Correlation of C-arm CT acquired parenchymal blood volume (PBV) with 99mTc-macroaggregated albumin (MAA) SPECT/CT for radioembolization work-up

Objective 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). Materials and methods 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. Results 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. Conclusion 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.

Abstract TP133: Assessment of Hemodynamic Compromise by Neuro-Parenchymal Blood-Volume System: Comparison With Acetazolamide Challenged Single Photon Emission Computed Tomography

Objective: To investigate whether Neuro-parenchymal blood-volume (PBV) measurements could be used instead of acetazolamide (ACZ)-challenged single-photon emission computed tomography (SPECT) to evaluate hemodynamic compromise in patients with cerebrovascular steno-occlusive disease. Methods: Thirteen patients with unilateral carotid artery steno-occlusive disease were enrolled from April 2018 to June 2019, and the severity of hemodynamic compromise was assessed by Neuro PBV system (syngo Neuro PBV IR, Siemens Medical Solutions, Erlangen, Germany) and acetazolamide-challenged SPECT of the brain. Cerebral blood volume (CBV) was measured using a C-arm flat detector angiographic system. The asymmetry ratio of CBV in the middle cerebral artery (MCA) territory (CBV AR ) was defined as the (CBV on the ipsilateral side / CBV on the contralateral side) х 100 (%). Cerebral blood flow (CBF) was quantified by SPECT using the quantitative SPECT/dual-table autoradiography method. Cerebrovascular reserve (CVR) in the MCA territory was defined as (CBF after ACZ challenge – CBF at rest) / CBF at rest х 100 (%) and classified as reduced (<18.4%) or non-reduced (≥18.4%). Results: Five patients showed reduced CVR. The CBV AR was significantly lower in the reduced CVR group than in the non-reduced CVR group (71.6% vs. 110.0%, P = 0.003). The cut-off value of CBV AR for predicting reduced CVR obtained from analysis of the receiver operating characteristic curve was 99.0% (sensitivity 100% and specificity 87.5%), and the area under the curve was 0.975 (95% confidence interval: 0.906-1). Conclusion: This is the first report to evaluate the correlation between CBV AR measured using the Neuro PBV system and CVR assessed by SPECT. CBV AR is useful indicator for evaluating reduced CVR in the MCA territory, as an alternative to ACZ-challenged SPECT.