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Objective: The objective of this study was to determine whether quantitative texture analysis of MR images would improve the ability to distinguish papillary renal cell carcinoma (RCC) subtypes, compared with analysis of qualitative MRI features alone., Materials and Methods: A total of 47 pathologically proven papillary RCC tumors were retrospectively evaluated, with 31 (66%) classified as type 1 tumors and 16 (34%) classified as type 2 tumors. MR images were reviewed by two readers to determine tumor size, signal intensity, heterogeneity, enhancement pattern, margins, perilesional stranding, vein thrombosis, and metastasis. Quantitative texture analysis of gray-scale images was performed. A logistic regression was derived from qualitative and quantitative features. Model performance was compared with and without texture features., Results: The significant qualitative MR features noted were necrosis, enhancement appearance, perilesional stranding, and metastasis. A multivariable model based on qualitative features did not identify any factor as an independent predictor of a type 2 tumor. The logistic regression model for predicting papillary RCCs on the basis of qualitative and quantitative analysis identified probability of the 2D volumetric interpolated breath-hold examination (VIBE) sequence (AUC value, 0.87; 95% CI, 0.77-0.98) as an independent predictor of a type 2 tumor. No difference in the model AUC value was noted when texture features were included in the analysis; however, the model had increased sensitivity and an improved predictive value without loss of specificity., Conclusion: The addition of texture analysis to analysis of conventional qualitative MRI features increased the probability of predicting a type 2 papillary RCC tumor, which may be clinically important.

Objective: The objective or our study was to assess the incidence rate and clinical characteristics of allergiclike reactions in patients who received both nonionic iodinated contrast medium (ICM) and gadolinium-based contrast medium (GBCM)., Materials and Methods: Acute allergiclike reactions in patients who received both ICM and GBCM to nonionic ICM or GBCM injections during a 5-year period were analyzed. Allergy preparation was not administered when patients received a different type of contrast material. Acute allergiclike reactions to both ICM and GBCM were evaluated., Results: Of 302,858 contrast injections (155,234 ICM and 147,624 GBCM) during a 5-year period, 1006 (752 ICM and 254 GBCM) acute allergiclike contrast reactions were reported. The overall rate of reaction to ICM was 0.48% (95% CI, 0.45-0.52%), and the overall rate of reaction to GBCM was 0.17% (95% CI, 0.15-0.19%). A total of 19,237 patients received at least one ICM injection and one GBCM injection, with a total of 56,310 injections (19,237 initial injections and 37,073 subsequent injections). Nine patients had reactions to both ICM and GBCM with the primary reaction rate of 9/19,237 (incidence rate, 0.047%; 95% CI, 0.044-0.050%), and the secondary reaction rate of 9/37,073 (incidence rate, 0.024%; 95% CI, 0.023-0.026%). All secondary reactions in patients who had a reaction to both ICM and GBCM were mild. None of the patients required medication for the treatment of the secondary reaction., Conclusion: An allergiclike reaction to both nonionic ICM and GBCM was an extremely rare event that presented as a mild acute reaction without significant clinical consequences despite the fact that an allergy preparation was not administered.

Objective: Differentiation of scrotal lesions is often dictated by whether they are intraor extratesticular. However, these regions are not entirely isolated, and disease processes can span both spaces. We review a variety of lesions that can involve both regions, describe the relevant anatomy, and illustrate their imaging appearances., Conclusion: Identification of involvement of both intra- and extratesticular regions by a single process can narrow the differential considerations and help arrive at the correct diagnosis.

Objective: Meckel diverticulum may become symptomatic if it is complicated by hemorrhage, intestinal obstruction, diverticulitis, or tumor. Although classically described in children, it is often missed in adults because of lack of suspicion and difficulty in detection. The purpose of this article is to review the imaging findings and management of Meckel diverticulum and its complications., Conclusion: Although it is infrequently encountered incidentally, Meckel diverticulum should be considered especially when interpreting examinations for abdominal pain, small-bowel obstruction, and gastrointestinal bleeding.

