Quantitative measurement of airway dimensions using ultra-high resolution computed tomography

Background

Quantitative measurement of airway dimensions using computed tomography (CT) is performed in relatively larger airways due to the limited resolution of CT scans. Nevertheless, the small airway is an important pathological lesion in lung diseases such as chronic obstructive pulmonary disease (COPD) and asthma. Ultra-high resolution scanning may resolve the smaller airway, but its accuracy and limitations are unclear.

Longitudinal study of airway dimensions in chronic obstructive pulmonary disease using computed tomography

Background and objective:   Chest CT has been widely used for the evaluation of structural changes in lung parenchyma and airways in cross-sectional studies. There has been no report on the annual changes in airway dimensions as assessed by CT in COPD patients. The objective of this study was to investigate the annual changes in airway dimensions and lung attenuation using CT in patients with COPD and to evaluate the correlations among annual changes in CT measurements and pulmonary function.
Methods:   Eighty-three men with COPD had completed five annual assessments of CT scans and pulmonary function tests over 4 years. Airway dimensions of the basal segment bronchi and lung attenuation on CT images were analysed in 38 subjects in whom the same airway could be measured at least three times, including at entry and at the end of the study.
Results:   Mean annual decline in FEV₁ was 21 mL/year. Annual changes in the percentage of low attenuation areas were not significantly correlated with decline in FEV₁. On the other hand, annual changes in the percentage of wall area (WA%/year) were significantly inversely correlated with annual changes in FEV₁ ( r  = −0.363, P  = 0.025), whereas WA%/year did not differ among severity stages at entry and did not correlate with baseline FEV₁.
Conclusions:   The results showing that annual changes in airway thickening correlated with annual decline in air flow limitation suggests the importance of treatment of airway inflammation in COPD. CT is a useful tool for quantitative estimation not only of emphysema but also of airway lesions in longitudinal studies.     

Changes in airway dimensions on computed tomography scans of children with cystic fibrosis

RATIONALE: In cystic fibrosis (CF), chronic bacterial infection and inflammation lead to progressive airway wall thickening and lumen dilatation. Objectives: To quantify airway wall thickening and lumen dilatation in children with CF over a 2-year interval. METHODS: Children with CF (n = 23) who had two computed tomography (CT) scans (CT(cf1) and CT(cf2)) combined with pulmonary function tests (PFTs), with a 2-year interval between measurements, were compared with control subjects (n = 21) who had one CT (CT(controls)). On cross-sectional cut airway-artery pairs, airway wall area (WA), airway lumen area (LA) and perimeter, and arterial area (AA) were quantified. LA/AA (= marker of bronchiectasis), airway wall thickness (AWT), and WA/AA (= markers of wall thickness) were calculated. CT scans were scored using four different scoring systems. PFTs were expressed as percent predicted. RESULTS: Airway WA-to-AA ratio was 1.45 (p < 0.001) and airway LA-to-AA ratio was 1.92 times higher (p < 0.001) in children with CF compared with age-matched control subjects. LA/AA and WA/AA remained unchanged from CT(cf1) to CT(cf2) and did not increase with age. AWT as a function of airway size increased from CT(cf1) to CT(cf2) by 2% (0.03 mm; p = 0.02). The change in AWT was inversely related to the change in forced expiratory flow between 25 and 75% of expiratory VC (p = 0.002). CONCLUSIONS: In CF, quantitative measurements of airways on CT scans show an increased ratio between airway LA and AA and progressive airway wall thickening. Scoring systems show progression of bronchiectasis but unchanged AWT. PFTs remained stable.     

In vivo measurements of airway reactivity using high-resolution computed tomography

Changes in airway resistance are reported to account for only a portion of changes in total lung resistance. The fraction of total lung resistance caused by airway resistance is difficult to quantify in vivo. High-resolution computed tomography (HRCT) has potential application for directly measuring changes in airway size in vivo. In the present investigation, we studied five anesthetized mongrel dogs using HRCT to locate and measure changes in airway area after aerosol histamine challenge in the absence and presence of deep inspiration. We also related changes in total lung resistance to changes in airway area. We found that in all dogs after histamine aerosol challenge, airway area decreased (range, 23 +/- 7 to 67 +/- 5%, mean +/- SEM), and total lung resistance increased (range, 191 to 378%). After deep inspiration (equal to three times tidal volume), four of the five dogs showed further significant decreases in airway area (range, 13 +/- 6 to 71 +/- 8%), whereas all five dogs showed decreases in RL (range, 3 to 35%). The fact that preconstricted airways constricted further after deep inspiration while the measured RL decreased suggests that RL may not always be a reliable indicator of changes in the size of conducting airways larger than 1 mm.     

