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Evaluation of elastix-based propagated align algorithm for VOI- and voxel-based analysis of longitudinal (18)F-FDG PET/CT data from patients with non-small cell lung cancer (NSCLC).

Kerner GS, Fischer A, Koole MJ, Pruim J, Groen HJ - EJNMMI Res (2015)

Bottom Line: Lesion statistics were compared to assess the impact on therapy response assessment.The elastix toolbox impacts lesion statistics and therefore therapy response assessment in a clinically significant way.Further optimization and validation of this technique is necessary prior to clinical implementation.

View Article: PubMed Central - PubMed

Affiliation: University of Groningen and Department of Pulmonary Diseases, University Medical Center Groningen, Hanzeplein 1, P.O. Box 30.001, , 9700 RB Groningen, The Netherlands.

ABSTRACT

Background: Deformable image registration allows volume of interest (VOI)- and voxel-based analysis of longitudinal changes in fluorodeoxyglucose (FDG) tumor uptake in patients with non-small cell lung cancer (NSCLC). This study evaluates the performance of the elastix toolbox deformable image registration algorithm for VOI and voxel-wise assessment of longitudinal variations in FDG tumor uptake in NSCLC patients.

Methods: Evaluation of the elastix toolbox was performed using (18)F-FDG PET/CT at baseline and after 2 cycles of therapy (follow-up) data in advanced NSCLC patients. The elastix toolbox, an integrated part of the IMALYTICS workstation, was used to apply a CT-based non-linear image registration of follow-up PET/CT data using the baseline PET/CT data as reference. Lesion statistics were compared to assess the impact on therapy response assessment. Next, CT-based deformable image registration was performed anew on the deformed follow-up PET/CT data using the original follow-up PET/CT data as reference, yielding a realigned follow-up PET dataset. Performance was evaluated by determining the correlation coefficient between original and realigned follow-up PET datasets. The intra- and extra-thoracic tumors were automatically delineated on the original PET using a 41% of maximum standardized uptake value (SUVmax) adaptive threshold. Equivalence between reference and realigned images was tested (determining 95% range of the difference) and estimating the percentage of voxel values that fell within that range.

Results: Thirty-nine patients with 191 tumor lesions were included. In 37/39 and 12/39 patients, respectively, thoracic and non-thoracic lesions were evaluable for response assessment. Using the EORTC/SUVmax-based criteria, 5/37 patients had a discordant response of thoracic, and 2/12 a discordant response of non-thoracic lesions between the reference and the realigned image. FDG uptake values of corresponding tumor voxels in the original and realigned reference PET correlated well (R (2)=0.98). Using equivalence testing, 94% of all the voxel values fell within the 95% range of the difference between original and realigned reference PET.

Conclusions: The elastix toolbox impacts lesion statistics and therefore therapy response assessment in a clinically significant way. The elastix toolbox is therefore not applicable in its current form and/or standard settings for PET response evaluation. Further optimization and validation of this technique is necessary prior to clinical implementation.

No MeSH data available.


Related in: MedlinePlus

Example image of patient 7: baseline (A), reference (B), elastix adjusted (C) and subtraction (D). Because of a mix of non-active and active tumor tissue between the two scans (and no visible decrease in anatomic tumor size with stable disease), only 57% of the voxels aligned within the 95% limits of agreement of −1.46 to 1.46 ΔSUV. However, on crude visual assessment, the images look very similar.
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Fig4: Example image of patient 7: baseline (A), reference (B), elastix adjusted (C) and subtraction (D). Because of a mix of non-active and active tumor tissue between the two scans (and no visible decrease in anatomic tumor size with stable disease), only 57% of the voxels aligned within the 95% limits of agreement of −1.46 to 1.46 ΔSUV. However, on crude visual assessment, the images look very similar.

Mentions: Further study of the 5 patients with a voxel alignment <80% revealed that the reason for misalignment in general was due to CT- to PET-specific-related inaccuracies. In some patients, these inaccuracies were specific to therapy as it involved tumor necrosis (Figure 4). The other reason for an inaccuracy was the subsequent presence or absence of collapsed lung tissue after therapy (Additional file 1: Table S1).Figure 4


Evaluation of elastix-based propagated align algorithm for VOI- and voxel-based analysis of longitudinal (18)F-FDG PET/CT data from patients with non-small cell lung cancer (NSCLC).

