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| ID | Type | Description | Link |
|---|---|---|---|
| ARRS / ID: 33071 | Other Identifier | Slovenian Research Agency (ARRS) |
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Esophageal cancer radiotherapy requires accurate delineation of the gross tumor volume (GTV) to ensure adequate tumor coverage and to minimize radiation dose to surrounding organs at risk. Computed tomography (CT) is routinely used for target delineation, while positron emission tomography-computed tomography (PET/CT) may provide additional functional information. However, uncertainty in tumor boundaries and inter-observer variation remain clinically relevant issues.
Magnetic resonance imaging (MRI) provides improved soft tissue contrast and diffusion-weighted imaging (DWI) information, which may improve visualization of esophageal tumors. This study evaluates whether MRI-based imaging, alone or fused with CT or PET/CT, reduces inter-observer variation in GTV delineation compared with standard CT and PET/CT-based delineation.
A total of 21 patients with locally advanced esophageal cancer undergoing standard radiotherapy preparation will undergo MRI simulation in addition to routine CT and PET/CT simulation. Five experienced radiation oncologists will independently delineate the primary tumor GTV on CT, MRI, PET/CT, CT-MRI fusion, and PET/CT-MRI fusion datasets. Inter-observer variation will be assessed using conformity indices and spatial analysis tools.
Accurate target volume delineation is essential in radiotherapy for esophageal cancer, as contouring uncertainty may lead to geographic miss or increased dose to organs at risk. CT imaging is the standard modality used for radiotherapy planning; however, CT has limited soft tissue contrast, which can make delineation of the proximal and distal tumor extent challenging. PET/CT may assist in staging and may provide functional tumor information, but its value for precise target delineation remains uncertain.
MRI has recently gained importance in radiotherapy planning due to improved anatomical soft tissue visualization and functional imaging such as diffusion-weighted imaging (DWI). Technical advances have improved thoracic MRI feasibility, and MRI may allow improved identification of tumor borders in the esophagus. The clinical role of MRI in reducing inter-observer delineation variability in esophageal cancer radiotherapy planning is not yet well established.
This prospective study compares inter-observer variation in gross tumor volume (GTV) delineation across different imaging modalities used in radiotherapy preparation. Patients with locally advanced esophageal cancer will undergo standard PET/CT simulation according to institutional protocol and additional MRI simulation performed with identical immobilization. MRI will include T2-weighted sequences and DWI sequences without intravenous contrast.
Five experienced radiation oncologists will independently delineate the primary tumor GTV on anonymized datasets using the Eclipse treatment planning system. Contouring will be performed separately on the following image sets: CT, MRI, PET/CT, CT fused with MRI, and PET/CT fused with MRI. Pathologic lymph nodes will not be included in the GTV. A washout period of at least 14 days will be maintained between contouring sessions for the same patient on different imaging modalities.
Inter-observer variation will be assessed using the generalized conformity index (CIgen). Additionally, reference contours will be generated using the STAPLE algorithm. The Contour Analysis Tool (CAT) will be used to calculate planar and volumetric conformity indices (PCI and VCI) and to perform spatial analysis based on inter-delineation distance measurements. Contouring time, image quality, and perceived delineation difficulty will also be recorded by observers.
The primary objective is to determine whether MRI-based imaging reduces inter-observer variability in GTV delineation compared with standard CT and PET/CT imaging in esophageal cancer radiotherapy planning.
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| Label | Type | Description | Intervention Names |
|---|---|---|---|
| CT | Active Comparator | Standard planning CT for GTV delineation. |
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| MRI | Experimental | MRI simulation for GTV delineation. |
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| PET/CT | Active Comparator | PET/CT simulation for GTV delineation. |
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| CT + MRI Fusion | Experimental | CT images fused with MRI for GTV delineation. |
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| PET/CT + MRI Fusion | Experimental | PET/CT images fused with MRI for GTV delineation. |
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| Name | Type | Description | Arm Group Labels | Other Names |
|---|---|---|---|---|
| Computed Tomography (CT) | Diagnostic Test | CT imaging performed as part of standard radiotherapy simulation and planning for esophageal cancer. CT datasets are used for gross tumor volume (GTV) delineation. |
| Measure | Description | Time Frame |
|---|---|---|
| Volumetric Conformity Index (VCI) Compared With Reference Contour | Volumetric conformity index (VCI) will be calculated using the Contour Analysis Tool (CAT) by comparing each observer's gross tumor volume (GTV) contour to a reference contour generated using the STAPLE algorithm. VCI is defined as the ratio of intersection volume to union volume and ranges from 0 to 1. The outcome will be reported as mean VCI for each imaging dataset. | Up to 14 days after completion of contouring for each imaging dataset |
| Inter-observer Variability in GTV Delineation (Generalized Conformity Index, CIgen) | Inter-observer agreement in gross tumor volume (GTV) delineation will be assessed using the generalized conformity index (CIgen) calculated using the Contour Analysis Tool (CAT). CIgen is defined as the ratio of the sum of pairwise intersections to the sum of pairwise unions of all observers' contours and ranges from 0 to 1. The outcome will be reported as CIgen for each imaging dataset. | Up to 14 days after completion of contouring for each imaging dataset |
| Image Quality Rating (5-point Likert Scale) | Observers will rate the image quality of each imaging dataset (CT, MRI, PET/CT, CT-MRI fusion, PET/CT-MRI fusion) using a 5-point Likert scale (1 = very poor, 5 = excellent). The outcome will be reported as mean image quality score. | During contouring sessions (up to 14 days per imaging dataset) |
| Measure | Description | Time Frame |
|---|---|---|
| Planar Conformity Index (PCI) Compared With Reference Contour | Planar conformity index (PCI) will be calculated using the Contour Analysis Tool (CAT) by comparing each observer's GTV contour to a reference contour generated using the STAPLE algorithm. PCI is defined as the ratio of intersection area to union area and ranges from 0 to 1. The outcome will be reported as mean PCI for each imaging dataset. |
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Inclusion Criteria:
Exclusion Criteria:
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| Facility | Status | City | State | ZIP | Country | Contacts |
|---|---|---|---|---|---|---|
| Institute of Oncology Ljubljana | Ljubljana | 1000 | Slovenia |
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Participants undergo multiple imaging modalities (CT, PET/CT, MRI) for radiotherapy planning. Target volume delineations are compared across modalities within the same participants.
