PubMed Health⌕ Search
Home/Archive/PubMed

PubMed · 11951662

Optimization technique for a Prompt Gamma-ray SPECT collimator system.

M Ishikawa·T Kobayashi·Y Sakurai·K Kanda
View original source ↗Export metadata ↓

Abstract

Because background radiation in an irradiation room creates a problem with the PG-SPECT (Prompt Gamma-ray Single Photon Emission Computed Tomography) system, which evaluates the absorbed dose for the Boron Neutron Capture Therapy treatment, optimization of a collimator system was performed while taking the shielding of background gamma-rays into consideration. Assuming that a parallel-beam collimator is used, three parameters--the diameter of a hole, the length of the collimator, and the number of detectors (the number of holes of the collimator)--were selected for optimization. Because the combinations of these parameters are limitless, it is difficult to determine them simultaneously. Therefore, a statistically derived Optimization Criterion has been proposed to optimize these parameters. When the spatial resolution was 1 cm-FWHM (full width at half maximum), the optimal diameter of the collimator was 5.4 mm, the optimal length was 321 mm, and the optimal number of detectors was 31 x 31.

Explore related subjects

Boron Neutron Capture TherapyGamma RaysRadiometryTomography, Emission-Computed, Single-PhotonJournal ArticleResearch Support, Non-U.S. Gov't

Keep this discovery

Explore connections, maps & timelines

BibTeXRIS

M Ishikawa, T Kobayashi, Y Sakurai, K Kanda. 2001. Optimization technique for a Prompt Gamma-ray SPECT collimator system.. https://doi.org/10.1269/jrr.42.387

Cite the original work for its findings. Save a collection to share your selection of sources.

KEEP EXPLORING

Related citations

PubMed2006

Neutron dosimetry with 6LiF-rich TL sheet.

A (6)LiF-rich thermoluminescent sheet-type dosemeter ((6)LiF-rich NTL sheet) was developed for neutron 2D dosimetry. The dosemeter utilises the (6)Li(n, alpha)(3)H reaction to detect thermal neutrons. Responses of the (6)LiF-rich NTL sheet to neutrons were measured at the neutron beam irradiation facility for BNCT in JRR-4 Research Reactor at the Japan Atomic Energy Research Institute. Placement of a multi-leaf collimator at the output port of the neutron (beam) irradiation facility, produced either stripe- or round-shaped neutron distributions; the spatial distribution was measured using the developed NTL sheets. Direct measurements of neutron attenuation in water were also carried out using the developed NTL sheet, submersed in a water phantom. In each experiment, NTL sheets having natural abundance (7.9%) of LiF, and (6)LiF-enriched NTL (18.94%) sheet were irradiated under the same conditions. The ratio of thermoluminescence intensities of the (6)LiF-rich NTL sheet to that of the normal NTL sheet was compared to a theoretically calculated value. The experimental measurements are shown to be in good agreement with the calculations.

Boron Neutron Capture Therapy↗
PubMed2006

Application of different TL detectors for the photon dosimetry in mixed radiation fields used for BNCT.

Different approaches for the measurement of a relatively small gamma dose in strong fields of thermal and epithermal neutrons as used for Boron Neutron Capture Therapy (BNCT) have been studied with various thermoluminescence detectors (TLDs). CaF(2):Tm detectors are insensitive to thermal neutrons but not tissue-equivalent. A disadvantage of applying tissue-equivalent (7)LiF detectors is a strong neutron signal resulting from the unavoidable presence of (6)Li traces. To overcome this problem it is usual to apply pairs of LiF detectors with different (6)Li content. The experimental determination of the thermal neutron response ratio of such a pair at the Geesthacht Neutron Facility (GeNF) operated by PTB enables measurement of the photon dose. In the experimental mixed field of thermal neutrons and photons of the TRIGA reactor at Mainz the photon dose measured with different types of (7)LiF/(nat)LiF TLD pairs agree within a standard uncertainty of 6% whereas the CaF(2):Tm detectors exhibit a photon dose by more than a factor of 2 higher. It is proposed to determine suitable photon energy correction factors for CaF(2):Tm detectors with the help of the (7)LiF/(nat)LiF TLD pairs in the radiation field of interest.

Boron Neutron Capture Therapy↗
PubMed2006

Characterization of moderator assembly dimension for accelerator boron neutron capture therapy of brain tumors using 7Li(p, n) neutrons at proton energy of 2.5 MeV.

The characteristics of moderator assembly dimension are investigated for the usage of 7Li(p,n) neutrons by 2.5 MeV protons in boron newtron capture therapy (BNCT) of brain tumors in the present study. The indexes checked are treatable protocol depth (TPD), which is the greatest depth of the region satisfying the dose requirements in BNCT protocol, proton current necessary to complete BNCT by 1 h irradiation, and the heat flux deposited in the Li target which should be removed. Assumed materials are D2O for moderator, and mixture of polyethylene and LiF with 50 wt % for collimator. Dose distributions have been computed with MCNP 4B and 4C codes. Consequently, realized TPD does not show a monotonical tendency for the Li target diameter. However, the necessary proton current and heat flux in the Li target decreases as the Li target diameter increases, while this trend reverses at around 10 cm of the Li target diameter for the necessary proton current in the condition of this study. As to the moderator diameter, TPD does not exhibit an apparent dependence. On the other hand, necessary proton current and heat flux decrease as the moderator diameter increases, and this tendency saturates at around 60 cm of the moderator diameter in this study. As to the collimator, increase in inner diameter is suitable from the viewpoint of increasing TPD and decreasing necessary proton current and heat flux, while these indexes do not show apparent difference for collimator inner diameters over 14 cm for the parameters treated here. The practical viewpoint in selecting the parameters of moderator assembly dimension is to increase TPD, within the technically possible condition of accelerated proton current and heat removal from the Li target. In this process, the values for which the resultant characteristics mentioned above saturate or reverse would be important factors.

Boron Neutron Capture Therapy↗