Transmission-less Attenuation Correction for Full and Partial Ring PET Scanners

The PETITION (PET for InTensive Care units and Innovative protON therapy) project aims to design two new bed-side Positron Emission Tomography (PET) scanners for Intensive Care Units (ICU) and proton beam therapy applications. The first device is intended to scan deeply sedated, critically-ill patients with sepsis infection directly at the ICU, as their condition does no allow for a transportation to regular PET/CT facilities. The second device is designed for online image acquisition for in vivo dosimetry and hypoxia tracking studies.While the ICU device is a conventional full ring PET scanner, the other system has a U-shaped design ensuring a suitable opening for protons irradiation. The attenuation of photons is the most important limiting factor of quantitative accuracy and quality of PET images. To perform attenuation correction, the knowledge of the patient-specific attenuation map (µ-map) is required. Several approaches, using either external information or emission data, already exist for the µ-map generation. The PETITION scanners do not offer the possibility to perform a transmission scan and therefore the attenuation map needs to be generated from emission data only. While the transmission-less method is already widely applied with full ring PET scanners, it is usually not used with partial ring devices. This document presents preliminary results of attenuation correction based on the emission of full and partial ring PET data only.