Pancreatic Cancer Imaging

Updated: Aug 18, 2022
  • Author: Mahesh Kumar Neelala Anand, MBBS, DNB, FRCR; Chief Editor: John Karani, MBBS, FRCR  more...
  • Print

Practice Essentials

Pancreatic cancer is the second most common cause of death from cancer. Prognosis has remained largely unchanged over the last 2 decades. Pancreatic cancer has a 5-year survival rate of 2-9%, and more than 90% of cases of pancreatic cancer are identified at the late stage of disease; Diagnostic imaging shows the tumor and its relationship to surrounding vasculature and reveals the possibility of resection. [1]

Guidelines on pancreatic cancer screening have been issued by a number of organizations, including the US Preventive Services Task Force (USPSTF), American Academy of Family Physicians (AAFP), and the International Cancer of the Pancreas Screening (CAPS) Consortium. [2, 3, 4, 5]

(Radiologic characteristics of pancreatic adenocarcinoma are shown in the images below.)

Scan from axial multisection CT in a patient with Scan from axial multisection CT in a patient with pancreatic cancer shows a low-attenuating mass in the head of the pancreas, adjacent to the superior mesenteric vein (SMV). Image courtesy of Dr Zahir Amin.
Coronal reconstruction shows a mass encasing and n Coronal reconstruction shows a mass encasing and narrowing the portal vein. Image courtesy of Dr Zahir Amin.

Imaging modalities

Tumors may arise from pancreatic ducts (99%) or from acinar cells (1%). The fact that over 90% of pancreatic cancer cases are discovered in the late stage emphasizes the role of radiology in early detection and determination of resectability of the tumor. The role of diagnostic imaging is to demonstrate the tumor and its relationship to surrounding vasculature, and the results determine the possibility of resection. 

Much debate surrounds the sensitivity and specificity of imaging investigations in the diagnosis and staging of pancreatic carcinoma. Imaging plays an essential role in surveillance, diagnosis, resectability evaluation, and treatment response evaluation. [6]  Multisection computed tomography (CT) scanning is generally accepted to be the first line of investigation in a patient with suspected pancreatic cancer. The best imaging technique is determined by local availability and expertise, but this will nearly always be spiral CT (ideally multisection CT). The reasons for this preference include its wide availability, speed, thin sections, optimal enhancement, high spatial resolution, and consistently good images. [7, 8, 9, 10]

In high-risk patients, magnetic resonance imaging (MRI) and positron emission tomography-computed tomography (PET/CT) may further guide treatment decisions. [11]  Some studies comparing CT and MRI have found detection and assessment of resectability to be similar. [12] However, MRI takes longer, costs more, is more complex, and is limited by artifacts. MRI probably is most often used for problem solving; that is, if the mass is not seen on CT and US, MRI can be used to evaluate the pancreas in obstructive jaundice. MRI is also helpful in evaluating and characterizing liver lesions in patients with pancreatic cancer.

The importance of good CT technique cannot be overemphasized; key elements include the following: oral water as negative intraluminal contrast, 120 to 150 mL of iodinated contrast material administered intravenously at a rate of 3 to 4 mL/s, and scanning with thin (2-3 mm) collimation during the pancreatic parenchymal phase (at 25-35 s), with scanning performed at 60 to 70 s during the liver phase. [13, 14]

If the patient is clinically jaundiced and if biliary ductal dilatation is demonstrated on ultrasonographic (US) examination, endoscopic retrograde cholangiopancreatography (ERCP) is the next investigation of choice, with a view toward a drainage procedure. ERCP reliably reveals the point of obstruction. [15]

Ultrasonography is often the initial test in symptomatic patients. US is used for diagnosis rather than for staging, although liver metastasis and ascites may be seen. Significant technical improvements in US have led to its use for problem solving in thin patients. Portal venous involvement may be more apparent on sonography than on CT and/or MRI, and liver lesions can be characterized as cystic or solid. [7]

For detection and staging of small tumors, endoscopic US (EUS) can be reliable when performed by experienced imagers. Researchers have reported higher sensitivity and specificity with EUS than with other modalities, but study findings probably reflect the use of suboptimal CT and MRI techniques. Evidence suggests that EUS is similar to CT for diagnosis and staging of pancreatic cancer. However, EUS requires special endoscopic skills and expertise and is not readily available worldwide. [7, 16]

EUS-guided fine-needle aspiration (FNA) is safe and effective, especially for pancreatic head masses. EUS-guided FNA has sensitivity and specificity similar to CT-guided FNA cytology (FNAC).