Objective: The purpose of this article is to review aspects of guidelines pertinent to radiologists involved in the diagnosis or treatment of hepatocellular carcinoma., Conclusion: Early diagnosis and treatment of hepatocellular carcinoma are important because only 10% of patients meet the criteria for curative therapy at the time of diagnosis. Several organizations have developed guidelines for screening, diagnosis, and treatment of hepatocellular carcinoma. Radiologists play a pivotal role in every aspect of these guidelines.

Objective: This article reviews optimal treatment of allergic reactions to iodinated contrast material in pregnant patients. Initial evaluation and treatment of a pregnant patient is similar to that for a nonpregnant patient. However, additional steps, including assessment for uterine cramping, using left uterine displacement to improve venous return, and maintaining blood pressure to ensure placental perfusion, may be required., Conclusion: Adequate preparation and a team approach will provide optimal care for a pregnant patient who has an allergic reaction to a contrast agent.

Objective: The 2012 revision of the Atlanta Classification emphasizes accurate characterization of collections that complicate acute pancreatitis: acute peripancreatic fluid collections, pseudocysts, acute necrotic collections, and walled-off necroses. As a result, the role of imaging in the management of acute pancreatitis has substantially increased., Conclusion: This article reviews the imaging findings associated with acute pancreatitis and its complications on cross-sectional imaging and discusses the role of imaging in light of this revision.

Objective: Conventional anatomic imaging biomarkers, including World Health Organization (WHO) criteria and Response Evaluation Criteria in Solid Tumors (RECIST), although effective, have limitations. This article will discuss the conventional and newer morphologic imaging biomarkers for the assessment of tumor response to therapy., Conclusion: Applying established methods of assessing tumor response to therapy allows consistency in image interpretation and facilitates communication with oncologists. Because of the new methods of treatment, assessment of necrosis and volumetric information will need to be incorporated into size-based criteria.

Objective: The purpose of our study was to compare the utility of MR elastography (MRE) and diffusion-weighted imaging (DWI) in characterizing fibrosis and chronic hepatitis in patients with chronic liver diseases., Subjects and Methods: Seventy-six patients with chronic liver disease underwent abdominal MRI, MRE, and DWI. Severities of liver fibrosis and chronic hepatitis were graded by histopathologic analysis according to standard disease-specific classifications. The overall predictive ability of MRE and DWI in assessment of fibrosis was compared by constructing a receiver operating characteristic (ROC) curve and calculating the area under the curve (AUC) on the basis of histopathologic analysis., Results: Using ROC analysis, MRE showed greater capability than DWI in discriminating stage 2 or greater (≥ F2), stage 3 or greater (≥ F3), and cirrhosis (≥ F4), shown as significant differences in AUC (p = 0.003, p = 0.001, and p = 0.001, respectively). Higher sensitivity and specificity were shown by MRE in predicting fibrosis scores ≥ F2 (91% and 97%), scores ≥ F3 (92% and 95%), and scores F4 (95% and 87%) compared with DWI (84% and 82%, 88% and 76%, and 85% and 68%, respectively). Although MRE had higher ability in identification of liver with fibrosis scores ≥ F1 than DWI, a significant difference was not seen (p = 0.398). Stiffness values on MRE increased in relation to increasing severity of fibrosis confirmed by histopathology scores; however, a consistent relationship between apparent diffusion coefficient (ADC) values and stage of fibrosis was not shown. In addition, liver tissue with chronic hepatitis preceding fibrosis may account for mild elevation of liver stiffness., Conclusion: MRE had greater predictive ability in distinguishing the stages of liver fibrosis than DWI.

