Multi-institutional survey on imaging practice patterns in pancreatic ductal adenocarcinoma

PURPOSE

To study the practice patterns for performance and interpretation of CT/MRI imaging studies in patients with pancreatic ductal adenocarcinoma (PDAC) at multiple institutions using a survey-based assessment.

METHODS

In this study, abdominal radiologists/body imagers on the Society of Abdominal Radiology disease-focused panel for PDAC and from multiple institutions participated in an online survey. The survey was designed to investigate the imaging and reporting practice patterns for PDAC. The survey questionnaire addressed the experience of referring providers, choice of imaging modality for diagnosis and follow-up of PDAC, structured imaging templates utilization for PDAC, and experiences with the use of structured reports.

RESULTS

The response rate was 89.6% (43/48), with majority of the respondents working in a teaching hospital or academic research center (95.4%). While 86% of radiologists reported use of structured reporting templates in their practice, only 60.5% used standardized templates specific to PDAC. This lower percentage was despite most of them (77%) being aware of existence of PDAC-specific templates and recognizing their benefits, such as preference by referring providers (83%), improved uniformity (100%), and higher accuracy of reports (76.2%). The common impediments to the use of PDAC-specific templates were interference with efficient workflow (67.5%), lack of interest (52.5%), and complexity of existing templates (47.5%). With regards to imaging practice, 92.7% (n = 40/43) of respondents reported performing dynamic multiphasic pancreatic protocol CT for evaluation of patients with initial suspicion or staging of PDAC.

CONCLUSION

Structured reporting templates for PDAC are not universally utilized in subspecialty abdominal/body imaging practices due to concerns of interference with efficient workflow and complexity of templates. Multiphasic pancreatic protocol CT is most frequently performed for evaluation of PDAC.

Imaging features of hepatocellular carcinoma compared to intrahepatic cholangiocarcinoma and combined tumor on MRI using liver imaging and data system (LI-RADS) version 2014

PURPOSE

To evaluate the prevalence of major and ancillary imaging features from liver imaging reporting and data systems (LI-RADS) version 2014 and their interreader agreement when comparing hepatocellular carcinoma (HCC) to intrahepatic cholangiocarcinoma (ICC) and combined tumor (cHCC-CC).

METHODS

The Institutional Review Board approved this HIPAA-compliant retrospective study and waived the requirement for patients' informed consent. Patients with resected HCC (n = 51), ICC (n = 40), and cHCC-CC (n = 11) and available pre-operative contrast-enhanced MRI were included from 2000 to 2015. Imaging features and final LI-RADS category were evaluated by four radiologists. Imaging features were compared by Fisher's exact test and interreader agreements were assessed by κ statistics.

RESULTS

None of the features were unique to either HCC or non-HCC. Imaging features that were significantly more common among HCC compared to ICC and cHCC-CC included washout (76%-78% vs. 10%-35%, p < 0.001), capsule (55%-71% vs. 16%-49%, p < 0.05), and intralesional fat (27%-52% vs. 2%-12%, p < 0.002). Features that were more common among ICC and cHCC-CC included peripheral arterial phase hyperenhancement (40%-64% vs. 10%-14%, p < 0.001) and progressive central enhancement (65%-82% vs. 14%-25%, p < 0.001). The interreader agreement was moderate for each of these imaging features (κ = 0.41-0.55). Moderate agreement was also achieved in the assignment of LR-M (κ = 0.53), with an overall sensitivity and specificity for non-HCC malignancy of 86.3% and 78.4%, respectively.

CONCLUSION

HCC and non-HCC show significant differences in the prevalence of imaging features defined by LI-RADS, and are identified by radiologists with moderate interreader agreement. Using LI-RADS, radiologists also achieved moderate interreader agreement in the assignment of the LR-M category.

