Preprocedural Preparation

It is imperative that before any embolization procedure, optimal imaging of the liver be performed to depict the anatomy and characteristics of the tumor to be embolized. In our institution, the preferred imaging study before any embolization procedure is a triphasic CT scan. This allows depiction of the arterial anatomy, including the identification of anatomic variations, which is extremely important before any attempt at embolization. It also demonstrates portal vein status. A good triphasic CT scan will also provide information about the vascularity and distribution of the tumor or tumors to be treated (Fig. 66-2, A and B). Angiography and embolization are performed in standard fashion via the femoral artery, with angiography used to depict the hepatic arterial anatomy and variations, as well as the distribution of vascular masses throughout the liver (Fig. 66-2, C).

Technical Aspects

Celiac axis and hepatic arteriography is always performed before embolization. Selective arteriography is necessary to identify tumors with a poor vascular component and, rarely, even hypervascular tumors that were not visualized on the celiac arteriogram. The catheter is advanced over a guidewire in the vessels expected to be supplying the target tumor, based on prior triple-phase CT information. When treating patients with multifocal bilobar disease (see Fig. 66-2, C), we select the lobe with the most disease for treatment at the first sitting. Initially, we perform arteriography with the catheter positioned selectively in the right or left hepatic artery, followed by embolization (Fig. 66-2, D). Several embolic agents are used for treatment, and even more regimens for the administration of TACE. In the following section, we describe the technique of bland embolization we routinely use in our institution.

Selection of the embolic agent for treatment is based on the preference of the interventional radiologist. We always start by using the smallest size of the desired particles (see Table 66-2). A vial of the smallest particle is poured into a small glass or stainless steel cup, and the vial is rinsed of residual particles by filling it with contrast material and then pouring the contents into the cup containing the particles. The suspension is made and then drawn into a syringe for administration into the target vessel under continuous fluoroscopic control to confirm antegrade flow toward the tumor until stasis is evident or until 10 mL of the embolic agent has been used. We evaluate flow after the administration of 10 mL of the smallest particles, and if antegrade flow is still evident, we continue embolization with the next smallest particles. Once again, 10 mL of these particles is administered, and if antegrade flow persists, the next size particles are used, again injecting up to 10 mL of the particles, and so on. When stasis (defined as lack of antegrade flow, with evidence of reflux on injection of even small amounts of contrast material) is achieved, we terminate the embolization and perform arteriography to document occlusion of the target vessel and identify any supply to the target tumor from other vessels, which we may then select and embolize. Finally, arteriography will show stasis in the embolized vessel, which will have a “pruned tree” appearance (see Fig. 66-2, D), and preservation of antegrade blood flow to nontarget vessels such as the gastroduodenal and, if visualized, the cystic artery (Fig. 66-3).

Though rare in the treatment of secondary hepatic malignancies, pooling of contrast material within the target tumor during embolization may be noted. This is known as an embolization sink, and it is accompanied by an endless capacity for contrast material and particles and maintains antegrade flow. In our experience, using small amounts of 50-µm polyvinyl alcohol particles at this point will cause cessation of flow into the sink and stasis. Rarely, accessory vessels of the right or left hepatic artery must be embolized superselectively with a coil before undertaking tumor embolization to avoid embolization of nontarget tissue.

We recommend and try to embolize solitary tumors (Fig. 66-4, A and B) superselectively with a coaxial technique and 3F microcatheters, again administering up to 10 mL of the smallest particle size available and following the same algorithm as described in the previous paragraph for lobar embolization. We repeat the same procedure until all vessels supplying the tumor are occluded according to our standard protocol, beginning with the smallest particles and continuing until stasis. As with any type of embolization, we perform a final arteriogram when stasis has been achieved in all target branches (Fig. 66-4, C). At this point we consider evaluation of vessels that have not been embolized, and if appropriate, we also perform angiography of nonhepatic vessels supplying the tumor (e.g., phrenic or internal mammary arteries). Provided the patient is doing well, excessive contrast agent has not been administered, and embolization of additional vessels is considered safe, embolization continues. When stasis has been achieved in all vessels supplying the target tumor or the hemiliver, embolization is concluded, and when necessary, a future treatment plan for repeat embolization of residual disease is devised.