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Depth of interaction with a 3-dimensional checkerboard arrangement LSO-LSO block
Stockholm University, Faculty of Science, Department of Physics. (Siemens Molecular Imaging)
(Siemens Molecular Imaging)
Stockholm University, Faculty of Science, Department of Physics. (Siemens Molecular Imaging)
(Siemens Molecular Imaging)
2010 (English)In: IEEE Transactions on Nuclear Science, ISSN 0018-9499, E-ISSN 1558-1578, Vol. 57, no 3, 971-975 p.Article in journal (Refereed) Published
Abstract [en]

In order to improve image quality in Positron Emission Tomography (PET) different routes are being pursued such as fast timing resolution for time-of-flight PET, higher spatial resolution by the use of smaller scintillator pixels and the use of depth-of-interaction information. The detection of the depth-of-interaction (DOI) of a gamma ray within a detector, deploying pulse shape discrimination (PSD), has been used to increase sensitivity and spatial resolution, especially at the edge of the field of view (FOV). The DOI information is used to reduce the parallax error; thus improving spatial resolution. Commonly, different scintillator materials with different decay times and light output and other differentiating factors, such as density, emission spectra, etc. are used for DOI detectors. We present a multi-layer phoswich detector comprised of LSO with different decay times in the range from 30 ns to 47 ns. The difference in decay times is achieved by co-doping LSO:Ce with Ca, resulting in short decay times of ~ 30 ns [1]. The use of a cut light guide allows the use of regular Photomultiplier tubes, giving the opportunity of a potential DOI detector replacement for current detectors. We were able to identify each pixel in the different detector layers

Place, publisher, year, edition, pages
2010. Vol. 57, no 3, 971-975 p.
Keyword [en]
Block detector, depth of interaction, lutetium oxyorthosilicate (LSO), positron emission tomography (PET)
National Category
Physical Sciences
URN: urn:nbn:se:su:diva-31658DOI: 10.1109/TNS.2010.2041070ISI: 000278812100008OAI: diva2:278545
Available from: 2009-11-26 Created: 2009-11-23 Last updated: 2011-11-22Bibliographically 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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