Brent P. Little

Mapping the future of cardiac MR imaging: case-based review of T1 and T2 mapping techniques.

Cardiac magnetic resonance (MR) imaging has grown over the past several decades into a validated, noninvasive diagnostic imaging tool with a pivotal role in cardiac morphologic and functional assessment and tissue characterization. With traditional cardiac MR imaging sequences, assessment of various pathologic conditions ranging from ischemic and nonischemic cardiomyopathy to cardiac involvement in systemic diseases (eg, amyloidosis and sarcoidosis) is possible; however, these sequences are most useful in focal myocardial disease, and image interpretation relies on subjective qualitative analysis of signal intensity. Newer T1 and T2 myocardial mapping techniques offer a quantitative assessment of the myocardium (by using T1 and T2 relaxation times), which can be helpful in focal disease, and demonstrate special utility in the evaluation of diffuse myocardial disease (eg, edema and fibrosis). Altered T1 and T2 relaxation times in disease states can be compared with published ranges of normal relaxation times in healthy patients. In conjunction with traditional cardiac MR imaging sequences, T1 and T2 mapping can limit the interpatient and interstudy variability that are common with qualitative analysis and may provide clinical markers for long-term follow-up.

Bronchiectasis: Mechanisms and Imaging Clues of Associated Common and Uncommon Diseases

Bronchiectasis is permanent irreversible dilatation of the airways and occurs in a variety of pathologic processes. Recurrent infection and inflammation and the resulting chemical and cellular cascade lead to permanent architectural changes in the airways. Bronchiectasis can confer substantial potential morbidity, usually secondary to recurrent infection. In severe cases of bronchiectasis, massive hemoptysis can lead to death. Thin-section computed tomography is the most sensitive imaging modality for the detection of bronchiectasis; findings include bronchial diameter exceeding that of the adjacent pulmonary artery and lack of normal tapering of terminal bronchioles as they course toward the lung periphery. The authors will review various causes of bronchiectasis, including common causes, such as recurrent infection or aspiration, and uncommon causes, such as congenital immunodeficiencies and disorders of cartilage development. The authors will also present an approach emphasizing the distribution (apical versus basal and central versus peripheral) and concomitant findings, such as nodules, cavities, and/or lymphadenopathy, that can assist in narrowing the differential diagnosis. Although an adequate understanding of these underlying causes in conjunction with their specific imaging appearances will allow radiologists to more confidently determine the process causing this common radiologic finding, clinical history and patient demographic characteristics play an integral role in determining a pertinent and concise differential diagnosis.

Conventional Medical Education and the History of Simulation in Radiology

Simulation is a promising method for improving clinician performance, enhancing team training, increasing patient safety, and preventing errors. Training scenarios to enrich medical student and resident education, and apply toward competency assessment, recertification, and credentialing are important applications of simulation in radiology. This review will describe simulation training for procedural skills, interpretive and noninterpretive skills, team-based training and crisis management, professionalism and communication skills, as well as hybrid and in situ applications of simulation training. A brief overview of current simulation equipment and software and the barriers and strategies for implementation are described. Finally, methods of measuring competency and assessment are described, so that the interested reader can successfully implement simulation training into their practice.

Mediastinal Lymph Node Staging: From Noninvasive to Surgical

OBJECTIVE The purpose of this review is to describe the current lymph node stations and lymph node staging of non-small cell lung carcinoma. Minimally invasive and invasive methods of mediastinal lymph node staging are emphasized, and the relative accuracy and limitations of each modality are described. CONCLUSION Lung carcinoma remains the most common cause of cancer death in the United States. Accurate staging of lung cancer is imperative for implementing the correct therapy and assessing patient prognosis.

