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Biomedical subjects

P Wootton

Publications and source records attributed to P Wootton.

At least 19 recordsLinked to original sources
PubMed1997

Integration of radiotherapy planning systems and radiotherapy treatment equipment: 11 years experience.

PURPOSE: We have investigated the requirements, design, implementation, and operation of a computer-controlled medical accelerator with multileaf collimator (MLC), integrated with a radiation treatment-planning system (RTPS), and we report on the performance, benefits, and lessons learned from this experience. METHODS AND MATERIALS: In 1984 the University of Washington installed a computer-controlled radiation therapy machine (the Clinical Neutron Therapy System, or CNTS) with a multileaf collimator. Since the beginning of operation the control system computer has been connected by commercially available network hardware and software to three generations of radiation treatment-planning systems. Semiautomated setup and completely computerized check and confirm were incorporated into the system from the beginning of clinical operation in 1984. The system cannot deliver a patient treatment without a computer-prepared treatment plan. RESULTS: The CNTS has been in use for routine patient treatments for over 11 years. The cost of the network connection and software was an insignificant fraction of the facility cost. Operation has been efficient and reliable. Of the 441 machine-related session reschedulings (out of 18,432 sessions total) during the past 9 years, only 20 were due to problems with data transfer between the RTPS and CNTS, associated primarily with two incidents. Close integration with the treatment-planning system allows complex treatments to be delivered. Dramatic evolution of the departmental treatment-planning system has not required any changes or redesign of either the accelerator control system or the network connection. CONCLUSIONS: Our experience shows that a large degree of automation is possible with reasonable effort, by using well-known software and hardware design strategies. The lessons we have learned from this can be carried over into photon therapy now that photon accelerators with MLC facilities are commercially available.

Computer Communication Networks↗
PubMed1997

Boron neutron capture enhanced fast neutron radiotherapy for malignant gliomas and other tumors.

Both fast neutron radiotherapy and boron neutron capture therapy have been investigated as new radiation treatment techniques for patients with malignant gliomas. While each of these techniques individually has shown the potential for pathological eradication of malignant glioma, to date neither has evolved into an accepted, improved method of treatment. We have recently begun a research program investigating the feasibility of combining the benefits of both types of therapy. As a fast neutron beam penetrates tissue some of the particles are degraded to thermal energies. These can be captured by 10B or other suitable isotopes resulting in a highly-localized release of additional energy during a course of fast neutron radiotherapy. In this article we will review the rationale for such an approach, and review the underlying physics as well as in vitro, in vivo, and early human studies testing its feasibility. If appropriate carrier agents can be found that preferentially-localize in tumor cells, this approach ena be applied to many different tumor systems.

Animals↗
PubMed1996

Fast neutron radiotherapy and boron neutron capture therapy: application to a human melanoma test system.

Fast neutron radiotherapy has proven to be an effective form of treatment in a selected subset of tumors (salivary gland tumors, sarcomas, and locally-advanced prostate cancer), but has not proven to be more beneficial than conventional photon irradiation for the majority of tumor types upon which it has been tested. Normal tissue tolerance limits preclude simply further escalating the neutron dose. Boron neutron capture (BNC) provides a way of selectively augmenting the radiation dose to the tumor. This process is described, and cell culture and animal model data reviewed. An irradiation configuration was developed where an enhancement of 2.10(-3) for 1 microgram of 10B per gram of tissue was achieved. This is similar to the enhancement achievable in the center of a 20 x 20 cm field envisioned for future applications such as metastases in the brain. A boron concentration of 50 micrograms per gram of tumor tissue leads to a 10% increase in the delivered physical dose in this scenario. The first human test of BNC enhancement of a fast neutron radiotherapy beam using pharmacologically-acceptable doses of orally-administered, 10B-enriched, L-paraboronophenylalanine is reported. An enhancement of tumor response was demonstrated for a melanoma skin nodule test system. Boron levels achieved in blood, skin, and tumors are presented. Future research plans are discussed.

Administration, Oral↗
PubMed1994

Impact of a multileaf collimator on treatment morbidity in localized carcinoma of the prostate.

PURPOSE: To evaluate the effectiveness of variable multileaf collimation, three-dimensional treatment planning, and computer-controlled conformal radiation therapy of prostate cancer. METHODS AND MATERIALS: Two hundred and forty-five patients with locally advanced prostate cancer have completed treatment over a 9-year time span using a multileaf collimator and conformal treatment techniques on the University of Washington cyclotron. All patients had three-dimensional treatment planning with computed tomography scans in the treatment position, and had treatment fields individually shaped to the target volume with a continuously variable multileaf collimator. Treatment was delivered under computer control with network transfer of the multileaf collimator settings from the treatment planning computer to the cyclotron control system. RESULTS: The multileaf collimator combined with three-dimensional treatment planning results in elegant dose distributions. These neuron dose distributions resulted in a reduced local/regional tumor failure rate with no increase in complications when compared to control treatment with photons in a randomized trial. Neutron treatment delivered at other institutions without conformal beam shaping resulted in the same improvement in local-regional tumor control rates, but was associated with a significantly higher normal tissue complication rate than seen with conformal neutron beam delivery techniques (grade 3 and 4 cumulative late normal tissue toxicity rates of 39% vs. 10%, p = 0.0007). CONCLUSIONS: Conformal treatment of prostate cancer using a multileaf collimated neutron beam results in increased local/regional tumor control rates with low normal tissue toxicities. This experience is directly applicable to the conformal treatment of prostate cancer with photons.