Specialized second-opinion radiology review of PET/CT examinations for patients with diffuse large B-cell lymphoma impacts patient care and management

To identify discrepancies in fludeoxyglucose positron emission tomography/computed tomography (FDG PET/CT) reports generated by general radiologists and subspecialized oncological radiologists for patients with diffuse large B-cell lymphoma (DLBCL), and to assess if such discrepancies impact patient management.Two radiologists retrospectively reviewed 72 PET/CT scans of patients with DLBCL referred to our institutions between 2009 and 2011, and recorded the discrepancies between the outside and second-opinion reports regarding multiple preset criteria using kappa statistic (Κ), including the disease stage. A multidisciplinary staging that considered all patient clinical data, pathology, and follow up radiological scans, was considered as standard of reference. A hemato-oncologist, blinded to the reports' origin, subjectively graded the quality and structure of these reports for each patient to determine if clinical stage and disease activity could be derived accurately from these reports.Agreement was not, or slightly, achieved between the reports regarding the binary and multilevel criteria (Κ < 0-0.2 and weighted Κ = 0.082, respectively). Second-opinion reviews of PET/CT scans were concordant with the multidisciplinary staging in 78% of cases with an almost perfect agreement (Κ = 0.860). A change in staging was demonstrated in 36% of cases. In addition, 68% of second-opinion reports were assigned the highest grades on quality (grades 4 and 5) by the hemato-oncologist, compared with 15% of outside reports, with no noted agreement (weighted Κ = -0.007).Second-opinion review of PET/CT scans by sub-specialized oncological radiologists increases accuracy of initial staging, posttreatment evaluation and also the clinical relevance of the radiology reports.

Hepatic angiosarcomatous transformation of a mediastinal germinal cell tumor: A care case report

RATIONALE

Mediastinal nonseminomatous germ cell tumor (NSGCT) is an uncommon entity. Metastatic hepatic sarcomatous transformation is rare.

PATIENT CONCERNS

We report a 24-year-old man with no previous related medical history presented with chest pain and left arm numbness.

DIAGNOSES

The x-ray showed an anterior mediastinal mass. The chest computed tomography (CT) confirmed the presence of a mildly enhancing mass in the same location, without invasion of any vascular structure. A CT-guided biopsy was performed, revealing a primary mediastinal nonseminomatous germ cell tumor (NSGCT), yolk sac histology, with areas of somatic transformation to malignant nerve sheath tumor. After surgery patient was followed-up with imaging. Two years later a CT scan showed a new hepatic hyper vascular lesion, confirmed by a subsequent magnetic resonance imaging (MRI) and positron emission tomography (PET) scan. A CT-guided biopsy revealed a hepatic metastatic transformation to angiosarcoma of the primitive NSGCT.

INTERVENTIONS

The patient went on to received palliative chemotherapy.

OUTCOMES

The patient is being followed-up regularly at the outpatient department.

LESSONS

Because of the potential of metastatic sarcoma arising from germ cell tumors, these patients should undergo periodical follow-up, with periodical scans. PET\CT scan might have a role in the follow-up of these patients.

Malignant transformation of glucagonoma with SPECT/CT In-111 OctreoScan features: A case report

RATIONALE

Glucagonoma is an uncommon disease but it has been associated with a pattern of symptoms defined as glucagonoma syndrome. These symptoms, if promptly recognized, could help to speed up the diagnosing process.

PATIENT CONCERNS

We report a case of a 68-year-old woman with a pancreatic glucagonoma. Her symptoms at the onset were typical of the glucagonoma syndrome.

DIAGNOSES

After a significant weight loss, she underwent a computer tomography scan of the abdomen, which showed a hypervascular lesion of the tail of the pancreas and hypervascular lesions of the liver. An ultrasound guided biopsy was performed and pathology was consistent with glucagonoma. Her blood glucagon levels were elevated.

OUTCOMES

She was treated with chemotherapy and somatostatin analogs. After 4 years, the disease had a malignant transformation, and metastases suddenly started to grow up. She stopped being responsive to treatment and eventually passed away.

LESSONS

Due to its rarity, clinical diagnosis is challenging and generally it comes after a long interval since the onset of symptoms. Awareness of physicians and dermatologists of the characteristic necrolytic migratory erythema, and of the other symptoms, often leads to early diagnosis.

