To investigate the in vivo performance and safety of a novel medical device for the injection of holmium-166 microspheres during radioembolization. The main potential advantage of this device is that it allows for injection of a during treatment determined dose, which is not possible with the current administration tool.

Inclusion Criteria:

1. Diagnosis of hepatocellular carcinoma or liver metastases originating from colorectal cancer.
2. At least one lesion of ≥10 mm in the longest diameter on contrast-enhanced MRI or contrast-enhanced CT
3. Patient is eligible for SIRT as determined by the tumour board (in Dutch: MDO)
4. Patient has a life expectancy of 12 weeks or longer
5. Patient has a WHO performance score of 0-2

Exclusion Criteria:

1. Significant extrahepatic disease (2x sum of diameters of lesions outside the liver > sum of lesions inside the liver)
2. Radiation therapy, chemotherapy or major surgery within 4 weeks before treatment
3. Serum bilirubin > 2.0 x the upper limit of normal
4. ALAT, ASAT, alkaline phosphatase (AF) > 5x the upper limit of normal
5. Glomerular filtration rate (GFR-MDRD) <35 ml/min
6. Leukocytes <4.0 * 109/L or platelet count <60 * 109/L
7. Significant heart disease that in the opinion of the physician increases the risk of ventricular arrhythmia.
8. Pregnancy or breast feeding
9. Disease with increased chance of liver toxicity, such as primary biliary cirrhosis or xeroderma pigmentosum
10. Patients ineligible to undergo MR-imaging (claustrophobia, metal implants, etc)
11. Portal vein thrombosis of the main branch (more distal branches are allowed)
12. Evidence of clinically relevant, untreated grade 3 portal hypertension
13. Untreated, active hepatitis
14. Body weight > 150 kg (because of maximum table load)
15. Severe allergy for i.v. contrast (Iomeron, Dotarem and/or Primovist)
16. Lung shunt > 30 Gy, as calculated using scout dose holmium-166 SPECT/CT
17. Uncorrectable extrahepatic deposition of scout dose activity. Activity in the falciform ligament, portal lymph nodes or gallbladder are accepted.

Participant data will be available upon reasonable request