Whole-Body ⁶⁸Ga-FAPI PET/CT in Cavernous Sinus Syndrome: A Prospective Comparison With ¹⁸F-FDG PET/CT
The goal of this observational study is to evaluate the diagnostic utility of whole-body ⁶⁸Ga-FAPI PET/CT in adults with cavernous sinus syndrome (CSS) in whom magnetic resonance imaging (MRI) failed to establish the underlying cause. The study also compares the performance of ⁶⁸Ga-FAPI PET/CT with paired ¹⁸F-FDG PET/CT.
The main questions it aims to answer are:
Can whole-body ⁶⁸Ga-FAPI PET/CT detect and characterize cavernous sinus lesions and disease extent in patients with MRI-indeterminate CSS? Does ⁶⁸Ga-FAPI PET/CT provide superior lesion conspicuity and help identify safer biopsy sites compared with ¹⁸F-FDG PET/CT? Researchers will compare whole-body ⁶⁸Ga-FAPI PET/CT with paired ¹⁸F-FDG PET/CT to evaluate lesion detection, quantitative imaging parameters, disease extent, and their impact on identifying appropriate biopsy targets.
Study Overview
Status
Conditions
Intervention / Treatment
Detailed Description
Cavernous sinus syndrome (CSS) is a clinically heterogeneous condition resulting from involvement of the cavernous sinus and its neurovascular contents. Although contrast-enhanced magnetic resonance imaging (MRI) is the imaging modality of choice for evaluating cavernous sinus pathology, it frequently cannot establish the underlying etiology because infectious, inflammatory, and neoplastic disorders often demonstrate overlapping imaging appearances. Establishing a tissue diagnosis is further complicated by the technical difficulty and potential risks associated with direct cavernous sinus biopsy. Consequently, identification of contiguous disease extension or extracranial lesions that can be safely sampled is an important component of the diagnostic work-up.
This prospective observational study evaluates the diagnostic utility of whole-body 68Ga-FAPI-46 PET/CT in adult patients with cavernous sinus syndrome in whom MRI failed to establish an etiological diagnosis. All enrolled participants undergo paired whole-body 18F-FDG PET/CT and 68Ga-FAPI-46 PET/CT prior to initiation of definitive therapy. The interval between the two PET/CT examinations does not exceed six days. MRI is performed as part of the standard diagnostic evaluation before PET/CT imaging.
The study compares the two PET tracers with respect to:
Detection of cavernous sinus lesions. Delineation of locoregional disease extension, including meningeal, pituitary/sellar, skull base, orbital, sinonasal, and adjacent soft-tissue involvement.
Detection of extracranial disease. Quantitative imaging parameters, including lesion SUVmax, background brain SUVmean, and target-to-background ratio (TBR).
Ability to identify safer and more accessible biopsy targets that may facilitate histopathological diagnosis.
PET/CT images are independently interpreted by experienced nuclear medicine physicians who are aware of the clinical presentation and MRI findings but blinded to the final diagnosis. Lesion uptake, disease distribution, and extracranial findings are assessed qualitatively, while SUVmax, background brain SUVmean, and TBR are measured for quantitative comparison. Final diagnosis is established using histopathological examination whenever feasible or established clinicoradiological diagnostic criteria when tissue confirmation is unavailable. Biopsy sites are selected following multidisciplinary discussion based on accessibility, anticipated diagnostic yield, and procedural safety. Participants are subsequently followed after initiation of etiology-directed therapy to document clinical and imaging response.
Statistical analyses include paired comparison of quantitative PET parameters using the Wilcoxon signed-rank test, comparison of lesion detection rates using the McNemar test, and comparison of quantitative imaging parameters between fungal infection and IgG4-related disease using the Mann-Whitney U test. Statistical significance is defined as a two-sided P value <0.05.
Study Type
Enrollment (Actual)
Contacts and Locations
Study Locations
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Chandigarh
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Chandigarh, Chandigarh, India, 160012
- Post Graduate Institute of Medical Education and Research, Chandigarh, Chandigarh 160012
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Participation Criteria
Eligibility Criteria
Ages Eligible for Study
Accepts Healthy Volunteers
Genders Eligible for Study
Sampling Method
Study Population
The study population consisted of consecutive adult patients presenting with clinically diagnosed cavernous sinus syndrome (CSS) at a tertiary care academic referral center between January 2023 and May 2024. Eligible participants had contrast-enhanced MRI demonstrating cavernous sinus pathology but without a definitive etiological diagnosis. All participants underwent paired whole-body ¹⁸F-FDG PET/CT and ⁶⁸Ga-FAPI-46 PET/CT prior to initiation of definitive therapy as part of the diagnostic evaluation.
