-
Y Nakano,
S Muro, H Sakai,
T Hirai,
K Chin,
M Tsukino,
K Nishimura,
H Itoh,
P D Paré,
J C Hogg,
M Mishima
[show abstract]
[hide abstract]
ABSTRACT: Chronic obstructive pulmonary disease (COPD) is characterized by the presence of airflow obstruction caused by emphysema or airway narrowing, or both. Low attenuation areas (LAA) on computed tomography (CT) have been shown to represent macroscopic or microscopic emphysema, or both. However CT has not been used to quantify the airway abnormalities in smokers with or without airflow obstruction. In this study, we used CT to evaluate both emphysema and airway wall thickening in 114 smokers. The CT measurements revealed that a decreased FEV(1) (%predicted) is associated with an increase of airway wall area and an increase of emphysema. Although both airway wall thickening and emphysema (LAA) correlated with measurements of lung function, stepwise multiple regression analysis showed that the combination of airway and emphysema measurements improved the estimate of pulmonary function test abnormalities. We conclude that both CT measurements of airway dimensions and emphysema are useful and complementary in the evaluation of the lung of smokers.
American Journal of Respiratory and Critical Care Medicine 10/2000; 162(3 Pt 1):1102-8. · 11.08 Impact Factor
-
S Muro,
Y Nakano, H Sakai,
Y Takubo,
Y Oku,
K Chin,
K Nishimura,
T Hirai,
K Kawakami,
T Nakamura,
M Mishima
[show abstract]
[hide abstract]
ABSTRACT: We evaluated the size and configuration of the trachea in patients with chronic obstructive pulmonary disease (COPD; n = 35) on high-resolution computed tomography (HRCT) images and compared them with those of healthy volunteers (n = 24).
Using a newly developed computed method for analyzing the digital data of HRCT, the size and configuration of the trachea were automatically evaluated.
The size of the trachea of the COPD subjects was the same as that of the control subjects; however, the configuration was more distorted in the COPD patients. There was no difference in the tracheal index (TI), which is the ratio of the coronal to the sagittal length, between these two groups; however, the ratio of the short to the long radius (SR/LR) was significantly smaller in the COPD group than in the control group. There was a significant correlation between SR/LR and airflow limitation as assessed by pulmonary function tests in the COPD group.
The SR/LR is a better index of tracheal deformity than the classical TI. This deformity is not a consequence secondary to hyperinflation or emphysematous change of the lung, because the low attenuation area of the lung was not correlated with SR/LR.
Respiration 02/2000; 67(6):638-44. · 2.26 Impact Factor
-
M Mishima,
T Hirai,
H Itoh,
Y Nakano, H Sakai,
S Muro,
K Nishimura,
Y Oku,
K Chin,
M Ohi,
T Nakamura,
J H Bates,
A M Alencar,
B Suki
[show abstract]
[hide abstract]
ABSTRACT: Increases in the low attenuation areas (LAA) of chest x-ray computed tomography images in patients with chronic obstructive pulmonary disease (COPD) have been reported to reflect the development of pathological emphysema. We examined the statistical properties of LAA clusters in COPD patients and in healthy subjects. In COPD patients, the percentage of the lung field occupied by LAAs (LAA%) ranged from 2.6 to 67.6. In contrast, LAA% was always <30% in healthy subjects. The cumulative size distribution of the LAA clusters followed a power law characterized by an exponent D. We show that D is a measure of the complexity of the terminal airspace geometry. The COPD patients with normal LAA% had significantly smaller D values than the healthy subjects, and the D values did not correlate with pulmonary function tests except for the diffusing capacity of the lung. We interpret these results by using a large elastic spring network model and find that the neighboring smaller LAA clusters tend to coalesce and form larger clusters as the weak elastic fibers separating them break under tension. This process leaves LAA% unchanged whereas it decreases the number of small clusters and increases the number of large clusters, which results in a reduction in D similar to that observed in early emphysema patients. These findings suggest that D is a sensitive and powerful parameter for the detection of the terminal airspace enlargement that occurs in early emphysema.
Proceedings of the National Academy of Sciences 09/1999; 96(16):8829-34. · 9.68 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: The low attenuation areas on computed tomographic (CT) scans have been reported to represent emphysematous changes of the lung. However, the regional distribution of emphysema between the inner and outer segments of the lung has not been adequately studied. In this study the regional distribution of low attenuation areas has been compared by quantitative CT analysis and the contribution of the regional distribution to pulmonary function tests evaluated in patients with chronic obstructive pulmonary disease (COPD).
Chest CT images and the results of pulmonary function tests were obtained from 73 patients with COPD. The lung images were divided into inner and outer segments in the upper (cranial), middle, and lower (caudal) sections. The percentage ratio of low attenuation area to corresponding lung area (LAA%) was then calculated. The LAA% of each segment was also compared with the results of pulmonary function tests.
The mean (SD) LAA% of the inner segment was 39.1 (18.5) compared with 28.1 (13.2) for the outer segment (p<0.0001). Linear and multiple regression analyses revealed that airflow limitation is closely correlated with the inner segment LAA% of the lower lung. In contrast, the carbon monoxide transfer factor is closely correlated with the inner segment LAA% of the upper lung.
Low attenuation areas on CT scans are more often found in the inner segment of the lung than in the outer segment, and the contribution of the inner segment to pulmonary function tests may be greater than the outer segment.
