A Technique for Simulating the Effect of Dose Reduction on Image Quality in Digital Chest Radiography

Abstract

Purpose: The purpose of this study is to provide a pragmatic tool for studying the relationship between dose and image quality in clinical chest images. To achieve this, we developed a technique for simulating the effect of dose reduction on image quality of digital chest images. Materials and Methods: The technique was developed for a digital charge-coupled-device (CCD) chest unit with slot-scan acquisition. Raw pixel values were scaled to a lower dose level, and a random number representing noise to each specific pixel value was added. After adding noise, raw images were post processed in the standard way. Validation was performed by comparing pixel standard deviation, as a measure of noise, in simulated images with images acquired at actual lower doses. To achieve this, a uniform test object and an anthropomorphic phantom were used. Additionally, noise power spectra of simulated and actual images were compared. Also, detectability of simulated lesions was investigated using a model observer. Results: The mean difference in noise values between simulated and real lower-dose phantom images was smaller than 5% for relevant clinical settings. Noise power spectra appeared to be comparable on average but simulated images showed slightly higher noise levels for higher spatial frequencies and slightly lower noise levels for lower spatial frequencies. Comparable detection performance was shown in simulated and actual images with slightly worse detectability for simulated lower dose images. Conclusion: We have developed and validated a method for simulating dose reduction. Our method seems an acceptable pragmatic tool for studying the relationship between dose and image quality.

Low-dose preview for patient-specific, task-specific technique selection in cone-beam CT

“…13 Subsequent studies used simulated dose reduction to demonstrate the potential for low-dose protocols in applications such as pediatric abdominal CT, 14 CT colonography, 15 chest CT, 16 and chest radiography. 17 More recently, simulated dose reduction methods have utilized more advanced models of noise beyond just quantum noise, such as inclusion of electronic noise, 18,19 that led to accurate reproduction of not only image noise magnitude but also noise power spectra. [20][21][22][23] Other extensions of simulated dose reduction include using dual energy scans to allow simulated changes in tube voltage 24 or using an image-based approach that does not assume availability of projection data (but does not allow for different reconstruction methods/parameters).…”

Review of a simple noise simulation technique in digital radiography

“…A number of researchers reported on methods for simulating reduced dose images. Such techniques have been applied in computed radiography (CR) [1], digital radiography (DR) [2,3], and computed tomography (CT) [4][5][6]. Bath et al developed an accurate simulation method for CR system.…”

Método de simulação da redução da dose de radiação na mamografia digital a partir da análise das características do ruído dos equipamentos mamográficos

“…This method was based on the local standard deviation of the image. However, as shown by the authors themselves (VELDKAMP et al, 2009), although the simulated images have the same local standard deviation as real images, they have different NPS. Since the standard deviation is not a good metric of the image noise when comparing images with different NPS (BURGESS, 1999) , the clinical application of such method can be questioned.…”

“…Such images are difficult to be arranged because it would imply exposing patients to several levels of radiation. To solve this issue, some works propose algorithms capable of simulating dose reduction in clinical mammograms (SAUNDERS; SAMEI, 2003;BATH et al, 2005;KROFT et al, 2006;VELDKAMP et al, 2009;SVALKVIST;BATH, 2010;MACKENZIE et al, 2012;MACKENZIE et al, 2014). The next chapter will present methods of performing this simulation and it will discuss limitations associated with these methods.…”

“…Another approach to validate the methods for dose reduction is to simulate the effect of reduced exposure in mammograms by post processing clinical images (SAUNDERS; SAMEI, 2003;BATH et al, 2005;KROFT et al, 2006;VELDKAMP et al, 2009;SVALKVIST;BATH, 2010;MACKENZIE et al, 2012;MACKENZIE et al, 2014). In fact, such simulation methods have been used as tools in most studies regarding the influence of dose reduction on the detection of breast lesions (TIMBERG et al, 2006;SAUNDERS et al, 2007;RUSCHIN et al, 2007).…”