Effects of rigid and non-rigid image registration on test-retest variability of quantitative [18F]FDG PET/CT studies

Floris Hp Van Velden,Paul Van Beers,Linda M Velasquez,Dirk Loeckx,Johan Nuyts,Adriaan A Lammertsma,Wendy Hayes,Ronald Boellaard

doi:10.1186/2191-219x-2-10

Floris Hp Van Velden, Paul Van Beers + Show 6 more

Open Access

https://doi.org/10.1186/2191-219x-2-10

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Abstract

Background[18F]fluoro-2-deoxy-D-glucose ([18F]FDG) positron emission tomography (PET) is a valuable tool for monitoring response to therapy in oncology. In longitudinal studies, however, patients are not scanned in exactly the same position. Rigid and non-rigid image registration can be applied in order to reuse baseline volumes of interest (VOI) on consecutive studies of the same patient. The purpose of this study was to investigate the impact of various image registration strategies on standardized uptake value (SUV) and metabolic volume test-retest variability (TRT).MethodsTest-retest whole-body [18F]FDG PET/CT scans were collected retrospectively for 11 subjects with advanced gastrointestinal malignancies (colorectal carcinoma). Rigid and non-rigid image registration techniques with various degrees of locality were applied to PET, CT, and non-attenuation corrected PET (NAC) data. VOI were drawn independently on both test and retest scans. VOI drawn on test scans were projected onto retest scans and the overlap between projected VOI and manually drawn retest VOI was quantified using the Dice similarity coefficient (DSC). In addition, absolute (unsigned) differences in TRT of SUVmax, SUVmean, metabolic volume and total lesion glycolysis (TLG) were calculated in on one hand the test VOI and on the other hand the retest VOI and projected VOI. Reference values were obtained by delineating VOIs on both scans separately.ResultsNon-rigid PET registration showed the best performance (median DSC: 0.82, other methods: 0.71-0.81). Compared with the reference, none of the registration types showed significant absolute differences in TRT of SUVmax, SUVmean and TLG (p > 0.05). Only for absolute TRT of metabolic volume, significant lower values (p < 0.05) were observed for all registration strategies when compared to delineating VOIs separately, except for non-rigid PET registrations (p = 0.1). Non-rigid PET registration provided good volume TRT (7.7%) that was smaller than the reference (16%).ConclusionIn particular, non-rigid PET image registration showed good performance similar to delineating VOI on both scans separately, and with smaller TRT in metabolic volume estimates.

Highlights

Positron emission tomography (PET) has been accepted as a valuable tool in oncology, for detecting or staging disease and estimating target volumes for radiotherapy purposes, and for monitoring response to therapy and predicting prognosis [1,2].To date, [18F]fluoro-2-deoxy-D-glucose ([18F]FDG) is the most widely used tracer for oncological applications
CT input data provided the highest Dice similarity coefficient (DSC), while for non-rigid image registration, both PET and CTPET input data resulted in the highest DSC
non-attenuation corrected PET (NAC) data did not provide an improvement in median DSC for rigid registration strategies and showed more artefacts in the registered images following non-rigid image registration, resulting in an increased number of outliers

Summary

Introduction

Positron emission tomography (PET) has been accepted as a valuable tool in oncology, for detecting or staging disease and estimating target volumes for radiotherapy purposes, and for monitoring response to therapy and predicting prognosis [1,2].To date, [18F]fluoro-2-deoxy-D-glucose ([18F]FDG) is the most widely used tracer for oncological applications. Positron emission tomography (PET) has been accepted as a valuable tool in oncology, for detecting or staging disease and estimating target volumes for radiotherapy purposes, and for monitoring response to therapy and predicting prognosis [1,2]. For monitoring response to therapy, it is likely that quantitative assessment of [18F]FDG uptake will become the standard. Baseline volumes of interest (VOI) cannot be reused directly. Reusing baseline VOI are of interest for measuring changes in tracer uptake (response) compared with baseline and for van Velden et al EJNMMI Research 2012, 2:10 http://www.ejnmmires.com/content/2/1/10 studying changes in uptake heterogeneity [3]. Rigid or non-rigid image registration needs to be applied to enable reuse of baseline VOI on response scans. De Moor et al [4] showed that non-rigid image registration of [18F]FDG images could be used for easier and faster therapy assessments

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