The goal of this prospective observational study is to learn whether magnetic resonance imaging (MRI) findings can help predict treatment response to dienogest in women with endometriosis. Endometriosis is a common gynecologic condition that can cause chronic pelvic pain and negatively affect quality of life. Although dienogest is widely used as a standard medical treatment, individual responses to treatment vary.

The main questions this study aims to answer are:

• Whether baseline MRI characteristics of endometriotic lesions are associated with improvement in pelvic pain after dienogest treatment.
• Whether MRI findings can help identify patients who are more likely to benefit from dienogest therapy.

Participants diagnosed with endometriosis who are prescribed dienogest as part of their routine clinical care will be enrolled. This study does not assign any investigational intervention. Participants will undergo standard clinical follow-up, including pelvic pain assessment using visual analog scale (VAS) scores, quality of life questionnaires, and routine MRI examinations. Clinical and imaging data will be collected prospectively and analyzed to explore imaging predictors of treatment response.

Inclusion Criteria:

• Female participants who have received a full explanation of the study and have provided written informed consent
• Women aged 19 to 45 years who have been diagnosed with endometriosis by a board-certified obstetrician-gynecologist
• Patients who have not received any hormonal treatment within the previous 3 months
• Patients who have never been treated with dienogest

Exclusion Criteria:

• Patients with a history of treatment with dienogest
• Patients with contraindications to dienogest
• Patients who are unable to undergo magnetic resonance imaging (MRI) (e.g., presence of metallic implants)
• Patients who are currently pregnant or planning pregnancy within the next 6 months
• Patients with poor general medical condition, as judged by the investigator

This study will include women aged 19 to 45 years who have been clinically diagnosed with endometriosis by an obstetrician-gynecologist. Eligible participants are those who have not received hormonal treatment within the previous 3 months and have never been treated with dienogest. All participants must provide written informed consent prior to enrollment. Patients with contraindications to dienogest, inability to undergo MRI, current or planned pregnancy within 6 months, or poor general medical condition will be excluded.