Kamisawa et al found that diffusion-weighted MRI (DWI) can be used to differentiate autoimmune pancreatitis (AIP) from pancreatic cancer. In a study of 13 patients with AIP and 40 patients with pancreatic cancer, pancreatic cancers were detected as high-signal intensity areas, which were diffuse, solitary, or multiple in patients with AIP, but solitary in patients with pancreatic cancer. Pancreatic cancer more often had a nodular shape, while AIP more often had a longitudinal shape. Apparent diffusion coefficient (ADC) values were significantly lower in AIP than in pancreatic cancer, and an optimal ADC cutoff value of 1.075 x 10-3 mm2/s could be used to distinguish AIP from pancreatic cancer. [17]

In a study by Zaheer et al, findings found to be helpful for diagnosing AIP, versus pancreatic adenocarcinoma (PA), were diffuse enlargement, parenchymal atrophy, and the absence of pancreatic duct dilatation and focal mass. Findings helpful for diagnosing PA were focal mass and pancreatic ductal dilatation. The authors noted that misdiagnosis of PA in patients with AIP was due to focal mass, pancreatic duct dilatation, and pancreatic atrophy, whereas misdiagnosis of AIP in patients with PA was due to absence of atrophy, presence of diffuse enlargement, and peripancreatic halo. [18]

According to a study by Takakura et al, DWI and multidetector-row CT were found to be equivalent in distinguishing pancreatic cancer in high-risk patients with main pancreatic duct dilation. The accuracy rates were 84% and 86%, respectively. The use of combined MR cholangiopancreatogrpahy and DWI allowed the authors to establish a high-risk population and detect tumors without a contrast medium. [19]

In a meta-analysis of CT and MRI for differentiation of autoimmune pancreatitis (AIP) from pancreatic ductal adenocarcinoma (PDAC), Ha and associates reported that the sensitivity and specificity for CT were 59% and 99%, respectively, and those for MRI were 84% and 97%, respectively. [20]

Limitations of techniques

Detection of a mass on imaging is nonspecific, and 5-15% of pancreatic resections show benign pathology.

Transabdominal US (TAUS) has relatively poor sensitivity, and its outcomes are not satisfactory for assessment in approximately 20% of patients because of a poor acoustic window due to bowel gas.

MRI is sensitive for detection and staging of pancreatic cancer, with sensitivity and specificity similar to those of multisection CT. MRI involves expensive equipment and meticulous attention to the image technique. Other technical limitations involve movement artifacts due to bowel peristalsis and breathing. Because high sensitivity and specificity of MRI in detecting and staging small tumors have not been achieved consistently and universally, debate continues about the superiority of MRI over CT.

Multisection CT should be used first for detection of pancreatic adenocarcinoma. When CT findings are negative, MRI or EUS should be performed for detection and for assessment of resectability. Although conventional angiography is obsolete in primary staging, it is occasionally required to assess peripancreatic vessels before surgery. Modern multislice CT scanners are capable of excellent depiction of arterial and venous branches. The role of MR angiography (MRA) in assessment of mesenteric vessels prior to surgery is not firmly established, although study results are encouraging.



Plain radiographs have no role in establishing a firm diagnosis of pancreatic carcinoma. Pancreatic calcifications may be seen concurrently in approximately 2% of patients who have chronic pancreatitis complicated by pancreatic carcinoma.

