Advanced Technologies for Imaging and Visualization of the Tracheobronchial Tree: From Computed Tomography and MRI to Virtual Endoscopy.

Advanced imaging plays an increasingly important role in the evaluation of the trachea. The use of computed tomography (CT) has evolved to include multi-planar reconstructions and 3-dimensional reconstructions for the evaluation of benign and malignant disease of the trachea. Advanced applications of CT include dynamic expiratory imaging for the diagnosis of tracheomalacia and virtual endoscopy as a complementary or alternative examination to flexible bronchoscopy. MRI of the trachea has limited applications but may see increased use in the future.

Low-dose computed tomography (LDCT) in workers previously exposed to asbestos: detection of parenchymal lung disease.

OBJECTIVES: To evaluate the lungs of asymptomatic asbestos-exposed workers who were screened for lung cancer and mesothelioma using low-dose computed tomography (LDCT) for parenchymal abnormalities. METHODS: Three hundred fifteen baseline LDCT studies of the chest of participants with at least 20 years' exposure to asbestos or presence of pleural plaques before enrollment on chest radiographs were analyzed. RESULTS: Three hundred fifteen subjects were studied. The mean age was 61.7 years, and the mean exposure to asbestos was 26.9 years. One hundred seventy-five (56%) participants had absence of parenchymal findings with a mean age of 58.7 years, mean exposure of 24.6 years, and a mean smoking pack years of 19. One hundred forty subjects (44%) had parenchymal findings (138 men and 2 women) with a mean age of 65.3 years, mean exposure of 29.73 years, and a mean smoking pack years of 21.5 years. Participants who had parenchymal manifestations were more likely to be older and have longer exposure to asbestos compared to participants who had no relevant parenchymal findings. There was no statistical difference in the mean smoking pack years between the groups with and without parenchymal findings. CONCLUSIONS: Low-dose CT could demonstrate parenchymal lung manifestations in this higher-risk asymptomatic group with prior exposure to asbestos in the setting of screening for lung cancer and mesothelioma. Individuals with longer exposure to asbestos and of higher age have more pulmonary abnormalities. The age and the latency of exposure play an important role given that the asbestos-related parenchymal abnormalities on LDCT were more prevalent in the elderly participants and with longer periods of exposure.

Lung cancer screening using low-dose computed tomography in at-risk individuals: the Toronto experience.

OBJECTIVE: The Department of Medical Imaging at the University Health Network in Toronto is performing a lung cancer screening study, utilizing low-dose computed tomography (LDCT) as the modality. Baseline and annual repeat results are reported on the first 3352 participants, enrolled between June 2003 and May 2007. METHODS: Enrollment was limited to those aged 50 years or older, with a smoking history of at least 10 pack-years, no previous cancer and general good health. A helical low-dose CT (LDCT) of the chest was performed using 120kVp, 40-60mA, images were reconstructed with 1-1.25mm overlapping slices. The primary objectives were the detection of parenchymal nodules and diagnosis of early stage lung cancer. Baseline LDCTs were termed positive if at least one indeterminate non-calcified nodule 5mm or larger in size, or non-solid nodule 8mm or larger in size was identified. Follow up periods for individuals with a positive baseline LDCT were determined by nodule characteristics. RESULTS: The median age at baseline was 60 years (range 50-83), with a median of 30 pack-years of cigarette smoking (range 10-189). Baseline CT evaluations were positive in 600 (18%) participants. To date, 2686 (80%) of the participants have returned for at least one annual repeat screening LDCT. Biopsies have been recommended for 82 participants since the study began, and 64 have been diagnosed with screen-detected cancer (62 lung, two plasmacytoma of the rib). A total of 65 lung cancers have been diagnosed (62 screen-detected, 3 interim), 57 are NSCLC (82% with known stage are stage I or II) and the rate of surgical resection was 80%. Sensitivity and specificity of the protocol in successfully diagnosing early stage lung cancers were 87.7% and 99.3%, respectively. CONCLUSIONS: Data indicate that LDCT can identify small lung cancers in an at-risk population. The diagnostic algorithm results in few false-positive invasive procedures. Most cancers are detected at an early stage, where the cancer is resectable with a greater potential for cure. Long-term follow up of lung cancer cases will be carried out to determine survival.

Tree-in-bud pattern on thoracic CT due to pulmonary intravascular metastases from pancreatic adenocarcinoma.