Humans↗
PubMed1994

Boron neutron capture therapy: a mechanism for achieving a concomitant tumor boost in fast neutron radiotherapy.

PURPOSE: For many years neutron radiation has been used to treat malignant disease both as fast neutron radiotherapy and as thermal neutron induced boron neutron capture therapy (BNCT). To date, these two approaches have been used independently of one another due to the large difference in neutron energies each employs. In this paper we discuss the potential application of BNCT to enhance the therapeutic effectiveness of a fast neutron radiotherapy beam. METHODS AND MATERIALS: Measurements are presented for the thermal neutron component that is spontaneously developed as the University of Washington fast neutron radiotherapy beam penetrates a water phantom. The biological effect of this thermalized component on cells "tagged" with boron-10 (10B) is modeled mathematically and the expected change in cell survival calculated. The model is then extended to estimate the effect this enhanced cell killing would have for increased tumor control. RESULTS: The basic predictions of the model on changes in cell survival are verified with in vitro measurements using the V-79 cell line. An additional factor of 10-100 in tumor cell killing appears achievable with currently available 10B carriers using our present neutron beam. A Poisson model is then used to estimate the change in tumor control this enhanced cell killing would produce in various clinical situations and the effect is sufficiently large so as to be clinically relevant. It is also demonstrated that the magnitude of the thermalized component can be increased by a factor of 2-3 with relatively simple changes in the beam generating conditions. CONCLUSION: BNCT may provide a means of enhancing the therapeutic effectiveness of fast neutron radiotherapy in a wide variety of clinical situations and is an area of research that should be aggressively pursued.

Boron Neutron Capture Therapy↗
PubMed1994

Enhancement of fast neutron beams with boron neutron capture therapy. A mechanism for achieving a selective, concomitant tumor boost.

Both fast neutron radiotherapy and boron neutron capture therapy (BNCT) have been utilized to treat malignant disease. Herein we discuss the potential of combining these treatments to enhance the effectiveness of fast neutron therapy through a concomitant BNCT boost. Using a fast neutron beam generated from a 50 MeV proton on beryllium reaction, we have determined that 0.1% of the beam per microgram of boron-10 per gram of tissue (microgram/g) can be deposited via BNCT. Our mathematical modeling predicts that BNCT enhancement of our beam will lead to an additional 1-2 logs of tumor cell kill for boron-10 concentrations of 30-50 micrograms/g. We have validated this via V-79 cell line in vitro measurements. A Poisson model estimation of how this additional cell kill will influence local tumor control, predicts that BNCT enhancement of fast neutron radiation will lead to a clinically significant improvement in outcome.

Animals↗
PubMed1991

The effect of intracisternal injection of thyrotropin-releasing hormone on gastric and duodenal motility in the urethane-anaesthetized rat.

Intracisternal injection of thyrotropin-releasing hormone (TRH; 1-3 micrograms) caused an increase in gastric motility and usually an inhibition of duodenal motility. These effects were abolished by vagotomy and atropine. No inhibition was seen even after tone and motility had been restored to a point at which vagal stimulation could evoke profound inhibition of gastric and duodenal motility. It is concluded that TRH is a specific activator of enteric excitatory pathways and that duodenal inhibition seen in control animals is a consequence of gastro-duodenal inhibitory reflexes.

Animals↗
PubMed1988

Rodent model of chemoradiotherapy-induced white matter necrosis.

This report describes a laboratory model that permits study of the radiochemotherapy interactions in the CNS. Rats are stereotaxically implanted with a cerebroventricular cannula attached to an osmotic minipump, which slowly infuses a chemotherapeutic agent into CSF for up to 14 days. The cervical cord is irradiated, and forelimb paralysis develops 4-6 months later at an effective dose for paresis in 50% of the animals; the doses with radiotherapy alone are 2,125 cGy for a single fraction and 2,950 cGy for split fractions. Investigations with the model indicate that mature CNS tissue is not sensitized to either single-fraction or split-dose irradiation with either simultaneous or post-radiation exposure to high concentrations of methotrexate.

Animals↗
PubMed1983

Neutron beam characteristics from 50 MeV protons on beryllium using a continuously variable multi-leaf collimator.

The dose distributional properties of a p(50) Be neutron beam using a continuously variable multi-leaf collimator are presented and compared with a 6 MV photon beam. The differences in physical dose delivery between these two radiation modalities are generally insignificant for radiation therapy, and stringent comparisons of neutron and photon treatments should therefore be possible. The flexibility in field shaping with the multi-leaf collimator opens new possibilities in the treatment of complex irregular target volumes. The collimator consists of 40 wedge-shaped leaves that are independently moved under computer control with their collimating surfaces always aligned with the effective radiation source to minimize the penumbra. The leaf collimator eliminates the need for handling of heavy insert collimators and beam blocks at the same time that it allows dynamic conformation therapy with neutrons.

Beryllium↗
PubMed1976

Interim report: mammographic exposures at the breast cancer detection demonstration project screening centers.

In the interests of uniformly high radiological physics standards at ACS-NCI Breast Cancer Detection Demonstration Projects, measurements were made at 29 breast cancer screening clinics. These measurements were made throughout the country with equipment calibrated with standards traceable to National Bureau of Standards. Histograms which indicate the frequency distribution of exposures to the surface of a 6 cm breast for various machine/receptor combinations were prepared.

Breast Neoplasms↗