Correlating Quantitative Para-Aortic Lymph Node Computed Tomography Parameters With Fluorodeoxyglucose Positron Emission Tomography for Cervical Cancer Staging: Possible Solution for Resource Constrained Countries.

OBJECTIVE: The aim of the study was to determine the most accurate quantitative morphological parameters on computed tomography (CT) that correlate with fluorodeoxyglucose (FDG)-avid para-aortic nodes (PANs) in patients with cervical cancer. METHODS: A single-institution retrospective evaluation was performed of women with cervical cancer who underwent pretreatment positron emission tomography (PET)/CT and radiotherapy therapy planning CT between 2009 and 2020. A node-by-node correlation between pretreatment CT and PET/CT was performed for the reference standard of FDG avidity for short- and long-axis diameters, volume, and long-/short-axis ratio (L/S). The FDG-avid PANs were defined as PET-positive and non-FDG-avid PANs from patients without PET-determined PAN metastasis were defined as PET negative. Area under the receiver operator curve was calculated to access diagnostic accuracy of the different quantitative parameters. RESULTS: A total of 94 women (mean age ± standard deviation, 52 ± 13 years) with cervical cancer were included. Forty-seven patients had PET-positive PANs (181 PET-positive PANs) and 47 patients had no PET-positive PANs (141 PET-negative PANs). The area under the receiver operator curve for volume (0.945) was greater ( P < 0.001) than that of short axis (0.895), long axis (0.885), and L/S (0.583). At a specificity set point of 0.90 (127/141 PANs), the cutoff for volume was 0.443 cm 3 or greater (0.85 sensitivity [154/181 PANs]; 95% confidence interval, 0.83-0.93) and for short-axis diameter was 5.9 mm or greater (0.75 sensitivity [135/181 PANs]; 95% confidence interval, 0.68-0.81). CONCLUSIONS: Para-aortic lymph node volume demonstrated that improved node-by-node correlation between CT and PET/CT compared with short-axis diameter, long-axis diameter, and L/S and is an alternative to improve detection of PAN suspicious of metastatic diseases in locations without access to PET/CT.

Multimodality Imaging of Uterine Cervical Malignancies.

OBJECTIVE. In this article, we provide an updated review on the role of imaging in initial staging, treatment monitoring, and follow-up of cervical cancer with a focus on the role of MRI and FDG PET/CT. In addition, the 2018 International Federation of Gynecology and Obstetrics staging system and its implication on management of cervical cancer are explored. CONCLUSION. Imaging plays a major role in treatment planning and as a prognostic indicator in patients with cervical cancer. MRI and PET/CT have complementary roles: MRI is essential for the local staging of the primary tumor, and PET/CT is the most useful modality for detecting regional nodal and distant metastases.

Value of Intratumoral Metabolic Heterogeneity and Quantitative 18F-FDG PET/CT Parameters in Predicting Prognosis for Patients With Cervical Cancer.

OBJECTIVE. The purpose of this study is to evaluate the prognostic value of quantitative metabolic parameters from pretreatment PET/CT scans of patients with squamous cell cervical cancer. MATERIALS AND METHODS. This retrospective study included 120 patients with biopsy-proven squamous cell carcinoma of the cervix who underwent FDG PET/CT for initial tumor staging. The primary tumor maximum standardized uptake value (SUVmax) and mean standardized uptake value (SUVmean), tumor glycolytic activity, metabolic tumor volume (MTV), and metabolic intratumoral heterogeneity index (calculated as the AUC for the cumulative standardized uptake value [SUV]-volume histogram [CSH] index) were obtained. Information on patient demographic characteristics and tumor staging were collected. Median follow-up was 27.5 months. Overall survival (OS) and progression-free survival (PFS) were calculated using a multivariate Cox proportional hazards regression model and log-rank (Mantel-Cox) test to generate Kaplan-Meier survival plots. RESULTS. The mean (± SD) age of the patients was 54.4 ± 13.1 years. Twenty-two patients had stage I disease; 58, stage II; 23, stage III; and 17, stage IV. Thirty-three patients died, 82 were living, and five were lost to follow-up and were censored; 29 patients had disease progression. The median survival was 74.9 months (95% CI, 63.6-86.9 months). A higher MTV was significantly associated with reduced OS in multivariate analysis (hazard ratio, 1.085; 95% CI, 1.036-1.136; p = 0.0005). A higher AUC-CSH index (denoting lower tumor heterogeneity) was significantly associated with increased OS (hazard ratio, 0.662; 95% CI, 0.448-0.979; p = 0.04) and PFS (hazard ratio, 0.683; 95% CI, 0.471-0.991; p = 0.045) in multivariate analysis. Kaplan-Meier survival analysis using the median value for MTV (61 mL) significantly predicted OS (p = 0.0009). CONCLUSION. Tumor heterogeneity on pretreatment PET/CT is associated with OS and PFS in patients with cervical cancer. MTV is significantly associated with OS.