Reproducibility of shear wave elastography (SWE) in patients with chronic liver disease

The presence of significant fibrosis is an indicator for liver disease staging and prognosis. The aim of the study was to determine reproducibility of real-time shear wave elastography using a hepatic biopsy as the reference standard to identify patients with chronic liver disease. Forty patients with chronic liver disease and 12 normal subjects received shear wave elastography performed by skilled operators. Interoperator reproducibility was studied in 29 patients. Fibrosis was evaluated using the Metavir score. The median and range shear wave elastography values in chronic liver disease subjects were 6.15 kPa and 3.14-16.7 kPa and were 4.49 kPa and 2.92-7.32 kPa in normal subjects, respectively. With respect to fibrosis detected by liver biopsy, shear wave elastography did not change significantly between F0 and F1 (p = 0.334), F1 and F2 (p = 0.611), or F3 and F4 (0.327); a significant difference was observed between the F0-F2 and F3-F4 groups (p = 0.002). SWE also correlated with inflammatory activity (Rs = 0.443, p = 0.0023) and ALT levels (Rs = 0.287, p = 0.0804). Age, sex and body mass index did not affect shear wave elastography measurements. Using receiver operator characteristic curves, two threshold values for shear wave elastography were identified: 5.62 kPa for patients with fibrosis (≥F2; sensitivity 80%, specificity 69.4%, and accuracy 77%) and 7.04 kPa for patients with severe fibrosis (≥F3; sensitivity 88.9%, specificity 81%, and accuracy 89%). Overall interobserver agreement was excellent and was analysed using an interclass correlation coefficient (0.94; CI 0.87-0.97).This study shows that shear wave elastography executed by skilled operators can be performed on almost all chronic liver disease patients with high reproducibility. It is not influenced by age, sex or body mass index, identifies severely fibrotic patients and is also related to inflammatory activity.

Subclinical focal Cholangitis mimicking liver metastasis in asymptomatic patients with history of pancreatic Ductal Adenocarcinoma and Biliary tree intervention

Background

Cholangitis is an inflammatory process of the biliary tract with a wide range of clinical manifestations and it is not always considered in the differential diagnosis in asymptomatic patients. To the best of our knowledge there is no previous report in the English literature of focal cholangitis manifesting exclusively as liver parenchymal changes mimicking liver metastasis in asymptomatic patients with pancreatic ductal adenocarcinoma (PDAC) and history of manipulation of the biliary tree. The purpose of this article is to present six cases of subclinical focal cholangitis mimicking liver metastasis in asymptomatic patients with history of PDAC and biliary tree intervention.

Case presentation

There are six cases with new hepatic lesions detected on follow-up scans in asymptomatic patients with history of PDAC and manipulation of biliary tree. Overall seven lesions were detected, all of them were on the liver periphery, five were hypovascular and two were hypervascular. None of those patients had elevation of CA 19.9 compared with the previous exams. The three patients that had magnetic resonance imaging presented restriction on diffusion weighted imaging and high signal intensity on T2-weighted image. Two patients underwent liver biopsy, which showed only inflammatory changes. All patients were treated with antibiotics and underwent imaging follow-up, which demonstrated resolution of the lesions. None of the patients showed imaging or clinical signs of disease progression during this interval.

Conclusion

Radiologists and oncologists need to be aware of the possibility of focal cholangitis causing hepatic lesions mimicking neoplasia in patients with history of biliary tree intervention, even in the absence of clinical symptoms.

Hepatic Lesions in a Cirrhotic Liver: Primary or Metastases?

Although prior studies showed that patients with cirrhosis have a lower risk of developing liver metastases, appropriate workup of incidental liver masses in cirrhotic liver is important for a correct diagnosis. Here we present a case of newly diagnosed liver cirrhosis with multifocal hepatic lesions, which was initially categorized as a LI-RADS (Liver Imaging Reporting and Data System) 5 lesions. Scintigraphy with ¹¹¹In-pentetreotide (Octreoscan) indicated a suspected thyroid nodule, later confirmed to represent medullary thyroid carcinoma lesion. The most relevant imaging finding of this rare form of thyroid malignancy is reviewed in this presentation.

