Sliding thin slab, minimum intensity projection technique in the diagnosis of emphysema: histopathologic-CT correlation

Ct-defined emphysema prevalence in a Chinese and Dutch general population

PURPOSE

We determine and compare the prevalence, subtypes, severity, and risk factors for emphysema assessed by low-dose CT(LDCT) in Chinese and Dutch general populations.

METHODS

This cross-sectional study included LDCT scans of 1143 participants between May and October 2017 from a Chinese Cohort study and 1200 participants with same age range and different smoking status between May and October 2019 from a Dutch population-based study. An experienced radiologist visually assessed the scans for emphysema presence (≥trace), subtype, and severity. Logistic regression analyses, overall and stratified by smoking status, were performed and adjusted for fume exposure, demographic and smoking data.

RESULTS

The Chinese population had a comparable proportion of women to the Dutch population (54.9 % vs 58.9 %), was older (61.7 ± 6.3 vs 59.8 ± 8.1), included more never smokers (66.4 % vs 38.3 %), had a higher emphysema prevalence ([58.8 % vs 39.7 %], adjusted odds ratio, aOR = 2.06, 95 %CI = 1.68-2.53), and more often had centrilobular emphysema (54.8 % vs 32.8 %, p < 0.001), but no differences in emphysema severity. After stratification, only in never smokers an increased odds of emphysema was observed in the Chinese compared to the Dutch (aOR = 2.55, 95 %CI = 1.95-3.35). Never smokers in both populations shared older age (aOR = 1.59, 95 %CI = 1.25-2.02 vs 1.26, 95 %CI = 0.97-1.64) and male sex (aOR = 1.50, 95 %CI = 1.02-2.22 vs 1.93, 95 %CI = 1.26-2.96) as risk factors for emphysema.

CONCLUSIONS

Only never smokers had a higher prevalence of mainly centrilobular emphysema in the Chinese general population compared to the Dutch after adjusting for confounders, indicating that factors other than smoking, age and sex contribute to presence of CT-defined emphysema.

AI-Driven Model for Automatic Emphysema Detection in Low-Dose Computed Tomography Using Disease-Specific Augmentation

The objective of this study is to evaluate the feasibility of a disease-specific deep learning (DL) model based on minimum intensity projection (minIP) for automated emphysema detection in low-dose computed tomography (LDCT) scans. LDCT scans of 240 individuals from a population-based cohort in the Netherlands (ImaLife study, mean age ± SD = 57 ± 6 years) were retrospectively chosen for training and internal validation of the DL model. For independent testing, LDCT scans of 125 individuals from a lung cancer screening cohort in the USA (NLST study, mean age ± SD = 64 ± 5 years) were used. Dichotomous emphysema diagnosis based on radiologists' annotation was used to develop the model. The automated model included minIP processing (slab thickness range: 1 mm to 11 mm), classification, and detection maps generation. The data-split for the pipeline evaluation involved class-balanced and imbalanced settings. The proposed DL pipeline showed the highest performance (area under receiver operating characteristics curve) for 11 mm slab thickness in both the balanced (ImaLife = 0.90 ± 0.05) and the imbalanced dataset (NLST = 0.77 ± 0.06). For ImaLife subcohort, the variation in minIP slab thickness from 1 to 11 mm increased the DL model's sensitivity from 75 to 88% and decreased the number of false-negative predictions from 10 to 5. The minIP-based DL model can automatically detect emphysema in LDCTs. The performance of thicker minIP slabs was better than that of thinner slabs. LDCT can be leveraged for emphysema detection by applying disease specific augmentation.

