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R Gahbauer

Publications and source records attributed to R Gahbauer.

13 recordsLinked to original sources
PubMed2007

The RBE issues in ion-beam therapy: conclusions of a joint IAEA/ICRU working group regarding quantities and units.

This paper summarises the conclusions of a working group established jointly by the International Atomic Energy Agency (IAEA) and the International Commission on Radiation Units and Measurements (ICRU) to address some of the relative biological effectiveness (RBE) issues encountered in ion-beam therapy. Special emphasis is put on the selection and definition of the involved quantities and units. The isoeffective dose, as introduced here for radiation therapy applications, is the dose that delivered under reference conditions would produce the same clinical effects as the actual treatment in a given system, all other conditions being identical. It is expressed in Gy. The reference treatment conditions are: photon irradiation, 2 Gy per fraction, 5 daily fractions a week. The isoeffective dose D(IsoE) is the product of the physical quantity absorbed dose D and a weighting factor W(IsoE). W(IsoE) is an inclusive weighting factor that takes into account all factors that could influence the clinical effects like dose per fraction, overall time, radiation quality (RQ), biological system and effects. The numerical value of W(IsoE) is selected by the radiation-oncology team for a given patient (or treatment protocol). It is part of the treatment prescription. Evaluation of the influence of RQ on W(IsoE) raises complex problems because of the clinically significant RBE variations with biological effect (late vs. early) and position in depth in the tissues which is a problem specific to ion-beam therapy. Comparison of the isoeffective dose with the equivalent dose frequently used in proton- and ion-beam therapy is discussed.

Heavy Ion Radiotherapy↗
PubMed1999

Cross-sectional nodal atlas: a tool for the definition of clinical target volumes in three-dimensional radiation therapy planning.

Virtual three-dimensional clinical target volume definition requires the identification of areas suspected of containing microscopic disease (frequently related to nodal stations) on a set of computed tomographic (CT) images, rather than the traditional approach based on anatomic landmarks. This atlas displays the clinically relevant nodal stations and their correlation with normal lymphatic pathways on a set of CT images.

Humans↗
PubMed1998

Boron neutron capture therapy: principles and potential.

This book on the therapeutic applications of neutrons and high-LET radiations in cancer therapy would not have been complete without a review of the present situation of boron neutron capture therapy (BNCT) and a discussion of its future perspectives. BNCT is a special type of high-LET radiation therapy that attempts to achieve a selectivity at the cellular level. The rationale is to incorporate boron atoms selectively in the cancer cells and then bombard those atoms with thermal neutrons to produce a neutron capture reaction and subsequent decay that emits alpha and lithium particles. The efficiency of the technique depends upon achieving selective incorporation of the boron atoms in the cancer cells and not (or to a lesser extent) in the normal cells. The present status and future directions are described, with emphasis on boron carriers (drugs) and their delivery, as well as physical and treatment planning aspects.

Boron Neutron Capture Therapy↗
PubMed1990

Analysis of 5-iodo-2'-deoxyuridine incorporation in murine melanoma for photon activation therapy.

Quantitative evaluation of the dose enhancement obtained with analog nucleoside agents such as iododeoxyuridine (IdUrd) requires knowledge of the degree to which the thymidine (Thd) in DNA is replaced by IdUrd. In the present investigation, mice were infused with IdUrd using an intravenous infusion apparatus capable of delivering continuous multi-day infusions without restraining the mice. The absolute incorporation of IdUrd in DNA was measured by 125IdUrd label, both in whole tissue and extracted DNA, showing a good correlation between levels observed in DNA and whole tissue. Replacement in a Harding-Passey murine melanoma tumor carried in BALB/c mice approached 10%. In addition, a Neutron Activation Analysis (NAA) technique was developed which showed in vitro, a sensitivity sufficient to evaluate the % replacement of Thd by IdUrd in small biological samples with a sensitivity greater than 0.1 ppm, at 1% replacement in mg samples. This method can provide information on iodine substitution in DNA in humans where the use of a radioactive DNA-seeking substance would be undesirable. Analyses of IdUrd incorporation in cultured cells by NAA and 125I counting showed good agreement.

Animals↗
PubMed1989

Treatment of radiation side effects with oral pilocarpine.

Radiation therapy is commonly utilized either alone or in combination with surgery in the treatment of malignancies arising in the upper aerodigestive tract. Frequent post-treatment sequelae include xerostomia, dysgeusia, and dysphagia. Numerous commercial products designed to decrease these symptoms have not been uniformly successful. This pilot study was designed to evaluate prospectively oral pilocarpine as a means of stimulating minor and major salivary gland flow to eradicate these radiation-induced symptoms. The results of this pilot study support the hypothesis that the salivary glands are capable of responding to oral pilocarpine, and this therapeutic approach warrants further study.

Administration, Oral↗
PubMed1988

Phase II evaluation of sequential hepatic artery infusion of 5-fluorouracil and hepatic irradiation in metastatic colorectal carcinoma.

