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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: 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.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.

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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SPECT intensities in reference region and region of interest. Comparison of the tracer uptake intensities in the region of interest (right column) relative to the intensities in a reference region (middle column) for patient 1 (top row) and patient 2 (bottom row). The SPECT histograms (left column) illustrate SPECT tracer distribution of the reference region ("saved") in comparison to the SPECT region of interest ("local") and the whole dataset ("global").
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Figure 7: SPECT intensities in reference region and region of interest. Comparison of the tracer uptake intensities in the region of interest (right column) relative to the intensities in a reference region (middle column) for patient 1 (top row) and patient 2 (bottom row). The SPECT histograms (left column) illustrate SPECT tracer distribution of the reference region ("saved") in comparison to the SPECT region of interest ("local") and the whole dataset ("global").

Mentions: We used a region in the middle of the femur to establish a clinically neutral reference region (Figure 7). The SPECT intensities within this neutral region were then used as a baseline distribution from which we could compare the SPECT intensities on the articular surfaces. For this comparison, we used three times the average intensity in the reference region to signify a clinically relevant level of increased tracer activity. (Again, the clinically optimal relationship between the reference region, the hotspot and clinical outcomes remains an area of active research.)


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)

SPECT intensities in reference region and region of interest. Comparison of the tracer uptake intensities in the region of interest (right column) relative to the intensities in a reference region (middle column) for patient 1 (top row) and patient 2 (bottom row). The SPECT histograms (left column) illustrate SPECT tracer distribution of the reference region ("saved") in comparison to the SPECT region of interest ("local") and the whole dataset ("global").
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 7: SPECT intensities in reference region and region of interest. Comparison of the tracer uptake intensities in the region of interest (right column) relative to the intensities in a reference region (middle column) for patient 1 (top row) and patient 2 (bottom row). The SPECT histograms (left column) illustrate SPECT tracer distribution of the reference region ("saved") in comparison to the SPECT region of interest ("local") and the whole dataset ("global").
Mentions: We used a region in the middle of the femur to establish a clinically neutral reference region (Figure 7). The SPECT intensities within this neutral region were then used as a baseline distribution from which we could compare the SPECT intensities on the articular surfaces. For this comparison, we used three times the average intensity in the reference region to signify a clinically relevant level of increased tracer activity. (Again, the clinically optimal relationship between the reference region, the hotspot and clinical outcomes remains an area of active research.)

Bottom Line: 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.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.

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