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Voxel-based dual-time 18F-FDG parametric imaging for rectal cancer: differentiation of residual tumor from postchemoradiotherapy changes.

Choi H, Yoon HJ, Kim TS, Oh JH, Kim DY, Kim SK - Nucl Med Commun (2013)

Bottom Line: Maximum delayed-to-standard SUV ratios (DSR) measured on the parametric images as well as the percentage of SUV decrease from pre-CRT to post-CRT scans (pre/post-CRT response index) were obtained for each tumor and correlated with pathologic response classified by the Dworak tumor regression grade (TRG).The maximum DSR showed significantly higher accuracy for identification of tumor regression compared with the pre/post-CRT response index in receiver-operating characteristic analysis (P<0.01).With a 1.25 cutoff value for the maximum DSR, 85.0% sensitivity, 95.5% specificity, and 93.0% overall accuracy were obtained for identification of good response.

View Article: PubMed Central - PubMed

Affiliation: aDepartment of Nuclear Medicine bCenter for Colorectal Cancer, National Cancer Center, Goyang, Korea.

ABSTRACT

Introduction: 18F-Fluorodeoxyglucose (18F-FDG) PET/computed tomography (CT) has been used for evaluation of the response of rectal cancer to neoadjuvant chemoradiotherapy (CRT), but differentiating residual tumor from post-treatment changes remains a problem. We propose a voxel-based dual-time 18F-FDG PET parametric imaging technique for the evaluation of residual rectal cancer after CRT.

Materials and methods: Eighty-six patients with locally advanced rectal cancer who underwent neoadjuvant CRT between March 2009 and February 2011 were selected retrospectively. Standard 60-min postinjection PET/CT scans followed by 90-min delayed images were coregistered by rigid-body transformation. A dual-time parametric image was generated, which divided delayed standardized uptake value (SUV) by 60-min SUV on a voxel-by-voxel basis. Maximum delayed-to-standard SUV ratios (DSR) measured on the parametric images as well as the percentage of SUV decrease from pre-CRT to post-CRT scans (pre/post-CRT response index) were obtained for each tumor and correlated with pathologic response classified by the Dworak tumor regression grade (TRG).

Results: With respect to the false-positive lesions in the nine post-CRT patients with false-positive standard 18F-FDG scans in case groups who responded to therapy (TRG 3 or 4 tumors), eight were undetectable on dual-time parametric images (P<0.05). The maximum DSR showed significantly higher accuracy for identification of tumor regression compared with the pre/post-CRT response index in receiver-operating characteristic analysis (P<0.01). With a 1.25 cutoff value for the maximum DSR, 85.0% sensitivity, 95.5% specificity, and 93.0% overall accuracy were obtained for identification of good response.

Conclusion: A voxel-based dual-time parametric imaging technique for evaluation of post-CRT rectal cancer holds promise for differentiating residual tumor from treatment-related nonspecific 18F-FDG uptake.

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Related in: MedlinePlus

Schematic workflow for dual-time parametric image reconstruction. Delayed and standard PET images were scaled to standardized uptake value (SUV) and coregistered. A spherical volume-of-interest (VOI) was drawn around a focus detectable on the postchemoradiotherapy 18F-FDG PET/CT scan and the delayed-to-standard SUV ratio was calculated on a voxel basis. CT, computed tomography; 18F-FDG, 18F-fluorodeoxyglucose.
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Figure 1: Schematic workflow for dual-time parametric image reconstruction. Delayed and standard PET images were scaled to standardized uptake value (SUV) and coregistered. A spherical volume-of-interest (VOI) was drawn around a focus detectable on the postchemoradiotherapy 18F-FDG PET/CT scan and the delayed-to-standard SUV ratio was calculated on a voxel basis. CT, computed tomography; 18F-FDG, 18F-fluorodeoxyglucose.

Mentions: To correct positioning artifacts, post-CRT standard and delayed images were coregistered using a statistical parametric mapping software package (SPM2; University College London, London, UK). More specifically, rigid-body transformation was carried out using three translations and three rotation parameters. All transformed images were visually confirmed. Each image was scaled and quantitatively displayed by the standardized uptake value (SUV). A spherical VOI was placed around abnormalities with increased 18F-FDG uptake on images, and the delayed SUV was divided by standard SUV on a voxel basis. A dual-time parametric image was created from each post-CRT image, with a delayed-to-standard SUV ratio (DSR) map (Fig. 1).


Voxel-based dual-time 18F-FDG parametric imaging for rectal cancer: differentiation of residual tumor from postchemoradiotherapy changes.

