Long axial field of view (LAFOV) PET-CT: implementation in static and dynamic oncological studies

Abstract

Long axial field of view (LAFOV) PET-CT scanners have been recently developed and are already in clinical use in few centers worldwide. Although still limited, the hitherto acquired experience with these novel systems highlights an increased sensitivity as their main advantage, which results in an increased lesion detectability. This attribute, alternatively, allows a reduction in PET acquisition time and/or administered radiotracer dose, while it renders delayed scanning of satisfying diagnostic accuracy possible. Another potential advantage of the new generation scanners is CT-less approaches for attenuation correction with the impact of marked reduction of radiation exposure, which may in turn lead to greater acceptance of longitudinal PET studies in the oncological setting. Further, the possibility for the first time of whole-body dynamic imaging, improved compartment modeling, and whole-body parametric imaging represent unique characteristics of the LAFOV PET-CT scanners. On the other hand, the advent of the novel LAFOV scanners is linked to specific challenges, such as the high purchase price and issues related to logistics and their optimal operation in a nuclear medicine department. Moreover, with regard to its research applications in oncology, the full potential of the new scanners can only be reached if different radiopharmaceuticals, both short and long-lived ones, as well as novel tracers, are available for use, which would, in turn, require the appropriate infrastructure in the area of radiochemistry. Although the novel LAFOV scanners are not yet widely used, this development represents an important step in the evolution of molecular imaging. This review presents the advantages and challenges of LAFOV PET-CT imaging for oncological applications with respect to static and dynamic acquisition protocols as well as to new tracers, while it provides an overview of the literature in the field.

Potential Clinical Impact of LAFOV PET/CT: A Systematic Evaluation of Image Quality and Lesion Detection

“…LAFOV PET/CT has also made a variety of advanced imaging feasible. This entails but is not limited to dual-tracer imaging, dynamic imaging with ongoing distribution in the body-organ interactions, as well as delayed imaging with improved differentiation of pathologic lesions as opposed to inflammation [43][44][45][46]. These might turn out to be the true benefit of LAFOV PET/CT.…”

The detection instrumentation and geometric design of clinical PET scanner: towards better performance and broader clinical applications

“…This design makes it possible to acquire data dynamically over an extended axial range (including multiple organs) in the body by simultaneously capturing tracer kinetic information not available with conventional static acquisition protocols [183], with absolute quantification provided non-invasively from an image-derived arterial input function that is always available in the field of view. Overall, the additional temporal data provided by dynamic acquisition as a complement to static wholebody imaging can significantly enhance the existing PET technique for tumour diagnosis, staging, and assessment of therapeutic response [13].…”

“…In parametric imaging, physiological parameters are extracted by dynamic PET acquisitions from a protocol based on dedicated mathematical models with precise voxel-by-voxel calculation instead of regionof-interest (ROI) based analysis [13,184]. Direct visualization of different kinetic parameters, such as influx or tracer transport rates (K1, k2), rather than providing their absolute values, can also be used to produce multiparametric images of Patlak slope (net influx rate) and intercept, while also providing a conventional 'SUV-equivalent' image for some protocols [183].…”

“…All these advances have considerably improved scanner performance; system sensitivity has increased by a factor of 40 (∼10-20 cps kBq −1 ) and spatial resolution by a factor of 10 (∼3-5 mm) between the first designs of the 1970s and today's state-of-the-art scanners [11]; temporal resolution has increased by a factor of 14, from around 2-10 ns to 500-700 ps [12]; and the scattering fraction has decreased due to improved energy resolution (∼10%-12%), resulting in improved reconstructed image quality. In addition, these advances in detection instrumentation and scanner design have also improved clinical practice by significantly reducing dose and examination time and creating new opportunities to cover a wider group of indications that are impossible for conventional scanners, including dynamic whole-body imaging acquisition and parametric imaging [13].…”

Computer-Aided Detection for Pancreatic Cancer Diagnosis: Radiological Challenges and Future Directions

“…Additionally, intelligent 4D imaging on ultra-high-sensitivity PET, such as Large Axial Field of View (LAFOV) PET, could enhance the detection of small lesions and improve image quality. 4D imaging refers to the acquisition of imaging data over time, allowing for the assessment of dynamic processes within the body [ 114 ]. Potentially, AI algorithms can analyze and interpret the data obtained from LAFOV PET, which could enable a more accurate assessment of tumor behavior or prediction of disease progression.…”