Comparison of CT and chemical-shift MRI for differentiating thymoma from non-thymomatous conditions in myasthenia gravis: value of qualitative and quantitative assessment.

AIM: To evaluate the usefulness of computed tomography (CT) and chemical-shift magnetic resonance imaging (MRI) in patients with myasthenia gravis (MG) for differentiating thymoma (THY) from thymic lymphoid hyperplasia (TLH) and normal thymus (NT), and to determine which technique is more accurate. MATERIALS AND METHODS: Eighty-three patients with generalised MG who underwent surgery were divided into the TLH/NT group (A; 65 patients) and THY group (B; 24 patients). Differences in qualitative characteristics and quantitative data (CT: radiodensity in Hounsfield units; MRI: signal intensity index [SII]) between groups were tested using Fisher's exact test and Student's t-test. Logistic regression models were estimated for both qualitative and quantitative analyses. At quantitative analysis, discrimination abilities were determined according to the area under the receiver operating characteristic (ROC) curve (AUROC) with computation of optimal cut-off points. The diagnostic accuracies of CT and MRI were compared using McNemar's test. RESULTS: At qualitative assessment, MRI had higher accuracy than CT (96.4%, 80/83 and 86.7%, 72/83, respectively). At quantitative analysis, both the radiodensity and SII were significantly different between groups (p<0.0001). For CT, at quantitative assessment, the AUROC of the radiodensity in discriminating between groups was 0.904 (optimal cut-off point, 20 HU) with an accuracy of 77.1% (64/83). For MRI, the AUROC of the SII was 0.989 (optimal cut-off point, 7.766%) with an accuracy of 96.4% (80/83), which was significantly higher than CT (p<0.0001). By using optimal cut-off points for cases with an erroneous diagnosis at qualitative assessment, accuracy improved both for CT (89.2%, 74/83) and MRI (97.6%, 81/83). CONCLUSION: Quantitative analysis is useful in evaluating patients with MG and improves the diagnostic accuracy of CT and MRI based on qualitative assessment. Chemical-shift MRI is more reliable than CT in differentiating THYs from non-thymomatous conditions.

Imaging of thymus in myasthenia gravis: from thymic hyperplasia to thymic tumor.

Myasthenia gravis (MG) is an autoimmune disorder often associated with thymic abnormalities. At onset, thymic lymphoid hyperplasia (TLH) and thymoma can be found in up to 65% and 15% of patients, respectively. Diagnostic imaging is crucial in this setting in order to detect the presence and type of the thymic abnormality and in the preoperative planning, when indicated. Chest radiography has a minor role due to its low accuracy. Computed tomography is the imaging modality of choice, although the differentiation between a small thymoma and TLH that appears as a focal soft-tissue mass may be not possible. Magnetic resonance imaging (MRI) is not usually employed, but it is useful in equivocal cases, especially in differentiating focal TLH from thymoma by using chemical-shift sequences for defining the proper management. In addition, diffusion-weighted (DW)-MRI can differentiate lipid-poor normal/hyperplastic thymus from thymoma and could be useful in differentiating non-advanced from advanced thymomas. Positron emission tomography (PET)-CT is not helpful in distinguishing early from advanced thymoma but can be used to differentiate thymic carcinoma from thymoma. Hereby, we discuss the imaging features of thymic abnormalities in MG, even focusing on novel aspects of chemical-shift and DW-MRI.

Computed tomography and thymoma: distinctive findings in invasive and noninvasive thymoma and predictive features of recurrence.

PURPOSE: Our goal was to assess the computed tomography (CT) imaging findings of thymoma and to correlate these features with Masaoka staging system and prognosis. MATERIALS AND METHODS: CT findings of thymoma were analysed in 58 patients who had undergone surgery between January 2002 and September 2007. All cases were classified according to the Masaoka staging system. The presence of various CT findings was correlated with tumour invasiveness and recurrence. In statistical analysis, a p value <0.05 was interpreted as significant. RESULTS: The study found 26 noninvasive thymomas and 32 invasive thymomas. Invasive thymomas were more likely to be greater in size (p<0.01), with lobulated or irregular contours (p<0.02), a necrotic or cystic component (p<0.04), foci of calcification (p<0.05) and heterogeneous contrast enhancement (p<0.01) than were noninvasive thymomas. Disease progression developed in nine of 58 patients. Tumour recurrence and metastasis correlated with greater size (p<0.04), lobulated or irregular contours (p<0.01), complete mediastinal fat obliteration (p<0.01), great vessel invasion (p<0.01) and pleural implants (p<0.02). CONCLUSIONS: CT is useful in differentiating invasive from noninvasive thymomas and plays an important role in evaluating and treating these patients for multimodal therapy with neoadjuvant approaches. Moreover, CT findings may serve as predictors of postoperative recurrence or metastasis.