Diagnostic Performance and Interreader Agreement of a Standardized MR Imaging Approach in the Prediction of Small Renal Mass Histology.

Purpose To assess the diagnostic performance and interreader agreement of a standardized diagnostic algorithm in determining the histologic type of small (≤4 cm) renal masses (SRMs) with multiparametric magnetic resonance (MR) imaging. Materials and Methods This single-center retrospective HIPAA-compliant institutional review board-approved study included 103 patients with 109 SRMs resected between December 2011 and July 2015. The requirement for informed consent was waived. Presurgical renal MR images were reviewed by seven radiologists with diverse experience. Eleven MR imaging features were assessed, and a standardized diagnostic algorithm was used to determine the most likely histologic diagnosis, which was compared with histopathology results after surgery. Interreader variability was tested with the Cohen κ statistic. Regression models using MR imaging features were used to predict the histopathologic diagnosis with 5% significance level. Results Clear cell renal cell carcinoma (RCC) and papillary RCC were diagnosed, with sensitivities of 85% (47 of 55) and 80% (20 of 25), respectively, and specificities of 76% (41 of 54) and 94% (79 of 84), respectively. Interreader agreement was moderate to substantial (clear cell RCC, κ = 0.58; papillary RCC, κ = 0.73). Signal intensity (SI) of the lesion on T2-weighted MR images and degree of contrast enhancement (CE) during the corticomedullary phase were independent predictors of clear cell RCC (SI odds ratio [OR]: 3.19; 95% confidence interval [CI]: 1.4, 7.1; P = .003; CE OR, 4.45; 95% CI: 1.8, 10.8; P < .001) and papillary RCC (CE OR, 0.053; 95% CI: 0.02, 0.2; P < .001), and both had substantial interreader agreement (SI, κ = 0.69; CE, κ = 0.71). Poorer performance was observed for chromophobe histology, oncocytomas, and minimal fat angiomyolipomas, (sensitivity range, 14%-67%; specificity range, 97%-99%), with fair to moderate interreader agreement (κ range = 0.23-0.43). Segmental enhancement inversion was an independent predictor of oncocytomas (OR, 16.21; 95% CI: 1.0, 275.4; P = .049), with moderate interreader agreement (κ = 0.49). Conclusion The proposed standardized MR imaging-based diagnostic algorithm had diagnostic accuracy of 81% (88 of 109) and 91% (99 of 109) in the diagnosis of clear cell RCC and papillary RCC, respectively, while achieving moderate to substantial interreader agreement among seven radiologists. © RSNA, 2018 Online supplemental material is available for this article.

Diagnostic Accuracy of Multiparametric Magnetic Resonance Imaging to Identify Clear Cell Renal Cell Carcinoma in cT1a Renal Masses.

PURPOSE: The detection of small renal masses is increasing with the use of cross-sectional imaging, although many incidental lesions have negligible metastatic potential. Among malignant masses clear cell renal cell carcinoma is the most prevalent and aggressive subtype. A method to identify such histology would aid in risk stratification. Our goal was to evaluate a likelihood scale for multiparametric magnetic resonance imaging in the diagnosis of clear cell histology. MATERIALS AND METHODS: We retrospectively reviewed the records of patients with cT1a masses who underwent magnetic resonance imaging and partial or radical nephrectomy from December 2011 to July 2015. Seven radiologists with different levels of experience who were blinded to final pathology findings independently reviewed studies based on a predefined algorithm. They applied a clear cell likelihood score, including 1-definitely not, 2-probably not, 3-equivocal, 4-probably and 5-definitely. Binary classification was used to determine the accuracy of clear cell vs all other histologies. Interobserver agreement was calculated with the weighted κ statistic. RESULTS: A total of 110 patients with 121 masses were identified. Mean tumor size was 2.4 cm and 50% of the lesions were clear cell. Defining clear cell as scores of 4 or greater demonstrated 78% sensitivity and 80% specificity while scores of 3 or greater showed 95% sensitivity and 58% specificity. Interobserver agreement was moderate to good with a mean κ of 0.53. CONCLUSIONS: A clear cell likelihood score used with magnetic resonance imaging can reasonably identify clear cell histology in small renal masses and may decrease the number of diagnostic renal mass biopsies. Standardization of imaging protocols and reporting criteria is needed to improve interobserver reliability.

