In hepatocellular carcinoma, target delineation is built on image timing, motion control, and disciplined reading of vascular invasion. The chapter makes that point immediately: planning quality depends on combining multiphasic CT, liver function assessment, reproducible respiratory coordination, and margins that match the actual pattern of disease. For the broader framework behind these decisions, see our Target Volume Delineation and Field Setup – Complete Clinical Guide.
The chapter also avoids one-size-fits-all liver planning. Its emphasis stays on limiting low-dose spill into normal liver, matching the treatment technique to bowel safety, and deciding when tumor thrombus should reshape the target. If you want a second upper abdominal example from the same series, compare this workflow with our article on gastric cancer target delineation.
In This Article
General planning principles for hepatocellular carcinoma
The chapter answers the technique question in plain terms. Step-and-shoot IMRT and volumetric modulated arc therapy remain standard for HCC when the gantry angle selection is intentionally limited so the normal liver is not bathed in unnecessary low dose.
That framing matters. In HCC, technique selection is tied to how much uninvolved liver can be protected, not just to whether a machine can produce a conformal plan. The text then gives a clear preference for SBRT in 5-6 fractions or fewer when bowel sparing is safe, high dose rate delivery is available, immobilization is solid, and image guidance is in place. Hypofractionated treatment is sometimes chosen because the target sits close to luminal gastrointestinal tissues, so the fractionation pattern has to respect that anatomy.
There is a practical message underneath those statements. The chapter is not simply ranking machines. It is linking the treatment technique to daily reproducibility, respiratory strategy, and the realistic ability to verify liver position before each fraction.
Multiphasic imaging for diagnosis, staging, and planning
Target delineation in hepatocellular carcinoma starts with complete clinical workup and the right scan set. The chapter calls for history and physical examination, laboratory evaluation, liver function assessment, and imaging studies for diagnosis, staging, and planning.
The imaging backbone is a contrast-enhanced liver CT, preferably tri-phasic with arterial, portal-venous, and delayed phases, acquired at 3-5 mm slice thickness. Multi-phase dynamic MRI can be used when the patient can sustain the breath hold required for acquisition or when CT contrast is contraindicated. With image fusion, MRI serves as a complement to CT for delineation. The chapter treats the two modalities as coordinated sources of information rather than interchangeable studies, which is a useful distinction in liver cases.
PET is presented more selectively. Images obtained with 18F-FDG or other tracers such as 11C-acetate and 11C-choline may help localize viable tumor in individual cases, especially when residual or recurrent disease sits in areas of previous lipiodol retention or prior radiofrequency ablation. That wording is deliberate. PET is useful when the question is viable tumor localization, not as a routine default for every patient.
The chapter keeps returning to image fusion because each dataset answers a different planning question. One phase is best for viable tumor conspicuity, another for vessel anatomy, and another for inferior vena cava involvement. Liver planning becomes cleaner when those roles are kept separate.
Immobilization and respiratory motion control
The text is explicit on reproducibility: half-body or whole-body immobilization with respiratory control is needed. Devices such as a vacuum bag or chest board can be used, preferably with the arms up, both at simulation and throughout treatment.
That setup serves two purposes at once. It improves day-to-day consistency, and it preserves beam freedom. The immobilization system also has to avoid attenuating the treatment beam and must not interfere with gantry positions needed for coplanar or non-coplanar delivery.
Respiratory management is where the chapter becomes especially practical. Active breath hold reduces treated volume and is preferred for patients who can hold their breath for more than 30 seconds. Abdominal compression is used when breath hold is not tolerated, although it may deform the abdomen or alter organ shape. Target delineation is most often performed on multiphasic, multimodality images obtained in breath hold, mirroring the way diagnostic HCC imaging is commonly interpreted.
Image-guided radiation therapy is required because liver position changes both within a fraction and between fractions. For patients who cannot tolerate breath control, passive abdominal compression combined with 4DCT provides information about internal organ motion and helps compensate for liver position changes. Gated treatment is another option, although the selected inspiratory or expiratory window lengthens treatment time.
What the chapter does well here is avoid pretending there is a universal motion solution. Instead, it describes a hierarchy of workable strategies and ties each one to what it can realistically deliver in image quality and positional stability.
Simulation CT and phase-by-phase image interpretation
Simulation CT has to be performed with intravenous contrast and multiphase acquisition. The chapter insists that this should happen in treatment position and with respiratory coordination, because the anatomy used for contouring needs to match the anatomy that will actually be treated.
Fusion across simulation phases, and when needed with diagnostic images, supports gross tumor volume definition. Viable HCC is usually best visualized and brightest on arterial-phase CT, while it shows less enhancement relative to the liver on venous and delayed images. That arterial conspicuity followed by washout is one of the core visual rules repeated in the text.
Portal-phase CT has a different job. It uses intrahepatic vessel distribution to define the anatomic boundaries of the treated tumor, a point that becomes especially important when immobilization and respiratory control alter liver shape. Portal-venous phase CT is also the best phase for evaluating tumor invasion into vascular structures. When the question is the extent of inferior vena cava invasion, the chapter points to delayed-phase CT.
This is a strong planning lesson because it prevents phase oversimplification. The chapter is not asking one phase to solve every delineation problem. It assigns each phase a specific diagnostic role, which is exactly how liver targets stay anatomically credible.
Target delineation in hepatocellular carcinoma
The central target definition rule is straightforward. In selected SBRT situations, the visible tumor alone may be targeted as GTV. More often, the GTV is enlarged to create a CTV that reflects the clinical risk of microscopic spread within the liver parenchyma, including areas around previous radiofrequency ablation or embolized zones.