Upper GI barium studies may reveal an extrinsic impression of the mass on the posteroinferior aspect of the antrum of the stomach. This is known as the antral pad sign. The medial margin of the descending duodenum may be pulled medially at the level of the ampulla, forming a reversed-3 appearance. This is known as the Frostberg 3 sign. Infiltration of the duodenal mucosa may cause a spiculated appearance with irregularity and thickening of the duodenal mucosa. These changes may represent a desmoplastic response to malignant disease. A nodular mass with an ampullary carcinoma may be observed.

Barium enema studies may reveal loss of a normal haustral pattern from haustral padding along the transverse colon. These studies may show infiltration of the colon with an irregular or serrated contour to the bowel margin along the transverse colon, up to the level of the splenic flexure. Tethering of colonic or small bowel margins resulting in asymmetry may result from intraperitoneal seeding of the pancreatic carcinoma.

In the presence of jaundice, barium studies have reasonably good specificity. The disease is usually advanced by the time the mass produces characteristic signs on barium studies. False-positive results may reflect a pseudocyst or other mass lesions producing a similar appearance on the duodenal C-loop. Small masses may produce false-negative results.


Computed Tomography

Multidetector CT is preferred for both staging and assessing pancreatic adenocarcinoma resectability. MRI may play an importand adjunctive role. [8, 21, 9, 10]   In a study of 3567 patients with pancreatic ductal adenocarcinoma, sensitivity, specificity, and diagnostic accuracy were 90%, 87%, and 89%, respectively, for CT. [7]  Because of a lack of visible attenuation difference between the tumor and the pancreatic parenchyma, up to 11% of ductal adenocarcinomas may not be detected by MDCT. [22]  Emerging techniques such as dual-energy CT and texture analysis of CT and MRI may have potential in improving lesion detection and characterization and in treatment monitoring. [8]

Features suggestive of underlying pancreatic cancer include the following: alterations in morphology of the gland with abnormalities of CT attenuation values, obliteration of peripancreatic fat, loss of sharp margins with surrounding structures, involvement of adjacent vessels and regional lymph nodes, pancreatic ductal dilatation, pancreatic atrophy, and obstruction of the common bile duct (CBD). [23, 24, 25, 26, 27, 28, 29, 30]  

(See the images below.)

Scan from axial multisection CT in a patient with Scan from axial multisection CT in a patient with pancreatic cancer shows a low-attenuating mass in the head of the pancreas, adjacent to the superior mesenteric vein (SMV). Image courtesy of Dr Zahir Amin.
Coronal reconstruction shows a mass encasing and n Coronal reconstruction shows a mass encasing and narrowing the portal vein. Image courtesy of Dr Zahir Amin.

Abnormal morphology of the gland such as change in size, shape, or attenuation values may involve focal or diffuse enlargement, a focal lobulated eccentric mass, or decreased attenuation of the mass, respectively.

Macari et al determined that at portal venous phase dual-source dual-energy CT, pancreatic malignant tumor conspicuity is greater at 80 kVp than with 120-kVp acquisition simulated with a weighted-average acquisition. The mean difference in attenuation for pancreatic tumors and adjacent normal pancreas was 83.27 +/- 29.56 (SD) HU at 80 kVp and 49.40 +/- 23.00 HU at weighted-average 120 kVp. At 80 kVp, contrast-to-noise ratio was significantly higher, as was duct visualization. [31]

Focal enlargement

A change in the size of the mass is usually focal; focal enlargement is seen in about 96% of patients with pancreatic adenocarcinoma. Size is an unreliable indicator of tumor, as a normally sized pancreatic head is consistent with carcinoma of the pancreas when atrophy of the body and tail is observed. This feature may be seen in pancreatic carcinoma in as many as 20% of patients. Focal enlargement also can occur in benign disease; thus, it is a nonspecific finding. Diffuse enlargement is uncommon and usually suggests pancreatitis.

By the time it has grown to produce a focal enlargement, the mass has often progressed to an inoperable stage. Some small tumors may cause biliary ductal obstruction and may appear early. A change in the shape of the gland in the absence of enlargement is a more important sign and may suggest underlying tumor. Evidence of fatty interstices within the mass suggests focal lobulation is of the normal pancreas. If fatty interstices are absent, and if the mass is completely solid, it is more likely to be abnormal, and biopsy is recommended.

