This is a prospective, multicenter, observational study designed to evaluate the clinical outcomes of the Ranger™ SL paclitaxel-coated balloon, a type of drug-coated balloon (DCB), in the treatment of below-the-knee (BTK) lesions in patients with chronic limb-threatening ischemia (CLTI) in China. All enrolled patients will be followed for six months. Patients diagnosed with CLTI who undergo treatment with the Ranger DCB will be included in the study. The primary outcome is the incidence of major adverse events (MAEs).

Inclusion Criteria:

1. Age ≥ 18 years, gender is not limited

2. The patient agreed to participate in the CEIBA study and signed the written informed consent

3. Diagnosis of chronic limb-threatening ischemia (Rutherford category 4-6)

4. Gangrene involving any part of the lower extremities or feet, with exclusion of patients who have:

   4.1 Pure venous ulcers 4.2 Pure traumatic wounds 4.3 Acute limb ischemia (symptoms present for 2 weeks or less) 4.4 Embolic disease 4.5 Non-atherosclerotic chronic lower extremity vascular diseases (e.g., vasculitis, Buerger's disease, radiation arteritis)

5. Outflow Tract Requirement: At least one direct or indirect, unobstructed outflow vessel in the submalleolar segment of the target limb planned for revascularization.

6. Lesion Type:

6.1 Unobstructed blood flow in the suprapopliteal access pathway (including inflow vessels that have been recanalized via staged or concurrent endovascular intervention or hybrid surgery).

6.2 Sub-knee stenotic lesions ≥ 5 cm in length with ≥ 70% diameter reduction. 6.3 Sub-knee occlusive lesions ≥ 1 cm in length. 6.4 Two separate lesions with a minimum 3 cm interval between them may be considered as a single lesion for study inclusion purposes.

Exclusion Criteria:

1. Presence of life-threatening diseases or comorbidities with an expected life expectancy of less than 1 year.
2. Concurrent participation in another interventional clinical trial requiring informed consent.
3. Diagnosis of Alzheimer's disease.
4. Hematologic disorders or known bleeding tendency.
5. Contraindications to antiplatelet or anticoagulant therapy.
6. Known allergy to contrast agents that cannot be managed with standard premedication (e.g., steroids).
7. Deficiency or dysfunction of protein C, protein S, or antithrombin III (ATIII).
8. New York Heart Association (NYHA) Class III or IV heart failure.
9. Pregnancy or lactation.
10. Prior suprapatellar or infrapatellar amputation of the target limb.
11. Presence of aneurysm, perforation, dissection, or other target vessel injury requiring intervention.
12. Presence of other comorbid conditions (unrelated to the index disease) that affect walking function.
13. History of cardiovascular events within the past 3 months, including nonfatal myocardial infarction, unstable angina, stable angina, nonfatal ischemic stroke, or hemorrhagic stroke.
14. Clinically significant liver or renal dysfunction, as determined by the investigator.
15. Any other condition that, in the opinion of the investigator, would interfere with study treatment or functional assessments.

Patients with below-the-knee (BTK) arterial lesions diagnosed with chronic limb-threatening ischemia (CLTI).