The chapter also warns that CTV is not fixed in space. Respiratory motion and organ dynamics can shift its size and position, so the margin strategy has to account for more than just contouring philosophy. It has to reflect what actually happens to the liver during acquisition and treatment.
Table 17.1. Suggested target volumes at the GTV and CTV regions
This table contains the operational core of the chapter. It lays out how visible tumor, contiguous macroscopic disease, optional microscopic risk, and final setup expansion are separated in HCC planning.
| Target volume | Definition and description |
|---|---|
| GTVa | Liver tumor: intrahepatic enhancing tumor on arterial-phase contrast CT with washout on venous- or delayed-phase CT. Lipiodol retaining tumor: lipiodol (white) contiguous to the enhancing tumor. Ablated refractory tumor: arterial enhancing tumor adjacent to the hypodense ablated zone. Vascular tumor thrombus: arterial enhancing thrombus with washout on venous-phase CT. |
| CTVmacroscopica | Liver tumor: the intrahepatic enhancing tumor on arterial-phase contrast CT. Embolized zone contiguous to the enhancing tumor included in GTV. Arterial enhancing tumor adjacent to the hypodense ablated zone. Arterial enhancing vascular tumor thrombus. |
| CTVmicroscopic (elective)b | 3-5 mm margin around intrahepatic GTV. Optional 2-3 mm margin around the tumor thrombus GTV within the vessel according to clinical indication or protocol. Bland thrombus adjacent to tumor thrombus GTV. Radiofrequency ablation zone adjacent to GTV. Embolized zone not directly adjacent to the GTV. CTV should not cross natural barriers such as the surface or boundary of the liver. |
| PTV | CTV, or GTV/CTVmacroscopic, plus 5-20 mm, which may be asymmetric depending on immobilization and respiration control. Internal organ motion and setup error form the basis of the PTV. 4DCT acquired from all respiratory phases may help define the PTV and cover the extent of internal organ motion. |
Source: Target Volume Delineation and Field Setup, 2nd Edition (Table 17.1)
Table notes: a GTV/CTV macroscopic disease may, for example, be treated to 45-54 Gy in 3-6 fractions, with the reminder that the safe dose may need to be reduced if limited by normal tissues. b Elective or microscopic CTV may, for example, be treated to 24-30 Gy in 3-6 fractions; the text also notes that author L.A.D. does not routinely recommend a microscopic CTV around the GTV. c The added margin around intrahepatic GTV may be treated to macroscopic or higher doses if that is safe.
The strength of the table is its restraint. It separates what is definitely visible from what is contiguous, and from what is only an optional microscopic concern. That is a more honest way to build margins in HCC than pretending every case deserves the same expansion.
What the clinical figures add to planning
The four clinical figures work like applied contouring tests. Each one uses multiphasic simulation imaging obtained with breath-hold coordination, and each one shows how prior local therapy or vascular extension changes the final target.
Figure 17.1
The first example shows residual hepatocellular carcinoma after transcatheter arterial chemoembolization and radiofrequency ablation. The tri-phasic simulation includes non-contrast CT, contrast-enhanced T1-weighted MRI, arterial phase CT, and venous delayed phase CT. The GTV in red includes the enhancing tumor and invaded inferior vena cava thrombosis. The CTV in green adds a 5 mm margin within the liver boundary and a 3 mm intravascular margin around the GTV.
Figure 17.2
The second case shows recurrent disease with partial inferior vena cava thrombosis after repeated radiofrequency ablation. Here the CTV in green includes the enhancing tumor and the tumor thrombus represented by the red GTV, plus a 5 mm margin around the GTV within the liver boundary and within the previous radiofrequency ablation zone when clinically needed.
Figure 17.3
The third figure presents recurrent hepatocellular carcinoma after surgery and radiofrequency ablation in a patient with high risk of bile duct injury from ablation. Simulation includes non-contrast, arterial, portal, and venous delayed phases obtained with breath-hold coordination. The green CTV contains the enhancing tumor shown as red GTV, a 5 mm margin of liver parenchyma, and a 3 mm intravascular margin around the GTV.
Figure 17.4
The fourth example involves hepatocellular carcinoma refractory to sorafenib with progression of portal vein and middle hepatic vein thromboses. The tri-phasic simulation again uses breath-hold coordination. In this setting, the CTV in green includes the enhancing tumor shown as red GTV together with a three-dimensional 5 mm margin around the GTV within the liver boundary.
Read together, these figures show a consistent contouring logic. The intrahepatic margin is used to cover adjacent risk when the disease pattern supports it, and intravascular expansion appears when tumor thrombus is part of the geometry. The chapter never expands volume by habit alone.
Further reading cited in the chapter
The chapter closes by pointing readers to studies and consensus work that support this planning approach: local radiotherapy with or without transcatheter arterial chemoembolization in unresectable disease, interobserver variability and consensus guidelines for HCC with or without portal vein thrombus, upper abdominal organ-at-risk contouring atlases, proton beam therapy versus radiofrequency ablation for recurrent HCC, APPLE consensus statements on radiotherapy and SBRT, individualized SBRT dose escalation, factors associated with microinvasion, and a randomized trial comparing transarterial chemoembolization plus external beam radiotherapy with sorafenib in macroscopic vascular invasion.
That ending fits the rest of the chapter. Hepatocellular carcinoma target delineation depends on the right phase of contrast, the right respiratory strategy, and margins that can be defended anatomically and clinically. For the wider map of how these ideas connect across disease sites, return to the complete clinical guide.