A review of visualization techniques of post-mortem computed tomography data for forensic death investigations

Postmortem computed tomography (PMCT) is a standard image modality used in forensic death investigations. Case- and audience-specific visualizations are vital for identifying relevant findings and communicating them appropriately. Different data types and visualization methods exist in 2D and 3D, and all of these types have specific applications. 2D visualizations are more suited for the radiological assessment of PMCT data because they allow the depiction of subtle details. 3D visualizations are better suited for creating visualizations for medical laypersons, such as state attorneys, because they maintain the anatomical context. Visualizations can be refined by using additional techniques, such as annotation or layering. Specialized methods such as 3D printing and virtual and augmented reality often require data conversion. The resulting data can also be used to combine PMCT data with other 3D data such as crime scene laser scans to create crime scene reconstructions. Knowledge of these techniques is essential for the successful handling of PMCT data in a forensic setting. In this review, we present an overview of current visualization techniques for PMCT.

Assessment Of Changes In Regional Xenon-Ventilation, Perfusion, And Ventilation-Perfusion Mismatch Using Dual-Energy Computed Tomography After Pharmacological Treatment In Patients With Chronic Obstructive Pulmonary Disease: Visual And Quantitative Analysis

Purpose

To assess changes in regional ventilation (V), perfusion (Q), and V-Q mismatch in patients with chronic obstructive pulmonary disease (COPD) after pharmacologic treatment using combined xenon-enhanced V and iodine-enhanced Q dual-energy CT (DECT).

Patients and methods

Combined V and Q DECT were performed at baseline and after three-month pharmacologic treatment in 52 COPD patients. Anatomically co-registered virtual non-contrast images, V, Q, and V/Q_ratio maps were obtained. V/Q pattern was visually determined to be matched, mismatched, or reversed-mismatched and compared with the regional parenchymal disease patterns of each segment. DECT parameters for V, Q, and V-Q imbalance were quantified.

Results

The parenchymal patterns on CT were not changed at follow-up. The segments with matched V/Q pattern were increased (80.2% to 83.6%) as the segments with reversed-mismatched V/Q pattern were decreased with improving ventilation (17.6% to 13.8%) after treatment. Changes of V/Q patterns were mostly observed in segments with bronchial wall thickening. Compared with patients without bronchial wall thickening, the quantified DECT parameters of V-Q imbalance were significantly improved in patients with bronchial wall thickening (p < 0.05). Changes in forced expiratory volume in one second after treatment were correlated with changes in the quantified DECT parameters (r = 0.327–0.342 or r = −0.406 and −0.303; p < 0.05).

Conclusion

DECT analysis showed that the V-Q imbalance was improved after the pharmacological treatment in COPD patients, although the parenchymal disease patterns remained unchanged. This improvement of V-Q imbalance may occur mostly in the areas with bronchial wall thickening.

Time-frequency analysis for bearing fault diagnosis using multiple Q-factor Gabor wavelets

Rolling element bearings are key and also vulnerable machine elements in rotating machinery. Fault diagnosis of rolling element bearings is significant for guaranteeing machinery safety and functionality. To accurately extract bearing diagnostic information, a time-frequency analysis method based on continuous wavelet transform (CWT) and multiple Q-factor Gabor wavelets (MQGWs) (termed CMQGWT) is introduced in this paper. In the CMQGWT method, Gabor wavelets with multiple Q-factors are adopted and sets of the continuous wavelet coefficients for each Q-factor are combined to generate time-frequency map. By this way, the resolution of the CWT time-frequency map can be greatly increased and the diagnostic information can be accurately identified. Numerical simulation is carried out and verified the effectiveness of the proposed method. Case studies and comparisons with the continuous Morlet wavelet transform (CMWT) and the tunable Q-factor wavelet transform (TQWT) demonstrate the effectiveness and superiority of the CMQGWT for bearing diagnostic information extraction and fault identification.

Minimum-intensity projection images in high-resolution computed tomography lung: Technology update

Chest physicians need to be aware about MinIP images, as these are increasingly being used for the evaluation of a wide range of lung diseases in HRCT study of lungs. MinIP images highlight the areas with reduced CT attenuation in the lung parenchyma. This allows prompt and early diagnosis of cystic lung diseases or airway, vascular or parenchymal disorders, which manifest with hypoattenuation, mosaic attenuation or air trapping. MiniP images are therefore useful for accurate pre-operative planning and disease monitoring.