Imaging for Oncologic Response Assessment in Lymphoma.

OBJECTIVE: The purpose of this article is to examine the role of different imaging biomarkers, focusing in particular on the use of updated CT and PET response criteria for the assessment of oncologic treatment effectiveness in patients with lymphoma but also discussing other potential functional imaging methods and their limitations. CONCLUSION: Lymph nodes are commonly involved by metastatic solid tumors as well as by lymphoma. Evolving changes in cancer therapy for lymphoma and metastases have led to improved clinical outcomes. Imaging is a recognized surrogate endpoint that uses established criteria based on changes in tumor bulk to monitor the effects of treatment. With the introduction of targeted therapies and novel antiangiogenic drugs, the oncologic expectations from imaging assessment are changing to move beyond simple morphologic methods. Molecular and functional imaging methods (e.g., PET, perfusion, DWI, and dual-energy CT) are therefore being investigated as imaging biomarkers of response and prognosis. The role of these advanced imaging biomarkers extends beyond measuring tumor burden and therefore might offer insight into early predictors of therapeutic response. Despite the potential benefits of these exciting imaging biomarkers, several challenges currently exist.

Prospective Comparison of Reduced-Iodine-Dose Virtual Monochromatic Imaging Dataset From Dual-Energy CT Angiography With Standard-Iodine-Dose Single-Energy CT Angiography for Abdominal Aortic Aneurysm.

OBJECTIVE: The purpose of this study was to compare the image quality of reduced-iodine-dose single-source dual-energy CT angiography (CTA) with that of standard-iodine-dose single-energy CTA in examinations of patients with abdominal aortic aneurysm and to assess the effect of the concentration of iodinated contrast medium on intravascular enhancement and image quality of reduced-iodine-dose CTA. SUBJECTS AND METHODS: In a prospective randomized clinical trial, 66 consecutively registered patients with abdominal aortic aneurysm who had previously undergone single-energy CTA (30-37 g I) underwent follow-up CTA at a reduced dose (21-27 g I) of iodinated contrast medium of either 270 mg I/mL (n = 33) or 320 mg I/mL (n = 33). Two readers independently evaluated virtual monochromatic imaging datasets (40-140 keV) and single-energy CTA images for image quality and noise and their preference for optimal energy virtual monochromatic imaging dataset. A value of p < 0.05 was considered statistically significant. RESULTS: All 66 dual-energy CTA examinations were rated diagnostic with mean image quality and image noise scores of 4.8 and 4.5 for reader 1 and 3.8 and 3.4 for reader 2 compared with single-energy CTA results of 4.5 and 4.2 for reader 1 and 4.5 and 4.1 for reader 2. Low-energy virtual monochromatic images (40-60 keV) from reduced-iodine-dose (28%) dual-energy CTA had significantly higher intravascular aortic attenuation (26-185%) and contrast-to-noise ratio (CNR) (20-25%) than standard-iodine-dose single-energy CTA images (p < 0.0001). No significant difference was found between patients who received 270 and those who received 320 mg I/mL with respect to intravascular aortic attenuation (p = 0.6331) or CNR (p = 0.9775). CONCLUSION: Low-energy virtual monochromatic imaging datasets from reduced-iodine (24 g I) single-source dual-energy CTA of the abdomen provide up to 185% higher attenuation and 25% higher CNR than standard-iodine-dose (33.3 g I) single-energy CTA while offering a wide range of energy settings irrespective of the concentration of IV contrast medium used.

Oncologic applications of dual-energy CT in the abdomen.

