Abstract
Image contrast recovery coefficient (CRC) of a large ring PET scanner “macroPET” was studied with septa and without septa configuration by ac-quiring data from a laboratory made 35.7 cm square phantom filled with 18-F. Images were reconstructed with simple 2D filtered back projection using Hann, Hamming and Parsen filters with different cut-off frequencies aiming to investigate the influence of filter and cut-off frequency on image contrast with septa and without septa mode. Results indicate that the CRC, for both hot and cold lesions, is excellent for diameters ≥ 3 cm using cut-off frequencies > 0.4. For a 2 cm hot lesion CRC is around 0.8 to 0.9. CRC for 1 cm hot and cold lesions is ~0.3, as expected. There is surprisingly little difference between results with and without septa. For hot lesions, septa appear to improve CRC slightly, but for cold lesions CRC is slightly poorer using septa.
Highlights
Positron emission tomography (PET) is a nuclear imaging technique which has been widely used over the last few decades in many clinical applications such as staging, evaluating treatment response, and predicting prognosis in malignant diseases [1] [2]
A large ring PET “macroPET” system was constructed as a prototype by reconfiguring components from an original ECAT 951 system [3]
In the macroPET system [4], the 32 modules are mounted in a single ring with an inner diameter of 2.34 m
Summary
A large ring PET “macroPET” system was constructed as a prototype by reconfiguring components from an original ECAT 951 system [3]. The original system had 32 detector modules (“buckets” or “packs”) mounted in two rings. In the macroPET system [4], the 32 modules are mounted in a single ring with an inner diameter of 2.34 m. It was not practicable to construct dedicated septa [5] for macroPET, but in an attempt to investigate the value of septa some measurements were performed using the septa from the original ECAT 951 and the results compared with those obtained without any septa. Septa reduce most of the scatter events and reduce photon flux from outside the field of view (FOV), but block many true events, and limit the scanner sensitivity
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