Comparison Between Dual Energy/Subtraction CT With MRI for the Identification of Predictors of Malignancy in Cystic Pancreatic Lesions
Comparison Between Dual Energy/Subtraction CT With MRI for the Identification of Predictors of Malignancy in Cystic Pancreatic Lesions
Cystic pancreatic lesions are increasingly detected incidentally in imaging studies,
 reportedly in up to 45% of the abdominal Magnetic Resonance (MR) examinations. The majority
 of these lesions have potential to become cancer, therefore requiring surgery or imaging
 follow-up to monitor the development of features indicative of malignant transformation.
 Abdominal MR is the current standard of care for the follow-up of pancreatic cysts (PCs).
 However, MR is expensive and access is limited, In our institution, more than 35 MR studies
 for assessment of PCs were performed each month in 2015, placing a significant burden on the
 health care system that includes contributing to longer MR wait times for other indications.

 The investigators will compare MR to two new computed tomography (CT) techniques - dual
 energy CT (DECT) and Subtraction imaging - with regards to their ability to detect features
 associated with increased risk of malignancy (enhancing septa and mural nodules) in PCs. For
 cases where there is disagreement between these 2 CT techniques and MR, histopathology of the
 surgical specimen or the results of Endoscopic Ultrasound (EUS) will serve as reference
 standard.

 Using DECT or Subtraction instead of MR for the assessment and follow-up of PCs would save
 significant healthcare costs and MR slots, which could be released to other indications and
 to reduce waiting times. Furthermore, if DECT and/or Subtraction imaging end up demonstrating
 to be superior to MR for this purpose, patients with cystic pancreatic lesions could have a
 direct benefit.
With the rapid technological advancement, growth and widespread use of cross-sectional
 imaging, there has been increased detection of pancreatic cystic lesions (PCs). The reported
 incidence of pancreatic cysts varies widely, with some studies reporting incidental
 pancreatic cysts detected in 0.7-2.6 % of asymptomatic adults undergoing imaging. The
 incidence reportedly increases with age with a greater than 8% detection rate in those over
 age 80 years. The prevalence of a cystic pancreatic lesion in one autopsy series was as high
 as 24%. For MRI, the frequency of detection of a pancreatic cyst is significantly higher than
 that of CT, with a reported prevalence of 13-45 % for MRI. Consequently, there has been a
 significant increased number of MRs ordered for follow-up of these lesions. In our
 institution, more than 35 MR studies for assessment of PCs were performed each month in 2015.
 This represents greater than 5% of all abdominal/pelvic MR examinations, and this number
 appears to be growing. The impact on health care system - particularly on health care costs
 as well as MR waiting times for patients with other conditions - is significant. For
 instance, in our institution, the average waiting period in 2015 for an outpatient MR
 enterography for patients with Crohn's disease is over 6 months.

 Recently, dual energy CT (DECT) has proven to be robust and clinically useful for many
 abdominal applications (including solid pancreatic masses). The investigators expect V2R
 kVmAS DECT and Subtraction imaging - two promising techniques which have scarcely been
 investigated in abdominal disease processes in the literature - to prove to be very useful
 for the characterization of pancreatic cysts and to demonstrate comparable diagnostic
 accuracy compared to MR

 The aim of the study is to investigate whether optimized DECT and/or Subtraction imaging
 protocols allow for characterization of cystic pancreatic lesions (in particular, the
 presence of enhancing septa and mural nodules) with a diagnostic accuracy equivalent to or
 greater than MRI.

 This is a prospective, single-institution study in patients who are being evaluated or
 followed for known pancreatic cystic lesions who are planned for a CT and MRI scan. All MRI
 scans performed during the study period will be monitored prospectively to identify
 consecutive patients undergoing MRI for assessment or follow-up of pancreatic cystic lesions
 and meeting the study inclusion/exclusion criteria.

 Patients will be divided into two groups:

 - Group 1 includes patients who will undergo surgery for their pancreatic cysts: For these
 patients, a pre-operative CT abdomen is routinely performed for surgical planning purposes.
 The treating surgeon will contact the study team to arrange for the CT scan - which will
 include a DECT scan - to be performed on the appropriate scanner.

 - Group 2 includes patients who are undergoing surveillance. For these patients, the standard
 of care is typically to follow these patients annually with serial MRI scans.

 In cases where findings on MRI are in doubt, a CT scan - which will include a DECT scan -
 will be requested as a problem solving tool and part of the standard of care.

 For most patients, a CT scan is not required as part of the standard of care. In these cases,
 patients will be recruited and consented for an additional CT scan - which will include a
 DECT scan - to be performed within 6 months of their MRI. This CT scan is in addition to the
 standard of care. The patient will be recruited at the time of the first follow-up
 appointment with their treating surgeon after their MRI scan.
Inclusion criteria:

 -  Patients of all ethnic groups older than 40 years old

 -  Cystic pancreatic lesions larger than 1 cm documented by MR

 -  Scheduled for surgery (Group 1) or undergoing surveillance (Group 2) for a pancreatic
 cyst by a hepatobiliary surgeon at UHN (University Health Network)

 Exclusion criteria:

 -  Patients with contraindication for contrast-enhanced CT or MRI

 -  Pregnancy

 -  Patients who do not consent to the study

 -  Patients younger than 40 years old or with pancreatic cysts less than 1 cm