Endovascular Cerebral Venous Sinus Imaging with Optical Coherence Tomography.

BACKGROUND AND PURPOSE: Imaging of the cerebral venous sinuses has evolved Substantially during the past 2 decades, and most recently intravascular sinus imaging with sonography has shed light on the pathophysiology of sinus thrombosis and intracranial hypertension. Optical coherence tomography is the highest resolution intravascular imaging technique available but has not been previously used in cerebral sinus imaging. The purpose of this study was to develop a preclinical animal model of endovascular optical coherence tomography cerebral venous sinus imaging and compare optical coherence tomography findings with histology. MATERIALS AND METHODS: Four consecutive Yorkshire swine were selected. The superior sagittal sinus was first catheterized with a microwire, and the optical coherence tomography catheter was delivered via a monorail technique into the sinus. Luminal blood was cleared with a single arterial injection. After structural and Doppler optical coherence tomography imaging, a craniotomy was performed and the sinus and adjacent dura/veins were resected. Bland-Altman analysis was performed to compare optical coherence tomography and histology. RESULTS: Technically successful optical coherence tomography images were obtained in 3 of 4 swine. The luminal environment and visualization of dural arteries and draining cortical veins were characterized. The average maximum diameters of the sinus, dural arteries, and cortical veins were 3.14 mm, 135 µm, and 260 µm, respectively. Bland-Altman analysis demonstrated good agreement between histology and optical coherence tomography images. CONCLUSIONS: Endovascular optical coherence tomography imaging was feasible in this preclinical animal study. Adoption of this imaging technique in the human cerebral venous sinus could aid in the diagnosis, treatment, and understanding of the pathophysiology of various diseases of the sinus. Human safety and feasibility studies are needed.

Clinical application of lung ultrasound in patients with acute dyspnea: differential diagnosis between cardiogenic and pulmonary causes.

This review discusses the usefulness of bedside lung ultrasound in the diagnostic distinction between the various causes of acute dyspnoea in the emergency department, with special attention to the differential diagnosis of pulmonary oedema and exacerbation of chronic obstructive pulmonary disease (COPD). This is made possible by using mid- to low-end scanners and simple acquisition techniques accessible to both radiologists and clinicians. Major advantages include ready availability at the bedside, the absence of ionising radiation, high reproducibility and cost efficiency. The technique is based on the recognition and analysis of sonographic artefacts rather than direct visualisation of the pulmonary structures. These artefacts are caused by the interaction of water-rich structures and air, called comet tails or B-lines. When such artefacts are widely detected on anterolateral transthoracic lung scans, diffuse alveolar-interstitial syndrome can be diagnosed, which is often a sign of acute pulmonary oedema. This condition rules out exacerbation of COPD as the main cause of acute dyspnoea.

Late presentation of ureteral injury following laparoscopic colorectal surgery.

Iatrogenic ureteral injury is an uncommon but dangerous complication of abdominal and pelvic surgery. When recognized and promptly treated, most ureteral lesions heal without sequelae. Instead, undetected injuries may last for a prolonged period of time since symptoms and signs are usually subtle and nonspecific, even if evolution may be life threatening. In doubtful cases the diagnostic role of modern multiphase helical computed tomography is crucial. We describe the late presentation in the Emergency Department of a case of double left ureteral injury after abdominal surgery, and illustrate the appearance of the lesions at computerized tomography.

CT-guided percutaneous transthoracic biopsy in the diagnosis of mediastinal masses: evaluation of 73 procedures.

PURPOSE: This study was performed to evaluate the factors affecting the diagnostic accuracy and rate of complications of CT-guided percutaneous transthoracic needle biopsy of mediastinal masses. MATERIALS AND METHODS: We reviewed 73 consecutive mediastinal biopsies in 70 patients. Final diagnoses were based on a retrospective analysis of surgical outcomes, results of repeat biopsies or findings of imaging and clinical follow-up lasting at least 4 months. Benign and malignant biopsy findings were compared with the final outcomes to determine the diagnostic accuracy of the method. Finally, we analysed the complications. RESULTS: CT-guided percutaneous transthoracic needle biopsy provided adequate samples in 61/73 cases, with a total sample rate of 83.6%. Of these 61 biopsies, 51 yielded a correct diagnosis with specific histological typing, mainly in the case of thymoma and metastasis. Lymphomas were less reliably diagnosed. The overall sensitivity, specificity, positive predictive value, negative predictive value and diagnostic accuracy values were 83.6%, 100%, 100%, 35.3% and 83.6%, respectively. Pneumothorax was the most common complication (5.5%). CONCLUSIONS: CT-guided percutaneous transthoracic needle biopsy is an easy, reliable and safe procedure that obviates the need for exploratory surgery in medically treatable or unresectable cases. It should be the first invasive procedure in the diagnostic workup of mediastinal masses.