Airway dimensions measured from micro-computed tomography and high-resolution computed tomography.

Volume averaging results in both over- and underestimation of airway dimensions when they are measured by high-resolution computed tomography (HRCT). The current authors calibrated computerised measurements of airway dimensions from HRCT against a novel three-dimensional micro-computed tomography (CT) standard, which has a 50-fold greater resolution, as well as against traditional morphometry. Inflation-fixed porcine lung cubes were scanned by HRCT and micro-CT. A total of 59 lumen area (Ai), 30 wall area (A(aw)) and 11 lumen volume (Vi) measurements were made. Ai was measured from the cut surface of 11 airways by morphometry. Airways in scanned images were matched using branching points. After calibration, the errors of Ai, A(aw) and Vi HRCT measurements were determined. The current authors found a systematic, size-dependent underestimation of Ai and overestimation of A(aw) from HRCT measurements. This was used to calibrate an HRCT measurement algorithm. The 95% limits of agreement of subsequent measurements were +/-3.2 mm2 for Ai, +/-4.3 mm2 for A(aw), and +/-11.2 mm3 for Vi with no systematic error. Morphometric measurements agreed with micro-CT (+/-2.5 mm2) without systematic error. In conclusion, micro-computed tomography image data from inflation-fixed airways can be used as calibration standards for three-dimensional lumen volume measurements from high-resolution computed tomography, while morphometry is acceptable for two-dimensional measurements. The image dataset could be used to validate other developmental three-dimensional segmentation algorithms.     

Three-dimensional computed tomography in acquired pediatric airway diseases

To investigate the role of three-dimensional computed tomography (CT) in pediatric tracheobronchial diseases. Eleven male, six female patients aged from two weeks to 12 years (mean age, 3.3 years) were referred to spiral CT with a preliminary diagnosis of foreign body aspiration, extrinsic airway compression, acquired tracheoesophageal fistula, post-intubation stenosis, and bronchial erosion by a cavitary lung lesion. Tracheobronchial tree was scanned with 3 mm collimation, 1.5/1 pitch, 1.5 mm reconstruction interval, and standard reconstruction algorithm. Surface-rendered three-dimensional images and virtual bronchoscopic images were created from the axial raw data. Three-dimensional and virtual bronchoscopy findings were compared with findings of bronchoscopy. Virtual bronchoscopy revealed the level of obstruction in five patients with foreign body aspiration, but failed to disclose the nature of the aspirated foreign body and distinguish between a foreign body and mucoid obstruction. Virtual bronchoscopy correctly ruled out foreign body aspiration in four patients. Axial CT images also showed extraluminal findings including atelectasis, air trapping, peribronchial thickening, and infiltrations. In a patient with tracheitis virtual bronchoscopy failed to identify necrotic plaques observed in bronchoscopy. In patients with extrinsic compression, three-dimensional images showed the site and degrees of stenosis, whereas axial images revealed the cause of compression. In one patient, an anomalous tracheal bronchus was demonstrated on three-dimensional and virtual bronchoscopy images. Three-dimensional CT can localize tracheobronchial obstructions accurately. Virtual images may eliminate the need for invasive bronchoscopy in patients with questionable foreign body aspiration. Inability to evaluate the mucosal changes remains an important disadvantage of this technique.     

The bifurcation study using 64 multislice computed tomography

Background: Various two‐stent techniques have been applied to aggressively treat bifurcation lesions as the introduction of drug‐eluting stents (DES) and the importance of the bifurcation angle and three‐dimensional (3D) structure has come to be recognized. Recent 64 multislice computed tomography (MSCT) technology provides accurate information about the 3D bifurcation geometry of the coronary arteries and with reproducibility. Objectives: The purpose of this study is to disclose the coronary bifurcation angle and 3D structure in humans and elucidate the importance of bifurcation angle for the crush technique using MSCT. Methods: Two hundred and nine patients who were suspected to have angina pectoris and underwent CT angiography using MSCT were examined. The 3D‐volume rendering (VR) image was reconstructed by two technicians and was used for the assessment of each coronary bifurcation angles. Results: The average LMT bifurcation angles (∠LMT‐LAD, ∠LMT‐LCx, ∠LAD‐LCx) were 143 ± 13°, 121 ± 21°, and 72 ± 22°, respectively, the average ∠LAD‐D was 138 ± 19°, the average ∠LCx‐OM was 134 ± 23°, the average distal RCA bifurcation angles (∠RCA‐4AV, ∠RCA‐4PD, ∠4AV‐4PD) were 152 ± 15°, 137 ± 20°, and 61 ± 21°, respectively. In addition, a percentage of steep angled bifurcation (<110°) was significantly higher in the LMT (26%) than in other bifurcations (P < 0.05). Conclusions: LMT bifurcation has been shown to have a higher rate of steep angled bifurcation in humans, it is therefore necessary to take the bifurcation angle into consideration in the case of LMT stenting. These data suggest that a bifurcation study using MSCT can clarify the 3D structure of coronary bifurcation and may provide useful information for bifurcation stenting. © 2009 Wiley‐Liss, Inc.     