The normal pancreas has an attenuation value of 30 to 50 HU. A central zone of decreased attenuation is noted in 83% of patients. Margins of the low-attenuating mass usually are poorly defined and correspond to a hypovascular scirrhous tumor. Pancreatic tumor also may undergo central necrosis to produce low density; the tumor then simulates a small pseudocyst.

Needle biopsy is occasionally needed to differentiate necrotic tumor from pseudocyst as a result of focal pancreatitis. Pancreatic tumors are hypovascular and are best demonstrated with intravenous administration of contrast material and with acquisition of images across the mass in the parenchymal arterial phase. The mass is seen as a low-attenuating lesion in the brightly enhancing surrounding parenchyma.


Ductal dilatation occurs in 58% of patients. Among patients with ductal dilatation, 75% have dilation of both pancreatic ducts and biliary ducts. Pancreatic ductal dilatation proximal to the obstructing tumor is detected in approximately 88% of pancreatic head tumors and in 60% of pancreatic body neoplasms. In pancreatic cancer, the duct measures 5 to 10 mm and may be smooth or beaded.

The pancreatic duct is dilated to more than 50% of the anteroposterior diameter of the gland in pancreatic cancer because of atrophy of the gland. In chronic pancreatitis, duct dilatation is less than 50% of the anteroposterior (AP) diameter. Loss of normal peripancreatic fat-plane attenuation is suggestive of extension of tumor beyond the margins of the gland with invasion. The peripancreatic fat shows an increase in attenuation. Extension to involve peripancreatic fat and surrounding structures is observed on CT scans in 92% of patients.


Vascular encasement usually determines unresectability and is seen on CT as narrowing, displacement, or obliteration of the vessel lumen by surrounding tumor. Collateral venous circulation may be observed from venous occlusion with contrast-enhanced vessels around the stomach and the splenic hilum. Arterial encasement is usually clearly visible on good-quality CT scans, and angiography is unnecessary.

The arterial involvement, in descending order of frequency, is as follows: superior mesenteric, splenic, celiac, hepatic, gastroduodenal, and left renal. Spread to surrounding organs may involve the spleen, stomach, duodenum, splenic flexure of the colon, transverse mesocolon, porta hepatis, kidney, and spine. Local, posterior tumoral extension into the porta hepatis is seen in approximately 68% of patients. The presence of ascites indicates peritoneal metastatic disease with implants. Ascites is seen in 13% of patients with pancreatic cancer. The peritoneal deposits are poorly demonstrated by means of CT.

Regional lymph node metastasis has been reported to vary from 38 to 65%. Metastasis to liver is the most common in pancreatic cancer, occurring in approximately 17-55%. The CBD is displaced anteriorly and medially when the pancreatic mass causes distal ductal obstruction. Intrahepatic ductal dilatation and gall bladder dilatation can be demonstrated.

Degree of confidence

CT is the most widely used and most sensitive test for evaluation of the pancreas for pancreatic carcinoma. Dynamic CT has a detection rate of approximately 99%. Multisection CT should be the first-line study used for detecting this tumor and for evaluating its resectability.

According to a study by Raman et al, MDCT can accurately stage patients with pancreatic cancer, but its accuracy in excluding distant metastatic disease depreciates over time. The authors concluded from their findings that patients should undergo a repeat MDCT within 25 days of any planned definitive operative intervention for pancreatic cancer to avoid unexpectedly finding metastatic disease at surgery. [32]

Cysts or focal pancreatitis can occasionally cause problems in diagnosis, and it can produce false-positive and false-negative results.


Magnetic Resonance Imaging

The role of magnetic resonance imaging (MRI) in the management of pancreatic adenocarcinoma has yet to be firmly established. Compared with other modalities, MRI appears to be more valuable for staging the extent and spread of pancreatic carcinoma than for detecting lesions smaller than 2 cm. The ability of MRI to identify pancreatic adenocarcinoma largely depends on demonstration of deformity of the gland, as reflected in its size, shape, contour, and signal intensity characteristics. [33, 34, 35, 36]

The criteria for suspicion of a mass are similar to those applied with CT. Rarely, nonenhanced MRI reveals a carcinoma of the pancreas before it deforms the gland. However, when such a feature is encountered, the dilemma of needing to distinguish the focal abnormality from focal pancreatitis becomes challenging.