CT-Definable Subtypes of Chronic Obstructive Pulmonary Disease: A Statement of the Fleischner Society

The purpose of this statement is to describe and define the phenotypic abnormalities that can be identified on visual and quantitative evaluation of computed tomographic (CT) images in subjects with chronic obstructive pulmonary disease (COPD), with the goal of contributing to a personalized approach to the treatment of patients with COPD. Quantitative CT is useful for identifying and sequentially evaluating the extent of emphysematous lung destruction, changes in airway walls, and expiratory air trapping. However, visual assessment of CT scans remains important to describe patterns of altered lung structure in COPD. The classification system proposed and illustrated in this article provides a structured approach to visual and quantitative assessment of COPD. Emphysema is classified as centrilobular (subclassified as trace, mild, moderate, confluent, and advanced destructive emphysema), panlobular, and paraseptal (subclassified as mild or substantial). Additional important visual features include airway wall thickening, inflammatory small airways disease, tracheal abnormalities, interstitial lung abnormalities, pulmonary arterial enlargement, and bronchiectasis.

Circulating endothelial microparticles as a measure of early lung destruction in cigarette smokers

RATIONALE

There is increasing evidence that emphysema is associated with primary loss of pulmonary capillary endothelium. Plasma levels of endothelial microparticles (EMPs), small vesicles released from activated or apoptotic endothelial cells, are elevated in vascular-related disorders.

OBJECTIVES

To evaluate whether plasma EMP levels are elevated in smokers with early lung destruction as assessed by normal spirometry but reduced diffusing capacity of the lung for carbon monoxide (Dl(co)).

METHODS

Lung health was assessed by pulmonary function tests (PFTs: spirometry, total lung capacity, Dl(co)) and chest X-ray; smoking status was assessed by urine nicotine and cotinine. EMP levels (CD42b(-)CD31(+) microparticles) were quantified as activated or apoptotic. The initial cohort (n = 92) included healthy nonsmokers (normal PFTs), healthy smokers (normal PFTs), and smokers with early evidence of lung destruction (normal spirometry, low Dl(co)). Two prospective cohorts were then tested: a group similar to the initial cohort and an HIV1(+) cohort.

MEASUREMENTS AND MAIN RESULTS

Healthy smokers had mildly increased levels of EMPs. Strikingly, 95% of smokers with normal spirometry, low Dl(co) had increased EMPs, with reduced CD62(+)/CD31(+) ratios (P < 10(-4)) and elevated CD42b(-)CD31(+) annexin V(+) EMPs (P < 10(-4)), suggesting derivation from endothelial apoptosis. Most elevated EMPs were angiotensin-converting enzyme positive, suggesting derivation from pulmonary capillaries. Both prospective cohorts confirmed the initial cohort data.

CONCLUSIONS

Plasma EMPs with apoptotic characteristics are elevated in smokers with normal spirometry but reduced Dl(co), consistent with the concept that emphysema is associated, in part, with capillary endothelium apoptosis, suggesting that the early development of emphysema might be monitored with plasma EMP levels.

Multidetector high-resolution computed tomography of the lungs: protocols and applications

Advances in computed tomography (CT) scanner technology have made isotropic volumetric, multiplanar high-resolution lung imaging possible in a single breath-hold, a significant advance over the incremental high-resolution CT (HRCT) technique in which noncontiguous images sampled the lung, but lacked anatomic continuity. HRCT of the lungs is an established imaging technique for the diagnosis and management of interstitial lung disease, emphysema, and small airway disease, providing a noninvasive detailed evaluation of the lung parenchyma, and providing information about the lungs as a whole and focally. In addition to having a high degree of specificity for diagnosing conditions such as emphysema, sarcoidosis, usual interstitial pneumonitis, Langerhans cell histiocytosis, and small airway disease, there is a growing body of medical evidence to support the use of HRCT findings or diagnosis to predict patient prognosis. In this article, we review the technique, advantages, and clinical applications of the current HRCT technique.