Contrast-enhanced MDCT in patients with pancreatic neuroendocrine tumours: correlation with histological findings and diagnostic performance in differentiation between tumour grades

AIM

To identify the multidetector computed tomography (MDCT) features of pancreatic neuroendocrine tumours (pNETs), which correlate with tumour histology and enable preoperative grading.

MATERIALS AND METHODS

Thirty-nine patients with histologically confirmed pNET who underwent preoperative contrast-enhanced MDCT were included in this study. Nineteen tumours were classified as Grade 1 (G1) and 20 as Grade 2 (G2). Histopathology slides were reviewed to assess the intratumoural microvascular density (MVD) and the amount of tumour stroma. Computed tomography (CT) image analysis included tumour size, margin delineation, calcifications, homogeneity, contrast enhancement (CE) pattern, tumour absolute and relative enhancement, presence of cystic changes, pancreatic duct dilatation, regional and distant metastases. The diagnostic ability to predict tumour grade was measured for each MDCT finding and their combinations.

RESULTS

The mean arterial enhancement ratio had a mean±standard deviation of 1.53±0.45 in G1 and 1.01±0.33 in G2 pNETs (p=0.0003) and correlated with intratumoural microvascular density (MVD; r=0.55, p=0.0002). Tissue stroma percentage did not correlate with imaging findings. Late CE of the tumour (the peak attenuation observed in the venous phase) was significantly associated with G2. Tumour size >20 mm, arterial enhancement ratio <1.1, and late CE showed 74.4%, 79.5%, and 74.4% accuracy, respectively, in diagnosing G2 tumours, while the accuracy of at least two of these criteria used in combination was 82%. Based on these results, a diagnostic algorithm was proposed, which showed high interobserver agreement (k=0.82) in the prediction of tumour grade.

CONCLUSION

Contrast-enhanced MDCT features correlate with histological findings and enable the differentiation between G1 and G2 pNETs during preoperative examination.

Cystic pancreatic lesions: From increased diagnosis rate to new dilemmas

Cystic pancreatic lesions vary from benign to malignant entities and are increasingly detected on cross-sectional imaging. Knowledge of the imaging appearances of cystic pancreatic lesions may help radiologists in their diagnostic reporting and management. In this review, we discuss the morphologic classification of these lesions based on a diagnostic algorithm as well as the management of these lesions.

Hepatocellular Carcinoma and Diffusion-Weighted MRI: Detection and Evaluation of Treatment Response

Differentiating between cancerous tissue and healthy liver parenchyma could represent a challenge with the only conventional Magnetic Resonance (MR) imaging. Diffusion weighted imaging (DWI) exploits different tissue characteristics to conventional Magnetic Resonance Imaging (MRI) sequences that enhance hepatocellular carcinoma (HCC) detection, characterization, and post-treatment evaluation. Detection of HCC is improved by DWI, infact this technology increases conspicuity of lesions that might otherwise not be identified due to obscuration by adjacent vessels or due to low contrast between the lesion and background liver. It is important to remember that DWI combined with contrast-enhanced MRI has higher sensitivity than DWI alone, and that some patients are not eligible for use of contrast on CT and MRI; in these patients DWI has a prominent role. MRI has advanced beyond structural anatomic imaging to now showing pathophysiologic processes. DWI is a promising way to characterize lesions utilizing the inherent contrast within the liver and has the benefit of not requiring contrast injection. DWI improves detection and characterization of HCC. Proposed clinical uses for DWI include: assessing prognosis, predicting response, monitoring response to therapy, and distinguishing tumor recurrence from treatment effect. Ideally, DWI will help risk stratify patients and will participate in prognostic modeling.

