An interventional study of Prone Breast PET/CT Acquisition in Breast Cancer and Breast - Female, sponsored by Universität Münster. Not yet recruiting at 1 site in Germany. Open to female participants aged 18 Years and older. Per ClinicalTrials.gov, last updated 2026-10-20.
Sponsored by Universität Münster · Not applicable, Interventional, and Diagnostic
The goal of this clinical trial is to improve the combined use of PET/CT and MRI for imaging of the breast. PET/CT and MRI are usually performed in different body positions, which can change the shape and position of the breast and make it difficult to accurately align findings between the two examinations.
The main questions this study aims to answer are:
Can dedicated breast positioning during PET/CT reduce differences in breast shape and position compared with MRI?
Can image registration methods further improve the alignment of PET/CT and MRI images of the breast?
How accurately can findings seen on PET/CT be transferred to the corresponding location on MRI?
Participants in this study are breast cancer patients who are already scheduled to undergo PET/CT and PET/MRI as part of their clinical care. As part of the study, they will undergo an additional low-dose CT scan and an additional PET acquisition in a dedicated prone breast position. The additional PET images will be acquired using the tracer that has already been administered for the clinically indicated PET examination; no additional tracer injection is required.
The imaging data will then be used to develop and evaluate different methods for aligning PET/CT and MRI images of the breast.
The study does not investigate a new drug or treatment.
PET/CT and MRI provide complementary functional and anatomical information for breast imaging. However, direct spatial integration of separately acquired PET/CT and MRI datasets is limited by differences in patient positioning and the resulting deformation of the breast. Routine PET/CT is generally performed in the supine position, whereas dedicated breast MRI is acquired in the prone position with the breasts positioned within a breast coil. These differences can lead to substantial spatial discrepancies between corresponding findings.
REPOSE-Breast investigates a combined acquisition- and registration-based approach to reduce these discrepancies. The study includes patients who are already scheduled to undergo both PET/CT and PET/MRI as part of their clinical diagnostic work-up.
As part of the study, participants undergo an additional low-dose CT acquisition and an additional PET acquisition in a dedicated prone breast position. The additional PET acquisition uses the radiotracer that has already been administered for the clinically indicated PET examination; no additional tracer injection is required. The study-specific prone acquisition is intended to reduce positioning-related differences between PET/CT and MRI before subsequent image registration is performed.
The acquired PET/CT and MRI datasets will then be spatially aligned using several registration approaches of increasing methodological complexity. These include rigid registration, simple deformable registration, diffeomorphic deformable registration, and a biomechanical registration approach incorporating tissue deformation.
Anatomical information derived from CT and MRI is used to support the registration process and its validation. The resulting transformations will be applied to the corresponding imaging data to assess how accurately anatomical and functional findings can be transferred between PET/CT and MRI.
The overall aim is to determine whether the combination of dedicated prone breast positioning and non-rigid image registration can improve the spatial integration of separately acquired PET/CT and MRI datasets. This approach is intended to facilitate more reliable assignment of PET findings to the corresponding anatomical structures on MRI without requiring simultaneous PET/MRI acquisition.
12,815 studies on the registry are indexed under Breast Neoplasms; 2,920 are open to participants now.
This study's planned enrollment of 20 is below the median of 72 across 9,494 interventional studies indexed under Breast Neoplasms.
Browse Breast Neoplasms studies →Universität Münster is the lead sponsor of 29 studies on the registry; 18 are open to participants now.
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Exclusion Criteria:
Participants undergo an additional PET acquisition and a low-dose CT scan in a dedicated prone breast position. The PET acquisition uses the radiotracer already administered for the clinically indicated PET examination; no additional tracer injection is required. The study-specific acquisition is performed to reduce positioning-related differences between PET/CT and breast MRI and to provide image data for subsequent multimodal image registration.
Diagnostic Test: Prone Breast PET/CT Acquisition
Participants undergo an additional PET acquisition and a low-dose CT acquisition in a dedicated prone breast position using a breast-specific positioning setup. The study-specific imaging procedure takes approximately 6-10 minutes. The PET acquisition is performed after the clinically indicated radiotracer administration and does not require an additional tracer injection. The study-specific acquisition is designed to reduce differences in breast shape and position between PET/CT and prone breast MRI and to provide image data for subsequent multimodal image registration.
Target Registration Error After Multimodal Breast Image Registration
Target Registration Error (TRE) will be used to quantify the spatial accuracy of registration between corresponding breast imaging datasets. TRE will be calculated as the distance in mm between predefined corresponding anatomical or imaging reference points after registration. Lower TRE values indicate greater registration accuracy. Registration performance will be assessed for datasets acquired in different body positions and for datasets acquired in comparable prone breast positions.