Comparison of postprocessing techniques for the detection of perfusion defects by cardiac computed tomography in patients presenting with acute ST-segment elevation myocardial infarction

BACKGROUND

Despite rapid advances in cardiac computed tomography (CT), a strategy for optimal visualization of perfusion abnormalities on CT has yet to be validated.

OBJECTIVE

We evaluated the performance of several postprocessing techniques of source data sets to detect and characterize perfusion defects in acute myocardial infarctions with cardiac CT.

METHODS

Twenty-one subjects (18 men; 60 +/- 13 years) that were successfully treated with percutaneous coronary intervention for ST-segment myocardial infarction underwent 64-slice cardiac CT and 1.5 Tesla cardiac magnetic resonance imaging (MRI) scans after revascularization. Delayed enhancement MR images were analyzed to identify the location of infarcted myocardium. Contiguous short-axis images of the left ventricular myocardium were created from the CT source images with 0.75-mm multiplanar reconstruction (MPR), 5-mm MPR, 5-mm maximal intensity projection (MIP), and 5-mm minimum intensity projection (MinIP) techniques. Segments already confirmed to contain infarction by MRI were then evaluated qualitatively and quantitatively with CT.

RESULTS

Overall, 143 myocardial segments were analyzed. On qualitative analysis, the MinIP and thick MPR techniques had greater visibility and definition than the thin MPR and MIP techniques (P < 0.001). On quantitative analysis, the absolute difference in Hounsfield unit attenuation between normal and infarcted segments was significantly greater for the MinIP (65.4 Hounsfield unit [HU]) and thin MPR (61.2 HU) techniques. However, the relative difference in Hounsfield unit attenuation was significantly greatest for the MinIP technique alone (95%; P < 0.001). Contrast to noise was greatest for the MinIP (4.2) and thick MPR (4.1) techniques (P < 0.001).

CONCLUSION

The results of our current investigation found that MinIP and thick MPR detected infarcted myocardium with greater visibility and definition than MIP and thin MPR.

Update on radiology of emphysema and therapeutic implications

Emerging treatments require appropriate CT targeting of a selected lobe or lobes and target airways to obtain a successful response. CT scan is used in pretreatment planning to select patients and plan treatment strategy and posttreatment to confirm correct deployment of devices and assess treatment response. Increasingly treatments are being developed to treat patients who have emphysema who require accurate quantitation of extent and distribution of the process. Functional assessment can be made by inference of detailed anatomic correlates and by direct measurement of regional function using dynamic scan protocols. This article summarizes the current role of imaging in the assessment of patients who have emphysema.

Imaging studies in emphysema

Definitions of types of emphysema within the framework of chronic obstructive pulmonary disease are given. The classic findings on the chest radiograph are described, and the advances in sensitivity and specificity achieved with computed tomography (CT) scanning are noted. The "density mask" and the "percentile point" measurements rely on the densitometric property of X-rays, but the scan also shows the severity and distribution of low-attenuation regions that usually represent pathologic emphysema. The alteration of absolute density with changes in lung inflation, CT slice thickness, collimation, and reconstruction algorithm make comparison between CT scans and across studies more difficult. Nevertheless, quantitative CT has superseded subjective scoring of scan appearance by readers as a sensitive way to measure emphysema.

Spectral near-infrared fluorescence imaging of curved surfaces using projection reconstruction algorithms

In vivo spectral fluorescence imaging has made it possible to non-invasively visualize superficial curved structures as well as structures deep to the skin. However, the defocus created by blurring has been an obstacle to creating anatomically interpretable surface images. Herein we present a methodology to correct for blurring induced by curved structures during spectral fluorescence imaging using signal intensity projection algorithms. In a phantom and an animal model in which the lymphatic system was visualized after the interstitial injection of quantum dots with emission spectra in the near-infrared (NIR) range, the planes of focus were sequentially adjusted to obtain a z-stack of images which contains images acquired from multiple focal points. Maximum, minimum, median and average intensity projections were applied to the resulting images. Using the phantom, the minimum and the median intensity projection images demonstrated improved deblurring whereas during in vivo imaging the median intensity projection images more clearly visualized important structures than did the other projection techniques. Image stacking with subsequent application of appropriate projection techniques provides a simple method for deblurring in vivo optical images obtained from curved surfaces, thus improving their anatomic resolution.

