PET/MRI for Evaluation of Endometriosis

March 10, 2026 updated by: Onofrio A. Catalano, MD, PhD, Massachusetts General Hospital

PET/MRI Evaluation of Endometriosis Using Intercellular Matrix Radiopharmaceuticals

This study aims to determine if PET/MRI can detect endometriosis and potentially improve upon currently available non-invasive diagnostic capabilities. Specifically, the authors will investigate the ability of PET/MRI to detect and quantify endometriosis, as well as differentiate among subcategories such as inflammatory peritoneal lesions, fibrotic deep infiltrating endometriosis lesions (DIE), and ovarian endometriomas. The authors will compare [68Ga]CBP8 or [18F]-FAPI-74 PET/MRI imaging versus the current gold standard diagnostic methods, including laparoscopic surgery, clinical follow-up, and follow-up imaging.

Study Overview

Status

Enrolling by invitation

Conditions

Intervention / Treatment

Detailed Description

Several imaging techniques, including ultrasound, computed tomography and magnetic resonance imaging (MRI), have been used for the detection of DIE, for mapping and staging endometriosis. Currently, the modalities most commonly used are transvaginal ultrasound (TVS) and magnetic resonance imaging MRI. TVS is generally considered a first-line technique.TVS, in highly experienced hands, meets the criteria for mapping DIE to the uterosacral ligaments, rectovaginal septum, vaginal wall, pouch of Douglas and rectosigmoid; however it is limited by its operator dependance and by the small field of view (FOV). MRI is commonly used for mapping lesions within the Douglas pouch and rectovaginal septum and rectosigmoid. MRI has shown acceptable diagnostic values, with pooled sensitivity and specificity for pelvic endometriosis of 94% and 77%, respectively. For rectosigmoid endometriosis, MRI's pooled sensitivity and specificity were 92% and 96%, respectively. However, MRI has limitations, specially in the evaluation of chronic fibrotic endometriosis and for assessing the peritoneum and extension beyond the pelvis as well as DIEs. There is a growing body of literature examining the role of PET/MRI in pelvic and abdominal malignancies and its potential superiority to MRI alone. However, there are no studies that used PET/MRI to investigate endometriosis.

This study aims to use [68Ga]CBP8- or [18F]FAPI PET/MRI to diagnose and quantify endometriosis. The novel radiopharmaceutical collagen-binding probe 8 labeled with Gallium-68 selectively binds to collagen type I, the predominant extracellular protein in fibrosis. [68Ga]CBP8 has already been investigated in patients affected by pulmonary fibrosis with success. Fibroblast activation protein (FAP) is a type II transmembrane serine protease that is overexpressed in CAFs and, to a lesser extent, in benign processes. It is associated with extracellular matrix remodeling, for example, chronic inflammation, degenerative bone and spine disease, arthritis, and cardiac remodelling after myocardial infarction. Quinolone-based FAP inhibitors (FAPIs) constitute a class of molecules with high affinity to FAP deployed to assess many types of solid tumors and some benign pathologies. 68Ga-FAPIs and, to a lesser extent, 18F-FAPI are being extensively studied in oncologic and non-oncologic positron emission tomography/computed tomography (PET/CT) and, to a lesser extent, PET/MRI, both in Europe and Asia.

In this single-arm, single-center, open label prospective study, the authors will recruit 60 patients with clinical diagnosis of endometriosis who candidate for laparoscopic surgery. Patients will be referred to FAPI- or CBP8-PET/MRI by their primary treating gynecologist physicians. Laparoscopy will serve as primary standard of reference; clinical and imaging follow up, as well as prior diagnostic imaging studies (CT, MRI, US), will serve as secondary standard of reference. In the case patients will not undergo laparoscopy, then clinical and imaging follow up, as well as prior diagnostic imaging studies (CT, MRI, US), will serve as primary standard of reference.

Board-certified radiologists will evaluate [18F]-FAPI-74 or [68Ga]CBP8-PET/MR images and standalone MR images in a blinded fashion on separate occasions. Assessment of of endometriosis will be performed according to consolidated published criteria for MRI. For endometriosis staging, the readers will follow rASRM criteria. Then, the authors will compare the sensitivity, specificity, and accuracy of regional/whole-body staging using FAPIor CBP-PET/MRI versus regional/wholebody MRI, with the standard reference set as pathology results, when available, or clinical and imaging follow-up otherwise. Hypothesis testing will be performed using McNemar's test for matched pairs testing.

