From the Guidelines
For radiation treatment planning in pancreatic cancer, a combination of CT simulation with intravenous contrast is the primary recommended imaging modality, supplemented by diagnostic CT, MRI, and PET/CT fusion when available. This approach is supported by recent studies, including 1, which highlights the importance of accurate staging and resectability assessment in pancreatic cancer. The use of CT simulation with intravenous contrast provides essential anatomical information and electron density data required for dose calculations, while diagnostic MRI with pancreatic protocol sequences offers superior soft tissue contrast to define the primary tumor extent and its relationship to critical structures.
Key considerations for imaging modalities in radiation treatment planning for pancreatic cancer include:
- CT simulation with intravenous contrast for anatomical information and electron density data
- Diagnostic MRI with pancreatic protocol sequences for superior soft tissue contrast
- PET/CT fusion for identifying metabolically active disease and potential metastases
- 4D-CT for patients receiving stereotactic body radiation therapy (SBRT) to account for respiratory motion of the pancreas
As noted in 1 and 1, multiphase contrast-enhanced multidetector CT and MRI are the imaging modalities of choice for pretreatment staging and presurgical determination of resectability. The addition of intravenous contrast during CT simulation enhances visualization of the tumor and surrounding vasculature, improving target delineation. Diagnostic MRI with pancreatic protocol sequences (T1-weighted, T2-weighted, and diffusion-weighted imaging) helps better define the primary tumor extent and its relationship to critical structures like the superior mesenteric artery and portal vein.
In terms of specific imaging modalities, 1 recommends specialized pancreatic CT or MRI, with CT being performed according to a defined pancreas protocol such as triphasic cross-sectional imaging and thin slices. The role of PET/CT scan remains unclear, but it may be considered after formal pancreatic CT protocol in “high-risk” patients to detect extra pancreatic metastases. Endoscopic ultrasound (EUS) may be complementary to CT for staging, and EUS-directed FNA biopsy is preferable to a CT-guided FNA in patients with resectable disease.
Overall, a multimodality approach to imaging is essential for accurate radiation treatment planning in pancreatic cancer, and the choice of imaging modality should be based on individual patient needs and institutional expertise.
From the Research
Imaging Modalities for Radiation Treatment Planning in Pancreatic Cancer
The following imaging modalities are recommended for radiation treatment planning in pancreatic cancer:
- Magnetic Resonance Imaging (MRI) 2: offers considerable advantages in optimizing soft tissue delineation and is an ideal modality for imaging and delineating a gross tumor volume (GTV) within the pancreas.
- Computed Tomography (CT) 3, 4: has evolved as an effective cross-sectional imaging modality for benign and malignant pancreatic diseases, and is regarded as the standard imaging in diagnosing pancreatic cancer.
- Positron Emission Tomography (PET) 5, 4: can be used in the diagnosis of pancreatic cancer, and is useful in assessing tumor viability, monitoring tumor response to treatment, and detecting distant metastases.
- Multimodality imaging 5: combining different imaging modalities such as DCE-MRI, ADC-DWI, and FDG-PET can provide more accurate information for radiation therapy planning.
Considerations for Imaging Modalities
When choosing an imaging modality for radiation treatment planning in pancreatic cancer, the following factors should be considered:
- Soft tissue contrast: MRI offers better soft tissue contrast than CT, making it ideal for delineating the GTV.
- Tumor size and location: CT and MRI can detect tumors larger than 1 cm, while smaller tumors may be more difficult to detect.
- Organ at risk (OAR) delineation: MRI-based OAR volumes are generally smaller than those based on CT.
- Motion management: imaging modalities that can account for tumor motion, such as 4D-CT, can improve the accuracy of radiation therapy planning. 6