Obliterative Bronchiolitis

Obliterative bronchiolitis (OB) is a condition characterized by inflammation and fibrosis of the bronchiolar walls resulting in narrowing or obliteration of the bronchiolar lumen. The most common causes are childhood lower respiratory tract infection, hematopoietic stem cell or lung and heart-lung transplantation, and toxic fume inhalation. The most frequent clinical manifestations are progressive dyspnea and dry cough. Pulmonary function tests demonstrate airflow obstruction and air trapping. Radiographic manifestations include reduction of the peripheral vascular markings, increased lung lucency, and overinflation. The chest radiograph, however, is often normal. High-resolution CT is currently the imaging modality of choice in the assessment of patients with suspected or proven OB. The characteristic findings on high-resolution CT consist of areas of decreased attenuation and vascularity (mosaic perfusion pattern) on inspiratory scans and air trapping on expiratory scans. Other CT findings of OB include bronchiectasis and bronchiolectasis, bronchial wall thickening, small centrilobular nodules, and three-in-bud opacities. Recent studies suggest that hyperpolarized ³He-enhanced magnetic resonance imaging may allow earlier recognition of obstructive airway disease and therefore may be useful in the diagnosis and follow-up of patients with OB.

Radiograma de tórax e tomografia computadorizada na avaliação do enfisema pulmonar

O enfisema é uma condição do pulmão, caracterizada pelo aumento acima do normal no tamanho dos espaços aéreos distais ao bronquíolo terminal. Atualmente, o enfisema é a quarta causa de morte nos EUA, afetando 14 milhões de pessoas. O presente artigo descreve as principais ferramentas no diagnóstico por imagem do enfisema, desde o início até os dias de hoje. Relata as técnicas tradicionais, como radiograma de tórax, e as evoluções no campo da tomografia computadorizada (TC), como a TC de alta resolução e a densitovolumetria pulmonar por TC tridimensional.

Computed tomography diagnosis of acute appendicitis: advantages of reviewing thin-section datasets using sliding slab average intensity projection technique

OBJECTIVES

We sought to compare sliding slab mode and standard stack mode in the computed tomography (CT) diagnosis of acute appendicitis.

MATERIALS AND METHODS

Contrast-enhanced CT was performed in 85 patients, 35 of whom had appendicitis. Four readers retrospectively reviewed 5-mm thick transverse sections (4-mm increment) using the stack mode and 2-mm thick sections (1-mm increment) with the sliding slab, average intensity projection. The sliding slab mode started with a 5-mm thick transverse slab, but the readers were encouraged to change the viewing angle and the slab thickness.

RESULTS

In sliding slab mode, the readers changed the viewing angle in 89 of 340 observations (24%) and decreased the slab thickness in 26 observations (8%). Although the receiver operating characteristic analysis did not show a significant difference (P = 0.18), the sliding slab mode enhanced the pooled sensitivity (93.6% vs. 98.6%, P = 0.02), specificity (92.0% vs. 97.5%, P = 0.01), and mean confidence for the diagnosis (P < 0.001) or exclusion (P = 0.002) of acute appendicitis; reduced inconclusive interpretations (5.6% vs. 1.8%, P = 0.01); and visualized the appendix more clearly (P < 0.001).

CONCLUSIONS

Compared with the stack mode, the sliding slab mode enhances diagnostic confidence and more clearly visualizes the appendix.

Sliding thin slab, minimum intensity projection imaging for objective analysis of emphysema

PURPOSE

The aim of this study was to determine whether sliding thin slab, minimum intensity projection (STS-MinIP) imaging is more advantageous than thin-section computed tomography (CT) for detecting and assessing emphysema.

MATERIALS AND METHODS

Objective quantification of emphysema by STS-MinIP and thin-section CT was defined as the percentage of area lower than the threshold in the lung section at the level of the aortic arch, tracheal carina, and 5 cm below the carina. Quantitative analysis in 100 subjects was performed and compared with pulmonary function test results.