Twenty-seven patients with measurable liver metastases from colorectal carcinoma were entered on a protocol of intermittent hepatic artery infusion (HAI) of 5-fluorouracil (5-FU) followed by consolidation with hepatic irradiation. Five partial responses were observed in 23 evaluable patients. Median duration of response was 3.5 months. A response was evident after chemotherapy alone in four of five responders. Hepatic irradiation converted one patient with stable disease after chemotherapy to a partial responder. Median survival for all patients was 9.0 months (range 1.5-34.0). Combined modality treatment with HAI of 5-FU followed hepatic irradiation was well tolerated but did not appear to be synergistic.

Colonic Neoplasms↗
PubMed1987

Phase II trial of sequential chemotherapy and low-dose radiotherapy in advanced gastric adenocarcinoma. A Southwest Oncology Group Pilot Study.

Thirty-four patients with metastatic gastric adenocarcinoma were treated with the combination of chemotherapy and radiation therapy in a Phase II trial. Induction chemotherapy consisted of one cycle of 5-fluorouracil (5-FU), adriamycin, and BCNU (FAB), followed in 4 weeks by a cycle of 5-FU, adriamycin and mitomycin-C (FAM). In responding and stable patients, consolidation radiotherapy to major sites of disease, followed by maintenance FAM, was administered. Twelve of 30 (40%) patients with measurable disease responded (3 complete responses and 9 partial responses), with a median response duration of 6.0 months. Toxicity was moderate and consisted of nausea, vomiting, and myelosuppression. No additive effects for this combined modality approach could be demonstrated.

Adenocarcinoma↗
PubMed1982

Mixed beam radiotherapy and combination chemotherapy in localized pancreatic adenocarcinoma-preliminary results.

A pilot study of mixed beam radiotherapy (fast neutrons alternating with photons) followed by combination chemotherapy with SMF (streptozotocin, 5-fluorouracil, mitomycin C) in localized pancreatic cancer was performed. Thirteen patients were treated and a median survival of 10.0 months was noted (range 5-30+). Toxicity was mild to moderate. Further studies of sequential radiation and chemotherapy are indicated.

Adenocarcinoma↗
PubMedDate not supplied

Effect of head phantom size on 10B and 1H[n,gamma]2H dose distributions for a broad field accelerator epithermal neutron source for BNCT.

The effect of head phantom size on the 10B and 1H[n,gamma]2H dose distributions for a broad epithermal neutron radiation field generated by an accelerator-based epithermal neutron source for boron neutron capture therapy (BNCT) have been studied. Also two techniques for calculating the absorbed gamma dose from a measured gamma-ray source distribution are compared: a Monte Carlo technique, which is well accepted in the BNCT community, and a Point Kernel technique. The count-rate distribution in the central plane of three rectangular parallelopiped head water phantoms irradiated with an epithermal neutron field was measured with a boron trifluoride (BF3) detector. This epithermal neutron field was produced at the Ohio State University Van de Graaff Accelerator Facility. The 10B absorbed dose and the gamma-ray source have the same distribution in the head phantom as the BF3 count-rate distribution. The absorbed gamma dose from the measured source distribution was calculated using MCNP, a Monte Carlo code, and QAD-CGGP, a Point Kernel code. The most pronounced effect of phantom size on 10B absorbed dose was on the dose rate at the depth of maximum dose, dmax. An increase in dose rate at dmax was observed with a decrease in phantom size, the dose rate in the smallest phantom being larger by a factor of 1.4 than the dose rate in the largest phantom. Also, dmax for the phantoms shifted deeper with a decrease in phantom dimensions. The shift between the largest and the smallest phantoms was 6 mm. Finally, the smaller phantoms had lower entrance 10B dose as a percent of the dose at dmax, or better skin sparing. Our calculations for the gamma dose show that a Point Kernel technique can be used to calculate the dose distribution as accurately as a Monte Carlo technique, in much shorter computation times.

Boron Neutron Capture Therapy↗
PubMedDate not supplied

Simultaneous treatment with cisplatin and radiation therapy for advanced solid tumors: a pilot study.

To study the toxicity and efficacy of simultaneous cisplatin chemotherapy and radiation therapy, 13 patients with metastatic solid tumors were treated with cisplatin on a weekly, outpatient basis during palliative radiation therapy. The dose of cisplatin ranged from 20 to 50 mg/m2 weekly, with most patients receiving 40 mg/m2. Radiation therapy was administered in a variety of dose-fraction schedules. Toxic effects were moderate and consisted of emesis (12 patients), transient elevation off BUN (three patients), myelosuppression (three patients), and radiation reactions (two patients). Twelve of 13 irradiated lesions (91%) responded with at least a 50% reduction in biperpendicular diameter. Four of the six patients with metastatic melanoma had complete regression of treated lesions; another melanoma patient had a partial response. Responses were also seen in patients with mesothelioma, bladder cancer, squamous cell carcinoma of the head and neck, and oat cell lung cancer. Only one responding patient has had disease progression in the treated field after 2+ to 7+ months of followup; two other patients have died of disseminated disease. Weekly cisplatin administration during radiotherapy deserves further evaluation, especially in the primary management of unresectable tumors that are responsive to cisplatin alone.

Cisplatin↗