsular nodal extension, and/or there was carcinoma-in-situ at the surgical margins. Radiation doses of 50-54 Gy were given to "low-risk" volumes and 60 Gy were given to "high-risk" volumes. A total of 442 analyzable patients were entered into this study with the mean-time-at-risk being 45.7 months at the time of the present analysis. The 4-year actuarial survival rate was 44% on the RT arm and 48% on the CT/RT arm (p = n.s.). Disease-free survival at 4 years was 38% on the RT arm compared to 46% on the CT/RT arm (p = n.s.). At 4 years the local/regional failure rate was 29% vs. 26% for the RT and CT/RT arms, respectively (p = n.s.). The incidence of first failure in the neck nodes was 10% on the RT arm compared to 5% on the CT/RT arm (p = 0.03 without adjusting for multiple testing) and the overall incidence of distant metastases was 23% on the RT arm compared to 15% on the CT/RT arm (p = 0.03). Treatment related toxicity is discussed in detail, but, in general, the chemotherapy was satisfactorily tolerated and did not affect the ability to deliver the subsequent radiotherapy. Implications for future clinical trials are discussed.

Antineoplastic Combined Chemotherapy Protocols↗
PubMed1992

Radiosurgery target point alignment errors detected with portal film verification.

Stereotactic radiosurgery with a linear accelerator requires an accurate match of the therapeutic radiation distribution to the localized target volume. Techniques for localization of the target volume using CT scans and/or angiograms have been described. Alignment of the therapeutic radiation distribution to the intended point in stereotactic space is usually accomplished using precision mechanical scales which attach to the head ring. The present work describes a technique used to verify that the stereotactic coordinates of the center of the intended radiation distribution are in agreement with the localized target point coordinates. This technique uses anterior/posterior and lateral accelerator portal verification films to localize the stereotactic coordinates of the center of the radiation distribution with the patient in the treatment position. The results of 26 cases have been analyzed. Alignment errors of the therapeutic radiation distribution in excess of 1 mm have been found using the portal film verification procedure.

Brain↗
PubMed1992

Dose determination in high dose-rate brachytherapy.

Although high dose-rate brachytherapy with a single, rapidly moving radiation source is becoming a common treatment modality, a suitable formalism for determination of the dose delivered by a moving radiation source has not yet been developed. At present, brachytherapy software simulates high dose-rate treatments using only a series of stationary sources, and consequently fails to account for the dose component delivered while the source is in motion. We now describe a practical model for determination of the true, total dose administered. The algorithm calculates both the dose delivered while the source is in motion within and outside of the implanted volume (dynamic component), and the dose delivered while the source is stationary at a series of fixed dwell points. It is shown that the dynamic dose element cannot be ignored because it always increases the dose at the prescription points and, in addition, distorts the dose distribution within and outside of the irradiated volume. Failure to account for the dynamic dose component results in dosimetric errors that range from significant (> 10%) to negligible (< 1%), depending on the prescribed dose, source activity, and source speed as defined by the implant geometry.

Brachytherapy↗
PubMed1992

Computer controlled stereotaxic radiotherapy system.

A computer-controlled stereotaxic radiotherapy system based on a low-frequency magnetic field technology integrated with a single fixation point stereotaxic guide has been designed and instituted. The magnetic field, generated in space by a special field source located in the accelerator gantry, is digitized in real time by a field sensor that is six degree-of-freedom measurement device. As this sensor is an integral part of the patient stereotaxic halo, the patient position (x, y, z) and orientation (azimuth, elevation, roll) within the accelerator frame of reference are always known. Six parameters--three coordinates and three Euler space angles--are continuously transmitted to a computer where they are analyzed and compared with the stereotaxic parameters of the target point. Hence, the system facilitates rapid and accurate patient set-up for stereotaxic treatment as well as monitoring of patient during the subsequent irradiation session. The stereotaxic system has been developed to promote the integration of diagnostic and therapeutic procedures, with the specific aim of integrating CT and/or MR aided tumor localization and long term (4- to 7-week) fractionated radiotherapy of small intracranial and ocular lesions.

Electromagnetic Phenomena↗