Standardized volumetric 3D-analysis of SPECT/CT imaging in orthopaedics: overcoming the limitations of qualitative 2D analysis

Abstract

BackgroundSPECT/CT combines high resolution anatomical 3D computerized tomography (CT) and single photon emission computerized tomography (SPECT) as functional imaging, which provides 3D information about biological processes into a single imaging modality. The clinical utility of SPECT/CT imaging has been recognized in a variety of medical fields and most recently in orthopaedics; however, clinical adoption has been limited due to shortcomings of analytical tools available. Specifically, SPECT analyses are mainly qualitative due to variation in overall metabolic uptake among patients. Furthermore, most analyses are done in 2D, although rich 3D data are available. Consequently, it is difficult to quantitatively compare the position, size, and intensity of SPECT uptake regions among patients, and therefore difficult to draw meaningful clinical conclusions.MethodsWe propose a method for normalizing orthopaedic SPECT/CT data that enables standardised 3D volumetric quantitative measurements and comparison among patients. Our method is based on 3D localisation using clinically relevant anatomical landmarks and frames of reference, along with intensity value normalisation using clinically relevant reference regions. Using the normalised data, we describe a thresholding technique to distinguish clinically relevant hot spots from background activity.ResultsUsing an exemplar comparison of two patients, we demonstrate how the normalised, 3D-rendered data can provide a richer source of clinical information and allow quantitative comparison of SPECT/CT measurements across patients. Specifically, we demonstrate how non-normalized SPECT/CT analysis can lead to different clinical conclusions than the normalized SPECT/CT analysis, and that normalized quantitative analysis can be a more accurate indicator of pathology.ConclusionsConventional orthopaedic frames of reference, 3D volumetric data analysis and thresholding are used to distinguish clinically relevant hot spots from background activity. Our goal is to facilitate a standardised approach to quantitative data collection and comparison of clinical studies using SPECT/CT, enabling more widespread clinical use of this powerful imaging tool.

SPECT/CT tracer uptake is influenced by tunnel orientation and position of the femoral and tibial ACL graft insertion site

“…In particular, information on the loading history of the joint can be obtained [21]. However, it is currently unclear whether SPECT/CT tracer uptake shows a significant correlation with stability and/or laxity of the knee joint or the position of the femoral or tibial tunnels.…”

“…The tracer activity on SPECT/CT was analysed using a specialised software allowing 3D volumetric quantitative analysis of SPECT data as previously published [21]. A previously published localisation scheme for anatomical localisation of the SPECT/CT tracer activity was used ( Fig.…”

“…SPECT/CT allows accurate anatomical localisation of metabolic tracer activity [9]. Recently, we have introduced a novel diagnostic SPECT/CT algorithm for the challenging group of patients with problems after ACL reconstruction [6,9,14,15]. This standardised algorithm including grading and anatomical localization of SPECT/CT tracer uptake promises the identification of specific pathological tracer uptake patterns and distributions [9].…”

Nuclear Medicine Imaging of Knee Injuries

“…Then, hybrid single-photon emission tomography (SPECT/CT) systems, which combine conventional computerized tomography (CT) with SPECT, were introduced and are now available for clinical routine use in an increasing number of institutions worldwide (Bybel et al 2008 ;Delbeke et al 2009 ). In the last 3 years, SPECT/CT has been increasingly recognized by the orthopaedic and sports medicine fraternity as a clinically helpful diagnostic imaging modality in patients after knee injuries or before/after surgical procedures (Hirschmann et al 2010a , b ;2011a , b , c , d ;2012c ;Horger et al 2007 ;Konala et al 2010 ;Scharf 2009 ;Strobel et al 2012 ).…”

“…In most of the patients with knee injuries, a SPECT/ CT is recommended. There has been tremendous effort to establish diagnostic standards and guidelines for the use of SPECT/CT in orthopaedics and sports medicine (Hirschmann et al 2010b ;2012c ). An increasing number of clinical indications and scenarios have been identifi ed, in which SPECT/CT holds the promise of establishing a better more specifi c diagnosis (Hirschmann et al 2010a , b ;2011a , b , c , d ;2012b ;Konala et al 2010 ).…”