Objective: The purpose of our study was to evaluate the utility of apparent diffusion coefficient (ADC) values for characterizing adrenal lesions and determine if diffusion-weighted imaging (DWI) can distinguish lipid-rich from lipid-poor adenomas., Materials and Methods: We retrospectively evaluated 160 adrenal lesions in 156 patients (96 women and 60 men; mean age, 63 years). ADCs and signal intensity (SI) decrease on chemical shift imaging were measured in adrenal lesions with a wide variety of pathologies. Lipid-rich and lipid-poor adenomas were identified by unenhanced CT. The overall predictive power of ADC, SI decrease, and lesion size were determined by receiver operating characteristic (ROC) analysis. Areas under the ROC curve (AUC) were compared for equivalence using nonparametric methods. Sensitivity, specificity, and positive and negative predictive values were calculated. Correlation coefficients were used to assess ADCs versus percentage SI decrease and ADCs versus CT attenuation., Results: ADCs of adrenal malignancies (median, 1.67 x 10(-3) mm(2)/s; interquartile range, 1.41-1.84 x 10(-3) mm(2)/s) were not different compared with those of benign lesions (1.61 x 10(-3) mm(2)/s; 1.27-1.96 x 10(-3) mm(2)/s; p > 0.05). Cysts (2.93 x 10(-3) mm(2)/s; 2.70-3.09 x 10(-3) mm(2)/s) showed higher ADCs than the remaining adrenal lesions (p < 0.05). The median ADCs of lipid-rich adenomas did not differ from those of lipid-poor ones (p > 0.05). The CT attenuation had no negative or positive correlation with the ADCs of adrenal adenomas (r = -0.05, p = 0.97)., Conclusion: Unlike lesion size and percentage decrease in SI, the ADCs were not useful in distinguishing benign from malignant adrenal lesions. Lipid-poor adenomas could not be distinguished from lipid-rich adenomas and all other nonfatty lesions of the adrenal gland with DWI.

Objective: Yttrium-90 radioembolization is an emerging treatment for liver malignancies. The purpose of this study was to evaluate the imaging response of liver metastases to 90Y microspheres based on size and necrosis criteria using CT and comparing the results to PET and to describe imaging features related to 90Y therapy., Materials and Methods: We reviewed the imaging studies of 42 patients with unresectable liver metastases treated with lobar radioembolization with 90Y. CT response was determined using traditional size criteria (World Health Organization [WHO] and Response Evaluation Criteria in Solid Tumors [RECIST]), necrosis criteria, and combined criteria (RECIST and necrosis). We compared the response on CT with the response on PET. Complications of treatment were assessed., Results: The response rate was 19% (8/42) by WHO criteria, 24% (10/42) by RECIST, 45% (19/42) by necrosis criteria, and 50% (21/42) by combined criteria. Stabilization of lesion size occurred in 50% of patients. Necrosis and combined criteria identified responders earlier than RECIST and WHO criteria. Seven responders by combined criteria had an increase in lesion size on initial follow-up and would have been considered nonresponders. PET scans were obtained in 23 patients (33 treated lobes). PET detected significantly more responses to treatment (21/33, 63%) than CT using RECIST (2/33, 6%) or combined criteria (8/33, 24%) (p < 0.05, McNemar test). Complications of treatment included radiation cholecystitis (10 patients, 23%) and liver edema (18 patients, 42%)., Conclusion: The use of necrosis and size criteria on CT and correlation with PET may improve the accuracy of assessment of response to 90Y treatment in patients with liver metastases and detect response earlier than standard size criteria.

Objective: Yttrium-90 radioembolization is an emerging therapy for unresectable hepatocellular carcinoma (HCC). Although therapeutic response based on size has been evaluated in numerous studies, necrosis has been used as a criterion of response in only a few studies. The purpose of our study was to describe the imaging features of HCC after 90Y treatment and to compare size criteria (World Health Organization [WHO] and Response Evaluation Criteria in Solid Tumors [RECIST]) with necrosis criteria and combined criteria (RECIST and necrosis) for assessment of response., Materials and Methods: CT images of 42 patients with 76 90Y-treated HCC lesions were analyzed. We used four response criteria: WHO size, RECIST size, necrosis, and combined criteria (RECIST and necrosis). Imaging features of treated lesions included both nodular and peripheral rim enhancement. Survival was assessed with the Kaplan-Meier method., Results: The response rate was 23% according to RECIST criteria, 26% according to WHO criteria, 57% according to necrosis criteria, and 59% according to combined criteria. Response according to necrosis and combined criteria was detected earlier than response according to size criteria alone. Ten responding lesions initially increased in size. After therapy, enhancing peripheral nodules increased in size in 10 lesions, decreased in size in two lesions, and disappeared in two lesions. Twenty-one of 25 lesions with thin rim enhancement after 90Y administration responded to treatment. The median survival times were 660 and 236 days for Okuda stage I and Okuda stage II disease, respectively., Conclusion: Use of combined size and necrosis criteria may lead to more accurate assessment of response to 90Y therapy than use of size criteria alone. Imaging features after 90Y treatment, including size, necrosis, peripheral enhancing nodules, and thin rim enhancement, are described.

