T/N RATIO
- 99mTc sulphur colloid scan – cold lesion as tumor does not contain reticuloendothelial cells
- 99mTc MAA – hot focal area in background of non-tumorous liver
- Therefore MAA itself represents vascularity of tumor and reflects the concentration of radioactivity that really stays in the tumor relative to that in non-tumorous liver.
HOW T/N RATIO IS EFFECTED:
| Effect of type | HCC shows a wider range of T/N ratio as compared to CRM, however no statistically significant difference was noted. |
| Effect of Vascularity | Grade 1: Presence of mild tumour staining without an increase in the number of vessels. (Lower T/N ratio) Grade 2: Moderate tumour staining and increased number of vessels. Grade 3: Intense tumour staining and marked increase in the number of vessels which were also dilated and tortuous. Grade 4: Tumours having all the grade 3 characteristics together with venous pooling. |
| Effect of size | 1. No significant difference on T/N ratio. 2. Large tumor size (> 20 cm) shows lower T/N ratio |
| Effect of LSF | 1. Mean T/N ratio decrease as LSF increase in HCC (suggest that AV connections responsible for shunt arise from tumor rather than non-tumorous liver) 2. No such correlation seen in patients with CRM 3. LSF Increase with Increased vascularity of tumor |
| Effect of Drugs | Intra-arterial injection of Angiotensin II can increase T/N ratio - bolus dose of 50 ug in main hepatic artery in pulsed fashion |