Low-dose high-resolution CT of lung parenchyma.

Abstract

To evaluate the efficacy of low-dose high-resolution computed tomography (HRCT) in the assessment of lung parenchyma, three observers reviewed the scans of 31 patients. The 1.5-mm-collimation, 2-second, 120-kVp scans were obtained at 20 and 200 mA at selected identical levels in the chest. The observers evaluated the visualization of normal pulmonary anatomy, various parenchymal abnormalities and their distribution, and artifacts. The low-dose and conventional scans were equivalent in the evaluation of vessels, lobar and segmental bronchi, and anatomy of secondary pulmonary lobules, and in characterizing the extent and distribution of reticulation, honeycomb cysts, and thickened interlobular septa. The low-dose technique failed to demonstrate ground-glass opacity in two of 10 cases (20%) and emphysema in one of nine cases (11%), in which they were evident but subtle on the high-dose scans. These differences were not statistically significant. Linear streak artifact was more prominent on images acquired with the low-dose technique, but the two techniques were judged equally diagnostic in 97% of cases. The authors conclude that HRCT images acquired at 20 mA yield anatomic information equivalent to that obtained with 200-mA scans in the majority of patients, without significant loss of spatial resolution or image degradation due to linear streak artifact.

Interstitial lung diseases in a lung cancer screening trial

“…Whilst REMY-JARDIN et al [5] found upper zone-predominant micronodules in 26 (27%) out of 98 asymptomatic smokers, we found signs of RB in 109 (15.7%) out of 692 smokers despite the fact that individuals recruited by MILD were heavier smokers. Such a discrepancy may have several explanations: in particular, the use of a low-dose CT protocol in our lung cancer screening trial may have lowered the detection rate of hazy nodules and ground-glass opacity [21]. Furthermore, in contrast with another study of REMY-JARDIN et al [22], which showed changes of centrilobular nodules over a mean period of 5.5 yrs in 11 (64.7%) out of 17 smokers, only five (12%) out of 42 cases with centrilobular nodules displayed changes after 3 yrs in our study.…”

The correlation of emphysema or airway obstruction with the risk of lung cancer: a matched case-controlled study

“…Although reduction of the milliamperage increases the image noise, NAIDICH et al [29] found that visualization of parenchymal structure was not affected by decreasing the milliamperage. ZWIREWICH et al [30] showed that the low-dose and the standard-dose HRCT scans were equivalent in the evaluation of anatomical information as well as interstitial and air-space abnormalities. A recent study reported that low-dose spiral CT was equivalent to the standard-dose spiral CT at visualizing lung abnormalities [31].…”

Nodular Ground-Glass Opacity at Thin-Section CT: Histologic Correlation and Evaluation of Change at Follow-up

“…Therefore, CT should be performed within objective parameters that make lesion depiction reliable and reproducible. Generally, a tube current of 200 -400 mA is acceptable (13,14). Low tube current may produce excessive noise that simulates ground-glass opacity or may lead to the failure to depict ground-glass opacity (14).…”

“…Generally, a tube current of 200 -400 mA is acceptable (13,14). Low tube current may produce excessive noise that simulates ground-glass opacity or may lead to the failure to depict ground-glass opacity (14). In this context, low-dose CT probably would not be appropriate for characterizing nodular ground-glass opacity (Fig 1).…”