Adjusted subpixel method enables optimisation of bronchial measurements in high-resolution CT

Abstract

Objectives: The purpose of this paper is to present a new technique of high-resolution computed tomography (HRCT) bronchial measurement, which was worked out in our centre and is based on a mathematically adjusted subpixel method (ASM). Methods: This study used a bronchial tree model comprising two polyvinyl chloride/ rubber pipes with various densities placed in a larger plastic object. External and internal diameters of both pipes corresponded to the sizes of structures that are usually evaluated in HRCT scans (i.e. the bronchus with accompanying blood vessel). The model was subjected to repeated HRCT measurements of the external and internal diameters of model pipes using a subpixel technique and ASM. Results: Significant differences were observed between mean values of external and internal diameters of model pipes determined by means of subpixel method or ASM, with the latter being the ones that resembled real diameters of the model pipes more closely. Mean external diameters of the larger and smaller model pipes determined by ASM differed from the real diameters by 0.23% and 0.57%, respectively. The internal diameter of the larger pipe was on average 25.96% larger, whereas the internal diameter of the smaller pipe was 48.05% smaller than the real diameter. Conclusion:The technique of non-linear prediction of HRCT bronchial measurements described in this paper raises attractive prospects in its clinical application owing to potential improvements in the objectivity and reproducibility of bronchial wall measurements. High-resolution CT (HRCT) has recently gained increasing attention as an evaluation method of bronchial remodelling in asthma patients [1]. The efficiency of HRCT has been proven by numerous studies [2][3][4][5]. Optimisation of the radiation beam parameters enables identification of structures down to 100-200 mm in size and allows for evaluation of even the smallest bronchi (1.5-2 mm in diameter) [6]. Because of the aforementioned characteristics, HRCT is useful in the diagnosis and evaluation of many pathologies, including bronchial wall thickening, bronchiectasis, mucus plugging and emphysema or atelectasis [7][8][9][10][11].Owing to its many advantages, HRCT is likely to become the standard tool for disease evaluation in patients with difficult/refractory asthma [12][13][14][15]. However, a number of constraints are associated with the application of this otherwise valuable method. The first constraint is the lack of clearly defined clinical criteria for asthma evaluation in HRCT scans [16]. Among the proposed criteria, disease-related changes in bronchial wall thickness and bronchial lumen diameter seem to be the most reasonable. However, repeating and comparing measurements obtained at different time points is often frustrated by the low reproducibility of HRCT-based measurements. This problem results mostly from the wide use of eye-driven, non-standardised techniques of measurements.A number of attempts towards optimising HRCT measurements have been undertaken, mostly based on model syste...

CT Scan Does Not Differentiate Patients with Hepatopulmonary Syndrome from Other Patients with Liver Disease

“…Although the mean basilar ABR measured in our normal subjects (0.98 +/- 0.10) was similar to that reported elsewhere (0.98 +/- 0.14)[ 15 ], measurement techniques were also different in our study than in these two previous studies. We chose to measure outer bronchial wall diameters instead of luminal diameters for ABR calculations[ 5 , 6 ] because they are less susceptible to the effects of bronchial wall thickening, secretions and bronchospasm[ 27 – 29 ], and more reliably measured than luminal diameters[ 30 ]. We defined the lower lung zone as the 20 contiguous slices after take-off of the basal segmental arteries, whereas both prior authors defined this more distally, as a region within 2 cm of the lung periphery[ 5 , 6 ].…”