Choi H, Yoon HJ, Kim TS, Oh JH, Kim DY, Kim SK - Nucl Med Commun (2013)

Schematic workflow for dual-time parametric image reconstruction. Delayed and standard PET images were scaled to standardized uptake value (SUV) and coregistered. A spherical volume-of-interest (VOI) was drawn around a focus detectable on the postchemoradiotherapy 18F-FDG PET/CT scan and the delayed-to-standard SUV ratio was calculated on a voxel basis. CT, computed tomography; 18F-FDG, 18F-fluorodeoxyglucose.
© Copyright Policy - open-access
Related In: Results  -  Collection

License
Show All Figures
getmorefigures.php?uid=PMC3815117&req=5

Figure 1: Schematic workflow for dual-time parametric image reconstruction. Delayed and standard PET images were scaled to standardized uptake value (SUV) and coregistered. A spherical volume-of-interest (VOI) was drawn around a focus detectable on the postchemoradiotherapy 18F-FDG PET/CT scan and the delayed-to-standard SUV ratio was calculated on a voxel basis. CT, computed tomography; 18F-FDG, 18F-fluorodeoxyglucose.
Mentions: To correct positioning artifacts, post-CRT standard and delayed images were coregistered using a statistical parametric mapping software package (SPM2; University College London, London, UK). More specifically, rigid-body transformation was carried out using three translations and three rotation parameters. All transformed images were visually confirmed. Each image was scaled and quantitatively displayed by the standardized uptake value (SUV). A spherical VOI was placed around abnormalities with increased 18F-FDG uptake on images, and the delayed SUV was divided by standard SUV on a voxel basis. A dual-time parametric image was created from each post-CRT image, with a delayed-to-standard SUV ratio (DSR) map (Fig. 1).

Bottom Line: Maximum delayed-to-standard SUV ratios (DSR) measured on the parametric images as well as the percentage of SUV decrease from pre-CRT to post-CRT scans (pre/post-CRT response index) were obtained for each tumor and correlated with pathologic response classified by the Dworak tumor regression grade (TRG).The maximum DSR showed significantly higher accuracy for identification of tumor regression compared with the pre/post-CRT response index in receiver-operating characteristic analysis (P<0.01).With a 1.25 cutoff value for the maximum DSR, 85.0% sensitivity, 95.5% specificity, and 93.0% overall accuracy were obtained for identification of good response.

View Article: PubMed Central - PubMed

Affiliation: aDepartment of Nuclear Medicine bCenter for Colorectal Cancer, National Cancer Center, Goyang, Korea.

ABSTRACT

Introduction: 18F-Fluorodeoxyglucose (18F-FDG) PET/computed tomography (CT) has been used for evaluation of the response of rectal cancer to neoadjuvant chemoradiotherapy (CRT), but differentiating residual tumor from post-treatment changes remains a problem. We propose a voxel-based dual-time 18F-FDG PET parametric imaging technique for the evaluation of residual rectal cancer after CRT.

Materials and methods: Eighty-six patients with locally advanced rectal cancer who underwent neoadjuvant CRT between March 2009 and February 2011 were selected retrospectively. Standard 60-min postinjection PET/CT scans followed by 90-min delayed images were coregistered by rigid-body transformation. A dual-time parametric image was generated, which divided delayed standardized uptake value (SUV) by 60-min SUV on a voxel-by-voxel basis. Maximum delayed-to-standard SUV ratios (DSR) measured on the parametric images as well as the percentage of SUV decrease from pre-CRT to post-CRT scans (pre/post-CRT response index) were obtained for each tumor and correlated with pathologic response classified by the Dworak tumor regression grade (TRG).

Results: With respect to the false-positive lesions in the nine post-CRT patients with false-positive standard 18F-FDG scans in case groups who responded to therapy (TRG 3 or 4 tumors), eight were undetectable on dual-time parametric images (P<0.05). The maximum DSR showed significantly higher accuracy for identification of tumor regression compared with the pre/post-CRT response index in receiver-operating characteristic analysis (P<0.01). With a 1.25 cutoff value for the maximum DSR, 85.0% sensitivity, 95.5% specificity, and 93.0% overall accuracy were obtained for identification of good response.

Conclusion: A voxel-based dual-time parametric imaging technique for evaluation of post-CRT rectal cancer holds promise for differentiating residual tumor from treatment-related nonspecific 18F-FDG uptake.

Show MeSH
Related in: MedlinePlus