Study Type

Observational

Enrollment (Estimated)

60

Contacts and Locations

This section provides the contact details for those conducting the study, and information on where this study is being conducted.

Study Locations

  • United States
    • Massachusetts
      • Charlestown, Massachusetts, United States, 02129
        • Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Harvard Medical School

Participation Criteria

Researchers look for people who fit a certain description, called eligibility criteria. Some examples of these criteria are a person's general health condition or prior treatments.

Eligibility Criteria

Ages Eligible for Study

  • Adult
  • Older Adult

Accepts Healthy Volunteers

N/A

Sampling Method

Non-Probability Sample

Study Population

In total, 60 subjects with clinically diagnosed endometriosis will be recruited. All subjects recruited for the study will be able to withdraw from the study at any time. The patients will be referred to the study by their treating physicians to investigate clinically diagnosed endometriosis. We will not recruit or enroll healthy volunteers in this study.

Description

Inclusion Criteria:

- Patients with clinical diagnosis of endometriosis, in any stage, candidate for diagnostic overtherapeutic laparoscopic surgery.

Exclusion Criteria:

  • Subjects less than 18 years of age or greater than 70 years of age.
  • Any contraindication to MRI, including electrical implants, such as cardiac pacemakers or perfusion pumps. MRI non-compatible ferromagnetic implants such as aneurysm clips, surgical clips, prostheses, artificial hearts, prosthetic heart valves that are not compatible with the gradient maps of our scanners, metal fragments, shrapnel, metallic tattoos anywhere on the body, tattoos near the eye, steel implants, and/or ferromagnetic objects such as jewelry, or metal clips in clothing that cannot be removed.
  • History of claustrophobic reactions.
  • Individuals who do not speak or understand English since providing a translated version of the entire consent form is not practicable
  • Any contraindication to PET including active breastfeeding (a negative STAT quantitative serum hCG pregnancy test is required on the day of the scan before the subject can participate)
  • History of research-related radiation exposure exceeding current Radiology Department guidelines (i.e., 50 mSv in the prior 12 months).
  • QTc>460msec obtained within 30 days from the PET/MR
  • eGFR <60mL/min/1.73m2 obtained within 30 days from the PET/MR
  • AST >40U/L and/or ALT >55 U/L obtained within 30 days from the PET/MR
  • A greater risk than normal for potential cardiac arrest such as history of non compensated congestive heart failure, poorly controlled arrythmias, symptomatic non compensated cardiopathies.
  • History of major head trauma (i.e., multiple concussions, traumatic brain injury).
  • History of bleeding disorders.
  • Inability to lie comfortably on a bed inside the PET/MRI bore as assessed by physical examination and medical history (e.g., back pain, severe arthritis).
  • Subjects under the direct supervision of the principal investigator.
  • Body weight of > 300 lbs. (weight limit of the MRI table) or BMI >33.0 per the standard operating procedure of PET/MRI safety at the Martinos Center.
  • Subjects from any other at-risk populations (e.g., children and minors cognitively impaired persons, prisoners).

Study Plan

This section provides details of the study plan, including how the study is designed and what the study is measuring.

How is the study designed?

Design Details

Cohorts and Interventions

Group / Cohort
Intervention / Treatment
Endometriosis
Patient with clinical diagnosis of endometriosis, in any stage, candidate for diagnostic or therapeutic laparoscopic surgery.
Drug: Radiotracer Injection

An intravenous catheter will be placed in an arm or hand vein for injection of [68Ga]CBP8;

6-10 mCi of [68Ga]CBP8 or 5-9 mCi of FAPI will be injected into the Biograph mMR system. The injected dose and the time of injection will be recorded; The catheter will be flushed with 0.9% saline solution; The subjects will then be positioned on the scanner table; support devices under the back or legs will be used to enable the patient to maintain his/her position throughout the scan comfortably.

