https://www.theragnostics.no/en/author/peter-van-luijk/ Peter Van Luijk Hugo Blox Builder (https://hugoblox.com)en-usWed, 01 Nov 2017 00:00:00 +0000 https://www.theragnostics.no/media/icon_hu14557955862192370321.png https://www.theragnostics.no/en/author/peter-van-luijk/ https://www.theragnostics.no/en/publications/abravan-2017-a/ Wed, 01 Nov 2017 00:00:00 +0000 https://www.theragnostics.no/en/publications/abravan-2017-a/ <hr> <p>¹⁸F-fluoro-2-deoxyglucose positron emission tomography (¹⁸F-FDG-PET) may be used for assessing radiation induced alterations in the lung. However, there is a need to further develop methodologies to improve quantification. Using computed tomography (CT), a local structure method has been shown to be superior to conventional CT-based analysis. Here, we investigate whether the local structure method based on ¹⁸F-FDG-PET improves radiotherapy (RT) dose-response quantification for lung cancer patients. Sixteen patients with lung cancer undergoing fractionated RT were examined by ¹⁸F-FDG-PET/CT at three sessions (pre, mid, post) and the lung was delineated in the planning CT images. The RT dose matrix was co-registered with the PET images. For each PET image series, mean (μ) and standard deviation (σ) maps were calculated based on cubes in the lung (3 × 3 × 3 voxels), where the spread in pre-therapy μ and σ was characterized by a covariance ellipse in a sub-volume of 3 × 3 × 3 cubes. Mahalanobis distance was used to measure the distance of individual cube values to the origin of the ellipse and to further form local structure &lsquo;S&rsquo; maps. The structural difference maps (ΔS) and mean difference maps (Δμ) were calculated by subtracting pre-therapy maps from maps at mid- and post-therapy. Corresponding maps based on CT images were also generated. ΔS identified new areas of interest in the lung compared to conventional Δμ maps. ΔS for PET and CT gave a significantly elevated lung signal compared to a control group during and post-RT (p &lt; .05). Dose-response analyses by linear regression showed that ΔS between pre- and post-therapy for ¹⁸F-FDG-PET was the only parameter significantly associated with local lung dose (p = .04). The new method using local structures on ¹⁸F-FDG-PET provides a clearer uptake dose-response compared to conventional analysis and CT-based approaches and may be valuable in future studies addressing lung toxicity.</p>