Imaging of Liver Tumors Using Surface-Enhanced Raman Scattering Nanoparticles

Complete surgical resection is the ideal first-line treatment for most liver malignancies. This goal would be facilitated by an intraoperative imaging method that enables more precise visualization of tumor margins and detection of otherwise invisible microscopic lesions. To this end, we synthesized silica-encapsulated surface-enhanced Raman scattering (SERS) nanoparticles (NPs) that act as a molecular imaging agent for liver malignancies. We hypothesized that, after intravenous administration, SERS NPs would avidly home to healthy liver tissue but not to intrahepatic malignancies. We tested these SERS NPs in genetically engineered mouse models of hepatocellular carcinoma and histiocytic sarcoma. After intravenous injection, liver tumors in both models were readily identifiable with Raman imaging. In addition, Raman imaging using SERS NPs enabled detection of microscopic lesions in liver and spleen. We compared the performance of SERS NPs to fluorescence imaging using indocyanine green (ICG). We found that SERS NPs delineate tumors more accurately and are less susceptible to photobleaching. Given the known advantages of SERS imaging, namely, high sensitivity and specific spectroscopic detection, these findings hold promise for improved resection of liver cancer.

[(18)F]Choline PET/CT and stereotactic body radiotherapy on treatment decision making of oligometastatic prostate cancer patients: preliminary results

BACKGROUND

A new entity of patients with recurrent prostate cancer limited to a small number of active metastatic lesions is having growing interest: the oligometastatic patients. Patients with oligometastatic disease could eventually be managed by treating all the active lesions with local therapy, i.e. either surgery or ablative stereotactic body radiotherapy. This study aims to assess the impact of [(18)F]Choline ([(18)F]FMCH) PET/CT and the use stereotactic body radiotherapy (SBRT) in patients (pts) with oligometastatic prostate cancer (PCa).

METHODS

Twenty-nine pts with oligometastatic PCa (≤3 synchronous active lesions detected with [(18)F]FMCHPET/CT) were treated with repeated salvage SBRT until disease progression (development of > three active synchronous metastases). Primary endpoint was systemic therapy-free survival measured from the baseline [(18)F]FMCHPET/CT.

RESULTS

A total of 45 lesions were treated with SBRT. After a median follow-up of 11.5 months (range 3-40 months), 20 pts were still in the study and did not receive any systemic therapy. Nine pts started systemic therapy, and the median time of the primary endpoint was 39.7 months (CI 12.20-62.14 months). No grade 3 or 4 toxicity was recorded.

CONCLUSIONS

Repeated salvage [(18)F]FMCHPET/CT-guided SBRT is well tolerated and could defer the beginning of systemic therapy in selected patients with oligometastatic PCa.

Intermediate hepatocellular carcinoma: the role of transarterial therapy

According to Barcelona Clinic Liver Cancer, the recommended first-line treatment for patients with intermediate stage of hepatocellular carcinoma (HCC) is transarterial chemoembolization. Patients with intermediate stage of HCC represent 20% with a 2-year survival of approximately 50%. Nowadays, transarterial therapies have proved precious in the treatment of hepatic malignancies. During the last years, there were important developments in practiced transarterial therapies and their efficacy is still controversial. The purpose of this review is to discuss in further details these transarterial therapies that have been used to treat cases of HCC.

Non-invasive diagnostic imaging of colorectal liver metastases

Colorectal cancer is one of the few malignant tumors in which synchronous or metachronous liver metastases [colorectal liver metastases (CRLMs)] may be treated with surgery. It has been demonstrated that resection of CRLMs improves the long-term prognosis. On the other hand, patients with un-resectable CRLMs may benefit from chemotherapy alone or in addition to liver-directed therapies. The choice of the most appropriate therapeutic management of CRLMs depends mostly on the diagnostic imaging. Nowadays, multiple non-invasive imaging modalities are available and those have a pivotal role in the workup of patients with CRLMs. Although extensive research has been performed with regards to the diagnostic performance of ultrasonography, computed tomography, positron emission tomography and magnetic resonance for the detection of CRLMs, the optimal imaging strategies for staging and follow up are still to be established. This largely due to the progressive technological and pharmacological advances which are constantly improving the accuracy of each imaging modality. This review describes the non-invasive imaging approaches of CRLMs reporting the technical features, the clinical indications, the advantages and the potential limitations of each modality, as well as including some information on the development of new imaging modalities, the role of new contrast media and the feasibility of using parametric image analysis as diagnostic marker of presence of CRLMs.