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Imaging datasets and observer identities are anonymized. Delineations are performed independently.
| Magnetic Resonance Imaging (MRI) | Diagnostic Test | MRI performed on a radiotherapy MRI simulator (T2-weighted sequences and diffusion-weighted imaging) using the same immobilization as CT/PET-CT simulation. MRI datasets are used for GTV delineation. |
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| Positron Emission Tomography/Computed Tomography (PET/CT) | Diagnostic Test | FDG PET/CT imaging performed as part of standard radiotherapy preparation. PET/CT datasets are used for GTV delineation, with contouring performed on CT and adjusted using PET information when appropriate. |
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| CT-MRI Image Fusion | Diagnostic Test | Image registration and fusion of MRI with CT datasets for radiotherapy planning. Fused CT-MRI images are used for GTV delineation to evaluate the effect of MRI information on contouring variability. |
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| PET/CT-MRI Image Fusion | Diagnostic Test | Image registration and fusion of MRI with PET/CT datasets for radiotherapy planning. Fused PET/CT-MRI images are used for GTV delineation to evaluate inter-observer variation compared with standard PET/CT-based contouring. |
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| Up to 14 days after completion of contouring for each imaging dataset |
| Spatial Inter-delineation Distance (IDD) Between Observer Contours and Reference Contour | Inter-delineation distance (IDD) will be calculated using the Contour Analysis Tool (CAT) as the shortest distance between each observer's GTV contour and the reference contour, expressed in millimeters (mm). The outcome will be reported as mean IDD (mm) for each imaging dataset. | Up to 14 days after completion of contouring for each imaging dataset |
| Contouring Time | Time required for gross tumor volume (GTV) delineation will be recorded for each observer and imaging dataset and reported in minutes. | During contouring sessions (up to 14 days per imaging dataset) |
| Perceived Difficulty of Delineation (5-point Likert Scale) | Observers will rate the perceived difficulty of GTV delineation for each imaging dataset using a 5-point Likert scale (1 = very easy, 5 = very difficult). The outcome will be reported as mean difficulty score. | During contouring sessions (up to 14 days per imaging dataset) |
| ID | Term |
|---|---|
| D004938 | Esophageal Neoplasms |
| ID | Term |
|---|---|
| D005770 | Gastrointestinal Neoplasms |
| D004067 | Digestive System Neoplasms |
| D009371 | Neoplasms by Site |
| D009369 | Neoplasms |
| D006258 | Head and Neck Neoplasms |
| D004066 | Digestive System Diseases |
| D004935 | Esophageal Diseases |
| D005767 | Gastrointestinal Diseases |
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| ID | Term |
|---|---|
| D014057 | Tomography, X-Ray Computed |
| D008279 | Magnetic Resonance Imaging |
| D049268 | Positron-Emission Tomography |
| D000072078 | Positron Emission Tomography Computed Tomography |
| ID | Term |
|---|---|
| D007090 | Image Interpretation, Computer-Assisted |
| D003952 | Diagnostic Imaging |
| D019937 | Diagnostic Techniques and Procedures |
| D003933 | Diagnosis |
| D011856 | Radiographic Image Enhancement |
| D007089 | Image Enhancement |
| D010781 | Photography |
| D011859 | Radiography |
| D014056 | Tomography, X-Ray |
| D014054 | Tomography |
| D014055 | Tomography, Emission-Computed |
| D011877 | Radionuclide Imaging |
| D003947 | Diagnostic Techniques, Radioisotope |
| D064847 | Multimodal Imaging |
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