Detection of small hepatocellular carcinomas in cirrhotic livers using iodised oil computed tomography

Background—The detection of hepatocellular cancers(HCC) is a major role of preoperative imaging in patients with endstage liver disease being considered for orthotopic livertransplantation (OLT).
Aims—To assess the sensitivity of iodised oilcomputed tomography (IOCT).
Patients and methods—A prospective evaluation in50 consecutive patients undergoing OLT included ultrasound scan,contrast enhanced CT, angiography (with intra-arterial injection ofiodised oil), and a second CT (IOCT) 10 days later. Followingtransplantation the explant liver was serially sectioned forpathological evaluation. Soft tissue radiographs of the liver sliceswere used to match histological lesions with CT findings.
Results—Eleven patients were excluded due toprotocol violations. Of the remaining 39, histological evaluationrevealed no cancers in 33 explant livers, in keeping with negativepreoperative imaging. Six explant livers contained 55 HCCs, 84% ofwhich were less than 1 cm in diameter. Pretransplant IOCT detected 3/6patients with cancer (50%) but only 7% of cancerous lesions.Ultrasound, contrast CT, and angiography each detected 2/6 patientswith cancer and 4% of cancerous lesions.
Conclusion—IOCT is an insensitive method for thedetection of small HCCs in livers with advanced cirrhosis but in thisstudy was slightly superior to ultrasound, CT, and angiography.

Keywords:liver cirrhosis; transplantation; hepatocellularcarcinoma; iodised oil; computed tomography

     

Etiology of small bowel thickening on computed tomography

BACKGROUND:

Abdominal pain is often evaluated using imaging, most often with computed tomography (CT). While CT is sensitive and specific for certain diagnoses, small bowel thickening is a nonspecific finding on CT with a broad differential diagnosis including infection, inflammation, ischemia and neoplasm.

METHOD:

A review of medical records of patients who underwent CT scans of the abdomen and pelvis over a one-year period and exhibited small bowel thickening were retrospectively evaluated to determine the final diagnosis.

RESULTS:

The etiologies of small bowel thickening on CT were as follows: infection (113 of 446 [25.34%]); reactive inflammation (69 of 446 [15.47%]); primary inflammation (62 of 446 [13.90%]); small bowel obstruction (38 of 446 [8.52%]); iatrogenic (33 of 446 [7.40%]); neoplastic (32 of 446 [7.17%]); ascites (30 of 446 [6.73%]); unknown (28 of 446 [6.28%]); ischemic (24 of 446 [5.38%]); and miscellaneous (17 of 446 [3.81%]).

CONCLUSION:

Infectious and inflammatory (primary or reactive) conditions were the most common cause of small bowel thickening in the present series; these data can be used to formulate a more specific differential diagnosis.     

Imaging of myocardial microvasculature using fast computed tomography and three-dimensional microscopic computed tomography

In the past, much attention in imaging research was focused on the macroscopic morphology and patency of arteries. Only recently, research and clinical interest have shifted to the microcirculation and its impact on the long-term prognosis in patients with vascular diseases. This focus and newly developed therapeutic strategies require high-resolution imaging modalities, which do not focus exclusively on the macroscopic aspects of the arterial tree. Provided here is a comprehensive perspective of using computed tomography technology to image and quantify the function and morphology of myocardial and vascular adventitial microvessels in normal and disease states.     

