### CT Phases #### Non-Contrast Phase Obtained before intravenous contrast administration. **Uses** - Baseline attenuation assessment - Detection of calcifications - Evaluation of hemorrhage - Assessment of true enhancement after contrast administration Particularly useful for: - pancreatic calcifications - treated liver lesions - hemorrhagic lesions - characterization of enhancement patterns > [!info] > Comparing pre- and post-contrast images helps determine whether a lesion truly enhances rather than simply appearing hyperdense at baseline. --- #### Arterial Phase Obtained approximately 20–35 seconds after contrast injection. **Best for** - Arterial anatomy - Hypervascular lesions - HCC - Neuroendocrine tumors - Assessment of arterial involvement Common findings - HCC arterial hyperenhancement - Hypervascular liver metastases - Hepatic arterial anatomy variants --- #### Portal Venous Phase Obtained approximately 60–80 seconds after contrast injection. **Best for** - Liver metastases - Venous anatomy - Portal vein assessment - General abdominal staging > [!tip] > The portal venous phase is the most commonly reviewed phase for routine abdominal imaging and often provides the best overall survey of the abdomen and pelvis. --- #### Delayed Phase Obtained approximately 3–10 minutes after contrast administration. **Uses** - Cholangiocarcinoma evaluation - Fibrotic lesions - Assessment of washout - Characterization of indeterminate lesions - Postoperative biliary evaluation > [!clinical] > Delayed enhancement may improve detection of desmoplastic tumors such as cholangiocarcinoma and can help characterize lesions with fibrotic stroma. --- #### Standard Contrast CT Most routine contrast-enhanced CT examinations are acquired during a late arterial / early portal venous phase and reconstructed in 3–5 mm slices. While adequate for general abdominal pathology, standard CT lacks the ==thin-slice multiphasic imaging== required for optimal HPB lesion characterization and resectability assessment. > [!note] > While adequate for many abdominal conditions, routine contrast CT is often insufficient for detailed HPB evaluation. Dedicated pancreas and liver protocols provide substantially better lesion characterization and vascular assessment. --- ### Pancreas Protocol CT (PPCT) #### Purpose Optimized evaluation of: - Pancreatic adenocarcinoma - Pancreatic cystic lesions - Pancreatitis complications - Vascular involvement - Surgical resectability #### Typical Components - Thin-slice acquisition (≤3 mm; often 1–2 mm reconstructions) - Pancreatic parenchymal phase - Portal venous phase - Coverage through the pelvis #### Advantages - Maximizes pancreatic tumor conspicuity - Improves vascular assessment - Facilitates NCCN resectability assessment - Supports operative planning > [!important] > PPCT is the preferred initial staging study for suspected pancreatic adenocarcinoma. --- ### Liver Protocol CT #### Purpose Optimized evaluation of: - Hepatocellular carcinoma (HCC) - Cholangiocarcinoma - Liver metastases - Transplant candidates - Operative planning #### Typical Components - Non-contrast phase - Arterial phase - Portal venous phase - Delayed phase - Coverage through the pelvis #### Advantages - Characterizes enhancement patterns - Improves lesion detection - Evaluates vascular anatomy - Assesses extrahepatic disease > [!important] > Multiphasic liver imaging is essential for diagnosing and staging HCC and frequently influences transplant eligibility. --- ### Slice Thickness Thin-slice imaging is essential for modern HPB evaluation. Typical reconstruction thickness: - 1–2 mm for pancreas protocol CT - 1–3 mm for liver protocol CT Advantages: - Improved vascular assessment - Better multiplanar reconstructions - Enhanced operative planning - More accurate resectability determination --- ### Resectability Assessment CT remains the primary imaging modality for assessing surgical candidacy. #### Pancreatic Cancer Important findings include: - SMA involvement - Celiac axis involvement - Common hepatic artery involvement - SMV/PV involvement - Metastatic disease #### Liver Tumors Important findings include: - Future liver remnant - Vascular inflow and outflow - Multifocal disease - Extrahepatic spread #### Biliary Malignancies Important findings include: - Vascular involvement - Longitudinal ductal extent - Lobar atrophy - Future liver remnant adequacy > [!clinical] > Resectability is determined not only by vascular involvement but also by tumor biology, metastatic disease, future liver remnant, and patient fitness for surgery.