Dual-energy computed tomographic (DECT) technology offers enhanced capabilities that may benefit oncologic imaging in the abdomen. By using two different energies, dual-energy CT allows material decomposition on the basis of energy-dependent attenuation profiles of specific materials. Although image acquisition with dual-energy CT is similar to that with single-energy CT, comprehensive postprocessing is able to generate not only images that are similar to single-energy CT (SECT) images, but a variety of other images, such as virtual unenhanced (VUE), virtual monochromatic (VMC), and material-specific iodine images. An increase in the conspicuity of iodine on low-energy VMC images and material-specific iodine images may aid detection and characterization of tumors. Use of VMC images of a desired energy level (40-140 keV) improves lesion-to-background contrast and the quality of vascular imaging for preoperative planning. Material-specific iodine images enable differentiation of hypoattenuating tumors from hypo- or hyperattenuating cysts and facilitate detection of isoattenuating tumors, such as pancreatic masses and peritoneal disease, thereby defining tumor targets for imaging-guided therapy. Moreover, quantitative iodine mapping may serve as a surrogate biomarker for monitoring effects of the treatment. Dual-energy CT is an innovative imaging technique that enhances the capabilities of CT in evaluating oncology patients.

Initial experience with single-source dual-energy CT abdominal angiography and comparison with single-energy CT angiography: image quality, enhancement, diagnosis and radiation dose.

OBJECTIVES: To assess image quality of virtual monochromatic spectral (VMS) images, compared to single-energy (SE) CT, and to evaluate the feasibility of material density imaging in abdominal aortic disease. METHODS: In this retrospective study, single-source (ss) dual-energy (DE) CT of the aorto-iliac system in 35 patients (32 male, mean age 76.5 years) was compared to SE-CT. By post-processing the data from ssDECT, VMS images at different energies and material density water (WD) images were generated. The image quality parameters were rated on 5-point scales. The aorto-iliac attenuation and contrast-to-noise ratio (CNR) were recorded. Quality of WD images was compared to true unenhanced (TNE) images. Radiation dose was recorded and statistical analysis was performed. RESULTS: Image quality and noise were better at 70 keV (P < 0.01). Renal artery branch visualisation was better at 50 keV (P < 0.005). Attenuation and CNR were higher at 50 and 70 keV (P < 0.0001). The WD images had diagnostic quality but higher noise than TNE images (P < 0.0001). Radiation dose was lower using single-phase ssDECT compared to dual-phase SE-CT (P < 0.0001). CONCLUSION: 70-keV images from ssDECT provide higher contrast enhancement and improved image quality for aorto-iliac CT when compared to SE-CT at 120 kVp. WD images are an effective substitute for TNE images with a potential for dose reduction.

Determination of renal stone composition in phantom and patients using single-source dual-energy computed tomography.

PURPOSE: This study aimed to characterize the urinary tract stones in phantom and patients using single-source dual-energy computed tomography. MATERIALS AND METHODS: Twenty stones of pure crystalline composition (uric acid [UA], struvite, cystine, and calcium oxalate monohydrate) were assessed in a phantom and 11 patients (age 39-67 years) with urinary tract stones were evaluated. An initial low-dose unenhanced CT (tube potential, 120 kilovolts [peak]; milliampere range, 150-450; noise index, 26; section thickness, 5 mm) followed by a targeted dual-energy computed tomography acquisition on a single-source dual-energy computed tomography (Discovery CT 750 HDCT, GE) was performed. Uric acid and non-UA stones were defined using a 2-material decomposition (material density-iodine/water) algorithm. The stone effective atomic number (Zeff) was used to subclassify non-UA stones. The stone attenuation (Hounsfield unit) was also studied to determine its performance in predicting the composition. Ex vivo chemical analysis of the stone served as a criterion standard. RESULTS: Of the 59 verified stones (phantom, 20; patients, 39; mean size, 6 mm), there were 16 UA and 43 non-UA type. The material density images were 100% sensitive and accurate in detecting UA and non-UA stones. The Zeff accurately stratified struvite, cystine, and calcium (calcium oxalate monohydrate) stones in the phantom. In patients, Zeff identified 83% of calcium stones (n = 24), and in stones of mixed type, it resembled dominant composition. The Hounsfield unit measurements alone were 71% sensitive and 69% accurate in detecting the UA stones. CONCLUSIONS: Single-source dual-energy computed tomography can accurately predict UA and non-UA stone composition in vitro and in vivo. Substratification of non-UA stones of pure composition can be made in vitro and in vivo. In stones of mixed composition, the Zeff values reflect the dominant composition.

