Abstract
SPECT/CT with 99mTc-macroaggregated albumin (MAA) is generally used for diagnostic work-up prior to transarterial radioembolization (TARE) to exclude shunts and to provide additional information for treatment stratification and dose calculation. C-arm CT is used for determination of lobular vascular supply and assessment of parenchymal blood volume (PBV). Aim of this study was to correlate MAA-uptake and PBV-maps in hepatocellular carcinoma (HCC) and hepatic metastases of the colorectal carcinoma (CRC). 34 patients underwent a PBV C-arm CT immediately followed by 99mTc-MAA injection and a SPECT/CT acquisition after 1 h uptake. MAA-uptake and PBV-maps were visually assessed and semi-quantitatively analyzed (MAA-tumor/liver-parenchyma = MAA-TBR or PBV in ml/100ml). In case of a poor match, tumors were additionally correlated with post-TARE 90Y-Bremsstrahlung-SPECT/CT as a reference. 102 HCC or CRC metastases were analyzed. HCC presented with significantly higher MAA-TBR (7.6 vs. 3.9, p<0.05) compared to CRC. Tumors showed strong intra- and inter-individual dissimilarities between TBR and PBV with a weak correlations for capsular HCCs (r = 0.45, p<0.05) and no correlation for CRC. The demarcation of lesions was slightly better for both HCC and CRC in PBV-maps compared to MAA-SPECT/CT (exact match: 52%/50%; same intensity/homogeneity: 38%/39%; insufficient 10%/11%). MAA-SPECT/CT revealed a better visual correlation with post-therapeutic 90Y-Bremsstrahlung-SPECT/CT. The acquisition of PBV can improve the detectability of small intrahepatic tumors and correlates with the MAA-Uptake in HCC. The results indicate that 99mTc-MAA-SPECT/CT remains to be the superior method for the prediction of post-therapeutic 90Y-particle distribution, especially in CRC. However, intra-procedural PBV acquisition has the potential to become an additional factor for TARE planning, in addition to improving the determination of segment and tumor blood supply, which has been demonstrated previously.
Highlights
Transarterial radioembolization (TARE), known as selective internal radiotherapy (SIRT) is a locoregional treatment option for patients suffering from unresectable primary and secondary tumors of the liver [1, 2]
hepatocellular carcinoma (HCC) presented with significantly higher MAATBR (7.6 vs. 3.9, p
The acquisition of parenchymal blood volume (PBV) can improve the detectability of small intrahepatic tumors and correlates with the macroaggregated albumin (MAA)-Uptake in HCC
Summary
Transarterial radioembolization (TARE), known as selective internal radiotherapy (SIRT) is a locoregional treatment option for patients suffering from unresectable primary and secondary tumors (metastases) of the liver [1, 2]. The primary mechanism of anti-tumoral action of TARE is local irradiation rather than stopping blood flow resulting from arterial embolization [3]. For the work-up of TARE a two-step approach is employed, starting with angiography and optional prophylactic coil-embolization of obvious shunt vessels. This is followed by injection of 99mTc-labeled macroaggregated albumin particles (99mTc-MAA) in order to simulate the therapeutic microspheres distribution. 99mTc-MAA deposition is thought to be dependent on regional arterial vascularization and is used to simulate microsphere distribution within the liver [5]. The role of 99mTc-MAA deposition in the prediction of intra-therapeutic 90Y-microspheredeposition [6], as well its correlation to absorbed tumor dose, tumor response and progression-free survival [7] is still discussed controversially
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