Impact of 99mTc-GSA SPECT Image-Guided Inverse Planning on Dose-Function Histogram Parameters for Stereotactic Body Radiation Therapy Planning for Patients With Hepatocellular Carcinoma: A Dosimetric Comparison Study

Abstract

Purpose: To evaluate the impact of ^99mTc-labeled diethylene triamine pentaacetate-galactosyl human serum albumin (^99mTc-GSA) single-photon emission computed tomography (SPECT) image-guided inverse planning on the dose-function histogram (DFH) parameters for stereotactic body radiation therapy planning in patients with hepatocellular carcinoma (HCC).

Methods: Eleven patients were enrolled in this study. The functional liver structure (FLS) was derived from SPECT thresholds of 60% to 80% of the maximum pixel value. Two treatment plans optimized without FLS (plan C) and with FLS (plan F) were designed for 50 Gy to the planning target volume (PTV). The DFH parameters were calculated as follows: Fx = (sum of the counts within the liver volume receiving a dose >x Gy/sum of the counts within the whole liver volume) × 100. Other parameters for the PTV included D₉₅, mean dose, conformity index (CI), and homogeneity index (HI).

Results: Compared with plan C, plan F significantly reduced DFH parameters of F₅ to F₄₀ (P < .05). There were no significant differences in the parameters of the PTV of D₉₅, mean dose, CI, and HI and organs at risks (stomach, duodenum, spinal cord, and kidneys) between plans C and F.

Conclusion: DFH analyses revealed that ^99mTc-GSA SPECT image-guided inverse planning provided dosimetric benefits related to sparing of liver function and may reduce hepatic toxicities.

Keywords: dose–function histogram; dose–volume histogram; hepatocellular carcinoma; molecular imaging; radiation-induced liver disease; stereotactic body radiation therapy.

Figure 1.

Patient with recurrent hepatocellular carcinoma in segment 5. He received multiple surgical treatments, transarterial chemoembolization, and radiofrequency ablation. A, Fused images from single-photon emission computed tomography (SPECT) and planning computed tomography. The SPECT image shows the inhomogeneity of the liver function. B, Dose distributions of the conventional plan (plan C) optimized without functional liver structure (FLS). C, Dose distributions of the functional image-guided plan (plan F) optimized with FLS. The FLS (purple) was derived from SPECT thresholds equal to 80% of the maximum pixel value. D, The dose–function histogram of plan C (red) and plan F (blue).