Page 12 - ARNM-3-1

Advances in Radiotherapy
& Nuclear Medicine Diagnostics gude of biliary tract cancer

Elastography is another non-invasive technique that improves tumor visibility, with tumors often being barely
assesses tissue stiffness by measuring changes in organ visible without it. The appearance of biliary tract cancer
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and focal tissue characteristics. Transient elastography on CT scans depends on the tumor’s location within the
and real-time elastography are commonly used to image biliary system, with intrahepatic bile duct carcinomas
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changes in the bile ducts. being particularly heterogeneous on CT scans. 50
The principle of elastography involves assessing the The accuracy of MDCT in imaging bile duct involvement
distribution of tissue elasticity, which is then converted into is 86%, although it tends to significantly underestimate the
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an image of the elastic modulus, known as an elastogram. extent of longitudinal involvement. CT and contrast-
This technique measures tissue deformation caused by enhanced CT can perform precise multidirectional
static or dynamic stress, allowing for the estimation of assessments of bile duct and vascular involvement, which
tissue stiffness and the differentiation between benign and helps accurately predict tumor resectability and facilitates
malignant changes. successful tumor resection. 32,51-53 Studies have shown that
Elastography is also valuable for visualizing, localizing, in the primary stage of intrahepatic biliary tract cancer,
and diagnosing various nodules, as well as pancreatic and CT is more sensitive than MRI in detecting extrahepatic
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liver masses. While traditional USG is often utilized to invasion and vascular involvement. Specifically, CT
exhibited 84% sensitivity and 93% specificity in detecting
detect liver lesions, it is typically considered less precise hepatic artery involvement, while the accuracy of
than CT, MRI, or histology. The combination of these detecting portal vein involvement was 87%. Infiltration
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modalities is considered the gold standard for patient
evaluation. However, the introduction of CEUS has of adjacent structures, particularly the hepatoduodenal
significantly improved the detection and characterization ligament, duodenum, transverse colon, liver, and lymph
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of liver lesions by providing superior visualization of nodes, often indicates the inoperability of the cancer.
the microvasculature, thereby enhancing its diagnostic CT arteriography and CT venography are reconstructed
accuracy. 43 using various techniques to visualize the vascular
anatomy, assist in surgical planning, and reduce the risk of
Ultrasound, and more recently CEUS, is often the first complications. Park et al. demonstrated that CT imaging
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method employed to assess biliary lesions. CEUS enables of vascularization can serve as a non-invasive, accessible,
the visualization of microcirculation in liver metastases, and valuable prognostic indicator for the treatment of
allowing for the monitoring of changes in tumor perfusion iCCA. A study involving 345 patients developed a pre-
following local ablation or new antiangiogenic therapies. operative model for predicting post-operative outcomes
in massive intrahepatic biliary tract cancer and showed
2.2. CT
that CT, along with clinical and radiomic features, can be
Over the past few years, CT imaging has evolved from useful for this purpose. Furthermore, a deep learning
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single-detector scanners to MDCT technology, enabling model based on CT imaging, developed by Wakiya et al.,
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the acquisition of high-resolution images in seconds. exhibited high predictive performance in forecasting early
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Multidetector row CT is now the imaging modality of choice post-operative recurrence of iCCA. Moreover, volumetric
for evaluating and staging CCA, due to its high spatial scanning techniques can assess the liver volume and
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and temporal resolution and widespread availability. 45,46 residual function before surgery, helping to prevent post-
CT allows for the detection of tumor masses, the definition operative small-size syndrome. A new CT technique,
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of local enlargement of cavitary tumors, the assessment functional CT volume perfusion imaging, may be valuable
of blood vessel invasion and adjacent organ involvement, in assessing treatment responses to targeted therapies or
and the identification of metastatic disease, including antiangiogenic drugs by demonstrating changes in tumor
lymph node and abdominal metastases. 38,45-47 This method vascularization. The sensitivity of CT in detecting lymph
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is more accurate than ultrasound for detecting biliary node metastases is 61%, with a specificity of 88%. For
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tract cancer, which is why CT is used in up to 90% of evaluating distant metastases, CT shows a sensitivity of
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patients with suspected biliary tract cancer. Multiphase 67% and a specificity of 94%. However, the accuracy of
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CT protocols, including late arterial phase and portal vein CT in assessing the progression of extrahepatic biliary
phase scanning, are now recommended for the primary tract cancer remains unestablished. A key challenge in
staging of biliary tract cancer. 40,48 Moreover, this diagnostic this regard is determining the extent of tumor spread
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test can differentiate between types of CCA. Nam et al. beyond the bile duct wall and its potential involvement
showed that pre-operative MDCT features of intrahepatic with adjacent anatomical structures. Liver Imaging
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mass-forming CCAs can help distinguish between small- Reporting and Data System (LI-RADS ) was created to
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duct and large-duct types. Contrast administration greatly standardize the reporting and data collection of CT and
Volume 3 Issue 1 (2025) 4 doi: 10.36922/arnm.4557