Diagnostic test: Imaging

MRI and PET scanner to be used:

3.0 T Laboratory (Bay 7) Siemens Biograph mMR.

Magnetic resonance images of the pelvis and abdomen will be acquired using the Martinos Center's combined 3 Tesla PET/MRI scanner. The image quality on these 3 Tesla devices will be very high, equivalent to or better than any other standard clinical MRI system. PET images of the target body site will be acquired when necessary, the data acquisition will be started shortly before radiotracer injection; Coincidence event data will be acquired and stored in list mode or compressed (i.e., sinogram space) format. Subjects will be asked to lie still for the duration of the study. The entire imaging session will last up to 120 minutes

Other: Rectal Ultrasound Gel Injection
About 50ml of ultrasound gel will be placed into the vagina using the blunt end of the ultrasound gel tube or a Foley catheter or a syringe with a blunt Christmas tree end. No ultrasound probe will be inserted into the vagina, no external ultrasound probe will be used. No ultrasound study will be performed. The ultrasound gel will only be used to distend the vagina and improve the quality of MRI images; this is standard of practice in MRI for endometriosis and for several other gynecological diseases.

What is the study measuring?

Primary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Diagnostic Accuracy of PET/MR in Preoperative Endometriosis Detection
Time Frame: 1-2 Months
To determine the accuracy, sensitivity, and specificity of [18F]-FAPI-74 and/or [68Ga]CBP8 PET/MRI in detecting and classifying endometriosis, using the gold standard methods as the reference.
1-2 Months
Diagnostic Performance of PET/MRI vs. Conventional Imaging
Time Frame: 1-2 Months
To determine the accuracy, sensitivity, and specificity of [18F]-FAPI-74 or [68Ga]CBP8-PET/MR images versus stand-alone wholebody MRI and/or pelvic MRI and/or ultrasound and/or computed tomography in pre-operative patients with suspected endometriosis lesion.
1-2 Months

Secondary Outcome Measures

Outcome Measure
Measure Description
Time Frame
Impact of [18F]-FAPI-74 and [68Ga]CBP8 PET/MRI on Diagnosis and Management in Endometriosis
Time Frame: 1-6 months
To determine if imaging with [18F]-FAPI-74 and/or [68Ga]CBP8 PET/MRI results in changes to diagnosis, medical or surgical management in endometriosis patients
1-6 months
Correlation of Pre-Treatment PET Uptake and Post-Treatment Response in Endometriosis
Time Frame: 6-12 months
To determine if pre-treatment measures of [18F]-FAPI-74 and/or [68Ga]CBP8 standardized uptake values (SUVs) are correlated to post-treatment response in patients with endometriosis.
6-12 months

Collaborators and Investigators

This is where you will find people and organizations involved with this study.

Sponsor

Massachusetts General Hospital

Investigators

  • Principal Investigator: Onofrio Catalano, Athinoula A. Martinos Center for Biomedical Imaging, Massachusetts General Hospital, Harvard Medical School

Publications and helpful links

The person responsible for entering information about the study voluntarily provides these publications. These may be about anything related to the study.

General Publications

Study record dates

These dates track the progress of study record and summary results submissions to ClinicalTrials.gov. Study records and reported results are reviewed by the National Library of Medicine (NLM) to make sure they meet specific quality control standards before being posted on the public website.

Study Major Dates

Study Start (Actual)

January 6, 2025

Primary Completion (Estimated)

January 3, 2028

Study Completion (Estimated)

May 3, 2029

Study Registration Dates

First Submitted

April 17, 2024

First Submitted That Met QC Criteria

April 17, 2024

First Posted (Actual)

April 22, 2024

Study Record Updates

Last Update Posted (Actual)

March 12, 2026

Last Update Submitted That Met QC Criteria

March 10, 2026

Last Verified

March 1, 2026

More Information

Terms related to this study

Keywords

Additional Relevant MeSH Terms

Other Study ID Numbers

  • 2023P000955

Plan for Individual participant data (IPD)

Plan to Share Individual Participant Data (IPD)?

NO

Drug and device information, study documents

Studies a U.S. FDA-regulated drug product

Yes

Studies a U.S. FDA-regulated device product

No

product manufactured in and exported from the U.S.

No

This information was retrieved directly from the website clinicaltrials.gov without any changes. If you have any requests to change, remove or update your study details, please contact register@clinicaltrials.gov. As soon as a change is implemented on clinicaltrials.gov, this will be updated automatically on our website as well.

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