Advances in diffusion-weighted imaging

Diffusion-weighted imaging (DWI) has become a routine component of clinical MR imaging. Its unique soft tissue contrast mechanism exploits differences in the motion of water molecules in vivo at a biologically meaningful scale. The clinical potential of DWI in lesion detection, characterization, and response assessment has been explored. This review briefly covers basic principles of DWI and introduces advances, specifically for abdominopelvic organs.

Grayscale and color Doppler features of testicular lymphoma

Pooled data from 16 radiology centers were retrospectively analyzed to seek patients with pathologically proven testicular lymphoma and grayscale and color Doppler images available for review. Forty-three cases were found: 36 (84%) primary and 7 (16%) secondary testicular lymphoma. With unilateral primary lymphoma, involvement was unifocal (n = 10), multifocal (n = 11), or diffuse (n = 11). Synchronous bilateral involvement occurred in 6 patients. Color Doppler sonography showed normal testicular vessels within the tumor in 31 of 43 lymphomas (72%). Testicular lymphoma infiltrates through the tubules, preserving the normal vascular architecture of the testis. Depiction of normal testicular vessels crossing the lesion is a useful adjunctive diagnostic criterion.

Dual energy computed tomography quantification of carotid plaques calcification: comparison between monochromatic and polychromatic energies with pathology correlation

PURPOSE

We compared carotid plaque calcification detection sensitivity and apparent cross-sectional area on CT as a function of CT beam energy using conventional CT techniques and virtual mono-energetic CT images generated from dual-energy acquisitions.

METHODS & MATERIALS

Five ex-vivo carotid endarterectomy (CEA) specimens were imaged with dual-energy computed tomography. Virtual monochromatic spectrum (VMS) CT images were reconstructed at energies between 40-140 keV. The same specimens were imaged using conventional polyenergetic spectrum (PS) CT with peak beam energies 80, 100, 120, and 140 kVp. The histological calcium areas on each corresponding CEA specimen were traced manually on digitized images of Toluidine-Blue/Basic-Fuchsin stained plastic sections.

RESULTS

40 keV VMS CT images provided high detection sensitivity (97 %) similar to conventional PS CT images (~96 %). The calcification size measured on CT decreased systematically with increasing CT beam energy; the rate of change was larger for the VMS images than for PS images.

CONCLUSION

From a single dual-energy CT, multiple VMS-CT images can be generated, yielding equivalent detection sensitivity and size correlations as conventional PS-CT in CEA calcification imaging. VMS-CT at 80-100 keV provided the most accurate estimates of calcification size, as compared to histology, but detection sensitivity was reduced for smaller calcifications on these images.

KEY POINTS

• Calcifications depicted at 80-100 keV were most similar to the histology standard. • Conventional polychromatic images demonstrated excellent correlation with plaque size at pathology. • Conventional polychromatic images systematically overestimate plaque size. • Plaque calcifications can be missed on high energy monochromatic images.

Optimization of tagged MRI for quantification of liver stiffness using computer simulated data

The heartbeat has been proposed as an intrinsic source of motion that can be used in combination with tagged Magnetic Resonance Imaging (MRI) to measure displacements induced in the liver as an index of liver stiffness. Optimizing a tagged MRI acquisition protocol in terms of sensitivity to these displacements, which are in the order of pixel size, is necessary to develop the method as a quantification tool for staging fibrosis. We reproduced a study of cardiac-induced strain in the liver at 3T and simulated tagged MR images with different grid tag patterns to evaluate the performance of the Harmonic Phase (HARP) image analysis method and its dependence on the parameters of tag spacing and grid angle. The Partial Volume Effect (PVE), T1 relaxation, and different levels of noise were taken into account. Four displacement fields of increasing intensity were created and applied to the tagged MR images of the liver. These fields simulated the deformation at different liver stiffnesses. An Error Index (EI) was calculated to evaluate the estimation accuracy for various parameter values. In the absence of noise, the estimation accuracy of the displacement fields increased as tag spacings decreased. EIs for each of the four displacement fields were lower at 0° and the local minima of the EI were found to correspond to multiples of pixel size. The accuracy of the estimation decreased for increasing levels of added noise; as the level increased, the improved estimation caused by decreasing the tag spacing tended to zero. The optimal tag spacing turned out to be a compromise between the smallest tag period that is a multiple of the pixel size and is achievable in a real acquisition and the tag spacing that guarantees an accurate liver displacement measure in the presence of realistic levels of noise.

