Stepwise diagnostic algorithm for high-attenuation pulmonary abnormalities on CT.

High-attenuation pulmonary abnormalities are commonly seen on CT. These findings are increasingly encountered with the growing number of CT examinations and the wide availability of thin-slice images. The abnormalities include benign lesions, such as infectious granulomatous diseases and metabolic diseases, and malignant tumors, such as lung cancers and metastatic tumors. Due to the wide spectrum of diseases, the proper diagnosis of high-attenuation abnormalities can be challenging. The assessment of these abnormal findings requires scrutiny, and the treatment is imperative. Our proposed stepwise diagnostic algorithm consists of five steps. Step 1: Establish the presence or absence of metallic artifacts. Step 2: Identify associated nodular or mass-like soft tissue components. Step 3: Establish the presence of solitary or multiple lesions if identified in Step 2. Step 4: Ascertain the predominant distribution in the upper or lower lungs if not identified in Step 2. Step 5: Identify the morphological pattern, such as linear, consolidation, nodular, or micronodular if not identified in Step 4. These five steps to diagnosing high-attenuation abnormalities subdivide the lesions into nine categories. This stepwise radiologic diagnostic approach could help to narrow the differential diagnosis for various pulmonary high-attenuation abnormalities and to achieve a precise diagnosis.Critical relevance statement Our proposed stepwise diagnostic algorithm for high-attenuation pulmonary abnormalities may help to recognize a variety of those high-attenuation findings, to determine whether the associated diseases require further investigation, and to guide appropriate patient management. Key points • To provide a stepwise diagnostic approach to high-attenuation pulmonary abnormalities.• To familiarize radiologists with the varying cause of high-attenuation pulmonary abnormalities.• To recognize which high-attenuation abnormalities require scrutiny and prompt treatment.

Clinical significance of chest CT for the exclusion of COVID-19 in pre-admission screening: Is it worthwhile using chest CT with reverse-transcription polymerase chain reaction test?

BACKGROUND: A single reverse-transcription polymerase chain reaction (RT-PCR) test is not sufficient to exclude COVID-19 in hospital pre-admission screening. However, repeated RT-PCR tests are time-consuming. This study investigates the utility of chest computed tomography (CT) for COVID-19 screening in asymptomatic patients. METHODS: Between April 2020 and March 2021, RT-PCR testing and chest CT were performed to screen COVID-19 in 10 823 asymptomatic patients prior to admission. Chest CT findings were retrospectively evaluated using the reporting system of the Radiological Society of North America. Using RT-PCR results as a reference, we assessed the diagnostic efficacy of chest CT during both the low- and high-prevalence periods of the COVID-19 pandemic. RESULTS: Following a positive RT-PCR test, 20 asymptomatic patients (0.18%) were diagnosed with COVID-19; in the low-prevalence period, 5 of 6556 patients (0.076%) were positive; and in the high-prevalence period, 15 of 4267 patients (0.35%) were positive. Of the 20 asymptomatic COVID-19 positive patients, chest CT results were positive for COVID-19 pneumonia in 8 patients. Chest CT results were false-positive in 185 patients (1.7% false-positive rate, and 60% false-negative rate). Pneumonia that was classified as a "typical appearance" of COVID-19 reported as false-positives in 36 of 39 patients (92.3%). Across the study period, the diagnostic efficacy of "typical appearance" on chest CT were characterized by a sensitivity, specificity, accuracy, positive predictive value (PPV), and negative predictive value (NPV) of 15%, 99.7%, 99.7%, 7.7%, and 99.8%; 20%, 99.6%, 99.6%, 4%, and 99.9%; and 13.3%, 99.7%, 99.7%, 14.3%, and 99.7%, in the entire study, low-, and high-prevalence periods, respectively. CONCLUSIONS: Addition of chest CT to RT-PCR testing provides no benefit to the detection of COVID-19 in asymptomatic patients.

Quantitative Histogram Analysis of T2-Weighted and Diffusion-Weighted Magnetic Resonance Images for Prediction of Malignant Thymic Epithelial Tumors.

PURPOSE: To assess the value of histogram analysis for differentiating a high-risk thymic epithelial tumor (TET) from a low-risk TET using T2-weighted images and the apparent diffusion coefficient (ADC). METHODS: Forty-nine patients with histopathologically proven TET after thymectomy were enrolled in this study and retrospectively classified as having low-risk TET (low-risk thymoma) or high-risk TET (high-risk thymoma or thymic carcinoma). Twelve parameters were obtained from the quantitative histogram analysis. The histogram parameters were compared using the Mann-Whitney U test. Diagnostic efficacy was estimated by receiver-operating characteristic curve analysis. RESULTS: Twenty-five patients were classified as having low-risk TET and 24 as having high-risk TET. The mean ADC value showed diagnostic efficacy for differentiating high-risk TET from low-risk TET, with an area under the curve of 0.7, and was better than when using conventional methods alone. CONCLUSION: The ADC-based histogram analysis could help to differentiate between high-risk and low-risk TETs.

