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Timing performance of Hi-Rez detector for time-of-flight (TOF) PET
(Siemens Molecular Imaging)
Stockholm University, Faculty of Science, Department of Physics. (Siemens Molecular Imaging)
(Siemens Molecular Imaging)
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2006 (English)In: IEEE Transactions on Nuclear Science, ISSN 0018-9499, Vol. 53, no 3, 1084-1089 p.Article in journal (Refereed) Published
Abstract [en]

Positron emission tomography (PET)-based on time-of-flight (TOF) is desired to enhance the image quality by improving the noise variance in the reconstruction. This benchtop study evaluates the timing performance of the current Hi-Rez detector which is based on a 13/spl times/13 LSO array of 4 mm/spl times/4 mm/spl times/20 mm crystals and not optimized for TOF PET applications. A Hamamatsu R9779, fast, 51-mm-diameter PMT was used for some experiments in this study as a reference PMT and its time resolution was measured to be 160 ps with a plastic scintillator. The average crystal time resolution of two Hi-Rez detectors, coupled to a 2/spl times/2 array of Hamamatsu 25-mm-diameter R8619 PMTs at +1050 V, in coincidence was measured to be 733 ps. The average crystal energy resolutions for two detectors were measured 13.1% and 13.2%. The average crystal time resolution of two Hi-Rez detectors improved from 733 ps to 642 ps when the PMT voltage was increased to +1300 V. The Hi-Rez detector was originally optimized for good energy resolution to reduce scatter and high packing fraction to obtain high sensitivity and improved spatial resolution for clinical PET.

Place, publisher, year, edition, pages
2006. Vol. 53, no 3, 1084-1089 p.
URN: urn:nbn:se:su:diva-31657OAI: diva2:278540
Available from: 2009-11-26 Created: 2009-11-23 Last updated: 2009-12-22Bibliographically approved
In thesis
1. Detector Considerations for Time-of-Flight in Positron Emission Tomography
Open this publication in new window or tab >>Detector Considerations for Time-of-Flight in Positron Emission Tomography
2009 (English)Doctoral thesis, comprehensive summary (Other academic)
Abstract [en]

Positron-Emission-Tomography (PET) is a modern imaging technique in nuclear medicine providing quantitative 3D distribution of a radioactive tracer substance in the human body. The gamma-detector is the first link in the chain of components that constitutes a PET. It converts incoming radiation into optical light pulses, which are detected by photo multiplier tubes. Here the light is converted into electric pulses, to be further processed by the acquisition electronics. Improving detector sensitivity and resolution is of great value in research and in clinical practice.

The focus of this work is to improve the detector to give it time-of-flight (TOF) capabilities, in order to further improve sensitivity, which in turn leads to increased image quality, faster scan time and/or reduced dose exposure for the patient.

Image quality has improved over the years, but losses in image quality have been reported for heavy patients, due to increased attenuation, and more dispersed counts over a larger volume. Instrumentation limits are still significant in heavy patient images, but the incorporation of TOF information promises to alleviate some of the limitations.

In order to improve the timing resolution of the detector fast photo-multipliers and a novel scheme to extract the event timing trigger from a detector by using the summed dynode signal were investigated.

When designing new PET detectors, it is important to have detailed understanding and control of the light sharing mechanisms in the crystal arrays. Therefore it was necessary to perform optical simulations and single crystal light output measurements to derive a model for an LSO block detector.

Another way to improve the image quality is to use the depth-of-interaction (DOI) of the gamma ray within the detector. It is shown that a multi-layer phoswich detector comprised of LSO with different decay times and TOF capability, combines the benefits of TOF and DOI in one detector, maximizing the effective sensitivity gain.

Place, publisher, year, edition, pages
Stockholm: Department of Physics, Stockholm University, 2009. 78 p.
Positron Emission Tomography, Time of Flight, Depth of Interaction, LSO
National Category
Radiology, Nuclear Medicine and Medical Imaging
Research subject
Medical Radiation Physics
urn:nbn:se:su:diva-31587 (URN)978-91-7155-979-1 (ISBN)
Public defence
2010-01-08, FB52, AlbaNova universitetscentrum, Roslagstullsbacken 21, Stockholm, 10:00 (English)
At the time of the doctoral defense, the following papers were unpublished and had a status as follows: Paper 7: Submitted. Available from: 2009-12-03 Created: 2009-11-19 Last updated: 2009-12-22Bibliographically approved

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