Intratumoral Metabolic Heterogeneity and Other Quantitative 18F-FDG PET/CT Parameters for Prognosis Prediction in Esophageal Cancer.

Purpose: To evaluate the impact of intratumoral metabolic heterogeneity (IMH) and other quantitative fluorine 18 (18F) fluorodeoxyglucose (FDG) PET/CT parameters for predicting progression-free survival (PFS) and overall survival (OS) in patients with esophageal cancer. Materials and Methods: In this retrospective study, an automated gradient-based segmentation method was used to assess the maximum standardized uptake value, mean standardized uptake value, metabolic tumor volume (MTV), and IMH index of the primary tumor in patients with biopsy-proven adenocarcinoma or squamous cell carcinoma of the esophagus with an initial staging 18F-FDG PET/CT. Data were collected between July 2006 and February 2016. OS and PFS were calculated using multivariable Cox proportional hazards regression with the adjustment (as covariates) of age, sex, weight, stage, tumor type, tumor grade, and treatment. All PET parameters were standardized before analysis. Log-rank tests were performed, and corresponding Kaplan-Meier survival plots were generated. Results: A total of 71 patients (mean age, 64 years ± 10 [standard deviation], 62:9 men:women) were included. Median follow-up time was 28.2 months (range, 4-38 months), and median survival was 16.1 months (range, 0.1-60.3 months). Higher MTV was associated with reduced PFS for every standard deviation increase (hazard ratio [HR], 0.193; 95% CI: 0.052, 0.711; P = .01). Higher IMH was associated with reduced PFS for every standard deviation decrease in the area under the curve (HR, 10.78; 95% CI: 1.31, 88.96; P = .03). Conclusion: PFS for patients with esophageal cancer was associated with MTV and with IMH.Keywords: Esophagus, Neoplasms-Primary, PET/CT, Tumor Response © RSNA, 2020.

Updating and Optimizing Anatomic Atlases for Elective Radiation of Para-Aortic Lymph Nodes in Cervical Cancer.

PURPOSE: Previous studies have proposed 2 different contouring guidelines for the prophylactic radiation of para-aortic lymph nodes (PANs) for locally advanced cervical cancer. Because PAN-mapping atlases in current literature are limited to small patient samples and nodal populations, we updated the PAN atlas with a large data set of positron emission tomography (PET)-positive PANs on PET/computed tomography (CT) from patients with cervical cancer. METHODS AND MATERIALS: We identified 176 PET-positive PANs on pretreatment PET/CT of 47 patients with diagnosed International Federation of Gynecology and Obstetrics stage IB to IVA cervical cancer. PANs were classified as left-lateral para-aortic (LPA), aortocaval (AC), or right paracaval (RPC). PAN clinical target volume (CTV) contours were drawn for all patients based on previously published guidelines by Takiar (CTV-T) and Keenan (CTV-K) and nodal volumetric coverage was assessed. RESULTS: We identified 94 LPA nodes (54%), 71 AC nodes (40%), and 11 (6%) RPC nodes. CTV-T had improved nodal center coverage of 97.6% compared with 85.0% for CTV-K (P < .001). Nodal center coverage for CTV-K and CTV-T (with corresponding PAN) were 79 (84.0%) and 93 (99.0%) LPA nodes (P = .001), 64 (90.1%) and 68 (95.8%) AC nodes (P = .221), and 5 (45.5%) and 9 (81.8%) RPC nodes (P = .134), respectively. Additionally, our updated PAN atlas identified nodal centers anterior to the aorta and inferior vena cava that are not covered by CTV-T but covered by CTV-K due to the 10 mm anterior aortic expansion of CTV-K. CONCLUSIONS: We have updated the PAN anatomic map of 176 PET-positive nodes from 47 patients and demonstrated that CTV-T has significantly better PAN coverage over CTV-K for posterior LPA and retrocaval regions for our data set. Additionally, we suggest a modification that includes a blend of CTV-T and CTV-K to provide optimal coverage for the mapped nodes anterior to the great vessels in our data set.

Spectrum of findings on ventilation‒perfusion lung scintigraphy after lung transplantation and association with outcomes.