RESULTS

The ratio of the low attenuation area in the lung measured by STS-MinIP was significantly higher than that found by thin-section CT (P < 0.01). The difference between STS-MinIP and thin-section CT was statistically evident even for mild emphysema and increased depending on whether the low attenuation in the lung increased. Moreover, STS-MinIP showed a stronger regression relation with pulmonary function results than did thin-section CT (P < 0.01).

CONCLUSION

STS-MinIP can be recommended as a new morphometric method for detecting and assessing the severity of emphysema.

Sliding thin slab, minimum intensity projection of the lung in asymptomatic subjects: lower limits of lung attenuation, without airways

PURPOSE

A sliding thin slab, minimum intensity projection (STS-MinIP) is considered to be useful for detecting diseases that decrease lung attenuation. For evaluating these diseases, it would be useful to ascertain the lower limits of normal lung attenuation, allowing a division between normal and subnormal attenuation. However, normal lung attenuation may vary depending on respiratory status, anatomical position, and patient background factors. Our aim was to determine whether the lower limits of lung attenuation, without airways, in asymptomatic subjects using STS-MinIP varies under different conditions.

MATERIALS AND METHODS

The study subjects were 43 volunteers without pulmonary symptoms. STS-MinIP was performed at full inspiration and full expiration at three levels of the lung. The lower limits of lung attenuation were compared among the three lung levels and between full inspiration and full expiration, the sexes, age groups, smokers and nonsmokers, and the right and left lungs.

RESULTS

The lower limits of lung attenuation had significantly different Hounsfield unit values among lung levels, between the sexes at full inspiration, and between age groups at full expiration.

CONCLUSION

This study shows that the lower limits of lung attenuation are influenced by lung fields, sex, and, on expiration, age.

Performance of long-term CT monitoring in diagnosing bronchiolitis obliterans after lung transplantation

AIM

The purpose of the study was to evaluate the ability of CT, including expiratory scans with minimum intensity projection in predicting the development of bronchiolitis obliterans syndrome after lung transplantation.

MATERIALS AND METHODS

Forty consecutive patients, 29 bilateral and 11 single lung transplanted, were followed-up with regular scans for a median of 36 months. Air trapping was evaluated on expiratory scans constructed from two short spiral scans with minimum intensity projection-technique, one at the level of the carina and the other midway between the right diaphragm and the carina. Air trapping was scored on a 16-point scale. Bronchiolitis obliterans syndrome was diagnosed according to established clinical criteria and quantified spirometrically.

RESULTS

Bronchiolitis obliterans syndrome developed in 17 patients (43%) after a median of 12 months. Air trapping and bronchiectasis was seen before the diagnosis of bronchiolitis obliterans syndrome in only two and one patient, respectively. Interobserver agreement for air trapping score was good (kappa = 0.65). Air trapping scores performed significantly better than that achieved by chance alone in determining the presence of bronchiolitis obliterans syndrome (P = 0.0025). An air trapping score of 4 or more provided the best results with regard to sensitivity and specificity in diagnosing bronchiolitis obliterans syndrome. The sensitivity, specificity, positive and negative predictive values of an air trapping of 4 or more in the diagnosis of bronchiolitis obliterans syndrome were 77, 74, 68 and 81%, respectively.

CONCLUSION

Expiratory CT scans with minimum intensity projection-reconstruction did not predict the development of bronchiolitis obliterans syndrome in most patients. The findings seriously limit the clinical usefulness of long-term CT monitoring for diagnosing bronchiolitis obliterans syndrome after lung transplantation.