Rapid growth of a mature mediastinal teratoma in a middle-aged woman: A case report.

A mediastinal mass was incidentally detected in a 42-year-old Japanese woman during a routine medical checkup. Computed tomography revealed a 7-cm, well-circumscribed multilocular cystic mass consistent with a mature cystic teratoma; however, no solid or cystic lesion had been detected at a voluntary complete medical checkup 1.5 years earlier. An anterior mediastinal tumor resection was performed, and the histopathological findings were compatible those of a mature teratoma. Although the mechanisms that underlie rapid growth of all tridermic components in a mature teratoma remain unclear, it is presumed that the mechanisms involve hemorrhage, rupture, inflammation caused by pancreatic enzymes, and estrogen hormone activity. We presented a rare case of a rapid formation of a mediastinal teratoma, which revealed that a mediastinal teratoma with all tridermic components could develop in a relatively short period.

A case of pulmonary tuberculosis with multiple nodules mimicking lung metastases.

Tuberculosis (TB) may present as multiple pulmonary nodules mimicking lung metastases. Many asymptomatic cases of TB are detected incidentally on chest radiography, and patients are often negative for acid-fast bacilli staining and culture in spite of having active TB. It is important to know the imaging findings characteristic of pulmonary TB and its variant forms. Multiple pulmonary nodules were detected in an 80-year-old female during a medical checkup. TB was not suspected until her imaging findings worsened; however, in retrospect, centrilobular micronodules were observed amongst multiple well-circumscribed nodules on the initial images and worsened during conservative management. Although bilateral multiple well-circumscribed pulmonary nodules are suggestive of metastases, when a nodule surrounded by centrilobular or satellite micronodules is found, even in the absence of characteristic findings such as cavitation or the tree-in-bud sign, pulmonary TB should be considered in the differential diagnosis to prevent delays in treatment.

A case of pseudocystic liver metastases from an atypical lung carcinoid tumor.

Metastatic neuroendocrine tumors of the liver typically appear as solid, hypervascular masses on imaging. Pseudocysts mimicking simple cysts are extremely rare. A 42-year-old Japanese woman was referred with a single pulmonary mass in the left lower lobe. No metastatic lesion was detected and no occupying lesion in the liver was observed. The lung tumor was diagnosed as an atypical carcinoid. Postoperative investigation revealed new hepatic simple cysts in the liver, which increased in size over time and changed into hemorrhagic cysts. Fluorodeoxyglucose positron emission tomography and somatostatin receptor scintigraphy using 111In-octreotide demonstrated no accumulation in the liver. Our patient did not have symptoms consistent with carcinoid syndrome. The patient underwent partial resection of the cystic lesions of the liver. Gross examination of the tumors demonstrated thin-wall cavitated lesions with hemorrhage which were metastases from the atypical carcinoid of the lung. When a growing cystic lesion with intracystic hemorrhage is found in the liver of a patient with a history of carcinoid tumors, pseudocysts caused by degeneration of a carcinoid metastasis should be considered as a differential diagnosis.

Pulmonary sclerosing pneumocytoma presenting as slow-growing multiple nodules over a long period.

Pulmonary sclerosing pneumocytoma is an uncommon slow-growing benign tumor that usually occurs in middle-aged women and generally presents as a solitary well-defined nodule. An 18-year-old woman was incidentally detected to have multiple lung nodules on chest radiography that slowly increased in size over a period of 7 years. Computed tomography images showed multiple well-defined nodules surrounded by numerous smaller nodules with a maximum diameter of 3 cm in the left lung. A percutaneous core needle biopsy was performed, but malignancy could not be excluded because of the high proportion of papillary structures. A video-assisted partial wedge resection was performed and the pathologic diagnosis was pulmonary sclerosing pneumocytoma. Pulmonary sclerosing pneumocytoma presenting as multiple lung nodules is a rare but very important condition to include in the differential diagnosis of multiple lung nodules. There is a possibility of misdiagnosis of another type of tumor or malignancy on preoperative biopsy. We should be aware not only of the clinical, radiologic, and pathologic features of pulmonary sclerosing pneumocytoma but also of the potential pitfalls in its diagnosis and management.

