| 1. |
- Wegdén, Marie, et al.
(författare)
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Nuclear microprobe analysis of the selective boron uptake obtained with BPA in brain tumour tissue
- 2004
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Ingår i: Nuclear Instruments & Methods in Physics Research. Section B: Beam Interactions with Materials and Atoms. - : Elsevier BV. - 0168-583X. ; 219-20, s. 67-71
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Tidskriftsartikel (refereegranskat)abstract
- The tumour selective ability of the boron compound boronophenylalanine (BPA), today used in Boron Neutron Capture Therapy in Sweden, has been investigated with the Lund Nuclear Microprobe. The tumour to tissue ratio of the boron concentration, as well as the location of boron within the cells, is critical for the efficiency of the therapy. It is desirable that the boron is accumulated as close as possible to the cell nucleus, since the alpha particles produced in the B-10(n,alpha)Li-7 reaction only have a range of about 10 microns, i.e. a cell diameter. The nuclear reaction B-11(p,alpha)2alpha, which has an especially high cross-section (300 mb) for 660 keV protons, has been used to analyse brain tissue from BPA-injected rats. Previous studies on other boron compounds have shown significant background problems when the alpha particles are detected in the backward direction. By a specially designed set-up, alpha particles in the forward and backward direction are detected simultaneously, and only the coincidences between the two directions are considered to be true boron events. In this way we could achieve excellent background suppression. The analysis shows that BPA indeed is tumour selective. Quantifications show a boron abundance of 150 +/- 20 ng/cm(2) in normal tissue and 567 70 ng/cm(2) in tumour tissue. If the rat is fed with L-dopa before the injection of BPA the uptake increases 3-4 times. The boron is homogeneously distributed in the cellular structure and no specific intracellular accumulation has been shown. (C) 2004 Elsevier B.V. All rights reserved.
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| 2. |
- Capala, J, et al.
(författare)
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Boron neutron capture therapy for glioblastoma multiforme : Clinical studies in Sweden
- 2003
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Ingår i: Journal of Neuro-Oncology. - 1573-7373. ; 62:1, s. 135-144
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Tidskriftsartikel (refereegranskat)abstract
- A boron neutron capture therapy (BNCT) facility has been constructed at Studsvik, Sweden. It includes two filter/moderator configurations. One of the resulting neutron beams has been optimized for clinical irradiations with a filter/moderator system that allows easy variation of the neutron spectrum from the thermal to the epithermal energy range. The other beam has been designed to produce a large uniform field of thermal neutrons for radio-biological research. Scientific operations of the Studsvik BNCT project are overseen by the Scientific Advisory Board comprised of representatives of major universities in Sweden. Furthermore, special task groups for clinical and preclinical studies have been formed to facilitate collaboration with academia. The clinical Phase II trials for glioblastoma are sponsored by the Swedish National Neuro-Oncology Group and, presently, involve a protocol for BNCT treatment of glioblastoma patients who have not received any therapy other than surgery. In this protocol, p-boronophenylalanine (BPA), administered as a 6-h intravenous infusion, is used as the boron delivery agent. As of January 2002, 17 patients were treated. The 6-h infusion of 900 mg BPA/kg body weight was shown to be safe and resulted in the average blood-boron concentration of 24 μg/g (range: 15-32 μg/g) at the time of irradiation (approximately 2-3 h post-infusion). Peak and average weighted radiation doses to the brain were in the ranges of 8.0-15.5 Gy(W) and 3.3-6.1 Gy(W), respectively. So far, no severe BNCT-related acute toxicities have been observed. Due to the short follow-up time, it is too early to evaluate the efficacy of these studies.
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| 3. |
- Munck af Rosenschöld, Per, et al.
(författare)
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Current status of dosimetry at the boron neutron capture therapy facility at Studsvik, Sweden
- 2002
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Ingår i: Research and Development in Neutron Capture Therapy. - 9788832329094 ; , s. 437-441
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Konferensbidrag (refereegranskat)abstract
- The beam was successfully characterized in air and in phantom using various radiation dosimeter:,. The determination of the thermal neutron and photon components of the mixed beam in phantom can be determined with acceptable uncertainties, while the uncertainty of the high-energy neutron component is considerable but of limited clinical significance. The beam intensity is sufficiently high for reasonably short treatment times. A novel approach to in-vivo dosimetry and quality assurance of treatment time in terms of monitor units was introduced in order to comply with national regulations regarding radiation therapy.
