Assessing Vascularity of Osseous Spinal Metastases with Dual-Energy CT-DSA: A Pilot Study Compared with Catheter Angiography

Abstract

Background and purpose: Spine debulking surgery in patients with hypervascular spinal metastasis is associated with massive intraoperative blood loss, but currently, the vascularity of tumor is determined by invasive conventional angiography or dynamic contrast MR imaging. We aimed to investigate the usefulness of noninvasive dual-energy CT-DSA, comparing it with conventional angiography in evaluating the vascularity of spinal metastasis.

Materials and methods: We conducted a retrospective study from January to December 2018. A total of 15 patients with spinal metastasis undergoing dual-energy CT, conventional DSA, and subsequent debulking surgery were included. CT-DSA images were produced after rigid-body registration and subtraction between CT phases. Qualitative and quantitative assessments of tumor vascularity were conducted. Correlations between CT-DSA and conventional DSA results were evaluated using the Spearman coefficient. The mean enhancement in the estimated tumor volume and surgical blood loss was compared between hypervascular and nonhypervascular groups using the Wilcoxon rank sum test.

Results: The CT-DSA and DSA results were strongly correlated, with ρ = 0.87 (P < .001). The DSA and the quantitative enhancement index also showed a strong correlation with ρ = 0.83 (P < .001). Wilcoxon rank sum testing between hypervascular and nonhypervascular CT-DSA groups showed a difference in enhancement indices (P = .0003). The blood loss between the hypervascular and nonhypervascular groups was nonsignificant (P = .09).

Conclusions: Dual-energy CT-DSA correlates well with conventional DSA in assessing the vascularity of spinal metastasis. It may serve as a noninvasive preoperative evaluation option before debulking surgery.

Fig 1.

Sagittal subtraction CT before and after rigid-body registration. If we set the subtracted image to a proper window, the quality of registration can be assessed using a DSA-like visual inspection method. A, Unregistered image shows an overt misalignment artifact over bony edges. B, After solid-body registration, the number of artifacts is greatly reduced.

Fig 2.

A 68-year-old male patient with hepatocellular carcinoma with a hypervascular bony metastasis in the T10 vertebral body. A, Coronal 40-keV monoenergetic image of the late arterial phase shows a T10 vertebral body osteolytic lesion with a pathologic compression fracture. B, Coronal 40-keV subtracted CTA after registration shows that the T10 vertebral body had been replaced by a metastatic tumor with avid enhancement stronger than that of the marrow in the adjacent vertebral body. An earlier segmental draining vein (white arrow) parallel to the segmental artery is shown for comparison with a single enhancing segmental artery at the adjacent normal level. C, Color-coded display of the subtracted images demonstrates the degree of enhancement more clearly. The color map is set to a 10-stepped scale with 10% increments for each step to assist in visual grading. D, Frontal view of DSA at the same level shows a typical hypervascular bone metastasis. Early venous drainage to a hemizygous vein is noted (arrowheads), indicating arteriovenous shunting within the metastatic lesion. A smaller part of the vertebral body supplied by the left segmental artery is not opacified in this DSA image. E, Iodine map derived from the material decomposition algorithm shows falsely high iodine content in normal bone marrow. The map failed to demonstrate the expected enhancement difference between the tumor and normal bone marrow because of limitations of the dual-energy CT iodine-based material decomposition in bony tissue.