Objective: The purpose of this study was to describe the CT diagnosis of chyluria after partial nephrectomy., Conclusion: Fat in the bladder can be identified on CT after partial nephrectomy. This finding is caused by chyluria secondary to lymphatic injury and should not be mistaken for other abnormalities. Our study population did not need treatment of chyluria.

Objective: CT is the most widely used imaging technique for the diagnosis of islet cell tumors, but MRI may be better for detecting small lesions and metastases because of its optimal contrast resolution and ability to easily perform dynamic imaging. The purpose of this pictorial essay is to highlight the MRI features of these tumors and underscore potential pitfalls., Conclusion: Although classically considered well-defined, arterially enhancing lesions that are bright on T2-weighted sequences, pancreatic islet cell tumors have quite a broad spectrum of appearances. MRI is well suited for detecting and characterizing pancreatic islet cell tumors as well as their local effects and metastases.

Objective: CT is the established imaging technique for evaluation of pancreatic adenocarcinoma. MRI, however, can play a major role in this disease. The objective of this study is to illustrate the strengths of MRI for evaluating pancreatic adenocarcinoma., Conclusion: The superior soft-tissue contrast of MRI compared with CT is useful in the detection and characterization of non-contour-deforming pancreatic masses. MRI compared with CT may be more sensitive in the detection of distant disease, better for defining appropriate surgical candidates, and better for characterizing small liver metastases and peritoneal and omental metastases.

Objective: The objective of our study was to assess the importance of nonvisualization of the appendix and its association with acute appendicitis on helical CT when secondary inflammatory changes are absent., Materials and Methods: After we received institutional review board approval, CT scans of 366 consecutive patients obtained for lower abdominal or right lower quadrant pain and to rule out appendicitis were retrospectively reviewed. Images were reviewed by an experienced abdominal radiologist and compared with the formal interpretation. The amount of right lower quadrant and pericecal fat was quantified on a scale of 0 (none) to 2 (abundant). Patients with a nonvisualized appendix and other findings compatible with acute appendicitis-such as abscess formation, localized perforation, periappendiceal fat stranding, or appendicolith-were excluded., Results: The appendix could not be visualized by both reviewers in 46 (13%) of 366 cases. CT findings indicated another cause for the patient's symptoms in 12 cases (26%), including gastrointestinal and genitourinary processes. An alternate diagnosis was subsequently reached in 11 additional patients (24%) with follow-up imaging or clinical evaluation. Only one patient (2%) with a nonvisualized appendix had acute appendicitis, proven by surgical pathology. In this patient, there was paucity of fat in the right lower quadrant., Conclusion: In the absence of a distinctly visualized appendix and secondary inflammatory changes, the incidence of acute appendicitis is low. Nonvisualization of the appendix even when a small amount of fat is present in the right lower quadrant may safely exclude acute appendicitis if no secondary CT findings are present.

Objective: The purpose of this article is to define and illustrate the radiologic findings in patients with enterohemorrhagic Escherichia coli colitis., Conclusion: Although not definitive, imaging studies in conjunction with an appropriate clinical history can aid in the early diagnosis of E. coli colitis and exclude surgical conditions. CT is more sensitive than conventional radiography for detection. Contiguous involvement, including the transverse colon, was seen in all patients. Because CT is becoming routine in the initial workup of patients with acute abdominal pain, it is important for the radiologist to suggest E. coli colitis in the proper setting.

Objective: This paper describes the clinical and imaging characteristics of seminoma complicating intraabdominal testes in three patients who had a history of negative findings from surgical exploration of the inguinal canal and scrotum., Conclusion: Because inguinal surgery for cryptorchidism may fail to disclose intraabdominal testes, surgery that has negative findings should be followed up by a close examination of the abdomen. Seminomas arising from an intraabdominal testis can be large and asymptomatic or may simulate other diseases. Torsion may occur and occasionally appear as acute abdomen. The imaging features can be nonspecific, and the history of cryptorchidism may not be provided. Awareness of the clinical and imaging features of neoplasms involving undescended intraabdominal testes is important for appropriate diagnosis and therapy.