BACKGROUND: Air trapping (AT) is one of the hallmarks of allograft dysfunction after lung transplantation (LT). Inert gas‒based ventilation‒perfusion (VQ) lung scintigraphy has excellent sensitivity in the detection of AT. METHODS: We reviewed the charts of patients who underwent single or double LT between January 2012 and December 2014 (N = 193). Patients without a VQ scintigraphy at the first annual visit (n = 16) and those who did not survive till 1 year (n = 26) were excluded (final n = 151, mean age = 55.8 [SD =14] years, male = 85, female = 66). VQ scintigraphy was independently reviewed and reconciled for the presence and severity of AT by 2 investigators blinded to the clinical data (D.F.P. and D.M.). A 3-year post-transplant survival was the primary end-point. RESULTS: AT was common (n = 73, 48.3%). Patients with obstructive lung diseases as the underlying diagnosis (adjusted odds ratio [OR], 4.36, 95% CI: 1.64‒11.6; p = 0.003) and those with lower body mass index (BMI) (BMI < 25 kg/m2 and 25‒30 kg/m2; p < 0.001) had an increased risk of developing AT in the allograft. The presence of AT (adjusted OR, 2.33, 95% CI: 1.01‒5.36; p = 0.04) and peak forced expiratory volume in 1 sec (FEV1) <60% predicted during the first year after LT were independently associated with 3-year mortality. The association of AT with post-transplant mortality was the strongest among patients with BMI <30 kg/m2 and peak FEV1 <60% predicted. CONCLUSIONS: The finding of AT on VQ scintigraphy at the first annual visit after LT is independently associated with worse post-transplant mortality. The sub-group of patients who fail to achieve a peak FEV1 of 60% predicted during the first year after LT appears to be the key driver of this association.

Ventilation perfusion pulmonary scintigraphy in the evaluation of pre-and post-lung transplant patients.

Lung transplantation is an established treatment for patients with a variety of advanced lung diseases. Imaging studies play a valuable role not only in evaluation of patients prior to lung transplantation, but also in the follow up of patients after transplantation for detection of complications. After lung transplantation, complications can occur as a result of surgical procedure, pulmonary embolism and ultimately chronic lung allograft dysfunction. Lung scintigraphy, which includes physiologic assessment of lung ventilation and perfusion by imaging, has become an important procedure in the evaluation of these patients, assuming a complementary role to high resolution anatomic imaging (computed tomography [CT]), as well as spirometry. The purpose of this atlas article is to demonstrate the uses of ventilation perfusion scintigraphy in the pre-transplantation setting for surgical planning and in the evaluation of complications post-lung transplantation based upon experience at our institution.

PET-Computed Tomography and Precision Medicine in Pancreatic Adenocarcinoma and Pancreatic Neuroendocrine Tumors.

18F-FDG PET/CT has been described as an accurate tool for initial diagnosis of pancreatic adenocarcinoma. It differentiates benign from malignant causes; detects local and, especially, distant spread of disease; and is a very good predictor of patient prognosis. Pancreatic neuroendocrine tumors are rare tumors that originate from the islet cells of the pancreas. Currently, 68Ga-DOTA-labeled somatostatin analogs are considered the best modality for detection of well-differentiated neuroendocrine tumors. 18F-FDG PET/CT has a role in patients with poorly differentiated tumors. Recent studies have demonstrated improved survival in patients with metastatic neuroendocrine tumors treated with radiolabeled somatostatin analogs.

Optimization of breathing instructions and timing of late arterial phase acquisition on gadobutrol-enhanced MRI of the liver.

PURPOSE: To compare a protocol with higher concentration macrocyclic gadolinium-based contrast agent (GBCA) [study group] to the traditional protocol with lower-concentration linear GBCAs [control group] for breath-held arterial phase magnetic resonance imaging. MATERIAL AND METHODS: A total of 136 patients were quantitatively evaluated for image quality (IQ), breathing artifacts (BA), and timing of the arterial phase (Tap). Quantitative analysis was also performed. RESULTS: No significant differences in IQ, BA and Tap (P>.05). Study group exhibited less enhancement of the aorta (P=.0091) and smaller standard deviation for the portal vein enhancement (P=.0173). CONCLUSION: Similar arterial-phase image quality can be achieved with a macrocyclic GBCA compared to traditional linear GBCA.

Endoluminal contrast for abdomen and pelvis magnetic resonance imaging.