Interstitial lung abnormalities in a CT lung cancer screening population: prevalence and progression rate.

PURPOSE: To determine the prevalence of interstitial lung abnormalities (ILAs) at initial computed tomography (CT) examination and the rate of progression of ILAs on 2-year follow-up CT images in a National Lung Screening Trial population studied at a single site. MATERIALS AND METHODS: The study was approved by the institutional review board and informed consent was obtained from all participants. Image review for this study was HIPAA compliant. We reviewed the CT images of 884 cigarette smokers who underwent low-dose CT at a single site in the National Lung Screening Trial. CT findings were categorized as having no evidence of ILA, equivocal for ILA, or ILA. We categorized the type of ILA as nonfibrotic (ground-glass opacity, consolidation, mosaic attenuation), or fibrotic (ground glass with reticular pattern, reticular pattern, honeycombing). We evaluated the temporal change of the CT findings (no change, improvement, or progression) of ILA at 2-year follow-up. A χ(2) with Fisher exact test or unpaired t test was used to determine whether smoking parameters were associated with progression of ILA at 2-year follow-up CT. RESULTS: The prevalence of ILA was 9.7% (86 of 884 participants; 95% confidence interval: 7.9%, 11.9%), with a further 11.5% (102 of 884 participants) who had findings equivocal for ILA. The pattern was fibrotic in 19 (2.1%), nonfibrotic in 52 (5.9%), and mixed fibrotic and nonfibrotic in 15 (1.7%) of the 86 participants with ILA. The percentage of current smokers (P = .001) and mean number of cigarette pack-years (P = .001) were significantly higher in those with ILA than those without. At 2-year follow-up of those with ILA (n = 79), findings of nonfibrotic ILA improved in 49% of cases and progressed in 11%. Fibrotic ILA improved in 0% and progressed in 37% of cases. CONCLUSION: ILA is common in cigarette smokers. Nonfibrotic ILA improved in about 50% of cases, and fibrotic ILA progressed in about 37%.

Infectious aortitis caused by Salmonella Dublin followed by aneurysmal dilatation of the abdominal aorta.

A 67-year-old woman was admitted for severe abdominal pain (stomach ache). Computed tomography (CT) revealed gas along the abdominal aortic wall. A blood culture was positive for Salmonella dublin, a gram-negative bacillus that is rare in humans. Treatment with an antibiotic improved the inflammatory signs; however, on the 11th hospital day, the patient complained of sudden severe abdominal pain. Enhanced CT revealed a pseudoaneurysm surrounded by a periaortic abscess. The infected aortic wall, including the aneurysm, was resected and an extra-anatomic bypass was constructed between the axillary artery and the external iliac arteries. The patient recovered fully and her course has been uneventful for the past two years since her discharge.

Longitudinal follow-up of fibrosing interstitial pneumonia: relationship between physiologic testing, computed tomography changes, and survival rate.

PURPOSE: The aim of this study was to evaluate the prognostic implications of computed tomography (CT) and physiologic variables at baseline and on sequential evaluation in patients with fibrosing interstitial pneumonia. MATERIALS AND METHODS: We identified 72 patients with fibrosing interstitial pneumonia (42 with idiopathic disease, 30 with collagen vascular disease). Pulmonary function tests and CT were performed at the time of diagnosis and at a median follow-up of 12 months, respectively. Two chest radiologists scored the extent of specific abnormalities and overall disease on baseline and follow-up CT. Rate of survival was estimated using the Kaplan-Meier method. Three Cox proportional hazards models were constructed to evaluate the relationship between CT and physiologic variables and rate of survival: model 1 included only baseline variables, model 2 included only serial change variables, and model 3 included both baseline and serial change variables. RESULTS: On follow-up CT, the extent of mixed ground-glass and reticular opacities (P<0.001), pure reticular opacity (P=0.04), honeycombing (P=0.02), and overall extent of disease (P<0.001) was increased in the idiopathic group, whereas these variables remained unchanged in the collagen vascular disease group. Patients with idiopathic disease had a shorter rate of survival than those with collagen vascular disease (P=0.03). In model 1, the extent of honeycombing on baseline CT was the only independent predictor of mortality (P=0.02). In model 2, progression in honeycombing was the only predictor of mortality (P=0.005). In model 3, baseline extent of honeycombing and progression of honeycombing were the only independent predictors of mortality (P=0.001 and 0.002, respectively). Neither baseline nor serial change physiologic variables, nor the presence of collagen vascular disease, was predictive of rate of survival. CONCLUSION: The extent of honeycombing at baseline and its progression on follow-up CT are important determinants of rate of survival in patients with fibrosing interstitial pneumonia.

