Fatih Akisik

Intraductal papillary mucinous neoplasms: Predictors of malignant and invasive pathology

Objective:Determine whether size and other preoperative parameters predict malignant or invasive intraductal papillary mucinous neoplasia (IPMN). Summary Background Data:From 1991 to 2006, 150 patients underwent 156 operations for IPMN. Methods:Prospectively collected, retrospective review of a single academic institutions experience. All preoperative parameters including a detailed radiologic-based classification of IPMN type, location, distribution, size, number, cytology, and mural nodularity were correlated with IPMN pathology. Results:Malignant IPMN was present in 32% of cases, whereas 19% of cases were invasive. IPMN type and main pancreatic duct diameter were significant predictors of malignant IPMN (P < 0.001). Side-branch lesion number was negatively associated with invasive IPMN (P = 0.03). Side-branch size, location, and distribution did not predict IPMN pathology. The presence of mural nodules was associated with malignant and invasive IPMN (P < 0.001; P < 0.02). Atypical cytopathology was significantly associated with malignant and invasive IPMN (P < 0.001; P < 0.001). Multivariate analysis demonstrated mural nodularity and atypical cytopathology were predictive of malignancy and/or invasion in branch-type IPMN. Conclusions:To lower the rate of invasive pathology, surgery should be recommended for fit patients with main-duct IPMN and for branch-duct IPMN with mural nodularity or positive cytology irrespective of location, distribution, or size.

CT vs MRCP: optimal classification of IPMN type and extent.

IntroductionIntraductal papillary mucinous neoplasms (IPMNs) of the pancreas are being diagnosed with increased frequency. CT scanning commonly serves as the primary imaging modality before surgery. We hypothesized MRCP provides better characterization of IPMN type/extent, which more closely matches actual pathology.MethodsOf 214 patients treated with IPMN (1991–2006), 30 had both preoperative CT and MRCP. Of these, 18 met imaging study criteria. Independent readers performed retrospective, blinded analyses using standardized criteria for IPMN type and extent.ResultsA ductal connection was detected on 73% of MRCP scans and only 18% of CT. IPMN type was classified differently in seven (39%); four (22%) of which were read on CT as having main duct involvement where this was not appreciated on MRCP or found on surgical pathology. MRCP showed multifocal disease in 13(72%) versus only 9(50%) on CT. A different disease distribution was seen in 9(50%). Finally, 101 branch lesions were identified on MRCP compared to 46 on CT.ConclusionsCT falls short of MRCP in detecting a ductal connection, estimating main duct involvement, and identification of small branch duct cysts. These factors influence diagnostic accuracy, cancer risk stratification and operative strategy. MRCP should be employed for optimal management of patients with IPMN.

Usefulness of diffusion-weighted imaging in the evaluation of renal masses.

OBJECTIVE The objective of our study was to assess the value of diffusion-weighted imaging in differentiating among the various subgroups of renal masses. MATERIALS AND METHODS This retrospective study measured the apparent diffusion coefficients (ADCs) of renal masses. Malignant lesions were confirmed with surgical pathology results. Benign cystic lesions were stable without treatment for a minimum follow-up of 24 months. RESULTS There were 20 and 22 patients, respectively, with benign lesions (three abscess, 31 cysts) and malignant lesions (17 clear cell, five papillary, one chromophobe, and two transitional cell cancers). The malignant lesions were larger than the benign lesions (mean diameter, 4.2 vs 2.6 cm, respectively; p = 0.01, Students t test). The ADC values of the benign lesions were significantly higher than those of the malignant lesions (mean, 2.72 vs 1.88 x 10(-3) mm(2)/s; p < 0.0001). The ADCs of the 31 benign cysts were significantly higher than those of the seven cystic renal cancers (2.77 vs 2.02 x 10(-3) mm(2)/s; p < 0.001). There was no significant difference between the ADCs of clear cell cancers and non-clear cell cancers (1.85 vs 1.97 x 10(-3) mm(2)/s; p = 0.18), but an ADC of less than 1.79 x 10(-3) mm(2)/s was seen only with clear cell cancer. The ADCs of high-grade clear cell cancers (Fuhrman grades III and IV) tended to be lower than those of low-grade clear cell cancers (1.77 vs 1.95 x 10(-3) mm(2)/s; p = 0.12). Among the clear cell cancers, an ADC value of greater than 2.12 x 10(-3) mm(2)/s was seen only with low-grade histology. For differentiating benign from malignant lesions, receiver operating characteristic (ROC) analysis showed an area under the ROC curve of 0.989 (95% CI, 0.919-0.996; p < 0.0001). CONCLUSION ADC measurements may aid in differentiating among the various subgroups of renal masses, particularly benign cystic lesions from cystic renal cell cancers.