We report a case of pulmonary intravascular metastases from pancreatic adenocarcinoma manifesting as tree-in-bud pattern on thoracic computed tomography. Although infectious bronchiolitis is the most common cause of tree-in-bud pattern, this case emphasizes that the differential diagnoses include pulmonary intravascular metastases, particularly in patients with extrapulmonary adenocarcinomas.

Imaging of lung transplantation: review.

OBJECTIVE Lung transplantation is an established treatment for end-stage pulmonary disease. Complications of lung transplantation include airway stenosis and dehiscence, reimplantation response, acute rejection, infection, posttransplantation lymphoproliferative disorder, and bronchiolitis obliterans syndrome. The incidence of graft rejection and airway anastomosis experienced in the early years of lung transplantation have been significantly reduced by advances in immunosuppression and surgical techniques. Infection is currently the most common cause of mortality during the first 6 months after transplantation, whereas chronic rejection or obliterative bronchiolitis is the most common cause of mortality thereafter. This article reviews the radiologic findings of different surgical techniques as well as the common early and late complications of lung transplantation. CONCLUSION Radiology plays a pivotal role in the diagnosis and management of complications of lung transplantation. Advancements in surgical technique and medical therapy influence the spectrum of expected radiologic findings. Familiarity with the radiologic appearances of common surgical techniques and complications of lung transplantation is important.

Lung cancer screening with low-dose computed tomography: Canadian experience.

INTRODUCTION: In 2003, the Department of Medical Imaging at the University Health Network in Toronto, Ontario, became the first Canadian site of the Intemational Early Lung Cancer Action Program (I-ELCAP). We report the results from the first 1000 baseline studies. METHODS: Between June 2003 and December 2005, we enrolled 1000 high-risk smokers (that is, smokers with a history of at least 10 pack years, or the equivalent of one pack daily for 10 years), aged 55 years or older. A low-dose helical computed tomography (CT) (40 to 60 mA, 120 kV) was performed with 1.0 mm to 1.25 mm collimation. Nodules found at baseline were followed according to the I-ELCAP protocol: (1) no noncalcified nodules (NCNs) or NCNs < or =4 mm or nonsolid nodules < 8 mm, annual repeat; (2) NCNs > or =5 mm or nonsolid nodules > or =8 mm, 3-month follow-up; or (3) nonsolid nodules > or =15 mm, antibiotics and 1-month follow-up. RESULTS: The first 1000 study participants were aged 63 years, standard deviation (SD) 6 years, with a smoking history of 38 pack years, SD 22 pack years; 662 (66%) were former smokers, and 338 (34%) were current smokers; 453 (45%) were men, and 547 (55%) were women. Of the participants, 256 (26%) had a positive baseline low-dose computed tomography (LDCT) scan; 227 (23%) were followed after 3 months and 16 (1.6%) after 1 month; 7 (0.7%) received a contrast-enhanced CT and 6 (0.6%) an immediate CT-guided biopsy. Twenty-six invasive procedures were performed: 22 CT-guided biopsies, 1 ultrasound-guided lymph node metastasis biopsy, 1 bronchoscopic biopsy, and 2 surgeries. The malignancy rate of the invasive procedures was 85%. Overall, the malignancy prevalence is 2.2%. Of the malignancies, 20 are lung carcinomas: 19 non-small-cell lung carcinomas (NSCLCs) (14 adenocarcinoma or bronchioalveolar carcinoma [BAC], 4 squamous carcinoma, and 1 large-cell carcinoma) and 1 small-cell carcinoma; 15 (78%) of the NSCLCs are Stage I. Fourteen patients underwent surgery (1 pneumonectomy, 9 lobectomies, and 4 segmentectomies). CONCLUSION: Our results confirm that LDCT identifies small, early-stage, resectable lung cancer in a high-risk population.

Bronchiolitis obliterans syndrome in lung transplant recipients: can thin-section CT findings predict disease before its clinical appearance?

