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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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3D reconstructions of SPECT and bone surface. The SPECT hot spots are demonstrated at our chosen SPECT threshold (three times mean of the reference region) as a 3D surface reconstruction (left) and radiolucent (right) views (patient 1 top, patient 2 bottom row).
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Figure 8: 3D reconstructions of SPECT and bone surface. The SPECT hot spots are demonstrated at our chosen SPECT threshold (three times mean of the reference region) as a 3D surface reconstruction (left) and radiolucent (right) views (patient 1 top, patient 2 bottom row).

Mentions: Using the above determined normalized threshold, we were able to analyze and re-render the SPECT data at what we considered a clinically significant threshold (Figure 8). This rendering supports the clinical diagnosis of isolated patellofemoral disease in P1 and bi-compartmental disease in P2. Comparison of the intensities of the maximum value in the region of interest against the intensity of the reference region further supported the conclusion of P2's increased degeneration. P1's maximum was less intense (4.55 times the mean reference intensity) than P2's (5.56 times the mean reference intensity). Similarly, comparing the mean value of the region of interest (using four times the mean of the reference region to focus on the patellofemoral hotspot in each patient) revealed that P1's mean was less intense (P1: 4.19 vs. P2: 4.49) (Figure 9). Finally, comparing the number of SPECT voxels above the clinical threshold show that P2's uptake region is larger in size (volume) than P1's.


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)

3D reconstructions of SPECT and bone surface. The SPECT hot spots are demonstrated at our chosen SPECT threshold (three times mean of the reference region) as a 3D surface reconstruction (left) and radiolucent (right) views (patient 1 top, patient 2 bottom row).
© Copyright Policy - open-access
Related In: Results  -  Collection

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

Figure 8: 3D reconstructions of SPECT and bone surface. The SPECT hot spots are demonstrated at our chosen SPECT threshold (three times mean of the reference region) as a 3D surface reconstruction (left) and radiolucent (right) views (patient 1 top, patient 2 bottom row).
Mentions: Using the above determined normalized threshold, we were able to analyze and re-render the SPECT data at what we considered a clinically significant threshold (Figure 8). This rendering supports the clinical diagnosis of isolated patellofemoral disease in P1 and bi-compartmental disease in P2. Comparison of the intensities of the maximum value in the region of interest against the intensity of the reference region further supported the conclusion of P2's increased degeneration. P1's maximum was less intense (4.55 times the mean reference intensity) than P2's (5.56 times the mean reference intensity). Similarly, comparing the mean value of the region of interest (using four times the mean of the reference region to focus on the patellofemoral hotspot in each patient) revealed that P1's mean was less intense (P1: 4.19 vs. P2: 4.49) (Figure 9). Finally, comparing the number of SPECT voxels above the clinical threshold show that P2's uptake region is larger in size (volume) than P1's.

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