Essay Submitted in partial fulfi llment of the M.Sc. Degree in diagnostic radiology

BY

WALEED AHMED ABDO ALRAYIS

M.B.B.Ch

Role of MSCT in evaluation of pancreatic tumors with prediction of

vascular invasion and its resectability

Prof. Dr. Tarek Mohammed El Zayyat

Dr. Amr Ahmed Mostafa

Supervised by

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INTRODUCTION

CT is the most commonly used imaging modality for the detection and preoperative staging of pancreatic tumors.

21-55% of patients were incorrectly diagnosed as having respectable tumor on CT only to be found to have un-resectable tumor at surgery ,most often, this type of misdiagnosis is due to undetected vascular invasion , small Peritoneal implants, or small hepatic metastases.

MDCT facilitates the generation of multiplanar reconstructions, such as curved planar reformations, providing the potential to improve the detection and staging of pancreatic tumors

ANATOMY OF THE PANCREAS

PATHOLOGY OF PANCREATIC NEOPLASM

The term “pancreatic cancer” usually refers to ductal adenocarcinoma. While this entity accounts for 85% of primary pancreatic tumors, a variety of other neoplasms can arise from the range of cell types present in the normal pancreas (ducts, acini and islets).

Most patients do not develop symptoms until after the cancer has metastasized.

Common presenting symptoms epigastric pain, unexplained weight loss, painless jaundice, light clay colored stool, dark urine, pruritus, and Nausea.

It represents about 85% to 90% of pancreatic tumors.

Ductal adenocarcinomas are mainly located in the head of the pancreas (60%), body of the pancreas (13%), tail of the pancreas (5%) and diffuse involvement (22%)

Ductal adenocarcinoma

TECHNICAL CONSIDERATION OF MDCT OF THE PANCREAS

Successful imaging detection of pancreatic neoplasms is significantly improved by the use of pancreas specific examination protocols.

MDCT should be used whenever possible to evaluate suspected pancreatic neoplasms because it enables large volume coverage in short imaging times.

In the assessment of pancreatic tumors, there are four basic components:

(a) detection of the pancreatic tumor; (b) assessment of peripancreatic arteries; (c) assessment of peripancreatic veins; (d) detection of extra pancreatic

metastases (most frequently liver)

Clinical IndicationsPatient PreparationRadiation DoseContrast MaterialAcquisition Timing and Phases of

Imaging:Reconstruction and post-processing

imaging modalities.

MDCT Pancreatic Protocol Components:

All patients suspected of pancreatic neoplasm

Acute pancreatitisChronic pancreatitisEvaluation of jaundiceSevere epigastric painRecent onset of diabetesWeight loss

Clinical indications:

Fast at least 6 hours before the examination.

Spasmolytic drug to dilate duodenum and to impair peristaltic contractions of the stomach and duodenum.

If spasmolytic is contraindicated the examination may be performed while the patient remains in the right lateral decubitus position.

Patient preparation

Assures the scanner will deliver the minimum dose necessary to maintain the noise level in the images that the user finds acceptable for diagnosis.

Tube current modulation software can reduce delivered dose by a factor of 30%.

Patient radiation exposure decreases with increasing numbers of detector rows due to increased x-ray dose efficiency.

Radiation Dose

Oral contrast material:Critical to delineate the bowel loops adjacent

to the pancreas and within the abdomen.Neutral contrast agent is preferable.

Intravenous contrast material:Non-contrast enhanced studies are

insufficient for detection of neoplasms, evaluation of peripancreatic vasculature or detection of distant metastases.

Peak hepatic enhancement and peak pancreatic parenchymal enhancement are directly related to the injection rate.

Peak hepatic enhancement and peak pancreatic parenchymal enhancement are directly related to the injection rate.

Contrast Material

A challenge of pancreatic imaging is that the timing of peak pancreatic enhancement differs from that of other organs in the abdomen, most notably the liver.

Most radiologists employ a dual-phase protocol which incorporates a pancreatic parenchymal phase and a portal venous (hepatic parenchymal) phase

A single-phase acquisition can be obtained with a 4-detector row scanner if careful scan timing is used.

Acquisition Timing and Phases

Scan timing can be determined with two methods:

A. Automatic pumping

B. Bolus tracking technique

Acquisition Timing and Phases

Other concept in pancreatic imaging says that contrast-enhanced imaging of the pancreas is performed in three distinct phases:

The early arterial phase

Delayed arterial phase or the pancreatic phase

Portal venous phase.

Acquisition Timing and Phases

Axial images

Multiplanar Reconstruction

Curved Multiplanar Reconstruction

Maximum Intensity Projection

Volume Rendering Technique

Reconstruction and post-processing imaging modalities

Current criteria for resectability include

Absence of distant metastases. Lack of evidence of tumor involvement of major

arteries.

If there is venous invasion suitable segment of portal vein (above) and superior mesenteric vein (below) the site of venous involvement to allow for venous reconstruction.