Multi-detector row CT and postprocessing techniques in the assessment of diffuse lung disease

Many acute and chronic lung diseases are characterized by diffuse infiltration of the lung parenchyma. High-resolution computed tomography (CT) has been widely accepted as the imaging standard of reference for the assessment of these diseases. However, only approximately 10% of the lung parenchyma is scanned with high-resolution CT, and characteristic foci of disease may be missed. With use of the established characteristic high-resolution CT patterns, multi-detector row chest CT has revolutionized the evaluation of diffuse lung disease. Multi-detector row CT generates isotropic volumetric high-resolution data, allowing contiguous three-dimensional (3D) visualization of the lung parenchyma, with the capacity to create high-quality two-dimensional (2D) and 3D reformatted images. Minimum intensity projection is the postprocessing technique of choice for the detection and characterization of most patterns of diffuse lung disease. Maximum intensity projection (MIP) allows the detection and characterization of micronodules; the recognition of enlarged pulmonary veins, which is extremely useful in the diagnosis of pulmonary edema and the assessment of mosaic perfusion; and differentiation between perilymphatic, miliary, and centrilobular distribution. MIP can also help differentiate between constrictive bronchiolitis and mixed emphysema. Two-dimensional reformatted images are now of equal importance with the 2D axial images in diagnosing specific diffuse lung diseases. In the future, 3D reformatted images may be used to help quantify these disorders.

Thoracic CT Performance and Interpretation in the Multi-Detector Era

Multi-detector CT (MDCT), in particular isotropic or nearly isotropic MDCT, changes the way in which imagers perform and interpret studies of the thorax. The speed of data acquisition enables new clinical applications of MDCT in the areas of angiography and dynamic perfusion. Cardiac gating software is available, and CT studies of the heart and coronary arteries are now feasible. This review, however, focuses on the impact of MDCT on the routine practice of thoracic imaging, rather than on newer specific MDCT applications. The topics of scan performance and interpretation are related, and MDCT changes each of these areas when compared with the era of axial CT.

Enhanced perfusion defect clarity and inhomogeneity in smokers' lungs with deep-inspiratory breath-hold perfusion SPECT images

PURPOSE

Deep-inspiratory breath-hold (DIBrH) Tc-99m-macroaggregated albumin (MAA) SPECT images were developed to accurately evaluate perfusion impairment in smokers' lungs.

METHODS

DIBrH SPECT was performed in 28 smokers with or without low attenuation areas (LAA) on CT images, using a triple-headed SPECT system and a laser light respiratory tracking device. DIBrH SPECT images were reconstructed from every 4 degrees projection of five adequate 360 degrees projection data sets with almost the same respiratory dimension at 20 sec DIBrH. Perfusion defect clarity was assessed by the lesion (defect)-to-contralateral normal lung count ratios (L/N ratios). Perfusion inhomogeneity was assessed by the coefficient of variation (CV) values of pixel counts and correlated with the diffusing capacity of the lungs for carbon monoxide/alveolar volume (DLCO/VA) ratios. The results were compared with those on conventional images.

RESULTS

Five DIBrH projection data sets with minimal dimension differences of 2.9+/-0.6 mm were obtained in all subjects. DIBrH images enhanced perfusion defects compared with conventional images, with significantly higher L/N ratios (P<0.0001), and detected a total of 109 (26.9%) additional detects (513 vs. 404), with excellent inter-observer agreement (kappa value of 0.816). CV values in the smokers' lungs on DIBrH images were also significantly higher compared with those on conventional images (0.31+/-0.10 vs. 0.19+/-0.06, P<0.0001). CV values in smokers on DIBrH images showed a significantly closer correlation with DLCO/VA ratios compared with conventional images (R = 0.872, P<0.0001 vs. R=0.499, P<0.01).

CONCLUSION

By reducing adverse effect of respiratory motion, DIBrH SPECT images enhance perfusion defect clarity and inhomogeneity, and provide more accurate assessment of impaired perfusion in smokers' lungs compared with conventional images.

