The advent of multislice CT, advanced computer workstations, and 3D and postprocessing algorithms has allowed for new perspectives from which to view imaging data. These are especially useful for pancreatic cancer and biliary pathology.
The advent of multislice CT, advanced computer workstations, and 3D and postprocessing algorithms has allowed for new perspectives from which to view imaging data. These are especially useful for pancreatic cancer and biliary pathology. They can be used by the radiologist for problem solving and facilitated communication between the radiologist and the referring clinician, aiding diagnosis, illustrating disease extent, describing staging clearly, and guiding surgical planning.
Acquisition of suitable source images for postprocessing is vital. We acquire 2.5-mm contiguous images for interpretation and reconstruct them to either 1.25 mm every 0.625 mm or as contiguous 0.625-mm images depending on the capabilities of the particular CT scanner being used for postprocessing.
Images are obtained of the entire abdomen during two phases: the peak pancreatic parenchymal phase of enhancement, to maximize visualization of tumor and arteries, and the portal venous phase for liver metastases, veins, and the pancreatic duct.1 Using a rapid injection rate of 4 to 5 cc/sec for 30 seconds, we achieve peak pancreatic enhancement at approximately 40 to 45 seconds after the start of contrast injection. The portal venous phase is approximately 60 seconds after the start. Bolus tracking is used to adjust for cardiac circulation time.2
Multiple techniques are available for postprocessing. Coronal multiplanar reconstructions (also known as raysum) using 2.5-mm-thick slices every 2.5 mm provide excellent visualization of the relationship of tumor to adjacent structures. Maximum intensity projection (MIP) images or angiographic technique volume-rendered images created as a rotating coronally oriented 5-cm slab or semithick 10-mm coronal images every 2.5 mm are useful to display vascular anatomy.
Minimum intensity projection (MinIP) images, 15-mm thick every 2.5 mm in the coronal plane, are useful to show hilar and extrahepatic biliary pathology, the pancreatic duct, and, particularly, side branch dilatation and potential communication with cystic lesions. Curved planar reformations can be very helpful in providing a concise summary of findings. In all cases, images should be reviewed by a radiologist to confirm that they convey information accurately, especially if they are ultimately to be viewed by a nonradiologist.
The approach must vary depending on the problem to be solved.
The presence of a vascular variant, particularly an accessory or replaced right hepatic artery, is important to note because it crosses the surgical field of resection and, in our experience, is often at risk for involvement by pancreatic head tumors (Figure 3). Coronally oriented images are also useful for showing dilated pancreatic duct side branches extending from small cystic lesions, which may help in the suggestion of pseudocysts or side branch intraductal papillary mucinous neoplasms.
Indeed, CT cholangiopancreatography has been shown to have image quality similar to endoscopic retrograde cholangiopancreatography as well as similar accuracy in identifying the level and cause of obstruction.5MR cholangiopancreatography data can also be manipulated using MIP or volume rendering, with selective editing, to provide additional detail regarding the biliary tree. Use of MRCP and MR angiography has been shown to be effective in diagnosing the level of obstruction, arterial ivolvement, and venous invasion.6-8
More complex techniques, such as segmental volume measurements, are useful when techniques like preoperative portal vein embolization are used to predict if the resultant hypertrophy of nonembolized segments is sufficient to preclude significant postoperative morbidity. 9
Postprocessing can also be very helpful in understanding postoperative changes. This approach is especially useful when tumor recurrence, such as in pancreatic cancer, distorts already complex surgical anatomy.
Images can be delivered to the clinician in a variety of ways, including CD, enterprise PACS, dedicated web server with illustrated reports, or even film. The ability to do real-time processing anywhere, such as with thin-client solutions, allows on-demand 3D processing at multidisciplinary conferences to convey complex data to clinicians regarding pancreatic cancer or biliary pathology.
Several postprocessing or 3D techniques allow the radiologist to gain new perspectives from which to view CT and MRI data. These can aid understanding of complex anatomy that would be extremely difficult to obtain from axial images alone, leading to improved diagnosis, staging, and communication of findings.
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9. Abdalla EK, Barnett CC, Doherty D, et al. Extended hepatectomy in patients with hepatobiliary malignancies with and without preoperative portal vein embolization. Arch Surg 2002;137:675-680; discussion 680-681.