Quantitative computed tomography detects peripheral airway disease in asthmatic children

The aim of this study was to compare air-trapping as quantified by high-resolution computed tomography (HRCT) of the chest with measures of lung function and airway inflammation in children with mild to moderate asthma. Plethysmography indices, respiratory resistance, and reactance before and after bronchodilator with impulse oscillation (IOS), exhaled nitric oxide (eNO), total eosinophil count (TEC), and serum eosinophil cationic protein (ECP) levels were measured in 21 subjects. A single-cut HRCT image at end-expiration was obtained. Air-trapping was quantified and expressed in terms of the pixel index (PI) by determining the percentage of pixels in lung fields below -856 and -910 Hounsfeld units (HU). Pairwise linear correlations between PI and other parameters were evaluated. Subjects had only mild airflow limitation based on prebronchodilator forced expiratory volume in 1 sec (FEV(1)), but were hyperinflated and had air-trapping based on elevated total lung capacity (TLC) and residual volume (RV)/TLC ratio, respectively. The PI at -856 HU was positively correlated with % predicted TLC, total gas volume (TGV), and ECP level, and was inversely correlated with FEV(1)/forced vital capacity (FVC) and % predicted forced expiratory flow between 25-75% FVC (FEF(25-75)). The PI at -910 HU correlated similarly with these variables, and also correlated positively with IOS bronchodilator reversibility. This data suggest that quantitative HRCT may be a useful tool in the evaluation of peripheral airflow obstruction in children with asthma.     

Thoracoscopic lung resection for extremely small nodular lesions using simultaneous intraoperative real-time computed tomography

Because the localization of small lung nodules at thoracoscopic resection is sometimes difficult, we have employed intraoperative real-time computed tomography (CT). Two patients with lung nodules less than 1 cm in diameter were treated using this technique. Detection of the lesion using CT and thoracoscopic resection is performed simultaneously in the interventional radiological CT examination room. After induction of general anesthesia with one-lung ventilation, the patient is placed in the lateral position. The lung nodule is detected using real-time CT and grasped with forceps. Thoracoscopic resection of the nodule is performed in the usual fashion. Frozen section examination is immediately performed to decide on further therapy.     

Bronchial arterial imaging using helical computed tomography

The bronchial arteries, which provide the systemic arterial supply to the lungs, are involved in a variety of disease processes in humans, including congenital disorders, infection, and pulmonary thromboembolism. In these conditions, the bronchial arteries hypertrophy and bronchial blood flow increases. Consequently, in many disorders, such as bronchiectasis, the bronchial arteries are a frequent source of haemoptysis, which may be massive and life-threatening. Evaluation of the bronchial circulation has typically required invasive imaging with angiography to determine the location of bleeding. Non-invasive assessment of bronchial arterial anatomy and morphology is currently being investigated with the use of helical computed tomography (CT). We evaluated eight patients with various lung diseases with helical CT (GE Medical Systems, LS16, Milwaukee, WI) to determine the imaging features of the bronchial circulation. Non-ionic contrast medium (iopromide) was injected intravenously (80-1000ml/30s) and scanning was triggered once contrast material was present in the pulmonary artery (average delay=15s) or ascending aorta (average delay=20s). Detector collimation (16-row unit) was 10mm. Imaging parameters included a section thickness of 0.6mm, kilovolt peak of 120, 150-440mA, pitch factor of 1.375, matrix of 512x512, and tube rotation time of 0.8s. The images were reconstructed and scanned isotropically (Advantage Workstation 4.1,GE Medical Systems). We conclude that helical computed tomography may provide a non-invasive means of evaluating the bronchial arteries and their role in pulmonary disease processes.     

Coronary artery visualization using ultrafast computed tomography

The advantages and limitations of ultrafast computed tomography in the imaging of normal and pathologic conditions of the coronary artery are discussed. The scanner's speed, resolution, and lack of significant motion artifact enhance the visualization of coronary arteries. Coronary artery calcification also is well visualized, and coronary artery fistuli, coronary bypass graft patency, and Kawasaki disease can be assessed accurately using contrast-enhanced flow studies. The inability to image stenoses and the lack of longitudinal images detract from its usefulness. Future scanner upgrades to provide increased resolution and thinner slices should improve the scanner's ability to evaluate the coronary artery.     

Non-invasive coronary angiography using multislice computed tomography

Non-invasive methods for detection of coronary atherosclerosis have been limited to indirect markers, such as myocardial perfusion or wall motion during exercise or pharmacological stress. However, advances in multislice computed tomography (MSCT) not allow sufficient spatial resolution for direct non-invasive imaging of the coronary arteries. This review focuses on imaging techniques and clinical applications of MSCT in human studies. Published studies of the diagnostic accuracy of MSCT in native coronary arteries and bypass grafts indicate excellent sensitivity and specificity for detection of 50% diameter stenosis. MSCT is particularly good for evaluating the origin and course of anomalous coronary arteries. MSCT offers the ability to visualise both the lumen and wall of artery, as well as to quantify coronary classification. Further technical developments promise to render MSCT the ideal non-invasive tool for direct visualisation of the coronary arteries.