Value of Diffusion-Weighted MRI for Assessing Liver Fibrosis and Cirrhosis

OBJECTIVE The objective of our study was to determine the usefulness of the apparent diffusion coefficient (ADC) of liver parenchyma for determining the severity of liver fibrosis. MATERIALS AND METHODS This study investigated 78 patients who underwent diffusion-weighted imaging (DWI) with 1.5-T MRI and pathologic staging of liver fibrosis based on biopsy. DWI was performed with b values of 50 and 400 s/mm(2). ADCs of liver were measured using 2.0- to 3.0-cm(2) regions of interest in the right and left lobes of the liver; the mean ADC value was used for analysis. Pathologic METAVIR scores for liver fibrosis stage were used as a reference standard. RESULTS The mean ADC values for fibrosis pathologically staged using the METAVIR classification system as F0 (n = 11), F1 (n = 16), F2 (n = 10), F3 (n = 14), and F4 (n = 27) were 125.9, 105.0, 104.5, 103.2, and 99.1 x 10(-5) s/mm(2), respectively. The correlation between the ADC values and the degree of liver fibrosis was moderate (Spearmans test, rho = -0.36). There was a significant difference in ADC values between patients with nonfibrotic liver (F0) and those with cirrhotic liver (F4) (p = 0.008). The best cutoff ADC value to distinguish between these groups was 118 x 10(-5) s/mm(2). However, ADC values were not useful for differentiating viral hepatitis patients with F2 fibrosis or higher from those with a lower degree of fibrosis (area under the receiver operating characteristic curve [AUC] = 0.66) or for differentiating low-stage fibrosis in all patients from high-stage fibrosis in all patients (AUC = 0.54). CONCLUSION The ADCs in cirrhotic livers are significantly lower than those in nonfibrotic livers. However, ADC values measured using the current generation of scanners are not reliable enough to replace liver biopsy for staging hepatic fibrosis.

Response Criteria in Oncologic Imaging: Review of Traditional and New Criteria

There has been a proliferation and divergence of imaging-based tumor-specific response criteria over the past 3 decades whose purpose is to achieve objective assessment of treatment response in oncologic clinical trials. The World Health Organization (WHO) criteria, published in 1981, were the first response criteria and made use of bidimensional measurements of tumors. The Response Evaluation Criteria in Solid Tumors (RECIST) were created in 2000 and revised in 2009. The RECIST criteria made use of unidimensional measurements and addressed several pitfalls and limitations of the original WHO criteria. Both the WHO and RECIST criteria were developed during the era of cytotoxic chemotherapeutic agents and are still widely used. However, treatment strategies changed over the past decade, and the limitations of using tumor size alone in patients undergoing targeted therapy (including arbitrarily determined cutoff values to categorize tumor response and progression, lack of information about changes in tumor attenuation, inability to help distinguish viable tumor from nonviable components, and inconsistency of size measurements) necessitated revision of these criteria. More recent criteria that are used for targeted therapies include the Choi response criteria for gastrointestinal stromal tumor, modified RECIST criteria for hepatocellular carcinoma, and Immune-related Response Criteria for melanoma. The Cheson criteria and Positron Emission Tomography Response Criteria in Solid Tumors make use of positron emission tomography to provide functional information and thereby help determine tumor viability. As newer therapeutic agents and approaches become available, it may be necessary to further modify existing anatomy-based response-assessment methodologies, verify promising functional imaging methods in large prospective trials, and investigate new quantitative imaging technologies.

The value of diffusion-weighted imaging in characterizing focal liver masses.

RATIONALE AND OBJECTIVES To determine if focal liver masses could be differentiated as benign or malignant on the basis of diffusion-weighted imaging (DWI). METHODS AND MATERIALS A total of 104 patients with focal liver masses were scanned using 1.5 T magnetic resonance imaging (MRI). DWI was performed with b values of 0, 50, and 400 s/mm(2). Of these, 76 patients had lesions larger than 2 cm diameter, radiologic or pathologic characterization of the lesion, and diagnostic quality DWI. The apparent diffusion coefficient (ADC) of the largest liver lesion was measured. The liver masses were diagnosed on histology or had characteristic computed tomography/MRI findings and follow up of more than 6 months. The analyzed lesions were hemangioma (n = 17), cysts (n = 5), hepatocellular cancer (HCC) (n = 41), adenoma (n = 3), focal nodular hyperplasia (FNH) (n = 6), and metastases (n = 4). RESULTS The mean (standard deviation) ADC values (10(-5) mm(2)/second) of hemangiomas, cysts, FNH, and HCC were 156.8 (54.1), 190.2 (43.0), 130.1 (81.9), and 107.6 (32.7). The ADC of cysts and hemangiomas were significantly higher than that of other lesions (P = .0003, t-test). There was no significant difference between ADC values of solid, benign liver lesions (FNH, adenoma) and malignant lesions (HCC, metastases) (P = .62). CONCLUSION Solid liver lesions have a lower ADC than cysts and hemangiomas. However, there is no significant difference in ADC between solid benign and malignant lesions. DWI appears to have only minimal additional value over currently used MRI sequences in characterizing liver masses.

