^99mTc-sulfur colloid SPECT/CT for quantitative imaging of global and regional liver function in hepatocellular carcinoma patients

Objectives Liver function assessment is critical in hepatocellular carcinoma (HCC) patient care and may be enhanced by quantitative imaging surrogates. Global and regional variability in ^99mTc-sulfur colloid (SC) SPECT/CT liver uptake was tested for association to Child-Pugh (CP) score and prior therapy in HCC patients.

Methods 12 HCC patients with variable CP score (A5-B9) and prior liver therapy underwent SC SPECT/CT scans. Reconstructed SPECT images were corrected for scatter, collimator blur and attenuation. Gross tumor volume (GTV), anatomic liver volume (ALV) and spleen were contoured on CT. Liver-to-spleen SC uptake ratios were calculated: maximum (L/S_max), mean (L/S_mean) and total (L/S_total). Functional liver volumes (FLV) were created by SC uptake thresholds within ALV. Heterogeneity was assessed by coefficient of variation in SC uptake (CV_ALV) and liver-to-spleen uptake ratio CV (L/S_CV). Wilcoxon sign-rank tested image parameters across all patients and non-parameteric ANOVA tested differences between patient groups (CP score or prior treatment).

Results FLV were smaller than ALV (FLV/ALV=53%, p<0.001) and SC uptake was heterogeneous (CV_ALV=0.44, p=0.001). Higher liver-to-spleen uptake ratios were associated with lower CP scores (superior liver function): L/S_max (CP_A=1.6 vs. CP_B=0.7, p=0.004), L/S_mean (CP_A=1.6 vs. CP_B=0.5, p=0.004), L/S_total (CP_A=5.7 vs. CP_B=1.2, p=0.03). Patients with lower CP score demonstrated higher %FLV/ALV (CP_A=63% vs. CP_B=47%, p=0.007). L/S_CV trended lower in CP_A patients (p=0.06), while CV_ALV was lower in untreated patients but did not reach significance (p=0.36).

Conclusions Quantitative sulfur colloid SPECT/CT liver uptake distinguishes between patients with differential liver function. These imaging parameters may aid in personalization of HCC radiotherapy and delineation of functional avoidance volumes.