PURPOSE: To determine whether there are thin-section computed tomographic (CT) features that predict bronchiolitis obliterans syndrome (BOS) in lung transplant recipients before the clinical appearance and during the early stages of the disease. MATERIALS AND METHODS: Two hundred ninety-eight thin-section CT scans obtained in 26 lung transplant recipients who did (study group) and 26 lung transplant recipients who did not (control group) develop BOS were reviewed for the presence of mosaic perfusion, bronchiectasis, bronchial wall thickening, and air trapping. BOS was defined by using the recently revised definition of the International Society for Heart and Lung Transplantation. CT scans obtained in the BOS group were divided into three groups: Group A consisted of the last scans obtained before the clinical appearance of BOS; groups B and C consisted of, respectively, the first and last scans obtained after the clinical appearance of BOS. Scans obtained in the control group were acquired during similar posttransplantation periods and matched to scans in each BOS group. Sensitivity, specificity, and positive and negative predictive values were calculated separately for each subgroup. The optimal threshold for each thin-section CT-depicted abnormality was defined by using receiver operating characteristics analysis. RESULTS: The sensitivities of air trapping for the diagnosis of BOS during the periods in which the scans in groups A, B, and C were obtained were 50%, 44%, and 64%, respectively; specificities were 80%, 100%, and 80% respectively. Sensitivities of mosaic perfusion were 4%, 20%, and 36%, respectively; specificities were 100%, 96%, and 96%, respectively. Sensitivities of bronchiectasis were 25%, 24%, and 32%, respectively; specificities were 80%, 80%, and 96%, respectively. Sensitivities of bronchial wall thickening were 4%, 24%, and 40%, respectively; specificities were 96%, 84%, and 80%, respectively. Air trapping was seen intermittently in nine (43%) of 21 patients with CT scans that depicted this finding at least once. CONCLUSION: The value of the finding of air trapping before the clinical appearance and during the early stages of BOS is lower than has been previously reported. When using the recently revised criteria for BOS, the role of thin-section CT as a screening test to evaluate patients with lung transplants appears to be limited.

Radiologic pattern of disease in patients with severe acute respiratory syndrome: the Toronto experience.

Severe acute respiratory syndrome (SARS) is a transmissible febrile respiratory illness caused by a recently discovered coronavirus. Various patterns of disease progression may be observed that have different implications for the prognosis in those affected by SARS. The appearance of the lungs on chest radiographs of patients with this condition may be normal or may include focal airspace opacity or multifocal or diffuse opacities. Thoracic computed tomography (CT) is more sensitive in depicting SARS than is conventional chest radiography, and CT images obtained in patients with normal chest radiographs may show extensive disease and airspace consolidation. However, because the radiologic appearance of SARS is not distinct from that of other diseases that cause lower respiratory tract infection, early identification of SARS will depend in part on the prompt recognition of clusters of cases of febrile respiratory tract illness. To aid in the differential diagnosis and management of SARS, radiologists must be familiar with the typical clinical and histopathologic findings, as well as the radiologic features of the disease.

Prognostic significance of the radiographic pattern of disease in patients with severe acute respiratory syndrome.

OBJECTIVE: This study was performed to evaluate the prognostic significance of the radiographic pattern of disease in probable cases of severe acute respiratory syndrome (SARS). MATERIALS AND METHODS: A retrospective review of 439 radiographs was performed for 51 patients with a final diagnosis of probable SARS. Forty-nine patients were followed up for a mean interval of 23 days (range, 2-63 days). RESULTS: Abnormal findings on a chest radiograph were noted at presentation in 80.4% (41/51) of patients. Four radiographic patterns were seen: normal (group 1) in 19.6% (10/51), focal opacity (group 2) in 39.2% (20/51), multifocal opacities (group 3) in 27.5% (14/51), and diffuse air-space opacification (group 4) in 13.7% (7/51). Radiographic progression of disease occurred in 38.8% (19/49) of the patients in groups 1-4. There were no deaths in groups 1 and 2. In group 3, one (7.7%) of the 13 patients died. Five (71.4%) of the seven patients in group 4 died. Overall, 12.2% (6/49) of the patients died, all of whom had diffuse air-space opacification on the last chest radiograph. In these patients, medical comorbidity was present in 66.7% (4/6), and the exposure history was known in 83.3% (5/6). Death occurred at a mean interval of 18.2 days (range, 9-36 days) from the initial exposure. CONCLUSION: Patients presenting with normal findings or focal air-space opacity on chest radiographs had a good clinical outcome. Patients with multifocal opacities that progressed to diffuse air-space opacification and patients presenting with diffuse air-space opacification had a high fatality rate, but patients in this group were also older and more likely to have comorbid conditions. Patients with SARS present with recognizable patterns of disease that have prognostic significance.

Fibrosis of the upper lobes: a newly identified late-onset complication after lung transplantation?

OBJECTIVE: The objective of this study was to describe the high-resolution CT findings of a previously unreported rare complication observed in seven patients who had undergone lung transplantation. CONCLUSION: High-resolution CT findings suggestive of gradual progressive lung fibrosis, predominantly in the upper lobes with relative sparing of the basal segments, may represent a specific and rare type of rejection of still unknown cause in lung transplant recipients.