Development of high speed imaging microscope and new software for track detection

International conference on nuclear tracks in solid

Development of high speed imaging microscope and new software for track detection

IReS semino

Measurement of total charge changing cross section of iron nuclei in hydrogen using CR-39 track detector

23rd International Conference on Nuclear Tracks in Solid

Contribution to dose in healthy tissue from secondary target fragments in therapeutic proton, He and C beams measured with CR-39 plastic nuclear track detectors

The linear energy transfer (LET) spectrum, absorbed dose and dose equivalent from secondary particles of LET∞H2O ≥15 keV/μm deposited within the plateau of the Bragg curve in primary particleinduced nuclear target fragmentation reactions in tissue during proton and heavy ion radiotherapy were measured using CR-39 plastic nuclear track detectors and analyzed by means of atomic force microscopy. It was found that secondary target fragments contributed 20% to dose equivalent for primary protons (157 MeV), 13% for primary helium ions (145 MeV/n) and 4% for primary carbon ions (383 MeV/n), respectively. Little research has been done on the contribution from these particles to primary given dose. The smaller contribution measured for energetic carbon ion beams compared to proton beams can be considered an advantage of carbon ion radiotherapy over proton radiotherapy

Precise track analysis and application for various radiation fields with high speed microscope and PitFit software

CR-39 plastic is well-known as most sensitive nuclear track detector for proton and heavy ions. CR-39 is widely utilized for not only dosimetric fields such as personal neutron dosimetry and heavy ion dosimetry, environment radiation monitoring, space radiation dosimetry but also various applications such as the spectroscopy of laser-driven ion beams, high energy cosmic ray physics and nuclear physics. Previously, we have developed a high speed microscope system (HSP-1000) for nuclear track measurement with a line sensor camera in place of a traditional CCD camera [1]. The actual scanning speed including all of procedure such as stage movement, image processing on board and writing out image data to hard disk was typically 8.8 min/cm^2. The scanning speed limit strongly depends on the brightness of image for taking picture. Recently, the scanning speed has been drastically improved to be 0.5 min/cm^2 by TDI (time delay integrator) sensor replacing a line sensor. TDI allows to take a high-intensity image by the integration of brightness of lines with two dimensional sensor of 4096 × 96 pixels. For the high speed image acquisition, the image is continuously and automatically focusing with two line sensors system. On the other hand, the track analysis software (PitFit) has been specifically designed for measuring the parameters of etch pit openings [1]. The edge of etch pit is detected through the image analysis procedure of noise eduction and binarization of the image after setting a greyscale threshold. The track size and its position of center are extracted with an ellipse fitting algorithms. This method can easily make analysis of heavy ion tracks due to the high contrast of etch pit compared with background gray level, while it was difficult to detect shallow tracks with similar gray level as background. Recently, thus kind of shallow tracks such as recoiled proton due to neutron and low LET (liner energy transfer) particles of space radiation are easily and automatically extracted with the differential edge detection algorithm. In this report, we will show the advanced track microscope and track analysis system and the applications for various radiation fields.The 26th International Conference on Nuclear Tracks in Solid

Validating α-particle emission from 211At-labeled antibodies in single cells for cancer radioimmunotherapy using CR-39 plastic nuclear track detectors

Recently, 211At has received increasing attention as a potential radionuclide for cancer radioimmunotherapy. It is a α-particle emitter, which is extremely effective against malignant cells. We demonstrate a method to verify the efficiency of 211At-labeled trastuzumab antibodies (211At-trastuzumab) against HER2 antigens, which has not been determined for radioimmunotherapy. A CR-39 plastic nuclear detector is used for measuring the position and the linear energy transfer (LET) of individual 211At α- particle tracks. The tracks and 211At-trastuzumab-binding cells were co-visualized by using the geometric information recorded on the CR-39. HER2-positive human gastric cancer cells (NCI-N87), labelled with 211At-trastuzumab, were dropped on the centre of the CR-39 plate. Microscope images of the cells and the corresponding α-tracks acquired by position matching were obtained. In addition, 3.5 cm × 3.5 cm macroscopic images of the whole plate were acquired. The distribution of number of α-particles emitted from single cells suggests that 80% of the 211At-trastuzumab-binding cells emitted α-particles. It also indicates that the α-particles may strike the cells several times along their path. The track-averaged LET of the α-particles is evaluated to be 131 keV/μm. These results will enable quantitative evaluation of delivered doses to target cells, and will be useful for the in vitro assessment of 211At-based radioimmunotherapeutic agents

Tracking method for the measurement of projectile charge changing cross-section using CR-39 detector with a high speed imaging microscope

A new method to trace heavy ion trajectories in a stack consisting of interleaved CR-39 plastic nuclear track detectors and target material layers was developed and tested for use in the measurement of projectile charge changing cross-sections of heavy ion fragmentation reactions. A high speed imaging microscope with sophisticated track analysis software was utilized to extract the charge information from multiple ion tracks belonging to a single fragmentation event. The systematic error of trajectory tracing was verified for the measurement system. In order to verify the validity of system, the projectile total charge changing cross-sections for Fe ions on carbon target was estimated and compared with previous experiments at initial beam energy of 1 GeV/n. The result is in good agreement with results obtained by other investigators. This method allows precise and fast measurement of the projectile charge changing cross-section with higher statistics on a level compatible to that of silicon spectrometer measurements