Objective: Our purpose was to determine the value of triphasic helical CT (unenhanced, hepatic arterial, and portal venous phases) in the detection and characterization of focal hepatic lesions due to hepatomas or metastases., Materials and Methods: One hundred two patients with known or suspected hepatomas or liver metastases underwent triphasic CT. The number and conspicuity of lesions were evaluated on each phase., Results: Five hundred eighty-four lesions were detected in 102 patients. Patients with hypovascular malignancies had more lesions detected on the portal venous phase with increased conspicuity than on the other phases. Patients with hypervascular malignancies had lesions best detected on the hepatic arterial phase, which revealed small lesions that were not seen on the other phases in seven (21%) of the 33 patients with hypervascular metastases and hepatomas. No lesions were detected on the unenhanced phase that were not seen on the other phases. However, arterial phase images introduced new diagnostic dilemmas because not all lesions seen on the arterial phase alone were caused by hepatomas or metastases, even in patients with known malignancies; several lesions represented benign abnormalities that included focal nodular hyperplasia., Conclusion: The unenhanced phase is not routinely necessary for the detection of metastases or hepatomas. Hypovascular malignancies are best evaluated during the portal venous phase. Small lesions due to hypervascular metastases and hepatomas are best evaluated and may be detected only during the hepatic arterial phase, which should be used routinely in these patients. New dilemmas may develop from the increased sensitivity of the hepatic arterial phase for lesions. However, the hepatic arterial phase is of limited value with hypovascular malignancies.

Objective: The purpose of this study was to determine the usefulness of axial MR imaging for diagnosing partial anterior cruciate ligament (ACL) tears and to determine if patients could be categorized as having stable or unstable partial ACL tears on the basis of criteria of axial MR imaging., Materials and Methods: We reviewed 238 patients who, over a 2-year period, underwent both MR imaging of the knee and arthroscopic evaluation of the ACL. According to arthroscopic examination, these patients had 143 normal ACLs, 67 complete ACL tears, and 28 partial tears. The 28 partial tears included 20 stable tears (no ACL deficiency) and eight unstable partial tears having ACL deficiency or requiring ACL reconstructive surgery. The axial MR images were retrospectively reviewed by two interpreters who were unaware of the arthroscopic findings, and decisions were reached by consensus. The ACL was classified according to its axial configuration and continuity., Results: By axial MR imaging criteria, we found 109 elliptical ACLs, 45 attenuated ACLs, three ACLs with increased intrasubstance signal intensity, six isolated ACL bundle signs, 19 ACLs that could not be visualized, and 56 cloudlike mass signs. Arthroscopically normal ACLs and stable partial tears were difficult to distinguish reliably on axial MR images. Unstable partial ACL tears could not be distinguished from complete ACL tears. However, using axial MR imaging, our observers were able to segregate stable ACLs (normal ligaments and stable partial tears) from unstable ACLs (unstable partial tears and complete tears) with 100% sensitivity and 96% specificity., Conclusion: Axial MR imaging of the ACL may provide important diagnostic information for patients who have ACL injury. On axial MR images, stable ACLs were elliptical, attenuated, or showed as areas of increased intrasubstance signal intensity. At arthroscopy, attenuated ACLs represented normal ACLs (76%) and stable partial tears (24%). On axial MR images, the configurations that indicated unstable ligaments were isolated ACL bundle, nonvisualized ACL, and cloudlike mass.

The pancreas and the biliary tract are frequent sites of infectious, Inflammatory, and neoplastic disease in patients with HIV infection. However, the symptoms of pancreaticobiliary involvement may be relatively mild so that the prevalence of these disorders is probably underestimated. An appreciation of the imaging findings of HIV-associated pancreaticobiliary disorders is important because involvement of these organs may be the only criterion that establishes the diagnosis of AIDS (Table 1).