Accuracy of CT-guided transthoracic needle biopsy of lung lesions: factors affecting diagnostic yield.

PURPOSE: This study was performed to analyse the variables affecting the diagnostic accuracy of computed tomography (CT)-guided transthoracic needle biopsy of pulmonary lesions. MATERIALS AND METHODS: A retrospective study of 612 consecutive procedures with confirmed final diagnoses was undertaken. Benign and malignant needle biopsy results were compared with final outcomes to determine diagnostic accuracy. A statistical analysis of factors related to patient characteristics, lung lesions and biopsy technique was performed to determine possible influences on diagnostic yield. A p value less than 0.05 was interpreted as statistically significant. RESULTS: There were 508 (83%) malignant and 104 (17%) benign lesions. Sensitivity, specificity, positive predictive value, negative predictive value and accuracy for a diagnosis of malignancy were 90.2%, 99.0%, 99.8%, 67.3% and 91.7%, respectively. Overall diagnostic accuracy was 83.3%. Variables affecting diagnostic accuracy were the final diagnosis (benign 67%, malignant 92%; p<0.001) and lesion size (lesions<1.5 cm 68%, lesions 1.5-5.0 cm 87%, lesions>5 cm 78%; p<0.05). CONCLUSIONS: In CT-guided transthoracic needle biopsy, the final diagnosis and lesion size affect diagnostic accuracy: benign lung lesions and lesions smaller than 1.5 cm or larger than 5.0 cm in diameter provide lower diagnostic yield.

The anterior mediastinum: anatomy and imaging procedures.

The mediastinum is divided into compartments (anterior, middle, posterior) on the basis of lateral chest radiographs. Several anatomical and radiological classifications of the mediastinum are reported in the literature. Most mediastinal abnormalities are initially suspected following chest radiography; the need for further investigation and the most appropriate imaging modality are largely dictated by the tentative diagnosis made on this examination. Although routine chest radiography initiates the evaluation of mediastinal disorders, it is rarely diagnostic: notable exceptions are teeth or bones within a mass, which are diagnostic of a teratoma; air/fluid levels suggest an oesophageal origin, hernia, cyst, or abscess. Chest radiography is followed by spiral computed tomography (sCT). However, even sCT with contrast material is occasionally diagnostic (a confident diagnosis can be made of some lesions such as mature teratoma and mediastinal goiter) but is usually sufficient for preoperative evaluation before mediastinotomy or mediastinoscopy: it is instrumental in planning further diagnostic workup. In certain cases, magnetic resonance imaging (MRI) may be complementary to sCT, but its use is not considered routine. Besides, although the anterior mediastinum is suitable for sonographic examination, the diagnostic value of ultrasonography has not been fully exploited. Thyroid scanning with radioactive iodine is useful in identifying and evaluating masses of suspected thyroid origin. The role of fluorodeoxyglucose positron emission tomography (FDG-PET) in mediastinal diseases continues to be evaluated: it has potential for differentiating between benign and malignant disease and is expected to play a more extensive role in the imaging of mediastinal neoplasms in the future. In this paper, the radiological features of masses located in the anterior mediastinum are discussed, with particular reference to radiographic and CT patterns useful to the clinician's everyday practice.

The anterior mediastinum: diseases.

Mediastinal tumours are frequently asymptomatic and first noted on routine chest radiograph. In most cases, evaluation should proceed to spiral computed tomography (sCT) of the chest with iodinated contrast material. The specific location and appearance of tumours on sCT is instrumental in planning further diagnostic and treatment strategies. Primary tumours in the anterior mediastinum account for half of all mediastinal masses. They comprise various benign and malignant neoplasms, but a wide variety of nonneoplastic lesions (developmental, inflammatory) can present as a localised mass in this compartment. The most common primary anterior mediastinal tumours are thymoma, teratoma and lymphoma; all other lesions are rare. Nonneoplastic conditions include thymic cysts, lymphangioma and intrathoracic goitre. Understanding the pathology, clinical presentation, imaging and diagnosis of the major tumour types is instrumental in the safe and efficient work-up of a mediastinal mass. Patients with primary mediastinal masses and cysts will usually undergo surgical resection; radiological and clinical features should prompt limited biopsy specimens followed by oncologic consultation, and chemotherapy or radiotherapy when appropriate. The objective of this review was to examine the role of diagnostic imaging in the management of masses of the anterior mediastinum.