Proton MRI in the evaluation of pulmonary sarcoidosis: Comparison to chest CT

PURPOSE The purpose of this study was to determine the feasibility of proton MRI of the lung in sarcoidosis patients and the agreement between the imaging appearance of pulmonary sarcoidosis on MRI and CT. MATERIALS AND METHODS Chest CT scans and dedicated pulmonary MRI scans (including HASTE, VIBE, and TrueFISP sequences) were performed within 90 days of each other in 29 patients. The scans were scored for gross parenchymal opacification, reticulation, nodules, and masses using a 3-point lobar scale. Total and subset scores for corresponding MRI and CT scans were compared using the Spearman correlation test, Bland-Altman plots, and Cohens quadratic-weighted kappa analysis. MRI scores were compared to CT by lobe and disease category, using percentage agreement, Spearman rank correlation, and Cohens quadratic-weighted kappa. RESULTS The mean (± s.d.) time between MRI and CT scans was 33 ± 32 days. There was substantial correlation and agreement between total disease scoring on MRI and CT with a Spearman correlation coefficient of 0.774 (p<0.0001) and a Cohens weighted kappa score of 0.646. Correlation and agreement were highest for gross parenchymal opacification (0.695, 0.528) and reticulation (0.609, 0.445), and lowest in the setting of nodules (0.501, 0.305). Agreement testing was not performed for mass scores due to low prevalence. Upper lobe scoring on MRI and CT demonstrated greater agreement compared to the lower lobes (average difference in Cohens weighted kappa score of 0.112). CONCLUSION There is substantial correlation and agreement between MRI and CT in the scoring of pulmonary sarcoidosis, though MRI evaluation in the upper lobes may be more accurate than in the lower lobes.

Should CT Play a Greater Role in Preventing the Resection of Granulomas in the Era of PET

OBJECTIVE PET cannot distinguish between bronchogenic carcinoma and granuloma, but positive scans may prompt surgery. We systematically evaluated the CT appearance of resected carcinomas and granulomas to identify features that could be used to reduce granuloma resections. MATERIALS AND METHODS We retrospectively identified 93 consecutive patients between January 2005 and November 2008 who had resection of a pulmonary nodule pathologically diagnosed as bronchogenic carcinoma or granuloma and preoperative imaging with CT and PET. Each nodule was evaluated on CT for size, doubling time, location, borders, shape, internal characteristics, calcification, clustering, air bronchograms, and cavitation. A diagnostic impression was rendered. Bivariate and logistic regression analyses were performed. Pre-PET data regarding the proportion of resected granulomas and carcinomas between January 1995 and December 1996 were reviewed. RESULTS Sixty-eight percent (65/96) of nodules were carcinomas and 32% (31/96) were granulomas. The CT impression was benign in 65% (20/31) of granulomas and 5% (3/65) of carcinomas (p < 0.0001; negative predictive value [NPV], 87% [20/23]). Specific CT features significantly associated with granuloma were clustering, cavitation, irregular shape, lack of pleural tags, and solid attenuation. The combination of nonspiculated borders, irregular shape, and solid attenuation had an NPV of 86% (12/14). Granulomas represented 18% (9/50) of resected nodules in 1995 and 1996 (p = 0.066). CONCLUSION CT findings reduce but cannot eliminate the possibility that a nodule is malignant. Outcomes-based clinical trials are needed to determine whether CT features of benignity can guide less-invasive initial management and reverse a concerning trend in granuloma resection.

Lung Tissue Concentrations of Pyrazinamide among Patients with Drug-Resistant Pulmonary Tuberculosis

ABSTRACT Improved knowledge regarding the tissue penetration of antituberculosis drugs may help optimize drug management. Patients with drug-resistant pulmonary tuberculosis undergoing adjunctive surgery were enrolled. Serial serum samples were collected, and microdialysis was performed using ex vivo lung tissue to measure pyrazinamide concentrations. Among 10 patients, the median pyrazinamide dose was 24.7 mg/kg of body weight. Imaging revealed predominant lung lesions as cavitary (n = 6 patients), mass-like (n = 3 patients), or consolidative (n = 1 patient). On histopathology examination, all tissue samples had necrosis; eight had a pH of ≤5.5. Tissue samples from two patients were positive for Mycobacterium tuberculosis by culture (pH 5.5 and 7.2). All 10 patients had maximal serum pyrazinamide concentrations within the recommended range of 20 to 60 μg/ml. The median lung tissue free pyrazinamide concentration was 20.96 μg/ml. The median tissue-to-serum pyrazinamide concentration ratio was 0.77 (range, 0.54 to 0.93). There was a significant inverse correlation between tissue pyrazinamide concentrations and the amounts of necrosis (R = −0.66, P = 0.04) and acid-fast bacilli (R = −0.75, P = 0.01) identified by histopathology. We found good penetration of pyrazinamide into lung tissue among patients with pulmonary tuberculosis with a variety of radiological lesion types. Our tissue pH results revealed that most lesions had a pH conducive to pyrazinamide activity. The tissue penetration of pyrazinamide highlights its importance in both drug-susceptible and drug-resistant antituberculosis treatment regimens.

