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Background and Purpose: To promote the development of auto-segmentation methods for head and neck (HaN) radiation treatment (RT) planning that exploit the information of computed tomography (CT) and magnetic resonance (MR) imaging modalities, we organized HaN-Seg: The Head and Neck Organ-at-Risk CT and MR Segmentation Challenge., Materials and Methods: The challenge task was to automatically segment 30 organs-at-risk (OARs) of the HaN region in 14 withheld test cases given the availability of 42 publicly available training cases. Each case consisted of one contrast-enhanced CT and one T1-weighted MR image of the HaN region of the same patient, with up to 30 corresponding reference OAR delineation masks. The performance was evaluated in terms of the Dice similarity coefficient (DSC) and 95-percentile Hausdorff distance (HD 95 ), and statistical ranking was applied for each metric by pairwise comparison of the submitted methods using the Wilcoxon signed-rank test., Results: While 23 teams registered for the challenge, only seven submitted their methods for the final phase. The top-performing team achieved a DSC of 76.9 % and a HD 95 of 3.5 mm. All participating teams utilized architectures based on U-Net, with the winning team leveraging rigid MR to CT registration combined with network entry-level concatenation of both modalities., Conclusion: This challenge simulated a real-world clinical scenario by providing non-registered MR and CT images with varying fields-of-view and voxel sizes. Remarkably, the top-performing teams achieved segmentation performance surpassing the inter-observer agreement on the same dataset. These results set a benchmark for future research on this publicly available dataset and on paired multi-modal image segmentation in general., Competing Interests: Declaration of competing interest The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper., (Copyright © 2024 The Authors. Published by Elsevier B.V. All rights reserved.)

Purpose: Various segmentation methods for 18F-fluoro-2-deoxy-d-glucose (FDG) positron emission tomography/computed tomography (PET/CT) images were correlated with pathological volume in breast cancer patients as a model of small mobile tumours., Methods: Thirty women with T2-T3/M0 breast invasive ductal carcinoma (IDC) were included prospectively. A FDG-PET/CT was acquired 4 ± 3d before surgery in prone and supine positions, with/without respiratory gating. The segmentation methods were as follows: manual (Vm), relative (Vt%) and adaptive (Va) standard uptake value (SUV) threshold and semi-automatic on CT (Vct). Pathological volumes (Vpath) were measured for 26 lesions., Results: The mean (±SD) Vpath was 4.1 ± 2.9 mL, and the lesion displacements were 3.9 ± 2.8 mm (median value: 3 mm). The delineated VOIs did not vary with the acquisition position nor with respiration, regardless of the segmentation method. The Vm, Va, Vct and Vt% methods, except Vt30%, were correlated with Vpath (0.5

Objectives: To test the influence of media injection in PET/CT on the functional or gross tumour volume measurement., Patients and Methods: Thirty-three patients (56 ± 19 years) with non-Hodgkin's lymphoma (n=22) or Hodgkin's disease (n=11) were prospectively studied at staging. PET/CTs were performed 60 min after injection of FDG. Iopamiron 300 (Iopamidol, 1.5cc/kg) was injected immediately after, followed 50s later by a second craniocaudal CT (CT+). PET images were successively reconstructed using the unenhanced CT (PET-) and the CT+ (PET+) for attenuation correction using iterative reconstruction (4 iterations, 8 subsets, 5mm post-filtering). The SUVmax, SUVmean, SUVpeak and functional tumoural volume were measured in tumoural lymphadenopathies or malignant tissues (n=56 VOIs) using 5 3D-thresholding methods on PET- and PET+ images: absolute SUV value of 2.5; 40% of SUVmax, and 3 adaptative thresholding methods (Vauclin, Black and Schaefer methods)., Results: The SUVmean and the volume measurement were significantly different (p<0.001) for the five segmentation methods for PET- (p<0.001) and PET+ (p<0.001). The SUVmax, SUVmean and SUVpeak increased significantly in PET+ compared to PET- (2-5%). The SUVpeak was not significantly different for the five segmentation methods. The functional volume measurements were significantly different between PET- and PET+ only for the 2.5 segmentation method (+3%; p=0.001), but not for the 40%, Vauclin, Black and Schaefer methods., Conclusion: The functional volume could be measured in PET/CT when CT was performed with enhanced media. Caution should be taken when using the volume delineation method. Volume delineation methods using absolute threshold may artefactually increase the functional volume when enhanced CT is used for attenuation correction. The delineation volume using the relative or adaptative method should be preferred when contrast media are used for PET/CT., (Copyright © 2013 Elsevier Ireland Ltd. All rights reserved.)

