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Biomedical subjects

J L Beach

Publications and source records attributed to J L Beach.

At least 37 records · Page 2Linked to original sources
PubMed1984

RBE of CF-252 neutrons by mouse testes weight loss.

Mouse testes weight decreased with increasing radiation dose following exposure to Cf-252 and its mixed neutron plus gamma radiation. The dose response for low dose rate (LDR) Cf-252 followed two components on an exponential plot of log percent weight loss vs. dose. Similar dose-response relationships were observed for acute 60Co or LDR Cs-137 radiations, but these required much larger doses to produce the same effect. The RBE was calculated against acute 60Co and Cs-137. There were no differences between acute 60Co and LDR Cs-137 effects. Cf-252 neutron RBE (n + gamma) was 3.7 for testes weight loss. RBEn for the neutrons-only was 5.1 RBE for the radiosensitive portion was 4.0.

Animals↗
PubMed1984

Five-year cure of cervical cancer treated using californium-252 neutron brachytherapy.

Female pelvic carcinoma is one of the common malignancies seen at the University of Kentucky Medical Center and often presents in an advanced stage. In 1976, we began to test californium-252 neutron brachytherapy (NT) for its efficacy for control of primary and recurrent advanced uterine, cervix, and vaginal cancers. The first protocol used was 5000-5500 rad of whole pelvis irradiation followed by 1-2 Cf-252 insertions using a single tandem placed in the utero-cervico-vaginal region. Of 27 patients with primary carcinomas treated, 10 are alive and well 5 years later (37%). Two of two recurrent tumors were locally controlled but failed later. These patients had advanced cervical, vaginal, or endometrial carcinomas. In 1977, a transitional year, treatment of only unfavorable stages and presentations with NT was initiated. Similar results were obtained with NT as compared to conventional photon therapy (PT). Further improvement in treatment results can be anticipated as NT brachytherapy is used for advanced cancer therapy by more effective treatment schedules and radiation doses. Cf-252 can be used as a radium substitute and achieved similar rates of tumor control and 5-year survivals.

Adenocarcinoma↗
PubMed1984

Implantation of brain tumors with Cf-252. Use of computed tomography and magnetic resonance imaging to guide insertion and evaluate response.

Magnetic resonance imaging (MR) was evaluated as a guide to planning and follow-up of Cf-252 neutron brachytherapy in 8 patients with malignant glioma of the cerebral hemispheres. A combination of sagittal, transverse, and coronal views allowed three-dimensional assessment of the dimensions and extent of tumor; by comparison, CT scans delineated the tumor less sharply, multiple views were not routinely obtained, and the reconstructed sagittal images were inadequate. Both techniques were complementary in enabling accurate tumor localization as well as separating enhanced zones from central avascular regions and tumor from edema. However, MR images provided more detail than serial CT scans, making MR the preferred method of follow-up.

Brachytherapy↗
PubMed1984

Californium-252: isotope for modern radiotherapy of cervix, uterine and vaginal carcinomas.

Cf-252 is an isotope that can easily be after loaded into available gynecological applicators and used for bulky cervix, uterus or vaginal cancer therapy. It is economical, time and cost effective in use, and can be applied to the therapy of many patients throughout the world. It is more effective for neutron therapy than machine fast neutron therapy and is the only form of neutron therapy producing consistent complication-free 5-year cure of advanced cancers currently available. Cf-252 is an isotope for modern gynecological tumor therapy for the future. Isodose curves for Cf-252 implants revealed dose distributions conforming well to tumor.

Brachytherapy↗
PubMed1983

RBE of spleen CFU-S to low dose rate Cf-252 neutron or photon radiation.

The RBE of Cf-252 neutron irradiation was determined for hemopoietic tissue using spleen CFU-S. Radiosensitivity was compared to acute Cobalt-60 radiation and low dose rate Cesium-137 under identical irradiation conditions. The RBE for the neutron component of the Cf-252 radiation was 2.1. No dose rate effect was observed for hemopoietic CFU-S to acute doses or low dose rate photon irradiation.

Animals↗
PubMed1983

RBE of spleen CFU-S to low dose rate Cf-252 or photon radiation in vivo.

The biological effects of low dose rate (LDR) Cf-252 radiation were compared to LDR Cs-137 photon radiation and acute 60Co radiation. The RBEn for endogenous CFU-S in vivo was 2.1 for neutron radiation at a dose rate of 9.9 cGy/hr of Cf-252 radiation. The value was consistent with previous in vitro experiments where a value of 2.1 was found. For the low doses and low dose rates studied, we tested an acute assay dose following the LDR irradiation to determine dose-effect and RBEn. Organ size shrinkage and regeneration patterns after LDR Cf-252 and Cs-137 were also studied and showed greater growth delay for Cf-252 irradiated lympho-hemopoietic tissues.

Animals↗
PubMed1983

A tumor/normal tissue advantage for low dose rate neutron brachytherapy.

Reports on clinical study of Cf-252 pelvic brachytherapy are reviewed and show that complication frequency is low. Low dose rate (LDR) neutron brachytherapy has been shown to be effective against cervical and advanced pelvic cancers; and produces 5 year cures without a high frequency of normal tissue complications. This is attributed to a high relative biological effectiveness (RBE) for the bulky, hypoxic tumor which along with an oxygen enhancement ratio (OER) advantage and dose-rate independent effects, produces rapid tumor regression and good local tumor control. Adjacent normal tissues which are oxygenated have lower RBE values than that of hypoxic tumors. Cf-252 brachytherapy increases the dose differential, therapeutic gain and the probability of local tumor control, since the high RBE of Cf-252 for hypoxic tumor is much less in normal tissues. Cf-252 radiation concentrated in the tumor, and for this reason, has had much fewer attendant normal tissue complications compared to neutron beam therapy.

