Spectral detector CT applications in advanced liver imaging

Abstract

Objective: Spectral detector CT (SDCT) has many applications in advanced liver imaging. If appropriately utilized, this technology has the potential to improve image quality, provide new diagnostic information, and allow for decreased radiation dose. The purpose of this review is to familiarize radiologists with the uses of SDCT in liver imaging.

Conclusion: SDCT has a variety of post-processing techniques, which can be used in advanced liver imaging and can significantly add value in clinical practice.

Figure 1.

46-year-old male undergoing preoperative CT for potential liver donation. At 40 keV, there is increased iodine conspicuity in comparison with the conventional image. 70 keV image is equivalent to conventional image at 120 kVp in terms of iodine contrast. At 200 keV, iodine conspicuity decreases.

Figure 2.

81-year-old male with pancreatic neuroendocrine tumor. There is increased conspicuity of hypovascular liver metastases on 40 keV image (right) compared with conventional image (left).

Figure 3.

66-year-old male with cirrhosis. There is increased conspicuity of hypervascular liver lesion (arrows) on 50 keV image (right) compared with conventional image (left). This was subsequently diagnosed as hepatocellular carcinoma.

Figure 4.

46-year-old male undergoing preoperative CT for potential liver donation. Accessory hepatic veins (arrows) are easier to visualize on 50 keV image (right) compared with conventional image (left).

Figure 5.

53-year-old male status post bowel resection; CT scan was performed to rule out intra-abdominal abscess. Incidentally noted is a noncalcified gallstone (arrows) that is more conspicuous on 50 keV image (right) compared with conventional image (left).

Figure 6.

64-year-old male with cirrhosis, 5 months status post microwave ablation of segment five hepatocellular carcinoma. Zone of ablation (arrows) contains areas of hyperattenuation on conventional image. However, no iodine is visualized within the zone on iodine no water image. Hyperattenuation remains on virtual non-contrast (VNC) image which appears similar totrue non-contrast (TNC) image.

Figure 7.

70-year-old male with cirrhosis and hepatocellular carcinoma, pre-treatment (A-B) and 3 months status post-TACE (C-D). (A) Conventional image showing arterially enhancing lesion in segments 5/6. (B) The lesion is demonstrated on an iodine overlay, with a measured iodine concentration of 2.2 mg dl⁻¹. (C) Following ablation, on conventional image, there is some peripheral high density in the ablation zone; it is unclear if this represents hemorrhagic debris or residual disease. (D) The absence of iodine is confirmed on iodine overlay with a measured iodine concentration of 0 mg dl⁻¹. This allows confident exclusion of residual or recurrent disease.

Figure 8.

73-year-old male with hepatocellular carcinoma status post transarterial chemoembolization. Hyperdensity is seen within the lesion on arterial phase image (left), which suppresses on the VNC image (middle). This could have been misinterpreted as enhancement. However, TNC image (right) from a recent examination demonstrated the same intralesional hyperdensity, suggesting lipiodol deposition rather than enhancement.

Figure 9.

48-year-old male with infiltrative hepatocellular carcinoma. Conventional image (left) demonstrates infiltrative hepatocellular carcinoma and expansile thrombus within the right portal vein. Faint iodine is seen within the thrombus on iodine overlay image (right), favoring tumor thrombus.

Figure 10.

87-year-old female with an incidentally visualized hepatic cyst containing a calcified septation (arrows). Conventional contrast enhanced image (left) demonstrates a cyst with a hyperdense septation. VNC image (middle) demonstrates persistent high attenuation focus within the septation, confirming that this represents calcification instead of enhancement. Calcification is confirmed on the TNC image (right).