A Comprehensive CT Dose Reduction Program Using the ACR Dose Index Registry

PURPOSE The purpose of this article is to demonstrate the role of the ACR Dose Index Registry(®) (DIR) in a dose reduction program at a large academic health care system. METHODS Using the ACR DIR, radiation doses were collected for four common CT examination types (head without contrast, chest with contrast, chest without contrast, and abdomen and pelvis with contrast). Baseline analysis of 7,255 CT examinations from seven scanners across the institution was performed for the period from December 1, 2011, to March 15, 2012. A comprehensive dose reduction initiative was guided by the identification of targets for dose improvement from the baseline analysis. Data for 14,938 examinations from the same seven scanners were analyzed for the postimplementation period of January 1, 2013, to July 1, 2013. RESULTS The program included protocol changes, iterative reconstruction, optimization of scan acquisition, technologist education, and continuous monitoring with feedback tools. Average decrease in median dose-length product (DLP) across scanners was 30% for chest CT without contrast, 29% for noncontrast head CT, 26% for abdominal and pelvic CT with contrast, and 10% for chest CT with contrast. Compared with average median DLP in the ACR DIR, the median institution-wide CT DLPs after implementation were lower by 33% for chest CT without contrast, 32% for chest CT with contrast, 26% for abdominal and pelvic CT with contrast, and 6% for head CT without contrast. CONCLUSIONS A comprehensive CT dose reduction program using the ACR DIR can lead to substantial dose reduction within a large health care system.

Outcome of Recommendations for Radiographic Follow-Up of Pneumonia on Outpatient Chest Radiography

OBJECTIVE Follow-up chest radiographs are frequently recommended by radiologists to document the clearing of radiographically suspected pneumonia. However, the clinical utility of follow-up radiography is not well understood. The purpose of this study was to examine the incidence of important pulmonary pathology revealed during follow-up imaging of suspected pneumonia on outpatient chest radiography. MATERIALS AND METHODS Reports of 29,138 outpatient chest radiography examinations performed at an academic medical center in 2008 were searched to identify cases in which the radiologist recommended follow-up chest radiography for presumed community-acquired pneumonia (n = 618). Descriptions of index radiographic abnormalities were recorded. Reports of follow-up imaging (radiography and CT) performed during the period from January 2008 to January 2010 were reviewed to assess the outcome of the index abnormality. Clinical history, demographics, microbiology, and pathology reports were reviewed and recorded. RESULTS Compliance with follow-up imaging recommendations was 76.7%. In nine of 618 cases (1.5%), a newly diagnosed malignancy corresponded to the abnormality on chest radiography initially suspected to be pneumonia. In 23 of 618 cases (3.7%), an alternative nonmalignant disease corresponded with the abnormality on chest radiography initially suspected to be pneumonia. Therefore, in 32 of 618 patients (5.2%), significant new pulmonary diagnoses were established during follow-up imaging of suspected pneumonia. CONCLUSION Follow-up imaging of radiographically suspected pneumonia leads to a small number of new diagnoses of malignancy and important nonmalignant diseases, which may alter patient management.

Approach to chest computed tomography.

Computed tomography (CT) is central to the detection and diagnosis of a wide variety of pulmonary, cardiovascular, and other diseases of the chest. Successful interpretation of thoracic CT requires both an appreciation of the spectrum of normal appearances of the chest and a systematic approach to the characterization of thoracic pathology. This article provides an introduction to basic CT techniques and protocols, a review of normal CT anatomy, and an overview of commonly encountered abnormalities.