Brachytherapy↗
PubMed1983

A simple device for loading radioactive seeds into absorbable sutures.

Radioactive I-125 seeds that are loaded into absorbable sutures are convenient for permanent or removable interstitial-implantation. A simple device for loading radioactive seeds into commercially available sutures is described. This loader permits fast placement of seeds in the suture with minimal exposure to the involved personnel. Variable spacing is accomplished either by absorbable spacers or by minor manipulation of the loaded suture.

Brachytherapy↗
PubMed1983

Radioprotection combined with hypoxic sensitization during radiotherapy of a solid murine tumor.

EMT6 tumors were transplanted intramuscularly in the right hind leg of female BALB/c mice and irradiated when they reached a diameter of 6-7 mm. Each mouse received an intraperitoneal injection of WR-2721, misonidazole, or both prior to irradiation, and the dose needed to control half of the tumors at 30 days (TCD50/30) was recorded. WR-2721 offered slight tumor protection, with a dose-modifying factor (DMF) of 1.04-1.15 for radioprotector doses of 150-500 mg/kg. Pretreatment with misonidazole at doses of 300-900 mg/kg yielded tumor sensitization with a DMF of 0.71-0.92. Pretreatment with both WR-2721 and misonidazole gave overall tumor sensitization with a DMF of 0.78-0.97. Possible combinations of sensitizers and protectors, while providing overall tumor sensitization, do not seem to improve the therapeutic ratio over what could be obtained from a sensitizer or protector alone.

Amifostine↗
PubMed1982

Interstitial 252Cf neutron therapy for glioblastoma multiforme.

252Cf brachytherapy has been combined with whole brain photon beam therapy to 6000 rads in 5-7 weeks. In early phase I studies, all patients selected for study tolerated the procedure and the subsequent photon beam therapy. All showed improvement in performance status and decreased tumor size by CT scan evaluation, but it became clear that these tumors are of large size and bulk, produce marked adjacent brain edema, and require individualized implant therapy as well as high-dose external beam irradiation if response is to occur.

Brachytherapy↗
PubMed1982

Work in progress: 252Cf neutron brachytherapy for hemispheric malignant glioma.

It has been shown that 252Cf neutron brachytherapy of hemispheric malignant glioma can be readily carried out and may be combined with external, whole brain photon beam therapy of 6,000 rad (60 Gy) administered over a five-week to seven-week period. The ten patients who were studied tolerated both procedures well. There was improvement in performance status, and a decrease in tumor size was observed upon computed tomographic scanning.

Aged↗
PubMed1981

Experimental radioimmunotherapy of a xenografted human colonic tumor (GW-39) producing carcinoembryonic antigen.

Experiments were undertaken to evaluate the antitumor effects of 131I-labeled goat antibody immunoglobulin G prepared against carcinoembryonic antigen in hamsters bearing the carcinoembryonic antigen-producing GW-39 human colonic carcinoma. At a single injection of 1 mCi 131I and higher, a marked growth inhibition of GW-39 tumors, as well as a considerable increase in the survival time of the tumor-bearing hamsters, could be achieved. At a dose of 1 mCi, the radioactive affinity-purified antibody appeared to be superior to radioactive normal goat immunoglobulin G in influencing tumor growth and survival time, but no significant difference could be seen at the higher dose of 2 mCi given. Radiobiological calculations indicated that the tumors received, at up to 20 days after therapy, 1325 rads for the specific antibody and only 411 rads for the normal immunoglobulin G preparation. These findings encourage the further evaluation of antibodies to tumor markers for isotopic cancer therapy.

Animals↗
PubMed1980

Scheduling of hypoxic-tumor therapy using neutron brachytherapy.

Fast-neutron-beam therapy and low-dose-rate fast-neutron intracavitary therapy of cervical carcinoma are effective in producing regression of advanced tumors. However, effectiveness is critically dependent on the schedule by which they are used in combination with fractionated external low-linear-energy-transfer (LET) therapy. Neutron-beam therapy is now alternated frequently with fractionated external radiotherapy (mixed beam). Intracavitary neutron therapy, scheduled before fractionated external-beam photon therapy, was maximally effective. These findings indicate that traditional concepts developed for the use of conventional low-LET therapy may need to be altered to use neutrons for therapy and to achieve improved local control of advanced cancers.

Brachytherapy↗
PubMed1979

Relative determination of W-values for alpha particles in tissue-equivalent and other gases.

W (the average energy to form an ion pair) for 5.4 MeV 241Am alpha particles in a Rossi-type tissue-equivalent (TE) gas, argon and methane was determined to an accuracy better than 0.2% using a new automated data handling system. A vibrating reed electrometer and current digitiser were used to measure the current produced by completely stopping the alpha particles in a large cylindrical ionisation chamber. A multichannel analyser, operating in a slow multiscaler mode, was used to store pulses from the current digitiser. The dwell time, of the order of 60 min per channel, was selected with an external timer gate. Current measurements were made at reduced pressures (200 Torr) to reduce ion recombination. The average current, over many repeated measurements, was compared to the current produced in nitrogen and its previously published W-value of 36.39+/-0.04 eV per ion pair. The resulting W-values were, in eV per ion pair, 26.29+/-0.05 for argon, 29.08+/-0.03 for methane and 30.72+/-0.04 for TE gas, which had an analysed composition of 64.6% methane, 32.4% CO2 and 2.7% nitrogen. Although the methane and argon values agree within 0.1% with previously published values, the value for TE is 1.2% lower than the single previously reported value.

Alpha Particles↗