Computed Tomography (CT) Perfusion in Abdominal Cancer: Technical Aspects

Abstract

Computed Tomography (CT) Perfusion is an evolving method to visualize perfusion in organs and tissue. With the introduction of multidetector CT scanners, it is now possible to cover up to 16 cm in one rotation, and thereby making it possible to scan entire organs such as the liver with a fixed table position. Advances in reconstruction algorithms make it possible to reduce the radiation dose for each examination to acceptable levels. Regarding abdominal imaging, CT perfusion is still considered a research tool, but several studies have proven it as a reliable non-invasive technique for assessment of vascularity. CT perfusion has also been used for tumor characterization, staging of disease, response evaluation of newer drugs targeted towards angiogenesis and as a method for early detection of recurrence after radiation and embolization. There are several software solutions available on the market today based on different perfusion algorithms. However, there is no consensus on which protocol and algorithm to use for specific organs. In this article, the authors give an introduction to CT perfusion in abdominal imaging introducing technical aspects for calculation of perfusion parameters, and considerations on patient preparation. This article also contains clinical cases to illustrate the use of CT perfusion in abdominal imaging.

Keywords: CT Perfusion; abdominal imaging; cancer imaging; motion correction.

Figure 1

Illustrates the benefit of applying motion correction with abdominal CT Perfusion. (A) Image created by adding two scans into one image. There is a difference in the z-axis of 1.52 cm; (B) is created by adding the same scans as in (A), but after applying motion correction. The diaphragm in the two volumes is now well aligned. Note the tumor (arrow) in the gastro-esophageal junction is less blurry in (B) compared to (A) which makes perfusion calculations more accurate. (A) Without motion correction; (B) With motion correction.

Figure 2

CT perfusion examination of a 54-year-old male with a solitary hepatocellular carcinoma (HCC) in the right liver lobe (arrow). (A) Perfusion shows high arterial blood supply and (B) lower portal blood supply compared with surrounding normal liver tissue (Images reconstructed with Vitrea 6.2, Vital Images A Toshiba Medical Systems Group).

Figure 3

CT perfusion examination of a 77-year-old female after right-sided portal vein embolization prior to liver resection. The patient has a large HCC in the right liver lobe and segment 4. (A) Perfusion shows the portal flow, which is eliminated on the right side and elevated in the left liver lobe; (B) Perfusion index (Arterial Flow/Arterial Flow + Portal Flow). This index is low in the left side due to elevated portal flow, and the index is high in all of the embolized segments, but highest in the vascular part of the HCC (arrow) (Images reconstructed with Vitrea 6.2, Vital Images A Toshiba Medical Systems Group).

Figure 4

CT perfusion examination of a 63-year-old male with a pancreatic mass. The tumor has a neuroendocrine component and CT perfusion shows higher blood flow (110.2 mL/min/100 mL) (arrow) compared to the normal pancreatic tissue (83.7 mL/min/100 mL) (B). The patient has stents in the common bile duct (A) which causes image and perfusion artifacts in the pancreatic head. (Images reconstructed with Vitrea 6.2, Vital Images A Toshiba Medical Systems Group).