Multi-modal CT scanning in the evaluation of cerebrovascular disease patients

Ischemic stroke currently represents one of the leading causes of severe disability and mortality in the Western World. Until now, angiography was the most used imaging technique for the detection of the extra-cranial and intracranial vessel pathology. Currently, however, non-invasive imaging tool like ultrasound (US), magnetic resonance (MR) and computed tomography (CT) have proven capable of offering a detailed analysis of the vascular system. CT in particular represents an advanced system to explore the pathology of carotid arteries and intracranial vessels and also offers tools like CT perfusion (CTP) that provides valuable information of the brain's vascular physiology by increasing the stroke diagnostic. In this review, our purpose is to discuss stroke risk prediction and detection using CT.

A comprehensive review of the retroperitoneal anatomy, neoplasms, and pattern of disease spread

A clear understanding of the normal anatomy and pattern of disease spread is important in evaluating many retroperitoneal disorders. Primary retroperitoneal tumors are uncommon, accounting for 0.1%-0.2% of all malignancies in the body; 80%-90% of all primary retroperitoneal tumors are malignant. The primary retroperitoneal neoplasms can be divided into solid or cystic masses. The solid neoplasms can be classified according to their tissue of origin into 3 main categories: mesodermal tumors, neurogenic tumors, and extragonadal germ cell tumors. Computed tomography and magnetic resonance imaging play a vital role in the localization, characterization, evaluation of the extent of local invasion, assessment of metastases, and determination of treatment response for these tumors. The diagnosis of a primary retroperitoneal malignancy is often challenging owing to overlap of imaging findings. A definitive diagnosis can be established only at histopathologic analysis. However, knowledge of the important tumor characteristics, growth pattern, and vascularity can assist in narrowing the differential diagnosis.

Imaging of the carotid artery vulnerable plaque

Atherosclerosis involving the carotid arteries has a high prevalence in the population worldwide. This condition is significant because accidents of the carotid artery plaque are associated with the development of cerebrovascular events. For this reason, carotid atherosclerotic disease needs to be diagnosed and those determinants that are associated to an increased risk of stroke need to be identified. The degree of stenosis typically has been considered the parameter of choice to determine the therapeutical approach, but several recently published investigations have demonstrated that the degree of luminal stenosis is only an indirect indicator of the atherosclerotic process and that direct assessment of the plaque structure and composition may be key to predict the development of future cerebrovascular ischemic events. The concept of "vulnerable plaque" was born, referring to those plaque's parameters that concur to the instability of the plaque making it more prone to the rupture and distal embolization. The purpose of this review is to describe the imaging characteristics of "vulnerable carotid plaques."

Magnetic resonance elastography in the diagnosis of hepatic fibrosis

Liver fibrosis is a common feature of many chronic liver diseases, and can ultimately progress to cirrhosis. Conventional imaging is insensitive to liver fibrosis, necessitating a liver biopsy for diagnosis and monitoring of progression. However, liver biopsy risks complications, and is an imperfect gold standard in view of sampling error and intraobserver or interobserver variation. Magnetic resonance elastography (MRE) is a noninvasive method for assessing the mechanical properties of tissues and is gaining credence as a method of assessment for hepatic fibrosis. The aim of this review is to describe how MRE is performed, to review the present literature on the subject, to compare MRE with other noninvasive techniques used to assess for liver fibrosis, and to highlight areas of future research.

Cyst with a mural nodule tumor of the brain

The purpose of this article is to illustrate the imaging findings of lesions that present as cyst with a mural nodule tumor (CMNT). CMNT is a subtype pattern of intra-axial enhancement in central nervous system tumors, typical of a variety of brain neoplasms, including, as the most common, hemangioblastoma, pilocytic astrocytoma, ganglioglioma and pleomorphic xanthoastrocytoma and as less common tanycytic ependymoma, intraparenchymal schwannoma, desmoplastic infantile ganglioglioma and cystic metastasis. A retrospective design was chosen given the rarity of CMNT. Relevant cases were obtained retrospectively to review the different lesions that can present with the appearance of CMNT.