Thorax 06/1999; 54(5):384-9. · 6.84 Impact Factor
-
[show abstract]
[hide abstract]
ABSTRACT: The effect of positive airway pressure (5.0 hPa) on airway impedance (Za) and tissue impedance (Zt) during the expiratory phase in chronic obstructive pulmonary disease (COPD) patients was evaluated using random noise oscillation and a body box method. The results were then compared with those obtained from normal subjects. In normal subjects, there was no significant difference between non-expiratory positive pressure (NPEP) and positive expiratory pressure (PEP) for the Zar (real part) and Zai (imaginary part) at 10 Hz (Zar NPEP: 2.14 +/- 0.76, PEP: 1.96 +/- 0.79; Zai NPEP: 1.42 +/- 0.66, PEP: 1.40 +/- 0.70 hPa l-1 s). However, in COPD patients, Zar decreased significantly and the Zai increased significantly during PEP as compared to the values during NPEP (Zar NPEP: 7.10 +/- 1.88, PEP: 5.97 +/- 1.67, P < 0.05; Zai NPEP: -4.10 +/- 2.27, PEP: -2.99 +/- 2.62 hPa l-1 s, P < 0.05). These results suggested that both central and peripheral airway resistance decreased during PEP in COPD patients. Tissue compliance (Ct) calculated from the Zt increased significantly during PEP as compared to during NPEP, in both normal subjects and in COPD patients (normal NPEP: 0.024 +/- 0.004, PEP: 0.021 +/- 0.003, P < 0.05; COPD NPEP: 0.024 +/- 0.004, PEP: 0.014 +/- 0.004 l hPa-1, P < 0.001). This may have been indicative of the stiffened chest wall during PEP.
Frontiers of Medical & Biological Engineering 02/1999; 9(1):63-73.
-
[show abstract]
[hide abstract]
ABSTRACT: We measured the change in total lung resistance (RL) and that in total lung elastance (EL) induced by hypoxia (n = 7) and compared the results with those by intravenous histamine bolus (n = 5) at three different positive end-expiratory pressure (PEEP) levels (2, 5, and 8 hPa) in open-chest and vagotomized rabbits. The percent increase ratio of RL (PIRR) and EL (PIRE) was defined as the change in RL and EL, respectively, induced by hypoxia compared with that in the normoxic condition, expressed as a percentage. PIR values for the change in RL and EL induced by bolus injection of histamine were also calculated. The PIRR and PIRE induced by hypoxia and by histamine were positive by a statistically significant amount at every PEEP level, except for the PIRE value at 8-hPa PEEP in the hypoxic challenge. The PIRE-to-PIRR ratio values in the hypoxic challenge at 2-hPa PEEP were significantly larger than those in the histamine challenge (hypoxia: 0.91 +/- 0.23%; histamine: 0.37 +/- 0. 065%, P < 0.05). The increase in EL induced by histamine in the acute phase has been reported to be mainly derived from tissue distortion secondary to bronchial constriction. Thus our results suggest that a part of the increase in EL by hypoxia was originated in different parenchymal responses from histamine and imply that this hypoxic response of lung parenchyma is sensitive to the increase in parenchymal tethering at high PEEP levels.
Journal of Applied Physiology 01/1999; 86(1):306-12. · 3.75 Impact Factor
-
M Mishima,
T Hirai,
Z Jin,
Y Oku,
N Sakai,
Y Nakano, H Sakai,
K Chin,
M Ohi,
K Kawakami,
K Shimada,
H Itoh,
K Yamaguchi,
T Sawa,
K Kuno
[show abstract]
[hide abstract]
ABSTRACT: We examined the methods for measuring the LAA% (100 x low attenuation area/total lung area) on thoracic X-ray CT scans in order to develop a useful indicator of chronic pulmonary emphysema (CPE). First, we modified the method for calculating the LAA% to be applicable by the programming tool installed in a commercially available CT machine in order to minimize manual procedures. This new method proved to be applicable in all CT machines produced after 1987. Second, we examined the difference in the Hounsfield Unit (HU) between different CT machines using two kinds of phantoms. One phantom was composed of Styrofoam, which has a density similar to the low attenuation areas. The other phantom was composed of Styrofoam and water, which has a density similar to the lung. We proved that the difference of LAA% with the correct value was 5% at maximum among four different CT machines. Thus, the phantom developed in the present study may play an important role in the standardization of HU. Finally, the possibility of decreasing the X-ray levels was examined. Twenty-five percent of the standard electrical current provided the same LAA% in cases where the subject was an established CPE patient, whereas the LAA% was overestimated in subjects with a normal LAA% value. However, a correction using a linear regression equation may be possible in the latter cases. It may be concluded that LAA% analysis can easily be performed in many city hospital, without much investment of manual procedures or any corrections to the HU levels between different CT machines. This method may be useful as a routine follow up for CPE patients because of the smaller irradiated dose given when using a CT machine.
Frontiers of Medical & Biological Engineering 02/1997; 8(2):79-86.
-
M Mishima,
H Itoh, H Sakai,
Y Nakano,
S Muro,
T Hirai,
Y Takubo,
K Chin,
M Ohi,
K Nishimura,
K Yamaguchi,
T Nakamura
[show abstract]
[hide abstract]
ABSTRACT: To address the optimal scanning condition of high resolution computerized tomography from the perspective of minimizing exposed dose.
The influence of the electric current, the slice number, and the slice thickness on precise percent ratio of the low attenuation area to whole lung field (LAA%) of chronic obstructive pulmonary disease patients was examined. The standard conditions were 250 mA, 3 slices, 2 mm slice thickness, and a varied parameter.
In cases showing an LAA% less than 30, LAA% obtained by < or =150 mA were significantly larger than those by 250 mA. The mean LAA% with 3 and 10 slices were well correlated and the correlation with lung function was similar. The correlation of LAA% with lung function was approximately the same between the 2 and 5 mm slice thicknesses.
The electrical current must be > or =200 mA, and 3 slices and 2 mm slice thickness are appropriate.
Journal of Computer Assisted Tomography 23(3):380-4. · 1.22 Impact Factor
