Non-invasive input function measurement for positron emission tomography using Doppler ultrasound imaging

Ziel/Aim PET is used to study metabolism using a tracer – a substance doped with small amounts of a radioactive isotope - that is specific for a given physiological process under examination. The uptake and metabolization of this tracer is a dynamic process, and an exact knowledge of the initial arterial tracer input is essential. Usually, this is achieved by taking blood samples invasively or with image derived input functions.

Methodik/Methods We plan to use a second imaging modality–Doppler ultrasound imaging–and a matrix of scintillators each attached to highly integrated optical sensors for non-invasive arterial input measurement. The US device is used to locate a large artery, for instance a carotid, and to aim the detectors onto that vessel by means of image-guidance techniques. By this approach, we propose that both - a measurement of the arterial input function and the background signal - is facilitated with high precision and high temporal resolution.

Ergebnisse/Results For initial measurements we used a BGO crystal whose scintillation signal was read by a SiPM photosensor. The measured ¹⁸F count rate is higher than that of the background providing decent count statistics and a promising signal-to-noise ratio (SNR). Our results also agree well with the outcome of a preliminary Monte Carlo.

Schlussfolgerungen/Conclusions Further studies will be performed to improve light collection efficiency, as well as to decrease DAQs deadtime. Finding the optimal number of detector modules with sufficient sensitivity, designing collimator and shielding and finding strategies for operation that minimizes scatter background will be among the main tasks to evolve the preliminary test bed into an operational demonstrator.

• Literatur/References

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