Alteration in signal characteristics is less specific for tumor because tissue relaxation times between pancreatic cancer, pancreatitis, and controls can overlap significantly. Mean T1 relaxation time of the normal pancreas is 507 ms ± 98, and T1 relaxation time of pancreatic tumor is about 660 ms ± 115. T2 relaxation time of normal pancreas is 59 ms ± 9, and T2 relaxation time of pancreatic tumor is 67 ms ± 29.

The normal pancreas is of low signal intensity on T1-weighted images and of intermediate signal intensity on T2-weighted images, with a variable amount of fat in the gland parenchyma.

Newer techniques to obtain images by using breath-hold techniques, advances in body coil technology, and faster techniques have made it possible to acquire images with excellent spatial resolution.

T1-weighted fat-suppressed spin-echo and single–breath-hold gradient-echo fast low-angle shot (FLASH) sequences with gadolinium enhancement are valuable for tumor detection. The mass is shown as a low-intensity lesion within a homogeneously enhancing normal pancreatic gland. Intravenous gadolinium-enhanced FLASH images obtained 10 s after contrast enhancement has proven to be more sensitive in demonstrating tumor than other techniques.

Gadolinium-based contrast agents have been linked to the development of nephrogenic systemic fibrosis (NSF) or nephrogenic fibrosing dermopathy (NFD). This disease has occurred in patients with moderate to end-stage renal disease after they were given a gadolinium-based contrast agent to enhance MRI or MRA scans. NSF/NFD is a debilitating and sometimes fatal disease. Characteristics include red or dark patches on the skin; burning, itching, swelling, hardening, and tightening of the skin; yellow spots on the whites of the eyes; joint stiffness with trouble moving or straightening the arms, hands, legs, or feet; pain deep in the hip bones or ribs; and muscle weakness.

Magnetic resonance cholangiopancreatography (MRCP) is as sensitive as ERCP and may prevent inappropriate exploration of the pancreatic and bile ducts in patients with suspected pancreatic carcinoma in whom interventional endoscopic therapy is unlikely. The sensitivity of MRCP has been estimated at 84%, with specificity of 97% for pancreatic cancer. Findings are complementary to those of ERCP and percutaneous transhepatic cholangiography (PTC).

It has been difficult to prove consistent results when MRI is used to detect tumor and to determine its resectability. The degree of confidence with MRI is less than that with CT because of wide variability in MRI techniques and limitations from motion artifacts. Some studies have confirmed greater reliability with MRI when meticulous technique is applied.



Lesions may have a variable appearance on ultrasonography (US). They may be hypoechoic, isoechoic, or hyperechoic to the normal pancreas. Pancreatic ductal dilatation and biliary ductal dilatation are easily seen in patients with a tumor in the head of the pancreas that causes an obstruction. [37, 38]

Lymphadenopathy, the relation of the tumor to peripancreatic vessels, and tumor margins are revealed less reliably with US than with other modalities. The mass appears as an irregular hypoechoic mass that infiltrates a bright pancreatic parenchyma.

The degree of confidence may be improved when endoscopic ultrasound (EUS) is used to detect tumors smaller than 2 cm.

US equipment has improved considerably, and this is likely to have reflected on its sensitivity for detecting pancreatic masses. [16] Transabdominal ultrasound (TAUS) examination is still less sensitive than other modalities for detection of pancreatic malignancies smaller than 2 cm. TAUS has been noted to have a sensitivity of 70% and a specificity of 95% for the diagnosis of pancreatic malignancy.

The specificity of EUS for differentiating benign from malignant lesions based on US appearance alone remains unsatisfactory. EUS has high sensitivity and specificity for pancreatic cancer, with overall staging accuracy greater than 80%. The possibility of performing EUS-guided fine-needle aspiration (FNA) significantly improves both diagnostic and staging capability of EUS. EUS-guided FNA is safe, with morbidity less than 2%.