Computed tomographic features of idiopathic fibrosing interstitial pneumonia: comparison with pulmonary fibrosis related to collagen vascular disease.

OBJECTIVE: To compare the computed tomographic (CT) features of idiopathic fibrosing interstitial pneumonia with those of pulmonary fibrosis related to collagen vascular disease (CVD). METHODS: We reviewed the CT scans of 177 patients with diffuse interstitial pulmonary fibrosis, of which 97 had idiopathic fibrosing interstitial pneumonia and 80 had CVD. The CT images were systematically scored for the presence and extent of pulmonary and extrapulmonary abnormalities. Computed tomographic diagnosis of usual interstitial pneumonia (UIP) or nonspecific interstitial pneumonia (NSIP) was assigned. RESULTS: A CT pattern of UIP was identified in 59 (60.8%) of patients with idiopathic fibrosing interstitial pneumonia compared with 15 (18.7%) of those patients with CVD; conversely, the CT diagnosis of NSIP was made in 51 (64%) of patients with CVD compared with 36 (37%) of patients with idiopathic disease (P < 0.01). In 113 patients who had lung biopsy, the CT diagnoses of UIP and NSIP were concordant with the histologic diagnoses in 36 of 50 patients and 34 of 41 patients, respectively. Pleural effusions, esophageal dilation, and pericardial abnormalities were more frequent in patients with CVD than in patients with idiopathic fibrosing interstitial pneumonia. CONCLUSIONS: Compared with patients with CVD, those patients with an idiopathic fibrosing interstitial pneumonia showed a higher prevalence of a UIP pattern and lower prevalence of an NSIP pattern as determined by CT. Identification of coexisting extrapulmonary abnormalities on CT can support a diagnosis of CVD.

Pericardial abnormalities predict the presence of echocardiographically defined pulmonary arterial hypertension in systemic sclerosis-related interstitial lung disease.

OBJECTIVES: To determine the prevalence and significance of pericardial abnormalities in systemic sclerosis (SSc)-related interstitial lung disease (ILD). METHODS: Retrospective study of 41 subjects with SSc-related ILD who underwent evaluation including thoracic high-resolution CT (HRCT) imaging, transthoracic echocardiography (TTE), and pulmonary function testing. HRCT review evaluated the pericardium for the presence of pericardial effusion (PEf), thickness of the anterior pericardial recess (APR) [abnormal defined as > 10 mm], and pericardial thickening as calculated by total pericardial score (TPS) [abnormal defined as > 8 mm]. Pulmonary arterial hypertension (PAH) was defined as a pulmonary artery pressure > 35 mm Hg estimated by TTE. RESULTS: Fifty-nine percent had an abnormal pericardium, 49% had a PEf, 56% had an abnormal APR, and 49% had an abnormal TPS. An abnormal pericardium was more common in men than women. Subjects with and without pericardial abnormalities were otherwise similar with respect to age, SSc classification, autoantibodies, ILD radiographic pattern, and presence of esophageal dilation. Both groups had similar median percentage of predicted total lung capacity, percentage of predicted FVC, percentage of predicted FEV(1), and percentage of predicted diffusion capacity of the lung for carbon monoxide. Subjects with pericardial abnormalities were more likely to have coexistent PAH (35% vs 75%; p = 0.02) and a higher median right ventricular systolic pressure (31 mm Hg vs 44 mm Hg; p = 0.03). Multiple logistic regression revealed that TPS was the best individual predictor of the presence of TTE-defined PAH. CONCLUSIONS: In patients with SSc-related ILD, pericardial abnormalities are commonly seen on HRCT, and their presence is strongly associated with echocardiographically defined PAH, with abnormal TPS as the best individual predictor.

Idiopathic pulmonary fibrosis/usual interstitial pneumonia: imaging diagnosis, spectrum of abnormalities, and temporal progression.

The role of high-resolution computed tomography in the diagnosis of interstitial lung disease is increasing as our understanding of its diagnostic accuracy improves. The characteristic findings on high-resolution computed tomography of usual interstitial pneumonia (UIP) are reticular abnormality and honeycombing with basal predominance. Honeycombing is a strong predictor of UIP and also is an important predictor of mortality. Because UIP carries the most adverse prognosis among the subtypes of idiopathic interstitial pneumonia, it is important to be able to differentiate this entity from nonspecific interstitial pneumonia and desquamative interstitial pneumonia from UIP, because these patients may show similar clinical presentations. A confident computed tomography diagnosis of UIP, in association with typical clinical features, will allow the clinician to avoid an unnecessary surgical biopsy.