Effects of reflector and crystal surface on the performance of a depth‐encoding PET detector with dual‐ended readout. Issue 7 (11th June 2014)

• Record Type: Journal Article
• Authors: Ren, Silin; Yang, Yongfeng; Cherry, Simon R.
• Is Part Of: Medical physics. Volume 41:Issue 7(2014)
• Page Start: n/a
• Page End: n/a
• Publication Date: 2014-06-11
• Subjects: Positron emission tomography (PET) -- Photodiodes; phototransistors; photoresistors -- Standards and calibration; brain -- calibration -- photodiodes -- position sensitive particle detectors -- positron emission tomography; reflector -- crystal surface -- positron emission tomography -- small animal imaging -- depth of interaction; Testing or calibrating of apparatus or arrangements provided for in groups G01D1/00 to G01D15/00 -- Biological material, e.g. blood, urine; Haemocytometers -- Measurement of nuclear or x‐radiation -- Calibrating of instruments or apparatus -- Tubes for determining the presence, intensity, density or energy of radiation or particles -- Including semiconductor components sensitive to infra‐red radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation -- Semiconductor devices sensitive to infra‐red radiation, light, electromagnetic radiation of shorter wavelength, or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof -- Characterised by only one potential barrier or surface barrier -- Scintigraphy -- Measuring half‐life of a radioactive substance; Floods -- Positron emission tomography -- Electron paramagnetic resonance spectroscopy -- Surface grinding -- Scintillation detectors -- Image scanners -- Position sensitive detectors -- Brain -- Spatial resolution -- Total energy calculations; Medical physics -- Periodicals; Medical physics; Geneeskunde; Natuurkunde; Toepassingen; Biophysics; Periodicals; Periodicals; Electronic journals; 610.153
• DOI: 10.1118/1.4881097
• Languages: English
• ISSNs: 0094-2405

Abstract

Abstract : Purpose: Depth encoding detectors are required to improve the spatial resolution and spatial resolution uniformity of small animal positron emission tomography (PET) scanners, as well as dedicated breast and brain scanners. Depth of interaction (DOI) can be measured by using dual‐ended readout of lutetium oxyorthosilicate (LSO) scintillator arrays with position‐sensitive avalanche photodiodes. Inter‐crystal reflectors and crystal surface treatments play important roles in determining the performance of dual‐ended detectors. In this paper, the authors evaluated five LSO arrays made with three different intercrystal reflectors and with either polished or unpolished crystal surfaces. Methods: The crystal size in all arrays was 1.5 mm, which is typical of the detector size used in small animal and dedicated breast scanners. The LSO arrays were measured with dual‐ended readout and were compared in terms of flood histogram, energy resolution, and DOI resolution performance. Results: The four arrays using enhanced specular reflector (ESR) and Toray reflector provided similar quality flood histograms and the array using Crystal Wrap reflector gave the worst flood histogram. The two arrays using ESR reflector provided the best energy resolution and the array using Crystal Wrap reflector yielded the worst energy resolution. All arrays except the polished ESR array provided good DOI resolution ranging from 1.9 mm to 2.9 mm. DOI resolution improved as the gradient in light collection efficiency with depth (GLCED) increased. The geometric mean energies were also calculated for these dual‐ended readout detectors as an alternative to the conventional summed total energy. It was shown that the geometric mean energy is advantageous in that it provides more uniform photopeak amplitude at different depths for arrays with high GLCED, and is beneficial in event selection by allowing a fixed energy window independent of depth. A new method of DOI calculation that improved the linearity of DOI ratio vs depth and simplifies the DOI calibration procedure also was developed and tested. Conclusions: The results of these studies provide useful guidance in selecting the proper reflectors and crystal surface treatments when LSO arrays are used for high‐resolution PET applications in small animal scanners or dedicated breast and brain scanners.