Small-vessel diseases of the lung: CT-pathologic correlates

Diseases that primarily affect the small vessels of the lung are difficult to diagnose. Many conditions are characterized by involvement of small pulmonary vessels, and pathologically they can be conveniently divided into occluding and inflammatory types. The former, typified by chronic pulmonary thromboembolism and primary pulmonary hypertension, are relatively cryptic in terms of imaging. In contrast, inflammatory vasculitides, which often cause pulmonary hemorrhage and infarction, result in florid but nonspecific radiographic abnormalities. The spectrum of thin-section computed tomographic abnormalities encountered in the inflammatory vasculitides is wide: For example, in Wegener granulomatosis the pattern ranges from cavitating nodules to lobar consolidation to ground-glass opacity. This review highlights some of the less obvious imaging manifestations of occlusive and inflammatory diseases of the small pulmonary vessels.

Chronic obstructive pulmonary disease. 4: imaging the lungs in patients with chronic obstructive pulmonary disease

The role of chest radiography and computed tomography in the evaluation of pulmonary emphysema and chronic bronchitis is reviewed.

Inspiratory and expiratory helical CT of normal adults: comparison of thin section scans and minimum intensity projection images

SUMMARY

To evaluate and compare thin section CT scans (TSS) and minimum intensity projection images (MinIPs) in healthy individuals, 10 nonsmokers with normal pulmonary function tests were studied using ten 1-mm collimated, helically acquired TSS images after full inspiration and expiration at two anatomic levels. Ten-millimeter-thick MinIPs were generated from the helical scans. Two thoracic radiologists compared TSS and MinIPs for artifacts and air trapping. Hounsfield unit (HU) measurements of TSS and MinIPs were obtained. The lung parenchyma on MinIPs demonstrates a smooth anterior-to-posterior attenuation gradient, accentuated by expiration. Motion and beam-hardening artifacts on TSS images resulted in regions of high and low attenuation on MinIPs, respectively. Expiratory TSS and MinIPs demonstrated air trapping (n = 31/40; range, 0-25%; mean, 7.2%). In comparison with TSS, MinIPs improved the conspicuity of air trapping (n = 20) and appeared to detect more air trapping (n = 7). No statistical differences were found when comparing the mean HU values of TSS and MinIPs. MinIPs demonstrated a smooth anterior-to-posterior attenuation gradient. Compared with TSS, MinIPs improve the conspicuity of air trapping in healthy individuals. Therefore, expiratory MinIPs may be useful in detecting air trapping as a result of disease.

From maximum intensity projection to volume rendering

Three-dimensional medical images can be generated with a variety of computer algorithms from computed tomography and magnetic resonance data sets. The most commonly used techniques are maximum intensity projection (MIP) and shaded surface display (SSD). Recently, volume rendering (VR) has become available on dedicated workstations, providing the possibility of interaction with data sets. All 3D rendering techniques represent a volume of data in 1 or more 2-dimensional (2D) planes, conveying the spatial relationships inherent in the data with the use of visual depth cues. Techniques and artefacts regarding MIP, SSD, and VR are described here, along with several models of clinical application.

Multi-detector row CT of thoracic disease with emphasis on 3D volume rendering and CT angiography

Multi-detector row computed tomography (CT) with three-dimensional (3D) volume rendering provides a unique perspective on thoracic anatomy and disease. Multi-detector row CT allows shorter acquisition times, greater coverage, and superior image resolution. Three-dimensional volume rendering now permits real-time, interactive modification of relative pixel attenuation in an infinite number of planes and projections. In vascular imaging, this technique provides image quality that equals or surpasses that of conventional angiography. Its use has expanded to aid in diagnosis and surgical planning, often obviating conventional or digital angiography and reducing costs. It is reliable in depicting clot and the pulmonary vasculature and may also be used to evaluate thoracic venous anomalies (eg, pulmonary arteriovenous malformations) and to plan therapy. Airway imaging with multi-detector row CT with 3D volume rendering is particularly useful in the planning and follow-up of stent placement. In diffuse lung disease, this technique can increase nodule detection and help differentiate between small nodules and vessels. It is also helpful in imaging the musculoskeletal system and the thoracic cage. Multi-detector row CT with 3D volume rendering has enhanced the conventional roles of thoracic CT and challenged the supremacy of other imaging modalities. It will likely play a leading role in future radiologic research and practice.