State-of-the-Art Pancreatic MRI

OBJECTIVE The purpose of this article is to discuss the most current techniques used for pancreatic imaging, highlighting the advantages and disadvantages of state-of-the-art and emerging pulse sequences and their application to pancreatic disease. CONCLUSION Given the technologic advances of the past decade, pancreatic MRI protocols have evolved. Most sequences can now be performed in one or a few breath-holds; 3D sequences with thin, contiguous slices offer improved spatial resolution; and better fat and motion suppression allow improved contrast resolution and image quality. The diagnostic potential of MRCP is now almost as good as ERCP, with pancreatic MRI as the main imaging technique to investigate biliopancreatic pain, chronic pancreatitis, and cystic pancreatic tumors at many institutions. In addition, functional information is provided with secretin-enhanced MRCP.

Peritoneal and Retroperitoneal Anatomy and Its Relevance for Cross-Sectional Imaging

It is difficult to identify normal peritoneal folds and ligaments at imaging. However, infectious, inflammatory, neoplastic, and traumatic processes frequently involve the peritoneal cavity and its reflections; thus, it is important to identify the affected peritoneal ligaments and spaces. Knowledge of these structures is important for accurate reporting and helps elucidate the sites of involvement to the surgeon. The potential peritoneal spaces; the peritoneal reflections that form the peritoneal ligaments, mesenteries, and omenta; and the natural flow of peritoneal fluid determine the route of spread of intraperitoneal fluid and disease processes within the abdominal cavity. The peritoneal ligaments, mesenteries, and omenta also serve as boundaries for disease processes and as conduits for the spread of disease.

Secretin-enhanced MR Cholangiopancreatography: Spectrum of Findings

Magnetic resonance cholangiopancreatography (MRCP) is the most effective, safe, noninvasive magnetic resonance (MR) imaging technique for the evaluation of the pancreaticobiliary ductal system. The MRCP imaging technique has substantially improved during the past 2 decades and is based mainly on the acquisition of heavily T2-weighted MR images, with variants of fast spin-echo sequences. MRCP can also be performed by utilizing the hormone secretin, which stimulates a normal pancreas to secrete a significant amount of fluid while transiently increasing the tone of the sphincter of Oddi. The transient increase in the diameter of the pancreatic duct improves the depiction of the ductal anatomy, which can be useful in patients in whom detailed evaluation of the pancreatic duct is most desired because of a suspicion of pancreatic disease. Improved depiction of the ductal anatomy can be important in (a) the differentiation of side-branch intraductal papillary mucinous neoplasms from other cystic neoplasms and (b) the diagnosis and classification of chronic pancreatitis, the disconnected pancreatic duct syndrome, and ductal anomalies such as anomalous pancreaticobiliary junction and pancreas divisum. In patients examined after pancreatectomy, stimulation with secretin can give information about the patency of the pancreaticoenteric anastomosis. Duodenal filling during the secretin-enhanced phase of the MRCP examination can be used to estimate the excretory reserve of the pancreas. Secretin is well tolerated, and complications are rarely seen. Secretin-enhanced MRCP is most useful in (a) the evaluation of acute and chronic pancreatitis, congenital variants of the pancreaticoduodenal junction, and intraductal papillary mucinous neoplasms and (b) follow-up of patients after pancreatectomy.

Primary epiploic appendagitis: CT diagnosis

The purpose of this study was to analyze the CT signs of primary epiploic appendagitis. A retrospective search of the CT database over 12 months for this diagnosis revealed 11 cases. The clinical findings were recorded. Softcopy CT images were reviewed by two experienced abdominal radiologists (KS, DM) for location of lesion, size, shape, presence of central hyperdense focus, degree of bowel wall thickening, mass effect, and ancillary signs. Abdominal pain was the primary symptom in all patients. Preliminary diagnoses were appendicitis (n=2), diverticulitis (n=5), pancreatitis (n=1), ovarian lesion (n=1), or unknown (n=2). Abdominal examination and white blood cell count were uninformative. CT examination revealed a solitary (n=11), ovoid (n=9) fatty lesion with some soft tissue stranding adjacent to the left colon (n=6), transverse colon (n=3), or right colon (n=2). Central hyperdensity (n=5), mild bowel wall thickening (n=2), and parietal peritoneal thickening (n=4) were also seen. In 4 patients the lesions were not visible on follow-up CT examination performed 23–184 days later. Primary epiploic appendagitis can clinically mimic other, more serious inflammatory conditions. Knowledge of its findings on CT would help the radiologist make the diagnosis and allow a more conservative approach to patient care.