Prediction of vascular invasion

Lu et al, grade system for predicting vascular invasion

Category Description Comment

Grade 0 No contiguity of tumor with a vessel Vascular invasion in 0% of cases

Grade 1 Tumor contiguous with <25% of the circumference of a vessel

Vascular invasion in 0% of cases

Grade 2 Tumor contiguous with 25–50% of the circumference of a vessel

Vascular invasion in 57% of cases

Grade 3 Tumor contiguous with 50–75% of the circumference of a vessel

Vascular invasion in 88% of cases

Grade 4 Tumor contiguous with >75% of the circumference of a vessel or any vessel constriction

Vascular invasion in all cases

Grading system by Layer et alCategory Description Comment

Type A Fat plane separates the tumor and/or the normal pancreatic parenchyma from adjacent vessels

Overall resection rate: 100%. Resection rate without venous resection: 95%. Conclusion: ‘‘Lesions with type A and B appearances are likely to be resectable lesions’’

Type B Normal parenchyma separates the hypo dense tumor from adjacent vessels

Overall resection rate: 100%. Resection rate without venous resection: 95%. Conclusion: ‘‘Lesions with type A and B appearances are likely to be resectable lesions’’

Type C Hypo dense tumor is inseparable from adjacent vessels, and the points of contact form a convexity against the vessels

Overall resection rate: 89%. Resection rate without venous resection: 55%. Conclusion: ‘‘Lesions of type C vascular involvement should be operated on with an intention to resect the tumor, but the tumor may or may not adhere to the wall of the vessels’’

Type D Hypo dense tumor is inseparable from adjacent vessels, and the points of contact form a concavity against the vessels or partially encircle the vessels

Overall resection rate: 47%. Resection rate without venous resection: 7%. Conclusion: ‘‘Lesions of type D vascular involvement would require pancreatic resection with a plan to perform venous resection and venous graft or patch or would be unresectable for surgeons who do not have that appearance’

Type E Hypo dense tumor encircles adjacent vessels, and no fat plane is identified between the tumor and the vessels

Overall resection rate: 0%. Resection rate with outvenous resection: 0%. Conclusion: ‘‘Lesions of the type E and F vascular involvement are not likely to be resectable’’

Type F Tumor occludes the vessels Overall resection rate: 0%. Resection rate without venous resection: 0%. Conclusion: ‘‘Lesions of the type E and F vascular involvement are not likely to be resectable’’

Grading system by Raptopoulos et al.

Category Description Comment

Grade 0 Normal, with a fat plane or normal pancreas between the tumor and the vessel

100% resectable

Grade 1 Loss of fat plane between the tumor and the vessel, with or without smooth displacement of the vessel

100% resectable

Grade 2 Flattening or slight irregularity of one side of the vessel

92 % resectable

Grade 3 Encased vessel with tumor extending around at least two sides (two-thirds of the perimeter), altering its contour and producing concentric or eccentric narrowing of the lumen

The recommended threshold for predicting vascular invasion. In this study, resection was performed in1 of 10 patients with grade 3 findings, but tumor along per vascular neural bundles was present at resection margins.

Grade 4 Occluded vessel No attempted surgery

Grading system by Raptopoulos et al.

CASES

DISCUSSION

Assessment of vascular invasion is an important parameter for determining resectability of pancreatic cancer.

The introduction of MDCT and real-time 3D volume-rendering software has greatly improved the visualization of the pancreas and adjacent vasculature.

An examination protocol should provide maximal

differentiation between normal and abnormal tissue.

From the point of view of the detection of vascular invasion, many studies have evaluated CT.

In a study by Wen Yi Zhao et al, The pooled sensitivity and specificity of CT in diagnosing vascular invasion were 77% and 81%. Since CT technology improved in different periods, in the recent five years (2004-2008) CT has shown a higher diagnostic accuracy, and the pooled sensitivity and specificity increased to 85% and 82%, respectively.

Subgroup analysis of CT studies was made to determine the involvement of different vessels, and the pooled sensitivities for the invasion of the venous system, portal vein, and arterial system were 75%, 75%, and 68%, and the pooled specificities were 84%, 91%, and 92%, respectively. For CT imaging with vascular reconstruction, the pooled sensitivity and specificity were 84% and 85%, higher than the estimates in studies without reconstruction.

SUMMARY

Thin-sections MDCT is an accurate technique for the diagnosis and assessment of the resectability in patient with a suspected pancreatic neoplasm.

The advantages of multidetector volumetric CT allow comprehensive preoperative assessment of pancreatic carcinoma. Carefully- timed scan acquisition maximizes the difference in attenuation between the neoplasm and the pancreatic parenchyma and allows accurate staging as well as assessment of local resectability

CONCLUSION

In conclusion the MDCT technique remains the first-line imaging modality in the evaluation of the majority of patients with suspected pancreatic disease because of low cost, greater widely used and easy technical approaches and its great value in staging pancreatic masses and predicting vascular invasion which helps in choosing the appropriate management for each case.

THANK YOU