Computer-aided Diagnosis of Retinopathy of Prematurity via Analysis of the Vascular Architecture in Retinal Fundus Images of Preterm Infants

摘要

Retinopathy of prematurity (ROP) is a disorder that affects the development of blood vessels in the retina of premature infants, and is the leading cause of preventable childhood blindness (International Committee for the Classification of Retinopathy of Prematurity, 2005). Because advanced ROP can progress rapidly in the first 8 to 12 weeks of life, prompt identification of high-risk features of the disease is critical to the management of the affected infants. The posterior signs that are indicative of the presence of ROP are the straightening of the major temporal arcade (MTA), a decrease in the angle of insertion of the MTA, and increased dilation and tortuosity of the arteriole and venular vessels (International Committee for the Classification of Retinopathy of Prematurity, 2005; Cryotherapy for Retinopathy of Prematurity Cooperative Group, 2001; Wilson et al., 2006; Wong et al., 2011; Wilson et al., 2008). The presence of plus disease can be indicative of the severity of active ROP. Plus disease is diagnosed by the presence of a certain amount of increase in venular dilation and arteriole tortuosity in at least two quadrants of the eye (International Committee for the Classification of Retinopathy of Prematurity, 2005). The presence of sufficient dilation and tortuosity of the posterior vessels for the diagnosis of plus disease is determined by visual comparison to a gold standard retinal fundus photograph (International Committee for the Classification of Retinopathy of Prematurity, 2005; Watzke et al., 1990; Wilson et al., 2008). A severe form of ROP, called aggressive posterior ROP, shows increase in the dilation and tortuosity of the blood vessels in all four quadrants at early stages of its development (International Committee for the Classification of Retinopathy of Prematurity, 2005). The angle of insertion of the MTA has been loosely defined as the angle between the superior and inferior temporal arcades (STA and ITA) as they diverge from the optic nerve head (ONH) and extend towards the periphery of the retina (Wilson et al., 2006; Cryotherapy for Retinopathy of Prematurity Cooperative Group, 2001). Despite the clinical importance of abnormal changes in the architecture of the MTA, only the angle of insertion of the MTA has been quantified manually in only two studies dealing with ROP (Wilson et al., 2006;Wong et al., 2011). Treatment of ROP is primarily driven by the identification of the above-mentioned features via clinical examination or photographic documentation. The current clinical method for diagnosis of plus disease is subjective. As shown by Chiang et al. (Chiang et al., 2007), among 22 recognized ROP experts who performed diagnosis of plus disease on 34 images of preterm infants based on a three-level classification (plus, preplus, and neither), the experts agreed on the diagnosis of only 12% of the images (four out of 34). It is likely that no optimal visual reference standard exists for the diagnosis of plus disease, as shown by disagreement even among recognized experts (Chiang et al., 2007; Wallace et al., 2008). Such studies show the need for computer-aided methods to quantify the changes in retinal blood vessels in the presence of plus disease. Computer-aided diagnosis (CAD) and quantitative analysis of the vascular architecture of the retina could assist in monitoring the evolution and stages of ROP, their effects on the visual system, and the response to treatment.