Magnetic resonance (MR) imaging of the abdomen and pelvis can be limited for assessment of different conditions when imaging inadequately distended hollow organs. Endoluminal contrast agents may provide improved anatomic definition and detection of subtle pathology in such scenarios. The available routes of administration for endoluminal contrast agents include oral, endorectal, endovaginal, intravesicular, and through non-physiologic accesses. Appropriate use of endoluminal contrast agents requires a thorough understanding of the clinical indications, available contrast agents, patient preparation, and interaction of the contrast agent with the desired MR imaging protocol. For example, biphasic oral enteric contrast agents are preferred in MR enterography as their signal properties on T1- and T2-weighted imaging allow for evaluation of both intraluminal and bowel wall pathology. In specific situations such as with MR enterography, MR defecography, and accurate local staging of certain pelvic tumors, the use of an endoluminal contrast agent is imperative in providing adequate diagnostic imaging. In other clinical scenarios, the use of an endoluminal contrast agent may serve as an indispensable problem-solving tool.

Mechanisms of Action of Liraglutide in Patients With Type 2 Diabetes Treated With High-Dose Insulin.

CONTEXT: The mechanisms of action of incretin mimetics in patients with long-standing type 2 diabetes (T2D) and high insulin requirements have not been studied. OBJECTIVE: To evaluate changes in ß-cell function, glucagon secretion, and fat distribution after addition of liraglutide to high-dose insulin. DESIGN: A single-center, randomized, double-blind, placebo-controlled trial. SETTING: University of Texas Southwestern and Parkland Memorial Hospital clinics. PATIENTS: Seventy-one patients with long-standing (median, 17 years) T2D requiring high-dose insulin treatment (>1.5 U/kg/d; average, 2.2 ± 0.9 U/kg/d). INTERVENTION: Patients were randomized to liraglutide 1.8 mg/d or matching placebo for 6 months. MAIN OUTCOME MEASURES: We measured changes in insulin and glucagon secretion using a 4-hour mixed-meal challenge test. Magnetic resonance-based techniques were used to estimate sc and visceral fat in the abdomen and ectopic fat in the liver and pancreas. RESULTS: Glycosylated hemoglobin improved significantly with liraglutide treatment, with an end-of-trial estimated treatment difference between groups of −0.9% (95% confidence interval, −1.5, −0.4%) (P = .002). Insulin secretion improved in the liraglutide group vs placebo, as measured by the area under the curve of C-peptide (P = .002) and the area under the curves ratio of C-peptide to glucose (P = .003). Insulin sensitivity (Matsuda index) and glucagon secretion did not change significantly between groups. Liver fat and sc fat decreased in the liraglutide group vs placebo (P = .0006 and P = .01, respectively), whereas neither visceral nor pancreatic fat changed significantly. CONCLUSIONS: Treatment with liraglutide significantly improved insulin secretion, even in patients with long-standing T2D requiring high-dose insulin treatment. Liraglutide also decreased liver and sc fat, but it did not alter glucagon secretion.

Incidental pancreatic cysts: role of magnetic resonance imaging.

The widespread adoption of multidetector computed tomography and magnetic resonance imaging (MRI) for evaluation of intraabdominal pathology has resulted to a steady increase in the number of incidentally discovered pancreatic cysts in clinical practice during the last decades. The differential diagnosis of these cysts is broad including pseudocysts, serous cystic neoplasms, mucinous cystic neoplasms, and intraductal papillary mucinous neoplasms. The MRI has an important role both in the initial characterization of incidentally detected pancreatic cysts and the follow-up of these lesions and has become an integral part of the diagnostic algorithm for pancreatic cysts at many institutions. The inherent soft-tissue contrast of magnetic resonance cholangiopancreatography provides the vehicle for providing a specific diagnosis in many pancreatic cysts. Furthermore, an MRI-based characterization of pancreatic cysts allows for selection of those cysts that are more likely to benefit from endoscopic ultrasound and fine-needle aspiration for analysis of the fluid contents. Moreover, small asymptomatic incidental pancreatic cysts without concerning MRI features such as internal septae and/or nodularity may be safely followed with serial imaging. The lack of risk associated to repeated exposure to ionizing radiation and its ability to characterize pancreatic cysts are strong arguments for selecting MRI as the preferred imaging modality for following up these lesions. However, the recommendations for imaging follow-up continue to evolve, and several of the proposed guidelines are reviewed in this manuscript.