Hepatocellular carcinoma: detection with diffusion-weighted versus contrast-enhanced magnetic resonance imaging in pretransplant patients

This study evaluates the performance of diffusion-weighted magnetic resonance imaging (DWI) for the detection of hepatocellular carcinoma (HCC) in pre-liver transplantation patients, compared and combined with contrast-enhanced T1-weighted imaging (CET1WI), using liver explant as the standard of reference. We included 52 patients with cirrhosis (40 men, 12 women; mean age, 56 years) who underwent DWI and CET1WI within 90 days of liver transplantation. Magnetic resonance images were analyzed for HCC detection in three separate sessions by two independent observers: DWI images (DW-set), CET1WI (CE-set), and all images together (All-set). Sensitivity, specificity, positive predictive value (PPV), negative predictive value (NPV), per-patient accuracy, and per-lesion PPV were calculated for each image set. A total of 72 HCCs were present in 33 patients at explant (mean size, 1.5 cm [range, 0.3-6.2 cm]). Per-patient sensitivity and NPV of CE-set were significantly higher than those of DW-set when using pooled data between observers (P = 0.02 and 0.03, respectively), whereas specificity, PPV, and accuracy were equivalent. Per-lesion sensitivity was significantly higher for CE-set versus DW-set (59.0% versus 43.8%; P = 0.008, pooled data from two observers). When stratified by lesion size, the difference was significant only for lesions with a size between 1 and 2 cm (42.0% for DW-set versus 74.0% for CE-set; P = 0.001). The addition of DWI to CET1WI improved sensitivity for the more experienced observer.

CONCLUSION

DWI is outperformed by CET1WI for detection of HCC, but represents a reasonable alternative to CET1WI for detection of HCC with a size above 2 cm. The addition of DWI to CET1WI slightly increases the detection rate.

Low-dose, prospective triggered high-pitch spiral coronary computed tomography angiography: comparison with retrospective spiral technique

RATIONALE AND OBJECTIVES

Cardiac computed tomographic angiography algorithms emphasize radiation reduction while maintaining diagnostic image quality (IQ). The aim of this study was to evaluate IQ and interreader variability using prospective electrocardiographically triggered high-pitch spiral cardiac computed tomographic angiography (FLASH-CT) compared to retrospective electrocardiographic gating (RETRO-CT) for coronary artery disease evaluation in a patient population including overweight and obese individuals.

MATERIALS AND METHODS

Seventy patients (24 women; mean age, 60 years) matched for gender, age, body mass index (27.4 ± 5.5 kg/m(2)), and calcium score (184 ± 328) underwent cardiac computed tomographic angiography, 35 with FLASH-CT (Definition Flash) and 35 with RETRO-CT (Somatom Definition). Images were reconstructed using standard protocols and least motion phase for RETRO-CT acquisitions. Two independent, blinded readers evaluated the coronary arteries using an 18-segment model, grading IQ on a 5-point, Likert-type scale and coronary stenosis on a 5-point semiquantitative and binary scale.

RESULTS

Effective radiation dose (1.50 vs 17.3 mSv, P < .0001) and mean heart rate (58 vs 62 beats/min, P < .05) were significantly lower for FLASH-CT compared to RETRO-CT. Seven hundred forty segments (> 1.5 mm) were evaluated. There was no significant difference between FLASH-CT and RETRO-CT scans in overall per-segment IQ (3.11 ± 0.75 vs 3.10 ± 0.82, P = .94). FLASH-CT had noninferior IQ relative to RETRO-CT (95% confidence interval, -0.25 to 0.26). There was no significant difference in interreader variability in diagnosis between FLASH-CT and RETRO-CT for all coronary segments (77.5% vs 78.2%, P = .83).

CONCLUSIONS

FLASH-CT is an acceptable coronary computed tomographic angiographic method for reducing radiation dose without compromising IQ for a patient population including overweight and obese individuals.