This is a prospective, open-label, single-arm, investigator-initiated study designed to evaluate the safety and efficacy of NRT6003 Injection, a yttrium-90 carbon microsphere product, administered by selective internal radiation therapy in previously treated patients with hepatocellular carcinoma.

Eligible participants will undergo protocol-specified screening assessments, hepatic vascular evaluation, 99mTc-MAA hepatic arterial perfusion imaging, and dosimetry assessment before treatment. Participants who meet the eligibility criteria and are considered suitable for selective internal radiation therapy will receive a single transarterial administration of NRT6003 Injection. Safety follow-up will be conducted for 12 months after treatment, and tumor response will be assessed using mRECIST and RECIST v1.1.

Inclusion Criteria:

1. Age 18 years or older, male or female, with body weight greater than 30 kg. 2. Clinically, radiologically, and/or pathologically diagnosed hepatocellular carcinoma. 3. Previously treated with TACE, and/or HAIC, and considered by the investigator to be able to tolerate yttrium-90 carbon microsphere radioembolization. 4. Child-Pugh score ≤7, ECOG performance status <2, and life expectancy >3 months. 5. Disease confined to the liver after systemic assessment. 6. At least one measurable lesion according to mRECIST and RECIST v1.1. 7. Adequate residual normal liver volume and adequate bone marrow, hepatic, renal, and coagulation function. 8. For participants with portal vein tumor thrombus, eligibility must be confirmed by the investigator based on hepatic angiography and 99mTc-MAA hepatic arterial perfusion imaging. 9. Suitable for SIRT based on hepatic vascular evaluation and 99mTc-MAA assessment. 10. Willing to use effective contraception as required by the protocol. 11. Able to understand and comply with the study requirements and willing to provide written informed consent.

Exclusion Criteria:

1. Extrahepatic metastasis, including regional lymph node metastasis. 2. Uncontrolled biliary obstruction or recent biliary infection within 6 months before informed consent. 3. Prior internal or external radiotherapy to the liver or upper abdomen. 4. Anticancer therapy within 30 days before NRT6003 treatment, or small-molecule targeted therapy within 14 days before treatment. 5. Known allergy, intolerance, or contraindication to any study-related drug, contrast agent, anesthetic agent, or excipient. 6. Severe pulmonary dysfunction. 7. Untreated or inadequately treated esophageal or gastric varices considered by the investigator to have a high bleeding risk. 8. Uncontrolled disease or infection that may affect study safety or efficacy, as judged by the investigator. 9. Positive HIV antibody test. 10. 99mTc-MAA imaging or hepatic angiography showing inadequate coverage of target intrahepatic lesions, uncorrectable gastrointestinal shunting, or estimated single-session lung absorbed dose >30 Gy. 11. Pregnant or breastfeeding women. 12. Any other condition that, in the investigator's opinion, makes the participant unsuitable for this study.