Objectives: The objectives were (i) to confirm that diagnostic FDG-PET images could be obtained during thoracic radiotherapy, (ii) to verify that significant changes in FDG uptake or volume could be measured early enough to adapt the radiotherapy plan and (iii) to determine an optimal time window during the radiotherapy course to acquire a single FDG-PET examination that would be representative of tumour response., Methods: Ten non-small cell lung carcinoma (NSCLC) patients with significant PET/CT-FDG tumour radioactivity uptake (versus the background level), candidates for curative radiotherapy (RT, n=4; 60-70 Gy, 2 Gray per fraction, 5 fractions per week) or RT plus chemotherapy (CT-RT, n=6), were prospectively evaluated. Using a Siemens Biograph, 5 or 6 PET/CT scans (PET(n), n=0-5) were performed for each patient. Each acquisition included a 15-min thoracic PET with respiratory gating (RG) 60±5 min post-injection of the FDG (3.5 MBq/kg), followed by a standard, 5-min non-gated (STD) thoracic PET. PET(0) was performed before the first RT fraction. During RT, PET(1-5) were performed every 7 fractions, i.e., at 14 Gy total dose increment. FDG uptake was measured as the variation of SUV(max,PETn) versus SUV(max,PET0). Each lesions' volume was measured by (i) visual delineation by an experienced nuclear physician, (ii) 40% SUV(max) fixed threshold and (iii) a semi-automatic adaptive threshold method., Results: A total of 53 FDG-PET scans were acquired. Seventeen lesions (6 tumours and 11 nodes) were visible on PET(0) in the 10 patients. The lesions were located either in or near the mediastinum or in the apex, without significant respiratory displacements at visual inspection of the gated images. Healthy lung did not cause motion artefacts in the PET images. As measured on 89 lesions, both the absolute and relative SUV(max) values decreased as the RT dose increased. A 50% SUV(max) decrease was obtained around a total dose of 45 Gy. Out of the 89 lesions, 75 remained visually identifiable during the entire course of treatment. The 40% fixed threshold and adaptive threshold methods failed to delineate otherwise visible lesions in 16/33 (48%) and 3/33 (9%) lesions, respectively. The failure rate increased with increasing RT doses. Restricting the analysis to the manually-defined volumes in 89 visible lesions, the relative volumes decreased with increased dose., Conclusions: FDG-PET images can be analysed during thoracic RT, given either alone or with chemotherapy, without disturbing radiation-induced artefacts. An average 50% decrease in SUV(max) was observed around 40-45 Gy (i.e., during week 5 of RT). The three delineation methods yielded consistent volume measurements before RT and during the first week of RT, while manual delineation appeared to be more reliable later on during RT., (Copyright © 2011 Elsevier Ireland Ltd. All rights reserved.)

Objectives: To investigate the changes in tumour proliferation (using FLT), metabolism (using FDG), and hypoxia (using F-miso) during curative (chemo-) radiotherapy (RT) in patients with non-small-cell lung cancer (NSCLC)., Patients and Methods: Thirty PET scans were performed in five patients (4 males, 1 female) that had histological proof of NSCLC and were candidates for curative-intent RT. Three PET-CT (Biograph S16, Siemens) scans were performed before (t(0)) and during (around dose 46 Gy, t(46)) RT with minimal intervals of 48 h between each PET-CT scan. The tracers used were (18)fluoro-2deoxyglucose (FDG) for metabolism, (18)fluorothymidine (FLT) for proliferation, and (18)F-misonidasole (F-miso) for hypoxia. The 3 image sets obtained at each time point were co-registered (rigid: n=9, elastic: n=1, Leonardo, TrueD, Siemens) using FDG PET-CT as reference. VOIs were delineated (40% SUV(max) values were used as a threshold) for tumours and lymph nodes on FDG PET-CT, and they were automatically pasted on FLT and F-miso PET-CT images. ANOVA and correlation analyses were used for comparison of SUV(max) values., Results: Four tumours and twelve nodes were identified on initial FDG PET-CT images. FLT SUV(max) values were significantly lower (p<0.0006) at t(46) in both tumours and nodes. The decrease in FDG SUV(max) values had a trend towards significance (p=0.048). F-Miso SUV(max) values were significantly higher in tumours than in nodes (p=0.02) and did not change during radiotherapy (p=0.39). A significant correlation was observed between FLT and FDG uptake (r=0.56, p<10(-4)) when all data were pooled together, and they remained similar when the before and during RT data were analysed separately. FDG and F-miso uptakes were significantly correlated (r=0.59, p=0.0004) when all data were analysed together. The best fit was obtained after adjusting for lesion type (tumour vs. node). This correlation was observed for the SUV(max) measured during RT (r=0.70, p=0.008) but not for the pre-RT data (r=0.19, p=0.35). The weak correlation between FLT and F-miso uptakes only became significant (r=0.66, p=0.002) when the analysis was restricted to the data acquired during RT., Conclusion: Three different PET acquisitions can be performed quasi-simultaneously (4-7 days) before and during radiotherapy in patients with NSCLC. Our results at 46 Gy suggest that a fast decrease in the proliferation of both tumours and nodes exists during radiotherapy with differences in metabolism (borderline significant decrease) and hypoxia (stable)., (Copyright © 2010 Elsevier Ireland Ltd. All rights reserved.)