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

Hirschmann MT, Wagner CR, Rasch H, Henckel J - BMC Med Imaging (2012)

Bottom Line: Furthermore, most analyses are done in 2D, although rich 3D data are available.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.Conventional orthopaedic frames of reference, 3D volumetric data analysis and thresholding are used to distinguish clinically relevant hot spots from background activity.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Orthopaedic Surgery and Traumatology, Kantonsspital Bruderholz, CH-4101 Bruderholz, Switzerland. michael.hirschmann@unibas.ch

ABSTRACT

Background: SPECT/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.

Methods: We 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.

Results: Using 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.

Conclusions: Conventional 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.

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Non-normalized SPECT renderings. Renderings of the SPECT uptake region for patient 1 (left column) and patient 2 (right column) at 90% maximum SPECT intensity (top row) and 60% maximum SPECT intensity (bottom row). Without a method to identify a clinically relevant threshold intensity, drawing clinical conclusions is problematic.
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Figure 5: Non-normalized SPECT renderings. Renderings of the SPECT uptake region for patient 1 (left column) and patient 2 (right column) at 90% maximum SPECT intensity (top row) and 60% maximum SPECT intensity (bottom row). Without a method to identify a clinically relevant threshold intensity, drawing clinical conclusions is problematic.

Mentions: Initial SPECT renderings (threshold SPECT voxels at 90% of maximum intensity) show similar tracer uptake patterns, in particular the size and intensity of the altered tracer uptake region (Figure 5), indicating isolated patellofemoral disease in both patients. However, thresholding at a lower value (60% of maximum) reveals a different uptake extent. At this lower threshold, P2's uptake region extents into the tibiofemoral joint, while P1's hotspot is localized within the patellofemoral joint only. Without a normalization procedure to inform a clinically relevant threshold, it is difficult to determine whether P2's observed uptake is part of normal physiological variation in tracer uptake or is an indication of pathology.


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

Hirschmann MT, Wagner CR, Rasch H, Henckel J - BMC Med Imaging (2012)

Non-normalized SPECT renderings. Renderings of the SPECT uptake region for patient 1 (left column) and patient 2 (right column) at 90% maximum SPECT intensity (top row) and 60% maximum SPECT intensity (bottom row). Without a method to identify a clinically relevant threshold intensity, drawing clinical conclusions is problematic.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3368747&req=5

Figure 5: Non-normalized SPECT renderings. Renderings of the SPECT uptake region for patient 1 (left column) and patient 2 (right column) at 90% maximum SPECT intensity (top row) and 60% maximum SPECT intensity (bottom row). Without a method to identify a clinically relevant threshold intensity, drawing clinical conclusions is problematic.
Mentions: Initial SPECT renderings (threshold SPECT voxels at 90% of maximum intensity) show similar tracer uptake patterns, in particular the size and intensity of the altered tracer uptake region (Figure 5), indicating isolated patellofemoral disease in both patients. However, thresholding at a lower value (60% of maximum) reveals a different uptake extent. At this lower threshold, P2's uptake region extents into the tibiofemoral joint, while P1's hotspot is localized within the patellofemoral joint only. Without a normalization procedure to inform a clinically relevant threshold, it is difficult to determine whether P2's observed uptake is part of normal physiological variation in tracer uptake or is an indication of pathology.

Bottom Line: Furthermore, most analyses are done in 2D, although rich 3D data are available.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.Conventional orthopaedic frames of reference, 3D volumetric data analysis and thresholding are used to distinguish clinically relevant hot spots from background activity.

View Article: PubMed Central - HTML - PubMed

Affiliation: Department of Orthopaedic Surgery and Traumatology, Kantonsspital Bruderholz, CH-4101 Bruderholz, Switzerland. michael.hirschmann@unibas.ch

ABSTRACT

Background: SPECT/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.

Methods: We 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.

Results: Using 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.

Conclusions: Conventional 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.

Show MeSH
Related in: MedlinePlus