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| 4. |
- Munck af Rosenschöld, Per
(författare)
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Mixed Beam Dosimetry - From Reactor Core to BNCT Patient
- 2003
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Doktorsavhandling (övrigt vetenskapligt/konstnärligt)abstract
- Accurate radiation dosimetry is of paramount importance in order to ensure safe delivery of radiotherapy, and for the possibility of meaningful evaluation of clinical trials, as the radiation absorbed dose is correlated to tissue response. The aim of the studies described in this thesis was to investigate and devise novel approaches to mixed beam dosimetry in boron neutron capture therapy (BNCT). The computer model of the epithermal neutron beam at the Studsvik BNCT facility was described and experimentally verified. Good agreement was generally obtained in phantom (<5%) for the photon and fast neutron absorbed dose, and thermal neutron fluence, which can be seen as verification of the computer model. However, the calculated in-air photon kerma (photon contamination) of the beam was about 39% lower than the measured value. The effective energy of this photon contamination was investigated using photon kerma transmission through bismuth. The calculated photon spectrum consisted mainly of 478 keV gamma-rays from boron neutron capture in the collimator, while the measurements indicated a higher effective energy; an actual photon spectrum comprising of 53% and 47% relative 478 keV and 2.22 MeV fluence free in air, respectively, reproduced the measured transmission within 3%. The validated computer model of the mixed beam was subsequently used to calculate beam-dependent correction factors for the detectors used for dosimetry under reference conditions. Efforts were made to adhere to the (kQ) formalism and practice used in conventional radiotherapy, rather than that previously used in neutron radiotherapy. The calculations showed that commonly used ionization chambers could be employed in the epithermal neutron beam at Studsvik with kQ factors ranging between 1.02 and 1.10. The methodology employed ensured measurements with uncertainties of the thermal neutron fluence (1.4%, 1 SD), and the photon absorbed dose (2.5%, 1 SD) comparable to conventional radiotherapy standards. The measurement of the fast neutron absorbed dose, however, was associated with substantial uncertainties (24%, 1 SD). Clinical trials ensued, and the treatment procedure, as well as aspects of the clinical dosimetry, at the Studsvik facility is discussed in this thesis. Novel methods for verification of the clinical dosimetry in BNCT, which are presented in this thesis, ensure therapeutic safety. The methods presented include verification of the clinical dosimetry both prior to and following therapy. The verification employed prior to therapy was shown to have an uncertainty of 6.0% (1 SD), while the in vivo dosimetry method utilized in a post-therapy analysis benefits from improvements, as the uncertainty of 11.2% (1 SD) was estimated. This thesis presents a comprehensive discourse on the mixed beam dosimetry of epithermal neutron beams designed for BNCT.
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| 5. |
- Munck af Rosenschöld, Per, et al.
(författare)
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Quality assurance of patient dosimetry in boron neutron capture therapy
- 2004
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Ingår i: Acta Oncologica. - : Informa UK Limited. - 1651-226X .- 0284-186X. ; 43:4, s. 404-411
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Tidskriftsartikel (refereegranskat)abstract
- The verification of the correctness of planned and executed treatments is imperative for safety in radiotherapy. The purpose of the present work is to describe and evaluate the quality assurance (QA) procedures for patient dosimetry implemented at the boron neutron capture therapy (BNCT) facility at Studsvik, Sweden. The dosimetric complexity of the mixed neutron-photon field during BNCT suggests a careful verification of routine procedures, specifically the treatment planning calculations. In the present study, two methods for QA of patient dosimetry are presented. The first is executed prior to radiotherapy and involves an independent check of the planned absorbed dose to be delivered to a point in the patient for each treatment field. The second QA procedure involves in vivo dosimetry measurements using posttreatment activation analysis. Absorbed dose conversion factors taking the difference in material composition and geometry of the patient and the PMMA phantom used for reference dosimetry were determined using the Monte Carlo method. The agreement of the QA procedure prior to radiotherapy reveals an acceptably small deviation for 60 treatment fields of ±4.2% (1 SD), while the in vivo dosimetry method presented may benefit from improvements, as the deviations observed were quite substantial (±12%, 1 SD), and were unlikely to be due to actual errors in the clinical dosimetry.
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