Kerner GS, Fischer A, Koole MJ, Pruim J, Groen HJ - EJNMMI Res (2015)

Example image of patient 7: baseline (A), reference (B), elastix adjusted (C) and subtraction (D). Because of a mix of non-active and active tumor tissue between the two scans (and no visible decrease in anatomic tumor size with stable disease), only 57% of the voxels aligned within the 95% limits of agreement of −1.46 to 1.46 ΔSUV. However, on crude visual assessment, the images look very similar.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC4385310&req=5

Fig4: Example image of patient 7: baseline (A), reference (B), elastix adjusted (C) and subtraction (D). Because of a mix of non-active and active tumor tissue between the two scans (and no visible decrease in anatomic tumor size with stable disease), only 57% of the voxels aligned within the 95% limits of agreement of −1.46 to 1.46 ΔSUV. However, on crude visual assessment, the images look very similar.
Mentions: Further study of the 5 patients with a voxel alignment <80% revealed that the reason for misalignment in general was due to CT- to PET-specific-related inaccuracies. In some patients, these inaccuracies were specific to therapy as it involved tumor necrosis (Figure 4). The other reason for an inaccuracy was the subsequent presence or absence of collapsed lung tissue after therapy (Additional file 1: Table S1).Figure 4

Bottom Line: Lesion statistics were compared to assess the impact on therapy response assessment.The elastix toolbox impacts lesion statistics and therefore therapy response assessment in a clinically significant way.Further optimization and validation of this technique is necessary prior to clinical implementation.

View Article: PubMed Central - PubMed

Affiliation: University of Groningen and Department of Pulmonary Diseases, University Medical Center Groningen, Hanzeplein 1, P.O. Box 30.001, , 9700 RB Groningen, The Netherlands.

ABSTRACT

Background: Deformable image registration allows volume of interest (VOI)- and voxel-based analysis of longitudinal changes in fluorodeoxyglucose (FDG) tumor uptake in patients with non-small cell lung cancer (NSCLC). This study evaluates the performance of the elastix toolbox deformable image registration algorithm for VOI and voxel-wise assessment of longitudinal variations in FDG tumor uptake in NSCLC patients.

Methods: Evaluation of the elastix toolbox was performed using (18)F-FDG PET/CT at baseline and after 2 cycles of therapy (follow-up) data in advanced NSCLC patients. The elastix toolbox, an integrated part of the IMALYTICS workstation, was used to apply a CT-based non-linear image registration of follow-up PET/CT data using the baseline PET/CT data as reference. Lesion statistics were compared to assess the impact on therapy response assessment. Next, CT-based deformable image registration was performed anew on the deformed follow-up PET/CT data using the original follow-up PET/CT data as reference, yielding a realigned follow-up PET dataset. Performance was evaluated by determining the correlation coefficient between original and realigned follow-up PET datasets. The intra- and extra-thoracic tumors were automatically delineated on the original PET using a 41% of maximum standardized uptake value (SUVmax) adaptive threshold. Equivalence between reference and realigned images was tested (determining 95% range of the difference) and estimating the percentage of voxel values that fell within that range.

Results: Thirty-nine patients with 191 tumor lesions were included. In 37/39 and 12/39 patients, respectively, thoracic and non-thoracic lesions were evaluable for response assessment. Using the EORTC/SUVmax-based criteria, 5/37 patients had a discordant response of thoracic, and 2/12 a discordant response of non-thoracic lesions between the reference and the realigned image. FDG uptake values of corresponding tumor voxels in the original and realigned reference PET correlated well (R (2)=0.98). Using equivalence testing, 94% of all the voxel values fell within the 95% range of the difference between original and realigned reference PET.

Conclusions: The elastix toolbox impacts lesion statistics and therefore therapy response assessment in a clinically significant way. The elastix toolbox is therefore not applicable in its current form and/or standard settings for PET response evaluation. Further optimization and validation of this technique is necessary prior to clinical implementation.

No MeSH data available.


Related in: MedlinePlus