Long-axial field-of-view PET/CT: perspectives and review of a revolutionary development in nuclear medicine based on clinical experience in over 7000 patients

Abstract

Recently introduced long-axial field-of-view (LAFOV) PET/CT systems represent one of the most significant advancements in nuclear medicine since the advent of multi-modality PET/CT imaging. The higher sensitivity exhibited by such systems allow for reductions in applied activity and short duration scans. However, we consider this to be just one small part of the story: Instead, the ability to image the body in its entirety in a single FOV affords insights which standard FOV systems cannot provide. For example, we now have the ability to capture a wider dynamic range of a tracer by imaging it over multiple half-lives without detrimental image noise, to leverage lower radiopharmaceutical doses by using dual-tracer techniques and with improved quantification. The potential for quantitative dynamic whole-body imaging using abbreviated protocols potentially makes these techniques viable for routine clinical use, transforming PET-reporting from a subjective analysis of semi-quantitative maps of radiopharmaceutical uptake at a single time-point to an accurate and quantitative, non-invasive tool to determine human function and physiology and to explore organ interactions and to perform whole-body systems analysis. This article will share the insights obtained from 2 years’ of clinical operation of the first Biograph Vision Quadra (Siemens Healthineers) LAFOV system. It will also survey the current state-of-the-art in PET technology. Several technologies are poised to furnish systems with even greater sensitivity and resolution than current systems, potentially with orders of magnitude higher sensitivity. Current barriers which remain to be surmounted, such as data pipelines, patient throughput and the hindrances to implementing kinetic analysis for routine patient care will also be discussed.

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

“…A prominent trend in recent PET scanner designs is the increasing inclination towards extending the AFOV to encompass as much of the human body as feasible-typically around 2 metres-catering to various clinical demands (like ultra-low dose, ultra-rapid imaging, dynamic, and parametric whole-body imaging) [5,6,[48][49][50][51][52][53][54][55][56]. PET scanners featuring extended AFOV have been progressively integrated into clinical settings, examples being the Biograph mCT (Siemens Healthineers, 22 cm AFOV), the Biograph Vision 600 (Siemens Healthineers, 26.3 cm AFOV) [50] , and the GE Discovery MI PET/CT system (General Electric, 30 cm AFOV) [57].…”

“…A prominent trend in recent PET scanner designs is the increasing inclination towards extending the AFOV to encompass as much of the human body as feasible-typically around 2 metres-catering to various clinical demands (like ultra-low dose, ultra-rapid imaging, dynamic, and parametric whole-body imaging) [5,6,[48][49][50][51][52][53][54][55][56]. PET scanners featuring extended AFOV have been progressively integrated into clinical settings, examples being the Biograph mCT (Siemens Healthineers, 22 cm AFOV), the Biograph Vision 600 (Siemens Healthineers, 26.3 cm AFOV) [50] , and the GE Discovery MI PET/CT system (General Electric, 30 cm AFOV) [57]. In recent times, elongated AFOV PET prototypes tailored for research purposes have emerged, such as the uEXPLORER (built as part of a collaboration between the University of California, Davis (UC Davis) and United Imaging Healthcare (UIH) in the USA, 194 cm AFOV) [58,59]; the Penn-PET Explorer (64 cm AFOV, designed at the University of Pennsylvania (Philips Technology), USA) [60,61]; and the Biograph Vision Quadra (Siemens Healthineers, 106 cm AFOV, situated in Bern, Switzerland).…”

“…Based on these previous studies, long axial FOV or whole-body PET scanners have been built recently, such as the uEXPLORER (United Imaging Healthcare, 195 cm AFOV), developed by the University of California, Davis (UC Davis), USA [58,59], the PennPET Explorer (64 cm AFOV) designed and built at the University of Pennsylvania (UPenn), USA [60,61,178], this system was installed with a 64 cm AFOV (three rings), then with a 142 cm AFOV (six rings) [179], and more recently the uMI Panorama (United Imaging Healthcare, 35 cm AFOV) [180]. Finally, Siemens introduced the Biograph Vision Quadra (Siemens Healthineers, 106 cm AFOV) in Bern, Switzerland [50,63]. These systems have been developed and oriented solely to research, explore new clinical applications, and understand tracer biodistribution better.…”

“…In addition, this reduction in acquisition time makes it more comfortable for patients suffering pain during the examination with minimal motion artefacts. It can facilitate the PET examination process in certain patients (e.g., claustrophobic or extremely nervous patients and children) [50,52].…”

“…Secondly, with the considerable gain in sensitivity and count rate reported, the reduction in injected dose and activity can be envisaged without affecting image quality [50]. This reduction may prove very useful in terms of radiation protection for scanned patients, particularly for paediatric patients and pregnant women.…”