Description
Inclusion Criteria:
- Adults aged 18 years or older.
- Clinical diagnosis of cavernous sinus syndrome (CSS), defined as involvement of two or more cranial nerves (III, IV, V1, V2, or VI) on the same side, or involvement of a single cranial nerve in the presence of a radiologically confirmed cavernous sinus lesion.
- Contrast-enhanced MRI demonstrating cavernous sinus pathology but failing to establish a definitive etiological diagnosis.
- Ability and willingness to provide written informed consent.
- Not receiving definitive etiology-directed therapy before completion of both PET/CT examinations.
Exclusion Criteria:
- Pregnant or lactating women.
- Unwilling or unable to provide written informed consent.
- Uncontrolled hyperglycemia precluding performance of ¹⁸F-FDG PET/CT.
Study Plan
How is the study designed?
Design Details
- Observational Models: CASE_ONLY
- Time Perspectives: PROSPECTIVE
Cohorts and Interventions
Group / Cohort |
Intervention / Treatment |
|---|---|
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adult patients with cavernous sinus syndrome in whom MRI failed to establish etiological diagnosis
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Pilot study evaluating the role of FAPI PET/CT in Cavernous sinus syndrome Whole-body ¹⁸F-fluorodeoxyglucose (¹⁸F-FDG) PET/CT performed after at least 6 hours of fasting and confirmation of blood glucose <200 mg/dL. ¹⁸F-FDG was administered intravenously at a dose of 3.7 MBq/kg body weight. Imaging was acquired approximately 60 minutes after tracer injection from the vertex to mid-thigh with an additional dedicated brain acquisition. This served as the comparator imaging modality for paired evaluation with ⁶⁸Ga-FAPI-46 PET/CT. |
What is the study measuring?
Primary Outcome Measures
Outcome Measure |
Measure Description |
Time Frame |
|---|---|---|
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Diagnostic performance of ⁶⁸Ga-FAPI PET/CT for detection of cavernous sinus lesions compared with paired ¹⁸F-FDG PET/CT
Time Frame: Baseline (prior to initiation of definitive therapy; both PET/CT examinations performed within 6 days of each other).
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Comparison of cavernous sinus lesion detection rates between whole-body ⁶⁸Ga-FAPI PET/CT and paired ¹⁸F-FDG PET/CT on a lesion basis using the McNemar test. A lesion is considered positive when tracer uptake exceeds adjacent background |
Baseline (prior to initiation of definitive therapy; both PET/CT examinations performed within 6 days of each other).
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Secondary Outcome Measures
Outcome Measure |
Measure Description |
Time Frame |
|---|---|---|
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Comparison of lesion target-to-background ratio (TBR) between ⁶⁸Ga-FAPI PET/CT and ¹⁸F-FDG PET/CT
Time Frame: Baselines
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Comparison of lesion TBR calculated as lesion SUVmax divided by background brain SUVmean for paired lesions. |
Baselines
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Comparison of lesion SUVmax between ⁶⁸Ga-FAPI PET/CT and ¹⁸F-FDG PET/CT
Time Frame: Baseline
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Comparison of maximum standardized uptake value (SUVmax) of paired cavernous sinus lesions between the two PET tracers. |
Baseline
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Proportion of participants in whom ⁶⁸Ga-FAPI PET/CT identified an alternative biopsy site
Time Frame: Baseline
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Percentage of participants in whom whole-body ⁶⁸Ga-FAPI PET/CT identified a safer and more accessible contiguous or extracranial lesion suitable for tissue diagnosis instead of direct cavernous sinus biopsy. |
Baseline
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Detection of clinically relevant extracranial disease by whole-body ⁶⁸Ga-FAPI PET/CT
Time Frame: Baseline
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Number of participants with disease-related extracranial lesions identified on whole-body ⁶⁸Ga-FAPI PET/CT |
Baseline
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Collaborators and Investigators
Study record dates
Study Major Dates
Study Start (Actual)
Primary Completion (Actual)
Study Completion (Estimated)
Study Registration Dates
First Submitted
First Submitted That Met QC Criteria
First Posted (Actual)
Study Record Updates
Last Update Posted (Actual)
Last Update Submitted That Met QC Criteria
Last Verified
More Information
Terms related to this study
Keywords
Additional Relevant MeSH Terms
Other Study ID Numbers
- ChandigarhPGIMER1
Drug and device information, study documents
Studies a U.S. FDA-regulated drug product
Studies a U.S. FDA-regulated device product
product manufactured in and exported from the U.S.
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