Novel detector technology for clinical PET

Abstract

The simple juxtaposition of tomographs around a common axial bed, such as with current PET/CT technology, is very successful in allowing sequential acquisition of PET and anatomical data. However, novel imaging combinations are being considered that would enable simultaneous, or at least concurrent, dual-modality imaging through combined PET/MR or PET/CT. The development of these new integrated instruments creates new bewildering challenges for PET detection systems, which, in addition to the ability to measure annihilation radiation in PET, must satisfy several other critical requirements.

Hybrid Imaging: Instrumentation and Data Processing

“…Most PET and SPECT systems are composed of pixelated scintillators to assign the interaction position of the gamma photon [74], although blocks made of continuous crystal have been proposed as well [75,76]. Table 3 lists some of the scintillators commonly used in CT, SPECT and PET detector systems together with their key properties [77][78][79][80][81]. New scintillator materials are being developed continuously.…”

Neuroimaging - Clinical Applications

“…Receptor ligands used for PET are radiolabelled with short-lived positron-emitting isotopes such as 15 O, 13 N, 11 C, and 18 F with half-lives of 2, 10, 20.4, and 109.6 min, respectively. The spatial resolution of recently developed clinical PET systems with about 2-3 mm allows tracing of radioligand distribution even within small cerebral nuclei in human brain (Heiss et al, 2004;Lecomte, 2009;Wienhard et al, 2002), and a detailed regional analysis also in rodents (Lancelot & Zimmer, 2010;Lecomte, 2009;Xi et al, 2011) can be achieved with dedicated small-animal PET scanners. To overcome the problem of the anatomic classification of areas with increased or diminished radioligand accumulation, coregistration of brain anatomy with MRI or CT is needed.…”

Estudio e implementación de algoritmos digitales para la mejora de la resolución temporal en sistemas de tomografía por emisión de positrones

“…Si se considera un error de ∆θ = 2 · 0,23 o = 0,46 o = 0,008 rad FWHM, queda que F W HM = 0,002 · D lo que implica un error aproximado de 2 mm por metro de diámetro del anillo. Estos errores son inherentes a las leyes físicas que rigen el funcionamiento del sistema y limitan la máxima resolución espacial que puede proporcionar [40,41].…”

“…Por tanto, NEC es un parámetro que relaciona directamente la SNR con la tasa de eventos aleatorios, la tasa de eventos que sufren dispersión y la tasa de eventos válidos en coincidencia [48]. El NEC se define como [2,38,40,49] :…”

“…donde T es la tasa de eventos válidos en coincidencia, S es la tasa de eventos que han sufrido dispersión, R es la tasa de eventos aleatorios y α es un parámetro que vale 2 o 1 dependiendo de si la tasa de eventos aleatorios se mide mediante una ventana de tiempos desplazada o si la tasa se estima a partir de la tasa de eventos simples de cada uno de los detectores [40,49]. NEC es un estadístico que relaciona el incremento de la tasa de eventos válidos con el incremento de la tasa de eventos en el FOV penalizado por las tasas de eventos no válidos.…”