In a retrospective study, Tanaka et al performed contrast-enhanced US and contrast-enhanced CT and found that the sensitivities of contrast-enhanced US and contrast-enhanced CT in characterizing adenocarcinoma were 97.0% and 77.0% for all 100 adenocarcinoma cases, 100% and 76.7% for 43 small cancers (≤20 mm), 100% and 58.3% for 12 smaller cancers (≤10 mm), and 100% and 72.2% for 36 stage IA cancers, respectively. [39]

In a review of 63 patients, the assessment of tumor resectability with EUS was compared with an assessment with MRI. The sensitivity for EUS for resectability was 61%, and that of MRI was 73%. When EUS and MRI were used together, the sensitivity was 89% for resectability.


Nuclear Imaging

Positron emission tomography (PET) is based on functional changes in the pancreatic cancer cells caused by enhanced glucose utilization, as in any other malignant tissue. With 2-[fluorine 18]-fluoro-2-deoxy-D-glucose (FDG), PET can be used to identify pancreatic cancer and to differentiate it from chronic pancreatitis, with a sensitivity of 85-98% and a specificity of 53-93%. [40, 41, 42]

PET maps metabolic activity at a molecular level; therefore, uptake of FDG by neoplastic tissue is dependent on factors such as tissue oxygenation, regional blood flow, and a peritumoral inflammatory reaction.

PET is also useful in staging and determination of resectability of the tumor at the time of initial diagnosis. PET also has been shown to be an effective tool in the follow-up care of patients with pancreatic cancer. In more than 50% of patients in one study, additional information using PET influenced the therapeutic procedure. [43, 44, 45]

FDG PET/CT has been found to be useful when contrast-enhanced computed tomography (CECT) is equivocal and to be able to detect recurrence in patients with normal CA 19-9. [42]

In a retrospective study, Furtado et al evaluated whether PET/ MRI elicited treatment modifications in pancreatic ductal adenocarcinoma (PDAC) when compared with standard of care imaging (SCI). Twenty-five patients underwent 37 PET/MRIs, and 49% (18/37) of PET/MRI scans were found to have changed clinical management. [46]



Angiography is an invasive procedure that demands considerable operator skill and high-quality radiographic technique. Selective arteriograms obtained with injection of iodinated contrast through the celiac axis and the superior mesenteric artery with some magnification techniques may be required to depict detail. [30, 47]

Pancreatic carcinoma is relatively avascular and is associated with neovascularity in 50% of patients. Pancreatic malignancy usually reveals arterial encasement of peripancreatic vessels or, actually, of vessels within the pancreas. Vessels involved include the following, in descending order of frequency: superior mesenteric artery (33%), splenic artery (14%), celiac artery (11%), hepatic artery (11%), gastroduodenal artery (3%), and left renal artery (0.6%).

When the disease is advanced, venous occlusions and venous encasement with collateral vessels may be observed. Superior mesenteric vein encasement by tumor is seen in 23%, and the splenic vein is encased by tumor in 15%, with portal vein infiltration in 4%.

Complete occlusion of the splenic vein is seen in 34%, and complete occlusion of the superior mesenteric vein is seen in 10%. Pancreatic carcinoma can be distinguished from pancreatitis. Evidence of hypervascularity with typical beaded changes of alternating narrowing with dilatation of internal pancreatic vessels is a feature of pancreatitis.

The mesenteric circulation has been evaluated via MRA, and this has been compared with conventional angiography. Excellent agreement has been noted between MRA and conventional angiography. Gadolinium-enhanced MRA is useful for evaluating proximal mesenteric arteries and portal hypertension. Conventional angiography is needed for evaluation of intrahepatic arteries and branches of the superior mesenteric artery.

Helical CT angiography shows useful information about peripancreatic vessels in patients with pancreatic carcinoma. The addition of helical CT angiography improves the radiologist's ability to predict the resectability of pancreatic tumors.