The results of this study apply only to ...

We have found that low dose CT measurement of emphysema index slightly from the measurements obtained on standard dose scans. However, the average difference is less than 3% is probably small enough to be clinically insignificant in quantitative research

emphysema, which compares the differences or cohort estimates for sequential changes in the index of emphysema. Also >> <<, relations between the two types of measurements were linear, the slope of the linear regression shows together

correspondence. These observations show that in the range of radiation used in the subjects in this study

impacts have minimal effect on CT quantification of emphysema. Therefore, for practical purposes, the low dose and standard dose

CT indices of emphysema severity may be considered equivalent. One of the practical implications of these results is that the exact sequence of influence factors is not necessary at CT

used for comparative studies of emphysema. This conclusion is in contrast to the differences related to the thickness of the slice [,,,

] and reconstruction filter [], which can make a significant impact on the index of emphysema. As long as the last two variables remain unchanged, valid comparison

cohorts, which influence factors are not fixed, it must be possible. Significant changes in emphysema indexes between low-and standard dose CT was found in some individual items

in this study, as shown inches difference in lung volume of these items during CT accounted for most of this change. Volume light, or >> << degree inspiration CT is widely recognized as the most important factor that affects CT measurement of emphysema [

]. In ideal conditions, a standard method to achieve consistent lung volume should be used. Because spirometry control

lung volume is usually bulky and not widely known, most researchers to standardize the volume of lung to coaching actors

- will breathe easy. In this retrospective study, CT was performed on quantitative emphysema

so it was not a promising attempt to optimize the sequence of inhalation levels. Thus, the effect of lung was

carefully studied. Although there was no statistically significant difference in CT-measured volume of lung to group all items >> << trend toward increasing lungs were found at low dose scan compared with standard-dose scans. Such great inspiration >> << volume may constitute or contribute to an increase in emphysema index. Multivariate analyzes showed that lung volume was the only variable

with a significant impact on differences in emphysema indexes between low and standard dose scans. However, when we

eliminated the influence of differences of the lungs, repeating the comparison using only cases in which the difference >> << lung volume was 3% or less, the picture above emphysema index on low dose scans stored despite the differences were less

. The effect of irradiation dose in emphysema index is supported by finding more >> << difference between the mean and standard low dose emphysema indexes in patients with a higher ratio of standard dose, low dose irradiation. The results of this study are similar to the results of more limited studies [], in which 20-80% reduction in CT milliamperage compared to some other level of re-scanning. Using 2 mm thick slice,

authors found an increase in emphysema index (-960 H threshold) with a reduction in radiation, and 3. 6% among

patients with emphysema index of less than 30%. Possible effects of lung volume were not considered. We found no clear trend

associated with the magnitude of emphysema index (such as emphysema severity). The optimal threshold for determining the attenuation of emphysema thickness cut is used for scanning in this study is uncertain. Although the threshold of -910 H for 10-mm thick, contiguous, contrast scans [

] and -950 H for unenhanced 1. 0-mm cubes each received 10 mm [

] has been shown to most accurately reflect the amount of emphysema present on histological analysis of samples of lung, >> << optimal threshold of 5 mm thick scanning has been defined. Given the results of previous studies, however, is

It is likely that the optimal threshold for defining emphysema with standard dose, 5 mm, scanning between -950 and -910 H. The link

band can not quite comparable, so as the standard dose in this study were approximately half the dose >> << used in one of exile studies [

] (report of another study showing no link impacts). In addition, the report links

research is not specified reconstruction algorithm used. For these reasons, the effect of dose reduction lasix 15 mg on weakening

frequencies were evaluated at several thresholds damping. Average emphysema at a low dose remained

a bit, but always above all attenuation thresholds. There were some limitations of this study. One is that the retrospective, so variables are not precisely controlled. In a prospective study in which subjects were consecutive images at low and standard doses in the same scanner with

verbal coaching to obtain reproducible inspiratory breath holds would be better, but would require additional radiation >> << . Since the reconstruction filters for 4-MSCT and 16-MSCT scanners are used in this study, technically equivalent

(M. Milite, H. Vestner, Research and Development Group, Siemens Medical Solutions, personal communication) and that scanner

type was not a factor in multivariable models, we believe, scanner type affected the comparisons. Another limitation

that low-and standard dose scan compared were obtained after an average duration of 3 months. Although we

nothing is known about long-term studies addressing imaging rate emphysema progression, it is unlikely for

actual number emphysema change significantly in this interval. Although lung volume increases over time as emphysema progresses,

we do not believe that this change is a factor, given the trend towards larger volume of low-dose scans that were obtained in the first

almost all cases. Finally, our study does not give reasons for the small differences found. Measurement of air

and blood attenuation obtained for this study and daily checks water phantom for clinical quality

exclude improper calibration drift of the scanner and the decrease of value as an explanation, measurement SD medium attenuation

(

) confirmed the expected relationship in which noise is reduced depending on the square root of the increase in radiative forcing

(for example, the action twice, SD decreases by the square root of 2) [,

]. The results of this study apply only to the effective tube current values ​​in the range 30-250 wt. Effect more >> << lower doses is unknown. It is likely that the critical effective tube current level or range below which there

signal to noise insufficient for accurate measurement index of emphysema. Effect of lower doses reconstructed

thickness of cut, which would increase noise levels for low-dose and standard dose scans are often unknown. Research

isolated lung or animal models with the same scanner and a few doses and thickness of the cut would be useful for determining

effect of low doses and a smaller slice thickness. Without this information, yet recognizable, that reconstruction

methods should be constantly in comparative studies of quantitative CT emphysema. We believe that in addition to its potential value as a tool for early detection of lung cancer, low-dose MSCT has great potential value >> << for quantitative studies of emphysema. Differences in emphysema index by doses of radiation were found

should be minimal. Although statistically significant, these differences may be a little clinical significance, especially

due to changes due to differences in lung volume that can occur. So much more important to try to optimize the sequence

breath effort to minimize changes due to technical factors. Clinical >> << acceptability of CT mainly quantified emphysema is likely to be more low-dose technique, because in fact

reduce radiation exposure. Possible areas of application include the studied transverse and longitudinal research to learn more about

interaction between cigarette smoking and other risk factors, genotype-phenotype relations, Natural History

, early stages of emphysema in young smokers, and individual rates of emphysema progression. Low dose scan also

potential value in clinical trials, evaluation of pharmacological therapy for emphysema as an alternative to the standard dose methods

have been used [<< >>] and can help determine the appropriate point to start any pharmacological intervention was effective. . << >>