Time frame: Up to 4 months after completion of imaging acquisition for each participant
Mean Three-Dimensional Structural Similarity Index (3D-SSIM) Between Registered PET Datasets
Structural similarity between the registered PET datasets acquired as part of PET/CT and PET/MRI will be assessed using the three-dimensional Structural Similarity Index (3D-SSIM), implemented in Python using the scikit-image library. The index provides a dimensionless measure of similarity in spatial image patterns, with higher values indicating greater structural similarity and a value of 1 representing perfect similarity. The 3D-SSIM will be calculated within the registered breast image volume for each registration approach and acquisition setting to assess registration performance and the effect of comparable breast positioning on registration quality.
Time frame: Up to 4 months after completion of imaging acquisition for each participant
Absolute Difference in SUVmax After Image Deformation
The maximum standardized uptake value (SUVmax) will be measured in corresponding regions of the original PET dataset and the PET dataset after application of the calculated deformation field. The absolute difference in SUVmax between the original and deformed datasets will be calculated to quantify changes in quantitative PET information introduced by image deformation. The mean absolute difference in SUVmax will be compared across registration methods and patient positioning conditions to assess the robustness of the registration approaches and whether reduced positioning differences improve quantitative stability.
Time frame: Up to 4 months after completion of imaging acquisition for each participant
Absolute Difference in SUVmean After Image Deformation
The mean standardized uptake value (SUVmean) will be measured in corresponding regions of the original PET dataset and the PET dataset after application of the calculated deformation field. The absolute difference in SUVmean between the original and deformed datasets will be calculated to quantify changes in quantitative PET information introduced by image deformation. The mean absolute difference in SUVmean will be compared across registration methods and patient positioning conditions to assess the robustness of the registration approaches and whether reduced positioning differences improve quantitative stability.
Time frame: Up to 4 months after completion of imaging acquisition for each participant
Absolute Difference in SUVpeak After Image Deformation
The peak standardized uptake value (SUVpeak) will be measured in corresponding regions of the original PET dataset and the PET dataset after application of the calculated deformation field. The absolute difference in SUVpeak between the original and deformed datasets will be calculated to quantify changes in quantitative PET information introduced by image deformation. The mean absolute difference in SUVpeak will be compared across registration methods and patient positioning conditions to assess the robustness of the registration approaches and whether reduced positioning differences improve quantitative stability.
Time frame: Up to 4 months after completion of imaging acquisition for each participant
Absolute Difference in SUVmax-Based Tumor-to-Background Ratio After Image Deformation
The tumor-to-background ratio based on maximum standardized uptake value (TBRmax) will be calculated in corresponding regions of the original PET dataset and the PET dataset after application of the calculated deformation field. The absolute difference in TBRmax between the original and deformed datasets will be calculated to quantify changes in quantitative PET contrast introduced by image deformation. The mean absolute difference in TBRmax will be compared across registration methods and patient positioning conditions to assess the robustness of the registration approaches and whether reduced positioning differences improve quantitative stability.
Time frame: Up to 4 months after completion of imaging acquisition for each participant
Plan to share: Yes — Pseudonymized imaging data and associated study data may be shared with designated external research collaborators involved in the development and evaluation of image registration methods within the scope of this study. Subject to the participants' informed consent, data may also be shared with future research collaborators for related methodological research purposes. Any data sharing will be limited to the purposes permitted by the study documents and applicable data protection requirements. No unrestricted public release of individual participant data is planned.
Supporting information: Study protocol
Time frame: Pseudonymized data may be made available to designated research collaborators after completion of the relevant study-specific data processing and quality control. Data will only be available within the retention period defined for the study and will not be shared beyond 10 years after study completion, after which all participant-related data will be deleted in accordance with the study documents.
Access criteria: Access will be limited to designated research collaborators who are involved in approved methodological research related to the aims of this study. Only pseudonymized imaging data and associated study data necessary for the respective research purpose will be shared. Access will require an appropriate research collaboration and compliance with applicable data protection requirements and the participants' informed consent. Data will be transferred through secure institutional data-sharing procedures. Public or unrestricted access is not planned.
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Start is estimated for Oct 2026; primary completion for Sep 2027, 11 months later.
Of 2,272 non-industry interventional studies with no phase under Breast Neoplasms, half reached primary completion within 34 months of starting (the median), counting those still running; a quarter within 16 and three quarters within 69. This study's planned 11 months is below that.
Counting every sponsor, half of 2,345 studies reached it within 34 months; a quarter within 16 and three quarters within 69.
How these figures are worked out, and which studies are left out of them.
From the registry record's own update history. This site started tracking changes on Sep 25, 2026; for anything earlier, see the record history on ClinicalTrials.gov ↗
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