Sensitivity improvement of YAP(Ce) cameras for imaging of secondary electron bremsstrahlung x-rays emitted during carbon-ion irradiation: problem and solution
| Autor: | Seiichi Yamamoto, Naoki Kawachi, Takashi Akagi, Mitsutaka Yamaguchi, Maki Kitano |
|---|---|
| Rok vydání: | 2020 |
| Předmět: |
Photomultiplier
Materials science chemistry.chemical_element Electrons Heavy Ion Radiotherapy Signal-To-Noise Ratio Tungsten Scintillator Secondary electrons Imaging phantom 030218 nuclear medicine & medical imaging 03 medical and health sciences 0302 clinical medicine Optics Humans Yttrium Radiology Nuclear Medicine and imaging Irradiation Image resolution Titanium Radiological and Ultrasound Technology Phantoms Imaging business.industry X-Rays Bremsstrahlung Oxides Cerium Calcium Compounds Radiography chemistry 030220 oncology & carcinogenesis Scintillation Counting business |
| Zdroj: | Physics in Medicine & Biology. 65:105008 |
| ISSN: | 1361-6560 |
| Popis: | Low-energy X-ray imaging of secondary electron bremsstrahlung X-rays emitted during carbon-ion irradiation is a promising method for range estimation and could be used for imaging with almost clinical dose levels of carbon ion. However, the number of counts in images with clinical dose levels is relatively small, making it difficult to obtain precise range estimations. Since improving the sensitivity of the X-ray camera may solve this issue, we developed two new types of X-ray cameras. One uses a 1-mm thick, 40 mm × 40-mm cerium-doped yttrium aluminum perovskite (YA1O3: YAP(Ce)) scintillator plate combined with a 2-inch square flat panel photomultiplier tube (FP-PMT) contained in a 2-cm thick tungsten shield with a pinhole collimator positioned 50 mm from the scintillator; the other uses a 0.5-mm thick, 20 mm × 20-mm YAP(Ce) scintillator plate combined with a 1-inch square position sensitive photomultiplier tube (PS-PMT) contained in the same tungsten shield with a pinhole collimator, but with the scintillator positioned closer (30 mm) to the pinhole collimator to obtain a similar field-of-view (FOV). For both cameras, we used a wider angle (~55 degrees) pinhole collimator to measure the phantom closer to improve sensitivity. Although the 40 mm × 40-mm YAP(Ce) camera had high system spatial resolution, the background count fractions were high and produced a high count area at the center of the images due to the pulse pileup of the signals. With the 20 mm × 20-mm YAP(Ce) camera, we obtained X-ray images with low background counts without a high count area at the image center. By smoothing the measured images, we were able to estimate the ranges even for clinical dose levels. We therefore confirmed that one of our newly developed YAP(Ce) cameras had high sensitivity and is promising for the imaging of secondary electron bremsstrahlung X-rays during irradiation of carbon ions in clinical conditions. |
| Databáze: | OpenAIRE |
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